Graphene oxide–cerium oxide nanocomposite modified gold electrode for ultrasensitive detection of chlorpyrifos pesticide

Abstract

This research presents a novel approach for the detection of the pesticide chlorpyrifos (CLP) using a gold working electrode immobilized with a graphene oxide–cerium oxide (GO–CeO₂) nanocomposite in a phosphate buffer (PBS) solution with a pH of 7.0. Graphene oxide (GO) was synthesized via a modified Hummer's method, while cerium oxide (CeO₂) nanoparticles were prepared using a coprecipitation technique. The GO–CeO₂ nanocomposite was synthesized via sonochemical methods. Structural and morphological characterization of the prepared material was conducted using X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDX). Fourier transform infrared (FTIR) spectroscopy has been conducted for the confirmation of functional group presence in the prepared materials. Cyclic voltammetry (CV) was employed to investigate the interaction between the prepared material and the analyte. Further investigations using varying scan rates (5 mV s⁻¹ to 300 mV s⁻¹) revealed a diffusion-controlled process at the electrode–electrolyte interface. Linear sweep voltammetry (LSV) experiments were conducted across a pH range of 5 to 9, with pH 7.0 showing enhanced response for the target pesticides in the presence of the buffer solution. Subsequent electrochemical measurements were performed at pH 7.0. Chronocoulometry was utilized to measure the effective electrode area for electrochemical interactions. Ultrasensitive square wave voltammetry (SWV) was employed for investigating the sensitivity over a concentration range of 1 fM to 100 μM and yielded the limit of detection (LOD) and limit of quantification (LOQ) as 47.7 fM and 159 fM respectively. Interference studies confirmed the selectivity of the prepared sensor, while stability and reproducibility were assessed through controlled experiments. Electrochemical impedance spectroscopy (EIS) was performed to investigate the interactions at the interface. This study provides insights into the development of selective electrochemical sensors for pesticide detection, with potential applications in environmental monitoring.