Abstract
Tannic acid-doped polypyrrole (PPY/TA) films have been grown on goldelectrodes for selective electrochemical detection of dopamine (DA). Electrochemicalquartz crystal microbalance (EQCM) studies revealed that, in vivid contrast toperchlorate-doped polypyrrole films (PPY/ClO4-), the redox switching of PPY/TA filmsin aqueous solutions involved only cation transport if the solution pH was greater than3~4. The PPY/TA Au electrodes also exhibited attractive permselectivity forelectroactive cations, namely, effectively blocking the electrochemical reactions ofanionic ferricyanide and ascorbic acid (AA) while well retaining the electrochemicalactivities of hexaammineruthenium (III) and dopamine as cationic species. A 500 HzPPY/TA film could effectively block the redox current of up to 5.0 mM AA. Thecoexistence of ascorbic acid in the measurement solution notably enhanced the currentsignal for dopamine oxidation, due probably to the chemical regeneration of dopaminethrough an ascorbic acid-catalyzed reduction of the electro-oxidation product ofdopamine (EC’ mechanism), and the greatest amplification was found at an ascorbic acidconcentration of 1.0 mM. The differential pulse voltammetry peak current for DAoxidation was linear with DA concentration in the range of 0 to 10 μM, with sensitivityof 0.125 and 0.268 μA/μM, as well as lower detection limit of 2.0 and 0.3 μM in a PBSsolution without AA and with 1.0 mM coexisting AA, respectively.
Highlights
The area of electroactive polymers confined to different electrode surfaces has received great attention
A major obstacle in the electrochemical detection of DA directly at metallic or carbon electrodes is the interference of ascorbic acid (AA), which coexists with DA in central nervous systems and is oxidized in the almost same potential range as DA is done on bare gold electrodes [11]
Despite the PPY/Tannic acid (TA) films being more porous than the PPY/ClO4- films, the oxidation of AA can be totally suppressed at the 500 Hz polypyrrole films with TA as the dopant (PPY/TA) film, which is attributed to higher density of phenyl, carbonyl and hydroxyl groups of tannic acid molecules which were entrapped in PPY/TA films during electropolymerization, the PPY/TA films has higher electron density which can repel anions
Summary
The area of electroactive polymers confined to different electrode surfaces has received great attention. Polymer-modified electrodes (PMEs), in contrast to metallic or carbon substrate electrodes, can be designed through polymer screening to provide tremendous improvements in sensitivity and selectivity to detect variety of analytes. These electrodes have been demonstrated to be useful for improving ionic permselectivity, the stability and reproducibility of the electrode response, and for favorably realizing electrocatalytic chemical analysis [1,2,3,4,5,6,7,8]. Polypyrrole films doped with tannic acid have been grown on gold electrodes by electropolymerization of pyrrole and used for selective electrochemical detection of DA.
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