Non-Enzymatic Electrochemical Detection of Acephate Using Graphene/Copper Tetraphenylporphyrin Nanocomposite: A Comprehensive Study with Multi-Technique Validation

The widespread application of organophosphate pesticides in modern agriculture has necessitated the development of rapid, robust, and cost‑effective detection methods for environmental monitoring and food safety assessment. In this study, we report a non‑enzymatic electrochemical sensor based on a reduced graphene oxide–copper tetraphenylporphyrin (RGO–CuTPP) nanocomposite for the detection of acephate, a representative organophosphate insecticide. Three graphene derivatives (graphene oxide, reduced graphene oxide, and pristine graphene) and tetraphenylporphyrin/copper tetraphenylporphyrin were synthesized and systematically compared as building blocks. Among all compositions, the RGO–CuTPP nanocomposite with a 1:0.5 mass ratio exhibited the most pronounced response toward acephate, with a linear range of 0.1–0.4 mM, a limit of detection of 0.054 mM, and a limit of quantification of 0.178 mM. The composite shows excellent reproducibility (RSD < 5%), operational stability, and high tolerance to common inorganic and organic interferents. Structural analyses confirm the successful integration of CuTPP on the RGO surface through π–π interactions and Cu–O/N coordination, which enhances electron transfer and provides specific interaction sites for acephate. Concentration‑dependent voltammetry supports a detection mechanism based on surface binding of acephate, leading to an increase in charge‑transfer resistance and a decrease in faradaic current. The sensor’s performance in spiked water and vegetable samples demonstrates its suitability for practical acephate monitoring, emphasizing simplicity of fabrication, good robustness, and compatibility with real matrices over ultra‑low detection limits.