Electrocatalytic Activity Enhancement Using Graphene-Metal Oxide Nanocomposites for the Ultra Low Level Detection of Biomolecules

Metal oxide/reduced graphene oxide (MO/RGO, MO = NiO, Co 3 O 4, and SnO 2 ) nanocomposites were synthesized by a cost-effective hydrothermal method. The structural, thermal, and morphological characteristics of composites were investigated using PXRD, FT-IR, TGA, Raman, SEM, and HR-TEM. Modified carbon paste electrochemical sensors based on NiO/RGO, Co 3 O 4 /RGO, and SnO 2 /RGO were developed and compared for the effective detection of Epinephrine (EPN), Serotonin (SER), and Tyrosine (TYR). The performance of the NiO/RGO/CPE sensor was superior to other composites modified electrodes. The electrochemical measurements were studied by cyclic voltammetry, differential pulse voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The modified electrodes showed excellent electrocatalytic activity towards EPN, SER, and TYR arising from the synergistic effect of reduced graphene oxide and metal oxide. The excellent electrical conductivity imparted by direct interphase of RGO to semiconductive metal oxide, increased surface area, and the increased number of active sites favor the sensitive determination of biomolecules. The NiO/RGO/CPE facilitated the analysis of EPN, SER, and TYR with a lower detection limit of 158 pM, 165 pM, and 519 pM respectively. The peaks for the three biomolecules are well separated from each other and the electrodes were effectively used for real samples.