A new bifunctional electrochemical sensor for oxidation of cysteine and reduction of iodate

In this work, a new organic-inorganic hybrid compound containing N,N'-bis(salicylidene)-1,2-phenylenediaminocobalt (III) (CoSal) complex and a Keggin type polyoxometalate, H4SiW12O40 (SiW12), has been synthesized and characterized. F1'-IR spectra showed the presence of both species, UV/Vis spectra displayed the interaction between CoSal and POM in the hybrid compound and XPS determined the oxidation states of cobalt in CoSal and in the hybrid compound. Elemental (CHN) and thermogravimetry analyses showed that 4 mol of CoSal complex react with one mole of SiW12 to form (CoSal)(4)SiW12. This compound was used as a bulk-modifier to fabricate the chemically modified carbon paste electrode (CPE) by direct mixing. The electrochemical behavior and electrocatalysis of bulk modified CPE was studied in 1 M H2SO4 acidic solution by cyclic voltammetry in detail. The results indicate that the modified electrode has a notable bifunctional catalytic activity. It reduces iodate and this property is attributed to the function of SiW12; on the other hand, it oxidizes cysteine due to the function of the CoSal complex. Analytical features of the sensor for amperometric determination of iodate and cysteine were also evaluated. The sensor has a good stability; moreover, it can be renewed easily and repeatedly through a mechanical polishing process. These properties make the modified CPE a good candidate to act as a bifunctional electrocatalyst and an electrochemical sensor as well. (C) 2013 Elsevier B.V. All rights reserved.