Electrochemically induced regioregularity of the binding sites of a polyaniline membrane as a powerful approach to produce selective recognition sites for silver ion

摘要

Polyaniline (PANI) modified electrodes based on the electrochemical polymerization of aniline in the presence of a chelating agent, 5-sulfosalicylic acid (SSA), were prepared. The resulting PANI/SSA membrane was templated with respect to silver ion by applying consecutive reduction/oxidation steps. The electrochemically mediated templating causes doping/undoping of silver ions into the polymeric membrane. It seems that repeated addition/removal of silver ions into/from the membrane, induces conformational changes in the binding sites of the PANI and SSA, and increases the number of proper binding sites. This electrochemically induced regioregularity of the binding sites of the membrane components was found to be a powerful approach to produce selective recognition sites for silver ions in the PANI/SSA membrane. The system was able to fulfill four main criteria of the recognition process, including selectivity, sensitivity, rapidity and chemical reversibility in the voltammetric and potentiometric detection of silver ion. The prepared sensor was employed for preconcentration and differential pulse anodic stripping voltammetric (DPASV) measurement of silver ion. The stripping peak current was found to be dependent on the silver ion concentration over the range 1.0 x 10(-10) to 1.0 x 10(-4) M. Several metal ions did not show appreciable interference in the voltammetric determination of Ag+, however, mercury ion led to a significant interference. During potentiometric measurements, the sensor demonstrated reproducible response with a near-Nernstian slope of 57.1 +/- 0.4 mV per decade of silver ion activity over a linear range extending five orders of magnitude (1.0 x 10(-8) to 1.0 x 10(-3) M Ag+), with a detection limit of 1.0 x 10(-9) M Ag+. The templated electrode provided improved potentiometric selectivity for silver ion with respect to various metal ions and could be used over a pH range of 3.0-5.5. (C) 2016 Elsevier B.V. All rights reserved.