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In 1997, Finke and Watzky proposed a new kinetic model for the nucleation and growth of nanoparticles. This 2-step model suggested that constant slow nucleation (occurring far from supersaturation) is followed by autocatalytic growth where dispersity of nanoparticles is largely determined. This F-W (Finke-Watzky) 2-step model provides a firmer mechanistic basis for the design of nanoparticles with a focus on size, shape, and dispersity control. The model was later expanded to a 3-step and two 4-step models between 2004-2008. Here, an additional step was included to account for small particle aggregation, where two smaller particles could aggregate to form a larger particle. Next, a fourth step (another autocatalytic step) was added to account for a small particle agglomerating with a larger particle. Finally in 2014, an alternative fourth step was considered that accounted for a atomistic surface growth on a large particle. | 0 | Colloidal Chemistry |
Synthetic methodology and characterization often go hand in hand in the sense that not one but a series of reaction mixtures are prepared and subjected to heat treatment. Stoichiometry, a numerical relationship between the quantities of reactant and product, is typically varied systematically. It is important to find which stoichiometries will lead to new solid compounds or solid solutions between known ones. A prime method to characterize the reaction products is powder diffraction because many solid-state reactions will produce polycrystalline molds or powders. Powder diffraction aids in the identification of known phases in the mixture. If a pattern is found that is not known in the diffraction data libraries, an attempt can be made to index the pattern. The characterization of a material's properties is typically easier for a product with crystalline structures. | 1 | Solid-state chemistry |
Using the MagPen (a Nano3D Biosciences, Inc. product), organized 3D co-cultures similar to native tissue architecture can be rapidly created. Endothelial cells (PEC), smooth muscle cells (SMC), fibroblasts (PF), and epithelial cells (EpiC) cultured with the Bio-Assembler can be sequentially layered in a drag-and-drop manner to create bronchioles that maintain phenotype and induce extracellular matrix formation. | 0 | Colloidal Chemistry |
The perturbed γ-γ angular correlation, PAC for short or PAC-Spectroscopy, is a method of nuclear solid-state physics with which magnetic and electric fields in crystal structures can be measured. In doing so, electrical field gradients and the Larmor frequency in magnetic fields as well as dynamic effects are determined. With this very sensitive method, which requires only about 10–1000 billion atoms of a radioactive isotope per measurement, material properties in the local structure, phase transitions, magnetism and diffusion can be investigated. The PAC method is related to nuclear magnetic resonance and the Mössbauer effect, but shows no signal attenuation at very high temperatures.
Today only the time-differential perturbed angular correlation (TDPAC) is used. | 1 | Solid-state chemistry |
Solid-state chemistry, also sometimes referred as materials chemistry, is the study of the synthesis, structure, and properties of solid phase materials. It therefore has a strong overlap with solid-state physics, mineralogy, crystallography, ceramics, metallurgy, thermodynamics, materials science and electronics with a focus on the synthesis of novel materials and their characterization. A diverse range of synthetic techniques, such as the ceramic method and chemical vapour depostion, make solid-state materials. Solids can be classified as crystalline or amorphous on basis of the nature of order present in the arrangement of their constituent particles. Their elemental compositions, microstructures, and physical properties can be characterized through a variety of analytical methods. | 1 | Solid-state chemistry |
Kaner was an adjunct professor at the Royal Melbourne Institute of Technology in Australia in 2010. He was the Eka-Granules Lecturer at the University of Tasmania, and was a visiting professor at the University of Wollongong. He is an associate editor of the Materials Research Bulletin. | 1 | Solid-state chemistry |
For metallic materials, their optical properties arise from the collective excitation of conduction electrons. The coherent oscillations of electrons under electromagnetic radiation along with associated oscillations of the electromagnetic field are called surface plasmon resonances. The excitation wavelength and frequency of the plasmon resonances provide information on the particle's size, shape, composition, and local optical environment.
For non-metallic materials or semiconductors, they can be characterized by their band structure. It contains a band gap that represents the minimum energy difference between the top of the valence band and the bottom of the conduction band. The band gap can be determined using Ultraviolet-visible spectroscopy to predict the photochemical properties of the semiconductors. | 1 | Solid-state chemistry |
Among his honors are: the 2019 Gregori Aminoff Prize (Royal Swedish Academy); the Bernal Distinguished Lecturer, University of Limerick, 2017; the World Class Professorship, KAIST, Korea, 2013; Newcomb Cleveland Prize from the American Association for the Advancement of Science in 2007; Regents' Professor, Arizona State University 1994; and D. Sc. “for excellence in published research” University of Bristol, 1976. | 1 | Solid-state chemistry |
Calcium hexaboride (sometimes calcium boride) is a compound of calcium and boron with the chemical formula CaB. It is an important material due to its high electrical conductivity , hardness, chemical stability, and melting point. It is a black, lustrous, chemically inert powder with a low density. It has the cubic structure typical for metal hexaborides, with octahedral units of 6 boron atoms combined with calcium atoms. CaB and lanthanum-doped CaB both show weak ferromagnetic properties, which is a remarkable fact because calcium and boron are neither magnetic, nor have inner 3d or 4f electronic shells, which are usually required for ferromagnetism. | 1 | Solid-state chemistry |
Sodium ethyl xanthate can be identified through optical absorption peaks in the infrared (1179, 1160, 1115, 1085 cm) and ultraviolet (300 nm) ranges. There are at least six chemical detection methods:
#Iodometric method relies on oxidation to dixanthogen by iodine, with the product detected with a starch indicator. This method is however is not selective and suffers from interferences with other sulfur-containing chemicals.
#Xanthate can be reacted with a copper sulfate or copper tartrate resulting in a copper xanthate residue which is detected with iodine. This method has an advantage of being is insensitive to sulfite, thiosulfate and carbonate impurities.
#In the acid-base detection method, a dilute aqueous xanthate solution is reacted with a copious amount of 0.01 M hydrochloric acid yielding carbon disulfide and alcohol, which are evaluated. The excess acid and impurities are removed through filtering and titration.
#In the argentometric method, sodium ethyl xanthate is reacted with silver nitrate in a dilute solution. The resulted silver xanthate is detected with 10% aqueous solution of iron nitrate. The drawbacks of this method are high cost of silver and blackening of silver xanthate by silver nitrate that reduces the detection accuracy.
#In the mercurimetric method, xanthate is dissolved in 40% aqueous solution of dimethylamine, followed by heating and titration with o-hydroxymercuribenzoate. The product is detected with dithiofluorescein.
#Perchloric acid method involves dissolution of xanthate in water-free acetic acid. The product is titrated with perchloric acid and detected with crystal violet.
Sodium ethyl xanthate can also be quantified using gravimetry, by weighing the lead xanthate residue obtained after reacting SEX with 10% solution of lead nitrate. There are also several electrochemical detection methods, which can be combined with some of the above chemical techniques. | 1 | Solid-state chemistry |
Methods for the polymerization of polyaniline nanofibers seen in literature primarily include [redox|chemical oxidative] polymerization, interfacial synthesis, and "rapid mixing" methods. Other less common methods include nanofiber seeding, electrosynthesis, electrospinning, and preforming polymerization in dilute aniline solutions. | 0 | Colloidal Chemistry |
There are two suggested mechanisms behind physical hydrogel formation, the first one being the gelation of nanofibrous peptide assemblies, usually observed for oligopeptide precursors. The precursors self-assemble into fibers, tapes, tubes, or ribbons that entangle to form non-covalent cross-links. The second mechanism involves non-covalent interactions of cross-linked domains that are separated by water-soluble linkers, and this is usually observed in longer multi-domain structures. Tuning of the supramolecular interactions to produce a self-supporting network that does not precipitate, and is also able to immobilize water which is vital for to gel formation. Most oligopeptide hydrogels have a β-sheet structure, and assemble to form fibers, although α-helical peptides have also been reported. The typical mechanism of gelation involves the oligopeptide precursors self-assemble into fibers that become elongated, and entangle to form cross-linked gels.
One notable method of initiating a polymerization fuving involves the use of light as a stimulus. In this method, photoinitiators, compounds that cleave from the absorption of photons, are added to the precursor solution which will become the hydrogel. When the precursor solution is exposed to a concentrated source of light, usually ultraviolet irradiation, the photoinitiators will cleave and form free radicals, which will begin a polymerization reaction that forms crosslinks between polymer strands. This reaction will cease if the light source is removed, allowing the amount of crosslinks formed in the hydrogel to be controlled. The properties of a hydrogel are highly dependent on the type and quantity of its crosslinks, making photopolymerization a popular choice for fine-tuning hydrogels. This technique has seen considerable use in cell and tissue engineering applications due to the ability to inject or mold a precursor solution loaded with cells into a wound site, then solidify it in situ.
Physically crosslinked hydrogels can be prepared by different methods depending on the nature of the crosslink involved. Polyvinyl alcohol hydrogels are usually produced by the freeze-thawed technique. In this, the solution is frozen for a few hours, then thawed at room temperature, and the cycle is repeated until a strong and stable hydrogel is formed. Alginate hydrogels are formed by ionic interactions between alginate and double-charged cations. A salt, usually calcium chloride, is dissolved into an aqueous sodium alginate solution, that causes the calcium ions to create ionic bonds between alginate chains. Gelatin hydrogels are formed by temperature change. A water solution of gelatin forms an hydrogel at temperatures below 37–35 °C, as Van der Waals interactions between collagen fibers become stronger than thermal molecular vibrations. | 0 | Colloidal Chemistry |
Nanocomposite hydrogels are tough, and can withstand stretching, bending, knotting, crushing, and other modifications. | 0 | Colloidal Chemistry |
Linda Faye Nazar is a Senior Canada Research Chair in Solid State Materials and Distinguished Research Professor of Chemistry at the University of Waterloo. She develops materials for electrochemical energy storage and conversion. Nazar demonstrated that interwoven composites could be used to improve the energy density of lithium–sulphur batteries. She was awarded the 2019 Chemical Institute of Canada Medal. | 1 | Solid-state chemistry |
The calculation made for the trap depth reduction is a one-dimensional calculation, resulting in an overestimation of the effective barrier lowering.
In fact, only in the direction of the external electric field the potential well height is lowered as much estimated accordingly to the Poole-Frenkel expression. More accurate calculation, performed by Hartke making an average of the electron emission probabilities with respect to any direction, shows that the growth of the free carriers concentration is about an order of magnitude less than that predicted by Poole-Frenkel equation.
The Hartke equation is equivalent to
where
From a theoretical point of view, Hartke's expression has to be preferred to Poole-Frenkel equation on the grounds that the threedimensionality of the problem of the trap barrier lowering is considered.
Additional three-dimensional models have been developed, differing by the treatment they do of the emission process in the upwind direction.
Ieda, Sawa, and Kato, for example, have proposed a model that includes the barrier variation in directions both forward and opposite to the electric field. | 1 | Solid-state chemistry |
Selenosulfides have been prepared by the reaction of selenyl halides with thiols:
The equilibrium between diselenides and disulfides lies on the left:
:RSeSeR + RSSR 2 RSeSR'
Because of the facility of this equilibrium, many of the best characterized examples of selenosulfides are cyclic, whereby S-Se bonds are stabilized intramolecularly. One example is the 1,8-selenosulfide of naphthalene. The selenium-sulfur bond length is about 220 picometers, the average of a typical S-S and Se-Se bond. | 1 | Solid-state chemistry |
Surface modification of materials has often led to new and improved properties. Corrosion inhibition, polymer adhesion and nucleation, preparation of organic superconductor/insulator/high-T superconductor trilayer structures, and the fabrication of metal/insulator/superconductor tunnel junctions have been developed using surface-modified YBCO.
These molecular layered materials are synthesized using cyclic voltammetry. Thus far, YBCO layered with alkylamines, arylamines, and thiols have been produced with varying stability of the molecular layer. It has been proposed that amines act as Lewis bases and bind to Lewis acidic Cu surface sites in YBaCuO to form stable coordination bonds. | 1 | Solid-state chemistry |
The objective of acoustic foam is to improve or change a room's sound qualities by controlling residual sound through absorption. This purpose requires strategic placement of acoustic foam panels on walls, ceilings, floors and other surfaces. Proper placement can help effectively manage resonance within the room and help give the room the desired sonic qualities. | 0 | Colloidal Chemistry |
A foam is said to be stochastic when the porosity distribution is random. Most foams are stochastic because of the method of manufacture:
* Foaming of liquid or solid (powder) metal
* Vapor deposition (CVD on a random matrix )
* Direct or indirect random casting of a mold containing beads or matrix | 0 | Colloidal Chemistry |
Syntactic foams are composite materials synthesized by filling a metal, polymer, cementitious or ceramic matrix with hollow spheres called microballoons or cenospheres or non-hollow spheres (e.g. perlite) as aggregates. In this context, "syntactic" means "put together." The presence of hollow particles results in lower density, higher specific strength (strength divided by density), lower coefficient of thermal expansion, and, in some cases, radar or sonar transparency. | 0 | Colloidal Chemistry |
The discharge is generally dumped back into the sea, through an underwater outfall or coastal release, due to its lower energy and economic cost compared to other discharge methods. Due to its increase in salinity, the discharge has a greater density compared to the surrounding seawater. Therefore, when the discharge reaches the sea, it can form a saline plume that can tends to follow the bathymetric line of the bottom until it is completely diluted. The distribution of the salt plume may depend on different factors, such as the production capacity of the plant, the discharge method, the oceanographic and environmental conditions of the discharge point, among others. | 1 | Solid-state chemistry |
In a now-concluded project, Girolami studied the chemistry and photophysics of bis(porphyrinate) metal sandwich complexes in collaboration with Illinois Professor of Chemistry Kenneth S. Suslick. These complexes were proposed to mimic the conversion of light to chemical energy in photosynthesis. Girolami's group synthesized bis(porphyrin) complexes of thorium, uranium, zirconium, and hafnium, and showed that these complexes displayed photophysical properties similar to those of the “special pair”, a chlorophyll dimer present in the photosystem I reaction center. | 1 | Solid-state chemistry |
By increasing order of stability:
* Iron(II) sulfide, FeS
* Greigite, FeS (cubic)
* Pyrrhotite, FeS (where x = 0 to 0.2) (monoclinic or hexagonal)
* Troilite, FeS, the endmember of pyrrhotite (hexagonal)
* Mackinawite, FeS (where x = 0 to 0.1) (tetragonal)
* Marcasite, orthorhombic FeS
* Pyrite, cubic FeS (fool's gold)
* Arsenopyrite (mispickel), FeAsS, or Fe(As-S), Fe(III) mixed arseno-sulfide (monoclinic) | 1 | Solid-state chemistry |
In materials science (specifically crystallography), cocrystals are "solids that are crystalline, single-phase materials composed of two or more different molecular or ionic compounds generally in a stoichiometric ratio which are neither solvates nor simple salts." A broader definition is that cocrystals "consist of two or more components that form a unique crystalline structure having unique properties." Several subclassifications of cocrystals exist.
Cocrystals can encompass many types of compounds, including hydrates, solvates and clathrates, which represent the basic principle of host–guest chemistry. Hundreds of examples of cocrystallization are reported annually. | 1 | Solid-state chemistry |
Particle agglomeration refers to the formation of assemblages in a suspension and represents a mechanism leading to the functional destabilization of colloidal systems. During this process, particles dispersed in the liquid phase stick to each other, and spontaneously form irregular particle assemblages, flocs, or agglomerates. This phenomenon is also referred to as coagulation or flocculation and such a suspension is also called unstable. Particle agglomeration can be induced by adding salts or other chemicals referred to as coagulant or flocculant.
Particle agglomeration can be a reversible or irreversible process. Particle agglomerates defined as "hard agglomerates" are more difficult to redisperse to the initial single particles. In the course of agglomeration, the agglomerates will grow in size, and as a consequence they may settle to the bottom of the container, which is referred to as sedimentation. Alternatively, a colloidal gel may form in concentrated suspensions which changes its rheological properties. The reverse process whereby particle agglomerates are re-dispersed as individual particles, referred to as peptization, hardly occurs spontaneously, but may occur under stirring or shear.
Colloidal particles may also remain dispersed in liquids for long periods of time (days to years). This phenomenon is referred to as colloidal stability and such a suspension is said to be functionally stable. Stable suspensions are often obtained at low salt concentrations or by addition of chemicals referred to as stabilizers or stabilizing agents. The stability of particles, colloidal or otherwise, is most commonly evaluated in terms of zeta potential. This parameter provides a readily quantifiable measure of interparticle repulsion, which is the key inhibitor of particle aggregation.
Similar agglomeration processes occur in other dispersed systems too. In emulsions, they may also be coupled to droplet coalescence, and not only lead to sedimentation but also to creaming. In aerosols, airborne particles may equally aggregate and form larger clusters (e.g., soot). | 0 | Colloidal Chemistry |
In recent physics literature, a large majority of the electronic structures and band plots are calculated using density-functional theory (DFT), which is not a model but rather a theory, i.e., a microscopic first-principles theory of condensed matter physics that tries to cope with the electron-electron many-body problem via the introduction of an exchange-correlation term in the functional of the electronic density. DFT-calculated bands are in many cases found to be in agreement with experimentally measured bands, for example by angle-resolved photoemission spectroscopy (ARPES). In particular, the band shape is typically well reproduced by DFT. But there are also systematic errors in DFT bands when compared to experiment results. In particular, DFT seems to systematically underestimate by about 30-40% the band gap in insulators and semiconductors.
It is commonly believed that DFT is a theory to predict ground state properties of a system only (e.g. the total energy, the atomic structure, etc.), and that excited state properties cannot be determined by DFT. This is a misconception. In principle, DFT can determine any property (ground state or excited state) of a system given a functional that maps the ground state density to that property. This is the essence of the Hohenberg–Kohn theorem. In practice, however, no known functional exists that maps the ground state density to excitation energies of electrons within a material. Thus, what in the literature is quoted as a DFT band plot is a representation of the DFT Kohn–Sham energies, i.e., the energies of a fictive non-interacting system, the Kohn–Sham system, which has no physical interpretation at all. The Kohn–Sham electronic structure must not be confused with the real, quasiparticle electronic structure of a system, and there is no Koopmans' theorem holding for Kohn–Sham energies, as there is for Hartree–Fock energies, which can be truly considered as an approximation for quasiparticle energies. Hence, in principle, Kohn–Sham based DFT is not a band theory, i.e., not a theory suitable for calculating bands and band-plots. In principle time-dependent DFT can be used to calculate the true band structure although in practice this is often difficult. A popular approach is the use of hybrid functionals, which incorporate a portion of Hartree–Fock exact exchange; this produces a substantial improvement in predicted bandgaps of semiconductors, but is less reliable for metals and wide-bandgap materials. | 1 | Solid-state chemistry |
Compliance is the ability of lungs and thorax to expand.
Lung compliance is defined as the volume change per unit of pressure change across the lung. Measurements of lung volume obtained during the controlled inflation/deflation of a normal lung show that the volumes obtained during deflation exceed those during inflation, at a given pressure. This difference in inflation and deflation volumes at a given pressure is called hysteresis and is due to the air-water surface tension that occurs at the beginning of inflation. However, surfactant decreases the alveolar surface tension, as seen in cases of premature infants with infant respiratory distress syndrome. The normal surface tension for water is 70 dyn/cm (70 mN/m) and in the lungs, it is 25 dyn/cm (25 mN/m); however, at the end of the expiration, compressed surfactant phospholipid molecules decrease the surface tension to very low, near-zero levels. Pulmonary surfactant thus greatly reduces surface tension, increasing compliance allowing the lung to inflate much more easily, thereby reducing the work of breathing. It reduces the pressure difference needed to allow the lung to inflate. The lung's compliance, and ventilation decrease when lung tissue becomes diseased and fibrotic. | 0 | Colloidal Chemistry |
Nigari is produced from seawater after first removing sodium chloride. It contains mostly magnesium chloride, smaller amounts of magnesium sulfate (Epsom salt), potassium chloride, calcium chloride, and trace amounts of other naturally occurring salts.
Nigari was the first coagulant used to make tofu in Japan. It is still used today because tofu made using bittern preserves the original flavor of the soybeans used to make it. Bittern causes rapid coagulation which influences the quality of the tofu. Alternatively calcium sulfate, calcium chloride or other substances are also used. | 1 | Solid-state chemistry |
Upon introducing surfactants (or any surface active materials) into a system, they will initially partition into the interface, reducing the system free energy by:
# lowering the energy of the interface (calculated as area times surface tension), and
# removing the hydrophobic parts of the surfactant from contact with water.
Subsequently, when the surface coverage by the surfactants increases, the surface free energy (surface tension) decreases and the surfactants start aggregating into micelles, thus again decreasing the system's free energy by decreasing the contact area of hydrophobic parts of the surfactant with water. Upon reaching CMC, any further addition of surfactants will just increase the number of micelles (in the ideal case).
According to one well-known definition, CMC is the total concentration of surfactants under the conditions:
:if C = CMC, (d/dC) = 0
: = A[C] + B[C]; i.e., in words C = [single surfactant ion] , C = [micelles] and A and B are proportionality constants
:C = C + NC; i.e., N = represents the number of detergent ions per micelle | 0 | Colloidal Chemistry |
It was mainly through the work of Nikolai Semenovich Kurnakov and his students that Berthollets opposition to Prousts law was shown to have merit for many solid compounds. Kurnakov divided non-stoichiometric compounds into berthollides and daltonides depending on whether their properties showed monotonic behavior with respect to composition or not. The term berthollide was accepted by IUPAC in 1960. The names come from Claude Louis Berthollet and John Dalton, respectively, who in the 19th century advocated rival theories of the composition of substances. Although Dalton "won" for the most part, it was later recognized that the law of definite proportions had important exceptions. | 1 | Solid-state chemistry |
Caliche forms where annual precipitation is less than per year and the mean annual temperature exceeds . Higher rainfall leaches excess calcium completely from the soil, while in very arid climates, rainfall is inadequate to leach calcium at all and only thin surface layers of calcite are formed. Plant roots play an important role in caliche formation, by releasing large amounts of carbon dioxide into the A horizon of the soil. Carbon dioxide levels here can exceed 15 times normal atmospheric values. This allows calcium carbonate to dissolve as bicarbonate. Where rainfall is adequate but not excessive, the calcium bicarbonate is carried down into the B horizon. Here there is less biological activity, the carbon dioxide level is much lower, and the bicarbonate reverts to insoluble carbonate. A mixture of calcium carbonate and clay particles accumulates, first forming grains, then small clumps, then a discernible layer, and finally, a thicker, solid bed.
However, caliche also forms in other ways. It can form when water rises through capillary action. In an arid region, rainwater sinks into the ground very quickly. Later, as the surface dries out, the water below the surface rises, carrying up dissolved minerals from lower layers. These precipitate as water evaporates and carbon dioxide is lost. This water movement forms a caliche that is close to the surface. Caliche can also form on outcrops of porous rocks or in rock fissures where water is trapped and evaporates. In general, caliche deposition is a slow process, requiring several thousand years.
The depth of the caliche layer is sensitive to mean annual rainfall. When rainfall is around per year, the caliche layer will be as shallow as . When rainfall is around per year, the caliche layer will be at a depth of around . The caliche layer disappears complete in temperate climates if annual rainfall exceeds .
The source of the calcium in caliche may be the underlying bedrock, but caliche can form even over bedrock that is not rich in calcium. This is attributed to calcium brought in as aeolian dust. | 1 | Solid-state chemistry |
SP-B is encoded by SFTPB, a single, 11425 nucleotide long gene on chromosome 2. Mutations in this gene are the basis for several of the lung conditions mentioned above. Both frameshift mutations and several single nucleotide polymorphisms (SNPs) have been found correlated to a variety of lung conditions. A frame shift mutation responsible for congenital alveolar proteinosis (CAP) was identified by Kattan et al. Many SNP's have been identified in relation to lung conditions. They have been correlated to severe influenza, neonatal respiratory distress syndrome, mechanical ventilation necessity, and more. | 0 | Colloidal Chemistry |
Band theory is only an approximation to the quantum state of a solid, which applies to solids consisting of many identical atoms or molecules bonded together. These are the assumptions necessary for band theory to be valid:
* Infinite-size system: For the bands to be continuous, the piece of material must consist of a large number of atoms. Since a macroscopic piece of material contains on the order of 10 atoms, this is not a serious restriction; band theory even applies to microscopic-sized transistors in integrated circuits. With modifications, the concept of band structure can also be extended to systems which are only "large" along some dimensions, such as two-dimensional electron systems.
* Homogeneous system: Band structure is an intrinsic property of a material, which assumes that the material is homogeneous. Practically, this means that the chemical makeup of the material must be uniform throughout the piece.
* Non-interactivity: The band structure describes "single electron states". The existence of these states assumes that the electrons travel in a static potential without dynamically interacting with lattice vibrations, other electrons, photons, etc.
The above assumptions are broken in a number of important practical situations, and the use of band structure requires one to keep a close check on the limitations of band theory:
* Inhomogeneities and interfaces: Near surfaces, junctions, and other inhomogeneities, the bulk band structure is disrupted. Not only are there local small-scale disruptions (e.g., surface states or dopant states inside the band gap), but also local charge imbalances. These charge imbalances have electrostatic effects that extend deeply into semiconductors, insulators, and the vacuum (see doping, band bending).
* Along the same lines, most electronic effects (capacitance, electrical conductance, electric-field screening) involve the physics of electrons passing through surfaces and/or near interfaces. The full description of these effects, in a band structure picture, requires at least a rudimentary model of electron-electron interactions (see space charge, band bending).
* Small systems: For systems which are small along every dimension (e.g., a small molecule or a quantum dot), there is no continuous band structure. The crossover between small and large dimensions is the realm of mesoscopic physics.
* Strongly correlated materials (for example, Mott insulators) simply cannot be understood in terms of single-electron states. The electronic band structures of these materials are poorly defined (or at least, not uniquely defined) and may not provide useful information about their physical state. | 1 | Solid-state chemistry |
Milton Kerker (September 25, 1920 — May 2, 2016) was an American physical chemist and former professor at department of chemistry at Clarkson University. He is best known for his work on aerosol, interface and colloid science, as well as for pioneering surface-enhanced Raman spectroscopy. Kerker effect in optics is named after him. | 0 | Colloidal Chemistry |
Expanded polyethylene (aka EPE foam) refers to foams made from polyethylene. Typically it is made from expanded pellets (EPE bead) made with use of a blowing agent, followed by expansion into a mold in a steam chest - the process is similar to that used to make expanded polystyrene foam. | 0 | Colloidal Chemistry |
In 1913 the structure of sodium chloride was determined by William Henry Bragg and William Lawrence Bragg. This revealed that there were six equidistant nearest-neighbours for each atom, demonstrating that the constituents were not arranged in molecules or finite aggregates, but instead as a network with long-range crystalline order. Many other inorganic compounds were also found to have similar structural features. These compounds were soon described as being constituted of ions rather than neutral atoms, but proof of this hypothesis was not found until the mid-1920s, when X-ray reflection experiments (which detect the density of electrons), were performed.
Principal contributors to the development of a theoretical treatment of ionic crystal structures were Max Born, Fritz Haber, Alfred Landé, Erwin Madelung, Paul Peter Ewald, and Kazimierz Fajans. Born predicted crystal energies based on the assumption of ionic constituents, which showed good correspondence to thermochemical measurements, further supporting the assumption. | 1 | Solid-state chemistry |
Janus-type material is used as a surfactant-like heterogeneous catalyst for the synthesis of adipic acid. | 0 | Colloidal Chemistry |
The effect of the interfacial layer is clearly seen in the interactions between nanoparticles. These interactions can be modelled using the DLVO theory. Classically this theory states that the potential of a particle is the sum of the electrostatic and van der Waals interaction. This is theory has proven to be very accurate for almost all Colloidal particles, but cannot describe all the interactions measured for nanoparticles. Therefore this theory has been extended with the so called non-DLVO terms. In this extension the hydration force, hydrofobic force, steric force and bridging force are also considered, resulting in a total potential as follows:
These last terms are mostly determined by the interfacial layer as this is the outermost part of the particle, thereby determining the surface interactions. For example, the bridging term only plays a role when the molecules in the interfacial layer tend to polymerize.
In the case of nanoparticles made of a crystal, quantum mechanical interactions would be expected, but due to the interfacial layer the cores cannot get close enough to each other, and therefore these interactions are neglectable.
An illustrative limit-case are non-charged semiconducting quantum dots (QD) in an ideal fluid. Due to the ideal fluid there is no difference between the QD–QD interaction and the QD–fluid interaction. For only the VDW interaction is of importance in the interaction between the interfacial layers, which are made of the superfluid, and other interfacial layers or the solvent. This means there is no attraction between the particles, so they can be accurately described using the Hard Sphere model. | 0 | Colloidal Chemistry |
Magnesium diboride was synthesized and its structure confirmed in 1953. The simplest synthesis involves high temperature reaction between boron and magnesium powders. Formation begins at 650 °C; however, since magnesium metal melts at 652 °C, the reaction may involve diffusion of magnesium vapor across boron grain boundaries. At conventional reaction temperatures, sintering is minimal, although grain recrystallization is sufficient for Josephson quantum tunnelling between grains.
Superconducting magnesium diboride wire can be produced through the powder-in-tube (PIT) ex situ and in situ processes. In the in situ variant, a mixture of boron and magnesium is reduced in diameter by conventional wire drawing. The wire is then heated to the reaction temperature to form MgB. In the ex situ variant, the tube is filled with MgB powder, reduced in diameter, and sintered at 800 to 1000 °C. In both cases, later hot isostatic pressing at approximately 950 °C further improves the properties.
An alternative technique, disclosed in 2003, employs reactive liquid infiltration of magnesium inside a granular preform of boron powders and was called Mg-RLI technique. The method allowed the manufacture of both high density (more than 90% of the theoretical density for MgB) bulk materials and special hollow fibers. This method is equivalent to similar melt growth based methods such as the Infiltration and Growth Processing method used to fabricate bulk YBCO superconductors where the non-superconducting YBaCuO is used as granular preform inside which YBCO based liquid phases are infiltrated to make superconductive YBCO bulk. This method has been copied and adapted for MgB and rebranded as Reactive Mg Liquid Infiltration. The process of Reactive Mg Liquid Infiltration in a boron preform to obtain MgB has been a subject of patent applications by the Italian company Edison S.p.A.
Hybrid physical–chemical vapor deposition (HPCVD) has been the most effective technique for depositing magnesium diboride (MgB) thin films. The surfaces of MgB films deposited by other technologies are usually rough and non-stoichiometric. In contrast, the HPCVD system can grow high-quality in situ pure MgB films with smooth surfaces, which are required to make reproducible uniform Josephson junctions, the fundamental element of superconducting circuits. | 1 | Solid-state chemistry |
Cubosomes are discrete, sub-micron, nanostructured particles of the bicontinuous cubic liquid crystalline phase. The term "bicontinuous" refers to two distinct hydrophilic regions separated by the bilayer. Bicontinuous cubic crystalline materials have been an active research topic because their structure lends itself well to controlled-release applications.
Cubosomes are liquid crystalline nano-structures formed from the cubic phase of lipids, such as monooleate, or any other amphiphilic macromolecules with the unique property to be dispersed into particles. Nano-vehicles are generated from a self-assembled lipid mixture and studied by means of high-resolution cryogenic transmission electron microscope (cryo-TEM). These structures have been observed to naturally occur in mitochondrial membranes and in stressed cells.
Cubosomes are formed at controlled temperatures into lipid bi-layer twisted into three dimension with minimal surface forming a tightly packed structure with bicontinuous domains of water and lipid.
There are three different proposed phases that these cubic structures can be in: the P-surface, G-surface and D-surface for primitive, gyroid and diamond structures respectively. This variation in structure allows for cubosomes to be the ultimate drug delivery system due to its ability to maintain the structural integrity of the ingredients that it carries. The uses of cubosomes are still being researched but they range from systems for efficient drug delivery into specific body systems to stabilizing and producing palladium nanoparticles. | 0 | Colloidal Chemistry |
Many properties of nanoparticles, notably stability, solubility, and chemical or biological activity, can be radically altered by coating them with various substances — a process called functionalization. Functionalized nanomaterial-based catalysts can be used for catalysis of many known organic reactions.
For example, suspensions of graphene particles can be stabilized by functionalization with gallic acid groups.
For biological applications, the surface coating should be polar to give high aqueous solubility and prevent nanoparticle aggregation. In serum or on the cell surface, highly charged coatings promote non-specific binding, whereas polyethylene glycol linked to terminal hydroxyl or methoxy groups repel non-specific interactions. By the immobilization of thiol groups on the surface of nanoparticles or by coating them with thiomers high (muco)adhesive and cellular uptake enhancing properties can be introduced.
Nanoparticles can be linked to biological molecules that can act as address tags, directing them to specific sites within the body specific organelles within the cell, or causing them to follow specifically the movement of individual protein or RNA molecules in living cells. Common address tags are monoclonal antibodies, aptamers, streptavidin, or peptides. These targeting agents should ideally be covalently linked to the nanoparticle and should be present in a controlled number per nanoparticle. Multivalent nanoparticles, bearing multiple targeting groups, can cluster receptors, which can activate cellular signaling pathways, and give stronger anchoring. Monovalent nanoparticles, bearing a single binding site, avoid clustering and so are preferable for tracking the behavior of individual proteins.
It has been shown that catalytic activity and sintering rates of a functionalized nanoparticle catalyst is correlated to nanoparticles' number density
Coatings that mimic those of red blood cells can help nanoparticles evade the immune system. | 0 | Colloidal Chemistry |
The Schrödinger equation was published in 1926. The first person to apply the Schrödinger equation to a problem which involved tunneling between two classically allowed regions through a potential barrier was Friedrich Hund in a series of articles published in 1927. He studied the solutions of a double-well potential and discussed molecular spectra. Leonid Mandelstam and Mikhail Leontovich discovered tunneling independently and published their results in 1928.
In 1927, Lothar Nordheim, assisted by Ralph Fowler, published a paper which discussed thermionic emission and reflection of electrons from metals. He assumed a surface potential barrier which confines the electrons within the metal and showed that the electrons have a finite probability of tunneling through or reflecting from the surface barrier when their energies are close to the barrier energy. Classically, the electron would either transmit or reflect with 100% certainty, depending on its energy. In 1928 J. Robert Oppenheimer published two papers on field emission, i.e. the emission of electrons induced by strong electric fields. Nordheim and Fowler simplified Oppenheimer's derivation and found values for the emitted currents and work functions which agreed with experiments.
A great success of the tunnelling theory was the mathematical explanation for alpha decay, which was developed in 1928 by George Gamow and independently by Ronald Gurney and Edward Condon. The latter researchers simultaneously solved the Schrödinger equation for a model nuclear potential and derived a relationship between the half-life of the particle and the energy of emission that depended directly on the mathematical probability of tunneling. All three researchers were familiar with the works on field emission, and Gamow was aware of Mandelstam and Leontovich's findings.
In the early days of quantum theory, the term tunnel effect was not used, and the effect was instead referred to as penetration of, or leaking through, a barrier. The German term wellenmechanische Tunneleffect was used in 1931 by Walter Schottky. The English term tunnel effect entered the language in 1932 when it was used by Yakov Frenkel in his textbook.
In 1957 Leo Esaki demonstrated tunneling of electrons over a few nanometer wide barrier in a semiconductor structure and developed a diode based on tunnel effect. In 1960, following Esaki's work, Ivar Giaever showed experimentally that tunnelling also took place in superconductors. The tunnelling spectrum gave direct evidence of the superconducting energy gap. In 1962, Brian Josephson predicted the tunneling of superconducting Cooper pairs. Esaki, Giaever and Josephson shared the 1973 Nobel Prize in Physics for their works on quantum tunneling in solids.
In 1981, Gerd Binnig and Heinrich Rohrer developed a new type of microscope, called scanning tunneling microscope, which is based on tunnelling and is used for imaging surfaces at the atomic level. Binnig and Rohrer were awarded the Nobel Prize in Physics in 1986 for their discovery. | 1 | Solid-state chemistry |
Surfactants are chemical compounds that decrease the surface tension or interfacial tension between two liquids, a liquid and a gas, or a liquid and a solid. The word "surfactant" is a blend of surface-active agent, coined . As they consist of a water-repellent and a water-attracting part, they enable water and oil to mix; they can form foam and facilitate the detachment of dirt.
Surfactants are among the most widespread and commercially important chemicals. Private households as well as many industries use them in large quantities as detergents and cleaning agents, but also for example as emulsifiers, wetting agents, foaming agents, antistatic additives, or dispersants.
Surfactants occur naturally in traditional plant-based detergents, e.g. horse chestnuts or soap nuts; they can also be found in the secretions of some caterpillars. Today the most commonly used surfactants, above all anionic linear alkylbenzene sulfates (LAS), are produced from petroleum products. However, surfactants are (again) increasingly produced in whole or in part from renewable biomass, like sugar, fatty alcohol from vegetable oils, by-products of biofuel production, or other biogenic material. | 0 | Colloidal Chemistry |
In addition to its use as a fertilizer, potassium chloride is important in many industrialized economies, where it is used in aluminium recycling, by the chloralkali industry to produce potassium hydroxide, in metal electroplating, oil-well drilling fluid, snow and ice melting, steel heat-treating, in medicine as a treatment for hypokalemia, and water softening. Potassium hydroxide is used for industrial water treatment and is the precursor of potassium carbonate, several forms of potassium phosphate, many other potassic chemicals, and soap manufacturing. Potassium carbonate is used to produce animal feed supplements, cement, fire extinguishers, food products, photographic chemicals, and textiles. It is also used in brewing beer, pharmaceutical preparations, and as a catalyst for synthetic rubber manufacturing. Also combined with silica sand to produce potassium silicate, sometimes known as waterglass, for use in paints and arc welding electrodes. These non-fertilizer uses have accounted for about 15% of annual potash consumption in the United States. | 1 | Solid-state chemistry |
Per- and polyfluoroalkyl substances (PFAS or PFASs) are a group of synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. The PubChem database lists more than 6 million unique compounds in this group. PFASs started being used in the mid-20th century to make fluoropolymer coatings and products that resist heat, oil, stains, grease, and water. They are used in a variety of products including waterproof clothing, furniture, adhesives, food packaging, heat-resistant non-stick cooking surfaces, and the insulation of electrical wire. They have played a key economic role for companies such as DuPont, 3M, and W. L. Gore & Associates that use them to produce widely known materials such as Teflon or Gore-Tex.
Only since the start of the 21st century has the environmental impact and toxicity to human and mammalian life been studied in depth. Many PFAS such as PFOS, PFOA are a concern because they do not break down via natural processes and are commonly described as persistent organic pollutants or "forever chemicals". They can also move through soils and contaminate drinking water sources and can build up (bioaccumulate) in fish and wildlife. Residues have been detected in humans and wildlife. Due to the large number of PFAS it is challenging to study and assess the potential human health and environmental risks; more research is necessary. According to the United States Environmental Protection Agency, exposure to some PFAS in the environment may be linked to harmful health effects in humans and animals. The International Agency for Research on Cancer (IARC) has classified PFOA as carcinogenic to humans and PFOS as possibly carcinogenic. According to the National Academies of Sciences, Engineering, and Medicine, PFAS exposure is linked to increased risk of dyslipidemia (abnormally high cholesterol), suboptimal antibody response, reduced infant and fetal growth, and higher rates of kidney cancer.
Health concerns related to PFASs have resulted in numerous litigations (see Timeline of events related to per- and polyfluoroalkyl substances). PFAS producers such as 3M, Chemours, DuPont and Corteva have reached billion dollar agreements to settle claims against them. The use of PFAS is regulated in several parts of the world, with some plans to phase them out entirely from products. | 0 | Colloidal Chemistry |
A “cuboct” cubic lattice of vertex connected octahedrons, similar to the perovskite mineral structure provides a regular polyhedral unit cell that satisfies Maxwell’s rigidity criterion and has a coordination number z of eight. The dependence of the relative density on the coordination number is small relative to the dependence on strut diameter. Winding the reinforcing fibers around the connection holes optimizes their load bearing capacity, while coupling them to struts which themselves retain uniaxial fiber orientation. | 0 | Colloidal Chemistry |
SP-B plays a critical role in the functioning of healthy lungs, and its absence inevitably leads to lung conditions, most common of which being acute respiratory distress syndrome (ARDS). Because of this, SP-B's function has been well researched, and has been found to exist in three parts. Beyond these three functions, it is worth noting that SP-B is also thought to have some anti-inflammatory function, though it is not well defined. | 0 | Colloidal Chemistry |
To date, Girolami's independent research career has encompassed five major themes: mechanistic studies of organometallic reactions such as the polymerization of alkenes and the activation of saturated alkanes, the chemical vapor deposition of thin films from designed molecular precursors, the construction and study of molecular analogs of the photosynthetic reaction center, actinide chemistry, and the synthesis of new molecule-based magnetic materials. His research approach emphasizes the synthesis of new inorganic and organometallic compounds and materials, investigations of their mechanisms of formation, and measurements and interpretations of their physical properties. | 1 | Solid-state chemistry |
A special class of closed-cell foams, known as syntactic foam, contains hollow particles embedded in a matrix material. The spheres can be made from several materials, including glass, ceramic, and polymers. The advantage of syntactic foams is that they have a very high strength-to-weight ratio, making them ideal materials for many applications, including deep-sea and space applications. One particular syntactic foam employs shape memory polymer as its matrix, enabling the foam to take on the characteristics of shape memory resins and composite materials; i.e., it has the ability to be reshaped repeatedly when heated above a certain temperature and cooled. Shape memory foams have many possible applications, such as dynamic structural support, flexible foam core, and expandable foam fill. | 0 | Colloidal Chemistry |
Taurates were first obtained by the Schotten-Baumann method which is the reaction of long-chain carboxylic acid chlorides with aqueous solutions of the sodium salt of N-methyltaurine.
The formation of (at least) equimolar amounts of sodium chloride is problematic, as they worsen the properties of surfactant mixtures with such taurates. The high salt content also makes the resulting taurates hygroscopic and corrosive. Another disadvantage of the Schotten-Baumann method is the hazardousness of the raw materials (such as phosphorus trichloride) and the intermediates (the acyl chlorides) and the accumulation of large amounts of waste materials, such as phosphonic acids. This synthesis pathway for taurates is therefore complicated and expensive. An advantage of the Schotten-Baumann method, however, is the very low content of free fatty acids in the end product. Taurates are also accessible by direct amidation of N-methyltaurine or its sodium salt with the corresponding fatty acid for 10 hours at 220 °C under nitrogen.
The excess fatty acid (added for a favorable equilibrium) usually remain in the product, which can interfere with some applications. The decomposition of N-methyltaurine already begins At temperatures above 200 °C and the resulting taurates darken and develop an unpleasant smell. Therefore, more recent variants of the direct amidation aim at gentler process conditions using suitable catalysts, such as sodium borohydride, boric acid or zinc oxide. | 0 | Colloidal Chemistry |
Living coral reefs are endangered and cannot be harvested without significant damage to the ecosystem, and because of this, coral calcium is harvested by grinding up above-ground limestone deposits that were once part of a coral reef. Calcium from coral sources needs to be refined to remove pollutants of the source environment. It is marketed as a dietary supplement, but its benefits over other calcium supplements are unproven and biologically unlikely, and several marketers have been found guilty of fraud and were ordered to pay $20.4 million and to refrain from making unsubstantiated claims in the future. Additionally, coral near Okinawa has absorbed relatively high amounts of lead and mercury, leading to concern that these unregulated supplements may be contaminated. Further, coral takes millennia to grow, leading to environmental concerns if harvesting of live coral becomes widespread. | 1 | Solid-state chemistry |
Although PFASs are not manufactured in Canada, they may be present in imported goods and products. In 2008, Canada prohibited the import, sale, or use of PFOS or PFOS-containing products, with some exceptions for products used in firefighting, the military, and some forms of ink and photo media.
Health Canada has published drinking water guidelines for maximum concentrations of PFOS and PFOA to protect the health of Canadians, including children, over a lifetime's exposure to these substances. The maximum allowable concentration for PFOS under the guidelines is 0.0002 milligrams per litre. The maximum allowable concentration for PFOA is 0.0006 milligrams per litre. | 0 | Colloidal Chemistry |
The chemical shift interaction can be used in conjunction with the dipolar interaction to determine the orientation of the dipolar interaction frame (principal axes system) with respect to the molecular frame (dipolar chemical shift spectroscopy). For some cases there are rules for the chemical shift interaction tensor orientation as for the C spin in ketones due to symmetry arguments (sp hybridisation). If the orientation of a dipolar interaction (between the spin of interest and e.g. another heteronucleus) is measured with respect to the chemical shift interaction coordinate system, these two pieces of information (chemical shift tensor/molecular orientation and the dipole tensor/chemical shift tensor orientation) combined give the orientation of the dipole tensor in the molecular frame. However, this method is only suitable for small molecules (or polymers with a small repetition unit like polyglycine) and it provides only selective (and usually intramolecular) structural information. | 1 | Solid-state chemistry |
Lipid molecules in the HII phase pack inversely to the packing observed in the hexagonal I phase described above. This phase has the polar head groups on the inside and the hydrophobic, hydrocarbon tails on the outside in solution. The packing ratio for this phase is larger than one, which is synonymous with an inverse cone packing.
Extended arrays of long tubes will form (as in the hexagonal I phase), but because of the way the polar head groups pack, the tubes take the shape of aqueous channels. These arrays can stack together like pipes. This way of packing may leave a finite hydrophobic surface in contact with water on the outside of the array. However, the otherwise energetically favorable packing apparently stabilizes this phase as a whole. It is also possible that an outer monolayer of lipid coats the surface of the collection of tubes to protect the hydrophobic surface from interaction with the aqueous phase.
It is suggested that this phase is formed by lipids in solution in order to compensate for the hydrophobic effect. The tight packing of the lipid head groups reduces their contact with the aqueous phase. This, in turn, reduces the amount of ordered, but unbound water molecules.
The most common lipids that form this phase include phosphatidylethanolamine (PE), when it has unsaturated hydrocarbon chains. Diphosphatidylglycerol (DPG, otherwise known as cardiolipin) in the presence of calcium is also capable of forming this phase. | 0 | Colloidal Chemistry |
* Boden und Bodenbildung Kolloidchemischer Betrachtung, 1918
* Anleitung zum quantitativischen agrikulturchemischen Praktikum, 1919 | 0 | Colloidal Chemistry |
* David W. Ward: [http://thesis.davidward.org Polaritonics: An Intermediate Regime between Electronics and Photonics], Ph.D. Thesis, Massachusetts Institute of Technology, 2005. This is the main reference for this article. | 1 | Solid-state chemistry |
Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive analysis of X-ray (EDX), UV-vis spectroscopy, and X-ray diffraction are used to characterize different aspects of nanoparticles. Both SEM and TEM can be used to visualize the location, size, and morphology of the nanoparticles, while UV-vis spectroscopy can be used to confirm the metallic nature, size and aggregation level. Energy dispersive analysis of X-ray is used to determine elemental composition, and X-ray diffraction is used to determine chemical composition and crystallographic structure. UV-Vis absorption peaks for silver, gold, and cadmium sulfide nanoparticles can vary depending on particle size: 25-50 nm silver particles peak ca. 415 nm, gold nanoparticles 30-40 nm peak ca. 450 nm, while a cadmium sulfide absorption edge ca. 450 is indicative of quantum size particles. Larger nanoparticle of each type will have UV-Vis absorption peaks or edges that shift to longer wavelengths while smaller nanoparticles will have UV-Vis absorption peaks or edges that shift to shorter wavelengths. | 0 | Colloidal Chemistry |
Jing Li is a professor at Rutgers University. She and her team are engaged in solid-state, inorganic and inorganic-organic hybrid materials research. Her current research focuses on designing and developing new materials for applications in the field of renewable and sustainable energy.
Li’s research has resulted in 15 patents (6 pending) and over 380 publications (articles, invited book chapters, feature and review papers), in high impact factor journals such as Nature Communications, the Journal of the American Chemical Society (JACS) and Angewandte Chemie International Edition. She was selected as a Highly Cited Researcher by Thomson Reuters in 2015 and 2016, and by Clarivate Analytics in 2019 and 2020. | 1 | Solid-state chemistry |
The depletion force is described as an entropic force because it is fundamentally a manifestation of the second law of thermodynamics, which states that a system tends to increase its entropy. The gain in translational entropy of the depletants, owing to the increased available volume, is much greater than the loss of entropy from flocculation of the colloids. The positive change in entropy lowers the Helmholtz free energy and causes colloidal flocculation to happen spontaneously. The system of colloids and depletants in a solution is modeled as a canonical ensemble of hard spheres for statistical determinations of thermodynamic quantities.
However, recent experiments and theoretical models found that depletion forces can be enthalpically driven. In these instances, the intricate balance of interactions between the solution components results in the net exclusion of cosolute from macromolecule. This exclusion results in an effective stabilization of the macromolecule self-association, which can be not only enthalpically dominated, but also entropically unfavorable. | 0 | Colloidal Chemistry |
Since the 1970s, forty years before the public health community, DuPont and 3M were aware that PFAS was “highly toxic when inhaled and moderately toxic when ingested.” Producers used several strategies to influence science and regulation – most notably, suppressing unfavorable research and distorting public discourse.
In 2018 White House staff and the EPA pressured the U.S. Agency for Toxic Substances and Disease Registry to suppress a study that showed PFASs to be even more dangerous than previously thought. | 0 | Colloidal Chemistry |
Quantum beats are observable in systems in which the total optical polarization is due to a finite number of discrete transition frequencies which are quantum mechanically coupled, e.g., by common ground or excited states.
Assuming for simplicity that all these transitions have the same dipole matrix element, after excitation with a short laser pulse at the optical polarization of the system evolves as
where the index labels the participating transitions.
A finite number of frequencies results in temporal modulations of the squared modulus of the polarization and thus of the intensity of the emitted electromagnetic field with time periods
For the case of just two frequencies the squared modulus of the polarization is proportional to
i.e., due to the interference of two contributions with the same amplitude but different frequencies, the polarization varies between a maximum and zero.
In semiconductors and semiconductor heterostructures, such as quantum wells, nonlinear optical quantum-beat spectroscopy has been widely used to investigate the temporal dynamics of excitonic resonances.
In particular, the consequences of many-body effects which depending on the excitation conditions may lead to, e.g., a coupling among different excitonic resonances via biexcitons and other Coulomb correlation contributions and to a decay of the coherent dynamics by scattering and dephasing processes, has been explored in many pump-probe and four-wave-mixing measurements.
The theoretical analysis of such experiments in semiconductors requires a treatment on the basis of quantum mechanical many-body theory as is provided by the SBEs with many-body correlations incorporated on an adequate level. | 1 | Solid-state chemistry |
Polaritonics is an intermediate regime between photonics and sub-microwave electronics (see Fig. 1). In this regime, signals are carried by an admixture of electromagnetic and lattice vibrational waves known as phonon-polaritons, rather than currents or photons. Since phonon-polaritons propagate with frequencies in the range of hundreds of gigahertz to several terahertz, polaritonics bridges the gap between electronics and photonics. A compelling motivation for polaritonics is the demand for high speed signal processing and linear and nonlinear terahertz spectroscopy. Polaritonics has distinct advantages over electronics, photonics, and traditional terahertz spectroscopy in that it offers the potential for a fully integrated platform that supports terahertz wave generation, guidance, manipulation, and readout in a single patterned material.
Polaritonics, like electronics and photonics, requires three elements: robust waveform generation, detection, and guidance and control. Without all three, polaritonics would be reduced to just phonon-polaritons, just as electronics and photonics would be reduced to just electromagnetic radiation. These three elements can be combined to enable device functionality similar to that in electronics and photonics. | 1 | Solid-state chemistry |
For hydrogels, their elasticity comes from the solid polymer matrix while the viscosity originates from the polymer network mobility and the water and other components that make up the aqueous phase. Viscoelastic properties of a hydrogel is highly dependent on the nature of the applied mechanical motion. Thus, the time dependence of these applied forces is extremely important for evaluating the viscoelasticity of the material.
Physical models for viscoelasticity attempt to capture the elastic and viscous material properties of a material. In an elastic material, the stress is proportional to the strain while in a viscous material, the stress is proportional to the strain rate. The Maxwell model is one developed mathematical model for linear viscoelastic response. In this model, viscoelasticity is modeled analogous to an electrical circuit with a Hookean spring, that represents the Young's modulus, and a Newtonian dashpot that represents the viscosity. A material that exhibit properties described in this model is a Maxwell material. Another physical model used is called the Kelvin-Voigt Model and a material that follow this model is called a Kelvin–Voigt material. In order to describe the time-dependent creep and stress-relaxation behavior of hydrogel, a variety of physical lumped parameter models can be used. These modeling methods vary greatly and are extremely complex, so the empirical Prony Series description is commonly used to describe the viscoelastic behavior in hydrogels.
In order to measure the time-dependent viscoelastic behavior of polymers dynamic mechanical analysis is often performed. Typically, in these measurements the one side of the hydrogel is subjected to a sinusoidal load in shear mode while the applied stress is measured with a stress transducer and the change in sample length is measured with a strain transducer. One notation used to model the sinusoidal response to the periodic stress or strain is:
in which G' is the real (elastic or storage) modulus, G" is the imaginary (viscous or loss) modulus. | 0 | Colloidal Chemistry |
Heat retention can be a disadvantage when used in mattresses and pillows, so in second-generation memory foam, companies began using open cell structure to improve breathability.
In 2006, the third generation of memory foam was introduced. Gel visco or gel memory foam consists of gel particles fused with visco foam to reduce trapped body heat, speed up spring back time and help the mattress feel softer. This technology was originally developed and patented by Peterson Chemical Technology, and gel mattresses became popular with the release of Sertas iComfort line and Simmons Beautyrest line in 2011. Gel-infused memory foam was next developed with what were described as "beads" containing the gel which, as a phase-change material, achieved the desired temperature stabilization or cooling effect by changing from a solid to a liquid "state" within the capsule. Changing physical states can significantly alter an element's heat absorption properties.
Since the development of gel memory foam, other materials have been added. Aloe vera, green tea extract and activated charcoal have been combined with it to reduce odors and even provide aromatherapy while sleeping. Rayon has been used in woven mattress covers over memory foam beds to wick moisture away from the body to increase comfort. Phase-change materials (PCMs) have also been used in covers on memory foam pillows, beds, and mattress pads. Materials other than polyurethane also have the properties necessary to make memory foam. Polyethylene terephthalate, one such polymeric material, provides certain benefits over polyurethane, such as recyclability, lightness, and thermal insulation. | 0 | Colloidal Chemistry |
An electride is an ionic compound in which an electron serves the role of the anion. Solutions of alkali metals in ammonia are electride salts. In the case of sodium, these blue solutions consist of [Na(NH)] and solvated electrons:
:Na + 6 NH → [Na(NH)] + e
The cation [Na(NH)] is an octahedral coordination complex. | 1 | Solid-state chemistry |
The ansatz is the special case of electron waves in a periodic crystal lattice using Bloch's theorem as treated generally in the dynamical theory of diffraction. Every crystal is a periodic structure which can be characterized by a Bravais lattice, and for each Bravais lattice we can determine the reciprocal lattice, which encapsulates the periodicity in a set of three reciprocal lattice vectors . Now, any periodic potential which shares the same periodicity as the direct lattice can be expanded out as a Fourier series whose only non-vanishing components are those associated with the reciprocal lattice vectors. So the expansion can be written as:
where for any set of integers .
From this theory, an attempt can be made to predict the band structure of a particular material, however most ab initio methods for electronic structure calculations fail to predict the observed band gap. | 1 | Solid-state chemistry |
The Born–Haber cycle is an approach to analyze reaction energies. It was named after two German scientists, Max Born and Fritz Haber, who developed it in 1919. It was also independently formulated by Kasimir Fajans and published concurrently in the same journal. The cycle is concerned with the formation of an ionic compound from the reaction of a metal (often a Group I or Group II element) with a halogen or other non-metallic element such as oxygen.
Born–Haber cycles are used primarily as a means of calculating lattice energy (or more precisely enthalpy), which cannot otherwise be measured directly. The lattice enthalpy is the enthalpy change involved in the formation of an ionic compound from gaseous ions (an exothermic process), or sometimes defined as the energy to break the ionic compound into gaseous ions (an endothermic process). A Born–Haber cycle applies Hess's law to calculate the lattice enthalpy by comparing the standard enthalpy change of formation of the ionic compound (from the elements) to the enthalpy required to make gaseous ions from the elements.
This lattice calculation is complex. To make gaseous ions from elements it is necessary to atomise the elements (turn each into gaseous atoms) and then to ionise the atoms. If the element is normally a molecule then we first have to consider its bond dissociation enthalpy (see also bond energy). The energy required to remove one or more electrons to make a cation is a sum of successive ionization energies; for example, the energy needed to form Mg is the ionization energy required to remove the first electron from Mg, plus the ionization energy required to remove the second electron from Mg. Electron affinity is defined as the amount of energy released when an electron is added to a neutral atom or molecule in the gaseous state to form a negative ion.
The Born–Haber cycle applies only to fully ionic solids such as certain alkali halides. Most compounds include covalent and ionic contributions to chemical bonding and to the lattice energy, which is represented by an extended Born–Haber thermodynamic cycle. The extended Born–Haber cycle can be used to estimate the polarity and the atomic charges of polar compounds. | 1 | Solid-state chemistry |
The sodium in this compound can be replaced by other alkali metals to form their tungsten bronzes, and by other metals such as tin and lead. Molybdenum bronzes also exist but are less stable than their tungsten counterparts. | 1 | Solid-state chemistry |
Many researches claim that nanoparticles can be used to enhance crude oil recovery. It is evident that development of nanofluids for oil and gas industry has a great practical aspects. | 0 | Colloidal Chemistry |
*1930–1938 Demonstrator and Assistant Lecturer at Imperial College, London
*1931 Travelling scholarship to work with Walter Hieber on metal carbonyls at the University of Heidelberg
*1938–1947 Senior Lecturer in Inorganic Chemistry, University of Melbourne
*1947–1954 Senior Principal and Deputy Chief Scientific Officer, Atomic Energy Research Establishment, Harwell
*1954–1959 Professor of Chemistry at the University of Melbourne
*1959–1963 Director of the National Chemical Laboratory, Teddington (closed 1965)
*1963–1975 Professor of Inorganic Chemistry, University of Oxford
*1975–1981 Honorary Professorial Fellow of University College, Aberystwyth
*1981–1990 Visiting Fellow, Research School of Chemistry, Australian National University, Canberra
Source | 1 | Solid-state chemistry |
Intermolecular forces govern the particle interaction in self-assembled systems. The forces tend to be intermolecular in type rather than ionic or covalent because ionic or covalent bonds will “lock” the assembly into non-equilibrium structures. The types intermolecular forces seen in self-assembly processes are van der Waals, hydrogen bonds, and weak polar forces, just to name a few. In self-assembly, regular structural arrangements are frequently observed, therefore there must be a balance of attractive and repulsive between molecules otherwise an equilibrium distance will not exist between the particles. The repulsive forces can be electron cloud-electron cloud overlap or electrostatic repulsion. | 0 | Colloidal Chemistry |
Hydrotropes have a low bioaccumulation potential, as the octanol-water partition coefficient is <1.0. Studies have found hydrotopes to be very slightly volatile, with vapor pressures <2.0x10-5 Pa. They are aerobically biodegradable. Removal via the secondary wastewater treatment process of activated sludge is >94%. Acute toxicity studies on fish show an LC50 >400 mg active ingredient (a.i.)/L. For Daphnia, the EC50 is >318 mg a.i./L. The most sensitive species is green algae with EC50 values in the range of 230–236 mg a.i./ L and No Observed Effect Concentrations (NOEC) in the range of 31–75 mg a.i./L. The aquatic Predicted No Effect Concentration (PNEC) was found to be 0.23 mg a.i./L. The Predicted Environmental Concentration (PEC)/PNEC ratio has been determined to be < 1 and, therefore, hydrotropes in household laundry and cleaning products have been determined to not be an environmental concern. | 0 | Colloidal Chemistry |
Random sequential adsorption (RSA) refers to a process where particles are randomly introduced in a system, and if they do not overlap any previously adsorbed particle, they adsorb and remain fixed for the rest of the process. RSA can be carried out in computer simulation, in a mathematical analysis, or in experiments. It was first studied by one-dimensional models: the attachment of pendant groups in a polymer chain by Paul Flory, and the car-parking problem by Alfréd Rényi. Other early works include those of Benjamin Widom. In two and higher dimensions many systems have been studied by computer simulation, including in 2d, disks, randomly oriented squares and rectangles, aligned squares and rectangles, various other shapes, etc.
An important result is the maximum surface coverage, called the saturation coverage or the packing fraction. On this page we list that coverage for many systems.
The blocking process has been studied in detail in terms of the random sequential adsorption (RSA) model. The simplest RSA model related to deposition of spherical particles considers irreversible adsorption of circular disks. One disk after another is placed randomly at a surface. Once a disk is placed, it sticks at the same spot, and cannot be removed. When an attempt to deposit a disk would result in an overlap with an already deposited disk, this attempt is rejected. Within this model, the surface is initially filled rapidly, but the more one approaches saturation the slower the surface is being filled. Within the RSA model, saturation is sometimes referred to as jamming. For circular disks, saturation occurs at a coverage of 0.547. When the depositing particles are polydisperse, much higher surface coverage can be reached, since the small particles will be able to deposit into the holes in between the larger deposited particles. On the other hand, rod like particles may lead to much smaller coverage, since a few misaligned rods may block a large portion of the surface.
For the one-dimensional parking-car problem, Renyi has shown that the maximum coverage is equal to
the so-called Renyi car-parking constant.
Then followed the conjecture of Ilona Palásti, who proposed that the coverage of d-dimensional aligned squares, cubes and hypercubes is equal to θ. This conjecture led to a great deal of work arguing in favor of it, against it, and finally computer simulations in two and three dimensions showing that it was a good approximation but not exact. The accuracy of this conjecture in higher dimensions is not known.
For -mers on a one-dimensional lattice, we have for the fraction of vertices covered,
When goes to infinity, this gives the Renyi result above. For k = 2, this gives the Flory result .
For percolation thresholds related to random sequentially adsorbed particles, see Percolation threshold. | 0 | Colloidal Chemistry |
Quenching is a heat-treatment process when forging metals such as steel. A brine solution, along with oil and other substances, is commonly used to harden steel. When brine is used, there is an enhanced uniformity of the cooling process and heat transfer. | 1 | Solid-state chemistry |
Brine is a common agent in food processing and cooking. Brining is used to preserve or season the food. Brining can be applied to vegetables, cheeses, fruit and some fish in a process known as pickling. Meat and fish are typically steeped in brine for shorter periods of time, as a form of marination, enhancing its tenderness and flavor, or to enhance shelf period. | 1 | Solid-state chemistry |
Yttrium barium copper oxide (YBCO) is a family of crystalline chemical compounds that display high-temperature superconductivity; it includes the first material ever discovered to become superconducting above the boiling point of liquid nitrogen [] at about .
Many YBCO compounds have the general formula (also known as Y123), although materials with other Y:Ba:Cu ratios exist, such as (Y124) or (Y247). At present, there is no singularly recognised theory for high-temperature superconductivity.
It is part of the more general group of rare-earth barium copper oxides (ReBCO) in which, instead of yttrium, other rare earths are present. | 1 | Solid-state chemistry |
*Shannon RD, Fischer RX (2021) Empirical electronic polarizabilities for use in refractive index measurements III. Structures with short [5]Ti-O and vanadyl bonds. Canadian Mineralogist 59, 107–124.
*Shannon RD, Fischer RX (2006) Empirical electronic polarizabilities in oxides, hydroxides, oxyfluorides, and oxychlorides. Physical Review B 73, 235111/1-235111/28.
*Shannon RD; Shannon RC, Medenbach O, Fischer RX (2002) Refractive index and dispersion of fluorides and oxides. Journal of Physical and Chemical Reference Data 31, 931–970.
*Medenbach O, Dettmar D, Shannon RD, Fischer RX, Yen WM (2001) Refractive index and optical dispersion of rare earth oxides using a small-prism technique. Journal of Optics A: Pure and Applied Optics 3, 174–177.
*Shannon RD (1993) Dielectric polarizabilities of ions in oxides and fluorides. Journal of Applied Physics 73, 348–66.
*Shannon RD, Oswald RA, Parise JB, Chai BHT, Byszewski P, Pajaczkowska A, Sobolewski R (1992) Dielectric constants and crystal structures of calcium yttrium aluminate (CaYAlO), calcium neodymium aluminate (CaNdAlO), and lanthanum strontium aluminate (SrLaAlO), and deviations from the oxide additivity rule. Journal of Solid State Chemistry 98, 90–98.
*Shannon RD, Rossman GR (1992) Dielectric constants of silicate garnets and the oxide additivity rule. American Mineralogist 77, 94–100.
*Coudurier G, Auroux A, Vedrine JC, Farlee RD, Abrams L, Shannon RD (1987) Properties of boron-substituted ZSM-5 and ZSM-11 zeolites. Journal of Catalysis 108, 1–14.
*Shannon RD, Gardner KH, Staley RH, Bergeret G, Gallezot P, Auroux A (1985) The nature of the nonframework aluminum species formed during the dehydroxylation of H-Y. Journal of Physical Chemistry 89, 4778–4788.
*Rossman GR; Shannon RD and Waring, RK (1981) Origin of the Yellow Color of Complex Nickel Oxides. Journal of Solid State Chemistry 39, 277–287.
*Tranqui D, Shannon RD, Chen Hy, Iijima S, Baur WH (1979) Crystal structure of ordered LiSiO Acta Crystallographica Section B-Structural Science 35, 2479–2487.
*Shannon RD, Taylor BE, Gier TE, Chen HY, Berzins T (1978) Ionic conductivity in sodium yttrium silicon oxide (NaYSiO)-type silicates. Inorganic Chemistry 17, 958–964.
*Shannon RD, Gillson JL, Bouchard RJ (1977) Single crystal synthesis and electrical properties of cadmium stannite and stannate, indium tellurate, and cadmium indicate. Journal of Physics and Chemistry of Solids 38, 877–881.
*Shannon RD, Taylor BE, English AD, Berzins T (1977) New lithium solid electrolytes. Electrochimica Acta (1977), 22(7), 783–796.
*Shannon RD (1976) Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallographica, Section A: Crystal Physics, Diffraction, Theoretical and General Crystallography, A32, 751–67.
*Brown, ID, Shannon RD (1973) Empirical bond-strength-bond-length curves for oxides. Acta Crystallographica Section A: Crystal Physics, Diffraction, Theoretical and General Crystallography 29, 266–282.
*Shannon RD, Calvo C (1973) Refinement of the crystal structure of low temperature lithium vanadate(V) and analysis of mean bond lengths in phosphates, arsenates, and vanadates. Journal of Solid State Chemistry 6, 538–49.
*Shannon RD, Rogers DB, Prewitt CT, Gillson JL (1971) Chemistry of noble metal oxide. III. Electrical transport properties and crystal chemistry of ABO compounds with the delafossite structure. Inorganic Chemistry 10, 723–727.
*Prewitt CT, Shannon RD, Rogers DB (1971) Chemistry of Nobel Metal Oxides. II. Chemistry of noble metal oxide. II. Crystal structures of platinum cobalt dioxide, palladium cobalt dioxide, copper iron dioxide, and silver iron dioxide. Inorganic Chemistry 10,.719–723.
*Shannon RD; Rogers DB, Prewitt, CT (1971) Chemistry of noble metal oxide. I. Syntheses and properties of ABO delafossite compounds. Inorganic Chemistry 10, 713–718.
*Shannon RD, Prewitt CT (1970) Revised Values of Effective Ionic Radii. Acta Crystallographica Section B-Structural Crystallography and Crystal Chemistry B 26, 1046–1048.
*Shannon RD and Prewitt CT (1970) Effective Ionic Radii and Crystal Chemistry. Journal of Inorganic & Nuclear Chemistry 32, 1427–1441.
*Shannon RD, Bierstedt PE (1970) Single-crystal growth and electrical properties of barium plumbate. Journal of the American Ceramic Society 53, 635–636.
*Prewitt CT, Shannon RD, Rogers D, Sleight AW (1969) C rare earth oxide-corundum transition and crystal chemistry of oxides having the corundum structure. Inorganic Chemistry 8, 1985–1993.
*Rogers DB, Shannon RD, Sleight AW, Gillson JL (1969) Crystal chemistry of metal dioxides with rutile-related structures. Inorganic Chemistry 8, 841–9.
*Shannon RD and Prewitt, CT (1969) Effective Ionic Radii in Oxides and Fluorides. Acta Crystallographica Section B-Structural Crystallography and Crystal Chemistry B 25, 925–946.
*Prewitt, CT and Shannon RD (1968) Crystal structure of a high-pressure form of boron sesquioxide. Acta Crystallographica Section B-Structural Crystallography and Crystal Chemistry B 24, 869–874.
*Shannon RD (1968) Synthesis and properties of two new members of the rutile family, RhO and PtO. Solid State Communications 6, 139–143.
*Shannon RD, Pask JA (1965) The kinetics and mechanism of the anatase-rutile transformation. Journal of the American Ceramic Society 48, 391–398
*Shannon RD, Pask JA (1964) Topotaxy in the anatase-rutile transformation. American Mineralogist 49, 1707–1717.
*Shannon RD (1964) Activated complex theory applied to the thermal decomposition of solids. Transactions of the Faraday Society 60 (503P), pp. 1902–1913. | 1 | Solid-state chemistry |
In combination with 1,2- or 1,3-diamine ligands, CuI catalyzes the conversion of aryl, heteroaryl, and vinyl bromides into the corresponding iodides. NaI is the typical iodide source and dioxane is a typical solvent (see aromatic Finkelstein reaction).
CuI is used as a co-catalyst with palladium catalyst in the Sonogashira coupling.
CuI is used in cloud seeding, altering the amount or type of precipitation of a cloud, or their structure by dispersing substances into the atmosphere which increase water's ability to form droplets or crystals. CuI provides a sphere for moisture in the cloud to condense around, causing precipitation to increase and cloud density to decrease.
The structural properties of CuI allow CuI to stabilize heat in nylon in commercial and residential carpet industries, automotive engine accessories, and other markets where durability and weight are a factor.
CuI is used as a source of dietary iodine in table salt and animal feed. | 1 | Solid-state chemistry |
Salt-like carbides are composed of highly electropositive elements such as the alkali metals, alkaline earth metals, lanthanides, actinides, and group 3 metals (scandium, yttrium, and lutetium). Aluminium from group 13 forms carbides, but gallium, indium, and thallium do not. These materials feature isolated carbon centers, often described as "C", in the methanides or methides; two-atom units, "", in the acetylides; and three-atom units, "", in the allylides. The graphite intercalation compound KC, prepared from vapour of potassium and graphite, and the alkali metal derivatives of C are not usually classified as carbides. | 1 | Solid-state chemistry |
Bernt Krebs (born in Gotha, Germany) is a German scientist. He is conducting research at the Faculty of Chemistry, University of Münster. | 1 | Solid-state chemistry |
Nano-particles can self-assemble on solid surfaces after external forces (like magnetic and electric) are applied. Templates made of microstructures, like carbon nanotubes or block polymers, can also be used to assist in self-assembly. They cause directed self-assembly (DSA), in which active sites are embedded to selectively induce nanoparticle deposition. Such templates are objects onto which different particles can be arranged into a structure with a morphology similar to that of the template. Carbon nanotubes (microstructures), single molecules, or block copolymers are common templates. Nanoparticles are often shown to self-assemble within distances of nanometers and micrometers, but block copolymer templates can be used to form well-defined self-assemblies over macroscopic distances. By incorporating active sites to the surfaces of nanotubes and polymers, the functionalization of these templates can be transformed to favor self-assembly of specified nanoparticles. | 0 | Colloidal Chemistry |
The Brus equation or confinement energy equation can be used to describe the emission energy of quantum dot semiconductor nanocrystals in terms of the band gap energy E, Plancks constant h, the radius of the quantum dot r, as well as the effective mass of the excited electron m* and of the excited hole m'*. The equation was named after Louis E. Brus who independently discovered it a few years later.
The radius of the quantum dot affects the wavelength of the emitted light due to quantum confinement, and this equation describes the effect of changing the radius of the quantum dot on the wavelength λ of the emitted light (and thereby on the emission energy ΔE = hc/λ, where c is the speed of light). This is useful for calculating the radius of a quantum dot from experimentally determined parameters.
The overall equation is
E, m*, and m* are unique for each nanocrystal composition.
For example, with cadmium selenide (CdSe) nanocrystals:
:E (CdSe) = 1.74 eV = 2.8·10 Joules,
:m* (CdSe) = 0.13 m = 1.18·10 kg,
:m* (CdSe) = 0.45 m = 4.09·10 kg. | 0 | Colloidal Chemistry |
Interferometric nanoparticle tracking analysis (iNTA) is the next generation of NTA technology. It is based on interferometric scattering microscopy (iSCAT), which enhances the signal of weak scatterers. In contrast to NTA, iNTA has a superior resolution based on a two-parameter analysis, including the size and the scattering cross-section of the particle. | 0 | Colloidal Chemistry |
Bocarsly has been recognized with the following awards.
* Sloan Research Fellow (1986)
* American Chemical Society, EXXON Solid State Chemistry Fellowship (1984)
* The Camille and Henry Dreyfus Foundation Newly Appointed Faculty Grant (1980)
* DuPont Young Faculty Grant (1980)
* Sigma Pi Sigma - National Physics Honor Society
* President's Undergraduate Research Fellowship UCLA (1975) | 1 | Solid-state chemistry |
In a report by the Nordic Council of Ministers, the total annual health-related costs associated with human exposure to PFASs were estimated to be at least €52–84 billion in the European Economic Area (EEA) countries. Aggregated annual costs covering environmental screening, monitoring where contamination is found, water treatment, soil remediation and health assessment total €821 million – 170 billion in the EEA plus Switzerland.
In the United States, estimated PFAS-attributable disease costs amount to 6–62 billion US$. Studies have estimated the annual healthcare costs in the United States of each of some of the major diseases attributed to PFAS. | 0 | Colloidal Chemistry |
Zwitterionic (ampholytic) surfactants have both cationic and anionic centers attached to the same molecule. The cationic part is based on primary, secondary, or tertiary amines or quaternary ammonium cations. The anionic part can be more variable and include sulfonates, as in the sultaines CHAPS (3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate) and cocamidopropyl hydroxysultaine. Betaines such as cocamidopropyl betaine have a carboxylate with the ammonium. The most common biological zwitterionic surfactants have a phosphate anion with an amine or ammonium, such as the phospholipids phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, and sphingomyelins.
Lauryldimethylamine oxide and myristamine oxide are two commonly used zwitterionic surfactants of the tertiary amine oxides structural type. | 0 | Colloidal Chemistry |
It is used in microelectronics as a contact material, with resistivity 60–80 μΩ cm; it forms at 1000 °C. It is often used as a shunt over polysilicon lines to increase their conductivity and increase signal speed. Tungsten disilicide layers can be prepared by chemical vapor deposition, e.g. using monosilane or dichlorosilane with tungsten hexafluoride as source gases. The deposited film is non-stoichiometric, and requires annealing to convert to more conductive stoichiometric form. Tungsten disilicide is a replacement for earlier tungsten films. Tungsten disilicide is also used as a barrier layer between silicon and other metals, e.g. tungsten.
Tungsten disilicide is also of value towards use in microelectromechanical systems, where it is mostly applied as thin films for fabrication of microscale circuits. For such purposes, films of tungsten disilicide can be plasma-etched using e.g. nitrogen trifluoride gas.
WSi performs well in applications as oxidation-resistant coatings. In particular, in similarity to Molybdenum disilicide, MoSi, the high emissivity of tungsten disilicide makes this material attractive for high temperature radiative cooling, with implications in heat shields. | 1 | Solid-state chemistry |
Both free and immobilized radicals display very different chemical characteristics from atoms and molecules containing only complete bonds. Generally, they are extremely reactive. Immobilized free radicals, like their mobile counterparts, are highly unstable, but they gain some kinetic stability because of limited mobility and steric hindrance. While free radicals are usually short-lived, immobilized free radicals often exhibit a longer lifetime because of this reduction in reactivity. | 1 | Solid-state chemistry |
Superconducting properties and low cost make magnesium diboride attractive for a variety of applications. For those applications, MgB powder is compressed with silver metal (or 316 stainless steel) into wire and sometimes tape via the Powder-in-tube process.
In 2006 a 0.5 tesla open MRI superconducting magnet system was built using 18 km of MgB wires. This MRI used a closed-loop cryocooler, without requiring externally supplied cryogenic liquids for cooling.
"...the next generation MRI instruments must be made of MgB coils instead of NbTi coils, operating in the 20–25 K range without liquid helium for cooling. ...
Besides the magnet applications MgB conductors have potential uses in superconducting transformers, rotors and transmission cables at temperatures of around 25 K, at fields of 1 T."
A project at CERN to make MgB cables has resulted in superconducting test cables able to carry 20,000 amperes for extremely high current distribution applications, such as the high luminosity upgrade of the Large Hadron Collider.
The IGNITOR tokamak design was based on MgB for its poloidal coils.
Thin coatings can be used in superconducting radio frequency cavities to minimize energy loss and reduce the inefficiency of liquid helium cooled niobium cavities.
Because of the low cost of its constituent elements, MgB has promise for use in superconducting low to medium field magnets, electric motors and generators, fault current limiters and current leads. | 1 | Solid-state chemistry |
The two branches of the APES for the case of strong PJTE resulting in the instability of the ground state (when the condition of instability (11) holds) are illustrated in Fig. 1b in comparison with the case when the two states have the same energy (Fig. 1a), i. e. when they are degenerate and the Jahn–Teller effect (JTE) takes place. We see that the two cases, degenerate and nondegenerate but close-in-energy (pseudo degenerate) are similar in generating two minima with distorted configurations, but there are important differences: while in the JTE there is a crossing of the two terms at the point of degeneracy (leading to conical intersections in more complicated cases), in the nondegenerate case with strong vibronic coupling there is an "avoided crossing" or "pseudo crossing". Even a more important difference between the two vibronic coupling effects emerges from the fact that the two interacting states in the JTE are components of the same symmetry type, whereas in the PJTE each of the two states may have any symmetry. For this reason, the possible kinds of distortion is very limited in the JTE, and unlimited in the PJTE. It is also noticeable that while the systems with JTE are limited by the condition of electron degeneracy, the applicability of the PJTE has no a priori limitations, as it includes also the cases of degeneracy. Even when the PJT coupling is weak and the inequality (11) does not hold, the PJTE is still significant in softening (lowering the corresponding vibrational frequency) of the ground state and increasing it in the excited state. When considering the PJTE in an excited state, all the higher in energy states destabilize it, while the lower ones stabilize it.
For a better understanding it is important to follow up on how the PJTE is related to intramolecular interactions. In other words, what is the physical driving force of the PJTE distortions (transformations) in terms of well-known electronic structure and bonding? The driving force of the PJTE is added (improved) covalence: the PJTE distortion takes place when it results in an energy gain due to greater covalent bonding between the atoms in the distorted configuration. Indeed, in the starting high-symmetry configuration the wavefunctions of the electronic states, ground and excited, are orthogonal by definition. When the structure is distorted, their orthogonality is violated, and a nonzero overlap between them occurs. If for two near-neighbor atoms the ground state wavefunction pertains (mainly) to one atom and the excited state wavefunction belongs (mainly) to the other, the orbital overlap resulting from the distortion adds covalency to the bond between them, so the distortion becomes energetically favorable (Fig. 2). | 1 | Solid-state chemistry |
In 2004, Wu won the best poster award at the Materials Research Society Solid State Chemistry Symposium. In 2005, she won the University of Pennsylvania S. J. Stein Prize for or superior achievement in the field of new or unique materials or applications for materials in electronics. Wu was honored with the outstanding poster presentation at the 14th annual NIST chapter of Sigma Xi poster competition. In 2010, Wu received the Sidhu Award from the Pittsburgh Diffraction Society for her exceptional contribution to the structural investigation of new materials for energy storage applications. In 2017, she received the Department of Commerce Bronze Medal for producing an entirely new route to synthesizing hydrogen-storage materials for fuel cells based on the complex chemistry of amines and boranes. In 2018, she was recognized by Clarivate Analytics as a highly cited researcher in the field of Cross-Field. | 1 | Solid-state chemistry |
Electrostatic forces between particles are strongest when the charges are high, and the distance between the nuclei of the ions is small. In such cases, the compounds generally have very high melting and boiling points and a low vapour pressure. Trends in melting points can be even better explained when the structure and ionic size ratio is taken into account. Above their melting point, ionic solids melt and become molten salts (although some ionic compounds such as aluminium chloride and iron(III) chloride show molecule-like structures in the liquid phase). Inorganic compounds with simple ions typically have small ions, and thus have high melting points, so are solids at room temperature. Some substances with larger ions, however, have a melting point below or near room temperature (often defined as up to 100 °C), and are termed ionic liquids. Ions in ionic liquids often have uneven charge distributions, or bulky substituents like hydrocarbon chains, which also play a role in determining the strength of the interactions and propensity to melt.
Even when the local structure and bonding of an ionic solid is disrupted sufficiently to melt it, there are still strong long-range electrostatic forces of attraction holding the liquid together and preventing ions boiling to form a gas phase. This means that even room temperature ionic liquids have low vapour pressures, and require substantially higher temperatures to boil. Boiling points exhibit similar trends to melting points in terms of the size of ions and strength of other interactions. When vapourized, the ions are still not freed of one another. For example, in the vapour phase sodium chloride exists as diatomic "molecules". | 1 | Solid-state chemistry |
Most anionic and non-ionic surfactants are non-toxic, having LD50 comparable to table salt. The toxicity of quaternary ammonium compounds, which are antibacterial and antifungal, varies. Dialkyldimethylammonium chlorides (DDAC, DSDMAC) used as fabric softeners have high LD50 (5 g/kg) and are essentially non-toxic, while the disinfectant alkylbenzyldimethylammonium chloride has an LD50 of 0.35 g/kg. Prolonged exposure to surfactants can irritate and damage the skin because surfactants disrupt the lipid membrane that protects skin and other cells. Skin irritancy generally increases in the series non-ionic, amphoteric, anionic, cationic surfactants.
Surfactants are routinely deposited in numerous ways on land and into water systems, whether as part of an intended process or as industrial and household waste.
Anionic surfactants can be found in soils as the result of sewage sludge application, wastewater irrigation, and remediation processes. Relatively high concentrations of surfactants together with multimetals can represent an environmental risk. At low concentrations, surfactant application is unlikely to have a significant effect on trace metal mobility.
In the case of the Deepwater Horizon oil spill, unprecedented amounts of Corexit were sprayed directly into the ocean at the leak and on the sea-water's surface. The apparent theory was that the surfactants isolate droplets of oil, making it easier for petroleum-consuming microbes to digest the oil. The active ingredient in Corexit is dioctyl sodium sulfosuccinate (DOSS), sorbitan monooleate (Span 80), and polyoxyethylenated sorbitan monooleate (Tween-80). | 0 | Colloidal Chemistry |
Plumbates are formed by the reaction of lead(IV) oxide, , with alkali. Plumbate salts contain either the hydrated hexahydroxoplumbate(IV) or plumbate anion , or the anhydrous anions (metaplumbate) or (orthoplumbate). For example, dissolving in a hot, concentrated aqueous solution of potassium hydroxide forms the potassium hexahydroxoplumbate(IV) salt . The anhydrous salts may be synthesized by heating metal oxides or hydroxides with .
The most widely discussed plumbates are derivatives of barium metaplumbate . When doped with some bismuth in place of lead, the material exhibits superconductivity at 13 K. At the time of this discovery, oxides did not show such properties. The surprise associated with this work was eclipsed by the advent of the cuprate superconductors. | 1 | Solid-state chemistry |
Memory foam was developed in 1966 under a contract by NASA's Ames Research Center to improve the safety of aircraft cushions. The temperature-sensitive memory foam was initially referred to as "slow spring back foam"; most called it "temper foam". Created by feeding gas into a polymer matrix, it had an open-cell solid structure that matched pressure against it, yet slowly returned to its original shape.
Later commercialisation of the foam included use in medical equipment such as X-ray table pads, and sports equipment such as American / Canadian football helmet liners.
When NASA released memory foam to the public domain in the early 1980s, Fagerdala World Foams was one of the few companies willing to work with it, as the manufacturing process remained difficult and unreliable. Their 1991 product, the Tempur-Pedic Swedish Mattress eventually led to the mattress and cushion company Tempur World.
Memory foam was subsequently used in medical settings. For example, when patients were required to lie immobile in bed, on a firm mattress, for an unhealthy period of time, the pressure on some of their body regions impaired blood flow, causing pressure sores or gangrene. Memory foam mattresses significantly decreased such events, as well as alternating pressure air mattresses.
Memory foam was initially too expensive for widespread use, but became cheaper. Its most common domestic uses are mattresses, pillows, shoes, and blankets. It has medical uses, such as wheelchair seat cushions, hospital bed pillows and padding for people suffering long-term pain or postural problems. | 0 | Colloidal Chemistry |
Pharmaceuticals:
This technique is widely used in the pharma market. Because of the small sample amounts and the high yields, it is ideal for spray drying expensive substances in basic research. The following list shows examples of what is possible:
*Inhalable drugs for dry powder inhalers (DPI‘s)
*Nano- and microencapsulation of liposomes
*Stabilization of heat-sensitive vaccines, insulin, growth hormones
*Encapsulation of nanoparticle drugs for high bioavailability
*Nanocapsules of biodegradable polymers (lactides, glycolides)
*Porous drug carriers for nanoparticle suspensions
*Excipients for controlled drug release studies: trehalose, mannitol, lactose, HPMC, PVA, chitosan, dextrin, PLGA, starch, gelatin
Materials science:
This new technique offers new prospects in materials science, specially in the nanomaterial field. Now it is possible to spray dry fine particles. The following list shows examples of what is possible:
*Fine metal particles for novel catalysts
*Fine magnetic powders
*Carbon nanotubes as additives
*High performance ceramics with novel structures and high specific surface area
*Titanium oxide particles
*Nanoparticle suspensions for agglomeration
*Silicon oxide nanoparticle agglomerates
*Finest pigments for paints and coatings
Food:
Also in the field of food science this technology offers new possibilities. Especially in the currently vibrant field of functional food, the following list shows examples of what is possible:
*Nano food – Functional additives
*Encapsulation of fruit aromas, flavours, or perfumes
*Spray drying of fine powder aromas for pet food
*Encapsulation of fish oil for smell protection
*Vitamins, other food additives, etc. | 0 | Colloidal Chemistry |
Nanoparticles can self-assemble as a result of their intermolecular forces. As systems look to minimize their free energy, self-assembly is one option for the system to achieve its lowest free energy thermodynamically. Nanoparticles can be programmed to self-assemble by changing the functionality of their side groups, taking advantage of weak and specific intermolecular forces to spontaneously order the particles. These direct interparticle interactions can be typical intermolecular forces such as hydrogen bonding or Van der Waals forces, but can also be internal characteristics, such as hydrophobicity or hydrophilicity. For example, lipophilic nanoparticles have the tendency to self-assemble and form crystals as solvents are evaporated. While these aggregations are based on intermolecular forces, external factors such as temperature and pH also play a role in spontaneous self-assembly. | 0 | Colloidal Chemistry |
Gerhard Martin Julius Schmidt (21 August 1919 in Berlin – 12 July 1971, in Zurich, buried in Rehovot), was an organic chemist and chemical crystallographer, dean of the chemistry faculty of the Weizmann Institute of Science, and its scientific director in 1969. Schmidt was the founder of X-ray crystallography at the Weizmann Institute and in Israel – a field in which Weizmann Institute's Professor Ada Yonath was awarded the Nobel Prize in Chemistry for 2009. | 1 | Solid-state chemistry |
Some allotropes of silicon, such as amorphous silicon, display a high concentration of dangling bonds. Besides being of fundamental interest, these dangling bonds are important in modern semiconductor device operation. Hydrogen introduced to the silicon during the synthesis process is well known to saturate most dangling bonds, as are other elements such as oxygen, making the material suitable for applications (see semiconductor devices).
The dangling bond states have wave functions that extend beyond the surface and can occupy states above the valence band. The resulting difference in surface and bulk Fermi level causes surface band bending and the abundancy of surface states pins the Fermi level.
For the compound semiconductor GaAs, stronger electron pairing is observed at the surface, making for almost filled orbitals in arsenic and almost empty orbitals for gallium. Consequently, the dangling bond density at the surface is much lower and no Fermi level pinning occurs.
In doped semiconductors, surface properties are still dependent on the dangling bonds, since they occur in a number density of around 10 per square centimeter, compared to dopant electrons or holes with a number density of 10 to 10 per cubic centimeter which are thus much less abundant on the material surface. | 1 | Solid-state chemistry |
The addition of surfactants does not always have a positive effect on all properties. The water resistance of the coating can be decreased with surfactant addition since surfactants can be very water-soluble and will easily wash out of a coating. This problem of moisture resistance is particularly prevalent problem for art conservation, as well as problems with adhesion, loss of optical clarity, and dirt pickup caused by polyether surfactants in contemporary acrylic emulsion used in artworks bearing acrylic coats. While the type and amount of surfactant determine what properties will be affected, other chemicals in a paint can alter the overall effect the surfactants may have on the paint. Elasticity has been found to either increase or decrease in latex paints depending on the amount of TiO present. | 0 | Colloidal Chemistry |