Highly-sensitive and anti-interferential electrochemical determination of hazardous metronidazole using w-NiSO₄·NiS₂ coated ZIF-67-derived cobalt/nitrogen-doped carbon

Metronidazole (MNZ) is non-biodegradable and highly soluble in water, it is easy to accumulate in the aquatic environment, which has toxic effects in clinical applications such as causing peripheral neuritis, cardiogenic shock and pseudomembranous colitis. In this paper, Co/NC@w-NiSO₄·NiS₂ nanospheres were successfully constructed by coating w-NiSO₄·NiS₂ on the surface of ZIF-67 as the growth substrate via hydrothermal method and subsequent calcination for electrochemical detection of metronidazole (MNZ). The nanostructure and composition of the materials were confirmed by SEM, TEM, FT-IR and XPS. The sensitivity of Co/NC@w-NiSO₄·NiS₂ sensor for MNZ detection is 1977.14 μA/(mM·cm²); the limit of detection (LOD) is as low as 0.009 μM and the linear range is 1 ∼ 200 and 200 ∼ 1000 μM. Moreover, the modified sensor can resist the interference from many traditional living substances, and has good reproducibility and stability. High catalytic activity requires effective molecular transport and exposure of active sites. The successful construction of Co/NC@w-NiSO₄·NiS₂ nanostructure promotes the dispersion of materials and the migration of reactants on the electrode surface, and the w-NiSO₄·NiS₂ coating on the irregular particles of ZIF-67-derived cobalt/nitrogen-doped carbon suppressed the stacking of the w-NiSO₄·NiS₂ nanosheets to expose more catalytic sites. These factors are conducive to increasing the catalytic activity of the modified sensor for highly sensitive MNZ detection and ensuring the activity of catalyst in multiple catalytic cycles.