Flower-like Ag-ZIF nanoparticles with petal-like structures as effective hot/cold-adapted oxidase mimic: Visual color tonality nitrite detection.

This study presents the synthesis of novel flower-like silver-based zeolitic imidazolate frameworks (Ag-ZIFs) with petal-like nanosheet structures, exhibiting robust oxidase-like activity. These nanozymes catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) effectively across a wide temperature range (5 °C to 80 °C), making them suitable for thermophilic and cryogenic applications. Leveraging this strong oxidase activity, Ag-ZIFs@TMB system was used to design a conventional ratiometric colorimetric method for nitrite detection in water and food samples, alongside a color tonality-based visual detection mode. Nitrite concentrations ranging from 1.0 to 54.0 μM were quantified, achieving a detection limit of 0.06 μM. The ratiometric approach demonstrated enhanced sensitivity, lower detection limits, and superior resistance to interference compared to traditional single-absorbance methods. Furthermore, the smartphone-assisted or naked-eye detection mode enabled rapid, portable, and accurate analysis, offering practical applications in environmental monitoring and food safety. These results highlight the multifunctional potential of Ag-ZIFs in advanced sensing technologies.