Monolayers diffusion limitation

The deposition takes place from HTeOs and cadmium-EDTA complex solutions at a potential whereat, whilst Te is deposited from HTeOs under a diffusion-limited condition, the Cd-EDTA complex ion is not reduced to metallic Cd. The first step is the dark deposition of one monolayer of elemental Te on the p-Si substrate (Fig. 4.11a, i). After completion of this step, as specified by measuring the charge passed, the electrode is illuminated by light with energy higher than the band gap energy of silicon for a limited time. Then conduction band electrons are... 

FIG. 28 Normalized steady-state diffusion-limited current vs. UME-interface separation for the reduction of oxygen at an UME approaching an air-water interface with 1-octadecanol monolayer coverage (O)- From top to bottom, the curves correspond to an uncompressed monolayer and surface pressures of 5, 10, 20, 30, 40, and 50 mN m . The solid lines represent the theoretical behavior for reversible transfer in an aerated atmosphere, with zero-order rate constants for oxygen transfer from air to water, h / Q mol cm s of 6.7, 3.7, 3.3, 2.5, 1.8, 1.7, and 1.3. (Reprinted from Ref. 19. Copyright 1998 American Chemical Society.)... 

Catalyst samples were pressed as a wafer in the stainless steel or perspex sample holder. It was calculated that, due to diffusion limitations, the aqueous samples needed at least 6 hours pretreatment in order to attain monolayer coverage of the platinum with oxygen or hydrogen throughout the sample. A pretreatment time of 20 hours was chosen. 

Fig. 9L Comparison of the peak current density for formation of an adsorbed monolayer / jj(max) with the peak current density observed for the diffusion-limited oxidation of an impurity...

A. Miller and H. Mohwald, Diffusion limited growth of crystalline domains in phospholipid monolayers, I. Chem. Phys. 86 4258 (1987). 

In the first case (see Eqn. 80) linear Koutecky-Levich behavior is observed for both waves, whereas in the second case (see Eqn. 81) only the mediated wave is observed, and nonlinear Koutecky-Levich plots are obtained. We can see from these expressions that such cases are relatively unattractive. We do not obtain a catalytic enhancement beyond that observed for a monolayer derivitized electrode, furthermore the catalysis is less efficient than a monolayer system due to substrate diffusion limitations inherent in the I//5 term in Eqn. 80 or electron hopping given by the 1 - ilis term in Eqn. 81. 

The same system was used to study the interactions between the polymer mono-layer and a water-soluble protein, bovine serum albumin (BSA) [54]. As could be expected, an increasing amount of PLA in monolayers considerably hindered BSA adsorption, as did the increase of PEO length in the block copolymers. However, many points of this study remain unclear, for example the details of polymer-protein molecular interactions and the protein concentration dependence. No proof was presented that the protein was actually integrated into the monolayer, rather than the interaction being unspecific adsorption (despite PEO-protein repellence), and there was no discussion on the diffusion limit of protein integration. 

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