A disposable and low-cost laser scribed graphene metal phosphate nanohybrid electrochemical sensor for the detection of serotonin and hydrogen peroxide

Abstract

The neurotransmitter serotonin plays a vital role in numerous biological and pathological processes. Hence, its specific and sensitive detection in human serum is essential for the preliminary identification of illness. In this study, an iron (Fe)-functionalized copper/zinc phosphate nanocomposite (Fe@Cu₃(PO₄)₂/Zn₃(PO₄)₂) (FCZP) was synthesised via a straightforward and effective hydrothermal method. The crystallite size and structural morphology were analysed by FT-IR, XRD, BET, HRSEM with EDS, and HRTEM, which revealed a crystallite size of 25.92 nm and a rod-like shape. The sensor demonstrated superior electrochemical sensing performance for both serotonin and H₂O₂ compared with the other electrodes examined. The sensor exhibited a linear range of 0.1–500 µM, with a limit of detection (LOD) of 0.0391 µM and a good sensitivity of 20.027 µA mM⁻¹ cm² against serotonin. In H₂O₂ sensing, FCZP/LIG exhibited a sensitivity of 23.80 μA mM⁻¹ cm⁻² in the linear range of 1 ng mL⁻¹–1.0 µg mL⁻¹ with a limit of detection (LOD) of 0.063 µM. In addition, the electrode showed brilliant stability, reproducibility, and repeatability. For instance, the proposed electrode demonstrated good selectivity among many interfering molecules. This enhanced performance is ascribed to its large specific surface area, numerous active sites, unique structure, and synergistic interaction between Fe@Cu₃(PO₄)₂ and Zn₃(PO₄)₂, all of which collectively enhance the electrochemical activity. Real samples, such as serum, milk, the HeLa cell line, and urine, were examined using the standard addition method, and the recovery rate was significant. The developed electrode material has considerable potential for analyte detection. Moreover, the antibacterial activity against E. coli and S. aureus reached 85% inhibition after 72 h of incubation.