Showing papers on "Nanotube published in 2006"
TL;DR: In this article, a review of polymer nanocomposites with single-wall or multi-wall carbon nanotubes is presented, and the current challenges to and opportunities for efficiently translating the extraordinary properties of carbon-nanotubes to polymer matrices are summarized.
Abstract: We review the present state of polymer nanocomposites research in which the fillers are single-wall or multiwall carbon nanotubes. By way of background we provide a brief synopsis about carbon nanotube materials and their suspensions. We summarize and critique various nanotube/polymer composite fabrication methods including solution mixing, melt mixing, and in situ polymerization with a particular emphasis on evaluating the dispersion state of the nanotubes. We discuss mechanical, electrical, rheological, thermal, and flammability properties separately and how these physical properties depend on the size, aspect ratio, loading, dispersion state, and alignment of nanotubes within polymer nanocomposites. Finally, we summarize the current challenges to and opportunities for efficiently translating the extraordinary properties of carbon nanotubes to polymer matrices in hopes of facilitating progress in this emerging area.
3,239 citations
TL;DR: Voltage-decay measurements indicate that the highly ordered TiO(2) nanotube arrays, in comparison to nanoparticulate systems, have superior electron lifetimes and provide excellent pathways for electron percolation.
Abstract: We describe the use of highly ordered transparent TiO2 nanotube arrays in dye-sensitized solar cells (DSCs). Highly ordered nanotube arrays of 46-nm pore diameter, 17-nm wall thickness, and 360-nm ...
2,142 citations
TL;DR: In this paper, the fabrication, properties, and solar energy applications of highly ordered TiO 2 nanotube arrays made by anodic oxidation of titanium in fluoride-based electrolytes are reviewed.
1,905 citations
TL;DR: The preparation of vertically grown carbon-doped TiO(2) (TiO( 2-x)C(x) nanotube arrays with high aspect ratios for maximizing the photocleavage of water under white-light irradiation showed much higher photocurrent densities and more efficient water splitting under visible-light illumination than pure TiO (2) nanOTube arrays.
Abstract: The photocatalytic splitting of water into hydrogen and oxygen using solar light is a potentially clean and renewable source for hydrogen fuel.1,2 There has been extensive investigation into metal-oxide semiconductors such as TiO2, WO3, and Fe2O3, which can be used as photoanodes in thin-film form.3-5 Of the materials being developed for photoanodes, TiO2 remains one of the most promising because of its low cost, chemical inertness, and photostability.6 However, the widespread technological use of TiO2 is hindered by its low utilization of solar energy in the visible region. In this study, we report the preparation of vertically grown carbon-doped TiO2 (TiO2-xCx) nanotube arrays with high aspect ratios for maximizing the photocleavage of water under white-light irradiation. The synthesized TiO2-xCx nanotube arrays showed much higher photocurrent densities and more efficient water splitting under visible-light illumination (> 420 nm) than pure TiO2 nanotube arrays. The total photocurrent was more than 20 t...
1,626 citations
TL;DR: In this paper, a comparative study on transparent conductive thin films made with two kinds of commercial carbon nanotubes: HiPCO and arc-discharge nanotube was carried out.
Abstract: We have carried out comparative studies on transparent conductive thin films made with two kinds of commercial carbon nanotubes: HiPCO and arc-discharge nanotubes. These films have been further exploited as hole-injection electrodes for organic light-emitting diodes (OLEDs) on both rigid glass and flexible substrates. Our experiments reveal that films based on arc-discharge nanotubes are overwhelmingly better than HiPCO-nanotube-based films in all of the critical aspects, including surface roughness, sheet resistance, and transparency. Further improvement in arc-discharge nanotube films has been achieved by using PEDOT passivation for better surface smoothness and using SOCl2 doping for lower sheet resistance. The optimized films show a typical sheet resistance of ∼160 Ω/□ at 87% transparency and have been used successfully to make OLEDs with high stabilities and long lifetimes.
976 citations
TL;DR: In this paper, a biomimetic artificial neuron was developed by extending the length of the sensor, which is a long continuous strain sensor that has a low cost, is simple to install and is lightweight.
Abstract: A carbon nanotube polymer material was used to form a piezoresistive strain sensor for structural health monitoring applications. The polymer improves the interfacial bonding between the nanotubes. Previous single walled carbon nanotube buckypaper sensors produced distorted strain measurements because the van der Waals attraction force allowed axial slipping of the smooth surfaces of the nanotubes. The polymer sensor uses larger multi-walled carbon nanotubes which improve the strain transfer, repeatability and linearity of the sensor. An electrical model of the nanotube strain sensor was derived based on electrochemical impedance spectroscopy and strain testing. The model is useful for designing nanotube sensor systems. A biomimetic artificial neuron was developed by extending the length of the sensor. The neuron is a long continuous strain sensor that has a low cost, is simple to install and is lightweight. The neuron has a low bandwidth and adequate strain sensitivity. The neuron sensor is particularly useful for detecting large strains and cracking, and can reduce the number of channels of data acquisition needed for the health monitoring of large structures.
973 citations
TL;DR: In this article, a 3D composite with carbon-nanotube forests is proposed to improve the in-plane fracture toughness, hardness, delamination resistance, inplane mechanical properties, damping, thermo-elastic behavior, and thermal and electrical conductivities.
Abstract: Traditional fibre-reinforced composite materials with excellent in-plane properties fare poorly when out-of-plane through-thickness properties are important1. Composite architectures with fibres designed orthogonal to the two-dimensional (2D) layout in traditional composites could alleviate this weakness in the transverse direction, but all of the efforts1,2 so far have only produced limited success. Here, we unveil an approach to the 3D composite challenge, without altering the 2D stack design, on the basis of the concept of interlaminar carbon-nanotube3,4 forests that would provide enhanced multifunctional properties along the thickness direction. The carbon-nanotube forests allow the fastening of adjacent plies in the 3D composite. We grow multiwalled carbon nanotubes on the surface of micro-fibre fabric cloth layouts, normal to the fibre lengths, resulting in a 3D effect between plies under loading. These nanotube-coated fabric cloths serve as building blocks for the multilayered 3D composites, with the nanotube forests providing much-needed interlaminar strength and toughness under various loading conditions. For the fabricated 3D composites with nanotube forests, we demonstrate remarkable improvements in the interlaminar fracture toughness, hardness, delamination resistance, in-plane mechanical properties, damping, thermoelastic behaviour, and thermal and electrical conductivities making these structures truly multifunctional.
754 citations
TL;DR: In this article, an analytic approach was proposed to determine the tension and bending rigidities of CNTs directly from the interatomic potential, which is useful in the study of multi-wall carbon nanotubes.
Abstract: Young's modulus and the thickness of single wall carbon nanotubes (CNTs) obtained from prior atomistic studies are largely scattered. In this paper we establish an analytic approach to bypass atomistic simulations and determine the tension and bending rigidities of graphene and CNTs directly from the interatomic potential. The thickness and elastic properties of graphene and CNTs can also be obtained from the interatomic potential. But the thickness, and therefore elastic moduli, also depend on type of loading (e.g., uniaxial tension, uniaxial stretching, equibiaxial stretching), as well as the nanotube radius $R$ and chirality when $Rl1\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. This explains why the thickness obtained from prior atomistic simulations is scattered. This analytic approach is particularly useful in the study of multiwall CNTs since their stress state may be complex even under simple loading (e.g., uniaxial tension) due to the van der Waals interactions between nanotube walls. The present analysis also provides an explanation of Yakobson's paradox that the very high Young's modulus reported from the atomistic simulations together with the shell model may be due to the not-well-defined CNT thickness.
625 citations
TL;DR: This critical review surveys non-covalent interactions of carbon nanotubes with molecular species from a chemical perspective, particularly emphasising the relationship between the structure and dynamics of these structures and their functional properties.
Abstract: In this critical review we survey non-covalent interactions of carbon nanotubes with molecular species from a chemical perspective, particularly emphasising the relationship between the structure and dynamics of these structures and their functional properties. We demonstrate the synergistic character of the nanotube–molecule interactions, as molecules that affect nanotube properties are also altered by the presence of the nanotube. The diversity of mechanisms of molecule–nanotube interactions and the range of experimental techniques employed for their characterisation are illustrated by examples from recent reports. Some practical applications for carbon nanotubes involved in non-covalent interactions with molecules are discussed.
609 citations
TL;DR: In this paper, the electrocatalytic oxidation of hydrazine at a basal-plane pyrolytic-graphite (BPPG) electrode treated with iron (III) was compared with that at a multiwalled-carbon-nanotube (MW-CNT)-modified BPPG electrode (red) and at an edge-plane graphite electrode (black).
Abstract: Its all done with metals: The title statement is confirmed by comparing the electrocatalytic oxidation of hydrazine at a basal-plane pyrolytic-graphite (BPPG) electrode treated with iron (III) (blue) with that at a multiwalled-carbon-nanotube (MW-CNT)-modified BPPG electrode (red) and at an edge-plane pyrolytic graphite electrode (black; ••••• and -•-• are the responses of iron(III)-treated and MW-CNT-modified BPPG electrode, respectively, in the absence of hydrazine). (Figure Presented) © 2006 Wiley-VCH Verlag GmbH and Co. KGaA.
578 citations
TL;DR: In this paper, a scalable calendering approach for achieving dispersion of CVD-grown multi-walled carbon nanotubes through intense shear mixing was investigated. And the as-processed nanocomposites exhibited significantly enhanced fracture toughness at low nanotube concentrations.
TL;DR: A critical review on recent research related to nanotube/polymer composites is given in this paper, where newly-adopted coiled nanotubes used to enhance the interfacial bonding strength of nanocomposites are also discussed.
Abstract: Since the last decade, research activities in the area of nano-materials have been increased dramatically. More than a 1000 of journal articles in this area have been published within the last 3 years. Materials scientists and researchers have realized that the mechanical properties of materials can be altered at the fundamental level, i.e. the atomic-scale. Carbon nanotubes (hereafter called ‘nanotubes’) have been well recognized as nano-structural materials that can be used to alter mechanical, thermal and electrical properties of polymer-based composite materials, because of their superior properties and perfect atom arrangement. In general, scientific research related to the nanotubes and their co-related polymer based composites can be distinguished into four particular scopes: (i) production of high purity and controllable nanotubes, in terms of their size, length and chiral arrangement; (ii) enhancement of interfacial bonding strength between the nanotubes and their surrounding matrix; (iii) control of the dispersion properties and alignment of the nanotubes in nanotube/polymer composites and (iv) applications of the nanotubes in real life. Although, so many remarkable results in the above items have been obtained recently, no concluding results have so far been finalized. In this paper, a critical review on recent research related to nanotube/polymer composites is given. Newly-adopted coiled nanotubes used to enhance the interfacial bonding strength of nanocomposites are also discussed. Moreover, the growth of nanotubes from nanoclay substrates to form exfoliated nanotube/nanoclay polymer composites is also introduced in detail.
TL;DR: In this paper, the authors compared the performance of carbon nanotubes (MWNTs) and Vulcan XC-72 in terms of surface oxide formation and 30% lower corrosion current under different treatment conditions.
TL;DR: In this paper, self-organized anodic titania nanotube layers were doped with nitrogen successfully using ion implantation, resulting in a N-doped crystalline anatase nanotubite structure with strongly enhanced photocurrent response in both the UV and the visible range.
Abstract: Self-organized anodic titania nanotube layers were doped with nitrogen successfully using ion implantation. Photoelectrochemical measurements combined with XRD measurements show that the damage created by ion bombardment (that leads to a drastic decrease of the photoconversion efficiency) can be “annealed out” by an adequate heat treatment. This results in a N-doped crystalline anatase nanotube structure with strongly enhanced photocurrent response in both the UV and the visible range.
TL;DR: Results demonstrate that debundled single-walled carbon nanotubes are high-contrast near-infrared fluorophores that can be sensitively and selectively tracked in mammalian tissues using optical methods and suggest the potential of carbon Nanotubes in future pharmaceutical applications.
Abstract: Individualized, chemically pristine single-walled carbon nanotubes have been intravenously administered to rabbits and monitored through their characteristic near-infrared fluorescence. Spectra indicated that blood proteins displaced the nanotube coating of synthetic surfactant molecules within seconds. The nanotube concentration in the blood serum decreased exponentially with a half-life of 1.0 ± 0.1 h. No adverse effects from low-level nanotube exposure could be detected from behavior or pathological examination. At 24 h after i.v. administration, significant concentrations of nanotubes were found only in the liver. These results demonstrate that debundled single-walled carbon nanotubes are high-contrast near-infrared fluorophores that can be sensitively and selectively tracked in mammalian tissues using optical methods. In addition, the absence of acute toxicity and promising circulation persistence suggest the potential of carbon nanotubes in future pharmaceutical applications.
TL;DR: The detection of the B-Z change in whole blood, tissue, and from within living mammalian cells is demonstrated.
Abstract: The transition of DNA secondary structure from an analogous B to Z conformation 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. The transition is thermodynamically identical for DNA on and off the nanotube, except that the propagation length of the former is shorter by five-sixths. The magnitude of the energy shift is described by using an effective medium model and the DNA geometry on the nanotube sidewall. We demonstrate the detection of the B-Z change in whole blood, tissue, and from within living mammalian cells.
TL;DR: In this article, carbon nanotubes (CNTs) were treated by an acidic solution to remove impurities and modified subsequently by amine treatment or plasma oxidation to improve interfacial bonding and dispersion of CNTs in the epoxy matrix.
TL;DR: The photoresponse of suspended SWNT films is sufficiently high that they may function as the sensitive element of an IR bolometric detector and support the band picture over the exciton model of excited states in carbon nanotubes.
Abstract: The photoresponse in the electrical conductivity of a single-walled carbon nanotube (SWNT) film is dramatically enhanced when the nanotube film is suspended in vacuum. We show here that the change in conductivity is bolometric (caused by heating of the SWNT network). Electron-phonon interactions lead to ultrafast relaxation of the photoexcited carriers, and the energy of the incident infrared (IR) radiation is efficiently transferred to the crystal lattice. It is not the presence of photoexcited holes and electrons, but a rise in temperature, that results in a change in resistance; thus, photoconductivity experiments cannot be used to support the band picture over the exciton model of excited states in carbon nanotubes. The photoresponse of suspended SWNT films is sufficiently high that they may function as the sensitive element of an IR bolometric detector.
TL;DR: The adhesion/propagation of the osteoblast is substantially improved by the topography of the TiO2 nanotubes with the filopodia of growing cells actually going into the nanotube pores, producing an interlocked cell structure.
Abstract: Vertically aligned yet laterally spaced nanoscale TiO2 nanotubes have been grown on Ti by anodization, and the growth of MC3T3-E1 osteoblast cells on such nanotubes has been investigated. The adhesion/propagation of the osteoblast is substantially improved by the topography of the TiO_2 nanotubes with the filopodia of growing cells actually going into the nanotube pores, producing an interlocked cell structure. The presence of the nanotube structure induced a significant acceleration in the growth rate of osteoblast cells by as much as ∼300–400%.
TL;DR: This work provides concrete experimental evidence on the effect of SW NT-DNA binding on DNA functionality, which will help to pave the way for future designing of SWNT biocomplexes for applications in biotechnology in general and also DNA-assisted nanotube manipulation techniques.
Abstract: We report the fabrication of single-walled carbon nanotube (SWNT) DNA sensors and the sensing mechanism The simple and generic protocol for label-free detection of DNA hybridization is demonstrated with random sequence 15mer and 30mer oligonucleotides DNA hybridization on gold electrodes, instead of on SWNT sidewalls, is mainly responsible for the acute electrical conductance change due to the modulation of energy level alignment between SWNT and gold contact This work provides concrete experimental evidence on the effect of SWNT-DNA binding on DNA functionality, which will help to pave the way for future designing of SWNT biocomplexes for applications in biotechnology in general and also DNA-assisted nanotube manipulation techniques
TL;DR: The growth of aligned multiwalled CNTs on a metallic alloy, Inconel 600 (Inconel), using vapour-phase catalyst delivery overcomes the substrate limitation for nanotube growth which should assist the development of future CNT-related technologies.
Abstract: There are several advantages of growing carbon nanotubes (CNTs) directly on bulk metals, for example in the formation of robust CNT-metal contacts during growth. Usually, aligned CNTs are grown either by using thin catalyst layers predeposited on substrates or through vapour-phase catalyst delivery. The latter method, although flexible, is unsuitable for growing CNTs directly on metallic substrates. Here we report on the growth of aligned multiwalled CNTs on a metallic alloy, Inconel 600 (Inconel), using vapour-phase catalyst delivery. The CNTs are well anchored to the substrate and show excellent electrical contact with it. These CNT-metal structures were then used to fabricate double-layer capacitors and field-emitter devices, which demonstrated improved performance over previously designed CNT structures. Inconel coatings can also be used to grow CNTs on other metallic substrates. This finding overcomes the substrate limitation for nanotube growth which should assist the development of future CNT-related technologies.
TL;DR: In this article, the authors investigate the electrochemical formation of layers of self-organized high aspect ratio TiO2 nanotubes, grown by anodization of Ti in viscous electrolytes at different temperatures.
TL;DR: In this article, halloysite nanotubes (HNTs) with hollow nanotubular structures were used as a new type filler for poly(propylene) (PP).
TL;DR: In this article, the in-plane elastic properties of carbon nanotubes are calculated using a composite cylinders micromechanics technique as a first step in a two-step process.
TL;DR: In this article, the performance of nanotubes and nanowires as antennas is analyzed, including the radiation resistance, the input reactance and resistance, and antenna efficiency, as a function of frequency and nanotube length.
Abstract: We present quantitative predictions of the performance of nanotubes and nanowires as antennas, including the radiation resistance, the input reactance and resistance, and antenna efficiency, as a function of frequency and nanotube length. Particular attention is paid to the quantum capacitance and kinetic inductance. We develop models for both far-field antenna patterns as well as near-field antenna-to-antenna coupling. In so doing, we also develop a circuit model for a transmission line made of two parallel nanotubes, which has applications for nanointerconnect technology. Finally, we derive an analog of Hallen's integral equation appropriate for single-walled carbon nanotube antennas
TL;DR: The first repeated in vitro stimulation of hippocampal neurons with CNT electrodes is demonstrated, suggesting that CNTs are capable of providing far safer and more efficacious solutions for neural prostheses than previous metal electrode approaches.
Abstract: We present a novel prototype neural interface using vertically aligned multiwalled carbon nanotube (CNT) pillars as microelectrodes. Functionalized hydrophilic CNT microelectrodes offer a high charge injection limit (1−1.6 mC/cm2) without faradic reactions. The first repeated in vitro stimulation of hippocampal neurons with CNT electrodes is demonstrated. These results suggest that CNTs are capable of providing far safer and more efficacious solutions for neural prostheses than previous metal electrode approaches.
TL;DR: In this article, a review of the literature on the synthesis of carbon nanotube-and nanofiber-supported Pt electrocatalysts for PEM fuel cell catalyst loading reduction through the improvement of catalyst utilization and activity, especially focusing on cathode nano-electrocatalyst preparation methods.
Abstract: This paper reviews the literature on the synthesis of carbon nanotube- and nanofiber-supported Pt electrocatalysts for proton exchange membrane (PEM) fuel cell catalyst loading reduction through the improvement of catalyst utilization and activity, especially focusing on cathode nano-electrocatalyst preparation methods. The features of each synthetic method were also discussed based on the morphology of the synthesized catalysts. It is clear that synthesis methods play an important role in catalyst morphology, Pt utilization and catalytic activity. Though some remarkable progress has been made in nanotube- and nanofiber-supported Pt catalyst preparation techniques, the real breakthroughs have not yet been made in terms of cost-effectiveness, catalytic activity, durability and chemical/electrochemical stability. In order to make such electrocatalysts commercially feasible, cost-effective and innovative, catalyst synthesis methods are needed for Pt loading reduction and performance optimization.
TL;DR: In this paper, the formation of self-organized titanium oxide nanotube layers at different fluoride concentrations and potentials in H3PO4 electrolytes was investigated and it was shown that the tube length and diameter can be controlled over a wide range by the applied potential.
TL;DR: A highly ordered array of micron-length undoped titania nanotubes exhibits an unprecedented variation in electrical resistance of about 8.7 orders of magnitude at room temperature, when exposed to alternating atmospheres of nitrogen containing 1000ppm hydrogen and air as discussed by the authors.
Abstract: A highly ordered array of micron-length undoped titania nanotubes exhibits an unprecedented variation in electrical resistance of about 8.7 orders of magnitude (50 000 000 000%), at room temperature, when exposed to alternating atmospheres of nitrogen containing 1000 ppm hydrogen and air. This represents the largest known change in electrical properties of any material, to any gas, at any temperature. The nanotube arrays were fabricated using anodic oxidation of titanium foil in a pH 4.0 electrolyte containing potassium fluoride, sodium hydrogen sulfate monohydrate and sodium citrate tribasic dihydrate. The dramatic change in resistance is believed to be due to the highly active surface states on the nanoscale walls of the tubes, high surface area of the nanotube architecture, and the well-ordered geometry allowing for hydrogen-sensitive tube-to-tube electrical connections.
TL;DR: In this article, the dispersive effects achieved by a wide range of surface active agents, as well as surface oxidation and functionalization, are investigated for uniform, multi-walled carbon nanotube (MWNT) distribution in water-soluble (poly(ethylene glycol)) and water-insoluble polymers.
Abstract: Microscale aggregate formation, resulting from high intrinsic filler attractions, is one of the major issues in nanocomposite preparation and processing. Herein, the dispersive effects achieved by a wide range of surface-active agents, as well as surface oxidation and functionalization, are investigated. The aim of our research is to form a uniform, multiwalled carbon nanotube (MWNT) distribution in water-soluble (poly(ethylene glycol)) and water-insoluble (polypropylene) polymers. In order to understand the surface-charge-related stability of the treated nanotubes solutions, zeta-potential measurements are applied. Quantification of the state of the MWNT dispersion is derived from particle-size analysis, while visual characterization is based on optical and electron microscopy. To estimate the nucleating ability of the surface-modified carbon nanotubes, the temperature of crystallization and the degree of crystallinity are calculated from differential scanning thermograms. Finally, we suggest general guidelines to produce uniform MWNT dispersions using a dispersive agent and/or surface treatment in water-soluble and water-insoluble polymers.