Instruct: Given a question, retrieve documents that answer the question.
Query: Who invented the carbon nanotube?
Sumio Iijima (飯島 澄男 Iijima Sumio, born May 2, 1939) is a Japanese physicist, often cited as the inventor of carbon nanotubes. Although carbon nanotubes had been observed prior to his "invention", Iijima's 1991 paper generated unprecedented interest in the carbon nanostructures and has since fueled intense research in the area of nanotechnology.
On January 22, 2009, a formal information request letter was sent to manufacturers who produce or import carbon nanotubes in California, or who may export carbon nanotubes into the State. This letter constitutes the first formal implementation of the authorities placed into statute by AB 289 and is directed to manufacturers of carbon nanotubes, both industry and academia within the State, and to manufacturers outside California who export carbon nanotubes to California. This request for information must be met by the manufacturers within one year. DTSC is waiting for the upcoming January 22, 2010 deadline for responses to the data call-in.
First studies on oxidation of carbon nanotubes involved a gas-phase reactions with nitric acid vapor in air, which indiscriminately functionalized the carbon nanotubes with carboxylic, carbonyl or hydroxyl groups. In liquid-phase reactions, carbon nanotubes were treated with oxidizing solutions of nitric acid or a combination of nitric and sulfuric acid to the same effect. However, overoxidation may occur causing the carbon nanotube to break up into fragments, which are known as carbonaceous fragments. Xing et al. revealed sonication assisted oxidation, with sulfuric and nitric acid, of carbon nanotubes and produced carbonyl and carboxyl groups. After the oxidation reaction in acidic solution, treatment with hydrogen peroxide limited the damage on the carbon nanotube network. Single-walled carbon nanotubes can be shortened in a scalable manner using oleum (100% HSO with 3% SO) and nitric acid. The nitric acid cuts carbon nanotubes while the oleum creates a channel.
The catalytic vapor phase deposition of carbon was reported in 1952 and 1959, but it was not until 1993 that carbon nanotubes were formed by this process. In 2007, researchers at the University of Cincinnati (UC) developed a process to grow aligned carbon nanotube arrays of length 18 mm on a FirstNano ET3000 carbon nanotube growth system.
My research interests include transport phenomena (charge, energy, and spin) in nanoscale systems, including carbon nanotubes and graphene, and hybrid nanostructures based on these materials conjugated with proteins, synthetic peptides, and DNA. Recent research accomplishments include: Creation of bio-inspired vapor sensors based on carbon nanotube transistors functionalized with mammalian olfactory receptors. Crystallographic etching of graphene. Large-scale production of very large graphene oxide membranes. Demonstration of Feedback Controlled Electromigration, an atomically precise fabrication method for nanogap contacts for molecular electronics (patent pending). Invention of a DNA/Nanotube Gas Sensor appropriate for use in an electronic nose system (patent awarded), and quantitative comparison of experiment with all-atom Molecular Dynamics simulation. Development of a quantitative theory of Scanning Conductance Microscopy, including a demonstration of direct measurement of the dielectric constant of a polymer nanowire. Quantitative characterization of individual defects in a nanotube device. First fabrication of air-stable, n-type nanotube field effect transistors. Design and demonstration of a nanotube memory cell. Discovery and control of the Schottky barriers in carbon nanotube field effect transistors using Scanning Gate Microscopy. First observation of the impurity-induced conversion of a nanotube FET into a nanotube diode, and elucidation of the mechanism. Demonstration of 20nm channel nanotube FETs and quantum dots. Discovery of 1-dimensional quantized phonon subbands in nanotubes. First production of nanotube-epoxy composite materials for thermal management (patent pending). Fabrication of “nanogap” electrical contacts for molecular electronic circuits (patent awarded).
Johnson has received over 25 grants for his research, given 97 talks related to his work, and supervised over 120 students in conducting research. He has been an author or co-author on over 140 papers, and received 9 patents.
Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. They can be considered a rolled up graphene. When rolled at specific and discrete ("chiral") angles, and the combination of the rolling angle and radius decides whether the nanotube has a bandgap (semiconducting) or no bandgap (metallic).
Metallic carbon nanotubes have also been proposed for nanoelectronic interconnects since they can carry high current densities. This is a useful property as wires to transfer current are another basic building block of any electrical system. Carbon nanotubes have specifically found so much use in NEMS that methods have already been discovered to connect suspended carbon nanotubes to other nanostructures. This allows carbon nanotubes to form complicated nanoelectric systems. Because carbon based products can be properly controlled and act as interconnects as well as transistors, they serve as a fundamental material in the electrical components of NEMS.
The modification of carbon nanotubes with aryl diazonium salts was studied first by Tour et al. Due to the harsh conditions needed for the "in situ" generated diazonium compound, other methods have been explored. Stephenson et al. reported using aniline derivatives with sodium nitrite in 96% sulfuric acid and ammonium persulfate. Price et al. demonstrated that stirring carbon nanotubes in water and treating with anilines and oxidizing agents proved to be a milder reaction. The diazonium chemistry functionalized carbon nanotubes which was used as a precursor to further modifications. Suzuki and Heck coupling reactions were performed on iodophenyl-functionalized carbon nanotubes. Wong et al. demonstrated mild photochemical reactions to silylate the carbon nanotubes with trimethoxysilane and hexaphenyldisilane.
Because of their hydrophobic nature, CNTs tend to agglomerate hindering their dispersion in solvents or viscous polymer melts. The resulting nanotube bundles or aggregates reduce the mechanical performance of the final composite. The surface of CNTs can be modified to reduce the hydrophobicity and improve interfacial adhesion to a bulk polymer through chemical attachment. 
Covalent modification attaches a functional group onto the carbon nanotube. The functional groups can be attached onto the side wall or ends of the carbon nanotube. The end caps of the carbon nanotubes have the highest reactivity
due to its higher pyrimidization angle and the walls of the carbon nanotubes have lower pyrimidization angles which has lower reactivity. Although covalent modifications are very stable, the bonding process disrupts the sp
hybridization of the carbon atoms because a σ-bond is formed. The disruption of the
extended sp hybridization typically decreases the conductance of the carbon nanotubes.
Carboxylic groups are used as the precursor for most esterification and amidation reactions. The carboxylic group is converted into an acyl chloride with the use of thionyl or oxalyl chloride which is then reacted with the
desired amide, amine, or alcohol. Carbon nanotubes have been deposited on with silver nanoparticles with the aid of amination reactions. Amide functionalized carbon nanotubes have been shown to chelate silver nanoparticles. Carbon nanotubes modified with acyl chloride react readily with highly branched molecules such as poly(amidoamine), which acts as a template for silver ion and later being reduced by formaldehyde. Amino-modified carbon nanotubes can be prepared by reacting ethylenediamine with an acyl chloride functionalized carbon nanotubes.
Smalley's latest research was focused on carbon nanotubes, specifically focusing on the chemical synthesis side of nanotube research. He is well known for his group's invention of the high-pressure carbon monoxide (HiPco) method of producing large batches of high-quality nanotubes. Smalley spun off his work into a company, Carbon Nanotechnologies Inc. and associated nanotechnologies.
Carbon nanobuds are a newly created material combining two previously discovered allotropes of carbon: carbon nanotubes and fullerenes. In this new material, fullerene-like "buds" are covalently bonded to the outer sidewalls of the underlying carbon nanotube. This hybrid material has useful properties of both fullerenes and carbon nanotubes. In particular, they have been found to be exceptionally good field emitters. In composite materials, the attached fullerene molecules may function as molecular anchors preventing slipping of the nanotubes, thus improving the composite’s mechanical properties.
Carbon nanotube computer refers to a computer built entirely using carbon nanotubes based transistors. Researchers from Stanford University said that they had successfully built a carbon nanotube computer and their research paper published on 25 September 2013 in the journal "Nature". They named their first carbon nanotube computer Cedric.
Carbon nanotubes provide a certain potential for metal-free catalysis of inorganic and organic reactions. For instance, oxygen groups attached to the surface of carbon nanotubes have the potential to catalyze oxidative dehydrogenations or selective oxidations. Nitrogen-doped carbon nanotubes may replace platinum catalysts used to reduce oxygen in fuel cells. A forest of vertically aligned nanotubes can reduce oxygen in alkaline solution more effectively than platinum, which has been used in such applications since the 1960s. Here, the nanotubes have the added benefit of not being subject to carbon monoxide poisoning.
As a result, carbon nanotubes have been shown to be great materials for actuation related applications. The subfield of carbon nanotube actuators have been quite successful and ready for scalable applications considering there are quite a few conventional and scalable methods for the synthesis of large scale carbon nanotubes. Carbon nanotube sheets used as electrodes in electrolyte solutions offered low voltage operations at room temperature with actuation strokes and rates comparable to the conducting polymer actuators, but with higher work densities per cycle and life times. However the actuation strokes are much smaller than those of the electrostrictive rubbers which operate at three orders of magnitude higher voltages. On the other hand, realization of carbon nanotube aerogels made giant strokes possible comparable to electrostrictive rubbers at room temperature, but carbon nanotube aerogels can perform at a very wide range of temperatures, and with very high actuation rates, which are even better than the actuation rate of the human muscles.
The differences in the chiral angle and the diameter cause the differences in the properties of the various carbon nanotubes. For example, it can be shown that an ("n,m") carbon nanotube is metallic when "n = m", has a small gap (i.e. semi-metallic) when "n" – "m" = 3"i", where "i" is an integer, and is semiconducting when "n" – "m" ≠ 3"i". This is due to the fact that the periodic boundary conditions for the one-dimensional carbon nanotubes permit only a few wave vectors to exist around the circumference of carbon nanotubes. Metallic conduction occurs when one of these wave vectors passes through the K-point of graphene’s 2D hexagonal Brillouin zone, where the valence and conduction bands are degenerate. For the semiconducting carbon nanotubes, there is a diameter dependency on bandgap. For example, according to a single-particle tight-binding description of the electronic structure,
formula_3
where γ is the hopping matrix element, and "a" is the carbon–carbon bond distance.
Over 800 nano-related patents were granted in 2003, with numbers increasing to nearly 19,000 internationally by 2012. Corporations are already taking out broad-ranging patents on nanoscale discoveries and inventions. For example, two corporations, NEC and IBM, hold the basic patents on carbon nanotubes, one of the current cornerstones of nanotechnology. Carbon nanotubes have a wide range of uses, and look set to become crucial to several industries from electronics and computers, to strengthened materials to drug delivery and diagnostics. Carbon nanotubes are poised to become a major traded commodity with the potential to replace major conventional raw materials.
On 22 January 2009, a formal information request letter was sent to manufacturers who produce or import carbon nanotubes in California, or who may export carbon nanotubes into the State. This letter constitutes the first formal implementation of the authorities placed into statute by AB 289 and is directed to manufacturers of carbon nanotubes, both industry and academia within the State, and to manufacturers outside California who export carbon nanotubes to California. This request for information must be met by the manufacturers within one year. DTSC is waiting for the upcoming 22 January 2010 deadline for responses to the data call-in.
 Junctions between two or more nanotubes have been widely discussed theoretically. Such junctions are quite frequently observed in samples prepared by arc discharge as well as by chemical vapor deposition. The electronic properties of such junctions were first considered theoretically by Lambin et al., who pointed out that a connection between a metallic tube and a semiconducting one would represent a nanoscale heterojunction. Such a junction could therefore form a component of a nanotube-based electronic circuit. The adjacent image shows a junction between two multiwalled nanotubes.
Junctions between nanotubes and graphene have been considered theoretically but not widely studied experimentally. Such junctions form the basis of pillared graphene, in which parallel graphene sheets are separated by short nanotubes. Pillared graphene represents a class of three-dimensional carbon nanotube architectures.
Recently, several studies have highlighted the prospect of using carbon nanotubes as building blocks to fabricate three-dimensional macroscopic (>100 nm in all three dimensions) all-carbon devices. Lalwani et al. have reported a novel radical-initiated thermal crosslinking method to fabricate macroscopic, free-standing, porous, all-carbon scaffolds using single- and multi-walled carbon nanotubes as building blocks. These scaffolds possess macro-, micro-, and nano-structured pores, and the porosity can be tailored for specific applications. These 3D all-carbon scaffolds/architectures may be used for the fabrication of the next generation of energy storage, supercapacitors, field emission transistors, high-performance catalysis, photovoltaics, and biomedical devices and implants.
Iijima's discovery of multi-walled carbon nanotubes in the insoluble material of arc-burned graphite rods in 1991 and Mintmire, Dunlap, and White's independent prediction that if single-walled carbon nanotubes could be made, then they would exhibit remarkable conducting properties helped create the initial buzz that is now associated with carbon nanotubes. Nanotube research accelerated greatly following the independent discoveries by Bethune at IBM and Iijima at NEC of "single-walled" carbon nanotubes and methods to specifically produce them by adding transition-metal catalysts to the carbon in an arc discharge. The arc discharge technique was well-known to produce the famed Buckminster fullerene on a preparative scale, and these results appeared to extend the run of accidental discoveries relating to fullerenes. The discovery of nanotubes remains a contentious issue. Many believe that Iijima's report in 1991 is of particular importance because it brought carbon nanotubes into the awareness of the scientific community as a whole.
The exceptional electrical and mechanical properties of carbon nanotubes have made them alternatives to the traditional electrical actuators for both microscopic and macroscopic applications. Carbon nanotubes are very good conductors of both electricity and heat, and are also very strong and elastic molecules in certain directions. These properties are difficult to find in the same material and very needed for high performance actuators. For current carbon nanotube actuators, multi-walled carbon nanotubes (MWNTs) and bundles of MWNTs have been widely used mostly due to the easiness of handling and robustness. Solution dispersed thick films and highly ordered transparent films of carbon nanotubes have been used for the macroscopic applications.
The "thinnest" carbon nanotube is the armchair (2,2) CNT with a diameter of 0.3 nm. This nanotube was grown inside a multi-walled carbon nanotube. Assigning of the carbon nanotube type was done by a combination of high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and density functional theory (DFT) calculations.
With chemical doping, the electronic characteristics of peapods can be further adjusted. When carbon peapod is doped with alkali metal atoms like potassium, the dopants will react with the C molecules inside the SWNT. It forms a negatively charged C covalently bound, one-dimensional polymer chain with metallic conductivity. Overall, the doping of SWNTs and peapods by alkali metal atoms actively enhances the conductivity of the molecule since the charge is relocated from the metal ions to the nanotubes. 
Doping carbon nanotubes with oxidized metal is another way to adjust conductivity. It creates a very interesting high temperature superconducting state as the Fermi level is significantly reduced. A good application would be the introduction of silicon dioxide to carbon nanotubes. It constructs memory effect as some research group has invented ways to create memory devices based on carbon peapods grown on Si/SiO surfaces.
Invention of the carbon nanotube is credited to Sumio Iijima in 1991, but Figure 8 in Bacon’s paper shows a carbon nanotube derived from a whisker subjected to heavy current that caused the outer layers to explode. Iijima's invention is a seamless tube of diameter <30 nm, as opposed to Bacon's scrolled sheet.
The discovery of carbon nanotubes is largely attributed to Sumio Iijima of NEC in 1991, although carbon nanotubes have been produced and observed under a variety of conditions prior to 1991. Iijima's discovery of multi-walled carbon nanotubes in the insoluble material of arc-burned graphite rods in 1991 and Mintmire, Dunlap, and White's independent prediction that if single-walled carbon nanotubes could be made, then they would exhibit remarkable conducting properties helped create the initial buzz that is now associated with carbon nanotubes. Nanotube research accelerated greatly following the independent discoveries by Bethune at IBM and Iijima at NEC of "single-walled" carbon nanotubes and methods to specifically produce them by adding transition-metal catalysts to the carbon in an arc discharge.
Carbon nanotubes can be functionalized to attain desired properties that can be used in a wide variety of applications. The two main methods of carbon nanotube functionalization are covalent and non-covalent modifications. Because of their apparent hydrophobic nature, carbon nanotubes tend to agglomerate hindering their dispersion in solvents or viscous polymer melts. The resulting nanotube bundles or aggregates reduce the mechanical performance of the final composite. The surface of the carbon nanotubes can be modified to reduce the hydrophobicity and improve interfacial adhesion to a bulk polymer through chemical attachment.