Carmine as a kind of food colorants is commonly used in food industry.However,irrational and inappropriate use of carmine will seriously threaten human health.At present,the detection of carmine mainly relies on the traditional methods such as high-performance liquid chromatography(HPLC),high performance capillary electrophoresis,etc.,which always involve expensive instruments,professional personnel and complicated pretreatment procedures.Thus,its indispensable to develop rapid,sensitive and visual detection methods for carmine.To meet this demand,a fluorescence method was established for the rapid detection of carmine in beverages specifically.Firstly,red carbon quantum dots(RCDs) were synthesized via hydrothermal treatment at 180 ℃ by using p-phenylenediamine as the carbon source.The morphology and particle size distribution of the prepared RCDs were observed by transmission electron microscopy(TEM).Furthermore,Fourier transform infrared spectroscopy(FTIR) was used to characterize the functional groups on the surface of RCDs,while the element composition of RCDs and their chemical states of elements were determined by X-ray photoelectron spectroscopy(XPS).To state the fluorescence quenching mechanism clearly,the fluorescence lifetime,the UV-Vis absorption spectra and fluorescence spectra were investigated.It was found that the absorption peak of carmine overlaps with the fluorescence emission spectrum of the prepared RCDs.Thus,a possible mechanism for fluorescence quenching was proposed as inner filter effect mechanism.Based on this mechanism,a fluorescence sensor for sensitive determination of carmine was designed,of which the detection performance depended on the detection conditions.To obtain the optimal analytical performance,the experimental parameters,including the excitation wavelength and pH values,were optimized.Under the optimized experimental conditions,the proposed sensor exhibited a linear response to carmine in the concentration range of 0.5-50 μg·mL-1,with a linear equation of IF0/IF=0.059c+0.979,a correlation coefficient(r2) of 0.978 and a detection limit of 0.397 μg·mL-1.The practical application of the proposed sensor was verified by HPLC with spiked beverage samples.The recoveries at three spiked levels ranged from 93.1% to 101%,with relative standard deviations(RSDs) of 0.97%-2.1%.Moreover,the color variation could be directly observed under the illumination of a 365 nm UV lamp with the naked eye,which could be used in the semiquantitative analysis for carmine content.With the advantages of rapidness,high sensitivity and stability,this method could be used for the detection of carmine in actual beverage samples.The research on this fluorescent method is of great theoretical value to develop new methods for carmine detection.In addition,the established method has a practical application value for on-site safety regulation on the illegal use of carmine.