Surface Charges and Electrical Double Layer Background

2 SURFACE CHARGES AND ELECTRICAL DOUBLE LAYER BACKGROUND 

A surface immersed in a liquid can acquire charges in a number of ways. For example  

One of the common charging mechanisms is the preferential adsorption of an ion from a solution on an initially uncharged surface. An example of this mechanism is the binding of a Ca2+ ion on a zwitterionic (which implies that the surface group consists of surface dipoles but no net charge) head group of a lipid layer. 

Another possible mechanism is the ionization or dissociation of a surface group (e.g., dissociation of a proton from a carboxylic group, namely, —COOH - —COO- + H +, which leaves the surface with a negative charge). 

TABLE 11.1 Examples of Charging Mechanisms that Lead to Charges at an Interface8 

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