Carbon Nanotubes--the Route Toward Applications
02 Aug 2002-Science (American Association for the Advancement of Science)-Vol. 297, Iss: 5582, pp 787-792
TL;DR: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects.
Abstract: Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.
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TL;DR: In this article, a comparative study of BN and C nanotubes using a full potential linear combination of atomic orbitals approach, as well as a planewave pseudopotential method is presented.
Abstract: We present a comprehensive comparative study of properties of BN and C nanotubes using a full potential linear combination of atomic orbitals approach, as well as a planewave pseudopotential method. This paper covers our results on the structural, mechanical, vibrational, and electronic properties, examining in detail the effects of intertube coupling. Structural aspects and mechanical properties are discussed and compared in BN and C nanotubes, and to experiment. Upshifts in the values of the radial breathing modes, due to intertube coupling, are found to be small and systematic, about 2% in zigzag nanotubes, and varying from 2 to 7 % in armchair tubes, for both materials. Finally, the effects of intertube interactions on the van Hove singularities are discussed.
140 citations
TL;DR: In this article, steady shear-induced destruction and formation of conductive and mechanical filler networks formed by multi-wall carbon nanotubes in polycarbonate melts were investigated by simultaneous time-resolved measurements of electrical conductivity and rheological properties.
140 citations
TL;DR: In this paper, electron diffraction was used to determine chiral vectors of single-wall carbon nanotubes (SWNTs) using a parallel electron beam over a section of tube of ∼50 nm long.
Abstract: In this letter, we report an electron diffraction determination of chiral vectors (n,m) of individual single-wall carbon nanotubes (SWNTs). Electron diffraction patterns from individual SWNTs were recorded on imaging plates using a parallel electron beam over a section of tube of ∼50 nm long. Using two tubes of 1.39 and 3.77 nm in diameter, we show that the details of electron diffuse scattering can be detected for both the small and large tubes. The quality of diffraction patterns allows the accurate measurement of both the diameters and chiral angles of SWNTs for a direct determination of chiral vectors. The electron diffraction technique is general and applicable to other forms of individual nanostructures.
140 citations
TL;DR: In this article, a large-scale formation of aligned CNT-ZnO heterojunction arrays was achieved by water-assisted chemical vapor deposition (WACVD) of carbon on a zinc foil.
Abstract: 1D heterojunction structures based on nanomaterials are of significance to both scientific fundamentals in nanoscience and potential applications in nanoscale systems, including various new electronic and photonic nanodevices. Consequently, considerable effort has been made in recent years to devise and characterize various heterojunctions between different low-dimensional nanomaterials. Examples include the syntheses of doped GaN-based core/shell/shell (n-GaN/InGaN/p-GaN) nanowire heterostructures through metal-organic chemical vapor deposition (MOCVD); aligned ZnO heterojunction arrays on GaN, Al0.5Ga0.5N, and AlN substrates by a vapor–liquid–solid phase process using gold as a catalyst; multiwalled CNT–zinc sulfide (CNT: carbon nanotube) heterojunctions by a combination of ultrasonic and heat treatments; CNT–silicon nanowire heterojunctions by localizing a suitable metal catalyst at the end of a preformed nanotube or nanowire; and SWNT–gold (SWNT: singlewalled carbon nanotube) nanorod heterojunctions through the selective solution growth of Au nanorods on an SWNT structure. Among them, CNT-based 1D heterojunctions are of particular interest because of the unique molecular geometry as well as excellent electronic, thermal, and mechanical properties intrinsically associated with CNTs. On the other hand, ZnO nanostructures are shown to possess superior optoelectronic properties useful in nanoscale transistors, sensors, electron emitters, and many other systems. The large-scale formation of heterojunctions of ZnO with other nanomaterials (particularly CNTs) should extend the scope of ZnO nanomaterials for potential applications. Although recent work has demonstrated the large-scale growth of aligned ZnO nanowire arrays, the formation of large-area ordered heterojunctions of ZnO nanostructures with other semiconducting materials has been much less discussed in the literature. In particular, the growth of aligned CNT–ZnO heterojunction arrays remains a big challenge. Here, we report the first synthesis of large-scale aligned CNT–ZnO heterojunctions simply by water-assisted chemical vapor deposition (WACVD) of carbon on a zinc foil, which acts as both the substrate for the CNT growth and zinc source for the formation of the ZnO nanostructures. Water, as a weak oxidizer, provides the oxygen source for the formation of ZnO nanostructures and also enhances CNT growth. This cost-effective and efficient approach requires no other catalytic reagent and allows the large-scale formation of heterojunctions between the perpendicularly aligned CNTs and ZnO nanostructures through a natural contact. As we shall see later, the intimately connected heterojunctions between the aligned CNTs and ZnO nanostructures thus prepared possess interesting optoelectronic properties attractive for many potential applications, including their use as electro-optic sensors and field emitters. Briefly, the formation of the aligned CNT and ZnO heterojunctions was achieved by carrying out pyrolysis of C2H2 on a zinc foil supported by a quartz glass plate in a tube furnace at 850 °C under a combined flow of Ar and H2, with a portion of the carrier gas passing through a water bubbler, followed by annealing with a flow of Ar via the water bubbler passing through the reaction system. Figure 1a shows a low-magnification scanning electron microscopy (SEM) image of the assynthesized CNT–ZnO sample, revealing a large-scale aligned array. Although the corresponding SEM images under higher magnification in Figure 1b and c show some misalignment at the top of the nanotube array, Figure 1b clearly shows the CNT–ZnO heterojunction with a ZnO crystal (bright spot) attached on the tip of each of the constituent aligned CNTs. Figure 1c further reveals that approximately 40 % of the ZnO nanoparticles are of hexagonal morphology. The corresponding transmission electron microscopy (TEM) image in Figure 1d shows that the CNT thus prepared is multiwalled, and that the ZnO nanoparticle is intimately connected to the aligned CNT structure. The multiwalled CNT with an inner diameter of approximately 30 nm and outer diameter of approximately 60 nm possesses a bamboolike structured hollow core, similar to those prepared by solvothermal reduction of ethanol in the presence of Mg or pyrolysis of FePc. Figure 1e shows the selected-area electron diffraction (SAED) pattern of the ZnO nanoparticle, which indicates that the asprepared ZnO nanoparticle is single crystalline and can be indexed as hexagonal wurtzite ZnO. The aligned CNT–ZnO heterojunctions thus prepared were further investigated using energy-dispersive X-ray spectroscopy (EDS) in a scanning electron microscope. As expected, the line-scanning EDS profiles for Zn and C clearly show a dramatic decrease in the Zn (and corresponding increase in C) content along the scanning C O M M U N IC A TI O N S
140 citations
22 Nov 2010
TL;DR: In this paper, a review of recent developments in the controlled growth and modification of vertically-aligned carbon nanotubes for multifunctional applications is presented, with a focus on the functionalization of the constituent carbon-nanotubes.
Abstract: Vertically-aligned carbon nanotubes possess many advantages for a wide range of multifunctional applications. Along with the controlled growth of aligned/micropatterned carbon nanotubes, surface modification of vertically-aligned carbon nanotubes are essential in order to meet specific requirements demanded for particular applications. While many innovative synthetic methods have been developed for controlled growth of vertically-aligned multiwalled and single-walled carbon nanotubes, various interesting physical and chemical approaches have recently been devised for functionalization of the constituent carbon nanotubes in vertically-aligned carbon nanotube arrays with their alignment being largely retained. In this article, recent developments in the controlled growth and modification of vertically-aligned carbon nanotubes for multifunctional applications are reviewed.
139 citations
References
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TL;DR: The nanotubes sensors exhibit a fast response and a substantially higher sensitivity than that of existing solid-state sensors at room temperature and the mechanisms of molecular sensing with nanotube molecular wires are investigated.
Abstract: Chemical sensors based on individual single-walled carbon nanotubes (SWNTs) are demonstrated. Upon exposure to gaseous molecules such as NO 2 or NH 3 , the electrical resistance of a semiconducting SWNT is found to dramatically increase or decrease. This serves as the basis for nanotube molecular sensors. The nanotube sensors exhibit a fast response and a substantially higher sensitivity than that of existing solid-state sensors at room temperature. Sensor reversibility is achieved by slow recovery under ambient conditions or by heating to high temperatures. The interactions between molecular species and SWNTs and the mechanisms of molecular sensing with nanotube molecular wires are investigated.
5,908 citations
TL;DR: In this paper, the fabrication of a three-terminal switching device at the level of a single molecule represents an important step towards molecular electronics and has attracted much interest, particularly because it could lead to new miniaturization strategies in the electronics and computer industry.
Abstract: The use of individual molecules as functional electronic devices was first proposed in the 1970s (ref 1) Since then, molecular electronics2,3 has attracted much interest, particularly because it could lead to conceptually new miniaturization strategies in the electronics and computer industry The realization of single-molecule devices has remained challenging, largely owing to difficulties in achieving electrical contact to individual molecules Recent advances in nanotechnology, however, have resulted in electrical measurements on single molecules4,5,6,7 Here we report the fabrication of a field-effect transistor—a three-terminal switching device—that consists of one semiconducting8,9,10 single-wall carbon nanotube11,12 connected to two metal electrodes By applying a voltage to a gate electrode, the nanotube can be switched from a conducting to an insulating state We have previously reported5 similar behaviour for a metallic single-wall carbon nanotube operated at extremely low temperatures The present device, in contrast, operates at room temperature, thereby meeting an important requirement for potential practical applications Electrical measurements on the nanotube transistor indicate that its operation characteristics can be qualitatively described by the semiclassical band-bending models currently used for traditional semiconductor devices The fabrication of the three-terminal switching device at the level of a single molecule represents an important step towards molecular electronics
5,258 citations
TL;DR: X-ray diffraction and electron microscopy showed that fullerene single-wall nanotubes (SWNTs) are nearly uniform in diameter and that they self-organize into “ropes,” which consist of 100 to 500 SWNTs in a two-dimensional triangular lattice with a lattice constant of 17 angstroms.
Abstract: The major part of this chapter has already appeared in [1], but because of the length restrictions (in Science), the discussion on why we think this form is given in only brief detail. This chapter goes into more depth to try to answer the questions of why the fullerenes form themselves. This is another example of the very special behavior of carbon. From a chemist’s standpoint, it is carbon’s ability to form multiple bonds that allows it to make these low dimensional forms rather than to produce tetrahedral forms. Carbon can readily accomplish this and it is in the mathematics and physics of the way this universe was put together, that carbon is given this property. One of the consequences of this property is that, if left to its own devices as carbon condenses from the vapor and if the temperature range is just right, above 1000°C, but lower than 1400°C, there is an efficient self-assembly process whose endpoint is C60.
5,215 citations
TL;DR: In this paper, the Young's modulus, strength, and toughness of nanostructures are evaluated using an atomic force microscopy (AFM) approach. And the results showed that the strength of the SiC NRs were substantially greater than those found previously for larger SiC structures, and they approach theoretical values.
Abstract: The Young's modulus, strength, and toughness of nanostructures are important to proposed applications ranging from nanocomposites to probe microscopy, yet there is little direct knowledge of these key mechanical properties. Atomic force microscopy was used to determine the mechanical properties of individual, structurally isolated silicon carbide (SiC) nanorods (NRs) and multiwall carbon nanotubes (MWNTs) that were pinned at one end to molybdenum disulfide surfaces. The bending force was measured versus displacement along the unpinned lengths. The MWNTs were about two times as stiff as the SiC NRs. Continued bending of the SiC NRs ultimately led to fracture, whereas the MWNTs exhibited an interesting elastic buckling process. The strengths of the SiC NRs were substantially greater than those found previously for larger SiC structures, and they approach theoretical values. Because of buckling, the ultimate strengths of the stiffer MWNTs were less than those of the SiC NRs, although the MWNTs represent a uniquely tough, energy-absorbing material.
4,627 citations
TL;DR: The thermal conductivity and thermoelectric power of a single carbon nanotube were measured using a microfabricated suspended device and shows linear temperature dependence with a value of 80 microV/K at room temperature.
Abstract: The thermal conductivity and thermoelectric power of a single carbon nanotube were measured using a microfabricated suspended device. The observed thermal conductivity is more than 3000 W/K m at room temperature, which is 2 orders of magnitude higher than the estimation from previous experiments that used macroscopic mat samples. The temperature dependence of the thermal conductivity of nanotubes exhibits a peak at 320 K due to the onset of umklapp phonon scattering. The measured thermoelectric power shows linear temperature dependence with a value of 80 microV/K at room temperature.
3,166 citations