Electrochemical detection of methyl-paraoxon based on bifunctional cerium oxide nanozyme with catalytic activity and signal amplification effect

A new electrochemical sensor for organophosphate pesticide (methyl-paraoxon) detection based on bifunctional cerium oxide (CeO₂) nanozyme is here reported for the first time. Methyl-paraoxon was degraded into p-nitrophenol by using CeO₂ with phosphatase mimicking activity. The CeO₂ nanozyme-modified electrode was then synthesized to detect p-nitrophenol. Cyclic voltammetry was applied to investigate the electrochemical behavior of the modified electrode, which indicates that the signal enhancement effect may attribute to the coating of CeO₂ nanozyme. The current research also studied and discussed the main parameters affecting the analytical signal, including accumulation potential, accumulation time, and pH. Under the optimum conditions, the present method provided a wider linear range from 0.1 to 100 μmol/L for methyl-paraoxon with a detection limit of 0.06 μmol/L. To validate the proof of concept, the electrochemical sensor was then successfully applied for the determination of methyl-paraoxon in three herb samples, i.e., Coix lacryma-jobi, Adenophora stricta and Semen nelumbinis. Our findings may provide new insights into the application of bifunctional nanozyme in electrochemical detection of organophosphorus pesticide.