Design Of Dual-emission Ratiometric Fluorescence Systems And Its Visual Detection Of Injurant In Foods

The contents of specific ions or small molecules in the foods can act as important indicators for insuring food quality and safety.Detecting harmful substances existed in foods accurately and timely is of vital importance.Visual detection based on ratiometric fluorescence has the advantages of sensitivity,selectivity,fast response,and real-time detection.In order to improve the optical signal transduction performance to the fluorescent analytes and the ability of visual detection in food samples,two kinds of signal response strategies were adopted to design ratiometric fluorescent detection system.（1）We designed a novel ratiometric fluorometric system（CDs/AuNCs）for the detection of cyanide ions with high sensitivity.It is based on the mixture of aqueous solutions of blue-emitting carbon dots（CDs）and red-emitting gold nanoclusters（AuNCs）.The presence of cyanide reduces the red fluorescence of the AuNCs through the formation of a stable complex Au（CN）₂^-.The blue emission of the CDs,in contrast,stays constant.The color of fluorescence changes from red to blue under the illumination of single excitation wavelength.The ratio of the fluorescence intensities located at 612 nm and 438 nm varies over a wide range,with 2 linear responses ranges（from 8 n M to 12.5μM,and from 12.5 to 75μM）.The method was applied to the determination and visual discrimination of cyanide in food and drink samples.（2）In addition,we also designed a ratiometric probe（FITC@EuMOFs）with double-stimuli-responsive fluorescence center for the monitoring of biogenic amines in food.The probe was constructed by covalently coupling the green-emitting FITC to the red-emitting EuMOFs.The presence of the target analyte changes the energy transfer from the ligand to Eu³⁺and FITC,resulting in the block of the antenna effect,and the red fluorescence reduces.At the same time,FITC transforms from non-luminous ester-type to dianion form with high quantum yield,appearing with the green fluorescence enhances.Ratiometric fluorescence with two reversible signal changes contributes to the sensitivity and highly discernible fluorescence color changes of probe（from red orange to green）.We also made FITC@EuMOFs test strips and successfully employed for the visual detection of biogenic amines vapor through intelligent detection platform.