Methods Citations. Results Citations. Figures and Tables from this paper. Citation Type. Has PDF. Publication Type. More Filters. New direction in nanotube science. We review the latest advances in the production and state-of-the art characterization of B- and N-doped carbon nanotubes CNTs and nanofibers. We briefly discuss different approaches to producing … Expand. Carbon Nanotubes: Synthesis, Properties, and Applications. This brief review presents a comprehensive outline of the present research status on the fast moving carbon nanotube CNT field.
It covers a short introduction to the relation between carbon … Expand. Highly Influenced. View 11 excerpts, cites background and methods. This overview critically examines some of the novel history relating to carbon nanotubes. It considers the nanotechnology being implemented in making and using such materials. While much new … Expand. These flames assist with the initiation and nents, argon, iron and methane, is critical for the synthesis growth of CNTs.
In the arc-discharge synthesis of nanotubes, C2H6, which are present in the post-flame area, are rich Bethune et al. The reaction is exothermic and chemical holes which were illed with a mixture of pure powdered energy released in the form of heat in the flame supports metals Fe, Ni or Co and graphite. The electrodes were endothermic carbon deposition reactions. Catalysts are also vaporized with a relatively low current of 95— A at — required to provide reaction sites for the deposition of solid Torr in a He atmosphere.
Large quantities of CNTs were black carbon. The If an appropriate catalyst and flame and reaction conditions arc was generated between two graphite electrodes in a reac- are provided, large amounts of CNTs can be gained com- tor under a helium atmosphere mbar. Recent trends in the synthesis of CNTs quasi-ballistic [42]. CNTs, due to their electronic nature, can be used in transistors and other switching applications in advanced A recent nebulized spray pyrolysis method has also been used electronics [43].
The most recent application of nanotubes was for the synthesis of MWNTs. A nebulized spray, the key factor as an emitter. The important aspect of CNT emitters is that the in this method, is generated by a special ultrasonic atomizer. MWNTs with fairly uniform diameters in aligned bundles have CNTs can also be used in sensors, micron-scale on-chip triodes been obtained via this technique.
Ethanol is used as a sol- 3. Mechanical properties of CNTs vent as well as a carbon source due to its non-polluting nature, low cost, harmless byproducts e. The ad- at this point.
The literature suggests that CNTs are very strong vantage of using a nebulized spray is the ease of scaling into an materials, especially in the axial direction [47]. Several reports have shown that in the radial direction, CNTs are rather soft [48].
The irst TEM observation of radial elasticity showed 3. Later, nano-indentations with an atomic force microscope CNTs reportedly have extremely high surface areas, large AFM were performed by different groups of researchers to aspect ratios, and remarkably high mechanical strength.
The results showed that CNTs are in fact very soft in copper [27,28]. These unique properties make CNTs good can- the radial direction. The radial direction elasticity of CNTs is didates as illers in different polymers and ceramics to realize important, especially for the formation of CNT nanocomposites desirable consumer products [29,30].
It has also been predicted and their mechanical properties, in which embedded tubes are that CNT-based ield-effect transistors FETs will soon supplant subjected to large deformation in the transverse direction when their silicon-based analog counterparts [31].
CNTs are also good a load is applied to a composite structure. Because the carbon- incorporating agents due to their unique electrical, mechanical carbon bonds observed in graphite are among the strongest in and thermal properties.
Studying 3. Earlier theoretical cal- CNTs show electrical properties in chiral forms. Researchers culations were carried out to predict the mechanical properties have demonstrated that CNTs exhibit unique conductive proper- of CNTs [].
These results were the irst to suggest that geometric differ- modulus for individual MWNTs was performed by Treacy et ences such as defects, chirality, different diameters and the de- al. They demonstrated that nanotubes pos- electronic properties of CNTs [32,33].
Various research groups performed direct arranged in a hexagonal lattice, each carbon atom is covalently measurements of the bending forces of MWNTs as a function bonded to three neighbor carbons via sp2 molecular orbitals.
Falvo et al. Thus, CNTs can be conducting sharp angles without undergoing any structural fracturing us- or semi-conducting types depending on the type of chirality [ ing an AFM tip. Endo et al. MWNTs are composed of many tubes of survive this pressure. Zhu et al. A pseudo-gap was observed in I —V measurements, MWNTs and noted that the tubes do not break but collapse; which attributes to its conducting nature [39].
This area has been a ield of great interest since the by Sinnot et al. Yakobson [71] tron transport, can be described as quantum wires. Guanghua et al. Hernandez et al. Yu et al. Most common types of functionalization. CNT, carbon nanotube. Thermal properties of CNTs As rolled graphitic structures, CNTs are of great importance and interest not only for their electronic and mechanical prop- erties, but also for their thermal properties.
Although their size is very small, the quantum effects are important and the low- temperature speciic heat and thermal conductivity show direct evidence of the 1-D quantization of the phonon band structure in CNTs [56,70,75]. The incorporation of pristine and function- Fig. Mechanism of carbon nanotube dispersion with the help of a sur- alized nanotubes to different materials can double the thermal factant. Reprinted from Vaisman et al. Kim et al. A similar study have also been reported.
Some common surface scattering []. These properties also depend on the examples of this type of functionalization include use of surfac- atomic arrangement, the diameter and length of the tubes, the tant, especially with SWNTs, CNT wrapping, and non-covalent number of structural defects and the morphology, as well as the protein interactions [84].
Covalent functionalization 4. Dispersion of CNTs In this type of functionalization, the desired groups are at- tached onto the sidewall or tips of the CNTs permanently in an One of the problems associated with CNTs is the agglomera- irreversible manner. The functionalization of CNTs is The advantages of chemical functionalization are that it can be carried out to overcome their agglomeration and bundle forma- attached covalently with polymeric materials and dispersed well tion, which also enhances their dispersion in polymeric materi- in different solvents.
The main disadvantage of the chemical als and solvents. Thus, the puriication or functionalization of function is the production of defects on CNTs. Puriication removes unwanted particles that remain after the synthesis process, while function- 4. Dispersion of CNTs using surfactants alization introduces a speciic functional group onto the side chains or ends of the CNTs [83].
Different methods are used The use of surfactants has also been reported for the purpose by researchers for the functionalization and dispersion of CNTs. Applications of CNTs. Functionalization of carbon nanotubes. Reprinted from Wu et al. Wastewater treat- ment by CNTs is also a rapidly growing ield for those who are interested in adsorption studies [95]. The major problem associ- sulfate, and dodecyl-benzene sodium sulfonate are commonly ated with CNTs is their high cost and nonrenewable characteris- use for the reduction of the aggregative tendency of CNTs in tic.
At present, special efforts are in progress to develop certain water and other related solvents. It was proposed that the pres- preparation methods for CNTs which minimize their cost. Some ence of benzene rings is responsible for the high dispersive ef- of the very important and promising applications of CNTs are iciency of CNTs.
The p-stacking interactions of benzene rings discussed below in detail. It was also determined that besides aromatic 5. CNTs as illers groups, naphthenic saturated rings groups also provide good surfactant-tube afinity.
Many researchers working in the ield of nanocomposites 4. Physical dispersion by ultrasonication have attempted to use CNTs as a iller. The main idea for incor- porating CNTs into different polymeric and other materials is Physical dispersion is also an important way to decrease the to improve the properties of these materials.
By doing so, the agglomeration tendency of CNTs. Sonication provides certain mechanical, electrical and thermal properties are improved to al- vibrational energies to agglomerated CNTs, overcoming the at- most an ideal range.
Garcia-Gutierrez et al. Soichia et al. With good dispersion, they showed that the mechanical prop- Nanotechnology is one of the latest and the most developed erties of polyimide were enhanced.
Bhattacharyya et al. Nanotechnol- sulated SWNTs with a polyamide PA12 matrix in a coni- ogy can be used in different applications in various ields, in- cal twin-screw extruder.
The process of encapsulation by the cluding nano-medicine, energy, the environment, and in sensors SMA copolymer leads to a greater dispersion of SWNT and thus [91]. This leads to enhanced mechanical properties promising.
Since their discovery by Iijima [5] in , CNTs are of the formed product. They used nology due to their various applications. Prashantha et al. Meunier et al. They suggested that by damaging the surface of the ites with various compositions of MWNTs using a range of SWNT materials chemically or mechanically, one can increase techniques. They reported that MWNTs have better dispersion the electrochemical storage of these batteries.
Zhang et al. The PA66 materials were grafted onto chemical devices []. Niu et al. Recently, a similar study was carried out by Frackowiak and Beguin [] and Ma et al. CNT supercapacitors are used in applications to devices that require high power capabili- CNTs can be used in electric devices as ield-emission sourc- ties and higher storage capacities. The power densities approach es.
Electrons are easily emitted from supercapacitors can be used to provide fast acceleration and to their tips due to the curvature present in the CNTs in the form store braking energy electrically for hybrid electric vehicles. Ac- of pentagons [,] or due to the presence of oxidized tips tuators are important devices, but the problem associated with [,].
Therefore, CNT-modiied actuators were prepared displays, intense light sources, bright lamps [93,,], and by several researchers. These work at relatively low voltages X-ray sources [46,]. Although CNTs are good emitters, and at temperatures as high as oC []. For example, the nanocomposites of CNTs are also excellent electron-emission maximum stress observed in SWNT actuators was 26 MPa surfaces which are vacuum stable []. There are many advan- []. This value is comparable to that of natural muscles, as it tages when using CNTs as an electron emitter.
These include is times larger than the value for natural muscle []. Sensors absence of the need for an ultra-high vacuum, and high current densities. The eficiency of biosensors and molecu- lar sensors can be enhanced by attaching CNTs onto them. With 5. Batteries Lithium ions batteries chemical force microscopy techniques, Wong et al. Thus, it is pos- ties due to its lowest electronegativity and because electrons sible to construct various types of sensors containing nanotube are easily donated from Li.
Thus, it is the best candidate for the composite pellets, which are very sensitive to gases and which fabrication of lightweight and eficient batteries. However, de- can be used to monitor leaks in chemical plants.
Collins et al. This problem can extremely sensitive to air and vacuum conditions by noting large be solved by the combining an application of CNTs and Li by in- variations in the electrical resistance levels of their SWNT sam- tercalating Li ions within CNTs.
They also added that MWNTs can be used as eficient sen- from a graphitic anode to the cathode. Varghese et al.
Inert gas determines the structure of carbons to be present in CNTS. Commonly used inert gas is helium gas. Reactor: It contains a quartz chamber which is connected to vacuum pump and a diffusion pump to inert gas supply. Initially the chamber is made vacuum by the vacuum pump and then the chamber is filled with helium gas by the diffusion pump [ 24 ]. In this method, a potential of 20—25 V is applied across the pure graphite electrodes separated by 1 mm distance and maintained at torr pressure of flowing helium gas filled inside the quartz chamber Figure 2.
When the electrodes are made to strike each other under these conditions it produces an electric arc. These positively charged carbon ions moves towards cathode, gets reduced and deposited and grow as CNTs on the cathode.
As the CNTs grow, the length of the anode decreases, but the electrodes are adjusted and always maintain a gap of 1 mm between the two electrodes. If proper cooling of electrodes are achieved uniform deposition of CNTs are formed on the cathode which is achieved by inert gas maintained at proper pressure [ 25 ]. By this method multi-walled carbon nanotubes are synthesized and to synthesize single-walled carbon nanotubes catalyst nanoparticles of Fe, Co, and Ni are incorporated in the central portion of the positive electrode.
Electric arc method. Physical vapor deposition PVD : PVD is a technique by which a material can be vaporized into gaseous form and then deposited on the surface of a substrate. Target source: The most common carbon source target used is solid graphite which is irradiated by laser source and vaporized into vapor carbon atoms. Substrate used: The substrate used in this method is the water cooled copper collector on which the vaporized carbon atoms deposit and grow as CNTs.
Inert gas atmosphere: Argon gas is commonly used as inert gas which flows at a constant flow rate towards the water cooled copper collector. Laser Ablation method is a Physical Vapor Deposition method in which graphite target is vaporized by laser source Figure 3.
The graphite target is vaporized by either continuous laser source or pulsed laser source. The vaporized target atoms carbon are sweeped toward cooled copper collector by the flow of argon gas. The carbon atoms are deposited and grown as CNTs on cooled copper collector. In case of continuous laser beam, the carbon atoms are continuously vaporized whereas in case of pulsed laser beam the amount of CNTs produced can be monitored as each shot of pulsed laser beam is directly proportional to the amount of carbon atoms vaporized [ 26 ].
By this method multi-walled carbon nanotubes are synthesized and to synthesize single-walled carbon nanotubes catalyst nanoparticles of Fe, Co, Ni are used. Laser ablation method—schematic representation. Pulsed Laser deposition is a thin film deposition technique in which the target material is vaporized by pulsed laser beam and vaporized target atoms are made to deposit on substrates Figure 4.
The furnace contains a target at bottom and substrate mounted on the top. A pulsed laser beam from Nd:YAG laser source is made to strike the target to produce vaporized target atoms called the plume plume is vaporized atoms at high temperature [ 27 ]. The plume moves towards the substrate and it is deposited and grown as CNTs.
Each shot of laser is directly related to the amount of material ablated, thus deposition rate can be controlled and calibrated. Pulsed laser ablation method—Schematic representation. The synthesized CNTs can be separated from the amorphous carbon, carbon nanoparticles, residual catalyst and other impurities by various methods.
The conventional methods of purification are not very successful but methods like gas phase, liquid phase and intercalation methods show good results. Gas phase purification of CNTs: In this method the CNTs are subjected to a high temperature oxidation followed by repeated extractions with nitric acid and hydrochloric acid.
This procedure makes the synthesized CNTs purer and high stability with fewer amounts of residual catalyst and other non CNTs forms. They are: Preliminary filtration to remove bulk graphite particles.
Dissolution in both organic solvents and concentrated acids to remove the fullerenes and catalyst, respectively. Chromatography to isolate multi-walled carbon nanotubes, single-walled carbon nanotubes, etc. Intercalation purification of CNTs: In this method the nanoparticle impurities present are oxidized by metallic copper which acts as oxidation catalyst formed from the reduction of copper chloride added during the process.
This process introduces intercalate residues and damage CNTs during oxidation process. There are numerous mechanisms available to build up structures occluded with various characteristics. The sp 2 nature of carbon hybridization constructs a layered pattern of arrangement with weaker plane bonding of Vander Waals forces at the outside and strong forces at inner plane bounds. Few numbers of concentric cylinders were equipped with regular spacing of interlayers that are located around central hollow section and demonstrated as multi walled CNTs Figure 5.
The inner diameter of multi-walled CNTs can even range from 0. Outer diameter can exist up to 25 nm. The tips on both sides were closed and protruding ends were capped using dome shaped half width fullerene molecules. Axial molecules can exist up to few centimeters. The primary function of half width fullerene molecules is to aid in shutting down the tubes at both the ends.
Length is up to micrometer range. Such arrangement is organized in a hexagon shape so as to develop a crystal [ 29 ]. Graphene to CNT. Based on wrapping mechanism, three different forms of SWCNTs include chiral, armchair, and zigzag pattern. The single walled structure is primarily characterized by a set of indices n and m which describes the vector mechanism of chiral and absolutely it impinges an impact on electrical tendency of both nanotubes Figure 6.
Hence, the radius of carbon nanotube can be estimated using. At most of the times, armchair type can be referred as metallic one whereas all other forms can be denoted as a semi-conductor. Various involved parameters and vector representations [ 31 ] can provide an impinging impact on structure of CNT as follows. If the diameter of outer CNT exceeds the inner tube, such a model is prescribed as Russian type model whereas, wrapping of a single graphite sheet to many a fold around itself constitutes the simple Parchment model.
Both multi walled and single walled CNTs possess similar properties. Due to multi-layered arrangement of multi walled nanotubes, the outer portion not only cover the inner tubes from certain chemical reactions when contaminate with ambient substances but also exhibit greater tensile characteristics, which would be a drawback of single walled CNTs [ 32 ].
Owing to the presence of sp 2 bonds available betwixt indigenous carbon atoms, CNTs possess higher tensile property compared to steel as well as Kevlar. Hence, SWCNTs possess maximum tensile property which may be nearly times as that of steel [ 33 ]. An amazing feature of CNTs is its elasticity. Under maximum force and high pressure by exposing it to greater compressive forces along axial direction, it can even bend, kink, twist and ultimately buckle without causing any damage to CNT.
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Difficulty Beginner Intermediate Advanced. Explore Documents. Application of Carbon Nanotubes in Neurology. Uploaded by Brck Heart's Aqil Mubarak. Did you find this document useful? Is this content inappropriate? Report this Document. Flag for inappropriate content. Download now. Related titles.
Carousel Previous Carousel Next. Handbook of Nanophase and Nano Structured Materials 4. Jump to Page. Search inside document. Arch Toxicol — DOI DBS ; Refractive nature of neurons to vector systems for chemical, genetic or other interventions; Serious challenges with other vectors in overcoming the blood—brain barrier BBB ; Limited therapeutic interventions for most neurological conditions; Suitability of the mechanical and chemical properties of CNT for long-term implantation within neuronal tissue; Biocompatibility and biodegradability of CNT within neural tissue In this review, the application of CNT interfacing with of CNT as a substrate for nerve cell growth.
VanHandal References trode interface research lies both in the reduction in elec- trical resistance to alternating currents impedance of the electrodes during the recording of signals and in the increase in the delivery of electrical charge whenever Evaluation of the uptake and toxicity of MWNT in glioma Investigation of the in vivo biocompatibility of MWNT CNT injection led to a transient and self-limiting local neurons are being stimulated.
MWNT were biocompatible, and no damage at the In the last few years, nanotechnology has opened up Preferential accumulation of MWNT into tumour macrophages and to lesser extent in microglia new directions of research in order to create innovative neuroprosthetic devices able to enhance neuron stimula- cellular structural level was observed tion.
The high inflammatory response electrical conductivity and excellent mechanical properties Aim and main results intracranial model of CNT make them a desirable material for neuroprosthetic devices. After the application of electrical current through SWNT films, the inward trans- membrane current in neurons was recorded by whole cell patch clamping, and the results indicated no differences over those induced by direct electrode-mediated patch Pluronic F Pluronic F clamp.
After incubation, neurons and glial cells showed a tendency to aggregate and accumulate in the CNT-coated Table 2 continued Coated Coated regions, whereas cell density on CNT-free regions was very low.
Nat Mater 2 5 — Joshua D. Rachel An. Cosmin Safta. Hykal Farid. Iqbal Baryar. Debashis Roy. Eiram Tactac. Jenny Ann Santos. Mekala Lakshman. Soufiane Karrakchou.
Bianca Floriano da Rocha. Nona Asola. Arish Ahmed. Sadaf Rizwanhumayoon. Mudit Nawani. Ravichandran B. Mohamed H. Katie Davies. Edward De Leon. Momade Santos. Florentin Smarandache.
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