Functionalization of amorphous nitrogenated carbon thin film electrodes for improved detection of cadmium vs. copper cations

The specificity of a sensor relative to specific cations can be modified by functionalization of amorphous nitrogenated carbon thin film (a-C:N-x) electrodes. This surface modification was performed through the reduction of diazonium salts presenting different functionalities which could interact selectively with ions in solution. Cyclic voltammetry from +0.3 to -1.0 V vs. SCE was used for the grafting process leading to the formation of covalent C-C bonds onto the film surface. The precursor concentration and number of cycles were optimized and correlated to the specificity and sensitivity for copper and/or cadmium ion detection. The coverage of the electrode was checked by cyclic voltammetry measurements using the Fe(CN)(6)(3-/4-) system, interface charge transfer and contact angle. It showed that the electroreduction of diazonium salt and grafting of substituted aryl groups was effective on the surface of the a-C:N-x electrodes. A greater sensitivity of the electrode to Cd2+ was observed for the highest concentrations of precursors (4-amino benzene carboxylic acid (4-ABA)) compared to the pristine electrodes. Moreover, a marked decrease of cadmium sensitivity is noted after grafting but at the same time with a decreased influence of copper on the Cd2+ signal, indicating a better specificity of these functionalized sensors. (C) 2014 Elsevier B.V. All rights reserved.