Bounded CPE

A bounded CPE (BCPE) describes the impedance of a bounded homogeneous layer with CPE behaviour. Its impedance is written as... 

The impedance of the series connected resistance and bounded CPE element (BCPE), shown in Figure 4.10a, is calculated by adding their impedances ... 

Figure 4.106 shows the Nyquist plot of the series connection between resistance and a bounded CPE. The angles of a and (3 are linked by the relationship... 

Figure 4.20. a Equivalent circuit of modified Randles cell with bounded CPE in series with Rc, (Model D19) b Nyquist plot of modified Randles cell having a bounded CPE in series with Rc, over the frequency range 6 kHz to 1 mHz (Model D19 Rei = 10 2, Rcl = 20 Q, R0 =... 

Figure D.26. Nyquist plot of a resistor and a bounded CPE in series over the frequency range28 kElz to 1 mHz (R = 50 2, Q = 0.01 2 sn, n = 0.45 )...

Figure D.65. Equivalent circuit of modified Randles cell with bounded CPE in series with Rct (Figure 4.20a)...

Stoynov has extended the CPE model for finite-thickness diffusion. He introduced a bounded CPE (BCP) impedance or finite constant phase element... 

If there are deviations from the ideal semi-infinite linear diffusion process, the bounded Randles cell can also be modified by replacing the Warburg impedance with a CPE. The structure of the model is shown in Figure 4.20a. This modification is applied when the transport limitations appear in a layer of finite thickness. 

The complex-plane impedance diagram of the modified bounded Randles cell is given in Figure 4.206. If distortions in the double-layer capacitance are assumed, a CPE can be used to replace Cdl. More examples of this modified bounded Randles cell can be found in Appendix D (Model D19). 

The effect of ionic strength onto MB accumulation behavior was also studied by our group [60]. Chronocoulometric and voltammetric parameters for MB on binding to DNA at CPE were monitored. It was found that 10 mM ionic strength is the critical salt concentration. MB interacts to guanine electrostatically up to 10 mM NaCl, in the presence of higher concentrations of 10 mM of NaCI, MB intercalates to hydrogen bounds of dsDNA. 

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