The Application of Electrochemical Impedance Techniques in Analyzing the AC Response of Some Two-electron Transfer Dye Systems

Abstract

Abstract:The Electrochemical Impedance Spectroscopic techniques (EIS) were used to investigate the behavior of some dye compounds (quinoid systems) characterized with 2e-transfer processes. For this purpose, Alizarin Red S (ARS), Alizarin Cyanine (AC), Alizarin Viridin (AV) and carminic acid were chosen for the measurements. The EIS experiments were performed using a small AC amplitude (10 mV p-p) in addition to a relatively wide frequency range (0.01 Hz ≤ f ≤ 10 5 Hz). The investigations were carried out at room temperature in aqueous media (HClO 4 , NaClO 4 and KNO 3 ) on the Hanging Mercury Drop Electrode (HMDE) and for comparison one experiment only was measured in aprotic solvent (DMF) on the Pt-disc electrode. The EIS diagrams of these systems were characterized in the complex plane by two fundamental observations, the first of which is a straight line crossing the real axis at an angle of 45 o (or at least nearly so) and the second one is two semicircles beside each other corresponding to high-frequency and low-frequency regions, which are implying the presence of wellseparated time constants. The EIS characteristic parameters for these dye systems were calculated and discussed.

Electrochemical impedance spectroscopy and cyclic voltammetry of ferrocene in acetonitrile/acetone system

“…The EIS results demonstrate that the diffusion of FeCp 2 species in the solution is the rate-determining step in the whole process, and consequently, the process can be characterized as diffusion-controlled process. This behavior reveals also that the k s values of the FeCp 2 ?/0 redox couple must be greater than k s [ 0.01 cm s -1 [36,37]. These results are in accordance with the CV results (Table 3).…”