Preparation of a novel hydrazine electrochemical sensor using Fe₂O₃@ZnO core-shell nanoparticles

The sensitive and selective detection of hydrazine (HAZ) is crucial due to its high toxicity and widespread environmental impact. This work reports a green synthesis of spindle-shaped Fe₂O₃@ZnO core-shell nanoparticles using walnut shells as a sustainable biomass precursor via a combined wet impregnation-calcination approach. The core-shell architecture was fabricated through wet impregnation of pre-formed Fe₂O₃ cores followed by calcination and thoroughly characterized by Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) mapping, and energy-dispersive X-ray spectroscopy (EDS). Electrochemical studies revealed that Fe₂O₃@ZnO exhibits superior activity for hydrazine oxidation, attributed to synergistic core-shell interactions that enhance electron transfer and increase the active site density. The resulting sensor demonstrates excellent performance, featuring a wide linear range (0.02-68 µM), a low detection limit (14 nM), high sensitivity (3.54 µA µM^-1), and notable selectivity, stability, and reproducibility. These findings underscore the potential of biomass-derived core-shell nanomaterials for advanced electrochemical sensing.