Metal Ion Incorporation in the Conducting Polymer Electrode Matrix Using an \u27Active\u27 Metal Substrate

The incorporation of free transition metal cations (potential redox catalyst centers) into conducting organic films by electrodeposition is relatively rare due to the repulsive nature of the positive cation radicals of the polymer itself during polymerization. This paper shows that such metal cations can be trapped in the polymer matrix as it is being electrodeposited on a metalsubstrate electrode, which itself simultaneously electro-oxidizes (corrodes).The electropolymerization of 3-methylthiophene on Mo(0), Ni(0) and Fe(0) substrate electrodes (\u27active electrodes\u27) is reported. SEM, EDXRF, and XPS were used to demonstrate the amount of metal cations in and/or on thepolymer matrix and to determine the valence states. The rates of diffusion ofthe incorporated metal ions into an LiClO4 electrolyte solution were also studied. The presence of trace amounts of all three metal cations were sufficient to destroy the electroactivity of the polymer film electrodes for theoxidation of catechol. (C) 1997 Elsevier Science S.A

Flow Injection Amperometric Detection of Catechol Using Dual-band Poly (3-methylthiophene) Electrodes

This work reports the electrochemical detection of catechol (10(-4) to 10(-6) M) in the presence of ascorbic acid (10(-4) to 10(-6) M) using dual-bandpoly(3-methylthiophene) (P3MT) electrode flow-injection amperometry without prior separation. The selectivity involved in this method is based on the differences in electrochemical behavior of catechol and ascorbic acid. A variety of dual-band Pt, Au, glassy carbon, and P3MT electrodes were constructed and used as the electrochemical detector. The upstream electrode of the series dual-band electrode unit is used for detection ofcatechol and ascorbic acid and the downstream electrode for detection ofthe oxidized catechol. The band dimensions range from 0.1 x 2.5 to 1 x 5.5 mm with the interelectrode gaps varying from 0.1 to 0.5 mm. Although this method is effective for dilute solutions of catechol (10(-5) M) unless the measurements are made under acidic conditions such as at pH 1.6. A negative deviation from the ideal calibration curve of the oxidizedcatechol reduction is found in the more concentrated mixtures (\u3e10(-5) M) at physiological pH 7.4. Charge-dipole interaction and hydrogen bonding between the oxidized products of,catechol and ascorbic acid in the concentrated neutral solutions are proposed to explain the suppression ofthe current signals. Variation of the flow rates from 0.5 to 3.0 ml/min has no effect on the performance of the detector. The dual-band P3MT electrode has less positive oxidation potentials for catechol and ascorbic acid oxidation compared to the bare Pt, Au, and glassy carbon electrodes because of the catalytic activity of the P3MT electrode surface. Dual-bandP3MT as well as glassy carbon electrodes have the best (highest) collection efficiency for catechol detection. The collection efficiency also remains constant when the interelectrode gaps vary from 0.1 to 0.5 mm. (C) 1998 Elsevier Science Ltd. All rights reserved