Electrostatic adsorption results

It can be generalized that the role of modifiers in the electron transfer process between the electrodes and redox proteins consists mainly in their capability to form a suitable electrode/electrolyte solution interface. At this interface only such surface configurations of the proteins are possible which prevent their strong electrostatic adsorption resulting in more extensive denaturation changes of the protein molecule [207,210,212]. 

Adsorption Forces. Coulomb s law allows calculations of the electrostatic potential resulting from a charge distribution, and of the potential energy of interaction between different charge distributions. Various elaborate computations are possible to calculate the potential energy of interaction between point charges, distributed charges, etc. See reference 2 for a detailed introduction. 

Surfactants greatly improve the performance of trans-cinnamaldehyde as a corrosion inhibitor for steel in HCl [741,1590,1591]. They act by enhancing the adsorption at the surface. Increased solubility or dispersibility of the inhibitor is an incidental effect. N-dodecylpyridinium bromide is effective in this aspect far below its critical micelle concentration, probably as a result of electrostatic adsorption of the monomeric form of N-dodecylpyridinium bromide. This leads to the formation of a hydrophobic monolayer, which attracts the inhibitor. On the other hand, an ethoxylated nonylphenol, a nonionic surfactant, acts by incorporating the inhibitor into micelles, which themselves adsorb on the steel surface and facilitate the adsorption of trans-cinnamaldehyde. 

Since immunosensors usually measure the signals resulting from the specific immu-noreactions between the analytes and the antibodies or antigens immobilized, it is clear that the immobilization procedures of the antibodies (antigens) on the surfaces of base transducers should play an important role in the construction of immunosensors. Numerous immobilization procedures have been employed for diverse immunosensors, such as electrostatic adsorption, entrapment, cross-linking, and covalent bonding procedures. They may be appropriately divided into two kinds of non-covalent interaction-based and covalent interaction-based immobilization procedures. 

Certain counterions may be held in the compact region of the donble layer by forces additional to those of purely electrostatic origin, resulting in their adsorption in the Stem layer. Specifically... 

Polymeric polyamines are also strongly adsorbed in the compact region of the electric double layer as a combination of multisite electrostatic and hydrophobic interactions. The adsorption results in masking the silanol groups and the other adsorption active sites on the capillary wall and in altering the EOF, which is lowered and in most cases reversed from cathodic to anodic. One of the most widely employed polyamine coating agents is polybrene (or hexadimetrine bromide), a linear hydrophobic polyquaternary amine polymer of the ionene type [129]. 

Physical adsorption, or van der Waals adsorption, results from a relatively weak interaction between the solid and the gas. The forces responsible for adsorption are dispersion forces (characterized by London see 3.3.1) and/or electrostatic forces (Coulombic see 3.3.2) if either the gas or the solid is polar in nature. Physical adsorption is reversible hence all the gas adsorbed by physical adsorption can be desorbed by evacuation at the same temperature. Chemical adsorption is a result of a more energetic interaction between the solid and the gas than that of physical adsorption. Reversal of chemical adsorption using a vacuum requires elevated temperature, and even that may not be sufficient. Physical adsorption, being of more interest in gas-solid flows, is the focus of the following sections. 

The foregoing electrostatic calculations hold, moreover, only for positions in the middle of a cubic face of a crystal of the NaCl type. Any deviation from this situation may result in a stronger electrostatic bond. Corners and edges of crystals, other crystallographic faces, lattice disturbances, etc., may all form active spots where the electrostatic adsorption of ions is relatively strong. We shall return to the problem of active spots in Sec. V,12. 

The dominant role of electrostatic adsorption has been obvious since the study of Dun et al. [160], who were surprised to find that there was an 18-fold decrease in the uptake of Mo(VI) anions when the pH was raised from 2.1 to 9.4. Solar et al. ]60] clarified this trend and explained their own adsorption results based... 

There are two methods of stabilization of lyophobic colloids electrostatic and polymeric. Electrostatic stabilization results from charge-charge repulsion, as discussed previously. Polymeric stabilization is achieved by the adsorption of macromolecules (lyophilic colloids) at the surface of a lyophobic colloid. Macromolecules of at least a few thousand molecular weight are required, as they must extend in space over... 

Polymeric polyamines are also strongly adsorbed in the compact region of the electric double layer as a combination of multisite electrostatic and hydrophobic interactions. The adsorption results in masking the silanol groups and the other adsorption active sites on... 

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