Nickel clusters grown on three-dimensional graphene oxide-multi-wall carbon nanotubes as an electrochemical sensing platform for luteolin at the picomolar level

This study focuses on enhancing the catalytic activity of metallic Ni by using various nanostructured carbon materials, including 1D multi-wall carbon nanotubes (MWCNTs), 2D graphene oxide (GO) and graphene (GR), and 3D graphene oxide-multi-wall carbon nanotubes (GO-MWCNTs) as supporting matrices for the fabrication of an electrochemical sensor for detecting the flavonoid luteolin. Ni clusters were prepared by a facile electrochemical approach and the metallic Ni on various carbon supports exhibited different morphologies, which were characterized by scanning electron microscopy (SEM) and Raman spectra. The electrocatalytic performance of Ni-based materials towards luteolin oxidation was studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that Ni clusters supported on GO-MWCNTs (Ni/GO-MWCNTs) were profoundly superior to other carbon materials, with a greatly enhanced current. This is attributed not only to the excellent electric conductivity and large surface-to-volume ratio of Ni/GO-MWCNTs, but also to the unique 3D carbon nanostructure that facilitates the easy access of the electrolyte and analyte to the modified electrode surface and promotes the reaction kinetics. Under the optimal conditions, the anodic peak current was linear to the concentration of luteolin in the range from 1 pM to 15 mu M with a detection limit of 0.34 pM (S/N = 3). The good analytical performance, low cost and straightforward preparation method made this novel electrode material promising for the development of an effective luteolin sensor.