Method for preparing a ratiometric fluorescent sensor for phycoerythrin based on a magnetic molecularly imprinted core-shell polymer

A method for preparing a ratiometric fluorescent sensor for phycoerythrin based on a magnetic molecularly imprinted core-shell polymer, comprising the following steps:

• (1) preparation of aminated blue fluorescence-emitting carbon quantum dots (B-CDs) comprising:
• mixing 0.3 mL of 1,4-dioxane with 25 mL of catechol solution by ultrasound to obtain a first solution;
• transferring the first solution to a 50 mL high-pressure reactor with a polytetrafluoroethylene liner;
• heating the first solution in the high-pressure reactor for a first reaction at 180° C. for 12 hours to obtain a dark brown mixture;
• diluting the dark brown mixture with 20 mL of double-distilled water and centrifuging at 12,000 rpm to remove larger particles to obtain a supernatant;
• filtering the supernatant through a 0.4 m micro-filtration membrane to obtain a filtrate, and dialyzing the filtrate through a dialysis bag with a molecular weight cut-off of 1000 Da to remove unreacted experimental materials to obtain a second solution in the dialysis bag;
• collecting the second solution and subjecting to a rotary evaporation to remove 90% of water;
• and drying in a vacuum to obtain the B-CDs;
• and then dispersing the dried B-CDs in water to obtain a B-CDs aqueous dispersion;
• (2) preparation of carboxylated Fe3O4 magnetic nanoparticles comprising:
• adding ferric chloride and ferrous chloride with a molar ratio of 2:1 into a 250 mL reaction flask to prepare a 100 mL mixed solution;
• adding 10 mL of ammonia water with a mass concentration of 25% to the mixed solution into the 250 mL reaction flask under N2 protection to obtain a third solution;
• stirring the third solution rapidly to cause a second reaction;
• adjusting pH of the third solution to alkaline with HCl after 10 minutes of the second reaction;
• adding 10 mL of trisodium citrate solution to the third solution to obtain a fourth solution;
• and then
• placing the 250 mL reaction flask containing the fourth solution in a water bath at 80° C. and continuously stirring the fourth solution for a third reaction for 30 minutes to obtain a first reaction production;
• obtaining the carboxylated Fe3O4 magnetic nanoparticles by centrifugation, washing and drying of the first reaction product and
• dispersing the carboxylated Fe3O4 magnetic nanoparticles in water to prepare a Fe3O4 aqueous dispersion;
• (3) preparation of magnetic molecularly imprinted core-shell polymers comprising:
• adding 2 mL of the B-CDs aqueous dispersion to 18 mL of aqueous dispersion containing 0.8 mL of the Fe3O4 aqueous dispersion to obtain a fifth solution;
• stirring the fifth solution for a period of 30 minutes, and then adding phycoerythrin and 20 μL of 3-aminopropyltriethoxysilane to the fifth solution to obtain a sixth solution and allowing reaction of the sixth solution to proceed for 1 hour;
• then
• adding 40 μL of ammonia water and 40 μL of tetraethyl silicate to the sixth solution to obtain a seventh solution, and allowing reaction to proceed in the seventh solution away from light for 12 hours to obtain a second reaction product;
• centrifuging the second reaction product;
• and washing three times with a solution consisting of ethanol and acetonitrile at a volume ratio of 8:2 to remove the template molecules to obtain a product, and
• obtaining Fe3O4/B-CDs/SiO2 magnetic molecularly imprinted core-shell polymer (Fe3O4/B-CDs/SiO2-MIPs) from the product by centrifugation, washing and drying;
• and then
• dispersing the Fe3O4/B-CDs/SO2-MIPs in water to provide a Fe3O4/B-CDs/SiO2-MIPs aqueous dispersion;
• and
• (4) adding a plurality of molar concentrations of phycoerythrin to the Fe3O4/B-CDs/SiO2-MIPs aqueous dispersion to form a plurality of homogeneous mixtures;
• incubating the plurality of homogeneous mixtures away from light for 5 minutes and measuring fluorescence emission spectra of the plurality of homogeneous mixtures;
• and by fitting a linear relationship between ratios Iphycoerythrin/IB-CDs of fluorescence emission peak intensities of the phycoerythrin and the B-CDs and the plurality of molar concentrations of the phycoerythrin, the ratiometric fluorescent sensor for the phycoerythrin is constructed;
• wherein, in step (3), the mass concentration of the B-CDs is 1-10 mg/mL, the mass concentration of the carboxylated Fe3O4 magnetic nanoparticles is 5-20 mg/mL, and the plurality of molar concentrations of the phycoerythrin in step (4) is 0.5-1 M.