Electrocatalytic Detection of Epinephrine at Polyaniline-Biosynthesized Nickel Oxide Modified Electrode. Supported By Computational Study

Abstract

The design of a simple, cost effective and reliable assay with fast response time for epinephrine (EP) is unceasing due to its dual function as a neurotransmitter and a fight-flight hormone released amid critical stress. In contribution, Polyaniline (PANI) and nickel oxide (NiO) nanoparticle was integrated unto glassy carbon electrode (GCE) in the design of a sensor for EP. PANI and NiO were synthesized through chemical oxidation polymerization and Callistemon viminalis leaf extracts, accordingly. The choice of electrode materials was based on the high surface area resulting from the synergistic catalytic properties of PANI and NiO, ease and cost of preparation. Fourier transform infrared spectroscopy, ultraviolet visible spectroscopy, x-ray diffraction and scanning electron microscopy results revealed successful synthesis of PANI, NiO and the composite (PANI/NiO). Electron transport properties of the bare and modified electrodes (GCE/PANI, GCE/NiO and GCE/PANI/NiO) as well as their electrocatalytic activity towards EP, was investigated using cyclic voltammetry and electrochemical impedance spectroscopy. Voltammetric and impedimetric response was enhanced at the PANI/NiO electrode compared with other electrode investigated. This was ascribed to improved synergistic Electrocatalytic effect of nanocomposite. Under optimized experimental conditions (pH and deposition time), the limit of detection measured was 8.2 μM and 6.1×10-3 μA/μM sensitivity over a linear EP concentrations ranging from 0 - 534 μM in 0.1 M phosphate buffer solution using square wave voltammetry. Good recovery of 102-105% was obtained for EP determination in adrenaline injection solution. The developed sensor demonstrated a good reproducibility, stability and selectivity to EP in the presence of ascorbic acid and uric acid.In addition, computational study of the LUMO (lowest unoccupied molecular orbitals)-HOMO (highest occupied molecular orbital) energy band gap of 5.48 eV calculated for EP at density functional theory level supports charge transfer and stability of EP at the nanocomposite modified electrode. Keywords. Electrocatalytic, Epinephrine, Detection, modified electrode, Polyaniline, Nickel oxide, Computational, Voltammetric, Impedimetric. Figure 1