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Monolayers
A monolayer is a single, closely packed layer of entities, commonly atoms or molecules. Monolayers can also be made out of #Cell culture, cells. ''Self-assembled monolayers'' form spontaneously on surfaces. Monolayers of layered crystals like graphene and molybdenum disulfide are generally called ''2D materials''. Types A Langmuir monolayer or ''insoluble monolayer'' is a one-molecule thick layer of an insoluble organic material spread onto an aqueous subphase (matter), phase in a Langmuir–Blodgett trough. Traditional compounds used to prepare Langmuir (unit), Langmuir monolayers are amphiphilic materials that possess a hydrophilic headgroup and a hydrophobic tail. Since the 1980s a large number of other materials have been employed to produce Langmuir monolayers, some of which are semi-amphiphilic, including polymeric, ceramic or metallic nanoparticles and macromolecules such as polymers. Langmuir monolayers are extensively studied for the fabrication of Langmuir–Blodgett ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Self-assembled Monolayer
Self-assembled monolayers (SAM) are assemblies of organic molecules that form spontaneously on surfaces by adsorption and organize themselves into more or less distinct domains (head group, chain/backbone, and tail/end group). In some cases, molecules that form the monolayer do not interact strongly with the substrate. This is the case for porphyrins on highly oriented pyrolytic graphite, HOPG and two-dimensional supramolecular networks of perylenetetracarboxylic dianhydride, PTCDA on gold. In other cases, the head group has a strong affinity for the substrate and anchors the molecule. Such an SAM consisting of a head group, chain (labeled "tail"), and functional end group is depicted in Figure 1. Common head groups include thiols, silanes, and phosphonates. SAMs are created by the chemisorption of head groups onto a substrate from either the vapor or liquid phase followed by a slower organization of "tail groups". Initially, at small molecular density on the surface, adsorbate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2D Materials
In materials science, the term single-layer materials or 2D materials refers to crystalline solids consisting of a single layer of atoms. These materials are promising for some applications but remain the focus of research. Single-layer materials derived from single elements generally carry the -ene suffix in their names, e.g. graphene. Single-layer materials that are compounds of two or more elements have -ane or -ide suffixes. 2D materials can generally be categorized as either 2D allotropes of various elements or as compounds (consisting of two or more covalently bonding elements). It is predicted that there are hundreds of stable single-layer materials. The atomic structure and calculated basic properties of these and many other potentially synthesisable single-layer materials, can be found in computational databases. 2D materials can be produced using mainly two approaches: top-down exfoliation and bottom-up synthesis. The exfoliation methods include sonication, mechanical, h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Langmuir–Blodgett Film
A Langmuir–Blodgett (LB) film is an emerging kind of 2D materials to fabricate heterostructures for nanotechnology, formed when Langmuir films—or Langmuir monolayers (LM)—are transferred from the liquid-gas interface to solid supports during the vertical passage of the support through the monolayers. LB films can contain one or more monolayers of an organic material, deposited from the surface of a liquid onto a solid by immersing (or emersing) the solid substrate into (or from) the liquid. A monolayer is adsorbed homogeneously with each immersion or emersion step, thus films with very accurate thickness can be formed. This thickness is accurate because the thickness of each monolayer is known and can therefore be added to find the total thickness of a Langmuir–Blodgett film. The monolayers are assembled vertically and are usually composed either of amphiphilic molecules (see chemical polarity) with a hydrophilic head and a hydrophobic tail (example: fatty acids) or nowad ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Langmuir–Blodgett Trough
A Langmuir–Blodgett trough (LB trough) is an item of laboratory apparatus that is used to compress monolayers of molecules on the surface of a given subphase (usually water) and to measure surface phenomena due to this compression. It can also be used to deposit single or multiple monolayers on a solid substrate. Description Overview The idea of a Langmuir–Blodgett (LB) film was first proven feasible in 1917 when Irving Langmuir (Langmuir, 1917) showed that single water-surface monolayers could be transferred to solid substrates. 18 years later, Katharine Blodgett made an important scientific advance when she discovered that several of these single monolayer films could be stacked on top of one another to make multilayer films (Blodgett 1935). Since then, LB films (and subsequently the troughs to make them) have been used for a wide variety of scientific experimentation, ranging from 2D crystallization of proteins to Brewster angle microscopy. The LB trough's general objectiv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molybdenum Disulfide
Molybdenum disulfide (or moly) is an inorganic chemistry, inorganic compound composed of molybdenum and sulfur. Its chemical formula is . The compound is classified as a transition metal dichalcogenide. It is a silvery black solid that occurs as the mineral molybdenite, the principal ore for molybdenum.Sebenik, Roger F. ''et al''. (2005) "Molybdenum and Molybdenum Compounds", ''Ullmann's Encyclopedia of Chemical Technology''. Wiley-VCH, Weinheim. is relatively unreactive. It is unaffected by dilute acids and oxygen. In appearance and feel, molybdenum disulfide is similar to graphite. It is widely used as a dry lubricant because of its low friction and robustness. Bulk is a Diamagnetism, diamagnetic, indirect bandgap semiconductor similar to silicon, with a bandgap of 1.23 eV. Production is naturally found as either molybdenite, a crystalline mineral, or jordisite, a rare low temperature form of molybdenite. Molybdenite ore is processed by Froth flotation, flotation to give ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atom
Atoms are the basic particles of the chemical elements. An atom consists of a atomic nucleus, nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished from each other by the number of protons that are in their atoms. For example, any atom that contains 11 protons is sodium, and any atom that contains 29 protons is copper. Atoms with the same number of protons but a different number of neutrons are called isotopes of the same element. Atoms are extremely small, typically around 100 picometers across. A human hair is about a million carbon atoms wide. Atoms are smaller than the shortest wavelength of visible light, which means humans cannot see atoms with conventional microscopes. They are so small that accurately predicting their behavior using classical physics is not possible due to quantum mechanics, quantum effects. More than 99.94% of an atom's mass is in the nucleus. Protons hav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Interface (matter)
In the physical sciences, an interface is the boundary between two spatial regions occupied by different matter, or by matter in different physical states. The interface between matter and air, or matter and vacuum, is called a surface, and studied in surface science. In thermal equilibrium, the regions in contact are called phases, and the interface is called a phase boundary. An example for an interface out of equilibrium is the grain boundary in polycrystalline matter. The importance of the interface depends on the type of system: the bigger the quotient area/volume, the greater the effect the interface will have. Consequently, interfaces are very important in systems with large interface area-to-volume ratios, such as colloids. Interfaces can be flat or curved. For example, oil droplets in a salad dressing are spherical but the interface between water and air in a glass of water is mostly flat. Surface tension is the physical property which rules interface process ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sticking Coefficient
Sticking coefficient is the term used in surface physics to describe the ratio of the number of adsorbate atoms (or molecules) that Adsorption, adsorb, or "stick", to a surface to the total number of atoms that impinge upon that surface during the same period of time. Sometimes the symbol Sc is used to denote this coefficient, and its value is between 1 (all impinging atoms stick) and 0 (no atoms stick). The coefficient is a function of surface temperature, surface coverage (θ) and Structure, structural details as well as the kinetic energy of the impinging particles. The original formulation was for molecules adsorbing from the gas phase and the equation was later extended to adsorption from the liquid phase by comparison with molecular dynamics simulations. For use in adsorption from liquids the equation is expressed based on solute density (molecules per volume) rather than the pressure. Derivation When arriving at a site of a surface, an Adatoms, adatom has three option ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and even by industry. Further, both spellings are often used ''within'' a particular industry or country. Industries in British English-speaking countries typically use the "gauge" spelling. is the pressure relative to the ambient pressure. Various #Units, units are used to express pressure. Some of these derive from a unit of force divided by a unit of area; the International System of Units, SI unit of pressure, the Pascal (unit), pascal (Pa), for example, is one newton (unit), newton per square metre (N/m2); similarly, the Pound (force), pound-force per square inch (Pound per square inch, psi, symbol lbf/in2) is the traditional unit of pressure in the imperial units, imperial and United States customary units, US customary systems. Pressure ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volume
Volume is a measure of regions in three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch). The definition of length and height (cubed) is interrelated with volume. The volume of a container is generally understood to be the capacity of the container; i.e., the amount of fluid (gas or liquid) that the container could hold, rather than the amount of space the container itself displaces. By metonymy, the term "volume" sometimes is used to refer to the corresponding region (e.g., bounding volume). In ancient times, volume was measured using similar-shaped natural containers. Later on, standardized containers were used. Some simple three-dimensional shapes can have their volume easily calculated using arithmetic formulas. Volumes of more complicated shapes can be calculated with integral calculus if a formula exists for the shape ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gibbs Isotherm
The Gibbs adsorption isotherm for multicomponent systems is an equation used to relate the changes in concentration of a component in contact with a surface with changes in the surface tension, which results in a corresponding change in surface energy. For a binary system, the Gibbs adsorption equation in terms of surface excess is : -\mathrm\gamma = \Gamma_1\,\mathrm\mu_1 + \Gamma_2\,\mathrm\mu_2, where : \gamma is the surface tension, : \Gamma_i is the surface excess concentration of component ''i'', : \mu_i is the chemical potential of component ''i''. Adsorption Different influences at the interface may cause changes in the composition of the near-surface layer.Shchukin, E. D., Pertsov, A. V., Amelina E. A. and Zelenev, A. S. Colloid and Surface Chemistry. 1st ed. Mobius D. and Miller R. Vol. 12. Amsterdam: Elsevier Science B.V. 2001. Substances may either accumulate near the surface or, conversely, move into the bulk. The movement of the molecules characterizes t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phase Transition
In physics, chemistry, and other related fields like biology, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic State of matter, states of matter: solid, liquid, and gas, and in rare cases, plasma (physics), plasma. A phase of a thermodynamic system and the states of matter have uniform physical property, physical properties. During a phase transition of a given medium, certain properties of the medium change as a result of the change of external conditions, such as temperature or pressure. This can be a discontinuous change; for example, a liquid may become gas upon heating to its boiling point, resulting in an abrupt change in volume. The identification of the external conditions at which a transformation occurs defines the phase transition point. Types of phase transition States of matter Phase transitions commonly refer to when a substance tran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
