Buckminsterfullerene is a type of fullerene with the formula C 60 . It has a cage-like fused-ring structure ( truncated icosahedron ) made of twenty hexagons and twelve pentagons , and resembles a football . Each of its 60 carbon atoms is bonded to its three neighbors.
128-624: Buckminsterfullerene is a black solid that dissolves in hydrocarbon solvents to produce a violet solution. The substance was discovered in 1985 and has received intense study, although few real world applications have been found. Molecules of buckminsterfullerene (or of fullerenes in general) are commonly nicknamed buckyballs . Buckminsterfullerene is the most common naturally occurring fullerene. Small quantities of it can be found in soot . It also exists in space . Neutral C 60 has been observed in planetary nebulae and several types of star . The ionised form, C 60 , has been identified in
256-451: A Charge-Coupled Device (CCD) detector for TEM was in 1982, but the technology didn't find widespread use until the late 1990s/early 2000s. Monolithic active-pixel sensors (MAPSs) were also used in TEM. CMOS detectors, which are faster and more resistant to radiation damage than CCDs, have been used for TEM since 2005. In the early 2010s, further development of CMOS technology allowed for
384-467: A cold trap to adsorb sublimated gases in the vicinity of the specimen largely eliminates vacuum problems that are caused by specimen sublimation . TEM specimen stage designs include airlocks to allow for insertion of the specimen holder into the vacuum with minimal loss of vacuum in other areas of the microscope. The specimen holders hold a standard size of sample grid or self-supporting specimen. Standard TEM grid sizes are 3.05 mm diameter, with
512-473: A convex lens . The field produced for the lens must be radially symmetrical, as deviation from the radial symmetry of the magnetic lens causes aberrations such as astigmatism , and worsens spherical and chromatic aberration . Electron lenses are manufactured from iron, iron-cobalt or nickel cobalt alloys, such as permalloy . These are selected for their magnetic properties, such as magnetic saturation , hysteresis and permeability . The components include
640-418: A fluorescent screen, a layer of photographic film , or a detector such as a scintillator attached to a charge-coupled device or a direct electron detector . Transmission electron microscopes are capable of imaging at a significantly higher resolution than light microscopes , owing to the smaller de Broglie wavelength of electrons. This enables the instrument to capture fine detail—even as small as
768-412: A tungsten filament, a lanthanum hexaboride ( LaB 6 ) single crystal or a field emission gun . The gun is connected to a high voltage source (typically ~100–300 kV) and emits electrons either by thermionic or field electron emission into the vacuum. In the case of a thermionic source, the electron source is mounted in a Wehnelt cylinder to provide preliminary focus of the emitted electrons into
896-496: A 1,2-addition, while Cl 2 and Br 2 add to remote C atoms due to steric factors . For example, in C 60 Br 8 and C 60 Br 24 , the Br atoms are in 1,3- or 1,4-positions with respect to each other. Under various conditions a vast number of halogenated derivatives of C 60 can be produced, some with an extraordinary selectivity on one or two isomers over the other possible ones. Addition of fluorine and chlorine usually results in
1024-416: A TEM consist of a phosphor screen , which may be made of fine (10–100 μm) particulate zinc sulfide , for direct observation by the operator, and an image recording system such as photographic film , doped YAG screen coupled CCDs, or other digital detector. Typically these devices can be removed or inserted into the beam path as required. (Photograph film is no longer used.) The first report of using
1152-425: A beam while also stabilizing the current using a passive feedback circuit. A field emission source uses instead electrostatic electrodes called an extractor, a suppressor, and a gun lens, with different voltages on each, to control the electric field shape and intensity near the sharp tip. The combination of the cathode and these first electrostatic lens elements is collectively called the "electron gun". After it leaves
1280-456: A brownish solid with an optical absorption threshold at ≈1.6 eV. It is an n-type semiconductor with a low activation energy of 0.1–0.3 eV; this conductivity is attributed to intrinsic or oxygen-related defects. Fcc C 60 contains voids at its octahedral and tetrahedral sites which are sufficiently large (0.6 and 0.2 nm respectively) to accommodate impurity atoms. When alkali metals are doped into these voids, C 60 converts from
1408-420: A cartridge that is several cm long with a bore drilled down the cartridge axis. The specimen is loaded into the bore, possibly using a small screw ring to hold the sample in place. This cartridge is inserted into an airlock with the bore perpendicular to the TEM optic axis. When sealed, the airlock is manipulated to push the cartridge such that the cartridge falls into place, where the bore hole becomes aligned with
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#17327984034801536-414: A common thermoplastic material. Addition reactions apply to alkenes and alkynes. It is because they add reagents that they are called unsaturated. In this reaction a variety of reagents add "across" the pi-bond(s). Chlorine, hydrogen chloride, water , and hydrogen are illustrative reagents. Polymerization is a form of addition. Alkenes and some alkynes also undergo polymerization by opening of
1664-511: A converging lens. But, unlike a glass lens, a magnetic lens can very easily change its focusing power by adjusting the current passing through the coils. Equally important to the lenses are the apertures. These are circular holes in thin strips of heavy metal. Some are fixed in size and position and play important roles in limiting x-ray generation and improving the vacuum performance. Others can be freely switched among several different sizes and have their positions adjusted. Variable apertures after
1792-458: A converging pattern the minimum size of which is the gun crossover diameter. The thermionic emission current density, J , can be related to the work function of the emitting material via Richardson's law where A is the Richardson's constant, Φ is the work function and T is the temperature of the material. This equation shows that in order to achieve sufficient current density it
1920-470: A diverse range of molecular structures and phases: they can be gases (such as methane and propane ), liquids (such as hexane and benzene ), low melting solids (such as paraffin wax and naphthalene ) or polymers (such as polyethylene and polystyrene ). In the fossil fuel industries, hydrocarbon refers to naturally occurring petroleum , natural gas and coal , or their hydrocarbon derivatives and purified forms. Combustion of hydrocarbons
2048-426: A double bond between carbon atoms are sometimes referred to as 'olefins'. The predominant use of hydrocarbons is as a combustible fuel source. Methane is the predominant component of natural gas. C through C alkanes, alkenes, cycloalkanes, and aromatic hydrocarbons are the main components of gasoline , naphtha , jet fuel , and specialized industrial solvent mixtures. With the progressive addition of carbon units,
2176-482: A factor of two. However this required expensive quartz optics, due to the absorption of UV by glass. It was believed that obtaining an image with sub-micrometre information was not possible due to this wavelength constraint. In 1858, Plücker observed the deflection of "cathode rays" ( electrons ) by magnetic fields. This effect was used by Ferdinand Braun in 1897 to build simple cathode-ray oscilloscope (CRO) measuring devices. In 1891, Eduard Riecke noticed that
2304-414: A few nm/minute while being able to move several μm/minute, with repositioning accuracy on the order of nanometres. Earlier designs of TEM accomplished this with a complex set of mechanical downgearing devices, allowing the operator to finely control the motion of the stage by several rotating rods. Modern devices may use electrical stage designs, using screw gearing in concert with stepper motors , providing
2432-401: A fixed distance from the optic axis may be excluded. These consist of a small metallic disc that is sufficiently thick to prevent electrons from passing through the disc, whilst permitting axial electrons. This permission of central electrons in a TEM causes two effects simultaneously: firstly, apertures decrease the beam intensity as electrons are filtered from the beam, which may be desired in
2560-435: A flattening of the C 60 framework into a drum-shaped molecule. Solutions of C 60 can be oxygenated to the epoxide C 60 O. Ozonation of C 60 in 1,2-xylene at 257K gives an intermediate ozonide C 60 O 3 , which can be decomposed into 2 forms of C 60 O. Decomposition of C 60 O 3 at 296 K gives the epoxide, but photolysis gives a product in which the O atom bridges a 5,6-edge. The Diels–Alder reaction
2688-461: A helium atmosphere where the electrode material evaporates and condenses forming soot in the quenching atmosphere. Among other features, the IR spectra of the soot showed four discrete bands in close agreement to those proposed for C 60 . Another paper on the characterization and verification of the molecular structure followed on in the same year (1990) from their thin film experiments, and detailed also
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#17327984034802816-433: A hexagon and a pentagon). Its average bond length is 0.14 nm. Each carbon atom in the structure is bonded covalently with 3 others. A carbon atom in the C 60 can be substituted by a nitrogen or boron atom yielding a C 59 N or C 59 B respectively. For a time buckminsterfullerene was the largest known molecule observed to exhibit wave–particle duality . In 2020 the dye molecule phthalocyanine exhibited
2944-399: A light microscope is limited by the wavelength of the photons ( λ ) and the numerical aperture NA of the system. where n is the index of refraction of the medium in which the lens is working and α is the maximum half-angle of the cone of light that can enter the lens (see numerical aperture ). Early twentieth century scientists theorized ways of getting around the limitations of
3072-479: A purple color. Upon drying, intermolecular interaction results in the overlap and broadening of the energy bands, thereby eliminating the blue light transmittance and causing the purple to brown color change. C 60 crystallises with some solvents in the lattice ("solvates"). For example, crystallization of C 60 from benzene solution yields triclinic crystals with the formula C 60 ·4C 6 H 6 . Like other solvates, this one readily releases benzene to give
3200-499: A regular basis. As such, TEMs are equipped with multiple pumping systems and airlocks and are not permanently vacuum sealed. The vacuum system for evacuating a TEM to an operating pressure level consists of several stages. Initially, a low or roughing vacuum is achieved with either a rotary vane pump or diaphragm pumps setting a sufficiently low pressure to allow the operation of a turbo-molecular or diffusion pump establishing high vacuum level necessary for operations. To allow for
3328-610: A semiconductor into a conductor or even superconductor. C 60 undergoes six reversible, one-electron reductions, ultimately generating C 60 . Its oxidation is irreversible. The first reduction occurs at ≈-1.0 V ( Fc / Fc ), showing that C 60 is a reluctant electron acceptor. C 60 tends to avoid having double bonds in the pentagonal rings, which makes electron delocalization poor, and results in C 60 not being " superaromatic ". C 60 behaves like an electron deficient alkene . For example, it reacts with some nucleophiles. C 60 exhibits
3456-529: A single C–C bond it is alkane metathesis , for a double C–C bond it is alkene metathesis (olefin metathesis), and for a triple C–C bond it is alkyne metathesis . The vast majority of hydrocarbons found on Earth occur in crude oil , petroleum, coal , and natural gas. Since thousands of years they have been exploited and used for a vast range of purposes. Petroleum ( lit. ' rock oil ' ) and coal are generally thought to be products of decomposition of organic matter. Coal, in contrast to petroleum,
3584-699: A single column of atoms, which is thousands of times smaller than a resolvable object seen in a light microscope. Transmission electron microscopy is a major analytical method in the physical, chemical and biological sciences. TEMs find application in cancer research , virology , and materials science as well as pollution , nanotechnology and semiconductor research, but also in other fields such as paleontology and palynology . TEM instruments have multiple operating modes including conventional imaging, scanning TEM imaging (STEM), diffraction, spectroscopy, and combinations of these. Even within conventional imaging, there are many fundamentally different ways that contrast
3712-443: A small degree of aromatic character, but it still reflects localized double and single C–C bond characters. Therefore, C 60 can undergo addition with hydrogen to give polyhydrofullerenes. C 60 also undergoes Birch reduction . For example, C 60 reacts with lithium in liquid ammonia, followed by tert -butanol to give a mixture of polyhydrofullerenes such as C 60 H 18 , C 60 H 32 , C 60 H 36 , with C 60 H 32 being
3840-402: A solution of C 60 in olive oil to rats, achieving a major prolongation of their lifespan. Since then, many oils with C 60 have been sold as antioxidant products, but it does not avoid the problem of their sensitivity to light, that can turn them toxic. A later research confirmed that exposure to light degrades solutions of C 60 in oil, making it toxic and leading to a "massive" increase of
3968-420: A supporting electrolyte with extremely high oxidation resistance and low nucleophilicity, such as [Bu 4 N] [AsF 6 ]. C 60 forms complexes akin to the more common alkenes. Complexes have been reported molybdenum , tungsten , platinum , palladium , iridium , and titanium . The pentacarbonyl species are produced by photochemical reactions . In the case of platinum complex, the labile ethylene ligand
Buckminsterfullerene - Misplaced Pages Continue
4096-476: A team of researchers to advance the CRO design. The team consisted of several PhD students including Ernst Ruska and Bodo von Borries . The research team worked on lens design and CRO column placement, to optimize parameters to construct better CROs, and make electron optical components to generate low magnification (nearly 1:1) images. In 1931, the group successfully generated magnified images of mesh grids placed over
4224-531: A thickness and mesh size ranging from a few to 100 μm. The sample is placed onto the meshed area having a diameter of approximately 2.5 mm. Usual grid materials are copper, molybdenum, gold or platinum. This grid is placed into the sample holder, which is paired with the specimen stage. A wide variety of designs of stages and holders exist, depending upon the type of experiment being performed. In addition to 3.05 mm grids, 2.3 mm grids are sometimes, if rarely, used. These grids were particularly used in
4352-468: A two neutral radical atoms ( homolytic fission ). all the way to CCl 4 ( carbon tetrachloride ) all the way to C 2 Cl 6 ( hexachloroethane ) Aromatic compounds, almost uniquely for hydrocarbons, undergo substitution reactions. The chemical process practiced on the largest scale is the reaction of benzene and ethene to give ethylbenzene : The resulting ethylbenzene is dehydrogenated to styrene and then polymerized to manufacture polystyrene ,
4480-500: A variable current, but typically use high voltages, and therefore require significant insulation in order to prevent short-circuiting the lens components. Thermal distributors are placed to ensure the extraction of the heat generated by the energy lost to resistance of the coil windings. The windings may be water-cooled, using a chilled water supply in order to facilitate the removal of the high thermal duty. Apertures are annular metallic plates, through which electrons that are further than
4608-409: Is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a grid. An image is formed from the interaction of the electrons with the sample as the beam is transmitted through the specimen. The image is then magnified and focused onto an imaging device, such as
4736-495: Is a cage-like molecule, a regular truncated icosahedron . The experimental evidence, a strong peak at 720 atomic mass units , indicated that a carbon molecule with 60 carbon atoms was forming, but provided no structural information. The research group concluded after reactivity experiments, that the most likely structure was a spheroidal molecule. The idea was quickly rationalized as the basis of an icosahedral symmetry closed cage structure. Kroto, Curl, and Smalley were awarded
4864-696: Is also potential to harvest hydrocarbons from plants like Euphorbia lathyris and E. tirucalli as an alternative and renewable energy source for vehicles that use diesel. Furthermore, endophytic bacteria from plants that naturally produce hydrocarbons have been used in hydrocarbon degradation in attempts to deplete hydrocarbon concentration in polluted soils. Saturated hydrocarbons are notable for their inertness. Unsaturated hydrocarbons (alkanes, alkenes and aromatic compounds) react more readily, by means of substitution, addition, polymerization. At higher temperatures they undergo dehydrogenation, oxidation and combustion. The cracking of saturated hydrocarbons
4992-400: Is called autoxidation , begins with the formation of hydroperoxides (ROOH). Combustion of hydrocarbons is currently the main source of the world's energy for electric power generation , heating (such as home heating), and transportation. Often this energy is used directly as heat such as in home heaters, which use either petroleum or natural gas . The hydrocarbon is burnt and the heat
5120-413: Is commonly employed to functionalize C 60 . Reaction of C 60 with appropriate substituted diene gives the corresponding adduct. The Diels–Alder reaction between C 60 and 3,6-diaryl-1,2,4,5-tetrazines affords C 62 . The C 62 has the structure in which a four-membered ring is surrounded by four six-membered rings. The C 60 molecules can also be coupled through a [2+2] cycloaddition , giving
5248-482: Is estimated at more than 58 million metric tons, which will increase to 60 million tons in 2022. Hydrocarbons are also prevalent in nature. Some eusocial arthropods, such as the Brazilian stingless bee, Schwarziana quadripunctata , use unique cuticular hydrocarbon "scents" in order to determine kin from non-kin. This hydrocarbon composition varies between age, sex, nest location, and hierarchal position. There
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5376-403: Is illuminated with the parallel beam, formed by electron beam shaping with the system of Condenser lenses and Condenser aperture. After interaction with the sample, on the exit surface of the specimen two types of electrons exist – unscattered (which will correspond to the bright central beam on the diffraction pattern) and scattered electrons (which change their trajectories due to interaction with
5504-505: Is mixed with a disulfide RSSR, the radical C 60 SR• forms spontaneously upon irradiation of the mixture. Stability of the radical species C 60 Y depends largely on steric factors of Y. When tert -butyl halide is photolyzed and allowed to react with C 60 , a reversible inter-cage C–C bond is formed: Cyclopropanation (the Bingel reaction ) is another common method for functionalizing C 60 . Cyclopropanation of C 60 mostly occurs at
5632-409: Is necessary to heat the emitter, taking care not to cause damage by application of excessive heat. For this reason materials with either a high melting point, such as tungsten, or those with a low work function (LaB 6 ) are required for the gun filament. Furthermore, both lanthanum hexaboride and tungsten thermionic sources must be heated in order to achieve thermionic emission, this can be achieved by
5760-425: Is often the case under standard TEM operating conditions. The theorem states that the wave amplitude at some point B as a result of electron point source A would be the same as the amplitude at A due to an equivalent point source placed at B. Simply stated, the wave function for electrons focused through any series of optical components that includes only scalar (i.e. not magnetic) fields will be exactly equivalent if
5888-681: Is one of the most common electron acceptors used in donor/acceptor based solar cells. Conversion efficiencies up to 5.7% have been reported in C 60 –polymer cells. C 60 is sensitive to light, so leaving C 60 under light exposure causes it to degrade, becoming dangerous. The ingestion of C 60 solutions that have been exposed to light could lead to developing cancer (tumors). So the management of C 60 products for human ingestion requires cautionary measures such as: elaboration in very dark environments, encasing into bottles of great opacity, and storing in dark places, and others like consumption under low light conditions and using labels to warn about
6016-433: Is placed near the tip of a long metal (brass or stainless steel) rod, with the specimen placed flat in a small bore. Along the rod are several polymer vacuum rings to allow for the formation of a vacuum seal of sufficient quality, when inserted into the stage. The stage is thus designed to accommodate the rod, placing the sample either in between or near the objective lens, dependent upon the objective design. When inserted into
6144-458: Is possible. Hydrocarbons are generally of low toxicity, hence the widespread use of gasoline and related volatile products. Aromatic compounds such as benzene and toluene are narcotic and chronic toxins, and benzene in particular is known to be carcinogenic . Certain rare polycyclic aromatic compounds are carcinogenic. Hydrocarbons are highly flammable . Transmission electron microscopy Transmission electron microscopy ( TEM )
6272-469: Is produced, called "image contrast mechanisms". Contrast can arise from position-to-position differences in the thickness or density ("mass-thickness contrast"), atomic number ("Z contrast", referring to the common abbreviation Z for atomic number), crystal structure or orientation ("crystallographic contrast" or "diffraction contrast"), the slight quantum-mechanical phase shifts that individual atoms produce in electrons that pass through them ("phase contrast"),
6400-463: Is richer in carbon and poorer in hydrogen. Natural gas is the product of methanogenesis . A seemingly limitless variety of compounds comprise petroleum, hence the necessity of refineries. These hydrocarbons consist of saturated hydrocarbons, aromatic hydrocarbons, or combinations of the two. Missing in petroleum are alkenes and alkynes. Their production requires refineries. Petroleum-derived hydrocarbons are mainly consumed for fuel, but they are also
6528-488: Is the leaving group in a thermal reaction: Titanocene complexes have also been reported: Coordinatively unsaturated precursors, such as Vaska's complex , for adducts with C 60 : One such iridium complex, [Ir( η -C 60 )(CO)Cl(Ph 2 CH 2 C 6 H 4 OCH 2 Ph) 2 ] has been prepared where the metal center projects two electron-rich 'arms' that embrace the C 60 guest. Metal atoms or certain small molecules such as H 2 and noble gas can be encapsulated inside
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#17327984034806656-616: Is the main industrial route to alkenes and alkyne . These reactions require heterogeneous catalysts and temperatures >500 °C. Widely practice conversions of hydrocarbons involves their reaction with oxygen. In the presence of excess oxygen, hydrocarbons combust. With, however, careful conditions, which have been optimized for many years, partial oxidation results. Useful compounds can obtained in this way: maleic acid from butane , terephthalic acid from xylenes , acetone together with phenol from cumene (isopropylbenzene), and cyclohexanone from cyclohexane]]. The process, which
6784-757: Is the main source of the world's energy. Petroleum is the dominant raw-material source for organic commodity chemicals such as solvents and polymers. Most anthropogenic (human-generated) emissions of greenhouse gases are either carbon dioxide released by the burning of fossil fuels , or methane released from the handling of natural gas or from agriculture. As defined by the International Union of Pure and Applied Chemistry 's nomenclature of organic chemistry , hydrocarbons are classified as follows: The term 'aliphatic' refers to non-aromatic hydrocarbons. Saturated aliphatic hydrocarbons are sometimes referred to as 'paraffins'. Aliphatic hydrocarbons containing
6912-398: Is the paucity of enzymes that act on them. Nonetheless, the area has received regular attention. Bacteria in the gabbroic layer of the ocean's crust can degrade hydrocarbons; but the extreme environment makes research difficult. Other bacteria such as Lutibacterium anuloederans can also degrade hydrocarbons. Mycoremediation or breaking down of hydrocarbon by mycelium and mushrooms
7040-707: Is triply degenerate, with the HOMO – LUMO separation relatively small. This small gap suggests that reduction of C 60 should occur at mild potentials leading to fulleride anions, [C 60 ] ( n = 1–6). The midpoint potentials of 1-electron reduction of buckminsterfullerene and its anions is given in the table below: C 60 forms a variety of charge-transfer complexes , for example with tetrakis(dimethylamino)ethylene : This salt exhibits ferromagnetism at 16 K. C 60 oxidizes with difficulty. Three reversible oxidation processes have been observed by using cyclic voltammetry with ultra-dry methylene chloride and
7168-423: Is twofold: first the allowance for the voltage difference between the cathode and the ground without generating an arc, and secondly to reduce the collision frequency of electrons with gas atoms to negligible levels—this effect is characterized by the mean free path . TEM components such as specimen holders and film cartridges must be routinely inserted or replaced requiring a system with the ability to re-evacuate on
7296-597: Is used to heat water, which is then circulated. A similar principle is used to create electrical energy in power plants . Both saturated and unsaturated hydrocarbons undergo this process. Common properties of hydrocarbons are the facts that they produce steam, carbon dioxide and heat during combustion and that oxygen is required for combustion to take place. The simplest hydrocarbon, methane , burns as follows: In inadequate supply of air, carbon black and water vapour are formed: And finally, for any linear alkane of n carbon atoms, Partial oxidation characterizes
7424-541: The Solar System . Lakes of liquid methane and ethane have been found on Titan , Saturn 's largest moon, as confirmed by the Cassini–Huygens space probe. Hydrocarbons are also abundant in nebulae forming polycyclic aromatic hydrocarbon compounds. Burning hydrocarbons as fuel, which produces carbon dioxide and water , is a major contributor to anthropogenic global warming . Hydrocarbons are introduced into
7552-507: The field emission gun and adding a high quality objective lens to create the modern STEM. Using this design, Crewe demonstrated the ability to image atoms using annular dark-field imaging . Crewe and coworkers at the University of Chicago developed the cold field electron emission source and built a STEM able to visualize single heavy atoms on thin carbon substrates. Theoretically, the maximum resolution, d , that one can obtain with
7680-484: The interstellar medium , where it is the cause of several absorption features known as diffuse interstellar bands in the near-infrared. Theoretical predictions of buckminsterfullerene molecules appeared in the late 1960s and early 1970s. It was first generated in 1984 by Eric Rohlfing, Donald Cox, and Andrew Kaldor using a laser to vaporize carbon in a supersonic helium beam, although the group did not realize that buckminsterfullerene had been produced. In 1985 their work
7808-461: The left hand rule , thus allowing electromagnets to manipulate the electron beam. Additionally, electrostatic fields can cause the electrons to be deflected through a constant angle. Coupling of two deflections in opposing directions with a small intermediate gap allows for the formation of a shift in the beam path, allowing for beam shifting. The lenses of a TEM are what gives it its flexibility of operating modes and ability to focus beams down to
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#17327984034807936-458: The 1996 Nobel Prize in Chemistry for their roles in the discovery of buckminsterfullerene and the related class of molecules, the fullerenes . In 1989 physicists Wolfgang Krätschmer , Konstantinos Fostiropoulos , and Donald R. Huffman observed unusual optical absorptions in thin films of carbon dust (soot). The soot had been generated by an arc-process between two graphite electrodes in
8064-552: The C 60 cage. These endohedral fullerenes are usually synthesized by doping in the metal atoms in an arc reactor or by laser evaporation. These methods gives low yields of endohedral fullerenes, and a better method involves the opening of the cage, packing in the atoms or molecules, and closing the opening using certain organic reactions . This method, however, is still immature and only a few species have been synthesized this way. Endohedral fullerenes show distinct and intriguing chemical properties that can be completely different from
8192-489: The PhD thesis of Louis de Broglie in 1924. Knoll's research group was unaware of this publication until 1932, when they realized that the de Broglie wavelength of electrons was many orders of magnitude smaller than that for light, theoretically allowing for imaging at atomic scales. (Even for electrons with a kinetic energy of just 1 electronvolt the wavelength is already as short as 1.18 nm .) In April 1932, Ruska suggested
8320-456: The Physics department of IG Farben -Werke. Further work on the electron microscope was hampered by the destruction of a new laboratory constructed at Siemens by an air raid , as well as the death of two of the researchers, Heinz Müller and Friedrick Krause during World War II . After World War II, Ruska resumed work at Siemens, where he continued to develop the electron microscope, producing
8448-653: The TEM stage allows movement of the sample in the XY plane, Z height adjustment, and commonly a single tilt direction parallel to the axis of side entry holders. Sample rotation may be available on specialized diffraction holders and stages. Some modern TEMs provide the ability for two orthogonal tilt angles of movement with specialized holder designs called double-tilt sample holders. Some stage designs, such as top-entry or vertical insertion stages once common for high resolution TEM studies, may simply only have X-Y translation available. The design criteria of TEM stages are complex, owing to
8576-475: The anode aperture. The device used two magnetic lenses to achieve higher magnifications, arguably creating the first electron microscope . In that same year, Reinhold Rudenberg , the scientific director of the Siemens company, patented an electrostatic lens electron microscope. At the time, electrons were understood to be charged particles of matter; the wave nature of electrons was not fully realized until
8704-401: The atomic scale and magnify them to get an image. A lens is usually made of a solenoid coil nearly surrounded by ferromagnetic materials designed to concentrate the coil's magnetic field into a precise, confined shape. When an electron enters and leaves this magnetic field, it spirals around the curved magnetic field lines in a way that acts very much as an ordinary glass lens does for light—it is
8832-415: The atoms are but what kinds of atoms they are and how they are bonded to each other. For this reason TEM is regarded as an essential tool for nanoscience in both biological and materials fields. The first TEM was demonstrated by Max Knoll and Ernst Ruska in 1931, with this group developing the first TEM with resolution greater than that of light in 1933 and the first commercial TEM in 1939. In 1986, Ruska
8960-432: The beam axis, such that the beam travels down the cartridge bore and into the specimen. Such designs are typically unable to be tilted without blocking the beam path or interfering with the objective lens. The electron gun is formed from several components: the filament, a biasing circuit, a Wehnelt cap, and an extraction anode. By connecting the filament to the negative component power supply, electrons can be "pumped" from
9088-413: The beam path, or moved in the plane perpendicular to the beam path. Aperture assemblies are mechanical devices which allow for the selection of different aperture sizes, which may be used by the operator to trade off intensity and the filtering effect of the aperture. Aperture assemblies are often equipped with micrometers to move the aperture, required during optical calibration. Imaging methods in TEM use
9216-449: The beams remain near the low-aberration centers of every lens in the lens stacks. The stigmators compensate for slight imperfections and aberrations that cause astigmatism—a lens having a different focal strength in different directions. Typically a TEM consists of three stages of lensing. The stages are the condenser lenses, the objective lenses, and the projector lenses. The condenser lenses are responsible for primary beam formation, while
9344-411: The case of beam sensitive samples. Secondly, this filtering removes electrons that are scattered to high angles, which may be due to unwanted processes such as spherical or chromatic aberration, or due to diffraction from interaction within the sample. Apertures are either a fixed aperture within the column, such as at the condenser lens, or are a movable aperture, which can be inserted or withdrawn from
9472-617: The cathode rays could be focused by magnetic fields, allowing for simple electromagnetic lens designs. In 1926, Hans Busch published work extending this theory and showed that the lens maker's equation could, with appropriate assumptions, be applied to electrons. In 1928, at the Technische Hochschule in Charlottenburg (now Technische Universität Berlin ), Adolf Matthias, Professor of High Voltage Technology and Electrical Installations, appointed Max Knoll to lead
9600-561: The construction of a new electron microscope for direct imaging of specimens inserted into the microscope, rather than simple mesh grids or images of apertures. With this device successful diffraction and normal imaging of an aluminium sheet was achieved. However the magnification achievable was lower than with light microscopy. Magnifications higher than those available with a light microscope were achieved in September 1933 with images of cotton fibers quickly acquired before being damaged by
9728-434: The detection of single electron counts ("counting mode"). These Direct Electron Detectors are available from Gatan , FEI , Quantum Detectors and Direct Electron . A TEM is composed of several components, which include a vacuum system in which the electrons travel, an electron emission source for generation of the electron stream, a series of electromagnetic lenses, as well as electrostatic plates. The latter two allow
9856-444: The diffusion of gas molecules into the higher vacuum gun area faster than they can be pumped out. For these very low pressures, either an ion pump or a getter material is used. Poor vacuum in a TEM can cause several problems ranging from the deposition of gas inside the TEM onto the specimen while viewed in a process known as electron beam induced deposition to more severe cathode damages caused by electrical discharge. The use of
9984-486: The dominating product. This mixture of polyhydrofullerenes can be re-oxidized by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone to give C 60 again. A selective hydrogenation method exists. Reaction of C 60 with 9,9′,10,10′-dihydroanthracene under the same conditions, depending on the time of reaction, gives C 60 H 32 and C 60 H 18 respectively and selectively. Addition of fluorine , chlorine , and bromine occurs for C 60 . Fluorine atoms are small enough for
10112-556: The duality that is more famously attributed to light, electrons and other small particles and molecules. Fullerenes are sparingly soluble in aromatic solvents and carbon disulfide , but insoluble in water. Solutions of pure C 60 have a deep purple color which leaves a brown residue upon evaporation. The reason for this color change is the relatively narrow energy width of the band of molecular levels responsible for green light absorption by individual C 60 molecules. Thus individual molecules transmit some blue and red light resulting in
10240-682: The dumbbell-shaped compound C 120 . The coupling is achieved by high-speed vibrating milling of C 60 with a catalytic amount of KCN . The reaction is reversible as C 120 dissociates back to two C 60 molecules when heated at 450 K (177 °C; 350 °F). Under high pressure and temperature, repeated [2+2] cycloaddition between C 60 results in polymerized fullerene chains and networks. These polymers remain stable at ambient pressure and temperature once formed, and have remarkably interesting electronic and magnetic properties, such as being ferromagnetic above room temperature. Reactions of C 60 with free radicals readily occur. When C 60
10368-531: The electron beam. At this time, interest in the electron microscope had increased, with other groups, such as that of Paul Anderson and Kenneth Fitzsimmons of Washington State University and that of Albert Prebus and James Hillier at the University of Toronto , who constructed the first TEMs in North America in 1935 and 1938, respectively, continually advancing TEM design. Research continued on
10496-415: The electron gun in high-resolution or field-emission TEMs. High-voltage TEMs require ultra-high vacuums on the range of 10 to 10 Pa to prevent the generation of an electrical arc, particularly at the TEM cathode. As such for higher voltage TEMs a third vacuum system may operate, with the gun isolated from the main chamber either by gate valves or a differential pumping aperture – a small hole that prevents
10624-480: The electron gun to the anode plate and the TEM column, thus completing the circuit. The gun is designed to create a beam of electrons exiting from the assembly at some given angle, known as the gun divergence semi-angle, α. By constructing the Wehnelt cylinder such that it has a higher negative charge than the filament itself, electrons that exit the filament in a diverging manner are, under proper operation, forced into
10752-501: The electron microscope at Siemens in 1936, where the aim of the research was the development and improvement of TEM imaging properties, particularly with regard to biological specimens. At this time electron microscopes were being fabricated for specific groups, such as the "EM1" device used at the UK National Physical Laboratory. In 1939, the first commercial electron microscope, pictured, was installed in
10880-492: The electron source and observation point are reversed. R Reciprocity is used to understand scanning transmission electron microscopy (STEM) in the familiar context of TEM, and to obtain and interpret images using STEM. The key factors when considering electron detection include detective quantum efficiency (DQE) , point spread function (PSF) , modulation transfer function (MTF) , pixel size and array size, noise, data readout speed, and radiation hardness. Imaging systems in
11008-586: The electron wavefunctions, where the wave that forms the exit beam is denoted by Ψ. Different imaging methods therefore attempt to modify the electron waves exiting the sample in a way that provides information about the sample, or the beam itself. From the previous equation, it can be deduced that the observed image depends not only on the amplitude of beam, but also on the phase of the electrons, although phase effects may often be ignored at lower magnifications. Higher resolution imaging requires thinner samples and higher energies of incident electrons, which means that
11136-432: The encapsulated atom or molecule, as well as the fullerene itself. The encapsulated atoms have been shown to perform circular motions inside the C 60 cage, and their motion has been followed using NMR spectroscopy . The optical absorption properties of C 60 match the solar spectrum in a way that suggests that C 60 -based films could be useful for photovoltaic applications. Because of its high electronic affinity it
11264-453: The energy lost by electrons on passing through the sample ("spectrum imaging") and more. Each mechanism tells the user a different kind of information, depending not only on the contrast mechanism but on how the microscope is used—the settings of lenses, apertures, and detectors. What this means is that a TEM is capable of returning an extraordinary variety of nanometre- and atomic-resolution information, in ideal cases revealing not only where all
11392-524: The environment through their extensive use as fuels and chemicals as well as through leaks or accidental spills during exploration, production, refining, or transport of fossil fuels. Anthropogenic hydrocarbon contamination of soil is a serious global issue due to contaminant persistence and the negative impact on human health. When soil is contaminated by hydrocarbons, it can have a significant impact on its microbiological, chemical, and physical properties. This can serve to prevent, slow down or even accelerate
11520-427: The extraction of an evaporable as well as benzene -soluble material from the arc-generated soot. This extract had TEM and X-ray crystal analysis consistent with arrays of spherical C 60 molecules, approximately 1.0 nm in van der Waals diameter as well as the expected molecular mass of 720 Da for C 60 (and 840 Da for C 70 ) in their mass spectra . The method was simple and efficient to prepare
11648-515: The first microscope with 100k magnification. The fundamental structure of this microscope design, with multi-stage beam preparation optics, is still used in modern microscopes. The worldwide electron microscopy community advanced with electron microscopes being manufactured in Manchester UK, the USA (RCA), Germany (Siemens) and Japan (JEOL). The first international conference in electron microscopy
11776-411: The fullerenes are dissolved in a hydrocarbon or halogenated hydrocarbon and separated using alumina columns. Buckminsterfullerene is a truncated icosahedron with 60 vertices , 32 faces (20 hexagons and 12 pentagons where no pentagons share a vertex), and 90 edges (60 edges between 5-membered & 6-membered rings and 30 edges are shared between 6-membered & 6-membered rings), with a carbon atom at
11904-495: The growth of vegetation depending on the exact changes that occur. Crude oil and natural gas are the two largest sources of hydrocarbon contamination of soil. Bioremediation of hydrocarbon from soil or water contaminated is a formidable challenge because of the chemical inertness that characterize hydrocarbons (hence they survived millions of years in the source rock). Nonetheless, many strategies have been devised, bioremediation being prominent. The basic problem with bioremediation
12032-434: The gun, the beam is typically accelerated until it reaches its final voltage and enters the next part of the microscope: the condenser lens system. These upper lenses of the TEM then further focus the electron beam to the desired size and location on the sample. Manipulation of the electron beam is performed using two physical effects. The interaction of electrons with a magnetic field will cause electrons to move according to
12160-403: The information contained in the electron waves exiting from the sample to form an image. The projector lenses allow for the correct positioning of this electron wave distribution onto the viewing system. The observed intensity, I , of the image, assuming sufficiently high quality of imaging device, can be approximated as proportional to the time-averaged squared absolute value of the amplitude of
12288-486: The junction of 2 hexagons due to steric factors. The first cyclopropanation was carried out by treating the β-bromomalonate with C 60 in the presence of a base. Cyclopropanation also occur readily with diazomethanes . For example, diphenyldiazomethane reacts readily with C 60 to give the compound C 61 Ph 2 . Phenyl-C 61 -butyric acid methyl ester derivative prepared through cyclopropanation has been studied for use in organic solar cells . The LUMO in C 60
12416-429: The lattice constant from 1.411 to 1.4154 nm. C 60 solid is as soft as graphite , but when compressed to less than 70% of its volume it transforms into a superhard form of diamond (see aggregated diamond nanorod ). C 60 films and solution have strong non-linear optical properties; in particular, their optical absorption increases with light intensity (saturable absorption). C 60 forms
12544-411: The lenses' ability to reproduce the object plane. The exact dimensions of the gap, pole piece internal diameter and taper, as well as the overall design of the lens is often performed by finite element analysis of the magnetic field, whilst considering the thermal and electrical constraints of the design. The coils which produce the magnetic field are located within the lens yoke. The coils can contain
12672-434: The low vacuum pump to not require continuous operation, while continually operating the turbo-molecular pumps, the vacuum side of a low-pressure pump may be connected to chambers which accommodate the exhaust gases from the turbo-molecular pump. Sections of the TEM may be isolated by the use of pressure-limiting apertures to allow for different vacuum levels in specific areas such as a higher vacuum of 10 to 10 Pa or higher in
12800-501: The material in gram amounts per day (1990) which has boosted the fullerene research and is even today applied for the commercial production of fullerenes. The discovery of practical routes to C 60 led to the exploration of a new field of chemistry involving the study of fullerenes. The discoverers of the allotrope named the newfound molecule after American architect R. Buckminster Fuller , who designed many geodesic dome structures that look similar to C 60 and who had died in 1983,
12928-405: The material). In Imaging mode, the objective aperture is inserted in a back focal plane (BFP) of the objective lens (where diffraction spots are formed). If using the objective aperture to select only the central beam, the transmitted electrons are passed through the aperture while all others are blocked, and a bright field image (BF image) is obtained. If we allow the signal from a diffracted beam,
13056-441: The mineral sciences where a large degree of tilt can be required and where specimen material may be extremely rare. Electron transparent specimens have a thickness usually less than 100 nm, but this value depends on the accelerating voltage. Once inserted into a TEM, the sample has to be manipulated to locate the region of interest to the beam, such as in single grain diffraction, in a specific orientation. To accommodate this,
13184-509: The multiple bonds to produce polyethylene , polybutylene , and polystyrene . The alkyne acetylene polymerizes to produce polyacetylene . Oligomers (chains of a few monomers) may be produced, for example in the Shell higher olefin process , where α-olefins are extended to make longer α-olefins by adding ethylene repeatedly. Some hydrocarbons undergo metathesis , in which substituents attached by C–C bonds are exchanged between molecules. For
13312-876: The objective lenses focus the beam that comes through the sample itself (in STEM scanning mode, there are also objective lenses above the sample to make the incident electron beam convergent). The projector lenses are used to expand the beam onto the phosphor screen or other imaging device, such as film. The magnification of the TEM is due to the ratio of the distances between the specimen and the objective lens' image plane. TEM optical configurations differ significantly with implementation, with manufacturers using custom lens configurations, such as in spherical aberration corrected instruments, or TEMs using energy filtering to correct electron chromatic aberration . The optical reciprocity theorem, or principle of Helmholtz reciprocity , generally holds true for elastically scattered electrons, as
13440-410: The observed intensities. To improve the contrast in the image, the TEM may be operated at a slight defocus to enhance contrast, owing to convolution by the contrast transfer function of the TEM, which would normally decrease contrast if the sample was not a weak phase object. The figure on the right shows the two basic operation modes of TEM – imaging and diffraction modes. In both cases the specimen
13568-447: The operator to guide and manipulate the beam as required. Also required is a device to allow the insertion into, motion within, and removal of specimens from the beam path. Imaging devices are subsequently used to create an image from the electrons that exit the system. To increase the mean free path of the electron gas interaction, a standard TEM is evacuated to low pressures, typically on the order of 10 Pa . The need for this
13696-404: The operator with a computer-based stage input, such as a joystick or trackball . Two main designs for stages in a TEM exist, the side-entry and top entry version. Each design must accommodate the matching holder to allow for specimen insertion without either damaging delicate TEM optics or allowing gas into TEM systems under vacuum. The most common is the side entry holder, where the specimen
13824-420: The problems with light. Solutions of C 60 dissolved in olive oil or water, as long as they are preserved from light, have been found nontoxic to rodents. Otherwise, a study found that C 60 remains in the body for a longer time than usual, especially in the liver, where it tends to be accumulated, and therefore has the potential to induce detrimental health effects. An experiment in 2011–2012 administered
13952-401: The reactions of alkenes and oxygen. This process is the basis of rancidification and paint drying . Benzene burns with sooty flame when heated in air: Saturated hydrocarbons react with chlorine and fluorine . In the case of chlorination, one of the chlorine atoms replaces a hydrogen atom. The reactions proceed via free-radical pathways , in which the halogen first dissociates into
14080-411: The relatively large wavelength of visible light (wavelengths of 400–700 nanometres ) by using electrons. Like all matter, electrons have both wave and particle properties ( matter wave ), and their wave-like properties mean that a beam of electrons can be focused and diffracted much like light can. The wavelength of electrons is related to their kinetic energy via the de Broglie equation, which says that
14208-414: The risk of developing cancer (tumors) after its consumption. Hydrocarbon In organic chemistry , a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon . Hydrocarbons are examples of group 14 hydrides . Hydrocarbons are generally colourless and hydrophobic ; their odor is usually faint, and may be similar to that of gasoline or lighter fluid . They occur in
14336-469: The same wavelength as had been emitted by the red carbon star. Hence, the inspiration came to Smalley and team to use the laser technique on graphite to generate fullerenes. Using laser evaporation of graphite the Smalley team found C n clusters (where n > 20 and even) of which the most common were C 60 and C 70 . A solid rotating graphite disk was used as the surface from which carbon
14464-402: The sample allow the user to select the range of spatial positions or electron scattering angles to be used in the formation of an image or a diffraction pattern. The electron-optical system also includes deflectors and stigmators, usually made of small electromagnets. The deflectors allow the position and angle of the beam at the sample position to be independently controlled and also ensure that
14592-424: The sample can no longer be considered to be absorbing electrons (i.e., via a Beer's law effect). Instead, the sample can be modeled as an object that does not change the amplitude of the incoming electron wave function, but instead modifies the phase of the incoming wave; in this model, the sample is known as a pure phase object. For sufficiently thin specimens, phase effects dominate the image, complicating analysis of
14720-737: The simple non-ring structured hydrocarbons have higher viscosities , lubricating indices, boiling points, and solidification temperatures. At the opposite extreme from methane lie the heavy tars that remain as the lowest fraction in a crude oil refining retort. They are collected and widely utilized as roofing compounds, pavement material ( bitumen ), wood preservatives (the creosote series) and as extremely high viscosity shear-resisting liquids. Some large-scale non-fuel applications of hydrocarbons begin with ethane and propane, which are obtained from petroleum and natural gas. These two gases are converted either to syngas or to ethylene and propylene respectively. Global consumption of benzene in 2021
14848-453: The simultaneous requirements of mechanical and electron-optical constraints and specialized models are available for different methods. A TEM stage is required to have the ability to hold a specimen and be manipulated to bring the region of interest into the path of the electron beam. As the TEM can operate over a wide range of magnifications, the stage must simultaneously be highly resistant to mechanical drift, with drift requirements as low as
14976-517: The source of virtually all synthetic organic compounds, including plastics and pharmaceuticals. Natural gas is consumed almost exclusively as fuel. Coal is used as a fuel and as a reducing agent in metallurgy . A small fraction of hydrocarbon found on earth, and all currently known hydrocarbon found on other planets and moons, is thought to be abiological . Hydrocarbons such as ethylene, isoprene, and monoterpenes are emitted by living vegetation. Some hydrocarbons also are widespread and abundant in
15104-428: The stage, the side entry holder has its tip contained within the TEM vacuum, and the base is presented to atmosphere, the airlock formed by the vacuum rings. Insertion procedures for side-entry TEM holders typically involve the rotation of the sample to trigger micro switches that initiate evacuation of the airlock before the sample is inserted into the TEM column. The second design is the top-entry holder consists of
15232-572: The use of a small resistive strip. To prevent thermal shock, there is often a delay enforced in the application of current to the tip, to prevent thermal gradients from damaging the filament, the delay is usually a few seconds for LaB 6 , and significantly lower for tungsten . Electron lenses are designed to act in a manner emulating that of an optical lens, by focusing parallel electrons at some constant focal distance. Electron lenses may operate electrostatically or magnetically. The majority of electron lenses for TEM use electromagnetic coils to generate
15360-422: The usual face-centred cubic C 60 . Millimeter-sized crystals of C 60 and C 70 can be grown from solution both for solvates and for pure fullerenes. In solid buckminsterfullerene, the C 60 molecules adopt the fcc ( face-centered cubic ) motif. They start rotating at about −20 °C. This change is associated with a first-order phase transition to an fcc structure and a small, yet abrupt increase in
15488-412: The vertices of each polygon and a bond along each polygon edge. The van der Waals diameter of a C 60 molecule is about 1.01 nanometers (nm). The nucleus to nucleus diameter of a C 60 molecule is about 0.71 nm. The C 60 molecule has two bond lengths. The 6:6 ring bonds (between two hexagons) can be considered " double bonds " and are shorter than the 6:5 bonds (between
15616-489: The wavelength is inversely proportional to the momentum. Taking into account relativistic effects (as in a TEM an electron's velocity is a substantial fraction of the speed of light, c ) the wavelength is where h is the Planck constant , m 0 is the rest mass of an electron and E is the kinetic energy of the accelerated electron. From the top down, the TEM consists of an emission source or cathode, which may be
15744-425: The year before discovery. Another common name for buckminsterfullerene is "buckyballs". Soot is produced by laser ablation of graphite or pyrolysis of aromatic hydrocarbons . Fullerenes are extracted from the soot with organic solvents using a Soxhlet extractor . This step yields a solution containing up to 75% of C 60 , as well as other fullerenes. These fractions are separated using chromatography . Generally,
15872-408: The yoke, the magnetic coil, the poles, the polepiece, and the external control circuitry. The pole piece must be manufactured in a very symmetrical manner, as this provides the boundary conditions for the magnetic field that forms the lens. Imperfections in the manufacture of the pole piece can induce severe distortions in the magnetic field symmetry, which induce distortions that will ultimately limit
16000-478: Was awarded the Nobel Prize in physics for the development of transmission electron microscopy. In 1873, Ernst Abbe proposed that the ability to resolve detail in an object was limited approximately by the wavelength of the light used in imaging or a few hundred nanometres for visible light microscopes. Developments in ultraviolet (UV) microscopes, led by Köhler and Rohr , increased resolving power by
16128-559: Was in Delft in 1949, with more than one hundred attendees. Later conferences included the "First" international conference in Paris, 1950 and then in London in 1954. With the development of TEM, the associated technique of scanning transmission electron microscopy (STEM) was re-investigated and remained undeveloped until the 1970s, with Albert Crewe at the University of Chicago developing
16256-550: Was repeated by Harold Kroto , James R. Heath , Sean C. O'Brien , Robert Curl , and Richard Smalley at Rice University , who recognized the structure of C 60 as buckminsterfullerene. Concurrent but unconnected to the Kroto-Smalley work, astrophysicists were working with spectroscopists to study infrared emissions from giant red carbon stars. Smalley and team were able to use a laser vaporization technique to create carbon clusters which could potentially emit infrared at
16384-420: Was vaporized using a laser beam creating hot plasma that was then passed through a stream of high-density helium gas. The carbon species were subsequently cooled and ionized resulting in the formation of clusters. Clusters ranged in molecular masses, but Kroto and Smalley found predominance in a C 60 cluster that could be enhanced further by allowing the plasma to react longer. They also discovered that C 60
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