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Surface science is the study of physical and chemical phenomena that occur at the interface of two phases, including solid–liquid interfaces, solid–gas interfaces, solid–vacuum interfaces, and liquid–gas interfaces. It includes the fields of surface chemistry and surface physics. Some related practical applications are classed as surface engineering. The science encompasses concepts such as heterogeneous catalysis, semiconductor device fabrication, fuel cells, self-assembled monolayers, and adhesives. Surface science is closely related to interface and colloid science. Interfacial chemistry and physics are common subjects for both. The methods are different. In addition, interface and colloid science studies macroscopic phenomena that occur in heterogeneous systems due to peculiarities of interfaces.
Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent. This process differs from absorption, in which a fluid is dissolved by or permeates a liquid or solid. Adsorption is a surface phenomenon, while absorption involves the whole volume of the material, although adsorption does often precede absorption. The term sorption encompasses both processes, while desorption is the reverse of it.
In chemistry, heterogeneous catalysis is catalysis where the phase of catalysts differs from that of the reactants or products. The process contrasts with homogeneous catalysis where the reactants, products and catalyst exist in the same phase. Phase distinguishes between not only solid, liquid, and gas components, but also immiscible mixtures, or anywhere an interface is present.
Desorption is the physical process where a previously adsorbed substance is released from a surface. This happens when a molecule gains enough energy to overcome the activation barrier of the bounding energy that keeps it in the surface.
Self-assembled monolayers (SAM) of organic molecules are molecular assemblies formed spontaneously on surfaces by adsorption and are organized into more or less large ordered domains. In some cases molecules that form the monolayer do not interact strongly with the substrate. This is the case for instance of the two-dimensional supramolecular networks of e.g. perylenetetracarboxylic dianhydride (PTCDA) on gold or of e.g. porphyrins on highly oriented pyrolitic graphite (HOPG). In other cases the molecules possess a head group that has a strong affinity to the substrate and anchors the molecule to it. Such a SAM consisting of a head group, tail and functional end group is depicted in Figure 1. Common head groups include thiols, silanes, phosphonates, etc.
Brunauer–Emmett–Teller (BET) theory aims to explain the physical adsorption of gas molecules on a solid surface and serves as the basis for an important analysis technique for the measurement of the specific surface area of materials. The observations are very often referred to as physical adsorption or physisorption. In 1938, Stephen Brunauer, Paul Hugh Emmett, and Edward Teller presented their theory in the Journal of the American Chemical Society. BET theory applies to systems of multilayer adsorption that usually utilizes a probing gas (called the adsorbate) that do not react chemically with the adsorptive (the material upon which the gas attaches to and the gas phase is called the adsorptive) to quantify specific surface area. Nitrogen is the most commonly employed gaseous adsorbate for probing surface(s). For this reason, standard BET analysis is most often conducted at the boiling temperature of N2 (77 K). Other probing adsorbates are also utilized, albeit less often, allowing the measurement of surface area at different temperatures and measurement scales. These include argon, carbon dioxide, and water. Specific surface area is a scale-dependent property, with no single true value of specific surface area definable, and thus quantities of specific surface area determined through BET theory may depend on the adsorbate molecule utilized and its adsorption cross section.
Reactions on surfaces are reactions in which at least one of the steps of the reaction mechanism is the adsorption of one or more reactants. The mechanisms for these reactions, and the rate equations are of extreme importance for heterogeneous catalysis. Via scanning tunneling microscopy, it is possible to observe reactions at the solid gas interface in real space, if the time scale of the reaction is in the correct range. Reactions at the solid–gas interface are in some cases related to catalysis.
The Freundlich equation or Freundlich adsorption isotherm, an adsorption isotherm, is an empirical relationship between the quantity of a gas adsorbed into a solid surface and the gas pressure. The same relationship is also applicable for the concentration of a solute adsorbed onto the surface of a solid and the concentration of the solute in the liquid phase. In 1909, Herbert Freundlich gave an expression representing the isothermal variation of adsorption of a quantity of gas adsorbed by unit mass of solid adsorbent with gas pressure. This equation is known as Freundlich adsorption isotherm or Freundlich adsorption equation. As this relationship is entirely empirical, in the case where adsorption behavior can be properly fit by isotherms with a theoretical basis, it is usually appropriate to use such isotherms instead. The Freundlich equation is also derived (non-empirically) by attributing the change in the equilibrium constant of the binding process to the heterogeneity of the surface and the variation in the heat of adsorption.
Specific surface area (SSA) is a property of solids defined as the total surface area of a material per unit of mass, or solid or bulk volume.
A foreign body reaction (FBR) is a typical tissue response to a foreign body within biological tissue. It usually includes the formation of a foreign body granuloma. Tissue-encapsulation of an implant is an example, as is inflammation around a splinter. Foreign body granuloma formation consists of protein adsorption, macrophages, multinucleated foreign body giant cells, fibroblasts, and angiogenesis. It has also been proposed that the mechanical property of the interface between an implant and its surrounding tissues is critical for the host response.
The Langmuir adsorption model explains adsorption by assuming an adsorbate behaves as an ideal gas at isothermal conditions. According to the model, adsorption and desorption are reversible processes. This model even explains the effect of pressure i.e at these conditions the adsorbate's partial pressure, , is related to the volume of it, V, adsorbed onto a solid adsorbent. The adsorbent, as indicated in the figure, is assumed to be an ideal solid surface composed of a series of distinct sites capable of binding the adsorbate. The adsorbate binding is treated as a chemical reaction between the adsorbate gaseous molecule and an empty sorption site, S. This reaction yields an adsorbed species with an associated equilibrium constant :
Within surface science, a quartz crystal microbalance with dissipation monitoring (QCM-D) is a type of quartz crystal microbalance (QCM) based on the ring-down technique. It is used in interfacial acoustic sensing. Its most common application is the determination of a film thickness in a liquid environment. It can be used to investigate further properties of the sample, most notably the layer's softness.
Adsorption is the accumulation and adhesion of molecules, atoms, ions, or larger particles to a surface, but without surface penetration occurring. The adsorption of larger biomolecules such as proteins is of high physiological relevance, and as such they adsorb with different mechanisms than their molecular or atomic analogs. Some of the major driving forces behind protein adsorption include: surface energy, intermolecular forces, hydrophobicity, and ionic or electrostatic interaction. By knowing how these factors affect protein adsorption, they can then be manipulated by machining, alloying, and other engineering techniques to select for the most optimal performance in biomedical or physiological applications.
Adsorption of polyelectrolytes on solid substrates is a surface phenomenon where long-chained polymer molecules with charged groups bind to a surface that is charged in the opposite polarity. On the molecular level, the polymers do not actually bond to the surface, but tend to "stick" to the surface via intermolecular forces and the charges created by the dissociation of various side groups of the polymer. Because the polymer molecules are so long, they have a large amount of surface area with which to contact the surface and thus do not desorb as small molecules are likely to do. This means that adsorbed layers of polyelectrolytes form a very durable coating. Due to this important characteristic of polyelectrolyte layers they are used extensively in industry as flocculants, for solubilization, as supersorbers, antistatic agents, as oil recovery aids, as gelling aids in nutrition, additives in concrete, or for blood compatibility enhancement to name a few.
Protein adsorption refers to the adhesion of proteins to solid surfaces. This phenomenon is an important issue in the food processing industry, particularly in milk processing and wine and beer making. Excessive adsorption, or protein fouling, can lead to health and sanitation issues, as the adsorbed protein is very difficult to clean and can harbor bacteria, as is the case in biofilms. Product quality can be adversely affected if the adsorbed material interferes with processing steps, like pasteurization. However, in some cases protein adsorption is used to improve food quality, as is the case in fining of wines.
Silanization of silicon and mica is the coating of these materials with a thin layer of self assembling units.
Titanium was first introduced into surgeries in the 1950s after having been used in dentistry for a decade prior. It is now the metal of choice for prosthetics, internal fixation, inner body devices, and instrumentation. Titanium is used from head to toe in biomedical implants. One can find titanium in neurosurgery, bone conduction hearing aids, false eye implants, spinal fusion cages, pacemakers, toe implants, and shoulder/elbow/hip/knee replacements along with many more. The main reason why titanium is often used in the body is due to titanium's biocompatibility and, with surface modifications, bioactive surface. The surface characteristics that affect biocompatibility are surface texture, steric hindrance, binding sites, and hydrophobicity (wetting). These characteristics are optimized to create an ideal cellular response. Some medical implants, as well as parts of surgical instruments are coated with titanium nitride (TiN).
Bovine submaxillary mucin (BSM) coatings are a surface treatment provided to biomaterials intended to reduce the growth of disadvantageous bacteria and fungi such as S. epidermidis, E. coli, and Candida albicans. BSM is a substance extracted from the fresh salivary glands of cows. It exhibits unique physical properties, such as high molecular weight and amphiphilicity, that allow it to be used for many biomedical applications.
Interfacial rheology is a branch of rheology that studies the flow of matter at the interface between a gas and a liquid or at the interface between two immiscible liquids. The measurement is done while having surfactants, nanoparticles or other surface active compounds present at the interface. Unlike in bulk rheology, the deformation of the bulk phase is not of interest in interfacial rheology and its effect is aimed to be minimized. Instead, the flow of the surface active compounds is of interest.
A protein corona is a dynamic coating of biomolecules, usually proteins, around the surface of a nanoparticle that forms spontaneously in colloidal nanomaterials upon exposure to biological mediums. Protein coronas can form in many different patterns depending on their size, shape, composition, charge, and surface functional groups, and have properties that vary in different environmental factors like temperature, pH, shearing stress, immersed media composition, and exposing time. These coatings are also changeable according to the conditions of the biochemical and physiochemical surface interactions. Types of protein coronas are known to be divided into two categories: “hard” and “soft”. “Hard” coronas have higher-affinity proteins that are irreversibly bonded to the nanoparticle surface, while “soft” coronas have lower-affinity proteins on the nanoparticle surface that are reversibly bound. These reversibly-bound proteins allow for the biomolecules in “soft” protein coronas to be exchanged or detached over time for various applications. This process is governed by the intermolecular protein-nanoparticle and protein-protein interactions that exist within a solution. In "soft" protein coronas, it is common to observe an exchange of proteins at the surface; larger proteins with lower affinities will often aggregate to the surface of the nanoparticle first, and over time, smaller proteins with higher affinities will replace them, "hardening" the corona, known as the Vroman effect.
References
- ↑ Noh, Hyeran; Vogler, Erwin A. (January 2007). "Volumetric Interpretation of Protein Adsorption: Competition from Mixtures and the Vroman Effect". Biomaterials. 28 (3): 405–422. doi:10.1016/j.biomaterials.2006.09.006. ISSN 0142-9612. PMC 2705830 . PMID 17007920.
- ↑ Horbett, Thomas A (October 2018). "Fibrinogen adsorption to biomaterials". Journal of Biomedical Materials Research. Part A. 106 (10): 2777–2788. doi:10.1002/jbm.a.36460. ISSN 1549-3296. PMC 6202247 . PMID 29896846.
- ↑ Vroman, L.; Adams, AL; Fischer, GC; Munoz, PC (1980). "Interaction of high molecular weight kininogen, factor XII, and fibrinogen in plasma at interfaces". Blood. 55 (1): 156–9. doi: 10.1182/blood.V55.1.156.156 . PMID 7350935.
- ↑ Ball, Vincent; Voegel, Jean-Claude; Schaaf, Pierre (2003-01-15), Mechanism of Interfacial Exchange Phenomena for Proteins Adsorbed at Solid – Liquid Interfaces, Surfactant Science, vol. 20033926, CRC Press, doi:10.1201/9780824747343.ch11, ISBN 978-0-8247-0863-4 , retrieved 2021-11-18
- ↑ Slack, Steven M; Horbett, Thomas A (November 1989). "Changes in the strength of fibrinogen attachment to solid surfaces: An explanation of the influence of surface chemistry on the Vroman effect". Journal of Colloid and Interface Science. 133 (1): 148–165. Bibcode:1989JCIS..133..148S. doi:10.1016/0021-9797(89)90288-9. ISSN 0021-9797.
- 1 2 Huetz, Ph.; Ball, V.; Voegel, J.-C.; Schaaf, P. (August 1995). "Exchange Kinetics for a Heterogeneous Protein System on a Solid Surface". Langmuir. 11 (8): 3145–3152. doi:10.1021/la00008a046. ISSN 0743-7463.
- ↑ Hirsh, Stacey L.; McKenzie, David R.; Nosworthy, Neil J.; Denman, John A.; Sezerman, Osman U.; Bilek, Marcela M. M. (2013-03-01). "The Vroman effect: Competitive protein exchange with dynamic multilayer protein aggregates". Colloids and Surfaces B: Biointerfaces. 103: 395–404. doi:10.1016/j.colsurfb.2012.10.039. ISSN 0927-7765. PMID 23261559.
- 1 2 Jung, Seung-Yong; Lim, Soon-Mi; Albertorio, Fernando; Kim, Gibum; Gurau, Marc C.; Yang, Richard D.; Holden, Matthew A.; Cremer, Paul S. (2003-09-25). "The Vroman Effect: A Molecular Level Description of Fibrinogen Displacement". Journal of the American Chemical Society. 125 (42): 12782–12786. doi:10.1021/ja037263o. hdl: 1969.1/1577 . ISSN 0002-7863. PMID 14558825.
- ↑ Slack, Steven M.; Horbett, Thomas A. (1995-05-05), The Vroman Effect, ACS Symposium Series, vol. 602, Washington, DC: American Chemical Society, pp. 112–128, doi:10.1021/bk-1995-0602.ch008, ISBN 9780841233041 , retrieved 2021-11-18
- ↑ LeDuc, Charles A.; Vroman, Leo; Leonard, Edward F. (October 1995). "A Mathematical Model for the Vroman Effect". Industrial & Engineering Chemistry Research. 34 (10): 3488–3495. doi:10.1021/ie00037a037. ISSN 0888-5885.