Charge neutralization memory

A very important electrochemical phenomenon, which is not well understood, is the so-called memory effect. This means that the charging/discharging response of a conducting polymer film depends on the history of previous electrochemical events. Thus, the first voltammetric cycle obtained after the electroactive film has been held in its neutral state differs markedly in shape and peak position from subsequent ones [126]. Obviously, the waiting time in the neutral state of the system is the main factor determining the extent of a relaxation process. During this waiting time, which extends over several decades of time (1-10 s), the polymer slowly relaxes into an equilibrium state. (Fig. 13) After relaxation, the first oxidation wave of the polymer appears at more... 

The result of the calculation is shown in Fig. 14, it is clear seen that the tunneling from the state 0,0) to the charged state and from the state 1,0) to the neutral state is exponentially suppressed in comparison with the bare tunneling rate F at large values of the electron-vibron interaction constant A. This polaron memory effect can be used to create nano-memory and nanoswitches. At finite voltage the switching between two states is easy accessible through the excited vibron states. It can be used to switch between memory states [112]. 

Polythiophenes present a multitude of color contrasts. These polymers, with a functional group terminal to a flexible alkyl chain at the 3-position of the ring, are used for many specialized applications. One such candidate of this class is poly(3-[12-(/7-methoxyphenoxy)dodecyl]thiophene [poly(12-MPDDT)], synthesized by Ribeiro et al., which exhibited a deposition charge of ca. 65 mCcm" presented greater stability over a large number of redox cycles (> 1000), a chromatic contrast of 40 % at 725 nm, a Coulombic efficiency of 80 % and good optical memory in the neutral state (E = 0.0 V) [15]. 

While some of this discussion brings back memories of the redox analysis described in the previous section, you should be careful to note that the current case is not redox chemistry. The sulfur ion in the reactant has a charge of —2, as described in the equation. The sulfur in the product CuS also has a charge of —2, but it is not shown that way since it is an element in a neutral molecule. Thus, there is no change in the oxidation of the sulfur, and this is not a redox reaction. 

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