Electrochemical synthesis of nickel-cobalt oxide nanoparticles on the glassy carbon electrode and its application for the voltammetric determination of 4-nitrophenol

In this article, a new voltammetric sensor for determination of 4-nitrophenol (4-NP) based on nickel-cobalt oxide nanoparticle (Ni-Co-OX NPs)-modified glassy carbon electrode (GCE) was presented. The nickel-cobalt nanoparticles (Ni-Co NPs) were firstly electrodeposited on the GCE by repetitive potential cycling method, and then, the deposited NPs were converted to Ni-Co-OX NPs by sweeping the potential of the electrode from 0.0 to 0.6 V in 0.1 M NaOH solution. The obtained electrocatalyst (Ni-Co-OX NPs) was analysed via scanning electron microscopy and energy-dispersive X-ray spectroscopy. 4-Nitrophenol showed a well-defined reduction peak at about -733 mV at the Ni-Co-OX NPs/GCE in the phosphate buffer solution (pH 6.0). Compared with the bare GCE, the reduction peak current was clearly enhanced and the overpotential was significantly decreased at the Ni-Co-OX NPs/GCE. The diffusion coefficient (D) of 4-nitrophenol at the modified electrode was also determined utilizing chronoamperometry. The current response of the modified electrode was linear with the 4-NP concentration in the range from 7 to 682 A mu M, with a detection limit of 4.8 A mu M (S/N = 3), using differential pulse voltammetry.