Indirect amperometric sensing of dopamine using a redox-switchable naphthoquinone-terminated self-assembled monolayer on gold electrode
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We report on the design of a simple yet sensitive and selective electrode for amperometric determination of dopamine at a cathodic potential as low as −0.30 V vs. Ag/AgCl. The electrode was obtained by self-assembly of ω-mercaptopropyl naphthoquinone (NQ-SAM) on the surface of a polycrystalline gold electrode. The presence of dopamine induces an increase of the reduction current peak at −0.30 V corresponding to the reduction of naphthoquinone to hydronaphthoquinone. Dopamine and dopamine-quinone accumulate on the surface to form a 3D network linked by hydrogen bonds. Raman and infrared spectroscopy as well as atomic force microscopy confirmed the multilayer formation. The method allows dopamine to be indirectly detected at a working potential that is lower by 0.50 V than the standard oxidation potential at a bare gold electrode. The sensor shows distinct oxidation potentials for dopamine (120 mV), ascorbic acid (280 mV) and uric acid (520 mV) which makes the method fairly selective. The analytical range extends from 1 to 100 μM concentrations of dopamine, and the limits of detection and quantification are 0.040 and 0.134 μM, respectively.
KeywordsElectroactive SAM Atomic force microscopy Cyclic voltammetry Dopamine Electron transfer Impedance
Authors wish to acknowledge the financial support from the Tunisian Ministry of Higher Education and Scientific Research for support to this work through the mobility grant “Bourse d’Alternance” awarded to A. Hammami. Thanks also go to the Prof K. Boujlel for helpful discussions and comments and Mr. Ghazi Jomaa (INRAP, Tunis, Tunisia) for the acquisition of the AFM images. We also acknowledge the help of Dr. Adel Moadhen form the laboratory “Nanomatériaux et Photonique” for the Raman spectroscopy facility and recording of the Raman spectra.
Compliance with ethical standards
The author(s) declare that they have no competing interests.
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