Electrochemical preparation of gold nanoparticles on ferrocenyl-dendrimer film modified electrodes and their application for the electrocatalytic oxidation and amperometric detection of nitrite

This work describes the preparation of sensors for electrochemical determination of nitrite, based on modified electrodes prepared by simple and reliable electrodeposition methods. Glassy carbon and platinum electrodes were modified with composite films made from gold nanoparticles (AuNPs) and a carbosilane-dendrimer possessing peripheral electronically communicated ferrocenyl units (Dend), using potentiostatic and cycling techniques. AuNPs with diameters in the range 12-24 nm were assembled to form fractal and flowerlike structures on the surface of electrodes. The modified electrodes exhibited remarkable electrocatalytic activity toward the oxidation of nitrite giving higher peak currents at lower oxidation overpotentials than those found for the bare electrode and the dendrimer-modified electrode. The voltammetric study showed that the electrochemical oxidation of nitrite involves one -electron in the rate -determining step reaction. It is proposed that the mechanism for the interaction of nitrite with ferrocene groups to be oxidized involves attachment to the ferrocene center. At the AuNP5 it is possible to consider that the oxidation of NO2- to NO2 probably proceeds through an adsorption stage. The heterogeneous rate constant, k, for the oxidation of nitrite at the surface of the modified electrodes was determined by rotating disk electrode voltammetry using Koutecicy-Levich plots. The transfer coefficients for electrocatalytic oxidation of nitrite under the experimental conditions were also investigated in this study. Under the optimum conditions the sensor has a linear response in the 10 mu M to 5 mM concentration range, a high sensitivity of 44.8 mu A mu M-1, and a low detection limit of 2.0 x 10(-7)M. Most common ions do not cause interferences. The sensor was successfully applied to the determination of nitrite in natural water samples. (C) 2017 Elsevier B.V. All rights reserved.