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: High-quality nanotubes dispersions with increased degrees of exfoliation are highly desirable, as the efficiency of nanotube separation techniques relies on highly individualized samples.
Abstract: The synthesis of perylene-based single-walled carbon nanotube (SWCNT) surfactants and the dispersion and exfoliation of SWCNTs in water by a variety of designed surfactants is investigated. The quality of the nanotube dispersions is evaluated by optical absorption and emission spectroscopy, zeta-potential measurements and statistical atomic force microscopy (AFM). Significantly the dispersion efficiency can be increased at higher pH, as water solubility of the surfactants is ensured by peripheral derivatization with carboxyl-functionalized first- and second-order Newkome dendrimers. Even at very low perylene concentrations of 0.1 g L(-1) and a nanotube-to-surfactant ratio of 1:1, the nanotube supernatant after centrifugation contains up to 73% of the pristine material with exfoliation degrees (the number of fractions of individualized nanotubes N(I)/N(T)) of up to 76%. The adsorption of the perylene core to the nanotube scaffold is indicated by red-shifted perylene-absorption and SWCNT-emission features except for the smallest perylene amphiphile, where solubilization is presumably based on a micellar arrangement. The nanotube fluorescence is significantly altered and reduced in intensity compared to nanotubes dispersed in sodium dodecylbenzene sulfonate (SDBS) being strongly dependent on the structure of the perylene surfactant. We attribute this observation to the homogeneity of the surfactant coverage, e.g., the supramolecular arrangement onto the nanotube backbone. This study represents a step forward in understanding the structure-property relationship of nanotube surfactants. Furthermore high-quality nanotube dispersions with increased degrees of exfoliation are highly desirable, as the efficiency of nanotube separation techniques relies on highly individualized samples.
129 citations
TL;DR: Bimetal-decorated, pyridinic N-dominated large-size carbon tubes are proposed for the first time as highly efficient and durable ORR and OER catalysts and achieve superior bifunctional oxygen catalytic performance, exceeding most of state-of-the-art catalysts.
Abstract: The addition of transition metals, even in a trace amount, into heteroatom-doped carbon (M-N/C) is intensively investigated to further enhance oxygen reduction reaction (ORR) activity. However, the influence of metal decoration on the electrolysis of the reverse reaction of ORR, that is, oxygen evolution reaction (OER), is seldom reported. Moreover, further improving the bifunctional activity and corrosion tolerance for carbon-based materials remains a big challenge, especially in OER potential regions. Here, bimetal-decorated, pyridinic N-dominated large-size carbon tubes (MM′-N/C) are proposed for the first time as highly efficient and durable ORR and OER catalysts. FeFe-N/C, CoCo-N/C, NiNi-N/C, MnMn-N/C, FeCo-N/C, NiFe-N/C, FeMn-N/C, CoNi-N/C, MnCo-N/C, and NiMn-N/C are systematically investigated in terms of their structure, composition, morphology, surface area, and active site densities. In contrast to conventional monometal and N-decorated carbon, small amounts of bimetal (≈2 at%) added during the one-step template-free synthesis contribute to increased pyridinic N content, much longer and more robust carbon tubes, reduced metal particle size, and stronger coupling between the encapsulated metals and carbon support. The synergy of those factors accounts for the dramatically improved ORR and OER activity and stability. By comparison, NiFe-N/C and MnCo-N/C stand out and achieve superior bifunctional oxygen catalytic performance, exceeding most of state-of-the-art catalysts.
129 citations
TL;DR: In this paper, a simple and environment friendly process using water as the proceeding medium was used to obtain the graphene oxide-reinforced polyvinyl alcohol (PVA) nanocomposites.
Abstract: Graphene, a single layer of graphite, has recently attracted a large amount of attention because of its extremely high electronic and thermal properties, as many nanoscale materials are based on individual graphene. Graphene oxide (GO), which is the intermediate during the chemical processing of graphene, consists of graphene functionalized with oxygen-containing functional groups that imparts the desirable solution-processability to the neat graphene. Herein, poly(vinyl alcohol) (PVA), a hydrophilic polymer, was selected as the matrix, and PVA/GO nanocomposites were prepared by a simple and environment friendly process using water as the proceeding medium. In the PVA matrix, GO was exfoliated and nanodispersed. We found that the nanocomposites constructed by the incorporation of GO up to 1% by weight possess remarkable properties, such as significantly high mechanical and thermal properties. These excellent reinforcement effects were achieved not only by the rigid structure and high aspect ratio of the exfoliated GO but also by the strong interaction between PVA and GO. Furthermore, owing to the sheet-like structure of GO, the barrier properties of the nanocomposites were found to be dramatically increased. The graphene oxide (GO)-reinforced poly(vinyl alcohol) (PVA) nanocomposites were prepared using a simple and environment friendly process using aqueous medium. GO was revealed to be nanodispersed in the PVA matrix. The Young’s modulus of the nanocomposites largely exceeded the predicted value with only a low content of GO. We also revealed the increase in the thermal resistance and the barrier properties. As a result, not only the excellent properties but also the advantageous effects derived from the sheet-like structure of GO were successfully imparted to the nanocomposites.
129 citations
27 May 2006
TL;DR: In this paper, the influence of catalyst film thickness on carbon nanostructures grown by plasma-enhanced chemical-vapor deposition from acetylene and ammonia mixtures was investigated.
Abstract: A systematic study is presented of the influence of catalyst film thickness on carbon nanostructures grown by plasma-enhanced chemical-vapor deposition from acetylene and ammonia mixtures. We show that reducing the Fe∕Co catalyst film thickness below 3nm causes a transition from larger diameter (>40nm), bamboolike carbon nanofibers to small diameter (∼5nm) multiwalled nanotubes with two to five walls. This is accompanied by a more than 50 times faster growth rate and a faster catalyst poisoning. Thin Ni catalyst films only trigger such a growth transition when pretreated with an ammonia plasma. We observe a limited correlation between this growth transition and the coarsening of the catalyst film before deposition. For a growth temperature of ⩽550°C, all catalysts showed mainly a tip growth regime and a similar activity on untreated silicon, oxidized silicon, and silicon nitride support.
129 citations
TL;DR: The incorporation of DPPA-MWCNT to PS significantly reduced peak heat release rate, smoke production rate, and carbon monoxide and carbon dioxide release in cone calorimeter tests, and the enhanced fire-retardant properties should be ascribed to the barrier effect of carbon nanotubes.
Abstract: Aminated multiwalled carbon nanotubes (A-MWCNT) were reacted with diphenylphosphinic chloride (DPP-Cl) to prepare the functionalized MWCNT (DPPA-MWCNT). A-MWCNT and DPPA-MWCNT were respectively mixed with polystyrene (PS) to obtain composites through the melt compounding method. SEM observations demonstrated that the DPPA-MWCNT nanofillers were more uniformly distributed within the PS matrix than A-MWCNT. PS/DPPA-MWCNT showed improved thermal stability, glass transition temperature, and tensile strength in comparison with PS/A-MWCNT, resulting from good dispersion and interfacial interactions between DPPA-MWCNT and PS matrix. The incorporation of DPPA-MWCNT to PS significantly reduced peak heat release rate, smoke production rate, and carbon monoxide and carbon dioxide release in cone calorimeter tests. The enhanced fire-retardant properties should be ascribed to the barrier effect of carbon nanotubes, which could provide enough time for DPPA-MWCNT and its functionalized groups to trap the degrading polym...
129 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