Facile preparation of an electrochemical sensor sensitive to diclofenac sodium using pencil graphite electrode modified with halloysite and Au-Pd bimetallic nanoparticles

This paper describes a new, simple, cheap, and accurate electrochemical sensor for measuring the concentration of diclofenac in solotions. The surface of a pencil graphite electrode (PGE) was modified with halloysite film and decorated with the gold–palladium bimetallic nanoparticles (Au–PdNPs) to fabricate the sensor. Cyclic voltammetric technique was employed for deposition of Au–PdNPs on the surface of the halloysite modified PGE. Field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS) and electrochemical impedance spectroscopy (EIS) were used to study the changes of the surface of the pencil graphite electrode during the modification process. The electrochemical behavior of the fabricated Au–PdNPs/halloysite/ PGE was evaluated for the quantitative determination of diclofenac using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The effect of the parameters such as pH of solution, electrodeposition cycle number and the amount of modifier that control the electroanalytical performance of the fabricated sensor was examined, and they were optimized. The developed sensor exhibited excellent catalytic activity for the electro-oxidation of diclofenac molecules in aqueous solutions. It also showed a high selectivity for diclofenac molecules in the presence of the interfering species. Moreover, the reproducibility (RSD 2.45%), repeatability (RSD 2.97%) and stability (reduction 4.7%) of the newly proposed sensor were satisfactory and the oxidation peak current of diclofenac molecules was linear in the range of 1–100 µM with a detection limit of 0.047 µM with respect to the concentration of diclofenac. The applicability of the prepared sensor in real samples such as tablet and tap water was proved by quantitative determination of diclofenac in these samples and satisfactory results were obtained in all experiments.