Electrochemical Measurement of Solute in Gels

As shown in Fig. 5, the volumetric degree of swelling (V/Vq) of polyacrylamide (PAAm) gel in a water/acetone mixed solvent changes from a 

In addition to solubility, a redox active solute should possess an electrochemically reversible redox reaction, chemical reactions accompanying the addition of this material should not occur, and there should be no adhesion on the electrode surface regardless of the degree of swelling of the gel. The aforementioned Fc satisfies all these requirements when it is used with PAAm gel (see Fig. 6). 

On the other hand, A-D are the results with faster sweeping rate. They show a clear current peak. The value of this peak current is given by Eqs. (4) and (5). When the acetone concentration became more than 60vol%, cases C(C ) and D(D ), the current value became extremely small. In addition, the limiting current and peak current values could not be obtained. This is possibly due to the reduction of the difiusion coefficient or the reduction of the solubility of Fc in the gel as it shrinks. 

Sweep rate A-D, ImV/s A -D, 300mV/s solvent composition (acetone concentration) A, A, 0 vol%  

Neither the current detected at the central electrode (I) nor flie electrode near the rim (O) reduces monotonically as the gel shrinks. 

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