A dual-mode sensor for colorimetric and fluorescent detection of nitrite in hams based on carbon dots-neutral red system

Nitrite residue in hams was detected by a fluorescent and colorimetric sensor based on carbon dots (C-dots) and neutral red (NR). C-dots with green fluorescence was synthesized by a microwave-assisted method. This novel sensor was fabricated by C-dots as donors and NR as acceptors. The presence of nitrite led to decrease of absorbance and increase of fluorescence. Colorimetric and fluorescent methods for nitrite detection were developed with excellent correlation coefficients (R-2 = 0.995 and 0.991) and low limits of detection (196 nM and 0.518 nM). Moreover, nitrite residue in seven types of ham was detected by the colorimetric and fluorescent methods which were verified by a standard method. The results obtained by the proposed method were comparable and agree with that of the Griess-based method (relative errors < 5%). C-dots-NR system as a sensor has a potential application for nitrite detection in hams to monitor its quality and safety.