A nanocomposite consisting of flower-like cobalt nanostructures, graphene oxide and polypyrrole for amperometric sensing of nitrite

A glassy carbon electrode (GCE) was modified with graphene oxide-doped polypyrrole (PPy), and flower-like cobalt nanostructures were then deposited on GCE by electrochemical reduction. The modified electrode shows improved catalytic behavior towards nitrite oxidation as the result of the nanoporous structure and the synergistic effect between cobalt nanostructures and GO/PPy. It is found that the amperometric oxidation current at 0.80 V (vs SCE) is about 2.5 times larger than that of a GCE modified with carbon nanotubes. Under optimum conditions, the modified electrode displays a linear range that extends over the 1.0 mu M to 3.2 mM and 6.8 - 12 mM concentration ranges, a lower detection limit of 15 nM (at an S/N ratio of 3), and a response time of 1 s. The modified electrode is adequately selective, highly stable and highly reproducible. The method was successfully applied to the determination of nitrite in pickled radish.