Nanotubes are dream come true in Science and Technology
Table of Contents
Definition of Nano Technology
Definition of Nanotubes
Types of Nanotubes
1. Zigzag nanotube (n, 0)
2. Armchair nanotube (n,n)
3. Chiral nanotube (n,m)
4. Membrane nanotubes, membrane nanotubules or cytonemes
5. Inorganic nanotube
6. DNA nanotube
7. Carbon nanotubes
7.1.Types of Carbon Nanotubes
7.1.1. Single-walled Carbon nanotubes
7.1.2. Multi-walled Carbon nanotubes
7.1.3. Nanotorus
7.1.4. Carbon nanobuds
7.1.5. Cup stacked carbon nanotubes
7.2.Properties of Carbon Nanotubes
Application of Nanotubes
Conclusion
Bibliography
Nanotubes are dream come true in Science and Technology
“Life is in flux”, said Heraclitus. Nothing in this universe is fixed. Human being and Cosmos keeps changing from time to time. Static life could be said as an enemy of human being because human being wants to move from good, better, best and beyond. In the process of evolving or changing science and technology also change from traditional to modern or from simplicity to complexity. Science and technology have changed from slow aircraft of Wright brothers to supersonic plane and people can perform experiment on tiniest particles which cannot be seen with our naked eyes. Science existed since the beginning of the universe and in fact the formation of the universe itself is part of science. Science and technology have a tremendous impact in human life and in Cosmos. Our body according to mechanical engineering is a complex machine. The different parts of our body, internal and external could be known and healed when we get sick due to the help of science and technology. Mentally, spiritually, physically, socially and even in our educational system we are affected by science and technology. Science and technology is a very broad concept because it includes every aspects of macro, medium and micro sciences and it includes space, time, mass, motion and simultaneity. It is wise to know different aspects of science and technology but it is also foolish to deal it in one single study. So here I will dwell only in one aspect of Science that is Nano-technology and within it I will talk more about Nano-tubes.
Ralph C. Merkle, Ph.D said, “Nanotechnology: It’s a Small, Small, Small, Small World”. Nano literally means 10 to the power -9. Nanotechnology is an innovative development in science and technology. It covers different walks of life like health, education, business, transports, and many more. Nanoscience is the world of atoms, molecules, macromolecules, quantum, dots, and macromolecular assemblies. Nanotechnology is the design, characterization, production and application of structures, devices and systems. The term “nanotechnology” was defined by Tokyo University professor Norio Taniguchi in 1974 as, “Nano-technology mainly consists of the processing, separation, consolidation, and deformation of materials by one atom of one molecule”. Nanotechnology includes many techniques used to create structures at a size scale below 100nm, including those used for fabrication of nanowires, those used in semiconductor fabrication such as deep ultraviolet lithography, electron beam lithography, further ion beam machining, nanoimprint lithography, and molecular vapor deposition, and copolymers.[1]
Nanotechnology is the study of manipulating matter on an atomic and molecular scale. Generally, nanotechnology deals with developing materials, devices, or other structures possessing at least one dimension sized from 1 to 100 nanometers. One nanometer (nm) is one billionth, or 10−9, of a meter. Nanotechnology may be able to create many new materials and devices with a vast range of applications, such as in medicine, electronics, biomaterials and energy production.[2] Nano technology is a technology of rearranging and processing of atoms and molecules to fabricate materials to nano specifications such as a nanometre. Materials and devices designed and made at the molecular level would be quite different from those of daily use today. It is so profound that it will touch all aspects of economy and society. Through the developments in nano technology, energy will be clean and abundant, the environment will have been repaired to a pristine state, and any kind of material artefact can be made for almost no cost.[3] Current applications for nanotechnology are dominated by tools for scientists, and by new materials that are structured on the nanoscale. Such materials are used in cosmetics, health and medicine and in a variety of manufactured goods. The electronics and information technology industries are also a prominent driver for these new technologies. Carbon nanotubes have potential applications in electronics, improved materials, and drug delivery. Studying about nanotechnology would be incomplete without knowing about Nanotubes because they are vital parts of nanotechnology.
A Nanotube is a nanometer-scale tube-like structure. Nanotubes are being studied for use as photon ballistic waveguides as interconnects in quantum dot/quantum effect well photon logic arrays.[4] Nanotubes come in a variety of flavors: long, short, single-walled, multi-walled, open, closed, with different types of spiral structure, etc. Nanotubes are of great importance in the field of industries, education, health, research and construction. One of the recent developments ‘Smart’ bio nanotubes is used to improve the delivery of drugs and gene systems. The nanotubes are ‘smart’ because in the future they could be designed to encapsulate and then open up to deliver a drug or gene in a particular location in the body. Nanotubes are members of the fullerene structural family, that includes the spherical buckyballs and at the ends of a nanotube it may be capped with a hemisphere of the buckyball structure. Nanotubes are considered close cousins of buckminsterfullerene. Nanotubes are mostly found with closed ends on either side, though open tubes are seen. Thus these are three dimensional closed-cage objects, and may be considered as elongated fullerences.[5] Nanotubes can be either electrically conductive or semiconductive, depending on their helicity, leading to nanoscale wires and electrical components. A nanotube is a nanometer-scale tube-like structure and may refer to Carbon nanotube, Inorganic nanotube, DNA nanotube, Membrane nanotube, Zigzag nanotube, Armchair nanotube and Chiral nanotube.
Types of Nanotubes
Nanotubes are stiffer than steel, and are essentially rolled-up sheets of carbon hexagons. Electrically, nanotubes can be insulators, semiconductors, or conductors and are expected to exhibit magnetoresistance qualities .[6] For every effect there will be a cause and so depending on the rolling angle, the types of nanotubes that are possible: Armchair, Zigzag, Chiral, Membrane nanotubes, Inorganic nanotube, DNA nanotube and Carbon nanotubes. The names ‘armchair’ and ‘zigzag’ refer to the pattern of carbon bonds around the tube’s circumference. The nanotube's chirality, along with its diameter, determine its electrical properties. The armchair structure has metallic characteristics. Both zigzag and chiral structures produce band gaps, making these nanotubes semiconductors. Types of Nanotubes are;
1. Zigzag nanotube (n, 0)
A carbon nanotube formed from a graphite sheet that is rolled up so that it has a zigzag is known as Zigzag nanotube. A thirty degree roll (green to blue) produces an armchair pattern and a zero degree roll (green to red) makes a zigzag.
2. Armchair nanotube (n,n)
When a carbon nanotube is formed from a graphite sheet that is rolled up so that the edge is in the shape of armchairs is known as Armchair nanotube. Carbon nanotubes at the fundamental level are a single sheet of graphite (hybridization) that is rolled upon itself and connected at the edge. Armchair nanotubes correspond to the configuration with no ‘twist’ in the rolling. The armchair structure has metallic characteristics. The thinnest carbon nanotube is armchair (2,2) CNT with a diameter of 3 A.[7]
3. Chiral nanotube (n,m)
When a carbon nanotube is formed from a graphite sheet that is rolled up so that the succession of hexagons of carbon atoms on a particular cylinder makes an angle with the axis of the nanotube it is known as Chiral nanotube. Rolling the lattice at different angles creates a visible twist or spiral in the nanotube’s molecular structure, though the overall shape remains cylindrical.[8] The nanotube's chirality, along with its diameter, determines its electrical properties. Nanotubes can have different electronic properties depending on the chirality.
4. Membrane nanotubes, membrane nanotubules or cytonemes
Membrane nanotubes, membrane nanotubules or cytonemes are long and thin tubes formed from the plasma membrane that connects different animal cells over long distances. The structures of these nanotubes may be involved in cell-to-cell communication, transfer of nucleic acids between cells in a tissue, and the spread of pathogens or toxins such as HIV and prions. Membrane nanotubes were first described in a 1999 Cell article examining the development of Drosophila melanogaster wing imaginal discs.[9] A membrane structure also connects various types of immune cell together, connects between cells in tissue culture, interconnect plant cells and interconnect plastids.
5. Inorganic nanotube
An inorganic nanotube is a cylindrical molecule often composed of metal oxides, and morphologically similar to a carbon nanotube. Inorganic nanotubes have been observed to occur naturally in some mineral deposits.[10] Inorganic nanotubes have been made out of materials like Tungsten disulfide, Boron nitride, Silicon, Titanium dioxide, Molybdenum disulfide, Copper, and Bismuth. Inorganic nanotubes are heavier than carbon nanotubes and not as strong under tensile stress, but they are particularly strong under compression, leading to potential applications in impact-resistant applications such as bulletproof vests. [11] Recent findings revealed that inorganic nanotubes are constructed from main group elements, boron nitride (borazine).
6. DNA nanotube
DNA nanotube is a branch of nanotechnology which uses the molecular recognition properties of DNA and other nucleic acids to create designed, artificial structures out of DNA for technological purposes. In DNA nanotube DNA is used as a structural material rather than as a carrier of genetic information, making it an example of bio-nanotechnology. DNA nanotechnology has applications in molecular self-assembly and in DNA computing.[12]The design of DNA nanotubes can be Structural design and Sequence design. Structural design includes Tile-based structures which breaks the target structure into smaller units and is used for DNA computing. Folding structures is a design which makes the nanostructure out of a single long strand. Kinetic assembly is a design to control the kinetics of DNA. Sequence design is a design of assigning a specific nucleic acid base sequence to each strand so that they will associate into a desired conformation.
7. Carbon nanotubes
Silicon is the wonder material of the computer age and Carbon nanotubes are the wonder materials of electronics and computing. One of the most prominent building blocks of nanotechnology is Carbon nanotubes. Carbon nanotubes was discovered by SumioIijima of NEC in 1991. The extraordinary properties of Carbon nanotubes revealed the potential to revolutionize many technologies. Carbon nanotubes (CNTs) are allotropes of carbon which are effectively long, thin cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than any other material. These cylindrical carbon molecules have novel properties, making them potentially useful in many applications in nanotechnology, electronics, optics, and other fields of materials science, as well as potential uses in architectural fields. Carbon nanotubes are basically sheets of graphite rolled up into a tube and it can also be curl in a number of ways. Carbon nanotubes is one hundred times the tensile strength of steel, thermal conductivity better than all but the purest diamond, and electrical conductivity similar to copper, but with the ability to carry much higher currents, they seem to be a wonder material. Carbon nanotubes can conduct heat as efficiently as most diamond, conduct electricity as efficiently as copper, and yet it is also a semiconductor.
Carbon nanotubes are one of the most extensively researched materials today which reveals numerous surprises. In types of nanotubes only carbon nanotubes will be covered in white paper. Carbon nanotubes were first noticed in the graphitic soot deposited on the negatively charged electrode used in the arc-discharge synthesis of fullness.[13] Single-walled nanotubes and Multi-walled nanotubes are microscopic rather than nanoscopic, i.e. greater than 100 nanometers. Carbon Nanotube Transistors exploit the fact that nm- scale nanotubes (NT) are ready-made molecular wires and can be rendered into a conducting, semiconducting, or insulating state, which make them valuable for future nanocomputer design. Carbon nanotubes are quite popular now for their prospective electrical, thermal, and even selective-chemistry applications.[14] The Synthesis of Carbon Nanotubes is Arc discharge, Laser ablation and Chemical vapor deposition (CVD). Carbon nanotubes are basically classified as Single-walled nanotubes (which have a single cylindrical wall), Multi-walled nanotubes (which have cylinders within cylinders), Nanothorus, carbon nanobuds, and Cup stacked carbon nanotubes.
7.1.Types of Carbon Nanotubes
7.1.1. Single-walled Carbon nanotubes
Single-walled nanotubes (SWNT) are those carbon nanotubes which have a diameter of nearly 1 nanometer, with a tube length that can be many millions of times longer. The structure of a SWNT can be conceptualized by wrapping a one-atom-thick layer of graphite called graphene into a seamless cylinder. Single-walled nanotubes are the most likely candidate for miniaturizing electronics beyond the micro electromechanical scale currently used in electronics.[15] Single-walled nanotubes (SWNT) can be used for miniaturizing electronics beyond the micro electromechanical scale, electric wire, conductors, and used for intramolecular field-effect transistors (FET). Single-walled nanotubes are more pliable than their multi-walled counterparts and can be twisted, flattened and bent into small circles or around sharp bends without breaking.[16] Single-walled nanotubes have oft-quoted amazing properties because they are basically tubes of graphite and are normally capped at the ends, although the caps can be removed. The electrical behavior of carbon nanotubes usually relate to experiments on the single-walled variety. Single-walled nanotubes are more complex in its structures and required tremendous care when it is in its developing process. To gain greater control over their diameters, lengths, and other properties, such as chirality is the main concerned of the Single-walled nanotubes producers today.
7.1.2. Multi-walled Carbon nanotubes
Multi-walled nanotubes (MWNT) consist of multiple rolled layers (concentric tubes) of graphite and. Mainly there are two models of Multi-walled nanotubes they are the Russian Doll model, in which the sheets of graphite are arranged in concentric cylinders, and the Parchment model, in which a single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled newspaper. Multi-walled nanotubes are 100 times longer, wide, have an outer diameters, greater complexity and variety comparing to Multi-walled nanotubes. However, Multi-walled nanotubes have more defects than Single-walled nanotubes and these diminish their desirable properties. Multitudes of exotic shapes and arrangements, often with imaginative names such as bamboo-trunks, sea urchins, necklaces or coils, have also been observed under different processing conditions.[17] For practical purposes Multi-walled nanotubes are easier to produce in large quantities, at a reasonable price and have been available in decent amounts comparing to Single-walled nanotubes. The telescopic motion ability of inner shells and their unique mechanical properties permit to use multi-walled nanotubes as main movable arms in coming nano-mechanical devices.[18] Multi-walled nanotubes are formed with significant quantities of carbonaceous material. One of the way of separating the tubes from the carbon mass is to heat-treat the product.[19] Hyperion Catalysis, Mitsui are some of the companies that produces Multi-walled nanotubes.
7.1.3. Nanotorus
When carbon nanotubes are bent into a torus (doughnut shape) then they are known as Nanotorus. Nanotori are predicted to have many unique properties, such as magnetic moments 1000 times larger than previously expected for certain specific radii. Properties such as magnetic moment, thermal stability, etc. vary widely depending on radius of the torus and radius of the tube.[20]
7.1.4. Carbon nanobuds
Carbon nanobuds is a hybrid materials which combines together carbon nanotubes and fullerenes. In carbon nanobuds the fullerene-like ‘buds’ are join together with the outer sidewalls of the underlying carbon nanotube. In composite materials, the attached fullerene molecules may function as molecular anchors preventing slipping of the nanotubes, thus improving the composite’s mechanical properties.[21] Carbon nanobuds have been found to be exceptionally good field emitters.
7.1.5. Cup stacked carbon nanotubes
Cup-stacked carbon nanotubes (CSCNTs) differ from other quasi-1D carbon structures, which normally behave as quasi-metallic conductors of electrons. They exhibit semiconducting behaviors due to the stacking microstructure of graphene layers.[22]
7.2. Properties of Carbon Nanotubes
Carbon nanotubes are very complex in structures and is made of strong, stiff, soft materials and possesses tensile strength and elastic modulus respectively. The properties of Carbon nanotubes include Hardness, Kinetic, Electrical, Optical, Thermal, Defects, One-dimensional transport and Toxicity. Carbon nanotubes are so hard that it can withstand a pressure up to 24GPa without deformation. The Kinetic aspects of Carbon nanotube is revealed when Multi-walled nanotubes exhibit a striking telescoping property whereby an inner nanotube core may slide, almost without friction, within its outer nanotube shell, thus creating an atomically perfect linear or rotational bearing. The symmetry and unique electronic structure of graphene, the structure of a nanotube strongly affects its electrical properties.[23] Carbon nanotubes are good thermal conductors along the tube and posses a property known as “ballistic conduction”. Carbon nanotubes have a defect which is known as Stone Wales defect due to the existence of a crystallographic defect which occurs in the form of atomic vacancies. Carbon nanotubes are frequently referred to as “one-dimensional” because of the nanoscale dimensions, electrons propagate only along the tube’s axis and electron transport involves many quantum effects. Carbon nanotubes are highly toxic because it involves many combinations of chemicals which are toxic and non toxic.
Application of Nanotubes
Nanotubes have tremendous impact on different fields some of the most prominent potential applications are in Structural design, electrical circuits, electrical cables and wires, paper batteries, Solar cells, Ultra capacitors, Medical, Education and other applications. The strength and flexibility of carbon nanotubes makes them of potential use in controlling other nanoscale structures, the superior mechanical properties of carbon nanotubes makes it possible to prepare varied materials like like clothes and sports gear to combat jackets and space elevators and nanotubes are also building blocks in bio-mimetic hierarchical composite materials because of their exceptional mechanical properties. Carbon nanotubes are also use as electrical cables and wires, paper batteries, solar cells, ultra capacitors, LCD (liquid crystal display) TVs, computer disk drives. The application of Nanotubes is possible to soar very high impacting a wide variety of industries from sports equipment to furniture, from the construction industry to kitchenware, and from automobiles to airplanes and spacecraft. Nanotubes are the ultimate high strength carbon fibers. It is possible to construct a heterojunction by having a junction between nanotubes of different helicities. This approach facilitiates the creation of a device with one molecule.[24] Nanotubes tips can be used for nanoprobes. Nanotubes have been used for various metallocenes such as ferrocene, cobaltocence and nickelocene. In recent times application of nanotubes in CNT-based field emission displays is of great interest in commercial world. One of the most promising applications of nanotubes is a thin panel called a field emitter display (FED). Depending on the charge, the flexible nanotube can bend upward, away from the electrode, or downward, into contact with the electrode. The nanotube-based memory can act like “flash” memory, a reprogrammable type of memory that can retain data even when power is switched off.[25] The characteristics such as increased surface area along with enhanced electrical, optical properties make nanotubes suitable for numerous applications such as nanoelectronics, photovoltaics and chemical, biological sensing. When the spinal cord receive trauma, the brain and the body are often cut off from each other by the lack of nerve signal transmission along the spinal cord but Nanotubes have actually been proven to be able to correct this problem in some patients.[26] Nanotubes have tremendous impact in the fabrication of multiple sensors. Nanotubes are a proving to be useful as molecular components for nanotechnology.
Conclusion
In nanotechnology a nanotube is a long, cylindrical carbon structure consisting of hexagonal graphite molecules attached at the edges which was developed from Fullerene by R. Buckminster Fuller. Nanotubes are of different designed some may have single concentric cylinders while others may have multiple concentric cylinders with different wall thickness, number of concentric cylinders, cylinder radius, and cylinder length. Nanotubes have the potential for making ultra-strong fabrics as well as reinforcing structural materials in buildings, cars and airplanes and in the future nanotubes may replace silicon in electronic circuits, and prototypes of elementary components have been developed. Nanotubes might be used to build microscopic resistors, capacitors, inductors, diodes, or transistors. Nanotubes have an amazing potential in a wide variety like in Field Emission Display (LED), Conductive plastics, Conductive adhesives & Connectors, Molecular electronics, Energy storage, Thermal materials (conduct or insulate), Structural composites (Boeing 787,buildings,etc), Catalytic & biomedical supports, Medical sciences, electronics engineering, optical technologies, nanotechnology, materials engineering and many others. Nanotubes have made a difference in science and technology in the past and present and it will continue to show wonders in the future. Science and technology with the development of nanotechnology will continue to have a tremendous impact in human life and in Cosmos. Nanotubes are dream come true in Science and Technology and make people in this world to live happier, easier, longer and better than the past life.
[2]en.wikipedia.org/wiki/Nanotechnology
[3]IGNOU; Philosophy of Technology, pg. 29
[4]Poorvi Dutta&Sushmita Gupta; Nano Science and Technology, pg. 40
[5] T. Pradeep; NANO: The essentials, pg. 118
[6] http://www.edinformatics.com/interactive_molecules/fullerene.htm
[7] http://en.wikipedia.org/wiki/Carbon_nanotube
[8]http://www.answers.com/topic/chiral-nanotube#ixzz1ZKiDc1XP
[9]http://en.wikipedia.org/wiki/Membrane_nanotube
[10]http://en.wikipedia.org/wiki/nanotube
[11]http://en.wikipedia.org/wiki/Inorganic_nanotube
[12]http://en.wikipedia.org/wiki/DNA_nanotechnology
[13] T. Pradeep; NANO: The essentials, pg. 117
[14] http://www.nanotech-now.com/nanotube-buckyball-sites.htm
[15]http://en.wikipedia.org/wiki/Carbon_nanotube
[16] http://nanoparticles.org/pdf/nanotubes.pdf
[17] http://nanoparticles.org/pdf/nanotubes.pdf
[18] http://en.wikipedia.org/wiki/Carbon_nanotube
[19] T. Pradeep; NANO: The essentials, pg. 119
[20] http://en.wikipedia.org/wiki/Carbon_nanotube
[21] http://en.wikipedia.org/wiki/Carbon_nanotube
[22] http://en.wikipedia.org/wiki/Carbon_nanotube
[23] http://en.wikipedia.org/wiki/Carbon_nanotube
[24] T. Pradeep; NANO: The essentials, pg. 123
[25] http://www.edinformatics.com/interactive_molecules/fullerene.htm
[26] http://nanogloss.com/nanotubes/what-are-the-nanotubes-used-for/#axzz1ZhN1hGdb
Bibliography
1. Pradeep T.: NANO: The essentials, New Delhi, Tata McGraw-Hill Publishing Company Limited, 2008.
2. IGNOU: Philosophy of Technology, New Delhi, IGNOU, 2011.
3. Dutta Poorvi & Gupta Sushmita: Understanding of Nano Science and Technology, New Delhi, Global Vision Publishing House, 2006.
4. http://www.edinformatics.com/interactive_molecules/fullerene.htm accessed on 19/9/2011.
5. http://nanogloss.com/nanotubes/what-are-the-nanotubes-used-for/#axzz1ZhN1hGdb accessed on 19/9/2011.
6. http://en.wikipedia.org/wiki/Carbon_nanotube accessed on 19/9/2011.
7. http://nanoparticles.org/pdf/nanotubes.pdf accessed on 19/9/2011.
8. http://www.nanotech-now.com/nanotube-buckyball-sites.htm accessed on 22/9/2011.
9. http://en.wikipedia.org/wiki/DNA_nanotechnology accessed on 22/9/2011.
10. http://www.answers.com/topic/chiral-nanotube#ixzz1ZKiDc1XP accessed on 28/9/2011.
11. http://en.wikipedia.org/wiki/Membrane_nanotube accessed on 1/10/2011.
12. http://en.wikipedia.org/wiki/Inorganic_nanotube accessed on 3/10/2011.
