Binary NiO-MnO catalyst for amperometric biosensors

Abstract

Transition metal oxides are used in a wide variety of technologically important catalytic processes. In this work, two types of transition metal oxides, nickel oxide and manganese oxide, were synthesized using hydrothermal technique. They were subjected to material characterization testing such as Brunaer-Emmett-Teller (BET), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. It was found that the morphology of nickel oxide and manganese oxide were nanowires and nano - spherical, respectively. The surface area of the particles were found to be affected by the starting material concentration, heating temperature and heating time. It was found that the highest surface area of nickel oxide and manganese oxide, 92.3 m2 g-1 and 102.9 m2 g-1, were obtained when 0.3 M nickel acetate and 0.5 M manganese acetate were used as starting material and synthesized at 200 °C and 100 °C for 7 hours and 3 hours, respectively. The both materials were then applied to construct amperometric biosensors for hydrogen peroxide detection. Layer by layer modified gold electrodes were fabricated by using the metal oxide nanoparticle, polydopamine and carbon nanotubes. The voltammetric responses greatly improved when carbon nanotubes, nickel oxide and manganese oxide were added on the modified gold electrodes. Modified gold electrodes with metal oxides and horseradish peroxidase showed the highest amperometric response. This is due to catalysis activity of both the binary catalyst and enzyme on hydrogen peroxide decomposition. The dynamic range for hydrogen peroxide detection was obtained from 32 µM – 3.0 mM.