Surface charge density gold electrodes

Figure 3.13 Surface charge density on a gold electrode surface plotted versus the electrode potential for (dotted curve) 50mM NaF supporting electrolyte and (circles) mixed 7 3 DMPC-cholesterol bilayer spread from vesicle solution. Figure taken from [84]. 

FIG. 8. Frequency shift versus surface charge density on gold and silver electrodes in 0.1 M solution of LiC104 in water (a) and in butanol (b). (Fig. 8a from Ref 98.)... 

FIG. 11. The frequency shift versus the surface charge density on gold electrode in 0.1 M LiC104 without (closed circles) and with (open circles) uracil (4 mM). 

While in the mentioned work on PABA on a charged silver electrode also the adsorption degree of the molecules was controlled by surface charge, Lahann et al. showed a concept in which molecules immobilized as a low-density self-assembled monolayer on a gold surface were electrically stimulated to undergo conformational transitions between a hydrophilic and a hydrophobic state (Lahann et al., 2003). Such a surface wetting switch may then be used to immobilize, for example, enzymes, as was discussed in the previous section. This is an example of switching both the orientation and the activity of adsorbed molecules. 

Figure 4.2 Impedimetric detection of DNA oligonucleotides. Sensor preparation as in Figure 4.1. The accessibility of the gold surface for ferri-/ferrocyanide depended on the amount of negative charge accumulated on the electrode surface. DNA hybridization increased the negative charge density and yielded increased charge transfer resistance as measured by impedance spectroscopy.

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