Rapid detection of nitrite in food by multi-colorimetric and fluorescence dual-mode based on crystal violet modulated carbon dots

A new method for the determination of nitrite (NO2–) by multicolor colorimetry and fluorescence dual-mode is presented. This sensing system involves the reaction of crystal violet modulated carbon dots (CV-CDs) with different concentrations of nitrite to produce multiple color signals, while the fluorescence intensity of CV-CDs increases with the increase of nitrite concentration. Therefore, the absorption wavelength shift and fluorescence intensity change can be used for the quantitative determination of nitrite. Furthermore, we combine the multicolor colorimetric output with a smartphone platform to perform on-site determination of nitrite without the need for a spectrometer. Intelligent recognition software was designed to take pictures of color signals and analyze R, G, and B channels. Good results of nitrite analysis were obtained.