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Sample records for nanotube formed ti-zr

  1. Various sized nanotubes on TiZr for antibacterial surfaces

    NASA Astrophysics Data System (ADS)

    Grigorescu, Sabina; Ungureanu, Camelia; Kirchgeorg, Robin; Schmuki, Patrik; Demetrescu, Ioana

    2013-04-01

    A two-step anodization of a Ti50Zr alloy results in a various sized nanotube oxide structures, which show an improved antibacterial activity. The nanotubes were formed in glycol with 15 vol.% H2O and 0.2 M NH4F by two-step anodization. The oxide layer grown during 2 h was removed by sonication in deionized water and anodized again for 1 h at the same conditions as in the first step. The removed layer acts as a nano-prepatterned surface, where higher ordered and open nanotubes can be achieved. The surface morphologies were analyzed by SEM and AFM, the surface wettability by contact angle measurements. The diameter and the length of the grown nanotubes are potential dependent between 20 and 100 nm in diameter and 2.3 and 5.7 μm in length, respectively. The antibacterial properties were evaluated in vitro on the formed nanotubes on the TiZr alloy against gram negative Escherichia coli bacteria. The E. coli (ATCC 8738) were cultured in a tube containing Luria Bertani medium at 37 °C. The optical density was determined after 18 h of incubation. In comparison, the smallest nanotubes exhibited the most efficient antibacterial behavior against E. coli bacterium. This suggests the use of small diameter nanotubes on TiZr for antimicrobial surface applications, which are susceptible for biofilms and microbial cultures.

  2. Surface Tension and Viscosity of Quasicrystal-Forming Ti-Zr-Ni Alloys

    NASA Technical Reports Server (NTRS)

    Hyers, R. W.; Bradshaw, R. C.; Rogers, J. R.; Rathz, T. J.; Lee, G. W.; Kelton, K. F.; Gangopadhyay, A. K.

    2003-01-01

    The surface tension and viscosity of quasicrystal-forming Ti-Zr-Ni alloys were measured over a range of temperature, including both stable and undercooled liquids by an Electrostatic Levitation (ESL) technique. ESL is a containerless technique which allows processing of samples without contact, greatly reducing contamination and increasing access to the metastable undercooled liquid. The measured viscosity is typical of glass-forming alloys of similar composition to the quasicrystal-forming alloys studied here, while the surface tension shows an anomaly at deep undercoolings.

  3. X-Ray and Electrostatic Levitation Undercooling Studies in Ti-Zr-Ni Quasicrystals Forming Alloys

    NASA Technical Reports Server (NTRS)

    Rogers, J. R.; Hyers, R. W.; Rathz, T. J.; Kelton, K. F.; Gangopadhyay, A. K.; Woo, G. L.; Hannet, L.; Krishnan, S.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    The first undercooling nucleation measurements of electrostatic-levitated droplets of TiZrNi alloys that form the icosahedral quasicrystal phase (i-phase) are presented. The reduced undercooling for crystallization decreases with an increasing polytetrahedral order of the primary solidifying phase, supporting the existence of a developing icosahedral short-range order in the undercooled liquid. X-ray diffraction measurements made at the Advance Photon Source on levitated liquid droplets of these alloys at their liquidus temperatures, however, show no evidence for increased icosahedral order. This suggests that significant ordering only occurs below the melting temperature.

  4. First-principles calculations of single-walled nanotubes in sulfides MS2 (M = Ti, Zr)

    NASA Astrophysics Data System (ADS)

    Evarestov, Robert A.; Bandura, Andrei V.

    2014-04-01

    Hybrid density functional theory has been applied for investigations of the electronic and atomic structure of nanotubes based on titanium and zirconium disulfides. The full optimization of all atomic positions in the considered systems has been performed to study the atomic relaxation and to determine the most favorable nanostructures. Our calculations on single-wall TiS2 and ZrS2 nanotubes confirmed that the nanotubes obtained by rolling of the hexagonal layers of 1T crystalline polymorphs with the octahedral morphology (and with the layer group P\\overline 3 m1) are the most stable. However, it is also possible to obtain the relatively stable nanotubes with lepidocrocite morphology by rolling up layers of the metastable tetragonal or orthorhombic phases. The strain energy of TiS2 is almost the same as that of ZrS2 but it is greater than the strain energy of TiO2 and ZrO2 nanotubes. However, the formation energy of the sulfide nanotubes is considerably less than the formation energy of the oxide nanotubes.

  5. Glass forming ability and thermodynamic properties of Ti(Zr,Hf)NiCu shape memory alloys

    NASA Astrophysics Data System (ADS)

    Pasko, A.; Kolomytsev, V.; Babanly, M.; Sezonenko, A.; Ochin, P.; Portier, R.; Vermaut, Ph.

    2003-10-01

    Rapidly solidified amorphous and crystalline-amorphous ribbons have been produced from a number of quatemary Ti{50+z-x}(Zr,Hf){ x}Ni{50- z-y}Cu{ y} alloys where z =(-5, 0, 5). Structural states were checked by XRD, crystallization behaviour of amorphous phase and martensitic transformations in crystalline material were studied by DSC. The glass transition and crystallization temperatures have been measured at different heating rates, and the crystallization activation energy for each composition and heat event bas been calculated. Isothermal crystallization gives an alternative method of determining the activation energy according to the Arrhenius equation. Contradictory requirements for the conditions of martensitic transformation and good glass forming ability is discussed.

  6. Crystal structure and thermal expansion of the low- and high-temperature forms of BaM{sup IV}(PO{sub 4}){sub 2} compounds (M=Ti, Zr, Hf and Sn)

    SciTech Connect

    Bregiroux, D.; Popa, K.; Jardin, R.; Raison, P.E.; Wallez, G.; Quarton, M.; Brunelli, M.; Ferrero, C.; Caciuffo, R.

    2009-05-15

    The crystal structure of beta-BaZr(PO{sub 4}){sub 2}, archetype of the high-temperature forms of BaM(PO{sub 4}){sub 2} phosphates (with M=Ti, Zr, Hf and Sn), has been solved ab initio by Rietveld analysis from synchrotron X-ray powder diffraction data. The phase transition appears as a topotactic modification of the monoclinic (S.G. C2/m) lamellar alpha-structure into a trigonal one (S.G. P3-barm1) through a simple mechanism involving the unfolding of the [Zr(PO{sub 4}){sub 2}]{sub n}{sup 2-} layers. The thermal expansion is very anisotropic (e.g., -4.1forms, as a consequence of symmetry. It stems from a complex combination of several mechanisms, involving bridging oxygen rocking in M-O-P linkages, and 'bond thermal expansion'. - Graphical abstract: The layered high-temperature form of BaM(PO{sub 4}){sub 2}, only expands along the c-axis.

  7. The Icosahedral Ti-Zr-Ni Quasicrystal - A Ground State Quasicrystal?

    NASA Astrophysics Data System (ADS)

    Hennig, R. G.; Carlsson, A. E.; Kelton, K. F.; Henley, C. L.

    2001-03-01

    The icosahedral Ti-Zr-Ni quasicrystal is known to be thermodynamically stable [1]. Most stable quasicrystals form at high temperatures from the liquid phase. In contrast to those quasicrystals, however, the Ti-Zr-Ni quasicrystal forms at lower temperatures, near 570^circC, by a solid state transformation of crystal phases that are stable at higher temperatures. A decorated canonical cell tiling for the structure of this quasicrystal was determined by a refinement to x-ray and neutron diffraction data and results from ab initio calculations. The energetic stability of the icosahedral Ti-Zr-Ni quasicrystal was investigated by total energy calculations using the density-functional code VASP [2]. The ternary ground state phase diagram for Ti-Zr-Ni was determined. The energy of the structural model of the quasicrystal is found to be lower than the energy of any known competing phase. This result, coupled with the continued stability with long anneals at lower temperatures, strongly suggest that the icosahedral Ti-Zr-Ni quasicrystal is a ground state quasicrystal. [1] K. F. Kelton, W. J. Kim, and R. M. Stroud. Appl. Phys. Let. 70, 3230 (1997). [2] G. Kresse and J. Hafner, Phys. Rev. B47, RC 558 (1993); G. Kresse and J. Furthmüller, Phys. Rev. B54, 11169 (1996).

  8. Superelastic properties of biomedical (Ti-Zr)-Mo-Sn alloys.

    PubMed

    Ijaz, Muhammad Farzik; Kim, Hee Young; Hosoda, Hideki; Miyazaki, Shuichi

    2015-03-01

    A new class of Ti-50Zr base biomedical superelastic alloys was developed in this study. The (Ti-Zr)-Mo-Sn alloys exhibited a shape memory effect and superelastic property by adjusting Mo and Sn contents. The (Ti-Zr)-1.5Mo-3Sn alloy revealed the most stable superelasticity among (Ti-Zr)-(1-2)Mo-(2-4)Sn alloys. The superelastic recovery strain showed a strong dependence on heat treatment temperature after cold working in the (Ti-Zr)-1.5Mo-3Sn alloy. The superelastic recovery strain increased as the heat treatment temperature increased although the critical stress for slip decreased. The (Ti-Zr)-1.5Mo-3Sn alloy heat treated at 1073K exhibited excellent superelastic properties with a large recovery strain as large as 7% which is due to the strong {001}β<110>β recrystallization texture.

  9. Ab initio Ti-Zr-Ni phase diagram predicts stability of icosahedral TiZrNi quasicrystals

    NASA Astrophysics Data System (ADS)

    Hennig, R. G.; Carlsson, A. E.; Kelton, K. F.; Henley, C. L.

    2005-04-01

    The ab initio phase diagram determines the energetic stability of the icosahedral TiZrNi quasicrystal. The complete ab initio zero-temperature ternary phase diagram is constructed from the calculated energies of the elemental, binary and ternary Ti-Zr-Ni phases. For this, the icosahedral i -TiZrNi quasicrystal is approximated by periodic structures of up to 123 atoms/unit cell, based on a decorated-tiling model [R. G. Hennig, K. F. Kelton, A. E. Carlsson, and C. L. Henley, Phys. Rev. B 67, 134202 (2003)]. The approximant structures containing the 45-atom Bergman cluster are nearly degenerate in energy, and are all energetically stable against the competing phases. It is concluded that i -TiZrNi is a ground-state quasicrystal, as it is experimentally the low-temperature phase for its composition.

  10. In vitro biocompatibility response of Ti-Zr-Si thin film metallic glasses

    NASA Astrophysics Data System (ADS)

    Ke, J. L.; Huang, C. H.; Chen, Y. H.; Tsai, W. Y.; Wei, T. Y.; Huang, J. C.

    2014-12-01

    In this study, the bio-electrochemical response of the Ti-Zr-Si thin film metallic glasses (TFMGs) in simulated body fluid with different contents of titanium is measured via potentiostat. According to the results of bio-corrosion potential and current, as well as the polarization resistance, it is concluded that the Ti66Zr25Si9 TFMGs possess the highest bio-electrochemical resistance. With increasing content of titanium, the corrosion resistance becomes progressively higher. The passive current results reveal that amorphous alloys can form a more protective and denser passive film on the metallic glass surface than the crystalline materials. In addition, the mechanical performance of the Ti-Zr-Si TFMGs is better than the crystalline counterparts. As a result, the Ti-based TFMGs are considered to be potential materials for bio-coating applications.

  11. Effect of pulsed bias on the properties of ZrN/TiZrN films deposited by a cathodic vacuum arc

    NASA Astrophysics Data System (ADS)

    Zhang, Guo-Ping; Wang, Xing-Quan; Lü, Guo-Hua; Zhou, Lan; Huang, Jun; Chen, Wei; Yang, Si-Ze

    2013-03-01

    ZrN/TiZrN multilayers are deposited by using the cathodic vacuum arc method with different substrate bias (from 0 to -800 V), using Ti and Zr plasma flows in residual N2 atmosphere, combined with ion bombardment of sample surfaces. The effect of pulsed bias on the structure and properties of films is investigated. Microstructure of the coating is analyzed by X-ray diffraction (XRD), and scanning electron microscopy (SEM). In addition, nanohardness, Young's modulus, and scratch tests are performed. The experimental results show that the films exhibit a nanoscale multilayer structure consisting of TiZrN and ZrN phases. Solid solutions are formed for component TiZrN films. The dominant preferred orientation of TiZrN films is (111) and (220). At a pulsed bias of -200 V, the nanohardness and the adhesion strength of the ZrN/TiZrN multilayer reach a maximum of 38 GPa, and 78 N, respectively. The ZrN/TiZrN multilayer demonstrates an enhanced nanohardness compared with binary TiN and ZrN films deposited under equivalent conditions.

  12. Oligomer functionalized nanotubes and composites formed therewith

    DOEpatents

    Zettl, Alexander K; Sainsbury, Toby; Frechet, Jean M.J.

    2014-03-18

    Disclosed herein is a sequential functionalization methodology for the covalent modification of nanotubes with between one and four repeat units of a polymer. Covalent attachment of oligomer units to the surface of nanotubes results in oligomer units forming an organic sheath around the nanotubes, polymer-functionalized-nanotubes (P-NTs). P-NTs possess chemical functionality identical to that of the functionalizing polymer, and thus provide nanoscale scaffolds which may be readily dispersed within a monomer solution and participate in the polymerization reaction to form a polymer-nanotube/polymer composite. Formation of polymer in the presence of P-NTs leads to a uniform dispersion of nanotubes within the polymer matrix, in contrast to aggregated masses of nanotubes in the case of pristine-NTs. The covalent attachment of oligomeric units to the surface of nanotubes represents the formation of a functional nanoscale building block which can be readily dispersed and integrated within the polymer to form a novel composite material.

  13. Research on the secondary electron yield of TiZrV-Pd thin film coatings

    NASA Astrophysics Data System (ADS)

    Wang, Jie; Wang, Yong; Xu, Yanhui; Zhang, Bo; Wei, Wei

    2016-09-01

    In particle accelerators, the build-up of electron cloud may have important influence on beam quality. Especially for the positron and proton accelerators, massive electrons lead to electron cloud, which affects the stability, energy, emittance and beam life adversely. A secondary electron emission (SEE) measurement system has been designed and used to study the SEE of palladium (Pd), TiZrV and TiZrV-Pd with an independently adjustable energy from 50 eV to 5 keV. Here, we obtained the characteristics of the SEE from Pd, TiZrV and TiZrV-Pd film coatings with different thickness under ultrahigh-vacuum (UHV) conditions. Moreover, the maximum secondary electron yield (SEY), {\\delta}max, of the Pd, TiZrV and TiZrV-Pd film coatings under different primary electron doses were obtained, respectively. Finally, the variation of the secondary electron yield with the incident electron energy will be discussed for Pd, TiZrV and TiZrV-Pd thin film coatings. Low SEY is a new advantage of TiZrV-Pd films, besides high H2 absorption ability and prolonging the lifetime of TiZrV film, which will be of great value in the design of beam screen for Super Proton-Proton Collider (SPPC).

  14. Structural and magnetic properties of TiZrNi thin films prepared by magnetron sputtering and thermal annealing.

    PubMed

    Shin, Hyemin; Choi, Soo-bin; Lee, Ik-jae; Yu, Chung-jong; Kim, Jae-yong

    2010-11-01

    Distinctive thin layers of TiZr and Ni were deposited by using a magnetron sputtering method and a thermal annealing was applied to discover metallic films of quasicrystals. After a heat treatment in vacuum, 70 nm thick deposited layers were well mixed with nominal compositions of 49.7, 29.3 and 21.0 for Ti, Zr and Ni, respectively, which is very close with the one forming a quasicrystalline phase. The magnetization values were significantly decreased from 0.286 to 0.142 emu/mm3 at 2000 Oe, after annealing, while a shape of magnetic hysteresis was maintained. It is believed that a different magnetic behavior after thermal annealing is due to the homogeneous mixing of atomic elements and possible existence of a metastable phase.

  15. Containerless Measurement of Thermophysical Properties of Ti-Zr-Ni Alloys

    NASA Technical Reports Server (NTRS)

    Hyers, Robert; Bradshaw, Richard C.; Rogers, Jan C.; Rathz, Thomas J.; Lee, Geun W.; Gangopadhyay, Anup K.; Kelton, Kenneth F.

    2004-01-01

    The surface tension, viscosity, density, and thermal expansion of Ti-Zr-Ni alloys were measured for a number of compositions by electrostatic levitation methods. Containerless methods greatly reduce heterogeneous nucleation, increasing access to the undercooled liquid regime at finite cooling rates. The density and thermal expansion are measured optically, while the surface tension and viscosity are measured by the oscillating drop method. The measured alloys include compositions which form a metastable quasicrystal phase from the undercooled liquid, and alloys close to the composition of several multi-component bulk metallic glass-forming alloys. Measurements of surface tension show behavior typical of transition metals at high temperature, but a sudden decrease in the deeply undercooled liquid for alloys near the quasicrystal-forming composition range, but not for compositions which form the solid-solution phase first.

  16. Structural refinement of 1/1 bcc approximants to quasicrystals: Bergman-type W(TiZrNi) and Mackay-type M(TiZrFe)

    NASA Astrophysics Data System (ADS)

    Kim, W. J.; Gibbons, P. C.; Kelton, K. F.; Yelon, W. B.

    1998-08-01

    We report the structural refinement of large-unit-cell bcc crystalline phases found in Ti-Zr-Ni and Ti-Zr-Fe alloys, which are 1/1 rational approximants of icosahedral quasicrystals in the same alloys. The structure of the stable 1/1 phase W(TiZrNi), lattice constant ao=14.317 Å, determined by a Rietveld analysis of x-ray and neutron powder diffraction data, is closely related to that of the 1/1 phases R(AlLiCu) and Bergman(AlMgZn), containing Bergman-type icosahedral clusters of atoms. Despite the similar chemistry of the 1/1 phases in Ti-Zr-Ni and Ti-Zr-Fe alloys, the 1/1 phase M(TiZrFe) contains double-shell Mackay icosahedra, like those found in the 1/1 phase α(TiCrSiO). These results provide starting structures for six-dimensional refinements of the related quasicrystals.

  17. Hydrogen absorption and structural analysis of TiZrNiV quasicrystals.

    PubMed

    Lee, Sang-Hwa; Jo, Youngsoo; Kim, Jaeyong

    2014-12-01

    Ti-based quasicrystals are known to store a high capacity of hydrogen exceeding the density of liquid hydrogen. Because TiZrNi quasicrystals contain a large number of tetrahedral sites formed with Ti and Zr atoms that are chemically favorable to hydrogen, these materials retain strong advantages for hydrogen storage applications in structurally and chemically. In fact, TiZrNi quasicrystals are known to absorb hydrogen maximum of the hydrogen to host metal ratio (H/M) value of near 2.0. The critical disadvantage, however, is that the equilibrium vapor pressure of hydrogen is very low (less than 1 Torr). To overcome this engineering drawback, we added a small amount of vanadium (V) in Ti(53-x)Zr27Ni20V(x), alloys (where x = 0 to 15) and rapidly quenched the molten ingots to form quasicrystals, and investigated the effects of V in terms of changes of structure, the H/M values, and an equilibrium vapor pressure of hydrogen. As the results, an equilibrium vapor pressure significantly increased from 0.84 to 2.16 Torr while the maximum H/M value decreased from 1.32 to 1.11 as increasing x = 0 to 8. After hydrogenation, the main peaks shifted evenly to the lower angle of 20 in X-ray diffraction patterns with uniform expansion of the quasilattice constants which demonstrates that hydrogen atoms homogeneously diffused into the samples. A Laves phase starts to form at x = 13 and the samples completely transformed to the phase at x = 15 suggesting the similarity between the quasicrystal and the Laves phase. PMID:25971068

  18. Thermal stability of nanocrystalline (Ti,Zr)0.54Al0.46N films implanted by He+ ions

    NASA Astrophysics Data System (ADS)

    Uglov, V. V.; Abadias, G.; Rovbut, A. Y.; Zlotski, S. V.; Saladukhin, I. A.; Skuratov, V. A.; Petrovich, S.

    2015-07-01

    The influence of irradiation with He+ ions on the thermal stability of TiZrN and (Ti,Zr)0.54Al0.46N nanocrystalline films was studied. The TiZrN and (Ti,Zr)0.54Al0.46N films were prepared by reactive magnetron sputtering. XRD research showed that the TiZrN and (Ti,Zr)0.54Al0.46N films were single-phase systems (based on cubic c-(Ti,Zr)N and cubic c-(Ti,Zr,Al)N solid solutions) with nanocrystalline (grain size 30 and 21 nm, respectively) structure. The irradiation with He+ ions and thermal annealing up to 800 °C do not affect the structure and phase composition of the (Ti,Zr)0.54Al0.46N film. The prior irradiation of the (Ti,Zr)0.54Al0.46N film with He+ ions activates spinodal decomposition of the c-(Ti,Zr,Al)N solid solution after thermal annealing at 1000 °C due to redistribution of the components of the solid solution inside the grains.

  19. Martensite transformation and shape memory effect on NiTi-Zr high temperature shape memory alloys

    SciTech Connect

    Pu, Z.; Tseng, H.; Wu, K.

    1995-10-17

    NiTi-Zr high temperature alloys possess relatively poor shape memory properties and ductility in comparison with NiTi-Hf and NiTi-Pd alloys. During martensite transformation of the newly-developed NiTi-Zr high temperature shape memory alloys (SMAs) the temperature increases along with Zr content when the Zr content is more than 10 at%. As the Zr content increases, the fully reversible strain of the alloys decreases. However, complete strain recovery behavior is exhibited by all the alloys studied in this paper, even those with a Zr content of 20 at%. Stability of the NiTi-Zr alloys during thermal cycling was also tested and results indicate that the NiTi-Zr alloys have poor stability against thermal cycling. The reasons for the deterioration of the shape memory effect and stability have yet to be determined.

  20. Deposition and characterization of TiZrV-Pd thin films by dc magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Wang, Jie; Zhang, Bo; Xu, Yan-Hui; Wei, Wei; Fan, Le; Pei, Xiang-Tao; Hong, Yuan-Zhi; Wang, Yong

    2015-12-01

    TiZrV film is mainly applied in the ultra-high vacuum pipes of storage rings. Thin film coatings of palladium, which are added onto the TiZrV film to increase the service life of nonevaporable getters and enhance H2 pumping speed, were deposited on the inner face of stainless steel pipes by dc magnetron sputtering using argon gas as the sputtering gas. The TiZrV-Pd film properties were investigated by atomic force microscope (AFM), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and X-Ray Diffraction (XRD). The grain size of TiZrV and Pd films were about 0.42-1.3 nm and 8.5-18.25 nm respectively. It was found that the roughness of TiZrV films is small, about 2-4 nm, but for Pd film it is large, about 17-19 nm. The PP At. % of Pd in TiZrV/Pd films varied from 86.84 to 87.56 according to the XPS test results. Supported by National Natural Science Funds of China (11205155) and Fundamental Research Funds for the Central Universities (WK2310000041)

  1. Biomimetic Hydroxyapatite Growth on Functionalized Surfaces of Ti-6Al-4V and Ti-Zr-Nb Alloys.

    PubMed

    Pylypchuk, Ie V; Petranovskaya, A L; Gorbyk, P P; Korduban, A M; Markovsky, P E; Ivasishin, O M

    2015-12-01

    A biomimetic approach for coating titanium-containing alloys with hydroxyapatite (HA) is reported in the article. Two types of Ti-containing alloys were chosen as an object for coating: Ti-6Al-4V (recommended for orthopedic application) and a novel highly biocompatible Ti-Zr-Nb alloy, with good mechanical compatibility due to a modulus that is more close to that of human bones (E ≈ 50 GPa instead of 110 GPa in Ti-6Al-4V). Coating process was carried out in a 10×-concentrated simulated body fluid (SBF)-synthetic analog of human body plasma. The effect of oxidized and carboxylated alloy surface on formation of biomimetic hydroxyapatite has been studied. By XRD, we found influence of thermal conditions on HA crystal formation and size. SEM images and Fourier transform infrared confirmed that hydroxyapatite with different morphology, crystallinity, and Ca/P ratio formed on metallic surfaces. X-ray photoelectron spectroscopy showed that in the Ti-6AL-4V sample the observed Ca/P ratio reach 0.97, whereas in the Ti-Zr-Nb sample the observed Ca/P ratio reach 1.15.

  2. Biomimetic Hydroxyapatite Growth on Functionalized Surfaces of Ti-6Al-4V and Ti-Zr-Nb Alloys

    NASA Astrophysics Data System (ADS)

    Pylypchuk, Ie V.; Petranovskaya, A. L.; Gorbyk, P. P.; Korduban, A. M.; Markovsky, P. E.; Ivasishin, O. M.

    2015-08-01

    A biomimetic approach for coating titanium-containing alloys with hydroxyapatite (HA) is reported in the article. Two types of Ti-containing alloys were chosen as an object for coating: Ti-6Al-4V (recommended for orthopedic application) and a novel highly biocompatible Ti-Zr-Nb alloy, with good mechanical compatibility due to a modulus that is more close to that of human bones (E ≈ 50 GPa instead of 110 GPa in Ti-6Al-4V). Coating process was carried out in a 10×-concentrated simulated body fluid (SBF)—synthetic analog of human body plasma. The effect of oxidized and carboxylated alloy surface on formation of biomimetic hydroxyapatite has been studied. By XRD, we found influence of thermal conditions on HA crystal formation and size. SEM images and Fourier transform infrared confirmed that hydroxyapatite with different morphology, crystallinity, and Ca/P ratio formed on metallic surfaces. X-ray photoelectron spectroscopy showed that in the Ti-6AL-4V sample the observed Ca/P ratio reach 0.97, whereas in the Ti-Zr-Nb sample the observed Ca/P ratio reach 1.15.

  3. Anion Exchange Behavior Of Ti, Zr, Hf, Nb And Ta As Homologues Of Rf And Db In Mixed HF--Acetone Solutions

    SciTech Connect

    Aksenov, N. V.; Bozhikov, G. A.; Starodub, G. Ya.; Dmitriev, S. N.; Filosofov, D. V.; Sun Jin, Jon; Radchenko, V. I.; Lebedev, N. A.; Novgorodov, A. F.

    2010-04-30

    We studied in detail the sorption behavior of Ti, Zr, Hf, Nb and Ta on AG 1 anion exchange resin in HF-acetone mixed solutions as a function of organic cosolvent and acid concentrations. Anion exchange behavior was found to be strongly acetone concentration dependent. The distribution coefficients of Ti, Zr, Hf and Nb increased and those of Ta decreased with increasing content of acetone in HF solutions. With increasing HF concentration anion exchange equilibrium analysis indicated the formation of fluoride complexes of group 4 elements with charge-3 and Ta---2. For Nb the slope of-2 increased up to-5. Optimal conditions for separation of the elements using AIX chromatography were found. Group 4 elements formed MF{sub 7}{sup 3-} (M = Ti, Zr, Hf) complexes whose sorption decreased Ti>Hf>Zr in reverse order of complex stability. This fact is of particular interest for studying ion exchange behavior of Rf compared to Ti. The advantages of studying chemical properties of Rf and Db in aqueous HF solutions mixed with organic solvents are briefly discussed.

  4. Local structure of equilibrium and supercooled Ti-Zr-Ni liquids

    SciTech Connect

    Lee, G. W.; Gangopadhyay, A.; Hyers, R.; Rathz, T.; Rogers, J.; Robinson, D.; Goldman, A.; Kelton, K.

    2008-05-01

    Recently, we reported the results of experimental in situ high-energy x-ray diffraction studies of electrostatically levitated equilibrium and supercooled metallic elements and alloy liquids, showing evidence for icosahedral short-range ordering (ISRO). In this paper, these studies are extended to binary Ti-Zr and ternary Ti-Zr-Ni alloys. From a cluster-based analysis of the x-ray structure factors, it is concluded that ISRO in the binary alloys becomes progressively more dominant, and the coherence length of the order becomes longer, with the addition of Ni, especially near the concentration of 21 at. % Ni. The effect of chemical interactions among Ti/Zr-Ni and the atomic size on the stabilization of the ISRO is discussed.

  5. Mechanocapillary forming of carbon nanotube microstructures

    NASA Astrophysics Data System (ADS)

    Hart, A. John

    2012-02-01

    The hierarchical structure and organization of filaments within both natural and synthetic materials can determine a wide variety of collective chemical and physical functionalities. Carbon nanotubes (CNTs) are known for their record properties, and densely packed CNTs are therefore expected to enable new materials having outstanding multifunctional performance. However, it remains a significant challenge to build highly ordered assembles of CNTs, and this challenge has largely limited the design and properties of macroscale CNT yarns and sheets, and CNT-based surfaces and interfaces. We have created a versatile technique called capillary forming to manipulate patterned vertically aligned (VA-) CNTs into diverse 3D microarchitectures, and to enable their integration in applications ranging from microsystems to macroscale functional films. Capillary forming relies on shape-directed capillary rise during solvent condensation, followed by evaporation-induced shrinkage. Three-dimensional transformations result from shrinkage of the vapor-liquid-solid interface and the resulting heterogeneous strain distribution in the microstructures. A portfolio of microscale CNT assemblies with highly ordered internal structure and freeform geometries including straight, bent, folded and helical profiles, are fabricated using capillary forming. The mechanical stiffness and electrical conductivity of capillary formed CNT micropillars are 5 GPa and 10^4 S/m respectively. These values are at least hundred-fold higher than as-grown CNT forests and exceed the properties of typical microfabrication polymers. Finally, the potential applications of these structures are demonstrates as vertical microsprings with geometrically tunable compliance, and hydrogel-driven microtransducers.

  6. A Liquid-Liquid Transition in an Undercooled Ti-Zr-Ni Liquid

    NASA Technical Reports Server (NTRS)

    Lee, G. W.; Gangopadhyay, A. K.; Kelton, K. F.; Hyers, R. W.; Rathz, T. J.; Rogers, J. R.

    2003-01-01

    If crystallization can be avoided, liquids enter a metastable (undercooled) state below their equilibrium liquidus temperatures, TI, finally freezing into a glass below a characteristic temperature called the glass transition temperature, T,. In rare cases, the undercooled liquid may undergo a liquid-liquid phase transition (liquid polymorphism) before entering the glassy state. This has been suggested from experimental studies of HzO and Si4. Such phase transitions have been predicted in some stable liquids, i.e. above TI at atmospheric pressure, for Si02 and BeF;, but these have not been verified experimentally. They have been observed in liquids of P7, Sis and C9, but only under high pressure. All of these transitions are driven by an anomalous density change, i.e. change in local structure, with temperature or pressure. In this letter we present the first experimental evidence for a phase transition in a low viscosity liquid that is not driven by an anomalous density change, but by an approach to a constant configuration state. A maximum in the specific heat at constant pressure, similar to what is normally observed near T,, is reported here for undercooled low viscosity liquids of quasicrystal- forming Ti-Zr-Ni alloys. that includes cooperativity, by incorporating a temperature dependent excitation energy fits the data well, signaling a phase transition.

  7. Thermal stability of nanostructured TiZrSiN thin films subjected to helium ion irradiation

    NASA Astrophysics Data System (ADS)

    Uglov, V. V.; Abadias, G.; Zlotski, S. V.; Saladukhin, I. A.; Skuratov, V. A.; Leshkevich, S. S.; Petrovich, S.

    2015-07-01

    The phase stability, upon vacuum annealing up to 1000 °C, of nanostructured (Ti,Zr)1-xSixN thin films is investigated by X-ray diffraction analysis as a function of Si content (0.13 ⩽ x ⩽ 0.25) and prior irradiation with He ions (40 kV). The quaternary TiZrSiN thin films were deposited by reactive magnetron sputtering from elemental targets at the substrate temperature of 600 °C. It was found that the increase in Si content, x, results in the transformation of structure from nanocrystalline (x = 0.13, grain size of 11 nm) to nanocomposite state (0.19 < x ⩽ 0.25, grain size of 5 nm). The phase composition of the films changes from single-phase, cubic c-(Ti,Zr)N columns with (1 1 1) preferred orientation to dual-phase system consisting of c-(Ti,Zr)N crystallites and amorphous SiNy. Irradiation with He ions at the doses of 2 × 1016 and 5 × 1016 cm-2 does change the phase composition of the films. It is found that the onset temperature for phase decomposition decreases from 1000 °C to 800 °C with increasing Si content for unirradiated films. The formation of a secondary ZrN phase is observed concomitantly with increased broadening of the (2 0 0) c-(Ti,Zr)N diffraction peak. For irradiated films, the subsequent annealing at 1000 °C leads to decomposition of the c-(Ti,Zr)N solid solution into TiN- and ZrN-rich phases as well as crystallization of hexagonal Si3N4 phase.

  8. Characterization of multi-principal-element (TiZrNbHfTa)N and (TiZrNbHfTa)C coatings for biomedical applications.

    PubMed

    Braic, V; Balaceanu, M; Braic, M; Vladescu, A; Panseri, S; Russo, A

    2012-06-01

    Multi-principal-element (TiZrNbHfTa)N and (TiZrNbHfTa)C coatings were deposited on Ti6Al4V alloy by co-sputtering of Ti, Zr, Nb, Hf and Ta metallic targets in reactive atmosphere. The coatings were analyzed for elemental and phase compositions, crystalline structure, morphology, residual stress, hardness, friction performance, wear-corrosion resistance and cell viability. For all the films, only simple fcc solid solutions with (111) preferred orientations were found, with crystallite sizes in the range 7.2-13.5 nm. The coatings were subjected to compressive stress, with values ranging from 0.8 to 1.6 GPa. The carbide coating with the highest carbon content (carbon/metal ≈1.3) exhibited the highest hardness of about 31 GPa, the best friction behavior (μ = 0.12) and the highest wear resistance (wear rate K=0.2×10(-6)mm(3)N(-1)m(-1)), when testing in simulated body fluids (SBFs). Cell viability tests proved that the osteoblast cells were adherent to the coated substrates, and a very high percentage of live cells were observed on sample surfaces, after 72 h incubation time.

  9. Modified carbon nanotubes and methods of forming carbon nanotubes

    DOEpatents

    Heintz, Amy M.; Risser, Steven; Elhard, Joel D.; Moore, Bryon P.; Liu, Tao; Vijayendran, Bhima R.

    2016-06-14

    In this invention, processes which can be used to achieve stable doped carbon nanotubes are disclosed. Preferred CNT structures and morphologies for achieving maximum doping effects are also described. Dopant formulations and methods for achieving doping of a broad distribution of tube types are also described.

  10. Microstructure and corrosion resistance of nanocrystalline TiZrN films on AISI 304 stainless steel substrate

    SciTech Connect

    Lin, Yu-Wei; Huang, Jia-Hong; Yu, Ge-Ping

    2010-07-15

    This study investigated the microstructure and properties of nanocrystalline TiZrN films on AISI 304 stainless steel substrate. TiZrN films were prepared by reactive magnetron sputtering based on the previous optimum coating conditions (substrate temperature, system pressure, nitrogen flow, etc.) for TiN and ZrN thin films. The composition ratio of TiZrN coatings were adjusted by changing the Zr target power, while keeping the Ti target power constant. Experiments were conduced to find the optimum composition with desired properties. The ratio of TiZrN composition was analyzed by x-ray photoelectron spectroscopy and Rutherford backscattering spectrometer. In terms of phase formation, there were two types of coatings that were considered: single-phase solid solutions of TiZrN and interlacing nuclei of TiZr in the matrix of TiZrN. The thickness of all TiZrN films as measured by the secondary ion mass spectroscopy was about 500 nm, and the composition depth profiles indicated that the compositions in the TiZrN films were uniform from the film surface to the 304 stainless steel substrate. The crystal structure of the TiZrN films was determined by x-ray diffraction using a M18XHF-SRA diffractometer with Cu K{sub {alpha}} radiation. A diffraction peak of TiZrN (002) was observed between that of TiN (002) and ZrN (002); similarly, a diffraction peak of TiZrN (111) was observed between that of TiN(111) and ZrN(111), respectively. The corrosion resistance of the TiZrN film deposited on the 304 stainless steel has been investigated by electrochemical measurement. The electrolyte, 0.5M H{sub 2}SO{sub 4} containing 0.05M KSCN, was used for the potentiodynamic polarization. The potentiodynamic scan was conducted from -800 to 800 mV standard calomel electrode (SCE).

  11. A Novel Liquid-Liquid Transition in Undercooled Ti-Zr-Ni Liquids

    NASA Technical Reports Server (NTRS)

    Lee, G. W.; Gangopadhyay, A. K.; Kelton, K. F.; Bradshaw, R. C.; Hyers, R. W.; Rathz, T. J.; Rogers, J. R.

    2004-01-01

    If crystallization can be avoided, liquids enter a metastable (undercooled) state below their equilibrium liquidus temperatures, T(sub l), finally 'freezing' into a glass below a characteristic temperature called the glass transition temperature, T(sub g). In rare cases, the undercooled liquid may undergo a liquid-liquid phase transition (liquid polymorphism) before entering the glassy state. This has been suggested from experimental studies of H2O and Si. Such phase transitions have been predicted in some stable liquids, ie. above T(sub l) at atmospheric pressure, for SiO2 and BeF2, but these have not been verified experimentally. They have been observed in liquids of P, Si and C, but only under high pressure. In this letter we present the first experimental evidence for a phase transition in a low viscosity metallic liquid that is driven by an approach to a constant entropy configuration state and correlated with a growing icosahedral order in the liquid. A maximum in the specific heat at constant pressure, similar to what is normally observed near T(sub g), is reported for undercooled liquids of quasicrystal-forming Ti-Zr-Ni alloys. A two-state excitation model that includes cooperativity by incorporating a temperature-dependent excitation energy, fits the specific heat data well, signaling a phase transition. An inflection in the liquid density with decreasing temperature instead of a discontinuity indicates that this is not a typical first order phase transition; it could be a weakly first order or higher order transition. While showing many similarities to a glass transition, this liquid-liquid phase transition occurs in a mobile liquid, making it novel.

  12. Forming transmembrane channels using end-functionalized nanotubes

    NASA Astrophysics Data System (ADS)

    Dutt, Meenakshi; Kuksenok, Olga; Little, Steven R.; Balazs, Anna C.

    2011-01-01

    Using dissipative particle dynamics (DPD) simulations, we examine the interaction between amphiphilic nanotubes and lipid bilayer membranes. The nanotubes are represented by a hydrophobic shaft that is end-functionalized with hydrophilic groups. Nanotubes that are capped by a monolayer of hydrophilic beads or also encompass hydrophilic ``hairs'' on just one end of the shaft are found to spontaneously penetrate and assume a transmembrane position; the process, however, depends critically on the membrane tension. On the other hand, nanotubes that include hydrophilic hairs at both ends of the hydrophobic shaft are not observed to spontaneously self-organize into the bilayer. When the membrane is stretched to form a pore, the nanotubes with two hairy ends adsorb on the edge of the pore and become localized in the membrane, thus forming a transmembrane channel. The findings from these studies provide guidelines for creating biomimetic nanotube channels that are capable of selectively transporting molecules through the membrane in response to changes in the local environment.

  13. Structure and mechanical properties of Ni-Cu-Ti-Zr composite materials with amorphous phase

    NASA Astrophysics Data System (ADS)

    Churyumov, A. Yu.; Bazlov, A. I.; Solonin, A. N.; Zadorozhnyi, V. Yu.; Xie, G. Q.; Li, S.; Louzguine-Luzgin, D. V.

    2013-09-01

    The structure of specimens of Ni-Cu-Ti-Zr alloys with an amorphous phase has been examined by X-ray diffraction, as well as by transmission and scanning electron microscopy. Mechanical characteristics of the alloys have been determined using universal testing machines. Transformation-induced plasticity has been found to exist. The specimens demonstrate a good combination of strength and plasticity owing to both the composite effect of a heterophase structure and the dynamic martensitic transformation that develops during deformation.

  14. Multiwalled nanotubes formed by catanionic mixtures of drug amphiphiles.

    PubMed

    Lin, Yi-An; Cheetham, Andrew G; Zhang, Pengcheng; Ou, Yu-Chuan; Li, Yuguo; Liu, Guanshu; Hermida-Merino, Daniel; Hamley, Ian W; Cui, Honggang

    2014-12-23

    Mixing of oppositely charged amphiphilic molecules (catanionic mixing) offers an attractive strategy to produce morphologies different from those formed by individual molecules. We report here on the use of catanionic mixing of anticancer drug amphiphiles to construct multiwalled nanotubes containing a fixed and high drug loading. We found that the molecular mixing ratio, the solvent composition, the overall drug concentrations, as well as the molecular design of the studied amphiphiles are all important experimental parameters contributing to the tubular morphology. We believe these results demonstrate the remarkable potential that anticancer drugs could offer to self-assemble into discrete nanostructures and also provide important insight into the formation mechanism of nanotubes by catanionic mixtures. Our preliminary animal studies reveal that the CPT nanotubes show significantly prolonged retention time in the tumor site after intratumoral injection.

  15. Multiwalled Nanotubes Formed by Catanionic Mixtures of Drug Amphiphiles

    PubMed Central

    2015-01-01

    Mixing of oppositely charged amphiphilic molecules (catanionic mixing) offers an attractive strategy to produce morphologies different from those formed by individual molecules. We report here on the use of catanionic mixing of anticancer drug amphiphiles to construct multiwalled nanotubes containing a fixed and high drug loading. We found that the molecular mixing ratio, the solvent composition, the overall drug concentrations, as well as the molecular design of the studied amphiphiles are all important experimental parameters contributing to the tubular morphology. We believe these results demonstrate the remarkable potential that anticancer drugs could offer to self-assemble into discrete nanostructures and also provide important insight into the formation mechanism of nanotubes by catanionic mixtures. Our preliminary animal studies reveal that the CPT nanotubes show significantly prolonged retention time in the tumor site after intratumoral injection. PMID:25415538

  16. Electron dominated thermoelectric response in MNiSn (M: Ti, Zr, Hf) half-Heusler alloys.

    PubMed

    Gandi, Appala Naidu; Schwingenschlögl, Udo

    2016-05-18

    We solve the transport equations of the electrons and phonons to understand the thermoelectric behaviour of the technologically important half-Heusler alloys MNiSn (M: Ti, Zr, Hf). Doping is simulated within the rigid band approximation. We clarify the origin of the electron dominated thermoelectric response and determine the carrier concentrations with maximal figures of merit. The phonon mean free path is studied to calculate the grain size below which grain refinement methods can enforce ballistic heat conduction to enhance the figure of merit.

  17. Electron dominated thermoelectric response in MNiSn (M: Ti, Zr, Hf) half-Heusler alloys.

    PubMed

    Gandi, Appala Naidu; Schwingenschlögl, Udo

    2016-05-18

    We solve the transport equations of the electrons and phonons to understand the thermoelectric behaviour of the technologically important half-Heusler alloys MNiSn (M: Ti, Zr, Hf). Doping is simulated within the rigid band approximation. We clarify the origin of the electron dominated thermoelectric response and determine the carrier concentrations with maximal figures of merit. The phonon mean free path is studied to calculate the grain size below which grain refinement methods can enforce ballistic heat conduction to enhance the figure of merit. PMID:27156360

  18. Surface morphology of nanotube formed Ti alloy by electrochemical methods.

    PubMed

    Kim, Sung-Hwan; Choe, Han-Cheol

    2014-11-01

    In order to investigate the surface morphology of nanotube formed Ti alloy by electrochemical methods, the Ti-6Al-4V alloys for dental implant were used in this study. Heat treatment was carried out at 800 degrees C for 1 hour and then water quenching in argon atmosphere, that will be have a specimen name of 800 WQ. The formation of nanotube structure was conducted by electrochemical method on Ti-6Al-4V alloy in mixed electrolytes at 30 V for 1 hour. Microstructure of β phases showed dot-like structures at non-treated Ti-6Al-4V alloy, and needle-like in equiaxed structure from treated the alloy at 800 WQ. In non-treated Ti-6Al-4V alloy case, nanotubes only exhibited at α phase region with dissolved V-oxide area of β phase. However, in the case of 800 WQ, nanotubes of Ti-6Al-4V alloy exhibited at both α and βphase region. Electrochemical corrosion studies showed that the nanotubular alloy of 800 WQ possesses slightly higher corrosion resistance than that of non-treated nanotubular alloy. PMID:25958530

  19. Stable and robust nanotubes formed from self-assembled polymer membranes

    NASA Astrophysics Data System (ADS)

    Helmerson, Kristian; Reiner, Joseph E.; Kishore, Rani B.; Jofre, Ana; Allegrini, Maria; Pfefferkorn, Candace; Wells, Jeffrey M.

    2006-08-01

    We create long polymer nanotubes by directly pulling on the membrane of polymersomes using either optical tweezers or a micropipette. The polymersomes are composed of amphiphilic diblock copolymers and the nanotubes formed have an aqueous core connected to the aqueous interior of the polymersome. We stabilize the pulled nanotubes by subsequent chemical cross-linking. The cross-linked nanotubes are extremely robust and can be moved to another medium for use elsewhere. We demonstrate the ability to form networks of polymer nanotubes and polymersomes by optical manipulation. The aqueous core of the polymer nanotubes together with their robust character makes them interesting candidates for nanofluidics and other applications in biotechnology.

  20. Functionalization of nitrogen-doped carbon nanotubes with gallium to form Ga-CNx-multi-wall carbon nanotube hybrid materials

    NASA Astrophysics Data System (ADS)

    Simmons, Trevor J.; Hashim, Daniel P.; Zhan, Xiaobo; Bravo-Sanchez, Mariela; Hahm, Myung Gwan; López-Luna, Edgar; Linhardt, Robert J.; Ajayan, Pulickel M.; Navarro-Contreras, Hugo; Vidal, Miguel A.

    2012-08-01

    In an effort to combine group III-V semiconductors with carbon nanotubes, a simple solution-based technique for gallium functionalization of nitrogen-doped multi-wall carbon nanotubes has been developed. With an aqueous solution of a gallium salt (GaI3), it was possible to form covalent bonds between the Ga3+ ion and the nitrogen atoms of the doped carbon nanotubes to form a gallium nitride-carbon nanotube hybrid at room temperature. This functionalization was evaluated by x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy

  1. Matrix Infrared Spectra and Quantum Chemical Calculations of Ti, Zr, and Hf Dihydride Phosphinidene and Arsinidene Molecules.

    PubMed

    Andrews, Lester; Cho, Han-Gook

    2016-09-01

    Laser ablated Ti, Zr, and Hf atoms react with phosphine during condensation in excess argon or neon at 4 K to form metal hydride insertion phosphides (H2P-MH) and metal dihydride phosphinidenes (HP═MH2) with metal phosphorus double bonds, which are characterized by their intense metal-hydride stretching frequencies. Both products are formed spontaneously on annealing the solid matrix samples, which suggests that both products are relaxed from the initial higher energy M-PH3 intermediate complex, which is not observed. B3LYP (DFT) calculations show that these phosphinidenes are strongly agostic with acute H-P═M angles in the 60° range, even smaller than those for the analogous methylidenes (carbenes) (CH2═MH2) and in contrast to the almost linear H-N═Ti subunit in the imines (H-N═TiH2). Comparison of calculated agostic and terminal bond lengths and covalent bond radii for HP═TiH2 with computed bond lengths for Al2H6 finds that these strong agostic Ti-H bonds are 18% longer than single covalent bonds, and the bridged bonds in dialane are 10% longer than the terminal Al-H single bonds, which show that these agostic bonds can also be considered as bridged bonds. The analogous arsinidenes (HAs═MH2) have 4° smaller agostic angles and almost the same metal-hydride stretching frequencies and double bond orders. Calculations with fixed H-P-Ti and H-As-Ti angles (170.0°) and Cs symmetry find that electronic energies increased by 36 and 44 kJ/mol, respectively, which provide estimates for the agostic/bridged bonding energies.

  2. Matrix Infrared Spectra and Quantum Chemical Calculations of Ti, Zr, and Hf Dihydride Phosphinidene and Arsinidene Molecules.

    PubMed

    Andrews, Lester; Cho, Han-Gook

    2016-09-01

    Laser ablated Ti, Zr, and Hf atoms react with phosphine during condensation in excess argon or neon at 4 K to form metal hydride insertion phosphides (H2P-MH) and metal dihydride phosphinidenes (HP═MH2) with metal phosphorus double bonds, which are characterized by their intense metal-hydride stretching frequencies. Both products are formed spontaneously on annealing the solid matrix samples, which suggests that both products are relaxed from the initial higher energy M-PH3 intermediate complex, which is not observed. B3LYP (DFT) calculations show that these phosphinidenes are strongly agostic with acute H-P═M angles in the 60° range, even smaller than those for the analogous methylidenes (carbenes) (CH2═MH2) and in contrast to the almost linear H-N═Ti subunit in the imines (H-N═TiH2). Comparison of calculated agostic and terminal bond lengths and covalent bond radii for HP═TiH2 with computed bond lengths for Al2H6 finds that these strong agostic Ti-H bonds are 18% longer than single covalent bonds, and the bridged bonds in dialane are 10% longer than the terminal Al-H single bonds, which show that these agostic bonds can also be considered as bridged bonds. The analogous arsinidenes (HAs═MH2) have 4° smaller agostic angles and almost the same metal-hydride stretching frequencies and double bond orders. Calculations with fixed H-P-Ti and H-As-Ti angles (170.0°) and Cs symmetry find that electronic energies increased by 36 and 44 kJ/mol, respectively, which provide estimates for the agostic/bridged bonding energies. PMID:27558006

  3. Continuous production of granular or powder Ti, Zr and Hf or their alloy products

    DOEpatents

    White, Jack C.; Oden, Laurance L.

    1993-01-01

    A continuous process for producing a granular metal selected from the group consisting of Ti, Zr or Hf under conditions that provide orderly growth of the metal free of halide inclusions comprising: a) dissolving a reducing metal selected from the group consisting of Na, Mg, Li or K in their respective halide salts to produce a reducing molten salt stream; b) preparing a second molten salt stream containing the halide salt of Ti, Zr or Hf; c) mixing and reacting the two molten streams of steps a) and b) in a continuous stirred tank reactor; d) wherein steps a) through c) are conducted at a temperature range of from about 800.degree. C. to about 1100.degree. C. so that a weight percent of equilibrium solubility of the reducing metal in its respective halide salt varies from about 1.6 weight percent at about 900.degree. C. to about 14.4 weight percent at about 1062.degree. C.; and wherein a range of concentration of the halide salt of Ti, Zn or Hf in molten halides of Na, Mg, Li or K is from about 1 to about 5 times the concentration of Na, Mg, Li or K; e) placing the reacted molten stream from step c) in a solid-liquid separator to recover an impure granular metal product by decantation, centrifugation, or filtration; and f) removing residual halide salt impurity by vacuum evaporator or inert gas sweep at temperatures from about 850.degree. C. to 1000.degree. C. or cooling the impure granular metal product to ambient temperature and water leaching off the residual metal halide salt.

  4. Deposition And Characterization of (Ti,Zr)N Thin Films Grown Through PAPVD By The Pulsed Arc Technique

    SciTech Connect

    Marulanda, D. M.; Trujillo, O.; Devia, A.

    2006-12-04

    The Plasma Assisted Physic Vapor Deposition (PAPVD) by the pulsed arc technique has been used for deposition of Titanium Zirconium Nitride (Ti,Zr)N coatings, using a segmented target of TiZr. The deposition was performed in a vacuum chamber with two faced electrodes (target and substrate) using nitrogen as working gas, and a power-controlled source used to produce the arc discharges. Films were deposited on stainless steel 304, and they were characterized using the X-Ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD), Energy Dispersion Spectroscopy (EDS) and Scanning Probe Microscopy (SPM) techniques. The XRD patterns show different planes in which the film grows. Through SPM, using Atomic Force Microscopy (AFM) and Lateral Force Microscopy (LFM) modes, a nanotribologic study of the thin film was made, determining hardness and friction coefficient.

  5. Studies of thin films of Ti- Zr -V as non-evaporable getter films prepared by RF sputtering

    SciTech Connect

    Gupta, Nidhi; Jagannath,; Sharma, R. K.; Gadkari, S. C.; Muthe, K. P.; Mukundhan, R.; Gupta, S. K.

    2013-02-05

    Non-Evaporable Getter (NEG) films of the Ti-Zr-V prepared on stainless steel substrates by Radio Frequency sputtering. To observe its getter behavior at the lowest activation temperature, the sample is heated continuously at different temperatures (100 Degree-Sign C, 150 Degree-Sign C, 200 Degree-Sign C and 250 Degree-Sign C) for 2 hours. The changes of the surface chemical composition at different temperaturesare analyzed by using XPS and SEM (Scanning Electron Microscopy) techniques. The volume elemental composition of the film has been measured by energy dispersive X-ray spectroscopy (EDX). The in-situ XPS measurements of the activated getter films show the disappearance of the superficial oxide layer through the variation in the oxygen stoichiometry during thermal activation. Results of these studies show that the deposited films of Ti-Zr-V could be used as NEG to produce extreme high vacuum.

  6. Atomic study of fracture progress of Fe[110]/TMC[100] (TM = Ti, Zr and Hf) semi-coherent interfaces

    NASA Astrophysics Data System (ADS)

    Li, Jinchun; Song, Hongquan; Qian, Ping; Shen, Jiang

    2014-09-01

    Using first-principle calculation in combination with the Chen-Möbius inversion method, we get the interfacial potentials of the Fe[110]/TMC[100] (TM = Ti, Zr and Hf) interface system. Based on the interfacial potentials, we investigate the interfacial stability, misfit dislocations and tensile fracture of the semi-coherent interfaces of Fe[110]/TMC[100] (TM = Ti, Zr and Hf). The different sizes of the misfit dislocation models are employed to compare the interfacial energy. Results indicate that Fe[110]/HfC[100] interface is more stable than Fe[110]/TMC[100] (TM = Ti and Zr). The analysis of different tensile fracture processes shows that the misfit dislocations play an important role in the fractures of interfaces between iron and transitional metal carbides.

  7. New insights into the initial stages of Ta oxide nanotube formation on polycrystalline Ta electrodes.

    PubMed

    El-Sayed, Hany A; Horwood, Corie A; Abhayawardhana, Anusha D; Birss, Viola I

    2013-02-21

    Ta oxide nanotubes (NTs) were formed by the anodization of Ta at 15 V in a solution of concentrated sulfuric acid containing 0.8-1.0 M hydrofluoric acid. To study the initial stages of NT formation, FESEM images of samples anodized for very short times were obtained. The results contradict the existing explanation of the current-time data collected during anodization, which has persisted in the literature for more than two decades. In addition to providing a first-time morphological study of Ta oxide NT formation at very early stages of anodization, we also propose a new interpretation of the i-t response, showing that pores are already present in the first few milliseconds of anodization and that NTs are formed well before present models predict. This behaviour may also extend to the anodization of other valve metals, such as Al, Ti, Zr, W, and Nb. PMID:23338813

  8. The adhesion performance of epoxy coating on AA6063 treated in Ti/Zr/V based solution

    NASA Astrophysics Data System (ADS)

    Zhu, Wen; Li, Wenfang; Mu, Songlin; Yang, Yunyu; Zuo, Xi

    2016-10-01

    An environment-friendly titanium/zirconium/vanadium-based (Ti/Zr/V) conversion coating was prepared on aluminum alloy 6063 (AA6063). The epoxy powder coatings were applied on the AA6063 samples with/without Ti/Zr/V conversion coatings via electrostatic spraying. The morphology and composition of the conversion coating were studied by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The surface free energy components of AA6063 samples were measured by a static contact angle measuring device with Owens method. The adhesion properties of the epoxy coating on AA6063 treated with different conversion times were evaluated using a pull-off tester. The Ti/Zr/V conversion coating was mainly composed of metal oxide (TiO2, ZrO2, V2O5, Al2O3, etc.), metal fluoride (ZrF4, AlF3, etc.) and metal organic complex. The formation time of this conversion coating was reduced to 50 s. After such surface treatment, the samples' surface roughness was increased and the contact angle with water was decreased. Both the surface free energy and the work of adhesion were increased. The adhesion strength between the epoxy coating and AA6063 was enhanced significantly.

  9. Preparation and wear resistance of Ti-Zr-Ni quasicrystal and polyamide composite materials

    NASA Astrophysics Data System (ADS)

    Wang, Xinlu; Li, Xuesong; Zhang, Zhenjiang; Zhang, Shanshan; Liu, Wanqiang; Wang, Limin

    2011-07-01

    Ti-Zr-Ni icosahedral quasicrystal powders (Ti-QC), prepared by mechanical alloying and then annealing in a vacuum furnace, were used as a novel filler material in polyamide 12 (PA12). The melt processability of the composite was studied using a Haake torque rheometer. This indicates that PA12/Ti-QC composites can be melt-processed into a wear-resistant material. Further, these composites, fabricated by compression molding, were tested in sliding wear against a polished bearing steel counterface. The results from wear testing show that the addition of Ti-QC filler to PA12 enhances wear resistance and reduces volume loss by half compared with neat PA12. Furthermore, it is found that the hardness of the composite increases with increasing content of Ti-QC filler. In addition, PA12/Ti-QC composites exhibit a slightly higher crystallization temperature and better thermal stability than PA12. These combined results demonstrate that Ti-QC filler may be a desirable alternative when attempting to increase the wear resistance of PA12.

  10. An Ultrasonic Study of Hydrogen Motion in a Ti-Zr-Ni Quasicrystalline Material

    NASA Astrophysics Data System (ADS)

    Hightower, J. E.; Foster, K.; Leisure, R. G.; Kim, J. Y.; Kelton, K. F.

    2000-09-01

    Previous ultrasonic attenuation measurements^1 for a Ti-Zr-Ni quasicrystalline material have been extended to cover a temperature range up to 425K. The samples were charged to a hydrogen to metal ratio of 0.79 for the quasicrystal and 0.20 for the related crystalline approximant. Hydrogen motion within these materials causes a peak in the ultrasonic loss as a function of temperature. The present higher temperature measurements complement the previous data and give a more reliable determination of the parameters of the hydrogen motion. The results suggest that the hydrogen motion is about an order of magnitude faster in the quasicrystal than in the approximant. The current measurements cannot determine whether this is due to basic differences between the two materials or to hydrogen concentration dependence. The research at Colorado State University was supported by NSF Grant No. DMR-0070808. The work at Washington University was supported by NSF Grant No. DMR-9705202. ^1K. Foster, R. G. Leisure, J. B. Shaklee, J. Y. Kim, and K. F. Kelton, Phys. Rev. B 61, 241 (2000).

  11. Matrix isolation spectra of metal atoms and ions: Ti, Zr, and Mo in Ar and Kr

    NASA Astrophysics Data System (ADS)

    Steinbrüchel, Christoph; Gruen, Dieter M.

    1981-01-01

    UV-absorption spectra are reported of neutral atoms and ions of Ti, Zr, and Mo in Ar and Kr matrices. The matrix-isolated species are produced by ion bombardment of a bulk metal target. Thermal and photoannealing experiments indicate that sputtered neutral atoms may occupy one or two distinct matrix sites, depending on the system. Sputtered ions, after being neutralized in the matrix, either go preferentially into the higher energy site, i.e., the site whose absorption bands are shifted farther to the blue, when atoms already populate two sites, or they create a new site at higher energy when there is only one site for atoms. Deconvolution of matrix isolation spectra into contributions from individual sites shows that spectra due to atoms in a particular site correspond much better to gas phase spectra than do total matrix isolation spectra. Matrix shifts of atomic absorption bands for both sites can be rationalized using a model by McCarty and Robinson if allowance is made for matrix distortion around solute atoms. The blue, or close-packed, site is found to correspond to a solute atom replacing a single matrix atom without inducing appreciable matrix distortion, whereas the red, or expanded, site requires the cage around a solute atom to be enlarged by a few percent.

  12. Evaluation of Ti-Zr-V (NEG) Thin Films for their pumping speed and pumping Capacity

    NASA Astrophysics Data System (ADS)

    Bansod, Tripti; Sindal, B. K.; Kumar, K. V. A. N. P. S.; Shukla, S. K.

    2012-11-01

    Deposition of NEG thin films onto the interior walls of the vacuum chambers is an advanced technique to convert a vacuum chamber from a gas source to an effective pump. These films offer considerably large pumping speed for reactive gases like CO, H2 etc. A UHV compatible pumping speed measurement system was developed in-house to measure the pumping speed of NEG coated chambers. To inject the fixed quantity of CO and H2 gas in pumping speed measurement set-up a calibrated leak was also developed. Stainless steel chambers were sputter coated with thin film of Ti-Zr-V getter material using varied parameters for different compositions and thickness. Pumping capacity which is a function of sorbed gas quantities was also studied at various activation temperatures. In order to optimize the activation temperature for maximum pumping speed for CO and H2, pumping speeds were measured at room temperature after activation at different temperatures. The experimental system detail, pumping performance of the NEG film at various activation temperatures and RGA analysis are presented.

  13. The first principle study of magnetic properties of Mn2WSn, Fe2YSn (Y=Ti, V), Co2YSn (Y=Ti, Zr, Hf, V, Mn) and Ni2YSn (Y=Ti, Zr, Hf, V, Mn) heusler alloys

    NASA Astrophysics Data System (ADS)

    Rauf, Sana; Arif, Suneela; Haneef, Muhammad; Amin, Bin

    2015-01-01

    The spin polarized electronic band structures, density of states (DOS) and magnetic properties of Mn2WSn, Fe2YSn (Y=Ti, V), Co2YSn (Y=Ti, Zr, Hf, V, Mn) and Ni2YSn (Y=Ti, Zr, Hf, V, Mn) huesler compounds are reported. The calculations are performed by using full-potential linearized augmented plane wave method (FP-LAPW) within density functional theory. The magnetic trend in these compounds is studied using values of magnetic moments, exchange interaction and calculated band gap. The results reveal that Mn2WSn and Ni2VSn show 100% spin polarization, Co2YSn (Y=Ti, Zr, Hf, Mn), Fe2YSn (Y=Ti, V), and Ni2MnSn exhibit metallic nature and Ni2YSn (Y=Ti, Zr, Hf) and Co2VSn show semi-conducting behavior.

  14. Comparative characteristics of the mineralogical composition of Ti-Zr potential placer district

    NASA Astrophysics Data System (ADS)

    Ovchinnikova, Mary

    2016-04-01

    Russia has a great off-balance reserves of TiO2 and it is ranked fourth in the world after Ukraine, China and Australia. Inferred resources are also very significant. But today Russia produces titanium products only from imported raw materials. Exploration of Ti-raw material is carried out in Russia only as passing on comprehensive deposits. As a result of work conducted in 1959, Stavropolsky elevation was discovered Stavropolsky Ti-Zr alluvial basin. The same mineralogical composition has Ti-Zr Ergeninsky potential alluvial district, which is located north-eastern of Stavropolsky littoral basin. Administratively, Ergeninsky area, basically, covers territory of Kalmikia, and partially Rostovsky and Volgogradsky area. In terms of tectonics, it occupies an area of the junction of the East European platform and Karpinsky Ridge. Alluvial basin holds really magnificent range. There are two hypotheses as to where was the demolition of ore sand. According to the first demolition of the original ore material was from crumbling crystalline rocks southern East European platform. The second hypothesis links the formation of these placers due to the erosion of crystalline basement rocks of the Greater Caucasus, which is explained by the fact of the existence of the Sarmatian paleo sea. There are two productive horizons on the territory of Ergeninsky potential placer district. First - the lower productive horizon it has a capacity of 1.5 to 6.3 m and the total content of titanium and zirconium minerals 12 to 66 kg m³. Second - upper productive horizon. 1.5 to 4.3 m and the total content of titanium and zirconium minerals from 21 to 50 kg m³. Earlier in the study of the area, only samples from the upper productive horizon were considered. At the beginning petrophysical analysis of all available samples, was conducted. Before you choose a basic test, each of the 26 studied several petrophysical properties: 1. Magnetic susceptibility (κ, 10-5 units. C) 2. The density (d, g / cm

  15. Location and energy of interstitial hydrogen in the 1/1 approximant W-TiZrNi of the icosahedral TiZrNi quasicrystal: Rietveld refinement of x-ray and neutron diffraction data and density-functional calculations

    SciTech Connect

    Hennig, R. G.; Majzoub, E. H.; Kelton, K. F.

    2006-05-01

    We present a determination of hydrogen sites in the 1/1 approximant structure of the icosahedral TiZrNi quasicrystal. A Rietveld refinement of neutron and x-ray diffraction data determines the locations of interstitial hydrogen atoms. Density-functional methods calculate the energy of hydrogen on all possible interstitial sites. The Rietveld refinement shows that the hydrogen atoms are preferentially located in the two lowest-energy sites. The filling of the remaining hydrogen sites is dominated by the repulsive hydrogen-hydrogen interaction at short distances.

  16. The Aβ peptide forms non-amyloid fibrils in the presence of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Luo, Jinghui; Wärmländer, Sebastian K. T. S.; Yu, Chien-Hung; Muhammad, Kamran; Gräslund, Astrid; Pieter Abrahams, Jan

    2014-05-01

    Carbon nanotubes have specific properties that make them potentially useful in biomedicine and biotechnology. However, carbon nanotubes may themselves be toxic, making it imperative to understand how carbon nanotubes interact with biomolecules such as proteins. Here, we used NMR, CD, and ThT/fluorescence spectroscopy together with AFM imaging to study pH-dependent molecular interactions between single walled carbon nanotubes (SWNTs) and the amyloid-beta (Aβ) peptide. The aggregation of the Aβ peptide, first into oligomers and later into amyloid fibrils, is considered to be the toxic mechanism behind Alzheimer's disease. We found that SWNTs direct the Aβ peptides to form a new class of β-sheet-rich yet non-amyloid fibrils.Carbon nanotubes have specific properties that make them potentially useful in biomedicine and biotechnology. However, carbon nanotubes may themselves be toxic, making it imperative to understand how carbon nanotubes interact with biomolecules such as proteins. Here, we used NMR, CD, and ThT/fluorescence spectroscopy together with AFM imaging to study pH-dependent molecular interactions between single walled carbon nanotubes (SWNTs) and the amyloid-beta (Aβ) peptide. The aggregation of the Aβ peptide, first into oligomers and later into amyloid fibrils, is considered to be the toxic mechanism behind Alzheimer's disease. We found that SWNTs direct the Aβ peptides to form a new class of β-sheet-rich yet non-amyloid fibrils. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr00291a

  17. The Study of Complex (Ti, Zr, Cs) Nanopowder Influencing the Effective Ionization Potential of Arc Discharge When Mma Welding

    NASA Astrophysics Data System (ADS)

    Sapozhkov, S. B.; Burakova, E. M.

    2016-08-01

    Strength is one of the most important characteristics of a weld joint. Mechanical properties of a weld metal can be improved in a variety of ways. One of the possibilities is to add a nanopowder to the weld metal. Authors of the paper suggest changing the production process of MMA welding electrodes via adding nanopowder Ti, Zr, Cs to electrode components through liquid glass. Theoretical research into the nanopowder influence on the effective ionization potential (Ueff) of welding arc discharge is also necessitated. These measures support arcing stability, improve strength of a weld joint, as the consequence, ensure quality enhancing of a weld joint and the structure on the whole.

  18. Mechanics of capillary forming of aligned carbon nanotube assemblies.

    PubMed

    Tawfick, Sameh; Zhao, Zhouzhou; Maschmann, Matthew; Brieland-Shoultz, Anna; De Volder, Michael; Baur, Jeffery W; Lu, Wei; Hart, A John

    2013-04-30

    Elastocapillary self-assembly is emerging as a versatile technique to manufacture three-dimensional (3D) microstructures and complex surface textures from arrangements of micro- and nanoscale filaments. Understanding the mechanics of capillary self-assembly is essential to engineering of properties such as shape-directed actuation, anisotropic wetting and adhesion, and mechanical energy transfer and dissipation. We study elastocapillary self-assembly (herein called "capillary forming") of carbon nanotube (CNT) microstructures, combining in situ optical imaging, micromechanical testing, and finite element modeling. By imaging, we identify sequential stages of liquid infiltration, evaporation, and solid shrinkage, whose kinetics relate to the size and shape of the CNT microstructure. We couple these observations with measurements of the orthotropic elastic moduli of CNT forests to understand how the dynamic of shrinkage of the vapor-liquid interface is coupled to the compression of the forest. We compare the kinetics of shrinkage to the rate of evporation from liquid droplets having the same size and geometry. Moreover, we show that the amount of shrinkage during evaporation is governed by the ability of the CNTs to slip against one another, which can be manipulated by the deposition of thin conformal coatings on the CNTs by atomic layer deposition (ALD). This insight is confirmed by finite element modeling of pairs of CNTs as corrugated beams in contact and highlights the coupled role of elasticity and friction in shrinkage and stability of nanoporous solids. Overall, this study shows that nanoscale porosity can be tailored via the filament density and adhesion at contact points, which is important to the development of lightweight multifunctional materials. PMID:23537107

  19. Microstructure and properties of rapidly solidified beryllium-transition metal alloys. [With small amounts of Ti, Zr and Y (1-3 wt %)

    SciTech Connect

    Jacobson, L.A.; Richardson, S.

    1988-01-01

    Alloys of beryllium with small amounts of Ti, Zr and Y (1-3 wt %) were rapidly solidified using an arc hammer splat technique. Each of these elements forms a dilute eutectic with beryllium, and has very low solid solubility in the alpha phase. In the case of Ti, the Be-rich compound is TiBe/sub 12/, and for Zr and Y, the compound is MBe. The objective of the work was to achieve a fine, uniform dispersion of particles of the intermetallic compound. Since these compounds have very high melting points, it was expected that rapidly solidified microstructures would be relatively stable at elevated temperatures. This microstructural stability should result in improved high temperature properties for the alloys. Microstructures have been characterized using optical, scanning and transmission electron microscopy. Microhardness measurements have been made in order to determine the effects of rapid solidification and to evaluate the effects of high temperature exposure on microstructural stability and property retention. The results will be presented in light of the potential of these alloys for intermediate temperature application. 12 refs., 8 figs.

  20. Ceria Nanotube Formed by Sacrificed Precursors Template through Oswald Ripening

    PubMed Central

    Pang, Laixue; Wang, Xiaoying; Tang, Xinde

    2015-01-01

    Controllable preparation of ceria nanotube was realized by hydrothermal treatment of Ce(OH)CO3 precursors. The gradually changing morphologies and microstructures of cerium oxide were characterized by X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. A top-down path is illuminated to have an insight to the morphological transformation from nanorod to nanotube by adjusting the reaction time. The growth process is investigated by preparing a series of intermediate morphologies during the shape evolution of CeO2nanostructure based on the scanning electron microscopy image observation. On the basis of the time-dependent experimental observation, the possible formation mechanism related to oriented attachment and Oswald ripening was proposed, which might afford some guidance for the synthesis of other inorganic nanotubes. PMID:26151866

  1. Diffusion-barrier contacts based on the TiN and Ti(Zr)B{sub x} interstitial phases in the microwave diodes for the range of 75-350 GHz

    SciTech Connect

    Boltovets, N. S. Ivanov, V. N.; Belyaev, A. E.; Konakova, R. V. Kudrik, Ya. Ya.; Milenin, V. V.; Arsent'ev, I. N.; Bobyl, A. V. Brunkov, P. N.; Tarasov, I. S.; Tonkikh, A. A.; Ulin, V. P.; Ustinov, V. V.; Cirlin, G. E.

    2006-06-15

    A new technology for thermally stable ohmic contacts with diffusion barriers based on the amorphous TiN and Ti(Zr)B{sub x} interstitial phases is used in the development of microwave diodes for the millimeter region (with the frequency higher than 100 GHz) based on GaAs, InP, and Si. It became possible to increase the reliability of the GaAs-and InP-based Gunn diodes that operate at the frequency of 200 GHz by using the epitaxial layers formed on porous III-V substrates by gas-phase, molecular-beam, and liquid-phase epitaxy as the initial device structures. The range of emission from the avalanche transit-time diodes based on Si is extended to 350 GHz. To this end, the technology of forming the active element on the silicon metallized diaphragm is used for the first time.

  2. The structure of nanochannels formed by block copolymer solutions confined in nanotubes.

    PubMed

    Chen, Houyang; Ruckenstein, Eli

    2009-09-21

    Monte Carlo simulations are employed to obtain information about the radius and the roughness of the inner surface of the channels, which are generated by a family of block copolymer solutions confined in nanotubes. The fluctuations of the above quantities also have been calculated. The simulations have been carried out by varying the interactions between various kinds of segments and those between segments and the wall of the nanotubes, as well as the chemical structure of the copolymer and the nanotube diameter. The present simulations provide insight regarding the structure of ionic and water channels formed by protein in the phospholipid bilayers of the cell membrane.

  3. Electron-stimulated desorption from polished and vacuum fired 316LN stainless steel coated with Ti-Zr-Hf-V

    SciTech Connect

    Malyshev, Oleg B. Valizadeh, Reza; Hogan, Benjamin T.; Hannah, Adrian N.

    2014-11-01

    In this study, two identical 316LN stainless steel tubular samples, which had previously been polished and vacuum-fired and then used for the electron-stimulated desorption (ESD) experiments, were coated with Ti-Zr-Hf-V with different morphologies: columnar and dense. ESD measurement results after nonevaporable getter (NEG) activation to 150, 180, 250, and 350 °C indicated that the values for the ESD yields are significantly (2–20 times) lower than the data from our previous study with similar coatings on nonvacuum-fired samples. Based on these results, the lowest pressure and best long-term performance in particle accelerators will be achieved with a vacuum-fired vacuum chamber coated with dense Ti-Zr-Hf-V coating activated at 180 °C. This is likely due to the following facts: after NEG activation, the hydrogen concentration inside the NEG was lower than in the bulk stainless steel substrate; the NEG coating created a barrier for gas diffusion from the sample bulk to vacuum; the dense NEG coating performed better as a barrier than the columnar NEG coating.

  4. Study of the surface wear resistance and biological properties of the Ti-Zr-Nb-Sn alloy for dental restoration.

    PubMed

    Hu, Xin; Wei, Qiang; Li, Chang-Yi; Deng, Jia-Yin; Liu, Shuang; Zhang, Lian-Yun

    2010-10-01

    A new titanium alloy (Ti-12.5Zr-3Nb-2.5Sn) was developed to meet the needs of clinical requirements for medical titanium alloys and improve the properties of existing titanium alloys. The as-prepared alloy was solution treated at 500 °C for 3 h in vacuum followed by water quenching. Tensile, wear and hardness tests were carried out to examine the mechanical properties of the Ti-Zr-Nb-Sn alloy. Oral mucous membrane irritation test was performed to evaluate the surface biological properties of the Ti-Zr-Nb-Sn alloy. The results suggested that the surface hardness and wear-resistant properties of the Ti-12.5Zr-3Nb-2.5Sn alloy were superior to commercially pure Ti. The oral mucous irritation test showed that all samples had no mucous membrane irritation. It indicates that Ti-12.5Zr-3Nb-2.5Sn has large potential to be used as dental restoration material.

  5. Phase Stability in the Mo-Ti-Zr-C System via Thermodynamic Modeling and Diffusion Multiple Validation

    NASA Astrophysics Data System (ADS)

    Kar, Sujoy Kumar; Dheeradhada, Voramon S.; Lipkin, Don M.

    2013-08-01

    Alloys in the Mo-rich corner of the Mo-Ti-Zr-C system have found broad applications in non-oxidizing environments requiring structural integrity well beyond 1273 K (1000 °C). Alloys such as TZM (Mo-0.5Ti-0.08Zr-0.03C by weight %) and TZC (Mo-1.2Ti-0.3Zr-0.1C by weight) owe much of their high temperature strength and microstructural stability to MC and M2C carbide phases. In turn, the stability of the respective carbides and the subsequent mechanical behavior of the alloys are strongly dependent on the alloying additions and thermal history. A CALPHAD-based thermodynamic modeling approach is employed to develop a quaternary thermodynamic database for the Mo-Ti-Zr-C system. The thermodynamic database thus developed is validated with diffusion multiple experiments and the validated database is exercised to elucidate the effects of alloying and thermal history on the phase equilibrium in Mo-rich alloys.

  6. Characterization and Evaluation of Ti-Zr-V Non-evaporable Getter Films Used in Vacuum Systems

    NASA Astrophysics Data System (ADS)

    Ferreira, M. J.; Seraphim, R. M.; Ramirez, A. J.; Tabacniks, M. H.; Nascente, P. A. P.

    Among several methods used to obtain ultra-high vacuum (UHV) for particles accelerators chambers, it stands out the internal coating with metallic films capable of absorbing gases, called NEG (non-evaporable getter). Usually these materials are constituted by elements of great chemical reactivity and solubility (such as Ti, Zr, and V), at room temperature for oxygen and other gases typically found in UHV, such as H2, CO, and CO2. Gold and ternary Ti-Zr-V films were produced by magnetron sputtering, and their composition, structure, morphology, and aging characteristics were characterized by energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field emission gun sc anning electronmicroscopy (FEG-SEM), atomic force microscopy (AFM), high resolution transmission electron microscopy (HRTEM). The comparison between the produced films and commercial samples indicated that the desirable characteristics depend on the nanometric structure of the films and that this structure is sensitive to the heat treatments.

  7. Functionalization of nitrogen-doped carbon nanotubes with gallium to form Ga-CN(x)-multi-wall carbon nanotube hybrid materials.

    PubMed

    Simmons, Trevor J; Hashim, Daniel P; Zhan, Xiaobo; Bravo-Sanchez, Mariela; Hahm, Myung Gwan; López-Luna, Edgar; Linhardt, Robert J; Ajayan, Pulickel M; Navarro-Contreras, Hugo; Vidal, Miguel A

    2012-08-17

    In an effort to combine group III-V semiconductors with carbon nanotubes, a simple solution-based technique for gallium functionalization of nitrogen-doped multi-wall carbon nanotubes has been developed. With an aqueous solution of a gallium salt (GaI(3)), it was possible to form covalent bonds between the Ga(3+) ion and the nitrogen atoms of the doped carbon nanotubes to form a gallium nitride-carbon nanotube hybrid at room temperature. This functionalization was evaluated by x-ray photoelectron spectroscopy, energy dispersive x-ray spectroscopy, Raman spectroscopy, scanning electron microscopy and transmission electron microscopy.

  8. Light-Harvesting Nanotubes Formed by Supramolecular Assembly of Aromatic Oligophosphates.

    PubMed

    Bösch, Caroline D; Langenegger, Simon M; Häner, Robert

    2016-08-16

    A 2,7-disubstituted phosphodiester-linked phenanthrene trimer forms tubular structures in aqueous media. Chromophores are arranged in H-aggregates. Incorporation of small quantities of pyrene results in the development of light-harvesting nanotubes in which phenanthrenes act as antenna chromophores and pyrenes as energy acceptors. Energy collection is most efficient after excitation at the phenanthrene H-band. Fluorescence quantum yields up to 23 % are reached in pyrene doped, supramolecular nanotubes. PMID:27375116

  9. The stability and electronic structure of lithium adsorbed in triplet form of (5.0) carbon nanotubes and (5.0) boron nitrogen nanotubes: Density functional theory studies

    NASA Astrophysics Data System (ADS)

    Li, Ke Jing; Shao, Qing Yi; Zhang, Juan; Yao, Xin Hua

    2016-07-01

    Using density functional theory (DFT), we have investigated the stability and electronic structure of lithium (Li) adsorbed in triplet form of (5.0) carbon nanotubes (CNTs) and (5.0) boron nitrogen nanotubes (BNNTs). We have mainly found that three (5.0) tubes are covalently connected. The triplet form is an energetically stable semiconductor. Li atom can be chemically adsorbed in the triplet form of nanotubes (NTs). Meanwhile, upon the adsorption of Li, the triplet form convert into metal. Hence, the triplet form can improve reactivity and sensitivity of NTs to Li significantly.

  10. The Aβ peptide forms non-amyloid fibrils in the presence of carbon nanotubes.

    PubMed

    Luo, Jinghui; Wärmländer, Sebastian K T S; Yu, Chien-Hung; Muhammad, Kamran; Gräslund, Astrid; Pieter Abrahams, Jan

    2014-06-21

    Carbon nanotubes have specific properties that make them potentially useful in biomedicine and biotechnology. However, carbon nanotubes may themselves be toxic, making it imperative to understand how carbon nanotubes interact with biomolecules such as proteins. Here, we used NMR, CD, and ThT/fluorescence spectroscopy together with AFM imaging to study pH-dependent molecular interactions between single walled carbon nanotubes (SWNTs) and the amyloid-beta (Aβ) peptide. The aggregation of the Aβ peptide, first into oligomers and later into amyloid fibrils, is considered to be the toxic mechanism behind Alzheimer's disease. We found that SWNTs direct the Aβ peptides to form a new class of β-sheet-rich yet non-amyloid fibrils.

  11. Microsegregation in and Phase Stability of As-Cast Ti-Zr-Hf-Ni-Pd-Pt High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Yokoyama, Yoshihiko; Itoh, Shun; Murakami, Yoshihiro; Narita, Issei; Wang, Gongyao; Liaw, Peter K.

    2015-04-01

    Microsegregation in as-cast Ti-Zr-Hf-Ni-Pd-Pt high-entropy alloys (HEAs) was examined by scanning electron microscopy and transmission electron microscopy. The structure of the microsegregated HEAs was composed of dendrite grains and grain boundaries. Since Hf, Zr, and Pt show both high melting temperatures and large negative mixing enthalpy, microsegregation on a micrometer scale occurred easily, similar to the spontaneous inoculation during solidification of copper-mold casts. In contrast, the grain boundaries were identified as being Ti- and Ni-enriched regions. Macroscopic X-ray data showed the combination of a distinct body-centered-cubic structure and broad halo peaks (amorphous structure). Microstructure analysis revealed that heteroamorphous and nanocrystalline regions are observed when the Ti group:Ni group molar ratio was 50/50. This unique microsegregated structure resulted in an ultimate compression strength of more than 2 GPa.

  12. Simultaneously Enhancing the Ductility and Strength in a Hierarchical and Multiphase Nanolaminated TiZrAlV

    NASA Astrophysics Data System (ADS)

    Shi, Yindong; Wang, Lina; Wu, Chunxia

    2015-12-01

    High strength and ductility are the prerequisite for structural materials for wide applications. Here, a simultaneous enhancement of both the ductility and strength is reported in a hierarchical and multiphase nanolaminated (HMN) TiZrAlV prepared via thermomechanical processing treatments. An excellent combination of high ultimate tensile strength of σb ~ 1550 MPa and good elongation to failure of ɛf ~ 8.0% is obtained in an appropriate HMN structure that consists of nanoscale α″ martensites, submicroscale α plates, and large microscale primary αp grains, much better than that (σb ~ 1440 MPa, ɛf ~ 3.6%) of its coarse-laminated counterpart without primary αp grains. The present study is significant for the enhancement of strength and ductility of engineering materials via the design of hierarchical-laminated structure.

  13. Ellenbergerite, a new high-pressure Mg-Al-(Ti,Zr)-silicate with a novel structure based on face-sharing octahedra

    NASA Astrophysics Data System (ADS)

    Chopin, Christian; Klaska, Rolf; Medenbach, Olaf; Dron, Dominique

    1986-09-01

    Ellenbergerite occurs as purple millimetre-size grains associated with talc, kyanite, clinochlore, rutile, and zircon in composite inclusions within decimetre-large pyrope crystals (90 98 mole percent end-member) in the quartzite layer of the Dora Maira massif, Western Alps, from which coesite has been recently reported (Chopin 1984). It is hexagonal, a=12.255(8), c=4.932(4) Å, Z=1, space group P63. Mohs hardness 6.5; Dmes 3.15, Dcal 3.10; no cleavage. Uniaxial negative and vividly pleochroic, ω colourless, ɛ colourless to deep lilac with colour zoning. The intensely coloured variety has ω 1.6789(5), ɛ 1.670(1); microprobe analysis yields SiO2 39.1, P2O5 0.45, Al2O3 25.1, TiO2 4.0, MgO 22.2, FeO 0.20, sum 99.05 wt.% including H2O 8.0 (coulometrically). The formula calculated on a O28(OH)10 basis (implying 7.5 wt.% H2O) is Mg6.71 Fe0.03 Ti0.61 Al6.00 Si7.92 P0.08 O28(OH)10 The colour zoning is due to nearly complete Ti⇌Zr substitution. In addition ellenbergerite may contain more than 8 wt.% P2O5 with strictly correlated changes of Si, Mg, Al and Ti+Zr contents, over 80% of which represent the SiAl⇌PMg substitution. The structure has been determined from 1049 observed independent reflections and refined to R=0.034, Rw=0.031, including six of ten protons. It consists of single chains of face-sharing octahedra with one third vacancies extending along the six-fold screw axes, and of pairs of fully occupied face-sharing octahedra linked by edge-sharing to form octahedral double chains parallel to the twofold screw axes, all interconnected by SiO4 tetrahedra. It may be compared with the dumortierite polymorph with space group P63mc derived hypothetically by Moore and Araki (1978). The structural formula is (Mg,Ti,Zr,□)2 Mg6(Al,Mg)6 (Si,P)2 Si6 O28(OH)10 Face-sharing octahedra are an unusual feature in silicates which results in a dense structure and reflects, considering the common bulk composition, the uncommon high-pressure formation conditions (about 25 30

  14. Heteroporphyrin nanotubes and composites

    DOEpatents

    Shelnutt, John A.; Medforth, Craig J.; Wang, Zhongchun

    2006-11-07

    Heteroporphyrin nanotubes, metal nanostructures, and metal/porphyrin-nanotube composite nanostructures formed using the nanotubes as photocatalysts and structural templates, and the methods for forming the nanotubes and composites.

  15. Heteroporphyrin nanotubes and composites

    DOEpatents

    Shelnutt, John A.; Medforth, Craig J.; Wang, Zhongchun

    2007-05-29

    Heteroporphyrin nanotubes, metal nanostructures, and metal/porphyrin-nanotube composite nanostructures formed using the nanotubes as photocatalysts and structural templates, and the methods for forming the nanotubes and composites.

  16. Determination of Ti, Zr, Nb, V, W and Mo in seawater by a new online-preconcentration method and subsequent ICP-MS analysis

    NASA Astrophysics Data System (ADS)

    Poehle, Sandra; Schmidt, Katja; Koschinsky, Andrea

    2015-04-01

    We present a new method for the determination of Ti, Zr, Nb, V, W and Mo in seawater by adapting the online-preconcentration procedure with the system SeaFAST and subsequent analysis by ICP-MS to these metals. The trace elements Ti, Zr, Nb and W are present in seawater in ultratrace concentrations in the range of pmol kg-1, whereas Mo and V, which are biologically essential elements, are present in the concentration range of nmol kg-1. The online-preconcentration system we used consists of an autosampler, a sample loop, a preconcentration column and two valves controlling the sample loop and the preconcentration processes. The pre-packed preconcentration column contains a chelating resin with two functional groups, ethylenediamine triacetic acid (EDTriA) and iminodiacetic acid (IDA), immobilized on a polymer backbone. The preconcentration process was optimized for loading the sample and subsequent rinsing to remove residues of seawater matrix prior to elution with the optimized elution acid (0.5 M HNO3-0.002 M HF). We used acidified North Sea seawater (0.02 M HCl-0.002 M HF) for the method development. Samples and calibration standards were loaded onto the preconcentration column and after elution directly transferred to the quadrupole ICP-MS and measured immediately. Best results were achieved with matrix-matched calibration standards (0.6 M NaCl-0.02 M HCl-0.002 M HF) simulating acidified seawater samples. Titanium, Zr, Nb and W are measured simultaneously in one run, whereas V and Mo are determined simultaneously in a separate run. Low procedure blanks were calculated for Ti, Zr, Nb, W (635, 14.5, 1.35, 10.2 pmol kg-1) and for V and Mo, 9.79 and 5.61 nmol kg-1, respectively. Very good spike recoveries achieved with spiked North Sea water demonstrate the applicability for all six elements. Analysis of the seawater standard NASS-6 gave recoveries of 97-99% (0.9-2.2% standard deviation, SD) for Mo and V. We also provide Zr, Nb and W data for this reference standard

  17. Guided proliferation and bone-forming functionality on highly ordered large diameter TiO2 nanotube arrays.

    PubMed

    Zhang, Ruopeng; Wu, Hongliu; Ni, Jiahua; Zhao, Changli; Chen, Yifan; Zheng, Chengjunyi; Zhang, Xiaonong

    2015-08-01

    The significantly enhanced osteoblast adhesion, proliferation and alkaline phosphatase (ALP) activity were observed on TiO2 nanotube surface in recent studies in which the scale of nanotube diameter was restricted under 100 nm. In this paper, a series of highly ordered TiO2 nanotube arrays with larger diameters ranging from 150 nm to 470 nm were fabricated via high voltage anodization. The behaviors of MC3T3-E1 cells in response to the diameter-controlled TiO2 nanotubes were investigated. A contrast between the trend of proliferation and the trend of cell elongation was observed. The highest cell elongation (nearly 10:1) and the lowest cell number were observed on the TiO2 nanotube arrays with 150 nm diameter. While, the lowest cell elongation and highest cell number were achieved on the TiO2 nanotube arrays with 470 nm diameter. Furthermore, the ALP activity peaked on the 150 nm diameter TiO2 nanotube arrays and decreased dramatically with the increase of nanotube diameter. Thus a narrow range of diameter (100-200 nm) that could induce the greatest bone-forming activity is determined. It is expected that more delicate design of orthopedic implant with regional abduction of cell proliferation or bone forming could be achieved by controlling the diameter of TiO2 nanotubes.

  18. Nanotube

    2007-09-13

    This is a source code to calculate the current-voltage characteristics, the charge distribution and the electrostatic potential in carbon nanotube devices. The code utilizes the non-equilibrium Green's function method, implemented in a tight-binding scheme, to calculate the charge distribution and the energy-dependent transmission function, from which the current or the conductance are obtained. The electrostatic potential is obtained by solving Poisson's equation on a grid with boundary conditions on the electrodes, and at other interfaces.more » Self-consistency between the charge and the electrostatic potential is achieved using a linear mixing method. Different versions of the code allow the modeling of different types of nanotube devices: Version 1.0: Modeling of carbon nanotube electronic devices with cylindrical symmetry Version 1.1: Modeling of planar carbon nanotube electronic devices Version 1.2: Modeling of photocurrent in carbon nanotube devices« less

  19. Patterns of Flexible Nanotubes Formed by Liquid-Ordered and Liquid-Disordered Membranes.

    PubMed

    Liu, Yonggang; Agudo-Canalejo, Jaime; Grafmüller, Andrea; Dimova, Rumiana; Lipowsky, Reinhard

    2016-01-26

    Biological membranes form both intra- and intercellular nanotubes that are used for molecular sorting within single cells and for long-distance connections between different cells. Such nanotubes can also develop from synthetic lipid bilayers in their fluid state. Each nanotube has a large area-to-volume ratio and stably encloses a water channel that is thereby shielded from its surroundings. The tubes are rather flexible and can easily change both their length and their conformation. Here, we study nanotubes formed by liquid-ordered (Lo) and liquid-disordered (Ld) membranes with three lipid components exposed to aqueous mixtures of two polymers, polyethylene glycol (PEG) and dextran. Both types of membranes form striking patterns of nanotubes when we reduce the volume of giant vesicles by osmotic deflation, thereby exposing the two bilayer leaflets of the membranes to polymer solutions of different composition. With decreasing volume, three different patterns are observed corresponding to three distinct vesicle morphologies that reflect the interplay of spontaneous curvature and aqueous phase separation. We show that tube nucleation and growth is governed by two kinetic pathways and that the tubes undergo a novel shape transformation from necklace-like to cylindrical tubes at a certain critical tube length. We deduce the spontaneous curvature generated by the membrane-polymer interactions from the observed vesicle morphologies using three different and independent methods of image analysis. The spontaneous curvature of the Ld membranes is found to be 4.7 times larger than that of the Lo membranes. We also show that these curvatures are generated by weak PEG adsorption onto the membranes, with a binding affinity of about 1.6 kBT per chain. In this way, our study provides a direct connection between nanoscopic membrane shapes and molecular interactions. Our approach is rather general and can be applied to many other systems of interest such as polymersomes or

  20. Single layer of MX₃ (M = Ti, Zr; X = S, Se, Te): a new platform for nano-electronics and optics.

    PubMed

    Jin, Yingdi; Li, Xingxing; Yang, Jinlong

    2015-07-28

    A serial of two-dimensional titanium and zirconium trichalcogenides nanosheets MX3 (M = Ti, Zr; X = S, Se, Te) were investigated based on first-principles calculations. The evaluated low cleavage energy indicates that stable two-dimensional monolayers can be exfoliated from their bulk crystals in the experiment. Electronic studies reveal the very rich electronic properties in these monolayers, including metallic TiTe3 and ZrTe3, direct band gap semiconductor, TiS3, and indirect band gap semiconductors, TiSe3, ZrS3 and ZrSe3. The band gaps of all the semiconductors are between 0.57 and 1.90 eV, which implies their potential applications in nano-electronics. In addition, the calculated effective masses demonstrate the highly anisotropic conduction properties for all the semiconductors. Optically, TiS3 and TiSe3 monolayers exhibit good light absorption in the visible and near-infrared region, respectively, indicating their potential applications in optical devices. In particular, the highly anisotropic optical absorption of the TiS3 monolayer suggests it could be used in designing nano-optical waveguide polarizers.

  1. Thermal stability of titanate nanorods and titania nanowires formed from titanate nanotubes by heating

    SciTech Connect

    Brunatova, Tereza; Matej, Zdenek; Oleynikov, Peter; Vesely, Josef; Danis, Stanislav; Popelkova, Daniela; Kuzel, Radomir

    2014-12-15

    The structure of titanate nanowires was studied by a combination of powder X-ray diffraction (XRD) and 3D precession electron diffraction. Titania nanowires and titanate nanorods were prepared by heating of titanate nanotubes. The structure of final product depended on heating conditions. Titanium nanotubes heated in air at a temperature of 850 °C decomposed into three phases — Na{sub 2}Ti{sub 6}O{sub 13} (nanorods) and two phases of TiO{sub 2} — anatase and rutile. At higher temperatures the anatase form of TiO{sub 2} transforms into rutile and the nanorods change into rutile nanoparticles. By contrast, in the vacuum only anatase phases of TiO{sub 2} were obtained by heating at 900 °C. The anatase transformation into rutile began only after a longer time of heating at 1000 °C. For the description of anisotropic XRD line broadening in the total powder pattern fitting by the program MSTRUCT a model of nanorods with elliptical base was included in the software. The model parameters — rod length, axis size of the elliptical base, the ellipse flattening parameter and twist of the base could be refined. Variation of particle shapes with temperature was found. - Highlights: • Titanate nanotubes changed to particles of TiO{sub 2} and nanorods of Na{sub 2}Ti{sub 6}O{sub 13} at 850 °C. • With heating time and temperature nanorods transformed to rutile nanoparticles. • X-ray diffraction powder pattern fitting indicated an elliptical shape of nanorod base. • No transition of titanate nanotubes to Na{sub 2}Ti{sub 6}O{sub 13} was found after heating in vacuum. • Heating of titanate nanotubes in vacuum leads to appearance of anatase nanowires.

  2. Can trans-polyacetylene be formed on single-walled carbon-doped boron nitride nanotubes?

    PubMed

    Chen, Ying; Wang, Hong-xia; Zhao, Jing-xiang; Cai, Qing-hai; Wang, Xiao-guang; Wang, Xuan-zhang

    2012-07-01

    Recently, the grafting of polymer chains onto nanotubes has attracted increasing attention as it can potentially be used to enhance the solubility of nanotubes and in the development of novel nanotube-based devices. In this article, based on density functional theory (DFT) calculations, we report the formation of trans-polyacetylene on single-walled carbon-doped boron nitride nanotubes (BNNTs) through their adsorption of a series of C(2)H(2) molecules. The results show that, rather than through [2 + 2] cycloaddition, an individualmolecule would preferentially attach to a carbon-doped BNNT via "carbon attack" (i.e., a carbon in the C(2)H(2) attacks a site on the BNNT). The adsorption energy gradually decreases with increasing tube diameter. The free radical of the carbon-doped BNNT is almost completely transferred to the carbon atom at the end of the adsorbed C(2)H(2) molecule. When another C(2)H(2) molecule approaches the carbon-doped BNNT, it is most energetically favorable for this C(2)H(2) molecule to be adsorbed at the end of the previously adsorbed C(2)H(2) molecule, and so on with extra C(2)H(2) molecules, leading to the formation of polyacetylene on the nanotube. The spin of the whole system is always localized at the tip of the polyacetylene formed, which initiates the adsorption of the incoming species. The present results imply that carbon-doped BNNT is an effective "metal-free" initiator for the formation of polyacetylene. PMID:22271098

  3. Dynamic DNA Nanotubes: Reversible Switching between Single and Double-Stranded Forms, and Effect of Base Deletions.

    PubMed

    Rahbani, Janane F; Hariri, Amani A; Cosa, Gonzalo; Sleiman, Hanadi F

    2015-12-22

    DNA nanotubes hold great potential as drug delivery vehicles and as programmable templates for the organization of materials and biomolecules. Existing methods for their construction produce assemblies that are entirely double-stranded and rigid, and thus have limited intrinsic dynamic character, or they rely on chemically modified and ligated DNA structures. Here, we report a simple and efficient synthesis of DNA nanotubes from 11 short unmodified strands, and the study of their dynamic behavior by atomic force microscopy and in situ single molecule fluorescence microscopy. This method allows the programmable introduction of DNA structural changes within the repeat units of the tubes. We generate and study fully double-stranded nanotubes, and convert them to nanotubes with one, two and three single-stranded sides, using strand displacement strategies. The nanotubes can be reversibly switched between these forms without compromising their stability and micron-scale lengths. We then site-specifically introduce DNA strands that shorten two sides of the nanotubes, while keeping the length of the third side. The nanotubes undergo bending with increased length mismatch between their sides, until the distortion is significant enough to shorten them, as measured by AFM and single-molecule fluorescence photobleaching experiments. The method presented here produces dynamic and robust nanotubes that can potentially behave as actuators, and allows their site-specific addressability while using a minimal number of component strands. PMID:26556531

  4. Dynamic DNA Nanotubes: Reversible Switching between Single and Double-Stranded Forms, and Effect of Base Deletions.

    PubMed

    Rahbani, Janane F; Hariri, Amani A; Cosa, Gonzalo; Sleiman, Hanadi F

    2015-12-22

    DNA nanotubes hold great potential as drug delivery vehicles and as programmable templates for the organization of materials and biomolecules. Existing methods for their construction produce assemblies that are entirely double-stranded and rigid, and thus have limited intrinsic dynamic character, or they rely on chemically modified and ligated DNA structures. Here, we report a simple and efficient synthesis of DNA nanotubes from 11 short unmodified strands, and the study of their dynamic behavior by atomic force microscopy and in situ single molecule fluorescence microscopy. This method allows the programmable introduction of DNA structural changes within the repeat units of the tubes. We generate and study fully double-stranded nanotubes, and convert them to nanotubes with one, two and three single-stranded sides, using strand displacement strategies. The nanotubes can be reversibly switched between these forms without compromising their stability and micron-scale lengths. We then site-specifically introduce DNA strands that shorten two sides of the nanotubes, while keeping the length of the third side. The nanotubes undergo bending with increased length mismatch between their sides, until the distortion is significant enough to shorten them, as measured by AFM and single-molecule fluorescence photobleaching experiments. The method presented here produces dynamic and robust nanotubes that can potentially behave as actuators, and allows their site-specific addressability while using a minimal number of component strands.

  5. Multifunctional nanocomposites of carbon nanotubes and nanoparticles formed via vacuum filtration

    DOEpatents

    Hersam, Mark C; Ostojic, Gordana; Liang, Yu Teng

    2013-10-22

    In one aspect, the present invention provides a method of forming a film of nanocomposites of carbon nanotubes (CNTs) and platinum (Pt) nanoparticles. In one embodiment, the method includes the steps of (a) providing a first solution that contains a plurality of CNTs, (b) providing a second solution that contains a plurality of Pt nanoparticles, (c) combining the first solution and the second solution to form a third solution, and (d) filtering the third solution through a nanoporous membrane using vacuum filtration to obtain a film of nanocomposites of CNTs and Pt nanoparticles.

  6. Modeling the self-assembly of lipids and nanotubes in solution: forming vesicles and bicelles with transmembrane nanotube channels.

    PubMed

    Dutt, Meenakshi; Kuksenok, Olga; Nayhouse, Michael J; Little, Steven R; Balazs, Anna C

    2011-06-28

    Via dissipative particle dynamics (DPD), we simulate the self-assembly of end-functionalized, amphiphilic nanotubes and lipids in a hydrophilic solvent. Each nanotube encompasses a hydrophobic stalk and two hydrophilic ends, which are functionalized with end-tethered chains. With a relatively low number of the nanotubes in solution, the components self-assemble into stable lipid-nanotube vesicles. As the number of nanotubes is increased, the system exhibits a vesicle-to-bicelle transition, resulting in stable hybrid bicelle. Moreover, our results reveal that the nanotubes cluster into distinct tripod-like structures within the vesicles and aggregate into a ring-like assembly within the bicelles. For both the vesicles and bicelles, the nanotubes assume trans-membrane orientations, with the tethered hairs extending into the surrounding solution or the encapsulated fluid. Thus, the hairs provide a means of regulating the transport of species through the self-assembled structures. Our findings provide guidelines for creating nanotube clusters with distinctive morphologies that might be difficult to achieve through more conventional means. The results also yield design rules for creating synthetic cell-like objects or microreactors that can exhibit biomimetic functionality.

  7. Texture and microstructure in co-sputtered Mg-M-O (M = Mg, Al, Cr, Ti, Zr, and Y) films

    NASA Astrophysics Data System (ADS)

    Saraiva, M.; Depla, D.

    2012-05-01

    Mg-M-O solid solution films (M = Mg, Al, Cr, Ti, Zr, and Y) with various M contents are grown employing reactive co-sputtering by varying the target-to-substrate distance. It is shown that all films are biaxially aligned. When the two cathodes are equipped with the same target material (Mg), the in-plane alignment is determined by the cathode closest to the substrate, i.e., by the largest material flux. In the case of nearly equal material fluxes from the two cathodes, double in-plane orientation is observed. This is also the case for the Mg-Al-O and Mg-Cr-O films, while the Mg-Ti-O, Mg-Zr-O and Mg-Y-O films exhibit single in-plane orientation. Pole figures indicate that the grains in Mg-M-O (M different than Mg) are titled; in the Mg-Al-O, Mg-Cr-O, and Mg-Ti-O films, the grains tilt towards the Al, Cr, and Ti metal flux, respectively, while the grain tilt of the Mg-Zr-O and Mg-Y-O films is found to be towards the Mg metal flux. Furthermore, SEM cross-sectional images of the Mg-M-O films reveal columnar microstructure with columns tilted to the same direction as the grains. A mechanism which is based on the cation radius change upon the incorporation of an M atom in the MgO lattice is proposed to explain the tilting.

  8. X-ray microstructural analysis of nanocrystalline TiZrN thin films by diffraction pattern modeling

    SciTech Connect

    Escobar, D.; Ospina, R.; Gómez, A.G.; Restrepo-Parra, E.; Arango, P.J.

    2014-02-15

    A detailed microstructural characterization of nanocrystalline TiZrN thin films grown at different substrate temperatures (T{sub S}) was carried out by X-ray diffraction (XRD). Total diffraction pattern modeling based on more meaningful microstructural parameters, such as crystallite size distribution and dislocation density, was performed to describe the microstructure of the thin films more precisely. This diffraction modeling has been implemented and used mostly to characterize powders, but the technique can be very useful to study hard thin films by taking certain considerations into account. Nanocrystalline films were grown by using the cathodic pulsed vacuum arc technique on stainless steel 316L substrates, varying the temperature from room temperature to 200 °C. Further surface morphology analysis was performed to study the dependence of grain size on substrate temperature using atomic force microscopy (AFM). The crystallite and surface grain sizes obtained and the high density of dislocations observed indicate that the films underwent nanostructured growth. Variations in these microstructural parameters as a function of T{sub S} during deposition revealed a competition between adatom mobility and desorption processes, resulting in a specific microstructure. These films also showed slight anisotropy in their microstructure, and this was incorporated into the diffraction pattern modeling. The resulting model allowed for the films' microstructure during synthesis to be better understood according to the experimental results obtained. - Highlights: • Mobility and desorption competition generates a critical temperature. • A microstructure anisotropy related to the local strain was observed in thin films. • Adatom mobility and desorption influence grain size and microstrain.

  9. Reactive magnetron cosputtering of hard and conductive ternary nitride thin films: Ti-Zr-N and Ti-Ta-N

    SciTech Connect

    Abadias, G.; Koutsokeras, L. E.; Dub, S. N.; Tolmachova, G. N.; Debelle, A.; Sauvage, T.; Villechaise, P.

    2010-07-15

    Ternary transition metal nitride thin films, with thickness up to 300 nm, were deposited by dc reactive magnetron cosputtering in Ar-N{sub 2} plasma discharges at 300 deg. C on Si substrates. Two systems were comparatively studied, Ti-Zr-N and Ti-Ta-N, as representative of isostructural and nonisostructural prototypes, with the aim of characterizing their structural, mechanical, and electrical properties. While phase-separated TiN-ZrN and TiN-TaN are the bulk equilibrium states, Ti{sub 1-x}Zr{sub x}N and Ti{sub 1-y}Ta{sub y}N solid solutions with the Na-Cl (B1-type) structure could be stabilized in a large compositional range (up to x=1 and y=0.75, respectively). Substituting Ti atoms by either Zr or Ta atoms led to significant changes in film texture, microstructure, grain size, and surface morphology, as evidenced by x-ray diffraction, x-ray reflectivity, and scanning electron and atomic force microscopies. The ternary Ti{sub 1-y}Ta{sub y}N films exhibited superior mechanical properties to Ti{sub 1-x}Zr{sub x}N films as well as binary compounds, with hardness as high as 42 GPa for y=0.69. All films were metallic, the lowest electrical resistivity {rho}{approx}65 {mu}{Omega} cm being obtained for pure ZrN, while for Ti{sub 1-y}Ta{sub y}N films a minimum was observed at y{approx}0.3. The evolution of the different film properties is discussed based on microstructrural investigations.

  10. Processing, structure and tribological property relations of ternary Zn-Ti-O and quaternary Zn-Ti-Zr-O nanocrystalline coatings

    NASA Astrophysics Data System (ADS)

    Ageh, Victor

    Conventional liquid lubricants are faced with limitations under extreme cyclic operating conditions, such as in applications that require lubrication when changing from atmospheric pressure to ultrahigh vacuum and ambient air to dry nitrogen (e.g., satellite components), and room to elevated (>500°C) temperatures (e.g., aerospace bearings). Alternatively, solid lubricant coatings can be used in conditions where synthetic liquid lubricants and greases are not applicable; however, individual solid lubricant phases usually perform best only for a limited range of operating conditions. Therefore, solid lubricants that can adequately perform over a wider range of environmental conditions are needed, especially during thermal cycling with temperatures exceeding 500°C. One potential material class investigated in this dissertation is lubricious oxides, because unlike other solid lubricant coatings they are typically thermodynamically stable in air and at elevated temperatures. While past studies have been focused on binary metal oxide coatings, such as ZnO, there have been very few ternary oxide and no reported quaternary oxide investigations. The premise behind the addition of the third and fourth refractory metals Ti and Zr is to increase the number of hard and wear resistant phases while maintaining solid lubrication with ZnO. Therefore, the major focus of this dissertation is to investigate the processing-structuretribological property relations of composite ZnO, TiO2 and ZrO2 phases that form ternary (ZnTi)xOy and quaternary (ZnTiZr) xOy nanocrystalline coatings. The coatings were processed by atomic layer deposition (ALD) using a selective variation of ALD parameters. The growth structure and chemical composition of as-deposited and ex situ annealed ternary and quaternary oxide coatings were studied by combined x-ray diffraction/focused ion beam microscopy/cross-sectional transmission electron microscopy, and x-ray photoelectron spectroscopy/Auger electron

  11. Influence of residual pressure and ion implantation on the structure, elemental composition, and properties of (TiZrAlYNb)N nitrides

    NASA Astrophysics Data System (ADS)

    Pogrebnjak, A. D.; Yakushchenko, I. V.; Sobol', O. V.; Beresnev, V. M.; Kupchishin, A. I.; Bondar, O. V.; Lisovenko, M. A.; Amekura, H.; Kono, K.; Oyoshi, K.; Takeda, Y.

    2015-08-01

    The nitrides of high-entropy alloys, (TiZrAlYNb)N, fabricated by cathodic vacuum arc evaporation are studied with electron microscopy, atomic force microscopy, laser scanning microscopy; energy-dispersive X-ray analysis, X-ray phase analysis, time-of-flight secondary-ion mass spectrometry; and hardness measurements. It is found that the deposition parameters influence the structure, surface morphology, element distribution, and mechanical properties. The structural—phase state of the coatings before and after the ion implantation of heavy negative gold ions Au- are compared.

  12. Structure and stability of the M8-nNnC12 (M=Ti, Zr; N=Sc, Y and n=1,2,3) Met-Cars as building blocks of cluster-assembled materials

    NASA Astrophysics Data System (ADS)

    Berkdemir, Cuneyt; Cheng, Shi-Bo; Welford Castleman, A., Jr.; Sofo, Jorge O.

    2012-02-01

    Clusters can be used as building blocks for new materials. However, in order to form a bulk material with clusters, they should be chemically stable. This stability can be characterized by a closed-shell electronic configuration having a large HOMO-LUMO gap. Met-Cars, metal-carbon species composed of early transition metals bonded to carbon, are stable but very reactive. We propose a method to lower their reactivity by metal atom substitution with lower atomic number atoms. We report DFT results on M8-nNnC12 (M = Ti, Zr; N = Sc, Y, and n=1,2,3) Met-Cars in the neutral, cationic and anionic charge states. Our results show that the isoelectronic M6N2C12, M5N3C12^- and M7N1C12^+ Met-Cars have closed-shell electronic configurations and larger HOMO-LUMO gaps (1.0-1.7 eV) than that of the M8C12. The intercluster interaction between two isolated neutral M6N2C12 Met-Cars is relatively weak compared to the M8C12 dimers. Due to the weak interaction of the isolated neutral Met-Cars, their unique properties would be retained during assembly.

  13. Linear and spiral forms of longitudinal cuts in graphitized N-doped multiwalled carbon nanotubes (g-N-MWCNTs).

    PubMed

    Meier, Mark S; Selegue, John P; Cassity, Kelby B; Kaur, Aman Preet; Qian, Dali

    2010-08-25

    Nitrogen-containing multiwalled nanotubes (N-MWCNTs), formed by CVD from a nitrogen-containing feedstock have a 'bamboo' structure in which the axes of the graphene planes are not parallel to the axis of the nanotube and the core is periodically bridged. We find that thermal and chemical treatment of these materials can produce nanotubes that have been cut longitudinally in either a linear or in a spiral manner. In addition, these longitudinally cut nanotubes can be partially or fully unrolled by sonication in an aqueous surfactant, producing graphite platelets as well as narrow structures that could be thin graphite ribbons or very narrow, intact N-MWCNTs. These different morphologies of graphite, available from one source, suggest that there are multiple structures of N-MWCNTs present, few as simple as stacked cups or nested scrolls.

  14. Synthesis and Structure of a New Lithium Amide Ligand Precursor: A Tridentate Nitrogen-Based Donor Set of the Formula N(SiMe(2)CH(2)NMe(2))(2). Synthesis and Structure of the Group 4 Amides MCl(3)[N(SiMe(2)CH(2)NMe(2))(2)] (M = Ti, Zr, Hf).

    PubMed

    Fryzuk, Michael D.; Hoffman, Vera; Kickham, James E.; Rettig, Steven J.; Gambarotta, Sandro

    1997-07-30

    The new lithium amide LiN(SiMe(2)CH(2)NMe(2))(2) was prepared by reaction of NH(3) with the corresponding silylamine Me(2)NSiMe(2)CH(2)NMe(2) followed by addition of butyllithium. This lithium derivative exists as a dimer in the solid state wherein the two lithium ions are bridged by the two amido units with the amine arms of each unit bonded to opposite lithium centers in an overall pseudo D(2) structure; however, in solution, a fluxional process serves to interconvert the enantiomeric forms of the dimer unit. The coordination chemistry of the lithium amide dimer has been investigated; reaction with a series of group 4 starting halides, MCl(4), leads to the corresponding complexes MCl(3)[N(SiMe(2)CH(2)NMe(2))(2)], where M = Ti, Zr, and Hf. The structures of these starting trihalides in solution and in the solid state are presented. PMID:11670025

  15. Dendritic carbon architectures formed by nanotube core-directed diffusion-limited aggregation of nanoparticles.

    PubMed

    Liu, Zhenyu; Kong, Xiaohui

    2010-08-28

    A regular array of fractal patterns with macroscopic dendritic carbon architecture was prepared by catalytic chemical vapor deposition (CVD). The dendritic carbon architectures have micrometre-sized stems and hyperbranches evolved by lateral growth, and they are formed by diffusion-limited aggregation of carbon-encapsulated iron nanoparticle building blocks generated from catalytic pyrolysis of toluene, which is directed by carbon nanotube cores, and followed by subsequent restructuring from surface to bulk. Incorporation of such proposed processes in Monte Carlo simulations generates dendritic architectures similar to the morphologies observed from the experiments. The findings provide direct information to the time resolved evolution of the morphology and microstructure of the dendritic carbon architecture, which mimic the nature behavior as snowflake attaching on the tree branches. Those will be important to understand the growth of vapor grown carbon fibers and carbon filamentous structures, and further possibility to control branching out of vapor grown carbon fibers. PMID:20607160

  16. High-T C fully compensated ferrimagnetic semiconductors as spin-filter materials: the case of CrVXAl (X = Ti, Zr, Hf) Heusler compounds.

    PubMed

    Galanakis, I; Özdoğan, K; Şaşıoglu, E

    2014-02-26

    We extend our recent work on spin-filter materials (Galanakis et al 2013 Appl. Phys. Lett.103 142404) to the case of CrVXAl (X = Ti, Zr, Hf) compounds, for which, using ab initio electronic structure calculations, we show that p-d hybridization leads to the formation of a fully compensated ferrimagnetic semiconducting state with moderate exchange splitting. The magnetism is of covalent-type and the very strong antiferromagnetic Cr-V exchange interactions lead to extremely high Curie temperature, TC, values. Furthermore, all three compounds are thermodynamically and magnetically stable. The combination of very high TC values with a zero total net magnetization makes them promising materials for spintronics applications.

  17. The microstructure of a multielement nanostructured (TiZrHfVNbTa)N coating and its resistance to irradiation with Au- ions

    NASA Astrophysics Data System (ADS)

    Pogrebnjak, A. D.; Yakushchenko, I. V.; Bondar, O. V.; Sobol', O. V.; Beresnev, V. M.; Oyoshi, K.; Amekura, H.; Takeda, Y.

    2015-11-01

    The formation of a phase with a FCC lattice of the NaCl structure type is observed following the deposition of a multielement nanostructured (TiZrHfVNbTa)N coating. An increase in pressure results in a change in the preferred orientation of crystallite growth from the [100] axis perpendicular to the growth plane to [111]. The implantation of negative Au- ions with a dose of 1 × 1017 cm-2 and a concentration of 2.1 at % leads to the formation of a disordered polycrystalline structure with no preferred orientation of the FCC phase, reduces the size of nanocrystallites from 8 to 1-3 nm in a layer with a depth of up to 30-35 nm, and increases the nanohardness to 33.0 GPa. The large difference in atomic radii of refractory metals and the reduction in the size of nanograins in the coating contribute to an increase in hardness (51 GPa).

  18. Preparation and Characterization of Ti-Zr-V Non-Evaporable Getter Films to Be Used in Ultra-High Vacuum

    SciTech Connect

    Ferreira, Marcelo J.; Tallarico, Denise A.; Nascente, Pedro A. P.

    2009-01-29

    An appealing procedure to obtain operating pressures in the 10{sup -8} Pa range, which is necessary for the insertion devices elements of synchrotron sources, is to coat the inner ultra-high vacuum chamber walls with a thin film of non-evaporable getter (NEG) metals. Titanium, zirconium, vanadium, and their alloys are used as NEG materials due to their low activation temperature, high chemical activity, large solubility, and high diffusivity for gases. In this work, magnetron sputtering was employed to deposit thin films of Ti-Zr-V on a Si(111) substrate. The morphological, structural, and chemical analyses were carried out by atomic force microscopy (AFM), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS)

  19. New dielectric ceramics Pb(Cd)BiM/sup IV/SbO/sub 7/ (M/sup IV/ = Ti, Zr, Sn) with the pyrochlore structure

    SciTech Connect

    Lambachri, A.; Monier, M.; Mercurio, J.P.; Frit, B.

    1988-04-01

    Dielectric ceramics have been obtained by natural sintering of pyrochlore phases with general formula Pb(Cd)BiM/sup IV/SbO/sub 7/ (M/sup IV/ = Ti, Zr, Sn). Low frequency dielectric characteristics have been studied with respect to the processing conditions: sintering without additive and in the presence of some low melting compounds (PbO, Pb/sub 5/Ge/sub 3/O/sub 11/, Bi/sub 12/PbO/sub 19/ and Bi/sub 12/CdO/sub 19/). The dielectric constants of these ceramics lie between 30 and 60, the dielectric losses range from 10 to 30.10/sup -4/ and the temperature coefficient of the dielectric constants (20 - 100/sup 0/C) can be tailored by means of additives in the +- 30 ppm K/sup -1/ range.

  20. Fabrication of nanotube arrays on commercially pure titanium and their apatite-forming ability in a simulated body fluid

    SciTech Connect

    Hsu, Hsueh-Chuan; Wu, Shih-Ching; Hsu, Shih-Kuang; Chang, Yu-Chen; Ho, Wen-Fu

    2015-02-15

    In this study, we investigated self-organized TiO{sub 2} nanotubes that were grown using anodization of commercially pure titanium at 5 V or 10 V in NH{sub 4}F/NaCl electrolyte. The nanotube arrays were annealed at 450 °C for 3 h to convert the amorphous nanotubes to anatase and then they were immersed in simulated body fluid at 37 °C for 0.5, 1, and 14 days. The purpose of this experiment was to evaluate the apatite-formation abilities of anodized Ti nanotubes with different tube diameters and lengths. The nanotubes that formed on the surfaces of Ti were examined using a field emission scanning electron microscope, X-ray diffraction, and X-ray photoelectron spectroscope. When the anodizing potential was increased from 5 V to 10 V, the pore diameter of the nanotube increased from approximately 24–30 nm to 35–53 nm, and the tube length increased from approximately 590 nm to 730 nm. In vitro testing of the heat-treated nanotube arrays indicated that Ca-P formation occurred after only 1 day of immersion in simulated body fluid. This result was particularly apparent in the samples that were anodized at 10 V. It was also found that the thickness of the Ca-P layer increases as the applied potential for anodized c.p. Ti increases. The average thickness of the Ca-P layer on Ti that was anodized at 5 V and 10 V was approximately 170 nm and 190 nm, respectively, after immersion in simulated body fluid for 14 days. - Highlights: • TiO{sub 2} nanotube on Ti surface was formed by anodic oxidation in a NaCl/NH{sub 4}F solution. • TiO{sub 2} layers show a tube length of 590 nm and 730 nm at 5 V and 10 V, respectively. • After soaking in SBF, Ca-P layer completely covered the entire nanotubular surfaces. • The Ca-P layer was thicker on the Ti surface anodized at 10 V.

  1. Conditions for forming composite carbon nanotube-diamond like carbon material that retain the good properties of both materials

    SciTech Connect

    Ren, Wei Avchaciov, Konstantin; Nordlund, Kai; Iyer, Ajai; Koskinen, Jari; Kaskela, Antti; Kauppinen, Esko I.

    2015-11-21

    Carbon nanotubes are of wide interest due to their excellent properties such as tensile strength and electrical and thermal conductivity, but are not, when placed alone on a substrate, well resistant to mechanical wear. Diamond-like carbon (DLC), on the other hand, is widely used in applications due to its very good wear resistance. Combining the two materials could provide a very durable pure carbon nanomaterial enabling to benefit from the best properties of both carbon allotropes. However, the synthesis of high-quality diamond-like carbon uses energetic plasmas, which can damage the nanotubes. From previous works it is neither clear whether the quality of the tubes remains good after DLC deposition, nor whether the DLC above the tubes retains the high sp{sup 3} bonding fraction. In this work, we use experiments and classical molecular dynamics simulations to study the mechanisms of DLC formation on various carbon nanotube compositions. The results show that high-sp{sup 3}-content DLC can be formed provided the deposition conditions allow for sidewards pressure to form from a substrate close beneath the tubes. Under optimal DLC formation energies of around 40–70 eV, the top two nanotube atom layers are fully destroyed by the plasma deposition, but layers below this can retain their structural integrity.

  2. Conditions for forming composite carbon nanotube-diamond like carbon material that retain the good properties of both materials

    NASA Astrophysics Data System (ADS)

    Ren, Wei; Iyer, Ajai; Koskinen, Jari; Kaskela, Antti; Kauppinen, Esko I.; Avchaciov, Konstantin; Nordlund, Kai

    2015-11-01

    Carbon nanotubes are of wide interest due to their excellent properties such as tensile strength and electrical and thermal conductivity, but are not, when placed alone on a substrate, well resistant to mechanical wear. Diamond-like carbon (DLC), on the other hand, is widely used in applications due to its very good wear resistance. Combining the two materials could provide a very durable pure carbon nanomaterial enabling to benefit from the best properties of both carbon allotropes. However, the synthesis of high-quality diamond-like carbon uses energetic plasmas, which can damage the nanotubes. From previous works it is neither clear whether the quality of the tubes remains good after DLC deposition, nor whether the DLC above the tubes retains the high sp3 bonding fraction. In this work, we use experiments and classical molecular dynamics simulations to study the mechanisms of DLC formation on various carbon nanotube compositions. The results show that high-sp3-content DLC can be formed provided the deposition conditions allow for sidewards pressure to form from a substrate close beneath the tubes. Under optimal DLC formation energies of around 40-70 eV, the top two nanotube atom layers are fully destroyed by the plasma deposition, but layers below this can retain their structural integrity.

  3. Cell interaction with modified nanotubes formed on titanium alloy Ti-6Al-4V.

    PubMed

    Moravec, Hynek; Vandrovcova, Marta; Chotova, Katerina; Fojt, Jaroslav; Pruchova, Eva; Joska, Ludek; Bacakova, Lucie

    2016-08-01

    Nanotubes with diameters ranging from 40 to 60nm were prepared by electrochemical oxidation of the Ti-6Al-4V alloy in electrolyte containing ammonium sulphate and ammonium fluoride. The nanotubes were further modified with calcium and phosphate ions or were heat treated. Polished Ti-6Al-4V alloy served as a reference sample. The spreading of human osteoblast-like cells was similar on all nanotube samples but lower than on polished samples. The number of initially adhered cells was higher on non-modified nanotubes, but the final cell number was the highest on Ca-enriched nanotubes and the lowest on heat-treated nanotubes. However, these differences were relatively small and less pronounced than the differences in the concentration of specific molecular markers of cell adhesion and differentiation, estimated by their intensity of immunofluorescence staining. The concentration of vinculin, i.e. a protein of focal adhesion plaques, was the lowest on nanotubes modified with calcium. Collagen I, an early marker of osteogenic cell differentiation, was also the lowest on samples modified with calcium and was highest on polished samples. Alkaline phosphatase, a middle marker of osteogenic differentiation, was observed in lowest concentration on nanotubes modified with phosphorus and the highest on heat-treated samples. Osteocalcin concentrations, a late marker of osteogenic cell differentiation, were similar on all tested samples, although they tended to be the highest on heat-treated samples. Thus, osteogenic differentiation can be modulated by various additional treatments of nanotube coatings on Ti-6Al-4V implants. PMID:27157757

  4. Endohedral confinement of a DNA dodecamer onto pristine carbon nanotubes and the stability of the canonical B form

    NASA Astrophysics Data System (ADS)

    Cruz, Fernando J. A. L.; de Pablo, Juan J.; Mota, José P. B.

    2014-06-01

    Although carbon nanotubes are potential candidates for DNA encapsulation and subsequent delivery of biological payloads to living cells, the thermodynamical spontaneity of DNA encapsulation under physiological conditions is still a matter of debate. Using enhanced sampling techniques, we show for the first time that, given a sufficiently large carbon nanotube, the confinement of a double-stranded DNA segment, 5'-D(*CP*GP*CP*GP*AP*AP*TP*TP*CP*GP*CP*G)-3', is thermodynamically favourable under physiological environments (134 mM, 310 K, 1 bar), leading to DNA-nanotube hybrids with lower free energy than the unconfined biomolecule. A diameter threshold of 3 nm is established below which encapsulation is inhibited. The confined DNA segment maintains its translational mobility and exhibits the main geometrical features of the canonical B form. To accommodate itself within the nanopore, the DNA's end-to-end length increases from 3.85 nm up to approximately 4.1 nm, due to a ˜0.3 nm elastic expansion of the strand termini. The canonical Watson-Crick H-bond network is essentially conserved throughout encapsulation, showing that the contact between the DNA segment and the hydrophobic carbon walls results in minor rearrangements of the nucleotides H-bonding. The results obtained here are paramount to the usage of carbon nanotubes as encapsulation media for next generation drug delivery technologies.

  5. Electrochemical monitoring of piroxicam in different pharmaceutical forms with multi-walled carbon nanotubes paste electrode.

    PubMed

    Abbaspour, Abdolkarim; Mirzajani, Roya

    2007-05-01

    The electrochemical behavior of piroxicam on a multi-walled carbon nanotubes electrode for the first time was investigated. A highly sensitive and fast responding sensor for determination of piroxicam was simply and conveniently fabricated. The constructed electrode exhibits efficiently catalytic activity for the electrooxidation of piroxicam at a reduced over potential with high sensitivity, stability, and long lifetime in the wide concentration rang of piroxicam. The oxidation process was found to be dependent on the pH of the supporting electrolyte. The behavior is further exploited as a sensitive detection method for piroxicam determination by differential pulse voltammetry. Under the optimized conditions the calibration plots are linear in the concentration range of 0.15-5 microg ml(-1). Application of the method for the determination of the drug in the dosage form (Feledene capsules and tablets and also piroxicam gel), without any interference, from the excipients, resulted in acceptable deviation from the stated concentrations. Recoveries were obtained in the range 96.35-104.16%. The detection limit of 0.1 microg ml(-1) was obtained for piroxicam determination.

  6. Topological insulators in the ordered double transition metals M2'M″C2 MXenes (M'=Mo , W; M″=Ti , Zr, Hf)

    NASA Astrophysics Data System (ADS)

    Khazaei, Mohammad; Ranjbar, Ahmad; Arai, Masao; Yunoki, Seiji

    2016-09-01

    The family of two-dimensional transition metal carbides, so called MXenes, has recently found new members with ordered double transition metals M2'M″C2 , where M' and M″ stand for transition metals. Here, using a set of first-principles calculations, we demonstrate that some of the newly added members, oxide M2'M″C2 (M'=Mo , W; M″=Ti , Zr, Hf) MXenes, are topological insulators. The nontrivial topological states of the predicted MXenes are revealed by the Z2 index, which is evaluated from the parities of the occupied bands below the Fermi energy at time reversal invariant momenta, and also by the presence of the edge states. The predicted M2'M″C2O2 MXenes show nontrivial gaps in the range of 0.041-0.285 eV within the generalized gradient approximation and 0.119-0.409 eV within the hybrid functional. The band gaps are induced by the spin-orbit coupling within the degenerate states with dx2-y2 and dx y characters of M' and M″, while the band inversion occurs at the Γ point among the degenerate dx2-y2/dx y orbitals and a nondegenerate d3 z2-r2 orbital, which is driven by the hybridization of the neighboring orbitals. The phonon dispersion calculations find that the predicted topological insulators are structurally stable. The predicted W-based MXenes with large band gaps might be suitable candidates for many topological applications at room temperature. In addition, we study the electronic structures of thicker ordered double transition metals M2'M2″C3O2 (M'=Mo , W; M″=Ti , Zr, Hf) and find that they are nontrivial topological semimetals. Among the predicted topological insulators and topological semimetals, Mo2TiC2 and Mo2Ti2C3 functionalized with a mixture of F, O, and OH have already been synthesized, and therefore some of the topological materials proposed here can be experimentally accessed.

  7. Palladium nanotubes formed by lipid tubule templating and their application in ethanol electrocatalysis.

    PubMed

    Wang, Yinan; Ma, Shenghua; Su, Yingchun; Han, Xiaojun

    2015-04-13

    Palladium nanotubes were fabricated by using lipid tubules as templates for the first time in a controlled manner. The positively charged lipid 1,2-dioleoyl-3-trimethylammoniumpropane (DOTAP) was doped into lipid tubules to adsorb PdCl4 (2-) on the tubule surfaces for further reduction. The lipid tubule formation was optimized by studying the growing dynamics and ethanol/water ratio. The DOTAP-doped tubules showed pH stability from 0 to 14, which makes them ideal templates for metal plating. The Pd nanotubes are open-ended with a tunable wall thickness. They exhibited good electrocatalytic performance in ethanol. Their electrochemically active surface areas were 6.5, 10.6, and 83.2 m(2)  g(-1) for Pd nanotubes with 77, 101, and 150 nm wall thickness, respectively. These Pd nanotubes have great potential in fuel cells. The method demonstrated also opens up a way to synthesize hollow metal nanotubes.

  8. Carbon nanotube composite materials

    DOEpatents

    O'Bryan, Gregory; Skinner, Jack L; Vance, Andrew; Yang, Elaine Lai; Zifer, Thomas

    2015-03-24

    A material consisting essentially of a vinyl thermoplastic polymer, un-functionalized carbon nanotubes and hydroxylated carbon nanotubes dissolved in a solvent. Un-functionalized carbon nanotube concentrations up to 30 wt % and hydroxylated carbon nanotube concentrations up to 40 wt % can be used with even small concentrations of each (less than 2 wt %) useful in producing enhanced conductivity properties of formed thin films.

  9. Mechanical and Electronic Properties of A1-xBxHy (A and B =Ti, Zr, Hf) Hydride Alloys: A First-principles Study

    SciTech Connect

    Dai, Yunya; Yang, Li; Nie, JL; Fan, K. M.; Peng, SM; Long, XG; Zhou, Xiaosong; Bing, Wenzeng; Zu, Xiaotao; Gao, Fei

    2013-12-01

    Using ab initio calculations, we investigated the mechanical and electronic properties of Ti1-xHfxHy, Ti1-xZrxHy and Zr1-xHfxTHy (x=0, 0.25, 0.5, 0.75, 1; y=1.5, 1.75, 2). The calculated results in binary hydrides show that the β-phase MH1.5[100] (M=Ti, Zr, Hf) are more stable than other possible structures. At the Fermi level, the density of states for metal d state increases with increasing the H concentration in MHy (y ranged from 1.5 to 2), which leads to the instability of their fcc structures and induces the tetragonal distortion. Ti0.75Hf0.25H1.5 and Zr0.25Hf0.75H1.5 exhibit the highest mechanical stability, while Ti0.25Zr0.75H1.5 has the lowest mechanical stability among the corresponding ternary systems considered. Moreover, the systems studied in the present work are all anisotropic and show a ductile behavior. The tetragonal distortion in Ti1-xHfxH1.5, Ti1-xZrxH1.5 and Zr1-xHfxH1.5 is not observed, retaining their fcc structures. The electronic structure of A1-xBxHy (A and B =Ti, Hf, Zr) exhibits metallic character.

  10. Stability and crystal chemistry of the ternary borides M2(Ni21-xMx)B6 (M tbnd Ti, Zr, Hf)

    NASA Astrophysics Data System (ADS)

    Artini, C.; Provino, A.; Valenza, F.; Pani, M.; Cacciamani, G.

    2016-01-01

    A crystallochemical study was undertaken to investigate the structural stability and the compositional extent of the ternary borides M2(Ni21-xMx)B6 (M tbnd Ti, Zr, Hf). This phase often occurs during the production of MB2 joints by means of Ni-B brazing alloys. Samples with the nominal compositions M2Ni21B6 and M3Ni20B6 were synthesized by arc melting and characterized by optical and electron microscopy, and X-ray diffraction. Crystal structure refinements were performed by the Rietveld method. The compositional boundaries of the ternary phases were experimentally determined and found strictly related to the M/Ni size ratio. The stability of this structure is mainly determined by the capability of the structure to expand under the effect of the Ni substitution by the M atom. The CALPHAD modeling of the three M-Ni-B ternary systems in the Ni-rich corner of the phase diagram, performed on the basis of the obtained structural data, shows a good agreement with experimental results.

  11. Endohedral confinement of a DNA dodecamer onto pristine carbon nanotubes and the stability of the canonical B form

    SciTech Connect

    Cruz, Fernando J. A. L.; Pablo, Juan J. de; Mota, José P. B.

    2014-06-14

    Although carbon nanotubes are potential candidates for DNA encapsulation and subsequent delivery of biological payloads to living cells, the thermodynamical spontaneity of DNA encapsulation under physiological conditions is still a matter of debate. Using enhanced sampling techniques, we show for the first time that, given a sufficiently large carbon nanotube, the confinement of a double-stranded DNA segment, 5′-D({sup *}CP{sup *}GP{sup *}CP{sup *}GP{sup *}AP{sup *}AP{sup *}TP{sup *}TP{sup *}CP{sup *}GP{sup *}CP{sup *}G)-3′, is thermodynamically favourable under physiological environments (134 mM, 310 K, 1 bar), leading to DNA-nanotube hybrids with lower free energy than the unconfined biomolecule. A diameter threshold of 3 nm is established below which encapsulation is inhibited. The confined DNA segment maintains its translational mobility and exhibits the main geometrical features of the canonical B form. To accommodate itself within the nanopore, the DNA's end-to-end length increases from 3.85 nm up to approximately 4.1 nm, due to a ∼0.3 nm elastic expansion of the strand termini. The canonical Watson-Crick H-bond network is essentially conserved throughout encapsulation, showing that the contact between the DNA segment and the hydrophobic carbon walls results in minor rearrangements of the nucleotides H-bonding. The results obtained here are paramount to the usage of carbon nanotubes as encapsulation media for next generation drug delivery technologies.

  12. Enhanced thermoelectric performance in the p-type half-Heusler (Ti/Zr/Hf)CoSb0.8Sn0.2 system via phase separation.

    PubMed

    Rausch, Elisabeth; Balke, Benjamin; Ouardi, Siham; Felser, Claudia

    2014-12-14

    A novel approach for optimization of the thermoelectric properties of p-type Heusler compounds with a C1b structure was investigated. A successful recipe for achieving intrinsic phase separation in the n-type material based on the TiNiSn system is isoelectronic partial substitution of Ti with its heavier homologues Zr and Hf. We applied this concept to the p-type system MCoSb0.8Sn0.2 by a systematic investigation of samples with different compositions at the Ti position (M = Ti, Zr, Hf, Ti0.5Zr0.5, Zr0.5Hf0.5, and Ti0.5Hf0.5). We thus achieved an approximately 40% reduction of the thermal conductivity and a maximum figure of merit ZT of 0.9 at 700 °C. This is a 80% improvement in peak ZT from 0.5 to 0.9 at 700 °C compared to the best published value of an ingot p-type half-Heusler compound. Thus far, comparable good thermoelectric p-type materials of this structure type have only been realized by a nanostructuring process via ball milling of premelted ingot samples followed by a rapid consolidation method, like hot pressing. The herein-presented simple arc-melting fabrication method reduces the fabrication time as compared to this multi-step nanostructuring process. The high mechanical stability of the Heusler compounds is favorable for the construction of thermoelectric modules. The Vickers hardness values are close to those of the n-type material, leading to good co-processability of both materials.

  13. Crystal chemistry of the G-phases in the {l_brace}Ti, Zr, Hf{r_brace}-Ni-Si systems

    SciTech Connect

    Grytsiv, A.; Chen Xingqiu; Rogl, P. Podloucky, R.; Schmidt, H.; Giester, G.; Pomjakushin, V.

    2007-02-15

    Ternary compounds M{sub 6}Ni{sub 16}Si{sub 7} (M=Ti, Zr, Hf) have been investigated by X-ray powder/single crystal and neutron powder diffraction. Compounds with Zr and Hf crystallize in the ordered Th{sub 6}Mn{sub 23} type (Mg{sub 6}Cu{sub 16}Si{sub 7}-type, space group Fm3-bar m), whereas Ti{sub 6}Ni{sub 16.7}Si{sub 7} contains an additional Ni atom partially occupying the 24e site (M2 site, x=0.4637,0,0; occ.=0.119) inside a Ti octahedron; Ti atoms occupy a split position. Ti{sub 6}Ni{sub 16.7}Si{sub 7} represents a new variant of the filled Th{sub 6}Mn{sub 23} type structure. Ab initio calculations confirm the structural difference: additional Ni atoms favour the 24e site for Ti{sub 6}Ni{sub 16.7}Si{sub 7}, however, for the Zr and Hf-based compounds the unoccupied site renders an energetically lower ground state. Enthalpies of formation of Ti{sub 6}Ni{sub 17}Si{sub 7}, Zr{sub 6}Ni{sub 16}Si{sub 7}, and Hf{sub 6}Ni{sub 16}Si{sub 7} were calculated to be -68.65, -74.78, and -78.59kJ/(mol of atoms), respectively.

  14. Single crystals of single-walled carbon nanotubes formed by self-assembly.

    PubMed

    Schlittler, R R; Seo, J W; Gimzewski, J K; Durkan, C; Saifullah, M S; Welland, M E

    2001-05-11

    We report the self-assembly of single crystals of single-walled carbon nanotubes (SWCNTs) using thermolysis of nano-patterned precursors. The synthesis of these perfectly ordered, single crystals of SWCNTs results in extended structures with dimension on the micrometer scale. Each crystal is composed of an ordered array of tubes with identical diameters and chirality, although these properties vary between crystals. The results show that SWCNTs can be produced as a perfect bulk material on the micrometer scale and point toward the synthesis of bulk macroscopic crystalline material.

  15. Adhesion strength and nucleation thermodynamics of four metals (Al, Cu, Ti, Zr) on AlN substrates

    NASA Astrophysics Data System (ADS)

    Tao, Yuan; Ke, Genshui; Xie, Yan; Chen, Yigang; Shi, Siqi; Guo, Haibo

    2015-12-01

    Devices based on AlN generally require adherent and strong interfaces between AlN and other materials, whereas most metals are known to be nonwetting to AlN and form relatively weak interfaces with AlN. In this study, we selected four representative metals (Al, Cu, Ti, and Zr) to study the adhesion strength of the AlN/metal interfaces. Mathematical models were constructed between the adhesion strength and enthalpy of formation of Al-metal solid solutions, the surface energies of the metals, and the lattice mismatch between the metals and AlN, based on thermodynamic parameters calculated using density functional theory. It appears that the adhesion strength is mainly determined by the lattice mismatch, and is in no linear correlation with either the Al-metal solution's formation enthalpies or the metals' surface energies. We also investigated the nucleation thermodynamics of the four metals on AlN substrates. It was found that Ti forms the strongest interface with AlN, and has the largest driving force for nucleation on AlN substrates among the four metals.

  16. Surface morphology of highly ordered nanotube formed and laser textured beta titanium alloys.

    PubMed

    Kim, Jae-Un; Jeong, Yong-Hoon; Choe, Han-Cheol

    2013-03-01

    The aim of the present study is to produce and characterize a well-controlled surface texture on Ti-35Nb-xHf alloys to promote osseointegration. Ti-35Nb-xHf (x = 0, 3, 7 and 15 wt.%) alloys were prepared by arc melting and heat treated for 12 hr at 1000 degrees C in an argon atmosphere and then water quenching. For surface texturing, an amplified Ti: sapphire laser system was used for generating 184 femtosecond (FS, 10(-15) sec) laser pulses with the pulse energy over 30 mJ at a 1 kHz repetition rate with a central wavelength of 800 nm. The nanotube formation was achieved by anodizing a Ti-35Nb-xHf alloy in H3PO4 electrolytes containing 0.8 wt.% NaF at room temperature. The surface morphology of nano/micro structure will enhance osseointegration and cell adhesion.

  17. Mineralogy and petrogenesis of a Ba-Ti-Zr-rich peralkaline dyke from Šebkovice (Czech Republic): Recognition of the most lamproitic Variscan intrusion

    NASA Astrophysics Data System (ADS)

    Krmíček, Lukáš; Cempírek, Jan; Havlín, Aleš; Přichystal, Antonín; Houzar, Stanislav; Krmíčková, Michaela; Gadas, Petr

    2011-01-01

    A peralkaline, ultrapotassic dyke found at Šebkovice (Třebíč district, western Moravia) is a mineralogically extreme member of a dyke swarm occurring along the south-eastern border of the Moldanubian Region of the Bohemian Massif. The dyke shows a simple zoning, with a very fine-grained marginal zone grading into a medium-grained central zone. It has a primary mineral assemblage of microcline and potassic amphiboles, with accessory apatite and altered phlogopite. The microcline exhibits an unusual red luminescence colour and pronounced substitution of Fe3+ for Al, with measured contents of Fe2O3 up to 8.5 wt.% (0.31 apfu Fe3+). Amphiboles have very high K (up to 0.99 apfu) and Si contents; their compositions follow an alkaline fractionation trend from potassic-richterite to potassic-magnesio-arfvedsonite, characterized by an increase of Na/K and a decrease of Ca, Mg, Fe2+ and Ti via heterovalent substitutions [B]Ca + [C](Mg,Fe2+) → [B]Na + [C]Fe3+ and Ti + Mg → 2Fe3+. The most evolved apatite is significantly enriched in SrO (up to 9.7 wt.%; 0.49 apfu Sr). The core of the dyke and late veinlets contain unique late- to post-magmatic Ba-Ti-Zr-bearing mineral assemblages of baotite, henrymeyerite, titanite, rutile, benitoite and bazirite. Anhedral baotite fills interstices distributed inhomogeneously in the dyke centre; it is locally replaced by a Ba-bearing titanite + henrymeyerite + rutile + quartz assemblage. Henrymeyerite (the second record in a lamproite) shows variable Fe/Ti ratios and represents a solid solution of the hepta- and hexatitanate components. Euhedral crystals of benitoite and bazirite are enclosed in the late-stage quartz-titanite-apatite veinlets in the fine-grained margin of the intrusion. In terms of a mineralogical-genetic classification, the Šebkovice dyke can be considered as a new high-silica (~ 57 wt.% SiO2) variety of lamproite (variety Šebkovice), and represents a unique expression of post-collisional potassic magmatism on the

  18. Expansion of cardiac ischemia/reperfusion injury after instillation of three forms of multi-walled carbon nanotubes

    PubMed Central

    2012-01-01

    Background The exceptional physical-chemical properties of carbon nanotubes have lead to their use in diverse commercial and biomedical applications. However, their utilization has raised concerns about human exposure that may predispose individuals to adverse health risks. The present study investigated the susceptibility to cardiac ischemic injury following a single exposure to various forms of multi-walled carbon nanotubes (MWCNTs). It was hypothesized that oropharyngeal aspiration of MWCNTs exacerbates myocardial ischemia and reperfusion injury (I/R injury). Methods Oropharyngeal aspiration was performed on male C57BL/6J mice with a single amount of MWCNT (0.01 - 100 μg) suspended in 100 μL of a surfactant saline (SS) solution. Three forms of MWCNTs were used in this study: unmodified, commercial grade (C-grade), and functionalized forms that were modified either by acid treatment (carboxylated, COOH) or nitrogenation (N-doped) and a SS vehicle. The pulmonary inflammation, serum cytokine profile and cardiac ischemic/reperfusion (I/R) injury were assessed at 1, 7 and 28 days post-aspiration. Results Pulmonary response to MWCNT oropharyngeal aspiration assessed by bronchoalveolar lavage fluid (BALF) revealed modest increases in protein and inflammatory cell recruitment. Lung histology showed modest tissue inflammation as compared to the SS group. Serum levels of eotaxin were significantly elevated in the carboxylated MWCNT aspirated mice 1 day post exposure. Oropharyngeal aspiration of all three forms of MWCNTs resulted in a time and/or dose-dependent exacerbation of myocardial infarction. The severity of myocardial injury varied with the form of MWCNTs used. The N-doped MWCNT produced the greatest expansion of the infarct at any time point and required a log concentration lower to establish a no effect level. The expansion of the I/R injury remained significantly elevated at 28 days following aspiration of the COOH and N-doped forms, but not the C-grade as

  19. Fabrication and characterization of tunnel barriers in a multi-walled carbon nanotube formed by argon atom beam irradiation

    SciTech Connect

    Tomizawa, H.; Yamaguchi, T.; Akita, S.; Ishibashi, K.

    2015-07-28

    We have evaluated tunnel barriers formed in multi-walled carbon nanotubes (MWNTs) by an Ar atom beam irradiation method and applied the technique to fabricate coupled double quantum dots. The two-terminal resistance of the individual MWNTs was increased owing to local damage caused by the Ar beam irradiation. The temperature dependence of the current through a single barrier suggested two different contributions to its Arrhenius plot, i.e., formed by direct tunneling through the barrier and by thermal activation over the barrier. The height of the formed barriers was estimated. The fabrication technique was used to produce coupled double quantum dots with serially formed triple barriers on a MWNT. The current measured at 1.5 K as a function of two side-gate voltages resulted in a honeycomb-like charge stability diagram, which confirmed the formation of the double dots. The characteristic parameters of the double quantum dots were calculated, and the feasibility of the technique is discussed.

  20. Catalytic effect of different forms of iron in purification of single-walled carbon nanotubes.

    PubMed

    Suzuki, Tomoko; Inoue, Sakae; Ando, Yoshinori

    2010-06-01

    In the arc plasma jet (APJ) method, a large amount of soot including single wall carbon nanotubes (SWNTs) can be produced in a short time. However, as-grown soot contains a lot of impurities, such as metallic particles used as catalyst and amorphous carbon. Hence it is necessary to purify the soot to obtain pure SWNTs. The biggest problem in purifying APJ-SWNTs is how to remove the thick amorphous carbon covering the catalyst metal particles. By refluxing APJ-SWNTs in hydrogen peroxide using iron particle as catalyst, it can be purified. The added fine particle of pure iron is found to be effective. Then, we examine whether SWNTs can be purified more effectively by adding solution containing the Fe ion instead of the iron particle. We used iron (III) nitrate nonahydrate, hydrogen peroxide decomposing agent which contains catalase and ammonium iron (II) sulfate hexahydrate. In the case of iron (III) nitrate and catalase, purification effect is not obvious. Under these conditions hydrogen peroxide was decomposed into H2O and O2, and the hydroxyl radical was not generated. On the other hand, ammonium iron (II) sulfate is effective. Because of existence of Fe2+ in solution Fenton's reaction takes place. Reaction rate is increased at high temperature. Therefore, APJ-SWNT is purified more effectively if refluxed in hydrogen peroxide using ammonium iron (II) sulfate as catalyst.

  1. ILQINS hexapeptide, identified in lysozyme left-handed helical ribbons and nanotubes, forms right-handed helical ribbons and crystals.

    PubMed

    Lara, Cecile; Reynolds, Nicholas P; Berryman, Joshua T; Xu, Anqiu; Zhang, Afang; Mezzenga, Raffaele

    2014-03-26

    Amyloid fibrils are implicated in over 20 neurodegenerative diseases. The mechanisms of fibril structuring and formation are not only of medical and biological importance but are also relevant for material science and nanotechnologies due to the unique structural and physical properties of amyloids. We previously found that hen egg white lysozyme, homologous to the disease-related human lysozyme, can form left-handed giant ribbons, closing into nanotubes. By using matrix-assisted laser desorption ionization mass spectrometry analysis, we here identify a key component of such structures: the ILQINS hexapeptide. By combining atomic force microscopy and circular dichorism, we find that this fragment, synthesized by solid-phase peptide synthesis, also forms fibrillar structures in water at pH 2. However, all fibrillar structures formed possess an unexpected right-handed twist, a rare chirality within the corpus of amyloid experimental observations. We confirm by small- and wide-angle X-ray scattering and molecular dynamics simulations that these fibrils are composed of conventional left-handed β-sheets, but that packing stresses between adjacent sheets create this twist of unusual handedness. We also show that the right-handed fibrils represent a metastable state toward β-sheet-based microcrystals formation.

  2. Carbon nanotube nanoelectrode arrays

    DOEpatents

    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.

  3. A Novel Investigation of the Formation of Titanium Oxide Nanotubes on Thermally Formed Oxide of Ti-6Al-4V.

    PubMed

    Butt, Arman; Hamlekhan, Azhang; Patel, Sweetu; Royhman, Dmitry; Sukotjo, Cortino; Mathew, Mathew T; Shokuhfar, Tolou; Takoudis, Christos

    2015-10-01

    Traditionally, titanium oxide (TiO2) nanotubes (TNTs) are anodized on Ti-6Al-4V alloy (Ti-V) surfaces with native TiO2 (amorphous TiO2); subsequent heat treatment of anodized surfaces has been observed to enhance cellular response. As-is bulk Ti-V, however, is often subjected to heat treatment, such as thermal oxidation (TO), to improve its mechanical properties. Thermal oxidation treatment of Ti-V at temperatures greater than 200°C and 400°C initiates the formation of anatase and rutile TiO2, respectively, which can affect TNT formation. This study aims at understanding the TNT formation mechanism on Ti-V surfaces with TO-formed TiO2 compared with that on as-is Ti-V surfaces with native oxide. Thermal oxidation-formed TiO2 can affect TNT formation and surface wettability because TO-formed TiO2 is expected to be part of the TNT structure. Surface characterization was carried out with field emission scanning electron microscopy, energy dispersive x-ray spectroscopy, water contact angle measurements, and white light interferometry. The TNTs were formed on control and 300°C and 600°C TO-treated Ti-V samples, and significant differences in TNT lengths and surface morphology were observed. No difference in elemental composition was found. Thermal oxidation and TO/anodization treatments produced hydrophilic surfaces, while hydrophobic behavior was observed over time (aging) for all samples. Reduced hydrophobic behavior was observed for TO/anodized samples when compared with control, control/anodized, and TO-treated samples. A method for improved surface wettability and TNT morphology is therefore discussed for possible applications in effective osseointegration of dental and orthopedic implants.

  4. Effects of Ti, Zr, and Hf on the Phase Stability of Mo-Mo3Si+Mo5SiB2 Alloys at 1600 C

    SciTech Connect

    Yang, Ying; Bei, Hongbin; Chen, Shuanglin; George, Easo P; Tiley, Jaimie; Chang, Y. Austin

    2010-01-01

    Understanding the stability of the three-phase Mo{_}+Mo{sub 3}Si+Mo{sub 5}SiB{sub 2} region is important for alloy design of Mo-Si-B-based refractory metal intermetallic composites. In this work, thermodynamic modeling is coupled with guided experiments to study phase stability in this three-phase region of the Mo-Si-B-X (X = Ti, Zr, Hf) system. Both the calculated and experimental results show that additions of Zr and Hf limit significantly the stability of the three-phase region because of the formation of the ternary phases MoSiZr and MoSiHf, while Ti addition leads to a much larger region of stability for the three-phase equilibrium.

  5. Alternating syn-anti bacteriochlorophylls form concentric helical nanotubes in chlorosomes

    PubMed Central

    Ganapathy, Swapna; Oostergetel, Gert T.; Wawrzyniak, Piotr K.; Reus, Michael; Gomez Maqueo Chew, Aline; Buda, Francesco; Boekema, Egbert J.; Bryant, Donald A.; Holzwarth, Alfred R.; de Groot, Huub J. M.

    2009-01-01

    Chlorosomes are the largest and most efficient light-harvesting antennae found in nature, and they are constructed from hundreds of thousands of self-assembled bacteriochlorophyll (BChl) c, d, or e pigments. Because they form very large and compositionally heterogeneous organelles, they had been the only photosynthetic antenna system for which no detailed structural information was available. In our approach, the structure of a member of the chlorosome class was determined and compared with the wild type (WT) to resolve how the biological light-harvesting function of the chlorosome is established. By constructing a triple mutant, the heterogeneous BChl c pigment composition of chlorosomes of the green sulfur bacteria Chlorobaculum tepidum was simplified to nearly homogeneous BChl d. Computational integration of two different bioimaging techniques, solid-state NMR and cryoEM, revealed an undescribed syn-anti stacking mode and showed how ligated BChl c and d self-assemble into coaxial cylinders to form tubular-shaped elements. A close packing of BChls via π–π stacking and helical H-bonding networks present in both the mutant and in the WT forms the basis for ultrafast, long-distance transmission of excitation energy. The structural framework is robust and can accommodate extensive chemical heterogeneity in the BChl side chains for adaptive optimization of the light-harvesting functionality in low-light environments. In addition, syn-anti BChl stacks form sheets that allow for strong exciton overlap in two dimensions enabling triplet exciton formation for efficient photoprotection. PMID:19435848

  6. High frequency nanotube oscillator

    DOEpatents

    Peng, Haibing; Zettl, Alexander K.

    2012-02-21

    A tunable nanostructure such as a nanotube is used to make an electromechanical oscillator. The mechanically oscillating nanotube can be provided with inertial clamps in the form of metal beads. The metal beads serve to clamp the nanotube so that the fundamental resonance frequency is in the microwave range, i.e., greater than at least 1 GHz, and up to 4 GHz and beyond. An electric current can be run through the nanotube to cause the metal beads to move along the nanotube and changing the length of the intervening nanotube segments. The oscillator can operate at ambient temperature and in air without significant loss of resonance quality. The nanotube is can be fabricated in a semiconductor style process and the device can be provided with source, drain, and gate electrodes, which may be connected to appropriate circuitry for driving and measuring the oscillation. Novel driving and measuring circuits are also disclosed.

  7. Reinforced Carbon Nanotubes.

    SciTech Connect

    Ren, Zhifen; Wen, Jian Guo; Lao, Jing Y.; Li, Wenzhi

    2005-06-28

    The present invention relates generally to reinforced carbon nanotubes, and more particularly to reinforced carbon nanotubes having a plurality of microparticulate carbide or oxide materials formed substantially on the surface of such reinforced carbon nanotubes composite materials. In particular, the present invention provides reinforced carbon nanotubes (CNTs) having a plurality of boron carbide nanolumps formed substantially on a surface of the reinforced CNTs that provide a reinforcing effect on CNTs, enabling their use as effective reinforcing fillers for matrix materials to give high-strength composites. The present invention also provides methods for producing such carbide reinforced CNTs.

  8. Comparison of the interactions of daunorubicin in a free form and attached to single-walled carbon nanotubes with model lipid membranes

    PubMed Central

    2016-01-01

    Summary In this work the interactions of an anticancer drug daunorubicin (DNR) with model thiolipid layers composed of 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPTE) were investigated using Langmuir technique. The results obtained for a free drug were compared with the results recorded for DNR attached to SWCNTs as potential drug carrier. Langmuir studies of mixed DPPTE–SWCNTs-DNR monolayers showed that even at the highest investigated content of the nanotubes in the monolayer, the changes in the properties of DPPTE model membranes were not as significant as in case of the incorporation of a free drug, which resulted in a significant increase in the area per molecule and fluidization of the thiolipid layer. The presence of SWCNTs-DNR in the DPPTE monolayer at the air–water interface did not change the organization of the lipid molecules to such extent as the free drug, which may be explained by different types of interactions playing crucial role in these two types of systems. In the case of the interactions of free DNR the electrostatic attraction between positively charged drug and negatively charged DPPTE monolayer play the most important role, while in the case of SWCNTs-DNR adducts the hydrophobic interactions between nanotubes and acyl chains of the lipid seem to be prevailing. Electrochemical studies performed for supported model membranes containing the drug delivered in the two investigated forms revealed that the surface concentration of the drug-nanotube adduct in supported monolayers is comparable to the reported surface concentration of the free DNR incorporated into DPPTE monolayers on gold electrodes. Therefore, it may be concluded that the application of carbon nanotubes as potential DNR carrier allows for the incorporation of comparable amount of the drug into model membranes with simultaneous decrease in the negative changes in the membrane structure and organization, which is an important aspect in terms of side effects of the drug

  9. Comparison of the interactions of daunorubicin in a free form and attached to single-walled carbon nanotubes with model lipid membranes.

    PubMed

    Matyszewska, Dorota

    2016-01-01

    In this work the interactions of an anticancer drug daunorubicin (DNR) with model thiolipid layers composed of 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPTE) were investigated using Langmuir technique. The results obtained for a free drug were compared with the results recorded for DNR attached to SWCNTs as potential drug carrier. Langmuir studies of mixed DPPTE-SWCNTs-DNR monolayers showed that even at the highest investigated content of the nanotubes in the monolayer, the changes in the properties of DPPTE model membranes were not as significant as in case of the incorporation of a free drug, which resulted in a significant increase in the area per molecule and fluidization of the thiolipid layer. The presence of SWCNTs-DNR in the DPPTE monolayer at the air-water interface did not change the organization of the lipid molecules to such extent as the free drug, which may be explained by different types of interactions playing crucial role in these two types of systems. In the case of the interactions of free DNR the electrostatic attraction between positively charged drug and negatively charged DPPTE monolayer play the most important role, while in the case of SWCNTs-DNR adducts the hydrophobic interactions between nanotubes and acyl chains of the lipid seem to be prevailing. Electrochemical studies performed for supported model membranes containing the drug delivered in the two investigated forms revealed that the surface concentration of the drug-nanotube adduct in supported monolayers is comparable to the reported surface concentration of the free DNR incorporated into DPPTE monolayers on gold electrodes. Therefore, it may be concluded that the application of carbon nanotubes as potential DNR carrier allows for the incorporation of comparable amount of the drug into model membranes with simultaneous decrease in the negative changes in the membrane structure and organization, which is an important aspect in terms of side effects of the drug. PMID

  10. Comparison of the interactions of daunorubicin in a free form and attached to single-walled carbon nanotubes with model lipid membranes.

    PubMed

    Matyszewska, Dorota

    2016-01-01

    In this work the interactions of an anticancer drug daunorubicin (DNR) with model thiolipid layers composed of 1,2-dipalmitoyl-sn-glycero-3-phosphothioethanol (DPPTE) were investigated using Langmuir technique. The results obtained for a free drug were compared with the results recorded for DNR attached to SWCNTs as potential drug carrier. Langmuir studies of mixed DPPTE-SWCNTs-DNR monolayers showed that even at the highest investigated content of the nanotubes in the monolayer, the changes in the properties of DPPTE model membranes were not as significant as in case of the incorporation of a free drug, which resulted in a significant increase in the area per molecule and fluidization of the thiolipid layer. The presence of SWCNTs-DNR in the DPPTE monolayer at the air-water interface did not change the organization of the lipid molecules to such extent as the free drug, which may be explained by different types of interactions playing crucial role in these two types of systems. In the case of the interactions of free DNR the electrostatic attraction between positively charged drug and negatively charged DPPTE monolayer play the most important role, while in the case of SWCNTs-DNR adducts the hydrophobic interactions between nanotubes and acyl chains of the lipid seem to be prevailing. Electrochemical studies performed for supported model membranes containing the drug delivered in the two investigated forms revealed that the surface concentration of the drug-nanotube adduct in supported monolayers is comparable to the reported surface concentration of the free DNR incorporated into DPPTE monolayers on gold electrodes. Therefore, it may be concluded that the application of carbon nanotubes as potential DNR carrier allows for the incorporation of comparable amount of the drug into model membranes with simultaneous decrease in the negative changes in the membrane structure and organization, which is an important aspect in terms of side effects of the drug.

  11. Energy efficient microwave synthesis of mesoporous Ce0.5M0.5O2 (Ti, Zr, Hf) nanoparticles for low temperature CO oxidation in an ionic liquid – a comparative study

    DOE PAGES

    Alammar, Tarek; Chow, Ying -Kit; Mudring, Anja -Verena

    2014-11-19

    Ce0.5M0.5O2 (M = Ti, Zr, Hf) nanoparticles have been successfully synthesized by microwave irradiation in the ionic liquid [C4mim][Tf2N] (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide). The morphology, crystallinity, and chemical composition of the obtained materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and N2–adsorption measurements. XRD and Raman spectroscopy analyses confirmed the formation of solid solutions with cubic fluorite structure. The catalytic activities of the Ce0.5M0.5O2 (M = Ti, Zr, Hf) nanoparticles were investigated in the low-temperature oxidation of CO. Ce0.5Zr0.5O2 nanospheres exhibit the best performance (100% conversion at 350 °C), followed by Ce0.5Hf0.5O2more » (55% conversion at 360 °C) and Ce0.5Ti0.5O2 (11% conversion at 350 °C). Heating the as-prepared Ce0.5Zr0.5O2 to 600 °C for extended time leads to a decrease in surface area and, as expected decreased catalytic activity. Depending on the ionic liquid the obtained Ce0.5Zr0.5O2 exhibits different morphologies, varying from nano-spheres in [C4mim][Tf2N] and [P66614][Tf2N] (P66614 = trishexyltetradecylphosphonium) to sheet-like assemblies in [C3mimOH][Tf2N] (C3mimOH = 1-(3-hydroxypropyl)-3-methylimidazolium). As a result, the microwave synthesis superiority to other heating methods like sonochemical synthesis and conventional heating was proven by comparative experiments where the catalytic activity of Ce0.5Zr0.5O2 obtained by alternate methods such as conventional heating was found to be poorer than that of the microwave-synthesised material.« less

  12. Carbon nanotube-polymer composite actuators

    DOEpatents

    Gennett, Thomas; Raffaelle, Ryne P.; Landi, Brian J.; Heben, Michael J.

    2008-04-22

    The present invention discloses a carbon nanotube (SWNT)-polymer composite actuator and method to make such actuator. A series of uniform composites was prepared by dispersing purified single wall nanotubes with varying weight percents into a polymer matrix, followed by solution casting. The resulting nanotube-polymer composite was then successfully used to form a nanotube polymer actuator.

  13. Templated Growth of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Siochik Emilie J. (Inventor)

    2007-01-01

    A method of growing carbon nanotubes uses a synthesized mesoporous si lica template with approximately cylindrical pores being formed there in. The surfaces of the pores are coated with a carbon nanotube precu rsor, and the template with the surfaces of the pores so-coated is th en heated until the carbon nanotube precursor in each pore is convert ed to a carbon nanotube.

  14. Mobilities in ambipolar field effect transistors based on single-walled carbon nanotube network and formed on a gold nanoparticle template

    SciTech Connect

    Wongsaeng, Chalao; Singjai, Pisith

    2014-04-07

    Ambipolar field effect transistors based on a single-walled carbon nanotube (SWNT) network formed on a gold nanoparticle (AuNP) template with polyvinyl alcohol as a gate insulator were studied by measuring the current–gate voltage characteristics. It was found that the mobilities of holes and electrons increased with increasing AuNP number density. The disturbances in the flow pattern of the carbon feedstock in the chemical vapor deposition growth that were produced by the AuNP geometry, resulted in the differences in the crystallinity and the diameter, as well as the changes in the degree of the semiconductor behavior of the SWNTs.

  15. Theoretical predictions of properties and volatility of chlorides and oxychlorides of group-4 elements. I. Electronic structures and properties of MCl{sub 4} and MOCl{sub 2} (M = Ti, Zr, Hf, and Rf)

    SciTech Connect

    Pershina, V.; Borschevsky, A.; Iliaš, M.

    2014-08-14

    Relativistic, infinite order exact two-component, density functional theory electronic structure calculations were performed for MCl{sub 4} and MOCl{sub 2} of group-4 elements Ti, Zr, Hf, and element 104, Rf, with the aim to predict their behaviour in gas-phase chromatography experiments. RfCl{sub 4} and RfOCl{sub 2} were shown to be less stable than their lighter homologs in the group, tetrachlorides and oxychlorides of Zr and Hf, respectively. The oxychlorides turned out to be stable as a bent structure, though the stabilization energy with respect to the flat one (C{sub 2v}) is very small. The trend in the formation of the tetrachlorides from the oxychlorides in group 4 is shown to be Zr < Hf < Rf, while the one in the formation of the oxychlorides from the chlorides is opposite. All the calculated properties are used to estimate adsorption energy of these species on various surfaces in order to interpret results of gas-phase chromatography experiments, as is shown in Paper II.

  16. Elastic properties of perovskite ATiO{sub 3} (A = Be, Mg, Ca, Sr, and Ba) and PbBO{sub 3} (B = Ti, Zr, and Hf): First principles calculations

    SciTech Connect

    Pandech, Narasak; Limpijumnong, Sukit; Sarasamak, Kanoknan

    2015-05-07

    The mechanical properties of perovskite oxides depend on two metal oxide lattices that are intercalated. This provides an opportunity for separate tuning of hardness, Poisson's ratio (transverse expansion in response to the compression), and shear strength. The elastic constants of series of perovskite oxides were studied by first principles approach. Both A-site and B-site cations were systematically varied in order to see their effects on the elastic parameters. To study the effects of A-site cations, we studied the elastic properties of perovskite ATiO{sub 3} for A being Be, Mg, Ca, Sr, or Ba, one at a time. Similarly, for B-site cations, we studied the elastic properties of PbBO{sub 3} for B being Ti, Zr, or Hf, one at a time. The density functional first principles calculations with local density approximation (LDA) and generalized gradient approximation (GGA) were employed. It is found that the maximum C{sub 11} elastic constant is achieved when the atomic size of the cations at A-site and B-site are comparable. We also found that C{sub 12} elastic constant is sensitive to B-site cations while C{sub 44} elastic constant is more sensitive to A-site cations. Details and explanations for such dependencies are discussed.

  17. Intriguing electronic properties of two-dimensional MoS2/TM2CO2 (TM = Ti, Zr, or Hf) hetero-bilayers: type-II semiconductors with tunable band gaps.

    PubMed

    Li, Xinru; Dai, Ying; Ma, Yandong; Liu, Qunqun; Huang, Baibiao

    2015-03-27

    Two-dimensional (2D) transition metal compound (TMC) monolayers, as well as their van der Waals heterostructures with unique properties, are fundamentally and technologically intriguing. Here, heterostructures consisting of a MoS2 monolayer and TM2CO2 (TM = Ti, Zr or Hf) monolayers are systematically researched by means of the density functional theory (DFT). Different from semiconductor/metal contacts, MoS2 and TM2CO2 monolayers are all semiconductors with band gaps ranging from 0.25-1.67 eV. According to rigorous screening of stacking patterns, MoS2/Zr2CO2 is shown to be an indirect type-II semiconductor with the maximum valence and minimum conduction bands spatially separated on opposite monolayers. Simultaneously, the interface charges transfer from Zr2CO2 to MoS2 results in a built-in field that separates the electrons and holes efficiently. Also, the smaller effective masses of electrons and the holes of band edges indicate the higher carrier mobility. Moreover, strain regulation can make the hetero-bilayer's character a semiconductor-semimetal-metal transition. The physical insights pave the way for the good performance of MoS2/TM2CO2 in next-generation electronic devices and photocatalysts.

  18. Intriguing electronic properties of two-dimensional MoS2/TM2CO2 (TM = Ti, Zr, or Hf) hetero-bilayers: type-II semiconductors with tunable band gaps

    NASA Astrophysics Data System (ADS)

    Li, Xinru; Dai, Ying; Ma, Yandong; Liu, Qunqun; Huang, Baibiao

    2015-03-01

    Two-dimensional (2D) transition metal compound (TMC) monolayers, as well as their van der Waals heterostructures with unique properties, are fundamentally and technologically intriguing. Here, heterostructures consisting of a MoS2 monolayer and TM2CO2 (TM = Ti, Zr or Hf) monolayers are systematically researched by means of the density functional theory (DFT). Different from semiconductor/metal contacts, MoS2 and TM2CO2 monolayers are all semiconductors with band gaps ranging from 0.25-1.67 eV. According to rigorous screening of stacking patterns, MoS2/Zr2CO2 is shown to be an indirect type-II semiconductor with the maximum valence and minimum conduction bands spatially separated on opposite monolayers. Simultaneously, the interface charges transfer from Zr2CO2 to MoS2 results in a built-in field that separates the electrons and holes efficiently. Also, the smaller effective masses of electrons and the holes of band edges indicate the higher carrier mobility. Moreover, strain regulation can make the hetero-bilayer’s character a semiconductor-semimetal-metal transition. The physical insights pave the way for the good performance of MoS2/TM2CO2 in next-generation electronic devices and photocatalysts.

  19. Atomic site preferences and its effect on magnetic structure in the intermetallic borides M2Fe(Ru0.8T0.2)5B2 (M=Sc, Ti, Zr; T=Ru, Rh, Ir)

    NASA Astrophysics Data System (ADS)

    Brgoch, Jakoah; Mahmoud, Yassir A.; Miller, Gordon J.

    2012-12-01

    The site preference for a class of intermetallic borides following the general formula M2Fe(Ru0.8T0.2)5B2 (M=Sc, Ti, Zr; T=Ru, Rh, Ir), has been explored using ab initio and semi-empirical electronic structure calculations. This intermetallic boride series contains two potential sites, the Wyckoff 2c and 8j sites, for Rh or Ir to replace Ru atoms. Since the 8j site is a nearest neighbor to the magnetically active Fe atom, whereas the 2c site is a next nearest neighbor, the substitution pattern should play an important role in the magnetic structure of these compounds. The substitution preference is analyzed based on the site energy and bond energy terms, both of which arise from a tight-binding evaluation of the electronic band energy, and are known to influence the locations of atoms in extended solids. According to these calculations, the valence electron-rich Rh and Ir atoms prefer to occupy the 8j site, a result also corroborated by experimental evidence. Additionally, substitution of Rh or Ir at the 8j site results in a modification of the magnetic structure that ultimately results in larger local magnetic moment on the Fe atoms.

  20. Membrane Nanotubes

    NASA Astrophysics Data System (ADS)

    Derényi, I.; Koster, G.; van Duijn, M. M.; Czövek, A.; Dogterom, M.; Prost, J.

    There is a growing pool of evidence showing the biological importance of membrane nanotubes (with diameter of a few tens of nanometers and length upto tens of microns) in various intra- and intercellular transport processes. These ubiquitous structures are often formed from flat membranes by highly localized forces generated by either the pulling of motor proteins or the pushing of polymerizing cytoskeletal filaments. In this chapter we give an overview of the theory of membrane nanotubes, their biological relevance, and the most recent experiments designed for the study of their formation and dynamics. We also discuss the effect of membrane proteins or lipid composition on the shape of the tubes, and the effect of antagonistic motor proteins on tube formation.

  1. Magnetic nanotubes

    DOEpatents

    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.

  2. Atomization methods for forming magnet powders

    SciTech Connect

    Sellers, C.H.; Branagan, D.J.; Hyde, T.A.

    2000-02-08

    The invention encompasses methods of utilizing atomization, methods for forming magnet powders, methods for forming magnets, and methods for forming bonded magnets. The invention further encompasses methods for simulating atomization conditions. In one aspect, the invention includes an atomization method for forming a magnet powder comprising: (a) forming a melt comprising R{sub 2.1}Q{sub 13.9}B{sub 1}, Z and X, wherein R is a rare earth element; X is an element selected from the group consisting of carbon, nitrogen, oxygen and mixtures thereof; Q is an element selected from the group consisting of Fe, Co and mixtures thereof; and Z is an element selected from the group consisting of Ti, Zr, Hf and mixtures thereof; (b) atomizing the melt to form generally spherical alloy powder granules having an internal structure comprising at least one of a substantially amorphous phase or a substantially nanocrystalline phase; and (c) heat treating the alloy powder to increase an energy product of the alloy powder; after the heat treatment, the alloy powder comprising an energy product of at least 10 MGOe. In another aspect, the invention includes a magnet comprising R, Q, B, Z and X, wherein R is a rare earth element; X is an element selected from the group consisting of carbon, nitrogen, oxygen and mixtures thereof; Q is an element selected from the group consisting of Fe, Co and mixtures thereof; and Z is an element selected from the group consisting of Ti, Zr, Hf and mixtures thereof; the magnet comprising an internal structure comprising R{sub 2.1}Q{sub 13.9}B{sub 1}.

  3. Atomization methods for forming magnet powders

    DOEpatents

    Sellers, Charles H.; Branagan, Daniel J.; Hyde, Timothy A.

    2000-01-01

    The invention encompasses methods of utilizing atomization, methods for forming magnet powders, methods for forming magnets, and methods for forming bonded magnets. The invention further encompasses methods for simulating atomization conditions. In one aspect, the invention includes an atomization method for forming a magnet powder comprising: a) forming a melt comprising R.sub.2.1 Q.sub.13.9 B.sub.1, Z and X, wherein R is a rare earth element; X is an element selected from the group consisting of carbon, nitrogen, oxygen and mixtures thereof; Q is an element selected from the group consisting of Fe, Co and mixtures thereof; and Z is an element selected from the group consisting of Ti, Zr, Hf and mixtures thereof; b) atomizing the melt to form generally spherical alloy powder granules having an internal structure comprising at least one of a substantially amorphous phase or a substantially nanocrystalline phase; and c) heat treating the alloy powder to increase an energy product of the alloy powder; after the heat treatment, the alloy powder comprising an energy product of at least 10 MGOe. In another aspect, the invention includes a magnet comprising R, Q, B, Z and X, wherein R is a rare earth element; X is an element selected from the group consisting of carbon, nitrogen, oxygen and mixtures thereof; Q is an element selected from the group consisting of Fe, Co and mixtures thereof; and Z is an element selected from the group consisting of Ti, Zr, Hf and mixtures thereof; the magnet comprising an internal structure comprising R.sub.2.1 Q.sub.13.9 B.sub.1.

  4. Fluidic nanotubes and devices

    DOEpatents

    Yang, Peidong; He, Rongrui; Goldberger, Joshua; Fan, Rong; Wu, Yiying; Li, Deyu; Majumdar, Arun

    2008-04-08

    Fluidic nanotube devices are described in which a hydrophilic, non-carbon nanotube, has its ends fluidly coupled to reservoirs. Source and drain contacts are connected to opposing ends of the nanotube, or within each reservoir near the opening of the nanotube. The passage of molecular species can be sensed by measuring current flow (source-drain, ionic, or combination). The tube interior can be functionalized by joining binding molecules so that different molecular species can be sensed by detecting current changes. The nanotube may be a semiconductor, wherein a tubular transistor is formed. A gate electrode can be attached between source and drain to control current flow and ionic flow. By way of example an electrophoretic array embodiment is described, integrating MEMs switches. A variety of applications are described, such as: nanopores, nanocapillary devices, nanoelectrophoretic, DNA sequence detectors, immunosensors, thermoelectric devices, photonic devices, nanoscale fluidic bioseparators, imaging devices, and so forth.

  5. Fluidic nanotubes and devices

    DOEpatents

    Yang, Peidong; He, Rongrui; Goldberger, Joshua; Fan, Rong; Wu, Yiying; Li, Deyu; Majumdar, Arun

    2010-01-10

    Fluidic nanotube devices are described in which a hydrophilic, non-carbon nanotube, has its ends fluidly coupled to reservoirs. Source and drain contacts are connected to opposing ends of the nanotube, or within each reservoir near the opening of the nanotube. The passage of molecular species can be sensed by measuring current flow (source-drain, ionic, or combination). The tube interior can be functionalized by joining binding molecules so that different molecular species can be sensed by detecting current changes. The nanotube may be a semiconductor, wherein a tubular transistor is formed. A gate electrode can be attached between source and drain to control current flow and ionic flow. By way of example an electrophoretic array embodiment is described, integrating MEMs switches. A variety of applications are described, such as: nanopores, nanocapillary devices, nanoelectrophoretic, DNA sequence detectors, immunosensors, thermoelectric devices, photonic devices, nanoscale fluidic bioseparators, imaging devices, and so forth.

  6. Carbon nanotubes on a substrate

    DOEpatents

    Gao, Yufei [Kennewick, WA; Liu, Jun [West Richland, WA

    2002-03-26

    The present invention includes carbon nanotubes whose hollow cores are 100% filled with conductive filler. The carbon nanotubes are in uniform arrays on a conductive substrate and are well-aligned and can be densely packed. The uniformity of the carbon nanotube arrays is indicated by the uniform length and diameter of the carbon nanotubes, both which vary from nanotube to nanotube on a given array by no more than about 5%. The alignment of the carbon nanotubes is indicated by the perpendicular growth of the nanotubes from the substrates which is achieved in part by the simultaneous growth of the conductive filler within the hollow core of the nanotube and the densely packed growth of the nanotubes. The present invention provides a densely packed carbon nanotube growth where each nanotube is in contact with at least one nearest-neighbor nanotube. The substrate is a conductive substrate coated with a growth catalyst, and the conductive filler can be single crystals of carbide formed by a solid state reaction between the substrate material and the growth catalyst. The present invention further provides a method for making the filled carbon nanotubes on the conductive substrates. The method includes the steps of depositing a growth catalyst onto the conductive substrate as a prepared substrate, creating a vacuum within a vessel which contains the prepared substrate, flowing H2/inert (e.g. Ar) gas within the vessel to increase and maintain the pressure within the vessel, increasing the temperature of the prepared substrate, and changing the H2/Ar gas to ethylene gas such that the ethylene gas flows within the vessel. Additionally, varying the density and separation of the catalyst particles on the conductive substrate can be used to control the diameter of the nanotubes.

  7. Nanotube composite carbon fibers

    NASA Astrophysics Data System (ADS)

    Andrews, R.; Jacques, D.; Rao, A. M.; Rantell, T.; Derbyshire, F.; Chen, Y.; Chen, J.; Haddon, R. C.

    1999-08-01

    Single walled carbon nanotubes (SWNTs) were dispersed in isotropic petroleum pitch matrices to form nanotube composite carbon fibers with enhanced mechanical and electrical properties. We find that the tensile strength, modulus, and electrical conductivity of a pitch composite fiber with 5 wt % loading of purified SWNTs are enhanced by ˜90%, ˜150%, and 340% respectively, as compared to the corresponding values in unmodified isotropic pitch fibers. These results serve to highlight the potential that exits for developing a spectrum of material properties through the selection of the matrix, nanotube dispersion, alignment, and interfacial bonding.

  8. Naturally produced carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Velasco-Santos, C.; Martínez-Hernández, A. L.; Consultchi, A.; Rodríguez, R.; Castaño, V. M.

    2003-05-01

    Carbon nanotubes represent an impressive kind of materials with diverse unexpected properties, and different methods to artificially produce them have been developed. Recently, they have also been synthesized at low temperatures, demonstrating that these materials might exist in fluids or carbon rocks of the Earth's crust. A new type of natural encapsulated carbon nanotubes found in a coal-petroleum mix is presented. These findings show that all allotropic carbon forms known up to date can be produced in Nature, where pressure, catalysts particles, shear stress and parameters other than exclusively very high temperature, seem to play an important role for producing nanotubes.

  9. Supported lipid bilayer/carbon nanotube hybrids

    NASA Astrophysics Data System (ADS)

    Zhou, Xinjian; Moran-Mirabal, Jose M.; Craighead, Harold G.; McEuen, Paul L.

    2007-03-01

    Carbon nanotube transistors combine molecular-scale dimensions with excellent electronic properties, offering unique opportunities for chemical and biological sensing. Here, we form supported lipid bilayers over single-walled carbon nanotube transistors. We first study the physical properties of the nanotube/supported lipid bilayer structure using fluorescence techniques. Whereas lipid molecules can diffuse freely across the nanotube, a membrane-bound protein (tetanus toxin) sees the nanotube as a barrier. Moreover, the size of the barrier depends on the diameter of the nanotube-with larger nanotubes presenting bigger obstacles to diffusion. We then demonstrate detection of protein binding (streptavidin) to the supported lipid bilayer using the nanotube transistor as a charge sensor. This system can be used as a platform to examine the interactions of single molecules with carbon nanotubes and has many potential applications for the study of molecular recognition and other biological processes occurring at cell membranes.

  10. INTERACTION PATTERN OF FULLERENES (C20-C180) AND CARBON NANOTUBES WITH DIFFERENT FORMS OF DNA: A COMPUTATIONAL BIOLOGY APPROACH.

    PubMed

    Firdaus, Sumbul; Dhasmana, Anupam; Haque, Shafiul; Mir, Snober S; Jahan, Roshan; Bano, Tasneem; Srivastava, Vandana; Khan, Saif; Lohani, Mohtashim

    2015-01-01

    Recently, the venues of exposure to nanoparticles have increased significantly owing to their increased deliberate production. In this study the interaction of fullerenes with DNA was analyzed along with various factors affecting this interaction like mol. wt. of fullerenes (C20 to C180), the form of DNA i.e., A, B and Z, and sequences of DNA, and was compared with the DNA binding of CNTs. Increase in the molecular weight of the fullerene showed increase in the binding score with A & B-form of DNA, but no regular affect was seen on binding with Z-form of DNA. Although the binding of all fullerenes was best with A form. While CNTs bind with all forms of DNA, but best scores were with B form, which were comparable with those of fullerene C80 and C84 with A form. The interaction of both fullerenes and CNTs were not affected by the sequence of DNA. The number of interacting base pairs increased from 1 base-pair to 4, as the molecular size of fullerene increases in all A & B-and Z form of DNA. Whereas CNTs interact with 5 bases in A and B form, and 3 bases in Z form. The groove where binding occurs depended on the form of DNA. Smaller (< C48) fullerenes bind in minor groove of B-DNA, and larger fullerenes bind in major groove. While in A form of DNA, fullerenes of all sizes bind in major groove. The binding was random and not size dependent in Z form of DNA. Whereas, CNTs bind to major groove of DNA in a parallel fashion in A and B form of DNA, and in minor groove attached perpendicularly in Z form.

  11. Boron Nitride Nanotubes

    NASA Technical Reports Server (NTRS)

    Smith, Michael W. (Inventor); Jordan, Kevin (Inventor); Park, Cheol (Inventor)

    2012-01-01

    Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

  12. Boron nitride nanotubes

    DOEpatents

    Smith, Michael W.; Jordan, Kevin; Park, Cheol

    2012-06-06

    Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

  13. Triphenylalanine peptides self-assemble into nanospheres and nanorods that are different from the nanovesicles and nanotubes formed by diphenylalanine peptides.

    PubMed

    Guo, Cong; Luo, Yin; Zhou, Ruhong; Wei, Guanghong

    2014-03-01

    Understanding the nature of the self-assembly of peptide nanostructures at the molecular level is critical for rational design of functional bio-nanomaterials. Recent experimental studies have shown that triphenylalanine(FFF)-based peptides can self-assemble into solid plate-like nanostructures and nanospheres, which are different from the hollow nanovesicles and nanotubes formed by diphenylalanine(FF)-based peptides. In spite of extensive studies, the assembly mechanism and the molecular basis for the structural differences between FFF and FF nanostructures remain poorly understood. In this work, we first investigate the assembly process and the structural features of FFF nanostructures using coarse-grained molecular dynamics simulations, and then compare them with FF nanostructures. We find that FFF peptides spontaneously assemble into solid nanometer-sized nanospheres and nanorods with substantial β-sheet contents, consistent with the structural properties of hundred-nanometer-sized FFF nano-plates characterized by FT-IR spectroscopy. Distinct from the formation mechanism of water-filled FF nanovesicles and nanotubes reported in our previous study, intermediate bilayers are not observed during the self-assembly process of FFF nanospheres and nanorods. The peptides in FFF nanostructures are predominantly anti-parallel-aligned, which can form larger sizes of β-sheet-like structures than the FF counterparts. In contrast, FF peptides exhibit lipid-like assembly behavior and assemble into bilayered nanostructures. Furthermore, although the self-assembly of FF and FFF peptides is mostly driven by side chain-side chain (SC-SC) aromatic stacking interactions, the main chain-main chain (MC-MC) interactions also play an important role in the formation of fine structures of the assemblies. The delicate interplay between MC-MC and SC-SC interactions results in the different nanostructures formed by the two peptides. These findings provide new insights into the structure

  14. High-Throughput Top-Down and Bottom-Up Processes for Forming Single-Nanotube Based Architectures for 3D Electronics

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama B.; Megerian, Krikor G.; von Allmen, Paul; Kowalczyk, Robert; Baron, Richard

    2009-01-01

    We have developed manufacturable approaches to form single, vertically aligned carbon nanotubes, where the tubes are centered precisely, and placed within a few hundred nm of 1-1.5 micron deep trenches. These wafer-scale approaches were enabled by chemically amplified resists and inductively coupled Cryo-etchers for forming the 3D nanoscale architectures. The tube growth was performed using dc plasma-enhanced chemical vapor deposition (PECVD), and the materials used for the pre-fabricated 3D architectures were chemically and structurally compatible with the high temperature (700 C) PECVD synthesis of our tubes, in an ammonia and acetylene ambient. Tube characteristics were also engineered to some extent, by adjusting growth parameters, such as Ni catalyst thickness, pressure and plasma power during growth. Such scalable, high throughput top-down fabrication techniques, combined with bottom-up tube synthesis, should accelerate the development of PECVD tubes for applications such as interconnects, nano-electromechanical (NEMS), sensors or 3D electronics in general.

  15. Triphenylalanine peptides self-assemble into nanospheres and nanorods that are different from the nanovesicles and nanotubes formed by diphenylalanine peptides

    NASA Astrophysics Data System (ADS)

    Guo, Cong; Luo, Yin; Zhou, Ruhong; Wei, Guanghong

    2014-02-01

    Understanding the nature of the self-assembly of peptide nanostructures at the molecular level is critical for rational design of functional bio-nanomaterials. Recent experimental studies have shown that triphenylalanine(FFF)-based peptides can self-assemble into solid plate-like nanostructures and nanospheres, which are different from the hollow nanovesicles and nanotubes formed by diphenylalanine(FF)-based peptides. In spite of extensive studies, the assembly mechanism and the molecular basis for the structural differences between FFF and FF nanostructures remain poorly understood. In this work, we first investigate the assembly process and the structural features of FFF nanostructures using coarse-grained molecular dynamics simulations, and then compare them with FF nanostructures. We find that FFF peptides spontaneously assemble into solid nanometer-sized nanospheres and nanorods with substantial β-sheet contents, consistent with the structural properties of hundred-nanometer-sized FFF nano-plates characterized by FT-IR spectroscopy. Distinct from the formation mechanism of water-filled FF nanovesicles and nanotubes reported in our previous study, intermediate bilayers are not observed during the self-assembly process of FFF nanospheres and nanorods. The peptides in FFF nanostructures are predominantly anti-parallel-aligned, which can form larger sizes of β-sheet-like structures than the FF counterparts. In contrast, FF peptides exhibit lipid-like assembly behavior and assemble into bilayered nanostructures. Furthermore, although the self-assembly of FF and FFF peptides is mostly driven by side chain-side chain (SC-SC) aromatic stacking interactions, the main chain-main chain (MC-MC) interactions also play an important role in the formation of fine structures of the assemblies. The delicate interplay between MC-MC and SC-SC interactions results in the different nanostructures formed by the two peptides. These findings provide new insights into the structure

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

    DOEpatents

    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. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon; Zettl, Alexander Karlwalte

    2004-12-28

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  18. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon Sheng; Zettl, Alexander Karlwalter

    2003-01-01

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  19. Amino acid-bile acid based molecules: extremely narrow surfactant nanotubes formed by a phenylalanine-substituted cholic acid.

    PubMed

    Travaglini, Leana; D'Annibale, Andrea; Schillén, Karin; Olsson, Ulf; Sennato, Simona; Pavel, Nicolae V; Galantini, Luciano

    2012-12-21

    An amino acid-substituted bile acid forms tubular aggregates with inner and outer diameters of about 3 and 6 nm. The diameters are unusually small for surfactant self-assembled tubes. The results enhance the spectrum of applications of supramolecular tubules and open up possibilities for investigating a novel class of biological amphiphiles.

  20. Comparison of bio-mineralization behavior of Ti-6Al-4V-1Nb and Zr-1Nb nano-tubes formed by anodization

    NASA Astrophysics Data System (ADS)

    Choi, Yong; Hong, Sun I.

    2014-12-01

    Nano-tubes of titanium and zirconium alloys like Ti-6Al-4V-1Nb and Zr-1Nb were prepared by anodization followed by coating with hydroxylapatite (HA) and their bio-mineralization behaviors were compared to develop a bio-compatible material for implants in orthopedics, dentistry and cardiology. Ti-6Al-4V-1Nb weight gain in a simulated body solution increased gradually. The bigger tube diameter was, the heavier HA was deposited. Surface roughness of both alloys increased highly with the increasing diameter of nano-tube. Their surface roughness decreased by HA deposition due to the removal of the empty space of the nano-tubes. Zr-1Nb alloy had faster growth of nano-tubes layers more than Ti-6Al-4V-1Nb alloy.

  1. Supported Lipid Bilayer/Carbon Nanotube Hybrids

    NASA Astrophysics Data System (ADS)

    Zhou, Xinjian; Moran-Mirabal, Jose; Craighead, Harold; McEuen, Paul

    2007-03-01

    We form supported lipid bilayers on single-walled carbon nanotubes and use this hybrid structure to probe the properties of lipid membranes and their functional constituents. We first demonstrate membrane continuity and lipid diffusion over the nanotube. A membrane-bound tetanus toxin protein, on the other hand, sees the nanotube as a diffusion barrier whose strength depends on the diameter of the nanotube. Finally, we present results on the electrical detection of specific binding of streptavidin to biotinylated lipids with nanotube field effect transistors. Possible techniques to extract dynamic information about the protein binding events will also be discussed.

  2. Amorphous Carbon-Boron Nitride Nanotube Hybrids

    NASA Technical Reports Server (NTRS)

    Kim, Jae Woo (Inventor); Siochi, Emilie J. (Inventor); Wise, Kristopher E. (Inventor); Lin, Yi (Inventor); Connell, John (Inventor)

    2016-01-01

    A method for joining or repairing boron nitride nanotubes (BNNTs). In joining BNNTs, the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures. In repairing BNNTs, the damaged site of the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures at the damage site.

  3. Stable and robust polymer nanotubes stretched from polymersomes

    PubMed Central

    Reiner, Joseph E.; Wells, Jeffrey M.; Kishore, Rani B.; Pfefferkorn, Candace; Helmerson, Kristian

    2006-01-01

    We create long polymer nanotubes by directly pulling on the membrane of polymersomes using either optical tweezers or a micropipette. The polymersomes are composed of amphiphilic diblock copolymers, and the nanotubes formed have an aqueous core connected to the aqueous interior of the polymersome. We stabilize the pulled nanotubes by subsequent chemical cross-linking. The cross-linked nanotubes are extremely robust and can be moved to another medium for use elsewhere. We demonstrate the ability to form networks of polymer nanotubes and polymersomes by optical manipulation. The aqueous core of the polymer nanotubes together with their robust character makes them interesting candidates for nanofluidics and other applications in biotechnology. PMID:16432242

  4. Architecture and Characteristics of Bacterial Nanotubes.

    PubMed

    Dubey, Gyanendra P; Malli Mohan, Ganesh Babu; Dubrovsky, Anna; Amen, Triana; Tsipshtein, Shai; Rouvinski, Alex; Rosenberg, Alex; Kaganovich, Daniel; Sherman, Eilon; Medalia, Ohad; Ben-Yehuda, Sigal

    2016-02-22

    Bacteria display an array of contact-dependent interaction systems that have evolved to facilitate direct cell-to-cell communication. We have previously identified a mode of bacterial communication mediated by nanotubes bridging neighboring cells. Here, we elucidate nanotube architecture, dynamics, and molecular components. Utilizing Bacillus subtilis as a model organism, we found that at low cell density, nanotubes exhibit remarkable complexity, existing as both intercellular tubes and extending tubes, with the latter frequently surrounding the cells in a "root-like" fashion. Observing nanotube formation in real time showed that these structures are formed in the course of minutes, displaying rapid movements. Utilizing a combination of super-resolution, light, and electron microscopy, we revealed that nanotubes are composed of chains of membranous segments harboring a continuous lumen. Furthermore, we discovered that a conserved calcineurin-like protein, YmdB, presents in nanotubes and is required for both nanotube production and intercellular molecular trade.

  5. Architecture and Characteristics of Bacterial Nanotubes.

    PubMed

    Dubey, Gyanendra P; Malli Mohan, Ganesh Babu; Dubrovsky, Anna; Amen, Triana; Tsipshtein, Shai; Rouvinski, Alex; Rosenberg, Alex; Kaganovich, Daniel; Sherman, Eilon; Medalia, Ohad; Ben-Yehuda, Sigal

    2016-02-22

    Bacteria display an array of contact-dependent interaction systems that have evolved to facilitate direct cell-to-cell communication. We have previously identified a mode of bacterial communication mediated by nanotubes bridging neighboring cells. Here, we elucidate nanotube architecture, dynamics, and molecular components. Utilizing Bacillus subtilis as a model organism, we found that at low cell density, nanotubes exhibit remarkable complexity, existing as both intercellular tubes and extending tubes, with the latter frequently surrounding the cells in a "root-like" fashion. Observing nanotube formation in real time showed that these structures are formed in the course of minutes, displaying rapid movements. Utilizing a combination of super-resolution, light, and electron microscopy, we revealed that nanotubes are composed of chains of membranous segments harboring a continuous lumen. Furthermore, we discovered that a conserved calcineurin-like protein, YmdB, presents in nanotubes and is required for both nanotube production and intercellular molecular trade. PMID:26906740

  6. The diameter of nanotubes formed on Ti-6Al-4V alloy controls the adhesion and differentiation of Saos-2 cells.

    PubMed

    Filova, Elena; Fojt, Jaroslav; Kryslova, Marketa; Moravec, Hynek; Joska, Ludek; Bacakova, Lucie

    2015-01-01

    Ti-6Al-4V-based nanotubes were prepared on a Ti-6Al-4V surface by anodic oxidation on 10 V, 20 V, and 30 V samples. The 10 V, 20 V, and 30 V samples and a control smooth Ti-6Al-4V sample were evaluated in terms of their chemical composition, diameter distribution, and cellular response. The surfaces of the 10 V, 20 V, and 30 V samples consisted of nanotubes of a relatively wide range of diameters that increased with the voltage. Saos-2 cells had a similar initial adhesion on all nanotube samples to the control Ti-6Al-4V sample, but it was lower than on glass. On day 3, the highest concentrations of both vinculin and talin measured by enzyme-linked immunosorbent assay and intensity of immunofluorescence staining were on 30 V nanotubes. On the other hand, the highest concentrations of ALP, type I collagen, and osteopontin were found on 10 V and 20 V samples. The final cellular densities on 10 V, 20 V, and 30 V samples were higher than on glass. Therefore, the controlled anodization of Ti-6Al-4V seems to be a useful tool for preparing nanostructured materials with desirable biological properties.

  7. The diameter of nanotubes formed on Ti-6Al-4V alloy controls the adhesion and differentiation of Saos-2 cells

    PubMed Central

    Filova, Elena; Fojt, Jaroslav; Kryslova, Marketa; Moravec, Hynek; Joska, Ludek; Bacakova, Lucie

    2015-01-01

    Ti-6Al-4V-based nanotubes were prepared on a Ti-6Al-4V surface by anodic oxidation on 10 V, 20 V, and 30 V samples. The 10 V, 20 V, and 30 V samples and a control smooth Ti-6Al-4V sample were evaluated in terms of their chemical composition, diameter distribution, and cellular response. The surfaces of the 10 V, 20 V, and 30 V samples consisted of nanotubes of a relatively wide range of diameters that increased with the voltage. Saos-2 cells had a similar initial adhesion on all nanotube samples to the control Ti-6Al-4V sample, but it was lower than on glass. On day 3, the highest concentrations of both vinculin and talin measured by enzyme-linked immunosorbent assay and intensity of immunofluorescence staining were on 30 V nanotubes. On the other hand, the highest concentrations of ALP, type I collagen, and osteopontin were found on 10 V and 20 V samples. The final cellular densities on 10 V, 20 V, and 30 V samples were higher than on glass. Therefore, the controlled anodization of Ti-6Al-4V seems to be a useful tool for preparing nanostructured materials with desirable biological properties. PMID:26648719

  8. A Combinatorial Approach to the Investigation of Metal Systems that Form Both Bulk Metallic Glasses and High Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Welk, Brian A.; Gibson, Mark A.; Fraser, Hamish L.

    2016-03-01

    In this work, compositionally graded specimens were deposited using the laser engineered net-shaping (LENS™) additive manufacturing technique to study the glass-forming ability of two bulk metallic glass (BMG) and high entropy alloy (HEA) composite systems. The first graded specimen varied from Zr57Ti5Al10Cu20Ni8 (BMG) to CoCrFeNiCu0.5 (HEA) and the second graded specimen varied from TiZrCuNb (BMG) to (TiZrCuNb)65Ni35 (HEA). After deposition, laser surface melting experiments were performed parallel to the gradient to remelt and rapidly solidify the specimen. Scanning electron microscopy and energy dispersive x-ray spectroscopy were used to determine the morphology and composition variations in the as-deposited and laser surface melted phases. Selected area diffraction of the melt pool regions confirmed an almost fully amorphous region in the first gradient and an amorphous matrix/crystalline dendrite composite structure in the second gradient.

  9. Splitting and joining in carbon nanotube/nanoribbon/nanotetrahedron growth.

    PubMed

    Hasegawa, Takayuki; Kohno, Hideo

    2015-02-01

    We report a novel phenomenon for carbon nanotube growth that results in a new carbon nanotube morphology. A carbon nanotube grown via metal nanoparticle-catalyzed chemical vapor deposition splits into two flattened nanotubes during growth and the two flattened nanotubes merge to form a ring of carbon nanotube/nanoribbon. This novel process is revealed by transmission electron microscopy observations of the carbon nanostructures. We propose that the splitting-and-joining process involves only one metal catalyst nanoparticle and a self-folding mechanism that we have named the origami mechanism to explain the process and the formation of nanoribbons and nanotetrahedra. PMID:25559588

  10. A carbon nanotube wall membrane for water treatment.

    PubMed

    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.

  11. Directional solidification of (Ti, Zr) carbide-(Ti, Zr) diboride eutectics

    SciTech Connect

    Sorrell, C.C.; Beratan, H.R.; Bradt, R.C.; Stubican, V.C.

    1984-03-01

    The ZrC-ZrB2, ZrC-TiB2, and TiC-TiB2 metal diboride-metal carbide pseudo-binary eutectic systems have been successfully solidified directionally by means of the floating zone method. The first and third of these eutectics possess a morphology consisting of columnar grains of parallel lamellae with interlamellar spacings that adhere to the lambda-squared (R) C relationship, while the second is noted to solidify in a Chinese calligraphy-like morphology of broken and deformed lamellae. This phenomenon may be related to solid solution effects, but it did not prevent the interlamellar spacings from following the aforementioned law. The calligraphic effect's values are larger than those of the other two systems, and the constant, C, is accordingly about an order of magnitude larger. All three of these cubic-hexagonal systems exhibited identical epitaxial relationships. 24 references.

  12. Dissymmetric carbon nanotubes by bipolar electrochemistry.

    PubMed

    Warakulwit, Chompunuch; Nguyen, Thi; Majimel, Jérome; Delville, Marie-Hélène; Lapeyre, Véronique; Garrigue, Patrick; Ravaine, Valérie; Limtrakul, Jumras; Kuhn, Alexander

    2008-02-01

    Short carbon nanotubes have been modified selectively on one end with metal using a bulk technique based on bipolar electrochemistry. A stabilized suspension of nanotubes is introduced in a capillary containing an aqueous metal salt solution, and a high electric field is applied to orientate and polarize the individual tubes. During their transport through the capillary under sufficient polarization (30 kV), each nanotube is the site of water oxidation on one end and the site of metal ion reduction on the other end with the size of the formed metal cluster being proportional to the potential drop along the nanotube.

  13. Development of Carbon-Nanotube/Polymer Composites

    NASA Technical Reports Server (NTRS)

    Reynolds, Thomas A.

    2005-01-01

    A report presents a short discussion of one company's effort to develop composites of carbon nanotubes in epoxy and other polymer matrices. The focus of the discussion is on the desirability of chemically modifying carbon nanotubes to overcome their inherent chemical nonreactivity and thereby enable the formation of strong chemical bonds between nanotubes and epoxies (or other polymeric matrix materials or their monomeric precursors). The chemical modification is effected in a process in which discrete functional groups are covalently attached to the nanotube surfaces. The functionalization process was proposed by the company and demonstrated in practice for the first time during this development effort. The covalently attached functional groups are capable of reacting with the epoxy or other matrix resin to form covalent bonds. Furthermore, the company uses this process to chemically modify the nanotube surfaces, affording tunable adhesion to polymers and solubility in select solvents. Flat-sheet composites containing functionalized nanotubes demonstrate significantly improved mechanical, thermal, and electrical properties.

  14. Method for producing carbon nanotubes

    DOEpatents

    Phillips, Jonathan; Perry, William L.; Chen, Chun-Ku

    2006-02-14

    Method for producing carbon nanotubes. Carbon nanotubes were prepared using a low power, atmospheric pressure, microwave-generated plasma torch system. After generating carbon monoxide microwave plasma, a flow of carbon monoxide was directed first through a bed of metal particles/glass beads and then along the outer surface of a ceramic tube located in the plasma. As a flow of argon was introduced into the plasma through the ceramic tube, ropes of entangled carbon nanotubes, attached to the surface of the tube, were produced. Of these, longer ropes formed on the surface portion of the tube located in the center of the plasma. Transmission electron micrographs of individual nanotubes revealed that many were single-walled.

  15. Exploration of R2XM2 (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge): Structural Motifs, the novel Compound Gd2AlGe2 and Analysis of the U3Si2 and Zr3Al2 Structure Types

    SciTech Connect

    McWhorter, Sean William

    2006-01-01

    In the process of exploring and understanding the influence of crystal structure on the system of compounds with the composition Gd5(SixGe1-x)4 several new compounds were synthesized with different crystal structures, but similar structural features. In Gd5(SixGe1-x)4, the main feature of interest is the magnetocaloric effect (MCE), which allows the material to be useful in magnetic refrigeration applications. The MCE is based on the magnetic interactions of the Gd atoms in the crystal structure, which varies with x (the amount of Si in the compound). The crystal structure of Gd5(SixGe1-x)4 can be thought of as being formed from two 32434 nets of Gd atoms, with additional Gd atoms in the cubic voids and Si/Ge atoms in the trigonal prismatic voids. Attempts were made to substitute nonmagnetic atoms for magnetic Gd using In, Mg and Al. Gd2MgGe2 and Gd2InGe2 both possess the same 32434 nets of Gd atoms as Gd5(SixGe1-x)4, but these nets are connected differently, forming the Mo2FeB2 crystal structure. A search of the literature revealed that compounds with the composition R2XM2 (R=Sc, Y, Ti, Zr, Hf, rare earth; X=main group element; M=transition metal, Si, Ge) crystallize in one of four crystal structures: the Mo2FeB2, Zr3Al2, Mn2AlB2 and W2CoB2 crystal structures. These crystal structures are described, and the relationships between them are highlighted. Gd2AlGe2 forms an entirely new crystal structure, and the details of its synthesis and characterization are given. Electronic structure calculations are performed to understand the nature of bonding in this compound and how

  16. Nanotube cathodes.

    SciTech Connect

    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

  17. Carbon nanotube materials characterization and devices design

    NASA Astrophysics Data System (ADS)

    Li, Weifeng

    The objective of this research is to characterize the electrical and mechanical properties of Carbon Nanotube (CNT) materials, and explore possible device applications for these materials. In order to achieve this goal, different forms of Carbon Nanotube materials---including Carbon Nanotubes, Carbon Nanotube Arrays, Carbon Nanotube Ribbon, Carbon Nanotube Thread, and sub-micrometer Carbon Nanotube Thread---were tested under a Scanning Electron Microscope (SEM) using a Micromanipulator (MM). Video and sound recording of the testing in the microscope provided new understanding how thread is formed and how nanotube materials fail. As-produced and thermally treated nanotubes were also tested. The main electrical parameters measured were electrical resistivity and maximum current density. The main mechanical property measured was strength. Together, these parameters are helping to determine the strongest and most conductive forms of CNT material. Putting nanotube materials into application is the ultimate goal of this continuing research. Several aggressive application ideas were investigated in a preliminary way in this work. In biomedical applications, a bundle of CNTs was formed for use as an electrode for accurate biosensing. A simple robot was designed using CNT electrical fiber. The robot was powered by two solenoids and could act as an in-body sensor and actuator to perform some impossible tasks from the viewpoint of current medical technology. In aerospace engineering, CNT materials could replace copper wire to reduce the weight of aircraft. Based on the excellent mechanical properties of CNT materials, a challenging idea is to use CNT material to build elevators to move payloads to outer space without using rockets. This dissertation makes contributions in the characterization of nanotube materials and in the design of miniature electromagnetic devices.

  18. Ophthalmologial Applications of Carbon Nanotube Nanotechology

    NASA Technical Reports Server (NTRS)

    Loftus, David; Girten, Beverly (Technical Monitor)

    2002-01-01

    The development of an implantable device consisting of an array of carbon nanotubes on a silicon chip for restoration of vision in patients with macular degeneration and other retinal disorders is presented. The use of carbon nanotube bucky paper for retinal cell transplantation is proposed. This paper is in viewgraph form.

  19. Stabilization of amphiphilic block copolymer nanotubes and vesicles by photopolymerization

    NASA Astrophysics Data System (ADS)

    Kishore, R.; Jofre, A.; Hutchison, J. B.; Allegrini, M.; Locascio, L. E.; Helmerson, K.

    2006-12-01

    We create long polymer nanotubes by directly pulling on the membrane of polymersomes using either optical tweezers or a micropipette. The polymersomes are composed of amphiphilic diblock copolymers and the nanotubes formed have an aqueous core connected to the aqueous interior of the polymersome. Stabilized membranes of nanotubes and vesicles were formed by the directed selfassembly of poly(ethylene oxide)-block-polybutadiene, followed by photopolymerization, initiated by UV light, to a maximum double bond conversion of 15%. The photopolymerized nanotubes are extremely robust. The applicability of photopolymerization for biophysics and bioanalytical science is demonstrated by electrophoresing DNA molecules through a stabilized nanotube with an integrated vesicle reservoir.

  20. Engineering molecular chains in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Chamberlain, Thomas W.; Pfeiffer, Rudolf; Howells, Jonathan; Peterlik, Herwig; Kuzmany, Hans; Kräutler, Bernhard; da Ros, Tatiana; Melle-Franco, Manuel; Zerbetto, Francesco; Milić, Dragana; Khlobystov, Andrei N.

    2012-11-01

    A range of mono- and bis-functionalised fullerenes have been synthesised and inserted into single-walled carbon nanotubes. The effect of the size and shape of the functional groups of the fullerenes on the resultant 1D arrays formed within the nanotubes was investigated by high resolution transmission electron microscopy and X-ray diffraction. The addition of non-planar, sterically bulky chains to the fullerene cage results in highly ordered 1D structures in which the fullerenes are evenly spaced along the internal nanotube cavity. Theoretical calculations reveal that the functional groups interact with neighbouring fullerene cages to space the fullerenes evenly within the confines of the nanotube. The addition of two functional groups to opposite sides of the fullerene cages results in a further increase in the separation of the fullerene cages within the nanotubes at the cost of lower nanotube filling rates.A range of mono- and bis-functionalised fullerenes have been synthesised and inserted into single-walled carbon nanotubes. The effect of the size and shape of the functional groups of the fullerenes on the resultant 1D arrays formed within the nanotubes was investigated by high resolution transmission electron microscopy and X-ray diffraction. The addition of non-planar, sterically bulky chains to the fullerene cage results in highly ordered 1D structures in which the fullerenes are evenly spaced along the internal nanotube cavity. Theoretical calculations reveal that the functional groups interact with neighbouring fullerene cages to space the fullerenes evenly within the confines of the nanotube. The addition of two functional groups to opposite sides of the fullerene cages results in a further increase in the separation of the fullerene cages within the nanotubes at the cost of lower nanotube filling rates. Electronic supplementary information (ESI) available: HRTEM images of 4@SWNT, space filling models of 1-6@SWNT structures and crystal packing

  1. Energy efficient microwave synthesis of mesoporous Ce0.5M0.5O2 (Ti, Zr, Hf) nanoparticles for low temperature CO oxidation in an ionic liquid – a comparative study

    SciTech Connect

    Alammar, Tarek; Chow, Ying -Kit; Mudring, Anja -Verena

    2014-11-19

    Ce0.5M0.5O2 (M = Ti, Zr, Hf) nanoparticles have been successfully synthesized by microwave irradiation in the ionic liquid [C4mim][Tf2N] (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide). The morphology, crystallinity, and chemical composition of the obtained materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and N2–adsorption measurements. XRD and Raman spectroscopy analyses confirmed the formation of solid solutions with cubic fluorite structure. The catalytic activities of the Ce0.5M0.5O2 (M = Ti, Zr, Hf) nanoparticles were investigated in the low-temperature oxidation of CO. Ce0.5Zr0.5O2 nanospheres exhibit the best performance (100% conversion at 350 °C), followed by Ce0.5Hf0.5O2 (55% conversion at 360 °C) and Ce0.5Ti0.5O2 (11% conversion at 350 °C). Heating the as-prepared Ce0.5Zr0.5O2 to 600 °C for extended time leads to a decrease in surface area and, as expected decreased catalytic activity. Depending on the ionic liquid the obtained Ce0.5Zr0.5O2 exhibits different morphologies, varying from nano-spheres in [C4mim][Tf2N] and [P66614][Tf2N] (P66614 = trishexyltetradecylphosphonium) to sheet-like assemblies in [C3mimOH][Tf2N] (C3mimOH = 1-(3-hydroxypropyl)-3-methylimidazolium). As a result, the microwave synthesis superiority to other heating methods like sonochemical synthesis and conventional heating was proven by comparative experiments where the catalytic activity of Ce0.5Zr0.5O2 obtained by alternate methods such as conventional heating was found to

  2. Estimation of the Number of Cross-Links of Multi-walled Carbon Nanotube Films Formed by a Dehydration Condensation Reaction

    NASA Astrophysics Data System (ADS)

    Ogino, S.; Sato, Y.; Yamamoto, G.; Sasamori, K.; Kimura, H.; Hashida, T.; Motomiiya, K.; Jeyadevan, B.; Tohji, K.

    2007-03-01

    Preparation procedure of multi-walled carbon nanotube (MWCNT) films shows as follows. First, as-grown MWCNTs heated in the air and treated with hydrochloric acid to remove amorphous carbon and catalytic metal particles respectively. Then, the o1btained MWCNT samples were treated with nitric acid at 373K to add carboxylic acid and hydroxyl groups on their surface. Finally, MWCNT films were prepared by employing a condensation reaction utilizing 1,3-dicyclohexylcarbodiimide (DCC) to cross-link each MWCNT with chemical bonds. Morphological changes in the resultant MWCNT films were monitored using scanning electron microscopy, and showed that the MWCNTs were randomly intertwined in the films. The prepared MWCNT films were 17mm in diameter and 20μm in thickness, and the apparent density was 0.59 g/cm3. Fourier transform-infrared spectroscopy confirmed that each MWCNT modified with carboxylic acid and hydroxyl groups was cross-linked through the ester bond. It was found that the ratio of the number of ester cross-links and carbon atoms of the nanotubes per unit apparent volume (cm3) of condensed-MWCNT films was 5.23×10-3 using TGA. The tensile strength and Vickers hardness of condensed-MWCNT films achieved an average of 15MPa and 9.2MPa, respectively, and was greater than those of free-standing MWCNT films without ester bond.

  3. Effects of single-walled carbon nanotubes on lysozyme gelation.

    PubMed

    Tardani, Franco; La Mesa, Camillo

    2014-09-01

    The possibility to disperse carbon nanotubes in biocompatible matrices has got substantial interest from the scientific community. Along this research line, the inclusion of single walled carbon nanotubes in lysozyme-based hydrogels was investigated. Experiments were performed at different nanotube/lysozyme weight ratios. Carbon nanotubes were dispersed in protein solutions, in conditions suitable for thermal gelation. The state of the dispersions was determined before and after thermal treatment. Rheology, dynamic light scattering and different microscopies investigated the effect that carbon nanotubes exert on gelation. The gelation kinetics and changes in gelation temperature were determined. The effect of carbon and lysozyme content on the gel properties was, therefore, determined. At fixed lysozyme content, moderate amounts of carbon nanotubes do not disturb the properties of hydrogel composites. At moderately high volume fractions in carbon nanotubes, the gels become continuous in both lysozyme and nanotubes. This is because percolating networks are presumably formed. Support to the above statements comes by rheology.

  4. “Brick-like” N-doped graphene/carbon nanotube structure forming three-dimensional films as high performance metal-free counter electrodes in dye-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Ma, Jie; Li, Cheng; Yu, Fei; Chen, Junhong

    2015-01-01

    The "brick-like" N-doped graphene-carbon nanotube (NGC) composites are designed by mechanically grinding the filtration films, which are fabricated to form a three-dimensional structure film as a counter electrode (CE). The N-doped graphene/carbon nanotube films with a three-dimensional "brick-like" structure can provide numerous vertical active edge sites. The excellent electrochemical catalytic activities of CE can be obtained by adjusting the different ratio of graphene to CNTs to control the size and N-doping content of breaking particles. NGC17 CE based dye-sensitized solar cells (DSSC) have reached a high efficiency (6.74%) close to platinum-based cells (6.89%). The excellent efficiency may be attributed to the following factors: a) the ΔEP of NGC17 (304 mV) is lower than that of the Pt electrode (389 mV); b) the charge transfer resistance (Rct) at the NGC17-CE/electrolyte interface was 1.78 Ω cm-2, which is lower than that of a Pt-CE/electrolyte interface (8.97 Ω cm-2).

  5. Nanotube phonon waveguide

    DOEpatents

    Chang, Chih-Wei; Zettl, Alexander K.

    2013-10-29

    Disclosed are methods and devices in which certain types of nanotubes (e.g., carbon nanotubes and boron nitride nanotubes conduct heat with high efficiency and are therefore useful in electronic-type devices.

  6. Polymer Self-assembly on Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Giulianini, Michele; Motta, Nunzio

    This chapter analyses the poly(3-hexylthiophene) self-assembly on carbon nanotubes and the interaction between the two materials forming a new hybrid nanostructure. The chapter starts with a review of the several studies investigating polymers and biomolecules self-assembled on nanotubes. Then conducting polymers and polythiophenes are briefly introduced. Accordingly, carbon nanotube structure and properties are reported in Sect. 3. The experimental section starts with the bulk characterisation of polymer thin films with the inclusion of uniformly distributed carbon nanotubes. By using volume film analysis techniques (AFM, TEM, UV-Vis and Raman), we show how the polymer's higher degree of order is a direct consequence of interaction with carbon nanotubes. Nevertheless, it is through the use of nanoscale analysis and molecular dynamic simulations that the self-assembly of the polymer on the nanotube surface can be clearly evidenced and characterised. In Sect. 6, the effect of the carbon templating structure on the P3HT organisation on the surface is investigated, showing the chirality-driven polymer assembly on the carbon nanotube surface. The interaction between P3HT and CNTs brings also to charge transfer, with the modification of physical properties for both species. In particular, the alteration of the polymer electronic properties and the modification of the nanotube mechanical structure are a direct consequence of the P3HT π-π stacking on the nanotube surface. Finally, some considerations based on molecular dynamics studies are reported in order to confirm and support the experimental results discussed.

  7. Modelling water molecules inside cyclic peptide nanotubes

    NASA Astrophysics Data System (ADS)

    Tiangtrong, Prangsai; Thamwattana, Ngamta; Baowan, Duangkamon

    2016-03-01

    Cyclic peptide nanotubes occur during the self-assembly process of cyclic peptides. Due to the ease of synthesis and ability to control the properties of outer surface and inner diameter by manipulating the functional side chains and the number of amino acids, cyclic peptide nanotubes have attracted much interest from many research areas. A potential application of peptide nanotubes is their use as artificial transmembrane channels for transporting ions, biomolecules and waters into cells. Here, we use the Lennard-Jones potential and a continuum approach to study the interaction of a water molecule in a cyclo[(- D-Ala- L-Ala)_4-] peptide nanotube. Assuming that each unit of a nanotube comprises an inner and an outer tube and that a water molecule is made up of a sphere of two hydrogen atoms uniformly distributed over its surface and a single oxygen atom at the centre, we determine analytically the interaction energy of the water molecule and the peptide nanotube. Using this energy, we find that, independent of the number of peptide units, the water molecule will be accepted inside the nanotube. Once inside the nanotube, we show that a water molecule prefers to be off-axis, closer to the surface of the inner nanotube. Furthermore, our study of two water molecules inside the peptide nanotube supports the finding that water molecules form an array of a 1-2-1-2 file inside peptide nanotubes. The theoretical study presented here can facilitate thorough understanding of the behaviour of water molecules inside peptide nanotubes for applications, such as artificial transmembrane channels.

  8. Nanotube News

    ERIC Educational Resources Information Center

    Journal of College Science Teaching, 2005

    2005-01-01

    Smaller, faster computers, bullet-proof t-shirts, and itty-bitty robots--such are the promises of nanotechnology and the cylinder-shaped collection of carbon molecules known as nanotubes. But for these exciting ideas to become realities, scientists must understand how these miracle molecules perform under all sorts of conditions. This brief…

  9. Peptide nanotubes.

    PubMed

    Hamley, Ian W

    2014-07-01

    The self-assembly of different classes of peptide, including cyclic peptides, amyloid peptides and surfactant-like peptides into nanotube structures is reviewed. The modes of self-assembly are discussed. Additionally, applications in bionanotechnology and synthetic materials science are summarized.

  10. Silicon nanotubes: Why not?

    NASA Astrophysics Data System (ADS)

    Zhang, R. Q.; Lee, S. T.; Law, Chi-Kin; Li, Wai-Kee; Teo, Boon K.

    2002-10-01

    A diamond nanowire (CNW), a silicon nanowire (SiNW), a carbon nanotube (CNT), and a silicon nanotube (SiNT) were studied using the semiempirical molecular orbital PM3 method, with confirmations by calculations at the HF/3-21G and HF/3-21G(d) levels. It was shown that the systems with a diamond structure generally possess larger band gaps than their tubular counterparts. Carbon nanotubular structure shows efficient sp 2 hybridization and π bonding, thus allowing a high stability of the carbon nanotube structure. In contrast, silicon prefers sp 3 hybridization and favors the tetrahedral diamond-like structures, thereby forming the commonly observed nanowires. This distinction can be traced to the differences in the energetics and overlaps of the valence s and p orbitals of C vs Si. Nevertheless, when the dangling bonds are properly terminated, SiNT can in principle be formed. The resulting energy minimized SiNT, however, adopts a severely puckered structure (with a corrugated surface) with SiSi distances ranging from 1.85 to 2.25 Å.

  11. Electrical properties and applications of carbon nanotube structures.

    PubMed

    Bandaru, Prabhakar R

    2007-01-01

    The experimentally verified electrical properties of carbon nanotube structures and manifestations in related phenomena such as thermoelectricity, superconductivity, electroluminescence, and photoconductivity are reviewed. The possibility of using naturally formed complex nanotube morphologies, such as Y-junctions, for new device architectures are then considered. Technological applications of the electrical properties of nanotube derived structures in transistor applications, high frequency nanoelectronics, field emission, and biological sensing are then outlined. The review concludes with an outlook on the technological potential of nanotubes and the need for new device architectures for nanotube systems integration. PMID:17450889

  12. Methods for producing reinforced carbon nanotubes

    SciTech Connect

    Ren, Zhifen; Wen, Jian Guo; Lao, Jing Y.; Li, Wenzhi

    2008-10-28

    Methods for producing reinforced carbon nanotubes having a plurality of microparticulate carbide or oxide materials formed substantially on the surface of such reinforced carbon nanotubes composite materials are disclosed. In particular, the present invention provides reinforced carbon nanotubes (CNTs) having a plurality of boron carbide nanolumps formed substantially on a surface of the reinforced CNTs that provide a reinforcing effect on CNTs, enabling their use as effective reinforcing fillers for matrix materials to give high-strength composites. The present invention also provides methods for producing such carbide reinforced CNTs.

  13. Carbon nanotube fiber spun from wetted ribbon

    SciTech Connect

    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.

  14. Process for derivatizing carbon nanotubes with diazonium species

    NASA Technical Reports Server (NTRS)

    Tour, James M. (Inventor); Bahr, Jeffrey L. (Inventor); Yang, Jiping (Inventor)

    2007-01-01

    The invention incorporates new processes for the chemical modification of carbon nanotubes. Such processes involve the derivatization of multi- and single-wall carbon nanotubes, including small diameter (ca. 0.7 nm) single-wall carbon nanotubes, with diazonium species. The method allows the chemical attachment of a variety of organic compounds to the side and ends of carbon nanotubes. These chemically modified nanotubes have applications in polymer composite materials, molecular electronic applications and sensor devices. The methods of derivatization include electrochemical induced reactions thermally induced reactions (via in-situ generation of diazonium compounds or pre-formed diazonium compounds), and photochemically induced reactions. The derivatization causes significant changes in the spectroscopic properties of the nanotubes. The estimated degree of functionality is ca. 1 out of every 20 to 30 carbons in a nanotube bearing a functionality moiety. Such electrochemical reduction processes can be adapted to apply site-selective chemical functionalization of nanotubes. Moreover, when modified with suitable chemical groups, the derivatized nanotubes are chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as, mechanical strength or electrical conductivity) to the properties of the composite material as a whole. Furthermore, when modified with suitable chemical groups, the groups can be polymerized to form a polymer that includes carbon nanotubes ##STR00001##.

  15. A label-free aptasensor based on polyethyleneimine wrapped carbon nanotubes in situ formed gold nanoparticles as signal probe for highly sensitive detection of dopamine.

    PubMed

    Azadbakht, Azadeh; Roushani, Mahmoud; Abbasi, Amir Reza; Menati, Saeid; Derikvand, Zohreh

    2016-11-01

    Herein, a highly sensitive and selective aptamer biosensor for quantitative detection of a model target, dopamine (DA), was developed by using a gold (Au) electrode modified with highly dispersed gold nanoparticles (AuNPs) and acid-oxidized carbon nanotubes (CNTs-COOH) functionalized with polyethyleneimine (PEI). Amine-terminated12-mercaptureprobe (ssDNA1) as a capture probe and specific DA-aptamer (ssDNA2) as a detection probe was immobilized on the surface of a modified electrode via the formation of covalent amide bond and hybridization, respectively. Methylene blue (MB) was used as the redox probe, which was intercalated into the aptamer through the specific interaction with its guanine bases. In the presence of DA, the interaction between aptamer and DA displaced the MB from the electrode surface, rendering a lowered electrochemical signal attributed to decreased amount of adsorbed MB. The developed electrochemical DA aptasensor showed a good linear response to DA from 5 to 300nM with detection limit of 2.1nM. The biosensor also exhibited satisfactory selectivity and could be successfully used to detect DA in blood serum sample. PMID:27524058

  16. Teslaphoresis of Carbon Nanotubes.

    PubMed

    Bornhoeft, Lindsey R; Castillo, Aida C; Smalley, Preston R; Kittrell, Carter; James, Dustin K; Brinson, Bruce E; Rybolt, Thomas R; Johnson, Bruce R; Cherukuri, Tonya K; Cherukuri, Paul

    2016-04-26

    This paper introduces Teslaphoresis, the directed motion and self-assembly of matter by a Tesla coil, and studies this electrokinetic phenomenon using single-walled carbon nanotubes (CNTs). Conventional directed self-assembly of matter using electric fields has been restricted to small scale structures, but with Teslaphoresis, we exceed this limitation by using the Tesla coil's antenna to create a gradient high-voltage force field that projects into free space. CNTs placed within the Teslaphoretic (TEP) field polarize and self-assemble into wires that span from the nanoscale to the macroscale, the longest thus far being 15 cm. We show that the TEP field not only directs the self-assembly of long nanotube wires at remote distances (>30 cm) but can also wirelessly power nanotube-based LED circuits. Furthermore, individualized CNTs self-organize to form long parallel arrays with high fidelity alignment to the TEP field. Thus, Teslaphoresis is effective for directed self-assembly from the bottom-up to the macroscale. PMID:27074626

  17. Silicon Carbide Nanotube Synthesized

    NASA Technical Reports Server (NTRS)

    Lienhard, Michael A.; Larkin, David J.

    2003-01-01

    Carbon nanotubes (CNTs) have generated a great deal of scientific and commercial interest because of the countless envisioned applications that stem from their extraordinary materials properties. Included among these properties are high mechanical strength (tensile and modulus), high thermal conductivity, and electrical properties that make different forms of single-walled CNTs either conducting or semiconducting, and therefore, suitable for making ultraminiature, high-performance CNT-based electronics, sensors, and actuators. Among the limitations for CNTs is their inability to survive in high-temperature, harsh-environment applications. Silicon carbon nanotubes (SiCNTs) are being developed for their superior material properties under such conditions. For example, SiC is stable in regards to oxidation in air to temperatures exceeding 1000 C, whereas carbon-based materials are limited to 600 C. The high-temperature stability of SiCNTs is envisioned to enable high-temperature, harsh-environment nanofiber- and nanotube-reinforced ceramics. In addition, single-crystal SiC-based semiconductors are being developed for hightemperature, high-power electronics, and by analogy to CNTs with silicon semiconductors, SiCNTs with single-crystal SiC-based semiconductors may allow high-temperature harsh-environment nanoelectronics, nanosensors, and nanoactuators to be realized. Another challenge in CNT development is the difficulty of chemically modifying the tube walls, which are composed of chemically stable graphene sheets. The chemical substitution of the CNTs walls will be necessary for nanotube self-assembly and biological- and chemical-sensing applications. SiCNTs are expected to have a different multiple-bilayer wall structure, allowing the surface Si atoms to be functionalized readily with molecules that will allow SiCNTs to undergo self-assembly and be compatible with a variety of materials (for biotechnology applications and high-performance fiber-reinforced ceramics).

  18. Method for synthesizing carbon nanotubes

    DOEpatents

    Fan, Hongyou

    2012-09-04

    A method for preparing a precursor solution for synthesis of carbon nanomaterials, where a polar solvent is added to at least one block copolymer and at least one carbohydrate compound, and the precursor solution is processed using a self-assembly process and subsequent heating to form nanoporous carbon films, porous carbon nanotubes, and porous carbon nanoparticles.

  19. Inorganic nanotubes and electro-fluidic devices fabricated therefrom

    DOEpatents

    Yang, Peidong; Majumdar, Arunava; Fan, Rong; Karnik, Rohit

    2011-03-01

    Nanofluidic devices incorporating inorganic nanotubes fluidly coupled to channels or nanopores for supplying a fluid containing chemical or bio-chemical species are described. In one aspect, two channels are fluidly interconnected with a nanotube. Electrodes on opposing sides of the nanotube establish electrical contact with the fluid therein. A bias current is passed between the electrodes through the fluid, and current changes are detected to ascertain the passage of select molecules, such as DNA, through the nanotube. In another aspect, a gate electrode is located proximal the nanotube between the two electrodes thus forming a nanofluidic transistor. The voltage applied to the gate controls the passage of ionic species through the nanotube selected as either or both ionic polarities. In either of these aspects the nanotube can be modified, or functionalized, to control the selectivity of detection or passage.

  20. Method of making carbon nanotubes on a substrate

    DOEpatents

    Gao, Yufei; Liu, Jun

    2006-03-14

    The present invention includes carbon nanotubes whose hollow cores are 100% filled with conductive filler. The carbon nanotubes are in uniform arrays on a conductive substrate and are well-aligned and can be densely packed. The uniformity of the carbon nanotube arrays is indicated by the uniform length and diameter of the carbon nanotubes, both which vary from nanotube to nanotube on a given array by no more than about 5%. The alignment of the carbon nanotubes is indicated by the perpendicular growth of the nanotubes from the substrates which is achieved in part by the simultaneous growth of the conductive filler within the hollow core of the nanotube and the densely packed growth of the nanotubes. The present invention provides a densely packed carbon nanotube growth where each nanotube is in contact with at least one nearest-neighbor nanotube. The substrate is a conductive substrate coated with a growth catalyst, and the conductive filler can be single crystals of carbide formed by a solid state reaction between the substrate material and the growth catalyst. The present invention further provides a method for making the filled carbon nanotubes on the conductive substrates. The method includes the steps of depositing a growth catalyst onto the conductive substrate as a prepared substrate, creating a vacuum within a vessel which contains the prepared substrate, flowing H2/inert (e.g. Ar) gas within the vessel to increase and maintain the pressure within the vessel, increasing the temperature of the prepared substrate, and changing the H2/Ar gas to ethylene gas such that the ethylene gas flows within the vessel. Additionally, varying the density and separation of the catalyst particles on the conductive substrate can be used to control the diameter of the nanotubes.

  1. Core-shell composite metal catalysts incased into natural ceramic nanotubes

    NASA Astrophysics Data System (ADS)

    Vinokurov, V.; Berberov, A.; Afonin, D.; Borzaev, H.; Ivanov, E.; Gushchin, P.; Lvov, Y.

    2014-08-01

    The bimetallic halloysite nanotubes were prepared by the injection of halloysite- containing aerosols into the microwave plasma reactor. Nanotubes contain metal nanoparticles formed from the metal salt solution in the lumen of nanotubes and the iron oxide nanoparticles at the outer surface of nanotubes. Such halloysite composites may be sputtered onto the surface of the porous carrier forming the nanostructured catalyst, as was shown by the pure halloysite sputtering onto the model porous ceramic surface.

  2. Novel Nanotube Manufacturing Streamlines Production

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Nanotubes have novel qualities that make them uniquely qualified for a plethora of uses, including applications in electronics, optics, and other scientific and industrial fields. The NASA process for creating these nanostructures involves using helium arc welding to vaporize an amorphous carbon rod and then form nanotubes by depositing the vapor onto a water-cooled carbon cathode, which then yields bundles, or ropes, of single-walled nanotubes at a rate of 2 grams per hour using a single setup. This eliminates costs associated with the use of metal catalysts, including the cost of product purification, resulting in a relatively inexpensive, high-quality, very pure end product. While managing to be less expensive, safer, and simpler, the process also increases the quality of the nanotubes. Goddard's Innovative Partnerships Program (IPP) Office promoted the technology, and in 2005, Boise-based Idaho Space Materials Inc. (ISM) was formed and applied for a nonexclusive license for the single-walled carbon nanotube (SWCNT) manufacturing technology. ISM commercialized its products, and the inexpensive, robust nanotubes are now in the hands of the scientists who will create the next generation of composite polymers, metals, and ceramics that will impact the way we live. In fact, researchers are examining ways for these newfound materials to be used in the manufacture of transistors and fuel cells, large screen televisions, ultra-sensitive sensors, high-resolution atomic force microscopy probes, supercapacitors, transparent conducting films, drug carriers, catalysts, and advanced composite materials, to name just a few of the myriad technologies to benefit.

  3. Studies of Nucleation, Growth, Specific Heat, and Viscosity of Undercooled Melts of Quasicrystals and Polytetrahedral-Phase-Forming Alloys

    NASA Technical Reports Server (NTRS)

    Kelton, K. F.; Croat, T. K.; Gangopadhyay, A.; Holland-Moritz, D.; Hyers, Robert W.; Rathz, Thomas J.; Robinson, Michael B.; Rogers, Jan R.

    2001-01-01

    Undercooling experiments and thermal physical property measurements of metallic alloys on the International Space Station (ISS) are planned. This recently-funded research focuses on fundamental issues of the formation and structure of highly-ordered non-crystallographic phases (quasicrystals) and related crystal phases (crystal approximants), and the connections between the atomic structures of these phases and those of liquids and glasses. It extends studies made previously by us of the composition dependence of crystal nucleation processes in silicate and metallic glasses, to the case of nucleation from the liquid phase. Motivating results from rf-levitation and drop-tube measurements of the undercooling of Ti/Zr-based liquids that form quasicrystals and crystal approximants are discussed. Preliminary measurements by electrostatic levitation (ESL) are presented.

  4. Characterization of Carbon Nanotube Reinforced Nickel

    NASA Technical Reports Server (NTRS)

    Gill, Hansel; Hudson, Steve; Bhat, Biliyar; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    Carbon nanotubes are cylindrical molecules composed of carbon atoms in a regular hexagonal arrangement. If nanotubes can be uniformly dispersed in a supporting matrix to form structural materials, the resulting structures could be significantly lighter and stronger than current aerospace materials. Work is currently being done to develop an electrolyte-based self-assembly process that produces a Carbon Nanotube/Nickel composite material with high specific strength. This process is expected to produce a lightweight metal matrix composite material, which maintains it's thermal and electrical conductivities, and is potentially suitable for applications such as advanced structures, space based optics, and cryogenic tanks.

  5. Lipid nanoscaffolds in carbon nanotube arrays.

    PubMed

    Paukner, Catharina; Koziol, Krzysztof K K; Kulkarni, Chandrashekhar V

    2013-10-01

    We present the fabrication of lipid nanoscaffolds inside carbon nanotube arrays by employing the nanostructural self-assembly of lipid molecules. The nanoscaffolds are finely tunable into model biomembrane-like architectures (planar), soft nanochannels (cylindrical) or 3-dimensionally ordered continuous bilayer structures (cubic). Carbon nanotube arrays hosting the above nanoscaffolds are formed by packing of highly oriented multiwalled carbon nanotubes which facilitate the alignment of lipid nanostructures without requiring an external force. Furthermore, the lipid nanoscaffolds can be created under both dry and hydrated conditions. We show their direct application in reconstitution of egg proteins. Such nanoscaffolds find enormous potential in bio- and nano-technological fields.

  6. Nanorods and nanotubes: Synthesis, manipulation and properties

    NASA Astrophysics Data System (ADS)

    Wong, Eric Warren

    Nanorods and nanotubes represent idealized structures for investigating phenomena associated with reduced dimensionality and are potential building blocks for nanostructured materials. Understanding their synthesis as well as physical properties is crucial if they are to form the basis for future devices. The synthesis of carbide nanotubes and nanorods is described. Also presented is a general method that combines micropatterning techniques with scanning force microscopy (SFM) to probe individual quasi-one-dimensional materials. Polycrystalline TiC and NbC nanorods, with 20-30 nm diameters and lengths exceeding 1 mum, were synthesized by reacting gaseous Ti-I or Nb-I at 550-1100sp°C with carbon nanotubes which served as structural templates. Template growth from nanotubes appears general since polycrystalline BCsb{x} and amorphous Fesb3C nanorods were produced from Bsb2Osb2 and FeClsb3, respectively. However, reaction of Si-I precursors with nanotubes or graphite above 1050sp°C resulted in single crystal SiC nanorods, with 1-20 nm diameters and 1-20 mum lengths, that grew catalytically from MoSisb2 nanoparticles by a vapor-solid mechanism. Above 1200sp°C, single crystal TiC nanorods grew from nanotubes and Ti-I or TiO by an undetermined mechanism. To probe electrical transport in carbon nanotubes, a method was devised where a static gold contact was lithographically formed with one end of a nanotube while a second dynamic contact was made by a conducting SFM probe. The conducting SFM tip can simultaneously map the topography and conductance of the nanotube. The transport properties of a series of structurally distinct nanotubes were studied and shown to sensitively depend on their structure, the presence of defects causing dramatic increases in resistivity. The mechanics of SiC nanorods and carbon nanotubes were studied using an analogous technique. An SFM tip was used to measure the forces required to bend nanobeams. The SiC nanorods had elastic moduli in close

  7. Electrochemical biosensing based on polypyrrole/titania nanotube hybrid.

    PubMed

    Xie, Yibing; Zhao, Ye

    2013-12-01

    The glucose oxidase (GOD) modified polypyrrole/titania nanotube enzyme electrode is fabricated for electrochemical biosensing application. The titania nanotube array is grown directly on a titanium substrate through an anodic oxidation process. A thin film of polypyrrole is coated onto titania nanotube array to form polypyrrole/titania nanotube hybrid through a normal pulse voltammetry process. GOD-polypyrrole/titania nanotube enzyme electrode is prepared by the covalent immobilization of GOD onto polypyrrole/titania nanotube hybrid via the cross-linker of glutaraldehyde. The morphology and microstructure of nanotube electrodes are characterized by field emission scanning electron microscopy and Fourier transform infrared analysis. The biosensing properties of this nanotube enzyme electrode have been investigated by means of cyclic voltammetry and chronoamperometry. The hydrophilic polypyrrole/titania nanotube hybrid provides highly accessible nanochannels for GOD encapsulation, presenting good enzymatic affinity. As-formed GOD-polypyrrole/titania nanotube enzyme electrode well conducts bioelectrocatalytic oxidation of glucose, exhibiting a good biosensing performance with a high sensitivity, low detection limit and wide linear detection range.

  8. Stable and robust polymer nanotubes stretched from polymersomes

    NASA Astrophysics Data System (ADS)

    Reiner, Joseph E.; Wells, Jeffrey M.; Kishore, Rani B.; Pfefferkorn, Candace; Helmerson, Kristian

    2006-01-01

    We create long polymer nanotubes by directly pulling on the membrane of polymersomes using either optical tweezers or a micropipette. The polymersomes are composed of amphiphilic diblock copolymers, and the nanotubes formed have an aqueous core connected to the aqueous interior of the polymersome. We stabilize the pulled nanotubes by subsequent chemical cross-linking. The cross-linked nanotubes are extremely robust and can be moved to another medium for use elsewhere. We demonstrate the ability to form networks of polymer nanotubes and polymersomes by optical manipulation. The aqueous core of the polymer nanotubes together with their robust character makes them interesting candidates for nanofluidics and other applications in biotechnology. cross-link | optical tweezers | nanofluidics | vesicles

  9. Electrons in semiconductors and nanotubes

    NASA Astrophysics Data System (ADS)

    Delaney, Paul Augustine

    In this thesis I will be presenting the results of my investigations into the electronic structure properties of various systems. The formalism used throughout is based on Density Functional Theory (DFT) in the local-density approximation (LDA), within the ab initio pseudopotential approximation for the valence wavefunctions, and the computations involve the solution of a self-consistent Schrodinger-like equation, which we solve by transforming this equation to reciprocal space and diagonalising the corresponding matrix. I organize these topics as follows: (1) The first chapter will be devoted to a discussion of the theoretical framework within which the calculations will be performed. First of all I will discuss the theory and history of the Compton profile. (2) In the second chapter, we shall study the computation of the Compton profiles of crystalline silicon. (3) Even without the pseudopotential approximation, the DFT-LDA formalism can include correlation between the various valence electrons only through an effective one-body potential in which these wavefunctions move. Thus it is very unlikely that the correct dynamical correlation between the valence electrons is present in the LDA wavefunctions. (4) In chapter four, we shall turn to a study of a novel material, carbon nanotubes, which have only recently been discovered. These nanotubes are long hollow cylinders formed by rolling up a graphene sheet (graphene is a single layer of graphite). When they occur individually they are called single-walled nanotubes, but they are also found to exist arranged concentrically around one central single-walled nanotube like the rings in a tree. These latter structures are called multi-walled nanotubes. Single-walled nanotubes are typically about 1 nm in diameter and many microns in length, and have exceptional mechanical strength. Depending on how the graphene sheet is rolled they may be metallic, small-gap semi-conductors or insulators. (Abstract shortened by UMI.)

  10. Polymerization initated at sidewalls of carbon nanotubes

    NASA Technical Reports Server (NTRS)

    Tour, James M. (Inventor); Hudson, Jared L. (Inventor); Krishnamoorti, Ramanan (Inventor); Yurekli, Koray (Inventor); Mitchell, Cynthia A. (Inventor)

    2011-01-01

    The present invention is directed to aryl halide (such as aryl bromide) functionalized carbon nanotubes that can be utilized in anionic polymerization processes to form polymer-carbon nanotube materials with improved dispersion ability in polymer matrices. In this process the aryl halide is reacted with an alkyllithium species or is reacted with a metal to replace the aryl-bromine bond with an aryl-lithium or aryl-metal bond, respectively. It has further been discovered that other functionalized carbon nanotubes, after deprotonation with a deprotonation agent, can similarly be utilized in anionic polymerization processes to form polymer-carbon nanotube materials. Additionally or alternatively, a ring opening polymerization process can be performed. The resultant materials can be used by themselves due to their enhanced strength and reinforcement ability when compared to their unbound polymer analogs. Additionally, these materials can also be blended with pre-formed polymers to establish compatibility and enhanced dispersion of nanotubes in otherwise hard to disperse matrices resulting in significantly improved material properties. The resultant polymer-carbon nanotube materials can also be used in drug delivery processes due to their improved dispersion ability and biodegradability, and can also be used for scaffolding to promote cellular growth of tissue.

  11. Membrane-targeted self-assembling cyclic peptide nanotubes.

    PubMed

    Rodríguez-Vázquez, Nuria; Ozores, H Lionel; Guerra, Arcadio; González-Freire, Eva; Fuertes, Alberto; Panciera, Michele; Priegue, Juan M; Outeiral, Juan; Montenegro, Javier; Garcia-Fandino, Rebeca; Amorin, Manuel; Granja, Juan R

    2014-01-01

    Peptide nanotubes are novel supramolecular nanobiomaterials that have a tubular structure. The stacking of cyclic components is one of the most promising strategies amongst the methods described in recent years for the preparation of nanotubes. This strategy allows precise control of the nanotube surface properties and the dimensions of the tube diameter. In addition, the incorporation of 3- aminocycloalkanecarboxylic acid residues in the nanotube-forming peptides allows control of the internal properties of the supramolecular tube. The research aimed at the application of membrane-interacting self-assembled cyclic peptide nanotubes (SCPNs) is summarized in this review. The cyclic peptides are designed to interact with phospholipid bilayers to induce nanotube formation. The properties and orientation of the nanotube can be tuned by tailoring the peptide sequence. Hydrophobic peptides form transmembrane pores with a hydrophilic orifice, the nature of which has been exploited to transport ions and small molecules efficiently. These synthetic ion channels are selective for alkali metal ions (Na(+), K(+) or Cs(+)) over divalent cations (Ca(2+)) or anions (Cl(-)). Unfortunately, selectivity was not achieved within the series of alkali metal ions, for which ion transport rates followed the diffusion rates in water. Amphipathic peptides form nanotubes that lie parallel to the membrane. Interestingly, nanotube formation takes place preferentially on the surface of bacterial membranes, thus making these materials suitable for the development of new antimicrobial agents. PMID:25515753

  12. Membrane-targeted self-assembling cyclic peptide nanotubes.

    PubMed

    Rodríguez-Vázquez, Nuria; Ozores, H Lionel; Guerra, Arcadio; González-Freire, Eva; Fuertes, Alberto; Panciera, Michele; Priegue, Juan M; Outeiral, Juan; Montenegro, Javier; Garcia-Fandino, Rebeca; Amorin, Manuel; Granja, Juan R

    2014-01-01

    Peptide nanotubes are novel supramolecular nanobiomaterials that have a tubular structure. The stacking of cyclic components is one of the most promising strategies amongst the methods described in recent years for the preparation of nanotubes. This strategy allows precise control of the nanotube surface properties and the dimensions of the tube diameter. In addition, the incorporation of 3- aminocycloalkanecarboxylic acid residues in the nanotube-forming peptides allows control of the internal properties of the supramolecular tube. The research aimed at the application of membrane-interacting self-assembled cyclic peptide nanotubes (SCPNs) is summarized in this review. The cyclic peptides are designed to interact with phospholipid bilayers to induce nanotube formation. The properties and orientation of the nanotube can be tuned by tailoring the peptide sequence. Hydrophobic peptides form transmembrane pores with a hydrophilic orifice, the nature of which has been exploited to transport ions and small molecules efficiently. These synthetic ion channels are selective for alkali metal ions (Na(+), K(+) or Cs(+)) over divalent cations (Ca(2+)) or anions (Cl(-)). Unfortunately, selectivity was not achieved within the series of alkali metal ions, for which ion transport rates followed the diffusion rates in water. Amphipathic peptides form nanotubes that lie parallel to the membrane. Interestingly, nanotube formation takes place preferentially on the surface of bacterial membranes, thus making these materials suitable for the development of new antimicrobial agents.

  13. Encapsulation of multi-walled carbon nanotubes (MWCNTs) in Ba(2+)-alginate to form coated micro-beads and their application to the pre-concentration/elimination of dibenzo-p-dioxin, dibenzofuran, and biphenyl from contaminated water.

    PubMed

    Fugetsu, Bunshi; Satoh, Shuya; Iles, Alexander; Tanaka, Kazuhiko; Nishi, Norio; Watari, Fumio

    2004-07-01

    We report preliminary data on the first use of multi-walled carbon nanotubes as adsorbents for the pre-concentration/elimination of dibenzo-p-dioxin, dibenzofuran and biphenyl from contaminated water.

  14. Substantial improvement of nanotube processability by freeze-drying.

    PubMed

    Maugey, M; Neri, W; Zakri, C; Derré, A; Pénicaud, A; Noé, L; Chorro, M; Launois, P; Monthioux, M; Poulin, P

    2007-08-01

    As-produced carbon nanotubes often contain a fraction of impurities such as metal catalysts, inorganic supports, and carbon by-products. These impurities can be partially removed by using acidic dissolution. The resulting nanotube materials have to be dried to form a powder. The processability of nanotubes subjected to regular (thermal vaporisation) drying is particularly difficult because capillary forces pack and stick the nanotubes irreversibly, which limits their dispersability in polymeric matrices or solvents. We show that this dramatic limitation can be circumvented by using freeze-drying instead of regular-drying during nanotube purification process. In this case, the nanotubes are trapped in frozen water which is then sublimated. As a result the final powder is significantly less compact and, more important, the nanotubes can be easily dispersed with no apparent aggregates, thereby greatly enhancing their processability, e.g., they can be used to make homogeneous composites and fibers. Results from coagulation spinning from water-based dispersions of regularly-dried and freeze-dried nanotubes are compared. We also show that freeze-dried materials, in contrast to regularly-dried materials, can be dissolved in organic polar solvents using alkali-doped nanotubes. High resolution TEM and XRD analysis demonstrate that the nanotube structure and quality are not affected at the nanoscale by freeze-drying treatments. PMID:17685277

  15. Tunneling nanotubes

    PubMed Central

    Austefjord, Magnus Wiger; Gerdes, Hans-Hermann; Wang, Xiang

    2014-01-01

    Tunneling nanotubes (TNTs) are recently discovered thin membranous tubes that interconnect cells. During the last decade, research has shown TNTs to be diverse in morphology and composition, varying between and within cell systems. In addition, the discovery of TNT-like extracellular protrusions, as well as observations of TNTs in vivo, has further enriched our knowledge on the diversity of TNT-like structures. Considering the complex molecular mechanisms underlying the formation of TNTs, as well as their different functions in intercellular communication, it is important to decipher how heterogeneity of TNTs is established, and to address what roles the compositional elements have in the execution of various functions. Here, we review the current knowledge on the morphological and structural diversity of TNTs, and address the relation between the formation, the structure, and the function of TNTs. PMID:24778759

  16. Effects of Zr and Si on the Glass Forming Ability and Compressive Properties of Ti-Cu-Co-Sn Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Tan; Wu, Yidong; Si, Jiajia; Hui, Xidong

    2015-06-01

    To succeed in finding novel Ti-based bulk metallic glasses, which are free from Be, Ni, and noble metallic elements, a comprehensive study was performed on the effects of Zr and Si on the microstructural evolution, glass-forming ability (GFA), and mechanical properties of Ti46Cu44- x Zr x Co7Sn3 ( x = 0, 5, 10, 12.5, and 16 at. pct) and Ti46Cu31.5Zr12.5- x Co7Sn3Si x ( x = 0.5, 1, and 1.5 at. pct) alloys. It is shown that with the increase of Zr, the sequence of phase formation is β-Ti + α-Ti + (Ti, Zr)3Cu4 ⇒ β-Ti + α-Ti + TiCu ⇒ β-Ti + Ti2Cu + glass ⇒ glass ⇒ β-Ti + Ti2Cu + TiCuSn. The quinary Ti-Zr-Cu-Co-Sn alloy with 12.5 pct Zr exhibits the best GFA. The addition of 1 pct Si results in the improvement of the critical size of glassy rods up to 3 mm in diameter. The yield stress and Young's modulus of Z-series alloys increases, and the plastic strain decreases with the addition of Zr. The yield stress and ultimate compression stress of Ti46Zr11.5Cu31.5Co7Sn3Si1 glassy alloy reach 2477.9 and 2623.3 MPa, respectively. It was found that the addition of Si promotes the generation and multiplication of shear bands, resulting in certain plasticity in these kinds of glassy alloys.

  17. Engineered Carbon Nanotube Materials for High-Q Nanomechanical Resonators

    NASA Technical Reports Server (NTRS)

    Choi, Daniel S.; Hunt, Brian; Bronikowski, Mike; Epp, Larry; Hoenk, Michael; Hoppe, Dan; Kowalczyk, Bob; Wong, Eric; Xu, Jimmy; Adam, Douglas; Young, Rob

    2003-01-01

    This document represents a presentation offered by the Jet Propulsion Laboratory, with assistance from researchers from Brown University and Northrop Grumman. The presentation took place in Seoul, Korea in July 2003 and attempted to demonstrate the fabrication approach regarding the development of high quality factor (high-Q) mechanical oscillators (in the forms of a tunable nanotube resonator and a nanotube array radio frequency [RF] filter) aimed at signal processing and based on carbon nanotubes. The presentation also addressed parallel efforts to develop both in-plane single nanotube resonators as well as vertical array power devices.

  18. Computational Nanotechnology of Materials, Devices, and Machines: Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Kwak, Dolhan (Technical Monitor)

    2000-01-01

    The mechanics and chemistry of carbon nanotubes have relevance for their numerous electronic applications. Mechanical deformations such as bending and twisting affect the nanotube's conductive properties, and at the same time they possess high strength and elasticity. Two principal techniques were utilized including the analysis of large scale classical molecular dynamics on a shared memory architecture machine and a quantum molecular dynamics methodology. In carbon based electronics, nanotubes are used as molecular wires with topological defects which are mediated through various means. Nanotubes can be connected to form junctions.

  19. Noncatalytic synthesis of carbon nanotubes by chemical vapor deposition

    SciTech Connect

    Ismagilov, R. R. Shvets, P. V.; Kharin, A. Yu.; Obraztsov, A. N.

    2011-03-15

    A new method is proposed to obtain uniform arrays of multiwall carbon nanotubes without catalysts. Nanotubes have been formed by carbon condensation from a hydrogen-methane gas mixture activated by a dc discharge. Structural and morphological investigations of the obtained material were performed by Raman spectroscopy, scanning and transmission electron microscopy, energy-dispersive X-ray analysis, and electron energy loss spectroscopy. It is shown that the obtained nanotubes contain no impurities that could act as catalysts. Based on these experimental data, it is concluded that the nanotube synthesis under study is noncatalytic. Possible mechanisms of this synthesis are considered.

  20. Graphene-carbon nanotube hybrid materials and use as electrodes

    DOEpatents

    Tour, James M.; Zhu, Yu; Li, Lei; Yan, Zheng; Lin, Jian

    2016-09-27

    Provided are methods of making graphene-carbon nanotube hybrid materials. Such methods generally include: (1) associating a graphene film with a substrate; (2) applying a catalyst and a carbon source to the graphene film; and (3) growing carbon nanotubes on the graphene film. The grown carbon nanotubes become covalently linked to the graphene film through carbon-carbon bonds that are located at one or more junctions between the carbon nanotubes and the graphene film. In addition, the grown carbon nanotubes are in ohmic contact with the graphene film through the carbon-carbon bonds at the one or more junctions. The one or more junctions may include seven-membered carbon rings. Also provided are the formed graphene-carbon nanotube hybrid materials.

  1. Mineral potential tracts for shoreline Ti-Zr placer deposits (phase V, deliverable 85): Chapter P in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

    USGS Publications Warehouse

    Beaudoin, Georges

    2015-01-01

    Shoreline placer Ti deposits are composed of ilmenite, rutile, zircon, monazite, and magnetite in well-sorted, fine- to medium-grained sand in coastal dunes, beaches and inlets. In addition to titanium, zirconium, in particular, and rare earth elements (REE) have become a major source of value in shoreline placer deposits. Shoreline placer deposits form mostly on tropical beaches around the world (fig. 1), and consist of dark sand layers rich in heavy minerals that are resistant to mechanical abrasion and chemical weathering. According to Hamilton (1995), shoreline placer deposits supply approximately 80 percent of the world’s rutile production, 25 percent of ilmenite, 100 percent of zircon, and 50 percent of both monazite and xenotime.

  2. General hypothesis and shell model for the synthesis of semiconductor nanotubes, including carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Mohammad, S. Noor

    2010-09-01

    Semiconductor nanotubes, including carbon nanotubes, have vast potential for new technology development. The fundamental physics and growth kinetics of these nanotubes are still obscured. Various models developed to elucidate the growth suffer from limited applicability. An in-depth investigation of the fundamentals of nanotube growth has, therefore, been carried out. For this investigation, various features of nanotube growth, and the role of the foreign element catalytic agent (FECA) in this growth, have been considered. Observed growth anomalies have been analyzed. Based on this analysis, a new shell model and a general hypothesis have been proposed for the growth. The essential element of the shell model is the seed generated from segregation during growth. The seed structure has been defined, and the formation of droplet from this seed has been described. A modified definition of the droplet exhibiting adhesive properties has also been presented. Various characteristics of the droplet, required for alignment and organization of atoms into tubular forms, have been discussed. Employing the shell model, plausible scenarios for the formation of carbon nanotubes, and the variation in the characteristics of these carbon nanotubes have been articulated. The experimental evidences, for example, for the formation of shell around a core, dipole characteristics of the seed, and the existence of nanopores in the seed, have been presented. They appear to justify the validity of the proposed model. The diversities of nanotube characteristics, fundamentals underlying the creation of bamboo-shaped carbon nanotubes, and the impurity generation on the surface of carbon nanotubes have been elucidated. The catalytic action of FECA on growth has been quantified. The applicability of the proposed model to the nanotube growth by a variety of mechanisms has been elaborated. These mechanisms include the vapor-liquid-solid mechanism, the oxide-assisted growth mechanism, the self

  3. Nonmagnetic carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Lipert, Kamil; Kretzschmar, Florian; Ritschel, Manfred; Leonhardt, Albrecht; Klingeler, Rüdiger; Büchner, Bernd

    2009-03-01

    We have synthesized by chemical vapor deposition (CVD) single-, double-, and multiwalled carbon nanotubes without magnetic impurities. In particular, we have applied a rhenium-based CVD technique yielding nonmagnetic carbon nanotubes with diamagnetic Re particles. In addition, carbon nanotubes prepared with iron as catalyst particles are annealed at very high temperatures in which the catalyst material is completely vaporized, while the carbon nanotubes are structurally preserved. Detailed magnetic studies show for both approaches a clear diamagnetic behavior typical for pure carbon nanotubes but no indication of ferromagnetic or paramagnetic material.

  4. Structure of boron nitride nanotubes

    SciTech Connect

    Buranova, Yu. S. Kulnitskiy, B. A.; Perezhogin, I. A.; Blank, V. D.

    2015-01-15

    The crystallographic structure of boron nitride nanotubes has been investigated. Various defects that may arise during nanotube synthesis are revealed by electron microscopy. Nanotubes with different numbers of walls and different diameters are modeled by molecular dynamics methods. Structural features of single-wall nanotubes are demonstrated. The causes of certain defects in multiwall nanotubes are indicated.

  5. Functionalized Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Lebron, Marisabel; Mintz, Eric; Meador, Michael A.; Hull, David R.; Scheiman, Daniel A.; Willis, Peter; Smalley, Richard E.

    2001-01-01

    Carbon nanotubes have created a great deal of excitement in the Materials Science community because of their outstanding mechanical, electrical, and thermal properties. Use of carbon nanotubes as reinforcements for polymers could lead to a new class of composite materials with properties, durability, and performance far exceeding that of conventional fiber reinforced composites. Organized arrays of carbon nanotubes, e.g., nanotube monolayers, could find applications as thermal management materials, light emitting devices, and sensor arrays. Carbon nanotubes could also be used as templates upon which nanotubes from other materials could be constructed. Successful use of carbon nanotubes in any of these potential applications requires the ability to control the interactions of nanotubes with each other and with other materials, e.g., a polymer matrix. One approach to achieving this control is to attach certain chemical groups to the ends and/or side-walls of the nanotubes. The nature of these chemical groups can be varied to achieve the desired result, such as better adhesion between the nanotubes and a polymer. Under a joint program between NASA Glenn, Clark Atlanta University, and Rice University researchers are working on developing a chemistry "tool-kit" that will enable the functionalization of carbon nanotubes with a variety of chemical groups. Recent results of this effort will be discussed.

  6. Process for derivatizing carbon nanotubes with diazonium species and compositions thereof

    NASA Technical Reports Server (NTRS)

    Tour, James M. (Inventor); Bahr, Jeffrey L. (Inventor); Yang, Jiping (Inventor)

    2011-01-01

    Methods for the chemical modification of carbon nanotubes involve the derivatization of multi- and single-wall carbon nanotubes, including small diameter (ca. 0.7 nm) single-wall carbon nanotubes, with diazonium species. The method allows the chemical attachment of a variety of organic compounds to the side and ends of carbon nanotubes. These chemically modified nanotubes have applications in polymer composite materials, molecular electronic applications, and sensor devices. The methods of derivatization include electrochemical induced reactions, thermally induced reactions, and photochemically induced reactions. Moreover, when modified with suitable chemical groups, the derivatized nanotubes are chemically compatible with a polymer matrix, allowing transfer of the properties of the nanotubes (such as, mechanical strength or electrical conductivity) to the properties of the composite material as a whole. Furthermore, when modified with suitable chemical groups, the groups can be polymerized to form a polymer that includes carbon nanotubes.

  7. Oxide Nanotube Analogues: CuO Nanobarrels

    SciTech Connect

    H. H. Farrell; R. D. Parra

    2011-11-01

    The principle 'form follows function' which dominated much of twentieth century architechture and industrial design has its parallel on the nanolevel in the concept of 'function follows form'. This has been realized in many technologically valuable ways on this level via nanoparticles such as nanotubes and quantum dots, for example. Now, a new material, copper oxide (CuO) nanobarrels, offers still another opportunity to exploit unusual form to obtain new functionality. Recently, CuO 'rings' on the order of 100 nm diameter have been observed experimentally by El-Azab and Liang (2003). In a separate effort, we have used first principles density functional calculations to investigate smaller, single walled CuO structures that appear to be nanotubes or nanobarrels with a square unit mesh rather than the hexagonal mesh of carbon nanotubes. These structures are unique and novel, and almost certainly will yield fascinating results when studied experimentally.

  8. Refoldable Peptide Barrel -- Carbon Nanotube Junctions

    NASA Astrophysics Data System (ADS)

    Titov, Alexey; Wang, Boyang; Kral, Petr

    2008-03-01

    We design hybrid bio-nano-junctions formed by cylindrical peptide structures covalently attached to carbon nanotubes. The cylinders are composed of 5 pairs of antiparallel peptide strands that are ``one-to-one'' matched and covalently bonded through ester and amide bonds to the terminal C atoms in two (20,0) carbon nanotubes. The remaining terminal carbons in the CNTs are replaced by nitrogens, forming embedded quinoline-like structures. The used peptide strands are composed of charged amino acids that form cylindrical patterns with preferred stable configurations. By applying a torque to the nanotubes, we can reversibly fold and control the overall structure of the peptide barrels. The junctions might allow the collection and delivery of drugs and activation of biological molecules attached to them.

  9. Noncovalent functionalization of multiwalled carbon nanotubes: application in hybrid nanostructures.

    PubMed

    Wang, Tie; Hu, Xiaoge; Qu, Xiaohu; Dong, Shaojun

    2006-04-01

    We developed a reproducible, noncovalent strategy to functionalize multiwalled carbon nanotubes (MWNTs) via embedding nanotubes in polysiloxane shells. (3-Aminopropyl)triethoxysilane molecules adsorbed to the nanotube surfaces via hydrophobic interactions are polymerized simply by acid catalysis and form a thin polysiloxane layer. On the basis of the embedded MWNTs, negatively charged gold nanoparticles are anchored to the nanotube surfaces via electrostatic interactions between the protonated amino groups and the gold nanoparticles. Furthermore, these gold nanoparticles can further grow and magnify along the nanotubes through heating in HAuCl4 aqueous solution at 100 degrees C; as a result these nanoparticles are joined to form continuous gold nanowires with MWNTs acting as templates. PMID:16570965

  10. Flattened Multiwalled Carbon Nanotube with Multi-Layered Structure.

    PubMed

    Kohno, Hideo; Hasegawa, Takayuki; Ichikawa, Satoshi

    2015-08-01

    Fabrication of novel nanostructures based on carbon nanotubes has been a focus of recent interest since they are expected to inherit excellent properties of carbon nanotube. To find new nanotube-based nanostructures, it is important to find a new growth mode or process. This paper reports the formation of a multiwalled carbon nanotube that has bi-layered structure and is partly flattened. Transmission electron microscopy observations suggest that the outer multiwalled layer was formed first from a Fe catalyst nanoparticle, and was partly flattened during the growth. Then the catalyst nanoparticle worked again to form the inner multiwalled tube moving inside the outer tube and became flattened at the same position of the outer tube. It is likely that the inner growth gave an expansion stress against the flattened outer tube; nevertheless, the flattened part of the outer tube remained. This observation evidences that the flattening of the nanotube occurred simultaneously during the growth and was stabilized by structural defect.

  11. Preparation of array of long carbon nanotubes and fibers therefrom

    DOEpatents

    Arendt, Paul N.; DePaula, Ramond F.; Zhu, Yuntian T.; Usov, Igor O.

    2015-11-19

    An array of carbon nanotubes is prepared by exposing a catalyst structure to a carbon nanotube precursor. Embodiment catalyst structures include one or more trenches, channels, or a combination of trenches and channels. A system for preparing the array includes a heated surface for heating the catalyst structure and a cooling portion that cools gas above the catalyst structure. The system heats the catalyst structure so that the interaction between the precursor and the catalyst structure results in the formation of an array of carbon nanotubes on the catalyst structure, and cools the gas near the catalyst structure and also cools any carbon nanotubes that form on the catalyst structure to prevent or at least minimize the formation of amorphous carbon. Arrays thus formed may be used for spinning fibers of carbon nanotubes.

  12. Experimental studies and micromagnetic simulations of electrodeposited Co nanotube arrays

    SciTech Connect

    Pathak, Sachin; Singh, Sukhvinder; Gaur, Rajmani; Sharma, Manish

    2014-08-07

    Magnetic hollow nanotubes of cobalt forming close-packed arrays are synthesized by controlling the growth during electrodeposition in AAO template. Superconducting quantum interference device (SQUID) magnetometry is used to experimentally measure the static magnetization of the array of nanotubes. Excellent qualitative agreements of SQUID and micromagnetic simulations for static measurements are observed. This motivates us to evaluate dynamic response measurements via micromagnetic simulations. The coercivity simulated along the longitudinal axis of the nanotube is found increase with the length of isolated as well as for array of nanotubes. The effect of interactions is also clearly observed both in static as well as in dynamic evaluations. The interactions cause reduction in coercivity along with the switching which depends upon the length of the nanotubes. The calculation for FMR modes also indicates that propagation of the spin waves are greatly influenced by the hollow centre of nanotube as compare to nanowire and support to maintain the stable vortex configuration. For array of nanotubes, multiple peaks are found over larger number of frequencies which is anticipated due the interactions between nanotubes. Simulation for bias field and angular dependence of spin wave modes also yields a significant influenced by the presence of neighbouring nanotubes.

  13. Carbon Nanotube Electron Gun

    NASA Technical Reports Server (NTRS)

    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.

  14. Carbon nanotube electron gun

    NASA Technical Reports Server (NTRS)

    Nguyen, Cattien V. (Inventor); Ribaya, Bryan P. (Inventor)

    2010-01-01

    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.

  15. Electrical device fabrication from nanotube formations

    DOEpatents

    Nicholas, Nolan Walker; Kittrell, W. Carter; Kim, Myung Jong; Schmidt, Howard K.

    2013-03-12

    A method for forming nanotube electrical devices, arrays of nanotube electrical devices, and device structures and arrays of device structures formed by the methods. Various methods of the present invention allow creation of semiconducting and/or conducting devices from readily grown SWNT carpets rather than requiring the preparation of a patterned growth channel and takes advantage of the self-controlling nature of these carpet heights to ensure a known and controlled channel length for reliable electronic properties as compared to the prior methods.

  16. A possible formation mechanism of double-walled and multi-walled carbon nanotube: a molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Han, Dianrong; Luo, Chenglin; Dai, Yafei; Zhu, Xingfeng

    2016-09-01

    Molecular dynamics simulations based on an empirical potential were performed to study the interaction of graphene nanoribbons and the single-walled carbon nanotubes. The results indicated that a piece of graphene nanoribbon can form a tube structure inside or outside single-walled carbon nanotubes spontaneously under certain condition. Based on this kind of spontaneous phenomenon, we proposed a new possible formation mechanism of double walled carbon nanotube and multi-walled carbon nanotube, and suggested the possibility of controlling the structure of double-walled carbon nanotube and/or multi-walled carbon nanotube.

  17. Texture and pyramidal slip in Ti, Zr and their alloys

    SciTech Connect

    Pochettino, A.A.; Gannio, N. ); Edwards, C.V. ); Penelle, R. )

    1992-12-15

    Zirconium, titanium and their alloys have a high anisotropic plastic behavior. One way to show this behavior is to analyze the evolution of the Lankford coefficient (R ([alpha]), values of which are obtained from tensile tests along different directions in the sheet plane). The variation of R([alpha]) can be explained from the crystallographic texture and the active deformation mechanisms. Microstructural observations show that prismatic slip is the most active deformation mode in these materials, but no dimensional change in the [lt][bar c][gt] direction of grains is possible by the activation of the (10[bar 1]0) [lt] 1[bar 2]10[gt] slip alone; so deformation along [0001] has to be accommodated either by (10[bar 1]o) [lt]1[bar 2]13[gt] (or [lt][bar c] + [bar a][gt]) pyramidal slip or by twinning. Many transmission electron microscopy (TEM) studies have shown evidence for [lt][bar c] + [bar a][gt] slip activity, and some authors have reported slip on (1[bar 1]01) planes in Ti alloys. The purpose of this paper is to contribute with another analysis of pyramidal slip activity in hcp textured materials, such as Ti and Zr alloys, and of the hardening mechanisms for this deformation mode. This analysis is performed both in a direct way, by means of TEM observations of deformed samples, and in an indirect way, by different mechanical tests.

  18. Applications of Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Ajayan, Pulickel M.; Zhou, Otto Z.

    Carbon nanotubes have attracted the fancy of many scientists worldwide. The small dimensions, strength and the remarkable physical properties of these structures make them a very unique material with a whole range of promising applications. In this review we describe some of the important materials science applications of carbon nanotubes. Specifically we discuss the electronic and electrochemical applications of nanotubes, nanotubes as mechanical reinforcements in high performance composites, nanotube-based field emitters, and their use as nanoprobes in metrology and biological and chemical investigations, and as templates for the creation of other nanostructures. Electronic properties and device applications of nanotubes are treated elsewhere in the book. The challenges that ensue in realizing some of these applications are also discussed from the point of view of manufacturing, processing, and cost considerations.

  19. Extended Platinum Nanotubes as Fuel Cell Catalysts

    SciTech Connect

    Alia, S.; Pivovar, B. S.; Yan, Y.

    2012-01-01

    Energy consumption has relied principally on fossil fuels as an energy source; fuel cells, however, can provide a clean and sustainable alternative, an answer to the depletion and climate change concerns of fossil fuels. Within proton exchange membrane fuel cells, high catalyst cost and poor durability limit the commercial viability of the device. Recently, platinum nanotubes (PtNTs) were studied as durable, active catalysts, providing a platform to meet US Department of Energy vehicular activity targets.[1] Porous PtNTs were developed to increase nanotube surface area, improving mass activity for oxygen reduction without sacrificing durability.[2] Subsurface platinum was then replaced with palladium, forming platinum-coated palladium nanotubes.[3] By forming a core shell structure, platinum utilization was increased, reducing catalyst cost. Alternative substrates have also been examined, modifying platinum surface facets and increasing oxygen reduction specific activity. Through modification of the PtNT platform, catalyst limitations can be reduced, ensuring a commercially viable device.

  20. B2C graphene, nanotubes, and nanoribbons.

    PubMed

    Wu, Xiaojun; Pei, Yong; Zeng, Xiao Cheng

    2009-04-01

    We report a first-principles prediction of a new two-dimensional inorganic material, namely, the B(2)C graphene in which the boron and carbon atoms are packed into a mosaic of hexagons and rhombuses. In the B(2)C graphene, each carbon atom is bonded with four boron atoms, forming a planar-tetracoordinate carbon (ptC) moiety, a notion first conceived by Hoffmann et al. The B(2)C graphene is possibly a metal with a small overlap in the energy of conduction and valence bands. Like the carbon graphene and nanotubes, a B(2)C graphene sheet can be rolled into various forms of B(2)C nanotubes as well. Depending on the roll-up vector, the B(2)C nanotubes may become either a metal or a semiconductor. All B(2)C graphene nanoribbons are predicted to be uniformly metallic, regardless of their width and edge structure.

  1. Preparation of High-Orderly TIO2 Nanotubes in Different Conditions and Electrolyte Solutions

    NASA Astrophysics Data System (ADS)

    Zhang, Yunhuai; Hu, Fu; Xiao, Peng; Fan, Xiaoyan

    High-orderly nanotubes of titania were fabricated by anodic oxidation of pure titanium substrate in different electrolytes containing fluoride. Different morphological nanotubes of titania were obtained through controlling the different pH value of inorganic electrolytes, and it was found that nanotubes of titanium oxide would not formed when pH value was above 6. The morphological and structural properties of nanotublar products were characterized by SEM. The synthesized nanotubes of titania in organic electrolytic solutions containing fluoride was of 60 μm in length. The experiments demonstrated the length and orderliness of nanotubes of titanium oxide in organic solutions were much better than those in inorganic solutions.

  2. Microfluidic sieve using intertwined, free-standing carbon nanotube mesh as active medium

    DOEpatents

    Bakajin, Olgica; Noy, Aleksandr

    2007-11-06

    A microfluidic sieve having a substrate with a microfluidic channel, and a carbon nanotube mesh. The carbon nanotube mesh is formed from a plurality of intertwined free-standing carbon nanotubes which are fixedly attached within the channel for separating, concentrating, and/or filtering molecules flowed through the channel. In one embodiment, the microfluidic sieve is fabricated by providing a substrate having a microfluidic channel, and growing the intertwined free-standing carbon nanotubes from within the channel to produce the carbon nanotube mesh attached within the channel.

  3. Gallium nitride nanotube lasers

    SciTech Connect

    Li, Changyi; Liu, Sheng; Hurtado, Antonio; Wright, Jeremy Benjamin; Xu, Huiwen; Luk, Ting Shan; Figiel, Jeffrey J.; Brener, Igal; Brueck, Steven R. J.; Wang, George T.

    2015-01-01

    Lasing is demonstrated from gallium nitride nanotubes fabricated using a two-step top-down technique. By optically pumping, we observed characteristics of lasing: a clear threshold, a narrow spectral, and guided emission from the nanotubes. In addition, annular lasing emission from the GaN nanotube is also observed, indicating that cross-sectional shape control can be employed to manipulate the properties of nanolasers. The nanotube lasers could be of interest for optical nanofluidic applications or application benefitting from a hollow beam shape.

  4. Carbon Nanotubes Synthesis Through Gamma Radiation

    NASA Astrophysics Data System (ADS)

    Tirado, Pablo; Garcia, Rafael; Montes, Jorge; Melendrez, Rodrigo; Barboza, Marcelino; Contreras, Oscar

    2015-03-01

    Carbon nanotubes show a great potential of applications since there discovery by Iijima in 1991[1] due to their numerous physical-chemical properties such as their high weight to strength relationship, which make them ideal to use in high resistance compound materials, and in many other applications[2] In this work, a novel method for the synthesis of carbon nanotubes is presented, starting from an ultra-thin sheet of graphite synthesized by the chemical vapor decomposition technique (CVD), using ultra high purity methane and hydrogen at 1200°C in a horizontal quartz reactor. For the synthesis of carbon nanotubes, the graphite sheets were exposed to different doses of radiation, with the objective of breaking the graphite bonds and form carbon nanotubes; a Gammacell equipment model 220 Excel was used for the purpose, which counts with a radiation source of cobalt 60, and a current radiation rate of 0.9 Gy/seconds. The time of exposure to radiation was varied in each sample, according to the desired dose of radiation in each case, afterwards the samples were characterized using the Raman spectroscopy and TEM microscopy techniques with the objective of observing the kind of nanotubes formed, their morphology and their number of defects. Results will be shown during the poster session.

  5. Membrane nanotubes facilitate long-distance interactions between natural killer cells and target cells.

    PubMed

    Chauveau, Anne; Aucher, Anne; Eissmann, Philipp; Vivier, Eric; Davis, Daniel M

    2010-03-23

    Membrane nanotubes are membranous tethers that physically link cell bodies over long distances. Here, we present evidence that nanotubes allow human natural killer (NK) cells to interact functionally with target cells over long distances. Nanotubes were formed when NK cells contacted target cells and moved apart. The frequency of nanotube formation was dependent on the number of receptor/ligand interactions and increased on NK cell activation. Most importantly, NK cell nanotubes contained a submicron scale junction where proteins accumulated, including DAP10, the signaling adaptor that associates with the activating receptor NKG2D, and MHC class I chain-related protein A (MICA), a cognate ligand for NKG2D, as occurs at close intercellular synapses between NK cells and target cells. Quantitative live-cell fluorescence imaging suggested that MICA accumulated at small nanotube synapses in sufficient numbers to trigger cell activation. In addition, tyrosine-phosphorylated proteins and Vav-1 accumulated at such junctions. Functionally, nanotubes could aid the lysis of distant target cells either directly or by moving target cells along the nanotube path into close contact for lysis via a conventional immune synapse. Target cells moving along the nanotube path were commonly polarized such that their uropods faced the direction of movement. This is the opposite polarization than for normal cell migration, implying that nanotubes can specifically drive target cell movement. Finally, target cells that remained connected to an NK cell by a nanotube were frequently lysed, whereas removing the nanotube using a micromanipulator reduced lysis of these target cells.

  6. Growing Aligned Carbon Nanotubes for Interconnections in ICs

    NASA Technical Reports Server (NTRS)

    Li, Jun; Ye, Qi; Cassell, Alan; Ng, Hou Tee; Stevens, Ramsey; Han, Jie; Meyyappan, M.

    2005-01-01

    A process for growing multiwalled carbon nanotubes anchored at specified locations and aligned along specified directions has been invented. Typically, one would grow a number of the nanotubes oriented perpendicularly to a silicon integrated-circuit (IC) substrate, starting from (and anchored on) patterned catalytic spots on the substrate. Such arrays of perpendicular carbon nanotubes could be used as electrical interconnections between levels of multilevel ICs. The process (see Figure 1) begins with the formation of a layer, a few hundred nanometers thick, of a compatible electrically insulating material (e.g., SiO(x) or Si(y)N(z) on the silicon substrate. A patterned film of a suitable electrical conductor (Al, Mo, Cr, Ti, Ta, Pt, Ir, or doped Si), having a thickness between 1 nm and 2 m, is deposited on the insulating layer to form the IC conductor pattern. Next, a catalytic material (usually, Ni, Fe, or Co) is deposited to a thickness between 1 and 30 nm on the spots from which it is desired to grow carbon nanotubes. The carbon nanotubes are grown by plasma-enhanced chemical vapor deposition (PECVD). Unlike the matted and tangled carbon nanotubes grown by thermal CVD, the carbon nanotubes grown by PECVD are perpendicular and freestanding because an electric field perpendicular to the substrate is used in PECVD. Next, the free space between the carbon nanotubes is filled with SiO2 by means of CVD from tetraethylorthosilicate (TEOS), thereby forming an array of carbon nanotubes embedded in SiO2. Chemical mechanical polishing (CMP) is then performed to remove excess SiO2 and form a flat-top surface in which the outer ends of the carbon nanotubes are exposed. Optionally, depending on the application, metal lines to connect selected ends of carbon nanotubes may be deposited on the top surface. The top part of Figure 2 is a scanning electron micrograph (SEM) of carbon nanotubes grown, as described above, on catalytic spots of about 100 nm diameter patterned by

  7. Production of single-walled carbon nanotube grids

    DOEpatents

    Hauge, Robert H; Xu, Ya-Qiong; Pheasant, Sean

    2013-12-03

    A method of forming a nanotube grid includes placing a plurality of catalyst nanoparticles on a grid framework, contacting the catalyst nanoparticles with a gas mixture that includes hydrogen and a carbon source in a reaction chamber, forming an activated gas from the gas mixture, heating the grid framework and activated gas, and controlling a growth time to generate a single-wall carbon nanotube array radially about the grid framework. A filter membrane may be produced by this method.

  8. Multi-walled carbon nanotubes with rectangular or square cross-section

    NASA Astrophysics Data System (ADS)

    Mizutani, Kanako; Kohno, Hideo

    2016-06-01

    Multi-walled carbon nanotubes with rectangular or square cross-section are formed. The nanotubes are about 50-200 nm in width, and their walls are around 5-30 nm thick. It is very likely that the rectangular cross-section is shaped simultaneously when nanotubes are formed from catalyst Fe nanoparticles during chemical vapor deposition process, and the shape is stabilized by the bonding between adjoining graphene layers in the multi-walled structure.

  9. Structure of ordered coaxial and scroll nanotubes: general approach.

    PubMed

    Khalitov, Zufar; Khadiev, Azat; Valeeva, Diana; Pashin, Dmitry

    2016-01-01

    The explicit formulas for atomic coordinates of multiwalled coaxial and cylindrical scroll nanotubes with ordered structure are developed on the basis of a common oblique lattice. According to this approach, a nanotube is formed by transfer of its bulk analogue structure onto a cylindrical surface (with a circular or spiral cross section) and the chirality indexes of the tube are expressed in the number of unit cells. The monoclinic polytypic modifications of ordered coaxial and scroll nanotubes are also discussed and geometrical conditions of their formation are analysed. It is shown that tube radii of ordered multiwalled coaxial nanotubes are multiples of the layer thickness, and the initial turn radius of the orthogonal scroll nanotube is a multiple of the same parameter or its half. PMID:26697865

  10. Coupling of mechanical and electronic properties of carbon nanotubes.

    PubMed

    Cristancho, Dahiyana; Benitez, Laura; Seminario, Jorge M

    2013-12-01

    Because of the potential importance of carbon nanotubes (CNT) in renewable energy and other fields, molecular orbital ab initio calculations are used to study the relation between mechanical and electronic properties of such structures. We estimate a modulus of elasticity of 1.3 TPa and find out that the mechanism of CNT structure deformation is dependent on their chirality. Armchair and chiral nanotubes have ductile deformation fracture while zigzag have both ductile and brittle; on the other hand armchair nanotubes fracture and form two caps while chiral nanotubes adopt a helical-structure conformation. In addition, the energy gap between occupied and unoccupied molecular orbitals increases when nanotubes are under plastic deformation. This strong coupling between mechanical and electrical properties can be used to tune CNT mechanically to specific electronic bandgaps, affecting directly their electromagnetic absorption properties.

  11. Atomic Entanglement in Carbon Nanotubes.

    NASA Astrophysics Data System (ADS)

    Bondarev, Igor; Vlahovic, Branislav

    2006-03-01

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

  12. Linked in: immunologic membrane nanotube networks.

    PubMed

    Zaccard, C R; Rinaldo, C R; Mailliard, R B

    2016-07-01

    Membrane nanotubes, also termed tunneling nanotubes, are F-actin-based structures that can form direct cytoplasmic connections and support rapid communication between distant cells. These nanoscale conduits have been observed in diverse cell types, including immune, neuronal, stromal, cancer, and stem cells. Until recently, little was known about the mechanisms involved in membrane nanotube development in myeloid origin APCs or how membrane nanotube networks support their ability to bridge innate and adaptive immunity. New research has provided insight into the modes of induction and regulation of the immune process of "reticulation" or the development of multicellular membrane nanotube networks in dendritic cells. Preprogramming by acute type 1 inflammatory mediators at their immature stage licenses mature type 1-polarized dendritic cells to reticulate upon subsequent interaction with CD40 ligand-expressing CD4(+) Th cells. Dendritic cell reticulation can support direct antigen transfer for amplification of specific T cell responses and can be positively or negatively regulated by signals from distinct Th cell subsets. Membrane nanotubes not only enhance the ability of immature dendritic cells to sense pathogens and rapidly mobilize nearby antigen-presenting cells in the peripheral tissues but also likely support communication of pathogen-related information from mature migratory dendritic cells to resident dendritic cells in lymph nodes. Therefore, the reticulation process facilitates a coordinated multicellular response for the efficient initiation of cell-mediated adaptive immune responses. Herein, we discuss studies focused on the molecular mechanisms of membrane nanotube formation, structure, and function in the context of immunity and how pathogens, such as HIV-1, may use dendritic cell reticulation to circumvent host defenses. PMID:26931578

  13. Electrical property measurements of metallized flagella-templated silica nanotube networks

    NASA Astrophysics Data System (ADS)

    Jo, Wonjin; Darmawan, Marten; Kim, Jihoon; Ahn, Chi Won; Byun, Doyoung; Baik, Seung Hyun; Kim, Min Jun

    2013-04-01

    We present an improvement in the electrical properties of silica nanotubes by coating metal nanoparticles on their surfaces. The silica nanotubes are formed from bacterial flagella bio-templates having a tubular structure. Successive depositions of metal nanoparticles on the silica nanotubes are performed through easily functionalized silica surfaces. The results show uniform metal nanoparticle sizes and a high surface area coverage. By incorporating gold, palladium and iron oxide nanoparticles, the metallized silica nanotubes gain electrical properties with the potential to create unique nanoelectronic materials. In this study, the metallized silica nanotubes with network structures are aligned and their electrical behaviors are investigated in both dry and wet conditions. The metallized silica nanotubes are found to be electrically conductive along the network structures. The current-voltage characteristics show remarkably improved electrical conductivities depending on the type of metal nanoparticle loading and nanotube network concentration.

  14. Melamine as an effective supramolecular modifier and stabilizer in a nanotube-constituted supergel.

    PubMed

    Xing, Pengyao; Chu, Xiaoxiao; Ma, Mingfang; Li, Shangyang; Hao, Aiyou

    2014-12-01

    Self-assembly of N-fluorenyl-9-methoxycarbonyl glutamic acid (Fmoc-Glu) in water generates metastable single-wall nanotubes. These nanotubes entangle and bundle together to form unstable gels that shrink with time and finally result in lamellar crystalline precipitates. Melamine (Mm) was employed as a supramolecular modifier and stabilizer to improve the stability of the nanotubes. Mm interacts with the carboxyl-rich surfaces of the nanotubes via H-bonds and static electronic forces to diminish the high affinity of individual nanotubes and facilitate Fmoc-Glu supergelation (critical gelation concentration <0.1 wt %). Although the basic process of nanotube formation is not disturbed, Mm inverts the supramolecular helicity of nanotubes from P to M.

  15. Electrical property measurements of metallized flagella-templated silica nanotube networks.

    PubMed

    Jo, Wonjin; Darmawan, Marten; Kim, Jihoon; Ahn, Chi Won; Byun, Doyoung; Baik, Seung Hyun; Kim, Min Jun

    2013-04-01

    We present an improvement in the electrical properties of silica nanotubes by coating metal nanoparticles on their surfaces. The silica nanotubes are formed from bacterial flagella bio-templates having a tubular structure. Successive depositions of metal nanoparticles on the silica nanotubes are performed through easily functionalized silica surfaces. The results show uniform metal nanoparticle sizes and a high surface area coverage. By incorporating gold, palladium and iron oxide nanoparticles, the metallized silica nanotubes gain electrical properties with the potential to create unique nanoelectronic materials. In this study, the metallized silica nanotubes with network structures are aligned and their electrical behaviors are investigated in both dry and wet conditions. The metallized silica nanotubes are found to be electrically conductive along the network structures. The current-voltage characteristics show remarkably improved electrical conductivities depending on the type of metal nanoparticle loading and nanotube network concentration.

  16. Inorganic nanotubes: One contribution of 12 to a Theme 'Nanotechnology of carbon and related materials'

    NASA Astrophysics Data System (ADS)

    Tenne, Reshef; Rao, C. N. R.

    2004-10-01

    Following the discovery of carbon fullerenes and carbon nanotubes, it was hypothesized that nanoparticles of inorganic compounds with layered (two-dimensional) structure, such as MoS2, will not be stable against folding and form nanotubes and fullerene-like structures: IF. The synthesis of numerous other inorganic nanotubes has been reported in recent years. Various techniques for the synthesis of inorganic nanotubes, including high-temperature reactions and strategies based on 'chemie douce' (soft chemistry, i.e. low-temperature) processes, are described. First-principle, density functional theory based calculations are able to provide substantial information on the structure and properties of such nanotubes. Various properties of inorganic nanotubes, including mechanical, electronic and optical properties, are described in brief. Some potential applications of the nanotubes in tribology, protection against impact, (photo)catalysis, batteries, etc., are discussed.

  17. Single-walled carbon nanotubes do not pierce aqueous phospholipid bilayers at low salt concentration.

    PubMed

    Shi, Liu; Shi, Dachuan; Nollert, Matthias U; Resasco, Daniel E; Striolo, Alberto

    2013-06-01

    Because of their unique physical, chemical, and electrical properties, carbon nanotubes are an attractive material for many potential applications. Their interactions with biological entities are, however, not yet completely understood. To fill this knowledge gap, we present experimental results for aqueous systems containing single-walled carbon nanotubes and phospholipid membranes, prepared in the form of liposomes. Our results suggest that dispersed single-walled carbon nanotubes, instead of piercing the liposome membranes, adsorb on them at low ionic strength. Transmission electron microscopy and dye-leakage experiments show that the liposomes remain for the most part intact in the presence of the nanotubes. Further, the liposomes are found to stabilize carbon nanotube dispersions when the surfactant sodium dodecylbenezenesulfonate is present at low concentrations. Quantifying the interactions between carbon nanotubes and phospholipid membranes could not only shed light on potential nanotubes cytotoxicity but also open up new research venues for their use in controlled drug delivery and/or gene and cancer therapy.

  18. Hemotoxicity of carbon nanotubes.

    PubMed

    Bussy, Cyrill; Methven, Laura; Kostarelos, Kostas

    2013-12-01

    Carbon nanotubes may enter into the bloodstream and interact with blood components indirectly via translocation following unintended exposure or directly after an intended administration for biomedical purposes. Once introduced into systemic circulation, nanotubes will encounter various proteins, biomolecules or cells which have specific roles in the homeostasis of the circulatory system. It is therefore essential to determine whether those interactions will lead to adverse effects or not. Advances in the understanding of how carbon nanotubes interact with blood proteins, the complement system, red blood cells and the hemostatic system are reviewed in this article. While many studies on carbon nanotube health risk assessment and their biomedical applications have appeared in the last few years, reports on the hemocompatibility of these nanomaterials remain surprisingly limited. Yet, defining the hemotoxicological profile is a mandatory step toward the development of clinically-relevant medications or contrast agents based on carbon nanotubes.

  19. Mechanical properties of nanotubes of polyelectrolyte multilayers

    NASA Astrophysics Data System (ADS)

    Cuenot, S.; Alem, H.; Louarn, G.; Demoustier-Champagne, S.; Jonas, A. M.

    2008-04-01

    The elastic properties of nanotubes fabricated by layer-by-layer (LbL) assembly of polyelectrolytes in the nanopores of polycarbonate track-etched membranes have been investigated by resonant contact Atomic Force Microscopy (AFM), for nanotube diameters in the range of 100 to 200nm. The elastic modulus of the nanotubes was computed from the resonance frequencies of a cantilever resting on freely suspended LbL nanotubes. An average value of 115MPa was found in air for Young's modulus of these nanostructures, well below the values reported for dry, flat multilayers, but in the range of values reported for water-swollen flat multilayers. These low values are most probably due to the lower degree of ionic cross-linking of LbL nanotubes and their consequently higher water content in air, resulting from the peculiar mode of growth of nanoconfined polyelectrolyte multilayers. The computation of the moment of inertia of the LbL nanostructures is only available in electronic form at 10.1140/epje/i2007-10291-3 and are accessible for authorised users.

  20. Coupling of carbon and peptide nanotubes.

    PubMed

    Montenegro, Javier; Vázquez-Vázquez, Carlos; Kalinin, Arseny; Geckeler, Kurt E; Granja, Juan R

    2014-02-12

    Two of the main types of nanotubular architectures are the single-walled carbon nanotubes (SWCNTs) and the self-assembling cyclic peptide nanotubes (SCPNs). We here report the preparation of the dual composite resulting from the ordered combination of both tubular motifs. In the resulting architecture, the SWCNTs can act as templates for the assembly of SCPNs that engage the carbon nanotubes noncovalently via pyrene "paddles", each member of the resulting hybrid stabilizing the other in aqueous solution. The particular hybrids obtained in the present study formed highly ordered oriented arrays and display complementary properties such as electrical conductivity. Furthermore, a self-sorting of the cyclic peptides toward semiconducting rather than metallic SWCNTs is also observed in the aqueous dispersions. It is envisaged that a broad range of exploitable properties may be achieved and/or controlled by varying the cyclic peptide components of similar SWCNT/SCPN hybrids.

  1. Applications of Titania Nanotubes in Bone Biology.

    PubMed

    Nair, Manitha; Elizabeth, Elmy

    2015-02-01

    Orthopedic implants, including artificial joints and fracture fixation devices, have helped to restore the physical independence of many patients, thereby improving the quality of their lives. Titania (Ti) and its alloys are better implant materials than stainless steel and Co-Cr alloys owing to their superior mechanical properties and biocompatibility; however, Ti-based implants may sometimes fail, leading to repeated surgeries. With the recent advancements in nanotechnology, the nanosurface modifications of Ti, especially in the form of Ti nanotubes (TNTs), have drastically improved the properties of orthopedic implants. In this review, we have summarized the fabrication of Ti nanotubes by electrochemical anodization and their influence on osteoblast cells and staphylococcus aureus. In addition, we have discussed the corrosion resistance of Ti nanotubes.

  2. Amyloid fibrils compared to peptide nanotubes.

    PubMed

    Zganec, Matjaž; Zerovnik, Eva

    2014-09-01

    Prefibrillar oligomeric states and amyloid fibrils of amyloid-forming proteins qualify as nanoparticles. We aim to predict what biophysical and biochemical properties they could share in common with better researched peptide nanotubes. We first describe what is known of amyloid fibrils and prefibrillar aggregates (oligomers and protofibrils): their structure, mechanisms of formation and putative mechanism of cytotoxicity. In distinction from other neuronal fibrillar constituents, amyloid fibrils are believed to cause pathology, however, some can also be functional. Second, we give a review of known biophysical properties of peptide nanotubes. Finally, we compare properties of these two macromolecular states side by side and discuss which measurements that have already been done with peptide nanotubes could be done with amyloid fibrils as well.

  3. Boron Nitride Nanotube: Synthesis and Applications

    NASA Technical Reports Server (NTRS)

    Tiano, Amanda L.; Park, Cheol; Lee, Joseph W.; Luong, Hoa H.; Gibbons, Luke J.; Chu, Sang-Hyon; Applin, Samantha I.; Gnoffo, Peter; Lowther, Sharon; Kim, Hyun Jung; Danehy, Paul M.; Inman, Jennifer A.; Jones, Stephen B.; Kang, Jin Ho; Sauti, Godfrey; Thibeault, Sheila A.; Yamakov, Vesselin; Wise, Kristopher E.; Su, Ji; Fay, Catharine C.

    2014-01-01

    Scientists have predicted that carbon's immediate neighbors on the periodic chart, boron and nitrogen, may also form perfect nanotubes, since the advent of carbon nanotubes (CNTs) in 1991. First proposed then synthesized by researchers at UC Berkeley in the mid 1990's, the boron nitride nanotube (BNNT) has proven very difficult to make until now. Herein we provide an update on a catalyst-free method for synthesizing highly crystalline, small diameter BNNTs with a high aspect ratio using a high power laser under a high pressure and high temperature environment first discovered jointly by NASA/NIA JSA. Progress in purification methods, dispersion studies, BNNT mat and composite formation, and modeling and diagnostics will also be presented. The white BNNTs offer extraordinary properties including neutron radiation shielding, piezoelectricity, thermal oxidative stability (> 800 C in air), mechanical strength, and toughness. The characteristics of the novel BNNTs and BNNT polymer composites and their potential applications are discussed.

  4. Boron-Filled Hybrid Carbon Nanotubes.

    PubMed

    Patel, Rajen B; Chou, Tsengming; Kanwal, Alokik; Apigo, David J; Lefebvre, Joseph; Owens, Frank; Iqbal, Zafar

    2016-07-27

    A unique nanoheterostructure, a boron-filled hybrid carbon nanotube (BHCNT), has been synthesized using a one-step chemical vapor deposition process. The BHCNTs can be considered to be a novel form of boron carbide consisting of boron doped, distorted multiwalled carbon nanotubes (MWCNTs) encapsulating boron nanowires. These MWCNTs were found to be insulating in spite of their graphitic layered outer structures. While conventional MWCNTs have great axial strength, they have weak radial compressive strength, and do not bond well to one another or to other materials. In contrast, BHCNTs are shown to be up to 31% stiffer and 233% stronger than conventional MWCNTs in radial compression and have excellent mechanical properties at elevated temperatures. The corrugated surface of BHCNTs enables them to bond easily to themselves and other materials, in contrast to carbon nanotubes (CNTs). BHCNTs can, therefore, be used to make nanocomposites, nanopaper sheets, and bundles that are stronger than those made with CNTs.

  5. Boron-Filled Hybrid Carbon Nanotubes

    PubMed Central

    Patel, Rajen B.; Chou, Tsengming; Kanwal, Alokik; Apigo, David J.; Lefebvre, Joseph; Owens, Frank; Iqbal, Zafar

    2016-01-01

    A unique nanoheterostructure, a boron-filled hybrid carbon nanotube (BHCNT), has been synthesized using a one-step chemical vapor deposition process. The BHCNTs can be considered to be a novel form of boron carbide consisting of boron doped, distorted multiwalled carbon nanotubes (MWCNTs) encapsulating boron nanowires. These MWCNTs were found to be insulating in spite of their graphitic layered outer structures. While conventional MWCNTs have great axial strength, they have weak radial compressive strength, and do not bond well to one another or to other materials. In contrast, BHCNTs are shown to be up to 31% stiffer and 233% stronger than conventional MWCNTs in radial compression and have excellent mechanical properties at elevated temperatures. The corrugated surface of BHCNTs enables them to bond easily to themselves and other materials, in contrast to carbon nanotubes (CNTs). BHCNTs can, therefore, be used to make nanocomposites, nanopaper sheets, and bundles that are stronger than those made with CNTs. PMID:27460526

  6. Boron-Filled Hybrid Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Patel, Rajen B.; Chou, Tsengming; Kanwal, Alokik; Apigo, David J.; Lefebvre, Joseph; Owens, Frank; Iqbal, Zafar

    2016-07-01

    A unique nanoheterostructure, a boron-filled hybrid carbon nanotube (BHCNT), has been synthesized using a one-step chemical vapor deposition process. The BHCNTs can be considered to be a novel form of boron carbide consisting of boron doped, distorted multiwalled carbon nanotubes (MWCNTs) encapsulating boron nanowires. These MWCNTs were found to be insulating in spite of their graphitic layered outer structures. While conventional MWCNTs have great axial strength, they have weak radial compressive strength, and do not bond well to one another or to other materials. In contrast, BHCNTs are shown to be up to 31% stiffer and 233% stronger than conventional MWCNTs in radial compression and have excellent mechanical properties at elevated temperatures. The corrugated surface of BHCNTs enables them to bond easily to themselves and other materials, in contrast to carbon nanotubes (CNTs). BHCNTs can, therefore, be used to make nanocomposites, nanopaper sheets, and bundles that are stronger than those made with CNTs.

  7. Boron-Filled Hybrid Carbon Nanotubes.

    PubMed

    Patel, Rajen B; Chou, Tsengming; Kanwal, Alokik; Apigo, David J; Lefebvre, Joseph; Owens, Frank; Iqbal, Zafar

    2016-01-01

    A unique nanoheterostructure, a boron-filled hybrid carbon nanotube (BHCNT), has been synthesized using a one-step chemical vapor deposition process. The BHCNTs can be considered to be a novel form of boron carbide consisting of boron doped, distorted multiwalled carbon nanotubes (MWCNTs) encapsulating boron nanowires. These MWCNTs were found to be insulating in spite of their graphitic layered outer structures. While conventional MWCNTs have great axial strength, they have weak radial compressive strength, and do not bond well to one another or to other materials. In contrast, BHCNTs are shown to be up to 31% stiffer and 233% stronger than conventional MWCNTs in radial compression and have excellent mechanical properties at elevated temperatures. The corrugated surface of BHCNTs enables them to bond easily to themselves and other materials, in contrast to carbon nanotubes (CNTs). BHCNTs can, therefore, be used to make nanocomposites, nanopaper sheets, and bundles that are stronger than those made with CNTs. PMID:27460526

  8. Undercooling, local structure and phase transition in icosahedral quasicrystals forming titanium-zirconium-nickel alloy liquids

    NASA Astrophysics Data System (ADS)

    Lee, Geun Woo

    While lacking the long-range translationally periodic order of crystalline solids, liquids contain a significant amount of short-range order (SRO), which distinguishes them from gases. The local structure of a liquid is important to understand its chemical and physical properties. One of the remarkable phenomena related to the short-range order of liquids is undercooling. That is, liquids can be retained below their melting temperature for a long time without crystallization. Turnbull first demonstrated this for metallic liquids in 1952. To explain the surprising results, Frank hypothesized in 1952 that the local structure of liquid metals is icosahedral. This structure is quite different from those of crystal phases giving a large nucleation barrier and making the undercooling of liquids possible. However, a complete verification of Frank's hypothesis has not been possible thus far. In this dissertation, this goal has been achieved by demonstrating a direct connection between the nucleation barrier and the icosahedral SRO (ISRO) in Ti-Zr-Ni alloy liquids. Containerless environments and in-situ x-ray scattering experiments, essential for such studies, were possible because of the development of electrostatic levitation (ESL) and Beamline-ESL techniques. In addition, distorted icosahedral SRO in liquids will be shown, which has been expected but never observed. The other important topic related to the undercooled liquids is a liquid-liquid (L-L) transition. Since the undercooled liquids are essentially metastable, the L-L transition could be expected. However, L-L transitions in undercooled liquids have not been observed experimentally, although elemental liquids of P, C, and Si have shown first order transitions above the liquidus temperatures under high pressure. From specific heat measurements of a series of Ti-Zr-Ni alloys by the ESL technique, a maximum in the specific heat at constant pressure was observed in a few quasicrystal forming alloy compositions in

  9. Lipid nanoscaffolds in carbon nanotube arrays

    NASA Astrophysics Data System (ADS)

    Paukner, Catharina; Koziol, Krzysztof K. K.; Kulkarni, Chandrashekhar V.

    2013-09-01

    We present the fabrication of lipid nanoscaffolds inside carbon nanotube arrays by employing the nanostructural self-assembly of lipid molecules. The nanoscaffolds are finely tunable into model biomembrane-like architectures (planar), soft nanochannels (cylindrical) or 3-dimensionally ordered continuous bilayer structures (cubic). Carbon nanotube arrays hosting the above nanoscaffolds are formed by packing of highly oriented multiwalled carbon nanotubes which facilitate the alignment of lipid nanostructures without requiring an external force. Furthermore, the lipid nanoscaffolds can be created under both dry and hydrated conditions. We show their direct application in reconstitution of egg proteins. Such nanoscaffolds find enormous potential in bio- and nano-technological fields.We present the fabrication of lipid nanoscaffolds inside carbon nanotube arrays by employing the nanostructural self-assembly of lipid molecules. The nanoscaffolds are finely tunable into model biomembrane-like architectures (planar), soft nanochannels (cylindrical) or 3-dimensionally ordered continuous bilayer structures (cubic). Carbon nanotube arrays hosting the above nanoscaffolds are formed by packing of highly oriented multiwalled carbon nanotubes which facilitate the alignment of lipid nanostructures without requiring an external force. Furthermore, the lipid nanoscaffolds can be created under both dry and hydrated conditions. We show their direct application in reconstitution of egg proteins. Such nanoscaffolds find enormous potential in bio- and nano-technological fields. Electronic supplementary information (ESI) available: Additional wide angle X-ray scattering (WAXS) data on the alignment of lipid nanostructures, control and time resolved 2-d images of egg ovalbumin encapsulation and a summary picture of the present work. See DOI: 10.1039/c3nr02068a

  10. Buckling of Carbon Nanotube-Reinforced Polymer Laminated Composite Materials Subjected to Axial Compression and Shear Loadings

    NASA Technical Reports Server (NTRS)

    Riddick, J. C.; Gates, T. S.; Frankland, S.-J. V.

    2005-01-01

    A multi-scale method to predict the stiffness and stability properties of carbon nanotube-reinforced laminates has been developed. This method is used in the prediction of the buckling behavior of laminated carbon nanotube-polyethylene composites formed by stacking layers of carbon nanotube-reinforced polymer with the nanotube alignment axes of each layer oriented in different directions. Linking of intrinsic, nanoscale-material definitions to finite scale-structural properties is achieved via a hierarchical approach in which the elastic properties of the reinforced layers are predicted by an equivalent continuum modeling technique. Solutions for infinitely long symmetrically laminated nanotube-reinforced laminates with simply-supported or clamped edges subjected to axial compression and shear loadings are presented. The study focuses on the influence of nanotube volume fraction, length, orientation, and functionalization on finite-scale laminate response. Results indicate that for the selected laminate configurations considered in this study, angle-ply laminates composed of aligned, non-functionalized carbon nanotube-reinforced lamina exhibit the greatest buckling resistance with 1% nanotube volume fraction of 450 nm uniformly-distributed carbon nanotubes. In addition, hybrid laminates were considered by varying either the volume fraction or nanotube length through-the-thickness of a quasi-isotropic laminate. The ratio of buckling load-to-nanotube weight percent for the hybrid laminates considered indicate the potential for increasing the buckling efficiency of nanotube-reinforced laminates by optimizing nanotube size and proportion with respect to laminate configuration.

  11. Photovoltaic device using single wall carbon nanotubes and method of fabricating the same

    DOEpatents

    Biris, Alexandru S.; Li, Zhongrui

    2012-11-06

    A photovoltaic device and methods for forming the same. In one embodiment, the photovoltaic device has a silicon substrate, and a film comprising a plurality of single wall carbon nanotubes disposed on the silicon substrate, wherein the plurality of single wall carbon nanotubes forms a plurality of heterojunctions with the silicon in the substrate.

  12. Synthesis of condensed phases containing polycyclic aromatic hydrocarbons fullerenes and nanotubes

    DOEpatents

    Reilly, Peter T. A.

    2004-10-19

    The invention relates to methods for producing polycyclic aromatic hydrocarbons, fullerenes, and nanotubes, comprising: a. heating at least one carbon-containing material to form a condensed phase comprising at least one polycyclic aromatic hydrocarbon; b. collecting at least some of the condensed phase; c. reacting the condensed phase to form fullerenes and/or nanotubes.

  13. Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes

    NASA Astrophysics Data System (ADS)

    López-Oyama, A. B.; Silva-Molina, R. A.; Ruíz-García, J.; Gámez-Corrales, R.; Guirado-López, R. A.

    2014-11-01

    We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH-MWCNT). Our MWCNTs have average diameters of ˜2 nm, lengths of approximately 100-300 nm, and a hydroxyl surface coverage θ˜0.1. When deposited on the air/water interface the OH-MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO-LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH-MWCNTs might have promising applications.

  14. Structure, electronic properties, and aggregation behavior of hydroxylated carbon nanotubes

    SciTech Connect

    López-Oyama, A. B.; Silva-Molina, R. A.; Ruíz-García, J.; Guirado-López, R. A.; Gámez-Corrales, R.

    2014-11-07

    We present a combined experimental and theoretical study to analyze the structure, electronic properties, and aggregation behavior of hydroxylated multiwalled carbon nanotubes (OH–MWCNT). Our MWCNTs have average diameters of ∼2 nm, lengths of approximately 100–300 nm, and a hydroxyl surface coverage θ∼0.1. When deposited on the air/water interface the OH–MWCNTs are partially soluble and the floating units interact and link with each other forming extended foam-like carbon networks. Surface pressure-area isotherms of the nanotube films are performed using the Langmuir balance method at different equilibration times. The films are transferred into a mica substrate and atomic force microscopy images show that the foam like structure is preserved and reveals fine details of their microstructure. Density functional theory calculations performed on model hydroxylated carbon nanotubes show that low energy atomic configurations are found when the OH groups form molecular islands on the nanotube's surface. This patchy behavior for the OH species is expected to produce nanotubes having reduced wettabilities, in line with experimental observations. OH doping yields nanotubes having small HOMO–LUMO energy gaps and generates a nanotube → OH direction for the charge transfer leading to the existence of more hole carriers in the structures. Our synthesized OH–MWCNTs might have promising applications.

  15. Nanotubes of Biomimetic Supramolecules Constructed by Synthetic Metal Chlorophyll Derivatives.

    PubMed

    Shoji, Sunao; Ogawa, Tetsuya; Hashishin, Takeshi; Ogasawara, Shin; Watanabe, Hiroaki; Usami, Hisanao; Tamiaki, Hitoshi

    2016-06-01

    Various supramolecular nanotubes have recently been built up by lipids, peptides, and other organic molecules. Major light-harvesting (LH) antenna systems in a filamentous anoxygenic phototroph, Chloroflexus (Cfl.) aurantiacus, are called chlorosomes and contain photofunctional single-wall supramolecular nanotubes with approximately 5 nm in their diameter. Chlorosomal supramolecular nanotubes of Cfl. aurantiacus are constructed by a large amount of bacteriochlorophyll(BChl)-c molecules. Such a pigment self-assembles in a chlorosome without any assistance from the peptides, which is in sharp contrast to the other natural photosynthetic LH antennas. To mimic chlorosomal supramolecular nanotubes, synthetic models were prepared by the modification of naturally occurring chlorophyll(Chl)-a molecule. Metal complexes (magnesium, zinc, and cadmium) of the Chl derivative were synthesized as models of natural chlorosomal BChls. These metal Chl derivatives self-assembled in hydrophobic environments, and their supramolecules were analyzed by spectroscopic and microscopic techniques. Cryo-transmission electron microscopic images showed that the zinc and cadmium Chl derivatives could form single-wall supramolecular nanotubes and their outer and inner diameters were approximately 5 and 3 nm, respectively. Atomic force microscopic images suggested that the magnesium Chl derivative formed similar nanotubes to those of the corresponding zinc and cadmium complexes. Three chlorosomal single-wall supramolecular nanotubes of the metal Chl derivatives were prepared in the solid state and would be useful as photofunctional materials.

  16. Nanotubes of Biomimetic Supramolecules Constructed by Synthetic Metal Chlorophyll Derivatives.

    PubMed

    Shoji, Sunao; Ogawa, Tetsuya; Hashishin, Takeshi; Ogasawara, Shin; Watanabe, Hiroaki; Usami, Hisanao; Tamiaki, Hitoshi

    2016-06-01

    Various supramolecular nanotubes have recently been built up by lipids, peptides, and other organic molecules. Major light-harvesting (LH) antenna systems in a filamentous anoxygenic phototroph, Chloroflexus (Cfl.) aurantiacus, are called chlorosomes and contain photofunctional single-wall supramolecular nanotubes with approximately 5 nm in their diameter. Chlorosomal supramolecular nanotubes of Cfl. aurantiacus are constructed by a large amount of bacteriochlorophyll(BChl)-c molecules. Such a pigment self-assembles in a chlorosome without any assistance from the peptides, which is in sharp contrast to the other natural photosynthetic LH antennas. To mimic chlorosomal supramolecular nanotubes, synthetic models were prepared by the modification of naturally occurring chlorophyll(Chl)-a molecule. Metal complexes (magnesium, zinc, and cadmium) of the Chl derivative were synthesized as models of natural chlorosomal BChls. These metal Chl derivatives self-assembled in hydrophobic environments, and their supramolecules were analyzed by spectroscopic and microscopic techniques. Cryo-transmission electron microscopic images showed that the zinc and cadmium Chl derivatives could form single-wall supramolecular nanotubes and their outer and inner diameters were approximately 5 and 3 nm, respectively. Atomic force microscopic images suggested that the magnesium Chl derivative formed similar nanotubes to those of the corresponding zinc and cadmium complexes. Three chlorosomal single-wall supramolecular nanotubes of the metal Chl derivatives were prepared in the solid state and would be useful as photofunctional materials. PMID:27172060

  17. A self-assembled nanotube for the direct aldol reaction in water.

    PubMed

    Lee, Kwang Soo; Parquette, Jon R

    2015-11-01

    Nanotubes formed by the aqueous assembly of a proline-lysine dipeptide (1) were used to create the hydrophobic microenvironments required to catalyze the aldol reaction in water. The self-assembly process occurred most efficiently in the presence of the substrates, producing an array of homogeneous nanotubes under the reaction conditions. The nanotubes formed by dipeptide 1 served as an efficient catalyst for the aldol reaction that functioned at low loading levels and provided good to excellent conversions. The catalytic activity of 1 was minimal under conditions that dissociated the nanotube into soluble monomers.

  18. Crystalline structures, thermal properties and crystallizing mechanism of polyamide 6 nanotubes in confined space

    NASA Astrophysics Data System (ADS)

    Li, Xiaoru; Peng, Zhi; Yang, Chao; Han, Ping; Song, Guojun; Cong, Longliang

    2016-09-01

    The polyamide 6 (PA6) nanotubes were prepared by infiltrating the anodic aluminum oxide templates with polymer solution. Crystalline regions in the nanotube walls were detected by high-resolution transmission electron microscopy (HRTEM). X-ray diffraction (XRD), Fast Fourier Transform (FFT) and differential scanning calorimetry (DSC) techniques were employed to investigate crystallization, crystal faces and thermodynamics. It was found that the crystals were transformed from α-form in bulk to γ-form in nanotubes. It was made a detailed analysis in this article. Moreover, schematic diagram for the crystallizing mechanism of PA6 nanotubes was given to explain PA6 molecules how to crystallize in the nano-pores.

  19. Preparation, loading, and cytotoxicity analysis of polymer nanotubes from an ethylene glycol dimethacrylate homopolymer in comparison to multi‐walled carbon nanotubes

    PubMed Central

    Thomas, Laurent; Zheng, Yu; Steinhart, Martin; Werner, Carsten; Wang, Wenxin

    2016-01-01

    Abstract Despite concerns over toxicity, carbon nanotubes have been extensively investigated for potential applications in nanomedicine because of their small size, unique properties, and ability to carry cargo such as small molecules and nucleic acids. Herein, we show that polymer nanotubes can be synthesized quickly and easily from a homopolymer of ethylene glycol dimethacrylate (EGDMA). The nanotubes formed via photo‐initiated polymerization of the highly functional prepolymer, inside an anodized aluminium oxide template, have a regular structure and large internal pore and can be loaded with a fluorescent dye within minutes representing a simple alternative to multi‐walled carbon nanotubes for biomedical applications. PMID:27512602

  20. Nanotube resonator devices

    DOEpatents

    Jensen, Kenneth J; Zettl, Alexander K; Weldon, Jeffrey A

    2014-05-06

    A fully-functional radio receiver fabricated from a single nanotube is being disclosed. Simultaneously, a single nanotube can perform the functions of all major components of a radio: antenna, tunable band-pass filter, amplifier, and demodulator. A DC voltage source, as supplied by a battery, can power the radio. Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation techniques, successful music and voice reception has been demonstrated. Also disclosed are a radio transmitter and a mass sensor using a nanotube resonator device.

  1. Tunable multiwalled nanotube resonator

    SciTech Connect

    Zettl, Alex K.; Jensen, Kenneth J.; Girit, Caglar; Mickelson, William E.; Grossman, Jeffrey C.

    2011-03-29

    A tunable nanoscale resonator has potential applications in precise mass, force, position, and frequency measurement. One embodiment of this device consists of a specially prepared multiwalled carbon nanotube (MWNT) suspended between a metal electrode and a mobile, piezoelectrically controlled contact. By harnessing a unique telescoping ability of MWNTs, one may controllably slide an inner nanotube core from its outer nanotube casing, effectively changing its length and thereby changing the tuning of its resonance frequency. Resonant energy transfer may be used with a nanoresonator to detect molecules at a specific target oscillation frequency, without the use of a chemical label, to provide label-free chemical species detection.

  2. Tunable multiwalled nanotube resonator

    SciTech Connect

    Jensen, Kenneth J; Girit, Caglar O; Mickelson, William E; Zettl, Alexander K; Grossman, Jeffrey C

    2013-11-05

    A tunable nanoscale resonator has potential applications in precise mass, force, position, and frequency measurement. One embodiment of this device consists of a specially prepared multiwalled carbon nanotube (MWNT) suspended between a metal electrode and a mobile, piezoelectrically controlled contact. By harnessing a unique telescoping ability of MWNTs, one may controllably slide an inner nanotube core from its outer nanotube casing, effectively changing its length and thereby changing the tuning of its resonance frequency. Resonant energy transfer may be used with a nanoresonator to detect molecules at a specific target oscillation frequency, without the use of a chemical label, to provide label-free chemical species detection.

  3. Formation and growth mechanisms of single-walled metal oxide nanotubes

    NASA Astrophysics Data System (ADS)

    Yucelen, Gulfem Ipek

    In this thesis, main objectives are to discover the first molecular-level mechanistic framework governing the formation and growth of single-walled metal-oxide nanotubes, apply this framework to demonstrate the engineering of nanotubular materials of controlled dimensions, and to progress towards a quantitative multiscale understanding of nanotube formation. In Chapter 2, the identification and elucidation of the mechanistic role of molecular precursors and nanoscale (1-3 nm) intermediates with intrinsic curvature, in the formation of single-walled aluminosilicate nanotubes is reported. The structural and compositional evolution of molecular and nanoscale species over a length scale of 0.1-100 nm, are characterized by electrospray ionization (ESI) mass spectrometry, and nuclear magnetic resonance (NMR) spectroscopy. DFT calculations revealed the intrinsic curvature of nanoscale intermediates with bonding environments similar to the structure of the final nanotube product. It is shown that curved nano-intermediates form in aqueous synthesis solutions immediately after initial hydrolysis of reactants at 25 °C, disappear from the solution upon heating to 95 °C due to condensation, and finally rearrange to form ordered single-walled aluminosilicate nanotubes. Integration of all results leads to the construction of the first molecular-level mechanism of single-walled metal oxide nanotube formation, incorporating the role of monomeric and polymeric aluminosilicate species as well as larger nanoparticles. Then, in Chapter 3, new molecular-level concepts for constructing nanoscopic metal oxide objects are demonstrated. The diameters of metal oxide nanotubes are shaped with Angstrom-level precision by controlling the shape of nanometer-scale precursors. The subtle relationships between precursor shape and structure and final nanotube curvature are measured (at the molecular level). Anionic ligands (both organic and inorganic) are used to exert fine control over precursor

  4. Titania carbon nanotube composites for enhanced photocatalysis

    NASA Astrophysics Data System (ADS)

    Pyrgiotakis, Georgios

    Photocatalytic composites have been used for the past few decades in a wide range of applications. The most common application is the purification of air and water by removing toxic compounds. There is limited use however towards biocidal applications. Despite their high efficiency, photocatalytic materials are not comparable to the effectiveness of conventional biocidal compounds such as chlorine and alcoholic disinfectants. On the other hand, nearly a decade ago with the discovery of the carbon nanotubes a new vibrant scientific field emerged. Nanotubes are unique structures of carbon that posse amazing electrical, mechanical and thermal properties. In this research carbon nanotubes are used as photocatalytic enhancers. They were coated with anatase titania to form a composite material. Two different types of nanotubes (metallic versus non-metallic) were used and the photocatalytic activity was measured. The metallic tubes demonstrated exceptional photocatalytic properties, while non-metallic tubes had low photocatalytic efficiency. The reason for that difference was investigated and was the major focus of this research. The research concluded that the reasons for the high efficiency of the carbon nanotubes were (i) the metallic nature of the tubes and (ii) the possible bond between the titania coating and the underlying graphite layers (C-O-Ti). Since both composites had the same indications regarding the C-O-Ti bond, the metallic nature of the carbon nanotubes is believed to be the most dominant factor contributing to the enhancement of the photocatalysis. The composite material may have other potential applications such as for sensing and photovoltaic uses.

  5. Electrical properties of carbon nanotube FETs

    NASA Astrophysics Data System (ADS)

    Mizutani, T.; Ohno, Y.; Kishimoto, S.

    2008-08-01

    The electrical properties of carbon nanotube FETs (CNTFETs) have been studied in detail. The conduction type of the CNTFETs was dependent on the work function of the contact metal, which suggests that Fermi level pinning at the metal/nanotube interface is not strong. Based on the two-probe and four-probe resistance measurements, it has been shown that the carrier transport at the contact is explained by the edge contact model even in the diffusive regime. The chemical doping using F4TCNQ was effective in reducing not only the channel resistance but also the contact resistance. In the CNTFETs fabricated using plasma-enhanced (PE) CVD-grown nanotubes, the drain current of the most of the devices could be modulated by the gate voltage with small OFF current suggesting the preferential growth of the nanotubes with semiconducting behavior. Multichannel top-gate CNTFETs with horizontally-aligned nanotubes as channels have been successfully fabricated using CNT growth on the ST-cut quartz substrate, arc-discharge plasma deposition of the catalyst metal, and ALD gate insulator deposition. The devices show normally-on and n-type conduction property with a relatively-high ON current of 13 mA/mm. CNTFETs with nanotube network have also been fabricated by direct growth on the SiO2/Si substrate using grid-inserted PECVD and using catalyst formed on the channel area of the FETs. The uniformity of the electrical properties of the network channel CNTFETs were very good. Finally, it has been shown that the surface potential profile measurement based on the electrostatic force detection in the scanning probe microscopy was effective in studying the behavior of the CNTFETs such as the transient behavior and the effect of the defects.

  6. Magnetic Properties of Al-Gd-TM Glass-Forming Alloys

    NASA Astrophysics Data System (ADS)

    Uporov, Sergey; Estemirova, Svetlana; Bykov, Viktor; Mitrofanov, Valentin

    2016-01-01

    We report results of magnetic studies of glass-forming alloys with nominal composition of Al86Gd6TM8 (where TM = Cu, Ni, Co, Fe, Mn, Cr, Ti, Zr, Mo, Ta) synthesized by arc-melting. X-ray diffraction analysis and vibrating sample magnetometry were applied to characterize the prepared samples. All the alloys exhibit antiferromagnetic ordering at low temperatures. In some compositions, we observed metamagnetic transitions in external magnetic fields up to 3 T. Analysis of the paramagnetic susceptibility of the considered Al-Gd-TM systems has revealed non-magnetic behavior of the transition metals. We found that the magnetic properties of the studied samples can be described satisfactorily using only the Gd trivalent ions. But in some cases the magnetic moments of gadolinium are slightly larger than the theoretical values, probably, because of an additional contribution of the 5 d electrons. The obtained results are discussed in framework of the assumptions of the strong s- p- d hybridization and frustrated magnetic states of gadolinium. We argue that the hybridization might be one of the main factors improving the glass-forming ability in these ternary alloys.

  7. Carbon Nanotube Memory Elements

    SciTech Connect

    Meunier, Vincent; Sumpter, Bobby G

    2010-01-01

    Carbon nanotubes are among the most cited prototypical materials for nanoelectronics and information storage devices, a dominant position that originates from their intrinsic structural and electronic properties. In this chapter we review the developments in memory elements that directly exploit the unique properties of carbon nanotubes. Fundamental operational principles and characteristics are examined for the different types of carbon nanotube-based memory devices along with the current status of experimental fabrication and scalability. These include memory elements based on carbon nanotube field-effect transistors (CNFET), nanoelectromechanical systems (NEMS), and electromigration. Many of these devices show tremendous promise for providing enhanced densities, lower power requirements, more efficient read/write processes, and non-volatility of data.

  8. Transport in Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Datta, S.; Xue, Yong-Qinag; Anantram, M. P.; Saini, Subhash (Technical Monitor)

    1999-01-01

    This presentation discusses coupling between carbon nanotubes (CNT), simple metals (FEG) and a graphene sheet. The graphene sheet did not couple well with FEG, but the combination of a graphene strip and CNT did couple well with most simple metals.

  9. Carbon nanotubes: Fibrillar pharmacology

    NASA Astrophysics Data System (ADS)

    Kostarelos, Kostas

    2010-10-01

    The mechanisms by which chemically functionalized carbon nanotubes flow in blood and are excreted through the kidneys illustrate the unconventional behaviour of these fibrillar nanostructures, and the opportunities they offer as components for the design of advanced delivery vehicles.

  10. Polymer composites containing nanotubes

    NASA Technical Reports Server (NTRS)

    Bley, Richard A. (Inventor)

    2008-01-01

    The present invention relates to polymer composite materials containing carbon nanotubes, particularly to those containing singled-walled nanotubes. The invention provides a polymer composite comprising one or more base polymers, one or more functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers and carbon nanotubes. The invention also relates to functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers, particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having side chain functionalization, and more particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having olefin side chains and alkyl epoxy side chains. The invention further relates to methods of making polymer composites comprising carbon nanotubes.

  11. Facile formation of branched titanate nanotubes to grow a three-dimensional nanotubular network directly on a solid substrate.

    PubMed

    Zhang, Haimin; Liu, Porun; Wang, Hongjuan; Yu, Hua; Zhang, Shanqing; Zhu, Huaiyong; Peng, Feng; Zhao, Huijun

    2010-02-01

    The hydrothermal formation of branched titanate nanotubes that grow a 3D nanotubular network directly onto a titanium substrate is reported. The resultant 3D nanotubular network exhibits a unique all-dimensional uniform porous structure. The inner and outer tubular diameters of branched titanate nanotubes were found to be approximately 6 and 12 nm, respectively. For the majority of the nanotubes, the wall is formed from three layers of titanate with an approximate 7.7 A interlayer space. In terms of individual nanotubes, these characteristics are quantitatively similar to those of previously reported nonbranched nanotubes. However, in terms of how nanotubes are arranged in the film, the all-dimensional uniform nanotubular network structure obtained here is distinctively different from those of previously reported structures. The 3D nanotubular network structure was formed by the jointing of branched nanotubes. In contrast, the previously reported nanotubes tend to grow vertically on the substrate, and the resultant tubular films are formed by interwoven nonbranched nanotubes. The branched titanate nanotubes can be readily formed on titanium substrates but not in solution suspension forms. A continuous seed formation-oriented crystal growth mechanism was proposed for the branched titanate nanotubular network formation. Such a network structure could be useful for applications such as photocatalysis, membrane separation, field emission, and photovoltaic devices. PMID:20039654

  12. Cell response of anodized nanotubes on titanium and titanium alloys.

    PubMed

    Minagar, Sepideh; Wang, James; Berndt, Christopher C; Ivanova, Elena P; Wen, Cuie

    2013-09-01

    Titanium and titanium alloy implants that have been demonstrated to be more biocompatible than other metallic implant materials, such as Co-Cr alloys and stainless steels, must also be accepted by bone cells, bonding with and growing on them to prevent loosening. Highly ordered nanoporous arrays of titanium dioxide that form on titanium surface by anodic oxidation are receiving increasing research interest due to their effectiveness in promoting osseointegration. The response of bone cells to implant materials depends on the topography, physicochemistry, mechanics, and electronics of the implant surface and this influences cell behavior, such as adhesion, proliferation, shape, migration, survival, and differentiation; for example the existing anions on the surface of a titanium implant make it negative and this affects the interaction with negative fibronectin (FN). Although optimal nanosize of reproducible titania nanotubes has not been reported due to different protocols used in studies, cell response was more sensitive to titania nanotubes with nanometer diameter and interspace. By annealing, amorphous TiO2 nanotubes change to a crystalline form and become more hydrophilic, resulting in an encouraging effect on cell behavior. The crystalline size and thickness of the bone-like apatite that forms on the titania nanotubes after implantation are also affected by the diameter and shape. This review describes how changes in nanotube morphologies, such as the tube diameter, the thickness of the nanotube layer, and the crystalline structure, influence the response of cells.

  13. Computational Design of a Carbon Nanotube Fluorofullerene Biosensor

    PubMed Central

    Hilder, Tamsyn A.; Pace, Ron J.; Chung, Shin-Ho

    2012-01-01

    Carbon nanotubes offer exciting opportunities for devising highly-sensitive detectors of specific molecules in biology and the environment. Detection limits as low as 10−11 M have already been achieved using nanotube-based sensors. We propose the design of a biosensor comprised of functionalized carbon nanotube pores embedded in a silicon-nitride or other membrane, fluorofullerene-Fragment antigen-binding (Fab fragment) conjugates, and polymer beads with complementary Fab fragments. We show by using molecular and stochastic dynamics that conduction through the (9, 9) exohydrogenated carbon nanotubes is 20 times larger than through the Ion Channel Switch ICS™ biosensor, and fluorofullerenes block the nanotube entrance with a dissociation constant as low as 37 pM. Under normal operating conditions and in the absence of analyte, fluorofullerenes block the nanotube pores and the polymer beads float around in the reservoir. When analyte is injected into the reservoir the Fab fragments attached to the fluorofullerene and polymer bead crosslink to the analyte. The drag of the much larger polymer bead then acts to pull the fluorofullerene from the nanotube entrance, thereby allowing the flow of monovalent cations across the membrane. Assuming a tight seal is formed between the two reservoirs, such a biosensor would be able to detect one channel opening and thus one molecule of analyte making it a highly sensitive detection design. PMID:23202018

  14. Deformation of carbon nanotubes by exposure to water vapor.

    PubMed

    Rossi, Maria Pia; Gogotsi, Yury; Kornev, Konstantin G

    2009-03-01

    The condensation of water inside multiwalled carbon nanotubes has been monitored and controlled using environmental scanning electron microscopy. Undersaturated vapor condenses inside nanotubes and forms nanometer-thick water films. Simultaneously, nanotubes deform and decrease their apparent diameter. When the vapor pressure in the chamber approaches the saturation pressure, we observe the formation of menisci and spontaneous buckling of the nanotubes. We derive a criterion of the buckling instability caused by capillary condensation. Remarkably, the buckling criterion appears to be independent of the meniscus shape. Using our experiments and models, we estimated the circumferential Young's modulus of large-diameter carbon nanotubes with disordered wall structure produced by the chemical vapor deposition method (CVD) to be E(thetatheta) approximately 13-18 MPa. It appears to be at least 2 orders of magnitude lower than the longitudinal modulus of nanotubes produced by arc discharge or catalytic CVD methods. The reported experiments and proposed theory suggest possible applications of "soft" nanotubes as sensors to probe minute concentrations of absorbable gases and vapors.

  15. Cutting and sharpening carbon nanotubes using a carbon nanotube 'nanoknife'

    NASA Astrophysics Data System (ADS)

    Wei, Xian Long; Chen, Qing; Liu, Yang; Mao Peng, Lian

    2007-05-01

    A new method has been developed to precisely cut and to sharpen carbon nanotubes using a 'nanoknife', which is a short carbon nanotube adhered to a metal tip. The mechanism for the cutting and the sharpening was proposed to be local vaporization of carbon caused by Joule heating. The 'nanoknife' was also found useful to cut other nanotubes and nanowires. The cutting process was also found useful to construct complex carbon nanotube structures.

  16. Carbon nanotube filters

    NASA Astrophysics Data System (ADS)

    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.

  17. Lipid-Protein Nanotubes with Open or Closed Ends, Microtubules Bundles and Inverted Tubulin Nanotubes

    NASA Astrophysics Data System (ADS)

    Raviv, Uri; Needleman, Daniel J.; Ojeda-Lopez, Miguel A.; Li, Youli; Miller, Herb P.; Wilson, Leslie; Safinya, Cyrus R.

    2006-03-01

    We describe synchrotron x-ray diffraction, electron microscopy, and optical imaging data of the self-assembly of microtubules (MTs) with various cationic agents. We established the conditions under which cationic liposomes can coat MTs and form lipid-protein nanotubes (LPNs). The LPNs exhibit a rather remarkable architecture with the cylindrical lipid bilayer sandwiched between a MT and outer tubulin oligomers forming rings or spirals. By controlling the cationic lipid/tubulin stoichiometry it is possible to switch between two states of nanotubes with either open ends or closed ends with lipid caps, a process which forms the basis for controlled chemical and drug encapsulation and release (Raviv et al, PNAS, 2005). Multivalent (3+,4+ and 5+) cations can form three dimensional MT bundles that in some cases become tubulin based inverted nanotubules. Divalent cations form two dimensional MT necklaces (Needleman et al, PNAS, 2004).

  18. Nitrogen doping in carbon nanotubes.

    PubMed

    Ewels, C P; Glerup, M

    2005-09-01

    Nitrogen doping of single and multi-walled carbon nanotubes is of great interest both fundamentally, to explore the effect of dopants on quasi-1D electrical conductors, and for applications such as field emission tips, lithium storage, composites and nanoelectronic devices. We present an extensive review of the current state of the art in nitrogen doping of carbon nanotubes, including synthesis techniques, and comparison with nitrogen doped carbon thin films and azofullerenes. Nitrogen doping significantly alters nanotube morphology, leading to compartmentalised 'bamboo' nanotube structures. We review spectroscopic studies of nitrogen dopants using techniques such as X-ray photoemission spectroscopy, electron energy loss spectroscopy and Raman studies, and associated theoretical models. We discuss the role of nanotube curvature and chirality (notably whether the nanotubes are metallic or semiconducting), and the effect of doping on nanotube surface chemistry. Finally we review the effect of nitrogen on the transport properties of carbon nanotubes, notably its ability to induce negative differential resistance in semiconducting tubes.

  19. Thermal-structural relationship of individual titania nanotubes

    NASA Astrophysics Data System (ADS)

    Brahmi, Hatem; Katwal, Giwan; Khodadadi, Mohammad; Chen, Shuo; Paulose, Maggie; Varghese, Oomman K.; Mavrokefalos, Anastassios

    2015-11-01

    The thermal properties of nano-scale materials are largely influenced by their geometry. The zero, one and quasi one dimensional forms of the same material could exhibit unique thermal transport properties depending upon the shape and nano-scale feature size. In order to gain a clear understanding of the contributions from geometrical scattering effects on thermal transport, it is required to study these nano-materials in a single isolated form rather than in clusters or films. In the past decade, titanium dioxide nanotube arrays fabricated by anodic oxidation of titanium emerged as a useful semiconductor architecture for a variety of applications, particularly for solar energy conversion. Nonetheless, the thermal properties of individual nanotubes that are important for their use in high temperature applications have not been clearly understood. Here we report the thermal transport properties of individual titania nanotubes as revealed by our preliminary study using a suspended microdevice that facilitates the thermal conductivity measurements and crystal structure investigation on the same nanotube. The nanotubes were prepared by anodic oxidation of a titanium foil in HF-DMSO electrolyte at 60 V, having outer diameters in the range of 200 to 300 nm and wall thicknesses of ~30 to 70 nm in either amorphous or polycrystalline anatase phase. The thermal conductivity of single nanotubes was found to be very close to that of the amorphous phase (1.5 W mK-1 and 0.85 W mK-1 respectively) and it was only half of the thermal conductivity of the nanotube arrays in the film form. The thermal conductivity of bulk TiO2 is known to be almost six times higher. The observed thermal conductivity suppression in single nanotubes was explained using a transport model developed by considering diffuse phonon-surface scattering and scattering of phonons by ionized impurities of concentrations in the order of 1018-1019 cm-3.

  20. Carbon Nanotubes for Space Photovoltaic Applications

    NASA Technical Reports Server (NTRS)

    Efstathiadis, Harry; Haldar, Pradeep; Landi, Brian J.; Denno, Patrick L.; DiLeo, Roberta A.; VanDerveer, William; Raffaelle, Ryne P.

    2007-01-01

    Carbon nanotubes (CNTs) can be envisioned as an individual graphene sheet rolled into a seamless cylinder (single-walled, SWNT), or concentric sheets as in the case of a multi-walled carbon nanotube (MWNT) (1). The role-up vector will determine the hexagonal arrangement and "chirality" of the graphene sheet, which will establish the nanotube to be metallic or semiconducting. The optoelectronic properties will depend directly on this chiral angle and the diameter of the SWNT, with semiconductor types exhibiting a band gap energy (2). Characteristic of MWNTs are the concentric graphene layers spaced 0.34 nm apart, with diameters from 10-200 nm and lengths up to hundreds of microns (2). In the case of SWNTs, the diameters range from 0.4 - 2 nm and lengths have been reported up to 1.5 cm (3). SWNTs have the distinguishable property of "bundling" together due to van der Waal's attractions to form "ropes." A comparison of these different structural types is shown in Figure 1. The use of SWNTS in space photovoltaic (PV) applications is attractive for a variety of reasons. Carbon nanotubes as a class of materials exhibit unprecedented optical, electrical, mechanical properties, with the added benefit of being nanoscale in size which fosters ideal interaction in nanomaterial-based devices like polymeric solar cells. The optical bandgap of semiconducting SWNTs can be varied from approx. 0.4 - 1.5 eV, with this property being inversely proportional to the nanotube diameter. Recent work at GE Global Research has shown where a single nanotube device can behave as an "ideal" pn diode (5). The SWNT was bridged over a SiO2 channel between Mo contacts and exhibited an ideality factor of 1, based on a fit of the current-voltage data using the diode equation. The measured PV efficiency under a 0.8 eV monochromatic illumination showed a power conversion efficiency of 0.2 %. However, the projected efficiency of these junctions is estimated to be > 5 %, especially when one considers the

  1. Carbon nanotube array based sensor

    DOEpatents

    Lee, Christopher L.; Noy, Aleksandr; Swierkowski, Stephan P.; Fisher, Karl A.; Woods, Bruce W.

    2005-09-20

    A sensor system comprising a first electrode with an array of carbon nanotubes and a second electrode. The first electrode with an array of carbon nanotubes and the second electrode are positioned to produce an air gap between the first electrode with an array of carbon nanotubes and the second electrode. A measuring device is provided for sensing changes in electrical capacitance between the first electrode with an array of carbon nanotubes and the second electrode.

  2. Lipid nanotube or nanowire sensor

    DOEpatents

    Noy, Aleksandr; Bakajin, Olgica; Letant, Sonia; Stadermann, Michael; Artyukhin, Alexander B.

    2009-06-09

    A sensor apparatus comprising a nanotube or nanowire, a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer. Also a biosensor apparatus comprising a gate electrode; a source electrode; a drain electrode; a nanotube or nanowire operatively connected to the gate electrode, the source electrode, and the drain electrode; a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer.

  3. Lipid nanotube or nanowire sensor

    DOEpatents

    Noy, Aleksandr; Bakajin, Olgica; Letant, Sonia; Stadermann, Michael; Artyukhin, Alexander B.

    2010-06-29

    A sensor apparatus comprising a nanotube or nanowire, a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer. Also a biosensor apparatus comprising a gate electrode; a source electrode; a drain electrode; a nanotube or nanowire operatively connected to the gate electrode, the source electrode, and the drain electrode; a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer.

  4. Weaving Nanotechnology Dreams with Nanotubes

    SciTech Connect

    Tomanek, David

    2003-01-15

    The continuous reduction of device sizes, which is rapidly approaching the atomic level, calls for new approaches to design and test future building blocks of nanotechnology. Computers will become the most powerful tools to interpret what happens on the nanometer scale, where as I will illustrate, structures of carbon may become stronger than steel, yet turn into quantum conductors or even efficient heat conductors. In nanostructures that form during a hierarchical self-assembly process, even defects may play a different, often helpful role. An efficient self-healing process may convert less stable atomic assemblies into other, more perfect structures, thus answering an important concern in molecular electronics. Defects may even be used in nano-scale engineering to form complex systems such as carbon foam or nanotube peapods. I will show how some of these challenging problems can be most efficiently addressed in simulations on recently available massively parallel supercomputers.

  5. Serpentine Nanotubes in CM Chondrites

    NASA Technical Reports Server (NTRS)

    Zega, Thomas J.; Garvie, Laurence A. J.; Dodony, Istvan; Buseck, Peter R.

    2004-01-01

    The CM chondrites are primitive meteorites that formed during the early solar system. Although they retain much of their original physical character, their matrices and fine-grained rims (FGRs) sustained aqueous alteration early in their histories [1- 3]. Serpentine-group minerals are abundant products of such alteration, and information regarding their structures, compositions, and spatial relationships is important for determining the reactions that produced them and the conditions under which they formed. Our recent work on FGRs and matrices of the CM chondrites has revealed new information on the structures and compositions of serpentine-group minerals [4,5] and has provided insights into the evolution of these primitive meteorites. Here we report on serpentine nanotubes from the Mighei and Murchison CM chondrites [6].

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

    PubMed

    Soldano, G; Mariscal, M M

    2009-04-22

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

  7. Activated boron nitride nanotubes: A potential material for room-temperature hydrogen storage

    NASA Astrophysics Data System (ADS)

    Jhi, Seung-Hoon

    2006-10-01

    Activated forms of boron nitride nanotubes are studied for potential applications to hydrogen storage with the use of pseudopotential density functional method. The binding and diffusion energies of adsorbed hydrogen are particularly calculated. The calculated binding energy of hydrogen on activated boron nitride nanotubes is found to lie in the right range for room-temperature storage. It is also shown that diffusion through the active sites enables hydrogen to access the inner surface of the nanotubes, which leads to the increase of the storage capacity. Current study provides a tangible solution to increase the operating temperature and capacity of hydrogen storage based on heteropolar nanomaterials such as boron nitride nanotubes.

  8. In situ templated synthesis of anatase single-crystal nanotube arrays.

    PubMed

    Zhao, Jianling; Wang, Xiaohui; Sun, Tieyu; Li, Longtu

    2005-10-01

    Anatase single-crystal nanotubes were obtained using an in situ templated method. First, highly ordered titania arrays were formed through an anodization process in H(3)PO(4) electrolytes containing 0.5 wt% HF. Under optimized conditions titania nanotubes with a diameter of up to 100 nm and a length of up to 1.1 microm were prepared. Second, the crystallization and stability of the titania nanotubes were studied in air at elevated temperatures. Anatase single-crystal nanotubes were fabricated after annealing the sample in air at 450 degrees C. The anatase single-crystal structure was verified by selected area diffraction pattern and HRTEM images.

  9. Collision-induced fusion of two single-walled carbon nanotubes: A quantitative study

    NASA Astrophysics Data System (ADS)

    Zhang, Chao; Mao, Fei; Meng, Xiang-Rui; Wang, Dong-Qi; Zhang, Feng-Shou

    2016-07-01

    The coalescence processes of two (6, 0) single-walled carbon nanotubes are investigated via coaxial collision based on the self-consistent-charge density-functional tight-binding molecular dynamics method. According to the structure characteristics of the nanotubes, five impact cases are studied to explore the coalescence processes of the nanotubes. The simulation shows that various kinds of carbon nanomaterials, such as graphene sheets, graphene nanoribbons, and single-walled carbon nanotubes with larger diameters, are created after collision. Moreover, some defects formed in the carbon nanomaterials can be eliminated, and even the final configurations which are originally fragmented can almost become intact structures by properly quenching and annealing.

  10. Field emission from carbon nanotubes produced using microwave plasma assisted CVD

    SciTech Connect

    Zhang, Q.; Yoon, S.F.; Ahn, J.; Gan, B.; Rusli; Yu, M.B.; Cheah, L.K.; Shi, X.

    2000-01-30

    Electron field emission from carbon nanotubes prepared using microwave plasma assisted CVD has been investigated. The nanotubes, ranging from 50 to 120 nm in diameter and a few tens of microns in length, were formed under methane and hydrogen plasma at 720 C with the aid of iron-oxide particles. The morphology and growth direction of the nanotubes are found to be strongly influenced by the flow ratio of methane to hydrogen. However, the electron field emission from these massive nanotubes show similar characteristics, i.e., high emission current at low electric fields.

  11. Single-walled carbon nanotube growth from ion implanted Fe catalyst

    SciTech Connect

    Choi, Yongho; Sippel-Oakley, Jennifer; Ural, Ant

    2006-10-09

    The authors present experimental evidence that single-walled carbon nanotubes can be grown by chemical vapor deposition from ion implanted iron catalyst. They systematically characterize the effect of ion implantation dose and energy on the catalyst nanoparticles and nanotubes formed at 900 deg. C. They also fabricate a micromachined silicon grid for direct transmission electron microscopy characterization of the as-grown nanotubes. This work opens up the possibility of controlling the origin of single-walled nanotubes at the nanometer scale and of integrating them into nonplanar three-dimensional device structures with precise dose control.

  12. Carbon nanotubes grown on bulk materials and methods for fabrication

    DOEpatents

    Menchhofer, Paul A.; Montgomery, Frederick C.; Baker, Frederick S.

    2011-11-08

    Disclosed are structures formed as bulk support media having carbon nanotubes formed therewith. The bulk support media may comprise fibers or particles and the fibers or particles may be formed from such materials as quartz, carbon, or activated carbon. Metal catalyst species are formed adjacent the surfaces of the bulk support material, and carbon nanotubes are grown adjacent the surfaces of the metal catalyst species. Methods employ metal salt solutions that may comprise iron salts such as iron chloride, aluminum salts such as aluminum chloride, or nickel salts such as nickel chloride. Carbon nanotubes may be separated from the carbon-based bulk support media and the metal catalyst species by using concentrated acids to oxidize the carbon-based bulk support media and the metal catalyst species.

  13. Chemical functionalization of carbon nanotubes for the mechanical reinforcement of polystyrene composites.

    PubMed

    Byrne, Michele T; McNamee, William P; Gun'ko, Yurii K

    2008-10-15

    An organometallic approach was used to functionalize multiwalled carbon nanotubes with n-butyllithium. This procedure was repeated two more times to achieve a higher degree of multiwalled carbon nanotube functionalization. The functionalized nanotubes have been characterized by Fourier transform infrared and Raman spectroscopy, thermogravimetrical analysis, scanning electron microscopy and sedimentation studies. It was possible to form stable suspensions of the functionalized nanotubes in tetrahydrofuran and they were used to make nanotube polymer composites. The mechanical properties of these new nanotube polymer composites were tested and they were found to show an increase of up to 25% in their Young's moduli and up to 50% in their tensile strength over pure polystyrene. PMID:21832658

  14. Air-pressure tunable depletion width, rectification behavior, and charge conduction in oxide nanotubes.

    PubMed

    Alivov, Yahya; Funke, Hans H; Singh, Vivek; Nagpal, Prashant

    2015-02-01

    Metal-oxide nanotubes provide large surface areas and functionalizable surfaces for a variety of optical and electronic applications. Here we report air-tunable rectifying behavior, depletion width modulation, and two-dimensional (2D) charge conduction in hollow titanium-dioxide nanotubes. The metal contact forms a Schottky-diode in the nanotubes, and the rectification factor (on/off ratio) can be varied by more than 3 orders of magnitude (1-2 × 10(3)) as the air pressure is increased from 2 mTorr to atmospheric pressure. This behavior is explained using a change in depletion width of these thin nanotubes by adsorption of water vapor on both surfaces of a hollow nanotube, and the resulting formation of a metal-insulator-semiconductor (MIS) junction, which controls the 2D charge conduction properties in thin oxide nanotubes.

  15. Mechanical behaviour of BC3 compound and pure carbon nanotubes with topological defects

    NASA Astrophysics Data System (ADS)

    Guo, Xu; Liao, Jingbo; Zhao, Jijun

    2007-03-01

    In the framework of all-electron density functional theory, we present a comparative study of the pure carbon and BC3 compound nanotubes containing different kinds of topological defects (seven-, eight- and nine-membered rings) under uniaxial tensions. The formation energies of the topological defects for pure carbon nanotubes are significantly higher than those for BC3 compound nanotubes. For both pure and compound nanotubes, sidewall defects by seven- and eight-membered rings become energetically preferred to form when the uniaxial strain approaches about 6.5%. In contrast, the total energy of the nanotube with a nine-membered ring defect is always much higher than the others. The formation mechanism of a Stone-Wales (5-7-7-5) defect in the pure carbon nanotubes is studied and we find that the barrier energy for the formation of a defect decreases monotonically with increasing strain.

  16. Highly selective dispersion of single-walled carbon nanotubes using aromatic polymers

    NASA Astrophysics Data System (ADS)

    Nish, Adrian; Hwang, Jeong-Yuan; Doig, James; Nicholas, Robin J.

    2007-10-01

    Solubilizing and purifying carbon nanotubes remains one of the foremost technological hurdles in their investigation and application. We report a dramatic improvement in the preparation of single-walled carbon nanotube solutions based on the ability of specific aromatic polymers to efficiently disperse certain nanotube species with a high degree of selectivity. Evidence of this is provided by optical absorbance and photoluminescence excitation spectra, which show suspensions corresponding to up to ~60% relative concentration of a single species of isolated nanotubes with fluorescence quantum yields of up to 1.5%. Different polymers show the ability to discriminate between nanotube species in terms of either diameter or chiral angle. Modelling suggests that rigid-backbone polymers form ordered molecular structures surrounding the nanotubes with n-fold symmetry determined by the tube diameter.

  17. Flame Synthesis Used to Create Metal-Catalyzed Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    VanderWal, Randy L.

    2001-01-01

    Metal-catalyzed carbon nanotubes are highly ordered carbon structures of nanoscale dimensions. They may be thought of as hollow cylinders whose walls are formed by single atomic layers of graphite. Such cylinders may be composed of many nested, concentric atomic layers of carbon or only a single layer, the latter forming a single-walled carbon nanotube. This article reports unique results using a flame for their synthesis. Only recently were carbon nanotubes discovered within an arc discharge and recognized as fullerene derivatives. Today metal-catalyzed carbon nanotubes are of great interest for many reasons. They can be used as supports for the metal catalysts like those found in catalytic converters. Open-ended nanotubes are highly desirable because they can be filled by other elements, metals or gases, for battery and fuel cell applications. Because of their highly crystalline structure, they are significantly stronger than the commercial carbon fibers that are currently available (10 times as strong as steel but possessing one-sixth of the weight). This property makes them highly desirable for strengthening polymer and ceramic composite materials. Current methods of synthesizing carbon nanotubes include thermal pyrolysis of organometallics, laser ablation of metal targets within hydrocarbon atmospheres at high temperatures, and arc discharges. Each of these methods is costly, and it is unclear if they can be scaled for the commercial synthesis of carbon nanotubes. In contrast, flame synthesis is an economical means of bulk synthesis of a variety of aerosol materials such as carbon black. Flame synthesis of carbon nanotubes could potentially realize an economy of scale that would enable their use in common structural materials such as car-body panels. The top figure is a transmission electron micrograph of a multiwalled carbon nanotube. The image shows a cross section of the atomic structure of the nanotube. The dark lines are individual atomic layer planes of

  18. Reinforcement of Epoxies Using Single Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Krishnamoorti, Ramanan; Sharma, Jitendra; Chatterjee, Tirtha

    2008-03-01

    The reinforcement of bisphenol-A and bisphenol-F epoxies using single walled carbon nanotubes has been approached experimentally by understanding the nature of interactions between the matrices and nanotubes. Unassisted dispersions of single walled carbon nanotubes in epoxies were studied by a combination of radiation scattering (elastic small angle scattering and inelastic scattering), DSC based glass transition determination, melt rheology and solid-state mechanical testing in order to understand and correlate changes in local and global dynamics to the tailoring of composite mechanical properties. Significant changes in the glass transition temperature of the matrix can successfully account for changes in the viscoelastic properties of the epoxy dispersions for concentrations below the percolation threshold, while above the percolation threshold the network superstructure formed by the nanotubes controls the viscoelastic properties.

  19. Manifestations of electron interactions in photogalvanic effect in chiral nanotubes

    NASA Astrophysics Data System (ADS)

    Matthews, Raphael; Agam, Oded; Andreev, Anton; Spivak, Boris

    2012-05-01

    Carbon nanotubes provide one of the most accessible experimental realizations of one-dimensional electron systems. In the experimentally relevant regime of low doping, the Luttinger liquid formed by electrons may be approximated by a Wigner crystal. The crystal-like electronic order suggests that nanotubes exhibit effects similar to the Mössbauer effect where the momentum of an emitted photon is absorbed by the whole crystal. We show that the circular photovoltaic effect in chiral nanotubes is of the same nature. We obtain the frequency dependence of the photovoltage and characterize its singularities in a broad frequency range where the electron correlations are essential. Our predictions provide a basis for using the photogalvanic effect as a new experimental probe of electron correlations in nanotubes.

  20. Synthesis of carbon nanotubes and nanotube forests on copper catalyst

    NASA Astrophysics Data System (ADS)

    Kruszka, Bartosz; Terzyk, Artur P.; Wiśniewski, Marek; Gauden, Piotr A.; Szybowicz, Mirosław

    2014-09-01

    The growth of carbon nanotubes on bulk copper is studied. We show for the first time, that super growth chemical vapor deposition method can be successfully applied for preparation of nanotubes on copper catalyst, and the presence of hydrogen is necessary. Next, different methods of copper surface activation are studied, to improve catalyst efficiency. Among them, applied for the first time for copper catalyst in nanotubes synthesis, sulfuric acid activation is the most promising. Among tested samples the surface modified for 10 min is the most active, causing the growth of vertically aligned carbon nanotube forests. Obtained results have potential importance in application of nanotubes and copper in electronic chips and nanodevices.

  1. Probing Photosensitization by Functionalized Carbon Nanotubes.

    PubMed

    Chen, Chia-Ying; Zepp, Richard G

    2015-12-01

    Carbon nanotubes (CNTs) photosensitize the production of reactive oxygen species that may damage organisms by biomembrane oxidation or mediate environmental transformations of CNTs. Photosensitization by derivatized carbon nanotubes from various synthetic methods, and thus with different intrinsic characteristics (e.g., diameter and electronic properties), has been investigated under environmentally relevant aquatic conditions. We used the CNT-sensitized photoisomerization of sorbic acid ((2E,4E)-hexa-2,4-dienoic acid) and singlet oxygen formation to quantify the triplet states ((3)CNT*) formed upon irradiation of selected single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs). The CNTs used in our studies were derivatized by carboxyl groups to facilitate their dispersion in water. Results indicate that high-defect-density (thus well-stabilized), small-diameter, and semiconducting-rich CNTs have higher-measured excited triplet state formation and therefore singlet oxygen ((1)O2) yield. Derivatized SWCNTs were significantly more photoreactive than derivatized MWCNTs. Moreover, addition of sodium chloride resulted in increased aggregation and small increases in (1)O2 production of CNTs. The most photoreactive CNTs exhibited comparable photoreactivity (in terms of (3)CNT* formation and (1)O2 yield) to reference natural organic matter (NOM) under sunlight irradiation with the same mass-based concentration. Selected reference NOM could therefore be useful in evaluating environmental photoreactivity or intended antibacterial applications of CNTs.

  2. New Method Developed To Purify Single Wall Carbon Nanotubes for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Lebron, Marisabel; Meador, Michael A.

    2003-01-01

    Single wall carbon nanotubes have attracted considerable attention because of their remarkable mechanical properties and electrical and thermal conductivities. Use of these materials as primary or secondary reinforcements in polymers or ceramics could lead to new materials with significantly enhanced mechanical strength and electrical and thermal conductivity. Use of carbon-nanotube-reinforced materials in aerospace components will enable substantial reductions in component weight and improvements in durability and safety. Potential applications for single wall carbon nanotubes include lightweight components for vehicle structures and propulsion systems, fuel cell components (bipolar plates and electrodes) and battery electrodes, and ultra-lightweight materials for use in solar sails. A major barrier to the successful use of carbon nanotubes in these components is the need for methods to economically produce pure carbon nanotubes in large enough quantities to not only evaluate their suitability for certain applications but also produce actual components. Most carbon nanotube synthesis methods, including the HiPCO (high pressure carbon monoxide) method developed by Smalley and others, employ metal catalysts that remain trapped in the final product. These catalyst impurities can affect nanotube properties and accelerate their decomposition. The development of techniques to remove most, if not all, of these impurities is essential to their successful use in practical applications. A new method has been developed at the NASA Glenn Research Center to purify gram-scale quantities of single wall carbon nanotubes. This method, a modification of a gas phase purification technique previously reported by Smalley and others, uses a combination of high-temperature oxidations and repeated extractions with nitric and hydrochloric acid. This improved procedure significantly reduces the amount of impurities (catalyst and nonnanotube forms of carbon) within the nanotubes, increasing

  3. Formation of anatase TiO2 nanoparticles on carbon nanotubes.

    PubMed

    Lee, Seung-woo; Sigmund, Wolfgang M

    2003-03-21

    Anatase TiO2 nanoparticles with a size range of 2 to 10 nm have been formed on carbon nanotubes by the controlled hydrolysis and condensation of titanium bis-ammonium lactato dihydroxide in water and electrosterically dispersed carbon nanotubes.

  4. Density controlled carbon nanotube array electrodes

    DOEpatents

    Ren, Zhifeng F.; Tu, Yi

    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.

  5. Specific features of low-frequency vibrational dynamics and low-temperature heat capacity of double-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Avramenko, M. V.; Roshal, S. B.

    2016-05-01

    A continuous model has been constructed for low-frequency dynamics of a double-walled carbon nanotube. The formation of the low-frequency part of the phonon spectrum of a double-walled nanotube from phonon spectra of its constituent single-walled nanotubes has been considered in the framework of the proposed approach. The influence of the environment on the phonon spectrum of a single double-walled carbon nanotube has been analyzed. A combined method has been proposed for estimating the coefficients of the van der Waals interaction between the walls of the nanotube from the spectroscopic data and the known values of the elastic moduli of graphite. The low-temperature specific heat has been calculated for doublewalled carbon nanotubes, which in the field of applicability of the model ( T < 35 K) is substantially less than the sum of specific heats of two individual single-walled nanotubes forming it.

  6. Inorganic nanotube nanofluidics

    NASA Astrophysics Data System (ADS)

    Fan, Rong

    The ability to manipulate charge carriers (electrons and holes) in metal-oxide semiconductor field effect transistors (MOSFETs) has revolutionized how information is processed and stored, and created the modern digital age. Introducing direct field effect modulation in fluidic systems would enable the manipulation of ionic and molecular species at a similar level and even logic operation. Due to strong Debye screening in aqueous solutions, field effect manipulation of ion transport arises only in systems whose dimensions are comparable to the critical Debye Length, i.e. in nanofluidic systems. Nanofluidics has already been explored in various cases, e.g. biological channel proteins and artificial solid-state nanopores. All these two terminal systems usually transport the ions the same way as passive electron conduction in a resistor. My work is aimed at developing nanotube nanofluidic units with a third terminal that can electrically turn on/off and control ion and biomolecule transport. Moreover, the systematic study on "doping" and transient phenomena can provide rich information to assess the electrokinetics theory and fluidic physics in nanoscale. Silica nanotubes were synthesized by oxidation/etching approach using vertical silicon nanowires as templates. A single nanotube was integrated into a metal-oxide-solution field effect transistor (MOSolFET) by interfacing with two microfluidic channels and a metallic gate electrode. Concentration dependence of ionic conductance through single nanotubes revealed the emergence of unipolar environment at low ionic strength regime. In this case, ionic conductance is only associated with majority ions and governed by surface potentials and charge densities. By applying a gate voltage, the ionic conductance can be quickly modulated. The gate voltages alter the surface potential of the silica nanotubes via capacitive coupling through the nanotube wall and the electrical double layer. In a negatively charged silica nanotube

  7. Theory of growth and mechanical properties of nanotubes

    NASA Astrophysics Data System (ADS)

    Bernholc, J.; Brabec, C.; Buongiorno Nardelli, M.; Maiti, A.; Roland, C.; Yakobson, B. I.

    remarkably accurate ``roadmap'' of nanotube behavior beyond Hooke's law. We have also investigated static and dynamical properties of carbon nanotubes under uniaxial tension by quantum and classical simulations. In strained nanotubes at high temperatures double pentagon-heptagon defect pairs are spontaneously formed. Their formation is energetically favorable at strains greater than 5%. They act as nucleation centers for the formation of dislocations in the originally ideal graphite network and lead to the onset of a plastic deformation of the carbon nanotube.

  8. Carbon Nanotube Purification and Functionalization

    NASA Technical Reports Server (NTRS)

    Lebron, Marisabel; Mintz, Eric; Smalley, Richard E.; Meador, Michael A.

    2003-01-01

    Carbon nanotubes have the potential to significantly enhance the mechanical, thermal, and electrical properties of polymers. However, dispersion of carbon nanotubes in a polymer matrix is hindered by the electrostatic forces that cause them to agglomerate. Chemical modification of the nanotubes is necessary to minimize these electrostatic forces and promote adhesion between the nanotubes and the polymer matrix. In a collaborative research program between Clark Atlanta University, Rice University, and NASA Glenn Research Center several approaches are being explored to chemically modify carbon nanotubes. The results of this research will be presented.

  9. Identification of Complex Carbon Nanotube Structures

    NASA Technical Reports Server (NTRS)

    Han, Jie; Saini, Subhash (Technical Monitor)

    1998-01-01

    A variety of complex carbon nanotube (CNT) structures have been observed experimentally. These include sharp bends, branches, tori, and helices. They are believed to be formed by using topological defects such as pentagons and heptagons to connect different CNT. The effects of type, number, and arrangement (separation and orientation) of defects on atomic structures and energetics of complex CNT are investigated using topology, quantum mechanics and molecular mechanics calculations. Energetically stable models are derived for identification of observed complex CNT structures.

  10. Copper-philic carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Belgamwar, Sachin U.; Sharma, Niti Nipun

    2016-04-01

    Carbon nanotube is having poor wet-ability with copper metal. Wet-ability of carbon nanotube was improved by exposing and creating more active sites on the surface of carbon nanotube. Carbon nanotubes were subjected to the prolong ultrasonication treatment of 20×103 Hz and 500W, which helped in disentanglement of carbon nanotube agglomerates and in breaking the weak bonds like pentagonal or heptagonal structure on the surface and on the CNT cap. Disentanglement of the carbon nanotube, resulted in exposing the defective sites on the surface and breaking of weak bonds, which assisted in creating the new defects on the surface. This process results in generates more active sites on the surface and it helps in improving the wet-ability of the carbon nanotube in copper.

  11. Nanotechnology with Carbon Nanotubes: Mechanics, Chemistry, and Electronics

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak

    2003-01-01

    This viewgraph presentation reviews the Nanotechnology of carbon nanotubes. The contents include: 1) Nanomechanics examples; 2) Experimental validation of nanotubes in composites; 3) Anisotropic plastic collapse; 4) Spatio-temporal scales, yielding single-wall nanotubes; 5) Side-wall functionalization of nanotubes; 6) multi-wall Y junction carbon nanotubes; 7) Molecular electronics with Nanotube junctions; 8) Single-wall carbon nanotube junctions; welding; 9) biomimetic dendritic neurons: Carbon nanotube, nanotube electronics (basics), and nanotube junctions for Devices,

  12. Conductance of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Datta, Supriyo; Anatram, M. P.

    1998-01-01

    The recent report of quantized conductance in a 4 m long multiwalled nanotube (MWNT) raises the exciting possibility of ballistic transport at room temperature over relatively long distances. We argue that this is made possible by the special symmetry of the eigenstates of the lowest propagating modes in metallic nanotubes which suppresses backscattering. This unusual effect is absent for the higher propagating modes so that transport is not ballistic once the bias exceeds the cut-off energy for the higher modes, which is estimated to be approximately 75 meV for nanotubes of diameter approximately 15 nm. Also, we show that the symmetry of the eigenstates can significantly affect their coupling to the reservoir and hence the contact resistance. A simple model is presented that can be used to understand the observed conductance-voltage characteristics.

  13. Carbon Nanotubes for Supercapacitor

    NASA Astrophysics Data System (ADS)

    Pan, Hui; Li, Jianyi; Feng, Yuan Ping

    2010-03-01

    As an electrical energy storage device, supercapacitor finds attractive applications in consumer electronic products and alternative power source due to its higher energy density, fast discharge/charge time, low level of heating, safety, long-term operation stability, and no disposable parts. This work reviews the recent development of supercapacitor based on carbon nanotubes (CNTs) and their composites. The purpose is to give a comprehensive understanding of the advantages and disadvantages of carbon nanotubes-related supercapacitor materials and to find ways for the improvement in the performance of supercapacitor. We first discussed the effects of physical and chemical properties of pure carbon nanotubes, including size, purity, defect, shape, functionalization, and annealing, on the supercapacitance. The composites, including CNTs/oxide and CNTs/polymer, were further discussed to enhance the supercapacitance and keep the stability of the supercapacitor by optimally engineering the composition, particle size, and coverage.

  14. Carbon Nanotubes for Supercapacitor

    PubMed Central

    2010-01-01

    As an electrical energy storage device, supercapacitor finds attractive applications in consumer electronic products and alternative power source due to its higher energy density, fast discharge/charge time, low level of heating, safety, long-term operation stability, and no disposable parts. This work reviews the recent development of supercapacitor based on carbon nanotubes (CNTs) and their composites. The purpose is to give a comprehensive understanding of the advantages and disadvantages of carbon nanotubes-related supercapacitor materials and to find ways for the improvement in the performance of supercapacitor. We first discussed the effects of physical and chemical properties of pure carbon nanotubes, including size, purity, defect, shape, functionalization, and annealing, on the supercapacitance. The composites, including CNTs/oxide and CNTs/polymer, were further discussed to enhance the supercapacitance and keep the stability of the supercapacitor by optimally engineering the composition, particle size, and coverage. PMID:20672061

  15. Quantum Dots in Gated Nanowires and Nanotubes

    NASA Astrophysics Data System (ADS)

    Churchill, Hugh Olen Hill

    This thesis describes experiments on quantum dots made by locally gating one-dimensional quantum wires. The first experiment studies a double quantum dot device formed in a Ge/Si core/shell nanowire. In addition to measuring transport through the double dot, we detect changes in the charge occupancy of the double dot by capacitively coupling it to a third quantum dot on a separate nanowire using a floating gate. We demonstrate tunable tunnel coupling of the double dot and quantify the strength of the tunneling using the charge sensor. The second set of experiments concerns carbon nanotube double quantum dots. In the first nanotube experiment, spin-dependent transport through the double dot is compared in two sets of devices. The first set is made with carbon containing the natural abundance of 12C (99%) and 13C (1%), the second set with the 99% 13C and 1% 12C. In the devices with predominantly 13C, we find evidence in spin-dependent transport of the interaction between the electron spins and the 13C nuclear spins that was much stronger than expected and not present in the 12C devices. In the second nanotube experiment, pulsed gate experiments are used to measure the timescales of spin relaxation and dephasing in a two-electron double quantum dot. The relaxation time is longest at zero magnetic field and goes through a minimum at higher field, consistent with the spin-orbit-modified electronic spectrum of carbon nanotubes. We measure a short dephasing time consistent with the anomalously strong electron-nuclear interaction inferred from the first nanotube experiment.

  16. Horizontal carbon nanotube alignment.

    PubMed

    Cole, Matthew T; Cientanni, Vito; Milne, William I

    2016-09-21

    The production of horizontally aligned carbon nanotubes offers a rapid means of realizing a myriad of self-assembled near-atom-scale technologies - from novel photonic crystals to nanoscale transistors. The ability to reproducibly align anisotropic nanostructures has huge technological value. Here we review the present state-of-the-art in horizontal carbon nanotube alignment. For both in and ex situ approaches, we quantitatively assess the reported linear packing densities alongside the degree of alignment possible for each of these core methodologies. PMID:27546174

  17. Carbon nanotube actuators

    PubMed

    Baughman; Cui; Zakhidov; Iqbal; Barisci; Spinks; Wallace; Mazzoldi; De Rossi D; Rinzler; Jaschinski; Roth; Kertesz

    1999-05-21

    Electromechanical actuators based on sheets of single-walled carbon nanotubes were shown to generate higher stresses than natural muscle and higher strains than high-modulus ferroelectrics. Like natural muscles, the macroscopic actuators are assemblies of billions of individual nanoscale actuators. The actuation mechanism (quantum chemical-based expansion due to electrochemical double-layer charging) does not require ion intercalation, which limits the life and rate of faradaic conducting polymer actuators. Unlike conventional ferroelectric actuators, low operating voltages of a few volts generate large actuator strains. Predictions based on measurements suggest that actuators using optimized nanotube sheets may eventually provide substantially higher work densities per cycle than any previously known technology.

  18. Horizontal carbon nanotube alignment.

    PubMed

    Cole, Matthew T; Cientanni, Vito; Milne, William I

    2016-09-21

    The production of horizontally aligned carbon nanotubes offers a rapid means of realizing a myriad of self-assembled near-atom-scale technologies - from novel photonic crystals to nanoscale transistors. The ability to reproducibly align anisotropic nanostructures has huge technological value. Here we review the present state-of-the-art in horizontal carbon nanotube alignment. For both in and ex situ approaches, we quantitatively assess the reported linear packing densities alongside the degree of alignment possible for each of these core methodologies.

  19. Analytical solutions for elastic binary nanotubes of arbitrary chirality

    NASA Astrophysics Data System (ADS)

    Jiang, Lai; Guo, Wanlin

    2016-09-01

    Analytical solutions for the elastic properties of a variety of binary nanotubes with arbitrary chirality are obtained through the study of systematic molecular mechanics. This molecular mechanics model is first extended to chiral binary nanotubes by introducing an additional out-of-plane inversion term into the so-called stick-spiral model, which results from the polar bonds and the buckling of binary graphitic crystals. The closed-form expressions for the longitudinal and circumferential Young's modulus and Poisson's ratio of chiral binary nanotubes are derived as functions of the tube diameter. The obtained inversion force constants are negative for all types of binary nanotubes, and the predicted tube stiffness is lower than that by the former stick-spiral model without consideration of the inversion term, reflecting the softening effect of the buckling on the elastic properties of binary nanotubes. The obtained properties are shown to be comparable to available density functional theory calculated results and to be chirality and size sensitive. The developed model and explicit solutions provide a systematic understanding of the mechanical performance of binary nanotubes consisting of III-V and II-VI group elements.

  20. Localization of the electronic excitations in single-walled carbon nanotubes with embedded line impurities

    NASA Astrophysics Data System (ADS)

    Komorowski, P. G.; Cottam, M. G.

    2016-01-01

    A matrix operator formalism is used to study the excitations in long, single-walled carbon nanotubes with the dynamic electronic properties described by a tight-binding model where the interactions between atoms take place via nearest-neighbour hopping. Defects in the form of substitutional impurity atoms are introduced to study the localized electronic modes of the nanotube as well as the propagating modes of the pure (host) material. The impurities are assumed to have the form of one or more line defects parallel to the nanotube axis. Two geometric configurations are investigated corresponding to the longitudinal axis of the nanotube being parallel to either a zigzag or an armchair direction of the graphene lattice. A tridiagonal matrix technique is employed to solve the electronic operator equations that provide a description of the frequencies of the discrete modes of the system and their spatial amplitudes. Numerical examples are presented for different nanotube diameters and spatial configurations of the impurity lines.

  1. Reinforcement of single-walled carbon nanotube bundles by intertube bridging.

    PubMed

    Kis, A; Csányi, G; Salvetat, J-P; Lee, Thien-Nga; Couteau, E; Kulik, A J; Benoit, W; Brugger, J; Forró, L

    2004-03-01

    During their production, single-walled carbon nanotubes form bundles. Owing to the weak van der Waals interaction that holds them together in the bundle, the tubes can easily slide on each other, resulting in a shear modulus comparable to that of graphite. This low shear modulus is also a major obstacle in the fabrication of macroscopic fibres composed of carbon nanotubes. Here, we have introduced stable links between neighbouring carbon nanotubes within bundles, using moderate electron-beam irradiation inside a transmission electron microscope. Concurrent measurements of the mechanical properties using an atomic force microscope show a 30-fold increase of the bending modulus, due to the formation of stable crosslinks that effectively eliminate sliding between the nanotubes. Crosslinks were modelled using first-principles calculations, showing that interstitial carbon atoms formed during irradiation in addition to carboxyl groups, can independently lead to bridge formation between neighbouring nanotubes. PMID:14991016

  2. High Bias Characteristics of Individual, Suspended Carbon Nanotube p-n Junction Photodiodes

    NASA Astrophysics Data System (ADS)

    Chang, Shun-Wen; Bergemann, Kevin; Dhall, Rohan; Zimmerman, Jeramy; Forrest, Stephen; Cronin, Stephen

    2013-03-01

    We have recently investigated p-n junction diodes formed by electrostatic doping of individual, suspended, single-walled carbon nanotubes (CNTs) using two gate electrodes positioned beneath a free standing nanotube that bridges source and drain electrodes. The electrostatic field imposed by the two gates polarizes the nanotube along its length, thereby allowing independent control of the ``doping'' in the nanotube without introducing impurities or defect states. These pn-devices exhibit rectifying diode behavior and finite photoresponse under illumination. Several interesting phenomena are observed at high bias that arise from Schottky contacts formed between the nanotube and its metal contact electrodes and electron tunneling between the n- and p-doped regions. A model is developed explaining this behavior showing evidence for plasmon-induced band gap shrinkage with electrostatic doping.

  3. Lipid nanotube formation using space-regulated electric field above interdigitated electrodes.

    PubMed

    Bi, Hongmei; Fu, Dingguo; Wang, Lei; Han, Xiaojun

    2014-04-22

    Lipid nanotubes have great potential in biology and nanotechnology. Here we demonstrate a method to form lipid nanotubes using space-regulated AC electric fields above coplanar interdigitated electrodes. The AC electric field distribution can be regulated by solution height above the electrodes. The ratio of field component in x axis (Ex) to field component in z axis (Ez) increases dramatically at solution height below 50 μm; therefore, at lower solution height, the force from Ex predominantly drives lipids to form lipid nanotubes along with the electric field direction. The forces exerted on the lipid nanotube during its formation were analyzed in detail, and an equation was obtained to describe the relationship among nanotube length and field frequency, amplitude, and time. We believe that the presented approach opens a way to design and prepare nanoscale materials with unique structural and functional properties using space-regulated electric fields.

  4. Facile synthesis of BaTiO3 nanotubes and their microwave absorption properties.

    PubMed

    Zhu, Yao-Feng; Zhang, Li; Natsuki, Toshiaki; Fu, Ya-Qin; Ni, Qing-Qing

    2012-04-01

    Uniform BaTiO(3) nanotubes were synthesized via a simple wet chemical route at low temperature (50 °C). The as-synthesized BaTiO(3) nanotubes were characterized using powder X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy. The results show that the BaTiO(3) nanotubes formed a cubic phase with an average diameter of ~10 nm and wall thickness of 3 nm at room temperature. The composition of the mixed solvent (ethanol and deionized water) was a key factor in the formation of these nanotubes; we discuss possible synthetic mechanisms. The microwave absorption properties of the BaTiO(3) nanotubes were studied at microwave frequencies between 0.5 and 15 GHz. The minimum reflection loss of the BaTiO(3) nanotubes/paraffin wax composite (BaTiO(3) nanotubes weight fraction = 70%) reached 21.8 dB (~99.99% absorption) at 15 GHz, and the frequency bandwidth less than -10 dB is from 13.3 to 15 GHz. The excellent absorption property of BaTiO(3) nanotubes at high frequency indicates that these nanotubes could be promising microwave-absorbing materials. PMID:22409350

  5. The Toxicology of Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Donaldson, Ken; Poland, Craig; Duffin, Rodger; Bonner, James

    2012-06-01

    1. Carbon nanotube structure, synthesis and applications C. Singh and W. Song; 2. The aerodynamic behaviour and pulmonary deposition of carbon nanotubes A. Buckley, R. Smith and R Maynard; 3. Utilising the concept of the biologically effective dose to define the particle and fibre hazards of carbon nanotubes K. Donaldson, R. Duffin, F. Murphy and C. Poland; 4. CNT, biopersistence and the fibre paradigm D. Warheit and M. DeLorme; 5. Length-dependent retention of fibres in the pleural space C. Poland, F. Murphy and K. Donaldson; 6. Experimental carcinogenicity of carbon nanotubes in the context of other fibres K. Unfried; 7. Fate and effects of carbon nanotubes following inhalation J. Ryman-Rasmussen, M. Andersen and J. Bonner; 8. Responses to pulmonary exposure to carbon nanotubes V. Castranova and R. Mercer; 9. Genotoxicity of carbon nanotubes R. Schins, C. Albrecht, K. Gerloff and D. van Berlo; 10. Carbon nanotube-cellular interactions; macrophages, epithelial and mesothelial cells V. Stone, M. Boyles, A. Kermanizadeh, J. Varet and H. Johnston; 11. Systemic health effects of carbon nanotubes following inhalation J. McDonald; 12. Dosimetry and metrology of carbon nanotubes L. Tran, L. MacCalman and R. Aitken; Index.

  6. Carbon Nanotubes as Resonators for RF Spectrum Analyzers

    NASA Technical Reports Server (NTRS)

    Hunt, Brian; Noca, Flavio; Hoenk, Michael

    2003-01-01

    Electromechanical resonators of a proposed type would comprise single carbon nanotubes suspended between electrodes (see Figure 1). Depending on the nanotube length, diameter, and tension, these devices will resonate at frequencies in a range from megahertz through gigahertz. Like the carbon-nanotube resonators described in the preceding article, these devices will exhibit high quality factors (Q values), will be compatible with integration with electronic circuits, and, unlike similar devices made from silicone and silicone carbide, will have tunable resonant frequencies as high as several GHz. An efficient electromechanical transduction method for the carbon nanotube resonators is provided by the previously observed variation of carbon nanotube length with charge injection. It was found that injection of electrons or holes, respectively, lengthens or shortens carbon nanotubes, by amounts of the order of a percent at bias levels of a few volts. The charge-dependent length change also enables a simple and direct means of tuning the resonant frequency by varying the DC bias and hence the tension along the tube, much like tuning a guitar string. In its basic form, the invention is a tunable high-Q resonator based on a suspended carbon nanotube bridge with attached electrodes (see Figure 1). An applied DC bias controls the tension and thus the frequency of resonance. If one were to superimpose a radio-frequency (RF) bias on the DC bias, then the resulting rapid variation in tension or length would set the tube into vibration. If, on the other hand, the carbon nanotube were to be set into vibration by interaction between an incident RF electric field and electric charges in the nanotube, then the vibration would give rise to an RF signal output that is proportional to the RF amplitude at the resonance frequency. Because the transduction mechanism is extremely sensitive and the active volume is only a few nanometers in diameter, this device is not well suited for use as

  7. Fast Electromechanical Switches Based on Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama; Wong, Eric; Epp, Larry

    2008-01-01

    Electrostatically actuated nanoelectromechanical switches based on carbon nanotubes have been fabricated and tested in a continuing effort to develop high-speed switches for a variety of stationary and portable electronic equipment. As explained below, these devices offer advantages over electrostatically actuated microelectromechanical switches, which, heretofore, have represented the state of the art of rapid, highly miniaturized electromechanical switches. Potential applications for these devices include computer memories, cellular telephones, communication networks, scientific instrumentation, and general radiation-hard electronic equipment. A representative device of the present type includes a single-wall carbon nanotube suspended over a trench about 130 nm wide and 20 nm deep in an electrically insulating material. The ends of the carbon nanotube are connected to metal electrodes, denoted the source and drain electrodes. At bottom of the trench is another metal electrode, denoted the pull electrode (see figure). In the off or open switch state, no voltage is applied, and the nanotube remains out of contact with the pull electrode. When a sufficiently large electric potential (switching potential) is applied between the pull electrode and either or both of the source and drain electrodes, the resulting electrostatic attraction bends and stretches the nanotube into contact with the pull electrode, thereby putting the switch into the "on" or "closed" state, in which substantial current (typically as much as hundreds of nanoamperes) is conducted. Devices of this type for use in initial experiments were fabricated on a thermally oxidized Si wafer, onto which Nb was sputter-deposited for use as the pull-electrode layer. Nb was chosen because its refractory nature would enable it to withstand the chemical and thermal conditions to be subsequently imposed for growing carbon nanotubes. A 200- nm-thick layer of SiO2 was formed on top of the Nb layer by plasma

  8. Carbon nanotubes for microelectronics?

    PubMed

    Graham, Andrew P; Duesberg, Georg S; Seidel, Robert V; Liebau, Maik; Unger, Eugen; Pamler, Werner; Kreupl, Franz; Hoenlein, Wolfgang

    2005-04-01

    Despite all prophecies of its end, silicon-based microelectronics still follows Moore's Law and continues to develop rapidly. However, the inherent physical limits will eventually be reached. Carbon nanotubes offer the potential for further miniaturization as long as it is possible to selectively deposit them with defined properties.

  9. Design of highly ordered Ag-SrTiO{sub 3} nanotube arrays for photocatalytic degradation of methyl orange

    SciTech Connect

    Sun Yue; Liu Jiawen; Li Zhonghua

    2011-08-15

    Ag-SrTiO{sub 3} nanotube arrays were successfully prepared for the degradation of methyl orange (MO) under ultraviolet irradiation. In order to form highly ordered SrTiO{sub 3} nanotube arrays, the preparation of TiO{sub 2} nanotube arrays by anodic oxidation of titanium foil in different electrolytes was investigated. The selected organic solvents in electrolytes include glycerol, dimethyl sulfoxide and glycol. The results indicate that the morphology of TiO{sub 2} nanotube arrays prepared in glycol containing ammonium fluoride electrolyte is more regular. Then SrTiO{sub 3} nanotube arrays were synthesized by a hydrothermal method using TiO{sub 2} nanotube arrays as the precursor. In order to further improve the photocatalytic activity of SrTiO{sub 3} nanotube arrays, Ag nanoparticles were loaded on SrTiO{sub 3} nanotube arrays by two sets of experiments. The loaded Ag results in an enhancement of photocatalytic activity of SrTiO{sub 3} nanotube arrays. Moreover, the effect of pH on the photocatalytic degradation of MO was also studied. - Graphical abstract: Ag-SrTiO{sub 3} nanotube arrays were successfully prepared. The photocatalytic activity was evaluated by degradation of methyl orange under ultraviolet irradiation. Highlights: > TiO{sub 2} nanotube arrays prepared in glycol+NH{sub 4}F electrolyte are more regular. > Highly ordered Ag-SrTiO{sub 3} nanotube arrays were successfully synthesized. > Ag loading could enhance the photocatalytic activity of SrTiO{sub 3} nanotube arrays. > Ag-SrTiO{sub 3} nanotube arrays show excellent catalytic activity at a low pH value.

  10. Aqueous nanosilica dispersants for carbon nanotube.

    PubMed

    Matsuda, Takafumi; Minami, Daiki; Khoerunnisa, Fitri; Sunaga, Motoo; Nakamura, Masahiro; Utsumi, Shigenori; Itoh, Tsutomu; Fujimori, Toshihiko; Hayashi, Takuya; Hattori, Yoshiyuki; Endo, Morinobu; Isobe, Hiroshi; Onodera, Hiroshi; Kaneko, Katsumi

    2015-03-17

    Nanosilicas can disperse single-wall carbon nanotube (SWCNT) in aqueous solution efficiently; SWCNTs are stably dispersed in aqueous media for more than 6 months. The SWCNT dispersing solution with nanosilica can produce highly conductive transparent films which satisfy the requirements for application to touch panels. Even multiwall carbon nanotube can be dispersed easily in aqueous solution. The highly stable dispersion of SWCNTs in the presence of nanosilica is associated with charge transfer interaction which generates effective charges on the SWCNT particles, giving rise to electrostatic repulsion between the SWCNTs in the aqueous solution. Adhesion of charged nanosilicas on SWCNTs in the aqueous solution and a marked depression of the S11 peak of optical absorption spectrum of the SWCNT with nanosilicas suggest charge transfer interaction of nanosilicas with SWCNT. Thus-formed isolated SWCNTs are fixed on the flexible three-dimensional silica jelly structure in the aqueous solution, leading to the uniform and stable dispersion of SWCNTs. PMID:25706991

  11. Rebar Graphene from Functionalized Boron Nitride Nanotubes

    PubMed Central

    2015-01-01

    The synthesis of rebar graphene on Cu substrates is described using functionalized boron nitride nanotubes (BNNTs) that were annealed or subjected to chemical vapor deposition (CVD) growth of graphene. Characterization shows that the BNNTs partially unzip and form a reinforcing bar (rebar) network within the graphene layer that enhances the mechanical strength through covalent bonds. The rebar graphene is transferrable to other substrates without polymer assistance. The optical transmittance and conductivity of the hybrid rebar graphene film was tested, and a field effect transistor was fabricated to explore its electrical properties. This method of synthesizing 2D hybrid graphene/BN structures should enable the hybridization of various 1D nanotube and 2D layered structures with enhanced mechanical properties. PMID:25486451

  12. Rebar graphene from functionalized boron nitride nanotubes.

    PubMed

    Li, Yilun; Peng, Zhiwei; Larios, Eduardo; Wang, Gunuk; Lin, Jian; Yan, Zheng; Ruiz-Zepeda, Francisco; José-Yacamán, Miguel; Tour, James M

    2015-01-27

    The synthesis of rebar graphene on Cu substrates is described using functionalized boron nitride nanotubes (BNNTs) that were annealed or subjected to chemical vapor deposition (CVD) growth of graphene. Characterization shows that the BNNTs partially unzip and form a reinforcing bar (rebar) network within the graphene layer that enhances the mechanical strength through covalent bonds. The rebar graphene is transferrable to other substrates without polymer assistance. The optical transmittance and conductivity of the hybrid rebar graphene film was tested, and a field effect transistor was fabricated to explore its electrical properties. This method of synthesizing 2D hybrid graphene/BN structures should enable the hybridization of various 1D nanotube and 2D layered structures with enhanced mechanical properties. PMID:25486451

  13. MODELING FUNCTIONALLY GRADED INTERPHASE REGIONS IN CARBON NANOTUBE REINFORCED COMPOSITES

    NASA Technical Reports Server (NTRS)

    Seidel, G. D.; Lagoudas, D. C.; Frankland, S. J. V.; Gates, T. S.

    2006-01-01

    A combination of micromechanics methods and molecular dynamics simulations are used to obtain the effective properties of the carbon nanotube reinforced composites with functionally graded interphase regions. The multilayer composite cylinders method accounts for the effects of non-perfect load transfer in carbon nanotube reinforced polymer matrix composites using a piecewise functionally graded interphase. The functional form of the properties in the interphase region, as well as the interphase thickness, is derived from molecular dynamics simulations of carbon nanotubes in a polymer matrix. Results indicate that the functional form of the interphase can have a significant effect on all the effective elastic constants except for the effective axial modulus for which no noticeable effects are evident.

  14. Theoretical study of the structure and electronic properties of carbon and B{sub X}C{sub Y}N{sub Z} nanotubes

    SciTech Connect

    Louie, S.G. |

    1995-06-01

    Theoretical studies of the electronic and structural properties of carbon nanotubes and nanotubes composed of boron, carbon and nitrogen are presented. Structural stability, hybridization effects, static dielectric response, incorporation of metal atoms, and collapsed tube structures are calculated. Nanotubes of BN, BC{sub 3}, and BC{sub 2}N are predicted to form and have very different properties from those of the carbon systems. BN nanotubes are found to be constant band gap insulators with novel free-electron tubule states at the conduction band minimum. The possibility of chiral currents in doped BC{sub 2}N nanotubes is shown.

  15. Nonlinear dynamics of bi-layered graphene sheet, double-walled carbon nanotube and nanotube bundle

    NASA Astrophysics Data System (ADS)

    Gajbhiye, Sachin O.; Singh, S. P.

    2016-05-01

    Due to strong van der Waals (vdW) interactions, the graphene sheets and nanotubes stick to each other and form clusters of these corresponding nanostructures, viz. bi-layered graphene sheet (BLGS), double-walled carbon nanotube (DWCNT) and nanotube bundle (NB) or ropes. This research work is concerned with the study of nonlinear dynamics of BLGS, DWCNT and NB due to nonlinear interlayer vdW forces using multiscale atomistic finite element method. The energy between two adjacent carbon atoms is represented by the multibody interatomic Tersoff-Brenner potential, whereas the nonlinear interlayer vdW forces are represented by Lennard-Jones 6-12 potential function. The equivalent nonlinear material model of carbon-carbon bond is used to model it based on its force-deflection relation. Newmark's algorithm is used to solve the nonlinear matrix equation governing the motion of the BLGS, DWCNT and NB. An impulse and harmonic excitations are used to excite these nanostructures under cantilevered, bridged and clamped boundary conditions. The frequency responses of these nanostructures are computed, and the dominant resonant frequencies are identified. Along with the forced vibration of these structures, the eigenvalue extraction problem of armchair and zigzag NB is also considered. The natural frequencies and corresponding mode shapes are extracted for the different length and boundary conditions of the nanotube bundle.

  16. Molecular recognition using nanotube-adsorbed polymer phases: nanotube antibodies

    PubMed Central

    Zhang, Jingqing; Landry, Markita P.; Barone, Paul W.; Kim, Jong-Ho; Lin, Shangchao; Ulissi, Zachary W.; Lin, Dahua; Mu, Bin; Heller, Daniel A.; Boghossian, Ardemis A.; Hilmer, Andrew J.; Rwei, Alina; Hinckley, Allison C.; Kruss, Sebastian; Shandell, Mia A.; Nair, Nitish; Blake, Steven; Sen, Fatih; Sen, Selda; Croy, Robert G.; Li, Deyu; Yum, Kyungsuk; Ahn, Jin-Ho; Jin, Hong; Essigmann, John M.; Blankschtein, Daniel; Strano, Michael S.

    2016-01-01

    Molecular recognition is central to the design of therapeutics, chemical catalysis and sensors. Motifs for doing so most commonly involve biological structures such as antibodies and aptamers. The key to such biological recognition consists of a folded and constrained heteropolymer that, via intra-molecular forces, forms a unique three dimensional structure that creates a binding pocket or an interface able to recognize a specific molecule. In this work, we demonstrate that synthetic heteropolymers can be alternatively constrained by adsorption around a nanoparticle, and specifically a single walled carbon nanotube (SWNT), forming a corona phase and resulting in a new form of molecular recognition of specific molecules. The phenomenon is shown to be generic, with new heteropolymer recognition complexes demonstrated for three distinct examples: Riboflavin, l-thyroxine, and estradiol, each predicted using a 2D thermodynamic model of surface interactions. The dissociation constants are continuously tunable by perturbing the chemical structure of the heteropolymer. Moreover, these complexes can be used as new types of spatial-temporal sensors based on modulation of SWNT photoemission in the near-infrared, as we show by tracking riboflavin diffusion in murine macrophages. PMID:24270641

  17. Carbon Nanotubes for Space Applications

    NASA Technical Reports Server (NTRS)

    Meyyappan, Meyya

    2000-01-01

    The potential of nanotube technology for NASA missions is significant and is properly recognized by NASA management. Ames has done much pioneering research in the last five years on carbon nanotube growth, characterization, atomic force microscopy, sensor development and computational nanotechnology. NASA Johnson Space Center has focused on laser ablation production of nanotubes and composites development. These in-house efforts, along with strategic collaboration with academia and industry, are geared towards meeting the agency's mission requirements. This viewgraph presentation (including an explanation for each slide) outlines the research focus for Ames nanotechnology, including details on carbon nanotubes' properties, applications, and synthesis.

  18. Spin transport in nanotubes (invited)

    SciTech Connect

    Alphenaar, B. W.; Tsukagoshi, K.; Wagner, M.

    2001-06-01

    We study electron spin transport through carbon nanotubes contacted by ferromagnetic electrodes. The resistance of a ferromagnetically contacted multiwalled nanotube switches hysteretically as a function of applied magnetic field, with a maximum resistance change of 9% at 4.2 K. Magnetoresistance measurements of carbon nanotubes having one cobalt contact and one platinum/gold contact, however, show no switching. In addition, we present calculations of the magnetoresistance ratio for the ferromagnetic nanotube device, and predict that a resistance change of 25% is possible. {copyright} 2001 American Institute of Physics.

  19. Nanotube-based nanoelectromechanical systems

    SciTech Connect

    Lozovik, Yu. E. Nikolaev, A. G.; Popov, A. M.

    2006-09-15

    Nanoelectromechanical systems based on multiwalled carbon nanotubes are considered. Control of motion and modes of operation of these systems are discussed. The structure of double-walled carbon nanotubes with atomic structural defects that can be used as bolt-nut pairs is analyzed. Energy barriers and threshold forces for relative motion of walls along and across the 'thread' are computed for double-walled nanotubes with various types of defects. It is found that the qualitative characteristics of the thread are independent of the type of defect. Feasibility of fabricating double-walled nanotubes for use as bolt-nut pairs by self-organization is discussed.

  20. Fabricating Copper Nanotubes by Electrodeposition

    NASA Technical Reports Server (NTRS)

    Yang, E. H.; Ramsey, Christopher; Bae, Youngsam; Choi, Daniel

    2009-01-01

    Copper tubes having diameters between about 100 and about 200 nm have been fabricated by electrodeposition of copper into the pores of alumina nanopore membranes. Copper nanotubes are under consideration as alternatives to copper nanorods and nanowires for applications involving thermal and/or electrical contacts, wherein the greater specific areas of nanotubes could afford lower effective thermal and/or electrical resistivities. Heretofore, copper nanorods and nanowires have been fabricated by a combination of electrodeposition and a conventional expensive lithographic process. The present electrodeposition-based process for fabricating copper nanotubes costs less and enables production of copper nanotubes at greater rate.

  1. Accelerated dynamics simulations of nanotubes.

    SciTech Connect

    Uberuaga, B. P.; Stuart, S. J.; Voter, A. F.

    2002-01-01

    We report on the application of accelerated dynamics techniques to the study of carbon nanotubes. We have used the parallel replica method and temperature accelerated dynamics simulations are currently in progress. In the parallel replica study, we have stretched tubes at a rate significantly lower than that used in previous studies. In these preliminary results, we find that there are qualitative differences in the rupture of the nanotubes at different temperatures. We plan on extending this investigation to include nanotubes of various chiralities. We also plan on exploring unique geometries of nanotubes.

  2. Nanotube-assisted protein deactivation

    NASA Astrophysics Data System (ADS)

    Joshi, Amit; Punyani, Supriya; Bale, Shyam Sundhar; Yang, Hoichang; Borca-Tasciuc, Theodorian; Kane, Ravi S.

    2008-01-01

    Conjugating proteins onto carbon nanotubes has numerous applications in biosensing, imaging and cellular delivery. However, remotely controlling the activity of proteins in these conjugates has never been demonstrated. Here we show that upon near-infrared irradiation, carbon nanotubes mediate the selective deactivation of proteins in situ by photochemical effects. We designed nanotube-peptide conjugates to selectively destroy the anthrax toxin, and also optically transparent coatings that can self-clean following either visible or near-infrared irradiation. Nanotube-assisted protein deactivation may be broadly applicable to the selective destruction of pathogens and cells, and will have applications ranging from antifouling coatings to functional proteomics.

  3. Carbon nanotube IR detectors (SV)

    SciTech Connect

    Leonard, F. L.

    2012-03-01

    Sandia National Laboratories (Sandia) and Lockheed Martin Corporation (LMC) collaborated to (1) evaluate the potential of carbon nanotubes as channels in infrared (IR) photodetectors; (2) assemble and characterize carbon nanotube electronic devices and measure the photocurrent generated when exposed to infrared light;(3) compare the performance of the carbon nanotube devices with that of traditional devices; and (4) develop and numerically implement models of electronic transport and opto-electronic behavior of carbon nanotube infrared detectors. This work established a new paradigm for photodetectors.

  4. Seed growth of tungsten diselenide nanotubes from tungsten oxides.

    PubMed

    Kim, Hyun; Yun, Seok Joon; Park, Jin Cheol; Park, Min Ho; Park, Ji-Hoon; Kim, Ki Kang; Lee, Young Hee

    2015-05-13

    We report growth of tungsten diselenide (WSe2) nanotubes by chemical vapor deposition with a two-zone furnace. WO3 nanowires were first grown by annealing tungsten thin films under argon ambient. WSe2 nanotubes were then grown at the tips of WO3 nanowires through selenization via two steps: (i) formation of tubular WSe2 structures on the outside of WO3 nanowires, resulting in core (WO3)-shell (WSe2) and (ii) growth of WSe2 nanotubes at the tips of WO3 nanowires. The observed seed growth is markedly different from existing substitutional growth of WSe2 nanotubes, where oxygen atoms are replaced by selenium atoms in WO3 nanowires to form WSe2 nanotubes. Another advantage of our growth is that WSe2 film was grown by simply supplying hydrogen gas, where the native oxides were reduced to thin film instead of forming oxide nanowires. Our findings will contribute to engineer other transition metal dichacogenide growth such as MoS2, WS2, and MoSe2. PMID:25581340

  5. Formation of carbon nanotubes from a silicon carbide/carbon composite

    NASA Astrophysics Data System (ADS)

    Joshi, Ravi; Engstler, Jörg; Haridoss, Prathap; Schneider, Jörg J.

    2009-02-01

    The reaction of a SiC/C composite powder in an arcing plasma forms carbon nanotubes in good yield. Besides carbon nanotubes, a Si/C composite composed of β SiC covered with a shell of graphite is formed. The graphitic carbon surface layers of the carbon shell of this composite reacts further to form carbon nanotubes when heated to 600 °C. This process seems highly effective since only a small overall low weight loss, indicative for a complete carbon shell oxidation is observed by thermal analysis. The formation of the carbon nanotubes from SiC is unlikely since no SiO 2 has been found when heating the SiC/C core shell composite to its reaction temperature of 600 °C under O 2. The CNTs formed are of good quality with 3 to 6 concentric walls and high aspect ratio. Occasionally even single walled carbon naotubes have been observed.

  6. Exchange of Surfactant by Natural Organic Matter on the Surfaces of Multi-Walled Carbon Nanotubes

    EPA Science Inventory

    The increasing production and applications of multi-walled carbon nanotubes (MWCNTs) have elicited concerns regarding their release and potential adverse effects in the environment. To form stable aqueous MWCNTs suspensions, surfactants are often employed to facilitate dispersion...

  7. Polymer-assisted deposition of films and preparation of carbon nanotube arrays using the films

    DOEpatents

    Luo, Hongmei; Li, Qingwen; Bauer, Eve; Burrell, Anthony Keiran; McCleskey, Thomas Mark; Jia, Quanxi

    2013-07-16

    Carbon nanotubes were prepared by coating a substrate with a coating solution including a suitable solvent, a soluble polymer, a metal precursor having a first metal selected from iron, nickel, cobalt, and molybdenum, and optionally a second metal selected from aluminum and magnesium, and also a binding agent that forms a complex with the first metal and a complex with the second metal. The coated substrate was exposed to a reducing atmosphere at elevated temperature, and then to a hydrocarbon in the reducing atmosphere. The result was decomposition of the polymer and formation of carbon nanotubes on the substrate. The carbon nanotubes were often in the form of an array on the substrate.

  8. "Suspended" Pt nanoparticles over TiO₂ nanotubes for enhanced photocatalytic H₂ evolution.

    PubMed

    Nguyen, Nhat Truong; Yoo, JeongEun; Altomare, Marco; Schmuki, Patrik

    2014-09-01

    In the present work we introduce a technique to form a photocatalyst based on Pt nanoparticles suspended over the mouth of anodic TiO2 nanotubes. These structures are obtained by decorating the top end of highly ordered TiO2 nanotubes with a web of TiO2 nanofibrils, followed by sputter deposition of a minimum amount of Pt. A subsequent thermal dewetting step forms 3-6 nm-sized Pt nanoparticles along the nanofibrils. These structures, when compared to conventional Pt decoration techniques of TiO2 nanotubes, show strongly enhanced photocatalytic H2 evolution efficiency.

  9. Carbon nanotubes for thermal interface materials in microelectronic packaging

    NASA Astrophysics Data System (ADS)

    Lin, Wei

    , an in situ functionalization process has for the first time been demonstrated. The in situ functionalization renders the vertically aligned carbon nanotubes a proper chemical reactivity for forming chemical bonding with other substrate materials such as gold and silicon. 2. An ultrafast microwave annealing process has been developed to reduce the defect density in vertically aligned carbon nanotubes. Raman and thermogravimetric analyses have shown a distinct defect reduction in the CNTs annealed in microwave for 3 min. Fibers spun from the as-annealed CNTs, in comparison with those from the pristine CNTs, show increases of ˜35% and ˜65%, respectively, in tensile strength (˜0.8 GPa) and modulus (˜90 GPa) during tensile testing; an ˜20% improvement in electrical conductivity (˜80000 S m-1) was also reported. The mechanism of the microwave response of CNTs was discussed. Such a microwave annealing process has been extended to the preparation of reduced graphene oxide. 3. Based on the fundamental understanding of interfacial thermal transport and surface chemistry of metals and carbon nanotubes, two major transfer/assembling processes have been developed: molecular bonding and metal bonding. Effective improvement of the interfacial thermal transport has been achieved by the interfacial bonding. 4. The thermal diffusivity of vertically aligned carbon nanotube (VACNT, multi-walled) films was measured by a laser flash technique, and shown to be ˜30 mm2 s-1 along the tube-alignment direction. The calculated thermal conductivities of the VACNT film and the individual CNTs are ˜27 and ˜540 W m-1 K-1, respectively. The technique was verified to be reliable although a proper sampling procedure is critical. A systematic parametric study of the effects of defects, buckling, tip-to-tip contacts, packing density, and tube-tube interaction on the thermal diffusivity was carried out. Defects and buckling decreased the thermal diffusivity dramatically. An increased packing

  10. Carbon nanotube-ceramic nanocomposites: Synthesis and characterization

    NASA Astrophysics Data System (ADS)

    Clark, Michael David

    Ceramic materials are widely used in modern society for a variety of applications including fuel cell electrolytes, bio-medical implants, and jet turbines. However, ceramics are inherently brittle making them excellent candidates for mechanical reinforcement. In this work, the feasibility of dispersing multi-walled carbon nanotubes into a silicon carbide matrix for mechanical property enhancement is explored. Prior to dispersing, nanotubes were purified using an optimized, three step methodology that incorporates oxidative treatment, acid sonication, and thermal annealing rendering near-superhydrophobic behavior in synthesized thin films. Alkyl functionalized nanotube dispersability was characterized in various solvents. Dispersability was contingent on fostering polar interactions between the functionalized nanotubes and solvent despite the purely dispersive nature of the aliphatic chains. Interpretation of these results yielded values of 45.6 +/- 1.2, 0.78 +/- 0.04, and 2 4 +/- 0.9 mJ/m2 for the Lifshitz-van der Waals, electron acceptor and electron donor surface energy components respectively. Aqueous nanotube dispersions were prepared using a number of surfactants to examine surfactant concentration and pH effects on nanotube dispersability. Increasing surfactant concentrations resulted in a solubility plateau, which was independent of the surfactant's critical micelle concentration. Deviations from neutral pH demonstrated negligible influence on non-ionic surfactant adsorption while, ionic surfactants showed substantial pH dependent behavior. These results were explained in the context of nanotube surface ionization and Debye length variation. Successful MWNT dispersion into a silicon carbide based matrix is reported by in-situ ceramic formation using two routes; sol-gel chemistry and pre-ceramic polymeric precursor workup. For the former, nanotube dispersion was assisted by PluronicRTM surfactants. Pyrolytic treatment and consolidation of formed powders

  11. High Stability of Faceted Nanotubes and Fullerenes of Multiphase Layered Phosphorus: A Computational Study.

    PubMed

    Guan, Jie; Zhu, Zhen; Tománek, David

    2014-11-28

    We present a paradigm in constructing very stable, faceted nanotube and fullerene structures by laterally joining nanoribbons or patches of different planar phosphorene phases. Our ab initio density functional calculations indicate that these phases may form very stable, nonplanar joints. Unlike fullerenes and nanotubes obtained by deforming a single-phase planar monolayer at substantial energy penalty, we find faceted fullerenes and nanotubes to be nearly as stable as the planar single-phase monolayers. The resulting rich variety of polymorphs allows us to tune the electronic properties of phosphorene nanotubes and fullerenes not only by the chiral index but also by the combination of different phosphorene phases. In selected phosphorene nanotubes, a metal-insulator transition may be induced by strain or by changing the number of walls.

  12. High Stability of Faceted Nanotubes and Fullerenes of Multiphase Layered Phosphorus: A Computational Study

    NASA Astrophysics Data System (ADS)

    Guan, Jie; Zhu, Zhen; Tománek, David

    2014-11-01

    We present a paradigm in constructing very stable, faceted nanotube and fullerene structures by laterally joining nanoribbons or patches of different planar phosphorene phases. Our ab initio density functional calculations indicate that these phases may form very stable, nonplanar joints. Unlike fullerenes and nanotubes obtained by deforming a single-phase planar monolayer at substantial energy penalty, we find faceted fullerenes and nanotubes to be nearly as stable as the planar single-phase monolayers. The resulting rich variety of polymorphs allows us to tune the electronic properties of phosphorene nanotubes and fullerenes not only by the chiral index but also by the combination of different phosphorene phases. In selected phosphorene nanotubes, a metal-insulator transition may be induced by strain or by changing the number of walls.

  13. Anomalously enhanced hydration of aqueous electrolyte solution in hydrophobic carbon nanotubes to maintain stability.

    PubMed

    Ohba, Tomonori

    2014-02-24

    An understanding of the structure and behavior of electrolyte solutions in nanoenvironements is crucial not only for a wide variety of applications, but also for the development of physical, chemical, and biological processes. We demonstrate the structure and stability of electrolyte in carbon nanotubes using hybrid reverse Monte Carlo simulations of X-ray diffraction patterns. Hydrogen bonds between water are adequately formed in carbon nanotubes, although some hydrogen bonds are restricted by the interfaces of carbon nanotubes. The hydrogen bonding network of water in electrolyte in the carbon nanotubes is further weakened. On the other hand, formation of the ion hydration shell is significantly enhanced in the electrolyte in the carbon nanotubes in comparison to ion hydration in bulk electrolyte. The significant hydrogen bond and hydration shell formation are a result of gaining stability in the hydrophobic nanoenvironment.

  14. Two-dimensional coalescence dynamics of encapsulated metallofullerenes in carbon nanotubes.

    PubMed

    Allen, Christopher S; Ito, Yasuhiro; Robertson, Alex W; Shinohara, Hisanori; Warner, Jamie H

    2011-12-27

    We report on the coalescence of a two-dimensional (2D) chain of La@C(82) metallofullerene molecules encapsulated inside a single-wall carbon nanotube (SWNT). 2D packing of metallofullerenes is known to adopt a zigzag arrangement and cause elliptical distortion to the cross-section of the SWNT host. We show that after coalescence of the metallofullerenes into an inner nanotube the carbon nanotube host returns to its original circular cross-section. This is due to a relaxation of the strain caused by the packing of the encapsulated La@C(82) molecules into the nanotube. We identify the formation of some novel but transient fullerene-based structures formed during the intermediate stages of coalescence of the La@C(82) into an inner nanotube. These results highlight the flexible nature of SWNTs and their ability to adapt their cross-sectional profile depending upon forces induced by material encapsulated within.

  15. Controlling the morphological, structural, and optical properties of one-dimensional PCDTBT nanotubes by template wetting.

    PubMed

    Bakar, Nor Asmaliza; Supangat, Azzuliani; Sulaiman, Khaulah

    2014-01-01

    In this study, the synthesis of poly [N-9'-heptadecanyl-2, 7-carbazole-alt-5, 5-(4', 7'-di-2-thienyl-2', 1', 3'-benzothiadiazole)] (PCDTBT) nanotubes via a templating method is reported. PCDTBT nanotubes were successfully grown by immersing the porous alumina template into 15 mg/ml of solution concentration for 2- and 24-h periods and annealed at 50°C. Changes in morphological and optical properties between nanotubes of different infiltration times (2 and 24 h) as well as its thin films are observed. The longer infiltration time of 24 h produced nanotubes with enhanced morphological, structural, and optical properties. Nanotubes that are formed between 2 and 24 h of infiltration show enhancement in absorption, photoluminescence, and shift in Raman peak if compared to their thin films.

  16. Synthesis of NiO nanotubes for use as negative electrodes in lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Needham, S. A.; Wang, G. X.; Liu, H. K.

    Nickel oxide (NiO) nanotubes have been produced for the first time via a template processing method. The synthesis involved a two step chemical reaction in which nickel hydroxide (Ni(OH) 2) nanotubes were firstly formed within the walls of an anodic aluminium oxide (AAO) template. The template was then dissolved away using concentrated NaOH, and the freed nanotubes were converted to NiO by heat treatment in air at 350 °C. Individual nanotubes measured 60 μm in length with a 200 nm outer diameter and a wall thickness of 20-30 nm. The NiO nanotube powder was used in Li-ion cells for assessment of the lithium storage ability. Preliminary testing indicates that the cells demonstrate controlled and sustainable lithium diffusion after the formation of an SEI. Reversible capacities in the 300 mAh g -1 range were typical.

  17. TiO2 nanotube structures for enhanced cell and biological functionality

    NASA Astrophysics Data System (ADS)

    Brammer, Karla S.; Oh, Seunghan; Frandsen, Christine J.; Jin, Sungho

    2010-04-01

    Nanostructures have pronounced effects on biological processes such as growth of cells and their functionality. Advances in biomaterial surface structure and design have resulted in improved tissue engineering. Nanotechnology can be utilized for optimization of titanium implants with a formation of vertically aligned TiO2 nanotube arrays on the implant surface. The anodic oxidation of the titanium implant surface to form a TiO2 nanotube array involves electrochemical processes and self assembly. In this paper, the mechanism of nanotube formation, nanotube bio-characteristics, and their emerging role in soft and hard tissue engineering as well as in regenerative medicine will be reviewed, and the beneficial effects of surface nanotubes on cell adhesion, proliferation, and functionality will be discussed in relation to potential orthopedics applications.

  18. Carbon Nanotube Based Molecular Electronics and Motors: A View from Classical and Quantum Dynamics Simulations

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Saini, Subhash (Technical Monitor)

    1998-01-01

    The tubular forms of fullerenes popularly known as carbon nanotubes are experimentally produced as single-, multiwall, and rope configurations. The nanotubes and nanoropes have shown to exhibit unusual mechanical and electronic properties. The single wall nanotubes exhibit both semiconducting and metallic behavior. In short undefected lengths they are the known strongest fibers which are unbreakable even when bent in half. Grown in ropes their tensile strength is approximately 100 times greater than steel at only one sixth the weight. Employing large scale classical and quantum molecular dynamics simulations we will explore the use of carbon nanotubes and carbon nanotube junctions in 2-, 3-, and 4-point molecular electronic device components, dynamic strength characterization for compressive, bending and torsional strains, and chemical functionalization for possible use in a nanoscale molecular motor. The above is an unclassified material produced for non-competitive basic research in the nanotechnology area.

  19. Facile Synthesis of Highly Aligned Multiwalled Carbon Nanotubes from Polymer Precursors

    DOE PAGES

    Han, Catherine Y.; Xiao, Zhi-Li; Wang, H. Hau; Lin, Xiao-Min; Trasobares, Susana; Cook, Russell E.

    2009-01-01

    We report a facile one-step approach which involves no flammable gas, no catalyst, and no in situ polymerization for the preparation of well-aligned carbon nanotube array. A polymer precursor is placed on top of an anodized aluminum oxide (AAO) membrane containing regular nanopore arrays, and slow heating under Ar flow allows the molten polymer to wet the template through adhesive force. The polymer spread into the nanopores of the template to form polymer nanotubes. Upon carbonization the resulting multi-walled carbon nanotubes duplicate the nanopores morphology precisely. The process is demonstrated for 230, 50, and 20 nm pore membranes. The synthesized carbonmore » nanotubes are characterized with scanning/transmission electron microscopies, Raman spectroscopy, and resistive measurements. Convenient functionalization of the nanotubes with this method is demonstrated through premixing CoPt nanoparticles in the polymer precursors.« less

  20. Facile synthesis of highly aligned multiwalled carbon nanotubes from polymer precursors.

    SciTech Connect

    Han, C. Y.; Xiao, Z.-L.; Wang, H. H.; Lin, X.-M.; Trasobares, S.; Cook, R. E.; Richard J. Daley Coll.; Northern Illinois Univ.; Univ. de Cadiz

    2009-01-01

    We report a facile one-step approach which involves no flammable gas, no catalyst, and no in situ polymerization for the preparation of well-aligned carbon nanotube array. A polymer precursor is placed on top of an anodized aluminum oxide (AAO) membrane containing regular nanopore arrays, and slow heating under Ar flow allows the molten polymer to wet the template through adhesive force. The polymer spread into the nanopores of the template to form polymer nanotubes. Upon carbonization the resulting multi-walled carbon nanotubes duplicate the nanopores morphology precisely. The process is demonstrated for 230, 50, and 20 nm pore membranes. The synthesized carbon nanotubes are characterized with scanning/transmission electron microscopies, Raman spectroscopy, and resistive measurements. Convenient functionalization of the nanotubes with this method is demonstrated through premixing CoPt nanoparticles in the polymer precursors.

  1. Boron-double-ring sheet, fullerene, and nanotubes: potential hydrogen storage materials.

    PubMed

    Wang, Jing; Zhao, Hui-Yan; Liu, Ying

    2014-11-10

    Similar to carbon-based graphene, fullerenes and carbon nanotubes, boron atoms can form sheets, fullerenes, and nanotubes. Here we investigate several of these novel boron structures all based on the boron double ring within the framework of density functional theory. The boron sheet is found to be metallic and flat in its ground state. The spherical boron cage containing 180 atoms is also stable and has I symmetry. Stable nanotubes are obtained by rolling up the boron sheet, and all are metallic. The hydrogen storage capacity of boron nanostructures is also explored, and it is found that Li-decorated boron sheets and nanotubes are potential candidates for hydrogen storage. For Li-decorated boron sheets, each Li atom can adsorb a maximum of 4 H2 molecules with g(d) =7.892 wt %. The hydrogen gravimetric density increases to g(d) =12.309 wt % for the Li-decorated (0,6) boron nanotube.

  2. Magnetic studies of polystyrene/iron-filled multi-wall carbon nanotube composite films

    NASA Astrophysics Data System (ADS)

    Makarova, T. L.; Zakharchuk, I.; Geydt, P.; Lahderanta, E.; Komlev, A. A.; Zyrianova, A. A.; Kanygin, M. A.; Sedelnikova, O. V.; Suslyaev, V. I.; Bulusheva, L. G.; Okotrub, A. V.

    2016-10-01

    Polystyrene/iron-filled multi-wall carbon nanotube composite films were prepared by solution processing, forge-rolling and stretching methods. Elongated iron carbide nanoparticles formed because of catalytic growth are situated inside the hollow cavity of the nanotubes. Magnetic susceptibility measurements as well as records of isothermal hysteresis loops performed in three perpendicular directions of magnetic field confirmed that the nanotubes have a preferential alignment in the matrix. Strong diamagnetic anisotropy in the composites emerges not only from the MWCNTs but also from the polystyrene matrix. The polymer sticks to the honeycomb lattice through the interaction of the π-orbitals of the phenyl ring and those of the carbon nanotube, contributing to anisotropic diamagnetic response. The contribution of iron nanoparticles to overall magnetic response strongly depends on nanotube concentration in the composite as well as on matrix-filler non-covalent stacking, which influences magnetic interparticle interactions.

  3. ABC triblock terpolymer self-assembled core-shell-corona nanotubes with high aspect ratios.

    PubMed

    Wang, Lulu; Huang, Haiying; He, Tianbai

    2014-08-01

    Nanotubes have attracted considerable attention due to their unique 1D hollow structure; however, the fabrication of pure nanotubes via block copolymer self-assembly remains a challenge. In this work, the successful preparation of core-shell-corona (CSC) nanotubular micelles with uniform diameter and high aspect ratio is reported, which is achieved via self-assembly of a poly (styrene-b-4-vinyl pyridine-b-ethylene oxide) triblock terpolymer in binary organic solvents with assistance of solution thermal annealing. Via direct visualization of trapped intermediates, the nanotube is believed to be formed via large sphere-large solid cylinderical aggregates-nanotube transformations, wherein the unique solid to hollow transition accompanied with the unidirectional growth is distinct from conventional pathway. In addition, by virtue of the CSC structure, gold nanoparticles are able to be selectively incorporated into different micellar domains of the nanotubes, which may have potential applications in nanoscience and nanotechnology.

  4. Peptide secondary structure modulates single-walled carbon nanotube fluorescence as a chaperone sensor for nitroaromatics

    PubMed Central

    Heller, Daniel A.; Pratt, George W.; Zhang, Jingqing; Nair, Nitish; Hansborough, Adam J.; Boghossian, Ardemis A.; Reuel, Nigel F.; Barone, Paul W.; Strano, Michael S.

    2011-01-01

    A class of peptides from the bombolitin family, not previously identified for nitroaromatic recognition, allows near-infrared fluorescent single-walled carbon nanotubes to transduce specific changes in their conformation. In response to the binding of specific nitroaromatic species, such peptide–nanotube complexes form a virtual “chaperone sensor,” which reports modulation of the peptide secondary structure via changes in single-walled carbon nanotubes, near-infrared photoluminescence. A split-channel microscope constructed to image quantized spectral wavelength shifts in real time, in response to nitroaromatic adsorption, results in the first single-nanotube imaging of solvatochromic events. The described indirect detection mechanism, as well as an additional exciton quenching-based optical nitroaromatic detection method, illustrate that functionalization of the carbon nanotube surface can result in completely unique sites for recognition, resolvable at the single-molecule level. PMID:21555544

  5. Carbon nanotubes on nanoporous alumina: from surface mats to conformal pore filling

    PubMed Central

    2014-01-01

    Control over nucleation and growth of multi-walled carbon nanotubes in the nanochannels of porous alumina membranes by several combinations of posttreatments, namely exposing the membrane top surface to atmospheric plasma jet and application of standard S1813 photoresist as an additional carbon precursor, is demonstrated. The nanotubes grown after plasma treatment nucleated inside the channels and did not form fibrous mats on the surface. Thus, the nanotube growth mode can be controlled by surface treatment and application of additional precursor, and complex nanotube-based structures can be produced for various applications. A plausible mechanism of nanotube nucleation and growth in the channels is proposed, based on the estimated depth of ion flux penetration into the channels. PACS 63.22.Np Layered systems; 68. Surfaces and interfaces; Thin films and nanosystems (structure and non-electronic properties); 81.07.-b Nanoscale materials and structures: fabrication and characterization PMID:25177216

  6. Laser irradiation of carbon nanotube films: Effects and heat dissipation probed by Raman spectroscopy

    SciTech Connect

    Mialichi, J. R.; Brasil, M. J. S. P.; Iikawa, F.; Verissimo, C.; Moshkalev, S. A.

    2013-07-14

    We investigate the thermal properties of thin films formed by single- and multi-walled carbon nanotubes submitted to laser irradiation using Raman scattering as a probe of both the tube morphology and the local temperature. The nanotubes were submitted to heating/cooling cycles attaining high laser intensities ({approx}1.4 MW/cm{sup 2}) under vacuum and in the presence of an atmosphere, with and without oxygen. We investigate the heat diffusion of the irradiated nanotubes to their surroundings and the effect of laser annealing on their properties. The presence of oxygen during laser irradiation gives rise to an irreversible increase of the Raman efficiency of the carbon nanotubes and to a remarkable increase of the thermal conductivity of multi-walled films. The second effect can be applied to design thermal conductive channels in devices based on carbon nanotube films using laser beams.

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

    PubMed

    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.

  8. Carbon nanotube Archimedes screws.

    PubMed

    Oroszlány, László; Zólyomi, Viktor; Lambert, Colin J

    2010-12-28

    Recently, nanomechanical devices composed of a long stationary inner carbon nanotube and a shorter, slowly rotating outer tube have been fabricated. In this paper, we study the possibility of using such devices as nanoscale transducers of motion into electricity. When the outer tube is chiral, we show that such devices act like quantum Archimedes screws, which utilize mechanical energy to pump electrons between reservoirs. We calculate the pumped charge from one end of the inner tube to the other, driven by the rotation of a chiral outer nanotube. We show that the pumped charge can be greater than one electron per 360° rotation, and consequently, such a device operating with a rotational frequency of 10 MHz, for example, would deliver a current of ≈1 pAmp.

  9. Engineering carbon nanotubes and nanotube circuits using electrical breakdown.

    PubMed

    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 plane fastener

    NASA Astrophysics Data System (ADS)

    Hirahara, Kaori; Ajioka, Shoichi; Nakayama, Yoshikazu

    2011-12-01

    We report a feature of carbon nanotubes (CNTs) that arises when the surfaces of two vertically-aligned CNT brushes are pressed together. Adhesion between the CNTs creates a plane fastener-like device. Observations from scanning electron microscopy and measurements of adhesion properties indicate a device-dependence on CNT density and shape near the tip region. Among other applications, such fasteners have the potential to attach small components onto micron-sized electronic devices.

  11. Carbon nanotube network varactor

    NASA Astrophysics Data System (ADS)

    Generalov, A. A.; Anoshkin, I. V.; Erdmanis, M.; Lioubtchenko, D. V.; Ovchinnikov, V.; Nasibulin, A. G.; Räisänen, A. V.

    2015-01-01

    Microelectromechanical system (MEMS) varactors based on a freestanding layer of single-walled carbon nanotube (SWCNT) films were designed, fabricated and tested. The freestanding SWCNT film was employed as a movable upper patch in the parallel plate capacitor of the MEMS. The measurements of the SWCNT varactors show very high tunability, nearly 100%, of the capacitance with a low actuation voltage of 10 V. The functionality of the varactor is improved by implementing a flexible nanocellulose aerogel filling.

  12. Carbon nanotube network varactor.

    PubMed

    Generalov, A A; Anoshkin, I V; Erdmanis, M; Lioubtchenko, D V; Ovchinnikov, V; Nasibulin, A G; Räisänen, A V

    2015-01-30

    Microelectromechanical system (MEMS) varactors based on a freestanding layer of single-walled carbon nanotube (SWCNT) films were designed, fabricated and tested. The freestanding SWCNT film was employed as a movable upper patch in the parallel plate capacitor of the MEMS. The measurements of the SWCNT varactors show very high tunability, nearly 100%, of the capacitance with a low actuation voltage of 10 V. The functionality of the varactor is improved by implementing a flexible nanocellulose aerogel filling.

  13. Hydrogen bond and halogen bond inside the carbon nanotube

    NASA Astrophysics Data System (ADS)

    Wang, Weizhou; Wang, Donglai; Zhang, Yu; Ji, Baoming; Tian, Anmin

    2011-02-01

    The hydrogen bond and halogen bond inside the open-ended single-walled carbon nanotubes have been investigated theoretically employing the newly developed density functional M06 with the suitable basis set and the natural bond orbital analysis. Comparing with the hydrogen or halogen bond in the gas phase, we find that the strength of the hydrogen or halogen bond inside the carbon nanotube will become weaker if there is a larger intramolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom donor to the antibonding orbital of the X-H or X-Hal bond involved in the formation of the hydrogen or halogen bond and will become stronger if there is a larger intermolecular electron-density transfer from the electron-rich region of the hydrogen or halogen atom acceptor to the antibonding orbital of the X-H or X-Hal bond. According to the analysis of the molecular electrostatic potential of the carbon nanotube, the driving force for the electron-density transfer is found to be the negative electric field formed in the carbon nanotube inner phase. Our results also show that the X-H bond involved in the formation of the hydrogen bond and the X-Hal bond involved in the formation of the halogen bond are all elongated when encapsulating the hydrogen bond and halogen bond within the carbon nanotube, so the carbon nanotube confinement may change the blue-shifting hydrogen bond and the blue-shifting halogen bond into the red-shifting hydrogen bond and the red-shifting halogen bond. The possibility to replace the all electron nanotube-confined calculation by the simple polarizable continuum model is also evaluated.

  14. Combining portable Raman probes with nanotubes for theranostic applications.

    PubMed

    Bhirde, Ashwinkumar A; Liu, Gang; Jin, Albert; Iglesias-Bartolome, Ramiro; Sousa, Alioscka A; Leapman, Richard D; Gutkind, J Silvio; Lee, Seulki; Chen, Xiaoyuan

    2011-01-01

    Recently portable Raman probes have emerged along with a variety of applications, including carbon nanotube (CNT) characterization. Aqueous dispersed CNTs have shown promise for biomedical applications such as drug/gene delivery vectors, photo-thermal therapy, and photoacoustic imaging. In this study we report the simultaneous detection and irradiation of carbon nanotubes in 2D monolayers of cancer cells and in 3D spheroids using a portable Raman probe. A portable handheld Raman instrument was utilized for dual purposes: as a CNT detector and as an irradiating laser source. Single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) were dispersed aqueously using a lipid-polymer (LP) coating, which formed highly stable dispersions both in buffer and cell media. The LP coated SWCNT and MWCNT aqueous dispersions were characterized by atomic force microscopy, transmission electron microscopy, dynamic light scattering, Fourier transform infrared spectroscopy and Raman spectroscopy. The cellular uptake of the LP-dispersed SWCNTs and MWCNTs was observed using confocal microscopy, and fluorescein isothiocyanate (FITC)-nanotube conjugates were found to be internalized by ovarian cancer cells by using Z-stack fluorescence confocal imaging. Biocompatibility of SWCNTs and MWCNTs was assessed using a cell viability MTT assay, which showed that the nanotube dispersions did not hinder the proliferation of ovarian cancer cells at the dosage tested. Ovarian cancer cells treated with SWCNTs and MWCNTs were simultaneously detected and irradiated live in 2D layers of cancer cells and in 3D environments using the portable Raman probe. An apoptotic terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay carried out after laser irradiation confirmed that cell death occurred only in the presence of nanotube dispersions. We show for the first time that both SWCNTs and MWCNTs can be selectively irradiated and detected in cancer cells using a simple

  15. Controlled fabrication of porous double-walled TiO2 nanotubes via ultraviolet-assisted anodization.

    PubMed

    Ali, Ghafar; Kim, Hyun Jin; Kim, Jae Joon; Cho, Sung Oh

    2014-04-01

    Double-walled TiO2 nanotubes with porous wall morphologies are fabricated by anodization under ultraviolet (UV) irradiation. TiO2 formed by anodization of Ti is activated to generate electrons and holes by UV and the anodization process is influenced by the photo-generated charges. As a consequence, morphologies of the fabricated TiO2 nanotubes can be adjusted by controlling the UV illumination. Double-walled TiO2 nanotubes or single-walled nanotubes can be selectively formed by switching on/off the UV illumination. The thickness of the inner and outer walls of the double-walled nanotubes can be tailored by changing the UV power. Due to their larger surface areas compared to single-walled nanotubes, the porous double-walled nanotubes exhibit an enhanced photo-degradation rate for methylene blue (MB). The mechanism of the porous double-walled TiO2 nanotubes is proposed based on the photoactive semiconducting property of the as-growing TiO2 nanotubes under UV.

  16. Interfaces Between Carbon Nanotubes and Nickel Nanoparticles in Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Liu, Bai; Liu, Lirui

    2013-12-01

    Carbon nanotubes (CNTs) filled with metals can be used in capacitors, sensors, rechargeable batteries, and so on. Their interface significantly affects the properties of the composites. Here, we show that three kinds of interfaces between crystalline Ni and CNTs exist, namely, ordered, distorted, and disordered. They presented lattice states of Ni atoms near the interface, whereas the (111)Ni plane was parallel to the CNTs' surface and appeared apart in a smaller or bigger angle. The coherent face-centered cubic (f.c.c)/hexagonal close-packed structure (h.c.p) boundary was formed between the crystalline Ni and CNTs at the ordered interface, in which the match was (111)Ni//(0001)Carbon. We suggested a dislocation model for the coherent interface. The model explained why the angle between (200)Ni and the CNTs' inner surface was 52.9° rather than the theoretical value of 54.75°. The (1)/(2)[11\\bar {1}] dislocation was formed to fit the coherent relationship. Thus, Ni lattice shrinkage occurred. Further study indicated that the formation mechanism of crystalline Ni in CNTs was through heterogeneous nucleation on the inner wall surface and growth of the crystal nucleus.

  17. An efficient growth of silver and copper nanoparticles on multiwalled carbon nanotube with enhanced antimicrobial activity.

    PubMed

    Mohan, Raja; Shanmugharaj, A M; Sung Hun, Ryu

    2011-01-01

    Transition metal nanoparticles (NPs) such as silver (Ag) and copper (Cu) have been grafted onto carbon nanotube surface through wet chemical approach leading to the development of densely packed NP decorated carbon nanotubes. Chemically active surface and high-temperature stability are the basic attributes to use carbon nanotubes as the template for the growth of NPs. Ag NP-grafted carbon nanotubes (Ag-MWCNT) are prepared by complexing Ag ion with acid functionalized carbon nanotubes followed by the reduction method. Alternatively, Cu-grafted carbon nanotubes (Cu-MWCNT) are prepared by simple chemical reduction method. X-ray diffraction results reveal that the Ag or Cu NPs formed on the surface of carbon nanotubes are determined to be face centered cubic crystals. The morphology and chemical structure of NP-grafted carbon nanotubes are investigated using transmission electron spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The antimicrobial properties of acid-treated MWCNT (MWCNT-COOH), Ag-MWCNT, and Cu-MWCNT are investigated against gram negative Escherichia coli bacteria. Ag-MWCNT and Cu-MWCNT (97% kill vs. 75% kill), whereas MWCNT-COOH only killed 20% of this bacteria. Possible mechanisms are proposed to explain the higher antimicrobial activity by NP-coated MWCNT. These findings suggest that Ag-MWCNT and Cu-MWCNT may be used as effective antimicrobial materials that find applications in biomedical devices and antibacterial controlling system.

  18. Impact of confinement on proteins concentrated in lithocholic acid based organic nanotubes.

    PubMed

    Lu, Qin; Kim, Youngchan; Bassim, Nabil; Collins, Greg E

    2015-09-15

    Organic nanotubes form in aqueous solution near physiological pH by self-assembly of lithocholic acid (LCA) with inner diameters of 20-40nm. The encapsulation of enhanced green fluorescent protein (eGFP) and resultant confinement effect for eGFP within these nanotubes is studied via confocal microscopy. Timed release rate studies of eGFP encapsulated in LCA nanotubes and fluorescence recovery after photobleaching (FRAP) indicate that the diffusive transport of eGFP out of and/or within the nanotubes is very slow, in contrast to the rapid introduction of eGFP into the nanotubes. By encapsulating two fluorescent proteins in LCA nanotubes, eGFP and mCherry, as a fluorescence resonance energy transfer (FRET) pair, the FRET efficiencies are determined using FRET imaging microscopy at three different protein concentrations with a fixed donor-to-acceptor ratio of 1:1. Förster theory reveals that the proteins are spatially separated by 4.8-7.2nm in distance inside these nanotubes. The biomimetic nanochannels of LCA nanotubes not only afford a confining effect on eGFP that results in enhanced chemical and thermal stability under conditions of high denaturant concentration and temperature, but also function as protein concentrators for enriching protein in the nanochannels from a diluted protein solution by up to two orders of magnitude.

  19. Self-assembly of Amphiphilic Nanotubes and Lipids into Synthetic Vehicles: Computer Simulation Study

    NASA Astrophysics Data System (ADS)

    Dutt, Meenakshi; Kuksenok, Olga; Little, Steven; Balazs, Anna C.

    2010-03-01

    Via Dissipative Particle Dynamics (DPD) approach, we study the self-assembly of amphiphilic nanotubes and lipids immersed into a hydrophilic solvent. Each nanotube encompasses an ABA triblock architecture, with a hydrophobic stalk and two hydrophilic ends. Individual lipids are composed of a hydrophilic head group and two hydrophobic tails. We show that an energetically unfavorable interaction between the solvent and the hydrophobic segments of the nanotube and the lipids drive them to self-assemble so as to shield the hydrophobic entities from the hydrophilic solvent. The equilibrium self-assembled structures formed depend upon the concentrations of the lipids and nanotubes, the hydrophobic fraction of the nanotube, the degree of hydrophobic mismatch between the nanotube and the bilayer, and the presence of hydrophilic end-tethers. We isolate the conditions that promote the formation of specific equilibrium self-assembled structures. The simulations are supported by free energy calculations for the amphiphilic nanotube-lipid-solvent system. Ultimately, these self-assembled structures of nanotube-lipid systems can be used for making hybrid control release vehicles.

  20. Controlled growth of carbon nanotubes.

    PubMed

    Vajtai, R; Wei, B Q; Ajayan, P M

    2004-10-15

    Carbon nanotubes have extraordinary mechanical and electronic properties and hold great promise for future applications. The most important aspects of this structure are its low density, high aspect ratio, one dimensionality, high mechanical strength and high electrical and thermal conductivity. We present a short, state-of-the-art account of tailored nanotube growth. To provide these properties in real devices there exists a need for producing nanotubes on substrates. The challenge in the creation of mesoscale nanotube-based architectures and tailored nanotube networks consisting of thousands of tubes in a predefined order is obviously great. Currently, chemical vapour deposition (CVD) appears to be the most powerful method for achieving such required structures. We describe our work on a new synthesis method, based on catalytic CVD using mainly gas-phase catalyst delivery. Gas-phase catalyst delivery allows us to assemble single-walled and multi-walled carbon nanotubes in predetermined multiple orientations on substrates to build one- to three-dimensional architectures. We are able to control, to a large extent, the types of nanotubes produced, their lengths, locations and their orientations. The ability to make mesoscale architectures with nanotubes should lead us to develop applications in areas such as nano-electromechanical systems.

  1. All About Chlorinated Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Erbahar, Dogan; Berber, Savas

    2011-03-01

    The halogens are viable alternatives to harsher chemicals in the post-process of purification of carbon nanotube production. However the chlorine is known to bind less agresively to carbon nanotubes than fluorine and hydrogen. Therefore, in principle the residual Cl left after the halogen gas treatment of the nanotubes can be removed without damaging the nanotube walls easier. We report ab initio density functional calculation results about pure and defective carbon nanotubes of various diameters interacting with single and multiple chlorine atoms. We first focus on pure nanotubes and investigate the adsorption of additional Cl atoms near the first adsorbtion site, investigate the clustering tendency and most favourable configurations. We report the energetics results as well as the alteration of electronic properties. We then focus on monovacancy and divacancy defects on carbon nanotubes. It is a known fact that the defective site to be more active in this case. We apply the same procedure as in the pure nanotubes but also investigate the effect of chlorination on reconstruction process and also electronic transport properties. Supported by TUBITAK Grant No 108T740.

  2. Robust liquid marbles stabilized with surface-modified halloysite nanotubes.

    PubMed

    Wu, Hui; Watanabe, Hirohmi; Ma, Wei; Fujimoto, Aya; Higuchi, Takeshi; Uesugi, Kentaro; Takeuchi, Akihisa; Suzuki, Yoshio; Jinnai, Hiroshi; Takahara, Atsushi

    2013-12-01

    We have demonstrated the fabrication of fluorine-free liquid marbles from halloysite nanotube. Halloysite is a naturally occurring inorganic nanotube that has a high aspect ratio, and the surface was modified with octadecyltrimethoxysilane. The surface-modified halloysite formed pincushion agglomerates on the surface of the liquid droplets, which create superhydrophobic surface similar to that of the plant gall surface prepared by aphids. As a result, the liquid marbles showed high mechanical strength upon impact without the use of low surface energy fluoroalkyl or fluorine-modified materials. Our results suggest a new strategy for designing novel materials for liquid marbles inspired by nature.

  3. Functional One-Dimensional Lipid Bilayers on Carbon Nanotube Templates

    SciTech Connect

    Artyukhin, A; Shestakov, A; Harper, J; Bakajin, O; Stroeve, P; Noy, A

    2004-07-23

    We present one-dimensional (1-D) lipid bilayer structures that integrate carbon nanotubes with a key biological environment-phospholipid membrane. Our structures consist of lipid bilayers wrapped around carbon nanotubes modified with a hydrophilic polymer cushion layer. Despite high bilayer curvature, the lipid membrane maintains its fluidity and can sustain repeated damage-recovery cycles. We also present the first evidence of spontaneous insertion of pore-forming proteins into 1-D lipid bilayers. These structures could lead to the development of new classes of biosensors and bioelectronic devices.

  4. Ceramic nanotubes for polymer composites with stable anticorrosion properties

    NASA Astrophysics Data System (ADS)

    Fakhrullin, R. F.; Tursunbayeva, A.; Portnov, V. S.; L'vov, Yu. M.

    2014-12-01

    The use of natural halloysite clay tubes 50 nm in diameter as nanocontainers for loading, storing, and slowly releasing organic corrosion inhibitors is described. Loaded nanotubes can be mixed well with many polymers and dyes in amounts of 5-10 wt % to form a ceramic framework (which increases the strength of halloysite composites by 30-50%), increase the adhesion of these coatings to metals, and allow for the slow release of corrosion inhibitors in defects of coatings. A significant improvement of protective anticorrosion properties of polyacryl and polyurethane coatings containing ceramic nanotubes loaded with benzotriazole and hydroxyquinoline is demonstrated.

  5. Nanotubes for noisy signal processing

    NASA Astrophysics Data System (ADS)

    Lee, Ian Yenyin

    Nanotubes can process noisy signals. We present two central results in support of this general thesis and make an informed extrapolation that uses nanotubes to improve body armor. The first result is that noise can help nanotubes detect weak signals. The finding confirmed a stochastic-resonance theoretical prediction that noise can enhance detection at the nano-level. Laboratory experiments with nanotubes showed that three types of noise improved three measures of detection. Small amounts of Gaussian, uniform, and Cauchy additive white noise increased mutual-information, cross-correlation, and bit-error-rate measures before degrading them with further increases in noise. Nanotubes can apply this noise-enhancement and nanotube electrical and mechanical properties to improve signal processing. Similar noise enhancement may benefit a proposed nanotube-array cochlear-model spectral processing. The second result is that nanotube antennas can directly detect narrowband electromagnetic (EM) signals. The finding showed that nanotube and thin-wire dipoles are similar: They are resonant and narrowband and can implement linear-array designs if the EM waves in the nanotubes propagate at or near the free-space velocity of light. The nanotube-antenna prediction is based on a Fresnel-zone or near-zone analysis of antenna impedance using a quantum-conductor model. The analysis also predicts a failure to resonate if the nanotube EM-wave propagation is much slower than free-space light propagation. We extrapolate based on applied and theoretical analysis of body armor. Field experiments used a baseball comparison and statistical and other techniques to model body-armor bruising effects. A baseball comparison showed that a large caliber handgun bullet can hit an armored chest as hard as a fast baseball can hit a bare chest. Adaptive fuzzy systems learned to predict a bruise profile directly from the experimental data and also from statistical analysis of the data. Nanotube signal

  6. From carbon nanotubes to carbon atomic chains

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

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

  7. Physical removal of metallic carbon nanotubes from nanotube network devices using a thermal and fluidic process.

    PubMed

    Ford, Alexandra C; Shaughnessy, Michael; Wong, Bryan M; Kane, Alexander A; Kuznetsov, Oleksandr V; Krafcik, Karen L; Billups, W Edward; Hauge, Robert H; Léonard, François

    2013-03-15

    Electronic and optoelectronic devices based on thin films of carbon nanotubes are currently limited by the presence of metallic nanotubes. Here we present a novel approach based on nanotube alkyl functionalization to physically remove the metallic nanotubes from such network devices. The process relies on preferential thermal desorption of the alkyls from the semiconducting nanotubes and the subsequent dissolution and selective removal of the metallic nanotubes in chloroform. The approach is versatile and is applied to devices post-fabrication.

  8. Bioactive Titanate Layers Formed on Titanium and Its Alloys by Simple Chemical and Heat Treatments

    PubMed Central

    Kokubo, Tadashi; Yamaguchi, Seiji

    2015-01-01

    To reveal general principles for obtaining bone-bonding bioactive metallic titanium, Ti metal was heat-treated after exposure to a solution with different pH. The material formed an apatite layer at its surface in simulated body fluid when heat-treated after exposure to a strong acid or alkali solution, because it formed a positively charged titanium oxide and negatively charged sodium titanate film on its surface, respectively. Such treated these Ti metals tightly bonded to living bone. Porous Ti metal heat-treated after exposure to an acidic solution exhibited not only osteoconductive, but also osteoinductive behavior. Porous Ti metal exposed to an alkaline solution also exhibits osteoconductivity as well as osteoinductivity, if it was subsequently subjected to acid and heat treatments. These acid and heat treatments were not effective for most Ti-based alloys. However, even those alloys exhibited apatite formation when they were subjected to acid and heat treatment after a NaOH treatment, since the alloying elements were removed from the surface by the latter. The NaOH and heat treatments were also not effective for Ti-Zr-Nb-Ta alloys. These alloys displayed apatite formation when subjected to CaCl2 treatment after NaOH treatment, forming Ca-deficient calcium titanate at their surfaces after subsequent heat and hot water treatments. The bioactive Ti metal subjected to NaOH and heat treatments has been clinically used as an artificial hip joint material in Japan since 2007. A porous Ti metal subjected to NaOH, HCl and heat treatments has successfully undergone clinical trials as a spinal fusion device. PMID:25893014

  9. Bioactive titanate layers formed on titanium and its alloys by simple chemical and heat treatments.

    PubMed

    Kokubo, Tadashi; Yamaguchi, Seiji

    2015-01-01

    To reveal general principles for obtaining bone-bonding bioactive metallic titanium, Ti metal was heat-treated after exposure to a solution with different pH. The material formed an apatite layer at its surface in simulated body fluid when heat-treated after exposure to a strong acid or alkali solution, because it formed a positively charged titanium oxide and negatively charged sodium titanate film on its surface, respectively. Such treated these Ti metals tightly bonded to living bone. Porous Ti metal heat-treated after exposure to an acidic solution exhibited not only osteoconductive, but also osteoinductive behavior. Porous Ti metal exposed to an alkaline solution also exhibits osteoconductivity as well as osteoinductivity, if it was subsequently subjected to acid and heat treatments. These acid and heat treatments were not effective for most Ti-based alloys. However, even those alloys exhibited apatite formation when they were subjected to acid and heat treatment after a NaOH treatment, since the alloying elements were removed from the surface by the latter. The NaOH and heat treatments were also not effective for Ti-Zr-Nb-Ta alloys. These alloys displayed apatite formation when subjected to CaCl2 treatment after NaOH treatment, forming Ca-deficient calcium titanate at their surfaces after subsequent heat and hot water treatments. The bioactive Ti metal subjected to NaOH and heat treatments has been clinically used as an artificial hip joint material in Japan since 2007. A porous Ti metal subjected to NaOH, HCl and heat treatments has successfully undergone clinical trials as a spinal fusion device.

  10. Electronic Structure and Properties of Deformed Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Yang, Liu; Arnold, Jim (Technical Monitor)

    2001-01-01

    A theoretical framework based on Huckel tight-binding model has been formulated to analyze the electronic structure of carbon nanotubes under uniform deformation. The model successfully quantifies the dispersion relation, density of states and bandgap change of nanotubes under uniform stretching, compression, torsion and bending. Our analysis shows that the shifting of the Fermi point away from the Brillouin zone vertices is the key reason for these changes. As a result of this shifting, the electronic structure of deformed carbon nanotubes varies dramatically depending on their chirality and deformation mode. Treating the Fermi point as a function of strain and tube chirality, the analytical solution preserves the concise form of undeformed carbon nanotubes. It predicts the shifting, merging and splitting of the Van Hove singularities in the density of states and the zigzag pattern of bandgap change under strains. Four orbital tight-binding simulations of carbon nanotubes under uniform stretching, compression, torsion and bending have been performed to verify the analytical solution. Extension to more complex systems are being performed to relate this analytical solution to the spectroscopic characterization, device performance and proposed quantum structures induced by the deformation. The limitations of this model will also be discussed.

  11. Fabrication and structural characterization of highly ordered titania nanotube arrays

    NASA Astrophysics Data System (ADS)

    Shi, Hongtao; Ordonez, Rosita

    Titanium (Ti) dioxide nanotubes have drawn much attention in the past decade due to the fact that titania is an extremely versatile material with a variety of technological applications. Anodizing Ti in different electrolytes has proved to be quite successful so far in creating the nanotubes, however, their degree of order is still not nearly as good as nanoporous anodic alumina. In this work, we first deposit a thin layer of aluminum (Al) onto electropolished Ti substrates, using thermal evaporation. Such an Al layer is then anodized in 0.3 M oxalic acid, forming an ordered nanoporous alumina mask on top of Ti. Afterwards, the anodization of Ti is accomplished at 20 V in solutions containing 1 M NaH2PO4 and 0.5% HF or H2SO4, which results in the creation of ordered titania nanotube arrays. The inner pore diameter of the nanotubes can be tuned from ~50 nm to ~75 nm, depending on the anodization voltage applied to Al or Ti. X-ray diffractometry shows the as-grown titania nanotubes are amorphous. Samples annealed at different temperatures in ambient atmosphere will be also reported.

  12. More About Arc-Welding Process for Making Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Benavides, Jeanette M.; Leidecker, Henning

    2005-01-01

    High-quality batches of carbon nanotubes are produced at relatively low cost in a modified atmospheric-pressure electric-arc welding process that does not include the use of metal catalysts. What would normally be a welding rod and a weldment are replaced by an amorphous carbon anode rod and a wider, hollow graphite cathode rod. Both electrodes are water-cooled. The cathode is immersed in ice water to about 0.5 cm from the surface. The system is shielded from air by flowing helium during arcing. As the anode is consumed during arcing at 20 to 25 A, it is lowered to maintain it at an approximately constant distance above the cathode. The process causes carbon nanotubes to form on the lowest 5 cm of the anode. The arcing process is continued until the anode has been lowered to a specified height. The nanotube-containing material is then harvested. The additional information contained in the instant report consists mostly of illustrations of carbon nanotubes and a schematic diagram of the arc-welding setup, as modified for the production of carbon nanotubes.

  13. Nanofluids containing multiwalled carbon nanotubes and their enhanced thermal conductivities

    NASA Astrophysics Data System (ADS)

    Xie, Huaqing; Lee, Hohyun; Youn, Wonjin; Choi, Mansoo

    2003-10-01

    Multiwalled carbon nanotubes (CNTs) as produced are usually entangled and not ready to be dispersed into fluids. We treated CNTs by using a concentrated nitric acid to disentangle CNT aggregates for producing CNT nanofluids. Oxygen-containing functional groups have been introduced on the CNT surfaces and more hydrophilic surfaces have been formed during this treatment, which enabled to make stable and homogeneous CNT nanofluids. Treated CNTs were successfully dispersed into polar liquids like distilled water, ethylene glycol without the need of surfactant and into nonpolar fluid like decene with oleylamine as surfactant. We measured the thermal conductivities of these nanotube suspensions using a transient hot wire apparatus. Nanotube suspensions, containing a small amount of CNTs, have substantially higher thermal conductivities than the base fluids, with the enhancement increasing with the volume fraction of CNTs. For the suspensions with the same loading, the enhanced thermal conductivity ratios are reduced with the increasing thermal conductivity of the base fluid. Comparison between the experimental data and the theoretical model indicates that the thermal conductivities of nanotube suspensions seem to be very dependent on the interfacial layer that exists between the nanotube and the liquid.

  14. Carbon nanotubes: properties, synthesis, purification, and medical applications

    PubMed Central

    2014-01-01

    Current discoveries of different forms of carbon nanostructures have motivated research on their applications in various fields. They hold promise for applications in medicine, gene, and drug delivery areas. Many different production methods for carbon nanotubes (CNTs) have been introduced; functionalization, filling, doping, and chemical modification have been achieved, and characterization, separation, and manipulation of individual CNTs are now possible. Parameters such as structure, surface area, surface charge, size distribution, surface chemistry, and agglomeration state as well as purity of the samples have considerable impact on the reactivity of carbon nanotubes. Otherwise, the strength and flexibility of carbon nanotubes make them of potential use in controlling other nanoscale structures, which suggests they will have a significant role in nanotechnology engineering. PMID:25170330

  15. Nanotube-Enabled Vesicle-Vesicle Communication: A Computational Model.

    PubMed

    Zhang, Liuyang; Wang, Xianqiao

    2015-07-01

    Cell-to-cell communications via the tunneling nanotubes or gap junction channels are vital for the development and maintenance of multicellular organisms. Instead of these intrinsic communication pathways, how to design artificial communication channels between cells remains a challenging but interesting problem. Here, we perform dissipative particle dynamics (DPD) simulations to analyze the interaction between rotational nanotubes (RNTs) and vesicles so as to provide a novel design mechanism for cell-to-cell communication. Simulation results have demonstrated that the RNTs are capable of generating local disturbance and promote vesicle translocation toward the RNTs. Through ligand pattern designing on the RNTs, we can find a suitable nanotube candidate with a specific ligand coating pattern for forming the RNT-vesicle network. The results also show that a RNT can act as a bridged channel between vesicles, which facilitates substance transfer. Our findings provide useful guidelines for the molecular design of patterned RNTs for creating a synthetic channel between cells. PMID:26266730

  16. Nanotube-Enabled Vesicle-Vesicle Communication: A Computational Model.

    PubMed

    Zhang, Liuyang; Wang, Xianqiao

    2015-07-01

    Cell-to-cell communications via the tunneling nanotubes or gap junction channels are vital for the development and maintenance of multicellular organisms. Instead of these intrinsic communication pathways, how to design artificial communication channels between cells remains a challenging but interesting problem. Here, we perform dissipative particle dynamics (DPD) simulations to analyze the interaction between rotational nanotubes (RNTs) and vesicles so as to provide a novel design mechanism for cell-to-cell communication. Simulation results have demonstrated that the RNTs are capable of generating local disturbance and promote vesicle translocation toward the RNTs. Through ligand pattern designing on the RNTs, we can find a suitable nanotube candidate with a specific ligand coating pattern for forming the RNT-vesicle network. The results also show that a RNT can act as a bridged channel between vesicles, which facilitates substance transfer. Our findings provide useful guidelines for the molecular design of patterned RNTs for creating a synthetic channel between cells.

  17. Ballasted and electrically steerable carbon nanotube field emitters

    NASA Astrophysics Data System (ADS)

    Cole, M. T.; Li, C.; Qu, K.; Zhang, Y.; Wang, B.; Pribat, D.; Milne, W. I.

    2012-09-01

    Here we present our on-going efforts toward the development of stable ballasted carbon nanotube-based field emitters employing hydrothermally synthesized zinc oxide nanowires and thin film silicon-on-insulator substrates. The semiconducting channel in each controllably limits the emission current thereby preventing detrimental burn-out of individual emitters that occurs due to unavoidable statistical variability in emitter characteristics, particularly in their length. Fabrication details and emitter characterization are discussed in addition to their field emission performance. The development of a beam steerable triode electron emitter formed from hexagonal carbon nanotube arrays with central focusing nanotube electrodes, is also described. Numerical ab-initio simulations are presented to account for the empirical emission characteristics. Our engineered ballasted emitters have shown some of the lowest reported lifetime variations (< 0.7%) with on-times of < 1 ms, making them ideally-suited for next-generation displays, environmental lighting and portable x-rays sources.

  18. Fluorescent single walled nanotube/silica composite materials

    DOEpatents

    Dattelbaum, Andrew M.; Gupta, Gautam; Duque, Juan G.; Doorn, Stephen K.; Hamilton, Christopher E.; DeFriend Obrey, Kimberly A.

    2013-03-12

    Fluorescent composites of surfactant-wrapped single-walled carbon nanotubes (SWNTs) were prepared by exposing suspensions of surfactant-wrapped carbon nanotubes to tetramethylorthosilicate (TMOS) vapor. Sodium deoxycholate (DOC) and sodium dodecylsulphate (SDS) were the surfactants. No loss in emission intensity was observed when the suspension of DOC-wrapped SWNTs were exposed to the TMOS vapors, but about a 50% decrease in the emission signal was observed from the SDS-wrapped SWNTs nanotubes. The decrease in emission was minimal by buffering the SDS/SWNT suspension prior to forming the composite. Fluorescent xerogels were prepared by adding glycerol to the SWNT suspensions prior to TMOS vapor exposure, followed by drying the gels. Fluorescent aerogels were prepared by replacing water in the gels with methanol and then exposing them to supercritical fluid drying conditions. The aerogels can be used for gas sensing.

  19. Working cycles of devices based on bistable carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Shklyaev, Oleg; Mockensturm, Eric; Crespi, Vincent; Carbon Nanotubes Collaboration

    2013-03-01

    Shape-changing nanotubes are an example of variable-shape sp2 carbon-based systems where the competition between strain and surface energies can be moderated by an externally controllable stimuli such as applied voltage, temperature, or pressure of gas encapsulated inside the tube. Using any of these stimuli one can transition a bistable carbon nanotube between the collapsed and inflated states and thus perform mechanical work. During the working cycle of such a device, energy from an electric or heat source is transferred to mechanical energy. Combinations of these stimuli allow the system to convert energy between different sources using the bistable shape-changing tube as a mediator. For example, coupling a bistable carbon nanotube to the heat and charge reservoirs can enable energy transfer between heat and electric forms. The developed theory can be extended to other nano-systems which change configurations in response to external stimuli.

  20. Highly Efficient Oxygen Reduction Electrocatalysts based on Winged Carbon Nanotubes

    PubMed Central

    Cheng, Yingwen; Zhang, Hongbo; Varanasi, Chakrapani V.; Liu, Jie

    2013-01-01

    Developing electrocatalysts with both high selectivity and efficiency for the oxygen reduction reaction (ORR) is critical for several applications including fuel cells and metal-air batteries. In this work we developed high performance electrocatalysts based on unique winged carbon nanotubes. We found that the outer-walls of a special type of carbon nanotubes/nanofibers, when selectively oxidized, unzipped and exfoliated, form graphene wings strongly attached to the inner tubes. After doping with nitrogen, the winged nanotubes exhibited outstanding activity toward catalyzing the ORR through the four-electron pathway with excellent stability and methanol/carbon monoxide tolerance. While the doped graphene wings with high active site density bring remarkable catalytic activity, the inner tubes remain intact and conductive to facilitate electron transport during electrocatalysis. PMID:24217312

  1. Density of states of helically symmetric boron carbon nitride nanotubes.

    PubMed

    Carvalho, A C M; Bezerra, C G; Lawlor, J A; Ferreira, M S

    2014-01-01

    Motivated by the existence of helical wrapping patterns in composite nanotube systems, in this work we study the effects of the helical incorporation of carbon atoms in boron nitride nanotubes. We consider the substitutional carbon atoms distributed in stripes forming helical patterns along the nanotube axis. The density of states and energy band gap were calculated adopting Green function formalism by using the Rubio-Sancho technique in order to solve the matrix Dyson equation. We report the effects of the helical atomic distribution of carbon atoms on the behaviour of the density of states and the energy band gap. In particular, we show that the electronic energy band gap displays a non-monotonical dependence on the helical pattern, oscillating as a function of the helical angle θ.

  2. Flavin-derived self-organization and chirality separation of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Ju, Sang-Yong

    2008-07-01

    Formed by rolling up a two-dimensional sheet of one or more layer of graphite, graphene, carbon nanotubes (SWNTs) are the marvel materials of modern materials science. They are phenomenally strong and stiff, and have the unusual property of being excellent conductors of heat along the tube's axis, but good thermal insulators across it. But it is their electrical characteristics that excite the most interest. Especially, single-walled carbon nanotube (SWNTs), formed by one layer of cylindrical graphene, has better physical properties over multi-walled carbon nanotubes (MWNTs) having over two layer of graphene. Depending on the precise way they are rolled up, which is defined by ( n,m) vector, SWNTs can be made into either metals or semiconductors. So far, SWNTs can generally only be fabricated in batches that vary widely, both in the diameter of the individual tubes and in the orientation of their graphene lattice relative to the tube axis, the property known as chirality. Separating out these various conformations is a challenging, but one that must be solved if nanotubes are ever to fulfill their electrifying potential in devices. This thesis presents that flavin-based helical self-assembly can impart multi degrees of SWNTs separation (i.e., metallicity, diameter, chirality, and handedness). As opening chapters for carbon nanotube and flavin derivative, Chapter 1 provide the introduction of carbon nanotubes, especially single-walled tubes, and the current state-of-the-art nanotube separation. Also, Chapter 1 presents a variety of naturally-occurring flavin derivatives, their redox behavior, and their biological utilization as cofactors for various proteins. Motivated by chemoluminescence of flavin mononucleotide (FMN, phosphorylated form of Vitamin B2) with bacterial luciferase, Chapter 2 discuss about the synthesis and covalent attachment of flavin mononucleotide (FMN, phosphorylated form of Vitamin B2) analogue to oxidized SWNTs. Along with nine step synthesis

  3. Formation of ordered ice nanotubes inside carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Koga, Kenichiro; Gao, G. T.; Tanaka, Hideki; Zeng, X. C.

    2001-08-01

    Following their discovery, carbon nanotubes have attracted interest not only for their unusual electrical and mechanical properties, but also because their hollow interior can serve as a nanometre-sized capillary, mould or template in material fabrication. The ability to encapsulate a material in a nanotube also offers new possibilities for investigating dimensionally confined phase transitions. Particularly intriguing is the conjecture that matter within the narrow confines of a carbon nanotube might exhibit a solid-liquid critical point beyond which the distinction between solid and liquid phases disappears. This unusual feature, which cannot occur in bulk material, would allow for the direct and continuous transformation of liquid matter into a solid. Here we report simulations of the behaviour of water encapsulated in carbon nanotubes that suggest the existence of a variety of new ice phases not seen in bulk ice, and of a solid-liquid critical point. Using carbon nanotubes with diameters ranging from 1.1nm to 1.4nm and applied axial pressures of 50MPa to 500MPa, we find that water can exhibit a first-order freezing transition to hexagonal and heptagonal ice nanotubes, and a continuous phase transformation into solid-like square or pentagonal ice nanotubes.

  4. Controlled Patterning and Growth of Single Wall and Multi-wall Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Delzeit, Lance D. (Inventor)

    2005-01-01

    Method and system for producing a selected pattern or array of at least one of a single wall nanotube and/or a multi-wall nanotube containing primarily carbon. A substrate is coated with a first layer (optional) of a first selected metal (e.g., Al and/or Ir) and with a second layer of a catalyst (e.g., Fe, Co, Ni and/or Mo), having selected first and second layer thicknesses provided by ion sputtering, arc discharge, laser ablation, evaporation or CVD. The first layer and/or the second layer may be formed in a desired non-uniform pattern, using a mask with suitable aperture(s), to promote growth of carbon nanotubes in a corresponding pattern. A selected heated feed gas (primarily CH4 or C2Hn with n=2 and/or 4) is passed over the coated substrate and forms primarily single wall nanotubes or multiple wall nanotubes, depending upon the selected feed gas and its temperature. Nanofibers, as well as single wall and multi-wall nanotubes, are produced using plasma-aided growth from the second (catalyst) layer. An overcoating of a selected metal or alloy can be deposited, over the second layer, to provide a coating for the carbon nanotubes grown in this manner.

  5. The formation of helical mesoporous silica nanotubes

    NASA Astrophysics Data System (ADS)

    Wan, Xiaobing; Pei, Xianfeng; Zhao, Huanyu; Chen, Yuanli; Guo, Yongmin; Li, Baozong; Hanabusa, Kenji; Yang, Yonggang

    2008-08-01

    Three chiral cationic gelators were synthesized. They can form translucent hydrogels in pure water. These hydrogels become highly viscous liquids under strong stirring. Mesoporous silica nanotubes with coiled pore channels in the walls were prepared using the self-assemblies of these gelators as templates. The mechanism of the formation of this hierarchical nanostructure was studied using transmission electron microscopy at different reaction times. The results indicated that there are some interactions between the silica source and the gelator. The morphologies of the self-assemblies of gelators changed gradually during the sol-gel transcription process. It seems that the silica source directed the organic self-assemblies into helical nanostructures.

  6. Magnesium doping of boron nitride nanotubes

    DOEpatents

    Legg, Robert; Jordan, Kevin

    2015-06-16

    A method to fabricate boron nitride nanotubes incorporating magnesium diboride in their structure. In a first embodiment, magnesium wire is introduced into a reaction feed bundle during a BNNT fabrication process. In a second embodiment, magnesium in powder form is mixed into a nitrogen gas flow during the BNNT fabrication process. MgB.sub.2 yarn may be used for superconducting applications and, in that capacity, has considerably less susceptibility to stress and has considerably better thermal conductivity than these conventional materials when compared to both conventional low and high temperature superconducting materials.

  7. Self-assembly of copper(II) ion-mediated nanotube and its supramolecular chiral catalytic behavior.

    PubMed

    Jin, Qingxian; Zhang, Li; Cao, Hai; Wang, Tianyu; Zhu, Xuefeng; Jiang, Jian; Liu, Minghua

    2011-11-15

    Self-assembly of several low-molecular-weight L-glutamic acid-based gelators, which individually formed helical nanotube or nanofiber structures, was investigated in the presence of Cu(2+) ion. It was found that, when Cu(2+) was added into the system, the self-assembly manner changed significantly. Only in the case of bolaamphiphilic glutamic acid, N,N'-hexadecanedioyl-di-L-glutamic acid (L-HDGA), were the hydrogel formation as well as the nanotube structures maintained. The addition of Cu(2+) ion caused a transition from monolayer nanotube of L-HDGA to a multilayer nanotube with the thickness of the tubular wall about 10 nm. For the other amphiphiles, the gel was destroyed and nanofiber structures were mainly formed. The formed Cu(2+)-containing nanostructures can function as an asymmetric catalyst for Diels-Alder cycloaddition between cyclopentadiene and aza-chalcone. In comparison with the other Cu(2+)-containing nanostructures, the Cu(2+)-mediated nanotube structure showed not only accelerated reaction rate, but enhanced enantiomeric selectivity. It was suggested that, through the Cu(2+) mediated nanotube formation, the substrate molecules could be anchored on the nanotube surfaces and produced a stereochemically favored alignment. When adducts reacted with the substrate, both the enantiomeric selectivity and the reaction rate were increased. Since the Cu(2+)-mediated nanotube can be fabricated easily and in large amount, the work opened a new way to perform efficient chiral catalysis through the supramolecular gel. PMID:21978005

  8. Junction-Controlled Elasticity of Single-Walled Carbon Nanotube Dispersions in Acrylic Copolymer Gels and Solutions

    SciTech Connect

    Schoch, Andrew B.; Shull, Kenneth R.; Brinson, L. Catherine

    2008-08-26

    Oscillatory shear rheometry is used to study the mechanical response of single-walled carbon nanotubes dispersed in solutions of acrylic diblock or triblock copolymers in 2-ethyl-1-hexanol. Thermal transitions in the copolymer solutions provide a route for the easy processing of these composite materials, with excellent dispersion of the nanotubes as verified by near-infrared photoluminescence spectroscopy. The nanotube dispersions form elastic networks with properties that are controlled by the junction points between nanotubes, featuring a temperature-dependent elastic response that is controlled by the dynamic properties of the matrix copolymer solution. The data are consistent with the formation of micelle-like aggregates around the nanotubes. At low temperatures the core-forming poly(methyl methacrylate) blocks are glassy, and the overall mechanical response of the composite does not evolve with time. At higher temperatures the enhanced mobility of the core-forming blocks enables the junctions to achieve more intimate nanotube-nanotube contact, and the composite modulus increases with time. These aging effects are observed in both diblock and triblock copolymer solutions but are partially reversed in the triblock solutions by cooling through the gel transition of the triblock copolymer. This result is attributed to the generation of internal stresses during gelation and the ability of these stresses to break or weaken the nanotube junctions.

  9. Systems and Methods for Fabricating Carbon Nanotube-Based Vacuum Electronic Devices

    NASA Technical Reports Server (NTRS)

    Manohara, Harish (Inventor); Toda, Risaku (Inventor); Del Castillo, Linda Y. (Inventor); Murthy, Rakesh (Inventor)

    2015-01-01

    Systems and methods in accordance with embodiments of the invention proficiently produce carbon nanotube-based vacuum electronic devices. In one embodiment a method of fabricating a carbon nanotube-based vacuum electronic device includes: growing carbon nanotubes onto a substrate to form a cathode; assembling a stack that includes the cathode, an anode, and a first layer that includes an alignment slot; disposing a microsphere partially into the alignment slot during the assembling of the stack such that the microsphere protrudes from the alignment slot and can thereby separate the first layer from an adjacent layer; and encasing the stack in a vacuum sealed container.

  10. Binding energies and electronic structures of adsorbed titanium chains on carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Yang, Chih-Kai; Zhao, Jijun; Lu, Jianping

    2002-03-01

    Our calculations based on first principles have shown that titanium is much favored energetically over gold and aluminum to form a continuous chain on a variety of single-wall carbon nanotubes (SWNT). Results from two zigzag nanotubes, (10,0) and (14,0), and two armchairs, (6,6) and (8,8), indicate that binding energy for a Ti-adsorbed SWNT is generally six to seven eV per unit cell larger than a Au or Al-adsorbed SWNT. Furthermore, the adsorbed Ti chain generates additional states in the band gaps of the two semi-conducting zigzag nanotubes, transforming them into metals.

  11. Hot wire production of single-wall and multi-wall carbon nanotubes

    DOEpatents

    Dillon, Anne C.; Mahan, Archie H.; Alleman, Jeffrey L.

    2010-10-26

    Apparatus (210) for producing a multi-wall carbon nanotube (213) may comprise a process chamber (216), a furnace (217) operatively associated with the process chamber (216), and at least one filament (218) positioned within the process chamber (216). At least one power supply (220) operatively associated with the at least one filament (218) heats the at least one filament (218) to a process temperature. A gaseous carbon precursor material (214) operatively associated with the process chamber (216) provides carbon for forming the multi-wall carbon nanotube (213). A metal catalyst material (224) operatively associated with the process (216) catalyzes the formation of the multi-wall carbon nanotube (213).

  12. Plasma stabilisation of metallic nanoparticles on silicon for the growth of carbon nanotubes

    SciTech Connect

    Esconjauregui, S.; Fouquet, M.; Bayer, B. C.; Gamalski, A. D.; Chen Bingan; Xie Rongsi; Hofmann, S.; Robertson, J.; Cepek, C.; Bhardwaj, S.; Ducati, C.

    2012-08-01

    Ammonia (NH{sub 3}) plasma pretreatment is used to form and temporarily reduce the mobility of Ni, Co, or Fe nanoparticles on boron-doped mono- and poly-crystalline silicon. X-ray photoemission spectroscopy proves that NH{sub 3} plasma nitrides the Si supports during nanoparticle formation which prevents excessive nanoparticle sintering/diffusion into the bulk of Si during carbon nanotube growth by chemical vapour deposition. The nitridation of Si thus leads to nanotube vertical alignment and the growth of nanotube forests by root growth mechanism.

  13. Nanotube networks in liquid crystals

    NASA Astrophysics Data System (ADS)

    Urbanski, Martin; Lagerwall, Jan Peter F.; Scalia, Giusy

    2016-03-01

    Liquid crystals (LCs) are very attractive hosts for the organization of anisotropic nanoparticles such as carbon nanotubes (CNTs) because of the macroscopic organization resulting in properties of nanoparticles manifest at a macroscopic scale. Different types of LCs have demonstrated the ability to organize nanotubes, showing the generality of the approach, i.e., that the liquid crystallinity per se is the driving factor for the organization. Compared to standard nanotube composites (e.g. with disordered polymer hosts) the introduction of carbon nanotubes into an LC allows not only the transfer of the outstanding CNT properties to the macroscopic phase, providing strength and conductivity, but these properties also become anisotropic, following the transfer of the orientational order from the LC to the CNTs. The LC molecular structure plays an important even if ancillary role since it enters in the surface interactions, fulfilling a mediating action between the particle and the bulk of the LC. Isolated nanotubes can be obtained by optimized dispersions at lower concentrations and this process requires the use or development of tailored strategies like using solvents or even another LC for pre-dispersing CNTs. Aggregates or networks can be observed in poor dispersions and at higher nanoparticle concentrations. In those, due to surface interactions, the LC behaviour can be strongly affected with changes in phase sequences or transition temperatures and the effect is expected to be more pronounced as the concentration of nanotubes increases. We present preliminary investigations and observations on nanotube - LC systems based on a smectic LC host.

  14. Carbon Nanotube Based Molecular Electronics

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Saini, Subhash; Menon, Madhu

    1998-01-01

    Carbon nanotubes and the nanotube heterojunctions have recently emerged as excellent candidates for nanoscale molecular electronic device components. Experimental measurements on the conductivity, rectifying behavior and conductivity-chirality correlation have also been made. While quasi-one dimensional simple heterojunctions between nanotubes with different electronic behavior can be generated by introduction of a pair of heptagon-pentagon defects in an otherwise all hexagon graphene sheet. Other complex 3- and 4-point junctions may require other mechanisms. Structural stability as well as local electronic density of states of various nanotube junctions are investigated using a generalized tight-binding molecular dynamics (GDBMD) scheme that incorporates non-orthogonality of the orbitals. The junctions investigated include straight and small angle heterojunctions of various chiralities and diameters; as well as more complex 'T' and 'Y' junctions which do not always obey the usual pentagon-heptagon pair rule. The study of local density of states (LDOS) reveal many interesting features, most prominent among them being the defect-induced states in the gap. The proposed three and four pointjunctions are one of the smallest possible tunnel junctions made entirely of carbon atoms. Furthermore the electronic behavior of the nanotube based device components can be taylored by doping with group III-V elements such as B and N, and BN nanotubes as a wide band gap semiconductor has also been realized in experiments. Structural properties of heteroatomic nanotubes comprising C, B and N will be discussed.

  15. Carbon Nanotubes for Polymer Photovoltaics

    NASA Astrophysics Data System (ADS)

    Anctil, Annick; Dileo, Roberta; Schauerman, Chris; Landi, Brian; Raffaelle, Ryne

    2007-03-01

    Carbon nanotubes are being investigated for optical absorption, exciton dissociation, and carrier transport in polymer photovoltaic devices. In the present work, single wall carbon nanotubes (SWNTs) were synthesized by an Alexandrite pulsed laser vaporization reactor at standard conditions and purified based upon our previously reported TOP procedure. The SWNTs were dispersed in polymer composites for pure MEH-PPV, pure P3HT, and [C60]-PCBM-P3HT (1:1 by weight) as a function of nanotube weight loading (0.1 -- 5% w/w). The AM0 current-voltage measurements for structures sandwiched between PEDOT/PSS coated ITO substrates and an evaporated aluminum contact demonstrate the dramatic effect of SWNT content on the short circuit current density, with conversions efficiencies consistently greater than 1%. The temperature coefficient for nanotube-containing polymer photovoltaics has been compared to conventional PCBM-P3HT devices, and the general relationship of increasing efficiency with increasing temperature is observed. However, the necessity to control nanotube percolation to prevent device shunting has led to recent developments which focus on controlling nanotube length through oxidative cutting, the deposition of intrinsic polymer layers, and the use of aligned carbon nanotube arrays for preferential charge transport.

  16. DNA nanotubes and helical nanotapes via self-assembly of ssDNA-amphiphiles.

    PubMed

    Pearce, Timothy R; Kokkoli, Efrosini

    2015-01-01

    DNA nanotubes were created using molecular self-assembly of single-stranded DNA (ssDNA)-amphiphiles composed of a hydrophobic dialkyl tail and polycarbon spacer and a hydrophilic ssDNA headgroup. The nanotube structures were formed by bilayers of amphiphiles, with the hydrophobic components forming an inner layer that was shielded from the aqueous solvent by an outer layer of ssDNA. The nanotubes appeared to form via an assembly process that included transitions from twisted nanotapes to helical nanotapes to nanotubes. Amphiphiles that contained different ssDNA headgroups were created to explore the effect of the length and secondary structure of the ssDNA headgroup on the self-assembly behavior of the amphiphiles in the presence and absence of the polycarbon spacer. It was found that nanotubes could be formed using a variety of headgroup lengths and sequences. The ability to create nanotubes via ssDNA-amphiphile self-assembly offers an alternative to the other purely DNA-based approaches like DNA origami and DNA tile assembly for constructing these structures and may be useful for applications in drug delivery, biosensing, and electronics.

  17. Dual-Responsive Lipid Nanotubes: Two-Way Morphology Control by pH and Redox Effects.

    PubMed

    Unsal, Hande; Schmidt, Judith; Talmon, Yeshayahu; Yildirim, Leyla Tatar; Aydogan, Nihal

    2016-05-31

    Lipid nanotubes are the preferred structures for many applications, especially biological ones, and thus have attracted much interest recently. However, there is still a significant need for developing more lipid nanotubes that are reversibly controllable to improve their functionality and usability. Here, we presented a two-way reversible morphology control of the nanotubes formed by the recently designed molecule AQUA (C25H29NO4). Because of its special design, the AQUA has both pH-sensitive and redox-active characters provided by the carboxylic acid and anthraquinone groups. Upon chemical reduction, the nanotubes turned into thinner ribbons, and this structural transformation was significantly reversible. The reduction of the AQUA nanotubes also switched the nanotubes from electrically conductive to insulative. Nanotube morphology can additionally be altered by decreasing the pH below the pKa value of the AQUA, at ∼4.9. Decreasing the pH caused the gradual unfolding of the nanotubes, and the interlayer distance in the nanotube's walls increased. This morphological change was fast and reversible at a wide pH range, including the physiological pH. Thus, the molecular design of the AQUA allowed for an unprecedented two-way and reversible morphology control with both redox and pH effects. These unique features make AQUA a very promising candidate for many applications, ranging from electronics to controlled drug delivery.

  18. Silicon Encapsulated Carbon Nanotubes

    PubMed Central

    2010-01-01

    A dual stage process of depositing bamboo-like carbon nanotubes (BCNTs) by hot filament chemical vapor deposition (HFCVD) and coating Si using Radio frequency sputtering (RFS) technique. The films were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron field emission studies (EFE). SEM results suggest a dense network of homogeneous silicon-coated BCNTs. From the comprehensive analysis of the results provided by these techniques emerges the picture of Si encapsulated BCNTs. PMID:20652067

  19. Functionalization of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Khare, Bishun N. (Inventor); Meyyappan, Meyya (Inventor)

    2007-01-01

    Method and system for functionalizing a collection of carbon nanotubes (CNTs). A selected precursor gas (e.g., H2, or F2, or CnHm) is irradiated to provide a cold plasma of selected target particles, such as atomic H or F, in a first chamber. The target particles are directed toward an array of CNTs located in a second chamber while suppressing transport of ultraviolet radiation to the second chamber. A CNT array is functionalized with the target particles, at or below room temperature, to a point of saturation, in an exposure time interval no longer than about 30 sec.

  20. Functionalization of carbon nanotubes

    NASA Technical Reports Server (NTRS)

    Khare, Bishun N. (Inventor); Meyyappan, Meyya (Inventor)

    2007-01-01

    Method and system for functionalizing a collection of carbon nanotubes (CNTs). A selected precursor gas (e.g., H.sub.2 or F.sub.2 or C.sub.nH.sub.m) is irradiated to provide a cold plasma of selected target particles, such as atomic H or F, in a first chamber. The target particles are directed toward an array of CNTs located in a second chamber while suppressing transport of ultraviolet radiation to the second chamber. A CNT array is functionalized with the target particles, at or below room temperature, to a point of saturation, in an exposure time interval no longer than about 30 sec.

  1. Functionalized boron nitride nanotubes

    DOEpatents

    Sainsbury, Toby; Ikuno, Takashi; Zettl, Alexander K

    2014-04-22

    A plasma treatment has been used to modify the surface of BNNTs. In one example, the surface of the BNNT has been modified using ammonia plasma to include amine functional groups. Amine functionalization allows BNNTs to be soluble in chloroform, which had not been possible previously. Further functionalization of amine-functionalized BNNTs with thiol-terminated organic molecules has also been demonstrated. Gold nanoparticles have been self-assembled at the surface of both amine- and thiol-functionalized boron nitride Nanotubes (BNNTs) in solution. This approach constitutes a basis for the preparation of highly functionalized BNNTs and for their utilization as nanoscale templates for assembly and integration with other nanoscale materials.

  2. Carbon Nanotube Interconnect

    NASA Technical Reports Server (NTRS)

    Li, Jun (Inventor); Meyyappan, Meyya (Inventor)

    2006-01-01

    Method and system for fabricating an electrical interconnect capable of supporting very high current densities ( 10(exp 6)-10(exp 10) Amps/sq cm), using an array of one or more carbon nanotubes (CNTs). The CNT array is grown in a selected spaced apart pattern, preferably with multi-wall CNTs, and a selected insulating material, such as SiOw, or SiuNv is deposited using CVD to encapsulate each CNT in the array. An exposed surface of the insulating material is planarized to provide one or more exposed electrical contacts for one or more CNTs.

  3. Fabrication of titanium dioxide nanotube arrays using organic electrolytes

    NASA Astrophysics Data System (ADS)

    Yoriya, Sorachon

    to ~2 microm. In comparison to DMSO electrolyte, the electrochemical anodization rates are relatively slower in DEG electrolyte; as a result, the nanotube length is typically less than 10 microm. Pore size of nanotubes grown in DEG has been extended from 150 nm up to approximately 400 nm. The approach to pore widening could be achieved by using a specific condition of low HF concentration and prolonged anodization time. The study of evolution of nanotubes grown in DEG electrolytes showed that a fibrous layer was formed in the early growth stages and then was chemically and gradually removed after a long duration, leaving behind the nanotubes with large pore size. In DEG electrolyte, the closer spacing between Ti and Pt electrodes resulted in the larger nanotube morphological parameters due to the enhanced electrode kinetics facilitating the electrode reactions. Furthermore, this dissertation showed possibilities to crystallize the titania nanotube array films at room temperature via anodization in either DMSO or DEG electrolytes. The partially crystallized films could be achieved specifically in the optimum slow growth process conditions. Due to partial crystallization of the as-anodized samples, the high temperature annealing study revealed that the temperatures of phase transformation are 260 ºC and 430°C for respectively amorphous to anatase and anatase to rutile, which are accounted as the lowest phase transformation temperatures reported to date (2010). Finally, the photoelectrochemical properties of the DMSO fabricated nanotubes were investigated. The maximum photocurrent density of ~ 11 mA cm--2 was achieved by using the 46-microm long nanotube array sample with completely open pores, and photoconversion efficiencies of 5.425 % (+/- 0.087) (under UV light) and 0.197 % (+/- 0.001) (under solar spectrum AM 1.5) have been demonstrated. Biomedical applications of the DEG fabricated nanotube arrays films such as blood clotting, hemocompatibility, and drug

  4. Electrodeposition and characterisation of polypyrroles containing sulfonated carbon nanotubes.

    PubMed

    Lynam, Carol; Wallace, Gordon G; Officer, David L

    2007-10-01

    Using facile diazonium chemistry, sulfonate groups have been covalently attached to single wall carbon nanotubes. The resulting sulfonated tubes form a stable aqueous dispersion in the presence of pyrrole monomer. Subsequent electropolymerisation results in a conductive, electroactive polypyrrole doped with sulfonated tubes being formed at unusually low potentials. The potential of this material as a host matrix for biomolecules has been demonstrated by entrapping horse-radish peroxidase directly in the polypyrrole during composite formation.

  5. Mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogels

    DOEpatents

    Worsley, Marcus A; Baumann, Theodore F; Satcher, Jr., Joe H

    2014-04-01

    A method of making a mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel, including the steps of dispersing nanotubes in an aqueous media or other media to form a suspension, adding reactants and catalyst to the suspension to create a reaction mixture, curing the reaction mixture to form a wet gel, drying the wet gel to produce a dry gel, and pyrolyzing the dry gel to produce the mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel. The aerogel is mechanically robust, electrically conductive, and ultralow-density, and is made of a porous carbon material having 5 to 95% by weight carbon nanotubes and 5 to 95% carbon binder.

  6. Mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogels

    DOEpatents

    Worsley, Marcus A.; Baumann, Theodore F.; Satcher, Jr, Joe H.

    2016-07-05

    A method of making a mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel, including the steps of dispersing nanotubes in an aqueous media or other media to form a suspension, adding reactants and catalyst to the suspension to create a reaction mixture, curing the reaction mixture to form a wet gel, drying the wet gel to produce a dry gel, and pyrolyzing the dry gel to produce the mechanically robust, electrically conductive ultralow-density carbon nanotube-based aerogel. The aerogel is mechanically robust, electrically conductive, and ultralow-density, and is made of a porous carbon material having 5 to 95% by weight carbon nanotubes and 5 to 95% carbon binder.

  7. Carbon nanotubes in hyperthermia therapy

    PubMed Central

    Singh, Ravi; Torti, Suzy V.

    2013-01-01

    Thermal tumor ablation therapies are being developed with a variety of nanomaterials, including single-and multiwalled carbon nanotubes. Carbon nanotubes (CNTs) have attracted interest due to their potential for simultaneous imaging and therapy. In this review, we highlight in vivo applications of carbon nanotube-mediated thermal therapy (CNMTT) and examine the rationale for use of this treatment in recurrent tumors or those resistant to conventional cancer therapies. Additionally, we discuss strategies to localize and enhance the cancer selectivity of this treatment and briefly examine issues relating the toxicity and long term fate of CNTs. PMID:23933617

  8. Carbon nanotubes in hyperthermia therapy.

    PubMed

    Singh, Ravi; Torti, Suzy V

    2013-12-01

    Thermal tumor ablation therapies are being developed with a variety of nanomaterials, including single- and multiwalled carbon nanotubes. Carbon nanotubes (CNTs) have attracted interest due to their potential for simultaneous imaging and therapy. In this review, we highlight in vivo applications of carbon nanotube-mediated thermal therapy (CNMTT) and examine the rationale for use of this treatment in recurrent tumors or those resistant to conventional cancer therapies. Additionally, we discuss strategies to localize and enhance the cancer selectivity of this treatment and briefly examine issues relating the toxicity and long term fate of CNTs.

  9. NASA Innovation Builds Better Nanotubes

    NASA Technical Reports Server (NTRS)

    2008-01-01

    Nanotailor Inc., based in Austin, Texas, licensed Goddard Space Flight Center's unique single-walled carbon nanotube (SWCNT) fabrication process with plans to make high-quality, low-cost SWCNTs available commercially. Carbon nanotubes are being used in a wide variety of applications, and NASA's improved production method will increase their applicability in medicine, microelectronics, advanced materials, and molecular containment. Nanotailor built and tested a prototype based on Goddard's process, and is using this technique to lower the cost and improve the integrity of nanotubes, offering a better product for use in biomaterials, advanced materials, space exploration, highway and building construction, and many other applications.

  10. Multiscale Modeling with Carbon Nanotubes

    SciTech Connect

    Maiti, A

    2006-02-21

    Technologically important nanomaterials come in all shapes and sizes. They can range from small molecules to complex composites and mixtures. Depending upon the spatial dimensions of the system and properties under investigation computer modeling of such materials can range from equilibrium and nonequilibrium Quantum Mechanics, to force-field-based Molecular Mechanics and kinetic Monte Carlo, to Mesoscale simulation of evolving morphology, to Finite-Element computation of physical properties. This brief review illustrates some of the above modeling techniques through a number of recent applications with carbon nanotubes: nano electromechanical sensors (NEMS), chemical sensors, metal-nanotube contacts, and polymer-nanotube composites.

  11. Carbon nanotubes as vaccine scaffolds

    PubMed Central

    Scheinberg, David A.; McDevitt, Michael R.; Dao, Tao; Mulvey, Justin J.; Feinberg, Evan; Alidori, Simone

    2013-01-01

    Carbon nanotubes display characteristics that are potentially useful in their development as scaffolds for vaccine compositions. These features include stability in vivo, lack of intrinsic immunogenicity, low toxicity, and the ability to be appended with multiple copies of antigens. In addition, the particulate nature of carbon nanotubes and their unusual properties of rapid entry into antigen-presenting cells, such as dendritic cells, make them especially useful as carriers of antigens. Early attempts demonstrating carbon nanotube-based vaccines can be used in both infectious disease settings and cancer are promising. PMID:23899863

  12. Method of manufacturing carbon nanotubes

    NASA Technical Reports Server (NTRS)

    Benavides, Jeanette M. (Inventor); Leidecker, Henning W. (Inventor); Frazier, Jeffrey (Inventor)

    2004-01-01

    A process for manufacturing carbon nanotubes, including a step of inducing electrical current through a carbon anode and a carbon cathode under conditions effective to produce the carbon nanotubes, wherein the carbon cathode is larger than the carbon anode. Preferably, a welder is used to induce the electrical current via an arc welding process. Preferably, an exhaust hood is placed on the anode, and the process does not require a closed or pressurized chamber. The process provides high-quality, single-walled carbon nanotubes, while eliminating the need for a metal catalyst.

  13. Clay nanotube-biopolymer composite scaffolds for tissue engineering

    NASA Astrophysics Data System (ADS)

    Naumenko, Ekaterina A.; Guryanov, Ivan D.; Yendluri, Raghuvara; Lvov, Yuri M.; Fakhrullin, Rawil F.

    2016-03-01

    Porous biopolymer hydrogels doped at 3-6 wt% with 50 nm diameter/0.8 μm long natural clay nanotubes were produced without any cross-linkers using the freeze-drying method. The enhancement of mechanical strength (doubled pick load), higher water uptake and thermal properties in chitosan-gelatine-agarose hydrogels doped with halloysite was demonstrated. SEM and AFM imaging has shown the even distribution of nanotubes within the scaffolds. We used enhanced dark-field microscopy to visualise the distribution of halloysite nanotubes in the implantation area. In vitro cell adhesion and proliferation on the nanocomposites occur without changes in viability and cytoskeleton formation. In vivo biocompatibility and biodegradability evaluation in rats has confirmed that the scaffolds promote the formation of novel blood vessels around the implantation sites. The scaffolds show excellent resorption within six weeks after implantation in rats. Neo-vascularization observed in newly formed connective tissue placed near the scaffold allows for the complete restoration of blood flow. These phenomena indicate that the halloysite-doped scaffolds are biocompatible as demonstrated both in vitro and in vivo. The chitosan-gelatine-agarose doped clay nanotube nanocomposite scaffolds fabricated in this work are promising candidates for tissue engineering applications.Porous biopolymer hydrogels doped at 3-6 wt% with 50 nm diameter/0.8 μm long natural clay nanotubes were produced without any cross-linkers using the freeze-drying method. The enhancement of mechanical strength (doubled pick load), higher water uptake and thermal properties in chitosan-gelatine-agarose hydrogels doped with halloysite was demonstrated. SEM and AFM imaging has shown the even distribution of nanotubes within the scaffolds. We used enhanced dark-field microscopy to visualise the distribution of halloysite nanotubes in the implantation area. In vitro cell adhesion and proliferation on the nanocomposites occur

  14. Development of novel single-wall carbon nanotube epoxy composite ply actuators

    NASA Astrophysics Data System (ADS)

    Yun, Yeo-Heung; Shanov, Vesselin; Schulz, Mark J.; Narasimhadevara, Suhasini; Subramaniam, Srinivas; Hurd, Douglas; Boerio, F. J.

    2005-12-01

    This paper describes a carbon nanotube epoxy ply material that has electrochemical actuation properties. The material was formed by dispersing single-wall carbon nanotubes in a solvent and then solution casting a thin paper using a mold and vacuum oven. In order to take advantage of the high elastic modulus of carbon nanotubes for actuation, epoxy as a chemically inert polymer is considered. An epoxy layer was cast on the surface of the nanotube paper to make a two-layer ply. A wet electrochemical actuator was formed by placing the nanotube epoxy ply in a 2 M NaCl electrolyte solution. Electrochemical impedance spectroscopy and cyclic voltammetry were carried out to characterize the electrochemical properties of the actuator. The voltage-current relationship and power to drive the actuator material were also determined. Compared to previous single-wall carbon nanotube buckypaper tape actuators, which had poor adhesion between the nanotubes and tape, and other nanotube-thermal plastic polymer actuators, which could not provide high strength, the epoxy based actuator has a higher elastic modulus and strength, which will be useful for future structural applications. This demonstrates that a polymer layer can reinforce nanotube paper, which is an important step in building a new structural material that actuates. Further work is under way to develop a solid electrolyte to allow dry actuation. Finally, these actuator plies will be laminated to build a carbon nanocomposite material. This smart structural material will have potential applications that range from use in robotic surgical tools to use as structures that change shape.

  15. Large-Scale Processing of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Finn, John; Sridhar, K. R.; Meyyappan, M.; Arnold, James O. (Technical Monitor)

    1998-01-01

    Scale-up difficulties and high energy costs are two of the more important factors that limit the availability of various types of nanotube carbon. While several approaches are known for producing nanotube carbon, the high-powered reactors typically produce nanotubes at rates measured in only grams per hour and operate at temperatures in excess of 1000 C. These scale-up and energy challenges must be overcome before nanotube carbon can become practical for high-consumption structural and mechanical applications. This presentation examines the issues associated with using various nanotube production methods at larger scales, and discusses research being performed at NASA Ames Research Center on carbon nanotube reactor technology.

  16. Bending fracture in carbon nanotubes.

    PubMed

    Kuo, Wen-Shyong; Lu, Hsin-Fang

    2008-12-10

    A novel approach was adopted to incur bending fracture in carbon nanotubes (CNTs). Expanded graphite (EG) was made by intercalating and exfoliating natural graphite flakes. The EG was deposited with nickel particles, from which CNTs were grown by chemical vapor deposition. The CNTs were tip-grown, and their roots were fixed on the EG flakes. The EG flakes were compressed, and many CNTs on the surface were fragmented due to the compression-induced bending. Two major modes of the bending fracture were observed: cone-shaped and shear-cut. High-resolution scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to examine the crack growth within the graphene layers. The bending fracture is characterized by two-region crack growth. An opening crack first appears around the outer-tube due to the bending-induced tensile stress. The crack then branches to grow along an inclined direction toward the inner-tube due to the presence of the shear stress in between graphene layers. An inner-tube pullout with inclined side surface is formed. The onset and development of the crack in these two regions are discussed. PMID:21730690

  17. Elastomer Reinforced with Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Hudson, Jared L.; Krishnamoorti, Ramanan

    2009-01-01

    Elastomers are reinforced with functionalized, single-walled carbon nanotubes (SWNTs) giving them high-breaking strain levels and low densities. Cross-linked elastomers are prepared using amine-terminated, poly(dimethylsiloxane) (PDMS), with an average molecular weight of 5,000 daltons, and a functionalized SWNT. Cross-link densities, estimated on the basis of swelling data in toluene (a dispersing solvent) indicated that the polymer underwent cross-linking at the ends of the chains. This thermally initiated cross-linking was found to occur only in the presence of the aryl alcohol functionalized SWNTs. The cross-link could have been via a hydrogen-bonding mechanism between the amine and the free hydroxyl group, or via attack of the amine on the ester linage to form an amide. Tensile properties examined at room temperature indicate a three-fold increase in the tensile modulus of the elastomer, with rupture and failure of the elastomer occurring at a strain of 6.5.

  18. Tumor exosomes induce tunneling nanotubes in lipid raft-enriched regions of human mesothelioma cells

    SciTech Connect

    Thayanithy, Venugopal; Babatunde, Victor; Dickson, Elizabeth L.; Wong, Phillip; Oh, Sanghoon; Ke, Xu; Barlas, Afsar; Fujisawa, Sho; Romin, Yevgeniy; Moreira, André L.; Downey, Robert J.; Steer, Clifford J.; Subramanian, Subbaya; Manova-Todorova, Katia; Moore, Malcolm A.S.; Lou, Emil

    2014-04-15

    Tunneling nanotubes (TnTs) are long, non-adherent, actin-based cellular extensions that act as conduits for transport of cellular cargo between connected cells. The mechanisms of nanotube formation and the effects of the tumor microenvironment and cellular signals on TnT formation are unknown. In the present study, we explored exosomes as potential mediators of TnT formation in mesothelioma and the potential relationship of lipid rafts to TnT formation. Mesothelioma cells co-cultured with exogenous mesothelioma-derived exosomes formed more TnTs than cells cultured without exosomes within 24–48 h; and this effect was most prominent in media conditions (low-serum, hyperglycemic medium) that support TnT formation (1.3–1.9-fold difference). Fluorescence and electron microscopy confirmed the purity of isolated exosomes and revealed that they localized predominantly at the base of and within TnTs, in addition to the extracellular environment. Time-lapse microscopic imaging demonstrated uptake of tumor exosomes by TnTs, which facilitated intercellular transfer of these exosomes between connected cells. Mesothelioma cells connected via TnTs were also significantly enriched for lipid rafts at nearly a 2-fold higher number compared with cells not connected by TnTs. Our findings provide supportive evidence of exosomes as potential chemotactic stimuli for TnT formation, and also lipid raft formation as a potential biomarker for TnT-forming cells. - Highlights: • Exosomes derived from malignant cells can stimulate an increased rate in the formation of tunneling nanotubes. • Tunneling nanotubes can serve as conduits for intercellular transfer of these exosomes. • Most notably, exosomes derived from benign mesothelial cells had no effect on nanotube formation. • Cells forming nanotubes were enriched in lipid rafts at a greater number compared with cells not forming nanotubes. • Our findings suggest causal and potentially synergistic association of exosomes and

  19. Template-synthesized nanotubes through layer-by-layer assembly under charge interaction.

    PubMed

    Li, Junbai; Cui, Yue

    2006-06-01

    Aqueous polymer nanotubes can be assembled by combining the layer-by-layer (LbL) assembly and template technique under charge interaction. This method allows lots of species, especially in an aqueous system to form a tubular structure in the pores of the template. The tubes functions can be readily modified by introducing various functional components. Such assembled nanotubes are often mechanically stable and highly flexible. They have also numerous potential applications in delivering materials.

  20. Self-Assembly of Subnanometer-Diameter Single-Wall MoS2 Nanotubes

    NASA Astrophysics Data System (ADS)

    Remskar, Maja; Mrzel, Ales; Skraba, Zora; Jesih, Adolf; Ceh, Miran; Demšar, Jure; Stadelmann, Pierre; Lévy, Francis; Mihailovic, Dragan

    2001-04-01

    We report on the synthesis, structure, and self-assembly of single-wall subnanometer-diameter molybdenum disulfide tubes. The nanotubes are up to hundreds of micrometers long and display diverse self-assembly properties on different length scales, ranging from twisted bundles to regularly shaped ``furry'' forms. The bundles, which contain interstitial iodine, can be readily disassembled into individual molybdenum disulfide nanotubes. The synthesis was performed using a novel type of catalyzed transport reaction including C60 as a growth promoter.

  1. Carbon nanotube array actuators

    NASA Astrophysics Data System (ADS)

    Geier, S.; Mahrholz, T.; Wierach, P.; Sinapius, M.

    2013-09-01

    Experimental investigations of highly vertically aligned carbon nanotubes (CNTs), also known as CNT-arrays, are the main focus of this paper. The free strain as result of an active material behavior is analyzed via a novel experimental setup. Previous test experiences of papers made of randomly oriented CNTs, also called Bucky-papers, reveal comparably low free strain. The anisotropy of aligned CNTs promises better performance. Via synthesis techniques like chemical vapor deposition (CVD) or plasma enhanced CVD (PECVD), highly aligned arrays of multi-walled carbon nanotubes (MWCNTs) are synthesized. Two different types of CNT-arrays are analyzed, morphologically first, and optically tested for their active characteristics afterwards. One type of the analyzed arrays features tube lengths of 750-2000 μm with a large variety of diameters between 20 and 50 nm and a wave-like CNT-shape. The second type features a maximum, almost uniform, length of 12 μm and a constant diameter of 50 nm. Different CNT-lengths and array types are tested due to their active behavior. As result of the presented tests, it is reported that the quality of orientation is the most decisive property for excellent active behavior. Due to their alignment, CNT-arrays feature the opportunity to clarify the actuation mechanism of architectures made of CNTs.

  2. Studies of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Caneba, Gerard T.

    2005-01-01

    The fellowship experience for this summer for 2004 pertains to carbon nanotube coatings for various space-related applications. They involve the following projects: (a) EMI protection films from HiPco-polymers, and (b) Thermal protection nanosilica materials. EMI protection films are targeted to be eventually applied onto casings of laptop computers. These coatings are composites of electrically-conductive SWNTs and compatible polymers. The substrate polymer will be polycarbonate, since computer housings are typically made of carbon composites of this type of polymer. A new experimental copolymer was used last year to generate electrically-conductive and thermal films with HiPco at 50/50 wt/wt composition. This will be one of the possible formulations. Reference films will be base polycarbonate and neat HiPco onto polycarbonate films. Other coating materials that will be tried will be based on HiPco composites with commercial enamels (polyurethane, acrylic, polyester), which could be compatible with the polycarbonate substrate. Nanosilica fibers are planned for possible use as thermal protection tiles on the shuttle orbiter. Right now, microscale silica is used. Going to the nanoscale will increase the surface-volume-per-unit-area of radiative heat dissipation. Nanoscale carbon fibers/nanotubes can be used as templates for the generation of nanosilica. A sol-gel operation is employed for this purpose.

  3. Structure of the glass-forming metallic liquids by ab-initio and classical molecular dynamics, a case study: Quenching the Cu60Ti20Zr20 alloy

    NASA Astrophysics Data System (ADS)

    Amokrane, S.; Ayadim, A.; Levrel, L.

    2015-11-01

    We consider the question of the amorphization of metallic alloys by melt quenching, as predicted by molecular dynamics simulations with semi-empirical potentials. The parametrization of the potentials is discussed on the example of the ternary Cu-Ti-Zr transition metals alloy, using the ab-initio simulation as a reference. The pair structure in the amorphous state is computed from a potential of the Stillinger-Weber form. The transferability of the parameters during the quench is investigated using two parametrizations: from solid state data, as usual and from a new parametrization on the liquid structure. When the adjustment is made on the pair structure of the liquid, a satisfactory transferability is found between the pure components and their alloys. The liquid structure predicted in this way agrees well with experiment, in contrast with the one obtained using the adjustment on the solid. The final structure, after quenches down to the amorphous state, determined with the new set of parameters is shown to be very close to the ab-initio one, the latter being in excellent agreement with recent X-rays diffraction experiments. The corresponding critical temperature of the glass transition is estimated from the behavior of the heat capacity. Discussion on the consistency between the structures predicted using semi-empirical potentials and ab-initio simulation, and comparison of different experimental data underlines the question of the dependence of the final structure on the thermodynamic path followed to reach the amorphous state.

  4. The effective Young's modulus of carbon nanotubes in composites.

    PubMed

    Deng, Libo; Eichhorn, Stephen J; Kao, Chih-Chuan; Young, Robert J

    2011-02-01

    A detailed study has been undertaken of the efficiency of reinforcement in nanocomposites consisting of single-walled carbon nanotubes (SWNTs) in poly(vinyl alcohol) (PVA). Nanocomposite fibers have been prepared by electrospinning and their behavior has been compared with nanocomposite films of the same composition. Stress transfer from the polymer matrix to the nanotubes has been followed from stress-induced Raman band shifts, which are shown to be controlled by both geometric factors such as the angles between the nanotube axis, the stressing direction and the direction of laser polarization, and by finite length effects and bundling. A theory has been developed that takes into account all of these factors and enables the behavior of the different forms of nanocomposite, both fibers and films, to be compared in different polarization configurations. The effective modulus of the SWNTs has been found to be in the range 530-700 GPa which, while being impressive, is lower than the generally accepted value of around 1000 GPa as a result of factors such as finite length effects and nanotube bundling. This value of effective modulus has, however, been shown to be consistent with the contribution of nanotubes to the 20% increase in Young's modulus found for the nanocomposite films with a loading of only 0.2% of SWNTs. Hence a self-consistent method has been developed which enables the efficiency of reinforcement by nanotubes, and potentially other high-aspect-ratio nanoparticles, to be evaluated from stress-induced Raman bands shifts in nanocomposites independent of the specimen geometry and laser polarization configuration.

  5. TiO{sub 2} nanotube, nanowire, and rhomboid-shaped particle thin films fixed on a titanium metal plate

    SciTech Connect

    Inoue, Yuko; Noda, Iwao; Torikai, Toshio; Watari, Takanori; Hotokebuchi, Takao; Yada, Mitsunori

    2010-01-15

    Titanium dioxide thin films having various nanostructures could be formed by various treatments on sodium titanate nanotube thin films approximately 5 {mu}m thick fixed on titanium metal plates. Using an aqueous solution with a lower hydrochloric acid concentration (0.01 mol/L) and a higher reaction temperature (90 deg. C) than those previously employed, we obtained a hydrogen titanate nanotube thin film fixed onto a titanium metal plate by H{sup +} ion-exchange treatment of the sodium titanate nanotube thin film. Calcination of hydrogen titanate nanotube thin films yielded porous thin films consisting of anatase nanotubes, anatase nanowires, and anatase nanoparticles grown directly from the titanium metal plate. H{sup +} ion-exchange treatment of sodium titanate nanotube thin films at 140 deg. C resulted in porous thin films consisting of rhomboid-shaped anatase nanoparticles. - Graphical abstract: Titanium dioxide nanotube, nanowire, and rhombic particle thin films could be formed by various treatments on a sodium titanate nanotube thin film fixed on a titanium metal plate.

  6. Single carbon nanotube photovoltaic device

    NASA Astrophysics Data System (ADS)

    Barkelid, M.; Zwiller, V.

    2013-10-01

    Here we present photocurrent measurements on a single suspended carbon nanotube p-n junction. The p-n junction was induced by electrostatic doping by local gates, and the E11 and E22 resonances in the nanotube could be probed using photocurrent spectroscopy. Current-voltage characteristics were recorded, revealing an enhanced optoelectronic response on resonance. The internal power conversion efficiency for the nanotube diode was extracted on and off resonance with the E11 and E22, and a large internal power conversion efficiency was observed. An internal efficiency of up to 23% is reported for the E11, showing the potential of carbon nanotubes to be used as the active element in photovoltaic devices. Finally, a photovoltaic device is proposed which exploits this enhanced efficiency.

  7. Elastic modulus of viral nanotubes

    NASA Astrophysics Data System (ADS)

    Zhao, Yue; Ge, Zhibin; Fang, Jiyu

    2008-09-01

    We report an experimental and theoretical study of the radial elasticity of tobacco mosaic virus (TMV) nanotubes. An atomic force microscope tip is used to apply small radial indentations to deform TMV nanotubes. The initial elastic response of TMV nanotubes can be described by finite-element analysis in 5nm indentation depths and Hertz theory in 1.5nm indentation depths. The derived radial Young’s modulus of TMV nanotubes is 0.92±0.15GPa from finite-element analysis and 1.0±0.2GPa from the Hertz model, which are comparable with the reported axial Young’s modulus of 1.1GPa [Falvo , Biophys. J. 72, 1396 (1997)].

  8. Improvements in Production of Single-Walled Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Balzano, Leandro; Resasco, Daniel E.

    2009-01-01

    A continuing program of research and development has been directed toward improvement of a prior batch process in which single-walled carbon nanotubes are formed by catalytic disproportionation of carbon monoxide in a fluidized-bed reactor. The overall effect of the improvements has been to make progress toward converting the process from a batch mode to a continuous mode and to scaling of production to larger quantities. Efforts have also been made to optimize associated purification and dispersion post processes to make them effective at large scales and to investigate means of incorporating the purified products into composite materials. The ultimate purpose of the program is to enable the production of high-quality single-walled carbon nanotubes in quantities large enough and at costs low enough to foster the further development of practical applications. The fluidized bed used in this process contains mixed-metal catalyst particles. The choice of the catalyst and the operating conditions is such that the yield of single-walled carbon nanotubes, relative to all forms of carbon (including carbon fibers, multi-walled carbon nanotubes, and graphite) produced in the disproportionation reaction is more than 90 weight percent. After the reaction, the nanotubes are dispersed in various solvents in preparation for end use, which typically involves blending into a plastic, ceramic, or other matrix to form a composite material. Notwithstanding the batch nature of the unmodified prior fluidized-bed process, the fluidized-bed reactor operates in a continuous mode during the process. The operation is almost entirely automated, utilizing mass flow controllers, a control computer running software specific to the process, and other equipment. Moreover, an important inherent advantage of fluidized- bed reactors in general is that solid particles can be added to and removed from fluidized beds during operation. For these reasons, the process and equipment were amenable to

  9. High pressure synthesis of amorphous TiO{sub 2} nanotubes

    SciTech Connect

    Li, Quanjun; Liu, Ran; Wang, Tianyi; Xu, Ke; Dong, Qing; Liu, Bo; Liu, Bingbing; Liu, Jing

    2015-09-15

    Amorphous TiO{sub 2} nanotubes with diameters of 8-10 nm and length of several nanometers were synthesized by high pressure treatment of anatase TiO{sub 2} nanotubes. The structural phase transitions of anatase TiO{sub 2} nanotubes were investigated by using in-situ high-pressure synchrotron X-ray diffraction (XRD) method. The starting anatase structure is stable up to ∼20GPa, and transforms into a high-density amorphous (HDA) form at higher pressure. Pressure-modified high- to low-density transition was observed in the amorphous form upon decompression. The pressure-induced amorphization and polyamorphism are in good agreement with the previous results in ultrafine TiO{sub 2} nanoparticles and nanoribbons. The relationship between the LDA form and α-PbO{sub 2} phase was revealed by high-resolution transmission electron microscopy (HRTEM) study. In addition, the bulk modulus (B{sub 0} = 158 GPa) of the anatase TiO{sub 2} nanotubes is smaller than those of the corresponding bulks and nanoparticles (180-240 GPa). We suggest that the unique open-ended nanotube morphology and nanosize play important roles in the high pressure phase transition of TiO{sub 2} nanotubes.

  10. Local modifications of single-wall carbon nanotubes induced by bond formation with encapsulated fullerenes.

    PubMed

    Yumura, Takashi; Kertesz, Miklos; Iijima, Sumio

    2007-02-01

    Defected fullerenes in nanopeapods form bonds with the encapsulating single-walled carbon nanotubes when irradiated by an electron beam leading to changes in the guest (fullerene) and the host (nanotube). Intrinsic reaction coordinate (IRC) analysis based on B3LYP hybrid density functional theory shows that a C1-C59 defect with a single protruding C atom is initially formed from the C60(Ih) cage. The high activation energy for this step (8.37 eV (193.0 kcal/mol)), being assumed to be accessible during irradiation, is lower than that of the Stone-Wales rearrangement on the sp2 network. The binding of the defected fullerene to the nanotube is preferential, orthogonal bonds relative to the tube axis being slightly preferred. Because of the covalent bonds formed between the guest and host, the carbon network on the nanotube is locally perturbed in the vicinity of the binding site. As a result of the new bonds, bisnorcaradiene-like as well as quinonoid-like patterns appear near the binding site. These results are interpreted using orbital interaction and Clar diagram arguments. The changes in the bonding pattern on the nanotube should be significant in further functionalization of carbon nanotubes.

  11. Separation of chiral nanotubes with an opposite handedness by chiral oligopeptide adsorption: A molecular dynamics study.

    PubMed

    Raffaini, Giuseppina; Ganazzoli, Fabio

    2015-12-18

    The separation of enantiomeric chiral nanotubes that can form non-covalent complexes with an unlike stability upon adsorption of chiral molecules is a process of potential interest in different fields and applications. Using fully atomistic molecular dynamics simulations, we report in this paper a theoretical study of the adsorption and denaturation of an oligopeptide formed by 16 chiral amino acids having a helical structure in the native state on both the inner and the outer surface of the chiral (10, 20) and (20, 10) single-walled carbon nanotubes having an opposite handedness, and of the armchair (16, 16) nanotube with a similar diameter for comparison. In the final adsorbed state, the oligopeptide loses in all cases its native helical conformation, assuming elongated geometries that maximize its contact with the surface through all the 16 amino acids. We find that the complexes formed by the two chiral nanotubes and the chosen oligopeptide have a strongly unlike stability both when adsorption takes place on the outer convex surface of the nanotube, and when it occurs on the inner concave surface. Thus, our molecular simulations indicate that separation of chiral, enantiomeric carbon nanotubes for instance by chromatographic methods can indeed be carried out using oligopeptides of a sufficient length.

  12. Titania nanotubes from weak organic acid electrolyte: fabrication, characterization and oxide film properties.

    PubMed

    Munirathinam, Balakrishnan; Neelakantan, Lakshman

    2015-04-01

    In this study, TiO2 nanotubes were fabricated using anodic oxidation in fluoride containing weak organic acid for different durations (0.5h, 1h, 2h and 3h). Scanning electron microscope (SEM) micrographs reveal that the morphology of titanium oxide varies with anodization time. Raman spectroscopy and X-ray diffraction (XRD) results indicate that the as-formed oxide nanotubes were amorphous in nature, yet transform into crystalline phases (anatase and rutile) upon annealing at 600°C. Wettability measurements show that both as-formed and annealed nanotubes exhibited hydrophilic behavior. The electrochemical behavior was ascertained by DC polarization and AC electrochemical impedance spectroscopy (EIS) measurements in 0.9% NaCl solution. The results suggest that the annealed nanotubes showed higher impedance (10(5)-10(6)Ωcm(2)) and lower passive current density (10(-7)Acm(-2)) than the as-formed nanotubes. In addition, we investigated the influence of post heat treatment on the semiconducting properties of the oxides by capacitance measurements. In vitro bioactivity test in simulated body fluid (SBF) showed that precipitation of Ca/P is easier in crystallized nanotubes than the amorphous structure. Our study uses a simple strategy to prepare nano-structured titania films and hints the feasibility of tailoring the oxide properties by thermal treatment, producing surfaces with better bioactivity.

  13. Commensurate Phases of Kr Adsorbed on Single-Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Mbaye, Mamadou T.; Maiga, Sidi M.; Gatica, Silvina M.

    2016-10-01

    In this paper, we show that Krypton atoms form a commensurate solid (CS) phase with a fractional coverage of one krypton atom per every four carbons on zigzag carbon nanotubes. This is a unique phase, different from the √{3} × √{3}R30° CS monolayer formed on graphite, which has a lower coverage of one krypton atom per every six carbons. Our prediction disagrees with experiments that observe in nanotubes the same solid structure found on graphite. In order to address this discrepancy, we simulated adsorption of Kr on zigzag and armchair single-walled carbon nanotubes with radii ranging from 4.7 to 28.83 Å. Our simulations confirm that the CS of coverage 1/4 forms on medium-sized zigzag nanotubes. We also found the 1/6-coverage solid on graphene, which represents the infinite-radius limit of a nanotube. Our findings are key to experiments of adsorption on nanotubes where the interpretation and justification of the results are based on the monolayer coverage, such as mass or conductance isotherms measurements.

  14. Preparation of polyaniline nanotubes array based on anodic aluminum oxide template

    SciTech Connect

    Xiong Shanxin; Wang Qi; Xia Hesheng

    2004-08-03

    In this article, the highly ordered polyaniline (PANI) nanotubes array was prepared by in situ polymerization using anodic aluminum oxide (AAO) as template. Polymerization of aniline was confined in the one-dimensional nanochannel of AAO template. The aniline was adsorbed and polymerized preferentially on the pore walls of template. The structure of PANI nanotubes array was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), selected area electron diffraction (SAED) and dynamic force microscope (DFM). The results show that PANI nanotubes are synthesized successfully in the nanopores of template, the diameter and length of PANI nanotubes are closed to the pore diameter and thickness of AAO template, respectively, the arrangement of PANI nanotubes is very regular and uniform, the crystal form of PANI nanotubes is hexagonal, different from pseudo-orthorhombic crystal form of PANI bulk sample, and cell parameters a and b are 0.5008 nm. The change of crystal form is due to the confinement of AAO template, which makes the molecular chain of PANI arrange more ordered.

  15. PECVD Growth of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    McAninch, Ian; Arnold, James O. (Technical Monitor)

    2001-01-01

    Plasma enhanced chemical vapor deposition (PECVD), using inductively coupled plasma, has been used to grow carbon nanotubes (CNTs) and graphitic carbon fibers (GCF) on substrates sputtered with aluminum and iron catalyst. The capacitive plasma's power has been shown to cause a transition from nanotubes to nanofibers, depending on the strength of the plasma. The temperature, placement, and other factors have been shown to affect the height and density of the tube and fiber growth.

  16. Selective functionalization of carbon nanotubes

    NASA Technical Reports Server (NTRS)

    Strano, Michael S. (Inventor); Usrey, Monica (Inventor); Barone, Paul (Inventor); Dyke, Christopher A. (Inventor); Tour, James M. (Inventor); Kittrell, W. Carter (Inventor); Hauge, Robert H. (Inventor); Smalley, Richard E. (Inventor)

    2009-01-01

    The present invention is directed toward methods of selectively functionalizing carbon nanotubes of a specific type or range of types, based on their electronic properties, using diazonium chemistry. The present invention is also directed toward methods of separating carbon nanotubes into populations of specific types or range(s) of types via selective functionalization and electrophoresis, and also to the novel compositions generated by such separations.

  17. Titanium dioxide nanotube films: Preparation, characterization and electrochemical biosensitivity towards alkaline phosphatase.

    PubMed

    Roman, Ioan; Trusca, Roxana Doina; Soare, Maria-Laura; Fratila, Corneliu; Krasicka-Cydzik, Elzbieta; Stan, Miruna-Silvia; Dinischiotu, Anca

    2014-04-01

    Titania nanotubes (TNTs) were prepared by anodization on different substrates (titanium, Ti6Al4V and Ti6Al7Nb alloys) in ethylene glycol and glycerol. The influence of the applied potential and processing time on the nanotube diameter and length is analyzed. The as-formed nanotube layers are amorphous but they become crystalline when subjected to subsequent thermal treatment in air at 550°C; TNT layers grown on titanium and Ti6Al4V alloy substrates consist of anatase and rutile, while those grown on Ti6Al7Nb alloy consist only of anatase. The nanotube layers grown on Ti6Al7Nb alloy are less homogeneous, with supplementary islands of smaller diameter nanotubes, spread across the surface. Better adhesion and proliferation of osteoblasts was found for the nanotubes grown on all three substrates by comparison to an unprocessed titanium plate. The sensitivity towards bovine alkaline phosphatase was investigated mainly by electrochemical impedance spectroscopy in relation to the crystallinity, the diameter and the nature of the anodization electrolyte of the TNT/Ti samples. The measuring capacity of the annealed nanotubes of 50nm diameter grown in glycerol was demonstrated and the corresponding calibration curve was built for the concentration range of 0.005-0.1mg/mL.

  18. Engineering bamboo-type TiO2 nanotube arrays to enhance their photocatalytic property.

    PubMed

    Guan, Dongsheng; Hymel, Paul J; Zhou, Chengjun; Wang, Ying

    2014-06-01

    Bamboo-type TiO2 nanotube arrays with high surface area can be synthesized by alternating voltage (AV) anodization for their important use as photocatalytic medium. Their morphologies are highly dependent on preparation parameters including anodization time and electrolyte composition. Minimum time of high-voltage steps required for forming desired bamboo ridge spacing on these nanotubes can be calculated from current-time profiles recorded during potentiostatic anodization at the voltage. Water content in NH4F-containing ethylene glycol (EG) electrolytes is optimized simply from analyses of current transients or current-voltage relations for anodization in EG electrolytes with different amount of water, in order to achieve efficient electrochemical growth of TiO2 nanotubes for large ridge density and long tube length. Two types of bamboo-type TiO2 nanotubes with the same length of 5.46 microm but different ridge spacing are synthesized for photocatalytic degradation of methylene blue (MB) under UV radiation. Both of the bamboo-type nanotube arrays show improved photo catalysis compared to smooth TiO2 nanotubes of the same length, due to their larger surface area favorable for heterogeneous catalytic processes. In particular, the apparent rate constant of photocatalytic degradation on bamboo-type nanotubes is up to 29.4% higher than that for degradation on smooth ones.

  19. Platinum and Palladium Overlayers Dramatically Enhance the Activity of Ruthenium Nanotubes for Alkaline Hydrogen Oxidation

    SciTech Connect

    St. John, Samuel; Atkinson, Robert W.; Unocic, Kinga A.; Unocic, Raymond R.; Zawodzinski, Thomas A.; Papandrew, Alexander B.

    2015-10-18

    Templated vapor synthesis and thermal annealing were used to synthesize unsupported metallic Ru nanotubes with Pt or Pd overlayers. By controlling the elemental composition and thickness of these overlayers, we obtain nanostructures with very high alkaline hydrogen oxidation activity. For nanotubes with a nominal atomic composition of Ru0.90Pt0.10 display a surface-specific activity (2.4 mA/cm2) that is 35 times greater than that of pure Ru nanotubes at a 50 mV overpotential and 2.5 times greater than that of pure Pt nanotubes (0.98 mA/cm2). The surface-segregated structure also confers dramatically increased Pt utilization efficiency. We find a platinum-mass-specific activity of 1240 A/gPt for the optimized nanotube versus 280 A/gPt for carbon-supported Pt nanoparticles and 109 A/gPt for monometallic Pt nanotubes. Here, we attribute the enhancement of both area- and platinum-mass-specific activity to the atomic-scale homeomorphism of the nanotube form factor with adlayer-modified polycrystals. Subsurface ligand and bifunctional effects previously observed on segregated, adlayer-modified polycrystals are translated to nanoscale catalysts.

  20. Platinum and Palladium Overlayers Dramatically Enhance the Activity of Ruthenium Nanotubes for Alkaline Hydrogen Oxidation

    DOE PAGES

    St. John, Samuel; Atkinson, Robert W.; Unocic, Kinga A.; Unocic, Raymond R.; Zawodzinski, Thomas A.; Papandrew, Alexander B.

    2015-10-18

    Templated vapor synthesis and thermal annealing were used to synthesize unsupported metallic Ru nanotubes with Pt or Pd overlayers. By controlling the elemental composition and thickness of these overlayers, we obtain nanostructures with very high alkaline hydrogen oxidation activity. For nanotubes with a nominal atomic composition of Ru0.90Pt0.10 display a surface-specific activity (2.4 mA/cm2) that is 35 times greater than that of pure Ru nanotubes at a 50 mV overpotential and 2.5 times greater than that of pure Pt nanotubes (0.98 mA/cm2). The surface-segregated structure also confers dramatically increased Pt utilization efficiency. We find a platinum-mass-specific activity of 1240 A/gPtmore » for the optimized nanotube versus 280 A/gPt for carbon-supported Pt nanoparticles and 109 A/gPt for monometallic Pt nanotubes. Here, we attribute the enhancement of both area- and platinum-mass-specific activity to the atomic-scale homeomorphism of the nanotube form factor with adlayer-modified polycrystals. Subsurface ligand and bifunctional effects previously observed on segregated, adlayer-modified polycrystals are translated to nanoscale catalysts.« less

  1. Fast diffusion of silver in TiO2 nanotube arrays.

    PubMed

    Zhang, Wanggang; Liu, Yiming; Zhou, Diaoyu; Wang, Hui; Liang, Wei; Yang, Fuqian

    2016-01-01

    Using magnetron sputtering and heat treatment, Ag@TiO2 nanotubes are prepared. The effects of heat-treatment temperature and heating time on the evolution of Ag nanofilms on the surface of TiO2 nanotubes and microstructure of Ag nanofilms are investigated by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Ag atoms migrate mainly on the outmost surface of the TiO2 nanotubes, and fast diffusion of Ag atoms is observed. The diffusivity for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes at 400 °C is 6.87 × 10(-18) m(2)/s, which is three orders of magnitude larger than the diffusivities for the diffusion of Ag through amorphous TiO2 films. The activation energy for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes in the temperature range of 300 to 500 °C is 157 kJ/mol, which is less than that for the lattice diffusion of Ag and larger than that for the grain boundary diffusion. The diffusion of Ag atoms leads to the formation of Ag nanocrystals on the outmost surface of TiO2 nanotubes. Probably there are hardly any Ag nanocrystals formed inside the TiO2 nanotubes through the migration of Ag. PMID:27547630

  2. Biogenic Production of Photosensitive Arsenic-Sulfide Nanotubes by Shwanella sp. strain HN-41

    SciTech Connect

    Lee, Ji-Hoon; Kim, Min-Gyu; Yoo, Bongyoung; Myung, Nosang V.; Maeng, Jongsun; Lee, Takhe; Dohnalkova, Alice; Fredrickson, Jim K.; Sadowsky, Michael J.; Hur, Hor-Gil

    2007-12-07

    This paper describes the novel production of extensive filamentous, arsenic-sulfide (As-S) nanotubes (20 - 100 nm dia. X ~30 μm length) resulting from the dissimilatoryreduction of thiosulfate and arsenate by the bacterium Shewanella sp. HN-41. While there have been several reports of bacterial-produced nanowires composed entirely of biological macromolecules, here we report for the first time the biogenic formation ofphotosensitive and electroconductive nanotubes comprised of crystalline As-S and bacterial extracellular polymeric substances (EPS). To our knowledge, there have been no previous reports of the synthesis of such a material either by chemical or biological means. The biogenic As-S nanotubes reported here represent a significant advancement as building blocks for the production of nanodevices because of their high aspect ratios and unique size dependent properties. We characterized the structural evolution of the bacterial As-S nanotubes formed by strain HN-41 using XAFS spectra as well as XRD analyses, as a function of time and extent of bacterial reduction. In addition, we characterized the electrical and photoconductive properties of the As-S nanotubes. Upon aging, the As-S nanotubes behaved as metals and semiconductors in terms of their electrical and photoconductive properties, respectively. These results indicate that the dissimilatory bacterium Shewanella may be an excellent biological tool to bioengineer As-S nanotubes, which may provide useful materials for novel nano- and optoelectronic devices.

  3. Fast diffusion of silver in TiO2 nanotube arrays

    PubMed Central

    Zhang, Wanggang; Liu, Yiming; Zhou, Diaoyu; Wang, Hui

    2016-01-01

    Summary Using magnetron sputtering and heat treatment, Ag@TiO2 nanotubes are prepared. The effects of heat-treatment temperature and heating time on the evolution of Ag nanofilms on the surface of TiO2 nanotubes and microstructure of Ag nanofilms are investigated by X-ray diffraction, field emission scanning electron microscopy, and transmission electron microscopy. Ag atoms migrate mainly on the outmost surface of the TiO2 nanotubes, and fast diffusion of Ag atoms is observed. The diffusivity for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes at 400 °C is 6.87 × 10−18 m2/s, which is three orders of magnitude larger than the diffusivities for the diffusion of Ag through amorphous TiO2 films. The activation energy for the diffusion of Ag atoms on the outmost surface of the TiO2 nanotubes in the temperature range of 300 to 500 °C is 157 kJ/mol, which is less than that for the lattice diffusion of Ag and larger than that for the grain boundary diffusion. The diffusion of Ag atoms leads to the formation of Ag nanocrystals on the outmost surface of TiO2 nanotubes. Probably there are hardly any Ag nanocrystals formed inside the TiO2 nanotubes through the migration of Ag. PMID:27547630

  4. Strategies for specifically directing metal functionalization of protein nanotubes: constructing protein coated silver nanowires

    NASA Astrophysics Data System (ADS)

    Carreño-Fuentes, Liliana; Ascencio, Jorge A.; Medina, Ariosto; Aguila, Sergio; Palomares, Laura A.; Ramírez, Octavio T.

    2013-06-01

    Biological molecules that self-assemble in the nanoscale range are useful multifunctional materials. Rotavirus VP6 protein self-assembles into tubular structures in the absence of other rotavirus proteins. Here, we present strategies for selectively directing metal functionalization to the lumen of VP6 nanotubes. The specific in situ metal reduction in the inner surface of nanotube walls was achieved by the simple modification of a method previously reported to functionalize the nanotube outer surface. Silver nanorods and nanowires as long as 1.5 μm were formed inside the nanotubes by coalescence of nanoparticles. Such one-dimensional structures were longer than others previously obtained using bioscaffolds. The interactions between silver ions and the nanotube were simulated to understand the conditions that allowed nanowire formation. Molecular docking showed that a naturally occurring arrangement of aspartate residues enabled the stabilization of silver ions on the internal surface of the VP6 nanotubes. This is the first time that such a spatial arrangement has been proposed for the nucleation of silver nanoparticles, opening the possibility of using such an array to direct functionalization of other biomolecules. These results demonstrate the natural capabilities of VP6 nanotubes to function as a versatile biotemplate for nanomaterials.

  5. A High-Flux, Flexible Membrane with Parylene-encapsulated Carbon Nanotubes

    SciTech Connect

    Park, H G; In, J; Kim, S; Fornasiero, F; Holt, J K; Grigoropoulos, C P; Noy, A; Bakajin, O

    2008-03-14

    We present fabrication and characterization of a membrane based on carbon nanotubes (CNTs) and parylene. Carbon nanotubes have shown orders of magnitude enhancement in gas and water permeability compared to estimates generated by conventional theories [1, 2]. Large area membranes that exhibit flux enhancement characteristics of carbon nanotubes may provide an economical solution to a variety of technologies including water desalination [3] and gas sequestration [4]. We report a novel method of making carbon nanotube-based, robust membranes with large areas. A vertically aligned dense carbon nanotube array is infiltrated with parylene. Parylene polymer creates a pinhole free transparent film by exhibiting high surface conformity and excellent crevice penetration. Using this moisture-, chemical- and solvent-resistant polymer creates carbon nanotube membranes that promise to exhibit high stability and biocompatibility. CNT membranes are formed by releasing a free-standing film that consists of parylene-infiltrated CNTs, followed by CNT uncapping on both sides of the composite material. Thus fabricated membranes show flexibility and ductility due to the parylene matrix material, as well as high permeability attributed to embedded carbon nanotubes. These membranes have a potential for applications that may require high flux, flexibility and durability.

  6. Synthesis of Silica Nanotube Using Myelin Figure as Template and their Formation Mechanism.

    PubMed

    Fukamachi, Takumi; Endo, Takeshi; Yabuki, Yukinori; Ogura, Taku; Misono, Takeshi; Torigoe, Kanjiro; Sakai, Kenichi; Abe, Masahiko; Sakai, Hideki

    2015-01-01

    Silica nanotubes are synthesized through a sol-gel reaction of tetraethyl orthosilicate (TEOS) using myelin figures of Pluronic P123 as the structure-directing agent. The simultaneous progression of the formation of molecular assemblies that act as templates and the formation of silica frameworks though a sol-gel reaction of the silica precursor is a characteristic of this reaction system. The synthesized silica nanotubes were characterized using transmission electron microscopy (TEM), nitrogen adsorption/desorption measurements, and Fourier-transform infrared spectroscopy (FT-IR). The silica nanotubes were unilamellar with diameters of approximately 30 nm, membrane thicknesses of approximately 10 nm, and lengths exceeding a few hundred nanometers. The Brunauer-Emmett-Teller (BET) specific surface area was 589.46 m(2)/g. Silica nanotubes can also be obtained using other Pluronic surfactants that can form myelin figures. In this work, we also investigated the formation mechanism of the silica nanotubes. The typical diameter of a myelin figure is a few tens of micrometers. However, myelin figures with diameters of approximately 10 µm can form in systems with TEOS because bifurcation is induced by minute silica nuclei that form during the initial reaction between TEOS and water. Freeze fracture TEM (FF-TEM) observations revealed the existence of myelin figures with diameters of 20 to 30 nm, which are the same size and shape as the synthesized silica nanotubes. These results indicate that bifurcation of the myelin figures is induced by the silica nuclei that form via the initial reaction of TEOS, which result in the formation of bifurcated myelin figures with diameters of ~10 µm. Myelin figures with diameters of 20 to 30 nm form on the surface, and they become templates where the reaction of TEOS progresses to form silica nanotubes with diameters of approximately 30 nm. PMID:26028328

  7. Synthesis of Silica Nanotube Using Myelin Figure as Template and their Formation Mechanism.

    PubMed

    Fukamachi, Takumi; Endo, Takeshi; Yabuki, Yukinori; Ogura, Taku; Misono, Takeshi; Torigoe, Kanjiro; Sakai, Kenichi; Abe, Masahiko; Sakai, Hideki

    2015-01-01

    Silica nanotubes are synthesized through a sol-gel reaction of tetraethyl orthosilicate (TEOS) using myelin figures of Pluronic P123 as the structure-directing agent. The simultaneous progression of the formation of molecular assemblies that act as templates and the formation of silica frameworks though a sol-gel reaction of the silica precursor is a characteristic of this reaction system. The synthesized silica nanotubes were characterized using transmission electron microscopy (TEM), nitrogen adsorption/desorption measurements, and Fourier-transform infrared spectroscopy (FT-IR). The silica nanotubes were unilamellar with diameters of approximately 30 nm, membrane thicknesses of approximately 10 nm, and lengths exceeding a few hundred nanometers. The Brunauer-Emmett-Teller (BET) specific surface area was 589.46 m(2)/g. Silica nanotubes can also be obtained using other Pluronic surfactants that can form myelin figures. In this work, we also investigated the formation mechanism of the silica nanotubes. The typical diameter of a myelin figure is a few tens of micrometers. However, myelin figures with diameters of approximately 10 µm can form in systems with TEOS because bifurcation is induced by minute silica nuclei that form during the initial reaction between TEOS and water. Freeze fracture TEM (FF-TEM) observations revealed the existence of myelin figures with diameters of 20 to 30 nm, which are the same size and shape as the synthesized silica nanotubes. These results indicate that bifurcation of the myelin figures is induced by the silica nuclei that form via the initial reaction of TEOS, which result in the formation of bifurcated myelin figures with diameters of ~10 µm. Myelin figures with diameters of 20 to 30 nm form on the surface, and they become templates where the reaction of TEOS progresses to form silica nanotubes with diameters of approximately 30 nm.

  8. Computational Nanotechnology of Nanotubes, Composites, and Electronics

    NASA Technical Reports Server (NTRS)

    Srivastava, D.; Biegel, Bryan A. (Technical Monitor)

    2002-01-01

    This viewgraph presentation addresses carbon nanotubes, their mechanical and thermal properties, and their structure, as well as possible miniature devices which may be assembled in the future from carbon nanotubes.

  9. Probing Photosensitization by Functionalized Carbon Nanotubes

    EPA Science Inventory

    Carbon nanotubes (CNTs) photosensitize the production of reactive oxygen species that can damage organisms by biomembrane oxidation or mediate CNTs' environmental transformations. The photosensitized nature of derivatized carbon nanotubes from various synthetic methods, and thus ...

  10. Scanning tunneling microscopy imaging of nanotubes

    SciTech Connect

    Antonenko, S. V. Malinovskaya, O. S.; Mal'tsev, S. N.

    2007-07-15

    Samples of carbon paper containing multiwalled carbon nanotube films are produced by current annealing. A scanning tunneling microscope is used to examine the structure of the modified carbon paper. X-, Y-, and V-shaped nanotubes are found.

  11. Occupational Exposure to Carbon Nanotubes and Nanofibers

    MedlinePlus

    ... Current Intelligence Bulletin 65: Occupational Exposure to Carbon Nanotubes and Nanofibers Recommend on Facebook Tweet Share Compartir ... composed of engineered nanoparticles, such as metal oxides, nanotubes, nanowires, quantum dots, and carbon fullerenes (buckyballs), among ...

  12. LDRD final report on carbon nanotube composites

    SciTech Connect

    Cahill, P.A.; Rand, P.B.

    1997-04-01

    Carbon nanotubes and their composites were examined using computational and experimental techniques in order to modify the mechanical and electrical properties of resins. Single walled nanotubes were the focus of the first year effort; however, sufficient quantities of high purity single walled nanotubes could not be obtained for mechanical property investigations. The unusually high electrical conductivity of composites loaded with <1% of multiwalled nanotubes is useful, and is the focus of continuing, externally funded, research.

  13. Carbon nanotubes by the metallocene route

    NASA Astrophysics Data System (ADS)

    Sen, Rahul; Govindaraj, A.; Rao, C. N. R.

    1997-03-01

    Pyrolysis of metallocenes such as ferrocene, cobaltocene and nickelocene, is shown to yield carbon nanotubes and metal-filled onion-like structures. Pyrolysis of benzene in the presence of a metallocene gives high yields of nanotubes, the wall thickness of the nanotubes depending on the metallocene content. Pyrolysis of benzene in the absence of any metal however gives monodispersed nanospheres of carbon rather than nanotubes.

  14. Carbon nanotube biosensors

    PubMed Central

    Tîlmaciu, Carmen-Mihaela; Morris, May C.

    2015-01-01

    Nanomaterials possess unique features which make them particularly attractive for biosensing applications. In particular, carbon nanotubes (CNTs) can serve as scaffolds for immobilization of biomolecules at their surface, and combine several exceptional physical, chemical, electrical, and optical characteristics properties which make them one of the best suited materials for the transduction of signals associated with the recognition of analytes, metabolites, or disease biomarkers. Here we provide a comprehensive review on these carbon nanostructures, in which we describe their structural and physical properties, functionalization and cellular uptake, biocompatibility, and toxicity issues. We further review historical developments in the field of biosensors, and describe the different types of biosensors which have been developed over time, with specific focus on CNT-conjugates engineered for biosensing applications, and in particular detection of cancer biomarkers. PMID:26579509

  15. Carbon Nanotube Biosensors

    NASA Astrophysics Data System (ADS)

    Tilmaciu, Carmen-Mihaela; Morris, May

    2015-10-01

    Nanomaterials possess unique features which make them particularly attractive for biosensing applications. In particular Carbon Nanotubes (CNTs) can serve as scaffolds for immobilization of biomolecules at their surface, and combine several exceptional physical, chemical, electrical and optical characteristics properties which make them one of the best suited materials for the transduction of signals associated with the recognition of analytes, metabolites or disease biomarkers. Here we provide a comprehensive review on these carbon nanostructures, in which we will describe their structural and physical properties, discuss functionalization and cellular uptake, biocompatibility and toxicity issues. We further review historical developments in the field of biosensors, and describe the different types of biosensors which have been developed over time, with specific focus on CNT-conjugates engineered for biosensing applications, and in particular detection of cancer biomarkers.

  16. Carbon nanotube optical mirrors

    NASA Astrophysics Data System (ADS)

    Chen, Peter C.; Rabin, Douglas

    2015-01-01

    We report the fabrication of imaging quality optical mirrors with smooth surfaces using carbon nanotubes (CNT) embedded in an epoxy matrix. CNT/epoxy is a multifunctional composite material that has sensing capabilities and can be made to incorporate self-actuation. Moreover, as the precursor is a low density liquid, large and lightweight mirrors can be fabricated by processes such as replication, spincasting, and three-dimensional printing. Therefore, the technology holds promise for the development of a new generation of lightweight, compact "smart" telescope mirrors with figure sensing and active or adaptive figure control. We report on measurements made of optical and mechanical characteristics, active optics experiments, and numerical modeling. We discuss possible paths for future development.

  17. Dispersible carbon nanotubes.

    PubMed

    Soulié-Ziakovic, Corinne; Nicolaÿ, Renaud; Prevoteau, Alexandre; Leibler, Ludwik

    2014-01-27

    A method is proposed to produce nanoparticles dispersible and recyclable in any class of solvents, and the concept is illustrated with the carbon nanotubes. Classically, dispersions of CNTs can be achieved through steric stabilization induced by adsorbed or grafted polymer chains. Yet, the surface modification of CNTs surfaces is irreversible, and the chemical nature of the polymer chains imposes the range of solvents in which CNTs can be dispersed. To address this limitation, supramolecular bonds can be used to attach and to detach polymer chains from the surface of CNTs. The reversibility of supramolecular bonds offers an easy way to recycle CNTs as well as the possibility to disperse the same functional CNTs in any type of solvent, by simply adapting the chemical nature of the stabilizing chains to the dispersing medium. The concept of supramolecular functionalization can be applied to other particles, for example, silica or metal oxides, as well as to dispersing in polymer melts, films or coatings.

  18. Carbon nanotube biconvex microcavities

    SciTech Connect

    Butt, Haider Ahmed, Rajib; Yetisen, Ali K.; Yun, Seok Hyun; Dai, Qing

    2015-03-23

    Developing highly efficient microcavities with predictive narrow-band resonance frequencies using the least amount of material will allow the applications in nonlinear photonic devices. We have developed a microcavity array that comprised multi-walled carbon nanotubes (MWCNT) organized in a biconvex pattern. The finite element model allowed designing microcavity arrays with predictive transmission properties and assessing the effects of the microarray geometry. The microcavity array demonstrated negative index and produced high Q factors. 2–3 μm tall MWCNTs were patterned as biconvex microcavities, which were separated by 10 μm in an array. The microcavity was iridescent and had optical control over the diffracted elliptical patterns with a far-field pattern, whose properties were predicted by the model. It is anticipated that the MWCNT biconvex microcavities will have implications for the development of highly efficient lenses, metamaterial antennas, and photonic circuits.

  19. Functionalization of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Khare, Bishun N. (Inventor); Meyyappan, Meyya (Inventor)

    2009-01-01

    Method and system for functionalizing a collection of carbon nanotubes (CNTs). A selected precursor gas (e.g., H2 or F2 or CnHm) is irradiated to provide a cold plasma of selected target species particles, such as atomic H or F, in a first chamber. The target species particles are d irected toward an array of CNTs located in a second chamber while suppressing transport of ultraviolet radiation to the second chamber. A CNT array is functionalized with the target species particles, at or below room temperature, to a point of saturation, in an exposure time interval no longer than about 30 sec. *Discrimination against non-target species is provided by (i) use of a target species having a lifetime that is much greater than a lifetime of a non-target species and/or (2) use of an applied magnetic field to discriminate between charged particle trajectories for target species and for non-target species.

  20. Cantilevered carbon nanotube hygrometer

    NASA Astrophysics Data System (ADS)

    Kuroyanagi, Toshinori; Terada, Yuki; Takei, Kuniharu; Akita, Seiji; Arie, Takayuki

    2014-05-01

    We investigate the effects of humidity on the vibrations of carbon nanotubes (CNTs) using two types of CNT cantilevers: open-ended and close-ended CNT cantilevers. As the humidity increases, the resonant frequency of the open-ended CNT cantilever decreases due to the adsorption of water molecules onto the CNT tip, whereas that of the close-ended CNT cantilever increases probably due to the change in the viscosity of the air surrounding the CNT cantilever, which is negatively correlated with the humidity of air. Our findings suggest that a close-ended CNT cantilever is more suitable for a quick-response and ultrasensitive hygrometer because it continuously reads the viscosity change of moist air in the vicinity of the CNT.