Construction Of Ratiometric Fluorescent Probes Based On Quantum Dots And Their Applications

In fluorescence sensing,fluorescent nanomaterials with long wavelength emission and multi-wavelength emission under single excitation have gained much attention.Compared with the single emission fluorescent nanomaterials,the ratiometric fluorescence probe can effectively reduce the background interference by taking the ratio of multiple fluorescence intensity as the signals.After adding the analyte,some ratiometric fluorescent probes show obvious color change,which can realize visual detection of the target.At present,it has been reported that semiconductor quantum dots（QDs）have been successfully used in ratiometric fluorescent system.Moreover,as a new type of fluorescent nanomaterial,carbon dots hold great potential in various research fields because of its low toxicity,wide range of raw materials,good biocompatibility and excellent fluorescence properties.Based on this,a series of ratiometric fluorescent sensing systems were constructed by taking advantage of the characteristic and superiority of fluorescent nanomaterials,and these fluorescent probes were successfully applied in the field of analytical detection.The main research contents are as follows:1.Preparation of dual-emission carbon dots N-CDs by one-pot method and its application in the detection of oxidizing and reducing substancesIn this work,dual-emission carbon dots were prepared by solvothermal method.The probe has two emission centers located at 548 nm and 640 nm respectively.The green emission peak is sensitive to the oxidizing compound HClO,and the red emission peak is sensitive to the reducing compound cysteine（Cys）.N-CDs can also apply to detect HClO and Cys in human serum.Furthermore,the biocompatibility of N-CDs is good,which make them can be applied in cell imaging.2.Preparation of novel carbon dots（Eu-CDs）and their application in ratiometric fluorescent determination of tetracyclinesIn this work,europium-doped carbon dots（Eu-CDs）were prepared from citric acid and europium nitrate via a one-pot pyrolytic method.The experimental process was quick and simple,which could be completed within 20 min.In the presence of TCs,the luminescence intensity(λ_em=616 nm)of Eu³⁺in Eu-CDs was significantly increased because of absorbance energy transfer-emission（AETE）effect,while the luminescence intensity of Eu-CDs at 472 nm was reduced because of inner filter effect.Silicone plate prepared by Eu-CDs showed obvious color variance in the presence of TCs under UV light.The quantitative analysis of TCs was successfully realized by combining the detection silicone plate with the image processing software Image J.3.Preparation of DCF-QDs/MnO₂ system and its application in ratiometric detection of glucose enantiomersIn this work,a novel DCF-QDs/MnO₂ complex was developed,and constructed a modification-free and efficient chiral selection platform based on enzyme-catalyzed reaction.DCF-QDs/MnO₂ showed the characteristic emission of QDs and DCF.With the catalysis of glucose oxidase（GOx）,D-glucose can react with GOx and produce H₂O₂,which leads to fluorescence signal recovery of DCF because of the decomposition of MnO₂ nanosheets.Meanwhile,the color changes can be directly observed by the naked eyes and colorimetric detected by UV-Vis spectrum,while L-glucose cannot generate the same effect.Glucose enantiomers（D/L-glucose）not only can be discriminated by this system,but also D-glucose can be quantitative analysis by ratiometric fluorescence and colorimetric mode.