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Journal ArticleDOI

Extreme oxygen sensitivity of electronic properties of carbon nanotubes

10 Mar 2000-Science (American Association for the Advancement of Science)-Vol. 287, Iss: 5459, pp 1801-1804
TL;DR: The results, although demonstrating that nanotubes could find use as sensitive chemical gas sensors, likewise indicate that many supposedly intrinsic properties measured on as-prepared nanotube may be severely compromised by extrinsic air exposure effects.
Abstract: The electronic properties of single-walled carbon nanotubes are shown here to be extremely sensitive to the chemical environment. Exposure to air or oxygen dramatically influences the nanotubes' electrical resistance, thermoelectric power, and local density of states, as determined by transport measurements and scanning tunneling spectroscopy. These electronic parameters can be reversibly "tuned" by surprisingly small concentrations of adsorbed gases, and an apparently semiconducting nanotube can be converted into an apparent metal through such exposure. These results, although demonstrating that nanotubes could find use as sensitive chemical gas sensors, likewise indicate that many supposedly intrinsic properties measured on as-prepared nanotubes may be severely compromised by extrinsic air exposure effects.
Citations
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Journal ArticleDOI
02 Aug 2002-Science
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.

9,693 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that micrometre-size sensors made from graphene are capable of detecting individual events when a gas molecule attaches to or detaches from graphene's surface.
Abstract: The ultimate aim of any detection method is to achieve such a level of sensitivity that individual quanta of a measured entity can be resolved. In the case of chemical sensors, the quantum is one atom or molecule. Such resolution has so far been beyond the reach of any detection technique, including solid-state gas sensors hailed for their exceptional sensitivity1, 2, 3, 4. The fundamental reason limiting the resolution of such sensors is fluctuations due to thermal motion of charges and defects5, which lead to intrinsic noise exceeding the sought-after signal from individual molecules, usually by many orders of magnitude. Here, we show that micrometre-size sensors made from graphene are capable of detecting individual events when a gas molecule attaches to or detaches from graphene's surface. The adsorbed molecules change the local carrier concentration in graphene one by one electron, which leads to step-like changes in resistance. The achieved sensitivity is due to the fact that graphene is an exceptionally low-noise material electronically, which makes it a promising candidate not only for chemical detectors but also for other applications where local probes sensitive to external charge, magnetic field or mechanical strain are required.

7,318 citations

Journal ArticleDOI
15 Feb 2010-ACS Nano
TL;DR: The resultant N-graphene was demonstrated to act as a metal-free electrode with a much better electrocatalytic activity, long-term operation stability, and tolerance to crossover effect than platinum for oxygen reduction via a four-electron pathway in alkaline fuel cells.
Abstract: Nitrogen-doped graphene (N-graphene) was synthesized by chemical vapor deposition of methane in the presence of ammonia. The resultant N-graphene was demonstrated to act as a metal-free electrode with a much better electrocatalytic activity, long-term operation stability, and tolerance to crossover effect than platinum for oxygen reduction via a four-electron pathway in alkaline fuel cells. To the best of our knowledge, this is the first report on the use of graphene and its derivatives as metal-free catalysts for oxygen reduction. The important role of N-doping to oxygen reduction reaction (ORR) can be applied to various carbon materials for the development of other metal-free efficient ORR catalysts for fuel cell applications, even new catalytic materials for applications beyond fuel cells.

3,604 citations

Journal ArticleDOI
TL;DR: The emerging ability to control the patterns of matter on the nanometer length scale can be expected to lead to entirely new types of biological sensors capable of sensing at the single-molecule level in living cells, and capable of parallel integration for detection of multiple signals.
Abstract: In the coming decade, the ability to sense and detect the state of biological systems and living organisms optically, electrically and magnetically will be radically transformed by developments in materials physics and chemistry. The emerging ability to control the patterns of matter on the nanometer length scale can be expected to lead to entirely new types of biological sensors. These new systems will be capable of sensing at the single-molecule level in living cells, and capable of parallel integration for detection of multiple signals, enabling a diversity of simultaneous experiments, as well as better crosschecks and controls.

2,960 citations

Journal ArticleDOI
TL;DR: Single-walled carbon nanotubes are molecular wires that exhibit interesting structural, mechanical, electrical, and electromechanical properties that make for an ideal miniaturized sensor.
Abstract: Single-walled carbon nanotubes (SWNTs) are molecular wires that exhibit interesting structural, mechanical, electrical, and electromechanical properties. 1-3 A SWNT is unique among solidstate materials in that every atom is on the surface. Surface chemistry could therefore be critical to the physical properties of SWNTs and their applications. 3-10 SWNT sidewall functionalization is important to soluble nanotubes, 4-6 self-assembly on surfaces, and chemical sensors. 8-10 For these purposes, it is imperative to functionalize the sidewalls of SWNTs in noncovalent ways to preserve the sp 2 nanotube structure and thus their electronic characteristics. Immobilization of biomolecules on carbon nanotubes has been pursued in the past, motivated by the prospects of using nanotubes as new types of biosensor materials. 11-15 The electronic properties of nanotubes coupled with the specific recognition properties of the immobilized biosystems would indeed make for an ideal miniaturized sensor. A prerequisite for research in this area is the development of chemical methods to immobilize biological molecules onto carbon nanotubes in a reliable manner. Thus far, only limited work has been carried out with multiwalled carbon nanotubes (MWNTs). 11-15 Metallothionein proteins were trapped inside and placed onto the outer surfaces of open-ended MWNTs.11-14 Streptavidin was found to adsorb on MWNTs presumably via hydrophobic interactions between the nanotubes and hydrophobic domains of the proteins. 15 DNA molecules adsorbed on MWNTs via nonspecific interactions were also observed. 12-14

2,516 citations

References
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Journal ArticleDOI
26 Jul 1996-Science
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

Book
01 Jan 1996
TL;DR: In this paper, the authors present a detailed overview of the properties of Fullerenes and their properties in surface science applications, such as scanning tunnel microscopy, growth and fragmentation studies, and chemical synthesis.
Abstract: Historical Introduction. Carbon Materials. Structure of Fullerenes. Symmetry Considerations. Growth and Fragmentation Studies. Crystalline Structure of Fullerenes. Synthesis of Fullerene Molecules and Solids. Doping of Fullerenes. Structure of Doped Fullerenes and Fullerene Compounds. Fullerene Chemistry. Vibrational Modes. Thermal Properties. Electronic Structure. Optical Properties. Electrical and Thermal Properties. Superconductivity. Nuclear Magnetic Resonance Studies. Electron Paramagnetic Resonance. Surface Science Techniques on Fullerenes. Magnetic Properties. Fullerene-Related Tubules and Spherules. Scanning Tunnel Microscopy. Applications.

4,008 citations

Journal ArticleDOI
27 Mar 1997-Nature
TL;DR: In this article, a gas can condense to high density inside narrow, single-walled nanotubes (SWNTs) under conditions that do not induce adsorption within a standard mesoporous activated carbon.
Abstract: Pores of molecular dimensions can adsorb large quantities of gases owing to the enhanced density of the adsorbed material inside the pores1, a consequence of the attractive potential of the pore walls. Pederson and Broughton have suggested2 that carbon nanotubes, which have diameters of typically a few nanometres, should be able to draw up liquids by capillarity, and this effect has been seen for low-surface-tension liquids in large-diameter, multi-walled nanotubes3. Here we show that a gas can condense to high density inside narrow, single-walled nanotubes (SWNTs). Temperature-programmed desorption spectrosocopy shows that hydrogen will condense inside SWNTs under conditions that do not induce adsorption within a standard mesoporous activated carbon. The very high hydrogen uptake in these materials suggests that they might be effective as a hydrogen-storage material for fuel-cell electric vehicles.

3,558 citations

Journal ArticleDOI
TL;DR: It is predicted that carbon microtubules exhibit striking variations in electronic transport, from metallic to semiconducting with narrow and moderate band gaps, depending on the diameter of the tubule and on the degree of helical arrangement of the carbon hexagons.
Abstract: On the basis of realistic tight-binding band-structure calculations, we predict that carbon microtubules exhibit striking variations in electronic transport, from metallic to semiconducting with narrow and moderate band gaps, depending on the diameter of the tubule and on the degree of helical arrangement of the carbon hexagons. The origin of this drastic variation in the band structure is explained in terms of the two-dimensional band structure of graphite.

2,954 citations

Journal ArticleDOI
03 Apr 1997-Nature
TL;DR: In this article, electrical transport measurements on individual single-wall nanotubes have been performed to confirm the theoretical predictions of single-walled nanotube quantum wires, and they have been shown to act as genuine quantum wires.
Abstract: 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 high yields and structural uniformity7. Particular varieties of these highly symmetric structures have been predicted to be metallic, with electrical conduction occurring through only two electronic modes8–10. Because of the structural symmetry and stiffness of SWNTs, their molecular wavefunctions may extend over the entire tube. Here we report electrical transport measurements on individual single-wall nanotubes that confirm these theoretical predictions. We find that SWNTs indeed act as genuine quantum wires. Electrical conduction seems to occur through well separated, discrete electron states that are quantum-mechanically coherent over long distance, that is at least from contact to contact (140nm). Data in a magnetic field indicate shifting of these states due to the Zeeman effect.

2,678 citations