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Chemisorption is a kind of adsorption which involves a chemical reaction between the surface and the adsorbate. New chemical bonds are generated at the adsorbent surface. Examples include macroscopic phenomena that can be very obvious, like corrosion [clarification needed], and subtler effects associated with heterogeneous catalysis, where the catalyst and reactants are in different pha
BET model of multilayer adsorption, that is, a random distribution of sites covered by one, two, three, etc., adsorbate molecules. The concept of the theory is an extension of the Langmuir theory, which is a theory for monolayer molecular adsorption, to multilayer adsorption with the following hypotheses:
The Freundlich isotherm has two parameters, while Langmuir's equations has only one: as a result, it often fits the data on rough surfaces better than the Langmuir isotherm. However, the Freundlich equation is not unique; consequently, a good fit of the data points does not offer sufficient proof that the surface is heterogeneous.
In chemisorption, molecules are adsorbed on the surface by valence bonds and only form monolayer adsorption. A direct transition from physisorption to chemisorption has been observed by attaching a CO molecule to the tip of an atomic force microscope and measuring its interaction with a single iron atom. [ 12 ]
Metal substrates for use in SAMs can be produced through physical vapor deposition techniques, electrodeposition or electroless deposition. [1] Thiol or selenium SAMs produced by adsorption from solution are typically made by immersing a substrate into a dilute solution of alkane thiol in ethanol, though many different solvents can be used [1] besides use of pure liquids. [16]
The Langmuir isotherm is nonetheless the first choice for most models of adsorption and has many applications in surface kinetics (usually called Langmuir–Hinshelwood kinetics) and thermodynamics. Langmuir suggested that adsorption takes place through this mechanism: A g + S ⇌ A S {\displaystyle A_{\text{g}}+S\rightleftharpoons AS} , where ...
A distinct, gelatinous glycocalyx is called a capsule, whereas an irregular, diffuse layer is called a slime layer. This coat is extremely hydrated and stains with ruthenium red . Bacteria growing in natural ecosystems, such as in soil, bovine intestines, or the human urinary tract, are surrounded by some sort of glycocalyx-enclosed microcolony ...
The lipid bilayer (or phospholipid bilayer) is a thin polar membrane made of two layers of lipid molecules. These membranes form a continuous barrier around all cells . The cell membranes of almost all organisms and many viruses are made of a lipid bilayer, as are the nuclear membrane surrounding the cell nucleus , and membranes of the membrane ...