One-dimensional hierarchical NixSy/Ni/N-CNTs electrochemical sensor for ultra-sensitive nitrite detection in real samples

A portable and highly sensitive electrochemical sensor for nitrite detection was developed using a NixSy/Ni/N-doped carbon nanotube (N-CNT) nanocomposite. The hybrid was fabricated by in situ growth of Ni nanoparticles on MOF-derived N-CNTs followed by hydrothermal sulfidation to form NixSy. This hierarchical nanostructure provided abundant active sites, large surface area, and enhanced conductivity. Electrochemical studies revealed outstanding nitrite sensing performance, with a wide linear range (0.2 μM–22 mM), high sensitivity (163.77 μA mM−1 cm−2), and a low detection limit (0.2 μM). The sensor showed excellent selectivity, reproducibility, and stability. Real sample analyses, including water, beverages, and pickled brine, yielded recoveries of 98.71–103.87% with low RSDs. A smartphone-integrated portable sensing system was also demonstrated, enabling accurate on-site nitrite monitoring. This work offers an effective strategy for designing advanced, field-deployable electrochemical sensors for food safety and environmental analysis.