Silver potential mapping

A few types of reference electrodes are used for potential mapping, mainly silver/ silver chloride (Ag/AgCl) or copper/copper sulfate (CSE). They differ in their standard potential, which is the potential difference to the standard hydrogen electrode (SHE). Standard potentials of these reference electrodes are given in Table 16.1, together with some other types used as embedded probes in concrete (Chapter 17). 

A method that has yielded very interesting information about the structure and interactions in the diffuse part of the double layer is the direct measurement of forces between colloidal particles [29].The forces between two mica plates are measured directly in the presence of different solutions These forces show pronoimced oscillations of a period similar to the dimensions of the molecules enclosed between the plates. And last, but certainly not least, there is a very extensive and important literature on the differential capacitance of solutions near either solid (polycrystalline or single crystal) or liquid (mercury) electrodes which we will not try to cover. We should mention the recent work on the influence of the crystallographic orientation of silver on the potential of zero charge of the electrodes, in which a detailed mapping of the influence of the crystal face on the differential capacitance of the inner layer is made [30]. 

Shear force constant distance scanning potentiometry has been employed to map the dissolution of calcite crystals and shells [74] and to map spatial variations in pH at high resolution over complex microcavity-pattemed substrates [75]. The ability to approach capillaries very close to a surface, using shear force feedback, was also used for the local deposition of silver microstructures on conducting surfaces using potential-assisted ion transfer at the tip of a micropipette [76]. 

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