Molecularly imprinted fluorescence sensor based on carbon dots for detecting chloramphenicol and its preparation method and its application

A method for preparing MIP@CD fluorescence sensor for detecting CAP, comprising the steps:

• (1) one-step hydrothermal synthesis of nitrogen-doped CD:
• taking citric acid as carbon source and urea as nitrogen source, completely dissolving citric acid and urea into ultrapure water through sonication;
• transferring the mixture into a well-sealed reactor;
• heating the reactor and cooling down to the room temperature;
• adding acetone into the reactor for demulsification, centrifuging and vacuum drying the precipitate obtained by centrifugation for obtaining the CD;
• the molar ratio of citric acid and urea is 1:3;
• (2) establishment of reversed micro-emulsion system:
• mixing oil phase cyclohexane, cosurfactant hexanol, and surfactant triton X-100, and stirring the mixture on a magnetic stirrer for 20 min;
• adding 1 mg/mL of CD solution and stirring for further 20 min;
• the volume ratio of cyclohexane, hexanol, triton X-100, and CD solution is 7.50:1.80:1.77:1.00;
• (3) mixing 3-aminopropyltriethoxysilane and CAP, and pre-polymerizing them at 4° C. for 2 h;
• the molar ratio of 3-aminopropyltriethoxysilane and CAP is 5:1;
• (4) adding tetraethyl silicate as a cross-linking agent and ammonia as a catalyst into the reversed micro-emulsion system in the step (2) and stirring for 2 h;
• mixing the mixture and the pre-polymerized solution in the step (3) and stirring for 24 h;
• for each milliliter of CD solution, 0.20 mmol of 3-aminopropyltriethoxysilane, 0.04 mmol of CAP, 0.80 mmol of tetraethyl silicate, and 60 μL it of ammonia are added;
• adding acetone, into the reactor, centrifuging and collecting the precipitate of MIP@CD precursor;
• (5) ultrasound-extracting of template molecular CAP in the MIP@CD precursor with a methanol-acetic acid solvent until the template molecular CAP is undetectable at 274 nm under the UV-Vis;
• (6) vacuum drying MIP@CD at 60° C. and obtaining the MIP@CD fluorescence sensor.