Sensitive detection of chromium (VI) using Au-NPs/MWCNT/chitosan composite via electrochemical approach

Abstract

A glassy carbon electrode (GCE) was nanostructurally modified with a scaffold of gold nanoparticles (AuNPs), multiwalled carbon nanotubes (MWCNTs) and chitosan (Chit) for a sensitive detection of hexavalent chromium Cr(VI) in aqueous solutions. Each step of modification was analyzed and characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Strong interfacial adhesion between gold nanoparticles and porous nanostructure of MWCNTs-Chit was depicted. This scaffold uniformly distributed hydroxyl and carboxylate groups, as well as amine group throughout the surface of glassy carbon electrode, and gold nanoparticles adhered to carbon nanotubes wall inside the polymeric matrix. This scaffold selectively coordinated and preconcentrated the chromate ions for ulterior Cr(VI) detection. Under the optimized conditions (deposition potential: + 0.8 V vs. SCE, deposition time: 120 s), differential pulse voltammetry (DPV) electroanalysis results indicated the linear increment of electrochemical signals with an increase in the concentration of Cr(VI). Fabrication of a calibration curve was performed in a concentration range of 0.003–0.1 μg L−1 and limit of detection (LOD, 3σ/m) was calculated as 0.007 μg L−1. This nanostructured electrochemical sensor coupled with differential pulsed voltammetry, constitutes a very effective prospective capable of high sensitivity, selectivity, precision, accuracy, and rapid trace determination of hexavalent chromium ion in aqueous medium.