Surface excess conductivity

Surface Conductivity The excess conductivity, relative to the bulk solution, in a surface or interfacial layer per unit length. Also termed the surface excess conductivity. 

Chemisorption of Carbon Monoxide. Chemisorption of carbon monoxide on NiO(250) does not change the electrical conductivity of the sample. The same result was obtained for NiO(200) (23). The curve of differential heats of adsorption of carbon monoxide on NiO(250) presents many similarities with the curve recorded in the case of NiO(200) (20). However, a few differences are noted. The heat of adsorption of the first dose (0.08 cc. per gram) of carbon monoxide on NiO(200) is high (42 kcal. per mole) (Table II). The adsorption of the next dose on the same oxide releases only 29 kcal. per mole. The initial high value of the heat adsorption was explained by the interaction of CO with excess surface oxygen (Table I), giving C02(ainitial heat of adsorption amounts to 29 kcal. per mole (Table II). It seems, therefore, that the surface excess oxygen... 

A comprehensive study on the sonochemical synthesis of colloidal solutions of noble metals was conducted by Grieser and coworkers [32-34]. The 515 kHz ultrasound-initiated reduction of AuCl4 to Au (0) was examined as a function of the concentration of various surface-active solutes [32]. The amount of AuCU reduced in the presence of ethanol, 1-propanol, and 1-butanol was found to be dependent on the surface excess of the alcohol at the gas/solution interface, i.e., the relative concentration of the alcohol at the gas/solution interface compared to the bulk solution concentration. The efficiency of reduction of AuCl4 in the presence of the surfactants sodium dodecyl sulfate or octaethylene glycol monodecyl ether was found to be related to the monomer concentration of the surfactant in solution. 

Investigating electron migration in nanostructured anatase Ti02 films with intensity-modulated photocurrent spectroscopy [288], it was found that, upon illumination, a fraction of the electrons accumulated in the nanostructured film is stored in deep surface states, whereas another fraction resides in the conduction band and is free to move. These data indicate that the average concentration of the excess conduction band electrons equals about one electron per nanoparticle, irrespective of the type of electrode, the film thickness, or the irradiation intensity. 

X is the concentration of the adsorbate A which is varied in order to study the effect of bulk concentration on the interfacial surface excess y is the concentration of the electrolyte whose activity is kept constant. The corresponding electrolyte concentration is kept reasonably high to provide electrical conductivity to the solution. For low values of x, the electrolyte concentration is constant. However, at higher concentrations of organic solute, the activity coefficient of the electrolyte varies with organic solute concentration. Thus, in general, the concentration of the electrolyte must also be varied in order to keep its activity constant. It is also important that the ions of the electrolyte not adsorb on the electrode to a significant extent. 

He also assumed that the surface charge density undergoes a tangential as well as a vertical variation when an electric field is applied. By solving the continuity equation with appropriate boundary conditions, he obtained an equation for an ellipsoid which has the same form as Fricke s Equation 17 except for the magnitude of the excess conductivity. 

The chemical composition of the (CsSb) film is Cs,Sb [5.56], with microscopic crystal structure in a DOj-symmetry cubic lattice. Within these microcrystals CSjSb is a semiconductor with 1.6 eV bandgap. In an optimized surface, excess Sb in the order of 10 /cm from perfect stoichiometry produces a large density of acceptor levels about 0.5 eV above the valence band the crystal is therefore p-type with a Fermi level somewhat below 0.5 eV, which produces a moderate conductivity through the film at room temperature. 

In the case of electrophoresis, the retardation and relaxation effects are influenced by surface conduction. In Equations 10.10 and 10.25, K p, the specific electric conductivity of the bulk solution should be replaced by a term accounting for the excess conduction at the surface as well. Taking the streaming potential as an example, the expression for Equation 10.24, should be modified to contain a contribution from the surface. Hence,... 

Nevertheless there is a certain danger in the application of (10) and therefore of (11) caused by the so-called surface conductance. As a consequence of the accumulation of ions in the double layer there exists an excess conductance along the surface of the capillary This excess conductance may be of the same order of magnitude as the conductance through the bulk of the liquid, especially in dilute solutions, and the proportionality between i and X is lost. Ixi that case (10) should be replaced by... 

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