Phenylamide-oxime and phenylamide nanolayer covalently grafted carbon via electroreduction of the corresponding diazonium salts for detection of nickel ions

This study focuses on the covalent grafting of thin organic layers on a glassy carbon electrode by aryl diazonium salts containing functional groups capable of complexing Ni(II) ions. The goal was to develop a modified electrode for the detection of Ni(II) ions in aqueous media. The glassy carbon electrode (GCE) surface was modified by electrochemical reduction of diazonium salts synthesized in-situ in aqueous acid medium from 4-amino-benzamide (4-AB) and 4-amino-benzamide-oxime (4-ABO). XPS, AFM, ellipsometry and cyclic voltammetry were used for surface characterization of the grafted GCE. The barrier properties of the grafted layer were determined and compared by cyclic voltammetry, using Fe(CN)63−/4−, Ru(NH3)63+/2+ and dopamine redox probes in different pH media. The adsorptive properties of the grafted glassy carbon were compared for Pb(II), Cu(II) and Ni(II) cations. The ability of these modified GCE to detect Ni(II) ions was then explored using a two-step method: i) complexation of Ni(II) by the grafted layer, followed by ii) electroreduction of the complexed Ni(II) and then its analysis by anodic square wave voltammetry. The 4-ABO grafted glassy carbon electrodes were able to detect Ni(II) in micro-molar concentration. The presence of ions such as Pb2+, Mg2+, Ca2+, K+ and Na+ did not interfere with the Ni(II) quantification. The phenyl-oxime functionalized electrodes showed good robustness during more than fifty electroanalysis.