FeMoO₄ based, enzyme-free electrochemical biosensor for ultrasensitive detection of norepinephrine

Herein, FeMoO₄ (FM) nanorods were synthesized by a template-free, facile, hydrothermal method in an aqueous medium. The surface morphology of FeMoO₄ was identified with field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). X-ray diffraction (XRD) was performed to identify the crystallographic nature of the as-synthesized FeMoO₄. The as-synthesized material was used as an active electrode material for the oxidation of a neurotransmitter (i.e. norepinephrine (NE)) by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. FeMoO₄ possesses polycrystallanity and bimetallic character, which helps to enhance the performance of the FM/GCE as compared to the GCE. The enhanced performance was also due to the formation of Fe (II)-dioxygen complexes, which catalyze the oxidation of NE. Meticulous observations taken from CV studies proved the diffusion-controlled nature of the reaction with a diffusion coefficient of 1.10×10^-4 cm²/s and a standard heterogeneous rate constant of 4.078×10^-3 cm/s. The amperometric response of NE on the FM/GCE showed a linear increase in the current between 5.0×10^-8 M and 2.0×10^-4 M with a detection limit of 3.7×10^-9 M. In the amperometric study, the time required to reach the 98% steady state response, after successive additions of 50 nM NE, was less than 3 s. The FM/GCE showed good sensitivity, and stability for the determination of NE.