Ratio fluorescent molecularly imprinted polymer, paper-based sensor and preparation and application thereof

Abstract

The invention relates to a ratiometric fluorescent molecularly imprinted polymer, a paper-based sensor and preparation and application thereof, and relates to the technical field of food safety detection. The preparation method comprises the following steps: uniformly mixing a functional monomer acrylamide, a template molecule fleroxacin, an initiator, modified SiO2 nanoparticles and a cross-linking agent A to obtain a mixture, then adding a binuclear Eu complex, a boron-nitrogen-doped titanium carbide two-dimensional layered material, a cross-linking agent B and acetic acid, initiating a polymerization reaction, and removing the template molecule to obtain the composite material. The ratio fluorescent molecularly imprinted polymer is obtained. The molecularly imprinted ratiometric fluorescent paper-based sensor can specifically recognize fleroxacin, can be used for detecting fleroxacin residues in meat products, and provides assistance for the development of a food rapid detection technology.

Description

Technical Field

[0001] The invention relates to the technical field of food safety detection, and in particular to a ratiometric fluorescent molecular imprinting polymer, a paper-based sensor, and preparation and application thereof. Background Art

[0002] Veterinary drug residues are short for "residues of veterinary drugs in animal-derived foods". They refer to the accumulation and storage of drugs or their metabolites in the cells, tissues or organs of animals over time after the animals are treated with drugs. The veterinary drug fleroxacin is used to treat infections caused by sensitive bacteria in animals. As the animal metabolizes, the drug content in the animal's body will decrease after ingestion, but there will still be some residues.

[0003] Rapid food testing technology has the advantages of simple use, short testing time, low cost, and easy portability. It can promptly detect safety problems in the market and food production process, quickly control the continued circulation of unqualified food in the market, and the continued production of unqualified food, reduce the supervision and law enforcement costs of regulatory authorities, avoid major food safety problems, and bring adverse effects to society. At present, at home and abroad, positive samples are first screened out through rapid testing technology, and then these positive samples are further analyzed and confirmed through large-scale precision instruments in the laboratory, which can save manpower, material resources, and financial costs. Therefore, with the increasing pressure on food safety testing today, it is of great significance to continuously explore and develop effective rapid testing technologies.

[0004] Visual rapid detection technology is an important method of food safety rapid detection technology. Visual rapid detection technology is a rapid detection technology that performs rapid qualitative and quantitative analysis based on specific color changes caused by the interaction between the medium and the target. Visual fluorescence rapid detection technology has a series of advantages such as rapidity, high sensitivity, good selectivity, and the potential for visualization of possible on-site sensing platforms, and has become a research hotspot for visual rapid detection technology.

[0005] Currently, there are no products and methods specifically targeted at detecting fleroxacin residues in food. Therefore, there is a need to provide ratiometric fluorescent molecular imprinting polymers, paper-based sensors, and their preparation and application. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a ratiometric fluorescent molecular imprinting polymer, a paper-based sensor and its preparation and application. The molecular imprinting ratiometric fluorescent paper-based sensor of the present invention can specifically identify fleroxacin and can be used for the detection of fleroxacin residues in meat products, providing support for the development of food rapid testing technology.

[0007] The technical solution of the present invention to solve the above technical problems is as follows:

[0008] The first object of the present invention is to provide a method for preparing a ratiometric fluorescent molecular imprinted polymer, comprising the following steps:

[0009] The functional monomer acrylamide, the template molecule fleroxacin, the initiator, the modified SiO2 nanoparticles, and the crosslinker A were mixed evenly to obtain a mixture, and then the binuclear Eu complex, the boron-nitrogen-doped titanium carbide two-dimensional layered material, the crosslinker B, and acetic acid were added to initiate the polymerization reaction and then remove the template molecule to obtain the ratio fluorescent molecular imprinting polymer, namely SiO2@binuclear Eu complex@B,N-Ti3C2T x MXeneQDs@MIPs.

[0010] Based on the above technical solution, the present invention can also be improved as follows.

[0011] Further, the preparation method of the modified SiO2 nanoparticles is as follows:

[0012] (1) under magnetic stirring, ammonia water and water are added to anhydrous ethanol in sequence, and then ethyl orthosilicate is slowly added dropwise, and after continuous stirring for reaction, centrifugation, washing, and vacuum drying are performed in sequence to obtain SiO2 nanoparticles;

[0013] (2) dispersing the nano-SiO2 nanoparticles in toluene, then adding a cross-linking agent 3-aminopropyltriethoxysilane (APTES), refluxing in a N2 atmosphere for 10 h-14 h, centrifuging, washing, and vacuum drying to obtain modified nano-SiO2 nanoparticles;

[0014] The mass fraction of the ammonia water is 25%-28%.

[0015] The beneficial effect of adopting the above further scheme is that a large amount of crosslinking agent is attached to the surface of the modified nano-SiO2 particles prepared by the present invention, which lays a foundation for the subsequent preparation of molecular imprinting polymers on the SiO2 surface and makes the polymerization process faster.

[0016] Further, the preparation method of the binuclear Eu complex is as follows:

[0017] Weigh 2,2'-bipyridine-6,6'-dicarboxylic acid (H2bpydcb), o-phenanthroline, and europium nitrate (Eu(N O3)3), mix them, add N,N-dimethylformamide (DMF), mix them, and then heat them to react. Then, cool them, filter them, and dry the solid to obtain the binuclear Eu complex, i.e., [Eu2(bpydcb)3(H2O)2(DMF)]·3H2O·0.5DMF.

[0018] Furthermore, the preparation method of the boron-nitrogen doped titanium carbide two-dimensional layered material is as follows: weigh Ti3C2T x, boric acid and dissolved, pH was adjusted under magnetic stirring, and then reacted. After the reaction was completed, the mixture was allowed to stand, and filtrated under reduced pressure to obtain a filtrate, which was then vacuum dried to obtain a boron-nitrogen doped titanium carbide two-dimensional layered material, namely B,N-Ti3C2T x MXeneQDs quantum dot solid.

[0019] Further, the usage ratio of the H2bpydcb, the o-phenanthroline, the Eu(NO3)3, and the DMF is (0.05-0.1) g: (0.3-1) g: (0.09-0.15) g: (5-10) mL;

[0020] The Ti3C2T x , the mass ratio of the boric acid is 10-15:5-9.

[0021] Furthermore, the mass ratio of the functional monomer acrylamide, the template molecule fleroxacin, the initiator, the modified SiO2 nanoparticles, and the crosslinking agent A in the mixture is 0.02-0.04:0.01-0.03:0.02-0.04:0.02-0.04:0.02-0.03;

[0022] The mixture, the [Eu2(bpydcb)3(H2O)2(DMF)]·3H2O·0.5DMF, the B,N-Ti3C2T x The dosage ratio of MXeneQDs quantum dot solid, the crosslinking agent B, and the acetic acid is (0.09-0.18) g: (0.06×10 -6 ~0.1×10 -5 )g:(0.04×10 -6 ~0.1×10 -5 )g:(0.09×10 -6 ~1.5×10 -5 )L:(8~10)g.

[0023] Furthermore, the crosslinking agent A is APTES; the crosslinking agent B is ethyl silicate; and the initiator is azobisisobutyronitrile.

[0024] The beneficial effects of adopting the above further scheme are: the amino group of the functional monomer in the present invention can react with the carboxyl group of the template molecule to form a hydrogen bond, and the addition of a crosslinking agent causes the molecule to undergo a polymerization reaction; after elution, the spatial structure of the template molecule is preserved in the polymer.

[0025] The second object of the present invention is to provide a method for preparing a paper-based sensor, comprising the following steps: xMXeneQDs@MIPs were dispersed in solvent to obtain SiO2@binuclear Eu complex@B,N-Ti3C2T x MXeneQDs@MIPs solution; placing a paper substrate on the SiO2@binuclear Eu complex@B,N-Ti3C2T x MXeneQDs@MIPs solution was infiltrated and then dried to obtain SiO2@binuclear Eu complex@B,N-Ti3C2T x MXeneQDs@MIPs paper-based sensors.

[0026] The beneficial effects of the present invention are as follows: the present invention integrates molecular imprinting technology, ratio fluorescence analysis, and paper-based sensors into one, and uses B, N-Ti3C2T x The ratiometric fluorescent probe constructed by MXeneQDs quantum dots and binuclear Eu complexes was finally constructed to rapidly and specifically detect the residual amount of fleroxacin in meat products using SiO2@orange fluorescent binuclear Eu complex@B,N-Ti3C2T x MXeneQDs@MIPs molecularly imprinted ratiometric fluorescent paper-based sensor.

[0027] A third object of the present invention is to provide a paper-based sensor.

[0028] The beneficial effects of the present invention are as follows: when the molecular imprinting ratio fluorescence paper-based sensor of the present invention recognizes fleroxacin, the fluorescence intensity of the europium complex in the probe is enhanced, and the B,N-Ti3C2T x The fluorescence intensity of MXeneQ Ds quantum dots remains unchanged, that is, the residual amount of fleroxacin is detected according to the ratiometric fluorescence on-state mechanism. This provides a new method for detecting the residual amount of fleroxacin in meat products. The present invention adopts a paper-based sensor, which is convenient, fast and efficient to use as a whole.

[0029] The fourth object of the present invention is to provide an application of a paper-based sensor, using the molecular imprinting ratio fluorescence paper-based sensor to visually identify and / or detect fleroxacin in meat products.

[0030] The beneficial effect of the present invention is that the molecular imprinting ratio fluorescence paper-based sensor provided by the present invention has a detection limit of 4.78 μmoL / L, which can meet the visual detection of fleroxacin veterinary drug residues in meat products. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a scanning electron microscope image of SiO2 before modification in Example 1 of the present invention;

[0032] Figure 2 This is a scanning electron microscope image of SiO2 after modification in Example 1 of the present invention;

[0033] Figure 3 The ratio fluorescence molecular imprinting polymer SiO2@binuclear Eu complex@B,N-Ti3C2T of Example 1 of the present invention is x Scanning electron microscopy image of MXeneQDs@MIPs;

[0034] Figure 4 The ratio fluorescence molecular imprinting polymer SiO2@binuclear Eu complex@B,N-Ti3C2T of Example 1 of the present invention is x MXeneQDs@MIPs infrared spectrum;

[0035] Figure 5 The molecular imprinting ratio fluorescence paper-based sensor SiO2@binuclear Eu complex@B,N-Ti3C2T x Working curve of MXeneQDs@MIPs for detecting fleroxacin residues. DETAILED DESCRIPTION

[0036] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific technology or conditions are specified in the embodiments, the technology or conditions described in the literature in this field or the product instructions are used. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased through regular channels.

[0037] Example 1: Preparation of Molecularly Imprinted Ratio Fluorescent Paper-Based Sensor

[0038] (1) Preparation of binuclear Eu complex: 0.0537g H2bpydcb, 0.0396g o-phenanthroline, 0.0981g Eu(NO3)3 were weighed into a 50mL beaker, and a magnetic rotor was placed. Then 6mL D MF and 4mL deionized water were added. The mixture was stirred magnetically for 5min, and then ultrasonicated for 10min. After sufficient dissolution, the mixture was transferred to a reactor and heated to 90°C for 3 days. After the reaction was completed, the reactor was cooled and filtered, and the obtained solid was transferred to a vacuum drying oven. After drying, 0.0681g of light pink solid binuclear Eu complex was obtained, with a yield of 44.86%. The chemical formula of the binuclear Eu complex was [E u2(bpydcb)3(H2O)2(DMF)]·3H2O·0.5DMF, and the elemental analysis result was C 81 H 76 4N 15 O 37 (%): C 39.55, N 8.54, H 3.11, found value (%): C 39.48, N8.44, H3.16;

[0039] (2) B, N-Ti3C2Tx Preparation of MXene QDs: Weigh 10 mg Ti3C2T x , 5mg boric acid in a 50mL beaker, then add 10mL deionized water, put in a magnetic rotor, and adjust pH to 9 with 0.5mol / L ammonia water under magnetic stirring at 700r / min. Transfer the solution and the bottom solid into the reactor and control the temperature at 100℃ for 6h. After the reaction, let the solution in the reactor stand until it becomes clear and then filter under reduced pressure. The filtrate is vacuum dried at 0.07MPa and 60℃ for 6h to obtain B,N-Ti3C2T x MXeneQDs quantum dot solid;

[0040] (3) Preparation of modified nano-SiO2: 50 mL of anhydrous ethanol was added to a 100 mL round-bottom flask. Under magnetic stirring, 2.0 mL of 25% ammonia water and 6.3 mL of deionized water were added in sequence at a speed of 700 r / min. Then 2.25 mL of TEOS was slowly added dropwise and stirring was continued for 24 hours. After centrifugation, the mixture was washed three times with anhydrous ethanol and vacuum dried for 6 hours to obtain nano-SiO2. Then 100 mg of the dried nano-SiO2 sample was weighed and dispersed in 50 mL of analytical pure toluene. Then 2 mL of cross-linking agent APTES was added, refluxed in a N2 atmosphere for 12 hours, centrifuged, washed three times with anhydrous ethanol, and dried in a vacuum drying oven to obtain a modified nano-SiO2 sample;

[0041] (4) SiO2@binuclear Eu complex@B,N-Ti3C2T x Preparation of MXeneQDs@MIPs: 0.0213 g functional monomer acrylamide, 0.0185 g template molecule floxacin FLX, 0.025 g initiator azobisisobutyronitrile, 0.025 g modified SiO2 nanoparticles and 0.020 g crosslinker APTES were accurately weighed in a round-bottom flask, and 5 mL chloroform solution was added. After complete dissolution, 0.3 mg / L binuclear Eu complex solution and 0.20 mg / L N-Ti3C2T x 200 μL of MXeneQDs solution was magnetically stirred for 5 hours in a nitrogen atmosphere, and then 300 μL of 0.3 mL / L crosslinker TEOS methanol solution (0.3 mL of TEOS dissolved in 1 mL of methanol) and 300 μL of 0.5 mol / L acetic acid solution were added, and then stirred for 15 hours in a nitrogen atmosphere. After the reaction was completed, the polymer product was vacuum dried and crushed. The polymer was repeatedly eluted with methanol solution until the template molecule fleroxacin could not be detected, and the polymer without the template molecule was vacuum dried to obtain SiO2@binuclear Eu complex@B,N-Ti3C2T xMXeneQDs@MIPs ratiometric fluorescent molecular imprinting polymers.

[0042] (5) SiO2@binuclear Eu complex@B,N-Ti3C2T x Preparation of MXeneQDs@MIPs ratiometric fluorescent molecular imprinting polymer probe solution: ultrasonically disperse the ratiometric fluorescent molecular imprinting polymer in methanol, and absorb the supernatant to obtain SiO2@binuclear Eu complex@B,N-Ti3C2T x MXe neQDs@MIPs molecular imprinting ratio fluorescence probe solution; finally, a paper substrate with a diameter of 14 mm was cut and immersed in the molecular imprinting ratio fluorescence probe solution. After 10 minutes, the thoroughly soaked paper was taken out with tweezers and dried at room temperature to obtain the molecular imprinting ratio fluorescence paper-based sensor SiO2@binuclear Eu complex@B,N-Ti3C2T x MXeneQDs@MIPs.

[0043] Comparative Example 1: Preparation of non-molecularly imprinted polymer

[0044] This comparative example is the same as Example 1, the only difference being that step (4) SiO2@binuclear Eu complex@B,N-Ti3C2T x No template molecule fleroxacin was added in the preparation of MXeneQDs@MIPs, and the remaining raw materials and steps were the same as in Example 1.

[0045] Test Example 1:

[0046] (1) The nano-SiO2 and modified nano-SiO2 prepared in step (3) of Example 1, and the ratio fluorescence molecular imprinting polymer SiO2@binuclear Eu complex@B,N-Ti3C2T prepared in step (4) were respectively subjected to the following conditions: x MXeneQDs@MIPs were analyzed using a scanning electron microscope (SU5000; Hitachi Scientific Instruments Co., Ltd.). Figure 1 , Figure 2 , Figure 3 shown.

[0047] (2) The ratio of the fluorescent imprinted polymer SiO2@binuclear Eu complex@B,N-Ti3C2T prepared in step (4) of Example 1 was measured using a fluorescence spectrometer (F-4600; Hitachi Scientific Instruments Co., Ltd.). x The emission spectrum of MXeneQDs@MIPs is shown in Figure 4 shown.

[0048] Depend on Figure 1-Figure 4 We can get:

[0049] (1) Figure 1 This is the scanning electron microscope of SiO2 before modification of the present invention. Figure 2 This is the scanning electron microscope of SiO2 after modification of the present invention. Figure 1 , Figure 2 A large amount of cross-linking agent APTES is attached to the surface of SiO2 particles, which lays the foundation for the subsequent preparation of molecular imprinting polymers on the SiO2 surface and makes the polymerization process faster.

[0050] (2) Figure 3 The ratio fluorescence molecular imprinting polymer SiO2@binuclear Eu complex@B,N-Ti3C2T x Scanning electron microscopy of MXeneQDs@MIPs. Figure 3 It can be seen that a molecular imprinting polymer (SiO2@binuclear Eu complex@B,N-Ti3C2T x MXeneQ Ds@MIPs).

[0051] (3) Figure 4 The ratio of the fluorescent imprinted polymer SiO2@binuclear Eu complex@B,N-Ti3C2T x MXeneQDs@MIPs infrared spectrum. Figure 4 It can be seen that SiO2 at 1108cm -1 、801cm -1 and 474cm -1 The peaks appearing are Si-O-Si and Si-O stretching vibrations, which shift to 1107 cm in molecularly imprinted polymers. -1 、806cm -1 and 474cm -1 It proves that SiO2 is successfully encapsulated in the molecular imprinting polymer; the binuclear Eu complex is at 3082cm -1 、1461cm -1 and 1410cm -1 、1189cm -1 and 1155cm -1 and 572cm -1 The peaks appearing at 3061 cm-1 are the stretching vibration of the heterocyclic CH, the stretching vibration of the heterocyclic skeleton, the in-plane deformation of the heterocyclic CH, and Eu-N. These peaks shift to 3061 cm-1 in the ratiometric fluorescence imprinted polymer. -1 、1465cm -1 and 1411cm -1 、1176cm -1 and 1142cm -1 This indicates that the binuclear Eu complex is also encapsulated in the ratiometric fluorescence imprinted polymer. In addition, the ratiometric fluorescence imprinted polymer has a -1and 2850cm -1 The appearance of antisymmetric and symmetric stretching vibration peaks of -CH2 of APTES proves the successful preparation of ratiometric fluorescent imprinted polymer.

[0052] Test Example 2:

[0053] The molecular imprinting ratiometric fluorescent paper-based sensor prepared in Example 3 was placed on a glass dish, and fleroxacin solutions (C FLX ) was added to the molecular imprinting ratio fluorescence paper-based sensor, completely wetted, and dried for 10 minutes. Then, a smartphone was used to take a photo in a 365nm UV analysis dark box instrument (DF-20D; Gongyi Yuhua Instrument Co., Ltd.), and the RGB value of the paper-based sensor was extracted using a WPS color absorber. The results are shown in Figure 5 shown.

[0054] Depend on Figure 5 We can get:

[0055] Under ultraviolet irradiation, the color of the paper-based sensor changes from dark blue to bright blue, and then from bright blue to yellow. The RGB extraction of the paper-based color shows that there is a linear relationship between the G value and the concentration of fleroxacin in the range of 0-100 μmoL / L, and the linear equation is Y=1.2563C FLX +91.0373(R 2 =0.9952), the calculated detection limit is 4.78 μmoL / L

[0056] Test Example 3:

[0057] (1) Pretreatment of shrimp meat samples: Take 9.94 g of chopped shrimp meat, add 50 mL of methanol solution, ultrasonically disperse, then add 0.5 g of activated carbon to absorb impurities, seal with plastic wrap and ultrasonicate again. Filter under reduced pressure to obtain the shrimp meat treatment liquid. Then transfer the treatment liquid to a rotary evaporator, set the temperature to 50 ° C, the speed to 200 r / min, and rotary evaporate for 20 minutes. After cooling, add 50 mL of methanol to obtain the methanol solution of the treatment liquid.

[0058] (2) Spiked recovery experiment: Fleroxacin was added to the pre-treated methanol solution of raw shrimp meat to prepare spiked solutions with fleroxacin concentrations of 20, 50, and 80 μmoL / L, respectively. The spiked solutions were added dropwise to the molecular imprinting ratio fluorescent paper substrate, completely wetted, and dried (10 minutes). The paper substrate was placed in a 365nm UV analysis darkroom instrument for photography, and the RGB value of the paper substrate was extracted using a WPS color absorber. The linear equation between the G value obtained in Experimental Example 2 and the fleroxacin concentration was used for calculation. The results are shown in Table 1.

[0059] Table 1

[0060]

[0061] From Table 1, we can see that:

[0062] When no fleroxacin was added, the molecular imprinting ratio fluorescence paper-based sensor prepared in Example 1 did not detect the presence of fleroxacin in the raw shrimp meat pre-treatment solution, and the spiked recovery experiment showed that the recovery rate of fleroxacin in the raw shrimp meat pre-treatment solution was 88.50%-95.13%, indicating that the ratio fluorescence paper-based sensor can be used for actual sample determination.

[0063] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a ratiometric fluorescent molecular imprinted polymer, characterized in that: The method comprises the following steps: uniformly mixing a functional monomer acrylamide, a template molecule fleroxacin, an initiator, modified SiO2 nanoparticles and a crosslinking agent A to obtain a mixture; then adding a binuclear Eu complex, a boron-nitrogen-doped titanium carbide two-dimensional layered material, a crosslinking agent B and acetic acid; initiating a polymerization reaction and then removing the template molecule to obtain a ratiometric fluorescent molecular imprinting polymer.

2. The method for preparing a ratiometric fluorescent molecularly imprinted polymer according to claim 1, characterized in that: The preparation method of the modified SiO2 nanoparticles is as follows: (1) under magnetic stirring, ammonia water and water are sequentially added to anhydrous ethanol, followed by dropwise addition of ethyl orthosilicate, and the mixture is continuously stirred for reaction and then centrifuged, washed, and vacuum dried to obtain SiO2 nanoparticles; (2) dispersing the SiO2 nanoparticles in toluene, then adding a crosslinking agent 3-aminopropyltriethoxysilane, refluxing in a N2 atmosphere for 10 h to 14 h, centrifuging, washing, and vacuum drying to obtain modified SiO2 nanoparticles; The mass fraction of the ammonia water is 25%-28%.

3. The method for preparing a ratiometric fluorescent molecularly imprinted polymer according to claim 1, characterized in that: The preparation method of the binuclear Eu complex is as follows: Weigh 2,2'-bipyridine-6,6'-dicarboxylic acid, o-phenanthroline and europium nitrate, mix them, add N,N-dimethylformamide, mix them, and then heat them for reaction. Then, cool them, filter them to obtain a solid, and dry the solid to obtain the binuclear Eu complex.

4. The method for preparing a ratiometric fluorescent molecularly imprinted polymer according to claim 3, characterized in that: The preparation method of the boron-nitrogen doped titanium carbide two-dimensional layered material is as follows: weigh Ti3C2T x , boric acid and dissolve them, adjust the pH under magnetic stirring, then react, let the reaction stand after the reaction is completed, filter under reduced pressure to obtain a filtrate, and vacuum dry the filtrate to obtain a boron and nitrogen doped titanium carbide two-dimensional layered material.

5. The method for preparing a ratiometric fluorescent molecularly imprinted polymer according to claim 4, characterized in that: The usage ratio of the 2,2'-bipyridine-6,6'-dicarboxylic acid, the o-phenanthroline, the europium nitrate, and the N,N-dimethylformamide is (0.05-0.1) g: (0.3-1) g: (0.09-0.15) g: (5-10) mL; The Ti3C2T x , the mass ratio of the boric acid is 10-15:5-9.

6. The method for preparing a ratiometric fluorescent molecularly imprinted polymer according to claim 1, characterized in that: The mass ratio of the functional monomer acrylamide, the template molecule fleroxacin, the initiator, the modified SiO2 nanoparticles, and the crosslinking agent A in the mixture is 0.02-0.04:0.01-0.03:0.02-0.04:0.02-0.04:0.02-0.03; The amount ratio of the mixture, the binuclear Eu complex, the boron-nitrogen doped titanium carbide two-dimensional layered material, the crosslinking agent B, and the acetic acid is (0.09-0.18) g: (0.06×10 -6 ~0.1×10 -5 )g:(0.04×10 -6 ~0.1×10 -5 )g:(0.09×10 -6 ~1.5×10 -5 )L:(8~10)g.

7. The method for preparing a ratiometric fluorescent molecularly imprinted polymer according to claim 6, characterized in that: The crosslinking agent A is APTES; the crosslinking agent B is ethyl silicate; and the initiator is azobisisobutyronitrile.

8. A method for preparing a paper-based sensor, characterized in that: The method for preparing the molecular imprinting ratio fluorescence paper-based sensor comprises the following steps: The ratiometric fluorescent molecular imprinting polymer according to any one of claims 1 to 7 is dispersed in a solvent to obtain a molecular imprinting ratiometric fluorescent probe solution; a paper substrate is soaked in the molecular imprinting ratiometric fluorescent probe solution and then dried to obtain a molecular imprinting ratiometric fluorescent paper-based sensor.

9. A paper-based sensor, characterized in that: The molecular imprinting ratio fluorescence paper-based sensor is prepared by the preparation method described in claim 8.

10. Application of paper-based sensors, characterized in that: The molecular imprinting ratiometric fluorescent paper-based sensor described in claim 9 is used for visually identifying and / or detecting fleroxacin in meat products.

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