Voltammetric sensing of dopamine based on a nanoneedle array consisting of NiCo₂S₄ hollow core-shells on a nickel...

An array consisting of homogeneous NiCo₂S₄ hollow core-shell nanoneedles was fabricated and is shown to enable sensitive electrochemical determination of dopamine (DA). The array was grown directly on a nickel foam (NF) substrate by a two-step hydrothermal process. The hierarchical nanoarray consists of a homogeneous NiCo₂S₄ nanoneedle core and a NiCo₂S₄ nanosheet shell. A 3-dimensional micro/nano structure is formed due to the presence of the micropores of the NF. The electrode was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy. Compared to a plain NF electrode, the NiCo₂S₄-modified NF electrode displays higher electrocatalytic activity for the oxidation of DA by differential pulse voltammetry (DPV). The sensor, best operated at a typical working voltage of 134 mV (vs. saturated calomel electrode), has a linear response in the 0.5-100 μM DA concentration range and a 0.2 μM detection limit (at S/N = 3). The electrode is selective over ascorbic acid and uric acid. Graphical abstract Schematic presentation of an electrochemical sensor for selective determination of dopamine based on the use of a homogeneous NiCo₂S₄ hollow core-shell nanoneedle array on nickel foam.