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Sample records for aligned zno nanotube

  1. Hybrid nanostructure heterojunction solar cells fabricated using vertically aligned ZnO nanotubes grown on reduced graphene oxide

    Energy Technology Data Exchange (ETDEWEB)

    Yang Kaikun; Huang Liwei; Zou Lianfeng; Wang, Howard [Institute for Materials Research, Binghamton University, State University of New York, Binghamton, NY 13902 (United States); Xu Congkang, E-mail: wangh@binghamton.edu [Department of Mechanical Engineering, Binghamton University, State University of New York, Binghamton, NY 13902 (United States)

    2011-10-07

    Using reduced graphene oxide (rGO) films as the transparent conductive coating, inorganic/organic hybrid nanostructure heterojunction photovoltaic devices have been fabricated through hydrothermal synthesis of vertically aligned ZnO nanorods (ZnO-NRs) and nanotubes (ZnO-NTs) on rGO films followed by the spin casting of a poly(3-hexylthiophene) (P3HT) film. The data show that larger interfacial area in ZnO-NT/P3HT composites improves the exciton dissociation and the higher electrode conductance of rGO films helps the power output. This study offers an alternative to manufacturing nanostructure heterojunction solar cells at low temperatures using potentially low cost materials.

  2. Aligned carbon nanotubes for nanoelectronics

    Science.gov (United States)

    Choi, Won Bong; Bae, Eunju; Kang, Donghun; Chae, Soodoo; Cheong, Byung-ho; Ko, Ju-hye; Lee, Eungmin; Park, Wanjun

    2004-10-01

    We discuss the central issues to be addressed for realizing carbon nanotube (CNT) nanoelectronics. We focus on selective growth, electron energy bandgap engineering and device integration. We have introduced a nanotemplate to control the selective growth, length and diameter of CNTs. Vertically aligned CNTs are synthesized for developing a vertical CNT-field effect transistor (FET). The ohmic contact of the CNT/metal interface is formed by rapid thermal annealing. Diameter control, synthesis of Y-shaped CNTs and surface modification of CNTs open up the possibility for energy bandgap modulation. The concepts of an ultra-high density transistor based on the vertical-CNT array and a nonvolatile memory based on the top gate structure with an oxide-nitride-oxide charge trap are also presented. We suggest that the deposited memory film can be used for the quantum dot storage due to the localized electric field created by a nano scale CNT-electron channel.

  3. Alignment of Carbon Nanotubes in Carbon Nanotube Fibers Through Nanoparticles: A Route for Controlling Mechanical and Electrical Properties.

    Science.gov (United States)

    Hossain, Muhammad Mohsin; Islam, Md Akherul; Shima, Hossain; Hasan, Mudassir; Lee, Moonyong

    2017-02-15

    This is the first study that describes how semiconducting ZnO can act as an alignment agent in carbon nanotubes (CNTs) fibers. Because of the alignment of CNTs through the ZnO nanoparticles linking groups, the CNTs inside the fibers were equally distributed by the attraction of bonding forces into sheetlike bunches, such that any applied mechanical breaking load was equally distributed to each CNT inside the fiber, making them mechanically robust against breaking loads. Although semiconductive ZnO nanoparticles were used here, the electrical conductivity of the aligned CNT fiber was comparable to bare CNT fibers, suggesting that the total electron movement through the CNTs inside the aligned CNT fiber is not disrupted by the insulating behavior of ZnO nanoparticles. A high degree of control over the electrical conductivity was also demonstrated by the ZnO nanoparticles, working as electron movement bridges between CNTs in the longitudinal and crosswise directions. Well-organized surface interface chemistry was also observed, which supports the notion of CNT alignment inside the fibers. This research represents a new area of surface interface chemistry for interfacially linked CNTs and ZnO nanomaterials with improved mechanical properties and electrical conductivity within aligned CNT fibers.

  4. Permanent bending and alignment of ZnO nanowires.

    Science.gov (United States)

    Borschel, Christian; Spindler, Susann; Lerose, Damiana; Bochmann, Arne; Christiansen, Silke H; Nietzsche, Sandor; Oertel, Michael; Ronning, Carsten

    2011-05-06

    Ion beams can be used to permanently bend and re-align nanowires after growth. We have irradiated ZnO nanowires with energetic ions, achieving bending and alignment in different directions. Not only the bending of single nanowires is studied in detail, but also the simultaneous alignment of large ensembles of ZnO nanowires. Computer simulations reveal how the bending is initiated by ion beam induced damage. Detailed structural characterization identifies dislocations to relax stresses and make the bending and alignment permanent, even surviving annealing procedures.

  5. Permanent bending and alignment of ZnO nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Borschel, Christian; Spindler, Susann; Oertel, Michael; Ronning, Carsten [Institut fuer Festkoerperphysik, Friedrich-Schiller-Universitaet Jena, Max-Wien-Platz 1, 07743 Jena (Germany); Lerose, Damiana [MPI fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle/Saale (Germany); Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Bochmann, Arne [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); Christiansen, Silke H. [Institut fuer Photonische Technologien, Albert-Einstein-Strasse 9, 07745 Jena (Germany); MPI fuer die Physik des Lichts, Guenther-Scharowsky-Str. 1, 91058 Erlangen (Germany); Nietzsche, Sandor [Zentrum fuer Elektronenmikroskopie, Friedrich-Schiller-Universitaet Jena, Ziegelmuehlenweg 1, 07743 Jena (Germany)

    2011-07-01

    Ion beams can be used to bend or re-align nanowires permanently, after they have been grown. We have irradiated ZnO nanowires with ions of different species and energy, achieving bending and alignment in various directions. We study the bending of single nanowires as well as the simultaneous alignment of large ensembles of ZnO nanowires in detail. Computer simulations show that the bending is initiated by ion beam induced damage. Dislocations are identified to relax stresses and make the bending and alignment permanent and resistant against annealing procedures.

  6. Controlled Deposition and Alignment of Carbon Nanotubes

    Science.gov (United States)

    Smits, Jan M. (Inventor); Wincheski, Russell A. (Inventor); Patry, JoAnne L. (Inventor); Watkins, Anthony Neal (Inventor); Jordan, Jeffrey D. (Inventor)

    2012-01-01

    A carbon nanotube (CNT) attraction material is deposited on a substrate in the gap region between two electrodes on the substrate. An electric potential is applied to the two electrodes. The CNT attraction material is wetted with a solution defined by a carrier liquid having carbon nanotubes (CNTs) suspended therein. A portion of the CNTs align with the electric field and adhere to the CNT attraction material. The carrier liquid and any CNTs not adhered to the CNT attraction material are then removed.

  7. Liquid crystal alignment on ZnO nanostructure films

    Science.gov (United States)

    Chung, Yueh-Feng; Chen, Mu-Zhe; Yang, Sheng-Hsiung; Jeng, Shie-Chang

    2016-03-01

    The study of liquid crystal (LC) alignment is important for fundamental researches and industrial applications. The tunable pretilt angles of liquid crystal (LC) molecules aligned on the inorganic zinc oxide (ZnO) nanostructure films with controllable surface wettability are demonstrated in this work. The ZnO nanostructure films are deposited on the ITO- glass substrates by the two-steps hydrothermal process, and their wettability can be modified by annealing. Our experimental results show that the pretilt angles of LCs on ZnO nanostructure films can be successfully adjusted over a wide range from ~90° to ~0° as the surface energy on the ZnO nanostructure films changes from ~30 to ~70 mJ/m. Finally we have applied this technique to fabricate a no-bias optically-compensated bend (OCB) LCD with ZnO nanostructure films annealed at 235 °C.

  8. Three dimensional ZnO nanotube arrays and their optical tuning through formation of type-II heterostructures

    OpenAIRE

    Wang, L; Huang, X.; Xia, J; Zhu, D.; Li, X.; Meng, X.

    2016-01-01

    In this paper, we report on the first successful attempt of chemical vapor deposition (CVD) synthesis of well-aligned single-crystalline ZnO nanotube arrays on Mo wire mesh. According to detailed morphology and composition analyses, a rational growth model is proposed to illustrate the growth process of the hollow ZnO nanotubes. Metastable Zn-rich ZnOx nanorods formed in the early stage are believed to play a vital role towards the formation of nanotube configuration. In addition, we also suc...

  9. Functionalization of vertically aligned carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Eloise Van Hooijdonk

    2013-02-01

    Full Text Available This review focuses and summarizes recent studies on the functionalization of carbon nanotubes oriented perpendicularly to their substrate, so-called vertically aligned carbon nanotubes (VA-CNTs. The intrinsic properties of individual nanotubes make the VA-CNTs ideal candidates for integration in a wide range of devices, and many potential applications have been envisaged. These applications can benefit from the unidirectional alignment of the nanotubes, the large surface area, the high carbon purity, the outstanding electrical conductivity, and the uniformly long length. However, practical uses of VA-CNTs are limited by their surface characteristics, which must be often modified in order to meet the specificity of each particular application. The proposed approaches are based on the chemical modifications of the surface by functionalization (grafting of functional chemical groups, decoration with metal particles or wrapping of polymers to bring new properties or to improve the interactions between the VA-CNTs and their environment while maintaining the alignment of CNTs.

  10. Synthesis of Vertically Aligned Dense ZnO Nanowires

    OpenAIRE

    Lihong Gong; Xiang Wu; Huibo Chen; Fengyu Qu; Maozhong An

    2011-01-01

    We reported the synthesis of vertically aligned dense ZnO nanowires using Zn powder as the source material by a hydrothermal method and a postannealing process at 200°C. The as-synthesized ZnO nanowires are 100–200 nm in diameter and several micrometers in length and each nanowire has a tapered tip. The morphologies of the products remain after post-annealing treatment. Structural analysis indicates the ZnO nanowire is single crystalline and grows along the [0001] direction. The possible grow...

  11. Growth of vertically aligned ZnO nanorods using textured ZnO films

    Directory of Open Access Journals (Sweden)

    Meléndrez Manuel

    2011-01-01

    Full Text Available Abstract A hydrothermal method to grow vertical-aligned ZnO nanorod arrays on ZnO films obtained by atomic layer deposition (ALD is presented. The growth of ZnO nanorods is studied as function of the crystallographic orientation of the ZnO films deposited on silicon (100 substrates. Different thicknesses of ZnO films around 40 to 180 nm were obtained and characterized before carrying out the growth process by hydrothermal methods. A textured ZnO layer with preferential direction in the normal c-axes is formed on substrates by the decomposition of diethylzinc to provide nucleation sites for vertical nanorod growth. Crystallographic orientation of the ZnO nanorods and ZnO-ALD films was determined by X-ray diffraction analysis. Composition, morphologies, length, size, and diameter of the nanorods were studied using a scanning electron microscope and energy dispersed x-ray spectroscopy analyses. In this work, it is demonstrated that crystallinity of the ZnO-ALD films plays an important role in the vertical-aligned ZnO nanorod growth. The nanorod arrays synthesized in solution had a diameter, length, density, and orientation desirable for a potential application as photosensitive materials in the manufacture of semiconductor-polymer solar cells. PACS 61.46.Hk, Nanocrystals; 61.46.Km, Structure of nanowires and nanorods; 81.07.Gf, Nanowires; 81.15.Gh, Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.

  12. Shear Flow Induced Alignment of Carbon Nanotubes in Natural Rubber

    Directory of Open Access Journals (Sweden)

    Yan He

    2015-01-01

    Full Text Available A new procedure for the fabrication of natural rubber composite with aligned carbon nanotubes is provided in this study. The two-step approach is based on (i the preparation of mixture latex of natural rubber, multiwalled carbon nanotubes, and other components and (ii the orientation of carbon nanotubes by a flow field. Rubber composite sheets filled with variable volume fraction of aligned carbon nanotubes were fabricated and then confirmed by transmission electron microscopy and Raman spectroscopy studies. An obvious increase in thermal conductivity has been obtained after the alignment of carbon nanotubes. The dynamic mechanical analysis was carried out in a tear mode for the composite.

  13. Continuous Growth of Vertically Aligned Carbon Nanotubes Forests

    OpenAIRE

    Guzman de Villoria, Roberto; Wardle, Brian L.

    2011-01-01

    Vertically aligned carbon nanotubes are one of the most promising materials due their numerous applications in flexible electronic devices, biosensors and multifunctional aircraft materials, among others. However, the costly production of aligned carbon nanotubes, generally in a batch process, prevents their commercial use. For the first time, a controlled process to grow aligned carbon nanotubes in a continuous manner is presented. Uniform growth is achieved using 2D and 3D substrates. A sig...

  14. Growth of ZnO nanotube arrays and nanotube based piezoelectric nanogenerators

    KAUST Repository

    Xi, Yi

    2009-01-01

    We present a systematic study of the growth of hexagonal ZnO nanotube arrays using a solution chemical method by varying the growth temperature (<100 °C), time and solution concentration. A piezoelectric nanogenerator using the as-grown ZnO nanotube arrays has been demonstrated for the first time. The nanogenerator gives an output voltage up to 35 mV. The detailed profile of the observed electric output is understood based on the calculated piezoelectric potential in the nanotube with consideration of the Schottky contact formed between the metal tip and the nanotube; and the mechanism agrees with that proposed for nanowire based nanogenerator. Our study shows that ZnO nanotubes can also be used for harvesting mechanical energy. © 2009 The Royal Society of Chemistry.

  15. Scalable ZnO nanotube arrays grown on CVD-graphene films

    Directory of Open Access Journals (Sweden)

    J. B. Park

    2016-10-01

    Full Text Available We report the growth of wafer-scale arrays of individually position-controlled and vertically aligned ZnO nanotube arrays on graphene deposited by chemical vapor deposition (CVD-graphene. Introducing two-dimensional layered materials such as graphene as a growth buffer has recently been suggested for growing nanomaterials on traditionally incompatible substrates. However, their growth has been restricted to small areas or had limited controllability. Here, we study the distinct growth behavior of ZnO on CVD-graphene that makes the selective area growth of individual nanostructures on its surface difficult, and propose a set of methods to overcome this. The resulting nanotube arrays, as examined by scanning electron microscopy and transmission electron microscopy, exhibited uniform morphologies and high structural quality over a large area and could be prepared on a broad variety of substrates, including amorphous, metallic, or flexible substrates.

  16. ZnO nanotube based dye-sensitized solar cells.

    Energy Technology Data Exchange (ETDEWEB)

    Martinson, A. B. F.; Elam, J. W.; Hupp, J. T.; Pellin, M. J. (Materials Science Division); (Northwestern Univ.)

    2007-05-25

    We introduce high surface area ZnO nanotube photoanodes templated by anodic aluminum oxide for use in dye-sensitized solar cells (DSSCs). Atomic layer deposition is utilized to coat pores conformally, providing a direct path for charge collection over tens of micrometers thickness. Compared to similar ZnO-based devices, ZnO nanotube cells show exceptional photovoltage and fill factors, in addition to power efficiencies up to 1.6%. The novel fabrication technique provides a facile, metal-oxide general route to well-defined DSSC photoanodes.

  17. ZnO nanotube based dye-sensitized solar cells.

    Science.gov (United States)

    Martinson, Alex B F; Elam, Jeffrey W; Hupp, Joseph T; Pellin, Michael J

    2007-08-01

    We introduce high surface area ZnO nanotube photoanodes templated by anodic aluminum oxide for use in dye-sensitized solar cells (DSSCs). Atomic layer deposition is utilized to coat pores conformally, providing a direct path for charge collection over tens of micrometers thickness. Compared to similar ZnO-based devices, ZnO nanotube cells show exceptional photovoltage and fill factors, in addition to power efficiencies up to 1.6%. The novel fabrication technique provides a facile, metal-oxide general route to well-defined DSSC photoanodes.

  18. Highly oriented carbon nanotube papers made of aligned carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Wang Ding; Song Pengcheng; Liu Changhong; Wu Wei; Fan Shoushan [Tsinghua-Foxconn Nanotechnology Research Center and Department of Physics, Tsinghua University, Beijing 100084 (China)], E-mail: chliu@tsinghua.edu.cn

    2008-02-20

    Paper-like carbon nanotube (CNT) materials have many important applications such as in catalysts, in filtration, actuators, capacitor or battery electrodes, and so on. Up to now, the most popular way of preparing buckypapers has involved the procedures of dispersion and filtration of a suspension of CNTs. In this work, we present a simple and effective macroscopic manipulation of aligned CNT arrays called 'domino pushing' in the preparation of the aligned thick buckypapers with large areas. This simple method can efficiently ensure that most of the CNTs are well aligned tightly in the buckypaper. The initial measurements indicate that these buckypapers have better performance on thermal and electrical conductance. These buckypapers with controllable structure also have many potential applications, including supercapacitor electrodes.

  19. Obtaining a Well-Aligned ZnO Nanotube Array Using the Hydrothermal Growth Method / Labi Sakārtotu Zno Nanocauruļu Kopu Iegūšana, Izmantojot Hidrotermālo Metodi

    Directory of Open Access Journals (Sweden)

    Krasovska M.

    2015-10-01

    Full Text Available Dotajā darbā tika noteikti optimāli parametri labi sakārtotu ZnO nanocaurulīšu kopu iegūšanai, izmantojot hidrotermālo metodi ar temperatūras pazemināšanu, jeb t.s. selektīvu paškodināšanas metodi (self-selective etching, ir uzsvērtas šās metodes priekšrocības salīdzinājumā ar ķīmiskās kodināšanas metodi, kā arī tika aprakstīta dažādu augšanas faktora (tādu, ka darba šķīduma koncentrācija, augšanas temperatūra un laiks, iedīgļu slāņa iegūšanas veids un iegūšanas parametri ietekme uz iegūtu nanostraktūra morfoloģiju.

  20. ZnO nanotube-based dye-sensitized solar cell and its application in self-powered devices

    KAUST Repository

    Han, Jingbin

    2010-09-10

    Abstract High-density vertically aligned ZnO nanotube arrays were fabricated on FTO substrates by a simple and facile chemical etching process from electrodeposited ZnO nanorods. The nanotube formation was rationalized in terms of selective dissolution of the (001) polar face. The morphology of the nanotubes can be readily controlled by electrodeposition parameters for the nanorod precursor. By employing the 5.1 μm-length nanotubes as the photoanode for a dye-sensitized solar cell (DSSC), a full-sun conversion efficiency of 1.18% was achieved. Furthermore, we show that the DSSC unit can serve as a robust power source to drive a humidity sensor, with a potential for self-powered devices. © 2010 IOP Publishing Ltd.

  1. Controlling growth of aligned carbon nanotubes from porous silicon templates

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Fabricating well-aligned carbon nanotubes, especially, on a silicon substrate is very important for their applications. In this paper, an aligned carbon nanotube array has been prepared by pyrolysis of hydrocarbons catalyzed by nickel nanoparticles embedded in porous silicon (PS) templates. High-magnification transmission electron microscopy images confirm that the nanotubes are well graphitized. The PS substrates with pore sizes between 10 and 100 nm play a control role on the growth of carbon nanotubes and the diameters of the tubes increase with the enlargement of the pores of the substrates. However, such a control role cannot be found in the macro-PS substrates.

  2. Thiol-capped ZnO nanowire/nanotube arrays with tunable magnetic properties at room temperature.

    Science.gov (United States)

    Deng, Su-Zi; Fan, Hai-Ming; Wang, Miao; Zheng, Min-Rui; Yi, Jia-Bao; Wu, Rong-Qin; Tan, Hui-Ru; Sow, Chorng-Haur; Ding, Jun; Feng, Yuan-Ping; Loh, Kian-Ping

    2010-01-26

    The present study reports room-temperature ferromagnetic behaviors in three-dimensional (3D)-aligned thiol-capped single-crystalline ZnO nanowire (NW) and nanotube (NT) arrays as well as polycrystalline ZnO NT arrays. Besides the observation of height-dependent saturation magnetization, a much higher M(s) of 166 microemu cm(-2) has been found in NTs compared to NWs (36 microemu cm(-2)) due to larger surface area in ZnO NTs, indicating morphology-dependent magnetic properties in ZnO NW/NT systems. Density functional calculations have revealed that the origin of ferromagnetism is mainly attributed to spin-polarized 3p electrons in S sites and, therefore, has a strong correlation with Zn-S bond anisotropy. The preferential magnetization direction of both single-crystalline NTs and NWs lies perpendicular to the tube/wire axis due to the aligned high anisotropy orientation of the Zn-S bonds on the lateral (100) face of ZnO NWs and NTs. Polycrystalline ZnO NTs, however, exhibit a preferential magnetization direction parallel to the tube axis which is ascribed to shape anisotropy dominating the magnetic response. Our results demonstrate the interplay of morphology, dimensions, and crystallinity on spin alignment and magnetic anisotropy in a 3D semiconductor nanosystem with interfacial magnetism.

  3. Hydrothermal Growth of Vertically Aligned ZnO Nanorods Using a Biocomposite Seed Layer of ZnO Nanoparticles

    Directory of Open Access Journals (Sweden)

    Zafar Hussain Ibupoto

    2013-08-01

    Full Text Available Well aligned ZnO nanorods have been prepared by a low temperature aqueous chemical growth method, using a biocomposite seed layer of ZnO nanoparticles prepared in starch and cellulose bio polymers. The effect of different concentrations of biocomposite seed layer on the alignment of ZnO nanorods has been investigated. ZnO nanorods grown on a gold-coated glass substrate have been characterized by X-ray diffraction (XRD and field emission scanning electron microscopy (FESEM techniques. These techniques have shown that the ZnO nanorods are well aligned and perpendicular to the substrate, and grown with a high density and uniformity on the substrate. Moreover, ZnO nanorods can be grown with an orientation along the c-axis of the substrate and exhibit a wurtzite crystal structure with a dominant (002 peak in an XRD spectrum and possessed a high crystal quality. A photoluminescence (PL spectroscopy study of the ZnO nanorods has revealed a conventional near band edge ultraviolet emission, along with emission in the visible part of the electromagnetic spectrum due to defect emission. This study provides an alternative method for the fabrication of well aligned ZnO nanorods. This method can be helpful in improving the performance of devices where alignment plays a significant role.

  4. Density-controlled growth of well-aligned ZnO nanowires using chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Well-aligned ZnO nanowires were grown on Si substrate by chemical vapor deposition.The experimental results showed that the density of nanowires was related to the heating process and growth temperature.High-density ZnO nanowires were obtained under optimal conditions.The growth mechanism of the ZnO nanowires was presented as well.

  5. Preparation of very long and open aligned carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    潘正伟; 常保和; 孙连峰; 钱露茜; 刘祖琴; 唐东升; 王刚; 解思深

    2000-01-01

    Very long and open aligned carbon nanotubes that reach about 2 mm long, an order of magnitude longer than previously reached, have been prepared by chemical vapor deposition over silica dioxide substrates on the surface, where iron/silica nano-composite particles are evenly positioned. The nanotubes are naturally opened at the bottom ends. The growth mechanism of the very long and open-ended nanotubes is also discussed.

  6. Synthesis of Aligned Carbon Nanotubes by Thermal Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    LI Gang; ZHOU Ming; MA Weiwei; CAI Lan

    2009-01-01

    Single crystal silicon was found to be very beneficial to the growth of aligned carbon nanotubes by chemical vapor deposition with C2H2 as carbon source. A thin film of Ni served as catalyst was deposited on the Si substrate by the K575X Peltier Cooled High Resolution Sputter Coater before growth. The growth properties of carbon nanotubes were studied as a function of the Ni catalyst layer thickness. The diameter, growth rate and areal density of the carbon nanotubes were controlled by the initial thickness of the catalyst layer. Steric hindrance between nanotubes forces them to grow in well-aligned manner at an initial stage of growth. Transmission electron microscope analysis revealed that nanotubes grew by a tip growth mechanism.

  7. Plasma Enhanced Chemical Vapour Deposition of Horizontally Aligned Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Matthew T. Cole

    2013-05-01

    Full Text Available A plasma-enhanced chemical vapour deposition reactor has been developed to synthesis horizontally aligned carbon nanotubes. The width of the aligning sheath was modelled based on a collisionless, quasi-neutral, Child’s law ion sheath where these estimates were empirically validated by direct Langmuir probe measurements, thereby confirming the proposed reactors ability to extend the existing sheath fields by up to 7 mm. A 7 mbar growth atmosphere combined with a 25 W plasma permitted the concurrent growth and alignment of carbon nanotubes with electric fields of the order of 0.04 V μm−1 with linear packing densities of up to ~5 × 104 cm−1. These results open up the potential for multi-directional in situ alignment of carbon nanotubes providing one viable route to the fabrication of many novel optoelectronic devices.

  8. ZnO nanotube waveguide arrays on graphene films for local optical excitation on biological cells

    Science.gov (United States)

    Baek, Hyeonjun; Kwak, Hankyul; Song, Minho S.; Ha, Go Eun; Park, Jongwoo; Tchoe, Youngbin; Hyun, Jerome K.; Park, Hye Yoon; Cheong, Eunji; Yi, Gyu-Chul

    2017-04-01

    We report on scalable and position-controlled optical nanoprobe arrays using ZnO nanotube waveguides on graphene films for use in local optical excitation. For the waveguide fabrication, position-controlled and well-ordered ZnO nanotube arrays were grown on chemical vapor deposited graphene films with a submicron patterned mask layer and Au prepared between the interspace of nanotubes. Mammalian cells were cultured on the nanotube waveguide arrays and were locally excited by light illuminated through the nanotubes. Fluorescence and optogenetic signals could be excited through the optical nanoprobes. This method offers the ability to investigate cellular behavior with a high spatial resolution that surpasses the current limitation.

  9. Growth, Structural and Optical Characterization of ZnO Nanotubes on Disposable-Flexible Paper Substrates by Low-Temperature Chemical Method

    Directory of Open Access Journals (Sweden)

    M. Y. Soomro

    2012-01-01

    Full Text Available We report the synthesis of vertically aligned ZnO nanotubes (NTs on paper substrates by low-temperature hydrothermal method. The growth of ZnO NTs on the paper substrate is discussed; further, the structural and optical properties are investigated by scanning electron microscope (SEM, transmission electron microscopy (TEM, X-ray diffraction (XRD, energy-dispersive X-ray spectroscopy (EDS, and cathodoluminescence (CL, and it was found that the ZnO NTs on paper substrate fulfill the structural and optical properties of ZnO NTs grown on other conventional substrates. This will be more beneficial in future usage of ZnO NTs in different fields and applications. Particularly, this approach opens the ways in research and development for high volume manufacturing of low-cost, flexible optoelectronics devices on disposable paper substrates and can be used in the future miniaturization trends.

  10. Anisotropic piezoresistivity characteristics of aligned carbon nanotube-polymer nanocomposites

    Science.gov (United States)

    Sengezer, Engin C.; Seidel, Gary D.; Bodnar, Robert J.

    2017-09-01

    Dielectrophoresis under the application of AC electric fields is one of the primary fabrication techniques for obtaining aligned carbon nanotube (CNT)-polymer nanocomposites, and is used here to generate long range alignment of CNTs at the structural level. The degree of alignment of CNTs within this long range architecture is observed via polarized Raman spectroscopy so that its influence on the electrical conductivity and piezoresistive response in both the alignment and transverse to alignment directions can be assessed. Nanocomposite samples consisting of randomly oriented, well dispersed single-wall carbon nanotubes (SWCNTs) and of long range electric field aligned SWCNTs in a photopolymerizable monomer blend (urethane dimethacrylate and 1,6-hexanediol dimethacrylate) are quantitatively and qualitatively evaluated. Piezoresistive sensitivities in form of gauge factors were measured for randomly oriented, well dispersed specimens with 0.03, 0.1 and 0.5 wt% SWCNTs and compared with gauge factors in both the axial and transverse to SWCNT alignment directions for electric field aligned 0.03 wt% specimens under both quasi-static monotonic and cyclic tensile loading. Gauge factors in the axial direction were observed to be on the order of 2, while gauge factors in the transverse direction demonstrated a 5 fold increase with values on the order of 10 for aligned specimens. Based on Raman analysis, it is believed the higher sensitivity of the transverse direction is related to architectural evolution of misaligned bridging structures which connect alignment structures under load due to Poisson’s contraction.

  11. Supercritical fluid attachment of palladium nanoparticles on aligned carbon nanotubes.

    Science.gov (United States)

    Ye, Xiang-Rong; Lin, Yuehe; Wai, Chien M; Talbot, Jan B; Jin, Sungho

    2005-06-01

    Nanocomposite materials consisting of Pd nanoparticles deposited on aligned multi-walled carbon nanotubes have been fabricated through hydrogen reduction of palladium-beta-diketone precursor in supercritical carbon dioxide. The supercritical fluid processing allowed deposition of high-density Pd nanoparticles (approximately 5-10 nm) on both as-grown (unfunctionalized) and functionalized (using HNO3 oxidation) nanotubes. However, the wet processing for functionalization results in pre-agglomerated, bundle-shaped nanotubes, thus significantly reducing the effective surface area for Pd particle deposition, although the bundling provides more secure, lock-in-place positioning of nanotubes and Pd catalyst particles. The nanotube bundling is substantially mitigated by Pd nanoparticle deposition on the unfunctionalized and geometrically separated nanotubes, which provides much higher catalyst surface area. Such nanocomposite materials utilizing geometrically secured and aligned nanotubes can be useful for providing much enhanced catalytic activities to chemical and electrochemical reactions (e.g., fuel cell reactions), and eliminate the need for tedious catalyst recovery process after the reaction is completed.

  12. Waferscale assembly of Field-Aligned nanotube Networks (FANs)

    DEFF Research Database (Denmark)

    Dimaki, Maria; Bøggild, Peter

    2006-01-01

    We demonstrate the integration of nanotube networks on 512 individual devices on a full 4-inch wafer in less than 60 seconds with a roughly 80% yield using dielectrophoresis. We present here investigations of the morphology and electrical resistance of such field aligned networks for different...... frequencies of the electrical field used to attract the nanotubes to the electrodes. Preliminary data of response to visible light irradiation as well as changes in the humidity indicate that the field aligned networks could be used as sensor components that may well integrate with CMOS due to mild assembly...

  13. Aligned, isotropic and patterned carbon nanotube substrates that control the growth and alignment of Chinese hamster ovary cells

    Energy Technology Data Exchange (ETDEWEB)

    Abdullah, Che Azurahanim Che; Asanithi, Piyapong; Brunner, Eric W; Jurewicz, Izabela; Bo, Chiara; Sear, Richard P; Dalton, Alan B [Department of Physics and Surrey Materials Institute, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom); Azad, Chihye Lewis; Ovalle-Robles, Raquel; Fang Shaoli; Lima, Marcio D; Lepro, Xavier; Collins, Steve; Baughman, Ray H, E-mail: r.sear@surrey.ac.uk [Alan G MacDiarmid NanoTech Institute, The University of Texas at Dallas, Richardson, TX 75080-3021 (United States)

    2011-05-20

    Here we culture Chinese hamster ovary cells on isotropic, aligned and patterned substrates based on multiwall carbon nanotubes. The nanotubes provide the substrate with nanoscale topography. The cells adhere to and grow on all substrates, and on the aligned substrate, the cells align strongly with the axis of the bundles of the multiwall nanotubes. This control over cell alignment is required for tissue engineering; almost all tissues consist of oriented cells. The aligned substrates are made using straightforward physical chemistry techniques from forests of multiwall nanotubes; no lithography is required to make inexpensive large-scale substrates with highly aligned nanoscale grooves. Interestingly, although the cells strongly align with the nanoscale grooves, only a few also elongate along this axis: alignment of the cells does not require a pronounced change in morphology of the cell. We also pattern the nanotube bundles over length scales comparable to the cell size and show that the cells follow this pattern.

  14. Aligned, isotropic and patterned carbon nanotube substrates that control the growth and alignment of Chinese hamster ovary cells

    Science.gov (United States)

    Azurahanim Che Abdullah, Che; Asanithi, Piyapong; Brunner, Eric W.; Jurewicz, Izabela; Bo, Chiara; Azad, Chihye Lewis; Ovalle-Robles, Raquel; Fang, Shaoli; Lima, Marcio D.; Lepro, Xavier; Collins, Steve; Baughman, Ray H.; Sear, Richard P.; Dalton, Alan B.

    2011-05-01

    Here we culture Chinese hamster ovary cells on isotropic, aligned and patterned substrates based on multiwall carbon nanotubes. The nanotubes provide the substrate with nanoscale topography. The cells adhere to and grow on all substrates, and on the aligned substrate, the cells align strongly with the axis of the bundles of the multiwall nanotubes. This control over cell alignment is required for tissue engineering; almost all tissues consist of oriented cells. The aligned substrates are made using straightforward physical chemistry techniques from forests of multiwall nanotubes; no lithography is required to make inexpensive large-scale substrates with highly aligned nanoscale grooves. Interestingly, although the cells strongly align with the nanoscale grooves, only a few also elongate along this axis: alignment of the cells does not require a pronounced change in morphology of the cell. We also pattern the nanotube bundles over length scales comparable to the cell size and show that the cells follow this pattern.

  15. Vertically aligned ZnO nanorods on porous silicon substrates:Effect of growth time

    Institute of Scientific and Technical Information of China (English)

    R. Shabannian

    2015-01-01

    Vertically aligned ZnO nanorods were successfully grown on porous silicon (PS) substrates by chemical bath deposition at a low temperature. X-ray diffraction, field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and photoluminescence (PL) analyses were carried out to investigate the effect of growth duration (2 h to 8 h) on the optical and structural properties of the aligned ZnO nanorods. Strong and sharp ZnO (0 0 2) peaks of the ZnO nanorods proved that the aligned ZnO nanorods were preferentially fabricated along the c-axis of the hexagonal wurtzite structure. FESEM images demonstrated that the ZnO nanorod arrays were well aligned along the c-axis and perpendicular to the PS substrates regardless of the growth duration. The TEM image showed that the top surfaces of the ZnO nanorods were round with a smooth curvature. PL spectra demonstrated that the ZnO nanorods grown for 5 h exhibited the sharpest and most intense PL peaks within the ultraviolet range among all samples.

  16. Preparation of aligned nanotube membranes for water and gas separation applications

    Science.gov (United States)

    Lulevich, Valentin; Bakajin, Olgica; Klare, Jennifer E.; Noy, Aleksandr

    2016-01-05

    Fabrication methods for selective membranes that include aligned nanotubes can advantageously include a mechanical polishing step. The nanotubes have their ends closed off during the step of infiltrating a polymer precursor around the nanotubes. This prevents polymer precursor from flowing into the nanotubes. The polishing step is performed after the polymer matrix is formed, and can open up the ends of the nanotubes.

  17. Transient reflectivity on vertically aligned single-wall carbon nanotubes

    NARCIS (Netherlands)

    Galimberti, Gianluca; Ponzoni, Stefano; Ferrini, Gabriele; Hofmann, Stephan; Arshad, Muhammad; Cepek, Cinzia; Pagliara, Stefania

    2013-01-01

    One-color transient reflectivity measurements are carried out on two different samples of vertically aligned single-wall carbon nanotube bundles and compared with the response recently published on unaligned bundles. The negative sign of the optical response for both samples indicates that the free

  18. Wafer-scale high-throughput ordered growth of vertically aligned ZnO nanowire arrays.

    Science.gov (United States)

    Wei, Yaguang; Wu, Wenzhuo; Guo, Rui; Yuan, Dajun; Das, Suman; Wang, Zhong Lin

    2010-09-01

    This article presents an effective approach for patterned growth of vertically aligned ZnO nanowire (NW) arrays with high throughput and low cost at wafer scale without using cleanroom technology. Periodic hole patterns are generated using laser interference lithography on substrates coated with the photoresist SU-8. ZnO NWs are selectively grown through the holes via a low-temperature hydrothermal method without using a catalyst and with a superior control over orientation, location/density, and as-synthesized morphology. The development of textured ZnO seed layers for replacing single crystalline GaN and ZnO substrates extends the large-scale fabrication of vertically aligned ZnO NW arrays on substrates of other materials, such as polymers, Si, and glass. This combined approach demonstrates a novel method of manufacturing large-scale patterned one-dimensional nanostructures on various substrates for applications in energy harvesting, sensing, optoelectronics, and electronic devices.

  19. Controlled growth of well-aligned ZnO nanowire arrays using the improved hydrothermal method

    Institute of Scientific and Technical Information of China (English)

    Han Zhitao; Li Sisi; Chu Jinkui; Chen Yong

    2013-01-01

    Well-aligned ZnO nanowires were hydrothermally synthesized based on a facile method for preparing the ZnO seed layer which was derived from the combination of a sol-gel process and the spin-coating technique.The effect of the contents of growth solution and the growth duration on the morphology ofZnO nanowires has been investigated.The results indicated that long and vertically aligned ZnO nanowires could be obtained by adjusting the contents of ammonia and polyethyleneimine (PEI) in the growth solution.Under the optimized condition,the length of ZnO nanowires increased fast and almost linearly with the growth duration.After 10 h incubation,ZnO nanowires more than 25μm in length were obtained.By combining the conventional photolithographic method with this hydrothermal approach,long and well-aligned ZnO nanowire arrays were selectively grown on the substrate.In addition,the bottom fusion at the foot of the nanowires has been obviously improved.The results demonstrated that the improved hydrothermal process is favorable to synthesize long and well-aligned ZnO nanowires,and possesses good process compatibility with the conventional photolithographic technique for preparing ZnO nanowire arrays.So it has great potential in applications such as display and field emission devices.

  20. Broadband laser polarization control with aligned carbon nanotubes

    CERN Document Server

    Yang, He; Lia, Diao; Chen, Ya; Mattila, Marco; Tian, Ying; Yong, Zhenzhong; Yang, Changxi; Tittonen, Ilkka; Ren, Zhaoyu; Bai, Jingtao; Li, Qingwen; Kauppinen, Esko I; Lipsanen, Harri; Sun, Zhipei

    2015-01-01

    We introduce a simple approach to fabricate aligned carbon nanotube (ACNT) device for broadband polarization control in fiber laser systems. The ACNT device was fabricated by pulling from as-fabricated vertically-aligned carbon nanotube arrays. Their anisotropic property is confirmed with optical and scanning electron microscopy, and with polarized Raman and absorption spectroscopy. The device was then integrated into fiber laser systems (at two technologically important wavelengths of 1 and 1.5 um) for polarization control. We obtained a linearly-polarized light output with the maximum extinction ratio of ~12 dB. The output polarization direction could be fully controlled by the ACNT alignment direction in both lasers. To the best of our knowledge, this is the first time that ACNT device is applied to polarization control in laser systems. Our results exhibit that the ACNT device is a simple, low-cost, and broadband polarizer to control laser polarization dynamics, for various photonic applications (such as ...

  1. Self-catalyst synthesis of aligned ZnO nanorods by pulsed laser deposition

    Institute of Scientific and Technical Information of China (English)

    LEN; Song-En; Andy

    2009-01-01

    High-density well-aligned ZnO nanorods were successfully synthesized on ZnO-buffer-layer coated indium phosphide (InP) (100) substrates by a pulsed laser deposition (PLD) method. Scanning electron microscopy images show that the ZnO buffer layer formed uniform drip-like structure and ZnO nano- rods were well-oriented perpendicular to the substrate surface. The sharp diffraction peak observed at 34.46° in X-ray diffraction scanning pattern suggests that the ZnO nanorods exhibit a (002)-preferred orientation. The PL spectra of ZnO samples shows a strong near band edge emission centered at about 380 nm and a weak deep level emission centered at around 495 nm, and it demonstrates that the ZnO nanorods produced in this work have high optical quality, which sheds light on further applications for nanodevices.

  2. Low-temperature solution growth of ZnO nanotube arrays

    Directory of Open Access Journals (Sweden)

    Ki-Woong Chae

    2010-12-01

    Full Text Available Single crystal ZnO nanotube arrays were synthesized at low temperature in an aqueous solution containing zinc nitrate and hexamethylenetetramine. It was found that the pH value of the reaction solution played an important role in mediating the growth of ZnO nanostructures. A change in the growth temperature might change the pH value of the solution and bring about the structure conversion of ZnO from nanorods to nanotubes. It was proposed that the ZnO nanorods were initially formed while the reaction solution was at a relatively high temperature (~90 °C and therefore enriched with colloidal Zn(OH2, which allowed a fast growth of ZnO nanocrystals along the [001] orientation to form nanorods. A decrease in the reaction temperature yielded a supersaturated solution, resulting in an increase in the concentration of OH− ions as well as the pH value of the solution. Colloidal Zn(OH2 in the supersaturated solution trended to precipitate. However, because of a slow diffusion process in view of the low temperature and low concentration of the colloidal Zn(OH2, the growth of the (001 plane of ZnO nanorods was limited and only occurred at the edge of the nanorods, eventually leading to the formation of a nanotube shape. In addition, it was demonstrated that the pH might impact the surface energy difference between the polar and non-polar faces of the ZnO crystal. Such a surface energy difference became small at high pH and hereby the prioritized growth of ZnO crystal along the [001] orientation was suppressed, facilitating the formation of nanotubes. This paper demonstrates a new strategy for the fabrication of ZnO nanotubes on a large scale and presents a more comprehensive understanding of the growth of tube-shaped ZnO in aqueous solution at low temperature.

  3. Mechanism of Carbon Nanotubes Aligning along Applied Electric Field

    Institute of Scientific and Technical Information of China (English)

    MA Shao-Jie; GUO Wan-Lin

    2008-01-01

    The mechanism of single-walled carbon nanotubes (SWCNTS)aligning in the direction of external electric field is studied by quantum mechanics calculations.The rotational torque on the carbon nanotubes is proportional to the difference between the longitudinal and transverse polarizabilities and varies with the angle of SWCNTs to the external electric field.The longitudinal polarizability increases with second power of length,while the transverse polarizability increases linearly with length.A zigzag SWCNT has larger longitudinal and transverse polarizabilities than an armchair SWCNT with the same diameter and the discrepancy becomes larger for longer tubes.

  4. Growth of aligned ZnO nanowires via modified atmospheric pressure chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yuping; Li, Chengchen [Faculty of Science, Jiangsu University, Zhenjiang, Jiangsu, 212013 (China); Chen, Mingming, E-mail: andychain@live.cn [Faculty of Science, Jiangsu University, Zhenjiang, Jiangsu, 212013 (China); Yu, Xiao; Chang, Yunwei [Faculty of Science, Jiangsu University, Zhenjiang, Jiangsu, 212013 (China); Chen, Anqi [State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics & Information Technology, Sun Yat-Sen University, Guangzhou Higher Education Mega Center (University Town), Guangzhou, 510006 (China); Zhu, Hai, E-mail: zhuhai5@mail.sysu.edu.cn [State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics & Information Technology, Sun Yat-Sen University, Guangzhou Higher Education Mega Center (University Town), Guangzhou, 510006 (China); Tang, Zikang, E-mail: zktang@umac.mo [State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics & Information Technology, Sun Yat-Sen University, Guangzhou Higher Education Mega Center (University Town), Guangzhou, 510006 (China); The Institute of Applied Physics and Materials Engineering, University of Macau, Avenida da Universidade, Taipa, Macau (China)

    2016-12-09

    In this work, we report the growth of high-quality aligned ZnO nanowires via a facile atmospheric pressure chemical vapor deposition (CVD) method. The CVD reactor chamber used was more complicated than a conventional one due to the quartz boats loaded with sources (ZnO/C) and substrates being inserted into a semi-open quartz tube, and then placed inside the CVD reactor. The semi-open quartz tube played a very important role in growing the ZnO nanowires, and demonstrated that the transportation properties of Zn and O vapor differ from those in the conventional CVD reactor chamber. Aligned ZnO nanowires were successfully obtained, though they were only found at substrates located upstream. The very high crystalline quality of the obtained ZnO nanowires was demonstrated by high-resolution transmission electron microscopy and room temperature photoluminescence investigations. Such ZnO nanowires with high crystalline quality may provide opportunities for the fabrication of ZnO-based nano-devices in future. - Highlights: • High-quality aligned ZnO nanowires were obtained via modified chemical vapor deposition under atmospheric pressure. • The semi-open quartz tube plays very important roles in growing ZnO nanowires. • The transportation properties of Zn and O vapor differ from those in the conventional CVD reactor chamber.

  5. Increased Alignment in Carbon Nanotube Growth

    Science.gov (United States)

    Delzeit, Lance D. (Inventor)

    2007-01-01

    Method and system for fabricating an array of two or more carbon nanotube (CNT) structures on a coated substrate surface, the structures having substantially the same orientation with respect to a substrate surface. A single electrode, having an associated voltage source with a selected voltage, is connected to a substrate surface after the substrate is coated and before growth of the CNT structures, for a selected voltage application time interval. The CNT structures are then grown on a coated substrate surface with the desired orientation. Optionally, the electrode can be disconnected before the CNT structures are grown.

  6. Photoanode Activity of ZnO Nanotube Based Dye-Sensitized Solar Cells

    Institute of Scientific and Technical Information of China (English)

    R. Ranjusha; P. Lekha; K.R.V. Subramanian; V. Nair Shantikumar; A. Balakrishnant

    2011-01-01

    Vertical ZnO nanotube (ZNT) arrays were synthesized onto an indium doped tin oxide (ITO) glass substrate by a simple electrochemical deposition technique followed by a selective etching process. Scanning electron microscopy (SEM) showed formation of well-faceted hexagonal ZNT arrays spreading uniformly over a large area. X-ray diffraction (XRD) of ZNT layer showed substantially higher intensity for the (0002) diffraction peak, indicating that the ZnO crystallites were well aligned with their c-axis. Profilometer measurements of the ZNT layer showed an average thickness of -7 μm. Diameter size distribution (DSD) analysis showed that ZNTs exhibited a narrow diameter size distribution in the range of 65-120 nm and centered at -75 nm. The photoluminescence (PL) spectrum measurement showed violet and blue luminescence peaks that were centered at 410 and 480 nm, respectively, indicating the presence of internal defects. Ultra-violet (UV) spectroscopy showed major absorbance peak at ,-348 nm, exhibiting an increase in energy gap value of 3.4 eV. By employing the formed ZNTs as the photo-anode for a dye-sensitized solar cell (DSSC), a full-sun conversion efficiency of 1.01% was achieved with a fill factor of 54%. Quantum efficiency studies showed the maximum of incident photon-to-electron conversion efficiency in a visible region located at 590-550 nm range.

  7. Terahertz Science and Technology of Macroscopically Aligned Carbon Nanotube Films

    Science.gov (United States)

    Kono, Junichiro

    One of the outstanding challenges in nanotechnology is how to assemble individual nano-objects into macroscopic architectures while preserving their extraordinary properties. For example, the one-dimensional character of electrons in individual carbon nanotubes leads to extremely anisotropic transport, optical, and magnetic phenomena, but their macroscopic manifestations have been limited. Here, we describe methods for preparing macroscopic films, sheets, and fibers of highly aligned carbon nanotubes and their applications to basic and applied terahertz studies. Sufficiently thick films act as ideal terahertz polarizers, and appropriately doped films operate as polarization-sensitive, flexible, powerless, and ultra-broadband detectors. Together with recently developed chirality enrichment methods, these developments will ultimately allow us to study dynamic conductivities of interacting one-dimensional electrons in macroscopic single crystals of single-chirality single-wall carbon nanotubes.

  8. Vertically aligned carbon nanotube field-effect transistors

    KAUST Repository

    Li, Jingqi

    2012-10-01

    Vertically aligned carbon nanotube field-effect transistors (CNTFETs) have been developed using pure semiconducting carbon nanotubes. The source and drain were vertically stacked, separated by a dielectric, and the carbon nanotubes were placed on the sidewall of the stack to bridge the source and drain. Both the effective gate dielectric and gate electrode were normal to the substrate surface. The channel length is determined by the dielectric thickness between source and drain electrodes, making it easier to fabricate sub-micrometer transistors without using time-consuming electron beam lithography. The transistor area is much smaller than the planar CNTFET due to the vertical arrangement of source and drain and the reduced channel area. © 2012 Elsevier Ltd. All rights reserved.

  9. Advanced Multifunctional Properties of Aligned Carbon Nanotube-Epoxy Composites from Carbon Nanotube Aerogel Method

    Science.gov (United States)

    Tran, Thang; Liu, Peng; Fan, Zeng; Ngern, Nigel; Duong, Hai

    2015-03-01

    Unlike previous methods of making carbon nanotube (CNT) thin films, aligned CNT thin films in this work are synthesized directly from CNT aerogels in a CVD process. CH4/H2/He gases and ferrocene/thiophene catalysts are mixed and reacted in the reactor at 1200 °C to form CNT aerogel socks. By pulling out the socks with a metal rod, CNT thin films with 15-nm diameter MWNTs are aligned and produced continuously at a speed of a few meters per minute. The number of the aligned CNT thin film layers/ thickness can also be controlled well. The as-synthesized aligned CNT films are further condensed by acetone spray and post-treated by UV light. The aligned CNT films without any above post-treatment have a high electrical conductivity of 400S/cm. We also develop aligned CNT-epoxy composites by infiltrating epoxy into the above aligned CNT thin films using Vacuum Assisted Resin Transfer Molding (VARTM) method. Our cost-effective fabrication method of the aligned CNT films is more advanced for developing the composites having CNT orientation control. The mechanical, electrical and optical properties of the aligned CNT epoxy composites are measured. About 2% of the aligned CNTs can enhance significantly the electrical conductivity and hardness of aligned CNT-epoxy composite films. Effects of morphologies, volume fraction, and alignment of the CNTs on the advanced multifunctional properties of the aligned CNT-epoxy composites are also quantified.

  10. Fabrication of Well-Aligned ZnO Nanorods Using a Composite Seed Layer of ZnO Nanoparticles and Chitosan Polymer

    Directory of Open Access Journals (Sweden)

    Anees A. Ansari

    2013-09-01

    Full Text Available In this study, by taking the advantage of both inorganic ZnO nanoparticles and the organic material chitosan as a composite seed layer, we have fabricated well-aligned ZnO nanorods on a gold-coated glass substrate using the hydrothermal growth method. The ZnO nanoparticles were characterized by the Raman spectroscopic techniques, which showed the nanocrystalline phase of the ZnO nanoparticles. Different composites of ZnO nanoparticles and chitosan were prepared and used as a seed layer for the fabrication of well-aligned ZnO nanorods. Field emission scanning electron microscopy, energy dispersive X-ray, high-resolution transmission electron microscopy, X-ray diffraction, and infrared reflection absorption spectroscopic techniques were utilized for the structural characterization of the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods on a gold-coated glass substrate. This study has shown that the ZnO nanorods are well-aligned, uniform, and dense, exhibit the wurtzite hexagonal structure, and are perpendicularly oriented to the substrate. Moreover, the ZnO nanorods are only composed of Zn and O atoms. An optical study was also carried out for the ZnO nanoparticles/chitosan seed layer-coated ZnO nanorods, and the obtained results have shown that the fabricated ZnO nanorods exhibit good crystal quality. This study has provided a cheap fabrication method for the controlled morphology and good alignment of ZnO nanorods, which is of high demand for enhancing the working performance of optoelectronic devices.

  11. Enhanced visible emission from vertically aligned ZnO nanostructures by aqueous chemical growth process

    Energy Technology Data Exchange (ETDEWEB)

    Amiruddin, R., E-mail: amirphy9@yahoo.com; Kumar, M.C. Santhosh, E-mail: santhoshmc@nitt.edu

    2014-11-15

    ZnO nanostructures consisting of nanowires and nanorods have been grown by aqueous chemical growth (ACG) process on the ZnO seed layers. ACG process has been carried out for 5 h and 15 h to obtain the one dimensional nanostructures. This ZnO nanostructure comprises mixture of vertically aligned nanorods and nanowires. Structural analysis reveals that the crystal orientation is along (002) plane exhibiting a hexagonal wurtzite structure. The crystallinity of ZnO nanostructures increases after aqueous chemical treatment with respect to the growth duration. Optical studies revealed that when the duration of aqueous chemical treatment is increased, the transmittance of the films decreases considerably. The as-deposited ZnO seed layers exhibit electron carrier concentration of 4.69×10{sup 14} cm{sup −3} and the value increases to 9.44×10{sup 15} cm{sup −3} after 5 h and 1.53×10{sup 16} cm{sup −3} after 15 h of aqueous chemical treatment. It has been observed that ZnO nanostructures exhibit enhanced luminescence properties in visible region which covers the entire visible region of the spectrum. - Highlights: • Mixture of nanorods and nanowires are grown upon same glass substrates. • The grown nanostructures are found to be vertically aligned. • Improved electron carrier concentration is observed. • Luminescence properties of these ZnO nanostructures are highly enhanced.

  12. Single-walled carbon nanotubes coated with ZnO by atomic layer deposition

    Science.gov (United States)

    Pal, Partha P.; Gilshteyn, Evgenia; Jiang, Hua; Timmermans, Marina; Kaskela, Antti; Tolochko, Oleg V.; Kurochkin, Alexey V.; Karppinen, Maarit; Nisula, Mikko; Kauppinen, Esko I.; Nasibulin, Albert G.

    2016-12-01

    The possibility of ZnO deposition on the surface of single-walled carbon nanotubes (SWCNTs) with the help of an atomic layer deposition (ALD) technique was successfully demonstrated. The utilization of pristine SWCNTs as a support resulted in a non-uniform deposition of ZnO in the form of nanoparticles. To achieve uniform ZnO coating, the SWCNTs first needed to be functionalized by treating the samples in a controlled ozone atmosphere. The uniformly ZnO coated SWCNTs were used to fabricate UV sensing devices. An UV irradiation of the ZnO coated samples turned them from hydrophobic to hydrophilic behaviour. Furthermore, thin films of the ZnO coated SWCNTs allowed us switch p-type field effect transistors made of pristine SWCNTs to have ambipolar characteristics.

  13. ZnO nanotube array: Gas sensing properties at room temperature

    Science.gov (United States)

    Dadhich, B.; Ganapathi, S. Kailasa; Priyam, A.; Kaur, Manmeet; Debnath, A. K.; Muthe, K. P.; Gadkari, S. C.

    2017-05-01

    In the present study, ZnO nanotube arrays were synthesized from hydrothermally grown ZnO nanowires by selective chemical etching, using KCl as dissolving solution. Synthesized ZnO nanotube arrays were characterized using X-ray diffraction, scanning electron microscopy, UV-visible and Raman spectroscopy. Room temperature gas sensing properties of these arrays were investigated towards various toxic gases and the results were compared to that of ZnO nanowire arrays. Samples of ZnO nano tube arrays showed better sensor response to both H2S (4.2 for 5 ppm) and NO2 (13 for 1.5 ppm) as compared to samples of ZnO nanowires array which exhibited a sensor response of 3.7 towards 5 ppm H2S and 1 towards 1.5 ppm NO2. The enhancement of sensor response in nanotube arrays can be attributed to the hollow morphology of the ZnO NT which offers higher surface area. Oxygen adsorption in this case takes place on both inner and outer surfaces of the tube resulting in larger change in resistance.

  14. Alignment and Load Transfer in Carbon Nanotube and Dicyclopentadiene Composites

    Science.gov (United States)

    Severino, Joseph Vincent

    Individual carbon nanotubes (CNTs) are the strongest materials available but their macroscopic assemblies are weak. This work establishes a new thermosetting dicyclopentadiene (DCPD) and CNT composite that increases the strength of CNT assemblies. These high volume fraction and void free structures constitute advanced materials that could one day replace traditional composite systems. To further the understanding of physical interactions between polymer and CNTs, a novel "capstan" load transfer mechanism is also introduced. Self-supporting assemblies of interconnected carbon nanotubes were stretched, twisted and compressed to fashion composites by the infusion and polymerization of low viscosity DCPD based monomeric resins. The properties of the CNTs, polymer and composite were characterized with thermal gravimetric analysis (TGA), dynamic mechanical analysis (DMA) and Raman spectroscopy. The microstructure was analyzed by wide angle X-ray scattering (WAXS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Sheets were drawn at 15 m/min from a growth furnace to impart alignment then stretched to further modify alignment. The mechanical properties were determined in five orientations with respect to the growth direction. The strength was nearly three times higher along this growth direction than it was perpendicular, and modulus was nearly six times higher. Transverse stretching achieved 1.5 times the elongation but alignment was inferior due to CNT kinking that prevented alignment and consolidation. Composites yarns and sheets were investigated for the mechanical properties, microstructure and load transfer. The DCPD resin was found to wet the CNTs and lubricated deformation. This reduced loads during processing, and curing solidified the aligned and consolidated structure. The stretched and twisted composite yarns increased the failure stress 51%. In aligned composite sheet, the failure stress increased 200%. The increased stresses

  15. Carbon Micronymphaea: Graphene on Vertically Aligned Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Jong Won Choi

    2013-01-01

    Full Text Available This paper describes the morphology of carbon nanomaterials such as carbon nanotube (CNT, graphene, and their hybrid structure under various operating conditions during a one-step synthesis via plasma-enhanced chemical vapor deposition (PECVD. We focus on the synthetic aspects of carbon hybrid material composed of heteroepitaxially grown graphene on top of a vertical array of carbon nanotubes, called carbon micronymphaea. We characterize the structural features of this unique nanocomposite by uses of electron microscopy and micro-Raman spectroscopy. We observe carbon nanofibers, poorly aligned and well-aligned vertical arrays of CNT sequentially as the growth temperature increases, while we always discover the carbon hybrids, called carbon micronymphaea, at specific cooling rate of 15°C/s, which is optimal for the carbon precipitation from the Ni nanoparticles in this study. We expect one-pot synthesized graphene-on-nanotube hybrid structure poses great potential for applications that demand ultrahigh surface-to-volume ratios with intact graphitic nature and directional electronic and thermal transports.

  16. White Electroluminescence Using ZnO Nanotubes/GaN Heterostructure Light-Emitting Diode

    Directory of Open Access Journals (Sweden)

    Sadaf JR

    2010-01-01

    Full Text Available Abstract We report the fabrication of heterostructure white light–emitting diode (LED comprised of n-ZnO nanotubes (NTs aqueous chemically synthesized on p-GaN substrate. Room temperature electroluminescence (EL of the LED demonstrates strong broadband white emission spectrum consisting of predominating peak centred at 560 nm and relatively weak violet–blue emission peak at 450 nm under forward bias. The broadband EL emission covering the whole visible spectrum has been attributed to the large surface area and high surface states of ZnO NTs produced during the etching process. In addition, comparison of the EL emission colour quality shows that ZnO nanotubes have much better quality than that of the ZnO nanorods. The colour-rendering index of the white light obtained from the nanotubes was 87, while the nanorods-based LED emit yellowish colour.

  17. Controlled growth of well-aligned ZnO nanorod arrays by hydrothermal method

    Science.gov (United States)

    Mihailova, I.; Gerbreders, V.; Bulanovs, A.; Tamanis, E.; Sledevskis, E.; Ogurcovs, A.; Sarajevs, P.

    2014-10-01

    The application prospect of zinc oxide (ZnO) nanostructures largely relies on the ability to grow nanoobjects with necessary geometry. In this study well-aligned ZnO nanorod arrays with a high density and uniformity were successfully synthesized on the glass substrates by a hydrothermal method at low-temperature. The aqueous solutions of zinc nitrate hexahydrate and hexamethylenetetramine was used. The effect of seed layer (obtained by electrochemical method and by vacuum deposition method) on the alignment of ZnO nanorods has been investigated. The morphological properties of the ZnO nanorods were also examined in accordance with varying the magnetron sputtering angle for ZnO seeds deposition. It is also shown that the electric field can control the direction of the growth of ZnO nanorods. Morphological, structural and compositional characterizations of obtained films were carried out by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analysis methods.

  18. Copper-encapsulated vertically aligned carbon nanotube arrays.

    Science.gov (United States)

    Stano, Kelly L; Chapla, Rachel; Carroll, Murphy; Nowak, Joshua; McCord, Marian; Bradford, Philip D

    2013-11-13

    A new procedure is described for the fabrication of vertically aligned carbon nanotubes (VACNTs) that are decorated, and even completely encapsulated, by a dense network of copper nanoparticles. The process involves the conformal deposition of pyrolytic carbon (Py-C) to stabilize the aligned carbon-nanotube structure during processing. The stabilized arrays are mildly functionalized using oxygen plasma treatment to improve wettability, and they are then infiltrated with an aqueous, supersaturated Cu salt solution. Once dried, the salt forms a stabilizing crystal network throughout the array. After calcination and H2 reduction, Cu nanoparticles are left decorating the CNT surfaces. Studies were carried out to determine the optimal processing parameters to maximize Cu content in the composite. These included the duration of Py-C deposition and system process pressure as well as the implementation of subsequent and multiple Cu salt solution infiltrations. The optimized procedure yielded a nanoscale hybrid material where the anisotropic alignment from the VACNT array was preserved, and the mass of the stabilized arrays was increased by over 24-fold because of the addition of Cu. The procedure has been adapted for other Cu salts and can also be used for other metal salts altogether, including Ni, Co, Fe, and Ag. The resulting composite is ideally suited for application in thermal management devices because of its low density, mechanical integrity, and potentially high thermal conductivity. Additionally, further processing of the material via pressing and sintering can yield consolidated, dense bulk composites.

  19. Nanoscratch technique for aligning multiwalled carbon nanotubes synthesized by the arc discharge method in open air

    Indian Academy of Sciences (India)

    A Joseph Berkmans; M Jagannatham; Prathap Haridoss

    2015-08-01

    Horizontally aligned and densely packed multiwalled carbon nanotubes (MWCNTs) were synthesized in an open air, without the need for a controlled atmosphere, using a rotating cathode arc discharge method with the help of a metal scraper. The physical force exerted by the scraper results in in-situ alignment of MWCNTs along the direction of scrape marks. This strategy, which enables the alignment of nanotubes in a controlled fashion to any length and direction of interest, was examined to determine the force required to align a nanotube. A model is developed to understand the alignment process. Using the nanoscratch technique to mimic this strategy, and incorporating the data obtained from the nanoscratch technique into the model developed, the minimum force required to align a MWCNT, as well as the energy required to align a gram of nanotubes, has been estimated. The method demonstrated represents an economical approach for large-scale synthesis of aligned MWCNTs at low costs.

  20. First-Principles Study on Magnetic Properties of V-Doped ZnO Nanotubes

    Institute of Scientific and Technical Information of China (English)

    ZHANG Fu-Chun; ZHANG Zhi-Yong; ZHANG Wei-Hu; YAN Jun-Feng; YUN Jiang-Ni

    2009-01-01

    Electronic and magnetic properties of V-doped ZnO nanotubes in which one of Zn2+ ions is substituted by V2+ ions are studied by the first-principles calculations of plane wave ultra-soft pseudo-potential technology based on the spin-density function theory. The computational results reveal that spontaneous magnetization in V-doped (9,0) ZnO nanotubes can be induced without p-type or n-type doping treatment, and the ferromagnetism is isotropic and independent of the chirality and diameter of the nanotubes. It is found that V-doped ZnO nanotubes have large magnetic moments and are ferromagnetic half-metal materials. Moreover, the ferromagnetic coupling among V atoms is generated by O 2p electron spins and V 3d electron spins localized at the exchanging interactions between magnetic transitional metal (TM) impurities. The appearance of ferromagnetism in V-doped ZnO nanotubes gives some reference to fabrication of a transparent ferromagnet which may have a great impact on industrial applications in magneto-optical devices.

  1. Vertically Aligned Carbon Nanotube Electrodes for Lithium-Ion Batteries

    Science.gov (United States)

    2011-01-01

    37] Z. Yang, H. Wu, Mater. Chem. Phys. 71 (2001) 7. [38] D. Linden , T.B. Reddy, Handbook of Batteries , 3rd ed., McGraw-Hill Co., Inc., New York, 2005. ...Lithium-ion Energy storage Battery a b s t r a c t As portable electronics becomemore advanced and alternative energy demands becomemore prevalent, the...aligned carbon nanotube electrodes for lithium-ion batteries 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR( S ) 5d. PROJECT

  2. Towards ultrathick battery electrodes: aligned carbon nanotube-enabled architecture.

    Science.gov (United States)

    Evanoff, Kara; Khan, Javed; Balandin, Alexander A; Magasinski, Alexandre; Ready, W Jud; Fuller, Thomas F; Yushin, Gleb

    2012-01-24

    Vapor deposition techniques were utilized to synthesize very thick (∼1 mm) Li-ion battery anodes consisting of vertically aligned carbon nanotubes coated with silicon and carbon. The produced anode demonstrated ultrahigh thermal (>400 W·m(-1) ·K(-1)) and high electrical (>20 S·m(-1)) conductivities, high cycle stability, and high average capacity (>3000 mAh·g(Si) (-1)). The processes utilized allow for the conformal deposition of other materials, thus making it a promising architecture for the development of Li-ion anodes and cathodes with greatly enhanced electrical and thermal conductivities.

  3. Vertically Aligned ZnO Nanorods: Effect of Synthesis Parameters.

    Science.gov (United States)

    Rehman, Zeeshan Ur; Heo, Si-Nae; Cho, Hyeon Ji; Koo, Bon Heun

    2016-06-01

    This report is devoted to the synthesis of high quality nanorods using spin coating technique for seed layer growth. Effect of different parameter i.e., spins coating counts, spin coating speed, and the effect of temperature during the drying process was analyzed. Hot plate and furnace technique was used for heating purpose and the difference in the morphology was carefully observed. It is worthy to mention here that there is a substantial effect of all the above mentioned parameters on the growth and morphology of the ZnO nanostructure. The ZnO nanorods were finally synthesized using wet chemical method. The morphological properties of the obtained nanostructures were analyzed by using FESEM technique.

  4. Wafer-Scale High-Throughput Ordered Growth of Vertically Aligned ZnO Nanowire Arrays

    KAUST Repository

    Wei, Yaguang

    2010-09-08

    This article presents an effective approach for patterned growth of vertically aligned ZnO nanowire (NW) arrays with high throughput and low cost at wafer scale without using cleanroom technology. Periodic hole patterns are generated using laser interference lithography on substrates coated with the photoresist SU-8. ZnO NWs are selectively grown through the holes via a low-temperature hydrothermal method without using a catalyst and with a superior control over orientation, location/density, and as-synthesized morphology. The development of textured ZnO seed layers for replacing single crystalline GaN and ZnO substrates extends the large-scale fabrication of vertically aligned ZnO NW arrays on substrates of other materials, such as polymers, Si, and glass. This combined approach demonstrates a novel method of manufacturing large-scale patterned one-dimensional nanostructures on various substrates for applications in energy harvesting, sensing, optoelectronics, and electronic devices. © 2010 American Chemical Society.

  5. Preparation and gas-sensing property of parallel-aligned ZnO nanofibrous films

    Indian Academy of Sciences (India)

    Zikui Bai; Weilin Xu; Changsheng Xie; Mingchao Dong; Shunping Zhang; Jie Xu; Shili Xiao

    2013-08-01

    Parallel-aligned zinc oxide (ZnO) nanofibrous films fabricated by using electrospinning technique were used in gas sensors for the detection of ethanol and formaldehyde. The morphologies and crystal structures of the films were characterized by field-emission scanning electron microscopy (FE–SEM) and X-ray diffraction (XRD), respectively. FE–SEM results showed that ZnO nanofibres had an approximate diameter of 100–300 nm and consisted of hexagonal wurtzite structure ZnO nanocrystals with a primary particle diameter of 20–50 nm. The results of resistance–temperature characteristics and responses to ethanol and formaldehyde indicated that the parallelaligned ZnO nanofibrous film had a low activation energy (0.246 eV), a low optimum operating temperature and a high response. The response and recovery had a high rate in the initial stage and a low rate in the later stage. The parallel-aligned ZnO nanofibrous film had excellent potential application for formaldehyde sensor.

  6. Electrochemical Synthesis of ZnO Nanorods/Nanotubes/Nanopencils on Transparent Aluminium-Doped Zinc Oxide Thin Films for Photocatalytic Applications.

    Science.gov (United States)

    Le, Thi Ngoc Tu; Pham, Tan Thi; Ngo, Quang Minh; Vu, Thi Hanh Thu

    2015-09-01

    We report an electrochemical synthesis of homogeneous and well-aligned ZnO nanorods (NRs) on transparent conducting aluminium-doped zinc oxide (AZO) thin films as electrodes. The selected ZnO NRs was then chemically corroded in HCl and KCl aqueous solutions to form nanopencils (NPs), and nanotubes (NTs), respectively. A DC magnetron sputtering was employed to fabricate AZO thin films at various thicknesses. The obtained AZO thin films have a c-direction orientation, transmittance above 80% in visible region, and sheet resistance approximately 40 Ω/sq. They are considered to be relevant as electrodes and seeding layers for electrochemical. The ZnO NRs are directly grown on the AZOs without a need of catalysts or additional seeding layers at temperature as low as 85 degrees C. Their shapes are strongly associated with the AZO thickness that provides a valuable way to control the diameter of ZnO NRs grown atop. With the addition of HCI and KCl aqueous solutions, ZnO NRs were modified their shape to NPs and NTs with the reaction time, respectively. All the ZnO NRs, NPs, and NTs are preferred to grow along c-direction that indicates a lattice matching between AZO thin films and ZnO nanostructrures. Photoluminescence spectra and XRD patterns show that they have good crystallinities. A great photocatalytic activity of ZnO nanostructures promises potential application in environmental treatment and protection. The ZnO NTs exhibits a higher photocatalysis than others possibly due to the oxygen vacancies on the surface and the polarizability of Zn2+ and O2-.

  7. Preparation and characterization of CeO_2 doped ZnO nano-tubes fluorescent composite

    Institute of Scientific and Technical Information of China (English)

    李酽; 刘秀琳; 栗建钢

    2010-01-01

    ZnO nanotubes were hydrothermally synthesized and the ZNTs/CeO2 fluorescent composite were prepared by introducing nano CeO2 particles into ZnO nano-tubes via a chemical solution adsorption and annealing process. The samples were characterized by X-ray diffraction, scanning electron microscopy, Fourier transformation infrared spectroscopy and room temperature photoluminescence measurement. Due to the interaction between Ce4+ and the surface atoms of ZnO2 nano-tubes, a photoluminescence enhancement was obser...

  8. Alignment of muscle precursor cells on the vertical edges of thick carbon nanotube films.

    Science.gov (United States)

    Holt, Ian; Gestmann, Ingo; Wright, Andrew C

    2013-10-01

    The development of scaffolds and templates is an essential aspect of tissue engineering. We show that thick (>0.5 mm) vertically aligned carbon nanotube films, made by chemical vapour deposition, can be used as biocompatible substrates for the directional alignment of mouse muscle cells where the cells grow on the exposed sides of the films. Ultra high resolution scanning electron microscopy reveals that the films themselves consist mostly of small diameter (10 nm) multi-wall carbon nanotubes of wavy morphology with some single wall carbon nanotubes. Our findings show that for this alignment to occur the nanotubes must be in pristine condition. Mechanical wiping of the films to create directional alignment is detrimental to directional bioactivity. Larger areas for study have been formed from a composite of multiply stacked narrow strips of nanotubes wipe-transferred onto elastomer supports. These composite substrates appear to show a useful degree of alignment of the cells.

  9. Enhanced UV photosensitivity from rapid thermal annealed vertically aligned ZnO nanowires

    Directory of Open Access Journals (Sweden)

    Dhara Soumen

    2011-01-01

    Full Text Available Abstract We report on the major improvement in UV photosensitivity and faster photoresponse from vertically aligned ZnO nanowires (NWs by means of rapid thermal annealing (RTA. The ZnO NWs were grown by vapor-liquid-solid method and subsequently RTA treated at 700°C and 800°C for 120 s. The UV photosensitivity (photo-to-dark current ratio is 4.5 × 103 for the as-grown NWs and after RTA treatment it is enhanced by a factor of five. The photocurrent (PC spectra of the as-grown and RTA-treated NWs show a strong peak in the UV region and two other relatively weak peaks in the visible region. The photoresponse measurement shows a bi-exponential growth and bi-exponential decay of the PC from as-grown as well as RTA-treated ZnO NWs. The growth and decay time constants are reduced after the RTA treatment indicating a faster photoresponse. The dark current-voltage characteristics clearly show the presence of surface defects-related trap centers on the as-grown ZnO NWs and after RTA treatment it is significantly reduced. The RTA processing diminishes the surface defect-related trap centers and modifies the surface of the ZnO NWs, resulting in enhanced PC and faster photoresponse. These results demonstrated the effectiveness of RTA processing for achieving improved photosensitivity of ZnO NWs.

  10. Solution Growth and Functional Properties of Vertically Aligned ZnO Nanowires

    OpenAIRE

    Fan, Jiandong

    2013-01-01

    This dissertation has focused on three main topics: (1) Synthesis and characterization of ZnO:Cl NWs; (2) Hetero and homo nanostructures based on ZnO:Cl NWs for efficient PEC cells; (3) Photovoltaic performance of DSCs based on ZnO NWs. (1) Vertically aligned single-crystal and chlorine-doped ZnO NWs can be grown by a low-cost, high-yield and seed-free electrochemical route with controlled morphology, structural and optoelectronic properties. The carrier concentration of such ZnO:Cl NWs ...

  11. Aligned Carbon Nanotubes Array by DC Glow Plasma Etching for Supercapacitor

    Directory of Open Access Journals (Sweden)

    Yongfeng Luo

    2013-01-01

    Full Text Available To open the end of carbon nanotubes and make these ends connect with functional carboxyl group, aligned carbon nanotubes (CNTs arrays was etched by DC glow oxygen-argon plasma. With these open-ended carbon nanotubes array as electrode materials to build supercapacitor, we found that the capacity (32.2 F/g increased significantly than that of pure carbon nanotubes (6.7 F/g.

  12. CMOS-analogous wafer-scale nanotube-on-insulator approach for submicrometer devices and integrated circuits using aligned nanotubes.

    Science.gov (United States)

    Ryu, Koungmin; Badmaev, Alexander; Wang, Chuan; Lin, Albert; Patil, Nishant; Gomez, Lewis; Kumar, Akshay; Mitra, Subhasish; Wong, H-S Philip; Zhou, Chongwu

    2009-01-01

    Massive aligned carbon nanotubes hold great potential but also face significant integration/assembly challenges for future beyond-silicon nanoelectronics. We report a wafer-scale processing of aligned nanotube devices and integrated circuits, including progress on essential technological components such as wafer-scale synthesis of aligned nanotubes, wafer-scale transfer of nanotubes to silicon wafers, metallic nanotube removal and chemical doping, and defect-tolerant integrated nanotube circuits. We have achieved synthesis of massive aligned nanotubes on complete 4 in. quartz and sapphire substrates, which were then transferred to 4 in. Si/SiO(2) wafers. CMOS analogous fabrication was performed to yield transistors and circuits with features down to 0.5 mum, with high current density approximately 20 muA/mum and good on/off ratios. In addition, chemical doping has been used to build fully integrated complementary inverter with a gain approximately 5, and a defect-tolerant design has been employed for NAND and NOR gates. This full-wafer approach could serve as a critical foundation for future integrated nanotube circuits.

  13. Vertically aligned carbon nanotube electrodes for lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Welna, Daniel T.; Taylor, Barney E. [Materials and Manufacturing Directorate, Air Force Research Laboratory, AFRL/RX, Wright-Patterson AFB, OH 45433 (United States); UTC, Inc., Beavercreek, OH 45431 (United States); Qu, Liangti [Department of Chemistry, Beijing Institute of Technology, 100081 Beijing (China); Dai, Liming [Department of Chemical Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH (United States); Durstock, Michael F. [Materials and Manufacturing Directorate, Air Force Research Laboratory, AFRL/RX, Wright-Patterson AFB, OH 45433 (United States)

    2011-02-01

    As portable electronics become more advanced and alternative energy demands become more prevalent, the development of advanced energy storage technologies is becoming ever more critical in today's society. In order to develop higher power and energy density batteries, innovative electrode materials that provide increased storage capacity, greater rate capabilities, and good cyclability must be developed. Nanostructured materials are gaining increased attention because of their potential to mitigate current electrode limitations. Here we report on the use of vertically aligned multi-walled carbon nanotubes (VA-MWNTs) as the active electrode material in lithium-ion batteries. At low specific currents, these VA-MWNTs have shown high reversible specific capacities (up to 782 mAh g{sup -1} at 57 mA g{sup -1}). This value is twice that of the theoretical maximum for graphite and ten times more than their non-aligned equivalent. Interestingly, at very high discharge rates, the VA-MWNT electrodes retain a moderate specific capacity due to their aligned nature (166 mAh g{sup -1} at 26 A g{sup -1}). These results suggest that VA-MWNTs are good candidates for lithium-ion battery electrodes which require high rate capability and capacity. (author)

  14. Impact of carbon nanotube length on electron transport in aligned carbon nanotube networks

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Jeonyoon; Stein, Itai Y. [Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (United States); Devoe, Mackenzie E. [Department of Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (United States); Lewis, Diana J.; Lachman, Noa; Buschhorn, Samuel T.; Wardle, Brian L., E-mail: wardle@mit.edu [Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, Massachusetts 02139 (United States); Kessler, Seth S. [Metis Design Corporation, 205 Portland St., Boston, Massachusetts 02114 (United States)

    2015-02-02

    Here, we quantify the electron transport properties of aligned carbon nanotube (CNT) networks as a function of the CNT length, where the electrical conductivities may be tuned by up to 10× with anisotropies exceeding 40%. Testing at elevated temperatures demonstrates that the aligned CNT networks have a negative temperature coefficient of resistance, and application of the fluctuation induced tunneling model leads to an activation energy of ≈14 meV for electron tunneling at the CNT-CNT junctions. Since the tunneling activation energy is shown to be independent of both CNT length and orientation, the variation in electron transport is attributed to the number of CNT-CNT junctions an electron must tunnel through during its percolated path, which is proportional to the morphology of the aligned CNT network.

  15. Impact of carbon nanotube length on electron transport in aligned carbon nanotube networks

    Science.gov (United States)

    Lee, Jeonyoon; Stein, Itai Y.; Devoe, Mackenzie E.; Lewis, Diana J.; Lachman, Noa; Kessler, Seth S.; Buschhorn, Samuel T.; Wardle, Brian L.

    2015-02-01

    Here, we quantify the electron transport properties of aligned carbon nanotube (CNT) networks as a function of the CNT length, where the electrical conductivities may be tuned by up to 10× with anisotropies exceeding 40%. Testing at elevated temperatures demonstrates that the aligned CNT networks have a negative temperature coefficient of resistance, and application of the fluctuation induced tunneling model leads to an activation energy of ≈14 meV for electron tunneling at the CNT-CNT junctions. Since the tunneling activation energy is shown to be independent of both CNT length and orientation, the variation in electron transport is attributed to the number of CNT-CNT junctions an electron must tunnel through during its percolated path, which is proportional to the morphology of the aligned CNT network.

  16. Field emission arrays fabricated utilizing conjugated ZnO quantum dot/carbon nanotube hybrid nanocomposite

    Energy Technology Data Exchange (ETDEWEB)

    Wu Chaoxing [Institute of Optoelectronic Display, Fuzhou University, Fuzhou 350002 (China); Li Fushan, E-mail: fushanli@hotmail.com [Institute of Optoelectronic Display, Fuzhou University, Fuzhou 350002 (China); Zhang Yongai [Institute of Optoelectronic Display, Fuzhou University, Fuzhou 350002 (China); Guo Tailiang, E-mail: gtl@fzu.edu.cn [Institute of Optoelectronic Display, Fuzhou University, Fuzhou 350002 (China); Qu Bo; Chen Zhijian [State Key Laboratory for Mesoscopic Physics, Peking University, Beijing 100871 (China)

    2011-02-15

    In situ growth of ZnO quantum dots (QDs) on the surface of multiwalled carbon nanotube (MWCNTs) was realized via a mild solution-process method, and their application in field emission device was demonstrated. High resolution transmission electron microscopy observation revealed the conjugation between ZnO QDs and MWCNTs. Field emission arrays based on ZnO QD/MWCNT hybrid nanocomposite exhibited significantly improved luminance intensity and emitting dot density when compared with the MWCNT-only arrays. It is proposed that the introduction of the ZnO QDs on the sidewall of MWCNTs can enhance the tunnelling probability, and result in the improved field emission property for the hybrid emitters.

  17. Magnetic alignment of Ni-coated single wall carbon nanotubes in heat transfer nanofluids

    Science.gov (United States)

    Horton, Mark; Hong, Haiping; Li, Chen; Shi, Bo; Peterson, G. P.; Jin, Sungho

    2010-05-01

    Thermal conductivity (TC) of heat transfer nanofluids containing magnetic-metal-coated carbon nanotubes can be significantly enhanced (>60%) by applied magnetic field. In this paper, we report the observed real images of Ni-coated single wall carbon nanotubes in water and oils (polyalphaolefin, polyol ester) under magnetic field by high speed microscopy, and correlate them with TC measurements. Initially, the nanotubes are randomly dispersed in the fluid, however, on longer holding in magnetic field the nanotubes gradually stretch and are finally aligned. The chain length in the images is found to be around 30˜150 μm, which is much longer than the real length of individual nanotubes (5˜40 μm), indicating that nanotubes are aligned and form some chains and clusters. Because of the semicontinuous nature of Ni magnetic nanoparticles, as well as the viscosity resistance of the fluid itself, it takes some time for the Ni-coated nanotubes to respond to the applied magnetic field and align. Time dependent TC experiments indicate that alignment process dominates the TC enhancement rather than microconvection. Finally, scanning electron microscopy images also show that the Ni coated nanotubes are aligned well under the influence of a magnetic field. Transmission electron microscopy images indicate that nickel remains stable and attached onto the nanotubes after the magnetic field exposure and movements.

  18. Freestanding Aligned Multi-walled Carbon Nanotubes for Supercapacitor Devices

    Science.gov (United States)

    Moreira, João Vitor Silva; Corat, Evaldo José; May, Paul William; Cardoso, Lays Dias Ribeiro; Lelis, Pedro Almeida; Zanin, Hudson

    2016-11-01

    We report on the synthesis and electrochemical properties of multi-walled carbon nanotubes (MWCNTs) for supercapacitor devices. Freestanding vertically-aligned MWCNTs and MWCNT powder were grown concomitantly in a one-step chemical vapour deposition process. Samples were characterized by scanning and transmission electron microscopies and Fourier transform infrared and Raman spectroscopies. At similar film thicknesses and surface areas, the freestanding MWCNT electrodes showed higher electrochemical capacitance and gravimetric specific energy and power than the randomly-packed nanoparticle-based electrodes. This suggests that more ordered electrode film architectures facilitate faster electron and ion transport during the charge-discharge processes. Energy storage and supply or supercapacitor devices made from these materials could bridge the gap between rechargeable batteries and conventional high-power electrostatic capacitors.

  19. Covering vertically aligned carbon nanotubes with a multiferroic compound

    KAUST Repository

    Mahajan, Amit

    2014-10-30

    This work highlights the possible use of vertically-aligned multiwall carbon nanotubes (VA-MWCNTs) as bottom electrodes for microelectronics, for example for memory applications. As a proof of concept BiFeO3 (BFO) films were fabricated in-situ deposited on the surface of VA-MWCNTs by RF (radio frequency) magnetron sputtering. For in situ deposition temperature of 400 °C and deposition time up to 2 h, BFO films cover the MWCNTs and no damage occurs either in the film or MWCNTs. In spite of the macroscopic lossy polarization behaviour, the ferroelectric nature, domain structure and switching of these conformal BFO films was verified by piezo force microscopy. G type antiferromagnetic ordering with weak ferromagnetic ordering loop was proved for BFO films on VA-MWCNTs having a coercive field of 700 Oe.

  20. Thin randomly aligned hierarchical carbon nanotube arrays as ultrablack metamaterials

    Science.gov (United States)

    De Nicola, Francesco; Hines, Peter; De Crescenzi, Maurizio; Motta, Nunzio

    2017-07-01

    Ultrablack metamaterials are artificial materials able to harvest all the incident light regardless of wavelength, angle, or polarization. Here, we show the ultrablack properties of randomly aligned hierarchical carbon nanotube arrays with thicknesses below 200 nm. The thin coatings are realized by solution processing and dry-transfer deposition on different substrates. The hierarchical surface morphology of the coatings is biomimetic and provides a large effective area that improves the film optical absorption. Also, such a morphology is responsible for the moth-eye effect, which leads to the omnidirectional and polarization-independent suppression of optical reflection. The films exhibit an emissivity up to 99.36% typical of an ideal black body, resulting in the thinnest ultrablack metamaterial ever reported. Such a material may be exploited for thermal, optical, and optoelectronic devices such as heat sinks, optical shields, solar cells, light and thermal sensors, and light-emitting diodes.

  1. ZnO Functionalization of Multi-walled Carbon Nanotubes for Methane Sensing at Single Parts Per Million Concentration Levels

    Science.gov (United States)

    This paper presents a novel atomic layer deposition (ALD) based ZnO functionalization of surface pre-treated multi-walled carbon nanotubes (MWCNTs) for highly sensitive methane chemoresistive sensors. The temperature optimization of the ALD process leads to enhanced ZnO nanopart...

  2. Halloysite Nanotubes Supported Ag and ZnO Nanoparticles with Synergistically Enhanced Antibacterial Activity.

    Science.gov (United States)

    Shu, Zhan; Zhang, Yi; Yang, Qian; Yang, Huaming

    2017-12-01

    Novel antimicrobial nanocomposite incorporating halloysite nanotubes (HNTs) and silver (Ag) into zinc oxide (ZnO) nanoparticles is prepared by integrating HNTs and decorating Ag nanoparticles. ZnO nanoparticles (ZnO NPs) and Ag nanoparticles (Ag NPs) with a size of about 100 and 8 nm, respectively, are dispersively anchored onto HNTs. The synergistic effects of ZnO NPs, Ag NPs, and HNTs led to the superior antibacterial activity of the Ag-ZnO/HNTs antibacterial nanocomposites. HNTs facilitated the dispersion and stability of ZnO NPs and brought them in close contact with bacteria, while Ag NPs could promote the separation of photogenerated electron-hole pairs and enhanced the antibacterial activity of ZnO NPs. The close contact with cell membrane enabled the nanoparticles to produce the increased concentration of reactive oxygen species and the metal ions to permeate into the cytoplasm, thus induced quick death of bacteria, indicating that Ag-ZnO/HNTs antibacterial nanocomposite is a promising candidate in the antibacterial fields.

  3. Halloysite Nanotubes Supported Ag and ZnO Nanoparticles with Synergistically Enhanced Antibacterial Activity

    Science.gov (United States)

    Shu, Zhan; Zhang, Yi; Yang, Qian; Yang, Huaming

    2017-02-01

    Novel antimicrobial nanocomposite incorporating halloysite nanotubes (HNTs) and silver (Ag) into zinc oxide (ZnO) nanoparticles is prepared by integrating HNTs and decorating Ag nanoparticles. ZnO nanoparticles (ZnO NPs) and Ag nanoparticles (Ag NPs) with a size of about 100 and 8 nm, respectively, are dispersively anchored onto HNTs. The synergistic effects of ZnO NPs, Ag NPs, and HNTs led to the superior antibacterial activity of the Ag-ZnO/HNTs antibacterial nanocomposites. HNTs facilitated the dispersion and stability of ZnO NPs and brought them in close contact with bacteria, while Ag NPs could promote the separation of photogenerated electron-hole pairs and enhanced the antibacterial activity of ZnO NPs. The close contact with cell membrane enabled the nanoparticles to produce the increased concentration of reactive oxygen species and the metal ions to permeate into the cytoplasm, thus induced quick death of bacteria, indicating that Ag-ZnO/HNTs antibacterial nanocomposite is a promising candidate in the antibacterial fields.

  4. Fabrication of Aligned-Carbon-Nanotube-Composite Paper with High and Anisotropic Conductivity

    OpenAIRE

    Yuki Fujitsuka; Takahide Oya

    2012-01-01

    A functional carbon-nanotube (CNT)-composite paper is described in which the CNTs are aligned. This “aligned-CNT composite paper” is a flexible composite material that has CNT functionality (e.g., electrical conductivity) despite being a paper. An advanced fabrication method was developed to overcome the problem of previous CNT-composite papers, that is, reduced conductivity due to random CNT alignment. Aligning the CNTs by using an alternating current (AC) field was hypothesized to increase ...

  5. Aligned carbon nanotube thin films for DNA electrochemical sensing

    Energy Technology Data Exchange (ETDEWEB)

    Berti, F. [Department of Chemistry, University of Florence, Via della Lastruccia 3, Sesto Fiorentino, Firenze 50019 (Italy); Lozzi, L. [Department of Physics, University of L' Aquila, Coppito, L' Aquila 67100 (Italy); Palchetti, I. [Department of Chemistry, University of Florence, Via della Lastruccia 3, Sesto Fiorentino, Firenze 50019 (Italy); Santucci, S. [Department of Physics, University of L' Aquila, Coppito, L' Aquila 67100 (Italy); Marrazza, G. [Department of Chemistry, University of Florence, Via della Lastruccia 3, Sesto Fiorentino, Firenze 50019 (Italy)], E-mail: giovanna.marrazza@unifi.it

    2009-09-01

    Carbon nanotubes are interesting materials for DNA electrochemical sensing due to their unique electric properties: high surface area, fast heterogeneous electron transfer, and electrochemical stability. In this work aligned Carbon NanoTube (CNT) thin films were designed and tested as candidate platforms for DNA immobilization and for the development of an electrochemical genosensor. The films were prepared by Chemical Vapor Deposition (CVD) using acetylene and ammonia as precursor gases and nickel particles as catalyst. A preliminary electrochemical characterization was performed using cyclic voltammetry since, so far, these films have been used only for gas sensing. The surfaces were then covalently functionalized with a DNA oligonucleotide probe, complementary to the sequence of the most common inserts in the GMOs: the Promoter 35S. The genosensor format involved the immobilization of the probe onto the sensor surface, the hybridization with the target-sequence and the electrochemical detection of the duplex formation. Careful attention was paid to the probe immobilization conditions in order to minimize the signal due to non-specifically adsorbed sequences. For the detection of the hybridization event both label-free and enzyme-labelled methods were investigated. In case of the enzyme-labelled method a target concentration at nanomolar level can be easily detected, with a linear response from 50 nM to 200 nM, whereas the label-free method showed a linear response between 0.5 {mu}M and 10 {mu}M. The reproducibility was 11% and 20% with the enzyme-labelled method and the label-free method, respectively. The batch-to-batch reproducibility of the different sensors was also evaluated.

  6. Controllable growth and characterization of highly aligned ZnO nanocolumnar thin films

    Science.gov (United States)

    Onuk, Zuhal; Rujisamphan, Nopporn; Murray, Roy; Bah, Mohamed; Tomakin, Murat; Shah, S. Ismat

    2017-02-01

    We investigated the effects of growth conditions during magnetron sputtering on the structural, morphological, and optical properties of nanostructured ZnO thin films. Undoped ZnO thin films are deposited onto p-type Si (100) and corning 7059 glass substrates by RF magnetron sputtering using a ZnO target in combination with various Ar-O2 sputtering gas mixtures at room temperature. The effect of the partial pressure of oxygen on the morphology of ZnO thin film structure and band alignment were investigated. Thickness, and therefore the growth rate of the samples measured from the cross-sectional SEM micrographs, is found to be strongly correlated with the oxygen partial pressure in the sputtering chamber. The optical transmittance spectrometry results show that the absorption edge shifts towards the longer wavelength at higher oxygen partial pressure. X-ray photoelectron spectroscopy (XPS) used for determining the surface chemical structure and valence band offsets show that conduction band can be controlled by changing the sputtering atmosphere.

  7. Self-fabrication of 3D Patterns on Aligned Carbon Nanotubes Films

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    Because of its outstanding performance, an aligned nanotube film with micropatterns has been a research focus in the field of nano-science and technology. Although quite a number of researchers have been successful in constructing such patterns, the precondition for the success, until recently, is to obtain the patterned substrates in advance.A research group at the CAS Institute of Chemistry (ICCAS) has succeeded in self-assembly of threedimensional (3-D) micropatterns on aligned carbon nanotube films.

  8. Growth of Well-Aligned ZnO Nanorod Arrays and Their Application for Photovoltaic Devices

    Science.gov (United States)

    Yuan, Zhaolin; Yao, Juncai

    2017-07-01

    We have fabricated well-aligned ZnO nanorod arrays (ZNRAs) on indium tin oxide-coated glass substrates by a facile chemical bath deposition method. We used field-emission scanning electron microscope, x-ray diffraction and UV-Vis absorption spectroscopy to study the morphology, crystalline structure and optical absorption of the fabricated ZNRAs, respectively. The results showed that ZnO nanorods stood almost perpendicularly on the substrate, were about 30-50 nm in diameter and 800-900 nm in length, and were wurtzite-structured (hexagonal) ZnO. In addition, well-aligned ZNRAs exhibited a weak absorption in the visible region and had an optical band gap value of 3.28 eV. Furthermore, a hybrid ZNRAs/polymer photovoltaic device was made, under 1 sun AM 1.5 illumination (light intensity, ˜100 mW/cm2), and the device showed an open circuit voltage (V oc) of 0.32 V, a short circuit current density (J sc) of 7.67 mA/cm2, and a fill factor (FF) of 0.37, yielding an overall power conversion efficiency of 0.91%. Also, the exciton dissociation and transportation processes of charge carriers in the device under illumination were explained according to its current density-voltage (J-V) curve and the energy level diagram.

  9. Influence of filler alignment in the mechanical and electrical properties of carbon nanotubes/epoxy nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Felisberto, M. [LPyMC, FCEyN-UBA and IFIBA-CONICET, Pab I Ciudad Universitaria, Buenos Aires 1428 (Argentina); INQUIMAE-CONICET-UBA, Pab II Ciudad Universitaria, Buenos Aires 1428 (Argentina); Arias-Duran, A. [LPyMC, FCEyN-UBA and IFIBA-CONICET, Pab I Ciudad Universitaria, Buenos Aires 1428 (Argentina); Ramos, J.A.; Mondragon, I. [Dep. Ingenieria Quimica y M. Ambiente. Esc. Politecnica. UPV/EHU, Pza. Europa 1, Donostia-San Sebastian 20018 (Spain); Candal, R. [INQUIMAE-CONICET-UBA, Pab II Ciudad Universitaria, Buenos Aires 1428 (Argentina); Escuela de Ciencia y Tecnologia-UNSAM, San Martin, Prov. De Buenos Aires (Argentina); Goyanes, S. [LPyMC, FCEyN-UBA and IFIBA-CONICET, Pab I Ciudad Universitaria, Buenos Aires 1428 (Argentina); Rubiolo, G.H., E-mail: rubiolo@cnea.gov.ar [LPyMC, FCEyN-UBA and IFIBA-CONICET, Pab I Ciudad Universitaria, Buenos Aires 1428 (Argentina); Dep. Materiales, Comision Nacional de Energia Atomica (CNEA-CAC), Avda Gral Paz 1499, B1650KNA San Martin (Argentina)

    2012-08-15

    In this work, we report the mechanical and electrical properties of carbon nanotubes/epoxy composites prepared with aligned and randomly oriented nanotubes as filler. The samples are disks of 30 mm in diameter and 3 mm in thickness. To obtain the carbon nanotubes alignment, an external electric field (250 VAC; 50 Hz) was applied through the thickness of the sample during all the cure process. The AC electrical current was measured, during the cure, as a strategy to determine the optimum time in which the alignment reaches the maximum value. DC conductivity measured after the cure shows a percolation threshold in the filler content one order of magnitude smaller for composites with aligned nanotubes than for composites with randomly oriented filler (from 0.06 to 0.5 wt%). In the percolation threshold, the achieved conductivity was 1.4 Multiplication-Sign 10{sup -5} Sm{sup -1}. In both cases, aligned and randomly distributed carbon nanotube composites, the wear resistance increases with the addition of the filler while the Rockwell hardness decreases independently of the nanotubes alignment.

  10. Polarization-dependent DANES study on vertically-aligned ZnO nanorods

    Science.gov (United States)

    Sun, Chengjun; Park, Chang-In; Jin, Zhenlan; Hwang, In-Hui; Heald, S. M.; Han, Sang-Wook

    2016-05-01

    The local structural and local density of states of vertically-aligned ZnO nanorods are examined by using polarization-dependent diffraction anomalous near edge structure (DANES) measurements from c-oriented ZnO nanorods at the Zn K edge at the geometry of the incident x-ray electric field parallel and perpendicular to the x-ray momentum transfer direction. Orientation-dependent local structures determined by DANES are comparable with polarization- dependent EXAFS results. Unlike other techniques, polarization-dependent DANES can uniquely describe the orientation-dependent local structural properties and the local density of states of a selected element in selected-phased crystals of compounds or mixed-phased structures.

  11. Fabrication and characterization of solution processed vertically aligned ZnO microrods

    Energy Technology Data Exchange (ETDEWEB)

    Gadallah, A.-S., E-mail: agadallah@niles.edu.eg [Laboratoire de Nanotechnologie et d’Instrumentation Optique, Institut Charles Delaunay, CNRS UMR 6279, Université de Technologie de Troyes, 12 rue Marie Curie, BP 2060, 10010 Troyes Cedex (France); Department of Laser Sciences and Interactions, National Institute of Laser Enhanced Sciences, Cairo University, 12613 Giza (Egypt)

    2014-08-30

    Simple and effective cost high quality vertically aligned densely packed ZnO microrods have been prepared using solution processed two-step deposition process, specifically sol–gel spin coating combined with chemical bath deposition. X-ray diffraction pattern and scanning electron microscope show that there has been preferential crystal orientation along c-axis and the growth of the microrods has occurred normal to the glass substrate and the facets of the these microrods are hexagons. Photoluminescence measurements showed an emission band in the UV region and another weak band in the visible region with the emission intensity of UV band grows superlinearly with the excitation intensity. The film shows an electrical resistivity of 136 Ω cm as evaluated from four-point probe method. The fabricated film has been used as UV detector through Au/SiO{sub 2}/ZnO structure on glass substrate as the structure shows higher current under illumination compared to without illumination.

  12. Modelling clustering of vertically aligned carbon nanotube arrays

    Science.gov (United States)

    Schaber, Clemens F.; Filippov, Alexander E.; Heinlein, Thorsten; Schneider, Jörg J.; Gorb, Stanislav N.

    2015-01-01

    Previous research demonstrated that arrays of vertically aligned carbon nanotubes (VACNTs) exhibit strong frictional properties. Experiments indicated a strong decrease of the friction coefficient from the first to the second sliding cycle in repetitive measurements on the same VACNT spot, but stable values in consecutive cycles. VACNTs form clusters under shear applied during friction tests, and self-organization stabilizes the mechanical properties of the arrays. With increasing load in the range between 300 µN and 4 mN applied normally to the array surface during friction tests the size of the clusters increases, while the coefficient of friction decreases. To better understand the experimentally obtained results, we formulated and numerically studied a minimalistic model, which reproduces the main features of the system with a minimum of adjustable parameters. We calculate the van der Waals forces between the spherical friction probe and bunches of the arrays using the well-known Morse potential function to predict the number of clusters, their size, instantaneous and mean friction forces and the behaviour of the VACNTs during consecutive sliding cycles and at different normal loads. The data obtained by the model calculations coincide very well with the experimental data and can help in adapting VACNT arrays for biomimetic applications. PMID:26464787

  13. Preparation and characterization of aligned carbon nanotubes coated with titania nanoparticles

    Institute of Scientific and Technical Information of China (English)

    YU Hongtao; ZHAO Huimin; QUAN Xie; CHEN Shuo

    2006-01-01

    Well-aligned carbon nanotubes coated with titania (TiO2) were prepared by atmospheric pressure chemical vapor deposition (APCVD), and the sequential experiments including carbon nanotubes preparation, air-oxidation purification and titania nanoparticles coating were performed at different temperatures in the same reactor. Scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction patterns (XRD), and energy- dispersive X-ray spectra (EDX) demonstrated the well-aligned nanotubes and TiO2 nanoparticles in close proximity and the average diameter of TiO2 nanoparticles was 11.5 nm.

  14. Synthesis and electron emission properties of aligned carbon nanotube arrays

    Science.gov (United States)

    Neupane, Suman

    Carbon nanotubes (CNTs) have become one of the most interesting allotropes of carbon due to their intriguing mechanical, electrical, thermal and optical properties. The synthesis and electron emission properties of CNT arrays have been investigated in this work. Vertically aligned CNTs of different densities were synthesized on copper substrate with catalyst dots patterned by nanosphere lithography. The CNTs synthesized with catalyst dots patterned by spheres of 500 nm diameter exhibited the best electron emission properties with the lowest turn-on/threshold electric fields and the highest field enhancement factor. Furthermore, CNTs were treated with NH3 plasma for various durations and the optimum enhancement was obtained for a plasma treatment of 1.0 min. CNT point emitters were also synthesized on a flat-tip or a sharp-tip to understand the effect of emitter geometry on the electron emission. The experimental results show that electron emission can be enhanced by decreasing the screening effect of the electric field by neighboring CNTs. In another part of the dissertation, vertically aligned CNTs were synthesized on stainless steel (SS) substrates with and without chemical etching or catalyst deposition. The density and length of CNTs were determined by synthesis time. For a prolonged growth time, the catalyst activity terminated and the plasma started etching CNTs destructively. CNTs with uniform diameter and length were synthesized on SS substrates subjected to chemical etching for a period of 40 minutes before the growth. The direct contact of CNTs with stainless steel allowed for the better field emission performance of CNTs synthesized on pristine SS as compared to the CNTs synthesized on Ni/Cr coated SS. Finally, fabrication of large arrays of free-standing vertically aligned CNT/SnO2 core-shell structures was explored by using a simple wet-chemical route. The structure of the SnO2 nanoparticles was studied by X-ray diffraction and electron microscopy

  15. Preparation of Aligned ZnO Nanorod Arrays on Sn-Doped ZnO Thin Films by Sonicated Sol-Gel Immersion Fabricated for Dye-Sensitized Solar Cell

    OpenAIRE

    Saurdi, I.; Mamat, M. H.; M. F. Malek; M. Rusop

    2014-01-01

    Aligned ZnO Nanorod arrays are deposited on the Sn-doped ZnO thin film via sonicated sol-gel immersion method. The structural, optical, and electrical properties of the Sn-doped ZnO thin films were investigated. Results show that the Sn-doped ZnO thin films with small grain size (~20 nm), high average transmittance (96%) in visible region, and good resistivity 7.7 × 102 Ω·cm are obtained for 2 at.% Sn doping concentration. The aligned ZnO nanorod arrays with large surface area were also obtai...

  16. Thermal conductivity of vertically aligned carbon nanotube arrays: Growth conditions and tube inhomogeneity

    Science.gov (United States)

    Bauer, Matthew L.; Pham, Quang N.; Saltonstall, Christopher B.; Norris, Pamela M.

    2014-10-01

    The thermal conductivity of vertically aligned carbon nanotube arrays (VACNTAs) grown on silicon dioxide substrates via chemical vapor deposition is measured using a 3ω technique. For each sample, the VACNTA layer and substrate are pressed to a heating line at varying pressures to extract the sample's thermophysical properties. The nanotubes' structure is observed via transmission electron microscopy and Raman spectroscopy. The presence of hydrogen and water vapor in the fabrication process is tuned to observe the effect on measured thermal properties. The presence of iron catalyst particles within the individual nanotubes prevents the array from achieving the overall thermal conductivity anticipated based on reported measurements of individual nanotubes and the packing density.

  17. Alignment control of carbon nanotube forest from random to nearly perfectly aligned by utilizing the crowding effect.

    Science.gov (United States)

    Xu, Ming; Futaba, Don N; Yumura, Motoo; Hata, Kenji

    2012-07-24

    Alignment represents an important structural parameter of carbon nanotubes (CNTs) owing to their exceptionally high aspect ratio, one-dimensional property. In this paper, we demonstrate a general approach to control the alignment of few-walled CNT forests from nearly random to nearly ideally aligned by tailoring the density of active catalysts at the catalyst formation stage, which can be experimentally achieved by controlling the CNT forest mass density. Experimentally, we found that the catalyst density and the degree of alignment were inseparably linked because of a crowding effect from neighboring CNTs, that is, the increasing confinement of CNTs with increased density. Therefore, the CNT density governed the degree of alignment, which increased monotonically with the density. This relationship, in turn, allowed the precise control of the alignment through control of the mass density. To understand this behavior further, we developed a simple, first-order model based on the flexural modulus of the CNTs that could quantitatively describe the relationship between the degree of alignment (HOF) and carbon nanotube spacing (crowding effect) of any type of CNTs.

  18. Exploring the sensitivity of ZnO nanotubes to tyrosine nitration: A DFT approach

    Energy Technology Data Exchange (ETDEWEB)

    Maddahi, Pari Sadat [Department of Physics, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Nanoresearch Center, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Shahtahmassebi, Nasser, E-mail: Nasser@um.ac.ir [Department of Physics, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Nanoresearch Center, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Rezaee Roknabadi, Mahmood [Department of Physics, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of); Moosavi, Fatemeh [Department of Chemistry, Ferdowsi University of Mashhad, Mashhad (Iran, Islamic Republic of)

    2016-05-27

    Due to association of protein tyrosine nitration (PTN) with development of some serious human disorders and diseases, in this paper, the possible applications of ZnO-based nanobiosensors in nitrated tyrosine (nTyr) detection were explored within the density functional framework. With this motivation, the interaction of nTyr with ZnO single walled nanotubes via all possible active sites of nTyr was investigated. The results show the tendency of nTyr to interact through its nitro site (forming nitro-site configuration) with ZnO SWNTs as it has the highest binding energy; while, the charge–solvent configuration involving the interaction of nTyr's phenolic ring has the second place in terms of binding energy magnitude. Regardless of which active site contributes in interaction, the binding energies exhibit an ascending trend with decrease of SWNTs' curvature. Electronic properties analysis indicates that nTyr interaction via its nitro group results in formation of some flat bands inside the band gap region leading to significant reduction of overall band gap energy. Similar behavior is also observed in charge–solvent configuration but the band gap energy is larger. These red shifts are mainly attributed to contribution of 2p orbitals of species present in nTyr. Also, the hybridization of 3d orbital of Zn atom with 2p orbitals of nitro group atomic species is found responsible for bonding formation in bioconjugated system possessing the highest binding energy. Comparison of the electronic band structure of ZnO SWNT–Tyr with that of ZnO SWNT–nTyr indicates the sensitivity of ZnO SWNTs toward tyrosine nitration hence, a considerable change in its optical spectra is expectable. This introduces ZnO SWNTs as a promising candidate for PTN detection. - Highlights: • Physical properties of ZnO SWNT conjugated with nTyr is studied by DFT method. • nTyr prefers to interact with ZnO SWNTs via the nitro site. • An ascending trend is observed in binding

  19. Growth of Aligned Multiwall Carbon Nanotubes and the Effect of Adsorbates on the Field Emission Properties

    Science.gov (United States)

    Milne, W. I.; Teo, K. B. K.; Lansley, S. B.; Chhowalla, M.; Amaratunga, G. A. J.; Semet, V.; Binh, Vu Thien; Pirio, G.; Legagneux, P.

    2003-10-01

    In attempt to decipher the field emission characteristics of multiwall carbon nanotubes (MWCNTs), we have developed a fabrication method based on plasma enhanced chemical vapour deposition (PECVD) to provide utmost control of the nanotube structure such as their alignment, individual position, diameter, length and morphology. We investigated the field emission properties of these nanotubes to elucidate the effect of adsorbates on the nanotubes. Our results show that although the adsorbates cause an apparent lowering of the required turn on voltage/field of the nanotubes, the adsorbates undesirably cause a saturation of the current, large temporal fluctuations in the current, and also a deviation of the emission characteristics from Fowler-Nordheim like emission. The adsorbates are easily removed by extracting an emission current of 1 uA per nanotube or using a high applied electric field (˜25V/um).

  20. Growth of Vertically Aligned ZnO Nanowire Arrays Using Bilayered Metal Catalysts

    Directory of Open Access Journals (Sweden)

    Hua Qi

    2012-01-01

    Full Text Available Vertically aligned, high-density ZnO nanowires (NWs were grown for the first time on c-plane sapphire using binary alloys of Ni/Au or Cu/Au as the catalyst. The growth was performed under argon gas flow and involved the vapor-liquid-solid (VLS growth process. We have investigated various ratios of catalyst components for the NWs growth and results indicate that very thin adhesion layers of Ni or Cu deposited prior to the Au layer are not deleterious to the ZnO NW array growth. Significant improvement of the Au adhesion on the substrate was noted, opening the potential for direct catalyst patterning of Au and subsequent NW array growth. Additionally, we found that an increase of in thickness of the Cu adhesion layer results in the simultaneous growth of NWs and nanoplates (NPs, indicating that in this case the growth involves both the VLS and vapor-solid (VS growth mechanisms. Energy dispersive X-ray spectroscopy (EDX and surface-enhanced Raman scattering (SERS studies were also performed to characterize the resulting ZnO NW arrays, indicating that the NWs grown using a thin adhesion layer of Ni or Cu under the Au show comparable SERS enhancement to those of the pure Au-catalyzed NWs.

  1. Structure and Characterization of Vertically Aligned Single-Walled Carbon Nanotube Bundles

    Directory of Open Access Journals (Sweden)

    Francisco Márquez

    2010-01-01

    Full Text Available Arrays of vertically aligned single-walled carbon nanotube bundles, SWCNTs, have been synthesized by simple alcohol catalytic chemical vapor deposition process, carried out at 800∘C. The formed SWCNTs are organized in small groups perpendicularly aligned and attached to the substrate. These small bundles show a constant diameter of ca. 30 nm and are formed by the adhesion of no more than twenty individual SWCNTs perfectly aligned along their length.

  2. Growth of Aligned Carbon Nanotubes through Microwave Plasma Chemical Vapor Deposition

    Institute of Scientific and Technical Information of China (English)

    王升高; 汪建华; 马志斌; 王传新; 满卫东

    2005-01-01

    Aligned carbon nanotubes (CNTs) were synthesized on glass by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at the low temperature of 550 ℃. The experimental results show that both the self-bias potential and the density of the catalyst particles are responsible for the alignment of CNTs. When the catalyst particle density is high enough, strong interactions among the CNTs can inhibit CNTs from growing randomly and result in parallel alignment.

  3. Simultaneous alignment and micropatterning of carbon nanotubes using modulated magnetic field

    Directory of Open Access Journals (Sweden)

    Kaoru Tsuda and Yoshio Sakka

    2009-01-01

    Full Text Available We report simultaneous alignment and micropatterning of carbon nanotubes (CNTs using a high magnetic field. It is important to prepare well-dispersed CNTs for alignment and patterning because CNT aggregation obstructs alignment. In magnetic field, highly anisotropic CNTs rotate in the direction stabilized in energy. Owing to their diamagnetic nature, CNTs suspended in a liquid medium are trapped in a weak magnetic field generated by a field modulator; meanwhile, they align to the applied strong magnetic field. The alignment has been achieved not only in polymers but also in ceramic and silicone composites.

  4. Superemission in vertically-aligned single-wall carbon nanotubes

    Science.gov (United States)

    Khmelinskii, Igor; Makarov, Vladimir

    2016-09-01

    Presently we used two samples of vertically aligned single-wall carbon nanotubes (VA SWCNTs) with parallelepiped geometry, sized 0.02 cm × 0.2 cm × 1.0 cm and 0.2 cm × 0.2 cm × 1.0 cm. We report absorption and emission properties of the VA SWCNTs, including strong anisotropy in both their absorption and emission spectra. We found that the emission spectra extend from the middle-IR range to the near-IR range, with such extended spectra being reported for the first time. Pumping the VA SWCNTs in the direction normal to their axis, superemission (SE) was observed in the direction along their axis. The SE band maximum is located at 7206 ± 0.4 cm-1. The energy and the power density of the superemission were estimated, along with the diffraction-limited divergence. At the pumping energy of 3 mJ/pulse, the SE energy measured by the detector was 0.74 mJ/pulse, corresponding to the total SE energy of 1.48 mJ/pulse, with the energy density of 18.5 mJ cm-2/pulse and the SE power density of 1.2 × 105 W cm-2/pulse. We report that a bundle of VA SWCNTs is an emitter with a relatively small divergence, not exceeding 3.9 × 10-3 rad. We developed a theoretical approach to explain such absorption and emission spectra. The developed theory is based on the earlier proposed SSH theory, which we extended to include the exchange interactions between the closest SWCNT neighbors. The developed theoretical ideas were implemented in a homemade FORTRAN code. This code was successfully used to calculate and reproduce the experimental spectra and to determine the SWCNT species that originate the respective absorption bands, with acceptable agreement between theory and experiment.

  5. Wafer-scale monodomain films of spontaneously aligned single-walled carbon nanotubes

    Science.gov (United States)

    He, Xiaowei; Gao, Weilu; Xie, Lijuan; Li, Bo; Zhang, Qi; Lei, Sidong; Robinson, John M.; Hároz, Erik H.; Doorn, Stephen K.; Wang, Weipeng; Vajtai, Robert; Ajayan, Pulickel M.; Adams, W. Wade; Hauge, Robert H.; Kono, Junichiro

    2016-07-01

    The one-dimensional character of electrons, phonons and excitons in individual single-walled carbon nanotubes leads to extremely anisotropic electronic, thermal and optical properties. However, despite significant efforts to develop ways to produce large-scale architectures of aligned nanotubes, macroscopic manifestations of such properties remain limited. Here, we show that large (>cm2) monodomain films of aligned single-walled carbon nanotubes can be prepared using slow vacuum filtration. The produced films are globally aligned within ±1.5° (a nematic order parameter of ∼1) and are highly packed, containing 1 × 106 nanotubes in a cross-sectional area of 1 μm2. The method works for nanotubes synthesized by various methods, and film thickness is controllable from a few nanometres to ∼100 nm. We use the approach to create ideal polarizers in the terahertz frequency range and, by combining the method with recently developed sorting techniques, highly aligned and chirality-enriched nanotube thin-film devices. Semiconductor-enriched devices exhibit polarized light emission and polarization-dependent photocurrent, as well as anisotropic conductivities and transistor action with high on/off ratios.

  6. Electrokinetics of scalable, electric-field-assisted fabrication of vertically aligned carbon-nanotube/polymer composites

    Science.gov (United States)

    Castellano, Richard J.; Akin, Cevat; Giraldo, Gabriel; Kim, Sangil; Fornasiero, Francesco; Shan, Jerry W.

    2015-06-01

    Composite thin films incorporating vertically aligned carbon nanotubes (VACNTs) offer promise for a variety of applications where the vertical alignment of the CNTs is critical to meet performance requirements, e.g., highly permeable membranes, thermal interfaces, dry adhesives, and films with anisotropic electrical conductivity. However, current VACNT fabrication techniques are complex and difficult to scale up. Here, we describe a solution-based, electric-field-assisted approach as a cost-effective and scalable method to produce large-area VACNT composites. Multiwall-carbon nanotubes are dispersed in a polymeric matrix, aligned with an alternating-current (AC) electric field, and electrophoretically concentrated to one side of the thin film with a direct-current (DC) component to the electric field. This approach enables the fabrication of highly concentrated, individually aligned nanotube composites from suspensions of very dilute ( ϕ = 4 × 10 - 4 ) volume fraction. We experimentally investigate the basic electrokinetics of nanotube alignment under AC electric fields, and show that simple models can adequately predict the rate and degree of nanotube alignment using classical expressions for the induced dipole moment, hydrodynamic drag, and the effects of Brownian motion. The composite AC + DC field also introduces complex fluid motion associated with AC electro-osmosis and the electrochemistry of the fluid/electrode interface. We experimentally probe the electric-field parameters behind these electrokinetic phenomena, and demonstrate, with suitable choices of processing parameters, the ability to scalably produce large-area composites containing VACNTs at number densities up to 1010 nanotubes/cm2. This VACNT number density exceeds that of previous electric-field-fabricated composites by an order of magnitude, and the surface-area coverage of the 40 nm VACNTs is comparable to that of chemical-vapor-deposition-grown arrays of smaller-diameter nanotubes.

  7. Determination of the effective Young's modulus of vertically aligned carbon nanotube arrays: a simple nanotube-based varactor.

    Science.gov (United States)

    Olofsson, Niklas; Ek-Weis, Johan; Eriksson, Anders; Idda, Tonio; Campbell, Eleanor E B

    2009-09-23

    The electromechanical properties of arrays of vertically aligned multiwalled carbon nanotubes were studied in a parallel plate capacitor geometry. The electrostatic actuation was visualized using both optical microscopy and scanning electron microscopy, and highly reproducible behaviour was achieved for actuation voltages below the pull-in voltage. The walls of vertically aligned carbon nanotubes behave as solid cohesive units. The effective Young's modulus for the carbon nanotube arrays was determined by comparing the actuation results with the results of electrostatic simulations and was found to be exceptionally low, of the order of 1-10 MPa. The capacitance change and Q-factor were determined by measuring the frequency dependence of the radio-frequency transmission. Capacitance changes of over 20% and Q-factors in the range 100-10 were achieved for a frequency range of 0.2-1.5 GHz.

  8. Re-grown aligned carbon nanotubes with improved field emission.

    Science.gov (United States)

    Lim, Xiaodai; Zhu, Yanwu; Varghese, Binni; Gao, Xingyu; Wee, Andrew Thye Shen; Sow, Chorng-Haur

    2012-01-01

    In this work, a simple technique to improve the field emission property of multi-walled carbon nanotubes is presented. Re-grown multi-walled carbon nanotubes are grown on the same substrates after the as-grown multi-walled carbon nanotubes are transferred to other substrates using polydimethylsiloxane as intermediation. For the duration of the synthesis of the re-grown multi-walled carbon nanotubes, similar synthesis parameters used in growing the as-grown multi-walled carbon nanotubes are utilized. As a form of possible application, field emission studies show -2.6 times improvement in field enhancement factor and more uniform emission for the re-grown multi-walled carbon nanotubes. In addition, the turn-on field is reduced from 2.85 V/microm to 1.40 V/microm. Such significant improvements are attributed to new emission sites comprising of sharp carbonaceous impurities encompassing both tip and upper portion of the multi-walled carbon nanotubes. As such, this technique presents a viable route for the production of multi-walled carbon nanotubes with better field emission quality.

  9. Alignment of Multi-walled Carbon Nanotubes in Polyacrylonitrile Fibers by Mechanical Drawing

    Institute of Scientific and Technical Information of China (English)

    WANG Biao; WEN Zhi-wei; PENG Kun; WANG Hua-ping

    2010-01-01

    Polyacrylonitrile(PAN)/multi-waUed carbon nanotubes(MWNTs)narmcomposites were prepared by an in-situ polymerization method and the fibers from these composites were obtained by a wet-spinning process.The orientation behavior of MWNTs in the PAN fibers was investigated by X-ray diffraction and sound velocity methods.The dispersion and the alignment of the nanotubes were also studied by scanning electron microscopy.

  10. Fast growth of well-aligned ZnO nanowire arrays by a microwave heating method and their photocatalytic properties

    Science.gov (United States)

    Cao, Guangxia; Hong, Kunquan; Wang, Wenda; Liu, Liqing; Xu, Mingxiang

    2016-10-01

    The fast growth of aligned ZnO nanowire arrays with optimized structure is attractive for electrical and optical devices. In this paper, we report a controllable and rapid growth of ZnO nanowire arrays by a microwave-assisted hydrothermal method. When using different zinc salts as the precursors, the morphology of the samples changes a lot and the length growth rate is several times different. The growth mechanism is also investigated. It is found that the solution near neutral pH value is ideal for fast nanowire growth, in which the length of the nanowires increases linearly with growth time and the growth rate is over ten times faster than that in the traditional hydrothermal method. Therefore, aligned ZnO nanowire arrays can grow up to tens of microns in a few hours, while the density and sizes of these nanowires can be well controlled. The ZnO nanowire arrays used as photocatalysts present good photocatalytic performance to the degradation of methyl orange (MO) due to the large surface area. So this paper provides an effective method to obtain vertically aligned ZnO nanowire arrays for practical applications.

  11. Multi-walled carbon nanotube-supported metal-doped ZnO nanoparticles and their photocatalytic property.

    Science.gov (United States)

    Chen, C S; Liu, T G; Lin, L W; Xie, X D; Chen, X H; Liu, Q C; Liang, B; Yu, W W; Qiu, C Y

    2013-01-01

    A simple and versatile approach has been developed to synthesize multi-walled carbon nanotubes/metal-doped ZnO nanohybrid materials (MWNT/M-doped ZnO) by means of the co-deposition method. The experimental results illuminate that MWNTs can be modified by metal-doped ZnO nanoparticles at 450 °C, such as Mn, Mg, and Co elements. Furthermore, the MWNT/Mg-doped ZnO hybrids have been proven to have a high photocatalytic ability for methyl orange (MO), in which the degraded rate for MO reaches 100 % in 60 min. The enhancement in photocatalytic activity is attributed to the excellent electriconal property of MWNTs and Mg-doping. The resultant MWNT/Mg-doped ZnO nanohybrids have potential applications in photocatalysis and environmental protection.

  12. Zipping, entanglement, and the elastic modulus of aligned single-walled carbon nanotube films.

    Science.gov (United States)

    Won, Yoonjin; Gao, Yuan; Panzer, Matthew A; Xiang, Rong; Maruyama, Shigeo; Kenny, Thomas W; Cai, Wei; Goodson, Kenneth E

    2013-12-17

    Reliably routing heat to and from conversion materials is a daunting challenge for a variety of innovative energy technologies--from thermal solar to automotive waste heat recovery systems--whose efficiencies degrade due to massive thermomechanical stresses at interfaces. This problem may soon be addressed by adhesives based on vertically aligned carbon nanotubes, which promise the revolutionary combination of high through-plane thermal conductivity and vanishing in-plane mechanical stiffness. Here, we report the data for the in-plane modulus of aligned single-walled carbon nanotube films using a microfabricated resonator method. Molecular simulations and electron microscopy identify the nanoscale mechanisms responsible for this property. The zipping and unzipping of adjacent nanotubes and the degree of alignment and entanglement are shown to govern the spatially varying local modulus, thereby providing the route to engineered materials with outstanding combinations of mechanical and thermal properties.

  13. Aligned carbon nanotube with electro-catalytic activity for oxygen reduction reaction

    Science.gov (United States)

    Liu, Di-Jia; Yang, Junbing; Wang, Xiaoping

    2010-08-03

    A catalyst for an electro-chemical oxygen reduction reaction (ORR) of a bundle of longitudinally aligned carbon nanotubes having a catalytically active transition metal incorporated longitudinally in said nanotubes. A method of making an electro-chemical catalyst for an oxygen reduction reaction (ORR) having a bundle of longitudinally aligned carbon nanotubes with a catalytically active transition metal incorporated throughout the nanotubes, where a substrate is in a first reaction zone, and a combination selected from one or more of a hydrocarbon and an organometallic compound containing an catalytically active transition metal and a nitrogen containing compound and an inert gas and a reducing gas is introduced into the first reaction zone which is maintained at a first reaction temperature for a time sufficient to vaporize material therein. The vaporized material is then introduced to a second reaction zone maintained at a second reaction temperature for a time sufficient to grow longitudinally aligned carbon nanotubes over the substrate with a catalytically active transition metal incorporated throughout the nanotubes.

  14. Theoretical Study on Structural and Elastic Properties of ZnO Nanotubes

    Institute of Scientific and Technical Information of China (English)

    YUAN Peng-Fei; DING Ze-Jun; JU Xin

    2008-01-01

    @@ A theoretical investigation on the structural and elastic properties of ZnO nanotubes is carried out by using atomistic calculations based on an inter-atomic pair potential within the shell-model approach.The calculation results are presented for the bond length,bond angle,radius dilation,strain energy,Young modulus and Poisson ratio as a function of tube radius.For small tube radius these properties depend on the helicity of the tube,while for the tube radius larger than 6.0 (A),they are independent of the tube radius and helicity except for the strain energy which decreases with increasing tube radius.

  15. Novel ZnO nanostructures grown on carbon nanotubes by thermal evaporation

    Energy Technology Data Exchange (ETDEWEB)

    Chrissanthopoulos, A. [Department of Materials Science, University of Patras, Rio Patras GR-26504 (Greece)], E-mail: acrissan@upatras.gr; Baskoutas, S.; Bouropoulos, N. [Department of Materials Science, University of Patras, Rio Patras GR-26504 (Greece); Dracopoulos, V. [Foundation for Research and Technology, Hellas-Institute of Chemical Engineering and High Temperature Chemical Processes - FORTH/ICE-HT, P.O. Box 1414, GR-26504 Patras (Greece); Tasis, D. [Department of Materials Science, University of Patras, Rio Patras GR-26504 (Greece); Yannopoulos, S.N. [Foundation for Research and Technology, Hellas-Institute of Chemical Engineering and High Temperature Chemical Processes - FORTH/ICE-HT, P.O. Box 1414, GR-26504 Patras (Greece)

    2007-10-15

    We report on the formation of ZnO/carbon nanotubes heterostructures achieved by means of a thermal evaporation method. Scanning electron microscopy revealed that the main building block of the observed morphologies was the nanorod whose self-assembling resulted in various structures such as polypods and nano-hedgehogs, depending on various factors as well as the location of the ZnO-CNT junction. X-ray diffraction and photoluminescence spectroscopy were used to study the structure and optical properties of obtained nanostructures. Semi-empirical molecular orbital calculations gave evidence for the nature of the binding between ZnO and CNTs.

  16. Effect of aligned carbon nanotubes on electrical conductivity behaviour in polycarbonate matrix

    Indian Academy of Sciences (India)

    M M Larijani; E J Khamse; Z Asadollahi; M Asadi

    2012-06-01

    This article reports effects of alignment of embedded carbon nanotubes in a polycarbonate polymer matrix under magnetic, direct and alternating current electric fields on the electrical properties of the resulting nanocomposites. Composites consisting of different quantities of carbon nanotubes in a polycarbonate matrix have been prepared using a solution casting technique. The effects of field strength and nanotube concentration on the resulted network structure and conductivity of the composites were studied by in situ optical microscopy, transmission electron microscopy and four-point probe technique. The results showed that the composites prepared in the presence of field had better conductivity than those of as-prepared composites. It was also concluded that the application of alternating current electric field and magnetic field in this system led to the formation of relatively continuing networks while direct current electric field only prevented agglomeration of the carbon nanotubes in the polycarbonate matrix and created relatively uniform distribution of nanotubes in the matrix.

  17. Fabrication and Optimization of Vertically Aligned ZnO Nanorod Array-Based UV Photodetectors via Selective Hydrothermal Synthesis

    Science.gov (United States)

    Ko, Yeong Hwan; Nagaraju, Goli; Yu, Jae Su

    2015-08-01

    Vertically aligned ZnO nanorod array (NRA)-based ultraviolet (UV) photodetectors (PDs) were successfully fabricated and optimized via a facile hydrothermal process. Using a shadow mask technique, the thin ZnO seed layer was deposited between the patterned Au/Ti electrodes to bridge the electrodes. Thus, both the Au electrodes could be connected by the ZnO seed layer. As the sample was immersed into growth solution and heated at 90 °C, the ZnO NRAs were crystallized and vertically grown on the ZnO seed layer, thus creating a metal-semiconductor-metal PD structure. To investigate the size effect of ZnO NRAs on photocurrent, the PDs were readily prepared with different concentrations of growth solution. For the ZnO NRAs grown at 25 mM of concentration, the PD with 10 μm of channel width (i.e., gap distance between two electrodes) exhibited a high photocurrent of 1.91 × 10-4 A at an applied bias of 10 V under 365 nm of UV light illumination. The PD was optimized by adjusting the channel width. For 15 μm of channel width, a relatively high photocurrent on-off ratio of 37.4 and good current transient characteristics were observed at the same applied bias. These results are expected to be useful for cost-effective and practical UV PD applications.

  18. Fabrication and Optimization of Vertically Aligned ZnO Nanorod Array-Based UV Photodetectors via Selective Hydrothermal Synthesis.

    Science.gov (United States)

    Ko, Yeong Hwan; Nagaraju, Goli; Yu, Jae Su

    2015-12-01

    Vertically aligned ZnO nanorod array (NRA)-based ultraviolet (UV) photodetectors (PDs) were successfully fabricated and optimized via a facile hydrothermal process. Using a shadow mask technique, the thin ZnO seed layer was deposited between the patterned Au/Ti electrodes to bridge the electrodes. Thus, both the Au electrodes could be connected by the ZnO seed layer. As the sample was immersed into growth solution and heated at 90 °C, the ZnO NRAs were crystallized and vertically grown on the ZnO seed layer, thus creating a metal-semiconductor-metal PD structure. To investigate the size effect of ZnO NRAs on photocurrent, the PDs were readily prepared with different concentrations of growth solution. For the ZnO NRAs grown at 25 mM of concentration, the PD with 10 μm of channel width (i.e., gap distance between two electrodes) exhibited a high photocurrent of 1.91 × 10(-4) A at an applied bias of 10 V under 365 nm of UV light illumination. The PD was optimized by adjusting the channel width. For 15 μm of channel width, a relatively high photocurrent on-off ratio of 37.4 and good current transient characteristics were observed at the same applied bias. These results are expected to be useful for cost-effective and practical UV PD applications.

  19. Synthesis and characterization of well-aligned carbon nitrogen nanotubes by microwave plasma chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Well-aligned carbon nitrogen nanotube films have been synthesized successfully on mesoporous silica substrates by microwave plasma chemical vapor deposition (MWPCVD) method. Studies on their morphology, structure, and composition by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX), respectively, indicate that these nanotubes consist of linearly polymerized carbon nitrogen nanobells, and the nitrogen atoms have been doped into carbon netweork to form a new structure C1-xNx (x=0.16±0.01). X-ray photoelectron spectroscopy (XPS) results of the samples further demonstrate that carbon bonds covalently with nitrogen in all the carbon nitrogen nanotube films.

  20. Vertically aligned carbon nanotube field emitter arrays with Ohmic base contact to silicon by Fe-catalyzed chemical vapor deposition

    NARCIS (Netherlands)

    Morassutto, M.; Tiggelaar, Roald M.; Smithers, M.A.; Smithers, M.A.; Gardeniers, Johannes G.E.

    2016-01-01

    Abstract In this study, dense arrays of aligned carbon nanotubes are obtained by thermal catalytic chemical vapor deposition, using Fe catalyst dispersed on a thin Ta layer. Alignment of the carbon nanotubes depends on the original Fe layer thickness from which the catalyst dispersion is obtained by

  1. Aligned carbon nanotubes physics, concepts, fabrication and devices

    CERN Document Server

    Ren, Zhifeng; Wang, Yang

    2012-01-01

    This book surveys the physics and fabrication of carbon nanotubes and their applications in optics, electronics, chemistry and biotechnology. The text illustrates major fabrication methods in detail, particularly the most widely used PECVD growth techniques.

  2. Secondary nanotube growth on aligned carbon nanofibre arrays for superior field emission.

    Science.gov (United States)

    Watts, Paul C P; Lyth, Stephen M; Henley, Simon J; Silva, S Ravi P

    2008-04-01

    We report substantial improvement of the field emission properties from aligned carbon nanotubes grown on aligned carbon nanofibres by a two-stage plasma enhanced chemical vapour deposition (PECVD) process. The threshold field decreased from 15.0 to 3.6 V/microm after the secondary growth. The field enhancement factor increased from 240 to 1480. This technique allows for superior emission of electrons for carbon nanotube/nanofibre arrays grown directly on highly doped silicon for direct integration in large area displays.

  3. Photocatalytic methane decomposition over vertically aligned transparent TiO2 nanotube arrays

    DEFF Research Database (Denmark)

    In, Su-il; Nielsen, Morten Godtfred; Vesborg, Peter Christian Kjærgaard

    2011-01-01

    Vertically aligned transparent TiO2 nanotube arrays grown by the one-step anodic oxidation technique (on non-conductive supports such as Pyrex) and their photocatalytic performance for methane decomposition in a single-pass micro-fabricated reactor under UV light.......Vertically aligned transparent TiO2 nanotube arrays grown by the one-step anodic oxidation technique (on non-conductive supports such as Pyrex) and their photocatalytic performance for methane decomposition in a single-pass micro-fabricated reactor under UV light....

  4. Vertically aligned multiwalled carbon nanotubes as electronic interconnects.

    OpenAIRE

    Gopee, Vimal C.

    2017-01-01

    The drive for miniaturisation of electronic circuits provides new materials challenges for the electronics industry. Indeed, the continued downscaling of transistor dimensions, described by Moore’s Law, has led to a race to find suitable replacements for current interconnect materials to replace copper. Carbon nanotubes have been studied as a suitable replacement for copper due to its superior electrical, thermal and mechanical properties. One of the advantages of using carbon nanotubes is th...

  5. Self-Assembly of Semiconducting Single-Walled Carbon Nanotubes into Dense, Aligned Rafts

    CERN Document Server

    Wu, Justin; Antaris, Alexander; Choi, Charina L; Xie, Liming; Wu, Yingpeng; Diao, Shuo; Chen, Changxin; Chen, Yongsheng; Dai, Hongjie

    2013-01-01

    Single-walled carbon nanotubes are promising nanoelectronic materials but face long-standing challenges including production of pure semiconducting SWNTs and integration into ordered structures. Here, highly pure semiconducting single-walled carbon nanotubes are separated from bulk materials and self-assembled into densely aligned rafts driven by depletion attraction forces. Microscopy and spectroscopy revealed a high degree of alignment and a high packing density of ~100 tubes/micron within SWNT rafts. Field-effect transistors made from aligned SWNT rafts afforded short channel (~150 nm long) devices comprised of tens of purely semiconducting SWNTs derived from chemical separation within a < 1 micron channel width, achieving unprecedented high on-currents (up to ~120 microamperes per device) with high on/off ratios. The average on-current was ~ 3-4 microamperes per tube. The results demonstrated densely aligned high quality semiconducting SWNTs for integration into high performance nanoelectronics.

  6. Alignment of Nanoscale Single-Walled Carb on Nanotub es Strands

    Institute of Scientific and Technical Information of China (English)

    Danna Yang; Lin Wang; Xiaoxian Zhang; Dongwei Wang; Zhiqiang Shen; Sai Li

    2011-01-01

    Depositing single-walled carbon nanotubes (SWNTs) with controllable density, pattern and ori-entation on electrodes presents a challenge in today’s research. Here, we report a novel solvent evaporation method to align SWNTs in patterns having nanoscale width and micronscale length. SWNTs suspension has been introduced dropwise onto photoresist resin microchannels; and the capillary force can stretch and align SWNTs into strands with nanoscale width in the microchannels. Then these narrow and long aligned SWNTs patterns were successfully transferred to a pair of gold electrodes with different gaps to fabricate carbon nan-otube field-effect transistor (CNTFET). Moreover, the electrical performance of the CNTFET show that the SWNTs strands can bridge different gaps and fabricate good electrical performance CNTFET with ON/OFF ratio around 106. This result suggests a promising and simple strategy for assembling well-aligned SWNTs into CNTFET device with good electrical performance.

  7. A novel flexible nanogenerator made of ZnO nanoparticles and multiwall carbon nanotube.

    Science.gov (United States)

    Sun, Hui; Tian, He; Yang, Yi; Xie, Dan; Zhang, Yu-Chi; Liu, Xuan; Ma, Shuo; Zhao, Hai-Ming; Ren, Tian-Ling

    2013-07-07

    In this paper, a novel flexible nanogenerator (FNG) made of zinc-oxide (ZnO) nanoparticles (NPs) and multiwall-carbon nanotubes (MW-CNTs) is presented. In this structure, ZnO NPs and MW-CNTs are mixed with polydimethylsiloxane (PDMS) uniformly to form an entire flexible nanogenerator. Serial tests illustrate that the output voltage and power density are as high as 7.5 V and 18.75 μW per cycle, respectively. Furthermore, by foot stamp on the FNG, a peak voltage as high as 30 V can be generated. Comparing to the control samples, it is also proved that adding MW-CNTs into the matrix could significantly enhance the output voltage from 0.8 to 7.5 V. In summary, our work indicates that the realization of flexible nanogenerators made of ZnO NPs and MW-CNTs is technologically feasible, which may bring out some important and interesting applications in energy harvesting.

  8. Macroscopic Ensembles of Aligned Carbon Nanotubes in Bubble Imprints Studied by Polarized Raman Microscopy

    Directory of Open Access Journals (Sweden)

    Shota Ushiba

    2014-01-01

    Full Text Available We study the alignment of single-wall carbon nanotubes (SWCNTs in bubble imprints through polarized Raman microscopy. A hemispherical bubble containing SWCNTs is pressed against a glass substrate, resulting in an imprint of the bubble membrane with a coffee ring on the substrate. We find that macroscopic ensembles of aligned SWCNTs are obtained in the imprints, in which there are three patterns of orientations: (i azimuthal alignment on the coffee ring, (ii radial alignment at the edge of the membrane, and (iii random orientation at the center of the membrane. We also find that the alignment of SWCNTs in the imprints can be manipulated by spinning bubbles. The orientation of SWCNTs on the coffee ring is directed radially, which is orthogonal to the case of unspun bubbles. This approach enables one to align SWCNTs in large quantities and in a short time, potentially opening up a wide range of CNT-based electronic and optical applications.

  9. Synthesis of TiO2 nanotubes with ZnO nanoparticles to achieve antibacterial properties and stem cell compatibility

    Science.gov (United States)

    Liu, Wenwen; Su, Penglei; Chen, Su; Wang, Na; Ma, Yuanping; Liu, Yiran; Wang, Jinshu; Zhang, Zhenting; Li, Hongyi; Webster, Thomas J.

    2014-07-01

    To endow titanium (Ti) with antibacterial properties, different concentrations of zinc oxide (ZnO) nanoparticles were decorated on anodized titanium dioxide (TiO2) nanotubes by a simple hydrothermal treatment method. The particle sizes of ZnO, which were evenly distributed and tightly adherent to the walls of the Ti nanotubes, ranged from 20-50 nm. Results from this study showed that Zn was released from the TiO2 nanotubes in a constant, slow, and biologically inspired manner. Importantly, the results showed that the ZnO decorated TiO2 nanotubular samples inhibited Streptococcus mutants and Porphyromonas gingivalis growth compared to control unmodified Ti samples. Specifically, S. mutants and P. gingivalis growth were both reduced 45-85% on the ZnO decorated Ti samples compared to Ti controls after 7 days of culture. When examining the mechanism of action, it has been further found for the first time that the ZnO decorated Ti samples inhibited the expression of Streptococcus mutans bacterial adhesion genes. Lastly, the results showed that the same samples which decreased bacterial growth the most (0.015 M precursor Zn(NO3)2 samples) did not inhibit mesenchymal stem cell growth compared to Ti controls for up to 7 days. In summary, results from this study showed that compared to plain TiO2 nanotubes, TiO2 decorated with 0.015 M ZnO provided unprecedented antibacterial properties while maintaining the stem cell proliferation capacity necessary for enhancing the use of Ti in numerous medical applications, particularly in dentistry.

  10. Synthesis of TiO2 nanotubes with ZnO nanoparticles to achieve antibacterial properties and stem cell compatibility.

    Science.gov (United States)

    Liu, Wenwen; Su, Penglei; Chen, Su; Wang, Na; Ma, Yuanping; Liu, Yiran; Wang, Jinshu; Zhang, Zhenting; Li, Hongyi; Webster, Thomas J

    2014-08-07

    To endow titanium (Ti) with antibacterial properties, different concentrations of zinc oxide (ZnO) nanoparticles were decorated on anodized titanium dioxide (TiO2) nanotubes by a simple hydrothermal treatment method. The particle sizes of ZnO, which were evenly distributed and tightly adherent to the walls of the Ti nanotubes, ranged from 20-50 nm. Results from this study showed that Zn was released from the TiO2 nanotubes in a constant, slow, and biologically inspired manner. Importantly, the results showed that the ZnO decorated TiO2 nanotubular samples inhibited Streptococcus mutants and Porphyromonas gingivalis growth compared to control unmodified Ti samples. Specifically, S. mutants and P. gingivalis growth were both reduced 45-85% on the ZnO decorated Ti samples compared to Ti controls after 7 days of culture. When examining the mechanism of action, it has been further found for the first time that the ZnO decorated Ti samples inhibited the expression of Streptococcus mutans bacterial adhesion genes. Lastly, the results showed that the same samples which decreased bacterial growth the most (0.015 M precursor Zn(NO3)2 samples) did not inhibit mesenchymal stem cell growth compared to Ti controls for up to 7 days. In summary, results from this study showed that compared to plain TiO2 nanotubes, TiO2 decorated with 0.015 M ZnO provided unprecedented antibacterial properties while maintaining the stem cell proliferation capacity necessary for enhancing the use of Ti in numerous medical applications, particularly in dentistry.

  11. Designing aligned inorganic nanotubes at the electrode interface: towards highly efficient photovoltaic wires

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Tao; Qiu, Longbin; Yang, Zhibin; Peng, Huisheng [State Key Laboratory of Molecular, Engineering of Polymers, Department of Macromolecular Science and Laboratory of Advanced Materials, Fudan University, Shanghai (China); Kia, Hamid G. [Chemical Sciences and Materials Systems Lab, GM Global R and D, Warren, MI (United States)

    2012-09-04

    Aligned carbon and titanium dioxide nanotubes are designed at the electrode interface to improve the charge separation and transport. The resulting organic photovoltaic wire exhibits high power conversion efficiency. This flexible photovoltaic wire can be easily integrated into a textile by a conventional weaving technique. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Shear Alignment of Bola-Amphiphilic Arginine-Coated Peptide Nanotubes.

    Science.gov (United States)

    Hamley, Ian W; Burholt, Samuel; Hutchinson, Jessica; Castelletto, Valeria; da Silva, Emerson Rodrigo; Alves, Wendel; Gutfreund, Philipp; Porcar, Lionel; Dattani, Rajeev; Hermida-Merino, Daniel; Newby, Gemma; Reza, Mehedi; Ruokolainen, Janne; Stasiak, Joanna

    2017-01-09

    The bola-amphiphilic arginine-capped peptide RFL4RF self-assembles into nanotubes in aqueous solution. The nanostructure and rheology are probed by in situ simultaneous rheology/small-angle scattering experiments including rheo-SAXS, rheo-SANS, and rheo-GISANS (SAXS: small-angle X-ray scattering, SANS: small-angle neutron scattering, GISANS: grazing incidence small-angle neutron scattering). Nematic alignment of peptide nanotubes under shear is observed at sufficiently high shear rates under steady shear in either Couette or cone-and-plate geometry. The extent of alignment increases with shear rate. A shear plateau is observed in a flow curve measured in the Couette geometry, indicating the presence of shear banding above the shear rate at which significant orientation is observed (0.1-1 s(-1)). The orientation under shear is transient and is lost as soon as shear is stopped. GISANS shows that alignment at the surface of a cone-and-plate cell develops at sufficiently high shear rates, very similar to that observed in the bulk using the Couette geometry. A small isotope effect (comparing H2O/D2O solvents) is noted in the CD spectra indicating increased interpeptide hydrogen bonding in D2O, although this does not influence nanotube self-assembly. These results provide new insights into the controlled alignment of peptide nanotubes for future applications.

  13. Alignment of carbon nanotubes on pre-structured silicon by surface acoustic waves

    Energy Technology Data Exchange (ETDEWEB)

    Seemann, Klaus M; Ebbecke, Jens; Wixforth, Achim [Institut fuer Physik der Universitaet Augsburg, Universitaetsstrasse 1, D-86159 Augsburg (Germany)

    2006-09-14

    Carbon nanotubes have been deposited and aligned onto the pre-structured metal contacts of a silicon chip. Crucial for the deposition and alignment process are micro-fluidic flow fields combined with electric dipole fields generated by surface acoustic waves within a gap filled with an aqueous carbon nanotube suspension. This gap is formed when the pre-structured silicon chip is flipped onto the piezoelectric lithium niobate substrate, allowing for the generation of surface acoustic waves. The contacting probability of carbon nanotubes on the prestructured metal contacts has been found to be 37%. In combination with back-gates, these structures define three-terminal devices and the first current-voltage characteristics.

  14. Fabrication of Vertically Aligned Carbon Nanotube or Zinc Oxide Nanorod Arrays for Optical Diffraction Gratings.

    Science.gov (United States)

    Kim, Jeong; Kim, Sun Il; Cho, Seong-Ho; Hwang, Sungwoo; Lee, Young Hee; Hur, Jaehyun

    2015-11-01

    We report on new fabrication methods for a transparent, hierarchical, and patterned electrode comprised of either carbon nanotubes or zinc oxide nanorods. Vertically aligned carbon nanotubes or zinc oxide nanorod arrays were fabricated by either chemical vapor deposition or hydrothermal growth, in combination with photolithography. A transparent conductive graphene layer or zinc oxide seed layer was employed as the transparent electrode. On the patterned surface defined using photoresist, the vertically grown carbon nanotubes or zinc oxides could produce a concentrated electric field under applied DC voltage. This periodic electric field was used to align liquid crystal molecules in localized areas within the optical cell, effectively modulating the refractive index. Depending on the material and morphology of these patterned electrodes, the diffraction efficiency presented different behavior. From this study, we established the relationship between the hierarchical structure of the different electrodes and their efficiency for modulating the refractive index. We believe that this study will pave a new path for future optoelectronic applications.

  15. Laser-Assisted Simultaneous Transfer and Patterning of Vertically Aligned Carbon Nanotube Arrays on Polymer Substrates for Flexible Devices

    KAUST Repository

    In, Jung Bin

    2012-09-25

    We demonstrate a laser-assisted dry transfer technique for assembling patterns of vertically aligned carbon nanotube arrays on a flexible polymeric substrate. A laser beam is applied to the interface of a nanotube array and a polycarbonate sheet in contact with one another. The absorbed laser heat promotes nanotube adhesion to the polymer in the irradiated regions and enables selective pattern transfer. A combination of the thermal transfer mechanism with rapid direct writing capability of focused laser beam irradiation allows us to achieve simultaneous material transfer and direct micropatterning in a single processing step. Furthermore, we demonstrate that malleability of the nanotube arrays transferred onto a flexible substrate enables post-transfer tailoring of electric conductance by collapsing the aligned nanotubes in different directions. This work suggests that the laser-assisted transfer technique provides an efficient route to using vertically aligned nanotubes as conductive elements in flexible device applications. © 2012 American Chemical Society.

  16. Dry-Transfer of Aligned Multiwalled Carbon Nanotubes for Flexible Transparent Thin Films

    Directory of Open Access Journals (Sweden)

    Matthew Cole

    2012-01-01

    Full Text Available Herein we present an inexpensive facile wet-chemistry-free approach to the transfer of chemical vapour-deposited multiwalled carbon nanotubes to flexible transparent polymer substrates in a single-step process. By controlling the nanotube length, we demonstrate accurate control over the electrical conductivity and optical transparency of the transferred thin films. Uniaxial strains of up to 140% induced only minor reductions in sample conductivity, opening up a number of applications in stretchable electronics. Nanotube alignment offers enhanced functionality for applications such as polarisation selective electrodes and flexible supercapacitor substrates. A capacitance of 17 F/g was determined for supercapacitors fabricated from the reported dry-transferred MWCNTs with the corresponding cyclic voltagrams showing a clear dependence on nanotube length.

  17. Investigation on the Photoelectrocatalytic Activity of Well-Aligned TiO2 Nanotube Arrays

    Directory of Open Access Journals (Sweden)

    Xiaomeng Wu

    2012-01-01

    Full Text Available Well-aligned TiO2 nanotube arrays were fabricated by anodizing Ti foil in viscous F− containing organic electrolytes, and the crystal structure and morphology of the TiO2 nanotube array were characterized and analyzed by XRD, SEM, and TEM, respectively. The photocatalytic activity of the TiO2 nanotube arrays was evaluated in the photocatalytic (PC and photoelectrocatalytic (PEC degradation of methylene blue (MB dye in different supporting solutions. The excellent performance of ca. 97% for color removal was reached after 90 min in the PEC process compared to that of PC process which indicates that a certain external potential bias favors the promotion of the electrode reaction rate on TiO2 nanotube array when it is under illumination. In addition, it is found that PEC process conducted in supporting solutions with low pH and containing Cl− is also beneficial to accelerate the degradation rate of MB.

  18. Biofunctionalization of carbon nanotubes/chitosan hybrids on Ti implants by atom layer deposited ZnO nanostructures

    Science.gov (United States)

    Zhu, Yizhou; Liu, Xiangmei; Yeung, Kelvin W. K.; Chu, Paul K.; Wu, Shuilin

    2017-04-01

    One-dimensional (1D) nanostructures of ZnO using atomic layer deposition (ALD) on chitosan (CS) modified carbon nanotubes (CNTs) were first introduced onto the surfaces of biomedical implants. When the content of ZnO is not sufficient, CNTs can strengthen the antibacterial activity against E. coli and S. aureus by 8% and 39%, respectively. CS can improve the cytocompatibility of CNTs and ZnO. The amount of Zn content can be controlled by changing the cycling numbers of ALD processes. This hybrid coating can not only endow medical implants with high self-antibacterial efficacy against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) of over 73% and 98%, respectively, but also regulate the proliferation and osteogenic differentiation of osteoblasts by controlling the amount of ZnO.

  19. Effect of Particle Density on the Aligned Growth of Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    WANG Sheng-gao; WANG Jian-hua; HAN Jian-jun

    2004-01-01

    Aligned carbon nanotubes (CNTs) were prepared on Ni-coated Ni substrate by microwave plasma chemical vapor deposition (MWPCVD) with a mixture of methane and hydrogen gases at temperature of 550℃.The experimental results show a direct correlation between the alignment of CNTs and the density of the catalyst particles at low temperature.When the particle density is high enough,among CNTs there are strong interactions that can inhibit CNTs from growing randomly.The crowding effect among dense CNTs results in the aligned growth of CNTs at low temperature.

  20. Vertically aligned carbon nanotubes as anode and air-cathode in single chamber microbial fuel cells

    Science.gov (United States)

    Amade, R.; Moreno, H. A.; Hussain, S.; Vila-Costa, M.; Bertran, E.

    2016-10-01

    Electrode optimization in microbial fuel cells is a key issue to improve the power output and cell performance. Vertically aligned carbon nanotubes (VACNTs) grown on low cost stainless-steel mesh present an attractive approach to increase the cell performance while avoiding the use of expensive Pt-based materials. In comparison with non-aligned carbon nanotubes (NACNTs), VACNTs increase the oxygen reduction reaction taking place at the cathode by a factor of two. In addition, vertical alignment also increases the power density up to 2.5 times with respect to NACNTs. VACNTs grown at the anode can further improve the cell performance by increasing the electrode surface area and thus the electron transfer between bacteria and the electrode. The maximum power density obtained using VACNTs was 14 mW/m2 and 160 mV output voltage.

  1. Comparison of Two Types of Vertically Aligned ZnO NRs for Highly Efficient Polymer Solar Cells

    DEFF Research Database (Denmark)

    Gonzalez-Valls, Irene; Angmo, Dechan; Gevorgyan, Suren

    2013-01-01

    Vertically aligned ZnO nanorods (NR) are prepared by two different synthesesmethods and applied on polymer solar cells (PSCs). The ZnO electrodes work as the electron transport layer with the P3HT:PCBM blend acting as the active material. Several organic blend solution conditions are optimized......: concentration, solvent, and deposition speed. The effect of different NR electrode morphologies is analyzed on the solar cell performance and characterized by current–voltage curves and IPCE analyses. The photovoltaic performance of the solar cells was observed to be influenced by many factors, among them...... infiltration of the organic P3HT:PCBM blend within the ZnO NR layer. The infiltration of the active layer was monitored by cross section SEM and energy dispersive X-ray spectroscopy analyses. Our results show that higher power conversion efficiencies are achieved when shorter NRs lengths are applied. The best...

  2. Synthesis, characterization and functionalization of vertically aligned carbon nanotube arrays

    OpenAIRE

    2012-01-01

    Ankara : The Materials Science and Nanotechnology Program of the Graduate School of Engineering and Sciences of Bilkent University, 2012. Thesis (Ph. D.) -- Bilkent University, 2012. Includes bibliographical refences. In the last decade, there has been an increased interest on carbon nanotubes (CNTs) for various applications due to their unique structural, electronic, mechanical and chemical properties. Synthesis of CNTs is no more a challenge with the enhancements and diver...

  3. Preparation and characterization of aligned carbon nanotubes/polylactic acid composite fibers

    Energy Technology Data Exchange (ETDEWEB)

    Kong Yuxia; Yuan Jie [School of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Qiu Jun, E-mail: qiujun@tongji.edu.cn [School of Materials Science and Engineering, Tongji University, Shanghai 201804 (China); Key Laboratory of Advanced Civil Engineering Materials of Education of Ministry, Shanghai 201804 (China)

    2012-07-01

    Aligned functionalized multiwalled carbon nanotubes/polylactic acid (MWNTs-PCL/PLA) composite fibers were successfully prepared by electrospinning processing. The MWNTs bonded with the polycaprolactone chains exhibited excellent uniform dispersion in PLA solution by comparing with the acid-functionalized MWNTs and amino-functionalized MWNTs. Optical microscopy was used to study the aligned degree of the fibers and to investigate the influences of the electrodes distance on the alignment and structure of the fibers, and results showed that the best quality of aligned fibers with dense structure and high aligned degree were obtained at an electrodes distance of 3 cm. Moreover, the MWNTs embedded inside the MWNTs-PCL/PLA fibers displayed well orientation along the axes of the fibers, which was demonstrated by field emission scanning electron microscopy, transmission electron microscopy and Raman spectroscopy.

  4. On the growth and photocatalytic activity of the vertically aligned ZnO nanorods grafted by CdS shells

    Energy Technology Data Exchange (ETDEWEB)

    Zirak, M. [Department of Physics, Sharif University of Technology, P.O. Box 11555-9161, Tehran (Iran, Islamic Republic of); Moradlou, O. [Department of Chemistry, Faculty of Sciences, Alzahra University, P.O. Box 1993893973, Tehran (Iran, Islamic Republic of); Bayati, M.R. [Department of Materials Science and Engineering, NC State University, Raleigh, NC 27695-7907 (United States); Nien, Y.T. [Department of Materials Science and Engineering, National Formosa University, Huwei District, Taiwan (China); Moshfegh, A.Z., E-mail: moshfegh@sharif.edu [Department of Physics, Sharif University of Technology, P.O. Box 11555-9161, Tehran (Iran, Islamic Republic of); Institute of Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588-8969, Tehran (Iran, Islamic Republic of)

    2013-05-15

    We have studied systematically photocatalytic properties of the vertically aligned ZnO@CdS core–shell nanorods where the features were grown through a multistep procedure including sol–gel for the formation of ZnO seed layer, hydrothermal process to grow ZnO nanorods, and successive ion layer adsorption and reaction (SILAR) process to deposit CdS nanoshells onto the ZnO nanorods. Formation of the ZnO seed layer and vertically aligned ZnO nanorods (d ∼ 40 nm) with a hexagonal cross-section was confirmed by AFM and SEM imaging. Successful capping of ZnO nanorods with homogeneous CdS nanocrystallites (∼5 nm) was ascertained by HRTEM diffraction and imaging. Optical properties of the samples were also studied using UV–vis spectrophotometry. It was found that the absorption edge of the CdS shell has a red shift when its thickness increases. Photocatalytic activity of the samples was examined by photodecomposition of methylene blue under UV and visible lights where the maximum reaction rate constant was found to be 0.012 min{sup −1} under UV illumination and 0.007 min{sup −1} under visible light. The difference in catalytic activities of the ZnO@CdS core–shell nanorods under UV and visible irradiations was explained based upon the electronic structure as well as the arrangement of the energy levels in the ZnO@CdS core–shells. It is shown that the structure and photocatalytic efficiency of the samples can be tuned by manipulating the SILAR variables.

  5. On the growth and photocatalytic activity of the vertically aligned ZnO nanorods grafted by CdS shells

    Science.gov (United States)

    Zirak, M.; Moradlou, O.; Bayati, M. R.; Nien, Y. T.; Moshfegh, A. Z.

    2013-05-01

    We have studied systematically photocatalytic properties of the vertically aligned ZnO@CdS core-shell nanorods where the features were grown through a multistep procedure including sol-gel for the formation of ZnO seed layer, hydrothermal process to grow ZnO nanorods, and successive ion layer adsorption and reaction (SILAR) process to deposit CdS nanoshells onto the ZnO nanorods. Formation of the ZnO seed layer and vertically aligned ZnO nanorods (d ∼ 40 nm) with a hexagonal cross-section was confirmed by AFM and SEM imaging. Successful capping of ZnO nanorods with homogeneous CdS nanocrystallites (∼5 nm) was ascertained by HRTEM diffraction and imaging. Optical properties of the samples were also studied using UV-vis spectrophotometry. It was found that the absorption edge of the CdS shell has a red shift when its thickness increases. Photocatalytic activity of the samples was examined by photodecomposition of methylene blue under UV and visible lights where the maximum reaction rate constant was found to be 0.012 min-1 under UV illumination and 0.007 min-1 under visible light. The difference in catalytic activities of the ZnO@CdS core-shell nanorods under UV and visible irradiations was explained based upon the electronic structure as well as the arrangement of the energy levels in the ZnO@CdS core-shells. It is shown that the structure and photocatalytic efficiency of the samples can be tuned by manipulating the SILAR variables.

  6. Epitaxial Growth of Aligned and Continuous Carbon Nanofibers from Carbon Nanotubes.

    Science.gov (United States)

    Lin, Xiaoyang; Zhao, Wei; Zhou, Wenbin; Liu, Peng; Luo, Shu; Wei, Haoming; Yang, Guangzhi; Yang, Junhe; Cui, Jie; Yu, Richeng; Zhang, Lina; Wang, Jiaping; Li, Qunqing; Zhou, Weiya; Zhao, Weisheng; Fan, Shoushan; Jiang, Kaili

    2017-02-28

    Exploiting the superior properties of nanomaterials at macroscopic scale is a key issue of nanoscience. Different from the integration strategy, "additive synthesis" of macroscopic structures from nanomaterial templates may be a promising choice. In this paper, we report the epitaxial growth of aligned, continuous, and catalyst-free carbon nanofiber thin films from carbon nanotube films. The fabrication process includes thickening of continuous carbon nanotube films by gas-phase pyrolytic carbon deposition and further graphitization of the carbon layer by high-temperature treatment. As-fabricated nanofibers in the film have an "annual ring" cross-section, with a carbon nanotube core and a graphitic periphery, indicating the templated growth mechanism. The absence of a distinct interface between the carbon nanotube template and the graphitic periphery further implies the epitaxial growth mechanism of the fiber. The mechanically robust thin film with tunable fiber diameters from tens of nanometers to several micrometers possesses low density, high electrical conductivity, and high thermal conductivity. Further extension of this fabrication method to enhance carbon nanotube yarns is also demonstrated, resulting in yarns with ∼4-fold increased tensile strength and ∼10-fold increased Young's modulus. The aligned and continuous features of the films together with their outstanding physical and chemical properties would certainly promote the large-scale applications of carbon nanofibers.

  7. Rainbow channeling of protons in very short carbon nanotubes with aligned Stone–Wales defects

    Energy Technology Data Exchange (ETDEWEB)

    Ćosić, M., E-mail: mcosic@vinca.rs [Laboratory of Physics, Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia); Petrović, S. [Laboratory of Physics, Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001 Belgrade (Serbia); Bellucci, S. [INFN-Laboratori Nazionali di Frascati, Via E. Fermi 40, 00044 Frascati (Italy)

    2016-01-15

    In this paper proton channeling through armchair single-walled-carbon-nanotubes (SWCNTs) with aligned Stone–Wales defects has been investigated. The energy of the proton beam was 1 GeV, while the lengths of the SWCNTs have been varied from 200 nm up to 1000 nm. The linear density of aligned defects has been varied in the whole range, from minimally up to maximally possible values. Here are presented results of a detailed morphological analysis concerning: the formation, evolution and interaction of the nanotube rainbows. The potential of the SWCNT has been constructed from Molère’s expression of the Thomas–Fermi’s proton–carbon interaction-energy, using the approximation of the continuous atomic string. Trajectories of the channeled protons were obtained by solving the corresponding classical equations of motions. Distributions of the transmitted protons were obtained by the Monte-Carlo simulation. The shape of angular distributions has been explained in the framework of the theory of nanotube rainbows. The aim of this study is also to investigate the applicability of the proton rainbow channeling for the characterization of nanotubes with aligned Stone–Wales defects.

  8. Label-free electronic detection of bio-toxins using aligned carbon nanotubes.

    Science.gov (United States)

    Palaniappan, Al; Goh, W H; Fam, D W H; Rajaseger, G; Chan, C E Z; Hanson, B J; Moochhala, S M; Mhaisalkar, S G; Liedberg, B

    2013-05-15

    A facile route for sensitive label-free detection of bio-toxins using aligned single walled carbon nanotubes is described. This approach involves patterning of a catalyst on the surface of a quartz substrate using a sub-100 μm stripe-patterned polydimethylsiloxane stamp for aligned carbon nanotube generation followed by fabrication of field effect transistor (FET). Atomic force microscopy, field emission scanning electron microscopy and Raman spectroscopy are employed to characterize the synthesized nanotubes. Unlike previous reports, the adopted approach enables direct electronic detection of bio-toxins with sensitivities comparable to ELISA. As a proof of concept, the fabricated FET responds to nM concentration levels (with a LOD of ∼2 nM) of epsilon toxin produced by Clostridium perfringens and a prominent food toxin. This facile approach could be customized to detect other classes of toxins and biomarkers upon appropriate functionalization of the aligned carbon nanotubes. Finally, we demonstrate the use of the FET-platform for detection of toxin in more complex matrices such as orange juice.

  9. Rainbow channeling of protons in very short carbon nanotubes with aligned Stone-Wales defects

    Science.gov (United States)

    Ćosić, M.; Petrović, S.; Bellucci, S.

    2016-01-01

    In this paper proton channeling through armchair single-walled-carbon-nanotubes (SWCNTs) with aligned Stone-Wales defects has been investigated. The energy of the proton beam was 1 GeV, while the lengths of the SWCNTs have been varied from 200 nm up to 1000 nm. The linear density of aligned defects has been varied in the whole range, from minimally up to maximally possible values. Here are presented results of a detailed morphological analysis concerning: the formation, evolution and interaction of the nanotube rainbows. The potential of the SWCNT has been constructed from Molère's expression of the Thomas-Fermi's proton-carbon interaction-energy, using the approximation of the continuous atomic string. Trajectories of the channeled protons were obtained by solving the corresponding classical equations of motions. Distributions of the transmitted protons were obtained by the Monte-Carlo simulation. The shape of angular distributions has been explained in the framework of the theory of nanotube rainbows. The aim of this study is also to investigate the applicability of the proton rainbow channeling for the characterization of nanotubes with aligned Stone-Wales defects.

  10. Enhanced field-emission from a mixture of carbon nanotubes, ZnO tetrapods and conductive particles.

    Science.gov (United States)

    Wei, Lei; Xiaobing, Zhang; Zhiwei, Zhao; Jing, Chen; Yiping, Cui; Baoping, Wang

    2012-08-01

    We report the enhancement of field-emission current from a mixture of carbon nanotubes, ZnO tetrapod-like nano structures, and conductive particles. Carbon nanotubes are deposited on the electrode as the field emitters. A MgO layer is printed around the cathode electrode, and ZnO tetrapod-like nano structures are deposited on this layer for the generation of secondary emission electrons. A few conductive particles are also distributed on the MgO layer by spraying or screen-printing. These conductive particles enhance the transverse electric field around the cathode electrode. Consequently, more primary electrons emitted from the carbon nanotubes bombard on the ZnO tetrapods, and secondary emission electrons and scattered electrons are yielded. Finally, the field-emission current is enhanced obviously. As experimental results shown, a high field-emission current about 32 mA in a direct current emission mode has been obtained from a 0.5 cm2 emission site when an electric field of 9 V/microm is applied between cathode and anode. Compared with a conventional carbon nanotube cathode, the field-emission current has been improved about 80%.

  11. Adaptive Neuro-Fuzzy Modeling of Mechanical Behavior for Vertically Aligned Carbon Nanotube Turfs

    Institute of Scientific and Technical Information of China (English)

    Mohammad A1-Khedher; Charles Pezeshki; Jeanne McHale; GFritz Knorr

    2011-01-01

    Several characterization methods have been developed to investigate the mechanical and structural properties of vertically aligned carbon nanotubes (VACNTs). Establishing analytical models at nanoscale to interpret these properties is complicated due to the nonuniformity and irregularity in quality of as-grown samples.In this paper, we propose a new methodology to investigate the correlation between indentation resistance of multi-wall carbon nanotube (MWCNT) turfs, Raman spectra and the geometrical properties of the turf structure using adaptive neuro-fuzzy phenomenological modeling. This methodology yields a novel approach for modeling at the nanoscale by evaluating the effect of structural morphologies on nanomaterial properties using Raman spectroscopy.

  12. Highly aligned carbon nanotube forests coated by superconducting NbC.

    Science.gov (United States)

    Zou, G F; Luo, H M; Baily, S; Zhang, Y Y; Haberkorn, N F; Xiong, J; Bauer, E; McCleskey, T M; Burrell, A K; Civale, L; Zhu, Y T; Macmanus-Driscoll, J L; Jia, Q X

    2011-08-16

    The formation of carbon nanotube and superconductor composites makes it possible to produce new and/or improved functionalities that the individual material does not possess. Here we show that coating carbon nanotube forests with superconducting niobium carbide (NbC) does not destroy the microstructure of the nanotubes. NbC also shows much improved superconducting properties such as a higher irreversibility and upper critical field. An upper critical field value of ~5 T at 4.2 K is much greater than the 1.7 T reported in the literature for pure bulk NbC. Furthermore, the aligned carbon nanotubes induce anisotropy in the upper critical field, with a higher upper critical field occurring when the magnetic field is parallel to the carbon nanotube growth direction. These results suggest that highly oriented carbon nanotubes embedded in superconducting NbC matrix can function as defects and effectively enhance the superconducting properties of the NbC.

  13. Integration and characterization of aligned carbon nanotubes on metal/silicon substrates and effects of water

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yong; Li Ruying; Liu Hao [Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON. N6A 5B9 (Canada); Sun Xueliang, E-mail: xsun@eng.uwo.ca [Department of Mechanical and Materials Engineering, University of Western Ontario, London, ON. N6A 5B9 (Canada); Merel, Philippe; Desilets, Sylvain [Defence Research and Development Canada- Valcartier, 2459 Boulevard Pie-XI nord, Quebec, QC G3J 1X5 (Canada)

    2009-02-15

    We report here a facile way to grow aligned multi-walled carbon nanotubes (MWCNTs) on various metal (e.g. gold, tungsten, vanadium and copper)/silicon electrically conductive substrates by aerosol-assisted chemical vapor deposition (AACVD). Without using any buffer layers, integration of high quality MWCNTs to the conductive substrates has been achieved by introducing appropriate amount of water vapor into the growth system. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) determination indicate tidy morphology and narrow diameter distribution of the nanotubes as well as promising growth rate suitable for industrial applications. Raman spectra analysis illustrates that the structural order and purity of the nanotubes are significantly improved in the presence of water vapor. The growth mechanism of the nanotubes has been discussed. It is believed that water vapor plays a key role in the catalyst-substrate interaction and nucleation of the carbon nanotubes on the conductive substrates. This synthesis approach is expected to be extended to other catalyst-conductive substrate systems and provide some new insight in the direct integration of carbon nanotubes onto conductive substrates, which promises great potential for applications in electrical interconnects, contacts for field emitters, and other electronic nanodevices.

  14. Reverse capillary flow of condensed water through aligned multiwalled carbon nanotubes

    Science.gov (United States)

    Yun, Jongju; Jeon, Wonjae; Alam Khan, Fakhre; Lee, Jinkee; Baik, Seunghyun

    2015-06-01

    Molecular transport through nanopores has recently received considerable attention as a result of advances in nanofabrication and nanomaterial synthesis technologies. Surprisingly, water transport investigations through carbon nanochannels resulted in two contradicting observations: extremely fast transport or rejection of water molecules. In this paper, we elucidate the mechanism of impeded water vapor transport through the interstitial space of aligned multiwalled carbon nanotubes (aligned-MWCNTs)—capillary condensation, agglomeration, reverse capillary flow, and removal by superhydrophobicity at the tip of the nanotubes. The origin of separation comes from the water’s phase change from gas to liquid, followed by reverse capillary flow. First, the saturation water vapor pressure is decreased in a confined space, which is favorable for the phase change of incoming water vapor into liquid drops. Once continuous water meniscus is formed between the nanotubes by the adsoprtion and agglomeration of water molecules, a high reverse Laplace pressure is induced in the mushroom-shaped liquid meniscus at the entry region of the aligned-MWCNTs. The reverse Laplace pressure can be significantly enhanced by decreasing the pore size. Finally, the droplets pushed backward by the reverse Laplace pressure can be removed by superhydrophobicity at the tip of the aligned-MWCNTs. The analytical analysis was also supported by experiments carried out using 4 mm-long aligned-MWCNTs with different intertube distances. The water rejection rate and the separation factor increased as the intertube distance decreased, resulting in 90% and 10, respectively, at an intertube distance of 4 nm. This mechanism and nanotube membrane may be useful for energy-efficient water vapor separation and dehumidification.

  15. Effect of boric acid composition on the properties of ZnO thin film nanotubes and the performance of dye-sensitized solar cell (DSSC)

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, M.Y.A., E-mail: mohd.yusri@ukm.edu.my; Roza, L.; Umar, A.A., E-mail: akrajas@ukm.edu.my; Salleh, M.M.

    2015-11-05

    The effect of boric acid (H{sub 3}BO{sub 3}) composition at constant concentration of hexamethylenetetramine (HMT) and zinc nitrate (Zn(NO{sub 3}){sub 2}) on the morphology, thickness, elemental composition, optical absorption, structure, photoluminescence of ZnO nanotubes has been investigated. The performance of the DSSC utilizing the ZnO samples has also been studied. It was found that the structure, thickness, elemental composition, optical absorption and morphology of ZnO nanostructure are significantly affected by the concentration of H{sub 3}BO{sub 3}. The diameter and thickness of ZnO nanotubes decreases as the composition of H{sub 3}BO{sub 3} increases. The DSSC utilizing ZnO nanotubes synthesized at 2 wt. % H{sub 3}BO{sub 3} performs the highest J{sub SC} and η of 2.67 mA cm{sup −2} and 0.29%, respectively. The highest performance of the device is due to the highest optical absorption of ZnO nanotubes sample and lowest charge interfacial resistance. - Graphical abstract: Nyquist plots of the DSSCs utilizing ZnO nanotubes prepared at various boric acid compositions. - Highlights: • Boron was doped into ZnO films by adding H{sub 3}BO{sub 3} into the growth solution. • Diameter and thickness of ZnO nanotubes decreases with the composition of H{sub 3}BO{sub 3}. • The DSSC performs the highest J{sub SC} and η of 2.67 mA cm{sup −2} and 0.29%, respectively. • This is due to high specific surface area and low charge interfacial resistance.

  16. Large-scale horizontally aligned ZnO microrod arrays with controlled orientation, periodic distribution as building blocks for chip-in piezo-phototronic LEDs.

    Science.gov (United States)

    Guo, Zhen; Li, Haiwen; Zhou, Lianqun; Zhao, Dongxu; Wu, Yihui; Zhang, Zhiqiang; Zhang, Wei; Li, Chuanyu; Yao, Jia

    2015-01-27

    A novel method of fabricating large-scale horizontally aligned ZnO microrod arrays with controlled orientation and periodic distribution via combing technology is introduced. Horizontally aligned ZnO microrod arrays with uniform orientation and periodic distribution can be realized based on the conventional bottom-up method prepared vertically aligned ZnO microrod matrix via the combing method. When the combing parameters are changed, the orientation of horizontally aligned ZnO microrod arrays can be adjusted (θ = 90° or 45°) in a plane and a misalignment angle of the microrods (0.3° to 2.3°) with low-growth density can be obtained. To explore the potential applications based on the vertically and horizontally aligned ZnO microrods on p-GaN layer, piezo-phototronic devices such as heterojunction LEDs are built. Electroluminescence (EL) emission patterns can be adjusted for the vertically and horizontally aligned ZnO microrods/p-GaN heterojunction LEDs by applying forward bias. Moreover, the emission color from UV-blue to yellow-green can be tuned by investigating the piezoelectric properties of the materials. The EL emission mechanisms of the LEDs are discussed in terms of band diagrams of the heterojunctions and carrier recombination processes.

  17. Titania nanotube arrays surface-modified with ZnO for enhanced photocatalytic applications

    Energy Technology Data Exchange (ETDEWEB)

    Nageri, Manoj; Kalarivalappil, Vijila; Vijayan, Baiju K.; Kumar, Viswanathan, E-mail: vkumar10@yahoo.co.in

    2016-05-15

    Highlights: • Heterostructures of TNA/ZnO synthesised through potentiostatic anodisation followed by hydrothermal method. • Evaluation of morphological features of the heterostructure with hydrothermal processing time. • Correlation of photocatalytic activity of the hetrostructure with its morphology and surface texture. - Abstract: Well ordered titanium dioxide nanotube arrays (TNA) of average diameter 129 nm and wall thickness of 25 nm were fabricated through potentiostatic anodisation of titanium (Ti) metal substrates. Such TNA were subsequently surface-modified with various amounts of zinc oxide (ZnO) nanopowders using hydrothermal technique to obtain heterogeneous TNA/ZnO nanostructures. The crystalline phase and surface microstructure of the heterostructures were determined by X-ray diffraction, Raman spectroscopy and scanning electron microscopy respectively. The morphology of the heterostructures strongly depended on the hydrothermal conditions employed. The photocatalytic activity of the heterostructures have also been investigated and correlated with their surface morphology and texture.

  18. Synthesis of mesoporous multiwall ZnO nanotubes by replicating silk and application for enzymatic biosensor.

    Science.gov (United States)

    Zhao, Minggang; Li, Zhenglong; Han, Ziqi; Wang, Ke; Zhou, Yu; Huang, Jingyun; Ye, Zhizhen

    2013-11-15

    A facial biotemplate-directed synthetic route for fabricating mesoporous multiwall ZnO nanotubes (ZnO-MMNTs) was proposed. Owing to the mesoporous multiwall based matrix, one dimensional (1D) tubes based channels and high isoelectric point (IEP), the prepared ZnO-MMNTs are wonderful platform to immobilize glucose oxidase (GOx) for glucose biosensing. Scale-adaptive cells are constructed to hold enzymes molecules, maintain enzymatic activity and keep stability. The prepared enzymatic electrode (chitosan/GOx/ZnO/Au) exhibits high sensitivity (47.2 μA mM(-1)cm(-2)), very fast response (ZnO-MMNTs are promising material for enzyme assembly and other biological applications.

  19. Woven Glass Fiber Composites with Aligned Carbon Nanotube Sheet Interlayers

    Directory of Open Access Journals (Sweden)

    Hardik Bhanushali

    2016-01-01

    Full Text Available This investigation describes the design, fabrication, and testing of woven glass fiber reinforced epoxy matrix laminates with aligned CNT sheets integrated between plies in order to improve the matrix dominated through thickness properties such as the interlaminar fracture toughness at ply interfaces. Using aligned CNT sheets allows for a concentration of millimeter long CNTs at the most likely point of laminate failure. Mode I and Mode II interlaminar fracture toughness of various CNT modified samples were investigated using double cantilever beam (DCB and end notched flexure (ENF experiments, respectively. Short beam strength (SBS and in-plane tensile properties of the CNT modified samples were also investigated. Moderate improvement was observed in Mode I and Mode II fracture toughness at crack initiation when aligned CNT sheets with a basis weight of 0.354 g/m2 were used to modify the ply interface. No compromise in the in-plane mechanical properties of the laminate was observed and very little improvement was observed in the shear related short beam strength of the CNT modified laminates as compared to the control samples. Integration of aligned CNT sheets into the composite laminate imparted in-plane and through thickness electrical properties into the nonconductive glass fiber reinforced epoxy composite laminates.

  20. Robust Nanogenerator Based on Vertically Aligned ZnO Nanorods Using Copper Substrate

    Directory of Open Access Journals (Sweden)

    Naveed Sheikh

    2013-01-01

    Full Text Available We report the growth of well-aligned ZnO nanorods that were successfully synthesized on copper (Cu substrate by using a simple hydrothermal method at low temperature leading to a robust large area nanogenerator (NG based on cost effective Cu electrode which could enable energy harvest from the walking motions. First, the seed layer of gold (Au has been deposited by plasma sputtering. Then, the growth process of nanorods was carried out in a sealed chemical bath. The lengths of nanorods 5-6 μm were achieved. The longer and bigger nanorods produced a surface with larger contact area and higher roughness. The larger contact area improves the absorption rate of incident light and the rougher surface strengthens the scattering effect. The surfaces were characterized by X-ray diffraction (XRD, scanning electron microscope (SEM, and energy dispersive X-ray spectroscopy (EDX. Then, Cu substrate was used for the development of high-output NG. Twenty-seven NGs were developed with maximum output voltage that exceeded to 1.8 V and maximum output current that exceeded to 148 nA. The structural simulation of nanorod has also been performed in ANSYS. The Cu substrate-based NG provides a feasible technique for effectively converting mechanical energies to electrical energy from external force.

  1. Robust nonsticky superhydrophobicity by the tapering of aligned ZnO nanorods.

    Science.gov (United States)

    Tian, Jian; Zhang, Yaping; Zhu, Jie; Yang, Zhongzhen; Gao, Xuefeng

    2014-04-04

    The robust nonsticky superhydrophobicity of aligned nanoneedle films is reported. A facile, efficient, cheap, and available method based on the diffusion-limited crystal growth principle is proposed for controlling the tapering of ZnO nanorods, the profiles of which can be tuned effectively by synergetic control over reaction time and temperature in an extremely strong alkaline reaction system. The synthesized nanoneedle, nanopencil, and nanorod arrays are chosen for studying the effects of nanoscale topography on anti-droplet-sticking ability. After silanization, all of them show excellent quasi-static anti-droplet-stickiness, and water adhesion along the normal and lateral directions can be greatly reduced by the tapering of nanorods and eliminated by sharp nanoneedles. However, their antisticking stability is distinct under the droplet impact: the nanoneedle sample is still nonsticky but the nanorod sample loses its antisticking ability. Only ensuring the liquid/air interface is in the suspended nonwetting state is insufficient to obtain robust nonsticky surfaces, which also require extremely low solid-liquid van der Waals attraction.

  2. Low temperature carving of ZnO nanorods into nanotubes for dye-sensitized solar cell application

    Energy Technology Data Exchange (ETDEWEB)

    Dehghan Nayeri, Fatemeh, E-mail: F.d.nayeri@ut.ac.ir; Kolahdouz, Mohammadreza; Asl-Soleimani, Ebrahim; Mohajerzadeh, S.

    2015-06-05

    Highlights: • Large scale arrays of highly oriented ZnO NTs have been fabricated and investigated. • The DSSCs made of these 2.5 μm NRs and NTs resulted in conversion efficiencies of 0.34% and 0.9%, respectively. • EIS measurements have demonstrated that the NTs could acquire a higher electron lifetime compared to NRs. • Twofold electron lifetime electron accompanied by half electron transport time for ZnO NTs compared to NRs. - Abstract: High aspect ratio zinc oxide (ZnO) nanotubes (NT) were synthesized based on a two-steps approach. In the first step, ZnO nanorod (NR) arrays were prepared by chemical bath deposition from an aqueous of zinc nitrate. In the second step, the cores of ZnO NRs were carved selectively in a KCl solution, resulting in the formation of a tubular structure. The influence of KCL concentration, temperature, and immersion time on the ZnO NT formation process was completely characterized and investigated. 12.5 μm NRs and NTs have been utilized to manufacture dye-sensitized solar cells (DSSCs) and as a result, conversion efficiencies of 1.06% and 2.87% were obtained, respectively. Electrochemical impedance spectroscopy measurements have demonstrated that the NTs could acquire a higher electron lifetime compared to NRs which causes a faster electron collection. The overall improvement in NT-based DSSC performance demonstrates a new approach to enhance the efficiency of dye-sensitized solar cells.

  3. Electron field emission characteristics of different surface morphologies of ZnO nanostructures coated on carbon nanotubes.

    Science.gov (United States)

    Li, Kuan-Wei; Lian, Huan-Bin; Cai, Jhen-Hong; Wang, Yao-Te; Lee, Kuei-Yi

    2011-12-01

    The optimal carbon nanotube (CNT) bundles with a hexagonal arrangement were synthesized using thermal chemical vapor deposition (TCVD). To enhance the electron field emission characteristics of the pristine CNTs, the zinc oxide (ZnO) nanostructures coated on CNT bundles using another TCVD technique. Transmission electron microscopy (TEM) images showed that the ZnO nanostructures were grown onto the CNT surface uniformly, and the surface morphology of ZnO nanostructures varied with the distance between the CNT bundle and the zinc acetate. The results of field emissions showed that the ZnO nanostructures grown onto the CNTs could improve the electron field emission characteristics. The enhancement of field emission characteristics was attributed to the increase of emission sites formed by the nanostructures of ZnO grown onto the CNT surface, and each ZnO nanostructure could be regarded as an individual field emission site. In addition, ZnO-coated CNT bundles exhibited a good emission uniformity and stable current density. These results demonstrated that ZnO-coated CNTs is a promising field emitter material.

  4. Growth of catalyst-assisted and catalyst-free horizontally aligned single wall carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ibrahim, Imad [IFW Dresden, P.O. Box 270116, 01171 Dresden (Germany); Technische Universitaet Dresden, 01062 Dresden (Germany); Bachmatiuk, Alicja; Ruemmeli, Mark H.; Wolff, Ulrike; Popov, Alexey; Buechner, Bernd [IFW Dresden, P.O. Box 270116, 01171 Dresden (Germany); Boltalina, Olga [Colorado State University, Fort Collins, 80523 Colorado (United States); Cuniberti, Gianaurelio [Technische Universitaet Dresden, 01062 Dresden (Germany)

    2011-11-15

    Here, we report the growth of homogenously horizontally aligned single wall carbon nanotubes on stable temperature cut single crystal quartz using chemical vapor deposition with controllable yield and length from binary metallic mixtures as well as fullerene derivatives. We manage the yield and length of the as-grown tubes on stable temperature cut single crystal quartz by controlling the surface roughness of the support substrates by thermal treatment in air. Carbon caps derived from pre-treated fullerenes are also explored for their potential to nucleate growth of single wall carbon nanotubes without the need of a catalyst particle. Exohedrally functionalized fullerenes are apparently better nucleators than C{sub 60} fullerenes. Yield of the as-grown single wall carbon nanotubes on thermally annealed ST-quartz substrates. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Synthesis and characterization of well-aligned carbon nitrogen nanotubes by microwave plasma chemical vapor deposition

    Institute of Scientific and Technical Information of China (English)

    马旭村; 徐贵昌; 王恩哥

    2000-01-01

    Well-aligned carbon nitrogen nanotube films have been synthesized successfully on meso-porous silica substrates by microwave plasma chemical vapor deposition (MWPCVD) method. Studies on their morphology, structure, and composition by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDX), respectively, indicate that these nanotubes consist of linearly polymerized carbon nitrogen nanobells, and the nitrogen atoms have been doped into carbon netweork to form a new structure C1-xNx( x = 0.16±0.01). X-ray photoelectron spectroscopy (XPS) results of the samples further demonstrate that carbon bonds cova-lently with nitrogen in all the carbon nitrogen nanotube films.

  6. Dynamics of capillary infiltration of liquids into a highly aligned multi-walled carbon nanotube film.

    Science.gov (United States)

    Boncel, Sławomir; Walczak, Krzysztof Z; Koziol, Krzysztof K K

    2011-01-01

    The physical compatibility of a highly aligned carbon nanotube (HACNT) film with liquids was established using a fast and convenient experimental protocol. Two parameters were found to be decisive for the infiltration process. For a given density of nanotube packing, the thermodynamics of the infiltration process (wettability) were described by the contact angle between the nanotube wall and a liquid meniscus (θ). Once the wettability criterion (θ capillarity for a steady process (Lucas-Washburn law), where the nanoscale capillary force, here supported by gravity, is compensated by viscous drag. This most general theory of capillarity can be applied in a prediction of both wettability of HACNT films and the dynamics of capillary rise in the intertube space in various technological applications.

  7. Effect of TiO2 thickness on nanocomposited aligned ZnO nanorod/TiO2 for dye-sensitized solar cells

    Science.gov (United States)

    Saurdi, I.; Shafura, A. K.; Azhar, N. E. A.; Ishak, A.; Malek, M. F.; Alrokayan, A. H. Salman; Khan, Haseeb A.; Mamat, M. H.; Rusop, M.

    2016-07-01

    The TiO2 films were deposited on glass substrate at different thicknesses with different deposition frequencies (1, 2, 3 and 4 times) using spin coating technique and their structural properties were investigated. Subsequently, the nanocomposited aligned ZnO nanorods and TiO2 were formed by deposited the TiO2 on top of aligned ZnO Nanorod on ITO-coated glass at different thicknesses using the same method of TiO2 deposited on glass substrate. The nanocomposited aligned ZnO nanorod/TiO2 were coated with different thicknesses of 900µm, 1815µm, 2710µm, 3620µm and ZnO without TiO2. The dye-sensitized solar cells were fabricated from the nanocomposited aligned ZnO nanorod/TiO2 with thickness of 900µm, 1815µm, 2710µm and 3620µm and ZnO without TiO2 and their photovoltaic properties of the DSSCs were investigated. From the solar simulator measurement the solar energy conversion efficiency (η) of 2.543% under AM 1.5 was obtained for the ZnO nanorod/TiO2 photoanode-2710µm Dye-Sensitized solar cell.

  8. Preparation and Characterization of Highly Aligned Carbon Nanotubes/Polyacrylonitrile Composite Nanofibers

    Directory of Open Access Journals (Sweden)

    Yanhua Song

    2017-01-01

    Full Text Available In the electrospinning process, a modified parallel electrode method (MPEM, conducted by placing a positively charged ring between the needle and the parallel electrode collector, was used to fabricate highly aligned carbon nanotubes/polyacrylonitrile (CNTs/PAN composite nanofibers. Characterizations of the samples—such as morphology, the degree of alignment, and mechanical and conductive properties—were investigated by a combination of scanning electron microscopy (SEM, transmission electron microscopy (TEM, universal testing machine, high-resistance meter, and other methods. The results showed the MPEM could improve the alignment and uniformity of electrospun CNTs/PAN composite nanofibers, and enhance their mechanical and conductive properties. This meant the successful preparation of highly aligned CNT-reinforced PAN nanofibers with enhanced physical properties, suggesting their potential application in appliances and communication areas.

  9. Pulse gas alignment and AFM manipulation of single-wall carbon nanotube

    Institute of Scientific and Technical Information of China (English)

    TIAN XiaoJun; WANG YueChao; XI Ning; DONG ZaiLi; TUNG Steve

    2008-01-01

    In the fabrication process of nanoelectronic device arrays based on single-wall carbon nanotube (SWCNT), oriented alignment of SWCNTs and property modification of metallic SWCNTs in the array are the key problems to be solved. Pulse gas alignment with substrate downward tilt is proposed to realize the controllable alignment of SWCNTs. Experimental results demonstrate that 84% SWCNTs are aligned in -15°- 15° angular to the pulse gas direction. A modified nanomanipulation technology based on atomic force microscope (AFM) is utilized to perform various kinds of SWCNT manipulation, such as SWCNT separation from the "Y" CNT, catalyst removal from the SWCNT end, continual nano buckles fabrication on SWCNT and even stretching to break, which provides a feasible way to modify the size, shape and the electrical property of SWCNTs.

  10. Effects of Temperature and Catalyst Concentration on the Growth of Aligned Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    BAI Xiaodong; LI Dan; WANG Ye; LIANG Ji

    2005-01-01

    The effects of preheating and pyrolysis temperatures and catalyst concentration on the synthesis of aligned carbon nanotubes (CNTs) using ferrocene as the catalyst and xylene as the carbon source in chemical vapor deposition were experimentally studied. The as-grown aligned CNTs were characterized by field emission scanning electron microscopy, transmission electronic microscopy, high-resolution transmission electronic microscopy, and Raman spectroscopy. The growth rate, the diameters, and the degree of crystal structure of the aligned CNTs were all found to depend on the preheating and pyrolysis temperatures and the catalyst concentration. The optimized conditions for the growth of aligned CNTs resulted in a rapid growth rate of 20.4 μm/min, with the CNTs having a good, uniform crystal structure, and clean surfaces with little amorphous carbon. The results also show that higher preheating temperatures and lower ferrocene concentrations favor the growth of single-walled CNTs.

  11. Fabrication of Aligned-Carbon-Nanotube-Composite Paper with High and Anisotropic Conductivity

    Directory of Open Access Journals (Sweden)

    Yuki Fujitsuka

    2012-01-01

    Full Text Available A functional carbon-nanotube (CNT-composite paper is described in which the CNTs are aligned. This “aligned-CNT composite paper” is a flexible composite material that has CNT functionality (e.g., electrical conductivity despite being a paper. An advanced fabrication method was developed to overcome the problem of previous CNT-composite papers, that is, reduced conductivity due to random CNT alignment. Aligning the CNTs by using an alternating current (AC field was hypothesized to increase the electrical conductivity and give the paper an anisotropic characteristic. Experimental results showed that a nonionic surfactant was not suitable as a CNT dispersant for fabricating aligned-CNT composite paper and that catechin with its six-membered rings and hydrophilic groups was suitable. Observation by scanning electron microscopy of samples prepared using catechin showed that the CNTs were aligned in the direction of the AC field on the paper fibers. Measurement of the electric conductivity showed that the surface resistance was different between the direction of the aligned CNTs (high conductivity and that of verticality (low. The conductivity of the aligned-CNT-composite paper samples was higher than that of nonaligned samples. This unique and functional paper, which has high and anisotropic conductivity, is applicable to a conductive material to control the direction of current.

  12. Optimal Synthesis of Horizontally Aligned Single-Walled Carbon Nanotubes and Their Biofunctionalization for Biosensing Applications

    Directory of Open Access Journals (Sweden)

    Dawoon Jung

    2016-01-01

    Full Text Available As an influential candidate for highly sensitive biomolecule sensor, which can capture disease related biomolecules, carbon nanotube is useful material due to its unique properties. To adopt as a sensing platform, it is strongly needed to find optimal refined synthetic condition. In order to find the optimal synthetic conditions of horizontally aligned CNT, we performed quantity control of the mixed gases of H2 and CH4 injected. We successfully find that the formation of amorphous-like carbon was critically affected by some gas condition such as the flow rate of injected gases and ratios of gas mixture. Moreover, it should be noted that our horizontally aligned carbon nanotube array platform developed would offer another potential in developing nanoscale light source, where light emission results from electron-hole carrier recombination.

  13. Towards large scale aligned carbon nanotube composites: an industrial safe-by-design and sustainable approach

    Science.gov (United States)

    Boulanger, P.; Belkadi, L.; Descarpentries, J.; Porterat, D.; Hibert, E.; Brouzes, A.; Mille, M.; Patel, S.; Pinault, M.; Reynaud, C.; Mayne-L'Hermite, M.; Decamps, J. M.

    2013-04-01

    We present the main results demonstrating the feasibility of high surface (> A4 format size) semi-industrial fabrication of composites embedding VACNT in organic matrices. The process of growing VACNT exhibits several advantages regarding safety issues: integrating de facto a safe collecting procedure on the substrate, avoiding additional preparation steps and simplifying handling and protection by impregnation into a matrix. The following steps of the overall process: VACNT carpet functionalization, alignment control and impregnation, can be processed on-line in a closed and safe continuous process and lead to dramatically reduced direct nanotube exposure for workers and users. This project opens the route to a continuous, roll-to-roll, safer, cost-effective and green industrial process to manufacture composites with controlled and aligned greener "black" carbon nanotubes.

  14. Low Temperature Growth of Vertically Aligned Carbon Nanotubes via Floating Catalyst Chemical Vapor Deposition Method

    Institute of Scientific and Technical Information of China (English)

    M.R. Atiyan; D.R. Awang Biak; F. Ahmadun; I.S. Ahamad; F. Mohd Yasin; H. Mohamed Yusoff

    2011-01-01

    Synthesis of carbon nanotubes (CNTs) below 600℃ using supporting catalyst chemical vapor deposition method was reported by many research groups. However, the floating catalyst chemical vapor deposition received less attention due to imperfect nanotubes produced. In this work, the effects of varying the preheating temperature on the synthesis of CNT were investigated. The reaction temperature was set at 570℃. The preheating set temperature was varied from 150 to 400℃ at 50℃ interval. Three O-ring shape heating mantels were used as heating source for the preheater. In situ monitoring device was used to observe the temperature profile in the reactor. Benzene and ferrocene were used as the carbon source and catalyst precursor, respectively. Vertically aligned CNTs were synthesized when the preheating temperature was set at 400℃. When the preheating temperature was increased up to 400℃, both the length and the alignment of CNTs produced were improved.

  15. Vertically aligned carbon nanotubes for sensing unidirectional fluid flow

    Energy Technology Data Exchange (ETDEWEB)

    Kiani, Keivan, E-mail: k_kiani@kntu.ac.ir

    2015-05-15

    From applied mechanics points of view, potential application of ensembles of single-walled carbon nanotubes (SWCNTs) as fluid flow sensors is aimed to be examined. To this end, useful nonlocal analytical and numerical models are developed. The deflection of the ensemble of SWCNTs at the tip is introduced as a measure of its sensitivity. The influences of the length and radius of the SWCNT, intertube distance, fluid flow velocity, and distance of the ensemble from the leading edge of the rigid base on the deflection field of the ensemble are comprehensively examined. The obtained results display how calibration of an ensemble of SWCNTs can be methodically carried out in accordance with the characteristics of the ensemble and the external fluid flow.

  16. Aligned, ultralong single-walled carbon nanotubes: from synthesis, sorting, to electronic devices.

    Science.gov (United States)

    Liu, Zhongfan; Jiao, Liying; Yao, Yagang; Xian, Xiaojun; Zhang, Jin

    2010-06-04

    Aligned, ultralong single-walled carbon nanotubes (SWNTs) represent attractive building blocks for nanoelectronics. The structural uniformity along their tube axis and well-ordered two-dimensional architectures on wafer surfaces may provide a straightforward platform for fabricating high-performance SWNT-based integrated circuits. On the way towards future nanoelectronic devices, many challenges for such a specific system also exist. This Review summarizes the recent advances in the synthesis, identification and sorting, transfer printing and manipulation, device fabrication and integration of aligned, ultralong SWNTs in detail together with discussion on their major challenges and opportunities for their practical application.

  17. Tritrichomonas foetus adhere to superhydrophilic vertically aligned multi-walled carbon nanotube surface

    Energy Technology Data Exchange (ETDEWEB)

    Moreira Machado, Susane [Laboratorio de Biologia Celular e Tecidual, Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraiba, Av. Shishima Hifumi 2911, 12244-000, Sao Jose dos Campos, SP (Brazil); Oliveira Lobo, Anderson, E-mail: loboao@yahoo.com [Laboratorio de Nanotecnologia Biomedica (NanoBio), Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraiba, Av. Shishima Hifumi 2911, Sao Jose dos Campos, 12244-000, SP (Brazil); Laboratorio de Espectroscopia Vibracional Biomedica, Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraiba, Avenida Shishima Hifumi, 2911, CEP 12244-000, Sao Jose dos Campos, SP (Brazil); Bueno Loureiro Sapucahy, Ariel [Laboratorio de Biologia Celular e Tecidual, Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraiba, Av. Shishima Hifumi 2911, 12244-000, Sao Jose dos Campos, SP (Brazil); Marciano, Fernanda Roberta [Laboratorio de Nanotecnologia Biomedica (NanoBio), Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraiba, Av. Shishima Hifumi 2911, Sao Jose dos Campos, 12244-000, SP (Brazil); Laboratorio de Espectroscopia Vibracional Biomedica, Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraiba, Avenida Shishima Hifumi, 2911, CEP 12244-000, Sao Jose dos Campos, SP (Brazil); Corat, Evaldo Jose [Instituto Nacional de Pesquisas Espaciais (INPE), Laboratorio Associado de Sensores e Materiais (LAS), Av. dos Astronautas 1758, Sao Jose dos Campos, 12227-010 SP (Brazil); Soares da Silva, Newton [Laboratorio de Biologia Celular e Tecidual, Instituto de Pesquisa e Desenvolvimento, Universidade do Vale do Paraiba, Av. Shishima Hifumi 2911, 12244-000, Sao Jose dos Campos, SP (Brazil)

    2011-10-10

    For the first time, we show that Tritrichomonas foetus can adhere on superhydrophilic vertically aligned carbon nanotubes (VACNT) films. Scanning electron microscopy shows an unusual adhesion with a higher membrane filopodium projection in all directions, directly attached to superhydrophilic VACNT tips. Highlights: {yields} This is a new method to study the T. foetus adhesion mechanism. {yields} SEM images and interfacial adhesion force show a high adhesion level. {yields} It is very important for future understanding mechanism adhesion and protein expression.

  18. Aligned carbon nanotube-Pt composite fuel cell catalyst by template electrodeposition

    Energy Technology Data Exchange (ETDEWEB)

    Nagle, Lorraine C.; Rohan, James F. [Tyndall National Institute, University College Cork, Lee Maltings, Prospect Row, Cork (Ireland)

    2008-10-15

    Solution phase deposition of aligned arrays of carbon nanotubes (CNTs) in a platinum (Pt) matrix composite is demonstrated. The catalyst material is electrodeposited in an oriented manner on the nanoscale using anodised aluminium oxide (AAO) templates. The catalyst performance of the composite for the oxidation of methanol is shown. The carbon monoxide (CO) tolerance is increased and the catalyst function is improved by minimising the influence of adsorbed CO on the kinetics of the methanol oxidation reaction. (author)

  19. Dielectrophoresis Aligned Single-Walled Carbon Nanotubes as pH Sensors

    OpenAIRE

    2011-01-01

    Here we report the fabrication and characterization of pH sensors using aligned single-walled carbon nanotubes (SWNTs). The SWNTs are dispersed in deionized (DI) water after chemical functionalization and filtration. They are deposited and organized on silicon substrates with the dielectrophoresis process. Electrodes with “teeth”-like patterns—fabricated with photolithography and wet etching—are used to generate concentrated electric fields and strong dielectrophoretic forces for the SWNTs to...

  20. Controlled Synthesis and Functionalization of Vertically-Aligned Carbon Nanotubes for Multifunctional Applications

    Science.gov (United States)

    2015-05-07

    with, we synthesized a vertically-aligned multiwalled carbon nanotube (VA-CNT) forest through chemical vapor deposition of ethylene onto a silicon...reduction peak attributable to the reduction of ethylene carbonate appeared at 1.2 V and then disappeared in the following scans due to the...Batteries (Adv. Mater. 2014, 26, 7317.) By simply ball-milling graphite with chlorine (Cl2), bromine (Br2) or iodine (I2), for instance, we have

  1. Field emission luminescence of nanodiamonds deposited on the aligned carbon nanotube array

    OpenAIRE

    Fedoseeva, Yu. V.; Bulusheva, L. G.; Okotrub, A. V.; Kanygin, M. A.; Gorodetskiy, D. V.; Asanov, I. P.; Vyalikh, D. V.; A. P. Puzyr; Bondar, V. S.

    2015-01-01

    Detonation nanodiamonds (NDs) were deposited on the surface of aligned carbon nanotubes (CNTs) by immersing a CNT array in an aqueous suspension of NDs in dimethylsulfoxide (DMSO). The structure and electronic state of the obtained CNT?ND hybrid material were studied using optical and electron microscopy and Infrared, Raman, X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy. A non-covalent interaction between NDs and CNT and preservation of vertical orientation of...

  2. Aligned Carbon Nanotube Reinforcement of Aerospace Carbon Fiber Composites: Substructural Strength Evaluation for Aerostructure Applications

    OpenAIRE

    Guzman de Villoria, Roberto; Ydrefors, L.; Hallander, P.; Ishiguro, Kyoko; Nordin, P.; Wardle, Brian L.

    2012-01-01

    Vertically aligned carbon nanotubes (VACNTs) are placed between all plies in an aerospace carbon fiber reinforced plastic laminate (unidirectional plies, [(0/90/±45)2]s) to reinforce the interlaminar region in the z-direction. Significant improvement in Mode I and II interlaminar toughness have been observed previously. In this work, several substructural in-plane strength tests relevant to aerostructures were undertaken: bolt/tension-bearing, open hole compression, and L-shape laminate be...

  3. Structure and Thermal Properties of Polymer Composites from Infiltrated Aligned Multiwall Carbon Nanotubes and Fibers

    Science.gov (United States)

    Ivanov, Ilia; Puretzky, A. A.; Eres, G.; Lance, M. J.; Jesse, S.; Geohegan, David

    2004-03-01

    Structural and thermal properties measurements were performed for millimeters-long, vertically aligned multiwall carbon nanotubes (VA-MWNTs) and their polymer composites. As-grown bundles of VA-MWNTs were tested on an Instron universal testing machine for breaking load and elongation, in order to understand and test their continuity. Polymer composites were obtained by infiltrating VA-MWNT arrays with aminoepoxy resin, preserving their alignment. The thermal properties of these composites were tested using a Xenon flash lamp thermal diffusivity system. Aligned VA-MWNT in aminoepoxy at less than 2 wt. higher thermal diffusivities than randomly-oriented CNT fibers at loadings of 40 wt.improvements by a factor of 20 compared to the pure polymer. Similar measurements on continuous pure carbon nanotube fibers (using single and multi wall nanotubes) and their polymer composites will also be discussed. This research was sponsored by NASA-Langley Research Center, DARPA, the U.S. Department of Energy under contract DE-AC05-00OR22725 with the Oak Ridge National Laboratory, managed by UT-Battelle, LLC , and the Laboratory-Directed Research and Development Program at ORNL.

  4. Screw-dislocation-driven growth of ZnO nanotubes seeded by self-perpetuating spirals during hydrothermal processing

    Science.gov (United States)

    Kim, Sojin; Kang, Hyon Chol

    2016-09-01

    We report the effects of precursor concentration on the characteristics of ZnO nanostructures during hydrothermal processing. Self-perpetuating surface spirals are fabricated at concentrations of 0.25 and 0.5 M, with samples grown at concentrations of 0.05 and 0.125 M exhibiting ZnO nanorods. This can be explained by a change in the growth mode from an initial columnar growth to a screw-dislocation-driven growth with decreased supersaturation. The screw dislocations nucleate at the V-shaped valleys of the columnar boundaries during the intermediate stage. We demonstrate that continuous screw-dislocation-driven growth leads to the formation of ZnO nanotubes having Burger's vectors of 1.45 nm.

  5. Electrical bistabilities and operating mechanisms of memory devices fabricated utilizing ZnO quantum dot-multi-walled carbon nanotube nanocomposites

    Science.gov (United States)

    Li, Fushan; Son, Dong Ick; Cho, Sung Hwan; Kim, Tae Whan

    2009-05-01

    Transmission electron microscopy images showed that the ZnO quantum dots (QDs) were conjugated with multi-walled carbon nanotubes (MWCNTs). Bistable memories utilizing an ensemble of the ZnO QD-MWCNT heterostructures were developed and the storage capability of the devices was significantly enhanced due to the conjugation of the ZnO QDs and the MWCNTs. Operating mechanisms of memory devices fabricated utilizing the ZnO QD-MWCNT heterostructures are described on the basis of the current-voltage results. The memory devices exhibited excellent environmental stability at ambient conditions.

  6. Synergistic toughening of composite fibres by self-alignment of reduced graphene oxide and carbon nanotubes

    Science.gov (United States)

    Shin, Min Kyoon; Lee, Bommy; Kim, Shi Hyeong; Lee, Jae Ah; Spinks, Geoffrey M.; Gambhir, Sanjeev; Wallace, Gordon G.; Kozlov, Mikhail E.; Baughman, Ray H.; Kim, Seon Jeong

    2012-01-01

    The extraordinary properties of graphene and carbon nanotubes motivate the development of methods for their use in producing continuous, strong, tough fibres. Previous work has shown that the toughness of the carbon nanotube-reinforced polymer fibres exceeds that of previously known materials. Here we show that further increased toughness results from combining carbon nanotubes and reduced graphene oxide flakes in solution-spun polymer fibres. The gravimetric toughness approaches 1,000 J g-1, far exceeding spider dragline silk (165 J g-1) and Kevlar (78 J g-1). This toughness enhancement is consistent with the observed formation of an interconnected network of partially aligned reduced graphene oxide flakes and carbon nanotubes during solution spinning, which act to deflect cracks and allow energy-consuming polymer deformation. Toughness is sensitive to the volume ratio of the reduced graphene oxide flakes to the carbon nanotubes in the spinning solution and the degree of graphene oxidation. The hybrid fibres were sewable and weavable, and could be shaped into high-modulus helical springs.

  7. Title: Using Alignment and 2D Network Simulations to Study Charge Transport Through Doped ZnO Nanowire Thin Film Electrodes

    KAUST Repository

    Phadke, Sujay

    2011-09-30

    Factors affecting charge transport through ZnO nanowire mat films were studied by aligning ZnO nanowires on substrates and coupling experimental measurements with 2D nanowire network simulations. Gallium doped ZnO nanowires were aligned on thermally oxidized silicon wafer by shearing a nanowire dispersion in ethanol. Sheet resistances of nanowire thin films that had current flowing parallel to nanowire alignment direction were compared to thin films that had current flowing perpendicular to nanowire alignment direction. Perpendicular devices showed ∼5 fold greater sheet resistance than parallel devices supporting the hypothesis that aligning nanowires would increase conductivity of ZnO nanowire electrodes. 2-D nanowire network simulations of thin films showed that the device sheet resistance was dominated by inter-wire contact resistance. For a given resistivity of ZnO nanowires, the thin film electrodes would have the lowest possible sheet resistance if the inter-wire contact resistance was one order of magnitude lower than the single nanowire resistance. Simulations suggest that the conductivity of such thin film devices could be further enhanced by using longer nanowires. Solution processed Gallium doped ZnO nanowires are aligned on substrates using an innovative shear coating technique. Nanowire alignment has shown improvement in ZnO nanowire transparent electrode conductivity. 2D network simulations in conjunction with electrical measurements have revealed different regimes of operation of nanowire thin films and provided a guideline for improving electrical performance of nanowire electrodes. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Aligned carbon nanotube-silicon sheets: a novel nano-architecture for flexible lithium ion battery electrodes.

    Science.gov (United States)

    Fu, Kun; Yildiz, Ozkan; Bhanushali, Hardik; Wang, Yongxin; Stano, Kelly; Xue, Leigang; Zhang, Xiangwu; Bradford, Philip D

    2013-09-25

    Aligned carbon nanotube sheets provide an engineered scaffold for the deposition of a silicon active material for lithium ion battery anodes. The sheets are low-density, allowing uniform deposition of silicon thin films while the alignment allows unconstrained volumetric expansion of the silicon, facilitating stable cycling performance. The flat sheet morphology is desirable for battery construction.

  9. Quantum dot decorated aligned carbon nanotube bundles for a performance enhanced photoswitch

    Science.gov (United States)

    Sreejith, Sivaramapanicker; Hansen, Reinack; Joshi, Hrishikesh; Kutty, R. Govindan; Liu, Zheng; Zheng, Lianxi; Yang, Jinglei; Zhao, Yanli

    2016-04-01

    Photoactive materials that are triggered by the irradiation of light to generate an electrical response provide an ecofriendly platform to afford efficient power sources and switches. A chemical assembly of well-known elements with aligned carbon nanotube bundles is reported here, which was employed to form an efficient photo-induced charge transfer device. The primary elements of this device are ultra-long multi-walled carbon nanotube (MWCNT) bundles, polyaniline (PANI) thin film coating, and CdSe quantum dots (QDs). Highly ordered and horizontally aligned MWCNT bundles were coated with PANI to enhance charge transfer properties of active QDs in this platform. The obtained device (CdSe-MWCNT@PANI) constructed on a silicon base exhibits highly efficient power conversion capabilities owing to the aligned MWCNT bundle assisted enhanced charge transport pathways generated within the device. The device also shows a short circuit current density (Jsc) of 9.81 mA cm-2 and an open circuit voltage (Voc) of 0.46 V. The power conversion efficiency (PCE) of the device is 5.41%, and the current response is quite stable, highly responsive, and reproducible.Photoactive materials that are triggered by the irradiation of light to generate an electrical response provide an ecofriendly platform to afford efficient power sources and switches. A chemical assembly of well-known elements with aligned carbon nanotube bundles is reported here, which was employed to form an efficient photo-induced charge transfer device. The primary elements of this device are ultra-long multi-walled carbon nanotube (MWCNT) bundles, polyaniline (PANI) thin film coating, and CdSe quantum dots (QDs). Highly ordered and horizontally aligned MWCNT bundles were coated with PANI to enhance charge transfer properties of active QDs in this platform. The obtained device (CdSe-MWCNT@PANI) constructed on a silicon base exhibits highly efficient power conversion capabilities owing to the aligned MWCNT bundle assisted

  10. Oxygen-promoted catalyst sintering influences number density, alignment, and wall number of vertically aligned carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Wenbo; Li, Jinjing; Polsen, Erik S.; Oliver, C. Ryan; Zhao, Yikun; Meshot, Eric R.; Barclay, Michael; Fairbrother, D. Howard; Hart, A. John; Plata, Desiree L.

    2017-01-01

    A lack of synthetic control and reproducibility during vertically aligned carbon nanotube (CNT) synthesis has stifled many promising applications of organic nanomaterials. Oxygen-containing species are particularly precarious in that they have both beneficial and deleterious effects and are notoriously difficult to control. Here, we demonstrated diatomic oxygen's ability, independent of water, to tune oxide-supported catalyst thin film dewetting and influence nanoscale (diameter and wall number) and macro-scale (alignment and density) properties for as-grown vertically aligned CNTs. In particular, single- or few-walled CNT forests were achieved at very low oxygen loading, with single-to-multi-walled CNT diameters ranging from 4.8 ± 1.3 nm to 6.4 ± 1.1 nm over 0–800 ppm O2, and an expected variation in alignment, where both were related to the annealed catalyst morphology. Morphological differences were not the result of subsurface diffusion, but instead occurred via Ostwald ripening under several hundred ppm O2, and this effect was mitigated by high H2 concentrations and not due to water vapor (as confirmed in O2-free water addition experiments), supporting the importance of O2 specifically. Further characterization of the interface between the Fe catalyst and Al2O3 support revealed that either oxygen-deficit metal oxide or oxygen-adsorption on metals could be functional mechanisms for the observed catalyst nanoparticle evolution. Taken as a whole, our results suggest that the impacts of O2 and H2 on the catalyst evolution have been underappreciated and underleveraged in CNT synthesis, and these could present a route toward facile manipulation of CNT forest morphology through control of the reactive gaseous atmosphere alone.

  11. Highly dense and perfectly aligned single-walled carbon nanotubes fabricated by diamond wire drawing dies.

    Science.gov (United States)

    Liu, Guangtong; Zhao, Yuanchun; Deng, Ke; Liu, Zheng; Chu, Weiguo; Chen, Jingran; Yang, Yanlian; Zheng, Kaihong; Huang, Haibo; Ma, Wenjun; Song, Li; Yang, Haifang; Gu, Changzhi; Rao, Guanghui; Wang, Chen; Xie, Sishen; Sun, Lianfeng

    2008-04-01

    We have developed a low-cost and effective method to align single-walled carbon nanotubes (SWNTs) using a series of diamond wire drawing dies. The obtained SWNTs are highly dense and perfectly aligned. X-ray diffraction (XRD) indicates that the highly dense and perfectly aligned SWNTs (HDPA-SWNTs) form a two-dimensional triangular lattice with a lattice constant of 19.62 A. We observe a sharp (002) reflection in the XRD pattern, which should be ascribed to an intertube spacing 3.39 A of adjacent SWNTs. Raman spectra reveal that the radical breath mode (RBM) of SWNTs with larger diameter in the HDPA-SWNTs is suppressed compared with that of as-grown SWNTs. The HDPA-SWNTs have a large density, approximately 1.09 g/cm 3, and a low resistivity, approximately 2 m Omega cm, at room temperature, as well as a large response to light illumination.

  12. Preparation of hierarchically aligned carbon nanotube films using the Langmuir-Blodgett technique.

    Science.gov (United States)

    Lee, Jae-Hyeok; Kang, Won-Seok; Nam, Gwang-Hyeon; Choi, Sung-Wook; Kim, Jae-Ho

    2009-12-01

    Hierarchically-aligned single-walled carbon nanotube (SWNT) films over large areas were fabricated by using Langmuir-Blodgett (LB) technique. Thiophenyl-modified SWNTs spreading solution in chloroform was prepared through amidation reaction of oxidized SWNTs. The resulting SWNTs were found to form stable colloidal suspensions in organic solvents, such as chloroform, which is a suitable solvent for the LB application. The compression of the thiophenyl-modified SWNTs spread onto the water surface of an LB trough leading to a uniform SWNT Langmuir monolayer, where SWNTs were aligned parallel to the trough barrier. Optical anisotropy of SWNTs LB films on quartz substrate was confirmed by polarized UV-Vis/NIR spectroscopic measurement. Moreover, the electrical conductivity of the resulting SWNT films, which were parallel to the tube axis, was found to be approximately 15 times higher than those that were perpendicular to the axis, reflecting anisotropic electrical properties due to the uniaxial alignment of individual SWNT bundles.

  13. TiO2 nanotube composite layers as delivery system for ZnO and Ag nanoparticles - an unexpected overdose effect decreasing their antibacterial efficacy.

    Science.gov (United States)

    Roguska, A; Belcarz, A; Pisarek, M; Ginalska, G; Lewandowska, M

    2015-06-01

    Enhancement of biocompatibility and antibacterial properties of implant materials is potentially beneficial for their practical value. Therefore, the use of metallic and metallic oxide nanoparticles as antimicrobial coatings components which induce minimized antibacterial resistance receives currently particular attention. In this work, TiO2 nanotubes layers loaded with ZnO and Ag nanoparticles were designed for biomedical coatings and delivery systems and evaluated for antimicrobial activity. TiO2 nanotubes themselves exhibited considerable and diameter-dependent antibacterial activity against planktonic Staphylococcus epidermidis cells but favored bacterial adhesion. Loading of nanotubes with moderate amount of ZnO nanoparticles significantly diminished S. epidermidis cell adhesion and viability just after 1.5h contact with modified surfaces. However, an increase of loaded ZnO amount unexpectedly altered the structure of nanoparticle-nanolayer, caused partial closure of nanotube interior and significantly reduced ZnO solubility and antibacterial efficacy. Co-deposition of Ag nanoparticles enhanced the antibacterial properties of synthesized coatings. However, the increase of ZnO quantity on Ag nanoparticles co-deposited surfaces favored the adhesion of bacterial cells. Thus, ZnO/Ag/TiO2 nanotube composite layers may be promising delivery systems for combating post-operative infections in hard tissue replacement procedures. However, the amount of loaded antibacterial agents must be carefully balanced to avoid the overdose and reduced efficacy.

  14. Efficiency improvement of InGaP/GaAs/Ge solar cells by hydrothermal-deposited ZnO nanotube structure.

    Science.gov (United States)

    Chung, Chen-Chen; Tran, Binh Tinh; Lin, Kung-Liang; Ho, Yen-Teng; Yu, Hung-Wei; Quan, Nguyen-Hong; Chang, Edward Yi

    2014-01-01

    In this paper, a zinc oxide (ZnO) nanotube, fabricated by the hydrothermal growth method on triple-junction (T-J) solar cell devices to enhance efficiency, is investigated. Compared to those of bare T-J solar cells (without antireflection (AR) coating) and solar cells with Si3N4 AR coatings, the experimental results show that the T-J solar cells, which use a ZnO nanotube as an AR coating, have the lowest reflectance in the short wavelength spectrum. The ZnO nanotube has the lowest light reflection among all experimental samples, especially in the range of 350 to 500 nm from ultraviolet (UV) to visible light. It was found that a ZnO nanotube can enhance the conversion efficiency by 4.9%, compared with a conventional T-J solar cell. The Si3N4 AR coatings also enhance the conversion efficiency by 3.2%.The results show that a cell with ZnO nanotube coating could greatly improve solar cell performances.

  15. Polymer-derived ceramic composite fibers with aligned pristine multiwalled carbon nanotubes.

    Science.gov (United States)

    Sarkar, Sourangsu; Zou, Jianhua; Liu, Jianhua; Xu, Chengying; An, Linan; Zhai, Lei

    2010-04-01

    Polymer-derived ceramic fibers with aligned multiwalled carbon nanotubes (MWCNTs) are fabricated through the electrospinning of polyaluminasilazane solutions with well-dispersed MWCNTs followed by pyrolysis. Poly(3-hexylthiophene)-b-poly (poly (ethylene glycol) methyl ether acrylate) (P3HT-b-PPEGA), a conjugated block copolymer compatible with polyaluminasilazane, is used to functionalize MWCNT surfaces with PPEGA, providing a noninvasive approach to disperse carbon nanotubes in polyaluminasilazane chloroform solutions. The electrospinning of the MWCNT/polyaluminasilazane solutions generates polymer fibers with aligned MWCNTs where MWCNTs are oriented along the electrospun jet by a sink flow. The subsequent pyrolysis of the obtained composite fibers produces ceramic fibers with aligned MWCNTs. The study of the effect of polymer and CNT concentration on the fiber structures shows that the fiber size increases with the increment of polymer concentration, whereas higher CNT content in the polymer solutions leads to thinner fibers attributable to the increased conductivity. Both the SEM and TEM characterization of the polymer and ceramic fibers demonstrates the uniform orientation of CNTs along the fibers, suggesting excellent dispersion of CNTs and efficient CNT alignment via the electrospinning. The electrical conductivity of a ceramic fibers with 1.2% aligned MWCNTs is measured to be 1.58 x 10(-6) S/cm, which is more than 500 times higher than that of bulk ceramic (3.43 x 10(-9) S/cm). Such an approach provides a versatile method to disperse CNTs in preceramic polymer solutions and offers a new approach to integrate aligned CNTs in ceramics.

  16. Functionalized carbon nanotubes in ZnO thin films for photoinactivation of bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Akhavan, O. [Department of Physics, Sharif University of Technology, P.O. Box 11155-9161, Tehran (Iran, Islamic Republic of); Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 14588-89694, Tehran (Iran, Islamic Republic of); Azimirad, R., E-mail: azimirad@yahoo.com [Malek-Ashtar University of Technology, Tehran (Iran, Islamic Republic of); Safa, S. [Department of Nanotechnology, Faculty of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran (Iran, Islamic Republic of)

    2011-10-17

    Highlights: {yields} Unfunctionalized and functionalized MWCNT/ZnO thin films were synthesized by sol-gel method. {yields} Zn-O-C carbonaceous bonds formed in the functionalized MWCNT/ZnO thin films. {yields} The functionalized MWCNT/ZnO had stronger photoinactivation of the bacteria than the unfunctionalize type. {yields} 10 wt% functionalized MWCNT content had the optimum antibacterial property. - Abstract: Two types of unfunctionalized and functionalized multi-wall carbon nanotubes (MWCNTs) were prepared to be applied in fabrication of MWCNT-ZnO nanocomposite thin films with various MWCNT contents. X-ray photoelectron spectroscopy indicated formation of functional groups on surface of the functionalized MWCNTs in the MWCNT-ZnO nanocomposite. Formation of the effective carbonaceous bonds between the ZnO and the MWCNTs was also investigated through photoinactivation of Escherichia coli bacteria on surface of the both unfunctionalized and functionalized MWCNT-ZnO nanocomposites. The functionalized MWCNT-ZnO nanocomposites showed significantly stronger photoinactivation of the bacteria than the unfunctionalized ones, for all of the various MWCNT contents (from 2 to 30 wt%). While the functionalized MWCNT-ZnO nanocomposites with the optimum MWCNT content of 10 wt% inactivated whole of the bacteria after 10 min UV-visible light irradiation, the unfunctionalized ones could inactivate only 63% of the bacteria under the same conditions. The significant enhancement of the photoinactivation of the bacteria onto the surface of the functionalized MWCNT-ZnO nanocomposites was assigned to charge transfer through Zn-O-C bands formed between the Zn atoms of the ZnO film and oxygen atoms of the carboxylic functional groups of the functionalized MWCNTs.

  17. Hydrothermal growth and characterization of vertically well-aligned and dense ZnO nanorods on glass and silicon using a simple optimizer system

    Energy Technology Data Exchange (ETDEWEB)

    Mohammad, Sabah M., E-mail: Sabahaskari14@gmail.com; Ahmed, Naser M.; Abd-Alghafour, Nabeel M. [Institute of Nano-Optoelectronics Research and Technology Laboratory (INOR), School of Physics, Universiti Sains Malaysia, Penang 11800 (Malaysia); Hassan, Z., E-mail: zai@usm.my [Institute of Nano-Optoelectronics Research and Technology Laboratory (INOR), School of Physics, Universiti Sains Malaysia, Penang 11800 (Malaysia); CRI Natural Sciences, Universiti Sains Malaysia, Penang 11800 (Malaysia); Talib, Rawnaq A. [Institute of Nano-Optoelectronics Research and Technology Laboratory (INOR), School of Physics, Universiti Sains Malaysia, Penang 11800 (Malaysia); Polymer Research Center, University of Basra (Iraq); Omar, A. F. [School of Physics, Universiti Sains Malaysia, Penang 11800 (Malaysia)

    2016-07-06

    Vertically, well-aligned and high density ZnO nanorods were successfully hydrothermally grown on glass and silicon substrates using a simple and low cost system. The mechanism of synthesis of ZnO nanorods, generated with our system under hydrothermal conditions, is investigated in this report. Field-emission scanning electron microscopy indicated that the fabricated ZnO nanorods on both substrates have hexagonal shape with diameters ranging from 20 nm to 70 nm which grew vertically from the substrate. XRD analysis confirms the formation of wurtzite ZnO phase with a preferred orientation along (002) direction perpendicular on the substrate and enhanced crystallinity. The low value of the tensile strain (0.126 %) revealed that ZnO nanorods preferred to grow along the c-axis for both substrates. Photoluminescence spectra exhibited a strong, sharp UV near band edge emission peak with narrow FWHM values for both samples.

  18. Doping effect of In{sub 2}O{sub 3} on structural and ethanol-sensing characteristics of ZnO nanotubes fabricated by electrospinning

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Baoyu; Zhao, Changhui; Zhang, Mingxiang; Zhang, Zemin; Xie, Erqing, E-mail: xieeq@lzu.edu.cn; Zhou, Jinyuan, E-mail: zhoujy@lzu.edu.cn; Han, Weihua

    2015-09-15

    Highlights: • IZO nanotubes with various indium contents were synthesized by electrospinning. • A well-crystallized indium-zinc-oxide solid solution formed in IZO-0.01 nanotubes. • Amorphous In{sub 2}O{sub 3} segregated at ZnO grain boundaries at high indium doping levels. • IZO-0.01 nanotubes show a high response and good selectivity to ethanol at 275 °C. - Abstract: Indium-doped ZnO (IZO) nanotubes with various indium contents (0.01–0.20) were synthesized via a facile electrospinning method. Results of X-ray diffraction and transmission electron microscopy demonstrate that all samples are consisted of hexagonal wurtzite-typed ZnO, showing a well-crystallized indium-zinc-oxide solid solution when only a small amount of zinc ions substituted by indium ions (0.01). Once the amount of indium dopants ≥0.05, there will form some amorphous In{sub 2}O{sub 3}, leading to a pronounced decrease in grain sizes. Gas-sensing performances revealed that the IZO nanotube-based sensors have enhanced ethanol-sensing characteristics, especially, sensor based on IZO-0.01 nanotubes shows the highest response (R{sub a}/R{sub g} = 81.7), which is twice that of the undoped ZnO nanotubes (40.0) toward 100 ppm ethanol at an operating temperature of 275 °C. And IZO-0.20 nanotube-based sensor presents a relatively high response at high ethanol concentrations. Our research suggested that these remarkable enhanced ethanol-sensing properties can be closely related to the formation of indium-zinc-oxide solid solutions and/or heterostructures between ZnO and amorphous In{sub 2}O{sub 3}.

  19. Vertically aligned ZnO nanorods on hot filament chemical vapor deposition grown graphene oxide thin film substrate: solar energy conversion.

    Science.gov (United States)

    Ameen, Sadia; Akhtar, M Shaheer; Song, Minwu; Shin, Hyung Shik

    2012-08-01

    Vertically aligned zinc oxide (ZnO) nanorods (NRs) were grown by the low-temperature hydrothermal method on graphene oxide (GO) coated FTO substrates, where GO was directly deposited on fluorine doped tin oxide (FTO) substrates using hydrogen (H(2), 65 sccm) and methane (CH(4), 50 sccm) through hot filament chemical vapor deposition (HFCVD) technique. The vertically aligned ZnO NRs were applied as effective photoanode for the fabrication of efficient dye sensitized solar cells (DSSCs). Highly uniform ZnO NRs were grown on GO deposited FTO substrate with the average length of ∼2-4 μm and diameter of ∼200-300 nm. The possible mechanism of grown ZnO NRs clearly revealed the significant role of GO on FTO in architecting the aligned growth of ZnO NRs. The grown vertically aligned ZnO NRs possessed a typical wurtzite hexagonal crystal structure. The structural and the optical studies confirmed the formation of partial hydrogen bonding between surface functional groups of GO and ZnO NRs. A solar-to-electricity conversion efficiency of ∼2.5% was achieved by DSSC fabricated with ZnO NRs deposited on graphene oxide (GO-ZnO NRs) thin film photoanode. The presence of GO on FTO substrate expressively increased the surface area of GO-ZnO photoanode, which resulted in high dye loading as well as high light harvesting efficiency and thus ensued the increased photocurrent density and the improved performance of DSSCs.

  20. Enhanced Photoelectrochemical Activity of ZnO-Coated TiO2 Nanotubes and Its Dependence on ZnO Coating Thickness.

    Science.gov (United States)

    Cai, Hua; Liang, Peipei; Hu, Zhigao; Shi, Liqun; Yang, Xu; Sun, Jian; Xu, Ning; Wu, Jiada

    2016-12-01

    One-dimensional heterogeneous nanostructures in the form of ZnO-coated TiO2 nanotubes (ZnO/TiO2 NTs) were fabricated by atomic layer deposition of an ultrathin ZnO coating on electrochemical anodization-formed TiO2 nanotubes (NTs) with the thickness of ZnO coating being precisely controlled at atomic scale, and the photoelectrochemical activity of the fabricated ZnO/TiO2 NTs and the influence of ZnO coating and its thickness were studied. The structures of TiO2 NTs and ZnO coatings were characterized by X-ray diffraction, Raman backscattering spectroscopy, and transmission electron microscopy. The photoelectrochemical activity was studied through the measurements of electrochemical impendence, flat-band potential, and transient photocurrent density. The TiO2 NTs exhibit anatase structure, and the ZnO coatings are structured with hexagonal wurtzite. The photoelectrochemical activity of the ZnO/TiO2 NTs is strongly dependent on the thickness of ZnO coating. ZnO/TiO2 NTs with a thinner rather than a thicker ZnO coating exhibit better photoelectrochemical activity with reduced charge transfer resistance, increased negative flat-band potentials, and enhanced photocurrent densities. Under visible illumination, an increase of about 60 % in the photoelectrochemical activity is obtained for ZnO/TiO2 NTs with an about 2-nm-thick ZnO coating.

  1. Single-walled Carbon Nanotubes Regularly Aligned in Channels of Zeolite Single Crystal

    Institute of Scientific and Technical Information of China (English)

    Zi Kang Tang; Handong Sun; Jiannong Wang

    2000-01-01

    @@ We report the synthesis of single-wall carbon nanotubes (SWCNs) formed in 1-nm-sized channels of zeolite crystal by pyrolysis of tripropylamine molecules. The SWCNs are mono-sized and parallelly aligned along the crystal direction. In the present paper, we report the polarized Raman spectra measured for the wellaligned SWCNs, which gives us information about structural symmetry. Electrical transport properties of the SWNTs are measured in the temperature range of 0.3 K ~ 300 K. The conductivity of the SWCNs is monotonically decreased with decreasing temperature. The observed temperature dependence of zero-field conductance, In(σ) ~ 1/√T, could be explained well in terms of electron localization caused by imperfections and impurities in the nanotubes.

  2. The effect of dry shear aligning of nanotube thin films on the photovoltaic performance of carbon nanotube–silicon solar cells

    Directory of Open Access Journals (Sweden)

    Benedikt W. Stolz

    2016-10-01

    Full Text Available Recent results in the field of carbon nanotube–silicon solar cells have suggested that the best performance is obtained when the nanotube film provides good coverage of the silicon surface and when the nanotubes in the film are aligned parallel to the surface. The recently developed process of dry shear aligning – in which shear force is applied to the surface of carbon nanotube thin films in the dry state, has been shown to yield nanotube films that are very flat and in which the surface nanotubes are very well aligned in the direction of shear. It is thus reasonable to expect that nanotube films subjected to dry shear aligning should outperform otherwise identical films formed by other processes. In this work, the fabrication and characterisation of carbon nanotube–silicon solar cells using such films is reported, and the photovoltaic performance of devices produced with and without dry shear aligning is compared.

  3. Directly measuring of thermal pulse transfer in one-dimensional highly aligned carbon nanotubes.

    Science.gov (United States)

    Zhang, Guang; Liu, Changhong; Fan, Shoushan

    2013-01-01

    Using a simple and precise instrument system, we directly measured the thermo-physical properties of one-dimensional highly aligned carbon nanotubes (CNTs). A kind of CNT-based macroscopic materials named super aligned carbon nanotube (SACNT) buckypapers was measured in our experiment. We defined a new one-dimensional parameter, the "thermal transfer speed" to characterize the thermal damping mechanisms in the SACNT buckypapers. Our results indicated that the SACNT buckypapers with different densities have obviously different thermal transfer speeds. Furthermore, we found that the thermal transfer speed of high-density SACNT buckypapers may have an obvious damping factor along the CNTs aligned direction. The anisotropic thermal diffusivities of SACNT buckypapers could be calculated by the thermal transfer speeds. The thermal diffusivities obviously increase as the buckypaper-density increases. For parallel SACNT buckypapers, the thermal diffusivity could be as high as 562.2 ± 55.4 mm(2)/s. The thermal conductivities of these SACNT buckypapers were also calculated by the equation k = Cpαρ.

  4. Photoluminescence enhancement of aligned arrays of single-walled carbon nanotubes by polymer transfer

    Science.gov (United States)

    Schweiger, Manuel; Zakharko, Yuriy; Gannott, Florentina; Grimm, Stefan B.; Zaumseil, Jana

    2015-10-01

    The photoluminescence of as-grown, aligned single-walled carbon nanotubes (SWNTs) on quartz is strongly quenched and barely detectable. Here we show that transferring these SWNTs to another substrate such as clean quartz or glass increases their emission efficiency by up to two orders of magnitude. By statistical analysis of large nanotube arrays we show at what point of the transfer process the emission enhancement occurs and how it depends on the receiving substrate and the employed transfer polymer. We find that hydrophobic polystyrene (PS) as the transfer polymer results in higher photoluminescence enhancement than the more hydrophilic poly(methyl methacrylate) (PMMA). Possible mechanisms for this enhancement such as strain relief, disruption of the strong interaction of SWNTs with the substrate and localized emissive states are discussed.The photoluminescence of as-grown, aligned single-walled carbon nanotubes (SWNTs) on quartz is strongly quenched and barely detectable. Here we show that transferring these SWNTs to another substrate such as clean quartz or glass increases their emission efficiency by up to two orders of magnitude. By statistical analysis of large nanotube arrays we show at what point of the transfer process the emission enhancement occurs and how it depends on the receiving substrate and the employed transfer polymer. We find that hydrophobic polystyrene (PS) as the transfer polymer results in higher photoluminescence enhancement than the more hydrophilic poly(methyl methacrylate) (PMMA). Possible mechanisms for this enhancement such as strain relief, disruption of the strong interaction of SWNTs with the substrate and localized emissive states are discussed. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05163k

  5. A possible role of the dipole moment of the catalyst droplet in nanotube growth, alignment, chirality, and characteristics.

    Science.gov (United States)

    Mohammad, S Noor

    2012-03-02

    Why vapor species land on the surface of the nanoparticle seed for nanotube synthesis is a vital question. An investigation has been carried out to find an answer to it. For this, a model of the dipole moment has been developed. A bimetallic alloy (non-alloy, solid solution) exhibiting the shape of a cap has been assumed to function as the nanoparticle seed. Various features of the dipole moment have been examined. The influence of the dipole moment on nanotube synthesis, alignment, chirality, and characteristics has also been studied. Available experiments on the synthesis of carbon nanotubes employing bimetallic catalysts have been compared with the results from calculations. Close correspondence between the two demonstrates that the catalysts may exhibit a dipole moment and have a crucial role in nanotube synthesis and characteristics. The dipole moment has also been employed to determine why some nanotubes grow vertically, while others are bent. Calculated results appear to explain the basic causes for this. These results suggest that the electric field resulting from the dipole moment of catalysts may be important for the vertical alignment of nanotubes. They may attest to the validity of the model and to the existence of a dipole moment in seeds. Although considered for nanotube syntheses, the results may be applicable to other nanomaterials (nanotubes, nanowires, nanodots).

  6. Cyclohexane triggers staged growth of pure and vertically aligned single wall carbon nanotubes

    Science.gov (United States)

    Ayala, P.; Grüneis, A.; Grimm, D.; Kramberger, C.; Engelhard, R.; Rümmeli, M.; Schumann, J.; Kaltofen, R.; Büchner, B.; Schaman, C.; Kuzmany, H.; Gemming, T.; Barreiro, A.; Pichler, T.

    2008-03-01

    An innovative staged chemical vapor deposition (SCVD) approach providing flexible control over the feedstock type during single wall carbon nanotube (SWNTs) growth is proposed. The efficiency of staged growth by means of a cyclohexane/methane system using thin film catalysts is here illustrated. The mechanism involves the nucleation stage efficiently triggered by cyclohexane, followed by methane assisting a growth stage yielding high purity SWNTs vertically aligned with lengths of several hundred μm. In addition, SCVD also facilitates catalyst free SWNT detachment enabling repeated growth.

  7. Aligned carbon nanotube, graphene and graphite oxide thin films via substrate-directed rapid interfacial deposition.

    Science.gov (United States)

    D'Arcy, Julio M; Tran, Henry D; Stieg, Adam Z; Gimzewski, James K; Kaner, Richard B

    2012-05-21

    A procedure for depositing thin films of carbon nanostructures is described that overcomes the limitations typically associated with solution based methods. Transparent and conductively continuous carbon coatings can be grown on virtually any type of substrate within seconds. Interfacial surface tension gradients result in directional fluid flow and film spreading at the water/oil interface. Transparent films of carbon nanostructures are produced including aligned ropes of single-walled carbon nanotubes and assemblies of single sheets of chemically converted graphene and graphite oxide. Process scale-up, layer-by-layer deposition, and a simple method for coating non-activated hydrophobic surfaces are demonstrated.

  8. Flow Field Induced Steady Alignment of Oxidized Multi-walled Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Ai Zhong XU; Ming Shu YANG; Qiang WU; Xiao Ming HU; Lei JIANG

    2005-01-01

    The steady ordered micro-ribbons of oxidized multi-walled carbon nanotubes (MWNTs)were obtained through micro-aperture PTFE membrane by vacuum filtration. After treatment by mixture of concentrated nitric acid and sulfuric acid, the surface functional groups modified MWNTs can be easily dispersed to form a homogeneous suspension. It is found that the steady micro-ribbons existed in the films obtained by vacuum filtration of the suspension. The filtration formed steady flow field and induced steady alignment of oxidized MWNTs. The chemical treatment of MWNTs forming strong interaction between MWNTs is necessity to keep steady of the micro-ribbons microstructure.

  9. High-rate capability silicon decorated vertically aligned carbon nanotubes for Li-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Gohier, Aurelien; Kim, Ki-Hwan; Maurice, Jean-Luc; Cojocaru, Costel Sorin [Laboratoire de Physique des Interfaces et des Couches Minces, LPICM, Ecole Polytechnique, route de Saclay, 91128 Palaiseau Cedex (France); Laik, Barbara; Pereira-Ramos, Jean-Pierre [Institut de Chimie et des Materiaux Paris-Est, ICMPE/GESMAT, UMR 7182 CNRS-UPEC, 2 rue Henri Dunant, 94320 Thiais (France); Van, Pierre Tran [Renault SAS, DREAM/DETA/SEE, 1, avenue du Golf, 78288 Guyancourt (France)

    2012-05-15

    The concept of a hybrid nanostructured collector made of thin vertically aligned carbon nanotubes (CNTs) decorated with Si nanoparticles provides high power density anodes in lithium-ion batteries. An impressive rate capability is achieved due to the efficient electronic conduction of CNTs combined with well defined electroactive Si nanoparticles: capacities of 3000 mAh g{sup -1} at 1.3C and 800 mAh g{sup -1} at 15C are achieved. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  10. Modeling and experimental study of resistive switching in vertically aligned carbon nanotubes

    Science.gov (United States)

    Ageev, O. A.; Blinov, Yu F.; Ilina, M. V.; Ilin, O. I.; Smirnov, V. A.

    2016-08-01

    Model of the resistive switching in vertically aligned carbon nanotube (VA CNT) taking into account the processes of deformation, polarization and piezoelectric charge accumulation have been developed. Origin of hysteresis in VA CNT-based structure is described. Based on modeling results the VACNTs-based structure has been created. The ration resistance of high-resistance to low-resistance states of the VACNTs-based structure amounts 48. The correlation the modeling results with experimental studies is shown. The results can be used in the development nanoelectronics devices based on VA CNTs, including the nonvolatile resistive random-access memory.

  11. Field emission from laterally aligned carbon nanotube flower arrays for low turn-on field emission

    Directory of Open Access Journals (Sweden)

    Hiroe Kimura

    2013-09-01

    Full Text Available Laterally aligned carbon nanotube (CNT arrays “blossomed” homogeneously in honeycomb holes of a metal grid substrate were explored as rational architecture for field emission. A low turn-on field (TOF of 1.09 V/μm for 10 μA/cm2 emission was achieved, which approaches or exceeds the lowest reported TOF values for field emitter arrays. We interpret that these lateral CNT arrays act as source of CNT “loop” arrays enabling a structure suited toward low TOF field emission.

  12. Macroscopic Transport of Mega-ampere Electron Currents in Aligned Carbon-Nanotube Arrays

    Science.gov (United States)

    Chatterjee, Gourab; Singh, Prashant Kumar; Ahmed, Saima; Robinson, A. P. L.; Lad, Amit D.; Mondal, Sudipta; Narayanan, V.; Srivastava, Iti; Koratkar, Nikhil; Pasley, John; Sood, A. K.; Kumar, G. Ravindra

    2012-06-01

    We demonstrate that aligned carbon-nanotube arrays are efficient transporters of laser-generated mega-ampere electron currents over distances as large as a millimeter. A direct polarimetric measurement of the temporal and the spatial evolution of the megagauss magnetic fields (as high as 120 MG) at the target rear at an intensity of (1018-1019)W/cm2 was corroborated by the rear-side hot electron spectra. Simulations show that such high magnetic flux densities can only be generated by a very well collimated fast electron bunch.

  13. Thermal property tuning in aligned carbon nanotube films and random entangled carbon nanotube films by ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jing [Department of Materials Science and Engineering, Texas A& M University, College Station, Texas 77843 (United States); Chen, Di; Wang, Xuemei [Department of Nuclear Engineering, Texas A& M University, College Station, Texas 77843 (United States); Bykova, Julia S.; Zakhidov, Anvar A. [The Alan G. MacDiarmid NanoTech Institute, University of Texas at Dallas, Richardson, Texas 75080 (United States); Shao, Lin, E-mail: lshao@tamu.edu [Department of Materials Science and Engineering, Texas A& M University, College Station, Texas 77843 (United States); Department of Nuclear Engineering, Texas A& M University, College Station, Texas 77843 (United States)

    2015-10-12

    Ion irradiation effects on thermal property changes are compared between aligned carbon nanotube (A-CNT) films and randomly entangled carbon nanotube (R-CNT) films. After H, C, and Fe ion irradiation, a focusing ion beam with sub-mm diameter is used as a heating source, and an infrared signal is recorded to extract thermal conductivity. Ion irradiation decreases thermal conductivity of A-CNT films, but increases that of R-CNT films. We explain the opposite trends by the fact that neighboring CNT bundles are loosely bonded in A-CNT films, which makes it difficult to create inter-tube linkage/bonding upon ion irradiation. In a comparison, in R-CNT films, which have dense tube networking, carbon displacements are easily trapped between touching tubes and act as inter-tube linkage to promote off-axial phonon transport. The enhancement overcomes the phonon transport loss due to phonon-defect scattering along the axial direction. A model is established to explain the dependence of thermal conductivity changes on ion irradiation parameters including ion species, energies, and current.

  14. Wafer-Level Patterned and Aligned Polymer Nanowire/Micro- and Nanotube Arrays on any Substrate

    KAUST Repository

    Morber, Jenny Ruth

    2009-05-25

    A study was conducted to fabricate wafer-level patterned and aligned polymer nanowire (PNW), micro- and nanotube arrays (PNT), which were created by exposing the polymer material to plasma etching. The approach for producing wafer-level aligned PNWs involved a one-step inductively coupled plasma (ICP) reactive ion etching process. The polymer nanowire array was fabricated in an ICP reactive ion milling chamber with a pressure of 10mTorr. Argon (Ar), O 2, and CF4 gases were released into the chamber as etchants at flow rates of 15 sccm, 10 sccm, and 40 sccm. Inert gasses, such as Ar-form positive ions were incorporated to serve as a physical component to assist in the material degradation process. One power source (400 W) was used to generate dense plasma from the input gases, while another power source applied a voltage of approximately 600V to accelerate the plasma toward the substrate.

  15. Behavior of oxidized platinum nanoparticles on an aligned carbon nanotube forest

    Science.gov (United States)

    Matsuda, Keita; Norimatsu, Wataru; Arai, Shigeo; Kusunoki, Michiko

    2016-10-01

    We observed and analyzed the behavior of platinum nanoparticles (PtNPs) supported on aligned-carbon nanotubes (CNTs) at high temperatures by X-ray photoelectron spectroscopy and high-resolution transmission electron microscope observations. We found that the PtNPs moved toward the inner-side along each CNT on which they were deposited. The mechanism of this behavior is related to the redox reaction of Pt with the carbon atoms in the CNT. We also performed in-situ observation of this process at a high temperature using an environmental transmission electron microscope under an oxygen atmosphere. We found that the PtNPs penetrated down into a high-density aligned CNT forest along the tube axis and that the PtNPs changed their shape to fit the structure of the CNTs during their movement.

  16. Importance of the alignment of polar π conjugated molecules inside carbon nanotubes in determining second-order non-linear optical properties.

    Science.gov (United States)

    Yumura, Takashi; Yamamoto, Wataru

    2017-09-20

    We employed density functional theory (DFT) calculations with dispersion corrections to investigate energetically preferred alignments of certain p,p'-dimethylaminonitrostilbene (DANS) molecules inside an armchair (m,m) carbon nanotube (n × DANS@(m,m)), where the number of inner molecules (n) is no greater than 3. Here, three types of alignments of DANS are considered: a linear alignment in a parallel fashion and stacking alignments in parallel and antiparallel fashions. According to DFT calculations, a threshold tube diameter for containing DANS molecules in linear or stacking alignments was found to be approximately 1.0 nm. Nanotubes with diameters smaller than 1.0 nm result in the selective formation of linearly aligned DANS molecules due to strong confinement effects within the nanotubes. By contrast, larger diameter nanotubes allow DANS molecules to align in a stacking and linear fashion. The type of alignment adopted by the DANS molecules inside a nanotube is responsible for their second-order non-linear optical properties represented by their static hyperpolarizability (β0 values). In fact, we computed β0 values of DANS assemblies taken from optimized n × DANS@(m,m) structures, and their values were compared with those of a single DANS molecule. DFT calculations showed that β0 values of DANS molecules depend on their alignment, which decrease in the following order: linear alignment > parallel stacking alignment > antiparallel stacking alignment. In particular, a linear alignment has a β0 value more significant than that of the same number of isolated molecules. Therefore, the linear alignment of DANS molecules, which is only allowed inside smaller diameter nanotubes, can strongly enhance their second-order non-linear optical properties. Since the nanotube confinement determines the alignment of DANS molecules, a restricted nanospace can be utilized to control their second-order non-linear optical properties. These DFT findings can assist in the design

  17. Vertically aligned ZnO nanorod grown by hydrothermal based chemical method on glass substrate

    Science.gov (United States)

    Srivastava, R.; Majumdar, S.; Bhunia, S.

    2012-06-01

    A low-temperature and effective precursor-based method has been demonstrated to synthesize nanostructured ZnO. It is found that the morphology of ZnO precursors has a strong dependence on the reaction conditions that include the molar ratio of reagents, solvent, and reaction temperature. In this work, ZnO nanostructures were synthesized via hydrothermal based chemical method. Zinc acetate dehydrate [Zn(Ac)2 2H2O] and 1-propanol(C3H8O) were adopted for a seed layer growth on glass substrate via spin coating technique. Zinc nitrate hexahydrate [Zn(NO3)2 6H2O], hexamethylenetetramine(C6H12N4) and diethylamine(C4H11N) were adopted as synthesis precursors. The ZnO nanostructures obtained were characterized by scanning electronic microscopy (SEM) and the PL method. The SEM image of the sample showed that the thin film of ZnO on glass substrate has, predominantly, a nanometric rod-like morphology with hexagonal wurtzite structure.

  18. Fabrication of Single, Vertically Aligned Carbon Nanotubes in 3D Nanoscale Architectures

    Science.gov (United States)

    Kaul, Anupama B.; Megerian, Krikor G.; Von Allmen, Paul A.; Baron, Richard L.

    2010-01-01

    Plasma-enhanced chemical vapor deposition (PECVD) and high-throughput manufacturing techniques for integrating single, aligned carbon nanotubes (CNTs) into novel 3D nanoscale architectures have been developed. First, the PECVD growth technique ensures excellent alignment of the tubes, since the tubes align in the direction of the electric field in the plasma as they are growing. Second, the tubes generated with this technique are all metallic, so their chirality is predetermined, which is important for electronic applications. Third, a wafer-scale manufacturing process was developed that is high-throughput and low-cost, and yet enables the integration of just single, aligned tubes with nanoscale 3D architectures with unprecedented placement accuracy and does not rely on e-beam lithography. Such techniques should lend themselves to the integration of PECVD grown tubes for applications ranging from interconnects, nanoelectromechanical systems (NEMS), sensors, bioprobes, or other 3D electronic devices. Chemically amplified polyhydroxystyrene-resin-based deep UV resists were used in conjunction with excimer laser-based (lambda = 248 nm) step-and-repeat lithography to form Ni catalyst dots = 300 nm in diameter that nucleated single, vertically aligned tubes with high yield using dc PECVD growth. This is the first time such chemically amplified resists have been used, resulting in the nucleation of single, vertically aligned tubes. In addition, novel 3D nanoscale architectures have been created using topdown techniques that integrate single, vertically aligned tubes. These were enabled by implementing techniques that use deep-UV chemically amplified resists for small-feature-size resolution; optical lithography units that allow unprecedented control over layer-to-layer registration; and ICP (inductively coupled plasma) etching techniques that result in near-vertical, high-aspect-ratio, 3D nanoscale architectures, in conjunction with the use of materials that are

  19. Atomic Layer Deposition of ZnO on Multi-walled Carbon Nanotubes and Its Use for Synthesis of CNT–ZnO Heterostructures

    Directory of Open Access Journals (Sweden)

    Li C

    2010-01-01

    Full Text Available Abstract In this article, direct coating of ZnO on PECVD-grown multi-walled carbon nanotubes (MWCNTs is achieved using atomic layer deposition (ALD. Transmission electron microscopy investigation shows that the deposited ZnO shell is continuous and uniform, in contrast to the previously reported particle morphology. The ZnO layer has a good crystalline quality as indicated by Raman and photoluminescence (PL measurements. We also show that such ZnO layer can be used as seed layer for subsequent hydrothermal growth of ZnO nanorods, resulting in branched CNT–inorganic hybrid nanostructures. Potentially, this method can also apply to the fabrication of ZnO-based hybrid nanostructures on other carbon nanomaterials.

  20. Fabrication of cm scale buckypapers of horizontally aligned multiwalled carbon nanotubes highly filled with Fe3C: the key roles of Cl and Ar-flow rates.

    Science.gov (United States)

    Boi, Filippo S; Guo, Jian; Wang, Shanling; He, Yi; Xiang, Gang; Zhang, Xi; Baxendale, Mark

    2016-03-18

    A key challenge in the fabrication of ferromagnetically filled carbon-nanotube buckypapers in the presence of Cl-radicals is the achievement of a preferential horizontal nanotube-alignment. We show that a horizontal-alignment can be achieved by tuning two main CVD parameters for a fixed dichlorobenzene concentration: the precursor-evaporation temperature and the flow rate.

  1. Magnetic behaviour of non-contacting Ni nanoparticles encapsulated in vertically aligned carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, J.A.; Elbaile, L. [Departamento de Fisica, Universidad de Oviedo, c/Calvo Sotelo s/n, 33007 Oviedo (Spain); Bertran, E.; Garcia-Cespedes, J. [Grupo FEMAN, IN2UB, Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Svalov, A. [Ural State University, Institute of Physics and Applied Mathematics, Lenin Ave. 51, 620083 Ekaterinburg (Russian Federation)

    2010-11-15

    Magnetic properties of carbon nanotubes (CNT) obtained by plasma-enhanced chemical vapour deposition (PECVD) have been studied. The growth of these nanotubes has been activated from Ni catalyst nanoparticles. Samples consist of Ni nanoparticles encapsulated at the tip of vertically aligned multiwalled carbon nanotubes (VACNTs) forming an homogeneous and dense large area monolayer of isolated (non-contacting) nanoparticles. The magnetic characterisation has been performed in the temperature range of 5-300 K with magnetic fields up to 9 T. The results show that the wide size range (30-180 nm) of the particles originates the coexistence of blocked and superparamagnetic particles and leads to the strong ferromagnetic behaviour of the whole assembly. The coercivity decreases monotonically with increasing temperature and the value for the intrinsic coercivity is 225 Oe. The encapsulation of Ni nanoparticles by VACNTs preserves them from aggregation. This makes possible to tune the coercivity by controlling size distribution of particle monolayers. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Dynamics of capillary infiltration of liquids into a highly aligned multi-walled carbon nanotube film

    Directory of Open Access Journals (Sweden)

    Sławomir Boncel

    2011-06-01

    Full Text Available The physical compatibility of a highly aligned carbon nanotube (HACNT film with liquids was established using a fast and convenient experimental protocol. Two parameters were found to be decisive for the infiltration process. For a given density of nanotube packing, the thermodynamics of the infiltration process (wettability were described by the contact angle between the nanotube wall and a liquid meniscus (θ. Once the wettability criterion (θ < 90° was met, the HACNT film (of free volume equal to 91% was penetrated gradually by the liquid in a rate that can be linearly correlated to dynamic viscosity of the liquid (η. The experimental results follow the classical theory of capillarity for a steady process (Lucas–Washburn law, where the nanoscale capillary force, here supported by gravity, is compensated by viscous drag. This most general theory of capillarity can be applied in a prediction of both wettability of HACNT films and the dynamics of capillary rise in the intertube space in various technological applications.

  3. Alignment of Gold Nanoparticle-Decorated DNA Origami Nanotubes: Substrate Prepatterning versus Molecular Combing.

    Science.gov (United States)

    Teschome, Bezu; Facsko, Stefan; Gothelf, Kurt V; Keller, Adrian

    2015-11-24

    DNA origami has become an established technique for designing well-defined nanostructures with any desired shape and for the controlled arrangement of functional nanostructures with few nanometer resolution. These unique features make DNA origami nanostructures promising candidates for use as scaffolds in nanoelectronics and nanophotonics device fabrication. Consequently, a number of studies have shown the precise organization of metallic nanoparticles on various DNA origami shapes. In this work, we fabricated large arrays of aligned DNA origami decorated with a high density of gold nanoparticles (AuNPs). To this end, we first demonstrate the high-yield assembly of high-density AuNP arrangements on DNA origami adsorbed to Si surfaces with few unbound background nanoparticles by carefully controlling the concentrations of MgCl2 and AuNPs in the hybridization buffer and the hybridization time. Then, we evaluate two methods, i.e., hybridization to prealigned DNA origami and molecular combing in a receding meniscus, with respect to their potential to yield large arrays of aligned AuNP-decorated DNA origami nanotubes. Because of the comparatively low MgCl2 concentration required for the efficient immobilization of the AuNPs, the prealigned DNA origami become mobile and displaced from their original positions, thereby decreasing the alignment yield. This increased mobility, on the other hand, makes the adsorbed origami susceptible to molecular combing, and a total alignment yield of 86% is obtained in this way.

  4. Dipole Alignment at the Carbon Nanotube and Methyl Ammonium Lead Iodide Perovskite Interface

    Energy Technology Data Exchange (ETDEWEB)

    Przepioski, Joshua [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-28

    This work correlates resonant peaks from first principles calculation on ammonia (NH3) Nitrogen 1s x-ray absorption spectroscopy (XAS) within the methyl ammonium lead iodide perovskite (CH3NH3PbI3), and proposes a curve to determine the alignment of the methyl ammonium dipole if there exists angular dependence. The Nitrogen 1s XAS was performed at varying incident angles on the perovskite with and without a carbon nanotube (CNT) interface produced from an ultrasonic spray deposition. We investigated the peak contribution from PbI2 and the poly(9,9-dioctylfluorene- 2,7-diyl) with bipyridine (PFO-BPy) wrapped around the CNT, and used normalization techniques to better identify the dipole alignment. There was angular dependence on samples containing the CNT interface suggesting an existing dipole alignment, but there was no angular dependence on the perovskite samples alone; however, more normalization techniques and experimental work must be performed in order to ensure its validity and to better describe its alignment, and possible controlling factors.

  5. Dipole Alignment at the Carbon Nanotube and Methyl Ammonium Lead Trihalide Perovskite Interface - Oral Presentation

    Energy Technology Data Exchange (ETDEWEB)

    Przepioski, Joshua [SLAC National Accelerator Lab., Menlo Park, CA (United States)

    2015-08-25

    This work correlates resonant peaks from first principles calculation on ammonia (NH3) Nitrogen 1s x-ray absorption spectroscopy (XAS) within the methyl ammonium lead iodide perovskite (CH3NH3PbI3), and proposes a curve to determine the alignment of the methyl ammonium dipole if there exists angular dependence. The Nitrogen 1s XAS was performed at varying incident angles on the perovskite with and without a carbon nanotube (CNT) interface produced from an ultrasonic spray deposition. We investigated the peak contribution from PbI2 and the poly(9,9-dioctylfluorene-2,7-diyl) with bipyridine (PFO-BPy) wrapped around the CNT, and used normalization techniques to better identify the dipole alignment. There was angular dependence on samples containing the CNT interface suggesting an existing dipole alignment, but there was no angular dependence on the perovskite samples alone; however, more normalization techniques and experimental work must be performed in order to ensure its validity and to better describe its alignment, and possible controlling factors.

  6. Electrodeposition of Various Au Nanostructures on Aligned Carbon Nanotubes as Highly Sensitive Nanoelectrode Ensembles

    Science.gov (United States)

    Fayazfar, H.; Afshar, A.; Dolati, A.

    2015-05-01

    An efficient method has been developed to synthesize well-aligned multi-walled carbon nanotubes (MWCNTs) on a conductive Ta substrate by chemical vapor deposition. Free-standing MWCNTs arrays were functionalized through electrochemical oxidation with the formation of hydroxyl and carboxyl functional groups. Facile template-free electrochemical routes were then developed for the shape-selective synthesis of less-common Au nanostructures, including flower, sphere, dendrite, rod, sheet, and cabbage onto the aligned MWCNTs at room temperature. Especially, among all the synthesis methods for Au nanocrystals, this is the first report using electrochemical technique to synthesize wide variety shapes of gold nanostructures (GNs) onto the aligned MWCNTs. The morphology of electrodeposited Au nanostructures was controlled by adjustment of the deposition time and potential, the number of potential cycles, the kind of deposition bath, and electrodeposition method. Transmission electron microscopy and field-emission scanning electron microscopy were used to characterize the products. Cyclic voltammograms showed that the MWCNT/Ta electrodes modified with GNs have higher sensitivity compared to the unmodified electrodes in the presence of Fe2+/Fe3+ redox couple. These kinds of aligned-CNT/Au nanostructure hybrid materials introduced by these efficient and simple electrochemical methods could lead to the development of a new generation device for ultrasensitive catalytic and biological application.

  7. Growth of well-aligned carbon nanotube structures in successive layers.

    Science.gov (United States)

    Deck, Christian P; Vecchio, Kenneth S

    2005-06-30

    Layered structures of well-aligned carbon nanotubes were grown using three variations of vapor-phase chemical vapor deposition growth processes. The reactants (typically ferrocene and benzene) were introduced either directly to a heated furnace or carried into the furnace by evaporation or spray pyrolysis in an argon flow. Thick mats of densely packed, well-aligned nanotubes were produced when the reactants were continuously introduced to the reaction; however, when the reactant flow was interrupted, the pauses allowed growth to stop and then restart as a new layer. These pauses were achieved by either completely stopping the reactant flow for a given time or by modifying the dispensing system to introduce the reactants in discrete drops. Time intervals between drops were varied between 20 s and 120 s, with distinct layers observed for pauses of 30 s or greater. The best results were achieved when drops of a catalyst-rich solution were alternated with drops of pure benzene. Layers were grown with thicknesses ranging from several microns to several hundred microns, and structures were grown with well over 100 layers.

  8. Nanomagnetic domains of chromium deposited on vertically-aligned carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Andrew C., E-mail: a.wright@glyndwr.ac.uk [Advanced Materials Research Laboratory, Materials Science Research Center, Glyndwr University, Wrexham LL11 2AW (United Kingdom); Faulkner, Michael K., E-mail: m.faulkner@manchester.ac.uk [Manchester Materials Science Centre, University of Manchester, Grosvenor Street, Manchester M13 9PL (United Kingdom); Harris, Robert C.; Goddard, Alex; Abbott, Andrew P., E-mail: apa1@le.ac.uk [Department of Chemistry, University of Leicester, Leicester LE1 7RH (United Kingdom)

    2012-12-15

    The drive to create ever smaller magnetic memory devices has led to the development of new nanomagnetic domains on surfaces. This paper reports the development of nano-chromium magnetic domains obtained using electrodeposition on vertically aligned carbon nanofibers arrays. Attempts to achieve this using conventional aqueous solutions were unsuccessful even after thin nickel underlayers were applied. The use of a novel electrolyte, a deep eutectic solvent, made from choline chloride: chromium (III) chloride enabled highly conformal overcoatings of chromium on individual bare carbon nanotubes to be obtained. Very high aspect ratio metal microstructures could be obtained by this novel technology. Magnetic imaging of the coated nanoarrays showed there to be clear magnetic character to the coating when the thin coatings were applied but this disappeared when the deposits were thicker and more contiguous. - Highlights: Black-Right-Pointing-Pointer Nanoscale chromium deposited from non-aqueous electrolyte shows magnetic behavior. Black-Right-Pointing-Pointer Vertically aligned carbon nanotubes conformally coated with chromium metal. Black-Right-Pointing-Pointer Ionic liquid electrolyte superior to chromic acid for plating high aspect ratio structures.

  9. Well-aligned carbon nanotube array membrane and its field emission properties

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Ensembles of aligned and monodispersed carbon nanotubes (CNTs)can be prepared by templating method which involves fabrication of porous anodic aluminum oxide (AAO) template, control of catalytic iron particle size and chemical vapor deposition of carbon in the cylindrical pores of AAO. Here we show that template-synthesized CNTs can be fabricated as well-aligned nanoporous CNTs membrane, which can be directly used as an electron field emitter. A low threshold electric field of 2-4 V/μm and maximum emission current density of ~12 mA/cm2 are observed. The results also show that the electron emission current is a function of the applied electrical field and the Fowler-Nordheim (F-N) plot almost follows a linear relationship which indicates a Fowler-Nordheim tunneling mechanism, and the field enhancement factor estimated is about 1100-7500. The simple and convenient approach should be significant for the development of nanotube devices integrated into field emission displays (FEDs) technology.

  10. Synthesis and Investigation of Millimeter-Scale Vertically Aligned Boron Nitride Nanotube Arrays

    Science.gov (United States)

    Tay, Roland; Li, Hongling; Tsang, Siu Hon; Jing, Lin; Tan, Dunlin; Teo, Edwin Hang Tong

    Boron nitride nanotubes (BNNTs) have shown potential in a wide range of applications due to their superior properties such as exceptionally high mechanical strength, excellent chemical and thermal stabilities. However, previously reported methods to date only produced BNNTs with limited length/density and insufficient yield at high temperatures. Here we present a facile and effective two-step synthesis route involving template-assisted chemical vapor deposition at a relatively low temperature of 900 degree C and subsequent annealing process to fabricate vertically aligned (VA) BN coated carbon nanotube (VA-BN/CNT) and VA-BNNT arrays. By using this method, we achieve the longest VA-BN/CNTs and VA-BNNTs to date with lengths of over millimeters (exceeding two orders of magnitude longer than the previously reported length of VA-BNNTs). In addition, the morphology, chemical composition and microstructure of the resulting products, as well as the mechanism of coating process are systematically investigated. This versatile BN coating technique and the synthesis of millimeter-scale BN/CNT and BNNT arrays pave a way for new applications especially where the aligned geometry of the NTs is essential such as for field-emission, interconnects and thermal management.

  11. Transparent electronics based on transfer printed aligned carbon nanotubes on rigid and flexible substrates.

    Science.gov (United States)

    Ishikawa, Fumiaki N; Chang, Hsiao-Kang; Ryu, Koungmin; Chen, Po-Chiang; Badmaev, Alexander; Gomez De Arco, Lewis; Shen, Guozhen; Zhou, Chongwu

    2009-01-27

    We report high-performance fully transparent thin-film transistors (TTFTs) on both rigid and flexible substrates with transfer printed aligned nanotubes as the active channel and indium-tin oxide as the source, drain, and gate electrodes. Such transistors have been fabricated through low-temperature processing, which allowed device fabrication even on flexible substrates. Transparent transistors with high effective mobilities (approximately 1300 cm(2) V(-1) s(-1)) were first demonstrated on glass substrates via engineering of the source and drain contacts, and high on/off ratio (3 x 10(4)) was achieved using electrical breakdown. In addition, flexible TTFTs with good transparency were also fabricated and successfully operated under bending up to 120 degrees . All of the devices showed good transparency (approximately 80% on average). The transparent transistors were further utilized to construct a fully transparent and flexible logic inverter on a plastic substrate and also used to control commercial GaN light-emitting diodes (LEDs) with light intensity modulation of 10(3). Our results suggest that aligned nanotubes have great potential to work as building blocks for future transparent electronics.

  12. Determination of the effective Young's modulus of vertically aligned carbon nanotube arrays: a simple nanotube-based varactor

    Energy Technology Data Exchange (ETDEWEB)

    Olofsson, Niklas; Eriksson, Anders [Department of Physics, Goeteborg University, SE-41296 Goeteborg (Sweden); Ek-Weis, Johan; Campbell, Eleanor E B [School of Chemistry, Edinburgh University, West Mains Road, Edinburgh EH9 3JJ (United Kingdom); Idda, Tonio, E-mail: eleanor.campbell@ed.ac.u [LAAS-CNRS, 7 Avenue du Colonel Roche, 31077 Toulouse Cedex (France)

    2009-09-23

    The electromechanical properties of arrays of vertically aligned multiwalled carbon nanotubes were studied in a parallel plate capacitor geometry. The electrostatic actuation was visualized using both optical microscopy and scanning electron microscopy, and highly reproducible behaviour was achieved for actuation voltages below the pull-in voltage. The walls of vertically aligned carbon nanotubes behave as solid cohesive units. The effective Young's modulus for the carbon nanotube arrays was determined by comparing the actuation results with the results of electrostatic simulations and was found to be exceptionally low, of the order of 1-10 MPa. The capacitance change and Q-factor were determined by measuring the frequency dependence of the radio-frequency transmission. Capacitance changes of over 20% and Q-factors in the range 100-10 were achieved for a frequency range of 0.2-1.5 GHz.

  13. Aligned Carbon Nanotube Reinforced Silicon Carbide Composites by Chemical Vapor Infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Zhan Jun [University of Georgia, Athens, GA; Yang, Ying Chao [University of South Carolina, Columbia; Li, Kai Yuan [University of Georgia, Athens, GA; Tao, Xin Yong [University of South Carolina, Columbia; Eres, Gyula [ORNL; Howe, Jane Y [ORNL; Zhang, Li Tong [Northwestern Polytechnical University, Xi' an, China; Li, Xiao Dong [University of South Carolina, Columbia; Pan, Zhengwei [ORNL

    2011-01-01

    Owing to their exceptional stiffness and strength1 4, carbon nanotubes (CNTs) have long been considered to be an ideal reinforcement for light-weight, high-strength, and high-temperature-resistant ceramic matrix composites (CMCs)5 10. However, the research and development in CNT-reinforced CMCs have been greatly hindered due to the challenges related to manufacturing including poor dispersion, damages during dispersion, surface modification, densification and sintering, weak tube/matrix interfaces, and agglomeration of tubes at the matrix grain boundaries5,11. Here we report the fabrication of high-quality aligned CNT/SiC composites by chemical vapor infiltration (CVI), a technique that is being widely used to fabricate commercial continuous-filament CMCs12 15. Using the CVI technique most of the challenges previously encountered in the fabrication of CNT composites were readily overcome. Nanotube pullouts, an important toughening mechanism for CMCs, were consistently observed on all fractured CNT/SiC samples. Indeed, three-point bending tests conducted on individual CNT/SiC nanowires (diameters: 50 200 nm) using an atomic force microscope show that the CNT-reinforced SiC nanowires are about an order of magnitude tougher than the bulk SiC. The tube/matrix interface is so intimate and the SiC matrix is so dense that a ~50-nm-thick SiC coating can effectively protect the inside nanotubes from being oxidized at 1600 C in air. The CVI method may be extended to produce nanotube composites from a variety of matrix

  14. Improved photoluminescence of vertically aligned ZnO nanorods grown on BaSrTiO{sub 3} by pulsed laser deposition

    Energy Technology Data Exchange (ETDEWEB)

    Varanasi, C V [University of Dayton Research Institute, Dayton, OH 45469 (United States); Leedy, K D; Tomich, D H [Air Force Research Laboratory, Wright-Patterson Air Force Base, OH 45433 (United States); Subramanyam, G [University of Dayton, Dayton, OH 45469 (United States); Look, D C, E-mail: Chakrapani.Varanasi@wpafb.af.mi [Semiconductor Research Center, Wright State University, Dayton, OH 45435 (United States)

    2009-09-23

    ZnO nanorods were grown on a variety of substrates such as Si, SiO{sub 2}/Si and sapphire in a large-area pulsed laser deposition chamber designed for sensor device fabrication. Processing conditions were optimized to grow ZnO nanorods with or without seed layers. Au, Cr and BaSrTiO{sub 3} (BST) seed layers were investigated to compare their effects on the diameter and orientation of ZnO nanorods. ZnO nanorods were observed to align better when grown on sapphire, Cr or BST seed layers as compared to Au or Si layers. The highest quality nanorods were those grown on BST seed layers, as shown by 4 K photoluminescence donor-bound-exciton linewidths of only 0.5 meV.

  15. Simulation study of radiation enhancement through an interaction between periodically aligned carbon nanotubes and an intense laser

    Science.gov (United States)

    Taguchi, Toshihiro; Inoue, Masahiko; Antonsen, Thomas

    2012-10-01

    Interaction between ultra-intense laser and solid material has a lot of applications. One is an emission of electromagnetic wave in a wide range of wavelength, which is from THz to X-ray. In order to select the wavelength, one of interesting target materials is single-walled carbon nanotube. Huge number of carbon nanotubes can be grown vertically on a substrate and they can be aligned periodically on the substrate. Once an ultra-intense laser is irradiated on the nanotubes, the strong electric field of the laser forcedly oscillates electrons in each nanotube and they irradiate electromagnetic wave. Waves emitted from periodically aligned nanotubes are expected to interfere each other, and then the amplitude of the output radiation is to be enhanced. In order to analyze such radiation processes from the laser-matter interaction, we have been developing an electromagnetic particle-in-cell (PIC) code including collisional and ionization processes. We will present recent results about an interaction between strong laser and carbon nanotubes analyzed by the PIC code. In the presentation, we will show the radiation spectrum and its enhancement due to the periodic structure.

  16. 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.

  17. Vertically aligned carbon nanotubes/diamond double-layered structure for improved field electron emission stability

    Energy Technology Data Exchange (ETDEWEB)

    Yang, L., E-mail: qiaoqin.yang@mail.usask.ca; Yang, Q.; Zhang, C.; Li, Y.S.

    2013-12-31

    A double-layered nanostructure consisting of a layer of vertically aligned Carbon Nanotubes (CNTs) and a layer of diamond beneath has been synthesized on silicon substrate by Hot Filament Chemical Vapor Deposition. The synthesis was achieved by first depositing a layer of diamond on silicon and then depositing a top layer of vertically aligned CNTs by applying a negative bias on the substrate holder. The growth of CNTs was catalyzed by a thin layer of spin-coated iron nitride. The surface morphology and structure of the CNTs/diamond double-layered structure were characterized by Scanning Electron Microscope, Energy Dispersive X-ray spectrum, and Raman Spectroscopy. Their field electron emission (FEE) properties were measured by KEITHLEY 237 high voltage measurement unit, showing much higher FEE current stability than single layered CNTs. - Highlights: • A new double-layered nanostructure consisting of a layer of vertically aligned CNTs and a layer of diamond beneath has been synthesized by hot filament chemical vapor deposition. • This double-layered structure exhibits superior field electron emission stability. • The improvement of emission stability is due to the combination of the unique properties of diamond and CNTs.

  18. Porosimetry and packing morphology of vertically aligned carbon nanotube arrays via impedance spectroscopy

    Science.gov (United States)

    Mutha, Heena K.; Lu, Yuan; Stein, Itai Y.; Cho, H. Jeremy; Suss, Matthew E.; Laoui, Tahar; Thompson, Carl V.; Wardle, Brian L.; Wang, Evelyn N.

    2017-02-01

    Vertically aligned one-dimensional nanostructure arrays are promising in many applications such as electrochemical systems, solar cells, and electronics, taking advantage of high surface area per unit volume, nanometer length scale packing, and alignment leading to high conductivity. However, many devices need to optimize arrays for device performance by selecting an appropriate morphology. Developing a simple, non-invasive tool for understanding the role of pore volume distribution and interspacing would aid in the optimization of nanostructure morphologies in electrodes. In this work, we combined electrochemical impedance spectroscopy (EIS) with capacitance measurements and porous electrode theory to conduct in situ porosimetry of vertically aligned carbon nanotube (VA-CNT) forests non-destructively. We utilized the EIS measurements with a pore size distribution model to quantify the average and dispersion of inter-CNT spacing (Γ), stochastically, in carpets that were mechanically densified from 1.7× {10}10 tubes cm-2 to 4.5× {10}11 tubes cm-2. Our analysis predicts that the inter-CNT spacing ranges from over 100 ± 50 nm in sparse carpets to sub 10 ± 5 nm in packed carpets. Our results suggest that waviness of CNTs leads to variations in the inter-CNT spacing, which can be significant in sparse carpets. This methodology can be used to predict the performance of many nanostructured devices, including supercapacitors, batteries, solar cells, and semiconductor electronics.

  19. Catalytic growth of vertically aligned neutron sensitive {sup 10}Boron nitride nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ahmad, Pervaiz, E-mail: pervaizahmad@siswa.um.edu.my, E-mail: Pervaiz-pas@yahoo.com; Khandaker, Mayeen Uddin, E-mail: mu-khandaker@yahoo.com, E-mail: mu-khandaker@um.edu.my; Amin, Yusoff Mohd [University of Malaya, Department of Physics, Faculty of Science (Malaysia); Khan, Ghulamullah [University of Malaya, Department of Mechanical Engineering (Malaysia); Ramay, Shahid M. [King Saud University, Department of Physics and Astronomy, College of Science (Saudi Arabia); Mahmood, Asif [King Saud University, Department of Chemical Engineering, College of Engineering (Saudi Arabia); Amin, Muhammad [University of the Punjab, Department of Physics (Pakistan); Muhammad, Nawshad [Interdisciplinary Research Centre in Biomedical Materials (IRCBM) COMSATS Institute of Information Technology (Pakistan)

    2016-01-15

    {sup 10}Boron nitride nanotubes ({sup 10}BNNTs) are a potential neutron sensing element in a solid-state neutron detector. The aligned {sup 10}BNNT can be used for its potential application without any further purification. Argon-supported thermal CVD is used to achieve vertically aligned {sup 10}BNNT with the help of nucleation sites produced in a thin layer of magnesium–iron alloy deposited at the top of Si substrate. FESEM shows vertically aligned {sup 10}BNNTs with ball-like catalytic tips at top. EDX reveals magnesium (Mg) contents in the tips that refer to catalytic growth of {sup 10}BNNT. HR-TEM shows tubular morphology of the synthesized {sup 10}BNNT with lattice fringes on its outer part having an interlayer spacing of ∼0.34 nm. XPS shows B 1 s and N 1 s peaks at 190.5 and 398 eV that correspond to hexagonal {sup 10}Boron nitride ({sup 10}h-BN) nature of the synthesized {sup 10}BNNT, whereas the Mg kll auger peaks at ∼301 and ∼311 eV represents Mg contents in the sample. Raman spectrum has a peak at 1390 (cm{sup −1}) that corresponds to E{sub 2g} mode of vibration in {sup 10}h-BN.

  20. Growth of primary motor neurons on horizontally aligned carbon nanotube thin films and striped patterns

    Science.gov (United States)

    Roberts, Megan J.; Leach, Michelle K.; Bedewy, Mostafa; Meshot, Eric R.; Copic, Davor; Corey, Joseph M.; Hart, A. John

    2014-06-01

    Objective. Carbon nanotubes (CNTs) are attractive for use in peripheral nerve interfaces because of their unique combination of strength, flexibility, electrical conductivity and nanoscale surface texture. Here we investigated the growth of motor neurons on thin films of horizontally aligned CNTs (HACNTs). Approach. We cultured primary embryonic rat motor neurons on HACNTs and performed statistical analysis of the length and orientation of neurites. We next presented motor neurons with substrates of alternating stripes of HACNTs and SiO2. Main results. The neurons survived on HACNT substrates for up to eight days, which was the full duration of our experiments. Statistical analysis of the length and orientation of neurites indicated that the longest neurites on HACNTs tended to align with the CNT direction, although the average neurite length was similar between HACNTs and glass control substrates. We observed that when motor neurons were presented with alternating stripes of HACNTs and SiO2, the proportion of neurons on HACNTs increases over time, suggesting that neurons selectively migrate toward and adhere to the HACNT surface. Significance. The behavior of motor neurons on CNTs has not been previously investigated, and we show that aligned CNTs could provide a viable interface material to motor neurons. Combined with emerging techniques to build complex hierarchical structures of CNTs, our results suggest that organised CNTs could be incorporated into nerve grafts that use physical and electrical cues to guide regenerating axons.

  1. Effects of vertically aligned carbon nanotubes on shear performance of laminated nanocomposite bonded joints

    Directory of Open Access Journals (Sweden)

    Davood Askari and Mehrdad N Ghasemi-Nejhad

    2012-01-01

    Full Text Available The main objective is to improve the most commonly addressed weakness of the laminated composites (i.e. delamination due to poor interlaminar strength using carbon nanotubes (CNTs as reinforcement between the laminae and in the transverse direction. In this work, a chemical vapor deposition technique has been used to grow dense vertically aligned arrays of CNTs over the surface of chemically treated two-dimensionally woven cloth and fiber tows. The nanoforest-like fabrics can be used to fabricate three-dimensionally reinforced laminated nanocomposites. The presence of CNTs aligned normal to the layers and in-between the layers of laminated composites is expected to considerably enhance the properties of the laminates. To demonstrate the effectiveness of our approach, composite single lap-joint specimens were fabricated for interlaminar shear strength testing. It was observed that the single lap-joints with through-the-thickness CNT reinforcement can carry considerably higher shear stresses and strains. Close examination of the test specimens showed that the failure of samples with CNT nanoforests was completely cohesive, while the samples without CNT reinforcement failed adhesively. This concludes that the adhesion of adjacent carbon fabric layers can be considerably improved owing to the presence of vertically aligned arrays of CNT nanoforests.

  2. Optimizing stem cell functions and antibacterial properties of TiO2 nanotubes incorporated with ZnO nanoparticles: experiments and modeling.

    Science.gov (United States)

    Liu, Wenwen; Su, Penglei; Gonzales, Arthur; Chen, Su; Wang, Na; Wang, Jinshu; Li, Hongyi; Zhang, Zhenting; Webster, Thomas J

    2015-01-01

    To optimize mesenchymal stem cell differentiation and antibacterial properties of titanium (Ti), nano-sized zinc oxide (ZnO) particles with tunable concentrations were incorporated into TiO2 nanotubes (TNTs) using a facile hydrothermal strategy. It is revealed here for the first time that the TNTs incorporated with ZnO nanoparticles exhibited better biocompatibility compared with pure Ti samples (controls) and that the amount of ZnO (tailored by the concentration of Zn(NO3)2 in the precursor) introduced into TNTs played a crucial role on their osteogenic properties. Not only was the alkaline phosphatase activity improved to about 13.8 U/g protein, but the osterix, collagen-I, and osteocalcin gene expressions was improved from mesenchymal stem cells compared to controls. To further explore the mechanism of TNTs decorated with ZnO on cell functions, a response surface mathematical model was used to optimize the concentration of ZnO incorporation into the Ti nanotubes for stem cell differentiation and antibacterial properties for the first time. Both experimental and modeling results confirmed (R (2) values of 0.8873-0.9138 and 0.9596-0.9941, respectively) that Ti incorporated with appropriate concentrations (with an initial concentration of Zn(NO3)2 at 0.015 M) of ZnO can provide exceptional osteogenic properties for stem cell differentiation in bone cells with strong antibacterial effects, properties important for improving dental and orthopedic implant efficacy.

  3. Direct growth of single-walled carbon nanotubes on conducting ZnO films and its field emission properties

    Science.gov (United States)

    Min, Yo-Sep; Bae, Eun Ju; Kim, Un Jeong; Park, Wanjun; Hwang, Cheol Seong

    2006-09-01

    Despite the necessity of direct growth of single-walled carbon nanotubes (SWNTs) on conducting films for versatility of designing device architectures for nanoelectronics and optoelectronics, most of SWNT growths have been carried out on insulating films or supporting materials such as SiO2 and Al2O3. Here, the authors report that conducting ZnO films can be used as both an underlying layer for the SWNT growth and an electrode for device operation. ZnO films with a resistivity in the order of 10-3Ωcm were deposited by atomic layer deposition. SWNTs were directly grown on the ZnO film by water plasma chemical vapor deposition. The authors demonstrate field emission properties from the SWNT/ZnO cathode, of which the turn-on electric field for a current density of 10μA /cm2 and the field enhancement factor are 1.8V/μm and 3200, respectively.

  4. Efficient Photocatalytic Degradation of Rhodamine B Dye by Aligned Arrays of Self-Assembled Hydrogen Titanate Nanotubes

    Directory of Open Access Journals (Sweden)

    Sriparna Chatterjee

    2014-01-01

    Full Text Available We show that an aligned array of hydrothermally grown, multiwalled hydrogen titanate (H2Ti3O7 nanotubes—anchored to both faces of a metallic Ti foil—acts as an efficient photocatalyst. We studied the degradation of rhodamine B dye in the presence of the nanostructured photocatalyst under UV irradiation, by monitoring the optical absorption of the dye. Rhodamine B was chosen as a representative—and particularly harmful—industrial pollutant dye. The inner and outer diameters of the H2Ti3O7 nanotubes were 5 nm and 10 nm, respectively. The nanotube array catalyst is recyclable and structurally stable. Most importantly, it shows comparable or higher photodecomposition rate constant than those of both H2Ti3O7 nanotube powder and P-25 (Degussa. The enhanced photocatalytic performance may be ascribed to the nanotube array having a superhydrophilic surface with a high accessible surface area.

  5. Load Transfer Analysis in Short Carbon Fibers with Radially-Aligned Carbon Nanotubes Embedded in a Polymer Matrix

    OpenAIRE

    2009-01-01

    A novel shortfiber composite in which the microscopic advanced fiber reinforcements are coated with radially aligned carbon nanotubes (CNTs) is analyzed in this study. A shear-lag model is developed to analyze the load transferred to such coated fibers from the aligned-CNT reinforced matrix in a hybrid composite application. It is found that if the carbon fibers are coated with radially aligned CNTs, then the axial load transferred to the fiber is reduced due to stiffening of the matrix by th...

  6. Printable nanoscale metal ring arrays via vertically aligned carbon nanotube platforms.

    Science.gov (United States)

    Lee, Sang Ho; Yoon, Seungha; Jeong, Huisu; Han, Mingu; Choi, Sung Mook; Kim, Jong Guk; Park, Ji-Woong; Jung, Gun Young; Cho, Beong Ki; Kim, Won Bae

    2013-11-01

    This paper reports a novel and efficient strategy for fabricating sub-100 nm metal ring arrays using a simple printing process. Vertically aligned carbon nanotubes that are supported by hexagonally ordered channels of alumina matrices are used as a stamp to print nanoscale ring patterns, which is a very unique stamping platform that has never been reported. Using this strategy, uniform nanoring patterns of various metals can be directly printed onto a wide range of substrate surfaces under ambient conditions. Significantly, the size and interval of the printed nanorings can be systematically tuned by controlling the ring-shaped tip dimensions of the pristine stamps. An advanced example of these printable nanoscale metal ring arrays is explicitly embodied in this work by investigation of the plasmon resonances of metal nanorings with different sizes and intervals.

  7. Highly uniform hole spacing micro brushes based on aligned carbon nanotube arrays

    Science.gov (United States)

    Yang, Zhi; Zhu, Xingzhong; Huang, Xiaolu; Cheng, Yingwu; Liu, Yun; Geng, Huijuan; Wu, Yue; Su, Yanjie; Wei, Hao; Zhang, Yafei

    2013-11-01

    Highly uniform hole spacing micro brushes were fabricated based on aligned carbon nanotube (CNT) arrays synthesized by chemical vapor deposition method with the assistance of anodic aluminum oxide (AAO) template. Different micro brushes from CNT arrays were constructed on silicon, glass, and polyimide substrates, respectively. The micro brushes had highly uniform hole spacing originating from the regularly periodic pore structure of AAO template. The CNT arrays, serving as bristles, were firmly grafted on the substrates. The brushes can easily clean particles with scale of micrometer on the surface of silicon wafer and from the narrow spaces between the electrodes in a series of cleaning experiments. The results show the potential application of the CNT micro brushes as a cleaning tool in microelectronics manufacture field.

  8. Surface-conduction electron-emitter characteristics and fabrication based on vertically aligned carbon nanotube arrays

    Science.gov (United States)

    Shih, Yi-Ting; Li, Kuan-Wei; Honda, Shin-ichi; Lin, Pao-Hung; Huang, Ying-Sheng; Lee, Kuei-Yi

    2017-06-01

    The carbon nanotube (CNT) has replaced palladium oxide (PdO) as the electrode material for surface-conduction electron-emitter (SCE) applications. Vertically aligned CNT arrays with a delta-star arrangement were patterned and synthesized onto a quartz substrate using photolithography and thermal chemical vapor deposition. Delta-star shaped VACNT arrays with 20° tips are used as cathodes that easily emit electrons because of their high electrical field gradient. In order to improve the field emission and secondary electrons (SEs) in SCE applications, magnesium oxide (MgO) nanostructures were coated onto the VACNT arrays to promote the surface-conduction electron-emitter display (SED) efficiency (η). According to the definition of η in SCE applications, in this study, the η was stably maintained in the 75-85% range. The proposed design provides a facile new method for developing SED applications.

  9. Calcification in vitro of biomineralizated nanohydroxyapatite/superydrophilic vertically aligned multiwalled carbon nanotube scaffolds

    Directory of Open Access Journals (Sweden)

    Marcele Florencio Neves

    2013-06-01

    Full Text Available Nanocomposites based on superhydrophilic vertically aligned multi-walled carbon nanotubes (VAMWCNT-O2 and nanohydroxyapatite (nHAp are of great interest in bone regenerative medicine. The biomineralization using simulated body fluid (SBF has been extensively studied to evaluate the bioactivity of biomaterials. Thus, the combination of nHAp and VAMWCNT-O2 is attractive and promising. The aim of this study was to evaluate the in vitro calcification of nHAp/VAMWCNT-O2 nanocomposites before and after the period of biomineralization in SBF. In vitro calcification of the extracellular matrix (ECM of HOB cells in culture after 24 hours was investigated through the assay of alkaline phosphatase. These promising in vitro results validate biomineralized nHAp/VAMWCNT-O2 as possible scaffolds for bone tissue regeneration.

  10. Flexible supercapacitor electrodes with vertically aligned carbon nanotubes grown on aluminum foils

    Directory of Open Access Journals (Sweden)

    Itir Bakis Dogru

    2016-06-01

    Full Text Available In this work, vertically aligned carbon nanotubes (VACNTs grown on aluminum foils were used as flexible supercapacitor electrodes. Aluminum foils were used as readily available, cheap and conductive substrates, and VACNTs were grown directly on these foils through chemical vapor deposition (CVD method. Solution based ultrasonic spray pyrolysis (USP method was used for the deposition of the CNT catalyst. Direct growth of VACNTs on aluminum foils ruled out both the internal resistance of the supercapacitor electrodes and the charge transfer resistance between the electrode and electrolyte. A specific capacitance of 2.61 mF/cm2 at a scan rate of 800 mV/s was obtained from the fabricated electrodes, which is further improved through the bending cycles.

  11. Wet catalyst-support films for production of vertically aligned carbon nanotubes.

    Science.gov (United States)

    Alvarez, Noe T; Hamilton, Christopher E; Pint, Cary L; Orbaek, Alvin; Yao, Jun; Frosinini, Aldo L; Barron, Andrew R; Tour, James M; Hauge, Robert H

    2010-07-01

    A procedure for vertically aligned carbon nanotube (VA-CNT) production has been developed through liquid-phase deposition of alumoxanes (aluminum oxide hydroxides, boehmite) as a catalyst support. Through a simple spin-coating of alumoxane nanoparticles, uniform centimer-square thin film surfaces were coated and used as supports for subsequent deposition of metal catalyst. Uniform VA-CNTs are observed to grow from this film following deposition of both conventional evaporated Fe catalyst, as well as premade Fe nanoparticles drop-dried from the liquid phase. The quality and uniformity of the VA-CNTs are comparable to growth from conventional evaporated layers of Al(2)O(3). The combined use of alumoxane and Fe nanoparticles to coat surfaces represents an inexpensive and scalable approach to large-scale VA-CNT production that makes chemical vapor deposition significantly more competitive when compared to other CNT production techniques.

  12. Calcification in vitro of Biomineralized nanohydroxyapatite / superhydrophilic vertically aligned multiwalled carbon nanotube scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Neves, Marcele Florencio; Silva, Gislene Rodrigues; Brazil, Tayra Rodrigues; Marciano, Fernanda Roberta; Lobo, Anderson Oliveira, E-mail: loboao@yahoo.com, E-mail: aolobo@univap.br [Universidade do Vale do Paraiba (UniVap), Sao Jose dos Campos, SP (Brazil). Lab. de Nanotecnologia Biomedica; Pacheco-Soares, Cristina [Universidade do Vale do Paraiba (UniVap), Sao Jose dos Campos, SP (Brazil). Lab. de Dinamica de Compartimentos Celulares

    2013-11-01

    Nanocomposites based on superhydrophilic vertically aligned multi-walled carbon nanotubes (VAMWCNT-O{sub 2}) and nanohydroxyapatite (nHAp) are of great interest in bone regenerative medicine. The biomineralization using simulated body fluid (SBF) has been extensively studied to evaluate the bioactivity of biomaterials. Thus, the combination of nHAp and VAMWCNT-O{sub 2} is attractive and promising. The aim of this study was to evaluate the in vitro calcification of nHAp/VAMWCNT-O{sub 2} nanocomposites before and after the period of biomineralization in SBF. In vitro calcification of the extracellular matrix (ECM) of HOB cells in culture after 24 hours was investigated through the assay of alkaline phosphatase. These promising in vitro results validate biomineralized nHAp/VAMWCNT-O{sub 2} as possible scaffolds for bone tissue regeneration. (author)

  13. Proposed model for biomineralization of novel nanohydroxyapatite/vertically aligned multiwalled carbon nanotube scaffolds

    Energy Technology Data Exchange (ETDEWEB)

    Brazil, Tayra Rodrigues; Neves, Marcele Florencio das; Marciano, Fernanda Roberta; Lobo, Anderson Oliveira, E-mail: aolobo@univap.br [Universidade do Vale do Paraiba (UniVap), Sao Jose dos Campos, SP (Brazil). Lab. de Nanotecnologia Biomedica; Regiani, Inacio [Instituto Tecnologico de Aeronautica (ITA), Sao Jose dos Campos, SP (Brazil)

    2013-11-01

    For the first time, the growth mechanism of biominerals formed on plate-like nanohydroxyapatite (nHAp) electrodeposited on superhydrophilic vertically aligned multi-walled carbon nanotubes (VAMWCNT-O{sub 2} ) is presented and a model for the specific growth preference is discussed. VAMWCNT-O{sub 2} films were obtained by microwave-assisted chemical vapor deposition method and functionalized by oxygen plasma. nHAp/VAMWCNT-O{sub 2} nanocomposites were fabricated with a direct electrodeposition of the thin nHAp films onto the VAMWCNT-O{sub 2} films. The biomineralized 'scaffolds' were obtained by soaking nHAp/VAMWCNT-O{sub 2} in simulated body fluid for 7, 14 and 21 days. Results show that the carboxyl functional groups directly attached onto VAMWCNT tips after oxygen plasma treatment were essential for the acceleration of the OH- formation and the deposition of plate-like nHAp crystals (author)

  14. Proposed model for biomineralization of novel nanohydroxyapatite/vertically aligned multiwalled carbon nanotube scaffolds

    Directory of Open Access Journals (Sweden)

    Tayra Rodrigues Brazil

    2013-06-01

    Full Text Available For the first time, the growth mechanism of biominerals formed on plate-like nanohydroxyapatite (nHAp electrodeposited on superhydrophilic vertically aligned multi-walled carbon nanotubes (VAMWCNT-O2 is presented and a model for the specific growth preference is discussed. VAMWCNT-O2 films were obtained by microwave-assisted chemical vapor deposition method and funcionalized by oxygen plasma. nHAp/VAMWCNT-O2 nanocomposites were fabricated with a direct electrodeposition of the thin nHAp films onto the VAMWCNT-O2 films. The biomineralized "scaffolds" were obtained by soaking nHAp/VAMWCNT-O2 in simulated body fluid for 7, 14 and 21 days. Results show that the carboxyl functional groups directly attached onto VAMWCNT tips after oxygen plasma treatment were essential for the acceleration of the OH- formation and the deposition of plate-like nHAp crystals.

  15. Field Emission Characteristics of the Structure of Vertically Aligned Carbon Nanotube Bundles

    Science.gov (United States)

    Lin, Pao-Hung; Sie, Cong-Lin; Chen, Ching-An; Chang, Hsuan-Chen; Shih, Yi-Ting; Chang, Hsin-Yueh; Su, Wei-Jhih; Lee, Kuei-Yi

    2015-07-01

    In this study, we performed thermal chemical vapor deposition for growing vertically aligned carbon nanotube (VACNT) bundles for a field emitter and applied photolithography for defining the arrangement pattern to simultaneously compare square and hexagonal arrangements by using two ratios of the interbundle distance to the bundle height ( R) of field emitters. The hexagon arrangement with R = 2 had the lowest turn-on electric field ( E to) and highest enhancement factor, whereas the square arrangement with R = 3 had the most stable field emission (FE) characteristic. The number density can reveal the correlation to the lowest E to and highest enhancement factor more effectively than can the R or L. The fluorescent images of the synthesized VACNT bundles manifested the uniformity of FE currents. The results of our study indicate the feasibility of applying the VACNT field emitter arrangement to achieve optimal FE performance.

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

    Science.gov (United States)

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

    2014-01-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Nuri Yazdani

    2014-03-01

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

  19. Aligned carbon nanotube array stiffness from stochastic three-dimensional morphology

    Science.gov (United States)

    Stein, Itai Y.; Lewis, Diana J.; Wardle, Brian L.

    2015-11-01

    The landmark theoretical properties of low dimensional materials have driven more than a decade of research on carbon nanotubes (CNTs) and related nanostructures. While studies on isolated CNTs report behavior that aligns closely with theoretical predictions, studies on cm-scale aligned CNT arrays (>1010 CNTs) oftentimes report properties that are orders of magnitude below those predicted by theory. Using simulated arrays comprised of up to 105 CNTs with realistic stochastic morphologies, we show that the CNT waviness, quantified via the waviness ratio (w), is responsible for more than three orders of magnitude reduction in the effective CNT stiffness. Also, by including information on the volume fraction scaling of the CNT waviness, the simulation shows that the observed non-linear enhancement of the array stiffness as a function of the CNT close packing originates from the shear and torsion deformation mechanisms that are governed by the low shear modulus (~1 GPa) of the CNTs.The landmark theoretical properties of low dimensional materials have driven more than a decade of research on carbon nanotubes (CNTs) and related nanostructures. While studies on isolated CNTs report behavior that aligns closely with theoretical predictions, studies on cm-scale aligned CNT arrays (>1010 CNTs) oftentimes report properties that are orders of magnitude below those predicted by theory. Using simulated arrays comprised of up to 105 CNTs with realistic stochastic morphologies, we show that the CNT waviness, quantified via the waviness ratio (w), is responsible for more than three orders of magnitude reduction in the effective CNT stiffness. Also, by including information on the volume fraction scaling of the CNT waviness, the simulation shows that the observed non-linear enhancement of the array stiffness as a function of the CNT close packing originates from the shear and torsion deformation mechanisms that are governed by the low shear modulus (~1 GPa) of the CNTs. Electronic

  20. Nanoscale optical and electrical characterization of horizontally aligned single-walled carbon nanotubes

    Science.gov (United States)

    Rodriguez, Raul D.; Toader, Marius; Hermann, Sascha; Sheremet, Evgeniya; Müller, Susanne; Gordan, Ovidiu D.; Yu, Haibo; Schulz, Stefan E.; Hietschold, Michael; Zahn, Dietrich RT

    2012-12-01

    During the recent years, a significant amount of research has been performed on single-walled carbon nanotubes (SWCNTs) as a channel material in thin-film transistors (Pham et al. IEEE Trans Nanotechnol 11:44-50, 2012). This has prompted the application of advanced characterization techniques based on combined atomic force microscopy (AFM) and Raman spectroscopy studies (Mureau et al. Electrophoresis 29:2266-2271, 2008). In this context, we use confocal Raman microscopy and current sensing atomic force microscopy (CS-AFM) to study phonons and the electronic transport in semiconducting SWCNTs, which were aligned between palladium electrodes using dielectrophoresis (Kuzyk Electrophoresis 32:2307-2313, 2011). Raman imaging was performed in the region around the electrodes on the suspended CNTs using several laser excitation wavelengths. Analysis of the G+/G- splitting in the Raman spectra (Sgobba and Guldi Chem Soc Rev 38:165-184, 2009) shows CNT diameters of 2.5 ± 0.3 nm. Neither surface modification nor increase in defect density or stress at the CNT-electrode contact could be detected, but rather a shift in G+ and G- peak positions in regions with high CNT density between the electrodes. Simultaneous topographical and electrical characterization of the CNT transistor by CS-AFM confirms the presence of CNT bundles having a stable electrical contact with the transistor electrodes. For a similar load force, reproducible current-voltage ( I/ V) curves for the same CNT regions verify the stability of the electrical contact between the nanotube and the electrodes as well as the nanotube and the AFM tip over different experimental sessions using different AFM tips. Strong variations observed in the I/ V response at different regions of the CNT transistor are discussed.

  1. Scalable synthesis of aligned carbon nanotubes bundles using green natural precursor: neem oil

    Directory of Open Access Journals (Sweden)

    Kumar Rajesh

    2011-01-01

    Full Text Available Abstract Practical application of aligned carbon nanotubes (ACNTs would have to be determined by a matter of its economical and large-scale preparation. In this study, neem oil (also named Margoaa oil, extracted from the seeds of the neem--Azadirachta indica was used as carbon source to fabricate the bundles of ACNTs. ACNTs have been synthesized by spray pyrolysis of neem oil and ferrocene mixture at 825°C. The major components of neem oil are hydrocarbon with less amount of oxygen, which provided the precursor species in spray pyrolysis growth of CNTs. The bundles of ACNTs have been grown directly inside the quartz tube. The as-grown ACNTs have been characterized through Raman spectroscopy, scanning and transmission electron microscopic (SEM/TEM techniques. SEM images reveal that the bundles of ACNTs are densely packed and are of several microns in length. High-resolution TEM analysis reveals these nanotubes to be multi-walled CNTs. These multi-walled CNTs were found to have inner diameter between 15 and 30 nm. It was found that present technique gives high yield with high density of bundles of ACNTs.

  2. Influence of contact height on the performance of vertically aligned carbon nanotube field-effect transistors

    KAUST Repository

    Li, Jingqi

    2013-01-01

    Vertically aligned carbon nanotube field-effect transistors (CNTFETs) have been experimentally demonstrated (J. Li et al., Carbon, 2012, 50, 4628-4632). The source and drain contact heights in vertical CNTFETs could be much higher than in flat CNTFETs if the fabrication process is not optimized. To understand the impact of contact height on transistor performance, we use a semi-classical method to calculate the characteristics of CNTFETs with different contact heights. The results show that the drain current decreases with increasing contact height and saturates at a value governed by the thickness of the oxide. The current reduction caused by the increased contact height becomes more significant when the gate oxide is thicker. The higher the drain voltage, the larger the current reduction. It becomes even worse when the band gap of the carbon nanotube is larger. The current can differ by a factor of more than five between the CNTEFTs with low and high contact heights when the oxide thickness is 50 nm. In addition, the influence of the contact height is limited by the channel length. The contact height plays a minor role when the channel length is less than 100 nm. © 2013 The Royal Society of Chemistry.

  3. Thermal diffusivity of aligned multi-walled carbon nanotubes measured by the flash method

    Energy Technology Data Exchange (ETDEWEB)

    Maeklin, Jani; Halonen, Niina; Toth, Geza; Jantunen, Heli [Microelectronics and Materials Physics Laboratories, University of Oulu (Finland); Sapi, Andras; Kukovecz, Akos; Konya, Zoltan [Department of Applied and Environmental Chemistry, University of Szeged (Hungary); Mikkola, Jyri-Pekka [Department of Chemistry, Technical Chemistry, Umeaa University (Sweden); Kordas, Krisztian [Microelectronics and Materials Physics Laboratories, University of Oulu (Finland); Department of Chemistry, Technical Chemistry, Umeaa University (Sweden)

    2011-11-15

    Thermal diffusivity of freestanding catalytic chemical vapor deposition (CCVD) grown multi-walled carbon nanotube (MWCNT) forests (height of 1.5 and 1.9 mm) was characterized in the temperature range between 25 and 200 C. Copper and Al-alloy metal blocks were used as references for validation of the experimental setup. The measurements were carried out along the MWCNT alignment direction with a thermal property analyzer that uses the flash method. The thermal diffusivities measured at room temperature for as-grown and post-annealed (2 h at 480 C in open air) samples were found to be {proportional_to}0.45 and {proportional_to}0.23 cm{sup 2}/s, respectively. In both cases, the thermal diffusivity values were slightly decreasing with increasing temperature. The observed decrease in diffusivity after annealing is most probably due to the loss of amorphous carbon in the specimens and also because of the increased defect density in the nanotube walls resulting in a more pronounced phonon scattering in the lattice. The measured thermal diffusivities for as-grown samples agree with data reported elsewhere for similar MWCNT materials [W. Yi et al., Rev. B 59, 9015 (1999) and T. Borca-Tasciuc et al., J. Appl. Phys. 98, 054309 (2005)]. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Production and mechanical properties of aligned multi-walled carbon nanotubes-M140 composites

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    This study investigated the production of M140, aligned multi-walled carbon nanotubes (A-MWNTs) reinforced M140 composites (A-MWNTs-M140) and their mechanical properties including their compressive and bending properties as well as their microstructure characteristic of bend fracture surface. M140 was first produced by speed change mixing technics with commercial materials, water-bath curing at normal temperature. In addition, two different A-MWNTs dispersions including carbonyl disper- sions of A-MWNTs (C-A-MWNTs) and aqueous dispersions of A-MWNTs (A-A-MWNTs) with the addition of 0.01wt% A-MWNTs were utilized to obtain enhanced mechanical properties with respect to plain M140. The results indicated that the use of A-MWNTs dispersions allows increasing compressive strength and flexural strength by 8.4% and 5.4%, respectively for the C-A-MWNTs-M140, and by 15.9% and 20.7% for the A-A-MWNTs-M140, respectively. The SEM and EPMA examinations of fracture surface also showed that the bond interface between the nanotubes and matrix is moderate and the main reinforcing mechanisms are microfilling effect, CNTs pull-out and debond. The aqueous dispersion of A-MWNTs is an appropriate method and is more compatible with the M140.

  5. Production and mechanical properties of aligned multi-walled carbon nanotubes-M140 composites

    Institute of Scientific and Technical Information of China (English)

    XU ShiLang; GAO LiangLi; JIN WeiJun

    2009-01-01

    This study investigated the production of M140, aligned multi-walled carbon nanotubes (A-MWNTs)reinforced M140 composites (A-MWNTs-M140) and their mechanical properties including their compressive and bending properties as well as their microstructure characteristic of bend fracture surface.M140 was first produced by speed change mixing technics with commercial materials, water-bath curing at normal temperature. In addition, two different A-MWNTs dispersions including carbonyl dispersions of A-MWNTs (C-A-MWNTs) and aqueous dispersions of A-MWNTs (A-A-MWNTs) with the addition of 0.01wt% A-MWNTs were utilized to obtain enhanced mechanical properties with respect to plain M140. The results indicated that the use of A-MWNTs dispersions allows increasing compressive strength and flexural strength by 8.4% and 5.4%, respectively for the C-A-MWNTs-M140, and by 15.9% and 20.7% for the A-A-MWNTs-M140, respectively. The SEM and EPMA examinations of fracture surface also showed that the bond interface between the nanotubes and matrix is moderate and the main reinforcing mechanisms are microfilling effect, CNTs pull-out and debond. The aqueous dispersion of A-MWNTs is an appropriate method and is more compatible with the M140.

  6. Continuous high-yield production of vertically aligned carbon nanotubes on 2D and 3D substrates.

    Science.gov (United States)

    Guzmán de Villoria, Roberto; Hart, A John; Wardle, Brian L

    2011-06-28

    Vertically aligned carbon nanotubes (VACNTs) have certain advantages over bulk CNT powders and randomly oriented CNT mats for applications in flexible electronic devices, filtration membranes, biosensors and multifunctional aerospace materials. Here, a machine and a process to synthesize VACNTs in a continuous manner are presented showing uniform growth on 2D and 3D substrates, including alumina fibers, silicon wafer pieces, and stainless steel foils. Aligned multiwalled carbon nanotubes (MWNT) are synthesized at substrate feed rates of up to 6.8 cm/min, and the CNTs reach up to 60 μm in length depending on residence time in the reactor. In addition to the aligned morphology indicative of high yield growth, transmission electron microscopy and Raman spectroscopy reveal that the CNTs are of comparable quality to CNTs grown via a similar batch process. A significant reduction in time, reaction products, gases, and energy is demonstrated relative to batch processing, paving the way for industrial production of VACNTs.

  7. Structural and optical properties of dense vertically aligned ZnO nanorods grown onto silver and gold thin films by galvanic effect with iron contamination

    Energy Technology Data Exchange (ETDEWEB)

    Scarpellini, D.; Paoloni, S.; Medaglia, P.G. [Department of Industrial Engineering, University of Rome “Tor Vergata”, 00133 Rome (Italy); Pizzoferrato, R., E-mail: pizzoferrato@uniroma2.it [Department of Industrial Engineering, University of Rome “Tor Vergata”, 00133 Rome (Italy); Orsini, A.; Falconi, C. [Department of Electronic Engineering, University of Rome “Tor Vergata”, 00133 Rome (Italy)

    2015-05-15

    Highlights: • ZnO nanorods were grown on Au and Ag films in aqueous solution by galvanic effect. • The method is prone to metal contamination which can influence the ZnO properties. • Iron doping improves the lattice matching between ZnO and the substrate. • Energy levels of point defects are lowered and the light emission is red-shifted. • Galvanic-induced nucleation starts and proceeds continuously during the growth. - Abstract: Dense arrays of vertically aligned ZnO nanorods have been grown onto either silver or gold seedless substrates trough a simple hydrothermal method by exploiting the galvanic effect between the substrate and metallic parts. The nanorods exhibit larger bases and more defined hexagonal shapes, in comparison with standard non-galvanic wet-chemistry synthesis. X-ray diffraction (XRD) shows that the iron contamination, associated with the galvanic contact, significantly improves the in-plane compatibility of ZnO with the Au and Ag cubic lattice. Photoluminescence (PL) measurements indicate that the contamination does not affect the number density of localized defects, but lowers their energy levels uniformly; differently, the band-edge emission is not altered appreciably. Finally, we have found that the ZnO hetero-nucleation by galvanic effect initiates at different times in different sites of the substrate area. Our results can be useful for the fabrication of high performance piezonanodevices comprising high-density metal-to-ZnO nanoscaled junctions without intermediate polycrystalline layers.

  8. Photoelectric response properties under UV/red light irradiation of ZnO nanorod arrays coated with vertically aligned MoS2 nanosheets

    Science.gov (United States)

    Zhang, Yuzhu; Xu, Jianping; Shi, Shaobo; Gao, Yanyan; Zhao, Xiangguo; Wei, Chengtai; Zhang, Xiaosong; Li, Lan

    2017-10-01

    MoS2 with layered structure and distinct physical properties has attracted attention for electronic or optoelectronic devices. The photoelectric response properties of MoS2/ZnO heterojunctions based devices fabricated by spin-coating MoS2 nanosheets solutions on ZnO nanorod arrays (NRs) were investigated. The results revealed that MoS2 nanosheets were vertically aligned on the surface of ZnO NRs and the devices exhibit good photoresponse stability and reproducibility under UV and red light illuminations. The vertically aligned MoS2 nanosheets facilitate the fast photogenerated carrier separation and transport. The devices with few-layered MoS2 nanosheets show a high responsivity and detectivity under UV and red light illuminations, which can be attributed to small contact resistance between MoS2 nanosheets and ZnO NRs. These results provide important insights in the facile fabrication strategy and understanding electronic and optoelectronic devices based on the heterostructures with vertically aligned MoS2.

  9. Effect of Nb-doped TiO2 on nanocomposited aligned ZnO nanorod/TiO2:Nb for dye-sensitized solar cells

    Science.gov (United States)

    Saurdi, I.; Shafura, A. K.; Azhar, N. E. A.; Ishak, A.; Malek, M. F.; Alrokayan, A. H. Salman; Khan, Haseeb A.; Mamat, M. H.; Rusop, M.

    2016-07-01

    The Nb-doped TiO2 films were deposited on glass substrate at different Nb concentrations of 0 at.%, 1 at.%, 3 at.%, 5 at.% and 7 at.%, respectively and their electrical and structural properties were investigated. Subsequently, the Nb-doped TiO2 films were deposited on top of aligned ZnO Nanorod on ITO glass substrates using spin coating technique. The nanocomposited aligned ZnO nanorod/Nb-doped TiO2 (TiO2:Nb) were coated with different Nb concentrations of 0 at.%, 1 at.%, 3 at.%, 5 at.% and 7 at.%, respectively. The Dye-sensitized solar cells were fabricated from the nanocomposited aligned ZnO nanorod/TiO2:Nb photoanodes and their effects on the performance of the DSSCs were investigated. From the solar simulator measurement of DSSC the solar energy conversion efficiency (η) of 5.376% under AM 1.5 was obtained for the ZnO nanorod/TiO2:Nb-5at.%.

  10. Growth of Vertically Aligned ZnO Nanowire Arrays Using Bilayered Metal Catalysts

    Science.gov (United States)

    2012-01-01

    2010. [9] K. S. Leschkies, R. Divakar, J. Basu et al., “Photosensitization of ZnO nanowires with CdSe quantum dots for photovoltaic devices,” Nano...376, no. 5-6, pp. 653–658, 2003. [25] G. Z. Dai, Q. L. Zhang, Z.W. Peng et al., “One-step synthesis of low-dimensional CdSe nanostructures and...vapor-solid) mechanism, which has been reported by Dong et al. and Dai et al. [24, 25], in the CdSe and CdS system. In our case, during the early

  11. 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.

  12. Mechanics of aligned carbon nanotube polymer matrix nanocomposites simulated via stochastic three-dimensional morphology

    Science.gov (United States)

    Stein, Itai Y.; Wardle, Brian L.

    2016-01-01

    The promise of enhanced and tailored properties motivates the study of one-dimensional nanomaterials, especially aligned carbon nanotubes (A-CNTs), for the reinforcement of polymeric materials. While CNTs have remarkable theoretical properties, previous work on aligned CNT polymer matrix nanocomposites (A-PNCs) reported mechanical properties that are orders of magnitude lower than those predicted by rule of mixtures. This large difference primarily originates from the morphology of the CNTs, because the CNTs that comprise the A-PNCs have significant local curvature commonly referred to as waviness. Here we present a simulation framework capable of analyzing 105 wavy CNTs with realistic three-dimensional morphologies to quantify the impact of waviness on the effective elastic modulus contribution of wavy CNTs. The simulation results show that due to the low shear modulus of the reinforcing CNT ‘fibers’, and large (\\gt 50%) compliance contribution of the shear deformation mode, waviness reduces the effective stiffness contribution of the A-CNTs by two to three orders of magnitude. Also, the mechanical property predictions resulting from the simulation framework outperform those previously reported using finite element analysis since representative descriptions of the morphology are required to accurately predict properties of the A-PNCs. Further work to quantify the morphology of A-PNCs in three-dimensions, simulate their full non-isotropic constitutive relations, and predict their failure mechanisms is planned.

  13. Alignment controlled growth of single-walled carbon nanotubes on quartz substrates.

    Science.gov (United States)

    Xiao, Jianliang; Dunham, Simon; Liu, Ping; Zhang, Yongwei; Kocabas, Coskun; Moh, Lionel; Huang, Yonggang; Hwang, Keh-Chih; Lu, Chun; Huang, Wei; Rogers, John A

    2009-12-01

    Single-walled carbon nanotubes (SWNTs) possess extraordinary electrical properties, with many possible applications in electronics. Dense, horizontally aligned arrays of linearly configured SWNTs represent perhaps the most attractive and scalable way to implement this class of nanomaterial in practical systems. Recent work shows that templated growth of tubes on certain crystalline substrates yields arrays with the necessary levels of perfection, as demonstrated by the formation of devices and full systems on quartz. This paper examines advanced implementations of this process on crystalline quartz substrates with different orientations, to yield strategies for forming diverse, but well-defined horizontal configurations of SWNTs. Combined experimental and theoretical studies indicate that angle-dependent van der Waals interactions can account for nearly all aspects of alignment on quartz with X, Y, Z, and ST cuts, as well as quartz with disordered surface layers. These findings provide important insights into methods for guided growth of SWNTs, and possibly other classes of nanomaterials, for applications in electronics, sensing, photodetection, light emission, and other areas.

  14. Photopolymerization of Diacetylene on Aligned Multiwall Carbon Nanotube Microfibers for High-Performance Energy Devices.

    Science.gov (United States)

    Ulaganathan, Mani; Hansen, Reinack Varghese; Drayton, Nateisha; Hingorani, Hardik; Kutty, R Govindan; Joshi, Hrishikesh; Sreejith, Sivaramapanicker; Liu, Zheng; Yang, Jinglei; Zhao, Yanli

    2016-12-07

    Linear two-dimensional materials have recently attracted an intense interest for supercapacitors because of their potential uses as electrodes in next-generation wearable electronics. However, enhancing the electrochemical properties of these materials without complicated structural modifications remains a challenge. Herein, we present the preparation of a hybrid electrode system via polydiacetylene (PDA) cloaking on the surface of aligned multiwall carbon nanotubes (MWCNTs) through self-assembly based in situ photopolymerization. This strategy eliminates the need for initiators and binders that hinder electrochemical performance in conventional conducting polymer based composite electrodes. As noncovalent PDA cloaking did not alter the chemical structure of MWCNTs, high inherent conductivity from sp(2) hybridized carbon was preserved. The resulting hybrid microfiber (MWCNT@PDA) exhibited a significant increase in specific capacitance (1111 F g(-1)) when compared to bare MWCNTs (500 F g(-1)) and PDA (666.7 F g(-1)) in a voltage window of 0-1.2 V at a current density of 3 A g(-1) in 0.5 M K2SO4 electrolyte. The specific capacitance was retained (ca. 95%) after 7000 charge/discharge cycles. The present results suggest that aligned MWCNTs cloaked with conjugated polymers could meet the demands for future flexible electronics.

  15. Synthesis of Vertically Aligned Carbon Nanotubes on Silicalite-1 Monolayer-Supported Substrate

    Directory of Open Access Journals (Sweden)

    Wei Zhao

    2014-01-01

    Full Text Available Monodisperse magnetic Fe3O4 nanoparticles (NPs with the size of ca. 3.5 nm were prepared and used as the catalysts for the synthesis of vertically aligned carbon nanotube (VACNT arrays. A silicalite-1 microcrystal monolayer was used as the support layer between catalyst NPs and the silicon substrate. Compared to our previous report which used radio-frequency- (rf- sputtered Fe2O3 film as the catalyst, Fe3O4 NPs that were synthesized by wet chemical method showed an improved catalytic ability with less agglomeration. The silicalite-1 crystal monolayer acted as an effective “buffer” layer to prevent the catalyst NPs from agglomerating during the reaction process. It is believed that this is the first report that realizes the vertical alignment of CNTs over the zeolite monolayer, namely, silicalite-1 microcrystal monolayer, instead of using the intermediate anodic aluminum oxide (AAO scaffold to regulate the growth direction of CNT products.

  16. Aligned carbon nanotube based ultrasonic microtransducers for durability monitoring in civil engineering

    Energy Technology Data Exchange (ETDEWEB)

    Lebental, B [Universite Paris-Est, IFSTTAR, 58 boulevard Lefebvre, 75732 Paris Cedex 15 (France); Chainais, P [INRIA Lille-Nord Europe (SEQUEL), 40 avenue Halley, 59650 Villeneuve d' Ascq (France); Chenevier, P [SPEC, IRAMIS, CEA/Saclay, Gif-sur-Yvette (France); Chevalier, N; Delevoye, E; Fabbri, J-M; Nicoletti, S; Renaux, P; Ghis, A, E-mail: berengere.lebental@ifsttar.fr [CEA, LETI, MINATEC Campus, F-38054 Grenoble (France)

    2011-09-30

    Structural health monitoring of porous materials such as concrete is becoming a major component in our resource-limited economy, as it conditions durable exploitation of existing facilities. Durability in porous materials depends on nanoscale features which need to be monitored in situ with nanometric resolution. To address this problem, we put forward an approach based on the development of a new nanosensor, namely a capacitive micrometric ultrasonic transducer whose vibrating membrane is made of aligned single-walled carbon nanotubes (SWNT). Such sensors are meant to be embedded in large numbers within a porous material in order to provide information on its durability by monitoring in situ neighboring individual micropores. In the present paper, we report on the feasibility of the key building block of the proposed sensor: we have fabricated well-aligned, ultra-thin, dense SWNT membranes that show above-nanometer amplitudes of vibration over a large range of frequencies spanning from 100 kHz to 5 MHz.

  17. Horizontally aligned single walled carbon nanotube arrays on quartz for electrochemical biosensing

    Science.gov (United States)

    Yang, Yuehai; Wang, Xuewen; Li, Wenzhi; He, Jin

    2014-03-01

    We have fabricated and characterized a simple and high performance electrochemical sensor using horizontally aligned single walled carbon nanotube arrays on transparent single crystal quartz substrates grown by chemical vapor deposition. The electrochemical activities of redox probes Fe(CN)63- / 4 - , Ru(NH3) 6 3 + and protein cytochrome c on these pristine SWCNT thin films have been studied. Because the surface coverage of CNTs is extremely low and aligned, the shape of cyclic voltammograms of these molecules in stationary solution is strongly affected by the mass transport rate of molecules and the interactions between molecules and the SWCNT surface. We also studied the electrochemical flow sensing capability of the device for detecting neurotransmitter dopamine at physiological conditions with the presence of Bovine serum albumin. Good sensitivity, fast response, high stability and anti-fouling capability are observed. Therefore, this device shows great potential for sensing applications in complex solution. This work was supported by a start-up fund (J. H.), NSF (CMMI-1334417) and the American Chemical Society under grant PRF #51766-ND10.

  18. Aligned carbon nanotube based ultrasonic microtransducers for durability monitoring in civil engineering.

    Science.gov (United States)

    Lebental, B; Chainais, P; Chenevier, P; Chevalier, N; Delevoye, E; Fabbri, J-M; Nicoletti, S; Renaux, P; Ghis, A

    2011-09-30

    Structural health monitoring of porous materials such as concrete is becoming a major component in our resource-limited economy, as it conditions durable exploitation of existing facilities. Durability in porous materials depends on nanoscale features which need to be monitored in situ with nanometric resolution. To address this problem, we put forward an approach based on the development of a new nanosensor, namely a capacitive micrometric ultrasonic transducer whose vibrating membrane is made of aligned single-walled carbon nanotubes (SWNT). Such sensors are meant to be embedded in large numbers within a porous material in order to provide information on its durability by monitoring in situ neighboring individual micropores. In the present paper, we report on the feasibility of the key building block of the proposed sensor: we have fabricated well-aligned, ultra-thin, dense SWNT membranes that show above-nanometer amplitudes of vibration over a large range of frequencies spanning from 100 kHz to 5 MHz.

  19. Advanced materials from natural materials: synthesis of aligned carbon nanotubes on wollastonites.

    Science.gov (United States)

    Zhao, Meng-Qiang; Zhang, Qiang; Huang, Jia-Qi; Nie, Jing-Qi; Wei, Fei

    2010-04-26

    The growth of carbon nanotubes (CNTs) on natural materials is a low-cost, environmentally benign, and materials-saving method for the large-scale production of CNTs. Directly building 3D CNT architectures on natural materials is a key issue for obtaining advanced materials with high added value. We report the fabrication of aligned CNT arrays on fibrous natural wollastonite. Strongly dispersed iron particles with small sizes were produced on a planar surface of soaked fibrous wollastonite by a reduction process. These particles then catalyzed the decomposition of ethylene, leading to the synchronous growth of CNTs to form leaf- and brush-like wollastonite/CNT hybrids. The as-obtained hybrids could be further transformed into porous SiO(2)/CNT hybrids by reaction with hydrochloric acid. Further treatment with hydrofluoric acid resulted in aligned CNT arrays, with purities as high as 98.7 %. The presented work is very promising for the fabrication of advanced materials with unique structures and properties that can be used as fillers, catalyst supports, or energy-absorbing materials.

  20. Conformal atomic layer deposition of alumina on millimeter tall, vertically-aligned carbon nanotube arrays.

    Science.gov (United States)

    Stano, Kelly L; Carroll, Murphy; Padbury, Richard; McCord, Marian; Jur, Jesse S; Bradford, Philip D

    2014-11-12

    Atomic layer deposition (ALD) can be used to coat high aspect ratio and high surface area substrates with conformal and precisely controlled thin films. Vertically aligned arrays of multiwalled carbon nanotubes (MWCNTs) with lengths up to 1.5 mm were conformally coated with alumina from base to tip. The nucleation and growth behaviors of Al2O3 ALD precursors on the MWCNTs were studied as a function of CNT surface chemistry. CNT surfaces were modified through a series of post-treatments including pyrolytic carbon deposition, high temperature thermal annealing, and oxygen plasma functionalization. Conformal coatings were achieved where post-treatments resulted in increased defect density as well as the extent of functionalization, as characterized by X-ray photoelectron spectroscopy and Raman spectroscopy. Using thermogravimetric analysis, it was determined that MWCNTs treated with pyrolytic carbon and plasma functionalization prior to ALD coating were more stable to thermal oxidation than pristine ALD coated samples. Functionalized and ALD coated arrays had a compressive modulus more than two times higher than a pristine array coated for the same number of cycles. Cross-sectional energy dispersive X-ray spectroscopy confirmed that Al2O3 could be uniformly deposited through the entire thickness of the vertically aligned MWCNT array by manipulating sample orientation and mounting techniques. Following the ALD coating, the MWCNT arrays demonstrated hydrophilic wetting behavior and also exhibited foam-like recovery following compressive strain.

  1. The concept of a novel hybrid smart composite reinforced with radially aligned zigzag carbon nanotubes on piezoelectric fibers

    Science.gov (United States)

    Ray, M. C.

    2010-03-01

    A new hybrid piezoelectric composite (HPZC) reinforced with zigzag single-walled carbon nanotubes (CNTs) and piezoelectric fibers is proposed. The novel constructional feature of this composite is that the uniformly aligned CNTs are radially grown on the surface of piezoelectric fibers. A micromechanics model is derived to estimate the effective piezoelectric and elastic properties. It is found that the effective piezoelectric coefficient e31 of the proposed HPZC, which accounts for the in-plane actuation, is significantly higher than that of the existing 1-3 piezoelectric composite without reinforcement with carbon nanotubes and the previously reported hybrid piezoelectric composite (Ray and Batra 2009 ASME J. Appl. Mech. 76 034503).

  2. Sheet resistance characterization of locally anisotropic transparent conductive films made of aligned metal-enriched single-walled carbon nanotubes.

    Science.gov (United States)

    Kang, Hosung; Kim, Duckjong; Baik, Seunghyun

    2014-09-21

    One-dimensional conductive fillers such as single-walled carbon nanotubes (SWNTs) can be aggregated and aligned during transparent conductive film (TCF) formation by the vacuum filtration method. The potential error of analysing the average sheet resistance of these anisotropic films, using the four-point probe in-line method and the conversion formula developed assuming uniform isotropic material properties, was systematically investigated by finite element analysis and experiments. The finite element analysis of anisotropic stripe-patterned TCFs with alternating low (ρ1) and high (ρ2) resistivities revealed that the estimated average sheet resistance approached ρ1/t when the probes were parallel to the aligned nanotubes. The thickness of the film is t. It was more close to ρ2/t when the probes were perpendicular to the aligned tubes. Indeed, TCFs fabricated by the vacuum filtration method using metal-enriched SWNTs exhibited highly anisotropic local regions where tubes were aggregated and aligned. The local sheet resistances of randomly oriented, aligned, and perpendicular tube regions of the TCF at a transmittance of 89.9% were 5000, 2.4, and 12 300 Ω □(-1), respectively. Resistivities of the aggregated and aligned tube region (ρ1 = 1.2 × 10(-5) Ω cm) and the region between tubes (ρ2 = 6.2 × 10(-2) Ω cm) could be approximated with the aid of finite element analysis. This work demonstrates the potential error of characterizing the average sheet resistance of anisotropic TCFs using the four-point probe in-line method since surprisingly high or low values could be obtained depending on the measurement angle. On the other hand, a better control of aggregation and alignment of nanotubes would realize TCFs with a very small anisotropic resistivity and a high transparency.

  3. Chemically grown vertically aligned 1D ZnO nanorods with CdS coating for efficient quantum dot sensitized solar cells (QDSSC): a controlled synthesis route.

    Science.gov (United States)

    Mali, Sawanta S; Kim, Hyungjin; Patil, Pramod S; Hong, Chang Kook

    2013-12-28

    In the present article, vertically aligned ZnO nanorod arrays were synthesized by an aqueous chemical growth (ACG) route on a fluoride doped tin oxide (FTO) coated glass substrate. These nanorods were further sensitized with cadmium sulfide (CdS) quantum dots (QDs) by a successive ionic layer adsorption and reaction (SILAR) technique. The synthesized CdS coated ZnO nanorods were characterized for their structural and morphological properties with X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FESEM). Finally, prepared CdS coated 1D ZnO photoelectrodes were tested for their photoelectrochemical performance. Our results show that the sample deposited after 40 SILAR cycles shows 5.61 mA cm(-2) short current density (JSC) with η = 1.61% power conversion efficiency.

  4. Heteroepitaxial Patterned Growth of Vertically Aligned and Periodically Distributed ZnO Nanowires on GaN Using Laser Interference Ablation

    KAUST Repository

    Yuan, Dajun

    2010-08-23

    A simple two-step method of fabricating vertically aligned and periodically distributed ZnO nanowires on gallium nitride (GaN) substrates is described. The method combines laser interference ablation (LIA) and low temperature hydrothermal decomposition. The ZnO nanowires grow heteroepitaxially on unablated regions of GaN over areas spanning 1 cm2, with a high degree of control over size, orientation, uniformity, and periodicity. High resolution transmission electron microscopy and scanning electron microscopy are utilized to study the structural characteristics of the LIA-patterned GaN substrate in detail. These studies reveal the possible mechanism for the preferential, site-selective growth of the ZnO nanowires. The method demonstrates high application potential for wafer-scale integration into sensor arrays, piezoelectric devices, and optoelectronic devices. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Large-scale fabrication of vertically aligned ZnO nanowire arrays

    Science.gov (United States)

    Wang, Zhong Lin; Hu, Youfan; Zhang, Yan; Xu, Chen; Zhu, Guang

    2014-09-09

    A generator includes a substrate, a first electrode layer, a dense plurality of vertically-aligned piezoelectric elongated nanostructures, an insulating layer and a second electrode layer. The substrate has a top surface and the first electrode layer is disposed on the top surface of the substrate. The dense plurality of vertically-aligned piezoelectric elongated nanostructures extends from the first electrode layer. Each of the nanostructures has a top end. The insulating layer is disposed on the top ends of the nanostructures. The second electrode layer is disposed on the non-conductive layer and is spaced apart from the nanostructures.

  6. Enhanced field emission from compound emitters of carbon nanotubes and ZnO tetrapods by electron beam bombardment.

    Science.gov (United States)

    Wei, Lei; Zhang, Xiaobing; Lou, Chaogang; Zhao, Zhiwei; Jing, Chen; Wang, Baoping

    2011-06-01

    The enhancement of field emission from compound emitters of carbon nanotubes and ZnO tetrapods by the electron beam bombardment is reported. After 20 minutes electron bombardment with 6 keV energy, a few bird-nest micro structures are formed in the compound emitters array. As the simulation results shown, the electric field and field emission current density at the tip of ZnO tetrapod are increased due to the influences of these bird-nest micro structures. From the measurement of the field emission performance, it can be seen that the turn-on electric field and threshold electric field of the field emitter array decrease to 0.4 V/microm and 2.4 V/microm respectively. They have decreased 62% and 15% after the electron bombardment. After the electron bombardment, the emission sites density is increased. The field emission images show that the uniformity of field emission has been improved obviously after the proper electron bombardment. The methodology proposed in this paper has a promising application in the field emission devices.

  7. DNA-wrapped carbon nanotubes aligned in stretched gelatin films: Polarized resonance Raman and absorption spectroscopy study

    Science.gov (United States)

    Glamazda, A. Yu.; Plokhotnichenko, A. M.; Leontiev, V. S.; Karachevtsev, V. A.

    2017-09-01

    We present the study of DNA-wrapped single-walled carbon nanotubes (SWNTs) embedded in the stretched gelatin film by the polarized resonance Raman spectroscopy and visible-NIR optical absorption. The polarized dependent absorption spectra taken along and normal to the stretching direction demonstrate a comparatively high degree of the alignment of isolated SWNTs in the gelatin matrix. The analysis of Raman spectra of isolated SWNTs in the gelatin stretched films showed that the degree of the alignment of carbon nanotubes along the stretching direction is about 62%. The dependence of the peak position of G+-band in Raman spectra on the polarization angle θ between the polarization of the incident light and the direction of the stretching of films was revealed. This shift is explained by the different polarization dependence of the most intensive A and E1 symmetry modes within the G+-band. The performed studies of embedded DNA-wrapped nanotubes in the gelatin film show the simple method for obtaining the controlled ordered biocompatible nanotubes inside a polymer matrix. It can be used for manufacturing sizable flexible self-transparent films with integrated nanoelectrodes.

  8. Rapid growth of nanotubes and nanorods of würtzite ZnO through microwave-irradiation of a metalorganic complex of zinc and a surfactant in solution

    Indian Academy of Sciences (India)

    Sanjaya Brahma; Kalya Jagannatha Rao; Srinivasarao Shivashankar

    2010-04-01

    Large quantities of single-crystalline ZnO nanorods and nanotubes have been prepared by the microwave irradiation of a metalorganic complex of zinc, in the presence of a surfactant. The method is simple, fast, and inexpensive (as it uses a domestic microwave oven), and yields pure nanostructures of the hexagonal würtzite phase of ZnO in min, and requires no conventional templating. The ZnO nanotubes formed have a hollow core with inner diameter varying from 140–160 nm and a wall of thickness, 40–50 nm. The length of nanorods and nanotubes varies in the narrow range of 500–600 nm. These nanostructures have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). The ZnO nanorods and nanotubes are found by SAED to be single-crystalline. The growth process of ZnO nanorods and nanotubes has been investigated by varying the surfactant concentration and microwave irradiation time. Based on the various results obtained, a tentative and plausible mechanism for the formation of ZnO nanostructures is proposed.

  9. Effect of AZO Substrates on Self-Seeded Electrochemical Growth of Vertically Aligned ZnO Nanorod Arrays and Their Optical Properties

    Directory of Open Access Journals (Sweden)

    A. Peić

    2012-01-01

    Full Text Available We present a single step and an electrochemical synthesis of vertically aligned ZnO nanorod (NR arrays, directly on transparent aluminium-doped zinc oxide (AZO electrodes. The NRs grow from mild, aqueous-based solution at low temperature, with no need for catalysts or additional seed layer. The use of textured AZO as substrate allows for highly effective growth of hexagonally faceted, single-crystalline ZnO NRs along the wurtzite c-axis. The matching of the crystal lattices initiates a self-seeding route, thus the inherent growth habit of the AZO crystallites advances the vertical growth and alignment of NRs. Moreover, the thickness-dependant grain size of the AZO layer provides a valuable feature for tuning the diameter of ZnO NRs grown atop. In the absence of any seed mediator, the interfacial quality is expected to improve significantly. This should enhance the thermal and electrical transport throughout the whole nanostructured transparent electrode. The NR growth was investigated under systematic manipulation of the synthesis variables in order to optimize growth conditions for highly aligned, single-crystalline NRs with a large aspect ratio and a good optical quality. The structure and optical property of the AZO/ZnO NR ensembles were characterized by atomic force microscopy, scanning electron microscopy, X-ray diffraction, photoluminescence, and ultraviolet-visible transmission spectroscopy.

  10. Dielectrophoresis Aligned Single-Walled Carbon Nanotubes as pH Sensors.

    Science.gov (United States)

    Li, Pengfei; Martin, Caleb M; Yeung, Kan Kan; Xue, Wei

    2011-01-31

    Here we report the fabrication and characterization of pH sensors using aligned single-walled carbon nanotubes (SWNTs). The SWNTs are dispersed in deionized (DI) water after chemical functionalization and filtration. They are deposited and organized on silicon substrates with the dielectrophoresis process. Electrodes with "teeth"-like patterns-fabricated with photolithography and wet etching-are used to generate concentrated electric fields and strong dielectrophoretic forces for the SWNTs to deposit and align in desired locations. The device fabrication is inexpensive, solution-based, and conducted at room temperature. The devices are used as pH sensors with the electrodes as the testing pads and the dielectrophoretically captured SWNTs as the sensing elements. When exposed to aqueous solutions with various pH values, the SWNTs change their resistance accordingly. The SWNT-based sensors demonstrate a linear relationship between the sensor resistance and the pH values in the range of 5-9. The characterization of multiple sensors proves that their pH sensitivity is highly repeatable. The real-time data acquisition shows that the sensor response time depends on the pH value, ranging from 2.26 s for the pH-5 solution to 23.82 s for the pH-9 solution. The long-term stability tests illustrate that the sensors can maintain their original sensitivity for a long period of time. The simple fabrication process, high sensitivity, and fast response of the SWNT-based sensors facilitate their applications in a wide range of areas.

  11. Dielectrophoresis Aligned Single-Walled Carbon Nanotubes as pH Sensors

    Directory of Open Access Journals (Sweden)

    Wei Xue

    2011-01-01

    Full Text Available Here we report the fabrication and characterization of pH sensors using aligned single-walled carbon nanotubes (SWNTs. The SWNTs are dispersed in deionized (DI water after chemical functionalization and filtration. They are deposited and organized on silicon substrates with the dielectrophoresis process. Electrodes with “teeth”-like patterns—fabricated with photolithography and wet etching—are used to generate concentrated electric fields and strong dielectrophoretic forces for the SWNTs to deposit and align in desired locations. The device fabrication is inexpensive, solution-based, and conducted at room temperature. The devices are used as pH sensors with the electrodes as the testing pads and the dielectrophoretically captured SWNTs as the sensing elements. When exposed to aqueous solutions with various pH values, the SWNTs change their resistance accordingly. The SWNT-based sensors demonstrate a linear relationship between the sensor resistance and the pH values in the range of 5–9. The characterization of multiple sensors proves that their pH sensitivity is highly repeatable. The real-time data acquisition shows that the sensor response time depends on the pH value, ranging from 2.26 s for the pH-5 solution to 23.82 s for the pH-9 solution. The long-term stability tests illustrate that the sensors can maintain their original sensitivity for a long period of time. The simple fabrication process, high sensitivity, and fast response of the SWNT-based sensors facilitate their applications in a wide range of areas.

  12. Liquid-Phase Deposition of Aligned Carbon Nanotubes Using Cobalt Catalyst

    Science.gov (United States)

    Nishitani-Gamo, Mikka; Shibasaki, Takeshi; Gamo, Hidenori; Nakagawa, Kiyoharu; Ando, Toshihiro

    2007-09-01

    We have recently developed a novel catalytic method for synthesizing a wide variety of carbon nanomaterials in the organic liquid. The method enabled us to realize a simple, rapid, and high-purity growth of carbon nanotubes (CNTs) in alcohol liquids. In this study, cobalt (Co) was used as a catalyst metal. In order to control the structure of carbon nanomaterials, we investigated the relationship between the growth conditions and the grown materials. Scanning electron microscopy (SEM) observation revealed that the morphology of the grown carbon nanomaterials strongly depended on the reaction temperature. Under the reaction temperature in the range from 873 to 973 K, fibriform deposits were mainly obtained. Transmission electron microscopy (TEM) revealed that the fibriform deposits were CNTs. The amount of the supported Co catalyst affected the fine tubular structure of the CNTs. We found that the existence of the reaction temperature of 873 K during the reaction time was essential for growing a fibriform structure in this study. The longer duration time for the reaction temperature of 1127 K resulted in a higher crystal quality for CNTs. We also demonstrated that the Co catalyst thermal oxidation at 1173 K resulted in the growth of aligned CNTs with the higher density.

  13. Enhanced cold wall CVD reactor growth of horizontally aligned single-walled carbon nanotubes

    Science.gov (United States)

    Mu, Wei; Kwak, Eun-Hye; Chen, Bingan; Huang, Shirong; Edwards, Michael; Fu, Yifeng; Jeppson, Kjell; Teo, Kenneth; Jeong, Goo-Hwan; Liu, Johan

    2016-05-01

    HASynthesis of horizontally-aligned single-walled carbon nanotubes (HA-SWCNTs) by chemical vapor deposition (CVD) directly on quartz seems very promising for the fabrication of future nanoelectronic devices. In comparison to hot-wall CVD, synthesis of HA-SWCNTs in a cold-wall CVD chamber not only means shorter heating, cooling and growth periods, but also prevents contamination of the chamber. However, since most synthesis of HA-SWCNTs is performed in hot-wall reactors, adapting this well-established process to a cold-wall chamber becomes extremely crucial. Here, in order to transfer the CVD growth technology from a hot-wall to a cold-wall chamber, a systematic investigation has been conducted to determine the influence of process parameters on the HA-SWCNT's growth. For two reasons, the cold-wall CVD chamber was upgraded with a top heater to complement the bottom substrate heater; the first reason to maintain a more uniform temperature profile during HA-SWCNTs growth, and the second reason to preheat the precursor gas flow before projecting it onto the catalyst. Our results show that the addition of a top heater had a significant effect on the synthesis. Characterization of the CNTs shows that the average density of HA-SWCNTs is around 1 - 2 tubes/ μm with high growth quality as shown by Raman analysis. [Figure not available: see fulltext.

  14. Real time radiation dosimeters based on vertically aligned multiwall carbon nanotubes and graphene

    Science.gov (United States)

    Funaro, Maria; Sarno, Maria; Ciambelli, Paolo; Altavilla, Claudia; Proto, Antonio

    2013-02-01

    Measurements of the absorbed dose and quality assurance programs play an important role in radiotherapy. Ionization chambers (CIs) are considered the most important dosimeters for their high accuracy, practicality and reliability, allowing absolute dose measurements. However, they have a relative large physical size, which limits their spatial resolution, and require a high bias voltage to achieve an acceptable collection of charges, excluding their use for in vivo dosimetry. In this paper, we propose new real time radiation detectors with electrodes based on graphene or vertically aligned multiwall carbon nanotubes (MWCNTs). We have investigated their charge collection efficiency and compared their performance with electrodes made of a conventional material. Moreover, in order to highlight the effect of nanocarbons, reference radiation detectors were also tested. The proposed dosimeters display an excellent linear response to dose and collect more charge than reference ones at a standard bias voltage, permitting the construction of miniaturized CIs. Moreover, an MWCNT based CI gives the best charge collection efficiency and it enables working also to lower bias voltages and zero volts, allowing in vivo applications. Graphene based CIs show better performance with respect to reference dosimeters at a standard bias voltage. However, at decreasing bias voltage the charge collection efficiency becomes worse if compared to a reference detector, likely due to graphene’s semiconducting behavior.

  15. Field emission luminescence of nanodiamonds deposited on the aligned carbon nanotube array

    Science.gov (United States)

    Fedoseeva, Yu. V.; Bulusheva, L. G.; Okotrub, A. V.; Kanygin, M. A.; Gorodetskiy, D. V.; Asanov, I. P.; Vyalikh, D. V.; Puzyr, A. P.; Bondar, V. S.

    2015-03-01

    Detonation nanodiamonds (NDs) were deposited on the surface of aligned carbon nanotubes (CNTs) by immersing a CNT array in an aqueous suspension of NDs in dimethylsulfoxide (DMSO). The structure and electronic state of the obtained CNT-ND hybrid material were studied using optical and electron microscopy and Infrared, Raman, X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy. A non-covalent interaction between NDs and CNT and preservation of vertical orientation of CNTs in the hybrid were revealed. We showed that current-voltage characteristics of the CNT-ND cathode are changed depending on the applied field; below ~3 V/µm they are similar to those of the initial CNT array and at the higher field they are close to the ND behavior. Involvement of the NDs in field emission process resulted in blue luminescence of the hybrid surface at an electric field higher than 3.5 V/µm. Photoluminescence measurements showed that the NDs emit blue-green light, while blue luminescence prevails in the CNT-ND hybrid. The quenching of green luminescence was attributed to a partial removal of oxygen-containing groups from the ND surface as the result of the hybrid synthesis.

  16. Local growth of aligned carbon nanotubes at surface sites irradiated by pulsed laser

    Science.gov (United States)

    Zimmer, K.; Böhme, R.; Rauschenbach, B.

    2008-05-01

    The utilization of the unique properties of nanostructures often requires their arrangement in mesoscopic patterns, e.g., to facilitate the connection to microelectrodes. Such arrangements can be achieved by local growth of nanostructures. The stimulation of the localized growth of carbon nanotubes (CNT) has been achieved by excimer laser irradiation of iron(III)nitride-coated silicon substrates at a wavelength of 248 nm. After the growth using a thermal CVD process, vertical aligned CNT bundles were found within the laser-irradiated areas. Pulsed UV-laser irradiation causes the transformation of the nitride film into nanoparticles at the substrate surface as AFM measurements show. Surface modification by direct writing techniques allows the growth of arbitrary shaped CNT-forest patterns. Despite the optimization of the processing parameters, an unequal growth of CNT has been observed at the regions of pulse overlap at direct writing. The dissimilar particle properties at the overlap regions are the reason for the different CNT heights. These differences in the catalytic particles properties are caused by the lower laser fluence at the mask edges and the interaction of the laser plasma plume with the pristine nitride film.

  17. High-performance supercapacitors using a nanoporous current collector made from super-aligned carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Ruifeng; Meng Chuizhou; Zhu Feng; Li Qunqing; Liu Changhong; Fan Shoushan; Jiang Kaili, E-mail: JiangKL@tsinghua.edu.cn [Department of Physics and Tsinghua-Foxconn Nanotechnology Research Center, Tsinghua University, Beijing 100084 (China)

    2010-08-27

    Nanoporous current collectors for supercapacitors have been fabricated by cross-stacking super-aligned carbon nanotube (SACNT) films as a replacement for heavy conventional metallic current collectors. The CNT-film current collectors have good conductivity, extremely low density (27 {mu}g cm{sup -2}), high specific surface area, excellent flexibility and good electrochemical stability. Nanosized active materials such as NiO, Co{sub 3}O{sub 4} or Mn{sub 2}O{sub 3} nanoparticles can be directly synthesized on the SACNT films by a straightforward one-step, in situ decomposition strategy that is both efficient and environmentally friendly. These composite films can be integrated into a pseudo-capacitor that does not use metallic current collectors, but nevertheless shows very good performance, including high specific capacitance ({approx}500 F g{sup -1}, including the current collector mass), reliable electrochemical stability (<4.5% degradation in 2500 cycles) and a very high rate capability (245 F g{sup -1} at 155 A g{sup -1}).

  18. Effect of ammonia gas etching on growth of vertically aligned carbon nanotubes/nanofibers

    Institute of Scientific and Technical Information of China (English)

    Sang-Gook KIM; Sooh-Yung KIM; Hytmg-Woo LEE

    2011-01-01

    The etching effect of ammonia (NH3) on the growth of vertically aligned nanotubes/nanofibers (CNTs) was investigated by direct-current plasma enhanced chemical vapor deposition (DC-PECVD). NH3 gas etches Ni catalyst layer to form nanoscale islands while NH3 plasma etches the deposited amorphous carbon. Based on the etching effect of NH3 gas on Ni catalyst, the differences of growing bundles of CNTs and single strand CNTs were discussed; specifically, the amount of optimal NH3 gas etchingis different between bundles of CNTs and single strand CNTs. In contrast to the CNT carpet growth. the single strand CNT growth requires shorter etching time (5 min) than large catalytic patterns (10 min) since nano dots already form catalyst islands for CNT growth. Through removing the plasma pretreatment process, the damage from being exposed at high temperature substrate occurring during the plasma generation time is minimized. High resolution transmission electron microscopy (HTEM) shows fishbone structure of CNTs grown by PECVD.

  19. Multiple thermal transitions and anisotropic thermal expansions of vertically aligned carbon nanotubes

    Science.gov (United States)

    Ya'akobovitz, Assaf

    2016-10-01

    Vertically aligned carbon nanotubes (VA-CNTs) hold the potential to play an instrumental role in a wide variety of applications in micro- and nano-devices and composites. However, their successful large-scale implementation in engineering systems requires a thorough understanding of their material properties, including their thermal behavior, which was the focus of the current study. Thus, the thermal expansion of as-grown VA-CNT microstructures was investigated while increasing the temperature from room temperature to 800 °C and then cooling it down. First thermal transition was observed at 191 ± 68 °C during heating, and an additional thermal transition was observed at 523 ± 138 °C during heating and at similar temperatures during cooling. Each thermal transition was characterized by a significant change in the coefficient of thermal expansion (CTE), which can be related to a morphological change in the VA-CNT microstructures. Measurements of the CTEs in the lateral directions revealed differences in the lateral thermal behaviors of the top, middle, and bottom portions of the VA-CNT microstructures, again indicating that their morphology dominates their thermal characteristics. A hysteretic behavior was observed, as the measured values of CTEs were altered due to the applied thermal loads and the height of the microstructures was slightly higher compared to its initial value. These findings provide an insight into the anisotropic thermal behavior of VA-CNT microstructures and shed light on the relationship between their morphology and thermal behavior.

  20. Field emission luminescence of nanodiamonds deposited on the aligned carbon nanotube array.

    Science.gov (United States)

    Fedoseeva, Yu V; Bulusheva, L G; Okotrub, A V; Kanygin, M A; Gorodetskiy, D V; Asanov, I P; Vyalikh, D V; Puzyr, A P; Bondar, V S

    2015-03-23

    Detonation nanodiamonds (NDs) were deposited on the surface of aligned carbon nanotubes (CNTs) by immersing a CNT array in an aqueous suspension of NDs in dimethylsulfoxide (DMSO). The structure and electronic state of the obtained CNT-ND hybrid material were studied using optical and electron microscopy and Infrared, Raman, X-ray photoelectron and near-edge X-ray absorption fine structure spectroscopy. A non-covalent interaction between NDs and CNT and preservation of vertical orientation of CNTs in the hybrid were revealed. We showed that current-voltage characteristics of the CNT-ND cathode are changed depending on the applied field; below ~3 V/µm they are similar to those of the initial CNT array and at the higher field they are close to the ND behavior. Involvement of the NDs in field emission process resulted in blue luminescence of the hybrid surface at an electric field higher than 3.5 V/µm. Photoluminescence measurements showed that the NDs emit blue-green light, while blue luminescence prevails in the CNT-ND hybrid. The quenching of green luminescence was attributed to a partial removal of oxygen-containing groups from the ND surface as the result of the hybrid synthesis.

  1. Functionalization of Aligned Carbon Nanotubes to Enhance the Performance of Fuel Cell

    Directory of Open Access Journals (Sweden)

    Jingbo Liu

    2013-12-01

    Full Text Available The focus of this research lies on fundamental research to provide guidelines for the design of new nanocatalyst toward improvement of the performance of proton exchange membrane fuel cells (PEMFCs. To achieve this overarching goal, several specific steps were taken with aims to: (1 provide guidelines for the design of new catalysts; (2 promote nanocatalyst applications towards alternative energy applications; and (3 integrate advanced instrumentation into nanocharacterization and fuel cell (FC electrochemical behavior. In tandem with these goals, the cathode catalysts were extensively refined to improve the performance of PEMFCs and minimize noble metal usage. In this study, the major accomplishment was producing aligned carbon nanotubes (ACNTs, which were then modified by platinum (Pt nanoparticles via a post-functionalization colloidal chemistry approach. The Pt-ACNTs demonstrated improved cathodic catalycity, by building better device endurance and decreased Pt loading. It was also determined that surface mechanical properties, such as elastic modulus and hardness were increased. Collectively, these enhancements provided an improved FC device. The electrochemical analyses indicated that the power density of the PEMFCs was increased to 900 mW/cm2 and current density to 3000 mA/cm2, respectively. The Pt loading was controlled at lower than 0.2 mg/cm2 to decrease the manufacturing expenses.

  2. Increasing mouse embryonic fibroblast cells adhesion on superhydrophilic vertically aligned carbon nanotube films

    Energy Technology Data Exchange (ETDEWEB)

    Lobo, A.O., E-mail: loboao@yahoo.com [Laboratory of Biomedical Nanotechnology (NanoBio), Instituto de Pesquisa e Desenvolvimento (IP and D), Universidade do Vale do Paraiba UniVap, Avenida Shishima Hifumi 2911, Sao Jose dos Campos, 12244-000, SP (Brazil) and Laboratory of Biomedical Vibrational Spectroscopy (LEVB), Instituto de Pesquisa e Desenvolvimento (IP and D), Universidade do Vale do Paraiba UniVap, Avenida Shishima Hifumi 2911, Sao Jose dos Campos, 12244-000, SP (Brazil); Marciano, F.R. [Laboratory of Biomedical Nanotechnology (NanoBio), Instituto de Pesquisa e Desenvolvimento (IP and D), Universidade do Vale do Paraiba UniVap, Avenida Shishima Hifumi 2911, Sao Jose dos Campos, 12244-000, SP (Brazil); Laboratory of Biomedical Vibrational Spectroscopy LEVB, Instituto de Pesquisa e Desenvolvimento (IP and D), Universidade do Vale do Paraiba (UniVap), Avenida Shishima Hifumi 2911, Sao Jose dos Campos, 12244-000, SP (Brazil); Ramos, S.C. [Laboratorio Associado de Sensores e Materiais (LAS), Instituto Nacional de Pesquisas Espaciais (INPE), Avenida dos Astronautas 1758, Sao Jose dos Campos, 12.245-970, SP (Brazil); Machado, M.M. [Centro Multidisciplinar para Investigacao Biologica na Area da Ciencia em Animais de Laboratorio (CEMIB), Universidade Estadual de Campinas (UNICAMP), Rua 05 de Junho s/no, Cidade Universitaria ' Zeferino Vaz' , 13083-877, Campinas (Brazil); Corat, E.J. [Laboratorio Associado de Sensores e Materiais (LAS), Instituto Nacional de Pesquisas Espaciais (INPE), Avenida dos Astronautas 1758, Sao Jose dos Campos, 12.245-970, SP (Brazil); Corat, M.A.F. [Centro Multidisciplinar para Investigacao Biologica na Area da Ciencia em Animais de Laboratorio (CEMIB), Universidade Estadual de Campinas (UNICAMP), Rua 05 de Junho s/no, Cidade Universitaria ' Zeferino Vaz' , 13083-877, Campinas (Brazil)

    2011-10-10

    We have analyzed the adhesion of mouse embryonic fibroblasts (MEFs) genetically modified by green fluorescence protein (GFP) gene cultured on vertically-aligned carbon nanotubes (VACNTs) after 6 days. The VACNTs films grown on Ti were obtained by microwave plasma chemical vapor deposition process using Fe catalyst and submitted to an oxygen plasma treatment, for 2 min, at 400 V and 80 mTorr, to convert them to superhydrophilic. Cellular adhesion and morphology were analyzed by scanning electron, fluorescence microscopy, and thermodynamics analysis. Characterizations of superhydrophilic VACNTs films were evaluated by contact angle and X-Ray Photoelectron Spectroscopy. Differences of crowd adhered cells, as well as their spreading on superhydrophilic VACNTs scaffolds, were evaluated using focal adhesion analysis. This study was the first to demonstrate, in real time, that the wettability of VACNTs scaffolds might have enhanced and differential adherence patterns to the MEF-GFP on VACNTs substrates. Highlights: {yields} A simple oxygen plasma treatment was used to obtain superhydrophilic CNT films. {yields} Superhydrophilic CNTs films were successfully produced by incorporation of carboxylic groups. {yields} Cellular adhesion on superhydrophilic VACNT films was analyzed in real time. {yields} Wettability of CNT films directly affects the cellular migration, proliferation and adhesion.

  3. Enhancement in visible light-responsive photocatalytic activity by embedding Cu-doped ZnO nanoparticles on multi-walled carbon nanotubes

    Science.gov (United States)

    Ahmad, M.; Ahmed, E.; Hong, Z. L.; Jiao, X. L.; Abbas, T.; Khalid, N. R.

    2013-11-01

    Copper doped ZnO nanoparticles embedded on multi-walled carbon nanotubes (CNTs) were successfully synthesized using a facile, nontoxic sol method. The resulting visible light-responsive Cu-doped ZnO/CNTs composites were characterized using powder X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM), transmission electron microscope (TEM), scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS) and Brunauer Emmett Teller (BET) surface area analyzer. Optical properties of Cu-doped ZnO/CNTs nanocomposites, studied using UV-vis diffuse reflectance spectroscopy and photoluminescence spectroscopy (PL), which exhibited extended light absorption in visible light region and possessed better charge separation capability, respectively as compared to Cu-doped ZnO, pure ZnO and ZnO/CNTs composite. The photocatalytic activity was tested by degradation of methyl orange (MO) dye under visible light irradiation. The results demonstrated that Cu-doped ZnO/CNTs nanocomposites effectively bleached out MO, showing an impressive photocatalytic enhancement over ZnO, commercial ZnO, Cu-doped ZnO nanoparticles and ZnO/CNTs nanocomposites. Chemical oxygen demand (COD) of textile wastewater was also measured before and after the photocatalysis experiment under sunlight to evaluate the mineralization of wastewater. The significant decrease in COD of the treated effluent revealed a complete destruction of the organic molecules along with color removal. This dramatically enhanced photoactivity of nanocomposite photocatalysts was attributed to greater adsorptivity of dyes, extended light absorption and increased charge separation efficiency due to excellent electrical properties of carbon nanotubes and the large surface area.

  4. Horizontally-aligned carbon nanotubes arrays and their interactions with liquid crystal molecules: Physical characteristics and display applications

    Directory of Open Access Journals (Sweden)

    Frédérick Roussel

    2012-03-01

    Full Text Available We report on the physical characteristics of horizonthally-grown Single-Walled Carbon Nanotubes (h-al-SWNT arrays and their potential use as transparent and conducting alignment layer for liquid crystals display devices. Microscopy (SEM and AFM, spectroscopic (Raman and electrical investigations demonstrate the strong anisotropy of h-al-SWNT arrays. Optical measurements show that h-al-SWNTs are efficient alignment layers for Liquid Crystal (LC molecules allowing the fabrication of optical wave plates. Interactions between h-al-SWNT arrays and LC molecules are also investigated evidencing the weak azimuthal anchoring energy at the interface, which, in turn, leads to LC devices with a high pretilt angle. The electro-optical reponses of h-al-SWNT/LC cells demonstrate that h-al-SWNT arrays are efficient nanostructured electrodes with potential use for the combined replacement of Indium Tin Oxyde and polymeric alignment layers in conventional displays.

  5. Highly efficient growth of vertically aligned carbon nanotubes on Fe-Ni based metal alloy foils for supercapacitors

    Science.gov (United States)

    Amalina Raja Seman, Raja Noor; Asyadi Azam, Mohd; Ambri Mohamed, Mohd

    2016-12-01

    Supercapacitors are highly promising energy devices with superior charge storage performance and a long lifecycle. Construction of the supercapacitor cell, especially electrode fabrication, is critical to ensure good performance in applications. This work demonstrates direct growth of vertically aligned carbon nanotubes (CNTs) on Fe-Ni based metal alloy foils, namely SUS 310S, Inconel 600 and YEF 50, and their use in symmetric vertically aligned CNT supercapacitor electrodes. Alumina and cobalt thin film catalysts were deposited onto the foils, and then CNT growth was performed using alcohol catalytic chemical vapour deposition. By this method, vertically aligned CNTs were successfully grown and used directly as a binder-free supercapacitor electrode to deliver excellent electrochemical performance. The device showed relatively good specific capacitance, a superior rate capability and excellent cycle stability, maintaining about 96% capacitance up to 1000 cycles.

  6. Oxygen and light sensitive field-effect transistors based on ZnO nanoparticles attached to individual double-walled carbon nanotubes

    Science.gov (United States)

    Chanaewa, Alina; Juárez, Beatriz H.; Weller, Horst; Klinke, Christian

    2011-12-01

    The attachment of semiconducting nanoparticles to carbon nanotubes is one of the most challenging subjects in nanotechnology. Successful high coverage attachment and control over the charge transfer mechanism and photo-current generation open a wide field of new applications such as highly effective solar cells and fibre-enhanced polymers. In this work we study the charge transfer in individual double-walled carbon nanotubes highly covered with uniform ZnO nanoparticles. The synthetic colloidal procedure was chosen to avoid long-chained ligands at the nanoparticle-nanotube interface. The resulting composite material was used as conductive channel in a field-effect transistor device and the electrical photo-response was analysed under various conditions. By means of the transfer characteristics we could elucidate the mechanism of charge transfer from non-covalently attached semiconducting nanoparticles to carbon nanotubes. The role of positive charges remaining on the nanoparticles is discussed in terms of a gating effect.The attachment of semiconducting nanoparticles to carbon nanotubes is one of the most challenging subjects in nanotechnology. Successful high coverage attachment and control over the charge transfer mechanism and photo-current generation open a wide field of new applications such as highly effective solar cells and fibre-enhanced polymers. In this work we study the charge transfer in individual double-walled carbon nanotubes highly covered with uniform ZnO nanoparticles. The synthetic colloidal procedure was chosen to avoid long-chained ligands at the nanoparticle-nanotube interface. The resulting composite material was used as conductive channel in a field-effect transistor device and the electrical photo-response was analysed under various conditions. By means of the transfer characteristics we could elucidate the mechanism of charge transfer from non-covalently attached semiconducting nanoparticles to carbon nanotubes. The role of positive

  7. Facile Synthesis of ZnO Nanoparticles on Nitrogen-Doped Carbon Nanotubes as High-Performance Anode Material for Lithium-Ion Batteries.

    Science.gov (United States)

    Li, Haipeng; Liu, Zhengjun; Yang, Shuang; Zhao, Yan; Feng, Yuting; Bakenov, Zhumabay; Zhang, Chengwei; Yin, Fuxing

    2017-09-21

    ZnO/nitrogen-doped carbon nanotube (ZnO/NCNT) composite, prepared though a simple one-step sol-gel synthetic technique, has been explored for the first time as an anode material. The as-prepared ZnO/NCNT nanocomposite preserves a good dispersity and homogeneity of the ZnO nanoparticles (~6 nm) which deposited on the surface of NCNT. Transmission electron microscopy (TEM) reveals the formation of ZnO nanoparticles with an average size of 6 nm homogeneously deposited on the surface of NCNT. ZnO/NCNT composite, when evaluated as an anode for lithium-ion batteries (LIBs), exhibits remarkably enhanced cycling ability and rate capability compared with the ZnO/CNT counterpart. A relatively large reversible capacity of 1013 mAh·g(-1) is manifested at the second cycle and a capacity of 664 mAh·g(-1) is retained after 100 cycles. Furthermore, the ZnO/NCNT system displays a reversible capacity of 308 mAh·g(-1) even at a high current density of 1600 mA·g(-1). These electrochemical performance enhancements are ascribed to the reinforced accumulative effects of the well-dispersed ZnO nanoparticles and doping nitrogen atoms, which can not only suppress the volumetric expansion of ZnO nanoparticles during the cycling performance but also provide a highly conductive NCNT network for ZnO anode.

  8. Facile Synthesis of ZnO Nanoparticles on Nitrogen-Doped Carbon Nanotubes as High-Performance Anode Material for Lithium-Ion Batteries

    Directory of Open Access Journals (Sweden)

    Haipeng Li

    2017-09-01

    Full Text Available ZnO/nitrogen-doped carbon nanotube (ZnO/NCNT composite, prepared though a simple one-step sol-gel synthetic technique, has been explored for the first time as an anode material. The as-prepared ZnO/NCNT nanocomposite preserves a good dispersity and homogeneity of the ZnO nanoparticles (~6 nm which deposited on the surface of NCNT. Transmission electron microscopy (TEM reveals the formation of ZnO nanoparticles with an average size of 6 nm homogeneously deposited on the surface of NCNT. ZnO/NCNT composite, when evaluated as an anode for lithium-ion batteries (LIBs, exhibits remarkably enhanced cycling ability and rate capability compared with the ZnO/CNT counterpart. A relatively large reversible capacity of 1013 mAh·g−1 is manifested at the second cycle and a capacity of 664 mAh·g−1 is retained after 100 cycles. Furthermore, the ZnO/NCNT system displays a reversible capacity of 308 mAh·g−1 even at a high current density of 1600 mA·g−1. These electrochemical performance enhancements are ascribed to the reinforced accumulative effects of the well-dispersed ZnO nanoparticles and doping nitrogen atoms, which can not only suppress the volumetric expansion of ZnO nanoparticles during the cycling performance but also provide a highly conductive NCNT network for ZnO anode.

  9. Structural and optical properties of ZnO nanorods by electrochemical growth using multi-walled carbon nanotube-composed seed layers.

    Science.gov (United States)

    Ko, Yeong Hwan; Kim, Myung Sub; Yu, Jae Su

    2012-01-05

    We reported the enhancement of the structural and optical properties of electrochemically synthesized zinc oxide [ZnO] nanorod arrays [NRAs] using the multi-walled carbon nanotube [MWCNT]-composed seed layers, which were formed by spin-coating the aqueous seed solution containing MWCNTs on the indium tin oxide-coated glass substrate. The MWCNT-composed seed layer served as the efficient nucleation surface as well as the film with better electrical conductivity, thus leading to a more uniform high-density ZnO NRAs with an improved crystal quality during the electrochemical deposition process. For ZnO NRAs grown on the seed layer containing MWCNTs (2 wt.%), the photoluminescence peak intensity of the near-band-edge emission at a wavelength of approximately 375 nm was enhanced by 2.8 times compared with that of the ZnO nanorods grown without the seed layer due to the high crystallinity of ZnO NRAs and the surface plasmon-meditated emission enhancement by MWCNTs. The effect of the MWCNT-composed seed layer on the surface wettability was also investigated.PACS: 81.07.-b; 81.16.-c; 81.07.Pr; 61.48.De.

  10. Morphology of hydrothermally synthesized ZnO nanoparticles tethered to carbon nanotubes affects electrocatalytic activity for H2O2 detection

    Science.gov (United States)

    Wayu, Mulugeta B.; Spidle, Ryan T.; Devkota, Tuphan; Deb, Anup K.; Delong, Robert K.; Ghosh, Kartik C.; Wanekaya, Adam K.; Chusuei, Charles C.

    2013-01-01

    We describe the synthesis of zinc oxide (ZnO) nanoparticles and demonstrate their attachment to multiwalled carbon tubes, resulting in a composite with a unique synergistic effect. Morphology and size of ZnO nanostructures were controlled using hydrothermal synthesis, varying the hydrothermal treatment temperature, prior to attachment to carboxylic acid functionalized multi-walled carbon nanotubes for sensing applications. A strong dependence of electrocatalytic activity on nanosized ZnO shape was shown. High activity for H2O2 reduction was achieved when nanocomposite precursors with a roughly semi-spherical morphology (no needle-like particles present) formed at 90 °C. A 2.4-fold increase in cyclic voltammetry current accompanied by decrease in overpotential from the composites made from the nanosized, needle-like-free ZnO shapes was observed as compared to those composites produced from needle-like shaped ZnO. Electrocatalytic activity varied with pH, maximizing at pH 7.4. A stable, linear response for H2O2 concentrations was observed in the 1–20 mM concentration range. PMID:25684785

  11. Optimizing stem cell functions and antibacterial properties of TiO2 nanotubes incorporated with ZnO nanoparticles: experiments and modeling

    Directory of Open Access Journals (Sweden)

    Liu W

    2015-03-01

    Full Text Available Wenwen Liu,1–3 Penglei S Su,2 Arthur Gonzales III,3 Su C Chen,1 Na Wang,1 Jinshu Wang,2 Hongyi Li,2,4 Zhenting Zhang,1Thomas J Webster3,51Laboratory of Biomaterials and Biomechanics, Beijing Key Laboratory of Tooth Regeneration and Function Reconstruction, School of Stomatology, Capital Medical University, 2Photoelectrochemical Research Group, Key Laboratory of Advanced Functional Materials, School of Materials Science and Engineering, Beijing University of Technology, Beijing, People’s Republic of China; 3Chemical Engineering Department, Northeastern University, Boston, MA, USA; 4Guangxi Research Institute of Chemical Industry, Nanning, People’s Republic of China; 5Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi ArabiaAbstract: To optimize mesenchymal stem cell differentiation and antibacterial properties of titanium (Ti, nano-sized zinc oxide (ZnO particles with tunable concentrations were incorporated into TiO2 nanotubes (TNTs using a facile hydrothermal strategy. It is revealed here for the first time that the TNTs incorporated with ZnO nanoparticles exhibited better biocompatibility compared with pure Ti samples (controls and that the amount of ZnO (tailored by the concentration of Zn(NO32 in the precursor introduced into TNTs played a crucial role on their osteogenic properties. Not only was the alkaline phosphatase activity improved to about 13.8 U/g protein, but the osterix, collagen-I, and osteocalcin gene expressions was improved from mesenchymal stem cells compared to controls. To further explore the mechanism of TNTs decorated with ZnO on cell functions, a response surface mathematical model was used to optimize the concentration of ZnO incorporation into the Ti nanotubes for stem cell differentiation and antibacterial properties for the first time. Both experimental and modeling results confirmed (R2 values of 0.8873–0.9138 and 0.9596–0.9941, respectively that Ti incorporated

  12. Efficient strategy to Cu/Si catalyst into vertically aligned carbon nanotubes with bamboo shape by CVD technique

    Indian Academy of Sciences (India)

    V MOHANA KRISHNA; T SOMANATHAN

    2016-08-01

    Bamboo-shaped vertically aligned carbon nanotubes (bs-VACNTs) were fabricated on Cu/Si catalyst by chemical vapour deposition (CVD) technique under the atmospheric pressure. The catalytic material (Cu/Si) playeda vital role in attaining bs-VACNTs, which is synthesized by drop cast method in a cost-effective manner. Using this catalytic support, we have achieved the tip growth bs-VACNTs at low temperature with well graphitization. The as-grown carbon material was then characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX) analyzer, high-resolution transmission electron microscope (HRTEM) and Raman spectroscopy. XRD technique confirms the formation of hexagonal graphitic carbon planes of carbon nanotubes (CNTs). The surface morphology of the material was characterized by SEM, which clearly infervertically aligned CNTs. The nature, diameter and crystallinity were noticed by HRTEM and Raman spectroscopy, respectively. Further, we have also studied the electrochemical properties of the bs-VACNTs and it seems to be proved as highly electroconductive when compared to multi-walled carbon nanotubes (MWCNTs).

  13. Effect of Different Catalyst Deposition Technique on Aligned Multiwalled Carbon Nanotubes Grown by Thermal Chemical Vapor Deposition

    Directory of Open Access Journals (Sweden)

    Mohamed Shuaib Mohamed Saheed

    2014-01-01

    Full Text Available The paper reported the investigation of the substrate preparation technique involving deposition of iron catalyst by electron beam evaporation and ferrocene vaporization in order to produce vertically aligned multiwalled carbon nanotubes array needed for fabrication of tailored devices. Prior to the growth at 700°C in ethylene, silicon dioxide coated silicon substrate was prepared by depositing alumina followed by iron using two different methods as described earlier. Characterization analysis revealed that aligned multiwalled carbon nanotubes array of 107.9 µm thickness grown by thermal chemical vapor deposition technique can only be achieved for the sample with iron deposited using ferrocene vaporization. The thick layer of partially oxidized iron film can prevent the deactivation of catalyst and thus is able to sustain the growth. It also increases the rate of permeation of the hydrocarbon gas into the catalyst particles and prevents agglomeration at the growth temperature. Combination of alumina-iron layer provides an efficient growth of high density multiwalled carbon nanotubes array with the steady growth rate of 3.6 µm per minute for the first 12 minutes and dropped by half after 40 minutes. Thicker and uniform iron catalyst film obtained from ferrocene vaporization is attributed to the multidirectional deposition of particles in the gaseous form.

  14. Field Emission Properties of the Dendritic Carbon Nanotubes Film Embedded with ZnO Quantum Dots

    Directory of Open Access Journals (Sweden)

    Shu Zuo

    2011-01-01

    Full Text Available Response on the effects of individual differences of common carbon nanotubes on the field emission current stability and the luminescence uniformity of cathode film, a new type of cathode film made of dendritic carbon nanotubes embedded with Zinc oxide quantum dots is proposed. The film of dendritic carbon nanotubes was synthesized through high-temperature pyrolysis of iron phthalocyanine on a silicon substrate coated with zinc oxide nanoparticles. The dendritic structure looks like many small branches protrude from the main branches in SEM and TEM images, and both the branch and the trunk are embedded with Zinc oxide quantum dots. The turn-on field of the dendritic structure film is ∼1.3 V/μm at a current of 2 μA, which is much lower than that of the common carbon nanotube film, and the emission current and the luminescence uniformity are better than that of the common one. The whole film emission uniformity has been improved because the multi-emission sites out from the dendritic structure carbon nanotubes cover up the failure and defects of the single emission site.

  15. Electrochemical Water Oxidation of Ultrathin Cobalt Oxide-Based Catalyst Supported onto Aligned ZnO Nanorods.

    Science.gov (United States)

    Koteeswara Reddy, Nandanapalli; Winkler, Stefanie; Koch, Norbert; Pinna, Nicola

    2016-02-10

    A stable and durable electrochemical water oxidation catalyst based on CoO functionalized ZnO nanorods (NRs) is introduced. ZnO NRs were grown on fluorine-doped tin oxide (FTO) by using a low-temperature chemical solution method and were functionalized with cobalt oxide by electrochemical deposition. The electrochemical water oxidation performance of cobalt oxide functionalized ZnO NRs was studied under alkaline (pH = 10) conditions. From these studies, it is noticed that cobalt oxide functionalized ZnO NRs show electrocatalytic activity toward water oxidation with current density on the order of several mA cm(-2). Further, 30 s CoO deposited ZnO nanorods exhibited excellent galvanostatic stability at a current density of 1 mA cm(-2) and potentiostatic stability at 1.25 V vs Ag/AgCl over an electrolysis period of 1 h.

  16. PARAMETRIC STUDY FOR THE PREPARATION OF ALIGNED SINGLE-WALLED CARBON NANOTUBES BY ANODE-ARC DISCHARGE METHOD

    Institute of Scientific and Technical Information of China (English)

    J.F. Dai; Q. Wang; W.X. Li; Z.Q. Wei; G.J. Xu

    2005-01-01

    Well aligned quasi-straight single-walled carbon nanotubes (SWCNTs) and straight SWCNTs bundle have been prepared in large scale by anode-arc vaporization of graphite with metallic catalysts. Various parameters such as the catalyst preparation, the kinds and pressure of the buffer gases, the quantity of anode-arc current intensity, and the method of purification have been examined. The influence of these parameters on the deposited carbon yield is reported, together with observations of the produced material. Improvement in synthetic techniques has resulted in the optimal conditions for the production of large quantities of high quality SWCNTs in our semi-continuous synthesis method. The formation of carbon nanotubes (CNTs) was studied briefly in this paper. Owing to the magnetic pinching effect of arc current, the CNTs arrange in parallel lines along the arc current direction.

  17. TLM-PSD model for optimization of energy and power density of vertically aligned carbon nanotube supercapacitor.

    Science.gov (United States)

    Ghosh, Arunabha; Le, Viet Thong; Bae, Jung Jun; Lee, Young Hee

    2013-10-22

    Electrochemical capacitors with fast charging-discharging rates are very promising for hybrid electric vehicle industries including portable electronics. Complicated pore structures have been implemented in active materials to increase energy storage capacity, which often leads to degrade dynamic response of ions. In order to understand this trade-off phenomenon, we report a theoretical model based on transmission line model which is further combined with pore size distribution function. The model successfully explained how pores length, and pore radius of active materials and electrolyte conductivity can affect capacitance and dynamic performance of different capacitors. The powerfulness of the model was confirmed by comparing with experimental results of a micro-supercapacitor consisted of vertically aligned multiwalled carbon nanotubes (v-MWCNTs), which revealed a linear current increase up to 600 Vs(-1) scan rate demonstrating an ultrafast dynamic behavior, superior to randomly entangled singlewalled carbon nanotube device, which is clearly explained by the theoretical model.

  18. Realizing one-dimensional quantum and high-frequency transport features in aligned single-walled carbon nanotube ropes

    Science.gov (United States)

    Ncube, Siphephile; Chimowa, George; Chiguvare, Zivayi; Bhattacharyya, Somnath

    2014-07-01

    The superiority of the electronic transport properties of single-walled carbon nanotube (SWNT) ropes over SWNT mats is verified from low temperature and frequency-dependent transport. The overall change of resistance versus in nanotube mats shows that 3D variable range hopping is the dominant conduction mechanism within the 2-300 K range. The magneto-resistance (MR) is found to be predominantly negative with a parabolic nature, which can also be described by the hopping model. Although the positive upturn of the MR at low temperatures establishes the contribution from quantum interference, the inherent quantum transport in individual tubes is suppressed at elevated temperatures. Therefore, to minimize multi-channel effects from inter-tube interactions and other defects, two-terminal devices were fabricated from aligned SWNT (extracted from a mat) for low temperature transport as well as high-frequency measurements. In contrast to the mat, the aligned ropes exhibit step-like features in the differential conductance within the 80-300 K temperature range. The effects of plasmon propagation, unique to one dimension, were identified in electronic transport as a non-universal power-law dependence of the differential conductance on temperature and source-drain voltage. The complex impedance showed high power transmission capabilities up to 65 GHz as well as oscillations in the frequency range up to 30 GHz. The measurements suggest that aligned SWNT ropes have a realistic potential for high-speed device applications.

  19. Realizing one-dimensional quantum and high-frequency transport features in aligned single-walled carbon nanotube ropes

    Energy Technology Data Exchange (ETDEWEB)

    Ncube, Siphephile; Chimowa, George; Chiguvare, Zivayi; Bhattacharyya, Somnath, E-mail: Somnath.Bhattacharyya@wits.ac.za [Nano-Scale Transport Physics Laboratory, School of Physics and DST/NRF Centre of Excellence in Strong Materials, University of the Witwatersrand, Private Bag 3, WITS 2050, Johannesburg (South Africa)

    2014-07-14

    The superiority of the electronic transport properties of single-walled carbon nanotube (SWNT) ropes over SWNT mats is verified from low temperature and frequency-dependent transport. The overall change of resistance versus in nanotube mats shows that 3D variable range hopping is the dominant conduction mechanism within the 2–300 K range. The magneto-resistance (MR) is found to be predominantly negative with a parabolic nature, which can also be described by the hopping model. Although the positive upturn of the MR at low temperatures establishes the contribution from quantum interference, the inherent quantum transport in individual tubes is suppressed at elevated temperatures. Therefore, to minimize multi-channel effects from inter-tube interactions and other defects, two-terminal devices were fabricated from aligned SWNT (extracted from a mat) for low temperature transport as well as high-frequency measurements. In contrast to the mat, the aligned ropes exhibit step-like features in the differential conductance within the 80–300 K temperature range. The effects of plasmon propagation, unique to one dimension, were identified in electronic transport as a non-universal power-law dependence of the differential conductance on temperature and source-drain voltage. The complex impedance showed high power transmission capabilities up to 65 GHz as well as oscillations in the frequency range up to 30 GHz. The measurements suggest that aligned SWNT ropes have a realistic potential for high-speed device applications.

  20. A facile route for controlled alignment of carbon nanotube-reinforced, electrospun nanofibers using slotted collector plates

    Directory of Open Access Journals (Sweden)

    G. R. Rakesh

    2015-02-01

    Full Text Available A facile route for controlled alignment of electrospun multiwalled carbon nanotube (MWCNT-reinforced Polyvinyl Alcohol (PVA nanofibers using slotted collector geometries has been realized. The process is based on analytical predictions using electrostatic field analysis for envisaging the extent of alignment of the electrospun fibers on varied collector geometries. Both the experimental and theoretical studies clearly indicate that the introduction of an insulating region into a conductive collector significantly influences the electrostatic forces acting on a charged fiber. Among various collector geometries, rectangular slotted collectors with circular ends showed good fiber alignment over a large collecting area. The electrospun fibers produced by this process were characterized by Atomic Force Microscopy (AFM, High Resolution Transmission Electron Microscopy (HRTEM, Scanning Electron Microscopy (SEM and Optical Microscopy. Effects of electrospinning time and slot widths on the fiber alignment have been analyzed. PVA-MWCNT nanofibers were found to be conducting in nature owing to the presence of reinforced MWCNTs in PVA matrix. The method can enable the direct integration of aligned nanofibers with controllable configurations, and significantly simplify the production of nanofibersbased devices.

  1. Angular dependent anisotropic terahertz response of vertically aligned multi-walled carbon nanotube arrays with spatial dispersion

    Science.gov (United States)

    Zhou, Yixuan; Yiwen, E.; Xu, Xinlong; Li, Weilong; Wang, Huan; Zhu, Lipeng; Bai, Jintao; Ren, Zhaoyu; Wang, Li

    2016-12-01

    Spatial dispersion effect of aligned carbon nanotubes (CNTs) in the terahertz (THz) region has significance for both theoretical and applied consideration due to the unique intrinsically anisotropic physical properties of CNTs. Herein, we report the angular dependent reflection of p-polarized THz wave from vertically aligned multi-walled CNT arrays in both experiment and theory. The spectra indicate that the reflection depends on the film thickness of vertically aligned CNTs, the incident angle, and the frequency. The calculation model is based on the spatial dispersion effect of aligned CNTs and performed with effective impedance method and the Maxwell-Garnett approximation. The results fit well with the experiment when the thickness of CNT film is thin, which reveals a coherent superposition mechanism of the CNT surface reflection and CNTs/Si interface reflection. For thick CNT films, the CNTs/Si interface response determines the reflection at small incident angles, while the CNTs surface effect dominates at large incident angles. This work investigates the spatial dispersion effect of vertically aligned CNT arrays in the THz region, and paves a way for potential anisotropic THz applications based on CNTs with oblique incidence requirements.

  2. Vertically aligned nitrogen doped (Sn,Nb)O{sub 2} nanotubes – Robust photoanodes for hydrogen generation by photoelectrochemical water splitting

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Prasad Prakash, E-mail: ppp4@pitt.edu [Department of Chemical and Petroleum Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Hanumantha, Prashanth Jampani [Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Velikokhatnyi, Oleg I.; Datta, Moni Kanchan [Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Center for Complex Engineered Multifunctional Materials, University of Pittsburgh, PA 15261 (United States); Gattu, Bharat [Department of Chemical and Petroleum Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Poston, James A.; Manivannan, Ayyakkannu [US Department of Energy, National Energy Technology Laboratory, Morgantown, WV 26507 (United States); Kumta, Prashant N., E-mail: pkumta@pitt.edu [Department of Chemical and Petroleum Engineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Center for Complex Engineered Multifunctional Materials, University of Pittsburgh, PA 15261 (United States); Mechanical Engineering and Materials Science, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); School of Dental Medicine, University of Pittsburgh, PA 15217 (United States)

    2016-06-15

    Graphical abstract: - Highlights: • Nb and N co-doping provides excellent optoelectronic properties for SnO{sub 2} NTs. • The optoelectronic properties of doped SnO{sub 2} are studied by first principles study. • (Sn{sub 0.95}Nb{sub 0.05})O{sub 2}:N-600 NTs exhibits superior ABPE (4.1%) to date. • Excellent photoelectrochemical stability of (Sn{sub 0.95}Nb{sub 0.05})O{sub 2}:N-600 NTs. - Abstract: Hydrogen generation from photoelectrochemical (PEC) water splitting is on the forefront of clean energy generation landscape. The efficiency of PEC system is dependent on the engineering of semiconductors with tailored narrow band gap coupled with superior photoelectrochemical activity and desired stability vital for the commercialization of PEC water splitting cells. We report herein the study of vertically aligned Nb and N doped SnO{sub 2} nanotubes (NTs), i.e., (Sn{sub 0.95}Nb{sub 0.05})O{sub 2}:N NTs for PEC water splitting. (Sn{sub 0.95}Nb{sub 0.05})O{sub 2} NTs was selected for co-doping with nitrogen by systematic analysis of applied bias photon-to-current efficiency of various Nb doped SnO{sub 2} (x = 0–0.1) compositions. Consequently, excellent photoelectrochemical stability and the highest efficiency of 4.1% is obtained for (Sn{sub 0.95}Nb{sub 0.05})O{sub 2}:N-600 NTs never observed for other known TiO{sub 2}, ZnO, and Fe{sub 2}O{sub 3} systems to date. Additionally, theoretical first principles study provides understanding of Nb and N co-doping on the electronic structure and band gap of SnO{sub 2} semiconductor, further corroborating results of the experimental study.

  3. Superior Thermal Interface via Vertically Aligned Carbon Nanotubes Grown on Graphite Foils

    Science.gov (United States)

    2012-01-01

    L.L. Zhang, Z. Xiong, and X.S. Zhao: Pillaring chemically exfoliated graphene oxide with carbon nanotubes for photocatalytic degrada- tion of dyes...and V.T. Renard: Few graphene layers/carbon nanotube composites grown at complimentary-metal-oxide- semiconductor compatible temper- ature. Appl

  4. Controlled Growth and Modification of Vertically-Aligned Carbon Nanotubes for Multifunctional Applications

    Science.gov (United States)

    2010-01-01

    addition of H2O into the nanotube-growth CVD system prevented Fe catalyst particles from aggregation through Ostwald ripening due to retarded...polymerization of acetaldehyde . The insets show TEM images of an individual nanotube (a) before and (b) after being coated with a layer of the acetaldehyde

  5. En route to controlled catalytic CVD synthesis of densely packed and vertically aligned nitrogen-doped carbon nanotube arrays

    Directory of Open Access Journals (Sweden)

    Slawomir Boncel

    2014-03-01

    Full Text Available The catalytic chemical vapour deposition (c-CVD technique was applied in the synthesis of vertically aligned arrays of nitrogen-doped carbon nanotubes (N-CNTs. A mixture of toluene (main carbon source, pyrazine (1,4-diazine, nitrogen source and ferrocene (catalyst precursor was used as the injection feedstock. To optimize conditions for growing the most dense and aligned N-CNT arrays, we investigated the influence of key parameters, i.e., growth temperature (660, 760 and 860 °C, composition of the feedstock and time of growth, on morphology and properties of N-CNTs. The presence of nitrogen species in the hot zone of the quartz reactor decreased the growth rate of N-CNTs down to about one twentieth compared to the growth rate of multi-wall CNTs (MWCNTs. As revealed by electron microscopy studies (SEM, TEM, the individual N-CNTs (half as thick as MWCNTs grown under the optimal conditions were characterized by a superior straightness of the outer walls, which translated into a high alignment of dense nanotube arrays, i.e., 5 × 108 nanotubes per mm2 (100 times more than for MWCNTs grown in the absence of nitrogen precursor. In turn, the internal crystallographic order of the N-CNTs was found to be of a ‘bamboo’-like or ‘membrane’-like (multi-compartmental structure morphology. The nitrogen content in the nanotube products, which ranged from 0.0 to 3.0 wt %, was controlled through the concentration of pyrazine in the feedstock. Moreover, as revealed by Raman/FT-IR spectroscopy, the incorporation of nitrogen atoms into the nanotube walls was found to be proportional to the number of deviations from the sp2-hybridisation of graphene C-atoms. As studied by XRD, the temperature and the [pyrazine]/[ferrocene] ratio in the feedstock affected the composition of the catalyst particles, and hence changed the growth mechanism of individual N-CNTs into a ‘mixed base-and-tip’ (primarily of the base-type type as compared to the purely

  6. Cytocompatibility studies of vertically-aligned multi-walled carbon nanotubes: Raw material and functionalized by oxygen plasma

    Energy Technology Data Exchange (ETDEWEB)

    Lobo, A.O., E-mail: loboao@yahoo.com [Laboratorio Associado de Sensores e Materiais, INPE, Sao Jose dos Campos/SP (Brazil); Instituto Tecnologico de Aeronautica, ITA, Sao Jose dos Campos/SP (Brazil); Laboratorio de Nanotecnologia Biomedica, Universidade do Vale do Paraiba, Sao Jose dos Campos/SP (Brazil); Corat, M.A.F. [Centro Multidisciplinar para Investigacao Biologica na Area da Ciencia em Animais de Laboratorio, CEMIB, UNICAMP, Campinas/SP (Brazil); Antunes, E.F. [Laboratorio Associado de Sensores e Materiais, INPE, Sao Jose dos Campos/SP (Brazil); Instituto Tecnologico de Aeronautica, ITA, Sao Jose dos Campos/SP (Brazil); Ramos, S.C. [Instituto Tecnologico de Aeronautica, ITA, Sao Jose dos Campos/SP (Brazil); Pacheco-Soares, C. [Laboratorio de Dinamica de Compartimentos Celulares, UNIVAP, Sao Jose dos Campos/SP (Brazil); and others

    2012-05-01

    It was presented a strong difference on cell adhesion and proliferation of functionalized vertically-aligned multi-walled carbon nanotube (VACNT) scaffolds compared to raw-VACNT. Biocompatibility in vitro tests were performed on raw-VACNT after superficial modification by oxygen plasma, which changes its superhydrophobic character to superhydrophilic. Two cytocompatibility tests were applied: 1) total lactate dehydrogenase colorimetric assay for the study of proliferating cells; and 2) cellular adhesion by scanning electron microscopy. Results showed that superhydrophilic VACNT scaffolds stimulate cell growth with proliferation up to 70% higher than normal growth of cell culture.

  7. Confocal Microscopy for Process Monitoring and Wide-Area Height Determination of Vertically-Aligned Carbon Nanotube Forests

    Directory of Open Access Journals (Sweden)

    Markus Piwko

    2015-08-01

    Full Text Available Confocal microscopy is introduced as a new and generally applicable method for the characterization of the vertically-aligned carbon nanotubes (VACNT forest height. With this technique process control is significantly intensified. The topography of the substrate and VACNT can be mapped with a height resolution down to 15 nm. The advantages of confocal microscopy, compared to scanning electron microscopy (SEM, are demonstrated by investigating the growth kinetics of VACNT using Al2O3 buffer layers with varying thicknesses. A process optimization using confocal microscopy for fast VACNT forest height evaluation is presented.

  8. Controlled synthesis of aligned ZnO nanowires and the application in CdSe-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Deng, Jianping; Wang, Minqiang, E-mail: mqwang@mail.xjtu.edu.cn; Song, Xiaohui; Liu, Jing

    2014-03-05

    Highlights: • ZnO NWs were synthesized by a composite hydrothermal method. • The morphology of ZnO NWs were optimized by pretreatment of seeds. • The growth of ZnO NWs were explained with vapor–liquid equilibrium theory. -- Abstract: According to the two-step hydrothermal method, ZnO nanowires (NWs) were successfully synthesized through the pretreatment of seeds in the NaOH/Zn(NO{sub 3}){sub 2} solution and the subsequent growth of ZnO NWs in the Zn(NO{sub 3}){sub 2}/HMTA/PEI/NH{sub 4}OH solution. The method overcomes the disadvantages in the fusion and tilt of NWs. The morphology of ZnO NWs was controlled through regulating the concentration of zinc acetate in the seed precursor and changing pretreatment time of ZnO seeds. SEM images show that the length of ZnO NWs increases with the increase of the volume ratio (V{sub gas}:V{sub liquid}) in the sealed system. The absorption spectra of the bulk solution confirm that decreasing vapor pressure can release more Zn{sup 2+} and accelerate the growth of NWs. The effect of vapor pressure on the growth of NWs was explained by the vapor–liquid equilibrium theory. With ZnO NW films synthesized in the three systems as the photoanodes, we fabricated CdSe quantum-dots-sensitized solar cells (QDSSCs) and tested photovoltaic (PV) performances. The result exhibits a remarkably enhanced short-circuit current density (J{sub sc}) of 6.71 mA/cm{sup 2} and power conversion efficiency (η) of 2.17%.

  9. Hydrothermal synthesis of highly crystalline ZnO nanorod arrays: Dependence of morphology and alignment on growth conditions

    Energy Technology Data Exchange (ETDEWEB)

    Azzez, Shrook A., E-mail: shurouq44@yahoo.com [Institutes of Nano-Optoelectronic Research and Technology Laboratory (INOR), Ministry of Science and Technology, Baghdad (Iraq); Hassan, Z.; Alimanesh, M.; Rasheed, Hiba S.; Sabah, Fayroz A.; Abdulateef, Sinan A. [Institutes of Nano-Optoelectronic Research and Technology Laboratory (INOR), Ministry of Science and Technology, Baghdad (Iraq); Hassan, J. J. [Department of Physics, College of Science, University of Basrah, Basrah (Iraq)

    2016-07-06

    Highly oriented zinc oxide nanorod were successfully grown on seeded p-type silicon substrate by hydrothermal methode. The morphology and the crystallinty of ZnO c-axis (002) arrays were systematically studied using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) methods. The effect of seed layer pre-annealing on nanorods properties was explained according to the nucleation site of ZnO nanoparticles on silicon substrate. In addition, the variation of the equal molarity of zinc nitrate hexahydrate and hexamine concentrations in the reaction vessel play a crucial role related to the ZnO nanorods.

  10. Functionalization of vertically aligned carbon nanotubes with polystyrene via surface initiated reversible addition fragmentation chain transfer polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Macdonald, Thomas; Gibson, Christopher T.; Constantopoulos, Kristina; Shapter, Joseph G. [Flinders Centre for Nanoscale Science and Technology, School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA, 5001 (Australia); Ellis, Amanda V., E-mail: amanda.ellis@flinders.edu.au [Flinders Centre for Nanoscale Science and Technology, School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA, 5001 (Australia)

    2012-01-15

    Here we demonstrate the covalent attachment of vertically aligned (VA) acid treated single-walled carbon nanotubes (SWCNTs) onto a silicon substrate via dicyclohexylcarbodiimide (DCC) coupling chemistry. Subsequently, the pendant carboxyl moieties on the sidewalls of the VA-SWCNTs were derivatized to acyl chlorides, and then finally to bis(dithioester) moieties using a magnesium chloride dithiobenzoate salt. The bis(dithioester) moieties were then successfully shown to act as a chain transfer agent (CTA) in the reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in a surface initiated 'grafting-from' process from the VA-SWCNT surface. Atomic force microscopy (AFM) verified vertical alignment of the SWCNTs and the maintenance thereof throughout the synthesis process. Finally, Raman scattering spectroscopy and AFM confirmed polystyrene functionalization.

  11. Direct current injection and thermocapillary flow for purification of aligned arrays of single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Xu; Islam, Ahmad E.; Seabron, Eric; Dunham, Simon N.; Du, Frank; Lin, Jonathan; Wilson, William L.; Rogers, John A., E-mail: jrogers@illinois.edu [Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Wahab, Muhammad A.; Alam, Muhammad A. [School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Li, Yuhang [Institute of Solid Mechanics, Beihang University, Beijing 100191 (China); Tomic, Bojan [Department of Electrical Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Huang, Jiyuan [Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Burns, Branden [Department of Physics, Purdue University, West Lafayette, Indiana 47907 (United States); Song, Jizhou [Department of Engineering Mechanics and Soft Matter Research Center, Zhejiang University, Hangzhou 310027 (China); Huang, Yonggang [Department of Civil and Environmental Engineering, Department of Mechanical Engineering, Center for Engineering and Health, and Skin Disease Research Center, Northwestern University, Evanston, Illinois 60208 (United States)

    2015-04-07

    Aligned arrays of semiconducting single-walled carbon nanotubes (s-SWNTs) represent ideal configurations for use of this class of material in high performance electronics. Development of means for removing the metallic SWNTs (m-SWNTs) in as-grown arrays represents an essential challenge. Here, we introduce a simple scheme that achieves this type of purification using direct, selective current injection through interdigitated electrodes into the m-SWNTs, to allow their complete removal using processes of thermocapillarity and dry etching. Experiments and numerical simulations establish the fundamental aspects that lead to selectivity in this process, thereby setting design rules for optimization. Single-step purification of arrays that include thousands of SWNTs demonstrates the effectiveness and simplicity of the procedures. The result is a practical route to large-area aligned arrays of purely s-SWNTs with low-cost experimental setups.

  12. Preparation of Aligned Ultra-long and Diameter-controlled Silicon Oxide Nanotubes by Plasma Enhanced Chemical Vapor Deposition Using Electrospun PVP Nanofiber Template

    Directory of Open Access Journals (Sweden)

    Zhou Ming

    2009-01-01

    Full Text Available Abstract Well-aligned and suspended polyvinyl pyrrolidone (PVP nanofibers with 8 mm in length were obtained by electrospinning. Using the aligned suspended PVP nanofibers array as template, aligned ultra-long silicon oxide (SiOx nanotubes with very high aspect ratios have been prepared by plasma-enhanced chemical vapor deposition (PECVD process. The inner diameter (20–200 nm and wall thickness (12–90 nm of tubes were controlled, respectively, by baking the electrospun nanofibers and by coating time without sacrificing the orientation degree and the length of arrays. The micro-PL spectrum of SiOx nanotubes shows a strong blue–green emission with a peak at about 514 nm accompanied by two shoulders around 415 and 624 nm. The blue–green emission is caused by the defects in the nanotubes.

  13. Preparation and photoelectrocatalytic activity of ZnO nanorods embedded in highly ordered TiO(2) nanotube arrays electrode for azo dye degradation.

    Science.gov (United States)

    Zhang, Zhonghai; Yuan, Yuan; Liang, Linhong; Cheng, Yuxiao; Shi, Guoyue; Jin, Litong

    2008-10-30

    In this article, the ZnO nanorods embedded in highly ordered TiO(2) nanotube arrays (ZnO/TiO(2) NR/Ts) electrodes were fabricated through two steps: (1) electrosynthesis of TiO(2) nanotube arrays (TiO(2) NTs) in HF solution by anodization method; (2) followed by cathodic electrodeposition of ZnO embedded in the TiO(2) nanotube arrays. The morphological characteristics and structures of ZnO/TiO(2) NR/Ts electrodes were examined by field-emission scanning electron microscopy (FE-SEM), energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD) analysis, and UV-vis spectra. The linear-sweep photovoltammetry response on the ZnO/TiO(2) NR/Ts electrode was presented and the photocurrent was dramatically enhanced on the ZnO/TiO(2) NR/Ts electrode, comparing with that on bare TiO(2) NTs electrode. The photocatalytic and photoelectrocatalytic activity of ZnO/TiO(2) NR/Ts electrode was evaluated in degradation of methyl orange (MO) in aqueous solution.

  14. Embedded Aligned Carbon Nanotube Sheets for Strain and Damage sensing in Composite Structures

    Science.gov (United States)

    Aly, Karim Aly Abdelomoaty Elsayed

    The world demand for fiber reinforced composite materials has been steadily increasing because of the widespread adoption of this class of material in many markets. The automotive, aerospace, marine and energy sectors account for a large percentage of this grow. Outstanding fatigue performance, high specific stiffness and strength, and low density are among the most important properties that fiber reinforced polymer composites offer. Furthermore, their properties can be tailored to meet the specific needs of the final applications. However, this class of material is composed of multiple layers of inhomogeneous and anisotropic constituents, i.e. fibers and matrix. Therefore, this laminated nature make the composite material prone to intrinsic damage including interfacial debonding and delamination and their strength and failure are dependent on the fiber architecture and direction of the applied stresses. Consequently, it is of prime importance to monitor the health of these structures. New and improved methods for early detection of damage and structural health monitoring of composite materials may allow for enhanced reliability, lifetime and performance while minimizing maintenance time during a composite part's service life. Over the last few decades different non-destructive methods and materials have been investigated for use as strain sensors. Since the discovery of carbon nanotubes (CNTs), they have attracted much research interest due to their superior electrical, thermal and mechanical properties as well as their high aspect ratio. In this context, CNTs have been used in the recent years to enable sensing capabilities. In this dissertation, the usage of CNTs for performing strain and damage sensing in composites is evaluated. This was enabled by embedding aligned sheets of two millimeters long, interconnected CNTs into laminated structures that were then subjected to different forms of mechanical loading. The localization of the CNT sheets inside the host

  15. Effects of external surface charges on the enhanced piezoelectric potential of ZnO and AlN nanowires and nanotubes

    Directory of Open Access Journals (Sweden)

    Seong Min Kim

    2012-12-01

    Full Text Available We theoretically investigate external surface charge effects on piezoelectric potential of ZnO and AlN nanowires (NWs and nanotubes (NTs under uniform compression. The free carrier depletion caused by negative surface charges via surface functionalization on vertically compressed ZnO and AlN NWs/NTs is simulated using finite element calculation; this indicates the enhancement of piezoelectric potential is due to the free carriers (electrons being fully depleted at the critical surface charge density. Numerical simulations reveal that full coverage of surface charges surrounding the NTs increases the piezoelectric output potential exponentially within a relatively smaller range of charge density compared to the case of NWs for a typical donor concentration (∼1017 cm−3. The model can be used to design functional high-power semiconducting piezoelectric nanogenerators.

  16. Electrospinning direct synthesis of magnetic ZnFe2O4/ZnO multi-porous nanotubes with enhanced photocatalytic activity

    Science.gov (United States)

    Wang, Chunlei; Tan, Xing; Yan, Juntao; Chai, Bo; Li, Jianfen; Chen, Shizhong

    2017-02-01

    Magnetic ZnFe2O4/ZnO (ZFO/ZnO) multi-porous nanotubes have been first fabricated via a facile electrospinning and subsequent calcination process. A series of ZFO/ZnO photocatalysts with different ZFO molar content and morphologies are also obtained by varying the molar ratio of Zn/Fe metal salt and its dosage. The morphology, composition, crystal structure and specific surface area of achieved photocatalysts are systematically examined. TEM images demonstrate ZFO/ZnO-3 multi-porous nanotubes possess perfect 1D nanotube profile with hierarchical pores. HRTEM images confirm the formation of ZFO/ZnO heterojunctions. DRS spectra show that ZFO/ZnO-3 multi-porous nanotubes exhibit an enhanced absorption both in UV and visible-light region. PL spectra and photocurrent responses of ZFO/ZnO-3 multi-porous nanotube demonstrated that the photogenerated electrons and holes are effectively separated. Above all, ZFO/ZnO-3 multi-porous nanotubes photocatalysts with a larger specific surface area of 57.79 m2 g-1 exhibit the best photocatalytic efficiency of 99% after 150 min under the solar irradiation for the decolorization of RhB. Moreover, ZFO/ZnO photocatalysts not only possess magnetic separation property, but also keep a relatively high photocatalytic efficiency even after four cycles, which is beneficial for practical application. In addition, both the formation and potential photocatalytic mechanisms of ZFO/ZnO-3 multi-porous nanotubes are proposed in detail.

  17. An electrical bio-chip to transfer and detect electromagnetic stimulation on the cells based on vertically aligned carbon nanotubes.

    Science.gov (United States)

    Rafizadeh-Tafti, Saeed; Haqiqatkhah, Mohammad Hossein; Saviz, Mehrdad; Janmaleki, Mohsen; Faraji Dana, Reza; Zanganeh, Somayeh; Abdolahad, Mohammad

    2017-01-01

    A highly sensitive impedimetric bio-chip based on vertically aligned multiwall carbon nanotubes (VAMWCNTs), was applied in direct interaction with lung cancer cells. Our tool provided both inducing and monitoring the bioelectrical changes in the cells initiated by electromagnetic (EM) wave stimulation. EM wave of 940MHz frequency with different intensities was used. Here, wave ablation might accumulate electrical charge on the tips of nanotubes penetrated into cell's membrane. The charge might induce ionic exchanges into the cell and cause alterations in electrical states of the membrane. Transmembrane electrostatic/dynamic states would be strongly affected due to such exchanges. Our novel modality was that, the cells' vitality changes caused by charge inductions were electrically detected with the same nanotubes in the architecture of electrodes for impedance measurement. The responses of the sensor were confirmed by electron and florescent microscopy images as well as biological assays. In summation, our method provided an effective biochip for enhancing and detecting external EM stimulation on the cells useful for future diagnostic and therapeutic applications, such as wave-guided drug-resistance breakage.

  18. Effect of Catalytic Layer Thickness on Diameter of Vertically Aligned Individual Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Hyun Kyung Jung

    2014-01-01

    Full Text Available The effect of catalytic thin film thickness on the diameter control of individual carbon nanotubes grown by plasma enhanced chemical vapor deposition was investigated. Individual carbon nanotubes were grown on catalytic nanodot arrays, which were fabricated by e-beam lithography and e-beam evaporation. During e-beam evaporation of the nanodot pattern, more catalytic metal was deposited at the edge of the nanodots than the desired catalyst thickness. Because of this phenomenon, carbon atoms diffused faster near the center of the dots than at the edge of the dots. The carbon atoms, which were gathered at the interface between the catalytic nanodot and the diffusion barrier, accumulated near the center of the dot and lifted the catalyst off. From the experiments, an individual carbon nanotube with the same diameter as that of the catalytic nanodot was obtained from a 5 nm thick catalytic nanodot; however, an individual carbon nanotube with a smaller diameter (~40% reduction was obtained from a 50 nm thick nanodot. We found that the thicker the catalytic layer, the greater the reduction in diameter of the carbon nanotubes. The diameter-controlled carbon nanotubes could have applications in bio- and nanomaterial scanning and as a contrast medium for magnetic resonance imaging.

  19. Charge transport in vertically aligned, self-assembled peptide nanotube junctions

    Science.gov (United States)

    Mizrahi, Mordechay; Zakrassov, Alexander; Lerner-Yardeni, Jenny; Ashkenasy, Nurit

    2012-01-01

    The self-assembly propensity of peptides has been extensively utilized in recent years for the formation of supramolecular nanostructures. In particular, the self-assembly of peptides into fibrils and nanotubes makes them promising building blocks for electronic and electro-optic applications. However, the mechanisms of charge transfer in these wire-like structures, especially in ambient conditions, are not yet fully understood. We describe here a layer-by-layer deposition methodology of short self-assembled cyclic peptide nanotubes, which results in vertically oriented nanotubes on gold substrates. Using this novel deposition methodology, we have fabricated molecular junctions with a conductive atomic force microscopy tip as a second electrode. Studies of the junctions' current-voltage characteristics as a function of the nanotube length revealed an efficient charge transfer in these supramolecular structures, with a low current attenuation constant of 0.1 Å-1, which indicate that electron transfer is dominated by hopping. Moreover, the threshold voltage to field-emission dominated transport was found to increase with peptide length in a manner that depends on the nature of the contact with the electrodes. The flexibility in the design of the peptide monomers and the ability to control their sequential order over the nanotube by means of the layer-by-layer assembly process, which is demonstrated in this work, can be used to engineer the electronic properties of self-assembled peptide nanotubes toward device applications.

  20. Protein-enabled layer-by-layer syntheses of aligned, porous-wall, high-aspect-ratio TiO{sub 2} nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Berrigan, John D.; Cai, Ye; Sandhage, Kenneth H. [School of Materials Science and Engineering, Air Force Center of Excellence on Bio-Nano-Enabled Inorganic/Organic Nanocomposites and Improved Cognition (BIONIC), Georgia Institute of Technology, 771 Ferst Drive, Atlanta, Georgia 30332-0400 (United States); Kang, Tae-Sik; Deneault, James R.; Durstock, Michael F. [Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, 45433-7702 (United States)

    2011-05-10

    An aqueous, protein-enabled (biomimetic), layer-by-layer titania deposition process is developed, for the first time, to convert aligned-nanochannel templates into high-aspect-ratio, aligned nanotube arrays with thin (34 nm) walls composed of co-continuous networks of pores and titania nanocrystals (15 nm ave. size). Alumina templates with aligned open nanochannels are exposed in an alternating fashion to aqueous protamine-bearing and titania precursor-bearing (Ti(IV) bis-ammonium-lactato-dihydroxide, TiBALDH) solutions. The ability of protamine to bind to alumina and titania, and to induce the formation of a Ti-O-bearing coating upon exposure to the TiBALDH precursor, enables the layer-by-layer deposition of a conformal protamine/Ti-O-bearing coating on the nanochannel surfaces within the porous alumina template. Subsequent protamine pyrolysis yields coatings composed of co-continuous networks of pores and titania nanoparticles. Selective dissolution of the underlying alumina template through the porous coating then yields freestanding, aligned, porous-wall titania nanotube arrays. The interconnected pores within the nanotube walls allow enhanced loading of functional molecules (such as a Ru-based N719 dye), whereas the interconnected titania nanoparticles enable the high-aspect-ratio, aligned nanotube arrays to be used as electrodes (as demonstrated for dye-sensitized solar cells with power conversion efficiencies of 5.2 {+-} 0.4%). (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Functionalized vertically aligned ZnO nanorods for application in electrolyte-insulator-semiconductor based pH sensors and label-free immuno-sensors

    Science.gov (United States)

    Kumar, Narendra; Senapati, Sujata; Kumar, Satyendra; Kumar, Jitendra; Panda, Siddhartha

    2016-04-01

    Vertically aligned ZnO nanorods were grown on a SiO2/Si surface by optimization of the temperature and atmosphere for annealing of the seed. The seed layer annealed at 500 °C in vacuum provided well separated and uniform seeds which also provided the best condition to get densely packed, uniformly distributed, and vertically aligned nanorods. These nanorods grown on the substrates were used to fabricate electrolyte-insulator-semiconductor (EIS) devices for pH sensing. Etching of ZnO at acidic pH prevents the direct use of nanorods for pH sensing. Therefore, the nanorods functionalised with 3-aminopropyltriethoxysilane (APTES) were utilized for pH sensing and showed the pH sensitivity of 50.1 mV/pH. APTES is also known to be used as a linker to immobilize biomolecules (such as antibodies). The EIS device with APTES functionalized nanorods was used for the label free detection of prostate-specific antigen (PSA). Finally, voltage shifts of 23 mV and 35 mV were observed with PSA concentrations of 1 ng/ml and 100 ng/ml, respectively.

  2. Optical Properties of ZnO Nanotubes and Their Photocatalytic Activity for Degradation of Methyl Orange%ZnO纳米管的光学性质及其对甲基橙降解的光催化活性

    Institute of Scientific and Technical Information of China (English)

    李长全; 罗来涛; 熊光伟

    2009-01-01

    以十二烷基硫酸钠为模板剂采用水热法合成了ZnO纳米管,以尿素和ZnSO_4为原料制备了ZnO纳米颗粒,并应用透射电镜、x射线衍射、光致发射光谱、拉曼光谱、比表面积测定、傅里叶红外光谱和紫外-可见漫反射光谱等技术对样品进行了表征.结果表明,ZnO纳米管的比表面积较大,在λ≈650nm的可见光波段ZnO纳米管开始出现吸收峰,而ZnO纳米颗粒在可见光波段几乎没有吸收.ZnO纳米管和纳米颗粒在紫外光照射下均对甲基橙有降解作用,其中ZnO纳米管的光催化活性较高.随着催化剂用量的增加和光照时间的延长,甲基橙降解率逐渐提高;甲基橙浓度的增大使甲基橙降解率降低.%ZnO nanotubes were synthesized by the hydrothermal method using sodium dodecyl sulfate as the template, and ZnO nanopar-tides were prepared with urea and ZnSO_4 as raw materials. The optical properties and photocatalytic activity of ZnO nanotubes and nanopar-ticles were studied, and the samples were characterized by transmission electron microscopy, X-ray diffraction, photoluminescence spec-troscopy, Raman spectroscopy, specific surface area determination, Fourier transform infrared spectroscopy, and ultraviolet-visual diffuse reflection spectroscopy. The ZnO nanotubes had larger specific surface area than the ZnO nanoparticles. The absorption peak of ZnO nanotubes began to appear atλ≈650 nm, but the ZnO nanoparticles nearly had no absorptive capacity in the visible band. ZnO nanotubes and nanoparticles can degradate methyl orange under ultraviolet light, and the catalytic activity of ZnO nanotubes was greater than that of ZnO nanoparticles. With the increase in the catalyst amount and illumination time, the degradation rate of methyl orange increased. Increasing the methyl orange concentration reduced the degradation rate.

  3. Synthesis of subnanometer-diameter vertically aligned single-walled carbon nanotubes with copper-anchored cobalt catalysts

    Science.gov (United States)

    Cui, Kehang; Kumamoto, Akihito; Xiang, Rong; An, Hua; Wang, Benjamin; Inoue, Taiki; Chiashi, Shohei; Ikuhara, Yuichi; Maruyama, Shigeo

    2016-01-01

    We synthesize vertically aligned single-walled carbon nanotubes (VA-SWNTs) with subnanometer diameters on quartz (and SiO2/Si) substrates by alcohol CVD using Cu-anchored Co catalysts. The uniform VA-SWNTs with a nanotube diameter of 1 nm are synthesized at a CVD temperature of 800 °C and have a thickness of several tens of μm. The diameter of SWNTs was reduced to 0.75 nm at 650 °C with the G/D ratio maintained above 24. Scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (EDS-STEM) and high angle annular dark field (HAADF-STEM) imaging of the Co/Cu bimetallic catalyst system showed that Co catalysts were captured and anchored by adjacent Cu nanoparticles, and thus were prevented from coalescing into a larger size, which contributed to the small diameter of SWNTs. The correlation between the catalyst size and the SWNT diameter was experimentally clarified. The subnanometer-diameter and high-quality SWNTs are expected to pave the way to replace silicon for next-generation optoelectronic and photovoltaic devices.We synthesize vertically aligned single-walled carbon nanotubes (VA-SWNTs) with subnanometer diameters on quartz (and SiO2/Si) substrates by alcohol CVD using Cu-anchored Co catalysts. The uniform VA-SWNTs with a nanotube diameter of 1 nm are synthesized at a CVD temperature of 800 °C and have a thickness of several tens of μm. The diameter of SWNTs was reduced to 0.75 nm at 650 °C with the G/D ratio maintained above 24. Scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (EDS-STEM) and high angle annular dark field (HAADF-STEM) imaging of the Co/Cu bimetallic catalyst system showed that Co catalysts were captured and anchored by adjacent Cu nanoparticles, and thus were prevented from coalescing into a larger size, which contributed to the small diameter of SWNTs. The correlation between the catalyst size and the SWNT diameter was experimentally clarified. The subnanometer-diameter and high

  4. High-performance Supercapacitors Based on Electrochemical-induced Vertical-aligned Carbon Nanotubes and Polyaniline Nanocomposite Electrodes

    Science.gov (United States)

    Wu, Guan; Tan, Pengfeng; Wang, Dongxing; Li, Zhe; Peng, Lu; Hu, Ying; Wang, Caifeng; Zhu, Wei; Chen, Su; Chen, Wei

    2017-01-01

    Supercapacitors, which store electrical energy through reversible ion on the surface of conductive electrodes have gained enormous attention for variously portable energy storage devices. Since the capacitive performance is mainly determined by the structural and electrochemical properties of electrodes, the electrodes become more crucial to higher performance. However, due to the disordered microstructure and low electrochemical activity of electrode for ion tortuous migration and accumulation, the supercapacitors present relatively low capacitance and energy density. Here we report a high-performance supercapacitor based on polyaniline/vertical-aligned carbon nanotubes (PANI/VA-CNTs) nanocomposite electrodes where the vertical-aligned-structure is formed by the electrochemical-induction (0.75 V). The supercapacitor displays large specific capacitance of 403.3 F g−1, which is 6 times higher than disordered CNTs in HClO4 electrolyte. Additionally, the supercapacitor can also present high specific capacitance (314.6 F g−1), excellent cycling stability (90.2% retention after 3000 cycles at 4 A g−1) and high energy density (98.1 Wh kg−1) in EMIBF4 organic electrolyte. The key to high-performance lies in the vertical-aligned-structure providing direct path channel for ion faster diffusion and high electrochemical capacitance of polyaniline for ion more accommodation. PMID:28272474

  5. Multilevel, Multicomponent Microarchitectures of Vertically-Aligned Carbon Nanotubes for Diverse Applications

    Science.gov (United States)

    2011-01-31

    Materials and Manufacturing Directorate, Air Force Research Laboratory, RXBP, Wright-Patterson Air Force Base, Ohio 45433, United States, and... materials with specific properties such as ZnO nanorods, SiO2 microspheres, and TiO2 thin film have also been inter- posed into the patterned...plate were synthesized by pyrolysis of iron phthalocyanine (FePc) in Ar/H2 atmosphere at 1100 C as we previously reported,19 while nonpatterned VA

  6. Dynamic mechanical analysis and high strain-rate energy absorption characteristics of vertically aligned carbon nanotube reinforced woven fiber-glass composites

    Science.gov (United States)

    The dynamic mechanical behavior and energy absorption characteristics of nano-enhanced functionally graded composites, consisting of 3 layers of vertically aligned carbon nanotube (VACNT) forests grown on woven fiber-glass (FG) layer and embedded within 10 layers of woven FG, with polyester (PE) and...

  7. Large-Scale Synthesis of ZnO Nanotubes via a Simple Method%一种制备大量氧化锌纳米管的简单方法

    Institute of Scientific and Technical Information of China (English)

    李大枝; 孙思修; 张卫民; 张长花; 张兰香

    2005-01-01

    ZnO nanotubes were synthesized in large scale by thermal decomposition of the precursors obtained via(SDS). The inner diameters of the tubes were in the range of 80~100 nm, and outer diameters in the range of 160~260 nm with lengths up to a few micrometers. The products were characterized with XRD, TEM, and SEM.

  8. Alignment and Use of Self-Assembled Peptide Nanotubes as Dry-Etching Mask

    DEFF Research Database (Denmark)

    Andersen, Karsten Brandt; Castillo, Jaime; Bakmand, Tanya

    2012-01-01

    Self-assembled diphenylalanine peptide nanotubes provide a means of achieving nanostructured materials in a very simple and fast way. Recent discoveries have shown that this unique material, in addition to remaining stable under dry conditions, rapidly dissolves in water making it a promising can...

  9. The fabrication of single-walled carbon nanotube/polyelectrolyte multilayer composites by layer-by-layer assembly and magnetic field assisted alignment

    Science.gov (United States)

    Tian, Ying; Park, Jin Gyu; Cheng, Qunfeng; Liang, Zhiyong; Zhang, Chuck; Wang, Ben

    2009-08-01

    Single-walled carbon nanotube (SWNT)/polymer composites are widely studied because of their potential for high mechanical performance and multifunctional applications. In order to realize highly ordered multilayer nanostructures, we combined the layer-by-layer (LBL) assembly method with magnetic force-induced alignment to fabricate SWNT/poly(ethylamine) (PEI) multilayer composites. The SWNTs were functionalized with the anionic surfactant sodium dodecylbenzenesulfonate (NaDDBS) to realize negative charge at pH>7, while the PEI is positively charged at pHPEI resin to form multilayer composites on a solid substrate polydimethylsiloxane. Since the fabricated thickness of each SWNT-NaDDBS/PEI bilayer is uniform (~150 nm), the multilayer film thickness can be strictly controlled via the number of deposition cycles. A high magnetic field (8.5 Tesla) was used to align the SWNTs during the LBL process. The resultant LBL composite samples demonstrated high SWNT loading of approximately 50 wt% and uniform distribution of SWNTs in the multilayer structures, which was verified using a quartz crystal microbalance. Good alignment was also realized and observed through using high magnetic fields to align the nanotubes during the LBL deposition process. The results indicate that the LBL/magnetic alignment approach has potential for fabricating nanotube composites with highly ordered nanostructures for multifunctional materials and device applications.

  10. Transparent, well-aligned TiO(2) nanotube arrays with controllable dimensions on glass substrates for photocatalytic applications.

    Science.gov (United States)

    Tan, Lee Kheng; Kumar, Manippady K; An, Wen Wen; Gao, Han

    2010-02-01

    Transparent, well-aligned TiO(2) nanotube arrays (NTAs) with controllable dimensions are grown on glass substrates via atomic layer deposition (ALD) of TiO(2) onto free-standing porous anodic alumina (PAA) templates. Photodegradation of aqueous methylene blue (MB) solution and solid stearic acid (SA) film using TiO(2) NTAs of various wall thicknesses are investigated. The Pd functionalized TiO(2) NTAs, with a wall thickness of 15 nm and height of 200 nm, has the highest photodegradation efficiency at 76% after 4 h of UV irradiation. These functionalized NTAs are able to photodegrade MB molecules completely as no obvious demethylated byproducts are observed during the process. It also demonstrates excellent photocatalytic activity for solid contaminants such as SA film. By using the ALD technique, the nanotube wall thickness can be precisely controlled so that it is sufficiently thin to be transparent while sufficiently thick for excellent photocatalytic performances. The transparent TiO(2) NTAs on glass substrates with excellent photocatalytic properties might have potential applications in self-cleaning coating, transparent electronics, and solar cells.

  11. 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.

  12. An evaluation of chondrocyte morphology and gene expression on superhydrophilic vertically-aligned multi-walled carbon nanotube films

    Energy Technology Data Exchange (ETDEWEB)

    Antonioli, Eliane, E-mail: eliane.antonioli@einstein.br [Research and Education Institute, Hospital Israelita Albert Einstein, Sao Paulo, SP (Brazil); Lobo, Anderson O., E-mail: aolobo@univap.br [Laboratory of Biomedical Nanotechnology, Universidade do Vale do Paraiba, Sao Jose dos Campos, Sao Paulo (Brazil); Ferretti, Mario, E-mail: ferretti@einstein.br [Research and Education Institute, Hospital Israelita Albert Einstein, Sao Paulo, SP (Brazil); Ortophedic Division, Federal University of Sao Paulo, SP (Brazil); Cohen, Moises, E-mail: m.cohen@uol.com.br [Research and Education Institute, Hospital Israelita Albert Einstein, Sao Paulo, SP (Brazil); Ortophedic Division, Federal University of Sao Paulo, SP (Brazil); Marciano, Fernanda R., E-mail: femarciano@uol.com.br [Laboratory of Biomedical Nanotechnology, Universidade do Vale do Paraiba, Sao Jose dos Campos, Sao Paulo (Brazil); Corat, Evaldo J., E-mail: corat@las.inpe.br [Laboratorio Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, Sao Jose dos Campos, Sao Paulo (Brazil); Trava-Airoldi, Vladimir J., E-mail: vladimir@las.inpe.br [Laboratorio Associado de Sensores e Materiais, Instituto Nacional de Pesquisas Espaciais, Sao Jose dos Campos, Sao Paulo (Brazil)

    2013-03-01

    Cartilage serves as a low-friction and wear-resistant articulating surface in diarthrodial joints and is also important during early stages of bone remodeling. Recently, regenerative cartilage research has focused on combinations of cells paired with scaffolds. Superhydrophilic vertically aligned carbon nanotubes (VACNTs) are of particular interest in regenerative medicine. The aim of this study is to evaluate cell expansion of human articular chondrocytes on superhydrophilic VACNTs, as well as their morphology and gene expression. VACNT films were produced using a microwave plasma chamber on Ti substrates and submitted to an O{sub 2} plasma treatment to make them superhydrophilic. Human chondrocytes were cultivated on superhydrophilic VACNTs up to five days. Quantitative RT-PCR was performed to measure type I and type II Collagen, Sox9, and Aggrecan mRNA expression levels. The morphology was analyzed by scanning electron microscopy (SEM) and confocal microscopy. SEM images demonstrated that superhydrophilic VACNTs permit cell growth and adhesion of human chondrocytes. The chondrocytes had an elongated morphology with some prolongations. Chondrocytes cultivated on superhydrophilic VACNTs maintain the level expression of Aggrecan, Sox9, and Collagen II determined by qPCR. This study was the first to indicate that superhydrophilic VACNTs may be used as an efficient scaffold for cartilage or bone repair. Highlights: Black-Right-Pointing-Pointer Chondrocytes were cultivated on Superhydrophilic Vertically Aligned Multiwall Carbon Nanotubes (VACNT). Black-Right-Pointing-Pointer We have shown a correlation between gene expression and thermodynamics aspects. Black-Right-Pointing-Pointer Superhydrhophilic VACNT will be an excellent substrate for cartilage and bone tissue regeneration.

  13. Band alignment at the interface between Ni-doped Cr2O3 and Al-doped ZnO: implications for transparent p-n junctions

    Science.gov (United States)

    Arca, Elisabetta; McInerney, Michael A.; Shvets, Igor V.

    2016-06-01

    The realization of transparent electronic and optoelectronic devices requires the use of transparent p-n junctions. In this context, understanding the band alignment at the interface between the p- and n-components represents a fundamental step towards the realization of high performance devices. In this work, the band alignment at the interface between Al-doped ZnO (AZO) and Ni-doped Cr2O3 has been analysed. The formation and evolution of the core levels as the interface progressively forms have been followed by means of x-ray Photoelectron Spectroscopy, x-ray diffraction and x-ray reflectivity. A type two (staggered) band alignment was identified, with the valence band offset and conduction band offset found to be 2.6 eV and 2.5 eV, respectively. The electrical behaviour will be discussed in terms of the position of the bands, the presence of band bending and the expected built-in potential and how these can be engineered in order to achieve the maximum performance for this hetero-structure.

  14. Aligned carbon nanotubes catalytically grown on iron-based nanoparticles obtained by laser-induced CVD

    Energy Technology Data Exchange (ETDEWEB)

    Le Normand, F. [Groupe Surfaces and Interfaces, IPCMS, UMR 7504 CNRS, Bat 70, 23 rue du Loess, 67034 Strasbourg Cedex (France)], E-mail: Francois.Le-Normand@ipcms.u-strasbg.fr; Cojocaru, C.S.; Ersen, O. [Groupe Surfaces and Interfaces, IPCMS, UMR 7504 CNRS, Bat 70, 23 rue du Loess, 67034 Strasbourg Cedex (France); Legagneux, P.; Gangloff, L. [THALES R and T, Departementale 128, 91747 Palaiseau Cedex (France); Fleaca, C. [Groupe Surfaces and Interfaces, IPCMS, UMR 7504 CNRS, Bat 70, 23 rue du Loess, 67034 Strasbourg Cedex (France); National Institute for Lasers, Plasma and Radiation Physics, Laser Department, P.O. Box MG-36, R-76900 Bucharest (Romania); Alexandrescu, R.; Dumitrache, F.; Morjan, I. [National Institute for Lasers, Plasma and Radiation Physics, Laser Department, P.O. Box MG-36, R-76900 Bucharest (Romania)

    2007-12-15

    Iron-based nanoparticles are prepared by a laser-induced chemical vapor deposition (CVD) process. They are characterized as body-centered Fe and Fe{sub 2}O{sub 3} (maghemite/magnetite) particles with sizes {<=}5 and 10 nm, respectively. The Fe particles are embedded in a protective carbon matrix. Both kind of particles are dispersed by spin-coating on SiO{sub 2}/Si(1 0 0) flat substrates. They are used as catalyst to grow carbon nanotubes by a plasma- and filaments-assisted catalytic CVD process (PE-HF-CCVD). Vertically oriented and thin carbon nanotubes (CNTs) were grown with few differences between the two samples, except the diameter in relation to the initial size of the iron particles, and the density. The electron field emission of these samples exhibit quite interesting behavior with a low turn-on voltage at around 1 V/{mu}m.

  15. Aligned carbon nanotubes catalytically grown on iron-based nanoparticles obtained by laser-induced CVD

    Science.gov (United States)

    Le Normand, F.; Cojocaru, C. S.; Ersen, O.; Legagneux, P.; Gangloff, L.; Fleaca, C.; Alexandrescu, R.; Dumitrache, F.; Morjan, I.

    2007-12-01

    Iron-based nanoparticles are prepared by a laser-induced chemical vapor deposition (CVD) process. They are characterized as body-centered Fe and Fe 2O 3 (maghemite/magnetite) particles with sizes ≤5 and 10 nm, respectively. The Fe particles are embedded in a protective carbon matrix. Both kind of particles are dispersed by spin-coating on SiO 2/Si(1 0 0) flat substrates. They are used as catalyst to grow carbon nanotubes by a plasma- and filaments-assisted catalytic CVD process (PE-HF-CCVD). Vertically oriented and thin carbon nanotubes (CNTs) were grown with few differences between the two samples, except the diameter in relation to the initial size of the iron particles, and the density. The electron field emission of these samples exhibit quite interesting behavior with a low turn-on voltage at around 1 V/μm.

  16. Morphology and composition controlled growth of polar c-axis and nonpolar m-axis well-aligned ternary III-nitride nanotube arrays

    Science.gov (United States)

    Li, Huijie; Zhao, Guijuan; Kong, Susu; Han, Dongyue; Wei, Hongyuan; Wang, Lianshan; Chen, Zhen; Yang, Shaoyan

    2015-10-01

    Control over the nanostructure morphology and growth orientation is in high demand for fundamental research and technological applications. Herein we report a general strategy to fabricate polar c-axis and nonpolar m-axis well-aligned III-nitride ternary nanotube arrays with controllable morphologies and compositions. By depositing AlN on the InN nanorod array templates and thermally removing the InN templates, InAlN nanotubes can be obtained. Polar c-axis and nonpolar m-axis nanotubes were formed on the c- and r-plane sapphire substrates, respectively. The nanotubes are single crystalline and highly ordered on the substrates, as revealed by X-ray diffraction, electron microscopy, and selected area electron microscopy characterization. It was found that the In droplets on top of the InN nanorods play a critical role in controlling the morphology of the nanotubes. By keeping or removing the In droplets, the obtained nanotubes exhibited both ends open or only one end open. And by varying the AlN deposition temperature, the In composition in the nanotubes can be changed from 0 to 0.29. The nanotube synthesis method is simple and can be applied to the formation of other III-nitride ternary (InGaN, and AlGaN) or quaternary (InAlGaN) alloy nanotube arrays.Control over the nanostructure morphology and growth orientation is in high demand for fundamental research and technological applications. Herein we report a general strategy to fabricate polar c-axis and nonpolar m-axis well-aligned III-nitride ternary nanotube arrays with controllable morphologies and compositions. By depositing AlN on the InN nanorod array templates and thermally removing the InN templates, InAlN nanotubes can be obtained. Polar c-axis and nonpolar m-axis nanotubes were formed on the c- and r-plane sapphire substrates, respectively. The nanotubes are single crystalline and highly ordered on the substrates, as revealed by X-ray diffraction, electron microscopy, and selected area electron microscopy

  17. Compressive Response of Vertically Aligned Carbon Nanotube Films Gleaned from in Situ Flat-Punch Indentations

    Science.gov (United States)

    2013-04-14

    individual multiwalled carbon nano - tubes using nanoindentation. Appl. Phys. Lett. 87, 103109 (2005). 8. S. Pathak, Z.G. Cambaz, S.R. Kalidindi, J.G...between the tubes (van der Waals ) is thought to balance the bending strain energy of their arrangement, resulting in a stable low energy configuration...bundles: An in situ study. ACS Nano 6(3), 2189–2197 (2012). 10. M. Kumar and Y. Ando: Chemical vapor deposition of carbon nanotubes: A review on growth

  18. Room-temperature ferromagnetism of diamagnetically-doped ZnO aligned nanorods fabricated by vapor reaction

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, ShaoMin; Liu, LiSheng; Lou, ShiYun; Wang, YongQiang; Chen, XiLiang; Yuan, HongLei; Hao, YaoMing; Yuan, RuiJian; Li, Ning [Henan University, Key Lab for Special Functional Materials of Ministry of Education, Kaifeng (China)

    2011-02-15

    Large-scale monocrystalline oxide-diluted magnetic semiconductor (ODMS) Zn{sub 1-x} Bi{sub x} O nanorods arrays (NAs) were prepared within a large doping concentration range from 5% to 20% by a simple chemical vapor deposition. X-ray diffraction and high-resolution transmission electron microscopy reveal the monotonous expansion of the lattice constants with increasing Bi content, due to the effective Bi doping. In particular, room-temperature ferromagnetic (RTFM) behavior with Curie temperature over 363.7 K has been observed based on Bi-doped ZnO nanoarrays, whereas undoped ZnO NAs disappear. The RTFM origin is suggested, in which vacancies can be controlled to tune the FM. The as-formed RTFM NAs would have potential applications in many areas of advanced nanotechnology, such as new spintronic devices and magneto-optic components. (orig.)

  19. Energy level alignment of catechol molecular orbitals on ZnO(1 1 2-bar 0) and TiO{sub 2}(1 1 0) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Rangan, Sylvie, E-mail: rangan@physics.rutgers.edu [Department of Physics and Astronomy and Laboratory for Surface Modification, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Theisen, Jean-Patrick; Bersch, Eric; Bartynski, R.A. [Department of Physics and Astronomy and Laboratory for Surface Modification, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States)

    2010-05-15

    The occupied and unoccupied electronic structure of catechol adsorbed onto two single crystal surfaces, rutile TiO{sub 2}(1 1 0) and wurtzite ZnO(1 1 2-bar 0), have been investigated using UV-photoemission and inverse photoemission spectroscopies (UPS and IPS) in an ultra-high vacuum environment. To aid in assignment of the spectral features, model metal-bound catechol structures were calculated using a DFT approach. From these measurements, the energy alignment of the catechol-related states with respect to the substrates band edges is directly determined and is in good agreement with a direct injection process of the photoexcited electron into the substrate conduction band, resulting in the characteristic absorption properties of adsorbed catechol.

  20. Energy level alignment of catechol molecular orbitals on ZnO(1 1 2¯ 0) and TiO 2(1 1 0) surfaces

    Science.gov (United States)

    Rangan, Sylvie; Theisen, Jean-Patrick; Bersch, Eric; Bartynski, R. A.

    2010-05-01

    The occupied and unoccupied electronic structure of catechol adsorbed onto two single crystal surfaces, rutile TiO 2(1 1 0) and wurtzite ZnO(1 1 2¯ 0), have been investigated using UV-photoemission and inverse photoemission spectroscopies (UPS and IPS) in an ultra-high vacuum environment. To aid in assignment of the spectral features, model metal-bound catechol structures were calculated using a DFT approach. From these measurements, the energy alignment of the catechol-related states with respect to the substrates band edges is directly determined and is in good agreement with a direct injection process of the photoexcited electron into the substrate conduction band, resulting in the characteristic absorption properties of adsorbed catechol.

  1. The role of catalytic nanoparticle pretreatment on the growth of vertically aligned carbon nanotubes by hot-filament chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ki-Hwan; Gohier, Aurélien; Bourée, Jean Eric; Châtelet, Marc; Cojocaru, Costel-Sorin, E-mail: costel-sorin.cojocaru@polytechnique.edu

    2015-01-30

    The effect of atomic hydrogen assisted pre-treatment on the growth of vertically aligned carbon nanotubes using hot-filament chemical vapor deposition was investigated. Iron nanoparticle catalysts were formed on an aluminum oxide support layer by spraying of iron chloride salt solutions as catalyst precursor. It is found that pre-treatment time and process temperature tune the density as well as the shape and the structure of the grown carbon nanotubes. An optimum pre-treatment time can be found for the growth of long and well aligned carbon nanotubes, densely packed to each other. To provide insight on this behavior, the iron catalytic nanoparticles formed after the atomic hydrogen assisted pre-treatment were analyzed by atomic force microscopy. The relations between the size and the density of the as-formed catalyst and the as-grown carbon nanotube's structure and density are discussed. - Highlights: • Effect of the atomic hydrogen assisted pre-treatment on the growth of VACNT using hot-filament CVD. • Pre-treatment time and process temperature tune the density, the shape and the structure of the CNTs. • Correlations between size and density of the as-formed catalyst and the CNT’s structure and density. • Carbon nanotubes synthesized at low temperature down to 500 °C using spayed iron chloride salts. • Density of the CNT carpet adjusted by catalytic nanoparticle engineering.

  2. Stacking dependent electronic properties of the nanofilms composing of super-aligned single-walled carbon nanotubes

    Science.gov (United States)

    Tan, Jie; He, Xiujie; Qu, Yuanyuan; Liu, Xiangdong; Zhao, Mingwen

    2015-06-01

    Films composed of super-aligned single-walled carbon nanotubes (SWCNTs) have been widely used in electronic devices. Using first-principles calculations, we investigate the energetically most favorable stacking patterns and the electronic structures of SWCNT monolayers and bilayers formed by super-aligned (5, 5) and (7, 0) SWCNTs. It is found that the (5, 5) SWCNT monolayer prefers a ‘face-by-face’ stacking pattern with the binding energy of 13.90 meV/atom, whereas the (7, 0) SWCNT monolayer favors an ‘edge-by-edge’ pattern with the binding energy of 10.82 meV/atom. The (5, 5) SWCNT arrays are semiconducting with a band gap up to 114 meV for the bilayer, while the (7, 0) SWCNT arrays are metallic with a tiny overlap between valence and conduction bands, in sharp contrast to the cases of isolated (5, 5) and (7, 0) SWCNTs. This implies that weak van der Waals interactions between SWCNTs play an important role in applications of SWCNT films in electronic devices.

  3. Vertically aligned carbon nanotubes/carbon fiber paper composite to support Pt nanoparticles for direct methanol fuel cell application

    Science.gov (United States)

    Zhang, Jing; Yi, Xi-bin; Liu, Shuo; Fan, Hui-Li; Ju, Wei; Wang, Qi-Chun; Ma, Jie

    2017-03-01

    Vertically aligned carbon nanotubes (VACNTs) grown on carbon fiber paper (CFP) by plasma enhanced chemical vapor deposition is introduced as a catalyst support material for direct methanol fuel cells (DMFCs). Well dispersed Pt nanoparticles on VACNTs surface are prepared by impregnation-reduction method. The VACNTs on CFP possess well-maintained alignment, large surface area and good electrical conductivity, which leading to the formation of Pt particles with a smaller size and enhance the Pt utilization rate. The structure and nature of resulting Pt/VACNTs/CFP catalysts for methanol oxidation are investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD) and scanning electron microscope (SEM). With the aid of VACNTs, well-dispersed Pt catalysts enable the reversibly rapid redox kinetic since electron transport efficiently passes through a one-dimensional pathway, which leads to enhance the catalytic activity and Pt utilization rate. Compared with the Pt/XC-72/CFP electrode, the electrochemical measurements results display that the Pt/VACNTs/CFP catalyst shows much higher electrocatalytic activity and better stability for methanol oxidation. In addition, the oxidation current from 200 to 1200 s decayed more slowly for the Pt/VACNTs/CFP than that of the Pt/XC-72/CFP catalysts, indicating less accumulation of adsorbed CO species. All those results imply that the Pt/VACNTs/CFP has a great potential for applications in DMFCs.

  4. Nanomanipulation of 2 inch wafer fabrication of vertically aligned carbon nanotube arrays by nanoimprint lithography

    DEFF Research Database (Denmark)

    Bu, Ian Y. Y.; Eichhorn, Volkmar; Carlson, Kenneth

    2011-01-01

    pattern transfer to a hard metal mask before deep reactive ion etching (RIE) to form the stamp protrusions. This stamp master is then pressed against a wafer covered with nanoimprint resist, at a temperature above the glass transition temperature, transferring the pattern to polymer. Using this process......, efficient production of wafer‐scale/larger arrays of CNTs has been achieved. The CNTs have been deposited by wafer‐scale plasma enhanced chemical vapour deposition (PECVD) of C2H2/NH3. Substrates containing such nanotubes have been used to automate nanorobotic manipulation sequences of individual CNTs...

  5. Aligned carbon nanotubes catalytically grown on iron-based nanoparticles obtained by laser-induced CVD

    OpenAIRE

    Le Normand, Francois; Cojocaru, Costel Sorin; Ersen, Ovidiu; Legagneux, Pierre; Gangloff, Laurent; Fleaca, C.; Alexandrescu, Rodica; Dumitrache, Florin; Morjan, Ion

    2007-01-01

    International audience; Iron-based nanoparticles are prepared by a laser-induced chemical vapor deposition (CVD) process. They are characterized as body-centered Fe and Fe2O3 (maghemite/magnetite) particles with sizes ::;5 and 10 nm, respectively. The Fe particles are embedded in a protective carbon matrix. Both kind of particles are dispersed by spin-coating on SiO2/Si(1 0 0) flat substrates. They are used as catalyst to grow carbon nanotubes by a plasma- and filaments-assisted catalytic CVD...

  6. Random Networks and Aligned Arrays of Single-Walled Carbon Nanotubes for Electronic Device Applications

    Science.gov (United States)

    2010-04-08

    roles of hydrogen and oxygen. Proc. Natl. Acad. Sci. U. S. A. 2005, 102, 16141 16145. [15] Cao, Q.; Hur, S. -H.; Zhu, Z. -T.; Sun , Y.; Wang, C...H. S.; Cao, Q.; Meitl, M. A.; Khang , D. Y.; Rogers, J. A. Printed multilayer superstructures of al igned single-walled carbon nanotubes for...E.; Meitl, M. A.; Sun , Y. G.; Park, J. U.; Shir, D. J. L.; Nam, Y. S.; Jeon, S.; Rogers, J. A. Micro- and nanopatterning techniques for organic

  7. Low-Temperature Growth of Well-Aligned ZnO Nanorod Arrays by Chemical Bath Deposition for Schottky Diode Application

    Science.gov (United States)

    Yuan, Zhaolin

    2015-04-01

    A well-aligned ZnO nanorod array (ZNRA) was successfully grown on an indium tin oxide (ITO) substrate by chemical bath deposition at low temperature. The morphology, crystalline structure, transmittance spectrum and photoluminescence spectrum of as-grown ZNRA were investigated by field emission scanning electron microscopy, x-ray diffraction, ultraviolet-visible spectroscopy and spectrophotometer, respectively. The results of these measurements showed that the ZNRA contained densely packed, aligned nanorods with diameters from 30 nm to 40 nm and a wurtzite structure. The ZNRA exhibited good optical transparency within the visible spectral range, with >80% transmission. Gold (Au) was deposited on top of the ZNRA, and the current-voltage characteristics of the resulting ITO/ZNRA/Au device in the dark were evaluated in detail. The ITO/ZNRA/Au device acted as a Schottky barrier diode with rectifying behaviour, low turn-on voltage (0.6 V), small reverse-bias saturation current (3.73 × 10-6 A), a high ideality factor (3.75), and a reasonable barrier height (0.65 V) between the ZNRA and Au.

  8. Optimal deposition conditions of TiN barrier layers for the growth of vertically aligned carbon nanotubes onto metallic substrates

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Cespedes, J; Bertran, E [FEMAN Group, IN2UB, Departament de Fisica Aplicada i Optica, Universitat de Barcelona, C/ Martii Franques, 1, E-08028, Barcelona (Spain); Alvarez-Garcia, J [Centre de Recerca i Investigacio de Catalunya, S.A., Travessera de Gracia 108, Entressol, E-08012, Barcelona (Spain); Zhang, X; Hampshire, J [Teer Coatings Ltd, West Stone House, Berry Hill Industrial Estate, Droitwich, Worcestershire, WR9 9AS (United Kingdom)

    2009-05-21

    Plasma enhanced chemical deposition (PECVD) has proven over the years to be the preferred method for the growth of vertically aligned carbon nanotubes and nanofibres (VACNTs and VACNFs, respectively). In particular, carbon nanotubes (CNTs) grown on metallic surfaces present a great potential for high power applications, including low resistance electrical contacts, high power switches, electron guns or supercapacitors. Nevertheless, the deposition of CNTs onto metallic substrates is challenging, due to the intrinsic incompatibility between such substrates and the metallic precursor layers required to promote the growth of CNTs. In particular, the formation of CNT films is assisted by the presence of a nanometric (10-100 nm) monolayer of catalyst clusters, which act as nucleation sites for CNTs. The nanometric character of the precursor layer, together with the high growth temperature involved during the PECVD process ({approx}700 deg. C), strongly favours the in-diffusion of the catalyst nanoclusters into the bulk of the metallic substrate, which results in a dramatic reduction in the nucleation of CNTs. In order to overcome this problem, it is necessary to coat the metallic substrate with a diffusion barrier layer, prior to the growth of the catalyst precursor. Unlike other conventional ceramic barrier layers, TiN provides high electrical conductivity, thus being a promising candidate for use as barrier material in applications involving low resistance contacts. In this work we investigate the anti-diffusion properties of TiN sputtered coatings and its potential applicability to the growth of CNTs onto copper substrates, using Fe as catalyst material. The barrier and catalyst layers were deposited by magnetron sputtering. Auger electron spectroscopy was used to determine the diffusivity of Fe into TiN. Morphological characterization of the CNTs coatings was performed on scanning and transmission electron microscopes. Raman spectroscopy and x-ray diffraction were

  9. Modeling and experiment of dye-sensitized solar cell with vertically aligned ZnO nanorods through chemical bath deposition

    Science.gov (United States)

    Wahyuono, Ruri Agung; Risanti, Doty D.

    2015-01-01

    A theoretical model based on electron diffusion differential equation and Schottky barrier model was developed to determine the current-voltage characteristics of DSSC. To verify the model DSSC with ZnO nanorods photoelectrode which was chemically bath deposited onto the TCO was fabricated. According to modeling results, increasing of recombination current density J at these interfaces results in a decrease in Schottky barrier height φb and therefore improves the photovoltage under the open-circuit condition. It is found that the open-circuit voltage remains constant when the TCO/ZnO Schottky barrier height was varied in the range of 0.45 - 0.6 eV. This theoretical model consistents with the experimental result in which the fabricated DSSCs can produce conversion efficiency in the range of 0.98 - 1.16%. The trend in photovoltage calculated in the theoretical model basically agrees with the experimental result, although the calculated photocurrent is somewhat over estimated compared to the experimental results. The model presents that the ideality factor for ZnO nanorods, which also contributes to the enhancement of photovoltage, increases in the range of 2.75 - 3.0 as the annealing temperature is increased in the experiment.

  10. Molecular scale buckling mechanics in individual aligned single-wall carbon nanotubes on elastomeric substrates.

    Science.gov (United States)

    Khang, Dahl-Young; Xiao, Jianliang; Kocabas, Coskun; MacLaren, Scott; Banks, Tony; Jiang, Hanqing; Huang, Yonggang Y; Rogers, John A

    2008-01-01

    We have studied the scaling of controlled nonlinear buckling processes in materials with dimensions in the molecular range (i.e., approximately 1 nm) through experimental and theoretical studies of buckling in individual single-wall carbon nanotubes on substrates of poly(dimethylsiloxane). The results show not only the ability to create and manipulate patterns of buckling at these molecular scales, but also, that analytical continuum mechanics theory can explain, quantitatively, all measurable aspects of this system. Inverse calculation applied to measurements of diameter-dependent buckling wavelengths yields accurate values of the Young's moduli of individual SWNTs. As an example of the value of this system beyond its use in this type of molecular scale metrology, we implement parallel arrays of buckled SWNTs as a class of mechanically stretchable conductor.

  11. Cycle stability of the electrochemical capacitors patterned with vertically aligned carbon nanotubes in an LiPF6-based electrolyte

    Science.gov (United States)

    Chiou, Yi-Deng; Tsai, Dah-Shyang; Lam, Hoa Hung; Chang, Chuan-Hua; Lee, Kuei-Yi; Huang, Ying-Sheng

    2013-08-01

    The miniature ultracapacitors, with interdigitated electrodes of vertically aligned carbon nanotubes (VACNTs) and an inter-electrode gap of 20 μm, have been prepared in the LiPF6 organic electrolyte with and without PVdF-HFP gel. PVdF-HFP between two opposing electrodes enhances the device reliability, but lessens its power performance because of the extra diffusion resistance. Also noteworthy are the gel influences on the cycle stability. When the applied voltage is 2.0 or 2.5 V, both the LiPF6 and the gel capacitors exhibit excellent stability, typified by a retention ratio of >=95% after 10 000 cycles. Their coulombic efficiencies quickly rise up, and hold steady at 100%. Nonetheless, when the applied voltage is 3.5 or 4.0 V, the cycle stability deteriorates, since the negative electrode potential descends below 0.9 V (vs. Li), leading to electrolyte decomposition and SEI formation. For the LiPF6 capacitor, its retention ratio could be around 60% after 10 000 cycles and the coulombic efficiency of 100% is difficult to reach throughout its cycle life. On the other hand, the gel capacitor cycles energy with a much higher retention ratio, >80% after 10 000 cycles, and a better coulombic efficiency, even though electrolyte decomposition still occurs. We attribute the superior stability of the gel capacitor to its extra diffusion resistance which slows down the performance deterioration.

  12. Effect of vertically aligned carbon nanotube density on the water flux and salt rejection in desalination membranes.

    Science.gov (United States)

    Trivedi, Samarth; Alameh, Kamal

    2016-01-01

    In this paper, vertically aligned carbon nanotube (VACNT) membranes of different densities are developed and their performances are investigated. VACNT arrays of densities 5 × 10(9), 10(10), 5 × 10(10) and 10(11) tubes cm(-2), are initially grown on 1 cm × 1 cm silicon substrates using chemical vapour deposition. A VACNT membrane is realised by attaching a 300 μm-thick 1 cm × 1 cm VACNT array on silicon to a 4″ glass substrate, applying polydimethylsiloxane (PDMS) through spin coating to fill the gaps between the VACNTs, and using a microtome to slice the VACNT-PDMS composite into 25-μm-thick membranes. Experimental results show that the permeability of the developed VACNT membranes increases with the density of the VACNTs, while the salt rejection is almost independent of the VACNT density. The best measured permeance is attained with a VACNT membrane having a CNT density of 10(11) tubes cm(-2) is 1203 LMH at 1 bar.

  13. Vertically aligned carbon nanotube-ruthenium dioxide core-shell cathode for non-aqueous lithium-oxygen batteries

    Science.gov (United States)

    Jung, C. Y.; Zhao, T. S.; Zeng, L.; Tan, P.

    2016-11-01

    Exploitation of hierarchical porous carbons is increasingly attractive for high-capacity lithium (Li)-oxygen (O2) battery cathodes. However, their practical applications in non-aqueous electrolytes are limited by poor rechargeability, primarily due to the decomposition of carbon electrode and electrolyte. In this work, we report a vertically aligned carbon nanotube (VACNT)-ruthenium dioxide (RuO2) core-shell (VACNT@RuO2) cathode for non-aqueous Li-O2 batteries. The cathode is fabricated with VACNT as the core material and hydrous RuO2 as the shell material, which eliminates the direct contact between the carbon and nucleophilic reactive intermediate species in the electrolyte. In comparison with the VACNT cathode, the VACNT@RuO2 cathode presents a superior rate capability (3.3-fold less reduction in capacity) and cycling stability (sustainable for 100 cycles), with a maximum capacity as large as 13.2 mAh cm-2 (6600 mAh gelectrode-1) at 1.0 mA cm-2. The proposed cathode exhibiting a binder-free and hierarchical core-shell structure is a promising candidate for rechargeable non-aqueous Li-O2 batteries.

  14. A comparative study of the field emission properties of aligned carbon nanostructures films, from carbon nanotubes to diamond

    Science.gov (United States)

    Le Normand, F.; Cojocaru, C. S.; Fleaca, C.; Li, J. Q.; Vincent, P.; Pirio, G.; Gangloff, L.; Nedellec, Y.; Legagneux, P.

    2007-05-01

    The electron field emission properties of different graphitic and diamond-like nanostructures films are compared. They are prepared in the same CVD chamber on SiO{2}/Si(100) and Si(100) flat surfaces, respectively. These nanostructures are thoroughly characterized by scanning electron emission (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Films of dense aligned carbon nanotubes by far display the lowest threshold fields around few V/μ m and the largest emission currents. Carbon nanofibers, with platelet arrangement of the graphitic planes parallel to the substrate, exhibit higher emission thresholds around 10 V/μ m. Diamond nanostructures, either modified through ammonia incorporation within the gas phase or not, exhibit the largest emission threshold around 25 V/μ m. The high enhancement factors, deduced from the Fowler-Nordheim plots, can explain the low emission thresholds whereas limitations to the electron transport ever occur through different processes (i) surface modifications of the surface, as the transformation of the SiO{2} barrier layer into SiN{x} in the presence of ammonia evidenced by XPS; (ii) different orientation of the graphitic basal planes relative to the direction of electron transport (carbon nanofiber) and (iii) presence of a graphitic nest at the interface of the carbon nanostructure and the substrate, observed when catalyst is deposited through mild evaporation.

  15. Vertically aligned carbon nanotube-sheathed carbon fibers as pristine microelectrodes for selective monitoring of ascorbate in vivo.

    Science.gov (United States)

    Xiang, Ling; Yu, Ping; Hao, Jie; Zhang, Meining; Zhu, Lin; Dai, Liming; Mao, Lanqun

    2014-04-15

    Using as-synthesized vertically aligned carbon nanotube-sheathed carbon fibers (VACNT-CFs) as microelectrodes without any postsynthesis functionalization, we have developed in this study a new method for in vivo monitoring of ascorbate with high selectivity and reproducibility. The VACNT-CFs are formed via pyrolysis of iron phthalocyanine (FePc) on the carbon fiber support. After electrochemical pretreatment in 1.0 M NaOH solution, the pristine VACNT-CF microelectrodes exhibit typical microelectrode behavior with fast electron transfer kinetics for electrochemical oxidation of ascorbate and are useful for selective ascorbate monitoring even with other electroactive species (e.g., dopamine, uric acid, and 5-hydroxytryptamine) coexisting in rat brain. Pristine VACNT-CFs are further demonstrated to be a reliable and stable microelectrode for in vivo recording of the dynamic increase of ascorbate evoked by intracerebral infusion of glutamate. Use of a pristine VACNT-CF microelectrode can effectively avoid any manual electrode modification and is free from person-to-person and/or electrode-to-electrode deviations intrinsically associated with conventional CF electrode fabrication, which often involves electrode surface modification with randomly distributed CNTs or other pretreatments, and hence allows easy fabrication of highly selective, reproducible, and stable microelectrodes even by nonelectrochemists. Thus, this study offers a new and reliable platform for in vivo monitoring of neurochemicals (e.g., ascorbate) to largely facilitate future studies on the neurochemical processes involved in various physiological events.

  16. Correlation between band alignment and enhanced photocatalysis: a case study with anatase/TiO2(B) nanotube heterojunction.

    Science.gov (United States)

    Wang, Changhua; Zhang, Xintong; Wei, Yongan; Kong, Lina; Chang, Feng; Zheng, Han; Wu, Liangzhuan; Zhi, Jinfang; Liu, Yichun

    2015-08-07

    It has long been known that efficient interfacial charge transfer between different phases of TiO2 is beneficial for enhanced photocatalysis. However, there has been considerable debate over the direction of the charge transfer across the interface of the different TiO2 phases. In this work, we study the case of TiO2 with a novel anatase/TiO2(B) heterojunction (ABHJ), wherein charge carrier transfer across the heterojunction interface is intensively investigated. The ABHJ is prepared by a two-step alkaline hydrothermal route and features nanotubes with a large surface area. Comprehensive analysis including UV-Vis-DRS, XPS, Mott-Schottky measurements, EPR and transient photovoltage techniques provides evidence for a type II band alignment in the ABHJ and migration of the photogenerated electrons from anatase to TiO2(B), which could effectively inhibit the recombination rate of photo-induced electron-hole pairs. Photocatalytic tests demonstrate that the as-obtained ABHJ shows higher activity than both the single phase and P25, not only for hydrogen production, but also for the photodegradation of gaseous acetaldehyde, which is due to the synergistic effect between an efficient charge separation at the interface and a high surface area.

  17. High Sensitivity Electrochemical Cholesterol Sensor Utilizing a Vertically Aligned Carbon Nanotube Electrode with Electropolymerized Enzyme Immobilization

    Directory of Open Access Journals (Sweden)

    Ditsayut Phokharatkul

    2009-10-01

    Full Text Available In this report, a new cholesterol sensor is developed based on a vertically aligned CNT electrode with two-step electrochemical polymerized enzyme immobilization. Vertically aligned CNTs are selectively grown on a 1 mm2 window of gold coated SiO2/Si substrate by thermal chemical vapor deposition (CVD with gravity effect and water-assisted etching. CNTs are then simultaneously functionalized and enzyme immobilized by electrochemical polymerization of polyaniline and cholesterol enzymes. Subsequently, ineffective enzymes are removed and new enzymes are electrochemically recharged. Scanning electron microscopic characterization indicates polymer-enzyme nanoparticle coating on CNT surface. Cyclic voltammogram (CV measurements in cholesterol solution show the oxidation and reduction peaks centered around 450 and −220 mV, respectively. An approximately linear relationship between the cholesterol concentration and the response current could be observed in the concentration range of 50–300 mg/dl with a sensitivity of approximately 0.22 μA/mg·dl−1, which is considerably higher compared to previously reported CNT bioprobe. In addition, good specificity toward glucose, uric acid acetaminophen and ascorbic acid have been obtained. Moreover, sensors have satisfactory stability, repeatability and life time. Therefore, the electropolymerized CNT bioprobe is promising for cholesterol detection in normal cholesterol concentration in human blood.

  18. Vertically aligned multiwalled carbon nanotubes for pressure, tactile and vibration sensing

    Science.gov (United States)

    Yilmazoglu, O.; Popp, A.; Pavlidis, D.; Schneider, J. J.; Garth, D.; Schüttler, F.; Battenberg, G.

    2012-03-01

    We report a simple method for the micro-nano integration of flexible, vertically aligned multiwalled CNT arrays sandwiched between a top and bottom carbon layer via a porous alumina (Al2O3) template approach. The electromechanical properties of the flexible CNT arrays have been investigated under mechanical stress conditions. First experiments show highly sensitive piezoresistive sensors with a resistance decrease of up to ˜35% and a spatial resolution of <1 mm. The results indicate that these CNT structures can be utilized for tactile sensing components. They also confirm the feasibility of accessing and utilizing nanoscopic CNT bundles via lithographic processing. The method involves room-temperature processing steps and standard microfabrication techniques.

  19. Shear Pressed Aligned Carbon Nanotubes and their use as Composite and Adhesive Interlayers

    Science.gov (United States)

    Stahl, James Joseph, III

    The following studies utilize shearing force to consolidate and re-orient multi-walled carbon nanotubes (MWCNT) into a shear pressed sheet (SPS) preform. Carbon nanotube (CNT) array growth and shear pressing angle are studied to improve the quality of SPSs. Heat assisted vacuum infusion is used to form a nano-composite from the SPS preform, and mechanical properties are characterized and compared between non-functionalized and functionalized nano-composite tensile specimens. A novel functionalization technique is applied which rinses SPSs with an acidic wet chemical oxidation treatment of H2SO4 and KMnO4 in order to add sidewall carboxyl groups to the CNTs. This is shown to impart hydrophilicity to the SPS and improves composite modulus by 62%, strain-to-failure 42% and failure stress 113%. Composite laminates and joints are vulnerable to shearing forces which cause delamination in the former and failure in the latter. Damage is initiated and propagated at defects and free edges often due to high peel stress, which is much higher than the shear stress and functions as a tensile opening of the joint just as in Mode I delamination failure of laminate composites. In order to resist failure it is necessary to improve the strain-to-failure of the interphase where a crack propagates without sacrificing strength or modulus of the material, thus toughening the material without impacting the rigidity of the composite. Due to the similarity between peel stress/strain and Mode I delamination, the initiation fracture toughness of a double cantilever beam (DCB) test should provide a good indication of peel toughness at a joint free edge. Many studies have explored the possibility of improving Mode I fracture toughness (G IC) of a composite through locally incorporating a tough material into the interlaminar interphase; this material is termed an interleaf. Common interleaf categories are toughened adhesive, disperse particle, disperse fiber, short fiber nonwoven, and continuous

  20. Synthesis of Aligned ZnO Nanorod Array on Silicon and Sapphire Substrates by Thermal Evaporation Technique

    Institute of Scientific and Technical Information of China (English)

    K.M.K. Srivatsa; Deepak Chhikara; M. Senthil Kumar

    2011-01-01

    High density ZnO nanorods were grown by thermal evaporation of Zn powder at 700℃ on Si (100) and sapphire (0001) substrates at atmospheric pressure without adding any catalyst. The nanorods were characterizated in terms of their structural and optical properties. The nanorods grown on Si have a diameter of 350-400 nm and a length of 1.2 μm while those on sapphire have a diameter of 600-800 nm and a length of 2.5 μm. During the structural characterization, it is noticed that the rods grow along the (0002) plane with perfect hexagonal facet. The room temperature photoluminescence spectrum showed a strong UV emission peak at 385 nm with a weak green band emission, which confirms that nanorods have good optical properties. It is observed that the oxygen partial pressure plays an important role to control the shape and size of the nanorods in thermal evaporation growth technique.

  1. Spatially branched hierarchical ZnO nanorod-TiO2 nanotube array heterostructures for versatile photocatalytic and photoelectrocatalytic applications: towards intimate integration of 1D-1D hybrid nanostructures

    Science.gov (United States)

    Xiao, Fang-Xing; Hung, Sung-Fu; Tao, Hua Bing; Miao, Jianwei; Yang, Hong Bin; Liu, Bin

    2014-11-01

    Hierarchically ordered ZnO nanorods (NRs) decorated nanoporous-layer-covered TiO2 nanotube array (ZnO NRs/NP-TNTAs) nanocomposites have been prepared by an efficient, two-step anodization route combined with an electrochemical deposition strategy, by which monodispersed one-dimensional (1D) ZnO NRs were uniformly grown on the framework of NP-TNTAs. The crystal phases, morphologies, optical properties, photocatalytic as well as photoelectrocatalytic performances of the well-defined ZnO NRs/NP-TNTAs heterostructures were systematically explored to clarify the structure-property correlation. It was found that the ZnO NRs/NP-TNTAs heterostructure exhibits significantly enhanced photocatalytic and photoelectrocatalytic performances, along with favorable photostability toward degradation of organic pollutants under UV light irradiation, as compared to the single component counterparts. The remarkably enhanced photoactivity of ZnO NRs/NP-TNTAs heterostructure is ascribed to the intimate interfacial integration between ZnO NRs and NP-TNTAs substrate imparted by the unique spatially branched hierarchical structure, thereby contributing to the efficient transfer and separation of photogenerated electron-hole charge carriers. Moreover, the specific active species during the photocatalytic process was unambiguously determined and photocatalytic mechanism was tentatively presented. It is anticipated that our work could provide new insights for the construction of various hierarchical 1D-1D hybrid nanocomposites for extensive photocatalytic applications.Hierarchically ordered ZnO nanorods (NRs) decorated nanoporous-layer-covered TiO2 nanotube array (ZnO NRs/NP-TNTAs) nanocomposites have been prepared by an efficient, two-step anodization route combined with an electrochemical deposition strategy, by which monodispersed one-dimensional (1D) ZnO NRs were uniformly grown on the framework of NP-TNTAs. The crystal phases, morphologies, optical properties, photocatalytic as well as

  2. A highly sensitive hydrogen peroxide amperometric sensor based on MnO{sub 2}-modified vertically aligned multiwalled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Xu Bin; Ye Minling; Yu Yuxiang [Nano Science Research Center, School of Chemistry and Chemical Engineering, South China University of Technology, 381 Wushan Road, Guangzhou 510640, Guangdong (China); Zhang Weide, E-mail: zhangwd@scut.edu.cn [Nano Science Research Center, School of Chemistry and Chemical Engineering, South China University of Technology, 381 Wushan Road, Guangzhou 510640, Guangdong (China)

    2010-07-26

    In this report, a highly sensitive amperometric sensor based on MnO{sub 2}-modified vertically aligned multiwalled carbon nanotubes (MnO{sub 2}/VACNTs) for determination of hydrogen peroxide (H{sub 2}O{sub 2}) was fabricated by electrodeposition. The morphology of the nanocomposite was characterized by scanning electron microscopy, energy-dispersive X-ray spectrometer and X-ray diffraction. Cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy were applied to investigate the electrochemical properties of the MnO{sub 2}/VACNTs nanocomposite electrode. The mechanism for the electrochemical reaction of H{sub 2}O{sub 2} at the MnO{sub 2}/VACNTs nanocomposite electrode was also discussed. In borate buffer (pH 7.8, 0.20 M), the MnO{sub 2}/VACNTs nanocomposite electrode exhibits a linear dependence (R = 0.998) on the concentration of H{sub 2}O{sub 2} from 1.2 x 10{sup -6} M to 1.8 x 10{sup -3} M, a high sensitivity of 1.08 x 10{sup 6} {mu}A M{sup -1} cm{sup -2} and a detection limit of 8.0 x 10{sup -7} M (signal/noise = 3). Meanwhile, the MnO{sub 2}/VACNTs nanocomposite electrode is also highly resistant towards typical inorganic salts and some biomolecules such as acetic acid, citric acid, uric acid and D-(+)-glucose, etc. In addition, the sensor based on the MnO{sub 2}/VACNTs nanocomposite electrode was applied for the determination of trace of H{sub 2}O{sub 2} in milk with high accuracy, demonstrating its potential for practical application.

  3. ZnO Functionalization of Surface Pre-treated Multi-walled Carbon Nanotubes for Methane Sensing

    Science.gov (United States)

    Bare carbon nanotubes (CNTs) cannot be used to sense most gases due to poor bonding between the chemically inert graphitic surface and the different compounds CNTs are exposed to. Consequently, for gas sensing applications, functionalization of CNTs with reactive compounds is req...

  4. Synthesis and Enhanced Field-Emission of Thin-Walled, Open-Ended, and Well-Aligned N-Doped Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Hu Qiang

    2010-01-01

    Full Text Available Abstract Thin-walled, open-ended, and well-aligned N-doped carbon nanotubes (CNTs on the quartz slides were synthesized by using acetonitrile as carbon sources. As-obtained products possess large thin-walled index (TWI, defined as the ratio of inner diameter and wall thickness of a CNT. The effect of temperature on the growth of CNTs using acetonitrile as the carbon source was also investigated. It is found that the diameter, the TWI of CNTs increase and the Fe encapsulation in CNTs decreases as the growth temperature rises in the range of 780–860°C. When the growth temperature is kept at 860°C, CNTs with TWI = 6.2 can be obtained. It was found that the filed-emission properties became better as CNT growth temperatures increased from 780 to 860°C. The lowest turn-on and threshold field was 0.27 and 0.49 V/μm, respectively. And the best field-enhancement factors reached 1.09 × 105, which is significantly improved about an order of magnitude compared with previous reports. In this study, about 30 × 50 mm2 free-standing film of thin-walled open-ended well-aligned N-doped carbon nanotubes was also prepared. The free-standing film can be transferred easily to other substrates, which would promote their applications in different fields.

  5. Synthesis and enhanced field-emission of thin-walled, open-ended, and well-aligned N-doped carbon nanotubes.

    Science.gov (United States)

    Cui, Tongxiang; Lv, Ruitao; Kang, Feiyu; Hu, Qiang; Gu, Jialin; Wang, Kunlin; Wu, Dehai

    2010-03-31

    Thin-walled, open-ended, and well-aligned N-doped carbon nanotubes (CNTs) on the quartz slides were synthesized by using acetonitrile as carbon sources. As-obtained products possess large thin-walled index (TWI, defined as the ratio of inner diameter and wall thickness of a CNT). The effect of temperature on the growth of CNTs using acetonitrile as the carbon source was also investigated. It is found that the diameter, the TWI of CNTs increase and the Fe encapsulation in CNTs decreases as the growth temperature rises in the range of 780-860°C. When the growth temperature is kept at 860°C, CNTs with TWI = 6.2 can be obtained. It was found that the filed-emission properties became better as CNT growth temperatures increased from 780 to 860°C. The lowest turn-on and threshold field was 0.27 and 0.49 V/μm, respectively. And the best field-enhancement factors reached 1.09 × 105, which is significantly improved about an order of magnitude compared with previous reports. In this study, about 30 × 50 mm2 free-standing film of thin-walled open-ended well-aligned N-doped carbon nanotubes was also prepared. The free-standing film can be transferred easily to other substrates, which would promote their applications in different fields.

  6. Preparation of TiO2/ZnO Nanotubes and Their Photocatalytic Activity%TiO2/ZnO纳米管的制备及其光催化性能

    Institute of Scientific and Technical Information of China (English)

    杨硕; 尹荔松; 阳素玉; 龚青

    2011-01-01

    Highly ordered TiO2 nanotube arrays were prepared by electrochemical anodization and TiO2/ ZnO nanotube arrays were also fabricated by slope capillary assembly technique with ZnO sol self-assembly on the surface of amorphous TiO2 due to super-hydrophilic properties of nanotubes. The impact of anodizing parameters on the morphology of nanotubes was discussed and the structure and shape of samples were characterized by X-ray diffractometer(XRD) and field emission scanning electron microscope (FE-SEM). The photocatalytic degradation activities of chloramine phosphorus were evaluated by analyzing the influence of annealing temperature, the diameter of tube, the length of tube and composite ratio of TiO2/ZnO on photocatalytic degradation. The results show that annealing temperature, the diameter of tube and composite ratio of ZnO are the main factors. As for TiO2/ZnO nanotubes with the diameter of 97 nm and the length of 315. 8 run, the best composite ratio of TiO2/ZnO is 4. 2% (mass fraction) and the degradation rate achieves 78% after 5 h.%采用电化学阳极氧化法制备了高度有序的TiO2纳米管阵列,并利用纳米管的光致超亲水特性,采用斜面毛细组装技术在无定形TiO2表面自组装ZnO溶胶后退火制备了TiO2/ZnO复合纳米管.探讨了阳极氧化各参数对纳米管形貌的影响.利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)等方法对样品的结构和形貌进行了表征.以有机磷农药氯胺磷为光催化降解对象,研究了焙烧温度、管径、管长和TiO2/ZnO复合比例等因素对降解效果的影响.结果表明,焙烧温度、管径以及ZnO复合比例对光催化降解率影响较大.对于管径97nm、管长315.8nm的TiO2/ZnO纳米管,ZnO最佳复合比例为4.2%(质量分数),5h后降解率达到78%.

  7. Photocatalysis-assisted water filtration: using TiO2-coated vertically aligned multi-walled carbon nanotube array for removal of Escherichia coli O157:H7.

    Science.gov (United States)

    Oza, Goldie; Pandey, Sunil; Gupta, Arvind; Shinde, Sachin; Mewada, Ashmi; Jagadale, Pravin; Sharon, Maheshwar; Sharon, Madhuri

    2013-10-01

    A porous ceramic was coated with vertically aligned multi-walled carbon nanotubes (MWCNTs) by spray pyrolysis. Titanium dioxide (TiO2) nanoparticles were then coated onto this densely aligned MWCNT. The presence of TiO2/MWCNT interfacial arrays was confirmed by X-ray diffraction (XRD), scanning electron microscope-energy dispersive analysis of X-ray (SEM-EDAX) and transmission electron microscope (TEM). This is a novel report in which water loaded with a most dreadful enterohemorrhagic pathogenic strain of Escherichia coli O157:H7 was filtered through TiO2/MWCNT coated porous ceramic filter and then analysed. Bacterial removal performance was found to be significantly lower in control i.e. plain porous ceramic (PTiO2/MWCNT coated ceramic. The photocatalytic killing rate constant for TiO2-ceramic and MWCNT/TiO2-ceramic under fluorescent light was found be 1.45×10(-2) min(-1) and 2.23×10(-2) min(-1) respectively. Further, when I-V characteristics were performed for TiO2/MWCNT composite, it was corroborated that the current under light irradiation is comparatively higher than that in dark, thus proving it to be photocatalytically efficient system. The enhanced photocatalysis may be a contribution of increased surface area and charge transfer rate as a consequence of aligned MWCNT network.

  8. Industrial compatible re-growth of vertically aligned multiwall carbon nanotubes by ultrafast pure oxygen purification process

    DEFF Research Database (Denmark)

    Bu, Ian Y.Y.; Hou, Kai; Engstrøm, Daniel Southcott

    2011-01-01

    Reproducible high-yield purification process of multiwalled carbon nanotubes (CNTs) was developed by thermal annealing in ultrapure oxygen. The optimized condition involves thermal annealing via a PID controlled heater in high purity oxygen at temperature of 450°C for 180s, which burns out...

  9. ZnO Nanostructures Grown on AlN/Sapphire Substrates by MOCVD

    Institute of Scientific and Technical Information of China (English)

    WEI Hong-Yuan; HU Wei-Guo; ZHANG Pan-Feng; LIU Xiang-Lin; ZHU Qin-Sheng; WANG Zhan-Guo

    2007-01-01

    ZnO nanorods and nanotubes are successful synthesized on AlN/sapphire substrates by metal-organic chemical vapour deposition (MOCVD). The different morphology and structure properties of ZnO nanorods and nanotubes are found to be affected by the A1N under-layer. The photoluminescence spectra show the optical properties of the ZnO nanorods and nanotubes, in which a blueshift of UV emission is observed and is attributed to the surface effect.

  10. Wet Purification of Aligned Carbon Nanotube Arrays and Its Impact on the Morphology of the Carbon Nanotube Arrays%湿法纯化碳纳米管阵列及其对碳纳米管阵列形貌的影响

    Institute of Scientific and Technical Information of China (English)

    曹灵超; 刘云圻; 王钰; 魏大程; 付磊; 胡平安; 张洪亮; 黄丽平; 于贵

    2008-01-01

    采用酸溶液处理方法对垂直于衬底生长的碳纳米管阵列的纯化进行了研究.利用扫描电子显微镜、X射线光电子能谱等手段对纯化前后的碳纳米管阵列的结构、形貌及化学组成进行表征.实验结果表明,通过控制条件,酸溶液处理方法能够在有效地去除催化剂粒子等杂质的同时又保持阵列的相对完整性.纯化后的碳纳米管阵列会促进其在电子学领域的进一步应用.%A simple acid treatment method was applied to remove the catalyst impurities and other residues contaminated in the vertically aligned carbon nanotube arrays. We demonstrated that acid treatment was an efficient approach for aligned carbon nanotube purification. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize the morphology of the aligned carbon nanotube arrays and to determine the efficiency of the purification. Using hydrochloric acid could efficiently eliminate catalyst impurities and retain the original structures of the aligned carbon nanotube arrays. The method provided a simple, economical, and effective way to purify the aligned carbon nanotubes, and it would promote the applications of vertically aligned carbon nanotube arrays in electronics field.

  11. Assembly, physics, and application of highly electronic-type purified semiconducting carbon nanotubes in aligned array field effect transistors and photovoltaics

    Science.gov (United States)

    Arnold, Michael

    2015-03-01

    Recent advances in (1) achieving highly monodisperse semiconducting carbon nanotubes without problematic metallic nanotubes and (2) depositing these nanotubes into useful, organized arrays and assemblies on substrates have created new opportunities for studying the physics of these one-dimensional conductors and for applying them in electronics and photonics technologies. In this talk, I will present on two topics that are along these lines. In the first, we have pioneered a scalable approach for depositing aligned arrays of ultrahigh purity semiconducting SWCNTs (prepared using polyfluorene-derivatives) called floating evaporative self-assembly (FESA). FESA is exploited to create FETs with exceptionally high combined on-conductance and on-off ratio of 261 μS/ μm and 2 x105, respectively, for a channel length of 240 nm. This is 1400 x greater on-off ratio than SWCNT FETs fabricated by other methods, at comparable on-conductance per width of 250 μS/ μm, and 30-100 x greater on-conductance per width, at comparable on-off ratio of 105-107. In the second, we have discovered how to efficiently harvest photons using semiconducting SWCNTs by driving the dissociation of excitons using donor/acceptor heterojunctions. The flow of energy in SWCNT films occurs across a complex energy landscape, temporally resolved using two-dimensional white light ultrafast spectroscopy. We have demonstrated simple solar cells driven by SWCNT excitons, based on bilayers between C60 and ultrathin (5 nm) films of SWCNTs that achieve a 1% solar power conversion efficiency (7% at the bandgap). High internal quantum efficiency indicates that future blended or multijunction cells exploiting multiple layers will be many times more efficient.

  12. Mesoporous Li4Ti5O12 nanoclusters anchored on super-aligned carbon nanotubes as high performance electrodes for lithium ion batteries

    Science.gov (United States)

    Sun, Li; Kong, Weibang; Wu, Hengcai; Wu, Yang; Wang, Datao; Zhao, Fei; Jiang, Kaili; Li, Qunqing; Wang, Jiaping; Fan, Shoushan

    2015-12-01

    Mesoporous lithium titanate (LTO) nanoclusters are in situ synthesized in a network of super aligned carbon nanotubes (SACNTs) via a solution-based method followed by heat treatment in air. In the LTO-CNT composite, SACNTs not only serve as the skeleton to support a binder-free electrode, but also render the composite with high conductivity, flexibility, and mechanical strength. The homogeneously dispersed LTO nanoclusters among the SACNTs allow each LTO grain to effectively access the electrolyte and the conductive network, benefiting both ion and electron transport. By the incorporation of LTO into the CNT network, mechanical reinforcement is also achieved. When serving as a negative electrode for lithium ion batteries, such a robust composite-network architecture provides the electrodes with effective charge transport and structural integrity, leading to high-performance flexible electrodes with high capacity, high rate capability, and excellent cycling stability.Mesoporous lithium titanate (LTO) nanoclusters are in situ synthesized in a network of super aligned carbon nanotubes (SACNTs) via a solution-based method followed by heat treatment in air. In the LTO-CNT composite, SACNTs not only serve as the skeleton to support a binder-free electrode, but also render the composite with high conductivity, flexibility, and mechanical strength. The homogeneously dispersed LTO nanoclusters among the SACNTs allow each LTO grain to effectively access the electrolyte and the conductive network, benefiting both ion and electron transport. By the incorporation of LTO into the CNT network, mechanical reinforcement is also achieved. When serving as a negative electrode for lithium ion batteries, such a robust composite-network architecture provides the electrodes with effective charge transport and structural integrity, leading to high-performance flexible electrodes with high capacity, high rate capability, and excellent cycling stability. Electronic supplementary information

  13. The fabrication of vertically aligned and periodically distributed carbon nanotube bundles and periodically porous carbon nanotube films through a combination of laser interference ablation and metal-catalyzed chemical vapor deposition.

    Science.gov (United States)

    Yuan, Dajun; Lin, Wei; Guo, Rui; Wong, C P; Das, Suman

    2012-06-01

    Scalable fabrication of carbon nanotube (CNT) bundles is essential to future advances in several applications. Here, we report on the development of a simple, two-step method for fabricating vertically aligned and periodically distributed CNT bundles and periodically porous CNT films at the sub-micron scale. The method involves laser interference ablation (LIA) of an iron film followed by CNT growth via iron-catalyzed chemical vapor deposition. CNT bundles with square widths ranging from 0.5 to 1.5 µm in width, and 50-200 µm in length, are grown atop the patterned catalyst over areas spanning 8 cm(2). The CNT bundles exhibit a high degree of control over square width, orientation, uniformity, and periodicity. This simple scalable method of producing well-placed and oriented CNT bundles demonstrates a high application potential for wafer-scale integration of CNT structures into various device applications, including IC interconnects, field emitters, sensors, batteries, and optoelectronics, etc.

  14. Synthesis and Characterization of Well-aligned ZnO Nanorod Arrays under Specific Conditions%特定条件下的定向ZnO纳米棒的制备及表征

    Institute of Scientific and Technical Information of China (English)

    郑建华; 张晓凯; 卢慧粉

    2011-01-01

    Well-aligned ZnO nanorod arrays were synthesized successfully on Ag-deposited glass sub-strates using a two-step process and controlling specific conditions.The process involved modified sol-gel and chemical solution growth methods.The surface morphologies and structure of as-prepared ZnO nano-rods were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscope(TEM),the selected-area electron diffraction(SAED),energy dispersive X-ray spec-trum(EDS),fourier transform infrared spectra(FTIR).The XRD and SEM results showed that the ZnO nanorod arrays have hexagonal wurtzite structure and have been completely oxidized and translated into crystalline ZnO in the hexagonal wurtzite phase.The TEM and SAED investigation indicated that the ZnO nanorods have regular morphology and are single crystalline ZnO nanorods with hexagonal wurtzite struc-ture.The main absorption bands appeared at 1384 and 1636 cm-1 is corresponding to the stretching vibra-tion peak of Zn—O,and the main bands at 418 and 541 cm-1 corresponds to rod structure of ZnO.Further-more,the growth mechanism of ZnO nanorods were illustrated.%采用改进的溶胶凝胶和化学溶液生长两步法,并控制特定条件在镀银载玻片上制备出定向ZnO纳米棒.利用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、选区电子衍射(SAED)、能谱(EDS)及傅里叶红外吸收光谱(FTIR)对纳米棒的表面形貌、结构、组分进行分析.XRD和SEM结果表明该ZnO纳米棒具有六角纤锌矿结构,结晶质量良好,垂直衬底生长.TEM和SAED结果表明该ZnO纳米棒形状规则,为单晶结构.FTIR谱中的位于418和541 cm-1的吸收峰对应于棒状ZnO结构的伸缩振动吸收峰,1384和1636 cm-1对应于六方纤锌矿ZnO晶体的Zn—O伸缩振动吸收峰.利用负离子配位四面体生长理论初步解释ZnO纳米棒的生长过程.

  15. Intrinsic Ferromagnetism in Eu doped ZnO

    OpenAIRE

    Assadi, M. H. N.; Zhang,Y.B.; Ionescu, M.; Photongkam, P.; Li, S.

    2010-01-01

    We report room temperature ferromagnetism in as-implanted Eu doped ZnO (ZnO:Eu). To address the origin of ferromagnetism ab initio calculations of ZnO:Eu system are performed. Results show that the ferromagnetism is induced by ZnO point defects as Eu ions in perfect ZnO tend to align antiferromagnetically.

  16. A comparative study of the field emission properties of aligned carbon nanostructures films, from carbon nanotubes to diamond

    OpenAIRE

    Le Normand, Francois; Cojocaru, Costel Sorin; Fleaca, Claudiu; Li, J. Q.; Vincent, Pascal; Pirio, Gilles; Gangloff, Laurent; Nedellec, Yanick; Legagneux, Pierre

    2007-01-01

    International audience; The electron field emission properties of different graphitic and diamond-like nanostructures films are compared. They are prepared in the same CVD chamber on SiO{2}/Si(100) and Si(100) flat surfaces, respectively. These nanostructures are thoroughly characterized by scanning electron emission (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Films of dense aligned carbon nan...

  17. Uniformly embedded metal oxide nanoparticles in vertically aligned carbon nanotube forests as pseudocapacitor electrodes for enhanced energy storage.

    Science.gov (United States)

    Jiang, Yingqi; Wang, Pengbo; Zang, Xining; Yang, Yang; Kozinda, Alina; Lin, Liwei

    2013-08-14

    Carbon nanotube (CNT) forests were grown directly on a silicon substrate using a Fe/Al/Mo stacking layer which functioned as both the catalyst material and subsequently a conductive current collecting layer in pseudocapacitor applications. A vacuum-assisted, in situ electrodeposition process has been used to achieve the three-dimensional functionalization of CNT forests with inserted nickel nanoparticles as pseudocapacitor electrodes. Experimental results have shown the measured specific capacitance of 1.26 F/cm(3), which is 5.7 times higher than pure CNT forest samples, and the oxidized nickel nanoparticle/CNT supercapacitor retained 94.2% of its initial capacitance after 10,000 cyclic voltammetry tests.

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

    Science.gov (United States)

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

    2015-04-01

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

  19. 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

  20. Imaging, spectroscopy, mechanical, alignment and biocompatibility studies of electrospun medical grade polyurethane (Carbothane™ 3575A) nanofibers and composite nanofibers containing multiwalled carbon nanotubes.

    Science.gov (United States)

    Sheikh, Faheem A; Macossay, Javier; Cantu, Travis; Zhang, Xujun; Shamshi Hassan, M; Esther Salinas, M; Farhangi, Chakavak S; Ahmad, Hassan; Kim, Hern; Bowlin, Gary L

    2015-01-01

    In the present study, we discuss the electrospinning of medical grade polyurethane (Carbothane™ 3575A) nanofibers containing multi-walled-carbon-nanotubes (MWCNTs). A simple method that does not depend on additional foreign chemicals has been employed to disperse MWCNTs through high intensity sonication. Typically, a polymer solution consisting of polymer/MWCNTs has been electrospun to form nanofibers. Physiochemical aspects of prepared nanofibers were evaluated by SEM, TEM, FT-IR and Raman spectroscopy, confirming nanofibers containing MWCNTs. The biocompatibility and cell attachment of the produced nanofiber mats were investigated while culturing them in the presence of NIH 3T3 fibroblasts. The results from these tests indicated non-toxic behavior of the prepared nanofiber mats and had a significant attachment of cells towards nanofibers. The incorporation of MWCNTs into polymeric nanofibers led to an improvement in tensile stress from 11.40 ± 0.9 to 51.25 ± 5.5 MPa. Furthermore, complete alignment of the nanofibers resulted in an enhancement on tensile stress to 72.78 ± 5.5 MPa. Displaying these attributes of high mechanical properties and non-toxic nature of nanofibers are recommended for an ideal candidate for future tendon and ligament grafts. Copyright © 2014 Elsevier Ltd. All rights reserved.

  1. 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.

  2. Super-aligned carbon nanotube films with a thin metal coating as highly conductive and ultralight current collectors for lithium-ion batteries

    Science.gov (United States)

    Wang, Ke; Wu, Yang; Wu, Hengcai; Luo, Yufeng; Wang, Datao; Jiang, Kaili; Li, Qunqing; Li, Yadong; Fan, Shoushan; Wang, Jiaping

    2017-05-01

    Cross-stacked super-aligned carbon nanotube (SACNT) films are promising for use as current collectors in lithium-ion batteries because of their outstanding capability to decrease the weight and thickness of inactive material and strong adhesion to the electrodes. However, the relatively poor conductivity of SACNT films may limit their application to large-size electrodes or at high current rate. Herein, a facile approach is proposed to improve the conductivity of SACNT films by electron-beam deposition of a thin metal film on their surface. Such modification lowers the sheet resistance by three orders of magnitude while keeping the extremely small fraction of SACNT current collectors. The metal-coated SACNT films strongly inhibit polarization during the electrochemical reaction, resulting in improved cell performance compared with that of metal and uncoated CNT current collectors. The improvement in conductivity and cell performance achieved by this approach is so large that the effect of the increase of inactive material is overwhelmed, leading to increased gravimetric energy density.

  3. Designing an optimum pulsed magnetic field by a resistance/self-inductance/capacitance discharge system and alignment of carbon nanotubes embedded in polypyrrole matrix.

    Science.gov (United States)

    Kazemikia, Kaveh; Bonabi, Fahimeh; Asadpoorchallo, Ali; Shokrzadeh, Majid

    2015-02-01

    In this work, an optimized pulsed magnetic field production apparatus is designed based on a RLC (Resistance/Self-inductance/Capacitance) discharge circuit. An algorithm for designing an optimum magnetic coil is presented. The coil is designed to work at room temperature. With a minor physical reinforcement, the magnetic flux density can be set up to 12 Tesla with 2 ms duration time. In our design process, the magnitude and the length of the magnetic pulse are the desired parameters. The magnetic field magnitude in the RLC circuit is maximized on the basis of the optimal design of the coil. The variables which are used in the optimization process are wire diameter and the number of coil layers. The coil design ensures the critically damped response of the RLC circuit. The electrical, mechanical, and thermal constraints are applied to the design process. A locus of probable magnetic flux density values versus wire diameter and coil layer is provided to locate the optimum coil parameters. Another locus of magnetic flux density values versus capacitance and initial voltage of the RLC circuit is extracted to locate the optimum circuit parameters. Finally, the application of high magnetic fields on carbon nanotube-PolyPyrrole (CNT-PPy) nano-composite is presented. Scanning probe microscopy technique is used to observe the orientation of CNTs after exposure to a magnetic field. The result shows alignment of CNTs in a 10.3 Tesla, 1.5 ms magnetic pulse.

  4. Effect of oxygen plasma treatment on horizontally aligned carbon nanotube thin film as pH-sensing membrane of extended-gate field-effect transistor

    Science.gov (United States)

    Wang, Kuang-Yu; Tsai, Wan-Lin; Yang, Po-Yu; Chou, Chia-Hsin; Li, Yu-Ren; Liao, Chan-Yu; Cheng, Huang-Chung

    2015-04-01

    The high-performance pH-sensing membrane of extended-gate field-effect transistors (EGFET) composed of high-conductivity horizontally aligned carbon nanotube thin films (HACNTFs) after oxygen plasma treatment is successfully demonstrated. The 10-µm-wide catalytic metal lines with 60 µm interspace produced CNT vertical plates, and the plates were mechanically pulled down and densified to form HACNTFs. A large amount of oxygen-containing functional groups are decorated on the CNTs after the oxygen plasma treatment. These functional groups act as the sensing sites and respond to the H+ or OH- ions in solutions with different pH values. Therefore, these functionalized HACNTFs as pH-EGFET-sensing membranes can achieve a high voltage sensitivity of 40 mV/pH and high current sensitivity of 0.78 µA1/2/pH. Moreover, large linearity of 0.998 is measured in a wide sensing range from pH 1 to 13. These results reveal that the oxygen plasma treatment is an effective way to improve the CNT-sensing characteristics in pH-EGFET sensors.

  5. Film fabrication of Fe or Fe3O4 nanoparticles mixed with palmitic acid for vertically aligned carbon nanotube growth using Langmuir-Blodgett technique

    Science.gov (United States)

    Nakamura, Kentaro; Kuriyama, Naoki; Takagiwa, Shota; Sato, Taiga; Kushida, Masahito

    2016-03-01

    Vertically aligned carbon nanotubes (VA-CNTs) were studied as a new catalyst support for polymer electrolyte fuel cells (PEFCs). Controlling the number density and the diameter of VA-CNTs may be necessary to optimize PEFC performance. As the catalyst for CNT growth, we fabricated Fe or Fe3O4 nanoparticle (NP) films by the Langmuir-Blodgett (LB) technique. The catalyst Fe or Fe3O4 NPs were widely separated by mixing with filler molecules [palmitic acid (C16)]. The number density of VA-CNTs was controlled by varying the ratio of catalyst NPs to C16 filler molecules. The VA-CNTs were synthesized from the catalyst NP-C16 LB films by thermal chemical vapor deposition (CVD) using acetylene gas as the carbon source. The developing solvents used in the LB technique and the hydrogen reduction conditions of CVD were optimized to improve the VA-CNT growth rate. We demonstrate that the proposed method can independently control both the density and the diameter of VA-CNTs.

  6. Development of Well-Aligned TiO2 Nanotube Arrays to Improve Electron Transport in Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Kyung-Ho Chung

    2012-01-01

    Full Text Available We fabricated well-aligned one-dimensional (1-D titania nanotubes (TNT on transparent conducting oxide (TCO by anodization of Ti foil. Different lengths of TNTs were prepared by varying the applied potential (70 V time, and we investigated the performance of these TNTs in dye-sensitized solar cells (DSSCs, transplanted onto a 6 μm TNP adhesion layer. The fabricated TNTs arrays (length 15 μm photoelectrode showed 24% increased efficiency compared to the TNP photoelectrode of 17 μm thickness. We further investigated the performances of DSSCs for the TNTs (1 wt% incorporated TNP photoelectrode and obtained 22% increased efficiency. The increased efficiency of the pure TNTs arrays and TNT-mixed TNP photoelectrodes was attributed to the directional electron movement of TNTs and light scattering effect of the TNT with the decreased rate of back electron transfer. The anodized and fabricated TNTs and DSSCs were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, transmission electron microscope (TEM, and electrochemical impedance spectroscopy (EIS.

  7. A highly order-structured membrane electrode assembly with vertically aligned carbon nanotubes for ultra-low Pt loading PEM fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Zhi Qun; Lim, San Hua; Poh, Chee Kok; Lin, Jianyi [Institute of Chemical and Engineering Sciences, 1 Pesek Road, Jurong Island, Singapore 627833 (Singapore); Tang, Zhe; Chua, Daniel [Department of Materials Science and Engineering, National University of Singapore, Singapore 117542 (Singapore); Xia, Zetao [Institute of Materials Research and Engineering, 3 Research Link, Singapore 117602 (Singapore); Luo, Zhiqiang; Shen, Zexiang [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371 Singapore (Singapore); Shen, Pei Kang [State Key Laboratory of Optoelectronic Materials and Technologies, and Key Laboratory of Low-carbon Chemistry and Energy Conservation of Guangdong Province, School of Physics and Engineering, Sun Yat-sen University, Guangzhou, 510275 (China); Feng, Yuan Ping [Department of Physics, National University of Singapore, Singapore 117542 (Singapore)

    2011-11-15

    A simple method was developed to prepare ultra-low Pt loading membrane electrode assembly (MEA) using vertically aligned carbon nanotubes (VACNTs) as highly ordered catalyst support for PEM fuel cells application. In the method, VACNTs were directly grown on the cheap household aluminum foil by plasma enhanced chemical vapor deposition (PECVD), using Fe/Co bimetallic catalyst. By depositing a Pt thin layer on VACNTs/Al and subsequent hot pressing, Pt/VACNTs can be 100% transferred from Al foil onto polymer electrolyte membrane for the fabrication of MEA. The whole transfer process does not need any chemical removal and destroy membrane. The PEM fuel cell with the MEA fabricated using this method showed an excellent performance with ultra-low Pt loading down to 35 {mu}g cm{sup -2} which was comparable to that of the commercial Pt catalyst on carbon powder with 400 {mu}g cm{sup -2}. To the best of our knowledge, for the first time, we identified that it is possible to substantially reduce the Pt loading one order by application of order-structured electrode based on VACNTs as Pt catalysts support, compared with the traditional random electrode at a comparable performance through experimental and mathematical methods. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Influence of the concentration of carbon nanotubes on electrical conductivity of magnetically aligned MWCNT–polypyrrole composites

    Indian Academy of Sciences (India)

    KAVEH KAZEMIKIA; FAHIMEH BONABI; ALI ASADPOORCHALLO; MAJID SHOKRZADEH

    2016-04-01

    The goal of this work is to study the effect of high magnetic pulses on electrical property of carbon nanotube–polypyrrole (CNT–PPy) composites with different CNT concentrations. CNT–PPy composites are produced in fractions of 1, 5 and 9 wt%. During the polymerization process, the CNTs are homogeneously dispersed throughout the polymer matrix in an ultrasonic bath. Nanocomposite rods are prepared. After exposure to 30 magnetic pulses, the resistivity of the rods is measured. The surface conductivity of thin tablets of composites is studied by 4-probe technique. The magnitude of the pulsed magnetic field is 10 Tesla with time duration of 1.5 ms. The results show that after applying 30 magnetic pulses, the electrical resistivity of the composites decreases depending on the concentration of CNTs in the composites. The orientation of CNTs is probed by atomic force microscopy (AFM) technique. AFM images approved alignment of CNT–polymer fibres in the magnetic field.We found that the enhancement in the electrical properties of CNT–PPy composites is due to rearrangement and alignment of CNTs in a high magnetic field. The stability of nano-composites is studied by Fourier transform infrared spectroscopy.

  9. Biosensors and Biofuel Cells based on Vertically Aligned Carbon Nanotubes for Integrated Energy Sensing, Generation, and Storage (SGS) Systems

    Science.gov (United States)

    Pandey, Archana; Prasad, Abhishek; Khin Yap, Yoke

    2010-03-01

    Diabetes is a growing health issue in the nation. Thus in-situ glucose sensors that can monitor the glucose level in our body are in high demand. Furthermore, it will be exciting if the excessive blood sugar can be converted into usable energy, and be stored in miniature batteries for applications. This will be the basis for an integrated energy sensing, generation, and storage (SGS) system in the future. Here we report the use of functionalized carbon nanotubes arrays as the glucose sensors as well as fuel cells that can convert glucose into energy. In principle, these devices can be integrated to detect excessive blood glucose and then convert the glucose into energy. They are also inline with our efforts on miniature 3D microbatteries using CNTs [1]. All these devices will be the basis for future SGS systems. Details of these results will be discussed in the meeting. [1] Wang et al., in 206^th Meeting of the Electrochemical Society, October 3-8, Honolulu, Hawaii (2004), Symposium Q1, abstract 1492. Y. K. Yap acknowledges supports from DARPA (DAAD17-03-C-0115), USDA (2007-35603-17740), and the Multi-Scale Technologies Institute (MuSTI) at MTU.

  10. Highly selective electrodeposition of sub-10 nm crystalline noble metallic nanorods inside vertically aligned multiwall carbon nanotubes

    Science.gov (United States)

    Wang, Xuyang; Wang, Ranran; Wu, Qiang; Zhang, Xiaohua; Yang, Zhaohui; Guo, Jun; Chen, Muzi; Tang, Minghua; Cheng, Yajun; Chu, Haibin

    2016-07-01

    In this paper crystalline noble metallic nanorods including Au and Ag with sub-10 nm diameter, are encapsulated within prealigned and open-ended multiwall carbon nanotubes (MWCNTs) through an electrodeposition method. As the external surface of CNTs has been insulated by the epoxy the CNT channel becomes the only path for the mass transport as well as the nanoreactor for the metal deposition. Highly crystallized Au and Ag2O nanorods parallel to the radial direction of CNTs are confirmed by high-resolution transmission electron microscopy, energy dispersive x-ray spectroscopy and x-ray powder diffraction spectroscopy. The Ag2O nanorods are formed by air oxidation on the Ag metals and show a single crystalline structure with (111) planes. The Au nanorods exhibit a complex crystalline structure including twin-crystal and lattice dislocation with (111) and (200) planes. These crystalline noble metallic nanostructures may have important applications for nanocatalysts for fuel cells as well as nanoelectronic and nanophotonic devices. This method is deemed to benefit the precise deposition of other crystalline nanostructures inside CNTs with a small diameter.

  11. Photoelectrocatalytic properties of a vertically aligned Ti-W alloy oxide nanotubes array and its applications in dye wastewater degradation.

    Science.gov (United States)

    Li, Mingfang; Zhao, Guohua; Li, Peiqiang; Zhang, Yanan; Wu, Meifen

    2012-01-01

    A highly ordered and vertically oriented array of nanotubes (NTs) of mixed oxide was prepared in situ by Ti-W alloy anodization. Compared with the traditional TiO2 NTs, the photoelectrocatalytic activity of the resulting Ti-W-O NTs was greatly enhanced. Results indicated a narrowing of the band gap from 3.2 eV for pristine TiO2 to 2.7 eV for Ti-W-O NTs. Under irradiation with 254 and 365 nm UV lights, Ti-W-O NTs showed much higher photoelectroconversion efficiency (eta) than TiO2 NTs and TiO2-WO3 coating. The eta254 and eta365 on Ti-W-O NTs reached as high as 51.8% and 57.0% respectively, four to five times those on TiO2 NTs and TiO2-WO3 coating. As a result of its narrow band gap energy and fast electron-hole separation, Ti-W-O NTs presented outstanding photoelectrocatalytic features. The electrochemically assisted photocatalytic degradation of highly concentrated Rhodamine 6G wastewaters was studied. The results showed that the rates of colour and TOC removal were much higher on Ti-W-O NTs than on TiO2 NTs and TiO2-WO3 coating. The photocatalytic material obtained by alloy anodization is of significance in the advanced oxidation of environmental pollutants.

  12. Aligned Carbon Nanotube Fiber for Energy Conversion and Storage%取向碳纳米管纤维及其能源应用

    Institute of Scientific and Technical Information of China (English)

    尤晓; 孙雪梅; 彭慧胜

    2014-01-01

    Carbon nanotubes (CNTs)have been widely studied due to its characteristic one-dimensional structure,re-markable mechanical,electronic and thermal properties.However,it remains challenging to extend them to a macroscopic scale due to the aggregation and random dispersion during preparation.Recently,CNTs are highly aligned through wet and dry spinning process to continuously produce CNT fibers that maintain the excellent properties of individual CNTs,and these aligned CNT fibers have been extensively used for wire-shaped solar cells,supercapacitors and other energy devices. This article reviews the preparation,structure,property and application of the aligned CNT fibers in recent years with an emphasis on the use in energy,as well as their future direction.%碳纳米管具有独特的一维纳米结构,优异的力学、电学和热学性能,但在实际应用中,由于碳纳米管无规分散且容易团聚,其优异的性能很难在材料宏观层面上充分体现出来。为了促进碳纳米管的实际应用,将碳纳米管的物理性能从纳米尺度拓展到宏观水平变得越来越迫切。近年来,人们通过湿法纺丝和干法纺丝等过程对碳纳米管取向排列,从而制备了具有高拉伸强度和高电导率的纤维,可广泛应用于线状太阳能电池和超级电容器等光电转换和储能器件,极大地推动了能源材料和器件的发展。综述了取向碳纳米管纤维的合成方法、结构和性能,重点介绍其作为电极材料在线状染料敏化太阳能电池和超级电容器等能源领域的应用,最后展望了取向碳纳米管纤维的未来发展方向。

  13. Surface structure and field emission properties of cost effectively synthesized zinc oxide nanowire/multiwalled carbon nanotube heterojunction arrays

    Science.gov (United States)

    Dehghan Nayeri, F.; Darbari, S.; Soleimani, E. A.; Mohajerzadeh, S.

    2012-07-01

    A cost-effective and efficient approach for the synthesis of single-crystalline zinc oxide nanowires on vertically aligned multiwalled carbon nanotube (CNT) array is presented. ZnO nanowires are grown on the base of individual CNT through the low-temperature wet-chemical batch deposition technique, while the size and interspacing of the nanowires can be controlled by precursor concentration, growth temperature and time duration. The scanning electron microscopy image showed that the ZnO nanostructures are successfully grown on the CNT's surface uniformly. The produced nanostructures are characterized by x-ray diffraction, x-ray photoelectron spectroscopy and Raman spectroscopy. Also, field emission characteristics of the fabricated double-stage ZnO nanowire/CNT array are investigated and compared with the emission behaviour of CNT and ZnO nanowire arrays. The ZnO nanowire/CNT heterojunction array resulted in a low turn-on field of 1.5 V µm-1 and a threshold field of 4.5 V µm-1, which were lower than both the vertical CNT and ZnO arrays. The field emission properties and stability of the fabricated nanostructures also demonstrated great potential for field emission applications.

  14. Carbon nanotube nanoelectrode arrays

    Science.gov (United States)

    Ren, Zhifeng; Lin, Yuehe; Yantasee, Wassana; Liu, Guodong; Lu, Fang; Tu, Yi

    2008-11-18

    The present invention relates to microelectode arrays (MEAs), and more particularly to carbon nanotube nanoelectrode arrays (CNT-NEAs) for chemical and biological sensing, and methods of use. A nanoelectrode array includes a carbon nanotube material comprising an array of substantially linear carbon nanotubes each having a proximal end and a distal end, the proximal end of the carbon nanotubes are attached to a catalyst substrate material so as to form the array with a pre-determined site density, wherein the carbon nanotubes are aligned with respect to one another within the array; an electrically insulating layer on the surface of the carbon nanotube material, whereby the distal end of the carbon nanotubes extend beyond the electrically insulating layer; a second adhesive electrically insulating layer on the surface of the electrically insulating layer, whereby the distal end of the carbon nanotubes extend beyond the second adhesive electrically insulating layer; and a metal wire attached to the catalyst substrate material.

  15. Super-fast switching of twisted nematic liquid crystals with a single-wall-carbon-nanotube-doped alignment layer

    Science.gov (United States)

    Liu, Yang; Lim, Young Jin; Kundu, Sudarshan; Lee, Seung Hee; Lee, Gi-Dong

    2015-03-01

    The application of a single-wall carbon-nanotube (SWCNT) and polyimide (PI) composite thin film on an indium tin-oxide (ITO) glass substrate, working as the command surface in a twisted nematic liquid crystal display (LCD), is described. SWCNTs were chopped and oxidized in a strong acid medium to make them more miscible in a polyimide solution. A film of this newly-developed PISWCNT composite was rubbed to determine the director direction for the LC molecules. The newlyfabricated command surface was examined using a laser beam profiler and atomic force microscopy. Sizes of shortened SWCNTs were characterized by using field-emission scanning electron microscopy (FE-SEM). Finally, small-sized test panels were fabricated from this composite-coated ITO glass, and their electro-optic performances were measured. Although the operating voltage to switch a cell was increased by around 41%, the switching speed was improved remarkably. The rise time of the test cells was found to be improved by around 10.12% and the decay time by around 29.77%. Thus, an overall improvement of around 16.12% in the total switching time was achieved. The change in the surface morphology of the newly-developed composite materials was found to be one of the factors responsible for the faster switching of the device. Detailed discussions are given in this report to explain the faster switching of the newly-developed twisted nematic liquid crystal display (TN-LCD). The device can be useful for practical applications.

  16. Study of Diamond like Carbon as template for nanoimprint lithography and as a filler material for vertically aligned carbon nanotube forests

    Science.gov (United States)

    Ramachandran, Seetharaman

    Due to its tunable properties like hardness, optical gap, chemical inertness, electrical resistivity, biocompatibility etc., coatings of the material Diamond like Carbon (DLC) have been used as protective layers for various applications. In this research effort, we add to the growing list of its potential applications by proposing them as a template material for the emerging field of nanoimprint lithography. Using capacitive and inductive plasmas, we demonstrate the possibility of depositing DLC films of reasonable hardness (10-25 GPa) and wear resistance (2X that of Si and 3X that of Quartz). We have successfully used these films as a mold material to obtain feature sizes as small as 40 nm. In addition, to further the understanding of the effect of the gas phase chemistry on the film properties, the Methane discharge used for obtaining these films has been studied using techniques like Fourier Transform Infrared Spectroscopy and Optical Emission Spectroscopy. The higher degree of dissociation (up to 70%) of the precursor in case of inductive plasmas leads to selected conditions under which hard DLC films are obtained. We also show that for the same deposition conditions, films deposited on the insulating Quartz substrates are softer and more polymeric than those deposited on Si substrates. Carbon nanotubes with their unique physical properties are seen as ideal candidates for applications like field effect transistors, supercapacitors, AFM tips and electronic devices. One of the chief challenges in using them for these applications is obtaining them in a form that is easier to handle, thus enabling them to withstand the various post-processing steps. The second part of this dissertation focuses on the possibility of obtaining a Carbon-Carbon composite structure by subjecting vertically aligned Carbon nanotube forests to a PECVD based process. The distance from the top of the CNT forest that is coated with the deposited film (termed as the depth of infusion) shows

  17. 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.

  18. Synthesis of Vertically-Aligned Carbon Nanotubes from Langmuir-Blodgett Films Deposited Fe Nanoparticles on Al2O3/Al/SiO2/Si Substrate.

    Science.gov (United States)

    Takagiwa, Shota; Kanasugi, Osamu; Nakamura, Kentaro; Kushida, Masahito

    2016-04-01

    In order to apply vertically-aligned carbon nanotubes (VA-CNTs) to a new Pt supporting material of polymer electrolyte fuel cell (PEFC), number density and outer diameter of CNTs must be controlled independently. So, we employed Langmuir-Blodgett (LB) technique for depositing CNT growth catalysts. A Fe nanoparticle (NP) was used as a CNT growth catalyst. In this study, we tried to thicken VA-CNT carpet height and inhibit thermal aggregation of Fe NPs by using Al2O3/Al/SiO2/Si substrate. Fe NP LB films were deposited on three typed of substrates, SiO2/Si, as-deposited Al2O3/Al/SiO2/Si and annealed Al2O3/Al/SiO2/Si at 923 K in Ar atmosphere of 16 Pa. It is known that Al2O3/Al catalyzes hydrocarbon reforming, inhibits thermal aggregation of CNT growth catalysts and reduces CNT growth catalysts. It was found that annealed Al2O3/Al/SiO2/Si exerted three effects more strongly than as-deposited Al2O3/Al/SiO2/Si. VA-CNTs were synthesized from Fe NPs-C16 LB films by thermal chemical vapor deposition (CVD) method. As a result, at the distance between two nearest CNTs 28 nm or less, VA-CNT carpet height on annealed Al2O3/Al/SiO2/Si was about twice and ten times thicker than that on SiO2/Si and that on as-deposited Al2O3/Al/SiO2/Si, respectively. Moreover, distribution of CNT outer diameter on annealed Al2O3/Al/SiO2/Si was inhibited compared to that on SiO2/Si. These results suggest that since thermal aggregation of Fe NPs is inhibited, catalyst activity increases and distribution of Fe NP size is inhibited.

  19. ENHANCEMENT OF PHOTOCATALYTIC ACTIVITY OF TiO2 NANOTUBES BY DEPOSITION OF ZnO NANOPARTICLES%ZnO纳米颗粒沉积增强TiO_2纳米管光催化活性

    Institute of Scientific and Technical Information of China (English)

    李平; 路海霞; 曾志军; 李元; 聂明; 梁宏; 覃礼钊

    2012-01-01

    采用阳极氧化法制备TiO2纳米管,用光化学沉积法、将纳米管浸没在硝酸锌(Zn(NO3)2)溶液中,在纳米管表面沉积ZnO纳米颗粒.对样品进行了Raman谱、XRD和SEM表征.结果显示,TiO2纳米管为锐钛矿相,沉积ZnO没有改变TiO2的相结构.用甲基橙在紫外光辐照下的降解速率来评价ZnO/TiO2纳米管的催化活性.结果表明,Zn(NO3)2浓度为10-4 mol.L-1时制备的ZnO/TiO2纳米管,其降解甲基橙的活性最高,效率提高40.7%.%TiO2 nanotubes were fabricated by anodic oxidation,ZnO nanoparticles were deposited on the surface of TiO2 nanotubes by optical chemical deposition technique with dipping the TiO2 nanotubes in Zn(NO3)2 aqueous solution.The final product was characterized by Raman and XRD spectroscopy,and by SEM.Data indicated that the TiO2 nanotubes were in anatase phase and ZnO nanoparticle deposition did not change the crystalline phase of TiO2.Photocatalytic activity of the photocatalyst was estimated by testing degradation rate constant of methyl orange aqueous solution under UV irradiation.With a precursor concentration of Zn(NO3)2 at 10-4 mol·L-1,the ZnO/TiO2 composite nano-photocatalyst showed the highest photocatalytic activity.The degradation efficiency was increased by 40.7%.

  20. Fabrication of high thermal conductivity arrays of carbon nanotubes and their composites

    Science.gov (United States)

    Geohegan, David B [Knoxville, TN; Ivanov, Ilya N [Knoxville, TN; Puretzky, Alexander A [Knoxville, TN

    2010-07-27

    Methods and apparatus are described for fabrication of high thermal conductivity arrays of carbon nanotubes and their composites. A composition includes a vertically aligned nanotube array including a plurality of nanotubes characterized by a property across substantially all of the vertically aligned nanotube array. A method includes depositing a vertically aligned nanotube array that includes a plurality of nanotubes; and controlling a deposition rate of the vertically aligned nanotubes array as a function of an in situ monitored property of the plurality of nanotubes.

  1. Effect of Size-Dependent Thermal Instability on Synthesis of Zn2 SiO4-SiOx Core–Shell Nanotube Arrays and Their Cathodoluminescence Properties

    Directory of Open Access Journals (Sweden)

    Dierre Benjamin

    2010-01-01

    Full Text Available Abstract Vertically aligned Zn2SiO4-SiOx(x < 2 core–shell nanotube arrays consisting of Zn2SiO4-nanoparticle chains encapsulated into SiOx nanotubes and SiOx-coated Zn2SiO4 coaxial nanotubes were synthesized via one-step thermal annealing process using ZnO nanowire (ZNW arrays as templates. The appearance of different nanotube morphologies was due to size-dependent thermal instability and specific melting of ZNWs. With an increase in ZNW diameter, the formation mechanism changed from decomposition of “etching” to Rayleigh instability and then to Kirkendall effect, consequently resulting in polycrystalline Zn2SiO4-SiOx coaxial nanotubes, single-crystalline Zn2SiO4-nanoparticle-chain-embedded SiOx nanotubes, and single-crystalline Zn2SiO4-SiOx coaxial nanotubes. The difference in spatially resolved optical properties related to a particular morphology was efficiently documented by means of cathodoluminescence (CL spectroscopy using a middle-ultraviolet emission at 310 nm from the Zn2SiO4 phase.

  2. A novel maskless approach towards aligned, density modulated and multi-junction ZnO nanowires for enhanced surface area and light trapping solar cells.

    Science.gov (United States)

    Kevin, M; Fou, Y H; Wong, A S W; Ho, G W

    2010-08-06

    A maskless method of employing polymer growth inhibitor layers is used to modulate the conflicting parameters of density and alignment of multi-junction nanowires via large-scale low temperature chemical route. This low temperature chemical route is shown to synthesize multi-junction nanostructures without compromising the crystal quality at the interfaces. The final morphology of optimized multi-junctions nanowire arrays can be demonstrated on various substrates due to substrate independence and low temperature processing. Here, we also fabricated devices based on density modulated multi-junction nanowires tuned to infiltrate nanoparticles. The fabrication of hierarchically structured nanowire/nanoparticles composites presents an advantageous structure, one that allows nanoparticles to provide large surface areas for dye adsorption, whilst the nanowires can enhance the light harvesting, electron transport rate, and also the mechanical properties of the films. This work can be of great scientific and commercial interest since the technique employed is of low temperature (<90 degrees C) and economical for large-scale solution processing, much valued in today's flexible display and photovoltaic industries.

  3. A novel maskless approach towards aligned, density modulated and multi-junction ZnO nanowires for enhanced surface area and light trapping solar cells

    Science.gov (United States)

    Kevin, M.; Fou, Y. H.; Wong, A. S. W.; Ho, G. W.

    2010-08-01

    A maskless method of employing polymer growth inhibitor layers is used to modulate the conflicting parameters of density and alignment of multi-junction nanowires via large-scale low temperature chemical route. This low temperature chemical route is shown to synthesize multi-junction nanostructures without compromising the crystal quality at the interfaces. The final morphology of optimized multi-junctions nanowire arrays can be demonstrated on various substrates due to substrate independence and low temperature processing. Here, we also fabricated devices based on density modulated multi-junction nanowires tuned to infiltrate nanoparticles. The fabrication of hierarchically structured nanowire/nanoparticles composites presents an advantageous structure, one that allows nanoparticles to provide large surface areas for dye adsorption, whilst the nanowires can enhance the light harvesting, electron transport rate, and also the mechanical properties of the films. This work can be of great scientific and commercial interest since the technique employed is of low temperature (economical for large-scale solution processing, much valued in today's flexible display and photovoltaic industries.

  4. 喷雾热解法在硅衬底上生长定向碳纳米管阵列%Growth of vertically aligned carbon nanotubes on a silicon substrate by a spray pyrolysis method

    Institute of Scientific and Technical Information of China (English)

    V S Angulakshmi; K Rajasekar; C Sathiskumar; S Karthikeyan

    2013-01-01

    Vertically aligned carbon nanotubes on a silicon substrate were synthesized by a spray pyrolysis method using the methyl ester of Helianthus annuus oil as a carbon source,ferrocene as a catalyst precursor and argon as a carrier gas.Results show that Fe catalyst nanoparticles are formed from ferrocene in-situ on the silicon substrate.As-grown vertically aligned carbon nanotubes are well graphitized as shown by Raman spectra,transmission electron microscopy images and X-ray diffraction patterns.The diameter of the carbon nanotubes is around 10-30 nm and their wall thickness is around 10 nm.The content of catalyst in the products is negligible.%以向日葵油的甲基酯为碳源,二茂铁为催化剂前驱体,Ar为载气,通过喷雾热解法在硅衬底上合成定向碳纳米管阵列.结果表明,在硅衬底上原位形成Fe催化剂纳米颗粒.由拉曼光谱、透射电镜图和X-射线衍射谱图显示所制定向碳纳米管阵列具有较好的石墨化程度,其直径为10~30 nm,管壁约为10nm.所制定向碳纳米管阵列中残留的催化剂含量可以忽略.

  5. 单壁碳纳米管显著增强的ZnO可见光催化活性%Visible-light photocatalytic activity of ZnO enhanced by single-walled carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    卢艳红; 徐艳红; 张素玲; 白晓杰; 黄毅; 陈永胜

    2014-01-01

    Nanocomposite ZnO/SWNTs of zinc oxide (ZnO) and single-walled carbon nanotubes (SWNTs) were fabricated by a sol-gel method using Zn(CH3COO)2·2H2O as raw material. The samples were characterized by X-ray diffraction spectroscopy, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, Fourier transformed infrared spectroscopy and ultraviolet-visible spectroscopy. The results show that ZnO nanoparticles with the size of about 10- 20 nm are closely deposited on the sidewalls of SWNTs and the nanocomposite presents enhanced absorption ability in the visible region. The composite exhibits a dramatically improved photocatalytic activity to decompose methyl orange and methylene blue in aqueous solutions under natural light. The photodegradation rate for methyl orange is 99.8% after 200 min, which is about 20 times that of pure ZnO (4.8%). For methylene blue, the degradation rate reaches 98.4% after 20 min, which is about 25 times that of pure ZnO (4.0%).%利用醋酸锌为原料,采用溶胶-凝胶法制备了单壁碳纳米管(SWMTs)和氧化锌的纳米复合物(ZnO/SWNTs)。用X射线衍射光谱(XRD)、拉曼光谱、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、热重分析(TGA)、傅里叶变换红外光谱(FT-IR)以及紫外-可见吸收光谱(UV-Vis)对复合物进行了表征。结果显示,粒径为10~20 nm的ZnO粒子均匀地负载在SWNTs表面,且在可见光区具有很好的光吸收性能。研究了ZnO/SWNTs光催化剂在太阳光照射下对甲基橙和亚甲基蓝的光催化降解情况。结果表明,复合物的催化活性明显高于ZnO。对于甲基橙,光照200 min后,降解率为99.8%,是纯ZnO(4.8%)的20倍;对于亚甲基蓝,仅光照20 min,降解率就达到了98.4%,是纯ZnO(4.0%)的25倍。

  6. Fabrication of Cellulose ZnO Hybrid Nanocomposite and Its Strain Sensing Behavior

    Directory of Open Access Journals (Sweden)

    Hyun-U Ko

    2014-10-01

    Full Text Available This paper reports a hybrid nanocomposite of well-aligned zinc oxide (ZnO nanorods on cellulose and its strain sensing behavior. ZnO nanorods are chemically grown on a cellulose film by using a hydrothermal process, termed as cellulose ZnO hybrid nanocomposite (CEZOHN. CEZOHN is made by seeding and growing of ZnO on the cellulose and its structural properties are investigated. The well-aligned ZnO nanorods in conjunction with the cellulose film shows enhancement of its electromechanical property. Strain sensing behaviors of the nanocomposite are tested in bending and longitudinal stretching modes and the CEZOHN strain sensors exhibit linear responses.

  7. Catalytic Synthesis of Substrate-Free, Aligned and Tailored High Aspect Ratio Multiwall Carbon Nanotubes in an Ultrasonic Atomization Head CVD Reactor

    OpenAIRE

    Fahad Ali Rabbani; Zuhair Omar Malaibari; Muataz Ali Atieh; Ammar Jamie

    2016-01-01

    Chemical vapor deposition (CVD) method has proven its benchmark, over other methods, for the production of different types of carbon nanotubes (CNT) on commercial and lab scale. In this study, an injection vertical CVD reactor fitted with an ultrasonic atomization head was used in a pilot-plant scale (height 274 cm, radius 25 cm) for semicontinuous production of multiwall carbon nanotubes (MWCNTs). p-Xylene was used as a hydrocarbon precursor in which ferrocene was dissolved and provided the ...

  8. Nanotube cathodes.

    Energy Technology Data Exchange (ETDEWEB)

    Overmyer, Donald L.; Lockner, Thomas Ramsbeck; Siegal, Michael P.; Miller, Paul Albert

    2006-11-01

    Carbon nanotubes have shown promise for applications in many diverse areas of technology. In this report we describe our efforts to develop high-current cathodes from a variety of nanotubes deposited under a variety of conditions. Our goal was to develop a one-inch-diameter cathode capable of emitting 10 amperes of electron current for one second with an applied potential of 50 kV. This combination of current and pulse duration significantly exceeds previously reported nanotube-cathode performance. This project was planned for two years duration. In the first year, we tested the electron-emission characteristics of nanotube arrays fabricated under a variety of conditions. In the second year, we planned to select the best processing conditions, to fabricate larger cathode samples, and to test them on a high-power relativistic electron beam generator. In the first year, much effort was made to control nanotube arrays in terms of nanotube diameter and average spacing apart. When the project began, we believed that nanotubes approximately 10 nm in diameter would yield sufficient electron emission properties, based on the work of others in the field. Therefore, much of our focus was placed on measured field emission from such nanotubes grown on a variety of metallized surfaces and with varying average spacing between individual nanotubes. We easily reproduced the field emission properties typically measured by others from multi-wall carbon nanotube arrays. Interestingly, we did this without having the helpful vertical alignment to enhance emission; our nanotubes were randomly oriented. The good emission was most likely possible due to the improved crystallinity, and therefore, electrical conductivity, of our nanotubes compared to those in the literature. However, toward the end of the project, we learned that while these 10-nm-diameter CNTs had superior crystalline structure to the work of others studying field emission from multi-wall CNT arrays, these nanotubes still

  9. Growth and optical properties of ZnO nanostructures grown on ZnO seed layers

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Yong; Feneberg, Martin; Reiser, Anton; Tischer, Ingo; Wiedenmann, Michael; Frey, Reinhard; Roeder, Uwe; Sauer, Rolf; Thonke, Klaus [Institut fuer Halbleiterphysik, Universitaet Ulm (Germany)

    2009-07-01

    Using a ZnO seed layer, we grow well-aligned ZnO nanopillars on different substrates including a-plane sapphire, c-plane GaN, and (100) silicon. We use Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) to characterize the morphology of the ZnO seed layers and of the ZnO nanopillars. Layers and nanopillars were also investigated by optical spectroscopy. For all kinds of substrates used, we find well-faceted nanopillars which are uniform along the whole length. The data indicate that they grow via the vapour-solid (VS) mechanism under well-controlled growth conditions. The photoluminescence of the ZnO nanopillars shows sharp near-band-edge luminescence and nearly no green or yellow band luminescence, indicating very low contamination.

  10. Photocatalysis-assisted water filtration: Using TiO{sub 2}-coated vertically aligned multi-walled carbon nanotube array for removal of Escherichia coli O157:H7

    Energy Technology Data Exchange (ETDEWEB)

    Oza, Goldie; Pandey, Sunil; Gupta, Arvind; Shinde, Sachin; Mewada, Ashmi [N.S. N. Research Centre for Nanotechnology and Bionanotechnology, Jambhul Phata, Kalyan-Badlapur Road, Ambernath (W) 421505, Maharashtra (India); Jagadale, Pravin [DISAT — Department of Applied Science and Technology, Carbon group, Politecnico di Torino (Italy); Sharon, Maheshwar [N.S. N. Research Centre for Nanotechnology and Bionanotechnology, Jambhul Phata, Kalyan-Badlapur Road, Ambernath (W) 421505, Maharashtra (India); Sharon, Madhuri, E-mail: sharonmadhuri@gmail.com [N.S. N. Research Centre for Nanotechnology and Bionanotechnology, Jambhul Phata, Kalyan-Badlapur Road, Ambernath (W) 421505, Maharashtra (India)

    2013-10-01

    A porous ceramic was coated with vertically aligned multi-walled carbon nanotubes (MWCNTs) by spray pyrolysis. Titanium dioxide (TiO{sub 2}) nanoparticles were then coated onto this densely aligned MWCNT. The presence of TiO{sub 2}/MWCNT interfacial arrays was confirmed by X-ray diffraction (XRD), scanning electron microscope–energy dispersive analysis of X-ray (SEM–EDAX) and transmission electron microscope (TEM). This is a novel report in which water loaded with a most dreadful enterohemorrhagic pathogenic strain of Escherichia coli O157:H7 was filtered through TiO{sub 2}/MWCNT coated porous ceramic filter and then analysed. Bacterial removal performance was found to be significantly lower in control i.e. plain porous ceramic (P < 0.05) as compared to TiO{sub 2}/MWCNT coated ceramic. The photocatalytic killing rate constant for TiO{sub 2}-ceramic and MWCNT/TiO{sub 2}-ceramic under fluorescent light was found be 1.45 × 10{sup −2} min{sup −1} and 2.23 × 10{sup −2} min{sup −1} respectively. Further, when I–V characteristics were performed for TiO{sub 2}/MWCNT composite, it was corroborated that the current under light irradiation is comparatively higher than that in dark, thus proving it to be photocatalytically efficient system. The enhanced photocatalysis may be a contribution of increased surface area and charge transfer rate as a consequence of aligned MWCNT network. - Highlights: • Coating of vertically aligned MWCNT on ceramic candle filter • Surface orchestration of TiO{sub 2} on MWCNT arrays • I–V characteristic studies are performed under dark and illumination. • Photocatalytic efficiency of TiO{sub 2}/MWCNT arrays is determined using E. coli O157:H7. • Proposed a mechanism of bacterial killing due to free radical formation.

  11. Low-temperature synthesis of ZnO nanonails

    Science.gov (United States)

    Song, Xubo; Zhang, Yaohua; Zheng, Jie; Li, Xingguo

    2007-09-01

    Wurtzite ZnO nanonails on silicon substrate were successfully synthesized by thermal vapor transport and condensation method at a low temperature without a metal catalyst. Pure Zn powders were used as raw material and O2/Ar powders as source gas. The products were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The results show that the deposited nanostructures include aligned ZnO nanonails. The ZnO nanonails, with crystalline cap and small-diameter shafts, grow along the c-axis. The optical properties have been revealed by photoluminescence spectra. We considered that the ZnO nanonails growth is a vapor solid process.

  12. Preparation of Zn-doped TiO2 nanotubes electrode and its application in pentachlorophenol photoelectrocatalytic degradation

    Institute of Scientific and Technical Information of China (English)

    ZHAO HuiMin; CHEN Yue; QUAN Xie; RUAN XiuLi

    2007-01-01

    Zn-doped titanium oxide (TiO2) nanotubes electrode was prepared on a titanium plate by direct anodic oxidation and immersing method in sequence. Field emission scanning electron microscopy (FESEM) showed that the Zn-doped TiO2 nanotubes were well aligned and organized into high density uniform arrays with diameter ranging from 50 to 90 nm. The length and the thickness were about 200 and 15 nm respectively. TiO2 anatase phase was identified by X-ray diffraction (XRD). X-ray photoelectronspectroscopy (XPS) indicated that Zn ions were mainly located on the surface of TiO2 nanotubes in form of ZnO clusters. Compared with TiO2 nanotubes electrode, about 20 nm red shift in the spectrum of UV-vis absorption was observed. The degradation of pentachlorophenol (PCP) in aqueous solution under the same condition (initial concentration of PCP: 20 mg/L; concentration of Na2SO4:0.01 mol/L and pH:7.03) was carried out using Zn-doped TiO2 nanotubes electrode and TiO2 nanotubes electrode. The degradation rates of PCP using Zn-doped TiO2 nanotubes electrode were found to be twice and 5.8times as high as that using TiO2 nanotubes electrode by UV radiation (400 μw/cm2) and visible light radiation (4500 μw/cm2), respectively. 73.5% of PCP was removed using Zn-doped TiO2 nanotubes electrode against 48.5% removed using TiO2 nanotubes electrode in 120 min under UV radiation. While under visible light radiation, the degradation efficiency of PCP was 18.4% using Zn-doped TiO2 nanotubes electrode against 3.2% using TiO2 nanotubes electrode in 120 min. The optimum concentration of Zn doping was found to be 0.909%. The PCP degradation efficiencies of the 10 repeated experiments by Zn-doped TiO2 nanotubes electrode were rather stable with the deviation within 3.0%.

  13. Highly Ordered Vertical Arrays of TiO2/ZnO Hybrid Nanowires: Synthesis and Electrochemical Characterization.

    Science.gov (United States)

    Gujarati, Tanvi P; Ashish, Ajithan G; Rai, Maniratnam; Shaijumon, Manikoth M

    2015-08-01

    We report the fabrication of vertically aligned hierarchical arrays of TiO2/ZnO hybrid nanowires, consisting of ZnO nanowires grown directly from within the pores of TiO2 nanotubes, through a combination of electrochemical anodization and hydrothermal techniques. These novel nano-architectured hybrid nanowires with its unique properties show promise as high performance supercapacitor electrodes. The electrochemical behaviour of these hybrid nanowires has been studied using Cyclic voltammetry, Galvanostatic charge-discharge and Electrochemical impedance spectroscopy (EIS) measurements using 1.5 M tetraethylammoniumtetrafluoroborate in acetonitrile as the electrolyte. Excellent electrochemical performances with a maximum specific capacitance of 2.6 mF cm-2 at a current density of 10 µA cm-2, along with exceptional cyclic stability, have been obtained for TiO2/ZnO-1 h hybrid material. The obtained results demonstrate the possibility of fabricating new geometrical architectures of inorganic hybrid nanowires with well adhered interfaces for the development of hybrid energy devices.

  14. Challenges in the simulation of dye-sensitized ZnO solar cells: quantum confinement, alignment of energy levels and excited state nature at the dye/semiconductor interface

    OpenAIRE

    Amat, Anna; De Angelis, Filippo

    2012-01-01

    We report a first principles density functional theory/time-dependent density functional theory (DFT/TDDFT) computational investigation on a prototypical perylene dye anchored to realistic ZnO nanostructures, approaching the size of the ZnO nanowires used in dye-sensitized solar cells devices. DFT calculations were performed on (ZnO)n clusters of increasing size, with n up to 222, of 1.3 1.5 3.4 nm dimensions, and for the related dye-sensitized models. We show that quantum co...

  15. Catalytic Synthesis of Substrate-Free, Aligned and Tailored High Aspect Ratio Multiwall Carbon Nanotubes in an Ultrasonic Atomization Head CVD Reactor

    Directory of Open Access Journals (Sweden)

    Fahad Ali Rabbani

    2016-01-01

    Full Text Available Chemical vapor deposition (CVD method has proven its benchmark, over other methods, for the production of different types of carbon nanotubes (CNT on commercial and lab scale. In this study, an injection vertical CVD reactor fitted with an ultrasonic atomization head was used in a pilot-plant scale (height 274 cm, radius 25 cm for semicontinuous production of multiwall carbon nanotubes (MWCNTs. p-Xylene was used as a hydrocarbon precursor in which ferrocene was dissolved and provided the cracking catalyst. Atomization of the feed solution resulted in full and even dispersion of the catalytic solution. This dispersion led to the production of high aspect ratio MWCNTs (ranging from 8,000 to 12,000 at 850°C. Different experimental parameters affecting the quality and quantity of the produced CNTs were investigated. These included temperature, reaction time, and flow rate of the reaction and carrier gases. Different properties of the produced CNTs were characterized using SEM and TEM, while TGA was used to evaluate their purity. Specific surface area of selected samples was calculated by BET.

  16. Morphology, structure and Raman scattering of carbon nanotubes produced by using mesoporous materials

    Institute of Scientific and Technical Information of China (English)

    解思深; 李文治; 王超英; 徐丽雯; 张昊; 张云; 钱露茜

    1997-01-01

    Carbon nanotubes were prepared by chemical vapor deposition (CVD) of hydrocarbon gas on various substrates.The effect of substrates on the growth,morphology and structure of carbon nanotubes were investigated.Aligned carbon nanotubes with high density and purity were achieved by CVD on mesoporous silica substrate.The Raman scattering of aligned carbon nanotubes was carried out,and the dependence of the phonon properties on the mi-crostructure of the nanotubes has been discussed.

  17. Carbon Nanotube Electron Gun

    Science.gov (United States)

    Nguyen, Cattien V. (Inventor); Ribaya, Bryan P. (Inventor)

    2013-01-01

    An electron gun, an electron source for an electron gun, an extractor for an electron gun, and a respective method for producing the electron gun, the electron source and the extractor are disclosed. Embodiments provide an electron source utilizing a carbon nanotube (CNT) bonded to a substrate for increased stability, reliability, and durability. An extractor with an aperture in a conductive material is used to extract electrons from the electron source, where the aperture may substantially align with the CNT of the electron source when the extractor and electron source are mated to form the electron gun. The electron source and extractor may have alignment features for aligning the electron source and the extractor, thereby bringing the aperture and CNT into substantial alignment when assembled. The alignment features may provide and maintain this alignment during operation to improve the field emission characteristics and overall system stability of the electron gun.

  18. A general deposition method for ZnO porous films: Occlusion electrosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Chen Haining, E-mail: chen-hn77@163.com [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Li Weiping; Hou Qin; Liu Huicong [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Zhu Liqun, E-mail: Zhulq@buaa.edu.cn [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China)

    2011-10-30

    In this paper, a modified electrodeposition method, occlusion electrosynthesis (OE), was used to prepare ZnO porous films. The processes of OE were similar to those of electrodeposition except the addition of ZnO nanoparticles in electrolyte. The ZnO porous film prepared by OE (OE-ZnO) was highly porous with considerable thickness (55 {mu}m). The quantum dots-sensitized solar cell based on OE-ZnO porous film showed superior photoelectrochemical performance to that based on the ZnO porous film prepared by doctor-blade (DB) method at the suitable concentrations of ZnO nanoparticles in electrolyte, about 16-32 g/L. In addition to the ZnO porous film constructed with ZnO nanoparticles, the ZnO porous film constructed with ZnO nanorods, ZnO/multi-walls carbon nanotubes and ZnO/TiO{sub 2} composite porous films have also been successfully synthesized by OE, which were expected to be widely applied in various fields. The low temperature (60 deg. C) processes without post treatment made OE more promising for preparing ZnO porous films than DB, especially the ZnO porous films for flexible devices.

  19. Fabrication and green emission of ZnO nanowire arrays

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Well-aligned single-crystalline wurzite zinc oxide (ZnO) nanowire arrays were successfully fabricated on a Si substrate by a simple physical vapor-deposition (PVD) method at a relatively low temperature of about 500℃. The as-fabricated nanowires were preferentially arranged along the [001] direction of ZnO. The photoluminescence spectrum of ZnO nanowire arrays showed two emission bands: a strong green emission at around 500 nm and a weak ultraviolet emission at 380 nm. The strong green light emission was related to the existence of the oxygen vacancies in ZnO crystals. Corresponding growth mecha- nism of the ZnO nanowires was briefly discussed.

  20. In- and out-of-plane dynamic flexural behaviors of two-dimensional ensembles of vertically aligned single-walled carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Kiani, Keivan, E-mail: k_kiani@kntu.ac.ir

    2014-09-15

    Useful nonlocal discrete and continuous models are developed to explain free vibration of two-dimensional (2D) ensembles of single-walled carbon nanotubes (SWCNTs) in bending. For this purpose, the models are constructed based on the nonlocal Rayleigh, Timoshenko, and higher-order beam theories. In contrast to an individual SWCNT exhibits identical bending behavior in different directions, for 2D ensemble networks of SWCNTs, it is shown that such a fact is completely dissimilar. Such an important issue leads to the definition of in-plane and out-of-plane flexural behaviors for such nanostructures. Subsequently, their corresponding fundamental frequencies are evaluated based on the proposed nonlocal models. The capabilities of the proposed nonlocal continuous models in predicting flexural frequencies of SWCNTs' ensembles with different numbers of SWCNTs as well as various levels of slenderness ratios are then explained. Such investigations confirm the high efficiency of the proposed continuous models. This matter would be of great importance in vibration analysis of highly populated ensembles of SWCNTs in which the discrete models may suffer from the size of the governing equations. The roles of the number of SWCNTs, slenderness ratio, intertube distance, small-scale parameter, and radius of the SWCNT on both in-plane and out-of-plane fundamental frequencies are addressed.

  1. Poly (vinylidene fluoride) / Poly (acrylonitrile)-based Superior Hydrophobic Piezoelectric Solid Derived by Aligned Carbon Nanotube in Electrospinning: Fabrication, the Phase Conversion and Surface Energy.

    Science.gov (United States)

    Aqeel, Salem M; Wang, Zhe; Than, Lisa; Sreenivasulu, Gollapudi; Zeng, Xiangqun

    2015-01-01

    Multifunctional materials have attracted many interests from both fundamental and practical aspects, such as field-effect transistor, electric protection, transducers and biosensor. Here we demonstrated the first superior hydrophobic piezoelectric surface based on the polymer blend of polyvinylidene fluoride (PVDF)-polyacrilonitrile (PAN) assisted with functionalized multiwalled nanotubes (MWNTs), by a modified electrospinning method. Typically the β-phase polyvinylidene fluoride (PVDF) was considered as the excellent piezoelectric and pyroelectric materials. However, polar β-phase of PVDF exhibited a natural high hydrophilicity. As a well-known fact, the wettability of the surface is dominated by two major factors: surface composition and surface roughness. The significant conversions derived by the incorporation of MWNTs, from nonpolar α-phase to highly polar β-phase of PVDF, were confirmed by FTIR. Meanwhile, the effects of MWNTs on the improvement of the roughness and the hydrophobicity of polymer blend were evaluated by atomic force microscopy (AFM) and contact angle (CA). Molar free energy of wetting of the polymer nanocomposite decreases with increasing the wt.% of MWNTs. All molar free energy of wetting of PVDF-PAN/MWNTs were negative, which means the non-wettability of film. The combination of surface roughness and low-surface-energy modification in nanostructured composites leads to high hydrophobicity. Particularly, fabrication of superior hydrophobic surfaces not only has fundamental interest but also various possible functional applications in micro- and nano-materials and devices.

  2. Poly (vinylidene fluoride) / Poly (acrylonitrile)–based Superior Hydrophobic Piezoelectric Solid Derived by Aligned Carbon Nanotube in Electrospinning: Fabrication, the Phase Conversion and Surface Energy

    Science.gov (United States)

    Aqeel, Salem M.; Than, Lisa; Sreenivasulu, Gollapudi

    2015-01-01

    Multifunctional materials have attracted many interests from both fundamental and practical aspects, such as field–effect transistor, electric protection, transducers and biosensor. Here we demonstrated the first superior hydrophobic piezoelectric surface based on the polymer blend of polyvinylidene fluoride (PVDF)–polyacrilonitrile (PAN) assisted with functionalized multiwalled nanotubes (MWNTs), by a modified electrospinning method. Typically the β–phase polyvinylidene fluoride (PVDF) was considered as the excellent piezoelectric and pyroelectric materials. However, polar β–phase of PVDF exhibited a natural high hydrophilicity. As a well–known fact, the wettability of the surface is dominated by two major factors: surface composition and surface roughness. The significant conversions derived by the incorporation of MWNTs, from nonpolar α–phase to highly polar β–phase of PVDF, were confirmed by FTIR. Meanwhile, the effects of MWNTs on the improvement of the roughness and the hydrophobicity of polymer blend were evaluated by atomic force microscopy (AFM) and contact angle (CA). Molar free energy of wetting of the polymer nanocomposite decreases with increasing the wt.% of MWNTs. All molar free energy of wetting of PVDF–PAN/MWNTs were negative, which means the non–wettability of film. The combination of surface roughness and low–surface–energy modification in nanostructured composites leads to high hydrophobicity. Particularly, fabrication of superior hydrophobic surfaces not only has fundamental interest but also various possible functional applications in micro– and nano–materials and devices. PMID:26989486

  3. Nanostructural evolution of one-dimensional BaTiO₃ structures by hydrothermal conversion of vertically aligned TiO₂ nanotubes.

    Science.gov (United States)

    Muñoz-Tabares, J A; Bejtka, K; Lamberti, A; Garino, N; Bianco, S; Quaglio, M; Pirri, C F; Chiodoni, A

    2016-03-28

    The use of TiO2 nanotube (NT) arrays as templates for hydrothermal conversion of one-dimensional barium titanate (BaTiO3) structures is considered a promising synthesis approach, even though the formation mechanisms are not yet fully understood. Herein we report a nanostructural study by means of XRD and (HR)TEM of high aspect ratio TiO2-NTs hydrothermally converted into BaTiO3. The nanostructure shows two different and well-defined regions: at the top the conversion involves complete dissolution of NTs and subsequent precipitation of BaTiO3 crystals by homogeneous nucleation, followed by the growth of dendritic structures by aggregation and oriented attachment mechanisms. Instead, at the bottom, the low liquid/solid ratio, due to the limited amount of Ba solution that infiltrates the NTs, leads to the rapid crystallization of such a solution into BaTiO3, thus allowing the NTs to act as a template for the formation of highly oriented one-dimensional nanostructures. The in-depth analysis of the structural transformations that take place during the formation of the rod-like arrays of BaTiO3 could help elucidate the conversion mechanism, thus paving the way for the optimization of the synthesis process in view of new applications in energy harvesting devices, where easy and low temperature processing, controlled composition, morphology and functional properties are required.

  4. Field emission and anode etching during formation of length-controlled nanogaps in electrical breakdown of horizontally aligned single-walled carbon nanotubes.

    Science.gov (United States)

    Otsuka, Keigo; Inoue, Taiki; Shimomura, Yuki; Chiashi, Shohei; Maruyama, Shigeo

    2016-09-15

    We observe field emission between nanogaps and voltage-driven gap extension of single-walled carbon nanotubes (SWNTs) on substrates during the electrical breakdown process. Experimental results show that the gap size is dependent on the applied voltage and humidity, which indicates high controllability of the gap size by appropriate adjustment of these parameters in accordance with the application. We propose a mechanism for the gap formation during electrical breakdown as follows. After small gaps are formed by Joule heating-induced oxidation, SWNTs on the anode side are electrochemically etched due to physically-adsorbed water from the air and the enhanced electric field at the SWNT tips. Field emission is measured in a vacuum as a possible mechanism for charge transfer at SWNT gaps. The relationship between the field enhancement factor and geometric features of SWNTs explains both the voltage dependence of the extended gap size and the field emission properties of the SWNT gaps. In addition, the similar field-induced etching can cause damage to adjacent SWNTs, which possibly deteriorates the selectivity for cutting metallic pathways in the presence of water vapor.

  5. Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: Optical and electrochemical properties

    Science.gov (United States)

    Romeiro, Fernanda C.; Marinho, Juliane Z.; Lemos, Samantha C. S.; de Moura, Ana P.; Freire, Poliana G.; da Silva, Luis F.; Longo, Elson; Munoz, Rodrigo A. A.; Lima, Renata C.

    2015-10-01

    We report for the first time a rapid preparation of Zn1-2xCoxNixO nanoparticles via a versatile and environmentally friendly route, microwave-assisted hydrothermal (MAH) method. The Co, Ni co-doped ZnO nanoparticles present an effect on photoluminescence and electrochemical properties, exhibiting excellent electrocatalytic performance compared to undoped ZnO sample. Photoluminescence spectroscopy measurements indicated the reduction of the green-orange-red visible emission region after adding Co and Ni ions, revealing the formation of alternative pathways for the generated recombination. The presence of these metallic ions into ZnO creates different defects, contributing to a local structural disorder, as revealed by Raman spectra. Electrochemical experiments revealed that the electrocatalytic oxidation of dopamine on ZnO attached to multi-walled carbon nanotubes improved significantly in the Co, Ni co-doped ZnO samples when compared to pure ZnO.

  6. Nanostructural evolution of one-dimensional BaTiO3 structures by hydrothermal conversion of vertically aligned TiO2 nanotubes

    Science.gov (United States)

    Muñoz-Tabares, J. A.; Bejtka, K.; Lamberti, A.; Garino, N.; Bianco, S.; Quaglio, M.; Pirri, C. F.; Chiodoni, A.

    2016-03-01

    The use of TiO2 nanotube (NT) arrays as templates for hydrothermal conversion of one-dimensional barium titanate (BaTiO3) structures is considered a promising synthesis approach, even though the formation mechanisms are not yet fully understood. Herein we report a nanostructural study by means of XRD and (HR)TEM of high aspect ratio TiO2-NTs hydrothermally converted into BaTiO3. The nanostructure shows two different and well-defined regions: at the top the conversion involves complete dissolution of NTs and subsequent precipitation of BaTiO3 crystals by homogeneous nucleation, followed by the growth of dendritic structures by aggregation and oriented attachment mechanisms. Instead, at the bottom, the low liquid/solid ratio, due to the limited amount of Ba solution that infiltrates the NTs, leads to the rapid crystallization of such a solution into BaTiO3, thus allowing the NTs to act as a template for the formation of highly oriented one-dimensional nanostructures. The in-depth analysis of the structural transformations that take place during the formation of the rod-like arrays of BaTiO3 could help elucidate the conversion mechanism, thus paving the way for the optimization of the synthesis process in view of new applications in energy harvesting devices, where easy and low temperature processing, controlled composition, morphology and functional properties are required.The use of TiO2 nanotube (NT) arrays as templates for hydrothermal conversion of one-dimensional barium titanate (BaTiO3) structures is considered a promising synthesis approach, even though the formation mechanisms are not yet fully understood. Herein we report a nanostructural study by means of XRD and (HR)TEM of high aspect ratio TiO2-NTs hydrothermally converted into BaTiO3. The nanostructure shows two different and well-defined regions: at the top the conversion involves complete dissolution of NTs and subsequent precipitation of BaTiO3 crystals by homogeneous nucleation, followed by the

  7. Magnetic nanotubes

    Science.gov (United States)

    Matsui, Hiroshi; Matsunaga, Tadashi

    2010-11-16

    A magnetic nanotube includes bacterial magnetic nanocrystals contacted onto a nanotube which absorbs the nanocrystals. The nanocrystals are contacted on at least one surface of the nanotube. A method of fabricating a magnetic nanotube includes synthesizing the bacterial magnetic nanocrystals, which have an outer layer of proteins. A nanotube provided is capable of absorbing the nanocrystals and contacting the nanotube with the nanocrystals. The nanotube is preferably a peptide bolaamphiphile. A nanotube solution and a nanocrystal solution including a buffer and a concentration of nanocrystals are mixed. The concentration of nanocrystals is optimized, resulting in a nanocrystal to nanotube ratio for which bacterial magnetic nanocrystals are immobilized on at least one surface of the nanotubes. The ratio controls whether the nanocrystals bind only to the interior or to the exterior surfaces of the nanotubes. Uses include cell manipulation and separation, biological assay, enzyme recovery, and biosensors.

  8. Growth and Characterization of Trumpet-Shaped ZnO Microtube Arrays on Si Substrates

    Institute of Scientific and Technical Information of China (English)

    LI Meng-Ke; WANG De-Zhen; SHI Feng; DING Sheng; JIN Hong

    2007-01-01

    @@ Aligned trumpet-shaped zinc oxide microtube arrays have been successfully prepared on silicon (100) substrates via the chemical vapour deposition method with a mixture of ZnO and active carbon powders as reactants. The results show that two types of trumpet-shaped ZnO microtubes can be obtained.

  9. Engineering carbon nanotubes and nanotube circuits using electrical breakdown.

    Science.gov (United States)

    Collins, P G; Arnold, M S; Avouris, P

    2001-04-27

    Carbon nanotubes display either metallic or semiconducting properties. Both large, multiwalled nanotubes (MWNTs), with many concentric carbon shells, and bundles or "ropes" of aligned single-walled nanotubes (SWNTs), are complex composite conductors that incorporate many weakly coupled nanotubes that each have a different electronic structure. Here we demonstrate a simple and reliable method for selectively removing single carbon shells from MWNTs and SWNT ropes to tailor the properties of these composite nanotubes. We can remove shells of MWNTs stepwise and individually characterize the different shells. By choosing among the shells, we can convert a MWNT into either a metallic or a semiconducting conductor, as well as directly address the issue of multiple-shell transport. With SWNT ropes, similar selectivity allows us to generate entire arrays of nanoscale field-effect transistors based solely on the fraction of semiconducting SWNTs.

  10. Carbon nanotube filters

    Science.gov (United States)

    Srivastava, A.; Srivastava, O. N.; Talapatra, S.; Vajtai, R.; Ajayan, P. M.

    2004-09-01

    Over the past decade of nanotube research, a variety of organized nanotube architectures have been fabricated using chemical vapour deposition. The idea of using nanotube structures in separation technology has been proposed, but building macroscopic structures that have controlled geometric shapes, density and dimensions for specific applications still remains a challenge. Here we report the fabrication of freestanding monolithic uniform macroscopic hollow cylinders having radially aligned carbon nanotube walls, with diameters and lengths up to several centimetres. These cylindrical membranes are used as filters to demonstrate their utility in two important settings: the elimination of multiple components of heavy hydrocarbons from petroleum-a crucial step in post-distillation of crude oil-with a single-step filtering process, and the filtration of bacterial contaminants such as Escherichia coli or the nanometre-sized poliovirus (~25 nm) from water. These macro filters can be cleaned for repeated filtration through ultrasonication and autoclaving. The exceptional thermal and mechanical stability of nanotubes, and the high surface area, ease and cost-effective fabrication of the nanotube membranes may allow them to compete with ceramic- and polymer-based separation membranes used commercially.

  11. Aligned SWNT films from low-yield stress gels and their transparent electrode performance.

    Science.gov (United States)

    Allen, Ranulfo; Fuller, Gerald G; Bao, Zhenan

    2013-08-14

    Carbon nanotube films are promising for transparent electrodes for solar cells and displays. Large-area alignment of the nanotubes in these films is needed to minimize the sheet resistance. We present a novel coating method to coat high-density, aligned nanotubes over large areas. Carbon nanotube gel dispersions used in this study have aligned domains and a low yield stress. A simple shearing force allows these domains to uniformly align. We use this to correlate the transparent electrode performance of single-walled carbon nanotube films with the level of partial alignment. We have found that the transparent electrode performance improves with increasing levels of alignment and in a manner slightly better than what has been previously predicted.

  12. Plasmonic Properties of Vertically Aligned Nanowire Arrays

    Directory of Open Access Journals (Sweden)

    Hua Qi

    2012-01-01

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

  13. Advances in growth control of vertically-aligned carbon nanotube forests%垂直碳纳米管阵列的生长控制研究进展

    Institute of Scientific and Technical Information of China (English)

    梁尤轩; 赵斌; 姜川; 杨俊和

    2014-01-01

    垂直碳纳米管(VACNT)阵列由于具有良好的排列、优异的导电导热能力、高比表面积、高纯度等优点而得到广泛应用。本文概述了用于碳纳米管阵列生长的热化学气相沉积(CVD)制备方法的最新进展,重点阐述了CVD法生长碳纳米管阵列的动力学与生长终止机理,指出CVD过程中的催化剂形貌演化是引发碳纳米管阵列生长停止的重要原因。介绍了人们通过生长条件控制与催化剂设计等方法调控碳纳米管阵列结构(包括管壁数、管径和密度)方面取得的进展,指出碳纳米管阵列的大批量制备及结构参数的精确调控是未来发展的重点。%Due to good alignment,excellent electrical and thermal conductivity,high surface area, and high carbon purity,vertically-aligned carbon nanotube (VACNT) forests have shown to be advantageous for numerous applications. This paper summarizes recent advances in several chemical vapor deposition (CVD) methods for synthesizing VACNT forests. It focuses on kinetics and termination mechanism of VACNT forest growth by the CVD technique,and catalyst morphology evolution was designated to be the main reason for termination of CNT forest growth. In addition,the progress in structure tailoring of VACNTs (including wall number,diameter and density) through condition control and catalyst designing are also introduced. And,massive growth of VACNT forests and precise control of their structure are regarded as important points to be further studied in the future.

  14. From Zn-Al layered double hydroxide to ZnO nanostructure:Gradually etching by sodium hydroxide

    Institute of Scientific and Technical Information of China (English)

    Gang Qiang Wan; Dong Xiang Li; Chun Fang Li; Jie Xu; Wan Guo Hou

    2012-01-01

    Zn-Al layered double hydroxide (LDH) was used as precursor to produce ZnO nanostructures through dissolution of aluminum hydroxide in caustic soda.The Zn-Al LDH could transform into different nanostructures of ZnO on LDH nanosheets and even pure ZnO nanorods under various NaOH concentration.The formed ZnO nanorods vertically aligned on both LDH sides.UV-vis diverse reflectance spectra show that the obtained ZnO nanorods have a band gap of approximately 3.05 eV.Such ZnO/LDH nanostructures might be used as photocatalyst in the organic pollutant decomposition.

  15. Epitaxial Approaches to Carbon Nanotube Organization

    Science.gov (United States)

    Ismach, Ariel

    Carbon nanotubes have unique electronic, mechanical, optical and thermal properties, which make them ideal candidates as building blocks in nano-electronic and electromechanical systems. However, their organization into well-defined geometries and arrays on surfaces remains a critical challenge for their integration into functional nanosystems. In my PhD, we developed a new approach for the organization of carbon nanotubes directed by crystal surfaces. The principle relies on the guided growth of single-wall carbon nanotubes (SWNTs) by atomic features presented on anisotropic substrates. We identified three different modes of surface-directed growth (or 'nanotube epitaxy'), in which the growth of carbon nanotubes is directed by crystal substrates: We first observed the nanotube unidirectional growth along atomic steps ('ledge-directed epitaxy') and nanofacets ('graphoepitaxy') on the surface of miscut C-plane sapphire and quartz. The orientation along crystallographic directions ('lattice-directed epitaxy') was subsequently observed by other groups on different crystals. We have proposed a "wake growth" mechanism for the nanotube alignment along atomic steps and nanofacets. In this mechanism, the catalyst nanoparticle slides along the step or facet, leaving the nanotube behind as a wake. In addition, we showed that the combination of surface-directed growth with external forces, such as electric-field and gas flow, can lead to the simultaneous formation of complex nanotube structures, such as grids and serpentines. The "wake growth" model, which explained the growth of aligned nanotubes, could not explain the formation of nanotube serpentines. For the latter, we proposed a "falling spaghetti" mechanism, in which the nanotube first grows by a free-standing process, aligned in the direction of the gas flow, then followed by absorption on the stepped surface in an oscillatory manner, due to the competition between the drag force caused by the gas flow on the suspended

  16. Cd-free buffer layer materials on Cu2ZnSn(SxSe1-x)4: Band alignments with ZnO, ZnS, and In2S3

    Science.gov (United States)

    Barkhouse, D. Aaron R.; Haight, Richard; Sakai, Noriyuki; Hiroi, Homare; Sugimoto, Hiroki; Mitzi, David B.

    2012-05-01

    The heterojunctions formed between Cu2ZnSn(SxSe1-x)4 (CZTSSe) and three Cd-free n-type buffers, ZnS, ZnO, and In2S3, were studied using femtosecond ultraviolet photoemission and photovoltage spectroscopy. The electronic properties including the Fermi level location at the interface, band bending in the CZTSSe substrate, and valence and conduction band offsets were determined and correlated with device properties. We also describe a method for determining the band bending in the buffer layer and demonstrate this for the In2S3/CZTSSe system. The chemical bath deposited In2S3 buffer is found to have near optimal conduction band offset (0.15 eV), enabling the demonstration of Cd-free In2S3/CZTSSe solar cells with 7.6% power conversion efficiency.

  17. Vertically Aligned Nanostructured Arrays of Inorganic Materials: Synthesis, Distinctive Physical Phenomena, and Device Integration

    Science.gov (United States)

    Velazquez, Jesus Manuel

    The manifestation of novel physical phenomena upon scaling materials to finite size has inspired new device concepts that take advantage of the distinctive electrical, mechanical, and optical, properties of nanostructures. The development of fabrication approaches for the preparation of their 1D nanostructured form, such as nanowires and nanotubes, has contributed greatly to advancing fundamental understanding of these systems, and has spurred the integration of these materials in novel electronics, photonic devices, power sources, and energy scavenging constructs. Significant progress has been achieved over the last decade in the preparation of ordered arrays of carbon nanotubes, II---VI and III---V semiconductors, and some binary oxides such as ZnO. In contrast, relatively less attention has been focused on layered materials with potential for electrochemical energy storage. Here, we describe the catalyzed vapor transport growth of vertical arrays of orthorhombic V2O 5 nanowires. In addition, near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is used to precisely probe the alignment, uniformity in crystal growth direction, and electronic structure of single-crystalline V2O5 nanowire arrays prepared by a cobalt-catalyzed vapor transport process. The dipole selection rules operational for core-level electron spectroscopy enable angle-dependant NEXAFS spectroscopy to be used as a sensitive probe of the anisotropy of these systems and provides detailed insight into bond orientation and the symmetry of the frontier orbital states. The experimental spectra are matched to previous theoretical predictions and allow experimental verification of features such as the origin of the split-off conduction band responsible for the n-type conductivity of V2O5 and the strongly anisotropic nature of vanadyl-oxygen-derived (V=O) states thought to be involved in catalysis. We have also invested substantial effort in obtaining shape and size control of metal oxide

  18. Alignment validation

    Energy Technology Data Exchange (ETDEWEB)

    ALICE; ATLAS; CMS; LHCb; Golling, Tobias

    2008-09-06

    The four experiments, ALICE, ATLAS, CMS and LHCb are currently under constructionat CERN. They will study the products of proton-proton collisions at the Large Hadron Collider. All experiments are equipped with sophisticated tracking systems, unprecedented in size and complexity. Full exploitation of both the inner detector andthe muon system requires an accurate alignment of all detector elements. Alignmentinformation is deduced from dedicated hardware alignment systems and the reconstruction of charged particles. However, the system is degenerate which means the data is insufficient to constrain all alignment degrees of freedom, so the techniques are prone to converging on wrong geometries. This deficiency necessitates validation and monitoring of the alignment. An exhaustive discussion of means to validate is subject to this document, including examples and plans from all four LHC experiments, as well as other high energy experiments.

  19. Effects of heat treatment on the dye adsorption of ZnO nanorods for dye-sensitized solar cells

    Science.gov (United States)

    Yun, Won Suk; Choi, Seok Cheol; Sohn, Sang Ho; Oh, Sang Jin

    2012-11-01

    Well-aligned ZnO nanorods for the photoelectrode of dye-sensitized solar cells (DSSCs) were grown via a sonochemical method, and the heat-treatment effects on the dye adsorption in the DSSCs were studied. The heat treatment of well-aligned ZnO nanorods was performed at 200 ˜ 500 °C for 1 h, which was immediately followed by the dye adsorption. The dye amounts adsorbed in the ZnO nanorods were estimated from the UV-Vis absorbance by using Beer-Lambert's law. The efficiency of the DSSCs with ZnO nanorods was measured to investigate the heat-treatment effects of ZnO nanorods on the dye adsorption properties. The heat-treatment of ZnO nanorods was found to yield a change in their dye adsorption ability, resulting in a change in the efficiency of the DSSCs.

  20. Effects of heat treatment on the dye adsorption of ZnO nanorods for dye-sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Won Suk; Choi, Seok Cheol; Sohn, Sang Ho [Kyungpook National University, Daegu (Korea, Republic of); Oh, Sang Jin [Phoenix Materials, Gumi (Korea, Republic of)

    2012-11-15

    Well-aligned ZnO nanorods for the photoelectrode of dye-sensitized solar cells (DSSCs) were grown via a sonochemical method, and the heat-treatment effects on the dye adsorption in the DSSCs were studied. The heat treatment of well-aligned ZnO nanorods was performed at 200 ∼ 500 .deg. C for 1 h, which was immediately followed by the dye adsorption. The dye amounts adsorbed in the ZnO nanorods were estimated from the UV-Vis absorbance by using Beer-Lambert's law. The efficiency of the DSSCs with ZnO nanorods was measured to investigate the heat-treatment effects of ZnO nanorods on the dye adsorption properties. The heat-treatment of ZnO nanorods was found to yield a change in their dye adsorption ability, resulting in a change in the efficiency of the DSSCs.

  1. Controllable Growth of Ultrathin P-doped ZnO Nanosheets.

    Science.gov (United States)

    Zhu, Yuankun; Yang, Hengyan; Sun, Feng; Wang, Xianying

    2016-12-01

    Ultrathin phosphor (P)-doped ZnO nanosheets with branched nanowires were controllably synthesized, and the effects of oxygen and phosphor doping on the structural and optical properties were systematically studied. The grown ZnO nanosheet exhibits an ultrathin nanoribbon backbone with one-side-aligned nanoteeth. For the growth of ultrathin ZnO nanosheets, both oxygen flow rate and P doping are essential, by which the morphologies and microstructures can be finely tuned. P doping induces strain relaxation to change the growth direction of ZnO nanoribbons, and oxygen flow rate promotes the high supersaturation degree to facilitate the growth of nanoteeth and widens the nanoribbons. The growth of P-doped ZnO in this work provides a new progress towards the rational control of the morphologies for ZnO nanostructures.

  2. Preparation and Application of Aligned Carbon Nanotube/Polymer Composite Material%取向碳纳米管/高分子新型复合材料的制备及应用

    Institute of Scientific and Technical Information of China (English)

    丘龙斌; 孙雪梅; 仰志斌; 郭文瀚; 彭慧胜

    2012-01-01

    Carbon nanotube (CNT)/polymer composite materials have been widely studied for two decades. However, there remains a common and critical challenge, i.e., random dispersion of CNTs in polymer matrices, which has largely lowered their properties and limited their applications. Herein, we have developed a general method to prepare highly aligned CNT/polymer composite materials in formats of array, film, and fiber. The key procedure is to synthesize spinnable CNT arrays with high quality by a chemical vapor deposition process. Fe/A1203 was used as catalyst, ethylene was used as carbon source, a mixture gas of argon and hydrogen was used as carrying gas. The optimal growth conditions were summarized as below: thickness of 1.2 nm for Fe, thickness of 3 nm for A1203, flow rate of 400 standard cm3/min for argon, flow rate of 90 standard cm3/min for ethylene, flow rate of 30 standard cm3/min for hydrogen, growth temperature of 740 ~C, and growth time of 10 rain. Here the catalyst system was coated on silicon substrate by electron beam evaporation with rates of 0.5 and 2 A/s for Fe and A1203, respectively. To prepare CNT sheets or fibers, the spinnable array was first stabilized in a stage. A blade was then used to draw a ribbon out of the array. A CNT sheet would be obtained if the ribbon was directly pulled out without rotation, while a fiber should be produced if a rotary spinning was used. The spinning speed was about 15 cm/min. Mono- mer/polymer solutions or melts were directly coated onto the aligned CNT sheet or fiber to produce the aligned CNT/polymer film or fiber. Due to the high alignment of CNTs in polymer matrices, the resulting composite materials exhibited remarkable physical properties, e.g., the mechanical strength and electrical conductivity can be improved for one and three orders com- pared with the conventional solution blending method, respectively. These novel composite materials are promising for a wide variety of applications. The use of them

  3. Optical and Morphological Properties of ZnO- and TiO2-Derived Nanostructures Synthesized via a Microwave-Assisted Hydrothermal Method

    Directory of Open Access Journals (Sweden)

    Nosipho Moloto

    2012-01-01

    Full Text Available A microwave-assisted hydrothermal method was used to synthesize ZnO and TiO2 nanostructures. The experimental results show that the method resulted in crystalline monodispersed ZnO nanorods that have pointed tips with hexagonal crystal phase. TiO2 nanotubes were also formed with minimum bundles. The mechanism for the formation of the tubes was validated by HRTEM results. The optical properties of both ZnO and TiO2 nanostructures showed characteristics of strong quantum confinement regime. The photoluminescence spectrum of TiO2 nanotubes shows good improvement from previously reported data.

  4. Synthesis and Luminescent Properties of Planar-tip and Tapered-tip ZnO Nanorod Arrays

    Institute of Scientific and Technical Information of China (English)

    Chun-wen WANG; Jr-hau HE; Lih-juann CHEN

    2008-01-01

    Vertically aligned ZnO nanorods were synthesized on a-plane sapphire via a metal catalyzed vapor phase transport and condensation process in a two-zone vacuum furnace. Planar-tip and tapered-tip ZnO nanorods were successfully synthesized by utilizing different source materials under the same growth conditions. The growth mechanisms were proposed to be vapor-liquid-solid (VLS) process for planar-tip ZnO nanorods and a combination of VLS and self-catalyzed processes for tapered-tip ZnO nanorods. From cathodoluminescence (CL) measurements, tapered-tip ZnO nanorods have more intense green emission than planar-tip ZnO nanorods, and therefore possess higher oxygen vacancy concentration than planar-tip ZnO nanorods. From CL characteristics, well-aligned planar-tip ZnO nanorods shall serve effectively as laser source, while well-aligned tapered-tip ZnO nanorods are suitable for direction-related optical applications.

  5. Effect of ZnO decoration on the photovoltaic performance of TiO{sub 2} based dye sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Long; Zhai, Bao-gai [School of Mathematics and Physics, Changzhou University, Jiangsu 213164 (China); Ma, Qing-lan [School of Electronics and Information, Nantong University, Jiangsu 226019 (China); Huang, Yuan Ming, E-mail: dongshanisland@126.com [School of Electronics and Information, Nantong University, Jiangsu 226019 (China)

    2014-08-25

    Highlights: • Various ZnO morphologies coated TiO{sub 2} photoanodes are formed and applied to DSSCs. • The effect of photoanode morphology on performance of DSSCs was studied. • ZnO NRs@TiO{sub 2} electrode provides more dye absorption and fast transfer pathway. • The η of DSSC with ZnO NRs@TiO{sub 2} is increased over fourfold than other DSSCs. - Abstract: ZnO nanoparticles and one-dimensional vertically aligned ZnO nanorods were grown on the TiO{sub 2} layers in the photoanodes via the hydrothermal method at 60 and 90 °C, respectively. The effect of ZnO decoration on the photovoltaic performance of TiO{sub 2} based dye sensitized solar cells (DSSCs) was investigated. The morphologies, crystalline structures and optical properties of the synthesized ZnO nanoparticles and ZnO nanorods were characterized by field-emission scanning electron microscope, X-ray diffractometer and photoluminescence spectroscopy, respectively. The photocurrent–voltage curves of the fabricated DSSCs showed that the ZnO nanorods decorated DSSCs exhibited better photovoltaic performance than the ZnO nanoparticles decorated DSSCs. The improved performance of the ZnO nanorods decorated DSSCs can be ascribed to the fact that the vertically aligned ZnO nanorods provide high specific surface area for dye adsorption and the efficient pathway for electron transportation.

  6. Structural studies of ZnO nanostructures by varying the deposition parameters

    Science.gov (United States)

    Yunus, S. H. A.; Sahdan, M. Z.; Ichimura, M.; Supee, A.; Rahim, S.

    2017-01-01

    The effect of Zinc Oxide (ZnO) thin film on the growth of ZnO nanorods (NRs) was investigated. The structures of ZnO NRs were synthesized by chemical bath deposition (CBD) method in aqueous solution of N2O6Zn.6H2O and C6H12N4 at 90°C of deposition temperature. One of the ZnO NRs samples was deposited on a ZnO seed layer coated on a glass substrate to investigate the properties of ZnO NRs without receiving effect of other materials. Next, for diode application, the ZnO NRs was deposited on tin monosulfide (SnS) coated on indium-tin-oxide (ITO) coated glass substrate (SnS/ITO). The next, the ZnO structural properties were studied from surface morphology, X-ray diffractometer (XRD) spectra, and chemical composition by using field emission scanning electron microscope (FESEM), XRD and energy dispersive X-ray Spectroscopy (EDX). The growth of ZnO NRs on ZnO seed layer was investigated by ZnO seed layer condition while the growth of ZnO NRs on SnS/ITO was investigated by deposition time and deposition temperature parameters. From FESEM images, aligned ZnO NRs were obtained, and the diameters of ZnO NRs were 0.024-3.94 µm. The SnS thin film was affected by the diameter of ZnO NRs which are the ZnO NRs grow on SnS thin films has a larger diameter compared to ZnO NRs grow on ZnO seed layer. Besides that, all of ZnO peaks observed from XRD corresponding to the wurzite structure and preferentially oriented along the c-axis. In addition, EDX shows a high composition of zinc (Zn) and oxygen (O) signals, which indicated that the NRs are indeed made up of Zn and O.

  7. Postgrowth Microwave Treatment to Align Carbon Nanotubes

    Science.gov (United States)

    2013-03-01

    and 1580 cm1 known as the D and G bands, respectively, which pro- vide a qualitative assessment of the inherent “diamond” and “ graphene ” like bonding...Interface Material for High-Brightness Light-Emit- ting- Diode Cooling,” Nanotechnology, 19, p. 215706. [22] Panzer, M. A., Zhang, G., Mann, D., Hu, X., and

  8. Aligned Carbon Nanotube Tape for Sensor Applications

    Science.gov (United States)

    Tucker, Dennis S.

    2013-01-01

    For this effort, will concentrate on three applications: Vibration Gyroscope utilizes piezoelectric properties of the tape and Coriolis effect Accelerometer utilizes the piezoresistive property Strain Gauge utilizes piezoresistive property Accelerometer and Strain Gauge can also utilize piezoelectric effect Test piezoelectric properties using facilities at the Microfabrication Laboratory (AMRDEC) . Enhance piezoelectric effect using polyvinylidine fluoride and P(VDF ]TrFE) which is readily polarizable .Spray matrix solution while winding fiber; Sandwich of CNT tape and PVDF film (DOE .Two Level) . Construct and test prototype vibration gyroscope . Construct and test prototype accelerometer using cantilever design . Test strain sensitivity of CNT tape against industrial strain gauge . Embed CNT tape in composite samples as well as on surface and test to failure (4 ]point bend) A piezoelectric device exhibits an electrical response from a mechanical applied stress. . A piezoelectric device has both capacitance and resistance properties in which by applying an electric field from a waveform will exert a mechanical stress that can be monitored for a response. . The typical waveform applied is a sinusoidal waveform of a defined voltage for a defined period. The defined voltage is driven from 0 volts to the positive defined volts then back to 0 and driven to negative defined volts then back to 0. . Example. Vmax set to 10V and period set to 10 ms. . Voltage will start at zero, go to 10 volts, return to zero, go to ]10 volts and return to zero during 10 ms. . Applying this electrical field to a DUT, the capacitance response and resistance response can be observed. CNT tape is easier to manufacture and cheaper than micromachining silicon or other ceramic piezoelectric used in gyroscopes and accelerometers CNT tape properties can be modified during manufacture for specific application CNT tape has enhanced mechanical and thermal properties in addition to unique electrical properties CNT tape as a strain gauge in Structural Health Monitoring will provide an excellent material to embed within composite structures

  9. Purification process for vertically aligned carbon nanofibers

    Science.gov (United States)

    Nguyen, Cattien V.; Delziet, Lance; Matthews, Kristopher; Chen, Bin; Meyyappan, M.

    2003-01-01

    Individual, free-standing, vertically aligned multiwall carbon nanotubes or nanofibers are ideal for sensor and electrode applications. Our plasma-enhanced chemical vapor deposition techniques for producing free-standing and vertically aligned carbon nanofibers use catalyst particles at the tip of the fiber. Here we present a simple purification process for the removal of iron catalyst particles at the tip of vertically aligned carbon nanofibers derived by plasma-enhanced chemical vapor deposition. The first step involves thermal oxidation in air, at temperatures of 200-400 degrees C, resulting in the physical swelling of the iron particles from the formation of iron oxide. Subsequently, the complete removal of the iron oxide particles is achieved with diluted acid (12% HCl). The purification process appears to be very efficient at removing all of the iron catalyst particles. Electron microscopy images and Raman spectroscopy data indicate that the purification process does not damage the graphitic structure of the nanotubes.

  10. Beyond Alignment

    DEFF Research Database (Denmark)

    Beyond Alignment: Applying Systems Thinking to Architecting Enterprises is a comprehensive reader about how enterprises can apply systems thinking in their enterprise architecture practice, for business transformation and for strategic execution. The book's contributors find that systems thinking...... is a valuable way of thinking about the viable enterprise and how to architect it....

  11. A carbon nanotube wall membrane for water treatment.

    Science.gov (United States)

    Lee, Byeongho; Baek, Youngbin; Lee, Minwoo; Jeong, Dae Hong; Lee, Hong H; Yoon, Jeyong; Kim, Yong Hyup

    2015-05-14

    Various forms of carbon nanotubes have been utilized in water treatment applications. The unique characteristics of carbon nanotubes, however, have not been fully exploited for such applications. Here we exploit the characteristics and corresponding attributes of carbon nanotubes to develop a millimetre-thick ultrafiltration membrane that can provide a water permeability that approaches 30,000 l m(-2) h(-1) bar(-1), compared with the best water permeability of 2,400 l m(-2) h(-1) bar(-1) reported for carbon nanotube membranes. The developed membrane consists only of vertically aligned carbon nanotube walls that provide 6-nm-wide inner pores and 7-nm-wide outer pores that form between the walls of the carbon nanotubes when the carbon nanotube forest is densified. The experimental results reveal that the permeance increases as the pore size decreases. The carbon nanotube walls of the membrane are observed to impede bacterial adhesion and resist biofilm formation.

  12. Electropolymerization of polyaniline on titanium oxide nanotubes for supercapacitor application

    Energy Technology Data Exchange (ETDEWEB)

    Mujawar, Sarfraj H.; Ambade, Swapnil B.; Battumur, T.; Ambade, Rohan B. [Organic Optoelectronic Materials Laboratory, Division of Semiconductor and Chemical Engineering, Nanomaterials Processing Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Lee, Soo-Hyoung, E-mail: shlee66@chonbuk.ac.k [Organic Optoelectronic Materials Laboratory, Division of Semiconductor and Chemical Engineering, Nanomaterials Processing Research Center, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2011-04-30

    Highlights: {yields} Polyaniline (PANI)-Titanium nanotube template (TNT) composite for supercapacitors. {yields} The mechanism of the controlled growth of hollow open ended PANI nanotubes using a TNT template is studied. {yields} A rare effort to electropolymerise PANI on TNTs resulting into an appreciable capacitance of 740 F g{sup -1}. - Abstract: Vertically aligned polyaniline (PANI) nanotubes have great potential application in supercapacitor electrode material. In this paper we have investigated facile growth of PANI nanotubes on a titanium nanotube template (TNT) using electrochemical polymerization. The morphology of PANI nanostructures grown over TNT is strongly influenced by the scan rate in the electrochemical polymerization. The growth morphology of PANI nanotubes has been carefully analyzed by field emission scanning electron microscopy. The detailed growth mechanism of PANI nanotubes has been put forward. Specific capacitance value of 740 F g{sup -1} was obtained for PANI nanotube structures (measured at charge-discharge rate of 3 A g{sup -1}).

  13. Growth and optical properties of ZnO nanostructures by vapor transport process

    Energy Technology Data Exchange (ETDEWEB)

    Tong, Y.H. [Key Laboratory of Excited State Process, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Graduate School of Chinese Academy of Science, Beijing 100039 (China); Center for Advanced Opto-Electronic Functional Material Research, Northeast Normal University, Changchun 130024 (China); Liu, Y.C. [Center for Advanced Opto-Electronic Functional Material Research, Northeast Normal University, Changchun 130024 (China)]. E-mail: ycliu@nenu.edu.cn; Dong, L. [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450052 (China); Lu, L.X. [School of Science, Hebei University of Technology, Tianjin 300130 (China); Zhao, D.X. [Key Laboratory of Excited State Process, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Zhang, J.Y. [Key Laboratory of Excited State Process, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Lu, Y.M. [Key Laboratory of Excited State Process, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Shen, D.Z. [Key Laboratory of Excited State Process, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China); Fan, X.W. [Key Laboratory of Excited State Process, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033 (China)

    2007-05-15

    ZnO nanorods and ZnO nanotubes have been fabricated by thermally evaporating the metal Zn powder. The ZnO nanorod obtained on the ITO substrate located above the Zn source has the uneven diameter with the abrupt change in its middle, which may originate from the decrease of the Zn vapor in the system. The ZnO nanotubes with the rough surfaces were obtained in the upstream region. The negative thermal quenching of the photoluminescence can be observed in the ZnO nanotubes. This is related with the abundant surface/interface defects which can introduce a large number of middle states in the band gap. According to Shibata's model, the activation energy of the electrons from the middle states to the initial states can be obtained by fitting the experimental data of the temperature dependence of the ultraviolet photoluminescence intensity. The fitting energy values are as high as {approx}100 meV, which may be responsible for the negative thermal quenching in a high-temperature range from 163.5 to 205.6 K.

  14. A Review of the Synthesis and Photoluminescence Properties of Hybrid ZnO and Carbon Nanomaterials

    Directory of Open Access Journals (Sweden)

    Protima Rauwel

    2016-01-01

    Full Text Available Photoluminescent ZnO carbon nanomaterials are an emerging class of nanomaterials with unique optical properties. They each, ZnO and carbon nanomaterials, have an advantage of being nontoxic and environmentally friendly. Their cost-effective production methods along with simple synthesis routes are also of interest. Moreover, ZnO presents photoluminescence emission in the UV and visible region depending on the synthesis routes, shape, size, deep level, and surface defects. When combined with carbon nanomaterials, modification of surface defects in ZnO allows tuning of these photoluminescence properties to produce, for example, white light. Moreover, efficient energy transfer from the ZnO to carbon nanostructures makes them suitable candidates not only in energy harvesting applications but also in biosensors, photodetectors, and low temperature thermal imaging. This work reviews the synthesis and photoluminescence properties of 3 carbon allotropes: carbon quantum or nanodots, graphene, and carbon nanotubes when hybridized with ZnO nanostructures. Various synthesis routes for the hybrid materials with different morphologies of ZnO are presented. Moreover, differences in photoluminescence emission when combining ZnO with each of the three different allotropes are analysed.

  15. Inorganic nanotube nanofluidics

    Science.gov (United States)

    Fan, Rong

    , a positive gate voltage depletes cations (majority) while a negative gate further enhances cation concentration. The resulting device is essentially a p-type ionic transistor. The inherent carrier concentration within nanotubes is determined by surface potentials and charge densities. Therefore, surface modification, which alters surface charges, can change the inherent carrier density and even switch channel polarity. We functionalize the hydroxyl group terminated silica surfaces with aminosilane chemistry, thus modifying the surface charge density and creating ambipolar and n-type nanofluidic transistors. We further employed the Poisson-Boltzmann model to systematically analyze these results. Transient responses upon switching on gate voltages lead us to propose a first kinetic model to explain the field effect modulation in nanofluidic systems. This single nanotube-based nanofluidic device, which has dimensions comparable to the size of biomolecules, represents a new-platform for single molecule detection. lambda-DNA translocations through single nanotubes were stochastically sensed by ionic current changes. The results turned out that both charge effect and geometrical effect play key roles in, single molecule sensing. These high aspect ratio nanotubes provide a novel approach to investigate the conformational evolution from the fine structure of ionic current curves, which is mechanistically different from that for narrow nanopores. The development of microtrench-based fabrication process enables the custom-designed and multiplexed nanotube nanofluidic systems. The anionic dye diffusion was regulated by ionic strength, in agreement with unipolar transport mechanism. A well-aligned mesoporous nanochannel thin film was exploited for sub-10nm nanofluidics. Nanofluidics is attracting increasing attention in bioanalytical technology and biophysics field. MOSolFETs represent the key units for building up large-scale nanofluidic processors and logic circuits. This

  16. Synthesis, Characterization and Photoluminescence of Well-Ordered ZnO Micropillars Grown on ZnO Buffer Layers

    Institute of Scientific and Technical Information of China (English)

    LU Hongbing; TIAN Yu; HU Meifeng; SHUAI Min; LI Jinchai

    2007-01-01

    Using ZnO buffer layers prepared by simply thermaloxidation of ion beam sputtered Zn films, highly oriented anduniformly aligned single-crystalline ZnO micropillars arrays have been synthesized by thermal evaporation of Zn powder with free catalysts at low temperature of 430 ℃. The ZnO micropillars show sharp hexagonal umbrella-like tips with thin ZnO nanowire grown on the tips. The umbrella-like tips grow in a layer-by-layer mode along the direction of [001]. The growth mechanism has been discussed. The formation of the micropillars basically depends on the gradually decreasing Zn vapor pressure and subse-quently cooling process. The photo1luminescence (PL) spectrum indicates a moderately good crystal quality of the ZnO micropillars. Our results may reinforce the understanding of the formation mechanism of different ZnO nano/microstructures. This kind of complex microstructures may find potential applications in multi-functional microdevices, optoelectronic and field emission devices.

  17. Decorating multiwalled carbon nanotubes with zinc oxide nano-crystallines through hydrothermal growth process

    Institute of Scientific and Technical Information of China (English)

    LI ChenSha; QIAO YingJie; LI YuMing

    2012-01-01

    Multiwalled-carbon nanotubes coated with nano-crystalline zinc oxide (ZnO) was prepared by in situ growth of nano zinc oxide on the surfaces of carbon nanotubes through hydrothermal method.X-ray diffraction,transmission electron microscopy and scanning electron microscopy analysis techniques were used to characterize the samples.It was observed that a layer of nano-crystalline ZnO with the wurtzite hexagonal crystal structure was uniformly coated on the nanotube surfaces with good adhesion,which resulted in the formation of a novel ZnO-nanotube nano composite.In this work,the carbon nanotubes decorated by metal oxide nanoparticles were synthesized by a simple chemical-solution route which is suitable for the large-scale production with low cost.

  18. Study on Thermal Interface Material Using Vertically Aligned Carbon Nanotube%定向生长碳纳米管阵列热界面材料技术研究

    Institute of Scientific and Technical Information of China (English)

    马梦颖; 罗斌; 王亭亭; 尚金堂

    2014-01-01

    热界面材料技术是三维系统级封装中的关键技术。文章采用新型定向生长碳纳米管阵列方法制备了热界面材料,并研究了其导热性能。实验结果表明,通过采用50/100/100 nm厚的Ti/Ni/Au金属层和Sn64Bi35Ag1导热焊料,可成功实现碳纳米管阵列的100%转移;通过热释放胶带(Nitto Denko,Part Number:#3198MS)可获得悬浮碳纳米管阵列。文章还通过LFA 447激光导热仪分别测量了热界面材料在25℃、75℃和125℃下的热扩散系数,并计算了其表观热导率,还进行了热循环可靠性测试。结果表明,所选用碳纳米管阵列的表观热导率高于42 W/(m·K),200次热循环后的表观热导率高于41 W/(m·K);转移后的碳纳米管阵列的表观热导率高于28 W/(m·K),200次热循环后仍高于24 W/(m·K)。%Thermal interface material (TIM) technology is of great importance in the 3D system packaging. In this paper, the preparation of thermal interface materials using vertically aligned carbon nanotube (VACNT) array and its characterization were investigated. The transfer process of VACNT was successfully performed by a Ti/Ni/Au metal layer with a thickness of 50/100/100 nm and Sn64Bi35Ag1 solder. A thermal release adhesive tape (Nitto Denko, Part Number:#3198MS) was used to obtain suspended VACNT array. The LFA 447 was used to characterize the thermal diffusivityα(T) and apparent thermal conductivityλ(T) of VACNT array at 25℃, 75℃and 125℃, respectively. Thermal cycle reliability test was also carried out. Results show that the apparentλ(T) is over 42 W/(m·K) for VACNT array on the Si growth substrate and over 41 W/(m·K) for transferred CNT array. After 200 thermal cycles, theλ(T) is over 28 W/(m·K) for CNT array on its Si growth substrate and over 24 W/(m·K) for transferred CNT array.

  19. Propeller-Shaped ZnO Nanostructures Obtained by Chemical Vapor Deposition: Photoluminescence and Photocatalytic Properties

    Directory of Open Access Journals (Sweden)

    S. L. Wang

    2012-01-01

    Full Text Available Propeller-shaped and flower-shaped ZnO nanostructures on Si substrates were prepared by a one-step chemical vapor deposition technique. The propeller-shaped ZnO nanostructure consists of a set of axial nanorod (50 nm in tip, 80 nm in root and 1 μm in length, surrounded by radial-oriented nanoribbons (20–30 nm in thickness and 1.5 μm in length. The morphology of flower-shaped ZnO nanostructure is similar to that of propeller-shaped ZnO, except the shape of leaves. These nanorods leaves (30 nm in diameter and 1–1.5 μm in length are aligned in a radial way and pointed toward a common center. The flower-shaped ZnO nanostructures show sharper and stronger UV emission at 378 nm than the propeller-shaped ZnO, indicating a better crystal quality and fewer structural defects in flower-shaped ZnO. In comparison with flower-shaped ZnO nanostructures, the propeller-shaped ZnO nanostructures exhibited a higher photocatalytic property for the photocatalytic degradation of Rhodamine B under UV-light illumination.

  20. Electrochemical deposition and superhydrophobic behavior of ZnO nanorod arrays

    Energy Technology Data Exchange (ETDEWEB)

    Hsieh, Chien-Te, E-mail: cthsieh@saturn.yzu.edu.t [Department of Chemical Engineering and Materials Science, Yuan Ze Fuel Cell Center, Yuan Ze University, Taoyuan 320, Taiwan (China); Yang, Shu-Ying; Lin, Jia-Yi [Department of Chemical Engineering and Materials Science, Yuan Ze Fuel Cell Center, Yuan Ze University, Taoyuan 320, Taiwan (China)

    2010-06-30

    Vertically aligned ZnO nanorod arrays with different heights are grown on the ZnO seeded indium tin oxide substrate by cathodic electrochemical deposition from zinc nitrate at two temperatures of 60 {sup o}C and 80 {sup o}C. As-grown ZnO nanorods exhibit wurzite crystal structure and their heights can be well controlled by different deposition times. The fluorination coating tends to induce a superhydrophobicity of ZnO nanorods, i.e., the maximal value of contact angle: 166.9{sup o}. The super water repellency can be attributed to the fact that an air layer is confined in the nanorod arrays, and thus leads to water droplets sitting on the ZnO surfaces, referring as Cassie state. Interestingly, their water contact angles are found to vary with the heights of ZnO nanorods, ranged from 99.8 to 746 nm. The superhydrophobicity of ZnO surfaces can be well predicted by a proposed model that is capable of determining the wetted fraction of ZnO pillars. This satisfactory result would shed one light on how the variation of rod height would induce the superhydrophobic behavior of ZnO nanorod arrays.

  1. Optimization of CVD parameters for long ZnO NWs grown on ITO/glass substrate

    Indian Academy of Sciences (India)

    ABDULQADER D FAISAL

    2016-12-01

    The optimization of chemical vapour deposition (CVD) parameters for long and vertically aligned (VA) ZnO nanowires (NWs) were investigated. Typical ZnO NWs as a single crystal grown on indium tin oxide (ITO)-coated glass substrate were successfully synthesized. First, the conducted side of ITO–glass substrate was coated with zinc acetate dihydrate to form seed layer of ZnO nanocrystals. Double zone tube furnace connected to vacuum pump was used for ZnO growth process. Zn metal powder was positioned at the first zone at temperature 900$^{\\circ}$C. The ITO–glass substrate with pre-coated seed layer was then located in the second zone of tube furnace at growth temperature of 550$^{\\circ}$C. The growth of ZnO NWs was controlled under constant concentration of seed layer, while other parameters such as argon and oxygen flow rates, substrate position, time and oxygen flow rate were varied.The VA ZnO NWs were finally characterized by scanning electron microscopy, X-ray diffractometer and high-resolution transmission electron microscope equipped with energy-dispersive X-ray spectroscopy. The results showthat long and VA ZnO NWs were single crystalline with hexagonal wurtzite structure. The ultimate length and average diameter of ZnO NWs were 10 $\\mu$m and 50–100 nm, respectively. These were achieved under optimized CVD growth parameters. The mechanism of vertical growth model of ZnO NWs is also discussed.

  2. Mapping the transition from catalyst-pool to bamboo-like growth-mechanism in vertically-aligned free-standing films of carbon nanotubes filled with Fe3C: The key role of water

    Science.gov (United States)

    Boi, Filippo S.; Wang, Shanling; He, Yi

    2016-08-01

    The control of carbon nanotube growth has challenged researchers for more than a decade due to the complex parameters-control necessary in the commonly used CVD approaches. Here we show that a direct transition from the catalyst-pool growth mechanism characterized by graphene-caps in the direction of growth to a bamboo-shaped mechanism characterized by the repetition of periodic elongated graphitic compartments is present when controlled quantities of water are added to ferrocene/dichlorobenzene. Our results suggest that water-addition allows enhancing the level of stress accumulated under the graphitic nanotubes-cap.

  3. Varied morphology carbon nanotubes and method for their manufacture

    Science.gov (United States)

    Li, Wenzhi; Wen, Jian Guo; Ren, Zhi Feng

    2007-01-02

    The present invention describes the preparation of carbon nanotubes of varied morphology, catalyst materials for their synthesis. The present invention also describes reactor apparatus and methods of optimizing and controlling process parameters for the manufacture carbon nanotubes with pre-determined morphologies in relatively high purity and in high yields. In particular, the present invention provides methods for the preparation of non-aligned carbon nanotubes with controllable morphologies, catalyst materials and methods for their manufacture.

  4. Scattering of terahertz radiation from oriented carbon nanotube films

    DEFF Research Database (Denmark)

    Eichhorn, Finn; Jepsen, Peter Uhd; Schroeder, Nicholas;

    2009-01-01

    Session title: IThC-THz Interactions with Condensed Matter. We report on the use of terahertz time-domain spectroscopy to measure scattering from multi-walled carbon nanotubes aligned normal to the film plane. Measurements indicate scattering from the nanotubes is significantly stronger than...

  5. Carbon nanotubes integrated in electrically insulated channels for lab-on-a-chip applications

    DEFF Research Database (Denmark)

    Mogensen, Klaus Bo; Gangloff, L.; Bøggild, Peter

    2009-01-01

    A fabrication process for monolithic integration of vertically aligned carbon nanotubes in electrically insulated microfluidic channels is presented. A 150 nm thick amorphous silicon layer could be used both for anodic bonding of a glass lid to hermetically seal the microfluidic glass channels an...... column containing vertical aligned carbon nanotubes. This is the first demonstration of electroosmotic pumping and electrokinetic separations in microfluidic channels with a monolithically integrated carbon nanotube forest....

  6. Medium scale carbon nanotube thin film integrated circuits on flexible plastic substrates

    Science.gov (United States)

    Rogers, John A; Cao, Qing; Alam, Muhammad; Pimparkar, Ninad

    2015-02-03

    The present invention provides device components geometries and fabrication strategies for enhancing the electronic performance of electronic devices based on thin films of randomly oriented or partially aligned semiconducting nanotubes. In certain aspects, devices and methods of the present invention incorporate a patterned layer of randomly oriented or partially aligned carbon nanotubes, such as one or more interconnected SWNT networks, providing a semiconductor channel exhibiting improved electronic properties relative to conventional nanotubes-based electronic systems.

  7. Carbon nanotube fiber spun from wetted ribbon

    Science.gov (United States)

    Zhu, Yuntian T; Arendt, Paul; Zhang, Xiefei; Li, Qingwen; Fu, Lei; Zheng, Lianxi

    2014-04-29

    A fiber of carbon nanotubes was prepared by a wet-spinning method involving drawing carbon nanotubes away from a substantially aligned, supported array of carbon nanotubes to form a ribbon, wetting the ribbon with a liquid, and spinning a fiber from the wetted ribbon. The liquid can be a polymer solution and after forming the fiber, the polymer can be cured. The resulting fiber has a higher tensile strength and higher conductivity compared to dry-spun fibers and to wet-spun fibers prepared by other methods.

  8. Enhanced field emission from ZnO nanowire arrays utilizing MgO buffer between seed layer and silicon substrate

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Si [The Key Laboratory for Magnetism and Magnetic Materials of MOE, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Chen, Jiangtao [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, 18 Tianshui Mid. Road, Lanzhou 730000 (China); Liu, Jianlin [Quantum Structures Laboratory, Department of Electrical and Computer Engineering, University of California, Riverside, CA 92521 (United States); Qi, Jing, E-mail: qijing@lzu.edu.cn [The Key Laboratory for Magnetism and Magnetic Materials of MOE, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China); Wang, Yuhua, E-mail: wyh@lzu.edu.cn [Department of Material Science, School of Physical Science and Technology, Lanzhou University, Lanzhou 730000 (China)

    2016-11-30

    Highlights: • We obtained ZnO nanowire arrays grown on ZnO seed layer on Si with MgO buffer. • FE properties of ZnO nanowire arrays grown on ZnO seed layer on Si with MgO buffer is better than that without MgO buffer. • With MgO buffer, the ZnO seed layer shows lower top-bottom resistance and better electron transport. • The enhanced field emission properties can be attributed to good electron transport in seed layer, good nanowire alignment because of MgO buffer. - Abstract: Field emitters based on ZnO nanowires and other nanomaterials are promising high-brightness electron sources for field emission display, microscopy and other applications. The performance of a ZnO nanowire field emitter is linked to the quality, conductivity and alignment of the nanowires on a substrate, therefore requiring ways to improve these parameters. Here, ZnO nanowire arrays were grown on ZnO seed layer on silicon substrate with MgO buffer between the seed layer and Si. The turn-on field and enhancement factor of these nanowire arrays are 3.79 V/μm and 3754, respectively. These properties are improved greatly compared to those of ZnO nanowire arrays grown on ZnO seed layer without MgO buffer, which are 5.06 V/μm and 1697, respectively. The enhanced field emission properties can be attributed to better electron transport in seed layer, and better nanowire alignment because of MgO buffer.

  9. Photoelectrochemical properties of hierarchical ZnO micro-nanostructure sensitized with Sb2S3 nanoparticles

    Directory of Open Access Journals (Sweden)

    Zhimin GUO

    2016-02-01

    Full Text Available By using electrochemical deposition method, and assisted with additions of PEG-400 and EDA, well-aligned ZnO nanorods and hierarchical ZnO micro-nanostructure are fabricated directly on indium doped tin oxide coated conducting glass (ITO substrate. The shell-core Sb2S3/ZnO nanorod structure and the shell-core hierarchical Sb2S3/ZnO micro-nanostructure are prepared by chemical bath deposition method. SEM, XRD, UV-Vis and photocurrent test are used to characterize the morphology, nanostructures and their photoelectrochemical properties. The studies show that the photocurrent on the array membranes with shell-core hierarchical Sb2S3/ZnO micro-nanostructure is apparently higher than that with shell-core Sb2S3/ZnO nanorods array.

  10. Growth of arrays of Al-doped ZnO nanocones by pulsed laser deposition.

    Science.gov (United States)

    Sun, Ye; Addison, Katherine E; Ashfold, Michael N R

    2007-12-12

    Arrays of aligned Al-doped ZnO nanocones have been synthesized by pulsed laser deposition following excimer laser ablation of a ceramic ZnO target containing 2% Al(2)O(3) (by weight). The elemental composition, microstructural and optical properties of the products were examined by laser induced breakdown spectroscopy, electron microscopy, x-ray diffraction and room temperature photoluminescence measurements. The incident laser fluence was identified as a key parameter in nanocone formation. Their tapered morphologies and small tip diameters (approximately 5 nm) suggest that Al-doped ZnO nanocones could find application as field emitters and as a gas sensing material.

  11. Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: Optical and electrochemical properties

    Energy Technology Data Exchange (ETDEWEB)

    Romeiro, Fernanda C.; Marinho, Juliane Z.; Lemos, Samantha C.S. [Instituto de Química, Universidade Federal de Uberlândia, 38400-902 Uberlândia, MG (Brazil); Moura, Ana P. de [LIEC, Instituto de Química, Universidade Estadual Paulista, 14800-900 Araraquara, SP (Brazil); Freire, Poliana G. [Instituto de Química, Universidade Federal de Uberlândia, 38400-902 Uberlândia, MG (Brazil); Silva, Luis F. da; Longo, Elson [LIEC, Instituto de Química, Universidade Estadual Paulista, 14800-900 Araraquara, SP (Brazil); Munoz, Rodrigo A.A. [Instituto de Química, Universidade Federal de Uberlândia, 38400-902 Uberlândia, MG (Brazil); Lima, Renata C., E-mail: rclima@iqufu.ufu.br [Instituto de Química, Universidade Federal de Uberlândia, 38400-902 Uberlândia, MG (Brazil)

    2015-10-15

    We report for the first time a rapid preparation of Zn{sub 1−2x}Co{sub x}Ni{sub x}O nanoparticles via a versatile and environmentally friendly route, microwave-assisted hydrothermal (MAH) method. The Co, Ni co-doped ZnO nanoparticles present an effect on photoluminescence and electrochemical properties, exhibiting excellent electrocatalytic performance compared to undoped ZnO sample. Photoluminescence spectroscopy measurements indicated the reduction of the green–orange–red visible emission region after adding Co and Ni ions, revealing the formation of alternative pathways for the generated recombination. The presence of these metallic ions into ZnO creates different defects, contributing to a local structural disorder, as revealed by Raman spectra. Electrochemical experiments revealed that the electrocatalytic oxidation of dopamine on ZnO attached to multi-walled carbon nanotubes improved significantly in the Co, Ni co-doped ZnO samples when compared to pure ZnO. - Graphical abstract: Rapid synthesis of Co, Ni co-doped ZnO nanoparticles: optical and electrochemical properties. Co, Ni co-doped ZnO hexagonal nanoparticles with optical and electrocatalytic properties were successfully prepared for the first time using a microwave hydrothermal method at mild conditions. - Highlights: • Co{sup 2+} and Ni{sup 2+} into ZnO lattice obtained a mild and environmentally friendly process. • The heating method strongly influences in the growth and shape of the particles. • Short-range defects generated by the ions insertion affects the photoluminescence. • Doped ZnO nanoparticles improve the electrocatalytic properties of pure oxide.

  12. Photovoltaic Performance of ZnO Nanosheets Solar Cell Sensitized with Beta-Substituted Porphyrin

    Directory of Open Access Journals (Sweden)

    Arumugam Mahesh

    2011-01-01

    Full Text Available The photoanode of dye-sensitized solar cell (DSSC was fabricated using two-dimensional ZnO nanosheets (2D ZnO NSs sensitized with beta-substituted porphyrins photosensitizer, and its photovoltaic performance in solid-state DSSC with TiO2 nanotubes (TiO2 TNs modified poly (ethylene oxide (PEO polymer electrolyte was studied. The ZnO NSs were synthesized through hydrothermal method and were characterized through high-resolution scanning electron microscopy (HRSEM, diffused reflectance spectra (DRS, photoluminescence spectra (PL, and X-ray diffraction (XRD analysis. The crystallinity of the polymer electrolytes was investigated using X-ray diffraction analysis. The photovoltaic performance of the beta-substituted porphyrins sensitized solar cells was evaluated under standard AM1.5G simulated illumination (100 mW cm−2. The efficiency of energy conversion from solar to electrical due to 2D ZnO NSs based DSSCs is 0.13%, which is about 1.6 times higher than that of the control DSSC using ZnO nanoparticles (ZnO NPs as photoanode (0.08%, when TiO2 NTs fillers modified PEO electrolyte was incorporated in the DSSCs. The current-voltage (- and photocurrent-time (- curves proved stable with effective collection of electrons, when the 2D ZnO nanostructured photoanode was introduced in the solid-state DSSC.

  13. Density controlled carbon nanotube array electrodes

    Science.gov (United States)

    Ren, Zhifeng F [Newton, MA; Tu, Yi [Belmont, MA

    2008-12-16

    CNT materials comprising aligned carbon nanotubes (CNTs) with pre-determined site densities, catalyst substrate materials for obtaining them and methods for forming aligned CNTs with controllable densities on such catalyst substrate materials are described. The fabrication of films comprising site-density controlled vertically aligned CNT arrays of the invention with variable field emission characteristics, whereby the field emission properties of the films are controlled by independently varying the length of CNTs in the aligned array within the film or by independently varying inter-tubule spacing of the CNTs within the array (site density) are disclosed. The fabrication of microelectrode arrays (MEAs) formed utilizing the carbon nanotube material of the invention is also described.

  14. Vacuum template synthesis of multifunctional nanotubes with tailored nanostructured walls

    Science.gov (United States)

    Filippin, A. Nicolas; Macias-Montero, Manuel; Saghi, Zineb; Idígoras, Jesús; Burdet, Pierre; Barranco, Angel; Midgley, Paul; Anta, Juan A.; Borras, Ana

    2016-02-01

    A three-step vacuum procedure for the fabrication of vertical TiO2 and ZnO nanotubes with three dimensional walls is presented. The method combines physical vapor deposition of small-molecules, plasma enhanced chemical vapor deposition of inorganic functional thin films and layers and a post-annealing process in vacuum in order to remove the organic template. As a result, an ample variety of inorganic nanotubes are made with tunable length, hole dimensions and shapes and tailored wall composition, microstructure, porosity and structure. The fabrication of multishell nanotubes combining different semiconducting oxides and metal nanoparticles is as well explored. This method provides a feasible and reproducible route for the fabrication of high density arrays of vertically alligned nanotubes on processable substrates. The emptying mechanism and microstructure of the nanotubes have been elucidated through SEM, STEM, HAADF-STEM tomography and energy dispersive X-ray spectroscopy. In this article, as a proof of concept, it is presented the straightforward integration of ZnO nanotubes as photoanode in a photovoltaic cell and as a photonic oxygen gas sensor.

  15. Growth of novel ZnO nanostructures by soft chemical routes

    Energy Technology Data Exchange (ETDEWEB)

    Saravana Kumar, R. [PG and Research, Department of Physics, Kongunadu Arts and Science College (Autonomous), Coimbatore 641 029, Tamil Nadu (India); Sathyamoorthy, R., E-mail: rsathya59@gmail.co [PG and Research, Department of Physics, Kongunadu Arts and Science College (Autonomous), Coimbatore 641 029, Tamil Nadu (India); Matheswaran, P. [PG and Research, Department of Physics, Kongunadu Arts and Science College (Autonomous), Coimbatore 641 029, Tamil Nadu (India); Sudhagar, P.; Kang, Yong Soo [Energy Materials Laboratory, WCU Program Department of Energy Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2010-09-10

    Research highlights: Fabrication of diverse ZnO nanostructures through soft chemical routes is both fundamentally interesting and technologically important. Accordingly, in the present work novel ZnO nanostructures namely nanorods/nanospines were grown on glass substrate by integrating SILAR and CBD techniques. This simple approach not only would lead to the development of an effective and commercial growth process for diverse ZnO nanostructures, but also lead to the large-scale preparation of other nanomaterials for many important applications in nanotechnology. - Abstract: We explore a facile route to prepare one-dimensional (1D) ZnO nanostructures including nanorods/nanospines on glass substrates by integrating inexpensive successive ionic layer adsorption and reaction (SILAR) and chemical bath deposition (CBD) methods. The effect of seed layer on the growth and morphology of the ZnO nanostructures was investigated. Accordingly, the surface modification of the seed layer prepared by SILAR was carried out by employing two different drying processes namely (a) allowing the hot substrate to cool for certain period of time before immersing in the ion-exchange bath, and (b) immediate immersion of the hot substrate into the ion-exchange bath. X-ray diffraction (XRD) analysis of the ZnO films revealed hexagonal wurtzite structure with preferential orientation along c-axis, while the scanning electron microscopy (SEM) revealed the dart-like and spherical shaped ZnO seed particles. ZnO nanostructures grown by CBD over the dart-like and spherical shaped ZnO seed particles resulted in the hierarchical and aligned ZnO nanospines/nanorods respectively. Room temperature photoluminescence (PL) study exhibited highly intense UV emission with weak visible emissions in the visible region. The growth mechanism and the role of seed layer morphology on the formation of ZnO nanostructures were discussed.

  16. Stability and electrorheology of ZnO nanofluids in the presence of anionic surfactants

    Science.gov (United States)

    Zaid, Hasnah Mohd; Adil, Muhammad; Chuan, Lee Kean; Latiff, Noor Rasyada Ahmad

    2016-11-01

    In this research, the preparation of stable ZnO nanofluids has been studied by the interaction of unmodified ZnO nanoparticles with anionic surfactant, and the impact of this on the electrorheological properties of nanofluid. Using laboratory experiments including measurement of sedimentation and adsorption of surfactant, the sedimentation behavior of ZnO nanoparticles was evaluated. The results show that the most stable aqueous dispersions of ZnO nanoparticles (calcined at 500 and 800°C) is obtained with the aid of 0.025 wt% sodium dodecylbenzenesulfonate (SDBS), at a fixed concentration of 0.1 wt% ZnO. The ZnO@500/SDBS dispersion exhibits better stability at high temperature of 95°C, with the percentage stability of 56.6% compare to 44.2% of ZnO@800/SDBS dispersion. The stabilized nanofluids were then subjected for measuring of electrorehological behaviour using a rotating viscometer attached to a custom-built solenoid coil. The rheological measurements indicated that all the nanofluids exhibit pseudoplastic (shear thinning) behavior. At a low shear rate, the viscosity of 0.1 wt% ZnO@500/SDBS dispersion provide an enhancement in the viscosity of nanofluid up to 133% compare to brine as a base fluid. Whereas, ZnO@800/SDBS dispersion shows an increment of 183% in its viscosity under electromagnetic waves. This depicts the role of stability in order to achieve an electrorheological effect by activating dielectric ZnO nanoparticles. Further these investigations explained how the polarization of induced dipoles affects the electrorheology of ZnO nanofluids, by creating chains that align with the applied electric field. Hence the mobility of a stabilized nanofluid can be efficiently controlled by regulating the applied field for EOR purposes.

  17. Photoluminescence Characterization of Nanocrystalline ZnO Array

    Institute of Scientific and Technical Information of China (English)

    CHANG Yong-Qin; YU Da-Peng; LI Guo-Hua; FANG Zai-Li; ZHANG Ye; CHEN Yao-Feng; YANG FU-Hua

    2004-01-01

    @@ High-density and uniform well-aligned ZnO sub-micron rods are synthesized on the silicon substrate over a large area. The morphology and structure of the ZnO sub-micron rods are investigated by x-ray diffraction, transmission electron microscopy and Raman spectra. It is found that the ZnO sub-micron rods are of high crystal quality with the diameter in the range of 400-600 nm and the length of several micrometres long. The optical properties were studied by photoluminescence spectra. The results show that the intensity of the ultraviolet emission at 3.3 eV is rather high, meanwhile the deep level transition centred at about 2.38eV is weak. The free exciton emission could also be observed at low temperature, which implies the high optical quality of the ZnO sub-micron rods.This growth technique provides one effective way to fabricate the high crystal quality ZnO nanowires array, which is very important for potential applications in the new-type optoelectronic nanodevices.

  18. {beta}-ray Angular Distribution from Purely Nuclear Spin Aligned {sup 20}Na

    Energy Technology Data Exchange (ETDEWEB)

    Minamisono, K., E-mail: minamiso@nscl.msu.edu [NSCL/MSU (United States); Matsuta, K.; Minamisono, T. [Osaka University, Department of Physics (Japan); Levy, C. D. P. [TRIUMF (Canada); Nagatomo, T.; Ogura, M. [Osaka University, Department of Physics (Japan); Sumikama, T. [RIKEN (Japan); Behr, J. A.; Jackson, K. P. [TRIUMF (Canada); Fujiwara, H.; Mihara, M.; Fukuda, M. [Osaka University, Department of Physics (Japan)

    2004-12-15

    The alignment correlation term in the {beta}-decay angular distribution from purely nuclear spin aligned {sup 20}Na has been measured for the first time. The final objective is to test the G parity symmetry, one of the fundamental symmetry in the weak nucleon current. For artificial creation of the alignment, the knowledge of the hyperfine interaction of {sup 20}Na implanted in a single-crystal ZnO was utilized.

  19. General Route to ZnO Nanorod Arrays on Conducting Substrates via Galvanic-cell-based approach

    Science.gov (United States)

    Zheng, Zhaoke; Lim, Zhi Shiuh; Peng, Yuan; You, Lu; Chen, Lang; Wang, Junling

    2013-08-01

    Wurtzite ZnO nanorod exhibits many unique properties, which make it promising for various optoelectronic applications. To grow well-aligned ZnO nanorod arrays on various substrates, a seed layer is usually required to improve the density and vertical alignment. The reported works about seedless hydrothermal synthesis either require special substrates, or require external electrical field to enhance the ZnO nucleation. Here, we report a general method for the one-pot synthesis of homogenous and well-aligned ZnO nanorods on common conducting substrates without a seed layer. This method, based on the galvanic-cell structure, makes use of the contact potential between different materials as the driving force for ZnO growth. It is applicable to different conducting substrates at low temperature. More importantly, the as-grown ZnO nanorods show enhanced photoelectric response. This unique large scale low-temperature processing method could be of great importance for the application of ZnO nanostructures.

  20. Magnetically aligned polymer-nanowire composites for solar energy harvesting

    Science.gov (United States)