1.
Transmission electron microscopy
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Transmission electron microscopy is a microscopy technique in which a beam of electrons is transmitted through an ultra-thin specimen, interacting with the specimen as it passes through it. TEMs are capable of imaging at a higher resolution than light microscopes. This enables the user to examine fine detail—even as small as a single column of atoms. TEM forms a major analysis method in a range of scientific fields, TEMs find application in cancer research, virology, materials science as well as pollution, nanotechnology and semiconductor research. At smaller magnifications TEM image contrast is due to absorption of electrons in the material, due to the thickness, at higher magnifications complex wave interactions modulate the intensity of the image, requiring expert analysis of observed images. The first TEM was built by Max Knoll and Ernst Ruska in 1931, with this group developing the first TEM with resolution greater than that of light in 1933, in 1986, Ruska was awarded the Nobel Prize in physics for the development of transmission electron microscopy. Developments into ultraviolet microscopes, led by Köhler and Rohr, allowed for an increase in resolving power of about a factor of two, however this required more expensive quartz optical components, due to the absorption of UV by glass. At this point it was believed that obtaining an image with sub-micrometer information was simply due to this wavelength constraint. It had earlier recognized by Plücker in 1858 that the deflection of cathode rays was possible by the use of magnetic fields. This effect had been utilized to build primitive cathode ray oscilloscopes as early as 1897 by Ferdinand Braun, indeed, in 1891 it was recognized by Riecke that the cathode rays could be focused by these magnetic fields, allowing for simple lens designs. Later this theory was extended by Hans Busch in his published in 1926. The team consisted of several PhD students including Ernst Ruska and Bodo von Borries, in 1931 the group successfully generated magnified images of mesh grids placed over the anode aperture. The device used two lenses to achieve higher magnifications, arguably the first electron microscope. In that same year, Reinhold Rudenberg, the director of the Siemens company, had patented an electrostatic lens electron microscope. At this time the nature of electrons, which were considered charged matter particles, had not been fully realized until the publication of the De Broglie hypothesis in 1927. In April 1932, Ruska suggested the construction of a new microscope for direct imaging of specimens inserted into the microscope. This goal was achieved in September 1933, using images of cotton fibers, research continued on the electron microscope at Siemens in 1936, the aim of the research was the development improvement of TEM imaging properties, particularly with regard to biological specimens. At this time electron microscopes were being fabricated for specific groups, in 1939 the first commercial electron microscope, pictured, was installed in the Physics department of IG Farben-Werke
2.
Carbon peapod
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Carbon peapod is a hybrid nanomaterial consisting of spheroidal fullerenes encapsulated within a carbon nanotube. It is named due to their resemblance to the seedpod of the pea plant, since the properties of carbon peapods differ from those of nanotubes and fullerenes, the carbon peapod can be recognized as a new type of a self-assembled graphitic structure. Single-walled nanotubes were first seen in 1993 as cylinders rolled from a single graphene sheet, in 1998, the first peapod was observed by Brian Smith, Marc Monthioux and David Luzzi. The idea of peapods came from the structure that was produced inside an electron microscope in 2000. They were first recognized in fragments obtained by a pulsed-laser vaporization synthesis followed by treatment with an acid, carbon peapods can be naturally produced during carbon nanotube synthesis by pulsed laser vaporization. C60 fullerene impurities are formed during the treatment and acid purification. The encapsulated fullerenes have diameters close to that of C60 and form a chain inside the tube, controlled production of carbon peapods allow for greater variety in both the nanotube structure and the fullerene composition. Varying elements can be incorporated into a carbon peapod through doping, the existence of carbon peapods demonstrates further properties of carbon nanotubes, such as potential to be a stringently controlled environment for reactions. Owing to the ease with which fullerenes can encapsulate or be doped with other molecules, additionally, due to the enclosed fullerenes being limited to only a one-dimensional degree of mobility, phenomena such as diffusion or phase transformations can easily be studied. The diameter of carbon peapods range from ca.1 to 50 nanometers, various combinations of fullerene C60 sizes and nanotube structures can lead to various electric conductivity property of carbon peapods due to orientation of rotations. For example, the C60 @ is a superconductor and the C60 @ peapod is a semiconductor. The calculated band gap of C60 @ equals 0.1 eV, research into their potential as semiconductors is still ongoing. Although both the doped fullerides and ropes of SWNTs are superconductors, unfortunately, the temperatures for the superconducting phase transition in these materials are low. There are hopes that carbon nano-peapods could be superconducting at room temperature, with chemical doping, the electronic characteristics of peapods can be further adjusted. When carbon peapod is doped with metal atoms like potassium. It forms a negatively charged C606− 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 and 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 and it constructs memory effect as some research group has invented ways to create memory devices based on carbon peapods grown on Si/SiO2 surfaces
3.
Nanotechnology
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Nanotechnology is manipulation of matter on an atomic, molecular, and supramolecular scale. It is therefore common to see the plural form nanotechnologies as well as nanoscale technologies to refer to the range of research. Because of the variety of applications, governments have invested billions of dollars in nanotechnology research. Until 2012, through its National Nanotechnology Initiative, the USA has invested 3.7 billion dollars, scientists currently debate the future implications of nanotechnology. Nanotechnology may be able to create new materials and devices with a vast range of applications, such as in nanomedicine, nanoelectronics, biomaterials energy production. These concerns have led to a debate among advocacy groups and governments on whether regulation of nanotechnology is warranted. The term nano-technology was first used by Norio Taniguchi in 1974, also in 1986, Drexler co-founded The Foresight Institute to help increase public awareness and understanding of nanotechnology concepts and implications. In the 1980s, two major breakthroughs sparked the growth of nanotechnology in modern era, the microscopes developers Gerd Binnig and Heinrich Rohrer at IBM Zurich Research Laboratory received a Nobel Prize in Physics in 1986. Binnig, Quate and Gerber also invented the atomic force microscope that year. Second, Fullerenes were discovered in 1985 by Harry Kroto, Richard Smalley, and Robert Curl, in the early 2000s, the field garnered increased scientific, political, and commercial attention that led to both controversy and progress. Controversies emerged regarding the definitions and potential implications of nanotechnologies, exemplified by the Royal Societys report on nanotechnology, challenges were raised regarding the feasibility of applications envisioned by advocates of molecular nanotechnology, which culminated in a public debate between Drexler and Smalley in 2001 and 2003. Meanwhile, commercialization of products based on advancements in nanoscale technologies began emerging and these products are limited to bulk applications of nanomaterials and do not involve atomic control of matter. Governments moved to promote and fund research into nanotechnology, such as in the U. S, by the mid-2000s new and serious scientific attention began to flourish. Projects emerged to produce nanotechnology roadmaps which center on atomically precise manipulation of matter and discuss existing and projected capabilities, goals, Nanotechnology is the engineering of functional systems at the molecular scale. This covers both current work and concepts that are more advanced, one nanometer is one billionth, or 10−9, of a meter. By comparison, typical carbon-carbon bond lengths, or the spacing between atoms in a molecule, are in the range 0. 12–0.15 nm. On the other hand, the smallest cellular life-forms, the bacteria of the genus Mycoplasma, are around 200 nm in length, by convention, nanotechnology is taken as the scale range 1 to 100 nm following the definition used by the National Nanotechnology Initiative in the US. The lower limit is set by the size of atoms since nanotechnology must build its devices from atoms and molecules
4.
Carbon
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Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds, three isotopes occur naturally, 12C and 13C being stable, while 14C is a radioactive isotope, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity, Carbon is the 15th most abundant element in the Earths crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. It is the second most abundant element in the body by mass after oxygen. The atoms of carbon can bond together in different ways, termed allotropes of carbon, the best known are graphite, diamond, and amorphous carbon. The physical properties of carbon vary widely with the allotropic form, for example, graphite is opaque and black while diamond is highly transparent. Graphite is soft enough to form a streak on paper, while diamond is the hardest naturally occurring material known, graphite is a good electrical conductor while diamond has a low electrical conductivity. Under normal conditions, diamond, carbon nanotubes, and graphene have the highest thermal conductivities of all known materials, all carbon allotropes are solids under normal conditions, with graphite being the most thermodynamically stable form. They are chemically resistant and require high temperature to react even with oxygen, the most common oxidation state of carbon in inorganic compounds is +4, while +2 is found in carbon monoxide and transition metal carbonyl complexes. The largest sources of carbon are limestones, dolomites and carbon dioxide, but significant quantities occur in organic deposits of coal, peat, oil. For this reason, carbon has often referred to as the king of the elements. The allotropes of carbon graphite, one of the softest known substances, and diamond. It bonds readily with other small atoms including other carbon atoms, Carbon is known to form almost ten million different compounds, a large majority of all chemical compounds. Carbon also has the highest sublimation point of all elements, although thermodynamically prone to oxidation, carbon resists oxidation more effectively than elements such as iron and copper that are weaker reducing agents at room temperature. Carbon is the element, with a ground-state electron configuration of 1s22s22p2. Its first four ionisation energies,1086.5,2352.6,4620.5 and 6222.7 kJ/mol, are higher than those of the heavier group 14 elements. Carbons covalent radii are normally taken as 77.2 pm,66.7 pm and 60.3 pm, although these may vary depending on coordination number, in general, covalent radius decreases with lower coordination number and higher bond order. Carbon compounds form the basis of all life on Earth
5.
Carbon nanotube
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Carbon nanotubes are allotropes of carbon with a cylindrical nanostructure. These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of materials science and technology. Owing to the exceptional strength and stiffness, nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000,1. In addition, owing to their thermal conductivity, mechanical. For instance, nanotubes form a portion of the material in some baseball bats, golf clubs. Nanotubes are members of the fullerene structural family and their name is derived from their long, hollow structure with the walls formed by one-atom-thick sheets of carbon, called graphene. Nanotubes are categorized as single-walled nanotubes and multi-walled nanotubes, individual nanotubes naturally align themselves into ropes held together by van der Waals forces, more specifically, pi-stacking. Applied quantum chemistry, specifically, orbital hybridization best describes chemical bonding in nanotubes, the chemical bonding of nanotubes is composed entirely of sp2 bonds, similar to those of graphite. These bonds, which are stronger than the sp3 bonds found in alkanes and diamond, most single-walled nanotubes have a diameter of close to 1 nanometer, and 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, the way the graphene sheet is wrapped is represented by a pair of indices. The integers n and m denote the number of unit vectors along two directions in the crystal lattice of graphene. If m =0, the nanotubes are called zigzag nanotubes, and if n = m, the diameter of an ideal nanotube can be calculated from its indices as follows d = a π =78.3 p m, where a =0.246 nm. SWNTs are an important variety of carbon nanotube because most of their properties change significantly with the values, in particular, their band gap can vary from zero to about 2 eV and their electrical conductivity can show metallic or semiconducting behavior. Single-walled nanotubes are likely candidates for miniaturizing electronics, the most basic building block of these systems is the electric wire, and SWNTs with diameters of an order of a nanometer can be excellent conductors. One useful application of SWNTs is in the development of the first intermolecular field-effect transistors, the first intermolecular logic gate using SWCNT FETs was made in 2001. A logic gate requires both a p-FET and an n-FET, because SWNTs are p-FETs when exposed to oxygen and n-FETs otherwise, it is possible to expose half of an SWNT to oxygen and protect the other half from it. The resulting SWNT acts as a not logic gate with both p and n-type FETs in the same molecule, prices for single-walled nanotubes declined from around $1500 per gram as of 2000 to retail prices of around $50 per gram of as-produced 40–60% by weight SWNTs as of March 2010. As of 2016 the retail price of as-produced 75% by weight SWNTs were $2 per gram, SWNTs are forecast to make a large impact in electronics applications by 2020 according to the The Global Market for Carbon Nanotubes report
6.
Fullerene
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A fullerene is a molecule of carbon in the form of a hollow sphere, ellipsoid, tube, and many other shapes. Spherical fullerenes, also referred to as Buckminsterfullerenes, resemble the balls used in football, cylindrical fullerenes are also called carbon nanotubes. Fullerenes are similar in structure to graphite, which is composed of stacked sheets of linked hexagonal rings. The name was an homage to Buckminster Fuller, whose geodesic domes it resembles, the structure was also identified some five years earlier by Sumio Iijima, from an electron microscope image, where it formed the core of a bucky onion. Fullerenes have since found to occur in nature. More recently, fullerenes have been detected in outer space, according to astronomer Letizia Stanghellini, It’s possible that buckyballs from outer space provided seeds for life on Earth. The discovery of fullerenes greatly expanded the number of carbon allotropes, which until recently were limited to graphite, graphene, diamond. The icosahedral C60H60 cage was mentioned in 1965 as a topological structure. Eiji Osawa of Toyohashi University of Technology predicted the existence of C60 in 1970 and he noticed that the structure of a corannulene molecule was a subset of an Association football shape, and he hypothesised that a full ball shape could also exist. Japanese scientific journals reported his idea, but neither it nor any translations of it reached Europe or the Americas, also in 1970, R. W. Henson proposed the structure and made a model of C60. Unfortunately, the evidence for new form of carbon was very weak and was not accepted. The results were never published but were acknowledged in Carbon in 1999, in 1973 independently from Henson, a group of scientists from the USSR, directed by Prof. Bochvar, made a quantum-chemical analysis of the stability of C60 and calculated its electronic structure. As in the cases, the scientific community did not accept the theoretical prediction. The paper was published in 1973 in Proceedings of the USSR Academy of Sciences, in mass spectrometry discrete peaks appeared corresponding to molecules with the exact mass of sixty or seventy or more carbon atoms. Kroto, Curl, and Smalley were awarded the 1996 Nobel Prize in Chemistry for their roles in the discovery of this class of molecules, C60 and other fullerenes were later noticed occurring outside the laboratory. By 1990 it was easy to produce gram-sized samples of fullerene powder using the techniques of Donald Huffman, Wolfgang Krätschmer, Lowell D. Lamb. Fullerene purification remains a challenge to chemists and to a large extent determines fullerene prices, so-called endohedral fullerenes have ions or small molecules incorporated inside the cage atoms. Fullerene is a reactant in many organic reactions such as the Bingel reaction discovered in 1993
7.
Allotropes of carbon
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Carbon is capable of forming many allotropes due to its valency. Well-known forms of carbon include diamond and graphite, in recent decades many more allotropes and forms of carbon have been discovered and researched including ball shapes such as buckminsterfullerene and sheets such as graphene. Larger scale structures of carbon nanotubes, nanobuds and nanoribbons. Other unusual forms of carbon exist at high temperatures or extreme pressures. Around 350 hypotetical 3-periodic allotropes of carbon are known at the present time according to SACADA database, Diamond is a well known allotrope of carbon. The hardness and high dispersion of light of diamond make it useful for industrial applications and jewelry. Diamond is the hardest known natural mineral and this makes it an excellent abrasive and makes it hold polish and luster extremely well. No known naturally occurring substance can cut a diamond, except another diamond, the market for industrial-grade diamonds operates much differently from its gem-grade counterpart. Industrial diamonds are valued mostly for their hardness and heat conductivity, making many of the characteristics of diamond, including clarity and color. This helps explain why 80% of mined diamonds are unsuitable for use as gemstones, the dominant industrial use of diamond is in cutting, drilling, grinding, and polishing. Most uses of diamonds in these technologies do not require large diamonds, in fact, diamonds are embedded in drill tips or saw blades, or ground into a powder for use in grinding and polishing applications. Specialized applications include use in laboratories as containment for high pressure experiments, high-performance bearings, with the continuing advances being made in the production of synthetic diamond, future applications are beginning to become feasible. Garnering much excitement is the use of diamond as a semiconductor suitable to build microchips from. Each carbon atom in a diamond is covalently bonded to four other carbons in a tetrahedron and these tetrahedrons together form a 3-dimensional network of six-membered carbon rings, in the chair conformation, allowing for zero bond angle strain. This stable network of covalent bonds and hexagonal rings, is the reason that diamond is so strong.1 kJ/mol compared to graphite, graphite, named by Abraham Gottlob Werner in 1789, from the Greek γράφειν is one of the most common allotropes of carbon. Unlike diamond, graphite is an electrical conductor, thus, it can be used in, for instance, electrical arc lamp electrodes. Likewise, under conditions, graphite is the most stable form of carbon. Therefore, it is used in thermochemistry as the state for defining the heat of formation of carbon compounds
8.
Bud
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In botany, a bud is an undeveloped or embryonic shoot and normally occurs in the axil of a leaf or at the tip of a stem. Once formed, a bud may remain for some time in a dormant condition, buds may be specialized to develop flowers or short shoots, or may have the potential for general shoot development. The term bud is used in zoology, where it refers to an outgrowth from the body which can develop into a new individual. The buds of many plants, especially in temperate or cold climates, are protected by a covering of modified leaves called scales which tightly enclose the more delicate parts of the bud. Many bud scales are covered by a substance which serves as added protection. When the bud develops, the scales may enlarge somewhat but usually just drop off, leaving on the surface of the growing stem a series of horizontally-elongated scars. By means of these one can determine the age of any young branch, since each years growth ends in the formation of a bud. Continued growth of the branch causes these scars to be obliterated after a few years so that the age of older branches cannot be determined by this means. In many plants scales do not form over the bud, the minute underdeveloped leaves in such buds are often excessively hairy. Naked buds are found in shrubs, like some species of the Sumac and Viburnums. In many of the latter, buds are more reduced. A terminal bud occurs on the end of a stem and lateral buds are found on the side, a head of cabbage is an exceptionally large terminal bud, while Brussels sprouts are large lateral buds. Since buds are formed in the axils of leaves, their distribution on the stem is the same as that of leaves, there are alternate, opposite, and whorled buds, as well as the terminal bud at the tip of the stem. In many plants buds appear in unexpected places, these are known as adventitious buds, often it is possible to find a bud in a remarkable series of gradations of bud scales. Such a series suggests that the scales of the bud are in truth leaves, buds are often useful in the identification of plants, especially for woody plants in winter when leaves have fallen. Buds may be classified and described according to different criteria, location, status, morphology, buds The term bud is used by analogy within zoology as well, where it refers to an outgrowth from the body which develops into a new individual. It is a form of asexual reproduction limited to animals or plants of relatively simple structure, in this process a portion of the wall of the parent cell softens and pushes out. The protuberance thus formed enlarges rapidly while at time the nucleus of the parent cell divides
9.
Covalent bond
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A covalent bond, also called a molecular bond, is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, for many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration. Covalent bonding includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding, agostic interactions, bent bonds, the term covalent bond dates from 1939. In the molecule H2, the atoms share the two electrons via covalent bonding. Covalency is greatest between atoms of similar electronegativities, thus, covalent bonding does not necessarily require that the two atoms be of the same elements, only that they be of comparable electronegativity. Covalent bonding that entails sharing of electrons more than two atoms is said to be delocalized. The term covalence in regard to bonding was first used in 1919 by Irving Langmuir in a Journal of the American Chemical Society article entitled The Arrangement of Electrons in Atoms and Molecules. Langmuir wrote that we shall denote by the term covalence the number of pairs of electrons that an atom shares with its neighbors. The idea of covalent bonding can be traced several years before 1919 to Gilbert N. Lewis and he introduced the Lewis notation or electron dot notation or Lewis dot structure, in which valence electrons are represented as dots around the atomic symbols. Pairs of electrons located between atoms represent covalent bonds, multiple pairs represent multiple bonds, such as double bonds and triple bonds. An alternative form of representation, not shown here, has bond-forming electron pairs represented as solid lines, Lewis proposed that an atom forms enough covalent bonds to form a full outer electron shell. In the diagram of methane shown here, the atom has a valence of four and is, therefore, surrounded by eight electrons, four from the carbon itself. Each hydrogen has a valence of one and is surrounded by two electrons – its own one electron plus one from the carbon, walter Heitler and Fritz London are credited with the first successful quantum mechanical explanation of a chemical bond in 1927. Their work was based on the valence bond model, which assumes that a bond is formed when there is good overlap between the atomic orbitals of participating atoms. Atomic orbitals have specific directional properties leading to different types of covalent bonds, sigma bonds are the strongest covalent bonds and are due to head-on overlapping of orbitals on two different atoms. A single bond is usually a σ bond, pi bonds are weaker and are due to lateral overlap between p orbitals. A double bond between two given atoms consists of one σ and one π bond, and a bond is one σ. Covalent bonds are also affected by the electronegativity of the atoms which determines the chemical polarity of the bond
10.
Electrical resistivity and conductivity
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Electrical resistivity is an intrinsic property that quantifies how strongly a given material opposes the flow of electric current. A low resistivity indicates a material that allows the flow of electric current. Resistivity is commonly represented by the Greek letter ρ, the SI unit of electrical resistivity is the ohm-metre. Electrical conductivity or specific conductance is the reciprocal of electrical resistivity and it is commonly represented by the Greek letter σ, but κ or γ are also occasionally used. Its SI unit is siemens per metre and CGSE unit is reciprocal second, many resistors and conductors have a uniform cross section with a uniform flow of electric current, and are made of one material. All copper wires, irrespective of their shape and size, have approximately the same resistivity, every material has its own characteristic resistivity – for example, resistivity of rubber is far larger than coppers. If the pipes are the size and shape, the pipe full of sand has higher resistance to flow. Resistance, however, is not solely determined by the presence or absence of sand and it also depends on the length and width of the pipe, short or wide pipes have lower resistance than narrow or long pipes. The above equation can be transposed to get Pouillets law, R = ρ ℓ A, the resistance of a given material increases with length, but decreases with increasing cross-sectional area. From the above equations, resistivity has the SI unit ohm metre, the formula R = ρ ℓ / A can be used to intuitively understand the meaning of a resistivity value. For example, if A = 7000100000000000000♠1 m2 ℓ = 7000100000000000000♠1 m, Conductivity, σ, is defined as the inverse of resistivity, σ =1 ρ. Conductivity has SI units of siemens per metre, the above definition was specific to resistors or conductors with a uniform cross-section, where current flows uniformly through them. A more basic and general definition starts from the fact that a field inside a material makes electric current flow. Conductivity is the inverse, σ =1 ρ = J E, for example, rubber is a material with large ρ and small σ—because even a very large electric field in rubber makes almost no current flow through it. On the other hand, copper is a material with small ρ, according to elementary quantum mechanics, electrons in an atom do not take on arbitrary energy values. Rather, electrons only occupy discrete energy levels in an atom or crystal. When a large number of such allowed energy levels are spaced close together —i. e. have similar energies— we can talk about these energy levels together as an energy band. There can be many such bands in a material, depending on the atomic number
