Surface electrostatic

Janssens et al. [38, 40] used photoemission of adsorbed noble gases to measure the electrostatic surface potential on the potassium-promoted (111) surface of rhodium, to estimate the range that is influenced by the promoter. As explained in Chapter 3, UPS of adsorbed Xe measures the local work function, or, equivalently, the electrostatic potential of adsorption sites. The idea of using Kr and Ar in addition to Xe was that by using probe atoms of different sizes one could vary the distance between the potassium and the noble gas atom. Provided the interpretation in terms of Expression (3-13) is permitted, and this is a point the authors checked [38], one thus obtains information about the variation of the electrostatic potential around potassium promoter atoms. 

C. J. Drummond and F. Grieser, Absorption spectra and acid-base dissociation of the 4-alkyl derivatives of 7-hydtoxycoumarin in self-assembled surfactant solution Comments on their use as electrostatic surface potential probes, Photochem. Photobiol. 45, 19-34 (1987). 

The real potential, a , of electrons in metals, as shown in Eqn. 2-4, comprises the electrostatic surface term, - ex, due to the surface dipole and the chemical potential term, M., determined by the bulk property of metal crystals. In general, the electrostatic surface term is greater the greater the valence electron density in metals whereas, the chemical potential term becomes greater the lower the valence electron density in metals. 

The unitary real potential, ay., of the surface metal ion consists of the chemical potential, Py, and the electrostatic surface term e x as shown in Eqn. 3-7 ... 

As mentioned in Chap. 1, the ion level represented by the real potential a consists of the chemical potential and the electrostatic surface energy Zi e x (a + 2i e x). Since the surface potential, x, of aqueous solutions is constant (x 0.13 V), the relative energy level of hydrated ions may be expressed in terms of the chemical potential... 

Woodle M, et al. Sterically stabilized liposomes. Reduction in electrophoretic mobility but not electrostatic surface potential. Biophys J 1992 61 902. 

One consequence of the molecular asymmetry is that the core particle presents two distinct faces, arbitrarily labeled ventral and dorsal in our images. These two faces have subtle yet distinct dilferences in the electrostatic surface potentials they present. 

An approximate quantum mechanical expressions- that allows one to calculate the electrostatic surface potential around atoms, radicals, ions, and molecules by assuming that the ground-state electron density uniquely specifies the Hamiltonian of the system and thereby all the properties of the ground state. This approach greatly facilitates computational schemes for exact calculation of the ground-state energy and electron density of orbitals. 

Shape descriptor derived from ray traces of the molecule s electrostatic surface potential. 

Reversed-phase chromatography is often used to separate both neutral and ionic organic compounds. In this section, some important aspects for the understanding of the behavior of ionic compounds in reversed-phase chromatography are discussed. The important concepts introduced here are the electrical double layer and the electrostatic surface potential. It will be shown that they are essential for the understanding of the elution profile of ionic compounds. These concepts are further explored in the next section where theoretical models for ion-pair chromatography are discussed. 

For low surface concentrations of charged solutes, the G-C model shows that the electrostatic surface potential created by the adsorbed ions is proportional to the surface concentration of the ion according to the following equation [2,3] ... 

From the previous discussion, it is clear that when an ionic solute adsorbs to the reversed-phase stationary phase, it will create an electrostatic surface potential that will repel ions with the same charge from the surface and that the magnitude of the repulsion is represented by Equation 15.11. With the help of Equations 15.11 and 15.12, the adsorption isotherm for an ionic solute can be derived in the following way ... 

To write down the electrochemical potential for the surface, we must consider that the ionic analyte changes the electrostatic surface potential, i.e.,... 

Equation 15.22 shows that it is the electrostatic surface potential created by the adsorbed pairing ion that is the driving force behind the regulation of retention. The electrostatic surface potential... 

When the electrostatic surface potential becomes high or when the monolayer capacity of the surface is approached. So far the models agree with experiments up to 60-70 mV but the upper limit is probably below 100 mV. 

The Poisson-Boltzmann equation. The slab model is based on a solution of the linearized Poisson-Boltzmann equation that is valid only for low electrostatic surface potentials. As... 

Fig. 2 Electrostatic surface rendering of Aspergillus oryzae (left) and Fusarium solani (right) cutinases. The solid density illustrates the groove on the surface proximal to the active site [53]...

Figure 7.11 A The electrostatic surface potential of trypsin (left) and gamma...

The influence of the surface polarity of powders on their adsorption and dispersion properties can be profound, as is discussed in Sec. VIII,A. The values of F are likely to be put to many uses as more of them are measured. The electrostatic surface fields are doubtless involved in the phenomena of chemisorption and catalysis, capable of inducing polarization or electron shift of adsorbing molecules. For silica-alumina catalysts, the production of active M-O-M surface groups must be considered the most important factor responsible for chemisorption and catalj ic activity. 

CODESSA Constitutional, topological, geometrical, electrostatic, surface property, quantum chemical, and thermodynamic descriptors 1,500... 

Figure 4. Calculated dependence of the ratio of the surface charge density to the surface excess on the electrostatic surface potential. Curve A is for the infinite flat plate case. Curve B is for a sphere with a 1000 A. radius...

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