Highly sensitive electrochemical sensing of fipronil using a ZnO/Graphene@C-dots hybrid nanocomposite

This study presents the development of a novel electrochemical sensor for the ultrasensitive detection of fipronil, a widely used pesticide, utilizing a hybrid nanocomposite material consisting of graphene (Gr), zinc oxide nanorods (ZnO NR), and carbon dots (C-dots). The hybrid nanocomposite, GZC (Graphene-ZnO@C-dots), was synthesized through a microwave-assisted method, leveraging the distinct physicochemical properties of each component to significantly enhance sensor performance. Electrochemical analysis conducted via cyclic vol- tammetry (CV) revealed a marked improvement in electron transfer efficiency and redox behavior compared to unmodified graphene electrodes, attributed to the synergistic interaction among ZnO NR, C-dots, and graphene. The GZC-based electrode demonstrated exceptional sensitivity in detecting fipronil, achieving an impressively low limit of detection (LOD) of 0.00490 μg/L and a limit of quantification (LOQ) of 0.01633 μg/L, outperforming numerous previously reported sensors. A strong linear correlation (R2 = 0.9931) was observed between the oxidation peak current and fipronil concentration, indicating excellent analytical performance. Additionally, the sensor exhibited high stability and reproducibility, with a relative standard deviation (RSD) of 0.26 % over 20 consecutive measurements. Validation using a commercial pesticide sample confirmed the sensor’s ability to detect fipronil at trace levels with high accuracy. Moreover, the Horwitz Ratio (HorRat) of 0.024 underscores the superior reproducibility of the sensor, well below the theoretical threshold. The GZC nanocomposite electrode provides a reliable, efficient, and highly sensitive platform for detecting fipronil in environmental samples, showcasing its potential in environmental monitoring to enhance food safety and environmental health through early pesticide residue detection.