Copper oxide nanoleaves covered with loose nickel oxide nanoparticles for sensitive and selective non-enzymatic nitrite sensors

• A new preparation method is firstly developed to directly grow CuO nanostructures on the surface of FTO electrode, which has the advantages of simple process and wide applicability compared with other complicated preparation methods previously reported. • Compared with nanostructures such as nanoparticles and nanowires, the prepared leaf-shaped nanostructures have a larger contact area and can reduce the transfer resistance between the electrode and CuO nanostructures, which is more conducive to the conversion of nitrite. • The combined modification of the leaf-shaped CuO nanostructures and NiO nanoparticles can overcome the limitations of single metal oxide modification through synergistic effects. • The prepared electrochemical sensor can be practically applied to the detection of NO 2 − in actual water samples, thereby providing a good application prospect for metal oxides with excellent electrochemical performance . In this work, we developed a new method for preparing copper oxide (CuO) nanostructures, designed and prepared a CuO NiO modified fluorine-doped SnO 2 transparent conductive glass (FTO) electrode for electrochemical sensor to effectively detect the nitrite. The leaf-shaped CuO nanostructures grow uniformly on the FTO electrode, resulting in the increased contact area and reduced transfer resistance. The NiO nanoparticles effectively dispersed in the gaps between the leaves can further improve the electron transfer and reduce the diffusion resistance. The electrochemical results demonstrated that the prepared electrode exhibited high sensitivity (7.2 mA mM −1 cm −2 ), broad linear range (0.001–1.8 mM) and low detection limit (0.013 μM). Moreover, the prepared sensor also reflected good reproducibility, stability and anti-interference in the detection of actual samples, which provides a good application prospect for metal oxides used in water quality and environmental monitoring. The CuO NiO modified FTO electrode prepared by hydrothermal, spin-coating and high-temperature calcination methods exhibits a wide range of linearity, high sensitivity and low detection limit when effectively detecting the content of nitrite in the sample, which is expected to be widely used in food, water quality and environmental monitoring.