Ce-Mn@CoOOH nanozyme for constructing a ratiometric colorimetric sensor for rapid and sensitive detection of nitrite in food

In this work, to meet the requirement of nitrite detection, a ratiometric colorimetric sensor was constructed for sensitive and rapid detection of nitrite using Ce-Mn@CoOOH nanozyme. The Ce-Mn@CoOOH nanozyme was prepared by the hydrothermal method, and exhibited excellent oxidase-like activity. Under the catalysis of Ce-Mn@CoOOH nanozyme, colorless TMB can be oxidized to blue TMB complex. Furthermore, the blue TMB complex was further oxidized and diazotized by nitrite, and then respectively produce yellow oxTMB (diimine derivative) and diazonium salt under acidic conditions. There was a good linear correlation between the absorbance (A652/A452) and nitrite concentrations in the range of 0.3-35 mu g mL- 1 with a low detection of 0.017 mu g mL- 1. In addition, the developed method was verified using ion chromatography. Importantly, a smartphone-assisted colorimetric sensor was designed for visual detection of nitrite, enabling convenient, lowcost and on-site analysis of nitrite in food.