1.
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
2.
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
3.
Hexagon
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In geometry, a hexagon is a six sided polygon or 6-gon. The total of the angles of any hexagon is 720°. A regular hexagon has Schläfli symbol and can also be constructed as an equilateral triangle, t. A regular hexagon is defined as a hexagon that is both equilateral and equiangular and it is bicentric, meaning that it is both cyclic and tangential. The common length of the sides equals the radius of the circumscribed circle, all internal angles are 120 degrees. A regular hexagon has 6 rotational symmetries and 6 reflection symmetries, the longest diagonals of a regular hexagon, connecting diametrically opposite vertices, are twice the length of one side. Like squares and equilateral triangles, regular hexagons fit together without any gaps to tile the plane, the cells of a beehive honeycomb are hexagonal for this reason and because the shape makes efficient use of space and building materials. The Voronoi diagram of a triangular lattice is the honeycomb tessellation of hexagons. It is not usually considered a triambus, although it is equilateral, the maximal diameter, D is twice the maximal radius or circumradius, R, which equals the side length, t. The minimal diameter or the diameter of the circle, d, is twice the minimal radius or inradius. If a regular hexagon has successive vertices A, B, C, D, E, F, the regular hexagon has Dih6 symmetry, order 12. There are 3 dihedral subgroups, Dih3, Dih2, and Dih1, and 4 cyclic subgroups, Z6, Z3, Z2 and these symmetries express 9 distinct symmetries of a regular hexagon. John Conway labels these by a letter and group order, r12 is full symmetry, and a1 is no symmetry. These two forms are duals of each other and have half the order of the regular hexagon. The i4 forms are regular hexagons flattened or stretched along one symmetry direction and it can be seen as an elongated rhombus, while d2 and p2 can be seen as horizontally and vertically elongated kites. G2 hexagons, with sides parallel are also called hexagonal parallelogons. Each subgroup symmetry allows one or more degrees of freedom for irregular forms, only the g6 subgroup has no degrees of freedom but can seen as directed edges. Hexagons of symmetry g2, i4, and r12, as parallelogons can tessellate the Euclidean plane by translation, other hexagon shapes can tile the plane with different orientations
4.
Pentagon
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In geometry, a pentagon is any five-sided polygon or 5-gon. The sum of the angles in a simple pentagon is 540°. A pentagon may be simple or self-intersecting, a self-intersecting regular pentagon is called a pentagram. A regular pentagon has Schläfli symbol and interior angles are 108°, a regular pentagon has five lines of reflectional symmetry, and rotational symmetry of order 5. The diagonals of a regular pentagon are in the golden ratio to its sides. The area of a regular convex pentagon with side length t is given by A = t 225 +1054 =5 t 2 tan 4 ≈1.720 t 2. A pentagram or pentangle is a regular star pentagon and its sides form the diagonals of a regular convex pentagon – in this arrangement the sides of the two pentagons are in the golden ratio. The area of any polygon is, A =12 P r where P is the perimeter of the polygon. Substituting the regular pentagons values for P and r gives the formula A =12 ×5 t × t tan 2 =5 t 2 tan 4 with side length t, like every regular convex polygon, the regular convex pentagon has an inscribed circle. The apothem, which is the r of the inscribed circle. Like every regular polygon, the regular convex pentagon has a circumscribed circle. For a regular pentagon with successive vertices A, B, C, D, E, the regular pentagon is constructible with compass and straightedge, as 5 is a Fermat prime. A variety of methods are known for constructing a regular pentagon, one method to construct a regular pentagon in a given circle is described by Richmond and further discussed in Cromwells Polyhedra. The top panel shows the construction used in Richmonds method to create the side of the inscribed pentagon, the circle defining the pentagon has unit radius. Its center is located at point C and a midpoint M is marked halfway along its radius and this point is joined to the periphery vertically above the center at point D. Angle CMD is bisected, and the bisector intersects the axis at point Q. A horizontal line through Q intersects the circle at point P, to determine the length of this side, the two right triangles DCM and QCM are depicted below the circle. Using Pythagoras theorem and two sides, the hypotenuse of the triangle is found as 5 /2
5.
Polygon
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In elementary geometry, a polygon /ˈpɒlɪɡɒn/ is a plane figure that is bounded by a finite chain of straight line segments closing in a loop to form a closed polygonal chain or circuit. These segments are called its edges or sides, and the points where two edges meet are the vertices or corners. The interior of the polygon is called its body. An n-gon is a polygon with n sides, for example, a polygon is a 2-dimensional example of the more general polytope in any number of dimensions. The basic geometrical notion of a polygon has been adapted in various ways to suit particular purposes, mathematicians are often concerned only with the bounding closed polygonal chain and with simple polygons which do not self-intersect, and they often define a polygon accordingly. A polygonal boundary may be allowed to intersect itself, creating star polygons and these and other generalizations of polygons are described below. The word polygon derives from the Greek adjective πολύς much, many and it has been suggested that γόνυ knee may be the origin of “gon”. Polygons are primarily classified by the number of sides, Polygons may be characterized by their convexity or type of non-convexity, Convex, any line drawn through the polygon meets its boundary exactly twice. As a consequence, all its interior angles are less than 180°, equivalently, any line segment with endpoints on the boundary passes through only interior points between its endpoints. Non-convex, a line may be found which meets its boundary more than twice, equivalently, there exists a line segment between two boundary points that passes outside the polygon. Simple, the boundary of the polygon does not cross itself, there is at least one interior angle greater than 180°. Star-shaped, the interior is visible from at least one point. The polygon must be simple, and may be convex or concave, self-intersecting, the boundary of the polygon crosses itself. Branko Grünbaum calls these coptic, though this term does not seem to be widely used, star polygon, a polygon which self-intersects in a regular way. A polygon cannot be both a star and star-shaped, equiangular, all corner angles are equal. Cyclic, all lie on a single circle, called the circumcircle. Isogonal or vertex-transitive, all lie within the same symmetry orbit. The polygon is cyclic and equiangular
6.
Chromatography
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Chromatography is a laboratory technique for the separation of a mixture. The mixture is dissolved in a called the mobile phase. The various constituents of the mixture travel at different speeds, causing them to separate, the separation is based on differential partitioning between the mobile and stationary phases. Subtle differences in a partition coefficient result in differential retention on the stationary phase. Chromatography may be preparative or analytical, the purpose of preparative chromatography is to separate the components of a mixture for later use, and is thus a form of purification. Analytical chromatography is done normally with smaller amounts of material and is for establishing the presence or measuring the proportions of analytes in a mixture. The two are not mutually exclusive, Chromatography was first employed in Russia by the Italian-born scientist Mikhail Tsvet in 1900. He continued to work with chromatography in the first decade of the 20th century, primarily for the separation of plant pigments such as chlorophyll, carotenes, since these components have different colors they gave the technique its name. New types of chromatography developed during the 1930s and 1940s made the technique useful for separation processes. Since then, the technology has advanced rapidly, researchers found that the main principles of Tsvets chromatography could be applied in many different ways, resulting in the different varieties of chromatography described below. Advances are continually improving the performance of chromatography, allowing the separation of increasingly similar molecules. The analyte is the substance to be separated during chromatography and it is also normally what is needed from the mixture. Analytical chromatography is used to determine the existence and possibly also the concentration of analyte in a sample, a bonded phase is a stationary phase that is covalently bonded to the support particles or to the inside wall of the column tubing. A chromatogram is the output of the chromatograph. In the case of a separation, different peaks or patterns on the chromatogram correspond to different components of the separated mixture. Plotted on the x-axis is the time and plotted on the y-axis a signal corresponding to the response created by the analytes exiting the system. In the case of a system the signal is proportional to the concentration of the specific analyte separated. A chromatograph is equipment that enables a sophisticated separation, e. g. gas chromatographic or liquid chromatographic separation, Chromatography is a physical method of separation that distributes components to separate between two phases, one stationary, the other moving in a definite direction
7.
Laser ablation
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Laser ablation is the process of removing material from a solid surface by irradiating it with a laser beam. At low laser flux, the material is heated by the laser energy. At high laser flux, the material is converted to a plasma. Usually, laser ablation refers to removing material with a pulsed laser, the total mass ablated from the target per laser pulse is usually referred to as ablation rate. Such features of laser radiation as laser beam scanning velocity and the covering of scanning lines can significantly influence the ablation process, laser pulses can vary over a very wide range of duration and fluxes, and can be precisely controlled. This makes laser ablation very valuable for both research and industrial applications, the simplest application of laser ablation is to remove material from a solid surface in a controlled fashion. Laser machining and particularly laser drilling are examples, pulsed lasers can drill extremely small, several workers have employed laser ablation and gas condensation to produce nano particles of metal, metal oxides and metal carbides. High power lasers clean a large spot with a single pulse, lower power lasers use many small pulses which may be scanned across an area. One of the advantages is that no solvents are used, therefore it is environmentally friendly and it is relatively easy to automate. The running costs are lower than dry media or dry-ice blasting, the process is gentler than abrasive techniques, e. g. carbon fibres within a composite material are not damaged. Heating of the target is minimal, another class of applications uses laser ablation to process the material removed into new forms either not possible or difficult to produce by other means. A recent example is the production of carbon nanotubes, in March 1995 Guo et al. were the first to report the use of a laser to ablate a block of pure graphite, and later graphite mixed with catalytic metal. The catalytic metal can consist of such as cobalt, niobium, platinum, nickel, copper. The composite block is formed by making a paste of graphite powder, carbon cement, the paste is next placed in a cylindrical mold and baked for several hours. After solidification, the block is placed inside an oven with a laser pointed at it. The oven temperature is approximately 1200 °C, as the laser ablates the target, carbon nanotubes form and are carried by the gas flow onto a cool copper collector. Like carbon nanotubes formed using the electric-arc discharge technique, carbon fibers are deposited in a haphazard. Single-walled nanotubes are formed from the block of graphite and metal catalyst particles and this process is used to manufacture some types of high temperature superconductor and laser crystals
8.
Pyrolysis
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Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures in the absence of oxygen. It involves the change of chemical composition and physical phase. The word is coined from the Greek-derived elements pyro fire and lysis separating, Pyrolysis is a type of thermolysis, and is most commonly observed in organic materials exposed to high temperatures. It is one of the involved in charring wood, starting at 200–300 °C. It also occurs in fires where solid fuels are burning or when vegetation comes into contact with lava in volcanic eruptions, in general, pyrolysis of organic substances produces gas and liquid products and leaves a solid residue richer in carbon content, char. Extreme pyrolysis, which leaves mostly carbon as the residue, is called carbonization and these specialized uses of pyrolysis may be called various names, such as dry distillation, destructive distillation, or cracking. Pyrolysis is also used in the creation of nanoparticles, zirconia, Pyrolysis also plays an important role in several cooking procedures, such as baking, frying, grilling, and caramelizing. It is a tool of analysis, for example, in mass spectrometry. Indeed, many important chemical substances, such as phosphorus and sulfuric acid, were first obtained by this process, Pyrolysis has been assumed to take place during catagenesis, the conversion of buried organic matter to fossil fuels. It is also the basis of pyrography, in their embalming process, the ancient Egyptians used a mixture of substances, including methanol, which they obtained from the pyrolysis of wood. Pyrolysis differs from other processes like combustion and hydrolysis in that it usually does not involve reactions with oxygen, water, in practice, it is not possible to achieve a completely oxygen-free atmosphere. Because some oxygen is present in any system, a small amount of oxidation occurs. The term has also applied to the decomposition of organic material in the presence of superheated water or steam, for example. Pyrolysis is usually the first chemical reaction occurs in the burning of many solid organic fuels, like wood, cloth, and paper. Thus, the pyrolysis of common materials like wood, plastic, in pyrolysis there is a gas phase present. Pyrolysis occurs whenever food is exposed to high temperatures in a dry environment, such as roasting, baking, toasting. It is the process responsible for the formation of the golden-brown crust in foods prepared by those methods. In normal cooking, the food components that undergo pyrolysis are carbohydrates
9.
Aromatic hydrocarbon
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An aromatic hydrocarbon or arene is a hydrocarbon with sigma bonds and delocalized pi electrons between carbon atoms forming a circle. In contrast, aliphatic hydrocarbons lack this delocalization, the term aromatic was assigned before the physical mechanism determining aromaticity was discovered, the term was coined as such simply because many of the compounds have a sweet or pleasant odour. The configuration of six carbon atoms in compounds is known as a benzene ring, after the simplest possible such hydrocarbon. Aromatic hydrocarbons can be monocyclic or polycyclic, some non-benzene-based compounds called heteroarenes, which follow Hückels rule, are also called aromatic compounds. In these compounds, at least one atom is replaced by one of the heteroatoms oxygen, nitrogen. Benzene, C6H6, is the simplest aromatic hydrocarbon, and it was the first one named as such, the nature of its bonding was first recognized by August Kekulé in the 19th century. Each carbon atom in the cycle has four electrons to share. One goes to the atom, and one each to the two neighbouring carbons. The structure is alternatively illustrated as a circle around the inside of the ring to show six electrons floating around in delocalized molecular orbitals the size of the ring itself. This depiction represents the equivalent nature of the six carbon–carbon bonds all of bond order 1.5, the electrons are visualized as floating above and below the ring with the electromagnetic fields they generate acting to keep the ring flat. The proper use of the symbol is debated, it is used to describe any cyclic π system in some publications, jensen argues that, in line with Robinsons original proposal, the use of the circle symbol should be limited to monocyclic 6 π-electron systems. In this way the symbol for a six-center six-electron bond can be compared to the Y symbol for a three-center two-electron bond. A reaction that forms a compound from an unsaturated or partially unsaturated cyclic precursor is simply called an aromatization. Many laboratory methods exist for the synthesis of arenes from non-arene precursors. Many methods rely on cycloaddition reactions, alkyne trimerization describes the cyclization of three alkynes, in the Dötz reaction an alkyne, carbon monoxide and a chromium carbene complex are the reactants. Diels–Alder reactions of alkynes with pyrone or cyclopentadienone with expulsion of carbon dioxide or carbon monoxide also form arene compounds, in Bergman cyclization the reactants are an enyne plus a hydrogen donor. Arenes are reactants in many organic reactions, in aromatic substitution one substituent on the arene ring, usually hydrogen, is replaced by another substituent. The two main types are electrophilic aromatic substitution when the reagent is an electrophile and nucleophilic aromatic substitution when the reagent is a nucleophile
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