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1

Proton irradiation of metallic single-walled carbon nanotubes  

Microsoft Academic Search

Metallic single-walled carbon nanotube (SWNT) films on space qualified solar cell coverglass were irradiated with 100 keV protons at doses of 1 × 1013 and 1 × 1014 protons\\/cm2. The samples were analyzed using UV-vis-NIR spectroscopy, Raman spectroscopy, and four-point probe measurements. The results indicate that defects are not introduced into the metallic carbon nanotubes after irradiation.

Don Walker; Colin J. Mann; John C. Nocerino; Simon H. Liu

2011-01-01

2

Energy gaps in "metallic" single-walled carbon nanotubes.  

PubMed

Metallic single-walled carbon nanotubes have been proposed to be good one-dimensional conductors. However, the finite curvature of the graphene sheet that forms the nanotubes and the broken symmetry due to the local environment may modify their electronic properties. We used low-temperature atomically resolved scanning tunneling microscopy to investigate zigzag and armchair nanotubes, both thought to be metallic. "Metallic" zigzag nanotubes were found to have energy gaps with magnitudes that depend inversely on the square of the tube radius, whereas isolated armchair tubes do not have energy gaps. Additionally, armchair nanotubes packed in bundles have pseudogaps, which exhibit an inverse dependence on tube radius. These observed energy gaps suggest that most "metallic" single-walled nanotubes are not true metals, and they have implications for our understanding of the electronic properties and potential applications of carbon nanotubes. PMID:11326093

Ouyang, M; Huang, J L; Cheung, C L; Lieber, C M

2001-04-27

3

Coating geometries of metals on single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

This paper studies the coating geometries of metals on single-walled carbon nanotubes (SWNTs) on the basis of the nucleation theory and wetting theory. The metal surface energy, cohesion energy, diffusion barrier, and metal-SWNT interfacial energy are calculated using first-principles calculation. Metals including Fe, Al, Au, Pd, Ni, and Ti are considered. For Ti, Ni, and Pd, low metal-SWNT interfacial energies and high diffusion barriers are responsible for forming continuous or quasicontinuous layers on the SWNT surface. In contrast, Al and Au have small diffusion barriers and poor SWNT surface wetting, thus they tend to aggregate and form large clusters. Although the binding energy between Fe and SWNTs is large, due to the large cohesion energy and poor wetting, Fe may form isolated clusters. All results are in good agreement with experimental observations.

He, Yu; Zhang, Jinyu; Wang, Yan; Yu, Zhiping

2010-02-01

4

Random telegraph noise in metallic single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We have investigated random telegraph noise (RTN) observed in individual metallic carbon nanotubes (CNTs). Mean lifetimes in high- and low-current states, ?high and ?low, have been studied as a function of bias-voltage and gate-voltage as well as temperature. By analyzing the statistics and features of the RTN, we suggest that this noise is due to the random transition of defects between two metastable states, activated by inelastic scattering with conduction electrons. Our results indicate an important role of defect motions in the 1/f noise in CNTs.

Chung, Hyun-Jong; Woo Uhm, Tae; Won Kim, Sung; Gyu You, Young; Wook Lee, Sang; Ho Jhang, Sung; Campbell, Eleanor E. B.; Woo Park, Yung

2014-05-01

5

Selective etching of metallic single-wall carbon nanotubes with hydrogen plasma  

Microsoft Academic Search

We present Raman scattering and scanning tunnelling microscopy (STM) measurements on hydrogen plasma etched single-wall carbon nanotubes (SWNTs). Interestingly, both the STM and Raman spectroscopy show that the metallic SWNTs are dramatically altered and highly defected by the plasma treatment. In addition, structural characterizations show that metal catalysts are detached from the ends of the SWNT bundles. For semiconducting SWNTs

A. Hassanien; M. Tokumoto; P. Umek; D. Vrbanic; M. Mozetic; D. Mihailovic; P. Venturini; S Pejovnik

2005-01-01

6

Bound excitons and optical absorption spectra of (10,10) metallic single-walled carbon nanotubes  

Microsoft Academic Search

Motivated by recent theoretical prediction of bound excitons [1] in small diameter metallic single-walled carbon nanotubes, we study the optical spectra of the larger diameter (10,10) metallic tube. We use an interacting-particle Green's function approach which includes calculations of the quasiparticle excitation spectrum (within the GW approximation for the electron self energy) and the electron-hole excitation spectrum (within the Bethe-Salpeter

Jack Deslippe; Catalin Spataru; Steven Louie

2006-01-01

7

Characterizations of Enriched Metallic Single-Walled Carbon Nanotubes in Polymer Composite  

NASA Technical Reports Server (NTRS)

Using different processing conditions, we disperse the single-walled carbon nanotube (SWNT) into the polymethyl methacrylate (PMMA) to form composites. In the melt-blended sample, the SWNTs originally semiconducting - became predominantly metallic after dispersion into the melt-blended composite. The interaction of the PMMA and SWNT is investigated by the polarized Raman studies. The structure changes in the PMMA and SWNT shows that the anisotropic interactions are responsible for SWNT electronic density of states (DOS) changes. The increased metallic SWNT percentage is confirmed by the conductivity and dielectric constant measurements .

Chen, Bin; Li, Jing; Lu, Yijiang; Cinke, Martin; Au, Dyng; Harmon, Julie P.; Muisener, Patricia Anne O.; Clayton, LaNetra; D'Angelo, John

2003-01-01

8

Photogenerated Free Carrier Dynamics in Metal and Semiconductor Single-Walled Carbon Nanotube Films  

SciTech Connect

Time-resolved THz spectroscopy (TRTS) is employed to study the photogenerated charge-carrier dynamics in transparent films of single-walled carbon nanotubes (SWNTs). Two films were investigated: a film with 94% semiconducting-type tubes (s-SWNTs) and a film with only 7% s-SWNT and 93% metal-type tubes (m-SWNTs). We conclude that charge-carriers are generated with >60% yields at low light intensities in both films. Free-carriers are generated by a linear exciton dissociation process that occurs within 1 ps and is independent of excitation wavelength or tube type.

Beard, M. C.; Blackburn, J. L.; Heben, M. J.

2008-01-01

9

Effect of doping on single-walled carbon nanotubes network of different metallicity.  

PubMed

Effects of doping on single-walled carbon nanotubes (SWNT) networks with different metallicity are reported through the study of sheet resistance changes upon annealing and acid treatment. SWNT film with high metallic tube content is found to have relatively good chemical stability against post treatments, as demonstrated from its stable film performance in ambient after annealing, and merely 15% reduction in sheet resistance upon sulfuric acid treatment. Conversely, film stability of SWNT film with low metallic content which comprises largely of semiconducting SWNT varies with days in ambient, and its sheet resistance changes drastically after treated with acid, indicating the extreme sensitivity of semiconducting SWNT to surrounding environment. The results suggest that annealing removes unintentional oxygen doping from the ambient and shifts the Fermi level towards the intrinsic Fermi level. Acid treatment, on the other hand, introduces physisorbed and chemisorbed oxygen and shifts the Fermi level away from the intrinsic level and increases the hole doping. PMID:23033837

Tey, Ju Nie; Ho, Xinning; Wei, Jun

2012-01-01

10

Metallic single-walled, carbon nanotube temperature sensor with self heating  

NASA Astrophysics Data System (ADS)

A metallic single-walled carbon nanotube (SWCNT) has been proposed as a highly sensitive temperature sensor with consideration of self-heating induced scattering. This sensor can be implemented to sense temperature spanning from 20º C to 400º C with high temperature coefficient of resistivity (TCR) ranging from 0.0035/ºC to 0.009/ ºC. Important aspect of this work is consideration of self-heating in SWCNT which was not considered in earlier carbon nanotube based temperature sensors. We have studied a metallic SWCNT over a silicon dioxide substrate and in between two metal contacts. Bias voltage of 0.1V has been applied in between these two contacts. For resistivity calculation, we have utilized one-dimensional semi-classical transport model assuming SWCNT is perfectly conducting. The heat flow equation has been solved assuming steady state flow of heat. We have also assumed that contact and substrate are in thermal equilibrium with the surroundings. Since self-heating significantly affects electro-thermal transport, incorporation of this phenomenon enables to design and model ambient temperature sensor accurately. We have studied CNT sensor with different lengths and chiralities. The results show that resistances of longest (3?m) and thinnest (9, 0) CNTs increase rapidly with temperature. For a 3?m long metallic SWCNT with chirality index (9, 0), TCR has the maximum value (~0.009/ ºC).

Mohsin, K. M.; Banadaki, Y. M.; Srivastava, A.

2014-04-01

11

Study on the electronic structure and hydrogen adsorption by transition metal decorated single wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

The ground state geometry and electronic structure of various 4d transition metal (TM) atom (Y, Zr, Nb and Mo) decorated single wall carbon nanotubes (SWCNTs) are obtained using density functional theory and the projector augmented wave (PAW) method. We found a systematic change in the adsorption site of the transition metal atom with increasing number of d electrons. We also predicted that Y and Zr decorated SWCNTs are metallic whereas Nb and Mo decorated SWCNTs are semiconducting. From detailed electronic structure and Bader charge analysis we found that the systematic variation of the adsorption site with the number of d electrons is related to the decreasing amount of charge transfer from the TM atom to the SWCNT along the 4d series. We have also studied the hydrogen adsorption capabilities of these decorated SWCNTs to understand the role of transition metal d electrons in binding the hydrogen molecules to the system. We found that metallic SWCNT + TM systems are better hydrogen adsorbers. We showed that the hydrogen adsorption by a TM decorated SWCNT will be maximum when all the adsorptions are physisorption and that the retention of magnetism by the system is crucial for physisorption.

Modak, P.; Chakraborty, Brahmananda; Banerjee, S.

2012-05-01

12

The effect of single wall carbon nanotube metallicity on genomic DNA-mediated chirality enrichment  

NASA Astrophysics Data System (ADS)

Achieving highly enriched single wall carbon nanotubes (SWNTs) is one of the major hurdles today because their chirality-dependent properties must be uniform and predictable for use in nanoscale electronics. Due to the unique wrapping and groove-binding mechanism, DNA has been demonstrated as a highly specific SWNT dispersion and fractionation agent, with its enrichment capabilities depending on the DNA sequence and length as well as the nanotube properties. Salmon genomic DNA (SaDNA) offers an inexpensive and scalable alternative to synthetic DNA. In this study, SaDNA enrichment capabilities were tested on SWNT separation with varying degrees of metallicity that were formulated from mixtures of commercial metallic (met-) and semiconducting (sem-) abundant SWNTs. The results herein demonstrate that the degree of metallicity of the SWNT sample has a significant effect on the SaDNA enrichment capabilities, and this effect is modeled based on deconvolution of the near-infrared (NIR) absorption spectra and verified with photoluminescence emission (PLE) measurements. Using molecular dynamics and circular dichroism, the preferential SaDNA mediated separation of the (6, 5) sem-tube is shown to be largely influenced by the presence of met-SWNTs.Achieving highly enriched single wall carbon nanotubes (SWNTs) is one of the major hurdles today because their chirality-dependent properties must be uniform and predictable for use in nanoscale electronics. Due to the unique wrapping and groove-binding mechanism, DNA has been demonstrated as a highly specific SWNT dispersion and fractionation agent, with its enrichment capabilities depending on the DNA sequence and length as well as the nanotube properties. Salmon genomic DNA (SaDNA) offers an inexpensive and scalable alternative to synthetic DNA. In this study, SaDNA enrichment capabilities were tested on SWNT separation with varying degrees of metallicity that were formulated from mixtures of commercial metallic (met-) and semiconducting (sem-) abundant SWNTs. The results herein demonstrate that the degree of metallicity of the SWNT sample has a significant effect on the SaDNA enrichment capabilities, and this effect is modeled based on deconvolution of the near-infrared (NIR) absorption spectra and verified with photoluminescence emission (PLE) measurements. Using molecular dynamics and circular dichroism, the preferential SaDNA mediated separation of the (6, 5) sem-tube is shown to be largely influenced by the presence of met-SWNTs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00458a

Kim, Steve S.; Hisey, Colin L.; Kuang, Zhifeng; Comfort, Donald A.; Farmer, Barry L.; Naik, Rajesh R.

2013-05-01

13

Thermal stability and reactivity of metal halide filled single-walled carbon nanotubes.  

PubMed

Thermal stability and reactivity to oxidation of several nanocomposite systems obtained by encapsulation of metal halides in single-walled carbon nanotubes are studied. Thermogravimetric analysis coupled with Raman spectroscopy allows insight into the various contributing factors, such as charge transfer, strain, and defect formation, and establishing a hierarchy of reactivity for the systems studied (AgX@SWCNTs, with X = Br, I; SWCNTs = arc discharge and HiPCO). The activation energy for oxidation decreases considerably after filling, indicating that filled nanotubes are more amenable to controlled modifications based on chemical reactivity than the originating empty nanotubes. The complete removal of the carbon shell at high temperatures does not preserve the nanowire morphology of the encapsulated halides; these are freed on surfaces in the form of nanoparticles arranged in 1D patterns. Metallic nanoparticles were obtained after hydrogen reduction of the halides, and growth of silicon nanowires in the footprint of the originating nanocomposites was demonstrated from such Co seeds. MX@SWCNTs (M = Ag, Co) can thus be used as environmentally stable nanoscale containers that allow the deliverance of catalytic nanoparticles in a prepatterned and aligned way. PMID:16570956

Bendall, J S; Ilie, A; Welland, M E; Sloan, J; Green, M L H

2006-04-01

14

Conversion of metallic single-walled carbon nanotube networks to semiconducting through electrochemical ornamentation.  

PubMed

Field-effect transistors (FETs) that incorporate single-walled carbon nanotube (SWNT) networks experience decreased on-off current ratios (I(on)/I(off)) due to the presence of metallic nanotubes. Herein, we describe a method to increase I(on)/I(off) without the need for either specialized SWNT growth methods or post growth processing steps to remove metallic nanotubes. SWNTs that were grown using conventional arc discharge methods were deposited from aqueous suspension. Then, the SWNTs in the network were decorated with Cu2O nanoparticles that acted as controllable valves that restricted current flow at positive gate voltages. This resulted in an unprecedented reduction in I(off), as the sub-10 nm sized nanoclusters acted as numerous tunable valves, providing greatly improved network sensitivity to gate voltages in the relatively small range of ±10 V, increasing I(on)/I(off) by up to 205-fold. Larger nanoclusters were found to increase the network conductivity but decrease I(on)/I(off). The ability to convert metallic SWNTs to semiconducting without removing them allows for enhanced I(on) and lower noise while still achieving greatly enhanced magnitudes of I(on)/I(off). PMID:23607878

Asheghali, Darya; Vichchulada, Pornnipa; Lay, Marcus D

2013-05-22

15

The effect of single wall carbon nanotube metallicity on genomic DNA-mediated chirality enrichment.  

PubMed

Achieving highly enriched single wall carbon nanotubes (SWNTs) is one of the major hurdles today because their chirality-dependent properties must be uniform and predictable for use in nanoscale electronics. Due to the unique wrapping and groove-binding mechanism, DNA has been demonstrated as a highly specific SWNT dispersion and fractionation agent, with its enrichment capabilities depending on the DNA sequence and length as well as the nanotube properties. Salmon genomic DNA (SaDNA) offers an inexpensive and scalable alternative to synthetic DNA. In this study, SaDNA enrichment capabilities were tested on SWNT separation with varying degrees of metallicity that were formulated from mixtures of commercial metallic (met-) and semiconducting (sem-) abundant SWNTs. The results herein demonstrate that the degree of metallicity of the SWNT sample has a significant effect on the SaDNA enrichment capabilities, and this effect is modeled based on deconvolution of the near-infrared (NIR) absorption spectra and verified with photoluminescence emission (PLE) measurements. Using molecular dynamics and circular dichroism, the preferential SaDNA mediated separation of the (6, 5) sem-tube is shown to be largely influenced by the presence of met-SWNTs. PMID:23624632

Kim, Steve S; Hisey, Colin L; Kuang, Zhifeng; Comfort, Donald A; Farmer, Barry L; Naik, Rajesh R

2013-06-01

16

Annealing single-walled metallic carbon nanotube devices in ultra-high vacuum  

Microsoft Academic Search

Single walled carbon nanotube (SWNT) devices were fabricated and annealed in ultra high vacuum (UHV) with simultaneous electrical characterization. As one-dimensional crystals with nanometer scale diameters and up to meter scale lengths, SWNTs offer a unique opportunity to probe 1D transport in mesoscopic electronics. Furthermore, all of the atoms in SWNTs are surface atoms which means that the electronic properties

Alexander Allen Kane

2010-01-01

17

Covalent sidewall functionalization of single-walled carbon nanotubes via reduction of benzophenone by potassium metal  

Microsoft Academic Search

Covalent sidewall functionalization of single-walled carbon nanotubes (SWNTs) via addition of diphenylcarbinol (DPC) anions and diphenylcarbinol radicals was reported. The reaction of a potassium atom with a benzophenone molecule results in transferring one electron from the potassium to the benzophenone, forming a radical which adds readily to nanotubes to form functionalized SWNTs (DPC-SWNTs). DPC anions were generated from two- electrons

Liangming Wei; Zijiong Li; Yafei Zhang

2008-01-01

18

Single walled carbon nanotube-metal oxide nanocomposites for reversible and reproducible storage of hydrogen.  

PubMed

Composite material consisting of single walled carbon nanotubes (SWCNTs) and metal oxide nanoparticles has been prepared and their hydrogen storage performance is evaluated. Metal oxides such as tin oxide (SnO2), tungsten trioxide (WO3), and titanium dioxide (TiO2) are chosen as the composite constituents. The composites have been prepared by means of ultrasonication. Then, the composite samples are deposited on alumina substrates and at 100 °C in a Sieverts-like hydrogenation setup. Characterization techniques such as transmission electron microscopy (TEM), Raman spectroscopy, scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, energy dispersive spectroscopy (EDS), CHN elemental analysis, and thermogravimetric (TG) measurements are used to analyze the samples at various stages of experiments. Hydrogen storage capacity of the composites namely, SWCNT-SnO2, SWCNT-WO3, and SWCNT-TiO2 are found to be 1.1, 0.9, and 1.3 wt %, respectively. Hydrogenated composite samples are stable at room temperature and desorption of hydrogen is found to be 100% reversible. Desorption temperature ranges and binding energy ranges of hydrogen have been measured from the desorption studies. The hydrogenation, dehydrogenation temperature, and binding energy of hydrogen fall in the recommended range of a suitable hydrogen storage medium applicable for fuel cell applications. Reproducibility and deterioration level of the composite samples have also been examined. PMID:24117025

Silambarasan, D; Surya, V J; Vasu, V; Iyakutti, K

2013-11-13

19

Metal coated functionalized single-walled carbon nanotubes for composite applications  

NASA Astrophysics Data System (ADS)

This study is considered as a method for producing multifunctional composite materials by using metals coated Single-walled Carbon Nanotubes (SWCNTs). In this research, various metals (Ni, Cu, Ag) were successfully deposited onto the surface of SWCNTs. It has been found that homogenous dispersion and dense nucleation sites are the necessary conditions to form uniform coatings on SWCNTs. Functionalization has been applied to achieve considerable improvement in the dispersion of purified SWCNTs and creates more nucleation sites for subsequent metal deposition. A three-step electroless plating approach was used and the coating mechanism is described in the paper. The samples were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Raman spectroscopy, fourier transform infrared spectroscopy (FTIR), and energy dispersive X-ray spectroscopy (EDX). Bulk copper/aluminum-SWNT composites were processed by powder metallurgy with wet mixing techniques. Coated SWCNTs were well dispersed in the metal matrix. Cold pressing followed by sintering was applied to control porosity. The relationships between hardness and SWCNTs addition were discussed. Ni-SWCNTs composite coatings were prepared by electro-composite deposition. SWCNTs were suspended in a Ni deposition electrolyte and deposited together with nickel during electrodeposition. SWCNTs concentrations in the coatings were found to be related to the SWCNTs concentration in the solution, current density and agitation rate. The microstructure of the coatings has been examined by electron microscopy. Ni coated SWCNTs were also incorporated into the high temperature Bismaleimide (BMI)/graphite composite to improve Electromagnetic Interference (EMI) shielding and surface conductivity. The vacuum assisted resin transfer molding (VARTM) was used to process these composites. Surface and volume resistivity and EMI shielding effectiveness of the composites were assessed. A comparison with baseline data of unfilled BMI fiber reinforced composites is presented.

Zeng, Qiang

20

Annealing single-walled metallic carbon nanotube devices in ultra-high vacuum  

NASA Astrophysics Data System (ADS)

Single walled carbon nanotube (SWNT) devices were fabricated and annealed in ultra high vacuum (UHV) with simultaneous electrical characterization. As one-dimensional crystals with nanometer scale diameters and up to meter scale lengths, SWNTs offer a unique opportunity to probe 1D transport in mesoscopic electronics. Furthermore, all of the atoms in SWNTs are surface atoms which means that the electronic properties can be examined and tailored using the well-developed tools of surface chemistry. However, electronic resistances and noise for technologically relevant small-diameter SWNT devices are too high for commercial applications. In this work, intrinsic and extrinsic sources of scattering in SWNTs were examined by heating SWNT field effect transistors in UHV with while monitoring changes in the devices' resistance, transconductance, and conductance fluctuations. The effects of the contact interface were studied by varying the electrode metal, including palladium, titanium, and platinum contacts. It was found that metal-SWNT contact interfaces are the primary scatterers in devices as fabricated, but the contact resistance can be greatly reduced by annealing to a limit that depends primarily on the surface chemistry of the electrode metal and the geometry of the interface. Secondary sources of scattering include surface adsorbates on the electrodes and substrate, sub-strate oxide phonons and SWNT phonons. Adsorbates are the primary source of 1/f conductance noise, followed by the electrode interface. Annealing devices in UHV was found to reduce the contact resistance, noise, and device to device inhomogeneity. Graphene, formed through catalysis on the Pt surface during the anneal, was found to make the best contact to SWNTs, rather than the conventional Pd, Ti, and Pt, both in terms of contact resistance and noise.

Kane, Alexander Allen

21

Theoretical studies of electronic properties of magnesium oxide catalysts and metal-intercalated single-wall carbon nanotubes  

Microsoft Academic Search

This dissertation presents a theoretical study of electronic properties for MgO surfaces and metal-intercalated single-wall carbon nanotubes (SWNT's). The ab initio embedded cluster model and ab initio periodic calculation have been introduced and applied to the MgO surface and metal-intercalated SWNT systems, respectively. For the MgO catalyst, the catalytic properties of the perfect and oxygen vacancy MgO(100) surfaces for water

Yan Wang

2006-01-01

22

Photocatalytic engineering of single-walled carbon nanotubes: from metal-to-semiconductor conversion to cutting and patterning.  

PubMed

With a TiO2 -based photocatalytic approach, both an arbitrary geometry tailoring of single-walled carbon nanotubes (SWCNTs) on various substrates and the conversion of metallic to semiconducting SWCNTs are demonstrated. Taking advantage of the selectivity on the diameter and metallicity of SWCNTs, 100% depletable SWCNT-based field-effect transistors are achieved, with Ion /Ioff improvements up to five orders of magnitude. PMID:23494958

Nie, Yufeng; Zhang, Liming; Wu, Di; Chen, Yubin; Zhang, Guoming; Xie, Qin; Liu, Zhongfan

2013-04-22

23

Hydrogen storage properties of catalyst metal-doped single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

In the past decade, hydrogen storage in solid-state materials has been one of the biggest hurdles to meet the storage density, safety, reliability and cost reduction needed for a hydrogen fuel economy. Single-walled carbon nanotubes (SWNTs) are particularly intriguing for hydrogen storage because each carbon atom is a surface site, and calculations have indicated that hydrogen bond strength can be tuned by adjusting the nanotube diameter. However, exposure to molecular hydrogen has resulted in only modest hydrogen uptake, as opposed to exposure to atomic hydrogen where significant hydrogen bonding has been observed. This has motivated studies of catalyst metal-doped SWNTs in order to facilitate the disassociation process of hydrogen molecules to improve hydrogen storage in these nanotubes. In this work, the hydrogen uptake and release properties were measured for undoped and catalyst metal-doped high pressure CO conversion (HiPco) SWNTs. Palladium and platinum catalytic nanoparticles were electrochemically (EC), UHV sputter (Sp)-deposited and e-beam evaporated (EE) on the surface of SWNT bundles. Rigorous and precise measurements were taken by employing a specially-designed Sieverts' volumetric apparatus up to 30 Bar of pressure that is capable of measuring hydrogen storage in milligram quantities. The undoped SWNTs exhibited a reversible hydrogen uptake capacity of 0.17 wt% in gravimetric basis at room temperature. The capacity of Pd-doped SWNTs was increased to 0.53 and 0.72 wt% for EC and Sp-doped samples, respectively. This corresponds to an increase of a factor of 3 to 4 over undoped material. For the case of Pt-doped SWNTs, the uptake capacities of EC and Sp-doped samples were also increased to 0.40 and 0.51 wt%, respectively. The increase of the stored hydrogen is explained by sequential processes of molecular hydrogen dissociation, spillover, and surface diffusion. Hydrogen uptake kinetics was also measured and compared between the samples. The formation of stable C-H bonds was confirmed by XPS and FTIR spectroscopy techniques. It was observed that the hydrogen stored in the metal catalyst-doped SWNTs could be completely removed after a prolonged evacuation process even at room temperature. A metal-catalyzed hydrogen desorption model was developed, and the curve fitting by the model replicated the experimental observation.

Lee, Yong-Won

24

Experimental characterization of single-walled carbon nanotube film-Si Schottky contacts using metal-semiconductor-metal structures  

NASA Astrophysics Data System (ADS)

We demonstrate that single-walled carbon nanotube (CNT) films make a Schottky contact on silicon by experimentally characterizing metal-semiconductor-metal (MSM) structures. We find that at temperatures above 240 K, thermionic emission is the dominant transport mechanism across CNT film-Si contacts, and at lower temperatures tunneling begins to dominate. At high bias voltages, the CNT film MSM devices exhibit a higher photocurrent-to-dark current ratio relative to that of metal control devices. Our results not only provide insight into the fundamental electronic properties of the CNT film-Si junction but also opens up the possibility of integrating CNT films as Schottky electrodes in conventional Si-based devices.

Behnam, Ashkan; Johnson, Jason L.; Choi, Yongho; Ertosun, M. Günhan; Okyay, Ali K.; Kapur, Pawan; Saraswat, Krishna C.; Ural, Ant

2008-06-01

25

The heterogeneous integration of single-walled carbon nanotubes onto complementary metal oxide semiconductor circuitry for sensing applications  

Microsoft Academic Search

A simple methodology for integrating single-walled carbon nanotubes (SWNTs) onto complementary metal oxide semiconductor (CMOS) circuitry is presented. The SWNTs were incorporated onto the CMOS chip as the feedback resistor of a two-stage Miller compensated operational amplifier utilizing dielectrophoretic assembly. The measured electrical properties from the integrated SWNTs yield ohmic behavior with a two-terminal resistance of ~37.5 kOmega and the

Chia-Ling Chen; Vinay Agarwal; Sameer Sonkusale; Mehmet R. Dokmeci

2009-01-01

26

High-Yield Separation of Metallic and Semiconducting Single-Wall Carbon Nanotubes by Agarose Gel Electrophoresis  

NASA Astrophysics Data System (ADS)

We have developed a novel separation method of metallic and semiconducting single-wall carbon nanotubes (SWCNTs) using agarose gel electrophoresis. When the SWCNTs were isolated with sodium dodecyl sulfate (SDS) and embedded in agarose gel, only the metallic SWCNTs separated from the starting gel by an electric field. After 20 min, almost all SWCNTs applied to gel electrophoresis were separated into two fractions, containing ˜95% semiconducting and ˜70% metallic nanotubes. The difference in the response to the electric field between metallic and semiconducting SWCNTs can be explained by the higher affinity of semiconducting SWCNTs to agarose than to SDS.

Tanaka, Takeshi; Jin, Hehua; Miyata, Yasumitsu; Kataura, Hiromichi

2008-11-01

27

Corrugation-induced metal-semiconductor transition in single-wall carbon nanotubes with a small radius  

NASA Astrophysics Data System (ADS)

Armchair single-wall carbon nanotubes (SWCNTs) are theoretically predicted to be metallic in the simple zone-folding scheme and protected from the curvature effects. They are, however, found to be small-gap semiconductors, experimentally. Lacking the genuine band-gap opening mechanism for armchair SWCNTs, the Mott insulator concept was proposed previously for the nominally metallic carbon nanotubes. Using the ab initio local density approximation method, we show, in this paper, that the carbon nanotubes without corrugation are, in fact, not metastable. The corrugated structures are always lower in energy than those without corrugation. The size of corrugation increases rapidly with the nanotubes’ curvature and vanishes for flat graphene. The corrugation breaks the local symmetry between two types of carbon sites, and a true band gap starts to develop once graphene sheets are rolled up into nanotubes.

Lu, Hongxia; Wu, Jianbao; Zhang, Weiyi

2013-07-01

28

Density functional theory investigation of the VIIIB transition metal atoms deposited on (5,5) single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

The binding of VIIIB transition metals i.e. Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, and Pt single atoms to single-walled carbon nanotube (SWCNT) was investigated using the density functional theory method. The B3LYP/LanL2DZ calculation shows that all these transition metal atoms have strong binding abilities to SWCNT. The binding abilities of these transition metals onto SWCNT are in following order: Os>Ru>Ir>Fe>Rh>Pt>Ni>Co>Pd. The Os single atom binding on SWCNT is the strongest binding of which the binding energy is -240.66 kcal/mol. The partial charge transfers from transition metal to SWCNT, density of states and energy gaps of metal atoms deposited on SWCNTs were analyzed and reported.

Tabtimsai, Chanukorn; Ruangpornvisuti, Vithaya; Wanno, Banchob

2013-03-01

29

Metal-Semiconductor-Metal (MSM) Photodetectors with Single-walled Carbon Nanotube Film Schottky Electrodes on GaAs  

NASA Astrophysics Data System (ADS)

We fabricate and experimentally characterize the dark and photocurrent in metal-semiconductor-metal (MSM) photodetectors with transparent and conductive single-walled carbon nanotube (CNT) film electrodes on GaAs. The dark current measurements of MSM structures reveal that the CNT film forms a Schottky contact on GaAs substrates. The Schottky barrier height and the CNT film workfunction are extracted to be approximately 0.55 and 4.6 eV, respectively, based on dark current measurements as a function of temperature. We also study the effect of device geometry on the dark current of the CNT film-GaAs MSM devices. Furthermore, we find that CNT film MSM devices exhibit a significantly lower dark current and higher normalized photo-to-dark current ratio compared to metal control samples. We explain these observations by comparing the interfaces in these structures. This work opens up the possibility of integrating CNT films as Schottky electrodes in conventional semiconductor electronic and optoelectronic devices.

Behnam, Ashkan; Johnson, Jason; Choi, Yongho; Noriega, Leila; Ertosun, Günhan; Wu, Zhuangchun; Rinzler, Andrew; Kapur, Pawan; Saraswat, Krishna; Ural, Ant

2008-03-01

30

Effect of first row transition metals on the conductivity of semiconducting single-walled carbon nanotube networks  

NASA Astrophysics Data System (ADS)

We demonstrate the ability of first row transition metals to form electrically conducting interconnects between semiconducting single-walled carbon nanotubes (SWNTs) by constructive rehybridization between sidewall benzene rings as a result of the formation of bis-hexahapto-metal-bonds [(?6-SWNT)M(?6-SWNT)], which bridge adjacent SWNTs. Metal deposition on SWNT films enhances the conductivity by three distinct mechanisms: physisorption of gold leads to the formation of a non-interacting gold film and a monotonic conductivity increase; ionic chemisorption of lithium strongly increases the conductivity due to charge transfer to the SWNTs; covalent chemisorption of first row transition metals leads to an abrupt change in conductivity due to formation of (?6-SWNT)M(?6-SWNT) interconnects.

Wang, Feihu; Itkis, Mikhail E.; Bekyarova, Elena B.; Tian, Xiaojuan; Sarkar, Santanu; Pekker, Aron; Kalinina, Irina; Moser, Matthew L.; Haddon, Robert C.

2012-05-01

31

Transparent Conductive Single-Walled Carbon Nanotube Networks with Precisely Tunable Ratios of Semiconducting and Metallic Nanaotubes  

SciTech Connect

We present a comprehensive study of the optical and electrical properties of transparent conductive films made from precisely tuned ratios of metallic and semiconducting single-wall carbon nanotubes. The conductivity and transparency of the SWNT films are controlled by an interplay between localized and delocalized carriers, as determined by the SWNT electronic structure, tube-tube junctions, and intentional and unintentional redox dopants. The results suggest that the main resistance in the SWNT thin films is the resistance associated with tube-tube junctions. Redox dopants are found to increase the delocalized carrier density and transmission probability through intertube junctions more effectively for semiconductor-enriched films than for metal-enriched films. As a result, redox-doped semiconductor-enriched films are more conductive than either intrinsic or redox-doped metal-enriched films.

Blackburn, J. L.; Barnes, T. M.; Beard, M. C.; Kim, Y.-H.; Tenent, R. C.; McDonald, T. J.; To, B.; Coutts, T. J.; Heben, M. J.

2008-01-01

32

Transparent conductive single-walled carbon nanotube networks with precisely tunable ratios of semiconducting and metallic nanotubes.  

PubMed

We present a comprehensive study of the optical and electrical properties of transparent conductive films made from precisely tuned ratios of metallic and semiconducting single-wall carbon nanotubes. The conductivity and transparency of the SWNT films are controlled by an interplay between localized and delocalized carriers, as determined by the SWNT electronic structure, tube-tube junctions, and intentional and unintentional redox dopants. The results suggest that the main resistance in the SWNT thin films is the resistance associated with tube-tube junctions. Redox dopants are found to increase the delocalized carrier density and transmission probability through intertube junctions more effectively for semiconductor-enriched films than for metal-enriched films. As a result, redox-doped semiconductor-enriched films are more conductive than either intrinsic or redox-doped metal-enriched films. PMID:19206344

Blackburn, Jeffrey L; Barnes, Teresa M; Beard, Matthew C; Kim, Yong-Hyun; Tenent, Robert C; McDonald, Timothy J; To, Bobby; Coutts, Timothy J; Heben, Michael J

2008-06-01

33

Metal-semiconductor-metal photodetectors based on single-walled carbon nanotube film-GaAs Schottky contacts  

NASA Astrophysics Data System (ADS)

We demonstrate the Schottky behavior of single-walled carbon nanotube (CNT) film contacts on GaAs by fabricating and characterizing metal-semiconductor-metal (MSM) photodetectors with CNT film electrodes. We extract the Schottky barrier height of CNT film contacts on GaAs by measuring the dark I-V characteristics as a function of temperature. The results show that at temperatures above ~260 K, thermionic emission of electrons with a barrier height of ~0.54 eV is the dominant transport mechanism in CNT film-GaAs junctions, whereas at lower temperatures, tunneling begins to dominate suggested by the weak dependence of current on temperature. Assuming an ideal MS diode, this barrier height corresponds to a CNT film workfunction of ~4.6 eV, which is in excellent agreement with the previously reported values. Furthermore, we characterize the effect of device geometry on the dark current and find that dark currents of the MSM devices scale rationally with device geometry, such as the device active area, finger width, and finger spacing. Finally, we compare the dark and photocurrent of the CNT film-based MSM photodetectors with standard metal-based MSMs. We find that MSM devices with CNT film electrodes exhibit a higher photocurrent-to-dark current ratio while maintaining a comparable responsivity relative to metal control devices. These results not only provide valuable information about the fundamental properties of the CNT film-GaAs interface but also open up the possibility of integrating CNT films as transparent and conductive Schottky electrodes in conventional semiconductor electronic and optoelectronic devices.

Behnam, Ashkan; Johnson, Jason; Choi, Yongho; Noriega, Leila; Ertosun, M. Günhan; Wu, Zhuangchun; Rinzler, Andrew G.; Kapur, Pawan; Saraswat, Krishna C.; Ural, Ant

2008-06-01

34

Nanocrystalline Ceramic Materials Reinforced with Single-Wall Carbon Nanotubes.  

National Technical Information Service (NTIS)

Composites of ceramic materials, notably alumina or metal oxides in general, with single-wall carbon nanotubes are consolidated by electric field-assisted sintering to achieve a fully dense material that has an unusually high fracture toughness compared t...

G. Zhan A. K. Mukherjee J. D. Kuntz J. Wan

2004-01-01

35

Structures, energetics and reaction mechanisms of nitrous oxide on transition-metal-doped and -undoped single-wall carbon nanotubes.  

PubMed

The catalytic activity of carbon nanotubes (CNTs) for the removal of greenhouse gases, like nitrous oxide (N(2)O), can be fine-tuned by metal doping. We modify the inert surfaces of CNTs with Sc, Ti and V transition metals in order to investigate their capability of converting N(2)O to N(2). The stable composite catalysts of Sc-, Ti- and V-doped (5,5)single-walled carbon nanotubes (SWCNTs), along with the unmodified one were investigated by periodic DFT calculations. Without metal doping, the N(2) O decomposition on the bare tube proceeds over a high energy barrier (54.3 kcal mol(-1)) which in the presence of active metals is reduced to 3.6, 8.0 and 10.2 kcal mol(-1) for V-, Ti- and Sc-doped (5,5)SWCNTs, respectively. The superior reactivity is a result of the facilitated electron transfer between the tube and N(2)O caused by the overlap between the d orbitals of the metal and the p orbitals of N(2)O. PMID:22241847

Pannopard, Panvika; Khongpracha, Pipat; Warakulwit, Chompunuch; Namuangruk, Supawadee; Probst, Michael; Limtrakul, Jumras

2012-02-01

36

Internal stress induced metallization of single-walled carbon nanotubes in a nanotube/glass conducting composite  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanotubes (SWCNTs) have been incorporated into a (Pb, Zn)—phosphate glass host by a melt-quenching technique. Studies of the optical and electronic properties show that the nanotubes in the composite have suffered conformational deformations and attained a band structure of quasimetallic type, making the composite a good electrical conductor. Possible strains in the nanotubes of the composite such as radial compression, torsion and bending have been considered and their role in modulating the band structures has been analyzed by judging the change in band gap energies (?E) of the deformed SWCNTs using an equation which is based on the ?-electron tight binding model. The effect of ?*-?* hybridization due to the radial compression in generating the metallicity is also discussed. The carrier transport in the composite above room temperature has been shown to be dominated by fluctuation induced tunneling.

Balaji, Sathravada; Debnath, Radhaballabh

2011-10-01

37

Selective removal of metallic single-walled carbon nanotubes in full length by organic film-assisted electrical breakdown.  

PubMed

An organic film-assisted electrical breakdown technique is proposed to selectively remove metallic (m-) single-walled carbon nanotubes (SWNTs) in full length towards creation of pure semiconducting SWNT arrays which are available for the large-scale fabrication of field effect transistors (FETs). The electrical breakdown of horizontally aligned SWNT arrays embedded in organic films resulted in a maximum removal length of 16.4 ?m. The removal of SWNTs was confirmed using scanning electron microscopy and Raman mapping measurements. The on/off ratios of FETs were improved up to ca. 10?000, similar to that achieved for in-air breakdown. The experimental results suggest that exothermic oxidation of organic films induces propagation of oxidation reaction, hence the long-length removal of m-SWNTs. PMID:24956406

Otsuka, Keigo; Inoue, Taiki; Chiashi, Shohei; Maruyama, Shigeo

2014-07-10

38

Direct intermolecular force measurements between functional groups and individual metallic or semiconducting single-walled carbon nanotubes.  

PubMed

Many electronic applications of single-walled carbon nanotubes (SWNTs) require electronic homogeneity in order to maximally exploit their outstanding properties. Non-covalent separation is attractive as it is scalable and results in minimal alteration of nanotube properties. However, fundamental understanding of the metallicity-dependence of functional group interactions with nanotubes is still lacking; this lack is compounded by the absence of methods to directly measure these interactions. Herein, a novel technology platform based on a recently developed atomic force microscopy (AFM) mode is reported which directly quantifies the adhesion forces between a chosen functional group and individual nanotubes of known metallicity, permitting comparisons between different metallicity. These results unambiguously show that this technology platform is able to discriminate the subtle adhesion force differences of a chosen functional group with pure metallic as opposed to pure semiconducting nanotubes. This new method provides a route towards rapid advances in understanding of non-covalent interactions of large libraries of compounds with nanotubes of varying metallicity and diameter; presenting a superior tool to assist the discovery of more effective metallicity-based SWNT separation agents. PMID:24106155

Thong, Ya Xuan; Poon, Yin Fun; Chen, Tzu-Yin; Li, Lain-Jong; Chan-Park, Mary B

2014-02-26

39

Impregnation of Catalytic Metals in Single-Walled Carbon Nanotubes for Toxic Gas Conversion in Life Support System  

NASA Technical Reports Server (NTRS)

Carbon nanotubes (CNTs) possess extraordinary properties such as high surface area, ordered chemical structure that allows functionalization, larger pore volume, and very narrow pore size distribution that have attracted considerable research attention from around the world since their discovery in 1991. The development and characterization of an original and innovative approach for the control and elimination of gaseous toxins using single walled carbon nanotubes (SWNTs) promise superior performance over conventional approaches due to the ability to direct the selective uptake of gaseous species based on their controlled pore size, increased adsorptive capacity due to their increased surface area and the effectiveness of carbon nanotubes as catalyst supports for gaseous conversion. We present our recent investigation of using SWNTs as catalytic supporting materials to impregnate metals, such as rhodium (Rh), palladium (Pd) and other catalysts. A protocol has been developed to oxidize the SWNTs first and then impregnate the Rh in aqueous rhodium chloride solution, according to unique surface properties of SWNTs. The Rh has been successfully impregnated in SWNTs. The Rh-SWNTs have been characterized by various techniques, such as TGA, XPS, TEM, and FTIR. The project is funded by a NASA Research Announcement Grant to find applications of single walled nanocarbons in eliminating toxic gas Contaminant in life support system. This knowledge will be utilized in the development of a prototype SWNT KO, gas purification system that would represent a significant step in the development of high efficiency systems capable of selectively removing specific gaseous for use in regenerative life support system for human exploration missions.

Li, Jing; Wignarajah, Kanapathipillai; Cinke, Marty; Partridge, Harry; Fisher, John

2004-01-01

40

Separation of single-walled carbon nanotubes into metallic and semiconducting groups: a simple and large-scale method  

NASA Astrophysics Data System (ADS)

Separation of a large number of single-walled carbon nanotubes (SWNTs) into groups each with specifically metallic and semiconducting properties is an extremely important task for technology application. Even though effective methods (1, 2) have been devised, they suffer from drawbacks such as either the yield is low (3) or expense is high (4). In this work, we study the problem from a theoretical approach, we notice that based on the first principles calculations the binding strengths of methylamine to the semiconducting [13, 0] SWNT are only 36˜61% of that to the metallic [7, 7] SWNT, which suggests that the amines is much more attractive toward the pure metallic than the semiconducting SWNTs. Therefore starting from as-prepared SWNTs and with the assistance of amines, we achieved SWNTs with enriched metallic properties over semiconducting in a convenient and large-scale manner. References: (1) D. Chattopadhyay, L. Galeska, F. Papadimitrakopoulos, Journal of the American Chemical Society 125, 3370 (MAR 19, 2003). (2) H. P. Li et al., Journal of the American Chemical Society 126, 1014 (FEB 4, 2004). (3) R. Krupke, F. Hennrich, H. von Lohneysen, M. Kappes, SCIENCE 301, 344 (JUL 18, 2003). (4) M. Zheng et al., Science 302, 1545 (NOV 28, 2003).

Lu, Jing; Maeda, Y.

2006-03-01

41

3-D perpendicular assembly of single walled carbon nanotubes for complimentary metal oxide semiconductor interconnects.  

PubMed

Due to their superior electrical properties such as high current density and ballistic transport, carbon nanotubes (CNT) are considered as a potential candidate for future Very Large Scale Integration (VLSI) interconnects. However, direct incorporation of CNTs into Complimentary Metal Oxide Semiconductor (CMOS) architecture by conventional chemical vapor deposition (CVD) growth method is problematic since it requires high temperatures that might damage insulators and doped semiconductors in the underlying CMOS circuits. In this paper, we present a directed assembly method to assemble aligned CNTs into pre-patterned vias and perpendicular to the substrate. A dynamic electric field with a static offset is applied to provide the force needed for directing the SWNT assembly. It is also shown that by adjusting assembly parameters the density of the assembled CNTs can be significantly enhanced. This highly scalable directed assembly method is conducted at room temperature and pressure and is accomplished in a few minutes. I-V characterization of the assembled CNTs was conducted using a Zyvex nanomanipulator in a scanning electron microscope (SEM) and the measured value of the resistance is found to be 270 komega s. PMID:24734611

Kim, Tae-Hoon; Yilmaz, Cihan; Somu, Sivasubramanian; Busnaina, Ahmed

2014-05-01

42

Preferential growth of short aligned, metallic-rich single-walled carbon nanotubes from perpendicular layered double hydroxide film  

NASA Astrophysics Data System (ADS)

Direct bulk growth of single-walled carbon nanotubes (SWCNTs) with required properties, such as diameter, length, and chirality, is the first step to realize their advanced applications in electrical and optical devices, transparent conductive films, and high-performance field-effect transistors. Preferential growth of short aligned, metallic-rich SWCNTs is a great challenge to the carbon nanotube community. We report the bulk preferential growth of short aligned SWCNTs from perpendicular Mo-containing FeMgAl layered double hydroxide (LDH) film by a facile thermal chemical vapor deposition with CH4 as carbon source. The growth of the short aligned SWCNTs showed a decreased growth velocity with an initial value of 1.9 nm s-1. Such a low growth velocity made it possible to get aligned SWCNTs shorter than 1 ?m with a growth duration less than 15 min. Raman spectra with different excitation wavelengths indicated that the as-grown short aligned SWCNTs showed high selectivity of metallic SWCNTs. Various kinds of materials, such as mica, quartz, Cu foil, and carbon fiber, can serve as the substrates for the growth of perpendicular FeMoMgAl LDH films and also the growth of the short aligned SWCNTs subsequently. These findings highlight the easy route for bulk preferential growth of aligned metallic-rich SWCNTs with well defined length for further bulk characterization and applications.Direct bulk growth of single-walled carbon nanotubes (SWCNTs) with required properties, such as diameter, length, and chirality, is the first step to realize their advanced applications in electrical and optical devices, transparent conductive films, and high-performance field-effect transistors. Preferential growth of short aligned, metallic-rich SWCNTs is a great challenge to the carbon nanotube community. We report the bulk preferential growth of short aligned SWCNTs from perpendicular Mo-containing FeMgAl layered double hydroxide (LDH) film by a facile thermal chemical vapor deposition with CH4 as carbon source. The growth of the short aligned SWCNTs showed a decreased growth velocity with an initial value of 1.9 nm s-1. Such a low growth velocity made it possible to get aligned SWCNTs shorter than 1 ?m with a growth duration less than 15 min. Raman spectra with different excitation wavelengths indicated that the as-grown short aligned SWCNTs showed high selectivity of metallic SWCNTs. Various kinds of materials, such as mica, quartz, Cu foil, and carbon fiber, can serve as the substrates for the growth of perpendicular FeMoMgAl LDH films and also the growth of the short aligned SWCNTs subsequently. These findings highlight the easy route for bulk preferential growth of aligned metallic-rich SWCNTs with well defined length for further bulk characterization and applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr00043a

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

2012-03-01

43

Noble metal coated single-walled carbon nanotubes for applications in surface enhanced Raman scattering imaging and photothermal therapy.  

PubMed

Single-walled carbon nanotubes (SWNTs) with various unique optical properties are interesting nanoprobes widely explored in biomedical imaging and phototherapies. Herein, DNA-functionalized SWNTs are modified with noble metal (Ag or Au) nanoparticles via an in situ solution phase synthesis method comprised of seed attachment, seeded growth, and surface modification with polyethylene glycol (PEG), yielding SWNT-Ag-PEG and SWNT-Au-PEG nanocomposites stable in physiological environments. With gold or silver nanoparticles decorated on the surface, the SWNT-metal nanocomposites gain an excellent concentration and excitation-source dependent surface-enhanced Raman scattering (SERS) effect. Using a near-infrared (NIR) laser as the excitation source, targeted Raman imaging of cancer cells labeled with folic acid (FA) conjugated SWNT-Au nanocomposite (SWNT-Au-PEG-FA) is realized, with images acquired in significantly shortened periods of time as compared to that of using nonenhanced SWNT Raman probes. Owing to the strong surface plasmon resonance absorption contributed by the gold shell, the SWNTs-Au-PEG-FA nanocomposite also offers remarkably improved photothermal cancer cell killing efficacy. This work presents a facile approach to synthesize water-soluble noble metal coated SWNTs with a strong SERS effect suitable for labeling and fast Raman spectroscopic imaging of biological samples, which has been rarely realized before. The SWNT-Au-PEG nanocomposite developed here may thus be an interesting optical theranostic probe for cancer imaging and therapy. PMID:22486413

Wang, Xiaojing; Wang, Chao; Cheng, Liang; Lee, Shuit-Tong; Liu, Zhuang

2012-05-01

44

Simultaneous discrimination of diameter, handedness, and metallicity of single-walled carbon nanotubes with chiral diporphyrin nanocalipers.  

PubMed

We have been developing the methodology to discriminate the handedness and diameter of single-walled carbon nanotubes (SWNTs) through molecular recognition using chiral diporphyrin nanotweezers. Although relatively small diameters of SWNTs (<1.0 nm) were recognized well, nanotweezers were not able to form stable complexes with the SWNTs having the diameters >1.0 nm. In this context, we designed chiral diporphyrin with a much larger cavity, namely, "nanocalipers". The feature of the newly designed host molecule is: (1) long spacer with more than 1.4 nm consisting of three aromatic moieties; (2) nearly parallel orientation of the two porphyrins; (3) restricted conformation by biaryl linkages of the porphyrin-carbazole and carbazole-anthracene; (4) strong interaction of two porphyrins and anthracene with the surface of a SWNT through ?-? stacking; and (5) stereogenic centers at the periphery of porphyrins discriminating helicity of SWNTs. As expected, we obtained optically active SWNTs with >1.0 nm in diameter and, unexpectedly, enriched metallic SWNTs over semiconducting ones. The optically active metallic SWNTs are identified for the first time, in addition to the optically active semiconducting SWNTs with such large diameters. The nanocalipers are found to recognize the diameter, handedness, and metallicity of SWNTs simultaneously. PMID:23452039

Liu, Gang; Wang, Feng; Chaunchaiyakul, Songpol; Saito, Yukie; Bauri, Ajoy K; Kimura, Takahide; Kuwahara, Yuji; Komatsu, Naoki

2013-03-27

45

Hydrogen Storage in metal-modified single-walled carbon nanotubes  

SciTech Connect

It has been known for over thirty years that potassium-intercalated graphites can readily adsorb and desorb hydrogen at {approx}1 wt% at 77 K. These levels are much higher than can be attained in pure graphite, owing to a larger thermodynamic enthalpy of adsorption. This increased enthalpy may allow hydrogen sorption at higher temperatures. Potassium has other beneficial effects that enable the design of a new material: (a) Increased adsorption enthalpy in potassium-intercalated graphite compared to pure graphite reduces the pressure and increases the temperature required for a given fractional coverage of hydrogen adsorption. We expect the same effects in potassium-intercalated SWNTs. (b) As an intercalant, potassium separates c-axis planes in graphite. Potassium also separates the individual tubes of SWNTs ropes producing swelling and increased surface area. Increased surface area provides more adsorption sites, giving a proportionately higher capacity. The temperature of adsorption depends on the enthalpy of adsorption. The characteristic temperature is roughly the adsorption enthalpy divided by Boltzmann's constant, k{sub B}. For the high hydrogen storage capacity of SWNTs to be achieved at room temperature, it is necessary to increase the enthalpy of adsorption. Our goal for this project was to use metal modifications to the carbon surface of SWNTs in order to address both enhanced adsorption and surface area. For instance, the enthalpy of sorption of hydrogen on KC8 is 450 meV/H{sub 2}, whereas it is 38 meV/H{sub 2} for unmodified SWNTs. By adsorption thermodynamics we expect approximately that the same performance of SWNTs at 77 K will be achieved at a temperature of [450/38] 77 K = 900 K. This is a high temperature, so we expect that adsorption on nearly all the available sites for hydrogen will occur at room temperature under a much lower pressure. This pressure can be estimated conveniently, since the chemical potential of hydrogen is approximately proportional to the logarithm of the pressure. Using 300 K for room temperature, the 100 bar pressure requirement is reduced to exp(-900/300) 100 bar = 5 bar at room temperature. This is in the pressure range used for prior experimental work such as that of Colin and Herold in the late 1960's and early 1970's.

Dr. Ahn

2004-04-30

46

Thermal stability of metallic single-walled carbon nanotubes: an O(N) tight-binding molecular dynamics simulation study  

NASA Astrophysics Data System (ADS)

Order(N) tight-binding molecular dynamics (TBMD) simulations are performed to investigate the thermal stability of (10,10) metallic single-walled carbon nanotubes (SWCNTs). Periodic boundary conditions (PBCs) are applied in the axial direction. The velocity Verlet algorithm along with the canonical ensemble molecular dynamics (NVT) is used to simulate the tubes at the targeted temperatures. The effects of slow and rapid temperature increases on the physical characteristics, structural stability and the energetics of the tube are investigated and compared. Simulations are carried out starting from room temperature and the temperature is raised in steps of 300 K. The stability of the simulated metallic SWCNT is examined at each step before it is heated to higher temperatures. The first indication of structural deformation is observed at 600 K. For higher heat treatments the deformations are more pronounced and the bond-breaking temperature is reached around 2500 K. Gradual (slow) heating and thermal equilibrium (fast heating) methods give the value of radial thermal expansion coefficient in the temperature range between 300 and 600 K as 0.31 × 10-5 and 0.089 × 10-5 K-1, respectively. After 600 K, both methods give the same value of 0.089 × 10-5 K-1. The ratio of the total energy per atom with respect to temperature is found to be 3 × 10-4 eV K-1.

Dereli, G.; Süngü, B.; Özdogan, C.

2007-06-01

47

Electrochemical and In-situ Studies of Alkali Metal Doping in Single Wall Carbon Nanotubes  

Microsoft Academic Search

Electrochemistry has proven to be extremely useful for the study of guest-host systems, in particular carbon-based intercalation compounds. Not only does it provide essential information about thermodynamics and kinetics, but it also offers accurate control of guest stoichiometry, which is difficult to achieve through other doping methods. Perhaps more importantly, in-situ electrochemical experiments afford continuous and reversible composition control, and

Agnes Claye

2000-01-01

48

Electrically robust metal nanowire network formation by in-situ interconnection with single-walled carbon nanotubes.  

PubMed

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

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

2014-01-01

49

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

50

Composite Films of Poly(3-hexylthiophene) Grafted Single-Walled Carbon Nanotubes for Electrochemical Detection of Metal Ions.  

PubMed

In this study, we prepared electrochemically active films of poly(3-hexylthiophene) grafted single-walled carbon nanotubes (SWNT-g-P3HT) by using a modified vacuum-assisted deposition approach, in which a SWNT-g-P3HT composite layer of various thicknesses was deposited on the top of a thin SWNT layer. Measurement of the optical and electrical properties of the SWNT-g-P3HT composite films demonstrated that the thickness of the SWNT-g-P3HT composite films was controllable. The data of transmission electron microscope observation and Raman spectroscopy indicated that the covalent grafting of P3HT onto the surfaces of SWNTs resulted in intimate and stable connectivity between the two components in the SWNT-g-P3HT composite. Capitalizing on these unique features, we successfully developed a new class of electrochemical sensors that used the SWNT-g-P3HT composite films deposited on an indium-tin oxide substrate as an electrochemical electrode for detection of metal ions. Significantly, such a SWNT-g-P3HT composite electrode showed advantages in selective, quantitative, and more sensitive detection of Ag(+) ions. PMID:24730434

Yang, Shaojun; Meng, Dongli; Sun, Jinhua; Huang, Yan; Huang, Yong; Geng, Jianxin

2014-05-28

51

Internal stress induced metallization of single-walled carbon nanotubes in a nanotube\\/glass conducting composite  

Microsoft Academic Search

Single-walled carbon nanotubes (SWCNTs) have been incorporated into a (Pb, Zn)---phosphate glass host by a melt-quenching technique. Studies of the optical and electronic properties show that the nanotubes in the composite have suffered conformational deformations and attained a band structure of quasimetallic type, making the composite a good electrical conductor. Possible strains in the nanotubes of the composite such as

Sathravada Balaji; Radhaballabh Debnath

2011-01-01

52

Effect of metal oxide and oxygen on the growth of single-walled carbon nanotubes by electric arc discharge  

Microsoft Academic Search

The effect of oxygen on the growth of single-walled carbon nanotubes was studied with Ni–Co alloy powder as catalyst under\\u000a helium atmosphere of 500 Torr by electric arc discharge. The oxygen included in nickel or (and) cobalt oxides was added in\\u000a catalyst. The content of oxygen in atmosphere was controlled by changing vacuum degree inside furnace before inputting buffer\\u000a gas. The

Delong He; Yongning Liu; Tingkai Zhao; Jiewu Zhu; Guang Yu

2008-01-01

53

Surfactant free fractions of metallic and semiconducting single-walled carbon nanotubes via optimised gel chromatography  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer The application of gel permeation chromatography technique in a field of SWCNT separation. Black-Right-Pointing-Pointer Non-commercial agarose gel used as a column filling. Black-Right-Pointing-Pointer Purification route is presented, quality and quantity estimation is shown. Black-Right-Pointing-Pointer Process is ready for high-scale separation of SWCNTs. -- Abstract: We report the procedure of sorting/purification of carbon nanotubes by electronic type using chromatographic column with sodium dodecylsulfate (SDS) and sodium deoxycholate (DOC) solutions as the eluents. The non-commercial agarose gel in different concentrations has been tested in the process. It was found that in optimal gel concentration the fractionation resulted in {approx}96.2% yield of semiconducting species. Importantly, to get surfactant-free fractions the post-separation purification procedure has been carried out. The UV-vis-NIR and Raman spectroscopy have been utilised for the samples analysis. High resolution transmission microscopy and thermogravimetric analysis allowed to study the sample morphology and purity, respectively.

Lukaszczuk, Pawel, E-mail: plukaszczuk@zut.edu.pl [West Pomeranian University of Technology, Institute of Chemical and Environment Engineering, ul. Pulaskiego 10, 70-322 Szczecin (Poland)] [West Pomeranian University of Technology, Institute of Chemical and Environment Engineering, ul. Pulaskiego 10, 70-322 Szczecin (Poland); Ruemmeli, Mark H.; Knupfer, Martin [Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstr. 20, 01069 Dresden (Germany)] [Leibniz Institute for Solid State and Materials Research Dresden, Helmholtzstr. 20, 01069 Dresden (Germany); Kalenczuk, Ryszard J.; Borowiak-Palen, Ewa [West Pomeranian University of Technology, Institute of Chemical and Environment Engineering, ul. Pulaskiego 10, 70-322 Szczecin (Poland)] [West Pomeranian University of Technology, Institute of Chemical and Environment Engineering, ul. Pulaskiego 10, 70-322 Szczecin (Poland)

2012-03-15

54

Electrochemical and In-situ Studies of Alkali Metal Doping in Single Wall Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

Electrochemistry has proven to be extremely useful for the study of guest-host systems, in particular carbon-based intercalation compounds. Not only does it provide essential information about thermodynamics and kinetics, but it also offers accurate control of guest stoichiometry, which is difficult to achieve through other doping methods. Perhaps more importantly, in-situ electrochemical experiments afford continuous and reversible composition control, and eliminate the need for glove box transfer. We have used in-situ and ex-situ electrochemical techniques to study the structural and electronic properties of Li/SWNT and K/SWNT compounds. In this paper we review their thermodynamic properties, investigated by cyclic voltammetry and galvanometry. More specifically, we demonstrate 1) the ability to reversibly dope SWNT with Li and K; and 2) the absence of phase transformations as a function of composition, in contrast to intercalation in graphite, polyacetylene and solid C_60. We present the effect of alkali doping on the structure of SWNT, as studied by in-situ X-ray diffraction. We show the changes in electronic transport properties as a function of doping level through in-situ resistivity, in-situ electron spin resonance, and electrochemical impedance spectroscopy. All three techniques show that the bulk resistance of SWNT decreases continuously as a function of doping level, confirming the charge transfer between dopant and host. We use in-situ conduction electron spin resonance to elucidate the electronic structure of doped SWNT. The spin relaxation rate is discussed in terms of the Elliot-Yafet mechanism (A. Claye et al., contributed abstract). Finally, we use electrochemical impedance spectroscopy to study kinetics and alkali doping mechanisms in SWNT. The properties described above are compared and contrasted to those of graphite intercalation compounds and doped conjugated polymers.

Claye, Agnes

2000-03-01

55

Molecular discriminators using single wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

The interaction between single wall carbon nanotubes (SWNTs) and amphiphilic molecules has been studied in a solid phase. SWNTs are allowed to interact with different amphiphilic probes (e.g. lipids) in a narrow capillary interface. Contact between strong hydrophobic and amphiphilic interfaces leads to a molecular restructuring of the lipids at the interface. The geometry of the diffusion front and the rate and the extent of diffusion of the interface are dependent on the structure of the lipid at the interface. Lecithin having a linear tail showed greater mobility of the interface as compared to a branched tail lipid like dipalmitoyl phosphatidylcholine, indicating the hydrophobic interaction between single wall carbon nanotube core and the hydrophobic tail of the lipid. Solid phase interactions between SWNT and lipids can thus become a very simple but efficient means of discriminating amphiphilic molecules in general and lipids in particular.

Bhattacharyya, Tamoghna; Dasgupta, Anjan Kr; Ranjan Ray, Nihar; Sarkar, Sabyasachi

2012-09-01

56

Optical modulation of single walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Recent advances in the spectroscopy of single walled carbon nanotubes have significantly enhanced our ability to understand and control their surface chemistry, both covalently and non-covalently. Our work has focused on modulating the optical properties of semiconducting single walled carbon nanotubes as near infrared photoluminescent sensors for chemical analysis. Molecular detection using near-infrared light between 0.9 and 1.3 eV has important biomedical applications because of greater tissue penetration and reduced auto-fluorescent background in thick tissue or whole-blood media. In one system, the transition of DNA secondary structure modulates the dielectric environment of the single-walled carbon nanotube (SWNT) around which it is adsorbed. The SWNT band-gap fluorescence undergoes a red shift when an encapsulating 30-nucleotide oligomer is exposed to counter ions that screen the charged backbone. We demonstrate the detection of the mercuric ions in whole blood, tissue, and from within living mammalian cells using this technology. Similar results are obtained for DNA hybridization and the detection of single nucleotide polymorphism. We also report the synthesis and successful testing of near-infrared ?-D-glucose sensors2 that utilize a different mechanism: a photoluminescence modulation via charge transfer. The results demonstrate new opportunities for nanoparticle optical sensors that operate in strongly absorbing media of relevance to medicine or biology.

Strano, Michael S.

2007-03-01

57

Effect of time on the metal-support (Fe-MgO) interaction in CVD synthesis of single-walled carbon nanotubes  

Microsoft Academic Search

A study on the effect of the metal-support interaction by employing iron particles supported on magnesium oxide (MgO) nanopowder\\u000a in an alcohol-CVD process for single-walled carbon nanotubes growth is presented. Upon the prolongation of the process time,\\u000a three main observations were detected: (i) decrease of the mean nanotubes diameter, (ii) reduction of the diameter distribution\\u000a by the factor of two,

Anna Steplewska; Ewa Borowiak-Palen; Ryszard J. Kalenczuk

2010-01-01

58

Electron promotion by surface functional groups of single wall carbon nanotubes to overlying metal particles in a fuel-cell catalyst.  

PubMed

A remarkable promotion: Functional groups added onto single-wall carbon nanotubes (SWNTs) can significantly influence the activity of a noble metal for formic acid oxidation. Phenolate groups on SWNTs under alkaline conditions can double the activity of 20 % w/w Pd compared to unmodified SWNTs. This catalyst has 14 times higher activity than the commercial benchmark catalyst (10 % w/w Pd on Vulcan). PMID:22674641

Luksirikul, Patraporn; Tedsree, Karaked; Moloney, Mark G; Green, Malcolm L H; Tsang, Shik Chi Edman

2012-07-01

59

Large Scale CVD Synthesis of Single-Walled Carbon Nanotubes  

Microsoft Academic Search

The synthesis of bulk amounts of high quality single-walled carbon nanotubes (SWNTs) is accomplished by optimizing the chemical compositions and textural properties of the catalyst material used in the chemical vapor deposition (CVD) of methane. A series of catalysts are derived by systematically varying the catalytic metal compounds and support materials. The optimized catalysts consist of Fe\\/Mo bimetallic species supported

Alan M. Cassell; Jeffrey A. Raymakers; Jing Kong; Hongjie Dai

1999-01-01

60

Progress towards monodisperse single-walled carbon nanotubes  

Microsoft Academic Search

The defining characteristic of a nanomaterial is that its properties vary as a function of its size. This size dependence can be clearly observed in single-walled carbon nanotubes, where changes in structure at the atomic scale can modify the electronic and optical properties of these materials in a discontinuous manner (for example, changing metallic nanotubes to semiconducting nanotubes and vice

Mark C. Hersam

2008-01-01

61

Metallic single-walled silicon nanotubes  

PubMed Central

Atomistic computer-simulation evidences are presented for the possible existence of one-dimensional silicon nanostructures: the square, pentagonal, and hexagonal single-walled silicon nanotubes (SWSNTs). The local geometric structure of the SWSNTs differs from the local tetrahedral structure of cubic diamond silicon, although the coordination number of atoms of the SWSNTs is still fourfold. Ab initio calculations show that the SWSNTs are locally stable in vacuum and have zero band gap, suggesting that the SWSNTs are possibly metals rather than wide-gap semiconductors.

Bai, Jaeil; Zeng, X. C.; Tanaka, Hideki; Zeng, J. Y.

2004-01-01

62

Hyperelastic behavior of single wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

Single wall carbon nanotubes (SWNTs) are shown to obey a hyperelastic constitutive model at moderate strains and temperatures. The finite temperature is considered via the local harmonic approach. The equilibrium configurations were obtained by minimizing the Helmholtz free energy of a representative atom in an atom-based cell model. While the concept of strain-dependent tangent modulus using linear elasticity was considered in prior literature, a constant ? for Ogden's hyperelastic model [R. W. Ogden, Nonlinear Elastic Deformation (Horwood, England, 1984)] is found in the current work for large tubes subjected to moderately large strains up to 900 K.

Ling, Xianwu; Atluri, S. N.

2007-03-01

63

Electroabsorption of Single-Walled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

We have measured the electric field modulated absorption (EA) of single-walled carbon nanotubes (SWNT) isolated in a poly-vinyl alcohol matrix (PVA). The derivative-like structure of the EA indicates that the low energy absorption bands are excitonic in origin. We report the voltage, temperature, and polarization dependence of the EA spectrum. Additionally, the sensitivity of the EA spectrum to the energy levels of the SWNT allows us to use EA spectroscopy to observe shifts in the absorption bands of our sampleS induced by various external fields that are difficult to resolve using CW techniques. Several examples will be discussed.

Kennedy, W. Joshua; Valy Vardeny, Z.

2006-03-01

64

Strain Sensitivity in Single Walled Carbon Nanotubes for Multifunctional Materials  

NASA Technical Reports Server (NTRS)

Single walled carbon nanotubes represent the future of structural aerospace vehicle systems due to their unparalleled strength characteristics and demonstrated multifunctionality. This multifunctionality rises from the CNT's unique capabilities for both metallic and semiconducting electron transport, electron spin polarizability, and band gap modulation under strain. By incorporating the use of electric field alignment and various lithography techniques, a single wall carbon nanotube (SWNT) test bed for measurement of conductivity/strain relationships has been developed. Nanotubes are deposited at specified locations through dielectrophoresis. The circuit is designed such that the central, current carrying section of the nanotube is exposed to enable atomic force microscopy and manipulation in situ while the transport properties of the junction are monitored. By applying this methodology to sensor development a flexible single wall carbon nanotube (SWNT) based strain sensitive device has been developed. Studies of tensile testing of the flexible SWNT device vs conductivity are also presented, demonstrating the feasibility of using single walled HiPCO (high-pressure carbon monoxide) carbon nanotubes as strain sensing agents in a multi-functional materials system.

Heath, D. M. (Technical Monitor); Smits, Jan M., VI

2005-01-01

65

Is there a Difference in Van Der Waals Interactions between Rare Gas Atoms Adsorbed on Metallic and Semiconducting Single-Walled Carbon Nanotubes?  

SciTech Connect

Differences in polarizabilities of metallic (M) and semiconducting (S) single-walled carbon nanotubes (SWNTs) might give rise to differences in adsorption potentials. We show from experiments and van der Waals-corrected density functional theory (DFT) that binding energies of Xe adsorbed on M- and S-SWNTs are nearly identical. Temperature programmed desorption of Xe on purified M- and S-SWNTs give similar peak temperatures, indicating that desorption kinetics and binding energies are independent of the type of SWNT. Binding energies computed from vdW-corrected DFT are in good agreement with experiments.

Chen, De-Li; Mandeltort, Lynn; Saidi, Wissam A.; Yates, John T Jr, Cole, Milton W Johnson,J Karl

2013-03-26

66

Exohydrogenated single-wall carbon nanotubes  

SciTech Connect

An extensive first-principles study of fully exohydrogenated zigzag (n,0) and armchair (n,n) single-wall carbon nanotubes (C{sub n}H{sub n}), polyhedral molecules including cubane, dodecahedrane, and C{sub 60}H{sub 60} points to crucial differences in the electronic and atomic structures relevant to hydrogen storage and device applications. C{sub n}H{sub n}'s are estimated to be stable up to the radius of a (8,8) nanotube, with binding energies proportional to 1/R. Attaching a single hydrogen to any nanotube is always exothermic. Hydrogenation of zigzag nanotubes is found to be more likely than armchair nanotubes with similar radius. Our findings may have important implications for selective functionalization and finding a way of separating similar radius nanotubes from each other.

Yildirim, T.; Guelseren, O.; Ciraci, S.

2001-08-15

67

Effects of fluorination on single-wall carbon nanotubes  

Microsoft Academic Search

Depending on their structure single-wall carbon nanotubes, SWNTs, are either semiconducting or metallic. The possibility of chemically modifying these intrinsic nanotube properties by exterior side-wall functionalization---while maintaining their tubular structure---is desirable but difficult. Using technology developed in the fluorination of graphite, Mickelson et al. [Chem. Phys. Lett. 296, 188 (1998)] have recently succeeded in fluorinating SWNTs. Stimulated by these results,

N. C. Braier; R. A. Jishi; J. W. Mintmire; C. T. White

2001-01-01

68

Synthesis of Single-Walled Carbon Nanotubes by AC Arc Discharge  

NASA Astrophysics Data System (ADS)

We evaporated carbon bilateral rods containing different catalytic metals by AC arc discharge in He gas. No carbonaceous deposit was formed on either of the two electrodes, which meant that all of the evaporated carbon became soot in which single-walled nanotubes existed. It was clarified that the method is superior for high-efficiency synthesis of single-walled nanotubes.

Ohkohchi, Masato

1999-07-01

69

Metal-semiconductor-metal (MSM) photodetectors based on single-walled carbon nanotube film-silicon Schottky contacts  

NASA Astrophysics Data System (ADS)

We fabricate and experimentally characterize metal-semiconductor-metal (MSM) photodetectors with CNT film Schottky electrodes on n-type and p-type silicon substrates. We extract a Schottky barrier height of ~0.45 eV and ~0.51 eV for CNT films on n-type and p-type Si respectively. The extracted barrier height corresponds to a CNT film workfunction of 4.5-4.7 eV, which is within the range of the previously reported workfunction values for individual CNTs. Furthermore, we find that while at temperatures above 240°K thermionic emission is the dominant transport mechanism, at lower temperatures tunneling begins to dominate. We also characterize the photoresponse of the CNT film-Si MSM photodetector by illuminating the samples with a 633 nm HeNe laser. We observe that while the photocurrent of the CNT film MSM devices is similar to that of the Ti/Au control samples at high biases, their lower dark current results in a higher photo-to-dark current ratio relative to the control devices. We explain these observations by comparing the two interfaces. This work opens up the possibility of integrating CNT films as transparent and conductive Schottky electrodes in conventional semiconductor electronic and optoelectronic devices.

Behnam, Ashkan; Johnson, Jason L.; Choi, Yongho; Ertosun, M. Günhan; Wu, Zhuangchun; Rinzler, Andrew G.; Kapur, Pawan; Saraswat, Krishna C.; Ural, Ant

2008-03-01

70

Thermochemistry of fluorinated single wall carbon nanotubes.  

PubMed

The gradient corrected Perdew-Burke-Ernzerhof density functional in conjunction with a 3-21G basis set and periodic boundary conditions was employed to investigate the geometries and energies of C(2)F fluorinated armchair single wall carbon nanotubes (F-SWNT's) with diameters ranging from 16.4 to 4.2 A [(12,12) to (3,3)] as well as a C(2)F graphene sheet fluorinated on one side only. Using an isodesmic equation, we find that the thermodynamic stability of F-SWNT's increases with decreasing tube diameter. On the other hand, the mean bond dissociation energies of the C-F bonds increase as the tubes become thinner. The C-F bonds in the (5,5) F-SWNT's are about as strong as those in graphite fluoride (CF)(n)() and are also covalent albeit slightly (<0.04 A) stretched. Whereas a fluorine atom is found not to bind covalently to the concave surface of [60]fullerene, endohedral covalent binding is possible inside a (5,5) SWNT despite a diameter similar to that of the C(60) cage. PMID:11749543

Bettinger, H F; Kudin, K N; Scuseria, G E

2001-12-26

71

Single-wall carbon nanotube aerogels  

NASA Astrophysics Data System (ADS)

Aerogels of single-wall carbon nanotubes (SWNTs) were created by freeze drying and critical point drying of aqueous SWNT gels. The resulting aerogels maintain the strongly-connected three-dimensional SWNT network of the original gel and have density less than 0.1 g/cm3. While these pure SWNT aerogels are self-supporting, reinforcement with small amounts of added polyvinylalcohol (PVA) produces much stronger structures that are easy to handle. Electrical conductivity of order 1 S/cm is observed in the self-supporting aerogels, and similar conductivity can be achieved in PVA-reinforced aerogels through additional processing. The aerogels can be backfilled with polymers such as epoxy to create composite materials that retain the high conductivity of the network. Other potential applications for these structures, such as sensors, actuators, and thermoelectric devices, are currently being explored. This work is supported by grants from NSF (MRSEC DMR05-20020 and DMR-0505048) and NASA NAG8-2172.

Bryning, M. B.; Islam, M. F.; Hough, L. A.; Yodh, A. G.

2006-03-01

72

Metal-functionalized single-walled graphitic carbon nitride nanotubes: a first-principles study on magnetic property  

PubMed Central

The magnetic properties of metal-functionalized graphitic carbon nitride nanotubes were investigated based on first-principles calculations. The graphitic carbon nitride nanotube can be either ferromagnetic or antiferromagnetic by functionalizing with different metal atoms. The W- and Ti-functionalized nanotubes are ferromagnetic, which are attributed to carrier-mediated interactions because of the coupling between the spin-polarized d and p electrons and the formation of the impurity bands close to the band edges. However, Cr-, Mn-, Co-, and Ni-functionalized nanotubes are antiferromagnetic because of the anti-alignment of the magnetic moments between neighboring metal atoms. The functionalized nanotubes may be used in spintronics and hydrogen storage.

2011-01-01

73

Thermoelectric Power of Single-Walled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

We have measured the temperature-dependent thermoelectric power (TEP) of crystalline ropes of single-walled carbon nanotubes. The TEP is large and holelike at high temperatures and approaches zero as T-->0. The results argue against the opening of a gap at low temperature in these materials. When derived from a simple band structure picture, the TEP of a single metallic nanotube is significantly lower than the measured TEP, strongly suggesting that the predicted electron-hole symmetry of metallic nanotubes is broken when the tubes self-assemble into ropes. Different models for the symmetry breaking are considered.

Hone, J.; Ellwood, I.; Muno, M.; Mizel, Ari; Cohen, Marvin L.; Zettl, A.; Rinzler, Andrew G.; Smalley, R. E.

1998-02-01

74

Electron diffraction study of single-wall carbon nanotubes  

Microsoft Academic Search

We have used selected-area electron diffraction techniques to investigate the structure of single-wall carbon nanotubes assembled into ropes. The diffraction is sensitive to details of the tube curvature, orientation, radius and chirality. Single-wall carbon nanotubes within the ropes are found to comprise largely tubes of armchair chirality, but not exclusively (10, 10) tubes.

D. Bernaerts; A. Zettl; Nasreen G. Chopra; A. Thess; R. E. Smalley

1998-01-01

75

Improvements in Production of Single-Walled Carbon Nanotubes  

NASA Technical Reports Server (NTRS)

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 modification for conversion from batch to continuous production.

Balzano, Leandro; Resasco, Daniel E.

2009-01-01

76

Metal impurities provide useful tracers for identifying exposures to airborne single-wall carbon nanotubes released from work-related processes  

NASA Astrophysics Data System (ADS)

This study investigated the use of metal impurities in single-wall carbon nanotubes (SWCNT) as potential tracers to distinguish engineered nanomaterials from background aerosols. TEM and SEM were used to characterize parent material and aerosolized agglomerates collected on PTFE filters using a cascade impactor. SEM image analysis indicated that the SWCNT agglomerates contained about 45% amorphous carbon and backscatter electron analysis indicated that metal impurities were concentrated within the amorphous carbon component. Two elements present as impurities (Y and Ni) were selected as appropriate tracers in this case as their concentrations were found to be highly elevated in the SWCNT parent material (% range) compared to ambient air particles (?g/g range), and background air concentrations were below detection limits for both elements. Bioaccessibility was also determined using physiologically-based extractions at pH conditions relevant to both ingestion and inhalation pathways. A portable wet electrostatic precipitation system effectively captured airborne Y and Ni released during sieving processes, in proportions similar to the bulk sample. These observations support the potential for catalysts and other metal impurities in carbon nanotubes to serve as tracers that uniquely identify emissions at source, after an initial analysis to select appropriate tracers.

Rasmussen, Pat E.; Jayawardene, Innocent; Gardner, H. David; Chénier, Marc; Levesque, Christine; Niu, Jianjun

2013-04-01

77

Thermionic Emission of Single-Wall Carbon Nanotubes Measured.  

National Technical Information Service (NTIS)

Researchers at the NASA Glenn Research Center, in collaboration with the Rochester Institute of Technology, have investigated the thermionic properties of high-purity, single-wall carbon nanotubes (SWNTs) for use as electron-emitting electrodes. Carbon na...

G. A. Landis I. L. Krainsky S. G. Bailey J. M. Elich B. J. Landi T. Gennett R. P. Raffaelle

2004-01-01

78

Investigation of ultraviolet optical properties of semiconducting-enriched and metal-enriched single-walled carbon nanotube networks using spectroscopic ellipsometry.  

PubMed

The ultraviolet optical properties of semiconducting-enriched and metallic-enriched single-walled carbon nanotube (semi-enriched and m-enriched SWCNT) networks were studied using spectroscopic ellipsometry. According to calculated energy loss function, the energy loss peak assigned to the maximum intensity of ?-plasmon energy was found to increase from 4.5 eV to 5.0 eV as SWCNT network composition was changed from m-SWCNT enriched to semi-SWCNT enriched. These results clearly demonstrate that the dielectric response in the 4-6 eV range is sensitive to changes in the surrounding dielectric environment depending on the semi-/m-SWCNT content. Therefore, the spectral shift of this energy loss is attributed to the enhanced electron confinement by the presence of the surface plasmon due to a small amount of m-SWCNT, which is an important phenomenon at the SWCNT network. PMID:22964891

Park, Young Ran; Kim, Woo-Jae; Ko, Min Jae; Min, Nam Ki; Lee, Cheol Jin

2012-10-21

79

Influence of van der Waals contact forces on the deformation mechanics of thin flexible membranes assembled from metallic or semiconducting single-wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

Thin membranes of single-wall carbon nanotubes (SWCNTs) assembled from either metallic or semiconducting SWCNTs are subjected to the compressive strains imposed by a stretched elastic substrate, and the mechanical characteristics of the membranes are inferred from the topography of the wrinkling instability that emerges. By depositing comparable films on quartz, we also use optical (UV-Vis-NIR) absorption spectroscopy to compute the effective London dispersion spectra of the purified materials, and from these we compute the attractive part of the van der Waals potential between nanotubes of identical electronic type as a function of separation and relative orientation. We find significant differences in the strength and shape of the contact potential depending on electronic type, which in turn are evident in the modulus and yield strain measured from the deformation of the films.

Hobbie, Erik K.; Harris, John; Iyer, Swathi; Huh, Ji Yeon; Fagan, Jeffrey A.; Hudson, Steven D.; Stafford, Christopher M.

2011-03-01

80

Liquid crystal behavior of single wall carbon nanotubes  

Microsoft Academic Search

Single wall carbon nanotubes are dispersed in water with the water-soluble polymer polyvinylpyrrolidone and the surfactant sodium dodecylbenzene sulfonate, and then deposited by evaporative deposition onto degeneratively-doped silicon wafer substrates. These deposits were examined by scanning electron microscopy, which revealed highly-ordered arrays of large single wall carbon nanotube bundles. Various solution concentrations were prepared and deposition conditions were varied to

M. Bravo-Sanchez; Trevor J. Simmons; M. A. Vidal

2010-01-01

81

Raman Spectroelectrochemistry - A Way of Switching the Peierls-like Transition in Metallic Single-walled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

The high-energy vibrational modes of metallic nanotubes are believed to be softened compared to the semiconducting ones by a Peierls-like transition. We examined the frequency shifts and the intensity of the peaks of the high-energy band in SWNT Raman spectra in dependence on the doping level, as excited with a red laser to enhance the metallic tubes. The metallic modes were indeed found to be exceptionally sensitive to electrochemical doping, exhibiting large frequency shifts and intensity fluctuations. Our data may be interpreted as controlling the Peierls-like instability in metallic tubes with the applied potential.

Rafailov, P. M.; Maultzsch, J.; Thomsen, C.

2005-09-01

82

Single-wall carbon nanotube coating on a pyroelectric detector  

NASA Astrophysics Data System (ADS)

Carbon single-wall nanotubes (SWNTs) are studied as the thermal-absorption coating on a large area pyroelectric detector. The SWNTs were produced by a laser vaporization method and dispersed onto the detector surface by use of a simple airbrush technique. The detector was based on a 1-cm-diameter, 60-?m-thick lithium tantalate disk having nickel electrodes. We report the spectral responsivity of the detector ranging from 600 to 1800 nm, as well as the spatial and directional uniformity at 850 nm. Using Drude and Lorentzian dielectric functions and an effective medium approximation to obtain the indices of refraction of semiconductor and metallic SWNTs, we compared the expected theoretical relative responsivity for the two types of tube with the measured relative responsivity of the detector. Values of thermal conductivity, specific heat, and damage threshold obtained from the literature are compared with properties of alternatives for thermal coatings such as gold-black and carbon-based paint.

Lehman, John H.; Engtrakul, Chaiwat; Gennett, Thomas; Dillon, Anne C.

2005-02-01

83

Supramolecular functionalization of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanotubes (SWNTs) possess extraordinary mechanical strength, thermal and electrical conductivity. These properties make them very attractive in many applications in the fields of nanotechnology, electronics, and optics. However, most of the SWNT syntheses methods result in different types of chiralities, which determine the electronic and optical properties of the sample. Thus, it is important to selectively solubilize and purify carbon nanotubes if one wants to use them in technological applications. Selective separation of SWNTs by chirality has been the research focus of many scientists. Here, a comparative study for the solubility of SWNTs with polyaromatic hydrocarbons and conjugated polymers was conducted. PEGylated corannulene derivative has been shown to disperse more metallic nanotubes than the commonly used sodium dodecyl sulfate dispersant. Phthalimide containing conjugated materials were found to be effective in solubilizing SWNTs. In addition, the structural and mechanistic implications for high solubility power were discussed for all dispersants.

Yilmaz, Baris

84

Laser-Irradiation-Induced Enrichment of Metallic Single-Walled Carbon Nanotubes from As-Synthesized Nanotubes Individually Dispersed in Aqueous Solution  

NASA Astrophysics Data System (ADS)

In the present study, we developed a novel technique for the enrichment of metallic (m-) single-walled carbon nanotubes (SWNTs) from as-synthesized SWNTs that are individually dispersed in carboxymethylcellulose (CMC) aqueous solution by irradiation with a nanosecond-pulsed optical parametric oscillator (OPO) laser with wavelength tunability. The 507 nm laser irradiation in the m-SWNT first-transition band (M11) resulted in the collapse of both m- and semiconducting (s-) SWNTs. In contrast, the irradiation with a laser with a wavelength (778 or 989 nm) corresponding to the typical absorption peaks in the s-SWNT second (S22)- or first (S11)-transition bands caused a preferential collapse of s-SWNTs, resulting in enriched m-SWNTs of high purity and in large quantity. The present m-SWNT collection technique can be generalized for various SWNT dispersion systems using different dispersing agents. The OPO laser irradiation discussed in this study is a promising technique for the selective separation of dispersed m-SWNTs.

Tsuchiya, Koji; Kumazawa, Akira; Tajima, Isamu; Uchida, Katsumi; Ishii, Tadahiro; Yajima, Hirofumi

2012-10-01

85

Laser ablation process for single-walled carbon nanotube production.  

PubMed

Different types of lasers are now routinely used to prepare single-walled carbon nanotubes. The original method developed by researchers at Rice University used a "double-pulse laser oven" process. Several researchers have used variations of the lasers to include one-laser pulse (green or infrared), different pulse widths (ns to micros as well as continuous wave), and different laser wavelengths (e.g., CO2, or free electron lasers in the near to far infrared). Some of these variations are tried with different combinations and concentrations of metal catalysts, buffer gases (e.g., helium), oven temperatures, flow conditions, and even different porosities of the graphite targets. This article is an attempt to cover all these variations and their relative merits. Possible growth mechanisms under these different conditions will also be discussed. PMID:15296222

Arepalli, Sivaram

2004-04-01

86

Single Wall Carbon Nanotube-Based Structural Health Sensing Materials  

NASA Technical Reports Server (NTRS)

Single wall carbon nanotube (SWCNT)-based materials represent the future aerospace vehicle construction material of choice based primarily on predicted strength-to-weight advantages and inherent multifunctionality. The multifunctionality of SWCNTs arises from the ability of the nanotubes to be either metallic or semi-conducting based on their chirality. Furthermore, simply changing the environment around a SWCNT can change its conducting behavior. This phenomenon is being exploited to create sensors capable of measuring several parameters related to vehicle structural health (i.e. strain, pressure, temperature, etc.) The structural health monitor is constructed using conventional electron-beam lithographic and photolithographic techniques to place specific electrode patterns on a surface. SWCNTs are then deposited between the electrodes using a dielectrophoretic alignment technique. Prototypes have been constructed on both silicon and polyimide substrates, demonstrating that surface-mountable and multifunctional devices based on SWCNTs can be realized.

Watkins, A. Neal; Ingram, JoAnne L.; Jordan, Jeffrey D.; Wincheski, Russell A.; Smits, Jan M.; Williams, Phillip A.

2004-01-01

87

Single-Wall Carbon Nanotubes as Transparent Electrodes for Photovoltaics  

SciTech Connect

Transparent and electrically conductive coatings and films have a variety of uses in the fast-growing field of optoelectronic applications. Transparent electrodes typically include semiconductive metal oxides such as indium tin oxide (ITO), and conducting polymers such as poly(3,4-ethylenedioxythiophene), doped and stabilized with poly(styrenesulfonate) (PEDOT/PSS). In recent years, Eikos, Inc. has conceived and developed technologies to deliver novel alternatives using single-wall carbon nanotubes (SWNT). These technologies offer products having a broad range of conductivity, excellent transparency, neutral color tone, good adhesion, abrasion resistance as well as mechanical robustness. Additional benefits include ease of ambient processing and patterning capability. This paper reports our recent findings on achieving 2.6% and 1.4% efficiencies on nonoptimized organic photovoltaic cells employing SWNT as a transparent electrode.

Weeks, C.; Peltola, J.; Levitsky, I.; Glatkowski, P.; van de Lagemaat, J.; Rumbles, G.; Barnes, T.; Coutts, T.

2006-01-01

88

Laser ablation process for single-walled carbon nanotube production  

NASA Technical Reports Server (NTRS)

Different types of lasers are now routinely used to prepare single-walled carbon nanotubes. The original method developed by researchers at Rice University used a "double-pulse laser oven" process. Several researchers have used variations of the lasers to include one-laser pulse (green or infrared), different pulse widths (ns to micros as well as continuous wave), and different laser wavelengths (e.g., CO2, or free electron lasers in the near to far infrared). Some of these variations are tried with different combinations and concentrations of metal catalysts, buffer gases (e.g., helium), oven temperatures, flow conditions, and even different porosities of the graphite targets. This article is an attempt to cover all these variations and their relative merits. Possible growth mechanisms under these different conditions will also be discussed.

Arepalli, Sivaram

2004-01-01

89

Thermoelectric power of a single-walled carbon nanotubes rope.  

PubMed

In this work, a rope of single-walled carbon nanotubes is prepared by using a diamond wire drawing die. At atmospheric condition, the electrical conductance and the thermoelectric voltage of single-walled carbon nanotubes rope have been investigated with the hot-side temperature ranging from 292 to 380 K, and cold-side temperature at 292 K. For different temperatures in the range of 292 to 380 K at hot-side, the current-voltage curves are almost parallel to each other, indicating that the electrical conductance does not change. The dynamic characteristics of voltage at positive, zero and negative current bias demonstrate that a thermoelectric voltage is induced with a direction from hot- to cold-side. The induced thermoelectric voltage shows linear dependence on the temperature difference between hot- and cold-side. The thermoelectric power of single-walled carbon nanotubes rope is found to be positive and has a value about 17.8 +/- 1.0 microV/K. This result suggests the hole-like carriers in single-walled carbon nanotubes rope. This study will pave the way for single-walled carbon nanotubes based thermoelectric devices. PMID:23646631

Yu, Fang; Hu, Lijun; Zhou, Haiqing; Qiu, Caiyu; Yang, Huaichao; Chen, Minjiang; Lu, Jianglei; Sun, Lianfeng

2013-02-01

90

The Effects of Alkali Metals on the Radial and Tangential Raman Modes of Single Wall Carbon Nanotubes (SWCNTs)  

NASA Astrophysics Data System (ADS)

We present a theoretical study of the Raman modes in SWCNTs, and in particular the effects of K, Rb, and Cs doping. It was previously shown that alkali-metal doping causes shifts of the RBM and G-bands (Bendiab, et al., Chem. Phys. Lett., 2001). Applying first principles density functional theory within the generalized gradient approximation, we report results of the Raman modes of pristine SWCNTs in crystalline-rope and isolated tube forms, and discuss changes for SWCNTs adsorbed with alkali atoms at various sites. For example, among the proposed models for Cs adsorption, we find intercalation to be the mechanism whereby the Raman modes are downshifted, which can be rationalized by the tube distortion, hence lowering its symmetry.

Akdim, Brahim; Duan, Xiaofeng; Pachter, Ruth

2004-03-01

91

Optimising the platinum–carbon bond in nitrogen-doped single-walled carbon nanotubes  

Microsoft Academic Search

The durability, high surface area and metallic properties demonstrated by single-walled carbon nanotubes (SWCNTs) show potential as a catalyst support. In this work, the effects of nitrogen doping of SWCNTs are examined using density functional theory. It will be shown that by adding nitrogen, the durability of a platinum catalyst, measured by the binding energy it has with the surface,

M. N. Groves; A. S. W. Chan; C. Malardier-Jugroot; M. Jugroot

2011-01-01

92

Electronic Property Control of Single-Walled Carbon Nanotubes by Functionalization  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanotubes exhibit remarkable electronic properties. It is well known that there are two types of single-walled carbon nanotubes: metallic and semiconducting. However, separating semiconducting carbon nanotubes from metallic ones is a ``holy grail'' problem in nanoelectronics fields. Using ab initio density functional theory, we will present the effects of various functional groups, such as 4-bromobenzene diazonium tetrafluoroborate, on SWNTs. Modifications in electronic and transport properties due to such functionalization will be discussed. Possible mechanism converting metallic tubes to semiconducting ones will be addressed.

Wu, Chiayun; Kwon, Young-Kyun

2008-03-01

93

Micromachined quartz resonator functionalized with single walled carbon nanotubes  

Microsoft Academic Search

Single walled carbon nanotubes (SWNTs) are reservoirs of gases as they can adsorb on their walls as well as retain gas molecules in their hollow cylindrical interior. This has important applications for example in fuel cell technology for hydrogen storage, as a gas sensor for realization of artificial nose, etc. Storage of gases by carbon nanotubes have been recently investigated

Abhijat Goyal; Prasoon Joshi; Srinivas Tadigadapa; Awnish Gupta; Peter Eklund

2005-01-01

94

On the vibrations of single-walled carbon nanotubes  

Microsoft Academic Search

In this paper, a detailed numerical study on the free and forced vibrations of single walled carbon nanotubes is presented. A simple and straightforward method developed such that the proximity of the mathematical model to the actual atomic structure of the nanotube is significantly retained, is used for this purpose. Both zigzag and armchair chiralities of the carbon nanotubes for

S. Arghavan; A. V. Singh

2011-01-01

95

Role of pH controlled DNA secondary structures in the reversible dispersion/precipitation and separation of metallic and semiconducting single-walled carbon nanotubes.  

PubMed

Single-stranded DNA (ss-DNA) oligomers (dA20, d[(C3TA2)3C3] or dT20) are able to disperse single-walled carbon nanotubes (SWNTs) in water at pH 7 through non-covalent wrapping on the nanotube surface. At lower pH, an alteration of the DNA secondary structure leads to precipitation of the SWNTs from the dispersion. The structural change of dA20 takes place from the single-stranded to the A-motif form at pH 3.5 while in case of d[(C3TA2)3C3] the change occurs from the single-stranded to the i-motif form at pH 5. Due to this structural change, the DNA is no longer able to bind the nanotube and hence the SWNT precipitates from its well-dispersed state. However, this could be reversed on restoring the pH to 7, where the DNA again relaxes in the single-stranded form. In this way the dispersion and precipitation process could be repeated over and over again. Variable temperature UV-Vis-NIR and CD spectroscopy studies showed that the DNA-SWNT complexes were thermally stable even at ?90 °C at pH 7. Broadband NIR laser (1064 nm) irradiation also demonstrated the stability of the DNA-SWNT complex against local heating introduced through excitation of the carbon nanotubes. Electrophoretic mobility shift assay confirmed the formation of a stable DNA-SWNT complex at pH 7 and also the generation of DNA secondary structures (A/i-motif) upon acidification. The interactions of ss-DNA with SWNTs cause debundling of the nanotubes from its assembly. Selective affinity of the semiconducting SWNTs towards DNA than the metallic ones enables separation of the two as evident from spectroscopic as well as electrical conductivity studies. PMID:24569668

Maji, Basudeb; Samanta, Suman K; Bhattacharya, Santanu

2014-04-01

96

Single-Wall Carbon Nanohorns and Nanocones  

Microsoft Academic Search

\\u000a In addition to sheet structures with purely hexagonal carbon rings, which\\u000a naturally form surfaces of zero Gaussian curvature such as sheets and tubes, a\\u000a graphenic membrane can also assume a conical shape whose apex is defined by one or\\u000a more disclinations taking the form of fivefold (or possibly smaller) rings.\\u000a Geometrically, just as a sheet of paper with a wedge

Masako Yudasaka; Sumio Iijima; Vincent H. Crespi

97

Mechanically interlocked single-wall carbon nanotubes.  

PubMed

Extensive research has been devoted to the chemical manipulation of carbon nanotubes. The attachment of molecular fragments through covalent-bond formation produces kinetically stable products, but implies the saturation of some of the C-C double bonds of the nanotubes. Supramolecular modification maintains the structure of the SWNTs but yields labile species. Herein, we present a strategy for the synthesis of mechanically interlocked derivatives of SWNTs (MINTs). In the key rotaxane-forming step, we employed macrocycle precursors equipped with two ?-extended tetrathiafulvalene SWNT recognition units and terminated with bisalkenes that were closed around the nanotubes through ring-closing metathesis (RCM). The mechanically interlocked nature of the derivatives was probed by analytical, spectroscopic, and microscopic techniques, as well as by appropriate control experiments. Individual macrocycles were observed by HR?STEM to circumscribe the nanotubes. PMID:24729452

de Juan, Alberto; Pouillon, Yann; Ruiz-González, Luisa; Torres-Pardo, Almudena; Casado, Santiago; Martín, Nazario; Rubio, Ángel; Pérez, Emilio M

2014-05-19

98

Purity Evaluation of Bulk Single Wall Carbon Nanotube Materials  

SciTech Connect

We report on our experience using a preliminary protocol for quality control of bulk single wall carbon nanotube (SWNT) materials produced by the electric arc-discharge and laser ablation method. The first step in the characterization of the bulk material is mechanical homogenization. Quantitative evaluation of purity has been performed using a previously reported procedure based on solution phase near-infrared spectroscopy. Our results confirm that this method is reliable in determining the nanotube content in the arc-discharge sample containing carbonaceous impurities (amorphous carbon and graphitic particles). However, the application of this method to laser ablation samples gives a relative purity value over 100 %. The possible reason for that might be different extinction coefficient meaning different oscillator strength of the laser ablation tubes. At the present time, a 100 % pure reference sample of laser ablation SWNT is not available, so we chose to adopt the sample showing the highest purity as a new reference sample for a quantitative purity evaluation of laser ablation materials. The graphitic part of the carbonaceous impurities has been estimated using X-ray diffraction of 1:1 mixture of nanotube material and C60 as an internal reference. To evaluate the metallic impurities in the as prepared and homogenized carbon nanotube soot inductive coupled plasma (ICP) has been used.

Dettlaff-Weglikowska, U.; Hornbostel, B.; Cech, J.; Roth, S. [Max Planck Institute for Solid State Research, 70569 Stuttgart (Germany); Wang, J.; Liang, J. [Max Planck Institute for Solid State Research, 70569 Stuttgart (Germany); Yangtze Nanomaterials Co. Ltd, Shanghai (China)

2005-09-27

99

Enhanced Raman Microprobe Imaging of Single-Wall Carbon Nanotubes  

NASA Technical Reports Server (NTRS)

We explore Raman microprobe capabilities to visualize single wall carbon nanotubes (SWCNTs). Although this technique is limited to a micron scale, we demonstrate that images of individual SWCNTs, bundles or their agglomerates can be generated by mapping Raman active elementary excitations. We measured the Raman response from carbon vibrations in SWCNTs excited by confocal scanning of a focused laser beam. Carbon vibrations reveal key characteristics of SWCNTs as nanotube diameter distribution (radial breathing modes, RBM, 100-300 cm(exp -1)), presence of defects and functional groups (D-mode, 1300-1350 cm(exp -1)), strain and oxidation states of SWCNTs, as well as metallic or semiconducting character of the tubes encoded in the lineshape of the G-modes at 1520-1600 cm(exp - 1). In addition, SWCNTs are highly anisotropic scatterers. The Raman response from a SWCNT is maximal for incident light polarization parallel to the tube axis and vanishing for perpendicular directions. We show that the SWCNT bundle shape or direction can be determined, with some limitations, from a set of Raman images taken at two orthogonal directions of the incident light polarization.

Hadjiev, V. G.; Arepalli, S.; Nikolaev, P.; Jandl, S.; Yowell, L.

2003-01-01

100

Thermogravimetric Analysis of Single-Wall Carbon Nanotubes  

NASA Technical Reports Server (NTRS)

An improved protocol for thermogravimetric analysis (TGA) of samples of single-wall carbon nanotube (SWCNT) material has been developed to increase the degree of consistency among results so that meaningful comparisons can be made among different samples. This improved TGA protocol is suitable for incorporation into the protocol for characterization of carbon nanotube material. In most cases, TGA of carbon nanotube materials is performed in gas mixtures that contain oxygen at various concentrations. The improved protocol is summarized.

Arepalli, Sivram; Nikolaev, Pavel; Gorelik, Olga

2010-01-01

101

Spectro-electrochemical studies of single wall carbon nanotubes films  

Microsoft Academic Search

The dependence of the resonance Raman spectra of single wall carbon nanotubes (SWNTs) on an externally applied potential (Vap) was studied in different media. The spectro-electrochemical data indicate that the reaching of van Hove singularities (vHSs) of SWNTs occurs at a different Vap for each electrolyte, and that there is a dependence of the charge transfer and intercalation processes on

P. Corio; A. Jorio; N. Demir; M. S Dresselhaus

2004-01-01

102

Functionalized Single Wall Carbon Nanotubes Based Gas Sensor  

Microsoft Academic Search

In this paper we report on functionalized single wall carbon nanotube (SWNT) based gas sensor. SWNT were functionalized with sodium dodecyl sulfate (SDS) which improved solubility of SWNT in the DI water significantly. Solutions of SWNTs were deposited on the alumina substrate prepatterned with Pt contacts and heater to form sensor. The morphology of the SWNT films were characterized by

M. Z. Atashbar; C. Baratto; G. Faglia; G. Sberveglieri

2006-01-01

103

Chemical Sensing with Polyaniline Coated Single-Walled Carbon Nanotubes  

SciTech Connect

Single-walled carbon nanotube/polyaniline (SWNT/PAni) nanocomposite with controlled core/shell morphology was synthesized by a noncovalent functionalization approach. Unique electron interactions between the SWNT core and the PAni shell were studied electrochemically and spectroscopically, and superior sensor performance to chemical gases and vapors was demonstrated.

Ding, Mengning; Tang, Yifan; Gou, Pingping; Reber, Michael J; Star, Alexander

2011-01-25

104

A Computational Experiment on Single-Walled Carbon Nanotubes  

ERIC Educational Resources Information Center

A computational experiment that investigates single-walled carbon nanotubes (SWNTs) has been developed and employed in an upper-level undergraduate physical chemistry laboratory course. Computations were carried out to determine the electronic structure, radial breathing modes, and the influence of the nanotube's diameter on the…

Simpson, Scott; Lonie, David C.; Chen, Jiechen; Zurek, Eva

2013-01-01

105

Molecular photodesorption from single-walled carbon nanotubes  

Microsoft Academic Search

Probing the photoelectrical properties of single-walled carbon nanotubes (SWNTs) led to the discovery of photoinduced molecular desorption phenomena in nanotube molecular wires. These phenomena were found to be generic to various molecule-nanotube systems. Photodesorption strongly depends on the wavelength of light, the details of which lead to a fundamental understanding of how light stimulates molecular desorption from nanotubes. The results

Robert J. Chen; Nathan R. Franklin; Jing Kong; Jien Cao; Thomas W. Tombler; Yuegang Zhang; Hongjie Dai

2001-01-01

106

Experimental Measurement of Single-Wall Carbon Nanotube Torsional Properties  

PubMed Central

We report on the characterization of nanometer-scale torsional devices based on individual single-walled carbon nanotubes as the spring elements. The axial shear moduli of the nanotubes are obtained through modeling of device reaction to various amounts of applied electrostatic force and are compared to theoretical values.

Hall, A. R.; An, L.; Liu, J.; Vicci, L.; Falvo, M. R.; Superfine, R.; Washburn, S.

2012-01-01

107

Flexural wave propagation in single-walled carbon nanotubes  

Microsoft Academic Search

The paper presents the study on the flexural wave propagation in a single-walled carbon nanotube through the use of the continuum mechanics and the molecular dynamics simulation based on the Terroff-Brenner potential. The study focuses on the wave dispersion caused not only by the rotary inertia and the shear deformation in the model of a traditional Timoshenko beam, but also

Lifeng Wang; Haiyan Hu

2005-01-01

108

Fully integrated single-walled carbon nanotube thermoplastic composites  

Microsoft Academic Search

The development of composites of single-walled carbon nanotubes (SWNTs) with thermoplastics requires methods for good dispersion and achieving good interaction between SWNTs and the matrix. This thesis presents a new method to achieve good dispersion by a preliminary treatment called incipient wetting. The SWNTs dispersed in a solvent are mixed with polymer particles and deposited over them as the solvent

Fernando J. Rodriguez-Macias

2004-01-01

109

Study of the probability excitation in single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

In this work we have studied the interaction of a laser pulse with single-walled metallic carbon nanotubes. We have discussed the Rabi oscillations in zigzag carbon nanotubes based on the two-band model. We have shown the interband coupling coefficient enters into the probability of excitation.

Rostami, Ali; Shafiei, S. Yousef; Shafi-e-asl, Amir; Marami Iranaq, A. R.

2013-06-01

110

Thermionic Emission of Single-Wall Carbon Nanotubes Measured  

NASA Technical Reports Server (NTRS)

Researchers at the NASA Glenn Research Center, in collaboration with the Rochester Institute of Technology, have investigated the thermionic properties of high-purity, single-wall carbon nanotubes (SWNTs) for use as electron-emitting electrodes. Carbon nanotubes are a recently discovered material made from carbon atoms bonded into nanometer-scale hollow tubes. Such nanotubes have remarkable properties. An extremely high aspect ratio, as well as unique mechanical and electronic properties, make single-wall nanotubes ideal for use in a vast array of applications. Carbon nanotubes typically have diameters on the order of 1 to 2 nm. As a result, the ends have a small radius of curvature. It is these characteristics, therefore, that indicate they might be excellent potential candidates for both thermionic and field emission.

Landis, Geoffrey A.; Krainsky, Isay L.; Bailey, Sheila G.; Elich, Jeffrey M.; Landi, Brian J.; Gennett, Thomas; Raffaelle, Ryne P.

2004-01-01

111

Resonant Raman effect in single-wall carbon nanotubes  

SciTech Connect

A resonant Raman study of single-wall carbon nanotubes (SWNT) using several laser lines between 0.94 and 3.05 eV is presented. A detailed lineshape analysis shows that the bands associated with the nanotube radial breathing mode are composed of a sum of individual peaks whose relative intensities depend strongly on the laser energy, in agreement with prior work. On the other hand, the shape of the Raman bands associated with the tangential C{endash}C stretching motions in the 1500{endash}1600 cm{sup {minus}1} range does not depend significantly on the laser energy for laser excitation energies in the ranges 0.94{endash}1.59 eV and 2.41{endash}3.05 eV. However, new C{endash}C stretching modes are observed in the spectra collected using laser excitations with energies close to 1.9 eV. The new results are discussed in terms of the difference between the 1D electronic density of states for the semiconducting and metallic carbon nanotubes. {copyright} {ital 1998 Materials Research Society.}

Pimenta, M.A.; Marucci, A.; Brown, S.D.; Matthews, M.J. [Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Rao, A.M.; Eklund, P.C. [Department of Physics and Astronomy and Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40506 (United States); Smalley, R.E. [Department of Chemistry and Center for Nanoscale Technology Science, Rice University, Houston, Texas 77005 (United States); Dresselhaus, G. [Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Dresselhaus, M.S. [Department of Electrical Engineering and Computer Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

1998-09-01

112

STM Studies of Single-walled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanotubes (SWNTs) are ideal systems for investigating fundamental properties in one-dimensional (1D) electronic systems and have the potential to revolutionize many aspects of nano/molecular electronics. Scanning tunneling microscopy (STM) has been used to characterize the atomic structure and tunneling density of states of individual SWNTs. Detailed spectroscopic measurements show 1D singularities in the SWNT density of states for both metallic and semiconducting nanotubes. These results have been compared to and agree well with theoretical predictions and tight-binding calculations. SWNTs have also been shortened using the STM to explore the role of finite size, which might be exploited for device applications. Nanotube segments less than 10 nm exhibited discrete peaks in the tunneling spectra, which correspond to quantized energy levels, and whose spacing scales inversely with length. Finally, the interaction between magnetic impurities and electrons confined to 1D has been studied by spatially resolving the local electronic density of states of small cobalt clusters on metallic SWNTs. Spectroscopic measurements performed on and near these clusters exhibit a narrow peak near the Fermi level that has been identified as a Kondo resonance. In addition, spectroscopic studies of ultra-small magnetic nanostructures, consisting of small cobalt clusters on short nanotube pieces, exhibited features characteristic of the bulk Kondo resonance, but also new features due to finite size.

Odom, Teri

2001-03-01

113

Production of single-walled carbon nanotube grids  

DOEpatents

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.

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

2013-12-03

114

Interlayer spacing anomaly of single-wall carbon nanohorn aggregate  

Microsoft Academic Search

Newly found single-wall carbon nanohorns (SWNH) are synthesized by a CO2 laser vaporization of a pure carbon target in an Ar gas. Purification method using centrifugal separation and structural features of aggregated form of SWNHs (SWNH aggregate) are studied in this Letter. Although the X-ray diffraction profile taken for highly purified SWNH aggregates does not show any sharp 002 diffraction

S. Bandow; F. Kokai; K. Takahashi; M. Yudasaka; L. C. Qin; S. Iijima

2000-01-01

115

Thiophene adsorption on Single Wall Carbon Nanotubes and graphene  

Microsoft Academic Search

We investigated the adsorption of thiophene inside and outside Single Wall Carbon Nanotubes (SWCNTs) and onto graphene, employing periodic boundary conditions and the VDW-DF and LDA methodologies. The results indicate that thiophene adopts a nearly parallel configuration with respect to the graphene plane. The sulfur atom is 3.7Å above the sheet, whereas the two hydrogen atoms located in carbon atoms

Pablo A. Denis; Federico Iribarne

2010-01-01

116

Single Wall Carbon Nano Tube Films and Coatings  

Microsoft Academic Search

Purified single wall carbon nano tubes (SWNTs) produced from the high-pressure carbon monoxide (HiPCO) process have been dissolved \\/dispersed in oleum. These solutions \\/dispersions were optically homogeneous and have been used to form stand-alone SWNT films. The washed, dried, and heat-treated films are isotropic. The scanning electron micrographs of the film surface shows that the nanotube ropes (or fibrils) of

T. V. Sreekumar; Satish Kumar; Lars M. Ericson; Richard E. Smalley

2002-01-01

117

Comparison of influence of incorporated 3d-, 4d- and 4f-metal chlorides on electronic properties of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

In the present work, the channels of single-walled carbon nanotubes were filled with melts of ZnCl2, CdCl2, and TbCl3 by a capillary method with subsequent slow cooling. The detailed study of electronic structure of filled nanotubes was performed using Raman, optical absorption, and X-ray photoelectron spectroscopy. The obtained data are in mutual agreement and it proves that the filling of carbon nanotube channels with all these salts leads to the charge transfer from nanotube walls to the incorporated compounds, thus acceptor doping of nanotubes takes place. It was found out that encapsulated terbium chloride has the largest influence on the electronic properties of carbon nanotubes.

Kharlamova, M. V.

2013-06-01

118

Spectroscopy-Based Characterization of Single Wall Carbon Nanotubes  

NASA Technical Reports Server (NTRS)

We present the initial results of our combined investigation of Raman scattering and optical absorption spectroscopy in a batch of single wall carbon nanotubes (SWNTs). The SWNT diameters are first estimated from the four radial breathing mode (RBM) peaks using a simple relation of omega(sub RBM) = 248/cm nm/d(sub t)(nm). The calculated diameter values are related to the optical absorption peaks through the expressions of first interband transition energies, i.e., E(sup S)(sub 11) = 2a gamma/d(sub t) for semiconducting and E(sup S)(sub 11) = 6a gamma/d(sub t) for metallic SWNTs, respectively, where a is the carbon-carbon bond length (0.144 nm) and gamma is the energy of overlapping electrons from nearest neighbor atoms, which is 2.9 eV for a SWNT. This analysis indicates that three RBM peaks are from semiconducting tubes, and the remaining one is from metallic tubes. The detailed analysis in the present study is focused on these three peaks of the first absorption band by determining the values of the representative (n,m) pairs. The first step of analysis is to construct a list of possible (n,m) pairs from the diameters calculated from the positions of the RBM peaks. The second step is to compute the first interband transition energy, E(sub 11), by substituting the constructed list of (n,m) into the expression of Reich and Thomsen, and Saito et al. Finally, the pairs with the energies closest to the experimental values are selected.

Namkung, Min; Namkung, Juock S.; Wincheski, Russell A.; Seo, J.; Park, Cheol

2003-01-01

119

Assessing the pulmonary toxicity of single-walled carbon nanohorns  

SciTech Connect

Previous studies have suggested that single-walled carbon nanotubes (SWCNTs) may pose a pulmonary hazard. We investigated the pulmonary toxicity of single-walled carbon nanohorns (SWCNHs), a relatively new carbon-based nanomaterial that is structurally similar to SWCNTs. Mice were exposed to 30 {micro}g of surfactant-suspended SWCNHs or an equal volume of vehicle control by pharyngeal aspiration and sacrificed 24 hours or 7 days post-exposure. Total and differential cell counts and cytokine analysis of bronchoalveolar lavage fluid demonstrated a mild inflammatory response which was mitigated by day 7 post-exposure. Whole lung microarray analysis demonstrated that SWCNH-exposure did not lead to robust changes in gene expression. Finally, histological analysis showed no evidence of granuloma formation or fibrosis following SWCNH aspiration. These combined results suggest that SWCNH is a relatively innocuous nanomaterial when delivered to mice in vivo using aspiration as a delivery mechanism.

Lynch, Rachel M [ORNL; Voy, Brynn H [ORNL; Glass-Mattie, Dana F [ORNL; Mahurin, Shannon Mark [ORNL; Saxton, Arnold [University of Tennessee, Knoxville (UTK); Donnel, Robert L. [University of Tennessee, Knoxville (UTK); Cheng, Mengdawn [ORNL

2007-01-01

120

Assessing the pulmonary toxicity of single-walled carbon nanohorns  

SciTech Connect

Previous studies have suggested that single-walled carbon nanotubes (SWCNTs) may be pose a pulmonary hazard. We investigated the pulmonary toxicity of single-walled carbon nanohorns (SWCNHs), a relatively new carbon-based nanomaterial that is structurally similar to SWCNTs. Mice were exposed to 30 g of surfactant-suspended SWCNHs by pharyngeal aspiration and sacrificed 24 hours or 7 days post exposure. Total and differential cell counts and cytokine analysis of bronchoalveolar lavage fluid demonstrated a mild inflammatory response which was mitigated by day 7 post exposure. Whole lung microarray analysis demonstrated that SWCNH-exposure did not lead to robust changes in gene expression. Finally, histological analysis showed no evidence of granuloma formation or fibrosis following SWCNH aspiration. These combined results suggest that SWCNH is a relatively innocuous nanomaterial when delivered to mice in vivo using aspiration as a delivery mechanism.

Lynch, Rachel M [ORNL; Voy, Brynn H [ORNL; Glass-Mattie, Dana F [ORNL; Mahurin, Shannon Mark [ORNL; Saxton, Arnold [University of Tennessee, Knoxville (UTK); Donnel, Robert L. [University of Tennessee, Knoxville (UTK); Cheng, Mengdawn [ORNL

2007-01-01

121

Probing Scattering in Single-Walled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

Transport measurements and atomic force microscopy were used to study electron scattering rates in metallic single-walled carbon nanotubes. From scaling of the resistance of the same nanotube with length in the low and high bias regimes, the mean free paths for both regimes are inferred. The observed scattering rates are consistent with calculations for acoustic phonon scattering at low biases and zone boundary/optical phonon scattering at high biases. We have also developed techniques to probe the high frequency transport properties of nanotube transistors. We have used the nanotube transistor as a microwave mixer operating at frequencies up to 50 GHz. The long-term goal is to directly measure the fundamental excitations and scattering rates. The author would like to acknowledge Ji-Yong Park, Yuval Yaish, Vera Sazonova, Xinjian Zhou, Hao Lin, Hande Ustunel, Stephan Braig, T.A. Arias, Piet W. Brower, Sandip Tiwari and Paul L. McEuen of Cornell University for their contributions to this work.

Rosenblatt, Sami

2005-03-01

122

Theory of electroabsorption in semiconducting single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Eletroabsorption (EA) is a standard nonlinear optical technique to probe the excitonic characteristics of semiconductors. In the context of single-walled carbon nanotubes (SWCNTs) the advantage of EA is that it can directly probe the excitons associated with higher bands, which lie in the continuum region of the lowest band, and cannot be probed by other nonlinear optical techniques like photoinduced absorption or two-photon absorption. Although currently it is still difficult to carry out EA experiments, because it requires separation of semiconducting SWCNTs from metallic ones, theoretical calculations can provide a benchmark results for future study. We have calculated EA for several S-SWCNTs with both zigzag and chiral tubes. For the lowest exciton we find the usual Stark shift, the emergence of absorption due to two-photon states and continuum band. We also find unusual and interesting behavior of the higher energy excitons from second band. L. Sebastian and G. Weiser, Phys. Rev. Lett. 46, 1156 (1981); D. Guo et al., Phys. Rev. B 48, 1433 (1993). J. W. Kennedy, Z. V. Vardeny, S. Collins, R. H. Baughman, H. Zhao, and S. Mazumdar, cond-mat/0505071.

Zhao, Hongbo; Mazumdar, Sumit

2006-03-01

123

Electron transport in single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We present electron transport experiments on single walled carbon nanotubes (SWNTs). By measuring the linear scaling of resistance with length, we determine an unusually long mean free path of Lm ˜1 mum at room temperature. From the temperature dependence of the mean free path for over 10 samples we show that inelastic scattering with acoustic phonons are the main source of scattering at room temperature and experimentally determine the electron-acoustic phonon strength. Disorder ultimately limits the low temperature mean free path (Lm ˜10 mum), which we show by employing scanning gate microscopy. We analyze the non-linear scaling of resistance with length and temperature to further elucidate the nature of this disorder. In general, we find that transport in 1-dimension is dominated by the strongest defect along the channel. For larger source-drain voltage (VSD > 0.2 V), we show that L m is significantly reduced in both metallic and semiconducting SWNTs, due to electrons scattering with the higher energy phonons. In semiconducting samples, when the Fermi energy is close to the energy band gap, we observe an anomalous conductance dip. Finally, we utilize locally controlled gate structures to fabricate a series of tunable barriers to form a superlattice and observe its mini-band structure superimposed on that of the nanotubes.

Purewal, Meninder S.

124

Fabrication of stretchable single-walled carbon nanotube logic devices.  

PubMed

The fabrication of a stretchable single-walled carbon nanotube (SWCNT) complementary metal oxide semiconductor (CMOS) inverter array and ring oscillators is reported. The SWCNT CMOS inverter exhibits static voltage transfer characteristics with a maximum gain of 8.9 at a supply voltage of 5 V. The fabricated devices show stable electrical performance under the maximum strain of 30% via forming wavy configurations. In addition, the 3-stage ring oscillator demonstrates a stable oscillator frequency of ?3.5 kHz at a supply voltage of 10 V and the oscillating waveforms are maintained without any distortion under cycles of pre-strain and release. The strains applied to the device upon deformation are also analyzed by using the classical lamination theory, estimating the local strain of less than 0.6% in the SWCNT channel and Pd electrode regions which is small enough to keep the device performance stable under the pre-strain up to 30%. This work demonstrates the potential application of stretchable SWCNT logic circuit devices in future wearable electronics. PMID:24700788

Yoon, Jangyeol; Shin, Gunchul; Kim, Joonsung; Moon, Young Sun; Lee, Seung-Jung; Zi, Goangseup; Ha, Jeong Sook

2014-07-01

125

Solid–liquid–solid growth mechanism of single-wall carbon nanotubes  

Microsoft Academic Search

Reasons are presented which suggest that the liquefaction of the catalytic particles is a decisive condition for formation of single wall carbon nanotubes (SWNTs) by physical synthesis techniques. It is argued that the SWNT growth mechanism is a kind of solid–liquid–solid graphitization of amorphous carbon or other imperfect carbon forms catalyzed by molten supersaturated carbon–metal nanoparticles. The assumption of low

A Gorbunov; O Jost; W Pompe; A Graff

2002-01-01

126

Single-walled carbon nanotube fibers, films and balls  

Microsoft Academic Search

Well-defined fibers and films of single-walled carbon nanotubes (SWNTs) with high purity and narrow diameter distributions were obtained from the strand-like raw soot produced by a dc arc-discharge method. These architectures made up of SWNTs have very uniform smooth surfaces. When the strand-like product was placed on a silicon substrate, dipped into water, treated ultrasonically, and then dried in air,

Lunhui Guan; Huanjun Li; Zujin Shi; Zhennan Gu

2007-01-01

127

Single Walled Carbon Nanotube-based Aqueous Sensors  

Microsoft Academic Search

Single walled carbon nanotube (SWNT) field effect transistors (FETs) have been utilized as chemical specific sensors by incorporating a sensitizing agent into the nanotube sidewalls. Here we report the non-covalent sidewall functionalization of SWNT FETs through the adsorption of macro-organic molecules. The modified SWNT FETs recognize changes in pH and oxidation states through a change in current flow across the

Sarah Lastella; Aravind Vijayaraghavan; Swastik Kar; Pulickel M. Ajayan; Chang Y. Ryu

2006-01-01

128

Electrochemically Functionalized Single-Walled Carbon Nanotube Gas Sensor  

Microsoft Academic Search

We demonstrate a facile fabrication method to make chemical gas sensors using single-walled carbon nanotubes (SWNT) electrochemically functionalized with polyaniline (PANI). The potential advantage of this method is to enable targeted functionalization with different materials to allow for creation of high-density individually addressable nanosensor arrays. PANI-SWNT network based sensors were tested for on-line monitoring of ammonia gas. The results show

Ting Zhang; Bong-Young Yoo

2006-01-01

129

Infrared spectroscopy of single-walled carbon nanotubes.  

PubMed

By using the spectral moments method, we calculate the infrared spectra of chiral and achiral single-walled carbon nanotubes (SWCNTs) of different diameters and lengths. We show that the number of the infrared modes, their frequencies, and intensities depend on the length and chirality of the nanotubes. Furthermore, the dependence of the infrared spectrum as a function of the size of the SWCNT bundle is analyzed. These predictions are useful to interpret the experimental infrared spectra of SWCNTs. PMID:16800564

Sbai, K; Rahmani, A; Chadli, H; Bantignies, J-L; Hermet, P; Sauvajol, J-L

2006-06-29

130

Exfoliated single-walled carbon nanotube-based hydrogen sensor  

Microsoft Academic Search

The paper presents a simple and inexpensive method for the preparation of an efficient hydrogen gas sensor based on exfoliated Pd-decorated single-walled carbon nanotubes (SWNTs). SWNTs were synthesized by catalytic chemical vapor deposition of methane using a fixed-bed catalytic reactor over hydrides of Mm0.2Tb0.8Co2 obtained through hydrogen decrepitation technique. Purified and chemically treated SWNTs were functionalized with Pd, resulting in

M. Krishna Kumar; A. Leela Mohana Reddy; S. Ramaprabhu

2008-01-01

131

Deactivation of singlet oxygen by single-wall carbon nanohorns  

NASA Astrophysics Data System (ADS)

The deactivation rate constant of singlet oxygen 1O 2 by single-wall carbon nanohorns (SWNHs) was determined. The estimated rate constant by SWNHs, 8 × 10 4 L g -1 s -1, was significantly larger than the physical quenching rate constant by ?-Tocopherol, 0.9 × 10 4 L g -1 s -1. The origin of this remarkable efficiency of SWNHs for 1O 2 deactivation is ascribed to the unique curvature of the graphitic tube in their horn shaped structure.

Yanagi, Kazuhiro; Okazaki, Toshiya; Miyata, Yasumitsu; Kataura, Hiromichi

2006-11-01

132

Individual single-wall carbon nanotubes as quantum wires  

Microsoft Academic Search

Carbon nanotubes have been regarded since their discovery1 as potential molecular quantum wires. In the case of multi-wall nanotubes, where many tubes are arranged in a coaxial fashion, the electrical properties of individual tubes have been shown to vary strongly from tube to tube2,3, and to be characterized by disorder and localization4. Single-wall nanotubes5,6 (SWNTs) have recently been obtained with

Sander J. Tans; Michel H. Devoret; Hongjie Dai; Andreas Thess; Richard E. Smalley; L. J. Geerligs; Cees Dekker

1997-01-01

133

Unidirectional growth of single-walled carbon nanotubes.  

PubMed

Unidirectional growth of single-walled carbon nanotubes (SWNTs) was achieved using the patterned Co-Mo salt catalyst on the r-plane sapphire substrate. This is in marked contrast with the SWNTs grown on an a-plane sapphire and ST-cut quartz, on which the SWNTs grew bidirectionally. This new growth mode is not dependent on the gas flow and attributed to the asymmetric surface atomic arrangement of the sapphire surface. PMID:19053802

Ishigami, Naoki; Ago, Hiroki; Nishi, Tetsushi; Ikeda, Ken-ichi; Tsuji, Masaharu; Ikuta, Tatsuya; Takahashi, Koji

2008-12-24

134

Modified Single-Wall Carbon Nanotubes for Reinforce Thermoplastic Polyimide  

NASA Technical Reports Server (NTRS)

A significant improvement in the mechanical properties of the thermoplastic polyimide film was obtained by the addition of noncovalently functionalized single-wall carbon nanotubes (SWNTs). Polyimide films were reinforced using pristine SWNTs and functionalized SWNTs (F-SWNTs). The tensile strengths of the polyimide films containing F-SWNTs were found to be approximately 1.4 times higher than those prepared from pristine SWNTs.

Lebron-COlon, Marisabel; Meador, Michael A.

2006-01-01

135

Ambipolar Electrical Transport in Semiconducting Single-Wall Carbon Nanotubes  

Microsoft Academic Search

Ambipolar electrical transport is reported in single-wall carbon nanotube (SWNT) field-effect transistors. In particular, the properties of SWNT junctions to TiC are discussed in detail. The carbide-nanotube junctions are abrupt and robust. In contrast to planar junctions, these contacts present low resistance for the injection of both p- and n-type carriers-the apparent barrier height of the junction is modified by

R. Martel; V. Derycke; C. Lavoie; J. Appenzeller; K. K. Chan; J. Tersoff; Ph. Avouris

2001-01-01

136

Electrical properties of single wall carbon nanotube reinforced polyimide composites  

Microsoft Academic Search

Electrical properties of single wall carbon nanotube (SWNT) reinforced polyimide composites were investigated as a function of SWNT concentration. AC and DC conductivities were measured, and the frequency behavior of the specific admittance was investigated. The experimental conductivity was found to obey a percolation-like power law with a relatively low percolation threshold. The current-voltage measurement results exhibited a non-ohmic behavior,

Z. Ounaies; K. E. Wise; E. J. Siochi; J. S. Harrison

2003-01-01

137

Excitons in single-walled carbon nanotubes: environmental effect  

Microsoft Academic Search

The properties of excitons in semiconducting single-walled carbon nanotubes\\u000a(SWCNTs), isolated in vacuum or a medium, and their contributions to the\\u000aoptical spectra of nanotubes are studied within the elementary potential model,\\u000ain which an exciton is represented as a bound state of two oppositely charged\\u000aquasi-particles confined to the nanotube surface. The emphasis is given on the\\u000ainfluence of

Oleksii A. Smyrnov; Odessa I. I. Mechnikov

2009-01-01

138

Investigation of ionomers as dispersants for single wall carbon nanotubes  

Microsoft Academic Search

A novel conjugated ionomer was prepared from a diamine and a bis(pyrylium salt). Single-walled carbon nanotubes (SWNT) were dispersed in solutions of the ionomer in N,N-dimethylacetamide resulting in homogenous suspensions or quasi-solutions. These suspensions were used to cast unoriented thin films. In addition, the ionomer\\/SWNT solutions were used to aid in the dispersal of SWNTs in a soluble, low color

D. M. Delozier; D. M. Tigelaar; K. A. Watson; J SMITHJR; D. J. Klein; P. T. Lillehei; J. W. Connell

2005-01-01

139

Large radius excitons in single-walled carbon nanotubes  

Microsoft Academic Search

The spectrum of large-radius excitons in an individual semiconducting single-walled carbon nanotube (SWCNT) is described within the framework of an elementary potential model, in which an exciton is modelled as a bound state of two oppositely charged quasi-particles confined on the tube surface. Due to the parity of the interaction potential the exciton states split into the odd and even

Vadym M. AdamyanOleksii; Oleksii A. Smyrnov

2007-01-01

140

Single-wall carbon nanotube\\/conjugated polymer photovoltaic devices  

Microsoft Academic Search

We report the optoelectronic properties occurring in single-walled carbon nanotubes (SWNTs)-conjugated polymer, poly(3-octylthiophene) composites. Composite films were drop or spin cast from a solution on indium-tin oxide (ITO) and quartz substrates and studied using absorption spectroscopy and electrical characterization methods. Diodes (Al\\/polymer-nanotube composite\\/ITO) with a low nanotube concentration (<1%) show photovoltaic behavior, with an open circuit voltage of 0.7-0.9 V.

E. Kymakis; G. A. J. Amaratunga

2002-01-01

141

Enhanced Subthreshold Slopes in Large Diameter Single Wall Carbon Nanotube Field Effect Transistors  

Microsoft Academic Search

The performance of single wall carbon nanotube field effect transistors (SWNT FETs) is greatly affected by the quality of its contacts. The presence of Schottky barriers imposes a strong scaling of the gate dielectric thickness. Here, we employ large diameter SWNTs in order to fabricate ohmically contacted FETs when a lower work function but higher adhesion strength metal such as

Simone Pisana; Can Zhang; Caterina Ducati; Stephan Hofmann; John Robertson

2008-01-01

142

Room temperature methane detection using palladium loaded single-walled carbon nanotube sensors  

Microsoft Academic Search

Single-walled carbon nanotubes (SWNTs) loaded with palladium (Pd) nanoparticles are used for detection of methane ranging from 6 to 100 ppm in air at room temperature. The Pd-SWNT nanosensors show advantages over conventional catalytic beads and metal oxide sensors for methane detection in terms of reduced size and power consumption by a factor of 100 and sensitivity by a factor

Yijiang Lu; Jing Li; Jie Han; H.-T. Ng; Christie Binder; Christina Partridge; M. Meyyappan

2004-01-01

143

Science of single-wall carbon nanotubes: Purification, characterization and chemistry  

Microsoft Academic Search

Characterization of raw nanotube materials produced by different methods is demonstrated. Depending on the production methods, tubes of different diameters can be produced. Purification of single wall carbon nanotubes produced by laser-oven and HiPco process is also discussed. Metal catalyzed oxidation at low temperature has been shown to selectively remove non-SWNT carbon and permit extraction of metals with concentrated HCl.

Ivana Wan-Ting Chiang

2001-01-01

144

Fluctuation theory of single-walled carbon nanotube formation.  

PubMed

In the framework of classical fluctuation theory an analytical formula is derived for the reversible work of formation of just detached carbon cap on the surface of catalyst nanoparticle (NP). This cap is considered as single walled carbon nanotube (SWCNT) formation center. The work of cap formation depends on the source carbon chemical potential ?C. Using the derived formula for this work an expression for the rate of SWCNT formation is determined. From this expression the SWCNT diameter distributions can be obtained. The obtained distributions have sharp maxima. It is found that the modal SWCNT diameter d(m) increases weakly with ?C being in the narrow window of 1.0 < d(m) < 1.8 nm when changing the source carbon chemical potential in a wide range. The determined diameter distributions proved to be in a good agreement with the typical values of the SWCNT diameters as experimentally measured in the chemical vapor deposition process. The increase of d(m) is accompanied by the increase of the distribution width ?d. The selectivity d(m)/?d is a function of ?C, the higher values of ?C the worse selectivity is observed. Although the value of the SWCNT formation rate I cannot be calculated precisely the relationship between I and the system parameters, such as the NP radius R(S), can be obtained. This relationship is derived for the solid-liquid-solid system. To determine the function I(R(S)) for nanotubes of a certain diameter d, formulas for catalyst?amorphous carbon mutual solubilities as functions of NP radius are derived in the framework of the rigorous Gibbs theory of interface. Using the derived formulas an expression giving the dependence I(R(S)) is obtained. The expression predicts an increase of I with the radius R(S). The estimations carried out for the metal/carbon interface surface tension of 1000 mN/m show that the SWCNT formation rate increases by a few orders of magnitude with the radius increase from 1 to 10 nm. PMID:24289367

Vosel, Sergey V; Onischuk, Andrei A; Purtov, Peter A; Nasibulin, Albert G

2013-11-28

145

Stiffness of single-walled carbon nanotubes under large strain  

PubMed

Large-scale molecular dynamic simulations of the axial deformations in single-walled carbon nanotubes have been performed using an O(N) tight-binding method. Our simulations indicate that under large strain, 0 K stress is remarkably sensitive to helicity, and that a zigzag nanotube and an armchair nanotube are the stiffest, respectively, under elongation and compression regimes. Furthermore, the elastic properties of a graphite sheet have been investigated using a simple harmonic potential and an analytic bond-order potential. The results suggest that the unique elastic properties of carbon nanotubes originate from those of a six-membered ring. PMID:11017607

Ozaki; Iwasa; Mitani

2000-02-21

146

Photophysics of polymer-wrapped single-walled carbon nanotubes  

Microsoft Academic Search

Single-walled carbon nanotubes (SWNTs) are successfully dispersed in two conjugated polymer poly(9,9-dioctylfluorenyl-2,7-diyl)\\u000a (PFO) and poly[2-methoxy-5- (2’-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEHPPV) solutions. Steady-state and time-resolved\\u000a photoluminescence spectroscopy in the near-infrared and visible spectral regions are used to study the interaction of the\\u000a dispersed carbon nanotube and the wrapped polymer in the \\u000a nano-hybrids. The SWNTs infrared emission is the signatures of the separation of

J. Gao; M. A. Loi

2010-01-01

147

Charging and defects in single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Single-Walled Carbon Nanotubes (SWCNTs) have been one of the most intensively studied materials. Because of their single-atomic-layer structure, SWCNTs are extremely sensitive to environmental interactions, in which charge transfer and defect formation are the most notable effects. Among a number of microscopic and spectroscopic methods, Raman spectroscopy is a widely used technique to characterize physics and chemistry of CNTs. By utilizing simultaneous Raman and electron transport measurements along with polymer electrolyte gating, this dissertation focuses on studying charging and defects in SWCNTs at single nanotube level and in single layer graphene, the building block of SWCNTs. By controllably charging metallic SWCNTs (m-CNTs), the intrinsic nature of the broad and asymmetric Fano lineshape in Raman G band of m-CNTs was first time evidenced. The observation that Fano component is most broadened and downshifted when Fermi level is close to the Dirac point (DP) reveals its origin as the consequence of coupling of phonon to vertical electronic transitions. Furthermore, we have systematically introduced covalent defects to m-CNTs to study how phonon softening and electrical characteristics are affected by disorders. In addition to decreasing electrical conductance with increasing on/off current ratio eventually leading to semiconducting behavior, adding covalent defects reduces the degree of softening and broadening of longitudinal optical (LO) phonon mode but enhances the softening of transverse optical (TO) mode of the G-band near the DP. Charging and defect effects in semiconducting SWCNTs and single layer graphene, a closely related material to SWCNTs, have also been discussed.

Nguyen, Khoi Thi

148

Aligned arrays of single walled carbon nanotubes for transparent electronics  

NASA Astrophysics Data System (ADS)

Single walled carbon nanotubes have garnered substantial interest in the electronic materials research community due to their unparalleled intrinsic electrical properties. In addition, their mechanical robustness and thin geometries make SWNTs ideal candidates for transparent electronics. Aligned arrays of SWNTs grown via chemical vapor deposition (CVD) on quartz enable device uniformity and wafer scale integration with existing commercial semiconductor processing methods. A crucial roadblock in incorporation of SWNTs in commercial electronics has been the co-existence of metallic and semiconducting SWNTs. Demanding device metrics in high performance and complex integrated electrical devices, sensors, and other applications dictate the necessity of pristine, purely semiconducting arrays of SWNTs. By exploiting a novel process in nanoscale flow of thin film organic coatings, we have demonstrated a method to purify as-grown aligned arrays to produce such as result. Comparison with single nanotube statistics, characterization using a novel thermal scanning probe microscopy technique, as well as corroboration with thermal modeling validated the result. Thin film field effect transistors exhibiting mobilities exceeding ~1000cm2/Vs and on/off ratios exceeding 10,000 were fabricated using the purified semiconducting SWNTs. This manuscript reviews some of these results, which represent the first successful demonstration of purification of aligned arrays of SWNTs, in a robust and scalable scheme that allows integration of aligned arrays into complex, high performance electrical devices. We separately also describe new results on the advanced development of soft lithography techniques with the ability to transfer print aligned arrays of SWNTs onto transparent substrates after synthesis and processing, thereby completing a direct pathway to achieve complex, high performance, and highly integrated transparent SWNTs electronics, sensors, or other devices.

Du, Frank; Rogers, John A.

2013-06-01

149

Magnetotransport in iodine-doped single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Magnetoresistance (MR) and magnetothermoelectric power (MTEP) of iodine-doped single-walled carbon nanotubes (I@SWNT) under magnetic fields up to 14 T are investigated from room temperature (300 K) down to 1.6 K. Our results on resistivity and thermoelectricpower (TEP) in a zero magnetic field are similar to those reported by Grigorian [Phys. Rev. Lett. 80, 5560 (1998)] The positive sign of the TEP values indicates that the majority of the carriers in the I@SWNT are holes. The broad enhancement of TEP at temperatures of 30-200 K shows quasilinear temperature dependence and is consistent with sharply varying density of states near the Fermi level with additional contribution from the spin-orbit scattering in the normal metallic characteristics of the I@SWNT. For T<7K , MR is negative and it decreases with H2 followed by the H1/2 dependence at around H=2T which is characteristic for the weak localization. In the range 7K90K , the thermal fluctuation dominates the effect of magnetic fields resulting the MTEP to be the same as the zero magnetic field TEP.

Ahn, Sejung; Kim, Yukyung; Nam, Youngwoo; Yoo, Honam; Park, Jihyun; Park, Yungwoo; Wang, Zhiyong; Shi, Zujin; Jin, Zhaoxia

2009-10-01

150

Dielectrophoretically Formed Single Wall Carbon Nanotube Network on Polyether Sulfone  

NASA Astrophysics Data System (ADS)

AC dielectrophoresis (DEP) is a useful method to fabricate single wall carbon nanotube (SWCNT) network structures on various kinds of substrates. We report on the fabrication of SWCNT networks with varying densities, on transparent and flexible polyether sulfone (PES) substrates by using DEP. From the scanning electron microscope observations and current-voltage measurements of the fabricated SWCNT network, we obtain the contour map of the density and conductance as functions of Vp-p and f. Our results show that the maximum density does not necessarily imply the maximum conductance. We find that there exists an optimum density for the maximum conductance.

Kim, T. G.; Hwang, J. S.; Kang, J.; Kim, S.; Roth, S.; Dettlaff-Weglikowska, U.; Hwang, S. W.

2011-12-01

151

Horizontally-aligned single-walled carbon nanotubes on sapphire.  

PubMed

Recently, we discovered the horizontally-aligned growth of single-walled carbon nanotubes (SWCNTs) on R- and A-plane sapphire substrates, which we call "atomic arrangement-programmed growth (AAP growth)". This is a unique method because the growth direction of SWCNTs is determined by the crystallographic direction of the sapphire surface. In this paper, we report on the characterization of the aligned SWCNTs by polarized Raman and electron transport measurements, and on the effect of the step/terrace structure formed on sapphire surface. These results may open up a possibility of creating the artificial SWCNT network, which can be applied to high-performance electronics. PMID:19198359

Ago, Hiroki; Ishigami, Naoki; Imamoto, Kenta; Suzuki, Tomoko; Ikeda, Ken-ichi; Tsuji, Masaharu; Ikuta, Tatsuya; Takahashi, Koji

2008-11-01

152

Single-walled carbon nanotubes as high pressure nanocontainer  

NASA Astrophysics Data System (ADS)

The single-walled carbon nanotubes (SWCNTs) under high internal pressure are studied by the constant-pressure molecular dynamics method. The results show that SWCNTs are suitable candidates for high pressure nanocontainer, and they can resist 30 GPa to 110 GPa internal pressure. We find that the ultimate internal pressure that nanotubes can sustain is mainly determined by the radius of the tube, and it is not sensitive to the tube chirality. The breaking of the nanotube induced by high internal pressure is mainly due to bond stretching rather than bond angle changing. An elastic model is used to explain the size-dependent ultimate internal pressure behavior for SWCNTs.

Chen, Na; Xu, Qing; Ye, Xiang

2014-03-01

153

Phase diffusion in single-walled carbon nanotube Josephson transistors  

Microsoft Academic Search

We investigate electronic transport in Josephson junctions formed by individual single-walled carbon nanotubes coupled to\\u000a superconducting electrodes. We observe enhanced zero-bias conductance (up to 10e\\u000a 2\\/h) and pronounced sub-harmonic gap structures in differential conductance, which arise from the multiple Andreev reflections\\u000a at superconductor\\/nanotube interfaces. The voltage-current characteristics of these junctions display abrupt switching from\\u000a the supercurrent branch to the resistive

Yong Zhang; Gang Liu; Chun Ning Lau

2008-01-01

154

Chemical doping of single-wall carbon nanotubes.  

PubMed

Single-wall carbon nanotubes can be doped, or intercalated, with electron donors or acceptors, similar to graphite and some conjugated polymers. The resulting materials show many of the same features: enhanced electrical conductivity, conduction electron paramagnetism, partial or complete reversibility, and cyclability. Reactions may be carried out in vapor or liquid phase, or electrochemically. Structural information is sketchy at best, due to the limited quality of currently available materials and solvent-related effects. Recent developments in coagulation-based fiber extrusion and partially aligned materials offer new opportunities for novel material modifications by chemical doping. PMID:12484796

Fischer, John E

2002-12-01

155

Functionalization of single-walled carbon nanotubes "on water".  

PubMed

Single-walled carbon nanotubes (SWNTs) are exfoliated and functionalized into small bundles and individuals by vigorous stirring "on water" in the presence of a substituted aniline and an oxidizing agent. This is an example of an "on water" reaction that leads to functionalized SWNTs, and it represents a "green", or environmentally friendly, process. A variety of reaction conditions were explored. The products were analyzed with Raman, UV-vis-NIR, and X-ray photoelectron spectroscopies, atomic force and transmission electron microscopies, and thermogravimetric analysis. PMID:17002385

Price, B Katherine; Tour, James M

2006-10-01

156

An integrated route for purification, cutting and dispersion of single-walled carbon nanotubes  

Microsoft Academic Search

We have developed purification and cutting process of single-walled carbon nanotubes (SWNTs) by integrating (1) an acid reflux treatment to eliminate metal particles, (2) an ultrasonication in the H2SO4\\/HNO3 and H2SO4\\/H2O2 to cut and polish the SWNTs, respectively, and (3) an ammonia gas treatment to remove residual carbon impurities and to repair the sidewalls of SWNTs. The final products with

Yan Wang; Lian Gao; Jing Sun; Yangqiao Liu; Shan Zheng; Hisashi Kajiura; Yongming Li; Kazuhiro Noda

2006-01-01

157

Hexahapto-lanthanide interconnects between the conjugated surfaces of single-walled carbon nanotubes.  

PubMed

We report the response of the electrical conductivity of semiconducting single-walled carbon nanotube (SWNT) thin films on exposure to metal vapors of the early lanthanides under high vacuum conditions. We attribute the strongly enhanced conductivities observed on deposition of samarium and europium to charge transfer from the metals to the SWNT backbone, thereby leading to the first examples of mixed covalent-ionic bis-hexahapto bonds [(?(6)-SWNT)M(?(6)-SWNT), where M = Sm, Eu]. PMID:24553843

Moser, Matthew L; Tian, Xiaojuan; Pekker, Aron; Sarkar, Santanu; Bekyarova, Elena; Itkis, Mikhail E; Haddon, Robert C

2014-04-23

158

Thermal conductivity of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We study numerically the thermal conductivity of single-walled carbon nanotubes for the cases of an isolated nanotube and a nanotube interacting with a substrate. We employ two different numerical methods: (i) direct modeling of the heat transfer by molecular-dynamics simulations and (ii) analysis of the equilibrium dynamics by means of the Green-Kubo formalism. For the numerical modeling of the effective interatomic interactions, we employ both the Brenner potentials and the intermolecular potentials used in the study of the dynamics of large macromolecules. We demonstrate that, quite independently of the methods employed and the potentials used, the character of the thermal conductivity depends crucially on the interaction between a nanotube and a substrate. While an isolated nanotube demonstrates anomalous thermal conductivity due to ballistic transport of long-wave acoustic phonons, the nanotube interacting with a flat substrate displays normal thermal conductivity due to both the appearance of a gap in the frequency spectrum of acoustic phonons and the absorption of long-wave acoustic phonons by the substrate. We study the dependence of the thermal conductivity on chirality, radius, and temperature of the single-walled carbon nanotubes in both the regimes and compare our findings with experimental data and earlier theoretical results for the thermal conductivity.

Savin, Alexander V.; Hu, Bambi; Kivshar, Yuri S.

2009-11-01

159

Oxidative Process for Cutting Single-Walled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

Cut single-walled carbon nanotubes (SWNTs) are needed for many applications. An efficient way to produce bulk amounts of cut SWNTs is a two step process consisting of sidewall damage and oxidative exploitation. In these experiments sidewall damage is introduced by ozonation in a perfluoropolyether (PFPE) while monitoring the degree of functionalization with in-situ Raman spectroscopy. Use of PFPE allows for a high degree of sidewall functionalization at room temperature, mainly in the form of epoxides. These damaged SWNTs are exposed to piranha (4:1 96%H2SO4:H2O2) for one hour and then quenched. The piranha exposed samples are then functionalized with alkyl groups and spin cast on mica for length analysis. The cut samples are found to have significantly shorter lengths while maintaining a relatively high carbon yield.

Shaver, Jonah

2005-03-01

160

Visible fluorescence from 5-Angstrom single-wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

We report the observation of visible fluorescence from the ultrathin single-wall carbon nanotubes (SWCNTs) with diameters of less than 5-Angstrom. Such ultrathin nanotubes were prepared by extracting the inner shells of double-wall carbon nanotubes using ultrasonication [1]. The extracted sample shows two visible photoluminescence (PL) peaks at 700 and 720 nm under light excitation at 410 and 540 nm, respectively. These peaks can be assigned, respectively, as the PL of (4,3) and (5,3) SWCNTs by comparison with the experimental Kataura plot proposed by Weisman et al. [2]. The present findings provide an important insight for the studies of the structural stability and electric structure of ultrathin SWCNTs. [1] Y. Miyata et al. ACS Nano. 4, 5807 (2010), [2] R. Weisman et. al., Nano Lett. 3, 1235 (2003).

Miyata, Yasumitsu; Nakamura, Toshiya; Fujihara, Miho; Lim, Hong En; Kitaura, Ryo; Shinohara, Hisanori

2012-02-01

161

Surface oxidation study of single wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

Functionalization of single wall carbon nanotubes (SWCNTs) is desirable to enhance their ability to be incorporated into polymers and enhance their bonding with the matrix. One approach to carbon nanotube functionalization is by oxidation via a strong oxidizing agent or refluxing in strong acids. However, this approach can damage the nanotubes, leading to the introduction of defects and/or shorter nanotubes. Such damage can adversely affect the mechanical, thermal, and electrical properties. A more benign approach to nanotube functionalization has been developed involving photo-oxidation. Chemical analysis by XPS revealed that the oxygen content of the photo-oxidized SWCNTs was 11.3 at.% compared to 6.7 at.% for SWCNTs oxidized by acid treatment. The photo-oxidized SWCNTs produced by this method can be used directly in various polymer matrices or can be further modified by additional chemical reactions.

Lebrón-Colón, M.; Meador, M. A.; Lukco, D.; Solá, F.; Santos-Pérez, J.; McCorkle, L. S.

2011-11-01

162

On the vibrations of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

In this paper, a detailed numerical study on the free and forced vibrations of single walled carbon nanotubes is presented. A simple and straightforward method developed such that the proximity of the mathematical model to the actual atomic structure of the nanotube is significantly retained, is used for this purpose. Both zigzag and armchair chiralities of the carbon nanotubes for clamped-free and clamped-clamped boundary conditions are analyzed and their natural frequencies and corresponding mode shapes are obtained. Results pertaining to axial, bending, and torsional modes of vibration are reported with discussions. These modes of vibration appear in the eigen-values and eigen-vectors without any distinction. The direct integration method by Newmark is used extensively along with the fast Fourier transform to identify different types of vibrational modes. In the case of zigzag nanotubes, the axial, bending, and torsional modes appear to be decoupled, whereas the armchair nanotubes show coupling between such modes.

Arghavan, S.; Singh, A. V.

2011-06-01

163

Control of electron transport related defects in in situ fabricated single wall carbon nanotube devices  

NASA Astrophysics Data System (ADS)

Metallic single wall carbon nanotube devices were characterized using low temperature transport measurements to study how the growth conditions affect defect formation in carbon nanotubes. Suspended carbon nanotube devices were grown in situ by a molecular beam growth method on a pair of catalyst islands located on opposing Au electrodes fabricated by electron beam lithography. The authors present experimental evidence that defect formation in carbon nanotubes, in addition to the well known growth temperature dependence, is also affected by the nature and the composition of the carbon growth gases.

Zhou, Zhixian; Jin, R.; Eres, Gyula; Subedi, Alaska; Mandrus, D.

2006-09-01

164

Stabilization and Carbonization of Gel Spun Polyacrylonitrile/Single Wall Carbon Nanotube Composite Fibers.  

National Technical Information Service (NTIS)

Gel spun polyacrylonitrile (PAN) and PAN/single wall carbon nanotube (SWNT) composite fibers have been stabilized in air and subsequently carbonized in argon at 1100 degrees C. Differential scanning calorimetry (DSC) and infrared spectroscopy suggests tha...

S. Kumar H. G. Chae M. Minus A. Rasheed

2007-01-01

165

Scanning gate microscopy of electronic inhomogeneities in single-walled carbon nanotube (SWCNT) devices  

NASA Astrophysics Data System (ADS)

The electronic properties of graphitic carbon devices are primarily determined by the contact metal and the carbon band structure. However, inhomogeneities such as substrate imperfections, surface defects, and mobile contaminants also contribute and can lead to transistor-like behaviors. We experimentally investigate this phenomena in the 1-D limit using metallic single-walled carbon nanotubes (SWCNTs) before and after the electrochemical creation of sidewall defects. While scanning gate microscopy readily identifies the defect sites, the energy-dependence of the technique allows quantitative analysis of the defects and discrimination of different defect types. This research is partly supported by the NSF (DMR 08-xxxx).

Hunt, Steven R.; Collins, Phillip G.

2010-03-01

166

Extracellular entrapment and degradation of single-walled carbon nanotubes.  

PubMed

Neutrophils extrude neutrophil extracellular traps (NETs) consisting of a network of chromatin decorated with antimicrobial proteins to enable non-phagocytic killing of microorganisms. Here, utilizing a model of ex vivo activated human neutrophils, we present evidence of entrapment and degradation of carboxylated single-walled carbon nanotubes (SWCNTs) in NETs. The degradation of SWCNTs was catalyzed by myeloperoxidase (MPO) present in purified NETs and the reaction was facilitated by the addition of H2O2 and NaBr. These results show that SWCNTs can undergo acellular, MPO-mediated biodegradation and imply that the immune system may deploy similar strategies to rid the body of offending microorganisms and engineered nanomaterials. PMID:24835568

Farrera, Consol; Bhattacharya, Kunal; Lazzaretto, Beatrice; Andón, Fernando T; Hultenby, Kjell; Kotchey, Gregg P; Star, Alexander; Fadeel, Bengt

2014-05-29

167

Hyperelastic axial buckling of single wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

This paper proposes a hyperelastic finite element-based lattice approach for the description of buckling behaviour in single wall carbon nanotubes (SWCNTs). A one-term incompressible Ogden-type hyperelastic model is adopted to describe the equivalent mechanical response of C-C bonds in SWCNTs under axial compression. The material constants of the model are chosen by matching the linearised response with the elastic constants adopted in the AMBER force field and by establishing equivalence between the Ogden strain energy and the variation of the interatomic strain energy obtained from molecular mechanics simulations. Numerical experiments are carried out and the results are compared to atomistic simulations, demonstrating the predictive capabilities of the present model in capturing initial buckling strain, deformation mechanisms and post-buckling behaviour under very large compressive deformations.

Saavedra Flores, E. I.; Adhikari, S.; Friswell, M. I.; Scarpa, F.

2011-11-01

168

Finely dispersed single-walled carbon nanotubes for polysaccharide hydrogels.  

PubMed

Here we demonstrate a polysaccharide hydrogel reinforced with finely dispersed single-walled carbon nanotubes (SWNTs) using biocompatible dispersants O-carboxymethylchitosan (OC) and chondroitin sulfate A (CS-A) as a structural support. Both of the dispersants can disperse SWNTs in aqueous solutions and hydrogel matrix as individual tubes or small bundles. Additionally, we have found that compressive modulus and strain of the hydrogels reinforced with SWNTs were enhanced as much as two times by the addition of a few weight percent of SWNTs. Moreover, the SWNT-incorporated hydrogels exhibited lower impedance and higher charge capacity than the alginate/dispersant hydrogel without SWNTs. The OC and the CS-A demonstrated much higher reinforcing enhancement than a commercially available dispersant, sodium dodecyl sulfate. Combined with the experimental data on the mechanical and electrical properties, the biocompatibility of OC and CS-A can provide the possibility of biomedical application of the SWNT-reinforced hydrogels. PMID:22909447

Yan, Liang Yu; Chen, Hailan; Li, Peng; Kim, Dong-Hwan; Chan-Park, Mary B

2012-09-26

169

Ultra-short suspended single-wall carbon nanotube transistors  

NASA Astrophysics Data System (ADS)

We describe a method to fabricate clean suspended single-wall carbon nanotube (SWCNT) transistors hosting a single quantum dot ranging in length from a few 10 s of nm down to ~3 nm. We first align narrow gold bow-tie junctions on top of individual SWCNTs and suspend the devices. We then use a feedback-controlled electromigration to break the gold junctions and expose nm-sized sections of SWCNTs. We measure electron transport in these devices at low temperature and show that they form clean and tunable single-electron transistors. These ultra-short suspended transistors offer the prospect of studying THz oscillators with strong electron-vibron coupling.

Island, J. O.; Tayari, V.; Yi?en, S.; McRae, A. C.; Champagne, A. R.

2011-12-01

170

Functionalization of single-walled carbon nanotubes with ribonucleic acids  

NASA Astrophysics Data System (ADS)

The optical properties of single-walled carbon nanotubes (SWCNTs) dispersed in aqueous solutions of ribonucleic acids (RNA) purified from Escherichia coli were studied using photoluminescence (PL), Raman, and absorption spectroscopy. SWCNT-RNA complexes, down to a single isolated nanotube level, were successfully synthesized. SWCNT signatures in Raman, PL, and absorption spectroscopy were observed from the SWCNT-RNA complexes. Observation of two distinct PL peaks, one at 1.248 eV and the other at 1.392 eV, confirmed the existence of isolated (6,5) and (6,4) SWCNTs, respectively. Atomic force microscope images and height profiles also showed evidence of isolated SWCNT-RNA complex.

Park, June; Kim, Sejin; Seong, Maeng-Je; Kim, Yu Jin; Go, Hayoung; Lee, Kangseok

2013-12-01

171

Single-wall carbon nanotubes based anticancer drug delivery system  

NASA Astrophysics Data System (ADS)

Conventional administration of chemotherapeutic agents is compromised by their lack of selectivity which is the cause of a lethal effect accomplishment on healthy tissues. Since therapeutic and diagnostic agents could functionalize the structure of carbon nanotubes (CNTs), the development of CNTs as drug containers would pave the way to their employment as nanovectors into the cells. Here a study on cisplatin (Cis-Diamminedichloroplatinum (CDDP) - a platinum-based chemotherapy drug) embedding to single-wall CNTs (SWCNTs) is shown.Being sure that the anticancer drug discharge occurred, in vitro analysis have been performed. The inhibition of prostate cancer cells (PC3 and DU145) viability from tubes encapsulating cisplatin proved the efficiency of the produced delivery system.

Tripisciano, C.; Kraemer, K.; Taylor, A.; Borowiak-Palen, E.

2009-08-01

172

Visible cathodoluminescence of 4 A? single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We report on cathodoluminescence (CL) of monosized and well-aligned 4 A? single-walled carbon nanotubes in a zeolite template (AlPO4-5 single crystal). The CL exhibits three emission bands centered at 1.87, 2.22, and 2.98 eV, which are assigned to three possible 4 A? tube structures (4,2), (5,0), and (3,3), respectively. The assignation is based on first-principles calculations, Raman scattering measurement, and CL behavior of various samples. The emission peak shift of the (5, 0) tube is explained by the transition mechanism being different from photoluminescence due to the excitation of electrons with high energy.

Mei, Y. F.; Siu, G. G.; Fu, Ricky K. Y.; Chu, Paul K.; Li, Z. M.; Zhai, J. P.; Liu, H. J.; Tang, Z. K.; Lai, C. W.; Ong, H. C.

2005-11-01

173

A shell theory for chiral single-wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

In this paper, we propose a characterization of the mechanical response of the linearly elastic shell we associate to a single-wall carbon nanotube of arbitrary chirality. In Bajaj et al. 2013, we gave such a characterization in the case of zigzag and armchair nanotubes; in particular, we showed that the orthotropic response we postulated for the associated shells is to become isotropic in the graphene-limit, that is, when the shell radius grows bigger and bigger. Here we give an explicit recipe to construct the generally anisotropic response of the shell associated to a nanotube of any chirality in terms of the response of the shell associated to a related zigzag or armchair nanotube. The expected coupling of mechanical effects that anisotropy entrains is demonstrated in the case of a torsion problem, where the axial extension accompanying twist is determined analytically and found in good agreement with the available experimental data.

Favata, Antonino; Podio-Guidugli, Paolo

2014-05-01

174

Single-wall carbon nanotube/conjugated polymer photovoltaic devices  

NASA Astrophysics Data System (ADS)

We report the optoelectronic properties occurring in single-walled carbon nanotubes (SWNTs)-conjugated polymer, poly(3-octylthiophene) composites. Composite films were drop or spin cast from a solution on indium-tin oxide (ITO) and quartz substrates and studied using absorption spectroscopy and electrical characterization methods. Diodes (Al/polymer-nanotube composite/ITO) with a low nanotube concentration (<1%) show photovoltaic behavior, with an open circuit voltage of 0.7-0.9 V. The short circuit current is increased by two orders of magnitude compared with the pristine polymer diodes and the fill factor also increases from 0.3 to 0.4 for the nanotube/polymer cells. It is proposed that the main reason for this increase is the photoinduced electron transfer at the polymer/nanotube interface. The results show that the conjugated polymer-SWNTs composite represents an alternative class of organic semiconducting material that is promising for organic photovoltaic cells with improved performance.

Kymakis, E.; Amaratunga, G. A. J.

2002-01-01

175

Single Wall Carbon Nanotube-polymer Solar Cells  

NASA Technical Reports Server (NTRS)

Investigation of single wall carbon nanotube (SWNT)-polymer solar cells has been conducted towards developing alternative lightweight, flexible devices for space power applications. Photovoltaic devices were constructed with regioregular poly(3-octylthiophene)-(P3OT) and purified, >95% w/w, laser-generated SWNTs. The P3OT composites were deposited on ITO-coated polyethylene terapthalate (PET) and I-V characterization was performed under simulated AM0 illumination. Fabricated devices for the 1.0% w/w SWNT-P3OT composites showed a photoresponse with an open-circuit voltage (V(sub oc)) of 0.98 V and a short-circuit current density (I(sub sc)) of 0.12 mA/sq cm. Optimization of carrier transport within these novel photovoltaic systems is proposed, specifically development of nanostructure-SWNT complexes to enhance exciton dissociation.

Bailey, Sheila G.; Castro, Stephanie L.; Landi, Brian J.; Gennett, Thomas; Raffaelle, Ryne P.

2005-01-01

176

Interaction of aromatic derivatives with single-walled carbon nanotubes.  

PubMed

Fluorescence of semiconducting single-walled carbon nanotubes (SWNTs) normally exhibits diameter-dependent oxidative quenching behaviour. This behaviour can be changed substantially to become an almost diameter-independent quenching phenomenon in the presence of electron-withdrawing nitroaromatic compounds, including o-nitrotoluene, 2,4-dinitrotoluene, and nitrobenzene. This change is observed for SWNTs suspended either in sodium dodecyl sulfate or in Nafion upon titration with hydrogen peroxide. Benzene, toluene, phenol, and nitromethane do not show such change. These findings suggest the possibility of forming an electron donor-acceptor complex between SWNTs and nitroaromatic compounds, resulting in leveling the redox potential of different SWNT species. The observation appears to provide a new method for modifying the electrochemical potentials of SWNTs through donor-acceptor complex formation. PMID:20878687

Hung, Wei-Chun; Elias, Gracy; Wai, Chien M

2010-11-15

177

Boron and nitrogen-doped single-walled carbon nanotube  

NASA Astrophysics Data System (ADS)

Boron nitride semiconducting zigzag single-walled carbon nanotube (SWCNT), BcbNcnC, as a potential candidate for making nanoelectronic devices is investigated by first-principle full potential density functional theory (DFT). In contrast to the previous DFT calculations, where just one boron and nitrogen doping configuration is considered, here for the average over all possible configurations density of states is calculated in terms of boron and nitrogen concentrations. For example in many body techniques (MBTs) [R. Moradian, Phys. Rev. B 89 (2004) 205425] it is found that semiconducting average gap, Eg, could be controlled by doping nitrogen and boron. But in contrast to MBTs where gap edge in the average density of states is sharp, the gap edge is smeared and impurity states appear in the SWCNT semiconducting gap.

Moradian, Rostam; Azadi, Sam

2006-10-01

178

Doping single-walled carbon nanotubes through molecular charge-transfer: a theoretical study  

Microsoft Academic Search

We study the effect of the molecular charge transfer on the electronic structure of metallic (5,5) and semiconducting (8,0) single-walled carbon nanotubes (SWNTs) induced by surface adsorption of various organic donor-acceptor molecules of different affinities using ab initio density functional theory. Our results, obtained from first-principles spin-polarized calculations show that the adsorption of molecules with different affinities reflects the difference

Arun K. Manna; Swapan K. Pati

2010-01-01

179

Integration of Single-Walled Carbon Nanotubes on to CMOS Circuitry with Parylene-C Encapsulation  

Microsoft Academic Search

This paper presents heterogeneous integration of single-walled carbon nanotubes (SWNTs) with CMOS integrated circuits using die-level post processing. The chip was fabricated using the AMI 0.5 mum CMOS Technology. An electroless zincation process was performed over the Aluminum assembly electrodes (Metal 3 of CMOS technology) to clean and to coat the electrodes with a thin Zinc layer. Low temperature dielectrophoretic

Chia-Ling Chen; Vinay Agarwal; Sameer Sonkusale; Mehmet R. Dokmeci

2008-01-01

180

Electrical measurements of individual semiconducting single-walled carbon nanotubes of various diameters  

Microsoft Academic Search

Individual semiconducting single-walled carbon nanotubes (SWNTs) of various diameters are studied by electrical measurements. Transport through a semiconducting SWNT involves thermal activation at high temperatures, and tunneling through a reverse biased metal-tube junction at low temperatures. Under high bias voltages, current-voltage (I-V) characteristics of semiconducting SWNTs exhibit pronounced asymmetry with respect to the bias polarity, as a result of local

Chongwu Zhou; Jing Kong; Hongjie Dai

2000-01-01

181

Raman and SERS Studies of Single-walled Carbon Nanotubes and Nanotubes\\/Conjugated Polymers Composites  

Microsoft Academic Search

In this paper, we recall the main characteristics of Raman spectra of single-walled carbon nanotubes. We illustrate our studies by results obtained on HiPCO samples on one hand, and ``arc electric'' samples on the other hand by using two different excitation wavelengths. We focus on the peculiarity of observing separately semi-conducting and metallic tubes. We emphasize also the role played

S. Lefrant; J. P. Buisson; J. Y. Mevellec; M. Baibarac; I. Baltog

2007-01-01

182

Extracellular entrapment and degradation of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Neutrophils extrude neutrophil extracellular traps (NETs) consisting of a network of chromatin decorated with antimicrobial proteins to enable non-phagocytic killing of microorganisms. Here, utilizing a model of ex vivo activated human neutrophils, we present evidence of entrapment and degradation of carboxylated single-walled carbon nanotubes (SWCNTs) in NETs. The degradation of SWCNTs was catalyzed by myeloperoxidase (MPO) present in purified NETs and the reaction was facilitated by the addition of H2O2 and NaBr. These results show that SWCNTs can undergo acellular, MPO-mediated biodegradation and imply that the immune system may deploy similar strategies to rid the body of offending microorganisms and engineered nanomaterials.Neutrophils extrude neutrophil extracellular traps (NETs) consisting of a network of chromatin decorated with antimicrobial proteins to enable non-phagocytic killing of microorganisms. Here, utilizing a model of ex vivo activated human neutrophils, we present evidence of entrapment and degradation of carboxylated single-walled carbon nanotubes (SWCNTs) in NETs. The degradation of SWCNTs was catalyzed by myeloperoxidase (MPO) present in purified NETs and the reaction was facilitated by the addition of H2O2 and NaBr. These results show that SWCNTs can undergo acellular, MPO-mediated biodegradation and imply that the immune system may deploy similar strategies to rid the body of offending microorganisms and engineered nanomaterials. Electronic supplementary information (ESI) available: Suppl. Fig. 1 - length distribution of SWCNTs; suppl. Fig. 2 - characterization of pristine vs. oxidized SWCNTs; suppl. Fig. 3 - endotoxin evaluation; suppl. Fig. 4 - NET characterization; suppl. Fig. 5 - UV-Vis/NIR analysis of biodegradation of oxidized SWCNTs; suppl. Fig. 6 - cytotoxicity of partially degraded SWCNTs. See DOI: 10.1039/c3nr06047k

Farrera, Consol; Bhattacharya, Kunal; Lazzaretto, Beatrice; Andón, Fernando T.; Hultenby, Kjell; Kotchey, Gregg P.; Star, Alexander; Fadeel, Bengt

2014-05-01

183

Amorphous carbon contamination monitoring and process optimization for single-walled carbon nanotube integration  

Microsoft Academic Search

We detail the monitoring of amorphous carbon deposition during thermal chemical vapour deposition of carbon nanotubes and propose a contamination-less process to integrate high-quality single-walled carbon nanotubes into micro-electromechanical systems. The amorphous content is evaluated by confocal micro-Raman spectroscopy and by scanning\\/transmission electron microscopy. We show how properly chosen process parameters can lead to successful integration of single-walled nanotubes, enabling

A. Jungen; C. Stampfer; L. Durrer; T. Helbling; C. Hierold

2007-01-01

184

Single-Wall Carbon Nanotube Anodes for Lithium Cells  

NASA Technical Reports Server (NTRS)

In recent experiments, highly purified batches of single-wall carbon nanotubes (SWCNTs) have shown promise as superior alternatives to the graphitic carbon-black anode materials heretofore used in rechargeable thin-film lithium power cells. The basic idea underlying the experiments is that relative to a given mass of graphitic carbon-black anode material, an equal mass of SWCNTs can be expected to have greater lithium-storage and charge/discharge capacities. The reason for this expectation is that whereas the microstructure and nanostructure of a graphitic carbon black is such as to make most of the interior of the material inaccessible for intercalation of lithium, a batch of SWCNTs can be made to have a much more open microstructure and nanostructure, such that most of the interior of the material is accessible for intercalation of lithium. Moreover, the greater accessibility of SWCNT structures can be expected to translate to greater mobilities for ion-exchange processes and, hence, an ability to sustain greater charge and discharge current densities.

Hepp, Aloysius F.; Raffaelle, Ryne; Gennett, Tom; Kumta, Prashant; Maranchi, Jeff; Heben, Mike

2006-01-01

185

Structure-Processing-Property Interrelationships of Vapor Grown Carbon Nanofiber, Single-Walled Carbon Nanotube and Functionalized Single-Walled Carbon Nanotube - Polypropylene Nanocomposites  

Microsoft Academic Search

This dissertation describes the first use of a design of experiments approach to investigate the interrelationships between structure, processing, and properties of melt extruded polypropylene (PP) carbon nanomaterial composites. The effect of nanomaterial structure was evaluated by exploring the incorporation of vapor grown carbon nanofibers (VGCFs), or pristine or functionalized single-walled carbon nanotubes (SWNTs or C12SWNTs) in polypropylene, while the

Vinod Karumathil Radhakrishnan

2010-01-01

186

Cutting of single-walled carbon nanotubes by ozonolysis.  

PubMed

Cutting of single-walled carbon nanotubes (SWNT) has been achieved by extensive ozonolysis at room temperature. Perfluoropolyether (PFPE) was selected as a medium for cutting SWNT due to its high solubility for ozone (O3). A mixture of 9 wt % of O3 in O2 was bubbled through a homogeneous suspension of pristine SWNT in PFPE, at room temperature. The intense disorder mode in the Raman spectra of ozonated SWNT indicates that extensive reaction with the sidewalls of SWNT occurs during ozonolysis. Atomic force microscopy (AFM) images of SWNT, before and after ozonolysis, provided a measure of the extent of the cutting effects. Monitoring of the evolved gases for both pristine and purified SWNT indicates CO2 was produced during the ozonolysis process with a dependence on both system pressure and temperature. During heating, FTIR analysis of gases released indicated that carbon oxygen groups on the sidewalls of SWNT are released as CO2. SWNT was found to be extensively cut after an ozone treatment with a yield of approximately 80% of the original carbon. PMID:16800455

Chen, Zheyi; Ziegler, Kirk J; Shaver, Jonah; Hauge, Robert H; Smalley, Richard E

2006-06-22

187

Single-wall carbon nanotube chemical attachment at platinum electrodes  

NASA Astrophysics Data System (ADS)

Self-assembled monolayer (SAM) techniques were used to adsorb 4-aminothiophenol (4-ATP) on platinum electrodes in order to obtain an amino-terminated SAM as the base for the chemical attachment of single-wall carbon nanotubes (SWCNTs). A physico-chemical, morphological and electrochemical characterizations of SWCNTs attached onto the modified Pt electrodes was done by using reflection-absorption infrared spectroscopy (RAIR), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and cyclic voltammetry (CV) techniques. The SWNTs/4-ATP/Pt surface had regions of small, medium, and large thickness of carbon nanotubes with heights of 100-200 nm, 700 nm to 1.5 ?m, and 1.0-3.0 ?m, respectively. Cyclic voltammetries (CVs) in sulfuric acid demonstrated that attachment of SWNTs on 4-ATP/Pt is markedly stable, even after 30 potential cycles. CV in ruthenium hexamine was similar to bare Pt electrodes, suggesting that SWNTs assembly is similar to a closely packed microelectrode array.

Rosario-Castro, Belinda I.; Contés-de-Jesús, Enid J.; Lebrón-Colón, Marisabel; Meador, Michael A.; Scibioh, M. Aulice; Cabrera, Carlos R.

2010-11-01

188

Photophysics of polymer-wrapped single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanotubes (SWNTs) are successfully dispersed in two conjugated polymer poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) and poly[2-methoxy-5- (2’-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEHPPV) solutions. Steady-state and time-resolved photoluminescence spectroscopy in the near-infrared and visible spectral regions are used to study the interaction of the dispersed carbon nanotube and the wrapped polymer in the nano-hybrids. The SWNTs infrared emission is the signatures of the separation of single semiconducting tubes, the lifetime of the photoluminescence of these tubes is bi-exponential with the first component varying from 6 ps (in MEHPPV wrapped SWNTs) to 14 ps (in PFO wrapped SWNTs), while the second component of the decay for all samples is in the range of 30-40 ps, revealing the intrinsic lifetime of the SWNTs. The study of the photoluminescence of the nano-hybrids in the visible spectral range shows, in the case of the PFO, a relatively strong quenching, the photoluminescence lifetime for the hybrid is more than 100 ps shorter than the one of the pristine polyfluorene solution. For the MEHPPV-SWNT hybrid an opposite behavior is revealed with the photoluminescence lifetime surprisingly longer than the polymer solution. The possible mechanism for the interaction of the two conjugated polymers and the SWNTs is discussed in terms of their electronic band structure.

Gao, J.; Loi, M. A.

2010-05-01

189

Single-Walled Carbon Nanotube Transporter for Gene Delivery  

NASA Astrophysics Data System (ADS)

Recent studies have shown great promises in integrating nanomaterials in biomedicine. To explore the feasibility of using single-walled carbon nanotubes (SWNTs) as transporters for gene delivery, we have investigated the binding of SWNTs and RNA polymer poly(rU), and the diffusion and the translocation of the SWNT-poly(rU) complexes. Through single-molecule fluorescence imaging, we have found that the pi- stacking dominates the hydrophobic interactions between the carbon rings on tubes and the nitrogenous bases of RNA. Our diffusion study has further demonstrated the feasibility of tracking the motion of water soluble SWNT-poly(rU) complexes. The uptake of SWNT-poly(rU) by breast cancer cells MCF7 was observed using confocal scanning fluorescence microscopy. It was evident that the complexes could penetrate through cell membrane into cytoplasm and cell nucleus. Our cell culture, MTS assay, and radioisotope labeling showed the negligible cytotoxicity of surface modified SWNTs with RNA polymer and amino acids in cell growth medium. These studies have paved the way for gene transfection using SWNTs as transporters.

Ke, Pu-Chun

2005-03-01

190

Hypergolic fuel detection using individual single walled carbon nanotube networks  

SciTech Connect

Accurate and reliable detection of hypergolic fuels such as hydrazine (N{sub 2}H{sub 4}) and its derivatives is vital to missile defense, aviation, homeland security, and the chemical industry. More importantly these sensors need to be capable of operation at low temperatures (below room temperature) as most of the widely used chemical sensors operate at high temperatures (above 300 deg. C). In this research a simple and highly sensitive single walled carbon nanotube (SWNT) network sensor was developed for real time monitoring of hydrazine leaks to concentrations at parts per million levels. Upon exposure to hydrazine vapor, the resistance of the air exposed nanotubes (p-type) is observed to increase rapidly while that of the vacuum-degassed nanotubes (n-type) is observed to decrease. It was found that the resistance of the sample can be recovered through vacuum pumping and exposure to ultraviolet light. The experimental results support the electrochemical charge transfer mechanism between the oxygen redox couple of the ambient and the Fermi level of the SWNT. Theoretical results of the hydrazine-SWNT interaction are compared with the experimental observations. It was found that a monolayer of water molecules on the SWNT is necessary to induce strong interactions between hydrazine and the SWNT by way of introducing new occupied states near the bottom of the conduction band of the SWNT.

Desai, S. C.; Willitsford, A. H. [Department of Electrical and Computer Engineering, University of Louisville, Louisville, Kentucky 40292 (United States); Sumanasekera, G. U. [Department of Electrical and Computer Engineering, University of Louisville, Louisville, Kentucky 40292 (United States); Department of Physics and Astronomy, University of Louisville, Louisville, Kentucky 40292 (United States); Yu, M.; Jayanthi, C. S.; Wu, S. Y. [Department of Physics and Astronomy, University of Louisville, Louisville, Kentucky 40292 (United States); Tian, W. Q. [State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023 (China)

2010-06-15

191

Reinforced Thermoplastic Polyimide with Dispersed Functionalized Single Wall Carbon Nanotubes  

NASA Technical Reports Server (NTRS)

Molecular pi-complexes were formed from pristine HiPCO single-wall carbon nanotubes (SWCNTs) and 1-pyrene- N-(4- N'-(5-norbornene-2,3-dicarboxyimido)phenyl butanamide, 1. Polyimide films were prepared with these complexes as well as uncomplexed SWCNTs and the effects of nanoadditive addition on mechanical, thermal, and electrical properties of these films were evaluated. Although these properties were enhanced by both nanoadditives, larger increases in tensile strength and thermal and electrical conductivities were obtained when the SWCNT/1 complexes were used. At a loading level of 5.5 wt %, the Tg of the polyimide increased from 169 to 197 C and the storage modulus increased 20-fold (from 142 to 3045 MPa). The addition of 3.5 wt % SWCNT/1 complexes increased the tensile strength of the polyimide from 61.4 to 129 MPa; higher loading levels led to embrittlement and lower tensile strengths. The electrical conductivities (DC surface) of the polyimides increased to 1 x 10(exp -4) Scm(exp -1) (SWCNT/1 complexes loading level of 9 wt %). Details of the preparation of these complexes and their effects on polyimide film properties are discussed.

Lebron-Colon, Marisabel; Meador, Michael A.; Gaier, James R.; Sola, Francisco; Scheiman, Daniel A.; McCorkle, Linda S.

2010-01-01

192

Biodegradation of Single-Walled Carbon Nanotubes by Eosinophil Peroxidase  

PubMed Central

Eosinophil peroxidase (EPO) is one of the major oxidant-producing enzymes during inflammatory states in the human lung. The degradation of single-walled carbon nanotubes (SWCNTs) upon incubation with human EPO and H2O2 is reported. Biodegradation of SWCNTs is higher in the presence of NaBr, but neither EPO alone nor H2O2 alone caused the degradation of nanotubes. Molecular modeling reveals two binding sites for SWCNTs on EPO, one located at the proximal side (same side as the catalytic site) and the other on the distal side of EPO. The oxidized groups on SWCNTs in both cases are stabilized by electrostatic interactions with positively charged residues. Biodegradation of SWCNTs can also be executed in an ex vivo culture system using primary murine eosinophils stimulated to undergo degranulation. Biodegradation is proven by a range of methods including transmission electron microscopy, UV-visible-NIR spectroscopy, Raman spectroscopy, and confocal Raman imaging. Thus, human EPO (in vitro) and ex vivo activated eosinophils mediate biodegradation of SWCNTs: an observation that is relevant to pulmonary responses to these materials.

Andon, Fernando T.; Kapralov, Alexandr A.; Yanamala, Naveena; Feng, Weihong; Baygan, Arjang; Chambers, Benedict J.; Hultenby, Kjell; Ye, Fei; Toprak, Muhammet S.; Brandner, Birgit D.; Fornara, Andrea; Klein-Seetharaman, Judith; Kotchey, Gregg P.; Star, Alexander; Shvedova, Anna A.

2014-01-01

193

Single walled carbon nanotube composites for bone tissue engineering.  

PubMed

The purpose of this study was to develop single walled carbon nanotubes (SWCNT) and poly lactic-co-glycolic acid (PLAGA) composites for orthopedic applications and to evaluate the interaction of human stem cells (hBMSCs) and osteoblasts (MC3T3-E1 cells) via cell growth, proliferation, gene expression, extracellular matrix production and mineralization. PLAGA and SWCNT/PLAGA composites were fabricated with various amounts of SWCNT (5, 10, 20, 40, and 100 mg), characterized and degradation studies were performed. Cells were seeded and cell adhesion/morphology, growth/survival, proliferation and gene expression analysis were performed to evaluate biocompatibility. Imaging studies demonstrated uniform incorporation of SWCNT into the PLAGA matrix and addition of SWCNT did not affect the degradation rate. Imaging studies revealed that MC3T3-E1 and hBMSCs cells exhibited normal, non-stressed morphology on the composites and all were biocompatible. Composites with 10 mg SWCNT resulted in highest rate of cell proliferation (p < 0.05) among all composites. Gene expression of alkaline phosphatase, collagen I, osteocalcin, osteopontin, Runx-2, and Bone Sialoprotein was observed on all composites. In conclusion, SWCNT/PLAGA composites imparted beneficial cellular growth capabilities and gene expression, and mineralization abilities were well established. These results demonstrate the potential of SWCNT/PLAGA composites for musculoskeletal regeneration and bone tissue engineering (BTE) and are promising for orthopedic applications. PMID:23629922

Gupta, Ashim; Woods, Mia D; Illingworth, Kenneth David; Niemeier, Ryan; Schafer, Isaac; Cady, Craig; Filip, Peter; El-Amin, Saadiq F

2013-09-01

194

Hypergolic fuel detection using individual single walled carbon nanotube networks  

NASA Astrophysics Data System (ADS)

Accurate and reliable detection of hypergolic fuels such as hydrazine (N2H4) and its derivatives is vital to missile defense, aviation, homeland security, and the chemical industry. More importantly these sensors need to be capable of operation at low temperatures (below room temperature) as most of the widely used chemical sensors operate at high temperatures (above 300 °C). In this research a simple and highly sensitive single walled carbon nanotube (SWNT) network sensor was developed for real time monitoring of hydrazine leaks to concentrations at parts per million levels. Upon exposure to hydrazine vapor, the resistance of the air exposed nanotubes (p-type) is observed to increase rapidly while that of the vacuum-degassed nanotubes (n-type) is observed to decrease. It was found that the resistance of the sample can be recovered through vacuum pumping and exposure to ultraviolet light. The experimental results support the electrochemical charge transfer mechanism between the oxygen redox couple of the ambient and the Fermi level of the SWNT. Theoretical results of the hydrazine-SWNT interaction are compared with the experimental observations. It was found that a monolayer of water molecules on the SWNT is necessary to induce strong interactions between hydrazine and the SWNT by way of introducing new occupied states near the bottom of the conduction band of the SWNT.

Desai, S. C.; Willitsford, A. H.; Sumanasekera, G. U.; Yu, M.; Tian, W. Q.; Jayanthi, C. S.; Wu, S. Y.

2010-06-01

195

"Smart Skin" optical strain sensor using single wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

Strain measurements are essential in structural health monitoring. Traditional strain gages require physical contact between the sensor and read-out device, perturb the surface being monitored, and allow measurement only at the specific location and orientation axis of the sensor. We demonstrate a novel non-contact, multi- point, multi-directional strain sensing approach that overcomes these limitations. In our method, the surface is coated with a thin film of "smart skin" containing individualized single-walled carbon nanotubes in a polymeric host. After curing, substrate strains are transmitted through the polymer film to embedded nanotubes. This induces axial strains in the nanotubes, systematically shifting the wavelengths of their characteristic near-infrared fluorescence peaks. To measure strain, a visible laser excites nanotubes at points of interest on the surface, and the near-infrared emission is collected and spectrally analyzed. Observed spectral shifts reveal quantitative strain values. Laboratory tests show sensitivity down to ~400µm, limited by mechanical properties of the polymeric host film. We also vary excitation beam polarization to find the axis of substrate strain. Our method provides spatial resolution down to its gage length of ~100µm. Because the entire substrate is coated with nanoscale strain sensors, measurements can be made at arbitrary locations to construct a full strain map. We will describe recent smart skin refinements involving selection of polymer host, nanotube surfactant, nanotube dispersion method, and preparation protocol. Finally, we characterize the orientational distribution of nanotubes using a probabilistic model.

Sun, Peng; Kim, Ji-Hoon; Bachilo, Sergei M.; Weisman, R. Bruce; Nagarajaiah, Satish

2014-04-01

196

Gas Separation by Kinked Single-Walled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

A kink model for gas separation is presented. Transport of pure nitrogen, oxygen and their mixture in single walled carbon nanotubes (SWCNTs) with a kink formed by bending is studied using molecular dynamics simulations. The results show that a kinked SWCNT results in transport resistance to nitrogen while allowing oxygen to pass even though the two gases have very similar molecular sizes. The permeability decreases while the selectivity increases with increasing the bending angle of SWCNTs. The tradeoff between permeability and selectivity is evaluated by linear weighting method to attain an optimum bending angle for gas separation. It is also found that the kink model can be used to improve the permeability by changing the diameter of the SWCNTs while keeping a high selectivity in the gas separation process. Both the permeability and purity of oxygen increase with increasing the gas pressure. Interestingly, it is very convenient to obtain the required purity and permeability of the oxygen by adjusting the bending angle of SWCNTs.

Zhang, Z. Q.; Zhang, H. W.

2010-05-01

197

Observation and Modeling of Single Wall Carbon Nanotube Bend Junctions  

NASA Technical Reports Server (NTRS)

Single wall carbon nanotube (SWNT) bends, with diameters from approx. 1.0 to 2.5 nm and bend angles from 18 deg. to 34 deg., are observed in catalytic decomposition of hydrocarbons at 600 - 1200 C. An algorithm using molecular dynamics simulation (MD) techniques is developed to model these structures that are considered to be SWNT junctions formed by topological defects (i.e. pentagon-heptagon pairs). The algorithm is used to predict the tube helicities and defect configurations for bend junctions using the observed tube diameters and bend angles. The number and arrangement of the defects at the junction interfaces are found to depend on the tube helicities and bend angle. The structural and energetic calculations using the Brenner potential show a number of stable junction configurations for each bend angle with the 34 deg. bends being more stable than the others. Tight binding calculations for local density of state (LDOS) and transmission coefficients are carried out to investigate electrical properties of the bend junctions.

Han, Jie; Anantram, M. P.; Jaffe, R. L.; Kong, J.; Dai, H.; Saini, Subhash (Technical Monitor)

1998-01-01

198

Bulk Mechanical Properties of Single Walled Carbon Nanotube Electrodes  

NASA Astrophysics Data System (ADS)

The unique properties of single walled carbon nanotubes (SWNTs) make them especially well suited for use as electrodes in power devices such as lithium ion batteries, hydrogen fuel cells, solar cells, and supercapacitors. The performances of such devices are expected to be influenced, at least in part, by the mechanical properties of the SWNTs used in composites or in stand alone ``papers.'' Therefore, the elastic moduli and ultimate tensile strengths of SWNT papers were measured as functions of temperature, SWNT purity, SWNT length, and SWNT bundling. The SWNTs used to produce the papers were synthesized in an alexandrite laser vaporization reactor at 1100^oC and purified using conventional acid-reflux conditions. Characterization of the SWNTs was performed using SEM, BET, TGA, and optical and Raman spectroscopy. The purified material was filtered and dried to yield papers of bundled SWNTs which were analyzed using dynamic mechanical analysis (DMA). It was observed that the mechanical properties of acid-refluxed SWNT papers were significantly improved by controlled thermal oxidation and strain-hardening. Elastic moduli of SWNT papers were measured between 3 and 6 GPa. Ultimate (breaking) tensile stresses were measured between 45 and 90 MPa at 1-3% strain. These results and their implications in regard to potential applications in power devices will be discussed.

Giarra, Matthew; Landi, Brian; Cress, Cory; Raffaelle, Ryne

2007-03-01

199

Electrochemical processing of discrete single-walled carbon nanotube anions.  

PubMed

The dissolution of single-walled carbon nanotubes (SWCNTs) remains a fundamental challenge, reliant on aggressive chemistry or ultrasonication and lengthy ultracentrifugation. In contrast, simple nonaqueous electrochemical reduction leads to spontaneous dissolution of individualized SWCNTs from raw, unprocessed powders. The intrinsic electrochemical stability and conductivity of these nanomaterials allow their electrochemical dissolution from a pure SWCNT cathode to form solutions of individually separate and distinct (i.e., discrete) nanotube anions with varying charge density. The integrity of the SWCNT sp² framework during the charge/discharge process is demonstrated by optical spectroscopy data. Other than a reversible change in redox/solvation state, there is no obvious chemical functionalization of the structure, suggesting an analogy to conventional atomic electrochemical dissolution. The heterogeneity of as-synthesized SWCNT samples leads to the sequential dissolution of distinct fractions over time, with fine control over the electrochemical potential. Initial preferential dissolution of defective nanotubes and carbonaceous debris provides a simple, nondestructive means to purify raw materials without recourse to the usual, damaging, competitive oxidation reactions. Neutral SWCNTs can be recovered either by electroplating at an anode or by reaction with a suitable electrophile. PMID:23336405

Hodge, Stephen A; Fogden, Siân; Howard, Christopher A; Skipper, Neal T; Shaffer, Milo S P

2013-02-26

200

Joule heating and thermoelectric properties in short single-walled carbon nanotubes: electron-phonon interaction effect  

Microsoft Academic Search

The electron-phonon interaction (EPI) effect in single-walled carbon nanotube is investigated by the nonequilibrium Green's function approach within the Born approximation. Special attention is paid to the EPI induced Joule heating phenomenon and the thermoelectric properties in both metallic armchair (10, 10) tube and semiconductor zigzag (10, 0) tube. For Joule heat in the metallic (10, 10) tube, the theoretical

Jin-Wu Jiang; Jian-Sheng Wang

2011-01-01

201

An integrated route for purification, cutting and dispersion of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We have developed purification and cutting process of single-walled carbon nanotubes (SWNTs) by integrating (1) an acid reflux treatment to eliminate metal particles, (2) an ultrasonication in the H 2SO 4/HNO 3 and H 2SO 4/H 2O 2 to cut and polish the SWNTs, respectively, and (3) an ammonia gas treatment to remove residual carbon impurities and to repair the sidewalls of SWNTs. The final products with a higher purity than 98% are well dispersed in aqueous solution using Pluronic P123 dispersant, which has been rarely used for the SWNTs dispersion. The dispersed SNWTs solution can exist stably for over two months.

Wang, Yan; Gao, Lian; Sun, Jing; Liu, Yangqiao; Zheng, Shan; Kajiura, Hisashi; Li, Yongming; Noda, Kazuhiro

2006-12-01

202

Donor doping of single-walled carbon nanotubes by filling of channels with silver  

SciTech Connect

The channels of single-walled carbon nanotubes (SWNTs) are filled with metallic silver. The synthesized nanocomposites are studied by Raman spectroscopy and optical absorption spectroscopy, and these data indicate a substantial modification of the electronic structure of the nanotubes upon their filling. Moreover, X-ray photoelectron spectroscopy shows that the incorporation of the metal leads to a change in the work function of SWNTs due to the Fermi level upshift and to the transfer of an electron density from inserted nanoparticles to the nanotube walls. Thus, the filling of the channels with silver results in donor doping of the nanotubes.

Kharlamova, M. V., E-mail: mv.kharlamova@gmail.com [Moscow State University (Russian Federation); Niu, J. J. [Drexel University, Department of Materials Science and Engineering (United States)

2012-09-15

203

Theoretical study of the interactions of carbon monoxide with Rh-decorated (8,0) single-walled carbon nanotubes  

Microsoft Academic Search

Recent laboratory studies have shown that metal nanoparticles-decorated single-walled carbon nanotubes (SWCNTs) can be used to detect carbon monoxide (CO) gases at room temperature, which is known not able to be adsorbed on pure SWCNTs. In this paper, we investigated the Rh-decorated (8,0) SWCNT and its interaction with CO gases by using density functional theory (DFT) methods. Upon Rh atom

Jing-Xiang Zhao; Yi-Hong Ding

2008-01-01

204

Production and characterization of polymer nanocomposite with aligned single wall carbon nanotubes  

Microsoft Academic Search

We reported a simple method to fabricate polymer nanocomposites with single-walled carbon nanotubes (SWNTs) having exceptional alignment and improved mechanical properties. The composite films were fabricated by casting a suspension of single walled carbon nanotubes in a solution of thermoplastic polyurethane and tetrahydrofuran. The orientation as well as dispersion of nanotubes was determined by scanning electron microscopy, transmission electron microscopy

Wei Chen; Xiaoming Tao

2006-01-01

205

Noncovalent functionalization of single-walled carbon nanotubes with porphyrins  

NASA Astrophysics Data System (ADS)

The covalent and noncovalent interactions of porphyrins and related tetraazamacrocyclic compounds with single-walled carbon nanotubes (SWNTs) is a subject of increasing research effort, directed toward the design of novel hybrid nanomaterials combining unique electronic and optical properties of both molecular species. In this report, we used different experimental techniques as well as molecular mechanics (MM) calculations to analyze the adsorption of meso-tetraphenylporphine (or 5,10,15,20-tetraphenyl-21H,23H-porphine, H2TPP) and its complexes with Ni(II) and Co(II) (NiTPP and CoTPP, respectively), as well as hemin (a natural porphyrin), onto the surface of SWNTs. Altogether, the results suggested that all four porphyrin species noncovalently interact with SWNTs, forming hybrid nanomaterials. Nevertheless, of all four porphyrin species, the strongest interaction with SWNTs occurs in the case of CoTPP, which is able to intercalate and considerably disperse SWNT bundles, and therefore absorb onto the surface of individual SWNTs. In contrast, NiTPP, CoTPP and hemin, due to a weaker interaction, are unable to do so and therefore are only capable to adsorb onto the surface of SWNT bundles. According to the scanning tunneling microscopy (STM) imaging and MM results, the adsorption of CoTPP onto SWNT sidewalls results in the formation of porphyrin arrays in the shape of long-period interacting helixes with variable periodicity, possibly due to different diameters and chiralities of SWNTs present in the samples. Since the remaining porphyrin species were found to adsorb onto the surface of SWNT bundles, the precise geometry of the corresponding porphyrin/SWNT complexes is difficult to characterize.

Bassiouk, María; Basiuk, Vladimir A.; Basiuk, Elena V.; Álvarez-Zauco, Edgar; Martínez-Herrera, Melchor; Rojas-Aguilar, Aaron; Puente-Lee, Iván

2013-06-01

206

Toroidal Single Wall Carbon Nanotubes in Fullerene Crop Circles  

NASA Technical Reports Server (NTRS)

We investigate energetics and structure of circular and polygonal single wall carbon nanotubes (SWNTs) using large scale molecular simulations on NAS SP2, motivated by their unusual electronic and magnetic properties. The circular tori are formed by bending tube (no net whereas the polygonal tori are constructed by turning the joint of two tubes of (n, n), (n+1, n-1) and (n+2, n-2) with topological pentagon-heptagon defect, in which n =5, 8 and 10. The strain energy of circular tori relative to straight tube decreases by I/D(sup 2) where D is torus diameter. As D increases, these tori change from buckling to an energetically stable state. The stable tori are perfect circular in both toroidal and tubular geometry with strain less than 0. 03 eV/atom when D greater than 10, 20 and 40 nm for torus (5,5), (8,8) and (10, 10). Polygonal tori, whose strain is proportional to the number of defects and I/D are energetically stable even for D less than 10 nm. However, their strain is higher than that of perfect circular tori. In addition, the local maximum strain of polygonal tori is much higher than that of perfect circular tori. It is approx. 0.03 eV/atom or less for perfect circular torus (5,5), but 0.13 and 0.21 eV/atom for polygonal tori (6,4)/(5,5) and (7,3)/(5,5). Therefore, we conclude that the circular tori with no topological defects are more energetically stable and kinetically accessible than the polygonal tori containing the pentagon-heptagon defects for the laser-grown SWNTs and Fullerene crop circles.

Han, Jie; Chancellor, Marisa K. (Technical Monitor)

1997-01-01

207

Decarboxylation of oxidized single-wall carbon nanotubes.  

PubMed

A classical protocol widely used in organic chemistry of aromatic and polyaromatic molecules has been successfully applied in this work for the decarboxylation of oxidized single-wall carbon nanotube (SWNT) to rend C-H SWNT derivatives. SWNT produced by arc discharge method have been oxidized during a purification process using strongly oxidant agents, such as hydrogen peroxide and nitric acid. The decarboxylation of oxidized SWNT has been conduced with copper(I) oxide in a 50:50 solution of N-methylpyrrolidone and quinoline. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and acid-base potentiometric titration analyses were carried out to characterize quali and quantitatively the changes in the chemical environment on the SWNT surface in each step of the purification and the decarboxylation process. Those techniques showed the appearance of mainly carboxylic and phenolic groups after the purification process and the disappearance of the carboxylic groups after the decarboxylation reaction. Fourier transform infrared spectroscopy analysis indicated also the formation of aliphatic and aromatic C-H groups. X-ray photoelectron spectroscopy and potentiometric titration results determined an efficiency higher than 90% for our decarboxylation procedure. The purity and structural quality of the SWNT sample used in the decarboxylation process were evaluated by thermogravimetry and Raman spectroscopy. Thermogravimetric analysis identified a purified sample with approximately 80 wt% of SWNT, in fractions distributed in highly structured SWNTs (25 wt%), with distribution in composition, length and structural quality (35 wt%) and with very defective and short tubes (25 wt%). The damages on the purified SWNT walls were characterized by the Raman scattering analysis. PMID:18330151

Vieira, H S; Andrada, D M; Mendonça, R; Santos, A P; Martins, M D; Macedo, W A A; Gorgulho, H F; Pimenta, L P S; Moreira, R L; Jorio, A; Pimenta, M A; Furtado, C A

2007-10-01

208

Effect of atomic interconnects on percolation in single-walled carbon nanotube thin film networks.  

PubMed

The formation of covalent bonds to single-walled carbon nanotube (SWNT) or graphene surfaces usually leads to a decrease in the electrical conductivity and mobility as a result of the structural rehybridization of the functionalized carbon atoms from sp(2) to sp(3). In the present study, we explore the effect of metal deposition on semiconducting (SC-) and metallic (MT-) SWNT thin films in the vicinity of the percolation threshold and we are able to clearly delineate the effects of weak physisorption, ionic chemisorption with charge transfer, and covalent hexahapto (?(6)) chemisorption on these percolating networks. The results support the idea that for those metals capable of forming bis-hexahapto-bonds, the generation of covalent (?(6)-SWNT)M(?(6)-SWNT) interconnects provides a conducting pathway in the SWNT films and establishes the transition metal bis-hexahapto organometallic bond as an electronically conjugating linkage between graphene surfaces. PMID:24893323

Tian, Xiaojuan; Moser, Matthew L; Pekker, Aron; Sarkar, Santanu; Ramirez, Jason; Bekyarova, Elena; Itkis, Mikhail E; Haddon, Robert C

2014-07-01

209

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

NASA Technical Reports Server (NTRS)

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 their stability significantly. The onset of decomposition of the purified nanotubes (determined by thermal gravimetric analysis in air) is more than 300 C higher than that of the crude nanotubes. Transmission electron microscopy analysis of nanotubes purified by this method reveals near complete removal of iron catalyst particles. Analysis of the nanotubes using inductively coupled plasma spectroscopy revealed that the iron content of the nanotubes was reduced from 22.7 wt% in the crude nanotubes to less than 0.02 wt%. X-ray photoelectron spectroscopy revealed a decrease in iron content after purification as well as an increase in oxygen content due to the formation of carboxylic acid groups on the surface of the nanotubes. Nanotubes purified by this improved method can be readily dispersed in common organic solvents, in particular N,N-dimethylformamide, using prolonged ultrasonic treatment. These dispersions can then be used to incorporate single wall carbon nanotubes into polymer films.

Lebron, Marisabel; Meador, Michael A.

2003-01-01

210

Structural modification of nanoporous carbon with single wall carbon nanotube  

Microsoft Academic Search

A novel CC nanocomposite was synthesized by pyrolysis of well dispersed individual functionalized SWNTs in a thermosetting resin, poly(furfuryl alcohol) (PFA). Strong interaction between SWNT and nanoporous carbon derived from PFA (PFA-NPC) was obtained with this strategy and the integrity of SWNTs was maintained after heat treatment. Usually, it is challenging to separate SWNT bundles and disperse them in preparation

Bo Yi

2007-01-01

211

Noncovalent functionalization of single-walled carbon nanotubes by aromatic diisocyanate molecules: A computational study  

NASA Astrophysics Data System (ADS)

We investigate the noncovalent functionalization of metallic single-walled carbon nanotubes (SWCNT) (6,0) by 4,4?-methylene diphenyl diisocyanate (MDI) and toluene-2,4-diisocyanate (TDI) molecules using the density functional theory (DFT) method with van der Waals dispersion correction. The obtained local minima show the dependence between the molecular arrangement of the adsorbates on SWCNT surface and their binding energies. We analyze the interplay between the ?-? stacking interactions and isocyanate functional groups. For the analysis of the changes in the electronic structure we calculate the density of states (DOS) and charge density plots.

Goclon, Jakub; Kozlowska, Mariana; Rodziewicz, Pawel

2014-04-01

212

Low-temperature conductive tip scanning measurements of single walled carbon nanotubes.  

NASA Astrophysics Data System (ADS)

We have built a low-temperature atomic force microscope (AFM) that fits inside a 38 mm bore cryostat. The scanning probe is attached to a quartz tuning fork, and a frequency shift is used as the feedback signal. By using a conductive tip we can locally tunnel into single walled carbon nanotubes grown on a non-conducting (SiO2) substrate. The nanotubes are contacted by a metal grid *electrode* evaporated on top of the sample. The tip is used as a second, movable contact. We measure the nanotube conduction as a function of the tip position and the gate voltage.

Prior, Matthew; Makarovski, Alexander; Zhukov, Alexei; Finkelstein, Gleb

2006-03-01

213

Synthesis of single-walled carbon nanotubes, their ropes and books  

NASA Astrophysics Data System (ADS)

The carbon nanotube (CNT) is a model system of one-dimensional nanomaterials, which shows numerous unique properties and vast potential applications. The synthesis and assembly of high-quality CNTs are the basis for studies of their properties and applications. In this contribution, we briefly review our works on the controlled synthesis of single-walled CNTs (SWCNTs) and double-walled CNTs via floating catalyst chemical vapor deposition and arc-discharge methods. The in situ assembly of such CNTs into ordered macrostructures with various dimensions including ropes, films, and buckybooks are also presented. Finally, we introduced our recent findings on metal-catalyst-free growth of SWCNTs.

Liu, Bilu; Liu, Qingfeng; Ren, Wencai; Li, Feng; Liu, Chang; Cheng, Hui-Ming

2010-06-01

214

Fabrication of carbon nanomechanical resonators with embedded single walled carbon nanotube stiffening layers  

Microsoft Academic Search

This study presents a new fabrication method for high frequency nanomechanical resonators by utilizing carbon layers with embedded single walled carbon-nanotube layers. The carbon layers, fabricated by pyrolysis of photo- or electron beam resists, showed low-density and moderate Young's modulus which is suitable to sensitive nanodevices. The carbon-nanotube layers underneath carbon layers enhanced conductivity and Young's modulus while maintaining low-density

Seung Hoon Lee; Bumki Min; Se Il Park; Kwang-Cheol Lee; S. S. Lee

2010-01-01

215

Dispersion of single wall carbon nanotubes by in situ polymerization under sonication  

Microsoft Academic Search

Single wall nanotube reinforced polyimide nanocomposites were synthesized by in situ polymerization of monomers of interest in the presence of sonication. This process enabled uniform dispersion of single wall carbon nanotube (SWNT) bundles in the polymer matrix. The resultant SWNT–polyimide nanocomposite films were electrically conductive (antistatic) and optically transparent with significant conductivity enhancement (10 orders of magnitude) at a very

Cheol Park; Zoubeida Ounaies; Kent A. watson; Roy E. crooks; Joseph Smith Jr; Sharon E. lowther; John W. connell; Emilie J. siochi; Joycelyn S. harrison; Terry L. st. clair

2002-01-01

216

Antimicrobial Biomaterials based on Single-Walled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

Biomaterials that inactivate bacteria are needed to eliminate medical device infections. We investigate the antimicrobial nature of single-walled carbon nanotubes (SWNT) incorporated within biomedical polymers. In the first part, we focus on SWNT dispersed in the common biomedical polymer poly(lactic-co-glycolic acid) (PLGA) as a potential antimicrobial biomaterial. We find Escherichia coli and Staphylococcus epidermidis viability and metabolic activity to be significantly diminished in the presence of SWNT-PLGA, and to correlate with SWNT length and concentration. Up to 98 % of bacteria die within one hour of SWNT-PLGA versus 15-20% on pure PLGA. Shorter SWNT are found to be more toxic, possibly due to an increased density of open tube ends. In the second part, we investigate the antimicrobial activity of SWNT layer-by-layer (LbL) assembled with the polyelectrolytes poly(L-lysine) (PLL) and poly(L-glutamic acid) (PGA). The dispersibility of SWNT in aqueous solution is significantly improved via the biocompatible nonionic surfactant polyoxyethylene(20)sorbitan monolaurate (Tween 20) and the amphiphilic polymer phospholipid-poly(ethylene glycol) (PL-PEG). Absorbance spectroscopy and transmission electron microscopy (TEM) show SWNT with either Tween 20 or PL-PEG in aqueous solution to be well dispersed. Quartz crystal microgravimetry with dissipation (QCMD) measurements show both SWNT-Tween and SWNT-PL-PEG to LbL assemble with PLL and PGA into multilayer films, with the PL-PEG system yielding the greater final SWNT content. Bacterial inactivation rates are significantly higher (up to 90%) upon 24 hour incubation with SWNT containing films, compared to control films (ca. 20%). In the third part, we study the influence of bundling on the LbL assembly of SWNT with charged polymers, and on the antimicrobial properties of the assembled film. QCMD measurements show the bundled SWNT system to adsorb in an unusually strong fashion—to an extent three times greater than that of isolated SWNT. Scanning electron micrographs reveal Escherichia coli on bundled SWNT films to be essentially engulfed by the nanotubes, whereas the bacteria rest upon the isolated SWNT films. While both systems inactivate 90% of bacteria following 24 h, the bundled SWNT system is "fast-acting", reaching this inactivation rate in 1 hr. This thesis demonstrates the potential usefulness of SWNT/polymer thin films as antimicrobial biomaterials.

Aslan, Seyma

217

Diffusion of single-walled carbon nanotube under physiological conditions.  

PubMed

Single-walled carbon nanotube (SWNT) can be functionalized to target cells for drug delivery or cancer cells for their detection and therapy. Understanding their transport phenomena in vivo is a necessary step to unlock their medical potential. This work estimates the diffusion characteristics of SWNTs and their DNA-conjugated bio-hybrids under simulated or postulated physiological conditions using EPI-fluorescence microscopy (EFM). SWNT was shortened and dispersed in aqueous solution with the average length and diameter of 253 nm (+/-30.6 nm) and 1.6 nm (+/-0.34 nm), respectively, and tagged with a fluorophore, 1-pyrenebutanoic succinimidyl ester (PSE), through non-covalent pi stacking. DNA was attached to the PSE-SWNTs through carboxiimide based coupling procedure. Using the EFM, real-time videos were recorded under four different viscosities corresponding to four kinds of human body fluids: lymph (1.4 cP), bile (2.4 cP), blood (3-6 cP), and cytoplasm (10-30 cP), and processed to calculate diffusion coefficients based on random walk and speed. At 37 degreeC, diffusion coefficients of the SWNTs were estimated to be: 1.45 (+/-0.652) x 10(4) nm2/s (lymph), 0.91 (+/-0.205) x 10(4) nm2/s (bile), 0.59 (+/-0.179)x 10(4) nm2/s (blood), and 0.26 (+/-0.114)x 10(4) nm2/s (cytoplasm). Estimated diffusion coefficients of SWNT-DNA bio-hybrids were: 1.45 (+/-0.402) x 10(4) nm2/s (plasma), 0.62 (+/-0.212) x 10(4) nm2/s (bile), 0.41 (+/-0.142) x 10(4) nm2/s (blood), 0.38 (+/-0.257) x 10(4) nm2/s (cytoplasm). These outcomes should serve as key data for developing mathematical models of SWNT-based drug delivery, cell targeting, and its biodistribution. PMID:23858971

Judkins, John; Lee, Hyun Ho; Tung, Steve; Kim, Jin-Woo

2013-06-01

218

Optical and vibrational properties of single-wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

This work is a study of the optical properties of single-wall carbon nanotubes (SWNTs) using continuous wave (CW) modulation spectroscopy and resonant Raman scattering. SWNTs comprise a nanoscale, quasi-1D system in which the electrons are strongly interacting, resulting in the photo-generation of excitons. Our optical studies have revealed the behavior of these excitons under a number of different perturbations to the system. We have used absorption, reflectance, electro-absorption (EA), photo-induced absorption (PA), charge-induced absorption (CIA), and resonant Raman scattering (RRS) on films of SWNTs. Our EA results provide strong evidence for the dominance of excitons in the optical absorption spectra of SWNT films. The absence of Franz-Keldysh oscillations and the presence of a derivative-like structure of the EA spectra indicate that the oscillator strength goes to the generation of excitons and not to interband electronic transitions. Furthermore, some of the photo-generated excitons are long-lived due to charge trapping in individual tubes within bundles, and this leads to a PA spectrum that is extraordinarily similar to the EA signal. When SWNTs are electrochemically doped we see that the exciton absorption is bleached due to k-space filling and screening of the excitons by the modified local dielectric, while there is very little shift in the exciton transition energies due to band-gap renormalization. Simultaneously the infrared absorption, which is due to Drude free-carriers absorption, is enhanced. A similar behavior is observed in the case of direct charge injection. The RRS of doped SWNT samples shows a frequency shift of many of the Raman-active modes that is commensurate with the macroscopic actuation observed in nanotube-based electrochemical devices. This indicates that doping-induced changes in the lattice are connected with softening and stiffening of the vibrational modes. Our results impact many proposed technologies that exploit the unique properties of SWNTs. Displays, batteries, and even photovoltaics that incorporate nanotubes are already in development. The performance and robustness of these devices could be improved when our results are taken into account.

Kennedy, W. Joshua

219

Fully integrated single-walled carbon nanotube thermoplastic composites  

NASA Astrophysics Data System (ADS)

The development of composites of single-walled carbon nanotubes (SWNTs) with thermoplastics requires methods for good dispersion and achieving good interaction between SWNTs and the matrix. This thesis presents a new method to achieve good dispersion by a preliminary treatment called incipient wetting. The SWNTs dispersed in a solvent are mixed with polymer particles and deposited over them as the solvent is evaporated to give an initial dispersion. Factors that make this more effective are: good wetting of the polymer by the solvent, swelling of the polymer, high surface area of the polymer. Swelling enhances the initial dispersion with some initial mixing. A high surface area is achieved using polymer powder. High shear mixing alone does not achieve the same uniform and repeatable level of dispersion that the combination with incipient wetting allows. The incipient wetting method was studied and applied to different polymers. The possibility of recovering SWNTs from thermoplastics by dissolving or burning away the matrix is an extension of this study. A new comprehensive approach to control the interface of thermoplastics with SWNTs is studied. This is based on achieving direct chemical bonding between polymer molecules and functional groups on oxidized open ends, sidewalls, or both, in the SWNTs. Different concepts and approaches to these "fully integrated nanotube composites" are discussed. The concepts have been applied to epoxies elsewhere and are tested here with nylon-6,6 as a model system. Nylon was synthesized by interfacial polymerization in the presence of SWNTs resulting in excellent dispersion in the composite without further processing. The essential requirement for good dispersion is that the SWNTs are well dispersed in the solvent. Interfacial polymerization opens the way to many types of polymer-SWNT composites. Tests of full integration of SWNTs with open ended nanotubes showed promising results and hints of integration but were limited by dispersion in the solvent. Fluorinated SWNTs were dispersed effectively with dichlorobenzene, another solvent may be better. There is no conclusive evidence of integration with F-SWNTs but they may react with the polymer chain with thermal post-processing.

Rodriguez-Macias, Fernando J.

220

Well-Dispersed Single Walled Carbon Nanotube Growth from Iron Nanoparticles Created from Poly(styrene-b-ethylmethylferrocenylsilane) Thin Films  

Microsoft Academic Search

Well dispersed single walled carbon nanotubes (SWNTs) have been grown directly from a diblock copolymer thin film, poly(styrene-b-ethylmethylferrocenylsilane), determined to be random spheres of polyethylmethylferrocenylsilane (PEMFS) in polystyrene (PS). When the spin cast block copolymer was heated in a chemical vapor deposition oven (CVD), iron nanoparticles formed from the ferrocene containing polymer block, acting as metal catalysts for SWNT growth.

Sarah Lastella; Yung Joon Jung; Hoichang Yang; Robert Vajtai; Pulickel Ajayan; Chang Ryu; David Rider; Ian Manners

2004-01-01

221

Industrially synthesized single-walled carbon nanotubes: compositional data for users, environmental risk assessments, and source apportionment  

Microsoft Academic Search

Commercially available single-walled carbon nanotubes (SWCNTs) contain large percentages of metal and carbonaceous impurities. These fractions influence the SWCNT physical properties and performance, yet their chemical compositions are not well defined. This lack of information also precludes accurate environmental risk assessments for specific SWCNT stocks, which emerging local legislation requires of nanomaterial manufacturers. To address these needs, we measured the

D. L. Plata; P. M. Gschwend; C. M. Reddy

2008-01-01

222

Isolation of specific small-diameter single-wall carbon nanotube species via aqueous two-phase extraction.  

PubMed

Aqueous two-phase extraction is demonstrated to enable isolation of single semiconducting and metallic single-wall carbon nanotube species from a synthetic mixture. The separation is rapid and robust, with remarkable tunability via modification of the surfactant environment set for the separation. PMID:24448916

Fagan, Jeffrey A; Khripin, Constantine Y; Silvera Batista, Carlos A; Simpson, Jeffrey R; Hároz, Erik H; Hight Walker, Angela R; Zheng, Ming

2014-05-01

223

Single-Wall Carbon Nanotube Production by the Arc Process: A Parametric Study  

NASA Technical Reports Server (NTRS)

Single wall carbon nanotubes are produced using the arc discharge process. Graphite anodes are filled with a mixture of nickel and yttrium metallic powders, then vaporized by creating a high current arc. By varying the current, gap distance, and ambient pressure it is shown that the best yield of single wall carbon nanotubes is obtained within a narrow range of conditions. The relative yield and purity of the product are indicated semi-quantitatively from scanning electric microscopy (SEM) and thermogravimetric analysis (TGA). Two types of anodes have been investigated. The first is hollow and filled with a powder mixture of graphite, nickel and yttrium. The second is filled with a paste made of a mixture of metal nitrates, graphite powder and carbon adhesive, then reduced in an argon atmosphere at high temperature. Product purity and yield will be compared for the two types of anodes. The graphite in the anodes may have hydrogen attached in the pores. To remove this impurity anodes have been baked up to 1400 - 1500 C. The effect of baking the anodes on impurities in the product will be given.

Scott, Carl D.; Gorelik, Olga; Proft, William J.

2000-01-01

224

From isotope labeled CH?CN to N? inside single-walled carbon nanotubes.  

PubMed

The observation of one-dimensional N? inside single-walled carbon nanotubes raises the questions, how are the N? molecules formed and how do they manage to make their way to this peculiar place? We have used N(15) and C(13) isotope labeled acetonitrile during the synthesis of single-walled carbon nanotubes to investigate this process. The isotope shifts of phonons and vibrons are observed by Raman spectroscopy and X-ray absorption. We identify the catalytic decomposition of acetonitrile as the initial step in the reaction pathway to single-walled carbon nanotubes containing encapsulated N?. PMID:24322271

Kramberger, Christian; Thurakitseree, Theerapol; Einarsson, Erik; Takashima, Akito; Kinoshita, Toyohiko; Muro, Takayuki; Maruyama, Shigeo

2014-01-16

225

From isotope labeled CH3CN to N2 inside single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

The observation of one-dimensional N2 inside single-walled carbon nanotubes raises the questions, how are the N2 molecules formed and how do they manage to make their way to this peculiar place? We have used N15 and C13 isotope labeled acetonitrile during the synthesis of single-walled carbon nanotubes to investigate this process. The isotope shifts of phonons and vibrons are observed by Raman spectroscopy and X-ray absorption. We identify the catalytic decomposition of acetonitrile as the initial step in the reaction pathway to single-walled carbon nanotubes containing encapsulated N2.

Kramberger, Christian; Thurakitseree, Theerapol; Einarsson, Erik; Takashima, Akito; Kinoshita, Toyohiko; Muro, Takayuki; Maruyama, Shigeo

2014-01-01

226

Scanning tunneling microscopy observation of tightly wound, single-wall coiled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Scanning tunneling microscopy (STM) images of carbon nanotubes grown by the catalytic cracking of hydrocarbons, which exhibit a well-defined axial periodicity in the 1 nm range, are reported. The data are interpreted as tightly wound, single-wall, coiled carbon nanotubes with an interspire distance of 0.34 nm as the distance between graphene layers in graphite or the distance of single-wall carbon nanotubes in ropes.

Biró, L. P.; Lazarescu, S. D.; Thiry, P. A.; Fonseca, A.; Nagy, J. B.; Lucas, A. A.; Lambin, Ph.

2000-05-01

227

Ultrashort single-walled carbon nanotubes in a lipid bilayer as a new nanopore sensor  

NASA Astrophysics Data System (ADS)

An important issue in nanopore sensing is to construct stable and versatile sensors that can discriminate analytes with minute differences. Here we report a means of creating nanopores that comprise ultrashort single-walled carbon nanotubes inserted into a lipid bilayer. We investigate the ion transport and DNA translocation through single-walled carbon nanotube nanopores and find that our results are fundamentally different from previous studies using much longer single-walled carbon nanotubes. Furthermore, we utilize the new single-walled carbon nanotube nanopores to selectively detect modified 5-hydroxymethylcytosine in single-stranded DNA, which may have implications in screening specific genomic DNA sequences. This new nanopore platform can be integrated with many unique properties of carbon nanotubes and might be useful in molecular sensing such as DNA-damage detection, nanopore DNA sequencing and other nanopore-based applications.

Liu, Lei; Yang, Chun; Zhao, Kai; Li, Jingyuan; Wu, Hai-Chen

2013-12-01

228

A remote sensor for detecting methane based on palladium-decorated single walled carbon nanotubes.  

PubMed

The remote detection of the concentration of methane at room temperature is performed by a sensor that is configured by the combination of radio frequency identification (RFID), and functionalized carbon nanotubes (CNTs). The proposed sensor is schemed as a thin film RFID tag in a polyethylene substrate, on which a metal trace dipole, a metal trace T impedance matching networks, a 0.5 µm-CMOS RF/DC rectifier chipset and a sensor head of palladium-decorated single walled carbon nanotubes (Pd-SWCNTs) are surface mounted in cascade. The performances of the sensor are examined and described by the defined parameters of the received signal strength index (RSSI) and the comparative analog identifier (?AID). Results validate the sensor's ability to detect molecules of methane at room temperature, showing that the RSSI can increase 4 dB and the ?AID can increase 3% in response to methane concentrations ranging from zero to 100 ppm. PMID:23845931

Liu, Jian; Li, Guomin

2013-01-01

229

A Remote Sensor for Detecting Methane Based on Palladium-Decorated Single Walled Carbon Nanotubes  

PubMed Central

The remote detection of the concentration of methane at room temperature is performed by a sensor that is configured by the combination of radio frequency identification (RFID), and functionalized carbon nanotubes (CNTs). The proposed sensor is schemed as a thin film RFID tag in a polyethylene substrate, on which a metal trace dipole, a metal trace T impedance matching networks, a 0.5 ?m-CMOS RF/DC rectifier chipset and a sensor head of palladium-decorated single walled carbon nanotubes (Pd-SWCNTs) are surface mounted in cascade. The performances of the sensor are examined and described by the defined parameters of the received signal strength index (RSSI) and the comparative analog identifier (?AID). Results validate the sensor's ability to detect molecules of methane at room temperature, showing that the RSSI can increase 4 dB and the ?AID can increase 3% in response to methane concentrations ranging from zero to 100 ppm.

Liu, Jian; Li, Guomin

2013-01-01

230

Electrical transport properties of selective area CVD grown single wall carbon nanotube devices  

NASA Astrophysics Data System (ADS)

Individual single wall carbon nanotube (SWNT) devices were constructed by the direct assembly of an individual SWNT on two opposing Au electrons using an acetylene based low temperature selective area Chemical Vapor Deposition (CVD) method. Standard electron beam lithography and subsequent electron-gun assisted metal deposition were used to fabricate both the electrodes and catalyst islands. Electrical transport properties of the SWNT circuits were measured by applying a gate voltage to the Si substrate at various temperatures down to 0.3 K. Both semiconducting and metallic individual SWNTs were found bridging the Au electrodes with relatively small contact resistances. The semiconducting SWNTs exhibit a significant electrical field effect at room temperature with the conductance modulation approaching 5 orders of magnitude. High bias measurements on both suspended and substrate-supported metallic SWNTs reveal strikingly different phenomena. The details of the electrical transport results will be discussed.

Zhou, Zhixian; Jin, Rongying; Eres, Gyula; Mandrus, David

2006-03-01

231

Hydrogen sensors based on Pd-functionalized Single-walled carbon nanotubes  

Microsoft Academic Search

We have demonstrated properties for hydrogen sensing by single-walled carbon nanotubes (SWNTs) with Pd nanoparticles functionalized on dendrimer. In conclusion, fabricated SWNTs with Pd nanoparticles functionalized on dendrimers can expect outstanding ability as hydrogen sensor.

J. M. Lee; Seonghwa Ju; Y. Jung; Sung-Jin Kim; Wooyoung Lee

2010-01-01

232

Photon induced effects in molecular assemblies of single walled carbon nanotubes  

Microsoft Academic Search

Single Walled Carbon Nanotubes (SWNT) are important for devices and sensors based on nanotechnology. Future optoelectronic devices can be made from the assemblies of diverse nanostructured materials and SWNTs, providing enhanced functionality. \\

Harsh Chaturvedi

2008-01-01

233

Controlling the crystalline three-dimensional order in bulk materials by single-wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

The construction of ordered single-wall carbon nanotube soft-materials at the nanoscale is currently an important challenge in science. Here we use single-wall carbon nanotubes as a tool to gain control over the crystalline ordering of three-dimensional bulk materials composed of suitably functionalized molecular building blocks. We prepare p-type nanofibres from tripeptide and pentapeptide-containing small molecules, which are covalently connected to both carboxylic and electron-donating 9,10-di(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene termini. Adding small amounts of single-wall carbon nanotubes to the so-prepared p-nanofibres together with the externally controlled self assembly by charge screening by means of Ca2+ results in new and stable single-wall carbon nanotube-based supramolecular gels featuring remarkably long-range internal order.

López-Andarias, Javier; López, Juan Luis; Atienza, Carmen; Brunetti, Fulvio G.; Romero-Nieto, Carlos; Guldi, Dirk M.; Martín, Nazario

2014-04-01

234

Controlling the crystalline three-dimensional order in bulk materials by single-wall carbon nanotubes.  

PubMed

The construction of ordered single-wall carbon nanotube soft-materials at the nanoscale is currently an important challenge in science. Here we use single-wall carbon nanotubes as a tool to gain control over the crystalline ordering of three-dimensional bulk materials composed of suitably functionalized molecular building blocks. We prepare p-type nanofibres from tripeptide and pentapeptide-containing small molecules, which are covalently connected to both carboxylic and electron-donating 9,10-di(1,3-dithiol-2-ylidene)-9,10-dihydroanthracene termini. Adding small amounts of single-wall carbon nanotubes to the so-prepared p-nanofibres together with the externally controlled self assembly by charge screening by means of Ca(2+) results in new and stable single-wall carbon nanotube-based supramolecular gels featuring remarkably long-range internal order. PMID:24777055

López-Andarias, Javier; López, Juan Luis; Atienza, Carmen; Brunetti, Fulvio G; Romero-Nieto, Carlos; Guldi, Dirk M; Martín, Nazario

2014-01-01

235

Evidence for substitutional boron in doped single-walled carbon nanotubes  

SciTech Connect

Precise determination of acceptors in the laser ablation grown B doped single-walled carbon nanotubes (SWCNTs) has been elusive. Photoemission spectroscopy finds evidence for subpercent substitutional B in this material, which leads to superconductivity in thin film SWNT samples.

Ayala, P.; Pichler, T. [Faculty of Physics, University of Vienna, 1090 Wien (Austria); Reppert, J.; Rao, A. M. [Department of Physics and Astronomy and COMSET, Clemson University (United States); Grobosch, M.; Knupfer, M. [IFW Dresden, P.O. Box 270116, D-01171 Dresden (Germany)

2010-05-03

236

Simple Empirical Model for Vibrational Spectra of Single-Wall Carbon Nanotubes.  

National Technical Information Service (NTIS)

A simple empirical model and approach are introduced for calculation of the vibrational spectra of arbitrary single wall carbon nanotubes. Differently from the frequently used force constants description, the model employs only invariant quantities such a...

Y. N. Garstein

2004-01-01

237

Nonlinear transmission properties of nanostructures with single-wall carbon nanotubes and conductive polymers  

Microsoft Academic Search

Using the concept of self-assembly, we formed orderly structured nanocomposites based on single-wall carbon nanotubes, which were electrochemically wrapped with conductive polymers. We report on the nonlinear optical transmission characteristics of such materials.

H. Han; J. Chen; Y. Diamant; M. Etienne; A. Walser; R. Dorsinville; H. Grebel

2005-01-01

238

Theoretical and experimental studies of Schottky diodes that use aligned arrays of single-walled carbon nanotubes  

Microsoft Academic Search

We present theoretical and experimental studies of Schottky diodes that use aligned arrays of single-walled carbon nanotubes.\\u000a A simple physical model, taking into account the basic physics of current rectification, can adequately describe the single-tube\\u000a and array devices. We show that for as-grown array diodes, the rectification ratio, defined by the maximum-to-minimum-current-ratio,\\u000a is low due to the presence of metallic-single-walled

Xinning Ho; Lina Ye; Slava V. Rotkin; Xu Xie; Frank Du; Simon Dunham; Jana Zaumseil; John A. Rogers

2010-01-01

239

Improving Dispersion of Single-Walled Carbon Nanotubes in a Polymer Matrix Using Specific Interactions  

Microsoft Academic Search

A novel approach is presented to improve the dispersion of oxidized single-walled carbon nanotubes (SWNTs) in a copolymer matrix by tuning hydrogen-bonding interactions to enhance dispersion. Nanocomposites of single-walled carbon nanotubes and copolymers of styrene and vinyl phenol (PSVPh) with varying vinyl phenol content were produced and examined. The dispersion of the SWNT in the polymer matrix is quantified by

Asif Rasheed; Mark D. Dadmun; Ilia N Ivanov; Phillip F. Britt; David B. Geohegan

2006-01-01

240

Mechanism of Enhanced Dispersion of Single-Walled Carbon Nanotubes with Proteins by Alcohols and Chaotropes  

Microsoft Academic Search

Protein-single-walled carbon nanotube (SWNT) conjugates have attracted remarkable attention for their application to biotechnology. However, low dispersion of the conjugates in aqueous solvents attributable to the strong interaction between sidewalls of SWNTs has limited their application. We previously reported that alcohols enhance the dispersion of single-walled carbon nanotubes with protein, but the mechanism has not been clarified. Herein we suggest

Atsushi Hirano; Yutaka Maeda; Takeshi Akasaka; Kentaro Shiraki

2010-01-01

241

Theoretical study of Ga -based nanowires and the interaction of Ga with single-wall carbon nanotubes  

Microsoft Academic Search

Gallium displays physical properties which can make it a potential element to produce metallic nanowires and high-conducting interconnects in nanoelectronics. Using first-principles pseudopotential plane method we showed that Ga can form stable metallic linear and zigzag monatomic chain structures. The interaction between individual Ga atom and single-wall carbon nanotube (SWNT) leads to a chemisorption bond involving charge transfer. Doping of

Engin Durgun; Sefa Dag; Salim Ciraci

2004-01-01

242

Low temperature conductive tip scanning of single walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

The low temperature conductance measurements of Carbon Nanotubes (CNT), and other nanostructures, are commonly conducted on samples with fixed leads, which provide the global information about the nanostructure's electronic properties. To measure local electronic properties, we have built a conductive tip Atomic Force Microscope (AFM). This AFM allows us to place a mobile contact anywhere along the tube and carry out local transport investigation, including measurements taken while we radially deform the nanotube with the tip. Our low temperature conductive tip AFM is suitable for operation in a helium refrigerator with a bore 1.25" or more, at temperatures of 4K or less. It uses a thermally compensated, nonmagnetic design based on the "Besocke Beetle". All movements are achieved by piezotubes, so heat load at low temperatures is small. For tip-surface distance control, we use a homemade frequency detection system based on a commercially available quartz tuning fork. The scanning tip is mounted on the tuning fork. We use a platinum/iridium tip rather than the more commonly used tungsten, as it does not form a native oxide. The tip is independently wired which allows us to measure the current flow along the tube. Previous low temperature AFMs used the conductive tip only to gate the nanotube. Our samples are CVD grown carbon nanotubes upon a silicon dioxide substrate, contacted by a palladium/gold grid. With our AFM, we have carried out the first low temperature scanning of conductance along nanotubes on insulating substrates. While radially deforming a metallic carbon nanotube with our tip, we have observed a reversible gap opening, indicating a metallic to semi-conducting transition. This result qualitatively matches theoretical predictions. We have observed Coulomb blockade in transport between carbon nanotubes and the tip by AFM for the first time. By gently perturbing the nanotube with the tip, we have increased the strength of some single electron conductance peaks while diminishing others. This result is probably due the perturbation of the probability density functions inside the nanotube. This novel instrument will allow us to study the local properties of a broad class of conductive nanostructures positioned on insulating substrates.

Prior, Matthew

243

Ohmic Contacts to P-GaN Based on the Single-Walled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

We have designed and verified a new structure for ohmic contacts to p-GaN, mainly for applications in light emitting devices based on a layer of single-walled carbon nanotubes (SWCNT) and metallic layers of Cr and Au, namely in configuration Au/Cr/SWCNT/p-GaN. The layer of carbon nanotubes was deposited on p-GaN by spraying a solution of synthesized SWCNTs, while the layers of Cr and Au were vapour deposited. The effects of the annealing temperature and time upon the electrical properties of Au/Cr/SWCNT/p-GaN contacts have been studied. It has been found that the contact structure provides a low resistivity ohmic contact after subsequent annealing in N2 ambient at 700 °C for 1 minute.

Liday, Jozef; Vogrin?i?, Peter; Vretenár, Viliam; Kotlár, Mário; Marton, Marián; Rehá?ek, Vlastimil

2013-09-01

244

A Timoshenko beam model for vibration analysis of chiral single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

In this paper, dynamic properties of a single-walled carbon nanotube (SWCNT) with small scale effects are studied. Based on the nonlocal continuum theory and the Timoshenko beam model, the equations of motion are derived. The influences of scale coefficients, the vibrational mode number, the chirality of carbon nanotube and the aspect ratio on the vibrational characteristics of the SWCNTs are discussed. Results indicate significant dependence of natural frequencies on the chirality of single-walled carbon, the small-scale parameter, the vibrational mode number and the aspect ratio. These findings are important in mechanical design considerations of devices that use carbon nanotubes.

Boumia, Lakhdar; Zidour, Mohamed; Benzair, Abdelnour; Tounsi, Abdelouahed

2014-05-01

245

Synthesis of single-walled carbon nanotubes by chemical vapor deposition and their electronic devices  

Microsoft Academic Search

This dissertation describes a series of studies on chemical vapor deposition (CVD) synthesis of single-walled carbon nanotubes (SWNTs) and their electronic applications. A novel finding on the relationship between the carbon feeding rate and the SWNT diameters and growth efficiency is summarized. Electronic devices, including polymer electrolyte gated carbon nanotube field effect transistors and Schottky barrier diodes, are fabricated and

Chenguang Lu

2006-01-01

246

Development of novel single-wall carbon nanotube epoxy composite ply actuators  

Microsoft Academic Search

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

Yeo-Heung Yun; Vesselin Shanov; Mark J. Schulz; Suhasini Narasimhadevara; Srinivas Subramaniam; Douglas Hurd; F. J. Boerio

2005-01-01

247

Electronic properties of electrochemically modified single-walled carbon nanotubes  

Microsoft Academic Search

The functionalization of carbon nanotubes is a research topic with applications in a wide range of fields, from carbon nanotube based electronic sensor development to improving the electrical properties of carbon nanotubes for use as interconnects between larger circuit elements. This dissertation examines the impact of point-functionalizations on the conductance of single carbon nanotube devices. Due to their reduced size

Vaikunth Rawloo Khalap

2010-01-01

248

Filling of single-walled carbon nanotubes by CuI nanocrystals via capillary technique  

NASA Astrophysics Data System (ADS)

The present study is focused on the synthesis and investigation of the nanocomposite CuI@SWNT obtained by the filling of metallic single-walled carbon nanotubes (SWNTs) (inner diameter 1-1.4 nm) by wide-gap semiconducting CuI nanocrystals using so-called capillary technique. The method is based on the impregnation of pre-opened SWNTs by molten CuI in vacuum with subsequent slow cooling to room temperature. SWNTs and CuI@SWNT nanocomposites were studied by nitrogen capillary adsorption method, EDX microanalysis, HRTEM microscopy and Raman spectroscopy. The changing of electronic properties of CuI@SWNT as compare to row nanotubes was observed.

Chernysheva, M. V.; Eliseev, A. A.; Lukashin, A. V.; Tretyakov, Yu. D.; Savilov, S. V.; Kiselev, N. A.; Zhigalina, O. M.; Kumskov, A. S.; Krestinin, A. V.; Hutchison, J. L.

2007-03-01

249

Length separation of Zwitterion-functionalized single wall carbon nanotubes by GPC.  

PubMed

The length-fractionation of shortened (250 to 25 nm), zwitterion-functionalized, single wall carbon nanotubes (SWNTs) has been demonstrated via gel permeation chromatography (GPC). The UV-Vis spectrum of each fraction indicates an apparent "solubilization", as evident by the direct observation of all predicted optically allowed interband transitions between the mirror image spikes in the density of states of both metallic and semiconducting SWNTs with various tube diameters. As evident by the presence or absence of the 270 nm, pi-plasmon absorption, this "solubilization" is a dynamic process and leads to re-aggregation if left undisturbed for a couple of weeks or upon dissociation of the pendant octadecylamine groups. This non-destructive and highly versatile separation methodology opens up an array of possible applications for shortened SWNTs in nanostructured devices. PMID:11817929

Chattopadhyay, Debjit; Lastella, Sarah; Kim, Sejong; Papadimitrakopoulos, Fotios

2002-02-01

250

All-printed and transparent single walled carbon nanotube thin film transistor devices  

NASA Astrophysics Data System (ADS)

We present fully transparent single-walled all-carbon nanotube thin film transistors (SWCNT TFT) fabricated using low-cost inkjet printing methods. Such a demonstration provides a platform towards low cost fully printed transparent electronics. The SWCNT TFTs were printed with metallic and semiconducting SWCNT using a room temperature printing process, without the requirement of expensive cleanroom facilities. The unoptimized SWCNT TFTs fabricated exhibited an Ion/off ratio of 92 and mobility of 2.27 cm2V-1s-1 and transmissivity of 82%. The combination of both high electrical performance and high transparency make all-SWCNT TFTs desirable for next generation transparent display backplanes and products such as Google Glass.

Sajed, Farzam; Rutherglen, Christopher

2013-09-01

251

Dysprosium-Catalyzed Growth of Single-Walled Carbon Nanotube Arrays on Substrates  

PubMed Central

In this letter, we report that dysprosium is an effective catalyst for single-walled carbon nanotubes (SWNTs) growth via a chemical vapor deposition (CVD) process for the first time. Horizontally superlong well-oriented SWNT arrays on SiO2/Si wafer can be fabricated by EtOH-CVD under suitable conditions. The structure and properties are characterized by scanning electron microscopy, transition electron microscopy, Raman spectroscopy and atomic force microscopy. The results show that the SWNTs from dysprosium have better structural uniformity and better conductivity with fewer defects. This rare earth metal provides not only an alternative catalyst for SWNTs growth, but also a possible method to generate high percentage of superlong semiconducting SWNT arrays for various applications of nanoelectronic device.

2010-01-01

252

Chirality-dependent reactivity of individual single-walled carbon nanotubes.  

PubMed

Electronic characteristics of a single-walled carbon nanotube (SWCNT) strongly depend on minor variations in its atomic arrangement, specifically chirality. Therefore, precise control over nanotube chirality is highly desired for their application. Theoretically, SWCNTs with different structures have different chemical reactivities, which can be further used for their chirality selection. Here, an approach is developed to examine the relationship between the chirality of SWCNTs and their intrinsic chemical reactivity. By oxidizing individual, high-quality, suspended SWCNTs and using the nanobeam electron diffraction technique, it is shown that the reactivity of SWCNTs to O2 is intricately related to their diameters, metallicity, and chiral angles. In particular, even minor differences in chiral angles lead to big differences in their reactivity, which concords with first-principles calculations. Based on the experimental observations, a chirality-dependent reactivity sequence is constructed for SWCNTs. These findings shed light on effective chiral separation of SWCNTs for their practical application in many fields. PMID:23495250

Liu, Bilu; Jiang, Hua; Krasheninnikov, Arkady V; Nasibulin, Albert G; Ren, Wencai; Liu, Chang; Kauppinen, Esko I; Cheng, Hui-Ming

2013-04-22

253

Vertical single-wall carbon nanotube forests as plasmonic heat pipes.  

PubMed

High thermal conductivity of carbon nanotubes (NTs) is attractive for the heat removal applications. However, the problem of efficient thermal coupling to the heater/cooler still needs to be resolved. We study near-field electromagnetic tunneling as a mechanism of heat transfer across the interface. We report interface thermal (Kapitza) conductance between a low-density vertical metallic single-wall NT forest and a quartz substrate on the order of 50 MW/Km(2) and explain it by strong electromagnetic interaction and near-field entanglement between the surface phonon-polaritons in the polar dielectric and the NT plasmons. We predict that the thickness of the NT film can be tweaked to the resonance wavelength of these entangled modes for performance optimization of nanocarbon thermal interconnects. PMID:22480248

Nemilentsau, Andrei M; Rotkin, Slava V

2012-05-22

254

Electron spin resonance signal of Luttinger liquids and single-wall carbon nanotubes.  

PubMed

A comprehensive theory of electron spin resonance (ESR) for a Luttinger liquid state of correlated metals is presented. The ESR measurables such as the signal intensity and the linewidth are calculated in the framework of Luttinger liquid theory with broken spin rotational symmetry as a function of magnetic field and temperature. We obtain a significant temperature dependent homogeneous line broadening which is related to the spin-symmetry breaking and the electron-electron interaction. The result crosses over smoothly to the ESR of itinerant electrons in the noninteracting limit. These findings explain the absence of the long-sought ESR signal of itinerant electrons in single-wall carbon nanotubes when considering realistic experimental conditions. PMID:18851238

Dóra, B; Gulácsi, M; Koltai, J; Zólyomi, V; Kürti, J; Simon, F

2008-09-01

255

Collective electronic excitations in magnetically aligned single wall carbon nanotubes studied by Raman spectroscopy  

NASA Astrophysics Data System (ADS)

Samples with magnetically aligned single wall carbon nanotubes (SWNT) have been studied by Raman spectroscopy in the low frequency spectral range: 10 - 700 cm-1. A novel Raman-active electronic collective excitation has been observed. At room temperature the excitation band is at about 30 cm-1. The band dramatically strengthens and softens down to about 15 cm-1 with sample cooling below 50 K. The polarization dependence of the Raman spectra was analyzed for laser excitation energies in resonance with electronic transitions and it was compared to that in the case of non-resonant excitation. Strong anisotropy of Raman response function of the SWNT has been observed: for polarization parallel to the direction of the nanotubes the electronic excitation band is about 4 times stronger than that for the perpendicular direction. The origin of the 1-D electronic excitation in metallic SWNT will be discussed.

Blumberg, G.; Gozar, A.; Dennis, B. S.; Sirenko, A. A.; Eklund, P. C.; Walters, D. A.; Casavant, M. J.; Schmidt, J.; Smalley, R. E.

2001-03-01

256

The Effects of Cs on the Raman Modes of Single Wall Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

We present a theoretical study of the Raman modes in single-wall carbon nanotubes (SWCNTs), and in particular the effects of Cs doping. It was previously shown that alkali-metal doping results in low-frequency modes involving both the radial motion of the tube and alkali-atoms vibrations (N. Bendiab, A. Righi, E. Anglaret, J. L. Suavajol, L. Duclaux, F. Beguin, Chem. Phys. Lett., 339, 305 (2001). Applying a first principles density functional theory approach, we report results for the radial breathing modes of pristine SWCNTs in crystalline-rope and isolated tube forms, validating the method for large diameter tubes, and then discuss the modes for tubes intercalated with Cs at various sites.

Duan, Xiaofeng; Akdim, Brahim; Pachter, Ruth

2003-03-01

257

Highly efficient exfoliation of individual single-walled carbon nanotubes by biocompatible phenoxylated dextran.  

PubMed

Highly efficient exfoliation of individual single-walled carbon nanotubes (SWNTs) was successfully demonstrated by utilizing biocompatible phenoxylated dextran, a kind of polysaccharide, as a SWNT dispersion agent. Phenoxylated dextran shows greater ability in producing individual SWNTs from raw materials than any other dispersing agent, including anionic surfactants and another polysaccharide. Furthermore, with this novel polymer, SWNT bundles or impurities present in raw materials are removed under much milder processing conditions compared to those of ultra-centrifugation procedures. There exists an optimal composition of phenoxy groups (?13.6 wt%) that leads to the production of high-quality SWNT suspensions, as confirmed by UV-vis-nIR absorption and nIR fluorescence spectroscopy. Furthermore, phenoxylated dextran strongly adsorbs onto SWNTs, enabling SWNT fluorescence even in solid-state films in which metallic SWNTs co-exist. By bypassing ultra-centrifugation, this low-energy dispersion scheme can potentially be scaled up to industrial production levels. PMID:23714851

Kwon, Taeyun; Lee, Gyudo; Choi, Hyerim; Strano, Michael S; Kim, Woo-Jae

2013-08-01

258

Three-dimensional polymeric structures of single-wall carbon nanotubes.  

PubMed

We explore by ab initio calculations the possible crystalline phases of polymerized single-wall carbon nanotubes (P-SWNTs) and determine their structural, elastic, and electronic properties. Based on direct cross-linking and intertube sliding-assisted cross-linking mechanisms, we have identified a series of stable three-dimensional polymeric structures for the zigzag nanotubes up to (10,0). Among proposed P-SWNT phases, the structures with favorable diamond-like sp(3) intertube bonding configuration and small tube cross-section distortion are found to be the most energetically stable ones. These polymeric crystalline phases exhibit high bulk and shear moduli superior to SWNT bundles, and show metallic or semiconducting properties depending on the diameter of constituent tubes. We also propose by hydrostatic pressure simulations that the intertube sliding between van der Waals bonded nanotubes may be an effective route to promote the polymerization of SWNTs under pressure. PMID:24880313

Lian, Chao-Sheng; Wang, Jian-Tao

2014-05-28

259

The controlled growth of single walled carbon nanotubes from ordered substrates  

NASA Astrophysics Data System (ADS)

We explore a single walled carbon nanotube (SWNT) growth process starting with an ordered substrate similar to a "bed-of-nails" membrane of SWNTs. The membrane consists of closely packed SWNTs aligned along the normal of the substrate. Each nanotube end is etched open such that a nanometer sized metal particle can be docked to the open end to serve as the catalyst. We have successfully grown SWNTs following this general scheme. The conditions will be optimized to enhance the possibility of growing a continuous fiber with the aid of the van der Waals force between SWNTs. If successful this may present a first step toward the synthesis of continuous fibers of crystalline nanotube materials comprising long, parallel nanotubes in an ordered array that have all the same extraordinary mechanical, chemical, thermal, and electrical properties that SWNT exhibits on the nanometer scale.

Wang, Yuhuang; Kittrell, Carter; Kim, Myung Jong; Brinson, Bruce E.; Ripley, Steve; Ramesh, Sivarajan; Hauge, Robert H.; Smalley, Richard E.

2003-03-01

260

Three-dimensional polymeric structures of single-wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

We explore by ab initio calculations the possible crystalline phases of polymerized single-wall carbon nanotubes (P-SWNTs) and determine their structural, elastic, and electronic properties. Based on direct cross-linking and intertube sliding-assisted cross-linking mechanisms, we have identified a series of stable three-dimensional polymeric structures for the zigzag nanotubes up to (10,0). Among proposed P-SWNT phases, the structures with favorable diamond-like sp3 intertube bonding configuration and small tube cross-section distortion are found to be the most energetically stable ones. These polymeric crystalline phases exhibit high bulk and shear moduli superior to SWNT bundles, and show metallic or semiconducting properties depending on the diameter of constituent tubes. We also propose by hydrostatic pressure simulations that the intertube sliding between van der Waals bonded nanotubes may be an effective route to promote the polymerization of SWNTs under pressure.

Lian, Chao-Sheng; Wang, Jian-Tao

2014-05-01

261

Heteroepitaxial Growth of Single-Walled Carbon Nanotubes from Boron Nitride  

PubMed Central

The growth of single-walled carbon nanotubes (SWCNTs) with predefined structure is of great importance for both fundamental research and their practical applications. Traditionally, SWCNTs are grown from a metal catalyst with a vapor-liquid-solid mechanism, where the catalyst is in liquid state with fluctuating structures, and it is intrinsically unfavorable for the structure control of SWCNTs. Here we report the heteroepitaxial growth of SWCNTs from a platelet boron nitride nanofiber (BNNF), which is composed of stacked (002) planes and is stable at high temperatures. SWCNTs are found to grow epitaxially from the open (002) edges of the BNNFs, and the diameters of the SWCNTs are multiples of the BN (002) interplanar distance. In situ transmission electron microscopy observations coupled with first principles calculations reveal that the growth of SWCNTs from the BNNFs follows a vapor-solid-solid mechanism. Our work opens opportunities for the control over the structure of SWCNTs by hetero-crystallographic epitaxy.

Tang, Dai-Ming; Zhang, Li-Li; Liu, Chang; Yin, Li-Chang; Hou, Peng-Xiang; Jiang, Hua; Zhu, Zhen; Li, Feng; Liu, Bilu; Kauppinen, Esko I.; Cheng, Hui-Ming

2012-01-01

262

Raman and SERS Studies of Single-walled Carbon Nanotubes and Nanotubes/Conjugated Polymers Composites  

NASA Astrophysics Data System (ADS)

In this paper, we recall the main characteristics of Raman spectra of single-walled carbon nanotubes. We illustrate our studies by results obtained on HiPCO samples on one hand, and ``arc electric'' samples on the other hand by using two different excitation wavelengths. We focus on the peculiarity of observing separately semi-conducting and metallic tubes. We emphasize also the role played by the radial breathing modes whose frequency depends on the tube diameter and on the need to take into account the interactions between tubes when they are in bundles in order to determine accurately the tube diameter distribution. Finally we demonstrate briefly the evidence of using the SERS (surface enhanced Raman scattering) spectroscopy to study reactions at interfaces or between components in nanotubes/conjugated polymers composites.

Lefrant, S.; Buisson, J. P.; Mevellec, J. Y.; Baibarac, M.; Baltog, I.

2007-09-01

263

Golden single-walled carbon nanotubes prepared using double layer polysaccharides bridge for photothermal therapy.  

PubMed

Golden single-walled carbon nanotubes (SWNTs) were prepared by growing gold nanoparticles onto the bilayer polysaccharide functionalized SWNTs. The layer-by-layer self-assembly of sodium alginate and chitosan on SWNTs provided an ideal surface with high density of active metal-binding groups such as amino and carboxylic acid groups, and then an approach of seed growth was adopted to facilitate the formation of gold nanoparticles coated SWNTs. The resulting golden SWNT hybrids have good water dispersibility and biocompatibility and tend to enter cancer cells. Interestingly, they have an enhanced NIR absorption and effectively transfer NIR laser into heat. The material can quickly cause localized hyperthermia, resulting in rapid cell death, and therefore appears to act as a highly effective photothermal converter for cancer ablation. PMID:24606763

Meng, Lingjie; Xia, Wenjian; Liu, Li; Niu, Lvye; Lu, Qinghua

2014-04-01

264

Ethanol sensor development using three-dimensional single-walled carbon nanotube networks  

NASA Astrophysics Data System (ADS)

A novel ethanol sensor using three-dimensional single-walled carbon nanotube networks (3D-SWNTs) with an alkaline electrolyte solution has been developed. A cyclic voltammetry was used to examine the electrochemical response of the sensor. The relationship between response currents and ethanol concentrations was found to be linear for the ethanol concentrations' range from 1 to 5%. The CV performance test showed the best sensitivity was 0.0024 mAmM -1cm-2 with the 3D-SWNT electrode having no Pt particle loading. The Pt-free electrode gave better performance than platinum-coated 3D-SWNTs electrodes did. Since the 3D-SWNTs electrode without using Pt metal loading detects ethanol concentrations (1--5%) with high sensitivity and accuracy, it can lower the fabrication cost for potential commercial application.

Chao, Wan-Jung

265

Single-walled carbon nanotubes/hydroxyapatite coatings on titanium obtained by electrochemical deposition  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanotubes/hydroxyapatite (SWNTs/HA) composite coatings were successfully fabricated by electrochemical deposition technique. Different concentrations of SWNTs were incorporated into the apatite coating by adding functionalized SWNTs into the electrolyte. Homogeneous and crack-free SWNTs/HA composite coatings were achieved and the coatings had higher crystallinity compared to pure HA coating. In addition, the highest bonding strength of the SWNTs/HA coating reached 25.7 MPa, which was nearly 70% higher than that of pure HA coating. The in-vitro cellular biocompatibility tests revealed that SWNTs/HA composite coatings exhibited higher in-vitro bioactivity than that of pure HA coating and pure titanium (Ti). It suggests that SWNTs/HA composite coating may have enormous potential applications in the field of biomaterials, especially for the metal implants.

Pei, Xibo; Zeng, Yongxiang; He, Rui; Li, Zhongjie; Tian, Lingyang; Wang, Jian; Wan, Qianbing; Li, Xiaoyu; Bao, Hong

2014-03-01

266

Heteroepitaxial Growth of Single-Walled Carbon Nanotubes from Boron Nitride  

NASA Astrophysics Data System (ADS)

The growth of single-walled carbon nanotubes (SWCNTs) with predefined structure is of great importance for both fundamental research and their practical applications. Traditionally, SWCNTs are grown from a metal catalyst with a vapor-liquid-solid mechanism, where the catalyst is in liquid state with fluctuating structures, and it is intrinsically unfavorable for the structure control of SWCNTs. Here we report the heteroepitaxial growth of SWCNTs from a platelet boron nitride nanofiber (BNNF), which is composed of stacked (002) planes and is stable at high temperatures. SWCNTs are found to grow epitaxially from the open (002) edges of the BNNFs, and the diameters of the SWCNTs are multiples of the BN (002) interplanar distance. In situ transmission electron microscopy observations coupled with first principles calculations reveal that the growth of SWCNTs from the BNNFs follows a vapor-solid-solid mechanism. Our work opens opportunities for the control over the structure of SWCNTs by hetero-crystallographic epitaxy.

Tang, Dai-Ming; Zhang, Li-Li; Liu, Chang; Yin, Li-Chang; Hou, Peng-Xiang; Jiang, Hua; Zhu, Zhen; Li, Feng; Liu, Bilu; Kauppinen, Esko I.; Cheng, Hui-Ming

2012-12-01

267

Heteroepitaxial growth of single-walled carbon nanotubes from boron nitride.  

PubMed

The growth of single-walled carbon nanotubes (SWCNTs) with predefined structure is of great importance for both fundamental research and their practical applications. Traditionally, SWCNTs are grown from a metal catalyst with a vapor-liquid-solid mechanism, where the catalyst is in liquid state with fluctuating structures, and it is intrinsically unfavorable for the structure control of SWCNTs. Here we report the heteroepitaxial growth of SWCNTs from a platelet boron nitride nanofiber (BNNF), which is composed of stacked (002) planes and is stable at high temperatures. SWCNTs are found to grow epitaxially from the open (002) edges of the BNNFs, and the diameters of the SWCNTs are multiples of the BN (002) interplanar distance. In situ transmission electron microscopy observations coupled with first principles calculations reveal that the growth of SWCNTs from the BNNFs follows a vapor-solid-solid mechanism. Our work opens opportunities for the control over the structure of SWCNTs by hetero-crystallographic epitaxy. PMID:23240076

Tang, Dai-Ming; Zhang, Li-Li; Liu, Chang; Yin, Li-Chang; Hou, Peng-Xiang; Jiang, Hua; Zhu, Zhen; Li, Feng; Liu, Bilu; Kauppinen, Esko I; Cheng, Hui-Ming

2012-01-01

268

Analysis of Stress Responsive Genes Induced by Single-Walled Carbon Nanotubes in BJ Foreskin Cells  

PubMed Central

Nanotechnology is finding its use as a potential technology in consumer products, defense, electronics, and medical applications by exploiting the properties of nanomaterials. Single-walled carbon nanotubes are novel forms of these nanomaterials with potential for large applications. However, the toxicity studies on this material are not explored in detail and therefore limiting its use. It has been earlier reported that single-walled carbon nanotubes induces oxidative stress and also dictates activation of specific signaling pathway in keratinocytes. The present study explores the effect of single-walled carbon nanotubes on stress genes in human BJ Foreskin cells. The results show induction of oxidative stress in BJ Foreskin cells by single-walled carbon nanotubes and increase in stress responsive genes. The genes included inducible genes like HMOX1, HMOX2, and Cyp1B1. In addition we validated increase for four genes by SWCNT, namely ATM, CCNC, DNAJB4, and GADD45A by RT-PCR. Moreover results of the altered stress related genes have been discussed and that partially explains some of the toxic responses induced by single-walled carbon nanotubes.

Sarkar, Shubhashish; Sharma, Chidananda; Yog, Rajeshwari; Periakaruppan, Adaikkappan; Jejelowo, Olufisayo; Thomas, Renard; Barrera, Enrique V.; Rice-Ficht, Allison C.; Wilson, Bobby L.; Ramesh, Govindarajan T.

2009-01-01

269

Systematic Conversion of Single Walled Carbon Nanotubes into n-type Thermoelectric Materials by Molecular Dopants  

PubMed Central

Thermoelectrics is a challenging issue for modern and future energy conversion and recovery technology. Carbon nanotubes are promising active thermoelectic materials owing to their narrow bandgap energy and high charge carrier mobility, and they can be integrated into flexible thermoelectrics that can recover any waste heat. We here report air-stable n-type single walled carbon nanotubes with a variety of weak electron donors in the range of HOMO level between ca. ?4.4?eV and ca. ?5.6?eV, in which partial uphill electron injection from the dopant to the conduction band of single walled carbon nanotubes is dominant. We display flexible films of the doped single walled carbon nanotubes possessing significantly large thermoelectric effect, which is applicable to flexible ambient thermoelectric modules.

Nonoguchi, Yoshiyuki; Ohashi, Kenji; Kanazawa, Rui; Ashiba, Koji; Hata, Kenji; Nakagawa, Tetsuya; Adachi, Chihaya; Tanase, Tomoaki; Kawai, Tsuyoshi

2013-01-01

270

Isotherm, thermodynamic, kinetics, and adsorption mechanism studies of Ethidium bromide by single-walled carbon nanotube and carboxylate group functionalized single-walled carbon nanotube.  

PubMed

The studies of kinetics and thermodynamics of adsorption of Ethidium bromide in aqueous solutions on single-walled carbon nanotube (SWCNT) and carboxylate group functionalized single-walled carbon nanotube (SWCNT-COOH) surfaces were by UV-Vis spectroscopy. The adsorption kinetics for SWCNT-COOH and SWCNTs were well described by a intra-particle diffusion model, while Langmuir, Freundlich, Harkins-Jura, and Halsey isotherms described the adsorption isotherms, and the adsorption thermodynamic parameters of equilibrium constant (K0), standard free energy (?G0), standard enthalpy (?H0), and standard entropy changes (?S0) were measured. The maximum surface coverage for SWCNTs is 36.10% and for SWCNT-COOH is 38.42%. The values of ?H0 and ?G0 suggested that the adsorption of EtBr on SWCNT-COOH and SWCNTs was endothermic and spontaneous. The adsorption of EtBr on SWCNT-COOH is more than SWCNTs surfaces. PMID:23261335

Moradi, Omid; Fakhri, Ali; Adami, Saeideh; Adami, Sepideh

2013-04-01

271

The calculations of phonon dispersion relations for single-wall carbon armchair and zigzag nanotubes.  

PubMed

A 3D single-wall carbon nanotube can be viewed as a 2D graphite sheet rolled into a 3D cylinder. In the study of dispersion relations of carbon nanotubes, the consistent force parameters for 2D graphite sheets have to be modified to include the curvature effect. The present paper reports a series of calculations of phonon dispersion relations for single-wall carbon armchair, zigzag nanotube in which the curvature effect has been properly treated. The symmetry of crystal vibration mode at the centre of Brillouin zone is analyzed based on our numeric results and the structure symmetry of the nanotubes. PMID:17329162

Wang, Yufang; Zhang, Bin; Jin, Qinghua; Li, Baohui; Ding, Datong; Cao, Xuewei

2007-12-31

272

Theoretical study of work function of conducting single-walled carbon nanotubes by a non-relativistic field theory approach  

Microsoft Academic Search

We study a non-relativistic many-fermion system on a small cylindrical surface. The interaction between the fermions is modeled as an attractive two-body contact effective potential, which allows binding of fermions on the cylinder surface. The N-fermion model is solved in a self-consistent Hartree–Fock (HF) approximation, and is applied to study the electronic properties of metallic single-walled carbon nanotubes (SWCNT). The

C. E. Cordeiro; A. Delfino; T. Frederico

2009-01-01

273

Amphoteric doping of single-wall carbon-nanotube thin films as probed by optical absorption spectroscopy  

Microsoft Academic Search

We have separately probed the doping behavior of semiconducting (S) and metallic (M) single-wall carbon-nanotube (SWNT) films, by optical absorption and dc resistance (R) measurements. Either electron acceptors (Br2, I2) or donors (K, Cs) were used as dopants with controlled stoichiometry. Disappearance of absorption bands at 0.68, 1.2, and 1.8 eV, and concomitant decrease of R by doping have been

S. Kazaoui; N. Minami; R. Jacquemin; H. Kataura; Y. Achiba

1999-01-01

274

Resonant micro-Raman spectroscopy of aligned single-walled carbon nanotubes on a-plane sapphire  

Microsoft Academic Search

Resonant micro-Raman spectroscopy was employed to characterize aligned single-walled carbon nanotubes grown on a-plane sapphire to address the alignment mechanism, the metal-to-semiconductor ratio, and the substrate surface influence in nanotube alignment and straightness. Nanotubes aligned predominantly following the [1100] direction on the a-plane instead of the atomic step direction. Detailed analysis of radial breathing mode (RBM) and G bands revealed

Lewis Gomez-de Arco; Bo Lei; Stephen Cronin; Chongwu Zhou

2008-01-01

275

Synthesis and chemical modification of single-walled carbon nanotubes and inorganic nanowires  

Microsoft Academic Search

This dissertation describes the study of single-walled carbon nanotubes (SWNTs), inorganic nanowires, and carbon aerogels. A novel catalyst of iron\\/molybdenum nanoparticles supported on alumina aerogel was developed for CVD synthesis of SWNTs. Using this catalyst, the yield of SWNTs was enhanced by at least three times compared to previously reported best results. The highest yield of SWNTs was achieved when

Bo Zheng

2002-01-01

276

Influence of catalyst supporters on catalyst nanoparticles in synthesis of single-walled carbon nanotubes  

Microsoft Academic Search

It is important to understand catalytic reactions involved in synthesizing carbon nanotubes. Usually, catalysts are used with supporters for better stability and influences of supporters on catalysis is negligible; however, catalysts used for synthesizing single-walled carbon nanotubes are too small to neglect their influence. Here, we experimentally investigated efficiencies of commonly used catalyst supporters such as magnesium oxide, zeolite, and

Shuhei Inoue; Kazuya Nomura; Yukihiko Matsumura

2009-01-01

277

Material incorporation inside single-walled carbon nanotubes using plasma-ion irradiation method  

Microsoft Academic Search

An original approach using plasma technology has been performed in order to develop novel functional nanocarbons such as fullerenes (C60) and carbon nanotubes. Fully ionized plasmas, which consist of alkali positive ions, fullerene negative ions, and a small fraction of residual electrons have been produced. When positive or negative bias voltages are applied to single-walled carbon nanotubes (SWNTs) in the

Rikizo Hatakeyama; Goo-Hwan Jeong; Takamichi Hirata

2004-01-01

278

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

Microsoft Academic Search

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

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

2007-01-01

279

Processing and assessment of poly(butylene terephthalate) nanocomposites reinforced with oxidized single wall carbon nanotubes  

Microsoft Academic Search

Thermoplastic composites with carbon nanotubes (CNT) have a great potential as structural material because of their superior mechanical properties and ease of processing. The objective of this report is to evaluate the effect of oxidized single walled carbon nanotubes (oSWCNT) on the properties of poly(butylene terephthalate) (PBT) thermoplastic polymers, as a function of their weight content. The nanocomposites are obtained

G. Broza; M. Kwiatkowska; Z. Ros?aniec; K. Schulte

2005-01-01

280

Electrical properties of Poly(ethylene glycol dimethacrylate-n-vinyl imidazole)\\/Single Walled Carbon Nanotubes\\/n-Si Schottky diodes formed by surface polymerization of Single Walled Carbon Nanotubes  

Microsoft Academic Search

In this paper we report the electrical characteristics of the Schottky diodes formed by surface polymerization of the Poly(ethylene glycol dimethacrylate-n-vinyl imidazole)\\/Single Walled Carbon Nanotubes on n-Si. The Single Walled Carbon Nanotubes were synthesized by CVD method. The main electrical properties of the Poly(ethylene glycol dimethacrylate-n-vinyl imidazole)\\/Single Walled Carbon Nanotubes\\/n-Si have been investigated through the barrier heights, the ideality factors

Ali Kara; Nalan Tekin; Saadet Beyaz; Hakan Köçkar

281

Achieving ultrahigh concentrations of fluorescent single-walled carbon nanotubes using small-molecule viscosity modifiers.  

PubMed

Surfactant dispersion is a well-established method for stabilizing individual single-walled carbon nanotubes in aqueous solutions. However, achieving high concentrations of individually dispersed nanotubes with this technique has proven challenging. Here it is demonstrated that the introduction of viscosity-enhancing compounds such as sucrose can increase the maximum concentration of surfactant-dispersed single-walled carbon nanotubes by more than a factor of 100 while still retaining the optical properties of individual nanotubes. When these solutions are used as inks for methods such as inkjet printing, they retain their fluorescent properties even after the ink has dried. PMID:22930552

Leeds, Jarrett D; Fourkas, John T; Wang, Yuhuang

2013-01-28

282

High frequency performance of individual and arrays of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We have studied the high frequency performance limits of single-walled carbon nanotube (SWNT) transistors in the diffusive transport regime limited by the acoustic phonon scattering. The relativistic band structure of single-walled carbon nanotubes combined with the acoustic phonon scattering provides an analytical model for the charge transport of the radio frequency transistors. We were able to obtain the intrinsic high frequency performance such as the cut-off frequency and the linearity of the SWNT transistors. We have extended our model to include transistors based on arrays of SWNTs. The effect of electrostatic screening in a dense array of SWNTs on the cut-off frequency is studied.

Balci, Osman; Kocabas, Coskun

2012-06-01

283

Photochemical modification of single-walled carbon nanotubes using HPHMP photoinitiator for enhanced organic solvent dispersion  

Microsoft Academic Search

Photochemical modification of single-walled carbon nanotubes (SWCNTs) was carried out by covalent attachment of 2-propanol-2-yl\\u000a radicals on the surface of SWCNTs, which were engendered by the photolysis of 1-[4-(2-Hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one\\u000a (HPHMP) under ultraviolet (UV) light. Pristine single-walled carbon nanotubes (p-SWCNTs) were dispersed in acetone along with\\u000a HPHMP photoinitiator. After that, the mixture was irradiated by UV light to generate the free

Mirza Nadeem Ahmad; Maria Nadeem; Yuhong Ma; Wantai Yang

2010-01-01

284

Energetics, structure, mechanical and vibrational properties of single-walled carbon nanotubes  

Microsoft Academic Search

In this paper, we present extensive molecular mechanics and molecular dynamics studies on the energy, structure, mechanical and vibrational properties of single-wall carbon nanotubes. In our study we employed an accurate interaction potential derived from quantum mechanics. We explored the stability domains of circular and collapsed cross section structures of armchair 0957-4484\\/9\\/3\\/007\\/img2, zigzag 0957-4484\\/9\\/3\\/007\\/img3, and chiral 0957-4484\\/9\\/3\\/007\\/img4 isolated single-walled carbon

Guanghua Gao; Tahir Cagin; William A. Goddard III

1998-01-01

285

Polyglycerol-derived amphiphiles for single walled carbon nanotube suspension  

NASA Astrophysics Data System (ADS)

Inspired by the commercially available SDS surfactant, a new polyglycerol-derived amphiphile has been synthesized for functionalizing carbon nanotubes. SDS' sulphate group was replaced by a polyglycerol dendron. The steric hindrance offered by the dendrons makes the compound much more efficient than SDS in isolating and stabilizing nanotubes in solution. Further amphiphiles have been synthesized by adding small aromatic moieties between head and tail groups. We show that this addition leads to selective interaction between surfactants and carbon nanotubes. Excitation photoluminescence and optical absorption spectroscopy analysis confirm the change in the distribution of nanotubes' chiralities in suspension, depending on the amphiphile.

Setaro, A.; Popeney, C. S.; Trappmann, B.; Datsyuk, V.; Haag, R.; Reich, S.

2010-06-01

286

Single-walled carbon nanotube biosensor for detection of E. coli  

Microsoft Academic Search

Single-walled carbon nanotube biosensor was developed for the detection of Escherichia coli using aptamer-functionalized carbon nanotube field effect transistors. RNA-based E. coli aptamer was chosen by the SELEX process, and immobilized on sidewalls of carbon nanotubes by CDI-Tween 20 linking molecules. The electrical response of the carbon nanotube sensor before and after the binding of E. coli aptamer and E.

Hye-Mi So; Dong-Won Park; Yo-Han Kim; Sun Young Choi; Young Mi Kim; Sung Chun Kim; Beom Soo Kim; Jeong-O Lee

2006-01-01

287

Low temperature conductive tip scanning of single walled carbon nanotubes  

Microsoft Academic Search

The low temperature conductance measurements of Carbon Nanotubes (CNT), and other nanostructures, are commonly conducted on samples with fixed leads, which provide the global information about the nanostructure's electronic properties. To measure local electronic properties, we have built a conductive tip Atomic Force Microscope (AFM). This AFM allows us to place a mobile contact anywhere along the tube and carry

Matthew Prior

2006-01-01

288

Carbon Single-Wall Nanatube Growth in a Volumetrically Confined Arc Discharge System  

SciTech Connect

Carbon nanotubes hold significant promise for a vast number of materials applications due to their unique mechanical, electrical, and gas storage properties. Although carbon single-wall nanotubes (SWNTs) have been synthesized since 1993 by the arc discharge method, and numerous other synthesis methods have since been developed, no method has yet produced 100% pure carbon nanotubes. Instead, a significant amount of impurities—various carbon structures and metal catalysts—are present in the raw soot. While arc discharge was the first method for SWNT synthesis, it also produces more impure raw soot in comparison to the more recently developed laser vaporization, which has produced the purest raw soot to date but is much slower. Geometry and thermal gradient are appreciably different between traditional arc discharge systems and laser vaporization systems. We report that, by incorporating some characteristics inherent to a laser vaporization system into an arc discharge system, improvement in the yield of SWNT raw soot may be achieved. This is accomplished by confining the arc within a 50 mm diameter quartz tube, similar to laser vaporization. We find through transmission electron microscopy and Raman spectroscopy that SWNTs are made in significant numbers in this confined arc discharge system, comparable to laser vaporization synthesized material. Further study is, however, required to prove reproducibility and attain an exact value for the purity of the produced raw soot.

Franz, K.J.; Alleman, J.L.; Jones, K.M.; Dillon, A.C.; Heben, M.J.

2004-01-01

289

Physical properties of single walled carbon nanotubes studied by optical spectroscopy  

NASA Astrophysics Data System (ADS)

In this dissertation, we present our recent studies of the physical properties of single walled carbon nanotubes (SWCNTs) using optical spectroscopy. The thesis is composed of four main sections focusing on different aspects of the physical properties of SWCNTs: electronic properties, mechanical properties, phonon properties, and ultrafast dynamics. We describe the ways in which we have applied Rayleigh spectroscopy to probe the modification of the nanotubes' electronic structure by applying strain or by the deposition of organic molecules on the nanotubes. These two methods effectively tune the band structure of the SWCNTs. Uniaxial strain applied to the suspended SWCNTs changes the electronic structure differently depending on the, chiral index of the nanotube. When we deposited organic molecules onto different semiconducting nanotubes, the electronic resonances all underwent a similar redshift. We also describe the first experimental determination of the Young's modulus of an isolated individual carbon nanotubes of known chirality. The absence of any significant dependence of the nanotubes' elastic properties on their structure confirms previous theoretical predictions. We also demonstrated a mechanical oscillator comprised of carbon nanotubes that operates in the nonlinear regime. A prototype of a bi-stable mechanical device is presented. We further present our study of the Raman spectra of the high-energy vibrational modes (HEMs) in metallic nanotubes. We clarified a long-standing controversy by showing that the broadening observed in metallic nanotubes' HEM is intrinsic and directly related to the coupling between phonons and low-energy electronic excitations. We also describe the way we studied ultrafast dynamics in individual carbon nanotubes by detecting transient Rayleigh scattering. We probed the ultrafast dynamics at the single nanotube level for both metallic and semiconducting nanotubes. We found that the lifetime of electronic excitations induced by pump pulses are > 3ps and < 1ps for semiconducting nanotube and metallic nanotube respectively. We also deduced that the phonons produced in this transient process are localized, while the electronic excitation migrates rapidly on a micron scale.

Wu, Yang

290

Gas detection mechanism for single-walled carbon nanotube networks  

NASA Astrophysics Data System (ADS)

We study field-effect transistors fabricated with carbon nanotube (CNT) networks to determine whether the gas sensing mechanism is due to molecules adsorbed on the nanotubes, or changes at the interface between the nanotubes and the contacts. Our previous work showed that in devices made with isolated CNT, the response to nitrogen dioxide was mainly due to the contact interfaces [1]. Here, we focus on CNT networks and use SU-8 layers patterned with e-beam lithography to passivate the contact interfaces, while leaving the network exposed. We look to investigate possible differences in sensing mechanism for devices made with isolated tubes versus networks. [4pt] [1] J. Zhang, A. Boyd, A. Tselev, M. Paranjape, and P. Barbara, Mechanism of NO2 detection in carbon nanotube field effect transistor chemical sensors, Applied Physics Letters 88, 123112-123115 (2006)

Boyd, Anthony; Dube, Isha; Fedorov, Georgy; Paranjape, Makarand; Barbara, Paola

2011-03-01

291

A Molecular Dynamics Study on the Exfoliation of Single Walled Carbon Nanotubes in Supercritical Carbon Dioxide  

NASA Astrophysics Data System (ADS)

Carbon nanotubes (CNTs) could be used in various technological applications due to their structural, electrical and mechanical properties. However, in order to get the theoretically predicted benefits, nanotubes have to be succesfully dispersed in the polymer matrix. Supercritical fluids were previously shown to result in good dispersion of nanofillers (in the case of clays and spherical nanofillers). In the current study, we investigated the potential use of supercritical carbon dioxide to unbundle single walled carbon nanotubes via molecular dynamics simulations. Various carbon nanotube systems were simulated with XenoView simulation software, and the effect of surface modification of nanotube with CO2-philic chemicals was investigted on nanotube dispersion. Results showed that surface modification of nanotubes improves their dispersion in supercritical carbon dioxide.

Senturk-Ozer, Semra; Rende, Deniz; Baysal, Nihat; Ozisik, Rahmi

2012-02-01

292

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

PubMed

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

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

2012-07-01

293

Selective polycarboxylation of semiconducting single-walled carbon nanotubes by reductive sidewall functionalization.  

PubMed

The efficient and controllable synthesis, the detailed characterization, and the chemical postfunctionalization of polycarboxylated single-walled carbon nanotubes SWCNT(COOH)(n) are reported. This innovative covalent sidewall functionalization method is characterized by (a) the preservation of the integrity of the entire ?-framework of SWCNTs; (b) the possibility of achieving very high degrees of addition; (c) control of the functionalization degrees by the variation of the reaction conditions (reaction time, ultrasonic treatment, pressure); (d) the identification of conditions for the selective functionalization of semiconducting carbon nanotubes, leaving unfunctionalized metallic tubes behind; (e) the proof that the introduced carboxylic acid functionalities can serve as versatile anchor points for the coupling to functional molecules; and (f) the application of a subsequent thermal degradation step of the functionalized semiconducting tubes leaving behind intact metallic SWCNTs. Functional derivatives have been characterized in detail by means of Raman, UV-vis/nIR, IR, and fluorescence spectroscopy as well as by thermogravimetric analysis combined with mass spectrometry, atomic force microscopy, and zeta-potential measurements. PMID:22035086

Gebhardt, Benjamin; Hof, Ferdinand; Backes, Claudia; Müller, Matthias; Plocke, Thomas; Maultzsch, Janina; Thomsen, Christian; Hauke, Frank; Hirsch, Andreas

2011-12-01

294

Hydrogen Adsorption in Purified Single Walled Carbon Nanotubes (SWNTs)  

NASA Astrophysics Data System (ADS)

We report results of H2 adsorption in SWNTs (produced by the arc-discharge method and purified), at 77K and moderate pressure (<20 atm.) We characterized the materials by HRTEM, Raman Spectroscopy and N2 adsorption isotherms, in order to determine the morphology and texture of sample for gas storage. HRTEM and temperature programed oxidation (TPO) results showed that the purified samples were clean from amorphous carbon, multishell carbons (MSC) and catalyst particles. In certain cases, HRTEM shows the tubes are in tact, while in other cases, it is observed that openings in the wall are created, and/or the tubes are cut into short tubelets. N2 adsorption studies allow us to obtain the specific surface area (SSA) and approximate pore size distribution. After purification, the SSA increases from ~280 m^2/g to 470 m^2/g. Measurements of H2 adsorption were performed in order to evaluate the adsorption capacity of the nanotubes at 77K and below 20 bar. We found up to 6 wt% H2 adsorbed in our purified material. (Work supported by Honda Motors R&D Co.)

Pradhan, B. K.; Harutyunyan, A. R.; Sumanasekera, G. U.; Eklund, P. C.; Tokune, T.; Fujiwara, Y.

2001-03-01

295

Nanoscale soldering of axially positioned single-walled carbon nanotubes: a molecular dynamics simulation study.  

PubMed

The miniaturization of electronics devices into the nanometer scale is indispensable for next-generation semi-conductor technology. Carbon nanotubes (CNTs) are considered to be the promising candidates for future interconnection wires. To study the carbon nanotubes interconnection during nanosoldering, the melting process of nanosolder and nanosoldering process between single-walled carbon nanotubes are simulated with molecular dynamics method. As the simulation results, the melting point of 2 nm silver solder is about 605 K because of high surface energy, which is below the melting temperature of Ag bulk material. In the nanosoldering process simulations, Ag atoms may be dragged into the nanotubes to form different connection configuration, which has no apparent relationship with chirality of SWNTs. The length of core filling nanowires structure has the relationship with the diameter, and it does not become longer with the increasing diameter of SWNT. Subsequently, the dominant mechanism of was analyzed. In addition, as the heating temperature and time, respectively, increases, more Ag atoms can enter the SWNTs with longer length of Ag nanowires. And because of the strong metal bonds, less Ag atoms can remain with the tight atomic structures in the gap between SWNT and SWNT. The preferred interconnection configurations can be achieved between SWNT and SWNT in this paper. PMID:24392855

Cui, Jianlei; Yang, Lijun; Zhou, Liang; Wang, Yang

2014-02-12

296

Comparison of double-walled with single-walled carbon nanotube electrodes by electrochemistry  

Microsoft Academic Search

Double-walled carbon nanotubes (DWCNTs) were selectively functionalised by treatment with concentrated nitric and sulphuric acid, resulting in carboxylated outer and pristine inner tube constituents. The functionalised DWCNTs were then incorporated into two types of pre-existing carbon nanotube (CNT) electrode platforms, and the performance of each was compared to single-walled carbon nanotubes (SWCNTs). To make the CNT electrode platforms DWCNTs were

Katherine E. Moore; Benjamin S. Flavel; Amanda V. Ellis; Joseph G. Shapter

2011-01-01

297

Anisotropic Thermal Properties of Single-Wall Carbon Nanotube Reinforced Nanoceramics  

SciTech Connect

Dense single-wall carbon nanotube (SWCNT) reinforced alumina nanocomposites have been fabricated by novel spark-plasma-sintering (SPS) technique. Anisotropic thermal properties have been found in the carbon nanotube composites. The introduction of ropes of SWCNT gives rise to a decrease of the transverse thermal diffusivity with increasing carbon nanotube content while it does not change the in-plane thermal diffusivity. This is scientifically interesting and technologically important for the development of materials for novel thermal barrier coatings.

Zhan, Guodong; Kuntz, Joshua D.; Wang, Hsin; Wang, Chong M.; Mukherjee, Amiya K.

2004-07-01

298

Electronic properties of Cs-intercalated single-walled carbon nanotubes derived from nuclear magnetic resonance  

NASA Astrophysics Data System (ADS)

We report on the electronic properties of Cs-intercalated single-walled carbon nanotubes (SWNTs). A detailed analysis of the 13C and 133Cs nuclear magnetic resonance (NMR) spectra reveals an increased metallization of the pristine SWNTs under Cs intercalation. The 'metallization' of CsxC materials where x=0-0.144 is evidenced from the increased local electronic density of states (DOS) n(EF) at the Fermi level of the SWNTs as determined from spin-lattice relaxation measurements. In particular, there are two distinct electronic phases called ? and ? and the transition between these occurs around x=0.05. The electronic DOS at the Fermi level increases monotonically at low intercalation levels x<0.05 (?-phase), whereas it reaches a plateau in the range 0.05<=x<=0.143 at high intercalation levels (?-phase). The new ?-phase is accompanied by a hybridization of Cs(6s) orbitals with C(sp2) orbitals of the SWNTs. In both phases, two types of metallic nanotubes are found with a low and a high local n(EF), corresponding to different local electronic band structures of the SWNTs.

Abou-Hamad, E.; Goze-Bac, C.; Nitze, F.; Schmid, M.; Aznar, R.; Mehring, M.; Wågberg, T.

2011-05-01

299

Single walled carbon nanotube growth and chirality dependence on catalyst composition.  

PubMed

Vertical arrays of single walled carbon nanotubes (VA-SWNTs) were grown using bi-metallic nanoparticle pro-catalysts. Iron oxide particles were doped with varying quantities of first row transition metals (Mn, Co, Ni, and Cu) for a comparative study of the growth of nanotubes. VA-CNT samples were verified using scanning electron microscopy, and characterized using resonance Raman spectroscopy. The length of the VA-CNTs is used as a measure of catalyst activity: the presence of dopants results in a change in the CNT length and length distribution. Cross correlation of the Raman spectra reveal variations in the distribution of radial breathing mode peaks according to the pro-catalyst composition. The formation of various chirality nanotubes is constant between repetitive runs with a particular catalyst, but may be controlled by the identity and concentration of the metal dopants within the iron catalyst. These results demonstrate that the composition of the catalyst is a major driving force toward type selective growth of nanotubes. PMID:23974219

Orbaek, Alvin W; Owens, Andrew C; Crouse, Christopher C; Pint, Cary L; Hauge, Robert H; Barron, Andrew R

2013-10-21

300

Discotic ionic liquid crystals of triphenylene as dispersants for orienting single-walled carbon nanotubes.  

PubMed

Orient and conduct: Triphenylene-based discotic ionic liquid crystals (ILCs) with six imidazolium ion pendants can disperse pristine single-walled carbon nanotubes (SWNTs). When the ILC is columnarly assembled, doping with SWNTs results in macroscopic homeotropic columnar orientation. Combination of shear and annealing treatments gives rise to three different orientation states, which determine the anisotropy of electrical conduction. PMID:22821897

Lee, Jeongho Jay; Yamaguchi, Akihisa; Alam, Md Akhtarul; Yamamoto, Yohei; Fukushima, Takanori; Kato, Kenichi; Takata, Masaki; Fujita, Norifumi; Aida, Takuzo

2012-08-20

301

Zeta-Potential Measurements of Surfactant-Wrapped Individual Single-Walled Carbon Nanotubes  

Microsoft Academic Search

A systematic study of the zeta (œ)-potential distribution of surfactant-wrapped individual single-walled carbon nanotubes (SWNTs) dissolved in water is presented here. The surface charge on the SWNT micelles, as measured by the œ-potential, has implications for the stability of the dispersions and for the electrophoretic and dielectrophoretic assembly and alignment of SWNTs. Very highly charged SWNTs are obtained by dispersing

Brian White; Sarbajit Banerjee; Stephen O'Brien; Nicholas J. Turro; Irving P. Herman

2007-01-01

302

Nanomechanical characterization of single-walled carbon nanotube reinforced epoxy composites  

Microsoft Academic Search

Nanomechanical properties of single-walled carbon nanotube (SWNT) reinforced epoxy composites with varying weight percentage (0, 1, 3, and 5 wt%) of nanotubes were measured by nanoindentation and nanoscratch techniques. Hardness and elastic modulus were measured using a nanoindenter. Scratch resistance and scratch damage were studied using the AFM tip sliding against the SWNT reinforced sample surfaces. Nanoindentation\\/nanoscratch deformation and fracture

Xiaodong Li; Hongsheng Gao; Wally A. Scrivens; Dongling Fei; Xiaoyou Xu; Michael A. Sutton; Anthony P. Reynolds; Michael L. Myrick

2004-01-01

303

On the Applicability of Single-Walled Carbon Nanotubes as VLSI Interconnects  

Microsoft Academic Search

This paper presents a comprehensive study of the applicability of single-walled carbon nanotubes (SWCNTs) as interconnects in nanoscale integrated circuits. A detailed analysis of SWCNT interconnect resistance (considering its dependence on all physical parameters, as well as factors affecting the contact resistance), the first full 3-D capacitance simulations of SWCNT bundles for realistic very large scale integration (VLSI) interconnect dimensions,

Navin Srivastava; Hong Li; Franz Kreupl; Kaustav Banerjee

2009-01-01

304

Single walled carbon nano-tube, ferroelectric liquid crystal composites: Excellent diffractive tool  

Microsoft Academic Search

We present a switchable grating based on chiral single walled carbon nano-tube (SWCNT) doped ferroelectric liquid crystals (FLCs). The presence of SWCNTs improves the diffraction profile of the pure FLC. The diffraction efficiency, i.e., the ratio of intensities of first order and zero order maxima is more than 100% for the higher concentration of SWCNTs in pure FLC. This phenomenon

A. K. Srivastava; E. P. Pozhidaev; V. G. Chigrinov; R. Manohar

2011-01-01

305

Engineered Carbohydrate-Binding Module (CBM) Protein-Suspended Single-Walled Carbon Nanotubes in Water  

SciTech Connect

Engineered protein, CtCBM4, the first carbohydrate-binding module (CBM) protein is successfully used to debundle and suspend single-walled carbon nanotubes (SWNTs) effectively in aqueous solution, which opens up a new avenue in further functionalizing and potential selectively fractionating SWNTs for diverse biology- and/or energy-related applications.

Xu,Q.; Song, Q.; Ai, X.; McDonald, T. J.; Long, H.; Ding. S. Y.; Himmel, M. E.; Rumbles, G.

2009-01-01

306

In vivo biosensing via tissue-localizable near-infrared-fluorescent single-walled carbon nanotubes.  

PubMed

Single-walled carbon nanotubes are particularly attractive for biomedical applications, because they exhibit a fluorescent signal in a spectral region where there is minimal interference from biological media. Although single-walled carbon nanotubes have been used as highly sensitive detectors for various compounds, their use as in vivo biomarkers requires the simultaneous optimization of various parameters, including biocompatibility, molecular recognition, high fluorescence quantum efficiency and signal transduction. Here we show that a polyethylene glycol ligated copolymer stabilizes near-infrared-fluorescent single-walled carbon nanotubes sensors in solution, enabling intravenous injection into mice and the selective detection of local nitric oxide concentration with a detection limit of 1 µM. The half-life for liver retention is 4 h, with sensors clearing the lungs within 2 h after injection, thus avoiding a dominant route of in vivo nanotoxicology. After localization within the liver, it is possible to follow the transient inflammation using nitric oxide as a marker and signalling molecule. To this end, we also report a spatial-spectral imaging algorithm to deconvolute fluorescence intensity and spatial information from measurements. Finally, we demonstrate that alginate-encapsulated single-walled carbon nanotubes can function as implantable inflammation sensors for nitric oxide detection, with no intrinsic immune reactivity or other adverse response for more than 400 days. PMID:24185942

Iverson, Nicole M; Barone, Paul W; Shandell, Mia; Trudel, Laura J; Sen, Selda; Sen, Fatih; Ivanov, Vsevolod; Atolia, Esha; Farias, Edgardo; McNicholas, Thomas P; Reuel, Nigel; Parry, Nicola M A; Wogan, Gerald N; Strano, Michael S

2013-11-01

307

Crosslinked polymer sheaths for dispersing individual single-walled carbon nanotubes in nonaqueous solvents  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanotubes have been suspended individually in water by encasing them in a thin, uniform layer of the crosslinkable polymer poly (N-vinylpyrrolidone-co-allylamine). When this polymer is crosslinked under dilute conditions, the polymer sheath, formerly stabilized by the hydrophobic effect, becomes stable to changes in the solvent system.

Ojha, L. R.; Tchoul, M. N.; Bastola, K. P.; Ausman, K. D.

2013-11-01

308

Transport of Single-Walled Carbon Nanotubes in Porous Media: Filtration Mechanisms and Reversibility  

Microsoft Academic Search

Deposition of nanomaterials onto surfaces is a key process governing their transport, fate, and reactivity in aquatic systems. We evaluated the transport and deposition behavior of carboxyl functionalized single-walled carbon nanotubes (SWNTs) in a well-defined porous medium composed of clean quartz sand over a range of solution chemistries. Our results showthatincreasingsolutionionicstrengthoradditionofcalcium ions result in increased SWNT deposition (filtration). This observation

DEB P. J AISI; NAVID B. S ALEH; RUTH E. B LAKE; MENACHEM E LIMELECH

309

High-performance electronics using dense, perfectly aligned arrays of single-walled carbon nanotubes  

Microsoft Academic Search

Single-walled carbon nanotubes (SWNTs) have many exceptional electronic properties. Realizing the full potential of SWNTs in realistic electronic systems requires a scalable approach to device and circuit integration. We report the use of dense, perfectly aligned arrays of long, perfectly linear SWNTs as an effective thin-film semiconductor suitable for integration into transistors and other classes of electronic devices. The large

Seong Jun Kang; Coskun Kocabas; Taner Ozel; Moonsub Shim; Ninad Pimparkar; Muhammad A. Alam; Slava V. Rotkin; John A. Rogers

2007-01-01

310

Alignment Controlled Growth of Single-Walled Carbon Nanotubes on Quartz Substrates  

Microsoft Academic Search

Single-walled carbon nanotubes (SWNTs) possess extraordinary electrical properties, with many possible applications in electronics. Dense, horizonally aligned arrays of linearly configured SWNTs represent perhaps the most attractive and scalable way to implement this class of nanomaterial in practical systems. Recent work shows that templated growth of tubes on certain crystalline substrates yields arrays with the necessary levels of perfection, as

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

2009-01-01

311

Aligning single-wall carbon nanotubes with an alternating-current electric field  

Microsoft Academic Search

Single-wall carbon nanotubes (SWCNTs) were highly aligned by an external electric field. The results suggest that the alignment of SWCNTs shows significant dependencies on the frequency and the magnitude of the applied electric field. The electric field with 5 MHz straightened out the SWCNTs and created highly oriented samples with fewer large particles. We also discussed the mechanism and applications.

X. Q. Chen; T. Saito; H. Yamada; K. Matsushige

2001-01-01

312

Flexible, transparent single-walled carbon nanotube transistors with graphene electrodes  

Microsoft Academic Search

This paper reports a mechanically flexible, transparent thin film transistor that uses graphene as a conducting electrode and single-walled carbon nanotubes (SWNTs) as a semiconducting channel. These SWNTs and graphene films were printed on flexible plastic substrates using a printing method. The resulting devices exhibited a mobility of ~ 2 cm2 V - 1 s - 1, On\\/Off ratio of

Sukjae Jang; Houk Jang; Youngbin Lee; Daewoo Suh; Seunghyun Baik; Byung Hee Hong; Jong-Hyun Ahn

2010-01-01

313

Quantification of thin graphene sheets contained in spherical aggregates of single-walled carbon nanohorns  

Microsoft Academic Search

Spherical aggregates of single-walled carbon nanohorns (SWNHs) produced by CO2 laser ablation of graphite contain thin graphene sheets (TGSs), and their quantities depend on formation conditions. To adjust laser ablation condition to increase TGS quantities, TGS quantification in products is necessary; however, its method has not been established. We have found that high resolution thermogravimetric analysis (HRTGA) showed SWNHs and

Michiko Irie; Maki Nakamura; Minfang Zhang; Ryota Yuge; Sumio Iijima; Masako Yudasaka

2010-01-01

314

Radial deformation and stability of single-wall carbon nanotubes under hydrostatic pressure  

Microsoft Academic Search

In this paper we have developed a theory of energetics for isolated single-wall carbon nanotubes (SWNTs) deformed in the radial direction, and applied this theory to investigate their deformation characteristics and stability under hydrostatic pressure. The starting point of the theory is the strain energy of SWNTs predicted by ab initio calculations based on the density functional theory (DFT), which

Masayuki Hasegawa; Kazume Nishidate

2006-01-01

315

Ultralow friction and wear behaviour of Ni\\/Y-based single wall carbon nanotubes (SWNTs)  

Microsoft Academic Search

Single wall carbon nanotubes (SWNTs) present interesting tribological properties under boundary lubrication at ambient temperature. Used as additive to PAO base oil, SWNTs lead to a decrease of both friction and wear of antagonist steel surfaces. With only 1 wt% of nanotubes added to polyalphaolefin (PAO), the friction coefficient is 0.08. This result is obtained under several contact pressures (from

L. Joly-Pottuz; F. Dassenoy; B. Vacher; J. M. Martin; T. Mieno

2004-01-01

316

Graphene nanoribbons produced by the oxidative unzipping of single-wall carbon nanotubes  

Microsoft Academic Search

Graphene nanoribbons were synthesized by oxidative unzipping of single-wall carbon nanotubes (SWCNTs). The nanoribbons produced from SWCNTs were characterized using FT-IR, Raman and X-ray photoelectron spectroscopy. For the morphological study of the product obtained from the SWCNT unzipping reaction, transmission electron microscopy and atomic force microscopy were used, confirming the typical graphene nanoribbon structure.

Franco Cataldo; Giuseppe Compagnini; Giacomo Patané; Ornella Ursini; Giancarlo Angelini; Primoz Rebernik Ribic; Giorgio Margaritondo; Antonio Cricenti; Giuseppe Palleschi; Federica Valentini

2010-01-01

317

Solution Casting and Transfer Printing Single-Walled Carbon Nanotube Films  

Microsoft Academic Search

This paper presents methods for solution casting and transfer printing collections of individual single-walled carbon nanotubes (SWNTs) onto a wide range of substrates, including plastic sheets. The deposition involves introduction of a solvent that removes surfactant from a suspension of SWNTs as it is applied to a substrate. The subsequent controlled flocculation (cF) produces films of SWNTs with densities that

Matthew A. Meitl; Yangxin Zhou; Anshu Gaur; Seokwoo Jeon; Monica L. Usrey; Michael S. Strano; John A. Rogers

2004-01-01

318

MICROWAVE-INDUCED RAPID CHEMICAL FUNCTIONALIZATION OF SINGLE-WALLED CARBON NANOTUBES (R830901)  

EPA Science Inventory

Abstract The microwave-induced chemical functionalization of single-walled carbon nanotubes (SWNTs) is reported. The major advantage of this high-energy procedure is that it reduced the reaction time to the order of minutes and the number of steps in the reac...

319

Micro Gas Preconcentrator Made of a Film of Single-Walled Carbon Nanotubes  

Microsoft Academic Search

The development of micro gas preconcentrators is crucial for the realization of miniaturized gas chromatography (micro-GC) systems which are expected to open up new applications such as breath analysis. One of the major problems with the reduction in the preconcentrator size by miniaturization is the availability of a sorbent material having high enough concentration factor. Single-walled carbon nanotubes (SWNTs) are

Shuji Takada; Takashi Nakai; Theerapol Thurakitseree; Junichiro Shiomi; Shigeo Maruyama; Hideki Takagi; Masaki Shuzo; Jean-Jacques Delaunay; Ichiro Yamada

2010-01-01

320

pi -electron theory of transverse optical excitons in semiconducting single-walled carbon nanotubes  

Microsoft Academic Search

We present a quantitative theory of optical absorption polarized transverse to the tube axes in semiconducting single-walled carbon nanotubes. Within one-electron theory, transverse optical absorption occurs at an energy that is exactly in the middle of the two lowest longitudinal absorption energies. For nonzero Coulomb interactions between the pi electrons, transverse optical absorption is to an exciton state that is

Zhendong Wang; Hongbo Zhao; Sumit Mazumdar

2007-01-01

321

Reversible water-solubilization of single-walled carbon nanotubes by polymer wrapping  

Microsoft Academic Search

Single-walled carbon nanotubes (SWNTs) have been solubilized in water by non-covalently associating them with linear polymers, most successfully with polyvinyl pyrrolidone (PVP) and polystyrene sulfonate (PSS). This association is characterized by tight, uniform association of the polymers with the sides of the nanotubes. A general thermodynamic drive for this wrapping is discussed, wherein the polymer disrupts both the hydrophobic interface

Michael J. O'Connell; Peter Boul; Lars M. Ericson; Chad Huffman; Yuhuang Wang; Erik Haroz; Cynthia Kuper; Jim Tour; Kevin D. Ausman; Richard E. Smalley

2001-01-01

322

Polymer-assisted dispersion of single-wall carbon nanotubes for transparent conducting film fabrication  

Microsoft Academic Search

Transparent electrodes, for instance ITO (indium tin oxide), are used in electronic devices such as touch screen, flat panel display, and solar cell technologies. It is costly to pattern and has a tendency to crack when used due to its brittle nature. The development of technologies to deliver low cost flexible alternatives using single walled carbon nanotubes (CNTs) are fledgling

Wei-Chao Chen; Hsiang-Ting Lien; Tzu-Wei Cheng; Kuei-Hsien Chen; Li-Chyong Chen

2010-01-01

323

Aligned single-wall carbon nanotubes in composites by melt processing methods  

Microsoft Academic Search

This Letter describes the production of single-wall carbon nanotube (SWNT) – polymer composites with enhanced mechanical and electrical properties and exceptional nanotube alignment. A combination of solvent casting and melt mixing was used to disperse SWNT materials in poly(methyl methacrylate) (PMMA). Composite films showed higher conductivity along the flow direction than perpendicular to it. Composite fibers were melt spun to

R. Haggenmueller; H. H. Gommans; A. G. Rinzler; J. E. Fischer; K. I. Winey

2000-01-01

324

Conductivity and mechanical properties of well-dispersed single-wall carbon nanotube\\/polystyrene composite  

Microsoft Academic Search

The morphologies, electrical and mechanical properties and structure of polystyrene (PS) composites with varying concentrations of single-wall carbon nanotubes (SWNT) are analyzed. Using Raman spectroscopy and electron microscopy, we demonstrate that initial thermal annealing of SWNT significantly improves their dispersion in PS. In dielectric measurements, the annealed SWNT\\/PS composites show higher electrical conductivity and a lower percolation threshold (less than

T.-E. Chang; A. Kisliuk; S. M. Rhodes; W. J. Brittain; A. P. Sokolov

2006-01-01

325

Stable dispersion of single wall carbon nanotubes in polyimide: the role of noncovalent interactions  

Microsoft Academic Search

Single wall carbon nanotubes (SWNTs) have been dispersed in a nitrile functionalized polyimide matrix and the resulting composite shows excellent stability with respect to reaggregation of the nanotubes. This contrasts with the behaviour of structurally similar polyimides in which the dispersion is only stable for short periods of time. Shifts in certain characteristic FTIR and Raman peaks which indicate a

Kristopher E. Wise; Cheol Park; Emilie J. Siochi; Joycelyn S. Harrison

2004-01-01

326

The Conformation of Polymers Dispersing Single-Walled Carbon Nanotubes in Water  

Microsoft Academic Search

Amphiphilic polymers have been used to disperse single-walled carbon nanotubes (SWCNT) in water. The polymer conformation around the nanotube surface is important for understanding the nature of the interactions leading to successful dispersions. Two extreme cases are ``tight wrapping'' of the polymer around the nanotube and ``loose adsorption'' of solvated polymer coils on the nanotube surface. We studied aqueous dispersions

Yael Dror; Yachin Cohen; Wim Pyckhout-Hintzen

2006-01-01

327

Thermophysical and impact properties of epoxy nanocomposites reinforced by single-wall carbon nanotubes  

Microsoft Academic Search

The thermo-physical properties and the impact strength of diglycidyl ether of bisphenol F (DGEBF) epoxy nanocomposites reinforced with fluorinated single-wall carbon nanotubes (FSWCNT) are reported. A sonication technique was used to disperse FSWCNT in the glassy epoxy network resulting in nanocomposites having large improvement in modulus with extremely small amount of FSWCNT. The glass transition temperature decreased approximately 30 °C

Hiroaki Miyagawa; Lawrence T Drzal

2004-01-01

328

Dispersion of single-walled carbon nanotubes in alcohol-cholic acid mixtures  

NASA Astrophysics Data System (ADS)

A procedure for dispersing single-walled carbon nanotubes (SWNTs) for the preparation of suspensions with high concentrations of individual nanotubes in various solvents was described. The most stable suspensions were obtained from a mixture of ethanol with cholic acid at an acid concentration of 0.018 mol/kg.

Dyshin, A. A.; Eliseeva, O. V.; Bondarenko, G. V.; Kolker, A. M.; Zakharov, A. G.; Fedorov, M. V.; Kiselev, M. G.

2013-12-01

329

Microwave?Assisted Synthesis of a Soluble Single Wall Carbon Nanotube Derivative  

Microsoft Academic Search

The development of a novel procedure based on microwave (MW) heating allowed to obtain a soluble derivative of Single Wall Carbon Nanotubes (SWNTs) by grafting poly(ethylene glycol) (PEG) chains to shortened SWNTs. The use of MW irradiation remarkably enhanced reaction rates compared to similar syntheses based on conventional heating.

Federico Della Negra; Moreno Meneghetti; Enzo Menna

2003-01-01

330

Structure of armchair single-wall carbon nanotubes under hydrostatic pressure  

Microsoft Academic Search

Based on the helical and rotational symmetries and Tersoff potential, the structural parameters, i.e., bond lengths and bond angles, have been investigated for armchair single-wall carbon nanotubes. The bond lengths and bond angles are determined for several radii tubes of various lengths. Results for armchair tubes show that one bond length is greater than that of the graphite while the

Ali Nasir Imtani; V. K. Jindal

2007-01-01

331

Environmental Detection of Single-Walled Carbon Nanotubes Utilizing Near-Infrared Fluorescence  

EPA Science Inventory

There are a growing number of applications for carbon nanotubes (CNT) in modern technologies and, subsequently, growth in production of CNT has expanded rapidly. Single-walled CNT (SWCNT) consist of a graphene sheet rolled up into a tube. With growing manufacture and use, the ...

332

Wave propagation in imperfectly bonded single walled carbon nanotube-polymer composites  

Microsoft Academic Search

In this paper, wave propagation in single walled carbon nanotube (SWNT) embedded polymer composites is studied, taking into account imperfect bonding between the SWNT and the matrix. The imperfect bonding is in terms of SWNT pull-out from the matrix and also partial interfacial shear stress transfer. The nanocomposite is considered as a continuum axisymmetric cylinder and modeled using the wavelet

Mira Mitra; S. Gopalakrishnan

2007-01-01

333

On the Likelihood of Single-Walled Carbon Nanotubes Causing Adverse Marine Ecological Effects  

EPA Science Inventory

This brief article discusses the ecological effects of single-walled carbon nanotubes (SWNTs)in the marine environment. Based on new research and a review of the scientific literature, the paper concludes that SWNTs are unlikely to cause adverse ecological effects in the marine ...

334

Easily made single-walled carbon nanotube surface microelectrodes for neuronal applications  

Microsoft Academic Search

The present work examines the feasibility of a simple method for using single-walled carbon nanotubes (SWNT) to fabricate multielectrode arrays (MEA) for electrophysiological recordings. A suspension of purified SWNTs produced by arc discharged was directly deposited onto standard platinum electrodes. The in vitro impedance and electrochemical characterizations demonstrated the enhanced electrical properties of the SWNT microelectrode array. To test its

Gemma Gabriel; Rodrigo Gómez; Markus Bongard; Nuria Benito; Eduardo Fernández; Rosa Villa

2009-01-01

335

Single-walled carbon nanotube growth from ion implanted Fe catalyst  

NASA Astrophysics Data System (ADS)

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 °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.

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

2006-10-01

336

Dispersion of Single Wall Carbon Nanotubes by in situ Polymerization Under Sonication  

NASA Technical Reports Server (NTRS)

Single wall nanotube reinforced polyimide nanocomposites were synthesized by in situ polymerization of monomers of interest in the presence of sonication. This process enabled uniform dispersion of single wall carbon nanotube (SWNT) bundles in the polymer matrix. The resultant SWNT-polyimide nanocomposite films were electrically conductive (antistatic) and optically transparent with significant conductivity enhancement (10 orders of magnitude) at a very low loading (0.1 vol%). Mechanical properties as well as thermal stability were also improved with the incorporation of the SWNT.

Park, Cheol; Ounaies, Zoubeida; Watson, Kent A.; Crooks, Roy E.; Smith, Joseph, Jr.; Lowther, Sharon E.; Connell, John W.; Siochi, Emilie J.; Harrison, Joycelyn S.; St.Clair, Terry L.

2002-01-01

337

Thermal transpiration through single walled carbon nanotubes and graphene channels  

SciTech Connect

Thermal transpiration through carbon nanotubes (CNTs) and graphene channels is studied using molecular dynamics (MD) simulations. The system consists of two reservoirs connected by a CNT. It is observed that a flow is developed inside the CNT from the low temperature reservoir to the high temperature reservoir when the two reservoirs are maintained at different temperatures. The influence of channel size and temperature gradient on the mean velocity is analysed by varying the CNT diameter and the temperature of one of the reservoirs. Larger flow rate is observed in the smaller diameter CNTs showing an increase in the mean velocity with increase in the temperature gradient. For the flow developed inside the CNTs, slip boundaries occur and the slip length is calculated using the velocity profile. We examine the effect of fluid-wall interaction strength (?{sub fw}), diffusivity (D), and viscosity of the fluid (?) on the temperature induced fluid transport through the CNTs. Similar investigations are also carried out by replacing the CNT with a graphene channel. Results show that the mean velocity of the fluid atoms in the graphene channel is lower than that through the CNTs. This can be attributed to the higher degree of confinement observed in the CNTs.

Thekkethala, Joe Francis; Sathian, Sarith P., E-mail: sarith@nitc.ac.in [Computational Nanotechnology Laboratory, School of Nano Science and Technology, National Institute of Technology Calicut, Kozhikode, Kerala - 673601 (India)

2013-11-07

338

True solutions of single-walled carbon nanotubes for assembly into macroscopic materials.  

PubMed

Translating the unique characteristics of individual single-walled carbon nanotubes into macroscopic materials such as fibres and sheets has been hindered by ineffective assembly. Fluid-phase assembly is particularly attractive, but the ability to dissolve nanotubes in solvents has eluded researchers for over a decade. Here, we show that single-walled nanotubes form true thermodynamic solutions in superacids, and report the full phase diagram, allowing the rational design of fluid-phase assembly processes. Single-walled nanotubes dissolve spontaneously in chlorosulphonic acid at weight concentrations of up to 0.5 wt%, 1,000 times higher than previously reported in other acids. At higher concentrations, they form liquid-crystal phases that can be readily processed into fibres and sheets of controlled morphology. These results lay the foundation for bottom-up assembly of nanotubes and nanorods into functional materials. PMID:19893518

Davis, Virginia A; Parra-Vasquez, A Nicholas G; Green, Micah J; Rai, Pradeep K; Behabtu, Natnael; Prieto, Valentin; Booker, Richard D; Schmidt, Judith; Kesselman, Ellina; Zhou, Wei; Fan, Hua; Adams, W Wade; Hauge, Robert H; Fischer, John E; Cohen, Yachin; Talmon, Yeshayahu; Smalley, Richard E; Pasquali, Matteo

2009-12-01

339

Single wall carbon nanotube supports for portable direct methanol fuel cells.  

PubMed

Single-wall and multiwall carbon nanotubes are employed as carbon supports in direct methanol fuel cells (DMFC). The morphology and electrochemical activity of single-wall and multiwall carbon nanotubes obtained from different sources have been examined to probe the influence of carbon support on the overall performance of DMFC. The improved activity of the Pt-Ru catalyst dispersed on carbon nanotubes toward methanol oxidation is reflected as a shift in the onset potential and a lower charge transfer resistance at the electrode/electrolyte interface. The evaluation of carbon supports in a passive air breathing DMFC indicates that the observed power density depends on the nature and source of carbon nanostructures. The intrinsic property of the nanotubes, dispersion of the electrocatalyst and the electrochemically active surface area collectively influence the performance of the membrane electrode assembly (MEA). As compared to the commercial carbon black support, single wall carbon nanotubes when employed as the support for anchoring the electrocatalyst particles in the anode and cathode sides of MEA exhibited a approximately 30% enhancement in the power density of a single stack DMFC operating at 70 degrees C. PMID:16471506

Girishkumar, G; Hall, Timothy D; Vinodgopal, K; Kamat, Prashant V

2006-01-12

340

Science of single-wall carbon nanotubes: Purification, characterization and chemistry  

NASA Astrophysics Data System (ADS)

Characterization of raw nanotube materials produced by different methods is demonstrated. Depending on the production methods, tubes of different diameters can be produced. Purification of single wall carbon nanotubes produced by laser-oven and HiPco process is also discussed. Metal catalyzed oxidation at low temperature has been shown to selectively remove non-SWNT carbon and permit extraction of metals with concentrated HCl. These multi-stage purification methods have been investigated and the sample purity is documented by EDAX, ESEM, TGA, Raman and UV-vis-Nir spectroscopy. Covalent attachment of functional groups and molecules, including fluorine, methyl, n-butyl and n-hexyl groups, to the sidewalls of single wall carbon nanotubes has been achieved. Further fluorination study is done to investigate the effect of HF which is used as catalysts. Parallel fluorination experiments are performed on both laser-oven-grown and HiPco SWNTs. Larger diameter tubes, i.e. laser-oven-grown SWNTs, require higher fluorination temperatures. A limiting stoichiometry of C2F can be reach for Fluorotubes. Quantitative measurement of the alkylation was done by thermal gravimetric analysis. A mechanism involving electron transfer and effects of reaction temperature, solvents and steric effects of the alkyl groups are discussed. Prolonged exposure of small diameter SWNT ropes (diameters < 5 nm) to hot fuming sulfuric acid has been shown to grow super-ropes with approximately 10,000 tubes in cross-section from rope sizes of approximately 10 tubes. This represents the largest rope sizes ever seen. Examination of the spectral properties of the SWNTs indicates that the roping occurs without changing the chemical state of the nanotubes. Acid intercalation of single wall carbon nanotubes is examined. Several super acids and strong acids are used to study the charge transfer and protonation effects on SWNTs. The degree of charge transfer is clearly correlated with the ability of acid to intercalate into the nanotube packs. A molecular mechanics calculation is used to optimize the proposed Fluorotube structures. This is the first theoretical work on the modeling of Fluorotubes. Results show that fluorine would like to add along the circumference of the tubes instead of going down the tube axis. The (1,4) isomer has the lower total steric energy (TSE) between the two proposed Fluorotube structures, but the energy difference is small. Scanning tunneling microscopy has been used for atomic scale imaging of the fluorotubes. Significant band features are seen on fluorotubes, not on pristine carbon nanotubes. Butylated tubes have also been investigated by STM imaging. Instead of bands, relatively large, distinct features with spacings of about 50 A are observed. Both theoretical and experimental results indicated the (1,4) isomer with bands around the tubes should be the preferred structure.

Chiang, Ivana Wan-Ting

341

Control of the Diameter and Chiral Angle Distributions during Production of Single-Wall Carbon Nanotubes  

NASA Technical Reports Server (NTRS)

Many applications of single wall carbon nanotubes (SWCNT), especially in microelectronics, will benefit from use of certain (n,m) nanotube types (metallic, small gap semiconductor, etc.) Especially fascinating is the possibility of quantum conductors that require metallic armchair nanotubes. However, as produced SWCNT samples are polydisperse, with many (n,m) types present and typical approx.1:2 metal/semiconductor ratio. Nanotube nucleation models predict that armchair nuclei are energetically preferential due to formation of partial triple bonds along the armchair edge. However, nuclei can not reach any meaningful thermal equilibrium in a rapidly expanding and cooling plume of carbon clusters, leading to polydispersity. In the present work, SWCNTs were produced by a pulsed laser vaporization (PLV) technique. The carbon vapor plume cooling rate was either increased by change in the oven temperature (expansion into colder gas), or decreased via "warm-up" with a laser pulse at the moment of nucleation. The effect of oven temperature and "warm-up" on nanotube type population was studied via photoluminescence, UV-Vis-NIR absorption and Raman spectroscopy. It was found that reduced temperatures leads to smaller average diameters, progressively narrower diameter distributions, and some preference toward armchair structures. "Warm-up" shifts nanotube population towards arm-chair structures as well, but the effect is small. Possible improvement of the "warm-up" approach to produce armchair SWCNTs will be discussed. These results demonstrate that PLV production technique can provide at least partial control over the nanotube (n,m) population. In addition, these results have implications for the understanding the nanotube nucleation mechanism in the laser oven.

Nikolaev, Pavel

2009-01-01

342

Efficient production of H 2 and carbon nanotube from CH 4 over single wall carbon nanohorn  

NASA Astrophysics Data System (ADS)

A new catalyst for efficient production of H 2 from CH 4 without CO 2 emission has been requested. We prepared highly-dispersed Pd nanoparticles on single wall carbon nanohorn (Pd-SWCNH) and on oxidized SWCNH (Pd-oxSWCNH) without an anti-aggregation agent. The Pd nanoparticle size on SWCNH and oxSWCNH determined by electron microscopy are around 2.5 and 2.7 nm, respectively. Each sample provides efficiently H 2 and hollow carbon nanofibers through CH 4 decomposition. The H 2 release over the Pd-dispersed SWCNH samples starts from ca. 820 K and is quite large amount compared with a commercial Pd-activated carbon.

Aoki, Yusuke; Urita, Koki; Noguchi, Daisuke; Itoh, Tsutomu; Kanoh, Hirofumi; Ohba, Tomonori; Yudasaka, Masako; Iijima, Sumio; Kaneko, Katsumi

2009-11-01

343

Nanocatalyst structure as a template to define chirality of nascent single-walled carbon nanotubes.  

PubMed

Chirality is a crucial factor in a single-walled carbon nanotube (SWCNT) because it determines its optical and electronic properties. A chiral angle spanning from 0° to 30° results from twisting of the graphene sheet conforming the nanotube wall and is equivalently expressed by chiral indexes (n,m). However, lack of chirality control during SWCNT synthesis is an obstacle for a widespread use of these materials. Here we use first-principles density functional theory (DFT) and classical molecular dynamics (MD) simulations to propose and illustrate basic concepts supporting that the nanocatalyst structure may act as a template to control the chirality during nanotube synthesis. DFT optimizations of metal cluster (Co and Cu)?cap systems for caps of various chiralities are used to show that an inverse template effect from the nascent carbon nanostructure over the catalyst may exist in floating catalysts; such effect determines a negligible chirality control. Classical MD simulations are used to investigate the influence of a strongly interacting substrate on the structure of a metal nanocatalyst and illustrate how such interaction may help preserve catalyst crystallinity. Finally, DFT optimizations of carbon structures on stepped (211) and (321) cobalt surfaces are used to demonstrate the template effect imparted by the nanocatalyst surface on the growing carbon structure at early stages of nucleation. It is found that depending on the step structure and type of building block (short chains, single atoms, or hexagonal rings), thermodynamics favor armchair or zigzag termination, which provides guidelines for a chirality controlled process based on tuning the catalyst structure and the type of precursor gas. PMID:21219018

Gómez-Gualdrón, Diego A; Zhao, Jin; Balbuena, Perla B

2011-01-01

344

INTERDISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Interaction of Methane with Single-Walled Carbon Nanotubes: Role of Defects, Curvature and Nanotubes Type  

Microsoft Academic Search

We investigate the interaction of single-walled carbon nanotubes (SWCNTs) and methane molecule from the first principles. Adsorption energies are calculated, and methane affinities for the typical semiconducting and metallic nanotubes are compared. We also discuss role of the structural defects and nanotube curvature on the adsorption capability of the SWCNTs. We could observe larger adsorption energies for the metallic CNTs

M. D. Ganji; M. Asghary; A. A. Najafi

2010-01-01

345

Spectroelectrochemical properties of the single walled carbon nanotubes functionalized with polydiphenylamine doped with heteropolyanions  

NASA Astrophysics Data System (ADS)

A combined chemical-electrochemical method was used for covalent functionalization of single-walled carbon nanotube (SWNT) with polydiphenylamine (PDPA) doped with heteropolyanions of H3PMo12O40·xH2O. The functionalization process induces in Raman spectra of SWNTs the following changes: (i) an increase in relative intensity of the D band, accompanied a gradual up-shift of the G band in the case of the semiconducting tubes and a decrease in the relative intensity of band peaked at 1540 cm-1 is remarked in the case of the metallic tubes; (ii) in the anti-Stokes Raman spectrum an increase in the relative intensity of Raman line of metallic tubes peaked at -1560 cm-1 is remarked when the cycles number increases. The additional down-shift of the FTIR bands belonging to H3PMo12O40 heteropolyanions (at 881, 943 and 1055 cm-1) and PDPA (at 688, 736 and 1016 cm-1) originates in hindrance steric effects induced the covalent functionalization of SWNTs with polymer molecules. Using Raman scattering and FTIR spectroscopy we demonstrate that chemical polymerization of diphenylamine in the presence of H3PMo12O40·xH2O and SWNTs results in a composite of the type blend based on PDPA in un-doped state and SWNTs doped with H3PMo12O40 heteropolyanions.

Smaranda, I.; Baibarac, M.; Baltog, I.; Mevellec, J. Y.; Lefrant, S.

2013-01-01

346

All-Organic Actuator Fabricated with Single Wall Carbon Nanotube Electrodes  

NASA Technical Reports Server (NTRS)

Compliant electrodes to replace conventional metal electrodes have been required for many actuators to relieve the constraint on the electroactive layer. Many conducting polymers have been proposed for the alternative electrodes, but they still have a problem of poor thermal stability. This article reports a novel all-organic actuator with single wall carbon nanotube (SWCNT) films as the alternative electrode. The SWCNT film was obtained by filtering a SWCNT solution through an anodized alumina membrane. The conductivity of the SWCNT film was about 280 S/cm. The performance of the SWCNT film electrode was characterized by measuring the dielectric properties of NASA Langley Research Center - Electroactive Polymer (LaRC-EAP) sandwiched by the SWCNT electrodes over a broad range of temperature (from 25 C to 280 C) and frequency (from 1 KHz to 1 MHz). The all-organic actuator with the SWCNT electrodes showed a larger electric field-induced strain than that with metal electrodes, under identical measurement conditions.

Lowther, Sharon E.; Harrison, Joycelyn S.; Kang, Jinho; Park, Cheol; Park, Chan Eon

2008-01-01

347

Highly efficient exfoliation of individual single-walled carbon nanotubes by biocompatible phenoxylated dextran  

NASA Astrophysics Data System (ADS)

Highly efficient exfoliation of individual single-walled carbon nanotubes (SWNTs) was successfully demonstrated by utilizing biocompatible phenoxylated dextran, a kind of polysaccharide, as a SWNT dispersion agent. Phenoxylated dextran shows greater ability in producing individual SWNTs from raw materials than any other dispersing agent, including anionic surfactants and another polysaccharide. Furthermore, with this novel polymer, SWNT bundles or impurities present in raw materials are removed under much milder processing conditions compared to those of ultra-centrifugation procedures. There exists an optimal composition of phenoxy groups (~13.6 wt%) that leads to the production of high-quality SWNT suspensions, as confirmed by UV-vis-nIR absorption and nIR fluorescence spectroscopy. Furthermore, phenoxylated dextran strongly adsorbs onto SWNTs, enabling SWNT fluorescence even in solid-state films in which metallic SWNTs co-exist. By bypassing ultra-centrifugation, this low-energy dispersion scheme can potentially be scaled up to industrial production levels.Highly efficient exfoliation of individual single-walled carbon nanotubes (SWNTs) was successfully demonstrated by utilizing biocompatible phenoxylated dextran, a kind of polysaccharide, as a SWNT dispersion agent. Phenoxylated dextran shows greater ability in producing individual SWNTs from raw materials than any other dispersing agent, including anionic surfactants and another polysaccharide. Furthermore, with this novel polymer, SWNT bundles or impurities present in raw materials are removed under much milder processing conditions compared to those of ultra-centrifugation procedures. There exists an optimal composition of phenoxy groups (~13.6 wt%) that leads to the production of high-quality SWNT suspensions, as confirmed by UV-vis-nIR absorption and nIR fluorescence spectroscopy. Furthermore, phenoxylated dextran strongly adsorbs onto SWNTs, enabling SWNT fluorescence even in solid-state films in which metallic SWNTs co-exist. By bypassing ultra-centrifugation, this low-energy dispersion scheme can potentially be scaled up to industrial production levels. Electronic supplementary information (ESI) available: Additional spectra (UV-vis-nIR absorption) demonstrating the effect of centrifugation speed, dextran chain length (molecular weight), and dextran concentration on the quality of SWNT suspensions in SDS or P-dextran, the SWNT re-suspension procedure, additional spectra (fluorescence) of fluorescent freeze-dried P-dextran-SWNT suspensions. See DOI: 10.1039/c3nr01352a

Kwon, Taeyun; Lee, Gyudo; Choi, Hyerim; Strano, Michael S.; Kim, Woo-Jae

2013-07-01

348

Synthesis of Single-Walled Carbon Nanotubes by Pulsed Wire Discharge  

NASA Astrophysics Data System (ADS)

Experimental studies have been carried out to produce single-walled carbon nanotubes (SWCNTs) by pulsed wire discharge (PWD). To prepare soot, carbon fibers were discharged in nitrogen gas by PWD. Soot was collected after the discharge and was observed by means of high-resolution transmission electron microscopy. In the soot collected, we found SWCNTs of 1.2 nm in diameter. On the basis of these results, we have concluded that PWD could be a novel SWCNTs synthesis method.

Kobayashi, Ryouta; Nishimura, Seigo; Suzuki, Tsuneo; Suematsu, Hisayuki; Jiang, Weihua; Yatsui, Kiyoshi

2005-01-01

349

A Finite Element Approach for Estimation of Young' s Modulus of Single-walled Carbon Nanotubes  

Microsoft Academic Search

In this paper, the Young' s modulus of single-walled carbon nanotubes is estimated by a finite element approach. Individual carbon nanotube is simulated as a frame-like structure and the primary bonds between two nearest-neighboring atoms are treated as beam members. The beam properties for input into a finite element model are calculated via the concept of energy equivalence between molecular

Cheng-Wen Fan; Jhih-Hua Huang; Chyanbin Hwu; Yu-Yang Liu

350

Investigation of the humidity effect on the electrical properties of single-walled carbon nanotube transistors  

Microsoft Academic Search

We investigated the effect of humidity on the electrical transport properties of single-walled carbon nanotube field effect transistors (SWNT-FETs). Water molecules are found to behave as electron donors to the nanotube: Current through the p-type carbon nanotube device is found to decrease under a modest humidity, and starts to increase as the humidity increases over 65%, which is believed to

Pil Sun Na; Hyojin Kim; Hye-Mi So; Ki-Jeong Kong; Hyunju Chang; Beyong Hwan Ryu; Youngmin Choi; Jeong-O. Lee; Byoung-Kye Kim; Ju-Jin Kim; Jinhee Kim

2005-01-01

351

Hydrogen Physisorption on Stone?Wales Defect?embedded Single?walled Carbon Nanotubes  

Microsoft Academic Search

The adsorption of H2 on single?walled carbon nanotubes with and without Stone?Wales defect is investigated as a function of temperature. The physisorption phenomenon is simulated by extensive equilibrium molecular dynamics. The interatomic interactions (covalent bonds) between the carbon atoms within the nanotube wall were modeled by the well known bond order Tersoff potential. To include curvature dependence in nonbonding interactions,

Afsaneh Okati; Alireza Zolfaghari; Fariba Sadat Hashemi; Nasim Anousheh; HosseinZolfaghari Jooya

2009-01-01

352

Polypropylene \\/Single Wall Carbon Nano Tube Composites Crystallization Behavior and Fiber Processing Studies  

Microsoft Academic Search

Single Wall Carbon Nanotubes (SWNTs) produced using high-pressure carbon monoxide (HiPCO) process have been purified using the previously developed method to remove the catalytic impurities. Polypropylene (PP) with 1 wtmelt blended in a Haake mixer at 240oC. The resulting PP\\/SWNT blend was optically inhomogeneous. The polymer melt was filtered through a 300, 250, 120 and 80 mesh stainless steel filter

T. V. Sreekumar; Arup R. Bhattacharyya; Atul Kumar; Huina Guo; Satish Kumar; Lars Ericson; Richard E. Smalley

2002-01-01

353

Structure and Properties of poly (para phynelyne benzobisoxazole) (PBO) \\/single wall carbon nano tube composite fibers  

Microsoft Academic Search

The liquid crystalline compositions are prepared by the in-situ polycondensation of diamines and diacid monomers in the presence of single wall carbon nano tubes (SWNT). Processing of the new compositions into fibers provide hybrid materials with improved mechanical properties. The in-situ polymerizations were carried out in polyphosphoric acid (PPA). Carbon nano tubes as high as 10 wt.polymer weight have been

Satish Kumar; Xiefei Zhang; Arup R. Bhattacharyya; Byung G. Min; T. D. Dang; F. E. Arnold; Richard A. Vaia; S. Ramesh; P. A. Willis; R. H. Hauge; R. E. Smalley

2002-01-01

354

Surface defect site density on single walled carbon nanotubes by titration  

Microsoft Academic Search

Closed end single walled carbon nanotubes (c-SWNT) purified by acidic oxidation have been studied in order to determine the fraction of oxidized carbon sites present. This has been done by measuring the evolution of CO2(g) and CO(g) on heating to 1273 K. Following a 1273 K treatment, the defect sites were titrated repeatedly with O3. The results indicate that ?5%

Douglas B. Mawhinney; Viktor Naumenko; Anya Kuznetsova; John T. Yates Jr; J. Liu; R. E. Smalley

2000-01-01

355

Tensile strength of single-walled carbon nanotubes directly measured from their macroscopic ropes  

Microsoft Academic Search

20 mm long ropes consisting of soundly aligned single-walled carbon nanotube (SWNT) ropes, synthesized by the catalytic decomposition of hydrocarbons, were employed for direct tensile strength measurements. The average tensile strength of SWNT rope composites is as high as 3.6+\\/-0.4 GPa, similar to that of carbon fibers. The tensile strength of SWNT bundles was extrapolated from the strength of the

F. Li; H. M. Cheng; S. Bai; G. Su; M. S. Dresselhaus

2000-01-01

356

Nano Surface Generation of Inconel 600 Material by Grinding Process using Single Wall Carbon Nanotubes  

Microsoft Academic Search

The mainstay of this work is to compare the surface roughness of Inconel600 material by grinding process using several samples of cutting fluid such as Mineral oil, SAE 20W40 oil and mixture of SAE 20W40 oil with Single Wall Carbon Nano Tube (SWCNT). Carbon nano tubes have been of great interest, both from a fundamental point of view and for

S. Prabhu; B. K. Vinayagam

357

Catalytic nanoreactors in continuous flow: hydrogenation inside single-walled carbon nanotubes using supercritical CO2.  

PubMed

One nanometre wide carbon nanoreactors are utilised as the reaction vessel for catalytic chemical reactions on a preparative scale. Sub-nanometre ruthenium catalytic particles which are encapsulated solely within single-walled carbon nanotubes offering a unique reaction environment are shown to be active when embedded in a supercritical CO2 continuous flow reactor. A range of hydrogenation reactions were tested and the catalyst displayed excellent stability over extended reaction times. PMID:24496498

Chamberlain, Thomas W; Earley, James H; Anderson, Daniel P; Khlobystov, Andrei N; Bourne, Richard A

2014-05-25

358

Poly(Butylene Terephthalate)\\/Single Wall Carbon Nanotubes Composite Nanofibers by Electrospinning  

Microsoft Academic Search

Poly(buthylene terephthalate)(PBT)\\/single wall carbon nanotubes (SWCNTs) composite nanofibers were prepared by electrospinning. The effect of carbon nanotubes on the morphology, crystallization, and mechanical properties of the electrospun composite nanofibers were investigated by SEM, DSC, and tensile testing, respectively. SEM observations indicated that the presence of SWCNTs resulted in finer nanofibers for lower loading; however, a broader distribution, especially for the

Omid Saligheh; Rouhollah Arasteh; Mehdi Forouharshad; Reza Eslami Farsani

2011-01-01

359

Focused electron beam from open-tip single-wall carbon nanotubes  

Microsoft Academic Search

Open-tip single-wall carbon nanotubes can produce focused electron spot in the field emission. We calculate direct evolution of the nanotube wavefunction under applied electric field by solving the time dependent Shrödinger equation in the first principles scheme. (5,5), (10,10), and (12,12) carbon nanotubes are investigated and We obtain the focused spot size of a few angstroms. The spot size of

Sangbong Lee; Seungchul Kim; Jisoon Ihm

2006-01-01

360

Electron nano-diffraction study of carbon single-walled nanotube ropes  

Microsoft Academic Search

Electron diffraction patterns from regions about 0.7 nm in diameter have been obtained, in conjunction with dark-field imaging, in a scanning transmission electron microscope to study the average helicity and the local variations of helicity of the individual carbon nanotubes within the ropes of single-walled carbon nanotubes recently produced by double laser irradiation. It has been found that the predominant

J. M. Cowley; Pavel Nikolaev; Andreas Thess; Richard E. Smalley

1997-01-01

361

Seed crystals and catalyzed epitaxy of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

This thesis demonstrates the continued growth of single-walled carbon nanotubes (SWNTs) from seeded SWNTs in a way analogous to epitaxy or cloning; that is, the SWNTs grow as a seamless extension to the existing seeded SWNTs and have the same diameter and chirality as those of the SWNT seeds. The experiments were carried out in three key steps, including: (1) preparing a macroscopic array of open-ended SWNTs; (2) reductively docking transition metals as a catalyst to the nanometer-sized open ends; and then (3) heating the whole up to 700--850°C in the presence of a carbon feedstock such as ethanol or ethylene. The resulting SWNT ropes inherit the diameters and chirality from the seeded SWNTs, as indicated by the closely matched frequencies of Raman radial breathing modes before and after the growth. As a control, only sparse nanotubes grew from closed-ended SWNTs, ruling out spontaneous nucleation as a dominating mechanism in our experiments. This experiment proved for the first time the growth of SWNTs can be separated from the nucleation step. The ability to separate the typically inefficient nucleation step from the growth of SWNTs and to restart the growth opens the possibility of amplifying SWNTs with only the desired (n, m). The success in the continued growth was enabled with the creation of macroscopic arrays of open-ended SWNTs from a neat SWNT fiber. A variety of techniques including cryo-microtoming and surface etching chemistry have been developed to produce a macroscopic (˜1200mum2), aligned, and clean---largely free of amorphous carbon, oxides, and metal residuals---SWNT substrate with open-ended SWNTs aligned along the fiber axis. Alternatively, the fiber was milled perpendicular to the fiber axis with a gallium focused ion beam to produce a planar, free-standing, ultra-thin, "bed-of-nails" SWNT membrane---a single layer of parallel SWNTs densely packed and aligned along the normal of the membrane.

Wang, Yuhuang

362

Chirality-specific growth of single-walled carbon nanotubes on solid alloy catalysts.  

PubMed

Carbon nanotubes have many material properties that make them attractive for applications. In the context of nanoelectronics, interest has focused on single-walled carbon nanotubes (SWNTs) because slight changes in tube diameter and wrapping angle, defined by the chirality indices (n,?m), will shift their electrical conductivity from one characteristic of a metallic state to one characteristic of a semiconducting state, and will also change the bandgap. However, this structure-function relationship can be fully exploited only with structurally pure SWNTs. Solution-based separation methods yield tubes within a narrow structure range, but the ultimate goal of producing just one type of SWNT by controlling its structure during growth has proved to be a considerable challenge over the last two decades. Such efforts aim to optimize the composition or shape of the catalyst particles that are used in the chemical vapour deposition synthesis process to decompose the carbon feedstock and influence SWNT nucleation and growth. This approach resulted in the highest reported proportion, 55 per cent, of single-chirality SWNTs in an as-grown sample. Here we show that SWNTs of a single chirality, (12,?6), can be produced directly with an abundance higher than 92 per cent when using tungsten-based bimetallic alloy nanocrystals as catalysts. These, unlike other catalysts used so far, have such high melting points that they maintain their crystalline structure during the chemical vapour deposition process. This feature seems crucial because experiment and simulation both suggest that the highly selective growth of (12,?6) SWNTs is the result of a good structural match between the carbon atom arrangement around the nanotube circumference and the arrangement of the catalytically active atoms in one of the planes of the nanocrystal catalyst. We anticipate that using high-melting-point alloy nanocrystals with optimized structures as catalysts paves the way for total chirality control in SWNT growth and will thus promote the development of SWNT applications. PMID:24965654

Yang, Feng; Wang, Xiao; Zhang, Daqi; Yang, Juan; Luo, Da; Xu, Ziwei; Wei, Jiake; Wang, Jian-Qiang; Xu, Zhi; Peng, Fei; Li, Xuemei; Li, Ruoming; Li, Yilun; Li, Meihui; Bai, Xuedong; Ding, Feng; Li, Yan

2014-06-26

363

Electronic-structure-dependent bacterial cytotoxicity of single-walled carbon nanotubes.  

PubMed

Single-walled carbon nanotubes (SWNTs) have been previously observed to be strong antimicrobial agents, and SWNT coatings can significantly reduce biofilm formation. However, the SWNT antimicrobial mechanism is not fully understood. Previous studies on SWNT cytotoxicity have concluded that membrane stress (i.e., direct SWNT-bacteria contact resulting in membrane perturbation and the release of intracellular contents) was the primary cause of cell death. Gene expression studies have indicated oxidative stress may be active, as well. Here, it is demonstrated for the first time how SWNT electronic structure (i.e., metallic versus semiconducting) is a key factor regulating SWNT antimicrobial activity. Experiments were performed with well-characterized SWNTs of similar length and diameter but varying fraction of metallic nanotubes. Loss of Escherichia coli viability was observed to increase with an increasing fraction of metallic SWNTs. Time-dependent cytotoxicity measurements indicated that in all cases the majority of the SWNT antimicrobial action occurs shortly after (<15 min) bacteria-SWNT contact. The SWNT toxicity mechanism was investigated by in vitro SWNT-mediated oxidation of glutathione, a common intracellular thiol that serves as an antioxidant and redox state mediator. The extent of glutathione oxidation was observed to increase with increasing fraction of metallic SWNTs, indicating an elevated role of oxidative stress. Scanning electron microscopy images of E. coli in contact with the SWNTs demonstrated electronic structure-dependent morphological changes consistent with cytotoxicity and glutathione oxidation results. A three-step SWNT antimicrobial mechanism is proposed involving (i) initial SWNT-bacteria contact, (ii) perturbation of the cell membrane, and (iii) electronic structure-dependent bacterial oxidation. PMID:20812689

Vecitis, Chad D; Zodrow, Katherine R; Kang, Seoktae; Elimelech, Menachem

2010-09-28

364

Directed assembly techniques for nano-manufacturing of scalable single walled carbon nanotube based devices  

NASA Astrophysics Data System (ADS)

Single Walled Carbon Nanotubes (SWNTs) are being considered building blocks for next generation electronics due to their unique electrical, mechanical and thermal properties. A number of SWNT based devices including scanning probes, field emitters, field effect transistors, biological and chemical sensors, and memory devices have been demonstrated. Despite successful demonstration of these single devices, the success of SWNT based nanoelectronics is hampered due to the lack of a successful nano-manufacturing method. Precise alignment and placement of SWNTs is necessary for successful integration of SWNTs into nanoelectronics. The work described in this thesis is focused on developing electric field assisted assembly techniques for precise placement and controlled orientation of SWNTs. In a first set of experiments we evaluate the use of micro/nano finger shaped metal electrodes to assemble SWNTs. Eventhough this assembly technique help in understanding the electrophoretic behavior of SWNTs, problems related with orientation, assembly at nanoscale and electrode degradation demanded evaluating alternative techniques. Nanotemplates that use trenches made in PMMA on a conductive substrate are utilized for the directed, controlled assembly of SWNTs This technique uses a combination of electrophoretic forces and fluidic forces to assemble and align the SWNTs. We were able to assemble SWNTs in trenches that are as small as 80 nm wide and 100,000 nm long over a 2.25 cm2 area in 30-90 seconds. Based on the experimental results and analysis a model is proposed to explain the assembly and alignment mechanism of SWNT s. The technique has been utilized to fabricated interconnects and field effect transistors to demonstrate the feasibility to make devices. Finally we introduce a novel room temperature assembly technique for fabricating a three dimensional single walled carbon nanotube platform. A top down lithographic approach is used to fabricate the platform while a bottom-up dielectrophoresis method is used to assemble the SWNTs in a 3D architecture. This is a scalable, high throughput and room temperature technique making it compatible with current CMOS technology. We demonstrate the ability to precisely control the density of SWNTs. A finite element model is used to simulate and study the behavior the SWNTs during assembly. We also demonstrate that these structures can be utilized directly as 3D interconnects. Finally, we show that the packaging of these devices, using a conformal pin-free parylene layer, provides a complete process flow for making SWNT based 3D nano-devices.

Makaram, Prashanth

365

Review of Laser Ablation Process for Single Wall Carbon Nanotube Production  

NASA Technical Reports Server (NTRS)

Different types of lasers are now routinely used to prepare single wall carbon nanotubes (SWCNTs). The original method developed by researchers at Rice University utilized a "double pulse laser oven" process. A graphite target containing about 1 atomic percent of metal catalysts is ablated inside a 1473K oven using laser pulses (10 ns pulse width) in slow flowing argon. Two YAG lasers with a green pulse (532 nm) followed by an IR pulse (1064 nm) with a 50 ns delay are used for ablation. This set up produced single wall carbon nanotube material with about 70% purity having a diameter distribution peaked around 1.4 nm. The impurities consist of fullerenes, metal catalyst clusters (10 to 100 nm diameter) and amorphous carbon. The rate of production with the initial set up was about 60 mg per hour with 10Hz laser systems. Several researchers have used variations of the lasers to improve the rate, consistency and study effects of different process parameters on the quality and quantity of SWCNTs. These variations include one to three YAG laser systems (Green, Green and IR), different pulse widths (nano to microseconds as well as continuous) and different laser wavelengths (Alexandrite, CO, CO2, free electron lasers in the near to far infrared). It is noted that yield from the single laser (Green or IR) systems is only a fraction of the two laser systems. The yield seemed to scale up with the repetition rate of the laser systems (10 to 60 Hz) and depended on the beam uniformity and quality of the laser pulses. The shift to longer wavelength lasers (free electron, CO and CO2) did not improve the quality, but increased the rate of production because these lasers are either continuous (CW) or high repetition rate pulses (kHz to MHz). The average power and the peak power of the lasers seem to influence the yields. Very high peak powers (MegaWatts per square centimeter) are noted to increase ablation of bigger particles with reduced yields of SWCNTs. Increased average powers seem to help the conversion of the carbon from target into vapor phase to improve formation of nanotubes. The use of CW far infrared lasers reduced the need for the oven, at the expense of controlled ablation. Some of these variations are tried with different combinations and concentrations of metal catalysts (Nickel with Cobalt, Iron, Palladium and Platinum) different buffer gases (e.g. Helium); with different oven temperatures (Room temperature to 1473K); under different flow conditions (1 to 1000 kPa) and even different porosities of the graphite targets. It is to be noted that the original Cobalt and Nickel combination worked best, possibly because of improved carbonization with stable crystalline phases. The mean diameter and yield seemed to increase with increasing oven temperatures. Thermal conductivity of the buffer gas and flow conditions dictate the quality as well as quantity of the SWCNTs. Faster flows, lower pressures and heavier gases seem to increase the yields. This review will attempt to cover all these variations and their relative merits. Possible growth mechanisms under these different conditions will also be discussed.

Arepalli, Sivaram

2003-01-01

366

Dimensional changes as a function of charge injection in single-walled carbon nanotubes.  

PubMed

Motivated by the central importance of charge-induced dimensional changes for carbon nanotube electromechanical actuators, we here predict changes in nanotube length and diameter as a function of charge injection for armchair and zigzag nanotubes having different diameters. Density functional theory with periodic boundary conditions is used, which we show provides results consistent with experimental observations for intercalated graphites. Strain-versus-charge relationships are predicted from dimensional changes calculated with a uniform background charge ("jellium") for representing the counterions. These jellium calculations are consistent with presented calculations that include specific counterions for intercalated graphite, showing that hybridization between the ions and the graphite sheets is unimportant. The charge-strain relationships calculated with the jellium approximation for graphite and isolated single-walled nanotubes are asymmetric with respect to the sign of charge transfer. The dependence of nanotube strain on charge approaches that for a graphite sheet for intermediate-sized metallic nanotubes and for larger diameter semiconducting nanotubes. However, the strain-charge curves strongly depend on nanotube type when the nanotube diameter is small. This reflects both the dependence of the frontier orbitals for the semiconducting nanotubes on the nanotube type and the pi-sigma mixing when the nanotube diameter is small. PMID:12475352

Sun, Guangyu; Kürti, Jenö; Kertesz, Miklos; Baughman, Ray H

2002-12-18

367

Defect-induced multicomponent electron scattering in single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We present a detailed comparison between theoretical predictions on electron scattering processes in metallic single-walled carbon nanotubes with defects and experimental data obtained by scanning tunneling spectroscopy of Ar+ irradiated nanotubes. To this purpose, we first develop a formalism for studying quantum transport properties of defected nanotubes in the presence of source and drain contacts and a scanning tunneling microscopy tip. The formalism is based on a field theoretical approach describing low-energy electrons. We account for the lack of translational invariance induced by defects within the so-called extended k·p approximation, which allows for multicomponent scattering with new scattering channels that are associated with exchanged momenta larger than the difference between the K points of the nanotube. The theoretical model reproduces the features of the particle-in-a-box-like states observed experimentally. Further, the comparison between theoretical and experimental Fourier-transformed local density of states maps yields clear signatures for intervalley and intravalley electron scattering processes depending on the tube chirality.

Bercioux, Dario; Buchs, Gilles; Grabert, Hermann; Gröning, Oliver

2011-04-01

368

High electrical conductance enhancement in Au-nanoparticle decorated sparse single-wall carbon nanotube networks  

NASA Astrophysics Data System (ADS)

We report high electrical conductance enhancement in sparse single-walled carbon nanotube networks by decoration with Au nanoparticles. The optimized hybrid network exhibited a sheet resistance of 650 ? sq-1, 1/1500 of the resistance of the host undecorated network, with a negligible optical transmission penalty (>90% transmittance at 550 nm wavelength). The electrical transport at room temperature in the host and decorated networks was dominated by two-dimensional variable range hopping. The high conductance enhancement was due to positive charge transfer from the decorating Au nanoparticles in intimate contact with the host network causing a Fermi energy shift into the high density of states at a van Hove singularity and enhanced electron delocalization relative to the host network which beneficially modifies the hopping parameters in such a way that the network behaves as an integral whole. The effect is most pronounced when the nanoparticle diameter is comparable to the electron mean free path in the bulk material at room temperature and there is minimum nanoparticle agglomeration. For higher than optimal values of nanoparticle coverage or nanoparticle diameter, the conductance enhancement is countered by metallic inclusions in the current pathways that are of higher resistance than the variable range hopping-controlled elements.

McAndrew, Calum F.; Baxendale, Mark

2013-08-01

369

Noncovalent interactions between organometallic metallocene complexes and single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

First principles density functional pseudopotential calculations have been used to investigate the nature of interactions between single-walled carbon nanotubes (SWNTs) and intercalated transition metal metallocene complexes, M(?-C5H5)2 (MCp2). Three composites, MCp2-graphene (dt=?), MCp2@(17,0) (dt=1.33 nm), and MCp2@(12,0) (dt=0.94 nm) (where M=Fe,Co), have been studied to probe the influence of the nanotube diameter (dt) on the nature and magnitude of the interactions. Theoretical results presented here demonstrate that these MCp2@SWNT composites are stabilized by weak ?-stacking and CH...? interactions, and in the case of the CoCp2@SWNT composites there is an additional electrostatic contribution as a result of charge transfer from CoCp2 to the nanotube. The extent of charge transfer (MCp2-->SWNT) can be rationalized in terms of the electronic structures of the two fragments, or more specifically, the relative positions of the metallocene highest occupied molecular orbital and the conduction band of the nanotube in the electronic structure of the composite.

Sceats, Emma L.; Green, Jennifer C.

2006-10-01

370

Nonlinear optical properties of boron doped single-walled carbon nanotubes.  

PubMed

Single-walled carbon nanotubes (SWCNTs) exhibit excellent nonlinear optical (NLO) properties due to the delocalized ? electron states present along their tube axis. Using the open aperture Z-scan method in tandem with X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, we demonstrate the simultaneous tailoring of both electronic and NLO properties of SWCNTs, from ultrafast (femtosecond) to relatively slow (nanosecond) timescales, by doping with a single substituent, viz., boron. SWCNTs were doped via a wet chemical method using B2O3, and the boron content and bonding configurations were identified using XPS. While in the ns excitation regime, the nonlinear absorption was found to increase with increasing boron concentration in the SWCNTs (due to the increasing disorder and enhanced metallicity of the SWCNTs), the saturation intensity in the fs excitation regime decreased. We attribute this counter-intuitive behavior to excited state absorption on ns timescales, and saturable absorption combined with weak two-photon transitions on fs timescales between van Hove singularities. PMID:23817830

Anand, Benoy; Podila, Ramakrishna; Ayala, Paola; Oliveira, Luciana; Philip, Reji; Sai, S Siva Sankara; Zakhidov, Anvar A; Rao, Apparao M

2013-08-21

371

Two photon polymerization lithography for 3D microfabrication of single wall carbon nanotube/polymer composites  

NASA Astrophysics Data System (ADS)

Two photon polymerization (TPP) lithography has been established as a powerful tool to develop 3D fine structures of polymer materials, opening up a wide range applications such as micro-electromechanical systems (MEMS). TPP lithography is also promising for 3D micro fabrication of nanocomposites embedded with nanomaterials such as metal nanoparticles. Here, we make use of TPP lithography to fabricate 3D micro structural single wall carbon nanotube (SWCNT)/polymer composites. SWCNTs exhibit remarkable mechanical, electrical, thermal and optical properties, which leads to enhance performances of polymers by loading SWCNTs. SWCNTs were uniformly dispersed in an acrylate UV-curable monomer including a few amounts of photo-initiator and photo-sensitizer. A femtosecond pulsed laser emitting at 780 nm was focused onto the resin, resulting in the photo-polymerization of a nanometric volume of the resin through TPP. By scanning the focus spot three dimensionally, arbitrary 3D structures were created. The spatial resolution of the fabrication was sub-micrometer, and SWCNTs were embedded in the sub-micro sized structures. The fabrication technique enables one to fabricate 3D micro structural SWCNT/polymer composites into desired shapes, and thus the technique should open up the further applications of SWCNT/polymer composites such as micro sized photomechanical actuators.

Ushiba, Shota; Shoji, Satoru; Kuray, Preeya; Masui, Kyoko; Kono, Junichiro; Kawata, Satoshi

2013-03-01

372

Noncovalent interactions between organometallic metallocene complexes and single-walled carbon nanotubes.  

PubMed

First principles density functional pseudopotential calculations have been used to investigate the nature of interactions between single-walled carbon nanotubes (SWNTs) and intercalated transition metal metallocene complexes, M(eta-C(5)H(5))(2) (MCp(2)). Three composites, MCp(2)-graphene (d(t)=infinity), MCp(2)@(17,0) (d(t)=1.33 nm), and MCp(2)@(12,0) (d(t)=0.94 nm) (where M=Fe,Co), have been studied to probe the influence of the nanotube diameter (d(t)) on the nature and magnitude of the interactions. Theoretical results presented here demonstrate that these MCp(2)@SWNT composites are stabilized by weak pi-stacking and CH...pi interactions, and in the case of the CoCp(2)@SWNT composites there is an additional electrostatic contribution as a result of charge transfer from CoCp(2) to the nanotube. The extent of charge transfer (MCp(2)-->SWNT) can be rationalized in terms of the electronic structures of the two fragments, or more specifically, the relative positions of the metallocene highest occupied molecular orbital and the conduction band of the nanotube in the electronic structure of the composite. PMID:17059280

Sceats, Emma L; Green, Jennifer C

2006-10-21

373

Infrared and optical transmittance of free-standing single-wall carbon nanotube films  

NASA Astrophysics Data System (ADS)

We studied the transmittance in the infrared and optical range (4 meV - 4 eV) of free-standing single-wall carbon nanotubes of 400 nm thickness. We will present the frequency-dependent conductivity obtained from Kramers-Kronig analysis of transmittance spectra at several temperatures on as-prepared ("unbaked") and purified ("baked") samples. The conductivity at low frequencies decreases during the final step of preparation, "baking" at 1000 °C. This step thus can be viewed as removing mobile carriers introduced by hole doping during purification using nitric acid. Mobile carriers also seem responsible for the temperature dependence of the optical properties of the baked sample. Transitions between density-of-states peaks, in the near-infrared and visible, remain essentially unchanged between 300 K and 20 K, while the far-infrared Drude component shows definite narrowing. This narrowing leads to a 30 per cent increase in the low-frequency optical conductivity when cooling from 300 K to 20 K. Beside the Drude part originating from metallic tubes, we also observe a pseudogap at 10-15 meV. Work supported by DARPA through grant DAAD19-00-1-0002, by the NSF through grant INT-9902050, and by OTKA through grant T032613.

Kamaras, K.; Nikolou, M.; Chen, Z.; Rinzler, A. G.; Tanner, David B.

2003-03-01

374

Spectroscopic evidence for the origin of the dumbbell cyclic voltammogram of single-walled carbon nanotubes.  

PubMed

We investigated the changes in charge carrier density responsible for the dumbbell-like cyclic voltammogram of single-walled carbon nanotubes (SWCNTs) used as electric double layer capacitor electrodes. We utilized in situ Raman spectroscopy of SWCNTs in the potential range where the dumbbell voltammogram is observed and electric double layer charging would be the dominant mechanism. The study revealed that, unexpectedly, the spectroscopic changes coinciding with the dumbbell steps on the voltammogram occur more sharply in metallic tubes, as seen from (1) the sudden enhancement in the intensity of the BWF Breit-Wigner-Fano (BWF) feature, (2) a considerably more significant frequency upshift of G(+) and G' bands, and (3) a drop in radial breathing mode intensity, compared to those in the spectra of semiconducting tubes. In addition, the spectroscopic changes observed with open-end SWCNT samples were more defined and correlated more accurately with the electronic structure of the tubes compared to those observed with closed-end SWCNTs. PMID:24189742

Al-zubaidi, Ayar; Ishii, Yosuke; Yamada, Saki; Matsushita, Tomohiro; Kawasaki, Shinji

2013-12-21

375

Improved memory behaviour of single-walled carbon nanotubes charge storage nodes  

NASA Astrophysics Data System (ADS)

To investigate their memory behaviours, single-walled carbon nanotubes (SWCNTs) were embedded in the floating gate of a hybrid metal-insulator-semiconductor structure using layer-by-layer deposition, and polymethylmethacrylate (PMMA) as the dielectric. Unlike longer SWCNT-based structures, shortened SWCNTs were shown to exhibit reliable and large memory windows by virtue of a better encapsulation which reduces charge leakage. The capacitance-voltage characteristics of the devices were consistent with electron injection into the SWCNT charge storage elements (in the floating) from the top electrode through the PMMA, using localized defects and crossing the PMMA energy barrier. In terms of material formulation, a combination of SWCNTs dispersed in sodium dodecyl sulfate and polyethyleneimine used as charge storage elements in the floating gate was shown to lead to repeatable and reliable memory characteristics. Fast switching and very large memory windows (˜7 V) exhibiting high charge density (2.6 × 1012 cm-2) and charge retention in excess of ˜76% were achieved under a ±10 V sweep voltage range. These results suggest that SWCNTs could lead to improved memory behaviour with the potential for application in plastic electronics.

Alba-Martin, Maria; Firmager, Timothy; Atherton, Joseph; Rosamond, Mark C.; Ashall, Daniel; Ghaferi, Amal Al; Ayesh, Ahmad; Gallant, Andrew J.; Mabrook, Mohammed F.; Petty, Michael C.; Zeze, Dagou A.

2012-07-01

376

Nonlinear optical properties of boron doped single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanotubes (SWCNTs) exhibit excellent nonlinear optical (NLO) properties due to the delocalized ? electron states present along their tube axis. Using the open aperture Z-scan method in tandem with X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy, we demonstrate the simultaneous tailoring of both electronic and NLO properties of SWCNTs, from ultrafast (femtosecond) to relatively slow (nanosecond) timescales, by doping with a single substituent, viz., boron. SWCNTs were doped via a wet chemical method using B2O3, and the boron content and bonding configurations were identified using XPS. While in the ns excitation regime, the nonlinear absorption was found to increase with increasing boron concentration in the SWCNTs (due to the increasing disorder and enhanced metallicity of the SWCNTs), the saturation intensity in the fs excitation regime decreased. We attribute this counter-intuitive behavior to excited state absorption on ns timescales, and saturable absorption combined with weak two-photon transitions on fs timescales between van Hove singularities.

Anand, Benoy; Podila, Ramakrishna; Ayala, Paola; Oliveira, Luciana; Philip, Reji; Sankara Sai, S. Siva; Zakhidov, Anvar A.; Rao, Apparao M.

2013-07-01

377

Porphyrins-Functionalized Single-Walled Carbon Nanotubes Chemiresistive Sensor Arrays for VOCs.  

PubMed

Single-walled carbon nanotubes (SWNTs) have been used extensively for sensor fabrication due to its high surface to volume ratio, nanosized structure and interesting electronic property. Lack of selectivity is a major limitation for SWNTs-based sensors. However, surface modification of SWNTs with a suitable molecular recognition system can enhance the sensitivity. On the other hand, porphyrins have been widely investigated as functional materials for chemical sensor fabrication due to their several unique and interesting physico-chemical properties. Structural differences between free-base and metal substituted porphyrins make them suitable for improving selectivity of sensors. However, their poor conductivity is an impediment in fabrication of prophyrin-based chemiresistor sensors. The present attempt is to resolve these issues by combining freebase- and metallo-porphyrins with SWNTs to fabricate SWNTs-porphyrin hybrid chemiresistor sensor arrays for monitoring volatile organic carbons (VOCs) in air. Differences in sensing performance were noticed for porphyrin with different functional group and with different central metal atom. The mechanistic study for acetone sensing was done using field-effect transistor (FET) measurements and revealed that the sensing mechanism of ruthenium octaethyl porphyrin hybrid device was governed by electrostatic gating effect, whereas iron tetraphenyl porphyrin hybrid device was governed by electrostatic gating and Schottky barrier modulation in combination. Further, the recorded electronic responses for all hybrid sensors were analyzed using a pattern-recognition analysis tool. The pattern-recognition analysis confirmed a definite pattern in response for different hybrid material and could efficiently differentiate analytes from one another. This discriminating capability of the hybrid nanosensor devices open up the possibilities for further development of highly dense nanosensor array with suitable porphyrin for E-nose application. PMID:22393460

Shirsat, Mahendra D; Sarkar, Tapan; Kakoullis, James; Myung, Nosang V; Konnanath, Bharatan; Spanias, Andreas; Mulchandani, Ashok

2012-09-01

378

A novel fluorescent aptasensor based on single-walled carbon nanohorns  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanohorns have been used to construct an aptasensor for the first time. This novel aptasensor was successfully used for the detection of thrombin with high sensitivity and excellent selectivity. This thrombin aptasensor has a detection limit of as low as 100 pM.Single-walled carbon nanohorns have been used to construct an aptasensor for the first time. This novel aptasensor was successfully used for the detection of thrombin with high sensitivity and excellent selectivity. This thrombin aptasensor has a detection limit of as low as 100 pM. Electronic supplementary information (ESI) available: Experimental section and supplementary figures. See DOI: 10.1039/c1nr10774g

Zhu, Shuyun; Han, Shuang; Zhang, Ling; Parveen, Saima; Xu, Guobao

2011-11-01

379

Acceptor doping of single-walled carbon nanotubes by encapsulation of zinc halogenides  

NASA Astrophysics Data System (ADS)

To modify the electronic properties of single-walled carbon nanotubes (SWCNTs), ZnX2@SWCNT (X = Cl, Br, I) nanostructures were prepared by capillary filling of 1.4-1.6 nm single-walled carbon nanotubes (SWCNT) with zinc halogenide melts. The loading factor is estimated as 30% for ZnCl2 and approximately 60% for ZnBr2 and ZnI2. Well-ordered 1D crystals were observed by TEM only for ZnI2@SWCNT. We propose two possible atomic structures of the 1D crystals, (Zn4I7) n and less stable (Zn4I9) n . According to the optical absorption and photoemission data, there is a charge transfer from the nanotube to the filler for all ZnX2@SWCNT nanostructures. The results of the DFT PW-GGA modeling indicate that the acceptor properties correspond to (Zn4I9) n only.

Kharlamova, M. V.; Yashina, L. V.; Volykhov, A. A.; Niu, J. J.; Neudachina, V. S.; Brzhezinskaya, M. M.; Zyubina, T. S.; Belogorokhov, A. I.; Eliseev, A. A.

2012-01-01

380

Synthesis of Single Wall Carbon Nanotubes by Plasma Arc: Role of Plasma Parameters  

NASA Technical Reports Server (NTRS)

Single wall carbon nanotubes (SWNT) are porous objects on the molecular scale and have a low density, which gives them potential applications as adsorbent for molecular hydrogen. Their H2 absorption capacity published in the literature varies from 4 to 10% by mass according to the purity of the materials and storage conditions. Optimization of production methods of SWNTs should permit improving these new materials for storage of hydrogen. In this article, we show the potential of using SWNTs in hydrogen storage. In particular, we pose problems associated with synthesis, purification, and opening up of the nanotubes. We present an electric arc process currently used at laboratory scale to produce single wall carbon nanotubes. We discuss, in particular, operating conditions that permit growth of nanotubes and some plasma parameters that assure control of the material. Analysis of the process is carried out with the aid of local measurements of temperature and scanning and transmission electron microscopy of the materials.

Farhart, Samir; Scott, Carl D.

2000-01-01

381

Production and characterization of polymer nanocomposite with aligned single wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

We reported a simple method to fabricate polymer nanocomposites with single-walled carbon nanotubes (SWNTs) having exceptional alignment and improved mechanical properties. The composite films were fabricated by casting a suspension of single walled carbon nanotubes in a solution of thermoplastic polyurethane and tetrahydrofuran. The orientation as well as dispersion of nanotubes was determined by scanning electron microscopy, transmission electron microscopy and polarized Raman spectroscopy. The macroscopic alignment probably results from solvent-polymer interaction induced orientation of soft segment chain during swelling and moisture curing. The tensile behavior of the aligned nanotube composite film was also studied. At a 0.5 wt.% nanotube loading, a 1.9-fold increase in Young's modulus was achieved.

Chen, Wei; Tao, Xiaoming

2006-03-01

382

High frequency performance of individual and arrays of single-walled carbon nanotubes.  

PubMed

We have studied the high frequency performance limits of single-walled carbon nanotube (SWNT) transistors in the diffusive transport regime limited by the acoustic phonon scattering. The relativistic band structure of single-walled carbon nanotubes combined with the acoustic phonon scattering provides an analytical model for the charge transport of the radio frequency transistors. We were able to obtain the intrinsic high frequency performance such as the cut-off frequency and the linearity of the SWNT transistors. We have extended our model to include transistors based on arrays of SWNTs. The effect of electrostatic screening in a dense array of SWNTs on the cut-off frequency is studied. PMID:22641245

Balci, Osman; Kocabas, Coskun

2012-06-22

383

G-quartet type self-assembly of guanine functionalized single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

The simple strategy of linking guanine to single-walled carbon nanotubes (CNTs) through covalent functionalization permitted generation of the alignment of the nanotubes into lozenges reminiscent of guanine quartets (G-quartets) in the presence of potassium ions as observed by atomic force microscopy.The simple strategy of linking guanine to single-walled carbon nanotubes (CNTs) through covalent functionalization permitted generation of the alignment of the nanotubes into lozenges reminiscent of guanine quartets (G-quartets) in the presence of potassium ions as observed by atomic force microscopy. Electronic supplementary information (ESI) available: Experimental procedures for the synthesis and characterization of the precursors and MWCNT conjugates. See DOI: 10.1039/c2nr11849a

Singh, Prabhpreet; Venkatesh, V.; Nagapradeep, N.; Verma, Sandeep; Bianco, Alberto

2012-03-01

384

Synthesis and Purification of Single-Walled Carbon Nanotubes by AC Arc Discharge  

NASA Astrophysics Data System (ADS)

Single-walled carbon nanotubes (SWNTs) were synthesized in a mixed gas of H2 and Ar by AC arc discharge. The catalyst used in the synthesis was a single Fe catalyst. SWNTs containing a negligible number of nanoparticles were obtained. A novel purification method, in which synthesized soot is heated and oxidized in situ, was adopted. As a result, high-quality SWNTs with excellent crystallinity containing very few coexisting nanoparticles and fine particles from the catalyst were obtained.

Ohkohchi, Masato; Zhao, Xinluo; Inoue, Sakae; Ando, Yoshinori

2004-12-01

385

Curing effects of single-wall carbon nanotube reinforcement on mechanical properties of filled epoxy adhesives  

Microsoft Academic Search

Enhancing epoxy adhesives using nanoscale fillers requires understanding processing-structure–property relationships as a function of nanoscale filler loading. In particular, the effects of adding nanoscale reinforcement to filled epoxies, such as those qualified for space applications, have yet to be characterized. In this effort, the addition of single-walled carbon nanotubes (SWNTs) to Hysol 9309.2 epoxy was investigated using a multi-scale mechanical

Alan L. Gerson; Hugh A. Bruck; Alan R. Hopkins; Kenneth N. Segal

2010-01-01

386

Poly(m-aminobenzene sulfonic acid) functionalized single-walled carbon nanotubes based gas sensor  

Microsoft Academic Search

We have demonstrated a NH3, NO2 and water vapour sensor based on poly(m-aminobenzene sulfonic acid) functionalized single-walled carbon nanotube (SWNT-PABS) networks. The SWNT-PABS based sensors were fabricated by simple dispersion of SWNT-PABS on top of pre-fabricated gold electrodes. SWNT-PABS sensors showed excellent sensitivity with ppbv level detection limits (i.e., 100 ppbv for NH3 and 20 ppbv for NO2) at room

Ting Zhang; Syed Mubeen; Elena Bekyarova; Bong Young Yoo; Robert C. Haddon; Nosang V. Myung; Marc A. Deshusses

2007-01-01

387

Electrospun single-walled carbon nanotube\\/polyvinyl alcohol composite nanofibers: structure property relationships  

Microsoft Academic Search

Polyvinyl alcohol (PVA) nanofibers and single-walled carbon nanotube (SWNT)\\/PVA composite nanofibers have been produced by electrospinning. An apparent increase in the PVA crystallinity with a concomitant change in its main crystalline phase and a reduction in the crystalline domain size were observed in the SWNT\\/PVA composite nanofibers, indicating the occurrence of a SWNT-induced nucleation crystallization of the PVA phase. Both

Minoo Naebe; Tong Lin; Mark P. Staiger; Liming Dai; Xungai Wang

2008-01-01

388

Theoretical studies of C 36 encapsulated in zigzag single-wall carbon nanotubes  

Microsoft Academic Search

The one-dimensional hybrid structures of C36 encapsulated in zigzag single-wall carbon nanotubes (C36@(n,0)) have been investigated using ab initio self-consistent-field crystal orbital method based on the density functional theory. The research focuses on the change of\\u000a geometric and band structures for the nanotubes upon C36 encapsulation. The obtained results show that the introduction of\\u000a C36 can modify the electronic properties

Baohua Yang; Yang Wang; Yuanhe Huang

2006-01-01

389

Interaction of molecular and atomic hydrogen with single-wall carbon nanotubes  

Microsoft Academic Search

Density functional calculations are performed to study the interaction of molecular and atomic hydrogen with (5,5) and (6,6) single-wall carbon nanotubes. Molecular physisorption is predicted to be the most stable adsorption state, with the molecule at equilibrium at a distance of 5-6 a.u. from the nanotube wall. The physisorption energies outside the nanotubes are approximately 0.07 eV, and larger inside,

Julio A. Alonso; Juan S. Arellano; Luis M. Molina; Angel Rubio; María J. López

2004-01-01

390

Lithium diffusion in single-walled carbon nanotubes: a theoretical study  

Microsoft Academic Search

Theoretical investigations on single-walled carbon nanotubes (SWCNT) have been carried out using ab initio and molecular interaction potential with and without polarization (MIPp and MIP, respectively) methodologies to explore the possibilities of Li+ ion insertion through the side-wall of the nanotube. Li-nanotube systems can improve the capacity of lithium batteries by using both nanotube exteriors and interiors. Ab inito calculations

Carolina Garau; Antonio Frontera; David Quiñonero; Antoni Costa; Pau Ballester; Pere M. Deyà

2003-01-01

391

Calculations of Encapsulation of Amino Acids Inside the (13, 0) Single?walled Carbon Nanotube  

Microsoft Academic Search

Encapsulation of few amino acids inside (13, 0) single?walled carbon nanotube (SWCNT) has been investigated through calculations within DFT?based method. We find that zwitterionic?Gly acid adsorption is bound stronger to the inner surface of the tube in comparison to nonionic?Gly counterparts, as well as on phenylalanine, histidine and cysteine amino acids. The interaction of amino acids with the outer surface

M. D. Ganji

2010-01-01

392

Radial elasticity of single-walled carbon nanotube measured by atomic force microscopy  

Microsoft Academic Search

Effective radial modulus (Eradial) of straight single-walled carbon nanotubes (SWCNTs) grown directly on quartz substrate have been measured by using well-calibrated tapping mode and contact mode atomic force microscopies. It is found that the measured Eradial decreases from 57 to 9 GPa as the diameter of the SWCNTs increases from 0.92 to 1.91 nm. The current experimental results are consistent

Y. H. Yang; W. Z. Li

2011-01-01

393

In situ TPO/Raman to characterize single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

Temperature programmed oxidation (TPO) coupled with in situ Raman spectroscopy has been used as an effective qualitative and quantitative analysis of raw and purified single-walled carbon nanotubes (SWNT) samples. The incorporation of Raman facilitates the identification of the nature of the oxidation peaks present in a TPO profile. Using different samples it was possible to evaluate the potential of the technique for quantifying different impurities in the SWNT samples as well as in SWNT-polymer composites.

Herrera, Jose E.; Resasco, Daniel E.

2003-07-01

394

Random networks and aligned arrays of single-walled carbon nanotubes for electronic device applications  

Microsoft Academic Search

Singled-walled carbon nanotubes (SWNTs), in the form of ultrathin films of random networks, aligned arrays, or anything in\\u000a between, provide an unusual type of electronic material that can be integrated into circuits in a conventional, scalable fashion.\\u000a The electrical, mechanical, and optical properties of such films can, in certain cases, approach the remarkable characteristics\\u000a of the individual SWNTs, thereby making

Qing Cao; John A. Rogers

2008-01-01

395

Nonradiative exciton decay dynamics in hole-doped single-walled carbon nanotubes  

Microsoft Academic Search

We studied exciton dynamics in hole-doped single-walled carbon nanotubes (SWNTs). The intensities of photoluminescence (PL) peaks decreased and the PL lifetimes became shorter with an addition of hole dopant tetrafluorotetracyano- p -quinodimethane (F4TCNQ) . We found that the nonradiative decay of excitons induced by the F4TCNQ was of the order of a few tens of picoseconds for densities of ˜0.1hole\\/nm

Kazunari Matsuda; Yuhei Miyauchi; Takero Sakashita; Yoshihiko Kanemitsu

2010-01-01

396

Electrocatalytic oxidation of formic acid and formaldehyde on nanoparticle decorated single walled carbon nanotubes  

Microsoft Academic Search

A potent catalyst has been prepared consisting of platinum (Pt), and platinum–palladium (Pt–Pd) nanoparticles supported on purified single-walled carbon nanotubes (Pt\\/CNT and Pt–Pd\\/CNT). Electrochemical characteristics of formic acid and formaldehyde oxidation on these catalysts are investigated via cyclic voltammetric analysis in mixed 0.5 M HCOOH (or 0.5 M HCHO) and 0.5 M H2SO4 solutions. The results imply that the Pt–Pd\\/CNT

V. Selvaraj; A. Nirmala Grace; M. Alagar

2009-01-01

397

Fabrication of single-walled carbon nanotube flexible strain sensors with high sensitivity  

Microsoft Academic Search

This work demonstrates a fabrication technique of high sensitivity flexible strain sensors at room temperature. The grown well-aligned millimeter-long single-walled carbon nanotube (SWCNT) was transferred from the silicon substrate to the pretrenched flexible substrate. The sensor design allows effective adhesion between SWCNT and flexible substrate for SWCNT lengthwise strain and piezoresistivity change. Experimental results show that the sensor achieves a

Neng-Kai Chang; Chi-Chung Su; Shuo-Hung Chang

2008-01-01

398

A high sensitivity single-walled carbon-nanotube-array-based strain sensor for weighing  

Microsoft Academic Search

A single-walled carbon-nanotube-array-based (SWCNT) strain sensor was proposed and its fabrication technique was presented, which afforded more simple process than individual SWCNT-based sensor. A novel selective treatment of strain-based electrical breakdown was utilized to leave the SGS-SWCNTs with high gauge factor in the array. The SWCNT-array strain sensor were used for weighing experiment and the results showed that the sensor's

X. Yang; Z. Y. Zhou; F. Z. Zheng; M. Zhang; J. Zhang; Y. G. Yao

2009-01-01

399

Synthesis and Characterization of Single-Walled Carbon Nanotube\\/Silicon Carbide Composites  

Microsoft Academic Search

Single-walled carbon nanotube (SWCNT)\\/SiC composites were successfully prepared by direct thermal decomposition of polycarbosilane (PCS) precursor. The SWCNT\\/SiC composites were prepared by the hot-pressing the SWCNTs-PCS (7:3 mass%) mixture at temperatures of 1000, 1400 and 1800°C under a pressure of 120 MPa. The effects of SiC synthesis and processing temperatures on the mechanical properties of the resultant composites were investigated

G. Yamamoto; K. Yokomizo; M. Omori; Y. Sato; T. Takahashi; T. Hashida; K. Motomiya; A. Okubo; S. Watanabe; K. Tohji

2006-01-01

400

Molecular Scale Buckling Mechanics in Individual Aligned Single-Wall Carbon Nanotubes on Elastomeric Substrates  

Microsoft Academic Search

We have studied the scaling of controlled nonlinear buckling processes in materials with dimensions in the molecular range (i.e., 1 nm) through experimental and theoretical studies of buckling in individual single-wall carbon nanotubes on substrates of poly(dimethylsiloxane). The results show not only the ability to create and manipulate patterns of buckling at these molecular scales, but also, that analytical continuum

Dahl-Young Khang; Jianliang Xiao; Coskun Kocabas; Scott MacLaren; Tony Banks; Hanqing Jiang; Yonggang Y. Huang; John A. Rogers

2008-01-01

401

Gate capacitance coupling of singled-walled carbon nanotube thin-film transistors  

Microsoft Academic Search

The electrostatic coupling between singled-walled carbon nanotube (SWCNT) networks\\/arrays and planar gate electrodes in thin-film transistors (TFTs) is analyzed both in the quantum limit with an analytical model and in the classical limit with finite-element modeling. The computed capacitance depends on both the thickness of the gate dielectric and the average spacing between the tubes, with some dependence on the

Qing Cao; Minggang Xia; Coskun Kocabas; Moonsub Shim; John A. Rogers; Slava V. Rotkin

2007-01-01

402

Directed assembly of high density single-walled carbon nanotube patterns on flexible polymer substrates  

Microsoft Academic Search

We report an effective technique for the controlled assembly of single-walled carbon nanotubes (SWNTs) and demonstrate organized high density network architectures on soft polymeric substrates. We utilize the surface energy differential between a plasma treated (hydrophilic) parylene-C surface and a photoresist (hydrophobic) surface to create microscale patterns of SWNT networks on a 10 µm thick parylene-C substrate. The large scale

Xugang Xiong; Chia-Ling Chen; Peter Ryan; Ahmed A. Busnaina; Yung Joon Jung; Mehmet R. Dokmeci

2009-01-01

403

Efficient Organometallic Spin Filter between Single-Wall Carbon Nanotube or Graphene Electrodes  

Microsoft Academic Search

We present a theoretical study of spin transport in a class of molecular systems consisting of an organometallic benzene-vanadium cluster placed in between graphene or single-wall carbon-nanotube-model contacts. Ab initio modeling is performed by combining spin density functional theory and nonequilibrium Green's function techniques. We consider weak and strong cluster-contact bonds. Depending on the bonding we find from 73% (strong

Mohammad Koleini; Magnus Paulsson; Mads Brandbyge

2007-01-01

404

Photocurrent of CdSe nanocrystals on single-walled carbon nanotube-field effect transistor  

Microsoft Academic Search

CdSe nanocrystals (NCs) have been decorated on single-walled carbon nanotubes (SWCNTs) by combining a method of chemically modified substrate along with gate-bias control. CdSe\\/ZnS core\\/shell quantum dots were negatively charged by adding mercaptoacetic acid. The silicon oxide substrate was decorated by octadecyltrichlorosilane and converted to hydrophobic surface. The negatively charged CdSe NCs were adsorbed on the SWCNT surface by applying

Seung Yol Jeong; Seong Chu Lim; Dong Jae Bae; Young Hee Lee; Hyun Jin Shin; Seon-Mi Yoon; Jae Young Choi; Ok Hwan Cha; Mun Seok Jeong; David Perello; Minhee Yun

2008-01-01

405

Morphology of single-wall carbon nanotube aggregates generated by electrospray of aqueous suspensions  

Microsoft Academic Search

Airborne single-wall carbon nanotubes (SWCNTs) have a high tendency to agglomerate due to strong interparticle attractive\\u000a forces. The SWCNT agglomerates generally have complex morphologies with an intricate network of bundles of nanotubes and nanoropes,\\u000a which limits their usefulness in many applications. It is thus desirable to produce SWCNT aerosol particles that have well-defined,\\u000a unagglomerated fibrous morphologies. We present a method

Bon Ki Ku; Pramod Kulkarni

2009-01-01

406

Thermal and Electrical Transport in Ultralow Density Single-Walled Carbon Nanotube Networks.  

PubMed

The thermal, electrical, and thermoelectric properties of aerogels of single-walled carbon nanotubes are characterized. Their ultralow density enables the transport properties of the junctions to be distinguished from those of the nanotubes themselves. Junction thermal and electrical conductances are found to be orders of magnitude larger than those found in typical dense SWCNT networks. In particular, the average junction thermal conductance is close to the theoretical maximum for a van der Waals bonded SWCNT junction. PMID:23606438

Zhang, Ke Jia; Yadav, Abhishek; Kim, Kyu Hun; Oh, Youngseok; Islam, Mohammad F; Uher, Ctirad; Pipe, Kevin P

2013-04-22

407

Single-walled carbon nanotube thin film emitter-detector integrated optoelectronic device.  

PubMed

We use the suspended single-walled carbon nanotube (SWNT) thin film technology to assemble the first prototype of an integrated optoelectronic SWNT device, a SWNT optocoupler in which a SWNT emitter and a SWNT detector couple two electrical circuits by the transmission of a signal through the optical channel. Our experiments show that the integrated SWNT emitter/SWNT detector is an ideal couple in which the broadband wavelength character of the emission matches the broadband detection capabilities. PMID:18598090

Itkis, Mikhail E; Yu, Aiping; Haddon, Robert C

2008-08-01

408

Fully transparent thin-film transistors based on aligned single-walled carbon nanotube arrays  

Microsoft Academic Search

The work describes the first demonstration of fully transparent thin-film-transistors (TFTs) based on well-aligned single-walled carbon nanotube (SWNT) arrays with indium tin oxide (ITO) source\\/drain\\/gate electrodes. The fully transparent SWNT-TFTs could be attractive candidates for future flexible\\/ or transparent electronics. The transistors provide suitable current levels to drive OLED pixels (e.g. for high resolution displays), and operated at relatively low

Sunkook Kim; Sanghyun Ju; David B Janes; Saeed Mohammadi

2008-01-01

409

In situ synthesis of amylose/single-walled carbon nanotubes supramolecular assembly.  

PubMed

A supramolecular assembly of amylose and single-walled carbon nanotubes (SWNTs) was synthesized in situ through vine-twining polymerization. Raman analysis indicated that the amylose-SWNTs supramolecular assembly was formed after the polymerization and SEM images displayed the twisted ribbons in the SWNTs wrapped by amylose. The dispersion stability of the SWNTs in aqueous solutions was improved by the wrapping of short-chain amylose molecules around the SWNTs. PMID:18653174

Yang, Liqun; Zhang, Bifang; Liang, Yuting; Yang, Bin; Kong, Tao; Zhang, Li-Ming

2008-09-22

410

Enhancement of field emission characteristics of tungsten emitters by single-walled carbon nanotube modification  

Microsoft Academic Search

We present a simple method for improving the field emission performance of tungsten-tip electron sources based on single-walled carbon nanotube (SWCNT) modification. By coating a sandwich-like thin film of Al-Fe-Al (with Fe as a catalyst) on a tungsten tip, SWCNTs were synthesized at 600 °C in a chemical vapor deposition (CVD) reactor. The influence of CNT modification on the electron

D. Ferrer; T. Tanii; I. Matsuya; G. Zhong; S. Okamoto; H. Kawarada; T. Shinada; I. Ohdomari

2006-01-01

411

Electron-ion quantum plasma excitations in single-walled carbon nanotubes.  

PubMed

The effect of a uniform static external magnetic field in the Voigt configuration on electron-ion quantum plasma oscillations in single-walled carbon nanotubes is discussed using the linearized quantum hydrodynamic model in conjunction with Maxwell's equations. Transverse magnetic waves which propagate parallel to the surface of the nanotubes, in the presence of an external magnetic field, yield a spectrum containing a quantum magnetosonic branch in addition to the magnetoplasmon branch. PMID:21715799

Moradi, Afshin

2009-01-28

412

Plasma-synthesized single-walled carbon nanotubes and their applications  

Microsoft Academic Search

Plasma-based nanotechnology is a rapidly developing area of research ranging from physics of gaseous and liquid plasmas to material science, surface science and nanofabrication. In our case, nanoscopic plasma processing is performed to grow single-walled carbon nanotubes (SWNTs) with controlled chirality distribution and to further develop SWNT-based materials with new functions corresponding to electronic and biomedical applications. Since SWNTs are

R. Hatakeyama; T. Kaneko; T. Kato; Y. F. Li

2011-01-01

413

Assistance of A-plane sapphire substrate to the growth of single-walled carbon nanotubes  

Microsoft Academic Search

High-quality single-walled carbon nanotubes (SWCNTs) were synthesized on A-plane sapphire and SiO2\\/Si substrates by thermal chemical vapor deposition (CVD) of methane at a temperature of 800°C. The yield of SWCNTs on A-plane sapphire surface was always found to be much higher than that on silica surface after the same CVD process. A-plane sapphire substrate was discovered to remarkably catalyze the

Fu-Bo Rao; Tie Li; Yue-Lin Wang

2008-01-01

414

80 GHz field-effect transistors produced using high purity semiconducting single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

This paper presents the high frequency performance of single-walled carbon nanotube (SWNT) field-effect transistors, with channel consisting of dense networks of high purity semiconducting SWNTs. Using SWNT samples containing 99% pure semiconducting SWNTs, we achieved operating frequencies above 80 GHz. This record frequency does not require aligned SWNTs, thus demonstrating the remarkable potential of random networks of sorted SWNTs for high frequency electronics.

Nougaret, L.; Happy, H.; Dambrine, G.; Derycke, V.; Bourgoin, J.-P.; Green, A. A.; Hersam, M. C.

2009-06-01

415

Bio–nano interaction of proteins adsorbed on single-walled carbon nanotubes  

Microsoft Academic Search

We applied X-ray absorption near edge structure (XANES) spectroscopy to investigate the adsorption of proteins onto single-walled carbon nanotubes (SWCNTs). Specific XANES spectral features such as peptide CO bonds in proteins were recognized and found to be affected by the corresponding aromatic structure of SWCNTs. Experimental data combined with first-principle calculation of the investigated nano-complex allow the understanding of adsorption

Jun Zhong; Li Song; Jie Meng; Bin Gao; Wangsheng Chu; Haiyan Xu; Yi Luo; Jinghua Guo; Augusto Marcelli; Sishen Xie; Ziyu Wu

2009-01-01

416

Effect of Solvents and Dispersants on the Bundle Dissociation of Single-walled Carbon Nanotube  

Microsoft Academic Search

Single-wall carbon nanotubes (SWCNTs) are severely restricted in their applications, as they exist in rope-like bundles. Recently, J. Coleman et al. demonstrated a spectroscopic method to monitor bundle dissociation in low concentration polymer-nanotube dispersions. The method relies on the measurement of the ratio of free-polymer to the nanotube-bound polymer in the SWCNT-polymer solutions via luminescent spectroscopy. A theory has been

Silvia Giordani; Shane D. Bergin; Anna Drury; Éimhín Ní Mhuircheartaigh; Jonathan N. Coleman; Werner J. Blau

2005-01-01

417

Calculations of organic-solvent dispersions of single-wall carbon nanotubes  

Microsoft Academic Search

The aqueous solubility Sw and 1-octanol-(Po), cyclohexane-(Pch), and chloroform-(Pcf) water partition coefficients are calculated. The properties of single-wall carbon nanotubes (SWNT) are related to the indices (n, m) designating the chiral vector. SWNTs are classified in zigzag (n, 0), armchair (n, n), and chiral (n, m). These properties permit classifying SWNTs according to (n, m). Correlations between (n2 + nm

Francisco Torrens

2006-01-01

418

EFFECT OF SOLVENT AND DISPERSANT ON THE BUNDLE DISSOCIATION OF SINGLE-WALLED CARBON NANOTUBES  

Microsoft Academic Search

Single-wall carbon nanotubes (SWNT) are severely restricted in their applications, as they exist in rope-like bundles. Recently, J. Coleman et al. demonstrated a spectroscopic method to monitor bundle dissociation in low concentration NT-polymer composites. In this work we present the results we obtained with 2,5-dioctyloxy-1,4-distyrylbenzene (pDSB), a short-chain analogues of the well known PPV. We found a strong dependence of

SILVIA GIORDANI; SHANE D. BERGIN; ANNA DRURY; ÉIMHÍN NÍ MHUIRCHEARTAIGH; JONATHAN COLEMAN; WERNER BLAU

419

Effect of solvent and dispersant on the bundle dissociation of single-walled carbon nanotube  

Microsoft Academic Search

Single-wall carbon nanotubes (SWCNT) are severely restricted in their applications, as they exist in rope-like bundles. Recently, J. Coleman et al. demonstrated a spectroscopic method to monitor bundle dissociation in low concentration NT-polymer composites. The method relies on the measurement of the ratio of free-polymer to the nanotube-bound polymer in the SWCNT-polymer solutions via luminescent spectroscopy. A theory has been

Silvia Giordani; Shane D. Bergin; Anna Drury; Eimhin Ni Mhuircheartaigh; Manuel Ruther; Jonathan N. Coleman; Werner J. Blau

2005-01-01

420

Variation of single wall carbon nanotube dispersion properties with alkyl amide and halogenated aromatic solvents  

Microsoft Academic Search

Organic solvents from the alkyl amide and halogenated aromatic classes have been analyzed as dispersion agents for high purity single wall carbon nanotubes (SWCNTs). The resulting dispersions from two novel SWCNT solvents, N,N,N?,N?-tetramethylmalonamide (TMMA) and 1-chloronaphthalene (1-CLN), have been compared to the well-established solvents, N,N-dimethylacetamide (DMA) and 1,2-dichlorobenzene (DCB). Optical absorption spectroscopy on a series of high purity SWCNT concentrations

Matthew J. Ganter; Brian J. Landi; James J. Worman; Christopher M. Schauerman; Cory D. Cress; Ryne P. Raffaelle

2009-01-01

421

Synthesis, electronic structure, and Raman scattering of phosphorous-doped single-wall carbon nanotubes  

SciTech Connect

Substitutional phosphorous doping in single-wall carbon nanotubes (SWNTs) is investigated by density functional theory and resonance Raman spectroscopy. Electronic structure calculations predict charge localization on the phosphorus atom, which is also responsible of generating non-dispersive valence and conduction bands close to the Fermi level. Analysis of electron and phonon renormalization in the double-resonance Raman process confirms the different nature of the phosphorous donor doping (localized) when compared to nitrogen substitutional doping (non-localized) in SWNTs.

Sumpter, Bobby G [ORNL; Cruz Silva, Eduardo [ORNL; Meunier, Vincent [ORNL; Terrones Maldonado, Humberto [ORNL; Terrones Maldonado, Mauricio [ORNL; Campos-Delgado, Jessica [IPICyT; Jorio, Ado [Universidade Federal de Minas Gerais; Pimenta, M. A. [Universidade Federal de Minas Gerais; Rao, A. M. [Clemson University; Maciel, I. O. [Universidad Federal de Minas Gerais

2009-01-01

422

Functional single-walled carbon nanotubes\\/chitosan conjugate for tumor cells targeting  

Microsoft Academic Search

The application of single-walled carbon nanotubes (SWCNTs) in the field of biomedicine is becoming an exciting topic because of their flexible structure and propensity for chemical functionalization. In this assay, a novel noncovalently functional SWCNTs based on a natural biocompatible polymer chitosan has been developed for tumor cells targeting. First, SWCNTs were modified by chitosan (CHIT-SWCNT). Second, CHIT-SWCNT was coupled

Baoyan Wu; Zhongmin Ou; Da Xing

2009-01-01

423

Effectiveness of sorting single-walled carbon nanotubes by diameter using polyfluorene derivatives  

Microsoft Academic Search

Semiconducting single-walled carbon nanotubes (SWCNTs) sorted by conjugated polymers are of great interest for electronic and optoelectronic applications. Here we demonstrate by optical methods that the selectivity of conjugated polymers for semiconducting SWCNTs is influenced by the structure of their side-chains and\\/or the molecular weight of the macromolecules, and that side chain functionalities determine the solubility in different dispersion media.

J. Gao; M. Kwak; J. Wildeman; A. Herrmann; M. A. Loi

2011-01-01

424

High energy E11 excitons above the continuum threshold in semiconducting single-walled carbon nanotubes  

Microsoft Academic Search

Although the excitonic nature of the primary photoexcitation has been firmly established in semiconducting single-walled carbon nanotubes (S-SWCNTs), the magnitude of the exciton binding energy is still being debated. Recent photoluminescence excitation experiments have detected excitons above the threshold of the continuum band predicted from two-photon absorption measurements in the (10,6) S-SWCNT footnotetextJ. Lefebvre and P. Finnie, Nano Lett. 8,

Hongbo Zhao; Sumit Mazumdar

2010-01-01

425

Universality in the Photophysics of pi-Conjugated Polymers and Single-Walled Carbon Nanotubes  

Microsoft Academic Search

We describe both pi-conjugated polymers and semiconducting single-walled carbon nanotubes because of the remarkable similarities in their behavior under photoexcitation. The common themes between these two seemingly different classes of materials are pi-conjugation, quasi one-dimensionality, and strong Coulomb interactions. Theoretical understanding of both systems requires going beyond traditional band theory. We present our current understanding of the electronic structures and

Sumit Mazumdar; Zhendong Wang; Hongbo Zhao

2008-01-01

426

Coulomb effect and nonlinear optical properties of single-walled carbon nanotubes  

Microsoft Academic Search

We investigated theoretically nonlinear optical properties of ten single-walled carbon nanotubes (SWCNTs) with a wide range of diameters, within a semiempirical Pariser-Parr-Pople model with a long- range Coulomb interaction. The excited states are calculated within Single Configuration Interaction (SCI) scheme. In our previous work ootnotetextHongbo Zhao and Sumit Mazumdar, Phys. Rev. Lett. 93, 157402 (2004) we have shown that there

Hongbo Zhao; Sumit Mazumdar

2005-01-01

427

Microwave-assisted functionalization of single-walled carbon nanotubes with 3-chloropropene  

Microsoft Academic Search

We have reported a highly efficient approach to functionalize single-walled carbon nanotubes by electrophilic addition polymerization\\u000a of 3-chloropropene under microwave irradiation. Using Lewis acids as catalysts, 3-chloropropene can undergo polymerization\\u000a followed by hydrolysis with alkaline methanol, and thus the reaction results in the attachment of polymer chains and hydroxyl\\u000a groups to the surface of the nanotubes. The resulting nanotubes were

Rong Tian; Xianbao Wang; Yang Xu; Shaoqing Li; Li Wan; Mingjian Li; Jing Cheng

2009-01-01

428

Spectroscopic investigation of conjugated polymer\\/single-walled carbon nanotube interactions  

Microsoft Academic Search

Composite materials, based on single-walled carbon nanotubes and a poly(p-phenylene vinylene) derivative, show an interaction between the components capable of solubilising the nanotubes, which has not been otherwise achieved. Here these materials are characterised by electron microscopy, and optical and vibrational spectroscopy. The spectroscopic behaviour of the polymer is seen to be dramatically affected, which is attributed to conformational changes

Brendan Mc Carthy; Alan B Dalton; Jonathan N Coleman; Hugh J Byrne; Patrick Bernier; Werner J Blau

2001-01-01

429

Photophysics of single-walled carbon nanotubes: similarity with pi-conjugated polymer  

Microsoft Academic Search

Coulomb electron-electron (e-e) interactions among the pi-electrons have a strong effect on the energy spectra of semiconducting single-walled carbon nanotubes (S-SWCNTs), because of their quasi-one-dimensionality. The primary photoexcitations in S-SWCNTs as a consequence of e-e interactions are excitons, as opposed to free electrons and holes. There already exists a vast literature on excitons in pi-conjugated polymers, the other class of

Hongbo Zhao

2006-01-01

430

Spectroscopic investigation of conjugated polymer/single-walled carbon nanotube interactions  

NASA Astrophysics Data System (ADS)

Composite materials, based on single-walled carbon nanotubes and a poly( p-phenylene vinylene) derivative, show an interaction between the components capable of solubilising the nanotubes, which has not been otherwise achieved. Here these materials are characterised by electron microscopy, and optical and vibrational spectroscopy. The spectroscopic behaviour of the polymer is seen to be dramatically affected, which is attributed to conformational changes due to the effect of the nanotubes.

Mc Carthy, Brendan; Dalton, Alan B.; Coleman, Jonathan N.; Byrne, Hugh J.; Bernier, Patrick; Blau, Werner J.

2001-12-01

431

Frequency dependent electrical transport between conjugated polymer and single-walled carbon nanotubes  

Microsoft Academic Search

This work focuses on the combination of the complementary properties of single-walled carbon nanotube (SWNTs) and poly3-octylthiophene (P3OT), following a dielectric route to the characterization of a novel composite material. The structural and electrical characterization of a SWNT\\/P3OT hybrid system performed by differential scanning calorimetry and a.c. impedance spectroscopy show interesting effects, including the tendency of the nanotube structure to

L. Valentini; I. Armentano; J. Biagiotti; E. Frulloni; J. M. Kenny; S. Santucci

2003-01-01

432

Dispersion of single-walled carbon nanotubes modified with poly-l-tyrosine in water  

Microsoft Academic Search

In this study, complexes composed of poly-l-tyrosine (pLT) and single-walled carbon nanotubes (SWCNTs) were produced and the dispersibility of the pLT\\/SWCNT complexes in water by measuring the ? potential of the complexes and the turbidity of the solution were investigated. It is found that the absolute value of the ? potential of the pLT\\/SWCNT complexes is as high as that

Mio Kojima; Tomoka Chiba; Junichiro Niishima; Toshiaki Higashi; Takahiro Fukuda; Yoshikata Nakajima; Shunji Kurosu; Tatsuro Hanajiri; Koji Ishii; Toru Maekawa; Akira Inoue

2011-01-01

433

Single wall carbon nanotube templated oriented crystallization of poly(vinyl alcohol)  

Microsoft Academic Search

Shearing of poly(vinyl alcohol) (PVA)\\/single wall carbon nanotube (SWNT) dispersions result in the formation of self-assembled oriented PVA\\/SWNT fibers or ribbons, while PVA solution results in the formation of unoriented fibers. Diameter\\/width and length of these self-assembled fibers was 5–45?m and 0.5–3mm, respectively. High-resolution transmission electron micrographs showed well resolved PVA (200) lattice with molecules oriented parallel to the nanotube

Marilyn L. Minus; Han Gi Chae; Satish Kumar

2006-01-01

434

Microwave-induced rapid nanocomposite synthesis using dispersed single-wall carbon nanotubes as the nuclei  

Microsoft Academic Search

Single-wall carbon nanotubes (SWNTs) provide a reactive environment in presence of microwave radiation because they absorb\\u000a the energy that leads to fast, direct heating. This makes composite formation in a microwave reactor highly feasible where\\u000a the SWNTs serve as the nuclei for polymerization. In this article, we demonstrate rapid, in situ synthesis of poly(methyl\\u000a methacrylate) (PMMA) and polyvinylpyrrolidone (PVP) nanocomposites using

Subhendu Ray Chowdhury; Yuhong Chen; Yubing Wang; Somenath Mitra

2009-01-01

435

Incorporation of highly dispersed single-walled carbon nanotubes in a polyimide matrix  

Microsoft Academic Search

Single-walled carbon nanotubes (SWNTs) were dispersed in the form of individual nanotubes and small bundles, and subsequently polymerized to prepare composite films. The nanotubes were first dispersed in dimethylacetamide in the presence of 1,3-bis(3-aminophenoxy)benzene (APB), which was then polymerized with 4,4?-hexafluoroisopropylidiene diphthalic anhydride (6-FDA). Optical microscopy, SEM and TEM studies of the composite show that the SWNTs are homogenously distributed

Aiping Yu; Hui Hu; Elena Bekyarova; Mikhail E. Itkis; Junbo Gao; Bin Zhao; Robert C. Haddon

2006-01-01

436

Terahertz Characterization of Single-Walled Carbon Nanotube and Graphene On-Substrate Thin Films  

Microsoft Academic Search

In this paper, single-walled carbon nanotube (SWNT) thin films with thicknesses on the order of hundreds nanometers on glass substrates and a graphene thin film (2-3 layers) on a glass substrate are characterized via terahertz time-domain spectroscopy. The substrate permittivity is first characterized. The thin film is then treated as a surface boundary condition between the substrate and air. Using

Min Liang; Ziran Wu; Liwei Chen; Li Song; Pulickel Ajayan; Hao Xin

2011-01-01

437

Condensation and phase transition of hydrogen molecules confined in single-walled carbon nanotubes  

Microsoft Academic Search

The condensation and phase transitions of hydrogen molecules confined in single-walled carbon nanotubes have been studied using ab initio calculations and molecular dynamics simulations. At low temperature the van der Waals surface of a narrow (5,5) tube forces the H2 molecules to form quasi-one-dimensional lattices with the H2 molecular orientation highly polarizing along the axial direction of the tube. Various

Yueyuan Xia; Mingwen Zhao; Yuchen Ma; Xiangdong Liu; Minju Ying; Liangmo Mei

2003-01-01

438

Quantum dot-single wall carbon nanotube complexes for polymeric solar cells  

Microsoft Academic Search

The enhancement of polymeric solar cells through the addition of nanostructured material complexes has been investigated. These novel materials are intended to facilitate exciton dissociation and carrier transport through the polymer matrix. The dispersion of single wall carbon nanotubes (SWNTs) into poly(3-octylthiophene)-(P3OT) has been shown to dramatically improve both the electrical conductivity and optical absorption of the polymer compared to

Ryne P. Raffaelle; Brian J. Landi; Christopher M. Evans; Stephanie L. Castro; Sheila G. Bailey

2005-01-01

439

Two layer 4:4 co-ordinated KI crystals grown within single walled carbon nanotubes  

Microsoft Academic Search

The formation of `all surface' 4:4 co-ordinated KI crystals within 1.4 nm diameter single walled carbon nanotubes (SWNT) is reported. KI was inserted into the SWNTs by a capillary method [J. Sloan, D.M. Wright, H.G. Woo, S. Bailey, G. Brown, A.P.E. York, K.S. Coleman, J.L. Hutchison, M.L.H. Green, J. Chem. Soc. Chem. Commun. (1999) 699], whereby the nanotubes were combined

J. Sloan; M. C. Novotny; S. R. Bailey; G. Brown; C. Xua; V. C. Williams; S. Friedrichs; E. Flahaut; R. L. Callender; A. P. E. York; K. S. Coleman; M. L. H. Green; R. E. Dunin-Borkowski; J. L. Hutchison

2000-01-01

440

Photoacoustic molecular imaging using single walled carbon nanotubes in living mice  

Microsoft Academic Search

Photoacoustic molecular imaging is an emerging technology offering non-invasive high resolution imaging of the molecular expressions of a disease using a photoacoustic imaging agent. Here we demonstrate for the first time the utility of single walled carbon nanotubes (SWNTs) as targeted imaging agents in living mice bearing tumor xenografts. SWNTs were conjugated with polyethylene-glycol-5000 connected to Arg-Gly-Asp (RGD) peptide to

Adam de La Zerda; Cristina Zavaleta; Shay Keren; Srikant Vaithilingam; Sunil Bodapati; Robert Teed; Zhuang Liu; Jelena Levi; Bryan R. Smith; Te-Jen Ma; Omer Oralkan; Zhen Cheng; Xiaoyuan Chen; Hongjie Dai; Butrus T. Khuri-Yakub; Sanjiv S. Gambhir

2009-01-01

441

Effects of pressure transmitting media on Raman features of single-walled carbon nanotubes  

NASA Astrophysics Data System (ADS)

We have performed high pressure Raman studies of single-walled carbon nanotubes (SWCNTs) by using different organic solvents as the pressure transmitting medium (PTM). A linear dependence of pressure coefficient of Raman G band is found with the molecular weight of organic solvent. In addition, according to the experimental data and a comparative analysis of pressure measurement without the PTM, we explain the occurrence of plateau and hardening behavior of Raman G and D ? bands upon increasing pressure.

Gao, Kun; Dai, R. C.; Zhao, Z.; Zhang, Z. M.; Ding, Z. J.

2008-07-01

442

Radiation Effects in Single-Walled Carbon Nanotube Thin-Film-Transistors  

Microsoft Academic Search

The fabrication, characterization, and radiation response of single-walled carbon nanotube (SWCNT) thin-film field effect transistors (SWCNT-TFTs) has been performed. SWCNT-TFTs were fabricated on SiO2-Si substrates from 98% pure semiconducting SWCNTs separated by density gradient ultracentrifugation. Optical and Raman characterization, in concert with measured drain current Ion\\/Ioff ratios, up to 104, confirmed the high enrichment of semiconducting-SWCNTs. Total ionizing dose (TID)

Cory D. Cress; Julian J. McMorrow; Jeremy T. Robinson; Adam L. Friedman; Brian J. Landi

2010-01-01

443

Multimodal optical sensing and analyte specificity using single-walled carbon nanotubes  

Microsoft Academic Search

Nanoscale sensing elements offer promise for single-molecule analyte detection in physically or biologically constrained environments. Single-walled carbon nanotubes have several advantages when used as optical sensors, such as photostable near-infrared emission for prolonged detection through biological media and single-molecule sensitivity. Molecular adsorption can be transduced into an optical signal by perturbing the electronic structure of the nanotubes. Here, we show

Daniel A. Heller; Hong Jin; Brittany M. Martinez; Dhaval Patel; Brigid M. Miller; Tsun-Kwan Yeung; Prakrit V. Jena; Claudia Höbartner; Taekjip Ha; Scott K. Silverman; Michael S. Strano

2009-01-01

444

Molecular simulation of hydrogen adsorption in single-walled carbon nanotubes and idealized carbon slit pores  

NASA Astrophysics Data System (ADS)

The adsorption of hydrogen gas into single-walled carbon nanotubes (SWNTs) and idealized carbon slit pores is studied by computer simulation. Hydrogen-hydrogen interactions are modeled with the Silvera-Goldman potential. The Crowell-Brown potential is used to model the hydrogen-carbon interactions. Calculations include adsorption inside the tubes, in the interstitial regions of tube arrays, and on the outside surface of isolated tubes. Quantum effects are included through implementation of the path integral formalism. Comparison with classical simulations gives an indication of the importance of quantum effects for hydrogen adsorption. Quantum effects are important even at 298 K for adsorption in tube interstices. We compare our simulations with experimental data for SWNTs, graphitic nanofibers, and activated carbon. Adsorption isotherms from simulations are in reasonable agreement with experimental data for activated carbon, but do not confirm the large uptake reported for SWNTs and nanofibers. Although the adsorption potential for hydrogen in SWNTs is enhanced relative to slit pores of the same size, our calculations show that the storage capacity of an array of tubes is less than that for idealized slit pore geometries, except at very low pressures. Ambient temperature isotherms indicate that an array of nanotubes is not a suitable sorbent material for achieving DOE targets for vehicular hydrogen storage.

Wang, Qinyu; Johnson, J. Karl

1999-01-01

445

Evidence for large hydrogen storage capacity in single-walled carbon nanotubes encapsulated by electroplating Pd onto a Pd substrate  

SciTech Connect

We report a study of hydrogen storage in an alternative material, representing single-walled carbon nanotubes (SWCNTs) encapsulated by thin Pd layers onto a Pd substrate. A synergetic effect resulting in combination of the Pd and the SWCNTs properties with regards to hydrogen has been achieved. Adding SWCNTs increases the H{sub 2} capacity of the Pd-SWCNT composite by up to 25% relative to Pd metal alone under electrochemical loading. This results in a storage capacity of 8-12 wt %. with regard to the added SWCNTs.

Lipson, A. G. [Department of Nuclear Plasma and Radiological Engineering, University of Illinois, Urbana, Illinois 61801 (United States); A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 119991, Moscow (Russian Federation); Lyakhov, B. F.; Saunin, E. I.; Tsivadze, A. Yu. [A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, 119991, Moscow (Russian Federation)

2008-02-15

446

Helicity-dependent single-walled carbon nanotube alignment on graphite for helical angle and handedness recognition  

PubMed Central

Aligned single-walled carbon nanotube arrays provide a great potential for the carbon-based nanodevices and circuit integration. Aligning single-walled carbon nanotubes with selected helicities and identifying their helical structures remain a daunting issue. The widely used gas-directed and surface-directed growth modes generally suffer the drawbacks of mixed and unknown helicities of the aligned single-walled carbon nanotubes. Here we develop a rational approach to anchor the single-walled carbon nanotubes on graphite surfaces, on which the orientation of each single-walled carbon nanotube sensitively depends on its helical angle and handedness. This approach can be exploited to conveniently measure both the helical angle and handedness of the single-walled carbon nanotube simultaneously at a low cost. In addition, by combining with the resonant Raman spectroscopy, the (n,m) index of anchored single-walled carbon nanotube can be further determined from the (d,?) plot, and the assigned (n,m) values by this approach are validated by both the electronic transition energy Eii measurement and nanodevice application.

Chen, Yabin; Shen, Ziyong; Xu, Ziwei; Hu, Yue; Xu, Haitao; Wang, Sheng; Guo, Xiaolei; Zhang, Yanfeng; Peng, Lianmao; Ding, Feng; Liu, Zhongfan; Zhang, Jin

2013-01-01

447

High-power supercapacitor electrodes from single-walled carbon nanohorn/nanotube composite.  

PubMed

A novel composite is presented as a supercapacitor electrode with a high maximum power rating (990 kW/kg; 396 kW/l) exceeding power performances of other electrodes. The high-power capability of the electrode stemmed from its unique meso-macro pore structure engineered through the utilization of single-walled carbon nanotubes (20 wt %) as scaffolding for single-walled carbon nanohorns (80 wt %). The novel composite electrode also exhibited durable operation (6.5% decline in capacitance over 100?000 cycles) as a result of its monolithic chemical composition and mechanical stability. The novel composite electrode was benchmarked against another high-power electrode made from single-walled carbon nanotubes (Bucky paper electrode). While the composite electrode had a lower surface area compared to the Bucky paper electrode (280 vs 470 m(2)/g from nitrogen adsorption), it had a higher meso-macro pore volume (2.6 vs 1.6 mL/g from mercury porosimetry) which enabled the composite electrode to retain more electrolyte, ensuring facile ion transport, hence achieving a higher maximum power rating (970 vs 400 kW/kg). PMID:21210712

Izadi-Najafabadi, Ali; Yamada, Takeo; Futaba, Don N; Yudasaka, Masako; Takagi, Hideyuki; Hatori, Hiroaki; Iijima, Sumio; Hata, Kenji

2011-02-22

448

Method for separating single-wall carbon nanotubes and compositions thereof  

NASA Technical Reports Server (NTRS)

The invention relates to a process for sorting and separating a mixture of (n, m) type single-wall carbon nanotubes according to (n, m) type. A mixture of (n, m) type single-wall carbon nanotubes is suspended such that the single-wall carbon nanotubes are individually dispersed. The nanotube suspension can be done in a surfactant-water solution and the surfactant surrounding the nanotubes keeps the