Novel electrochemical platform based on ZnO–Fe₃O₄ heterojunction for sensitive tinidazole detection

In this study, an efficient electrochemical sensor for tinidazole (TND) detection was developed using a glassy carbon electrode (GCE) modified with a ZnO–Fe₃O₄ heterostructured nanocomposite synthesized via a green, biomass-assisted, combined wet impregnation – calcination approach employing walnut shell as a sustainable precursor. The successful formation of a closely integrated ZnO–Fe₃O₄ heterostructure was confirmed by XRD, electron microscopy (FESEM/TEM), EDS, and BET analysis. This architecture, characterized by intimate interfacial contact and increased surface area, synergistically promotes electron transport and maximizes the availability of electroactive sites. Owing to the synergistic interaction between ZnO and Fe₃O₄, the modified electrode exhibited enhanced electrocatalytic activity toward the reduction of TND, operating at a lower overpotential with a markedly amplified current response. Under optimized conditions, the sensor demonstrated a wide linear range from 0.1 to 70 μM, a low detection limit of 12 nM, and a high sensitivity of 1.36 μA μM −1 . The sensor also showed good selectivity, reproducibility, and long-term stability. Its practical applicability was validated by the accurate determination of TND in pharmaceutical tablets and water samples, with recoveries ranging from 98.3% to 100.4%. These results highlight the potential of ZnO–Fe₃O₄ heterostructured nanocomposite as an effective modifier for electrochemical sensing applications. • A ZnO–Fe₃O₄ heterostructured nanocomposite was successfully synthesized via a sustainable, biomass-assisted wet impregnation – calcination method using walnut shell. • The intimate heterojunction between ZnO and Fe₃O₄ creates a synergistic effect, significantly boosting electrocatalytic activity for tinidazole (TND) reduction. • The fabricated sensor achieves a remarkably low detection limit (12 nM), a wide linear range (0.1–70 μM), and high sensitivity (1.36 μA μM −1 ). • The platform demonstrates excellent selectivity, reproducibility, and long-term stability, validating its use in complex matrices. • The sensor was effectively applied to determine TND in pharmaceutical tablets and water samples with high accuracy and recovery (98.3–100.4%).