Silver-integrated Fe₃O₄-Mn₃O₄ heterostructure: a robust and ultra-sensitive electrochemical nitrite sensor

Iron oxide-based heterostructure nanocomposites have emerged as promising electrode materials for electrochemical sensing applications. In this study, a facile hydrothermal method was employed to synthesize a ternary iron−manganese−silver (Fe₃O₄-Mn₃O₄-Ag) nanocomposite, which was used as a modified electrode for electrochemical detection of nitrite (NO₂⁻). The formation of a cubic-tetragonal-cubic mixed crystal structure of Fe, Mn, and Ag nanocomposite was demonstrated and characterized by comprehensive techniques such as – X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), high-resolution-transmission electron microscopy (HR-TEM), Fourier transform-infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and UV–visible spectroscopy (UV–Vis). The sensor results demonstrated exceptional activity with linear response over a wide concentration range (0.01–728 μM), remarkable sensitivity (0.2 μA. μM⁻¹.cm⁻²), good selectivity (100 μM), and long-term stability (20 days, std. deviation <2.45%) for NO₂⁻ detection in real water samples. This investigation brings forth a promising approach for the development of advanced sensing platforms for environmental monitoring and water quality assessment.