The Application of Electrochemical Impedance Techniques in Analyzing the AC Response of Some Two-electron Transfer Dye Systems
DOI : 10.3844/ajassp.2005.1595.1599
American Journal of Applied Sciences
Volume 2, Issue 12
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 ? 105 Hz). The investigations were carried out at room temperature in aqueous media (HClO4, NaClO4 and KNO3) 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° (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 well-separated time constants. The EIS characteristic parameters for these dye systems were calculated and discussed.
© 2005 Farouk Rashwan. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.