Non-enzyme picomolar sensing of acephate by modified glassy carbon electrode using bimetallic Zn-Cu metal-organic framework

Abstract

Organophosphate pesticides are used ubiquitously in agriculture; however, their excessive use can cause problems for human health and the environment. Herein, a non-enzymatic electrochemical sensor has been designed and developed for sensing acephate, which is based on modifying a glassy carbon electrode (GCE) with a zinc-copper metal–organic framework (Zn-Cu MOF) as a sensing material and activated charcoal (AC) as an additive for enhancing conductivity and charge transfer rate. Bimetallic Zn-Cu MOF was synthesized using the one-pot solvothermal method and was characterized by different analytical techniques, viz., Field Emission scanning microscope (FE-SEM), High-Resolution Transmission Electron Microscopy (HR-TEM), X-ray Photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), Raman spectroscopy, and Fourier-transform infrared (FTIR) spectroscopy. The electro-catalytic behavior of the modified GCE was studied using Cyclic voltammetry (CV), Electrochemical impedance spectroscopy (EIS), and Differential pulse voltammetry (DPV), which shows better performance as compared to the bare electrode. The modified GCE demonstrates excellent electro-catalytic activity towards acephate molecules, which may be attributed to the synergistic effect of metal ions, high porosity, enhanced active sites, superior conductivity, higher specific surface area, and faster electron transfer rate. After optimization of parameters such as electrolyte pH and volume of coating on GCE, the Zn-Cu MOF/AC/GCE-based electrochemical sensor provides excellent performance in terms of a more comprehensive linear range from 0.1 to 10 nM, the limit of detection (LOD) of 3.3 pM (S/N = 3), excellent selectivity and reproducibility. The extract of vegetable samples spiked with acephate gave satisfactory recovery results in 95.2–103% for tomato juice and 97–107% for cucumber juice.