A molecularly imprinted electrochemical sensor and its preparation method and application

Abstract

The present invention discloses a molecularly imprinted electrochemical sensor and a preparation method and application thereof. A magnetic molecularly imprinted polymer is obtained by ATRP polymerization using a magnetic MOFs material as a carrier; the magnetic molecularly imprinted polymer is modified onto an electrode surface to obtain the molecularly imprinted electrochemical sensor. In the present invention, a silicon dioxide layer is coated on the surface of a magnetic core to effectively prevent the magnetic core from being oxidized or corroded. Hydroxyl groups are introduced by coating polydopamine on the surface of the magnetic core, which facilitates complexation with metal ions during the synthesis of the MOFs material. The introduction of the MOFs material enriches the recognition sites. An initiator for ATRP polymerization is introduced on the surface of magnetic nanoparticles coated with the MOFs material to prepare a molecularly imprinted polymer layer by surface-initiated atom transfer radical polymerization. The sensor has the characteristics of low separation and recovery difficulty, high recognition efficiency and short detection cycle, avoids the risk of template molecule leakage during use, and has high safety and reliability.

Description

Technical Field

[0001] The present invention belongs to the technical field of molecular imprinted polymers, and in particular relates to a molecular imprinted electrochemical sensor and a preparation method and application thereof. Background Art

[0002] Molecularly imprinted polymers (MIPs) are receptors with special affinity and specific recognition functions for target compounds. Due to their specific recognition function, MIPs are widely used in the field of chemical / biosensors. Currently, bulk polymerization is the traditional method for preparing molecularly imprinted polymers. The molecularly imprinted polymers prepared by this method often require steps such as grinding and screening. The preparation process is cumbersome, and a large number of recognition sites are embedded, resulting in low recognition efficiency. At the same time, there is a risk of template molecule leakage during use, which affects the detection results. Summary of the Invention

[0003] In response to the technical problems existing in the prior art, the present invention provides a molecularly imprinted electrochemical sensor and its preparation method and application, so as to solve the technical problems of the existing molecularly imprinted polymer, such as the complicated preparation process, the embedding of a large number of recognition sites and the low recognition efficiency.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] The present invention provides a preparation method of a molecularly imprinted electrochemical sensor, which is characterized by using a magnetic MOFs material as a carrier and polymerizing it through ATRP to obtain a magnetic molecularly imprinted polymer; and modifying the magnetic molecularly imprinted polymer onto an electrode surface to obtain the molecularly imprinted electrochemical sensor.

[0006] Further, the following steps are included:

[0007] Step 1: Using Fe3O4 magnetic nanoparticles as cores, silica-coated magnetic nanoparticles are prepared;

[0008] Step 2: using the silica-coated magnetic nanoparticles as cores to prepare polydopamine-coated magnetic nanospheres;

[0009] Step 3: Using the polydopamine-coated magnetic nanospheres as carriers, preparing MOFs-coated magnetic porous nanospheres;

[0010] Step 4, modifying the MOFs-coated magnetic porous nanospheres with 2-bromoisobutyryl bromide to obtain modified magnetic porous nanospheres;

[0011] Step 5: After the template molecule and the functional monomer are evenly mixed, a cross-linking agent, CuBr, pentamethyldiethylenetriamine and the modified magnetic porous nanospheres are added to initiate a polymerization reaction to obtain a magnetic molecularly imprinted polymer;

[0012] Step 6, removing the template molecule from the magnetic molecularly imprinted polymer to obtain a magnetic molecularly imprinted polymer after the template molecule is removed;

[0013] Step 7: modifying the magnetic molecularly imprinted polymer after removing the template molecules onto a glassy carbon electrode to obtain the molecularly imprinted electrochemical sensor.

[0014] Furthermore, in step 1, the process of preparing silica-coated magnetic nanoparticles using Fe3O4 magnetic nanoparticles as cores specifically includes the following steps:

[0015] Step 1.1, ultrasonically dispersing Fe3O4 magnetic nanoparticles in a mixed solvent of anhydrous ethanol and water, adding ammonia water, and continuing ultrasonic dispersion to obtain a uniform dispersion system;

[0016] Step 1.2: adding ethyl orthosilicate to the uniformly dispersed system, performing magnetic separation after the reaction, washing, and vacuum drying to obtain the silica-coated magnetic nanoparticles.

[0017] Furthermore, in step 2, the process of preparing polydopamine-coated magnetic nanoparticles using the silica-coated magnetic nanoparticles as cores is as follows:

[0018] Step 2.1, dispersing dopamine hydrochloride in Tris-HCl buffer, adding the silica-coated magnetic nanoparticles, and stirring to react to obtain a reaction product A;

[0019] Step 2.2: Wash the reaction product A until the supernatant is clear, and vacuum dry it to obtain the polydopamine-coated magnetic nanoparticles.

[0020] Furthermore, in step 3, the process of preparing MOFs material-coated magnetic porous nanospheres using the polydopamine-coated magnetic nanospheres as carriers is as follows:

[0021] Step 3.1, dispersing the polydopamine-coated magnetic nanospheres in N,N-dimethylformamide, adding zirconium chloride and 2-aminoterephthalic acid, ultrasonically mixing, reacting, and cooling to obtain magnetic porous nanospheres coated with UiO-66-NH2;

[0022] Step 3.2: The magnetic porous nanospheres coated with UiO-66-NH2 are subjected to magnetic separation, washing, and vacuum drying to obtain the magnetic porous nanospheres coated with the MOFs material.

[0023] Furthermore, the process of modifying the MOFs-coated magnetic porous nanospheres with 2-bromoisobutyryl bromide to obtain the modified magnetic porous nanospheres is as follows:

[0024] Step 4.1, dissolving the MOFs-coated magnetic porous nanospheres in a mixed solution of anhydrous tetrahydrofuran and triethylamine, adding 2-bromoisobutyryl bromide, stirring, and reacting to obtain a reaction product B;

[0025] Step 4.2: Wash the reaction product B until the supernatant is clear, and vacuum dry to obtain the modified magnetic porous nanospheres.

[0026] Furthermore, in step 5, the template molecule is sulfadiazine, the functional monomer is methacrylic acid, and the cross-linking agent is ethylene glycol dimethacrylate.

[0027] Furthermore, in step 6, the process of removing the template molecule from the magnetic molecularly imprinted polymer to obtain the magnetic molecularly imprinted polymer after the template molecule is removed is as follows:

[0028] extracting the magnetic molecularly imprinted polymer with a methanol-acetic acid solution to obtain a magnetic molecularly imprinted polymer with the template molecule removed;

[0029] In step 7, the process of modifying the magnetic molecularly imprinted polymer after removing the template molecule onto a glassy carbon electrode to obtain the molecularly imprinted electrochemical sensor is as follows:

[0030] Dispersing the reduced graphene oxide in ultrapure water to obtain a dispersion system 1; dispersing the magnetic molecularly imprinted polymer after removing the template molecules in ultrapure water to obtain a dispersion system 2;

[0031] The dispersion system 1 and the dispersion system 2 are sequentially drop-coated on a glassy carbon electrode, dried, and placed in a buffer solution. Cyclic voltammetry is performed until a symmetrical and reversible redox peak appears and the peak potential difference is less than 85 mV, thereby obtaining the molecularly imprinted electrochemical sensor.

[0032] The present invention also provides a molecular imprinting electrochemical sensor, which is prepared by adopting the preparation method of a molecular imprinting electrochemical sensor.

[0033] The present invention also provides an application of a molecular imprinting electrochemical sensor in the specific recognition and detection of sulfadiazine.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The molecularly imprinted electrochemical sensor and preparation method thereof described in the present invention use Fe3O4 magnetic nanoparticles as magnetic cores, which facilitates the separation of imprinted materials from the medium during preparation and use; coating the surface of the magnetic core with a silicon dioxide layer can effectively prevent the magnetic core from being oxidized or corroded; introducing hydroxyl groups by coating the surface of the magnetic core with polydopamine is beneficial for complexation with metal ions during the synthesis of MOFs materials; the introduction of MOFs materials enriches the recognition sites, and by introducing an ATRP polymerization initiator on the surface of magnetic nanoparticles coated with MOFs materials, a molecularly imprinted polymer layer is prepared by surface-initiated atom transfer radical polymerization; the molecularly imprinted electrochemical sensor has the characteristics of low separation and recovery difficulty, high recognition efficiency and short detection cycle; at the same time, it avoids the risk of template molecule leakage during use and has high safety and reliability.

[0036] Furthermore, the mass of Fe3O4@SiO2@PDA magnetic nanospheres, zirconium chloride and 2-aminoterephthalic acid directly affects the morphology of the magnetic MOFs material and the recognition performance of the molecular imprinting polymer; UiO-66-NH2 particles are most evenly distributed on the surface of Fe3O4 microspheres and are of appropriate size; this structure can provide a larger specific surface area in subsequent polymerization experiments, thereby improving the polymer's recognition ability of template molecules.

[0037] Furthermore, using magnetic UiO-66-NH2 material as a carrier, 2-bromoisobutyryl bromide was modified on UiO-66-NH2. After ATRP polymerization, a magnetic molecularly imprinted polymer was obtained, and the magnetic molecularly imprinted polymer was modified onto the electrode. The prepared magnetic molecularly imprinted polymer exhibited a regular spherical morphology and good dispersion, with an obvious multilayer core-shell structure. In electrochemical tests, it had sensitive recognition ability for trace amounts of sulfadiazine and stable performance.

[0038] Furthermore, the imprinted layer is distributed on the surface of the solid support, making the imprinted sites easily accessible and enabling rapid recognition of the template molecule. Once the imprinted cavities are filled, electron transfer is blocked, and the electrochemical workstation monitors the current changes in real time. In applications for the identification and detection of sulfadiazine (SDZ) in environmental and food systems, the device achieves high adsorption capacity, high sensitivity, selectivity, and reusability, ensuring selective recognition of SDZ in complex environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the preparation process of the molecularly imprinted polymer of the magnetic MOFs material described in Example 1.

[0040] Figure 2Transmission electron microscopy images of the magnetic molecularly imprinted polymer Fe3O4@UiO-66@MIP (a) and thermally reduced graphene oxide (b) in Example 1.

[0041] Figure 3 These are the infrared spectra of the polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA (a), the MOFs material-coated magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2 (b), and the magnetic molecular imprinting polymer Fe3O4@UiO-66@MIP (c) with the template molecules removed, prepared in Example 1.

[0042] Figure 4 X-ray diffraction spectra of the magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2 (a) coated with MOFs material prepared in Example 1 and the magnetic molecular imprinted polymer Fe3O4@UiO-66@MIP (b) with the template molecules removed.

[0043] Figure 5 Electrochemical cyclic voltammetry curves of the glassy carbon electrode GCE (a) prepared in Example 1, the reduced graphene oxide modified glassy carbon electrode rGO / GCE (b), the MIP / rGO / GCE obtained by drop-coating a magnetic molecularly imprinted polymer on rGO / GCE (c), and the NIP / rGO / GCE obtained by drop-coating a magnetic non-molecularly imprinted polymer on rGO / GCE (d).

[0044] Figure 6 These are the electrochemical impedance spectra of electrodes modified with different materials prepared in Example 1, including those of glassy carbon electrode GCE, reduced graphene oxide-modified glassy carbon electrode rGO / GCE, MIP / rGO / GCE obtained by drop-coating a magnetic molecularly imprinted polymer on rGO / GCE, and NIP / rGO / GCE obtained by drop-coating a magnetic non-molecularly imprinted polymer on rGO / GCE. DETAILED DESCRIPTION

[0045] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail in the following specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0046] The present invention provides a method for preparing a molecularly imprinted electrochemical sensor. The method comprises the following steps: using a magnetic MOFs material as a carrier, modifying an initiator of an ATRP polymerization reaction on a magnetic porous carrier, and obtaining a magnetic molecularly imprinted polymer after ATRP polymerization; and modifying the magnetic molecularly imprinted polymer onto an electrode surface to obtain the molecularly imprinted electrochemical sensor.

[0047] In the present invention, the method for preparing the molecularly imprinted electrochemical sensor specifically comprises the following steps:

[0048] Step 1: preparing Fe3O4 magnetic nanoparticles by a solvothermal method;

[0049] The preparation process of the Fe3O4 magnetic nanoparticles is as follows:

[0050] Step 1.1, dissolving anhydrous ferric chloride, sodium citrate and anhydrous sodium acetate in ethylene glycol, and sonicating to obtain a homogeneous solution;

[0051] Step 1.2, adding the homogeneous solution into a hydrothermal reactor to carry out a hydrothermal reaction. After the reaction is completed, cooling to room temperature to obtain a black product;

[0052] Step 1.3: Wash the black product with ethanol and deionized water in sequence until the supernatant is clear, and vacuum dry to obtain the Fe3O4 magnetic nanoparticles.

[0053] Step 2: Using Fe3O4 magnetic nanoparticles as cores, preparing silica-coated magnetic nanoparticles Fe3O4@SiO2; specifically, silica is coated on the surface of the Fe3O4 magnetic nanoparticles by a sol-gel method to obtain the silica-coated magnetic nanoparticles Fe3O4@SiO2;

[0054] The preparation process of the silica-coated magnetic nanoparticles Fe3O4@SiO2 is as follows:

[0055] Step 2.1, ultrasonically dispersing Fe3O4 magnetic nanoparticles in a mixed solvent of anhydrous ethanol and water, adding ammonia water, and continuing ultrasonic dispersion to obtain a uniform dispersion system;

[0056] Step 2.2: Adding ethyl orthosilicate to the uniformly dispersed system, performing magnetic separation after the reaction, washing, and vacuum drying to obtain the silica-coated magnetic nanoparticles Fe3O4@SiO2.

[0057] Step 3: Using the silica-coated magnetic nanoparticles as cores, preparing polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA;

[0058] The preparation process of the polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA is as follows:

[0059] Step 3.1, dispersing dopamine hydrochloride in Tris-HCl buffer, adding the silica-coated magnetic nanoparticles Fe3O4@SiO2, and stirring to react to obtain a reaction product A;

[0060] Step 3.2: Wash the reaction product A until the supernatant is clear, and vacuum dry it to obtain the polydopamine-coated magnetic nanoparticles Fe3O4@SiO2@PDA.

[0061] Step 4, using the polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA as a carrier, preparing MOFs material-coated magnetic porous nanospheres; specifically, by a solvothermal method, coating UiO-66-NH2 on the polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA to obtain the MOFs material-coated magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2;

[0062] The preparation process of the MOFs material-coated magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2 is as follows:

[0063] Step 4.1, dispersing the polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA in N,N-dimethylformamide, adding zirconium chloride and 2-aminoterephthalic acid, ultrasonically mixing, reacting, and cooling to obtain magnetic porous nanospheres coated with UiO-66-NH2;

[0064] Step 4.2: The magnetic porous nanospheres coated with UiO-66-NH2 are subjected to magnetic separation, washing, and vacuum drying to obtain the magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2 coated with the MOFs material.

[0065] During the modification process of UiO-66-NH2 of the present invention, the polydopamine-coated magnetic nanoparticles

[0066] The mass of Fe3O4@SiO2@PDA, zirconium chloride and 2-aminoterephthalic acid can directly affect the morphology of the magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2 coated with the MOFs material and the recognition performance of the molecular imprinting polymer; in terms of mass, the masses of the polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA, zirconium chloride and 2-aminoterephthalic acid are 0.05g, 1.165g and 0.905g, or 0.05g, 0.466g and 0. 362g, or 0.05g, 0.233g and 0.181g; wherein, preferably, the masses of the polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA, zirconium chloride and 2-aminoterephthalic acid are 0.05g, 0.233g and 0.181g, respectively. Under this condition, UiO-66-NH2 particles can be grown on the surface of the magnetic carrier with uniform size; at the same time, the specific surface area of ​​the surface imprinted solid phase carrier can be effectively increased, thereby enhancing the specific recognition ability and rapid mass transfer ability of the magnetic molecular imprinted polymer for the template molecule.

[0067] Step 5. Modify 2-bromoisobutyryl bromide on the magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2 coated with the MOFs material to obtain modified magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-Br; specifically, the ATRP initiator is modified on the magnetic MOFs carrier by reacting the amino groups on the surface of the magnetic MOFs material with 2-bromoisobutyryl bromide, and then a molecular imprinting polymer layer is prepared by surface-initiated atom transfer radical polymerization reaction to obtain the modified magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-Br.

[0068] The preparation process of the modified magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-Br is as follows:

[0069] Step 5.1, dissolving the MOFs-coated magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2 in a mixed solution of anhydrous tetrahydrofuran and triethylamine, adding 2-bromoisobutyryl bromide, and reacting under nitrogen with stirring in an ice bath, followed by reaction at room temperature to obtain reaction product B;

[0070] Step 5.2: Wash the reaction product B until the supernatant is clear, and vacuum dry to obtain the modified magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-Br.

[0071] Step 6: After the template molecule and the functional monomer are evenly mixed, a cross-linking agent, CuBr, pentamethyldiethylenetriamine and the modified magnetic porous nanospheres are added to initiate a polymerization reaction to obtain a magnetic molecularly imprinted polymer;

[0072] The preparation process of the magnetic molecularly imprinted polymer is as follows:

[0073] The template molecule and the functional monomer are added to anhydrous acetonitrile and mixed evenly. Then, a cross-linking agent, CuBr, pentamethyldiethylenetriamine and the modified magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-Br are added. Nitrogen is introduced to deoxygenate, and a polymerization reaction is carried out under nitrogen protection to obtain the magnetic molecularly imprinted polymer.

[0074] Step 7, removing the template molecules in the magnetic molecularly imprinted polymer to obtain the magnetic molecularly imprinted polymer Fe3O4@UiO-66@MIP after the template molecules are removed;

[0075] The preparation process of the magnetic molecularly imprinted polymer Fe3O4@UiO-66@MIP after removing the template molecules is as follows:

[0076] The magnetic molecular imprinted polymer is extracted with a methanol-acetic acid solution to obtain a magnetic molecular imprinted polymer Fe3O4@UiO-66@MIP with the template molecule removed.

[0077] Step 8, modifying the magnetic molecularly imprinted polymer Fe3O4@UiO-66@MIP after removing the template molecule onto a glassy carbon electrode to obtain the molecularly imprinted electrochemical sensor;

[0078] The preparation process of the molecular imprinting electrochemical sensor is as follows:

[0079] Dispersing the reduced graphene oxide in ultrapure water to obtain a dispersion system 1; dispersing the magnetic molecularly imprinted polymer after removing the template molecules in ultrapure water to obtain a dispersion system 2;

[0080] The dispersion system 1 and the dispersion system 2 are sequentially drop-coated on a glassy carbon electrode, dried, and placed in a buffer solution. Cyclic voltammetry is performed until a symmetrical and reversible redox peak appears and the peak potential difference is less than 85 mV, thereby obtaining the molecularly imprinted electrochemical sensor.

[0081] Preparation principle:

[0082] The preparation method of the molecular imprinted electrochemical sensor of the present invention adopts Fe3O4 magnetic nanoparticles prepared by a solvothermal method as the magnetic core, thereby ensuring that the magnetic molecular imprinted polymer can be easily separated from the medium during use and preparation; by coating the surface of the Fe3O4 magnetic nanoparticles with a silicon dioxide layer, the magnetic core can be effectively prevented from being oxidized or etched; by introducing a polydopamine layer on the surface of the silicon dioxide-coated magnetic nanospheres Fe3O4@SiO2, the aromatic ring of the polydopamine can chelate with the zirconium ion, thereby facilitating the growth of UiO-66-NH2; by a hydrothermal method, the Fe3O4 magnetic nanoparticles are coated with a silicon dioxide layer, thereby facilitating the growth of UiO-66-NH2. The surface of polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA was modified with MOFs materials, which facilitated the modification of ATRP initiators to the surface of MOFs-coated magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2. It also ensured that molecularly imprinted polymers could be prepared on the surface of magnetic MOFs microspheres through surface-initiated ATRP polymerization. The porous carrier ensured that the prepared imprinted polymers had more abundant recognition sites. By modifying the magnetic molecularly imprinted polymers onto the electrode, an electrochemical sensor capable of detecting trace amounts of SDZ was obtained.

[0083] Example 1

[0084] As attached Figure 1 As shown, this embodiment 1 provides a method for preparing a molecular imprinting electrochemical sensor, comprising the following steps:

[0085] Step 1: preparing Fe3O4 magnetic nanoparticles by a solvothermal method;

[0086] The preparation process of Fe3O4 magnetic nanoparticles is as follows:

[0087] Step 1.1, weigh 2.6g of anhydrous ferric chloride, 1.0g of sodium citrate and 4.0g of anhydrous sodium acetate; dissolve the weighed anhydrous ferric chloride, sodium citrate and anhydrous sodium acetate in 80mL of ethylene glycol, and sonicate for 30min to fully dissolve them to obtain a homogeneous solution;

[0088] Step 1.2, pouring the homogeneous solution into a stainless steel hydrothermal kettle to carry out a horizontal reaction; wherein the reaction temperature is 200°C and the reaction time is 24 hours; after the reaction is completed, cooling to room temperature to obtain a black product;

[0089] Step 1.3: Wash the black product with ethanol and deionized water in sequence until the supernatant is clear, and vacuum dry it to obtain Fe3O4 magnetic nanoparticles; wherein the vacuum drying temperature is 60°C and the vacuum drying time is 6 hours.

[0090] Step 2: using a sol-gel method to coat a silicon dioxide layer on the surface of the Fe3O4 magnetic nanoparticles to obtain silicon dioxide-coated magnetic nanoparticles Fe3O4@SiO2;

[0091] The preparation process of the silica-coated magnetic nanoparticles Fe3O4@SiO2 is as follows:

[0092] Step 2.1, ultrasonically disperse 0.4 g of Fe3O4 magnetic nanoparticles into a mixed solvent of ethanol and water; wherein the mixed solvent of ethanol and water includes 30 mL of ethanol and 10 mL of deionized water; add 1.2 mL of ammonia water, and continue ultrasonic dispersion for 1 hour to obtain a uniform dispersion system;

[0093] Step 2.2, add ethyl orthosilicate to the uniformly dispersed system, react at room temperature for 6 hours, magnetically separate, wash, and vacuum dry to obtain silica-coated magnetic nanoparticles Fe3O4@SiO2; wherein, the washing process is washed three times with ethanol and deionized water in sequence; the vacuum drying temperature is 60°C, and the vacuum drying time is 6 hours.

[0094] Step 3: Using the silica-coated magnetic nanoparticles as cores, preparing polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA;

[0095] The process of preparing the polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA is as follows:

[0096] Step 3.1. Disperse 40 mg of dopamine hydrochloride in 40 mL of Tris-HCl buffer (pH 8.5), add 50 mg of silica-coated magnetic nanoparticles Fe3O4@SiO2, and react. After the reaction is completed, cool to room temperature to obtain reaction product A. The reaction temperature is 25°C and the reaction time is 12 hours.

[0097] Step 3.2: Wash the reaction product A with anhydrous ethanol and deionized water in sequence until the supernatant is clear, and vacuum dry to obtain polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA; wherein the vacuum drying temperature is 45°C and the vacuum drying time is 10 h.

[0098] Step 4: coating UiO-66-NH2 on the polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA by a solvothermal method to obtain the MOFs material-coated magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2;

[0099] The preparation process of the MOFs material-coated magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2 is as follows:

[0100] Step 4.1. Disperse polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA in 40 mL of N,N-dimethylformamide, add zirconium chloride and 2-aminoterephthalic acid, mix ultrasonically, transfer to a stainless steel hydrothermal autoclave, and react at 120°C for 12 h. After the reaction is complete, cool to room temperature to obtain magnetic porous nanospheres coated with UiO-66-NH2. The masses of the polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA, zirconium chloride, and 2-aminoterephthalic acid are 0.05 g, 0.233 g, and 0.181 g, respectively.

[0101] Step 4.2: The magnetic porous nanospheres coated with UiO-66-NH2 are magnetically separated, washed, and vacuum dried to obtain magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2 coated with MOFs material; wherein, the washing process is carried out by washing with ethanol and deionized water several times in sequence; the vacuum drying temperature is 60°C, and the vacuum drying time is 6 hours.

[0102] Step 5: The ATRP initiator is modified on the magnetic MOFs carrier by reacting the amino groups on the surface of the magnetic MOFs material with 2-bromoisobutyryl bromide. Then, a surface-initiated atom transfer radical polymerization reaction is performed to prepare a molecularly imprinted polymer layer, thereby obtaining the modified magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-Br.

[0103] The preparation process of the modified magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-Br is as follows:

[0104] Step 5.1. Dissolve 50 mg of MOFs-coated magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2 in a mixture of 15 mL of anhydrous tetrahydrofuran and 500 μL of triethylamine, add 500 μL of 2-bromoisobutyryl bromide, and stir the mixture in an ice bath after ultrasonic stirring for 2 h. Then, react at room temperature under nitrogen protection for 12 h to obtain reaction product B. The volume ratio of anhydrous tetrahydrofuran, triethylamine, and 2-bromoisobutyryl bromide is 30:1:1.

[0105] Step 5.2: The reaction product B is washed with anhydrous tetrahydrofuran, anhydrous ethanol, and deionized water in sequence until the supernatant is clear, and then vacuum-dried to obtain modified magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-Br; wherein the vacuum drying temperature is 60°C and the vacuum drying time is 5 h.

[0106] Step 6: After the template molecule and the functional monomer are evenly mixed, a cross-linking agent, CuBr, pentamethyldiethylenetriamine and the modified magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-Br are added to initiate a polymerization reaction to obtain a magnetic molecularly imprinted polymer;

[0107] The preparation process of the magnetic molecularly imprinted polymer is as follows:

[0108] Step 6.1. Dissolve 0.1722 g of methacrylic acid and 0.1251 g of sulfadiazine in 20 mL of anhydrous acetonitrile and stir at room temperature under nitrogen for 1 h. Then, add 1.9822 g of ethylene glycol dimethacrylate, 0.01435 g of CuBr, 0.01733 g of pentamethyldiethylenetriamine, and 0.02 g of modified magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-Br in sequence, and carry out polymerization reaction under nitrogen atmosphere to obtain reaction product C. The polymerization reaction temperature is 60°C, and the reaction time is 24 h.

[0109] Step 6.2: Wash the reaction product C several times with anhydrous acetonitrile and anhydrous ethanol in sequence until the supernatant is clear, and then dry it in vacuum to obtain a magnetic molecularly imprinted polymer; wherein the vacuum temperature is 60° C. and the reaction time is 6 h.

[0110] Step 7, removing the template molecules in the magnetic molecularly imprinted polymer to obtain the magnetic molecularly imprinted polymer Fe3O4@UiO-66@MIP after the template molecules are removed;

[0111] Specifically, the dried magnetic molecularly imprinted polymer was placed in a Soxhlet extractor and extracted with a methanol-acetic acid solution to obtain the magnetic molecularly imprinted polymer Fe3O4@UiO-66@MIP after the template molecules were removed; wherein the methanol-acetic acid solution was prepared by methanol and acetic acid in a volume ratio of 9:1.

[0112] Step 8, modifying the magnetic molecularly imprinted polymer Fe3O4@UiO-66@MIP after removing the template molecule onto a glassy carbon electrode to obtain the molecularly imprinted electrochemical sensor;

[0113] The preparation process of the molecular imprinting electrochemical sensor is as follows:

[0114] Step 8.1. The glassy carbon electrode (GCE) was ground and polished with 1.0 μm and 0.05 μm α-Al2O3 powders, respectively, rinsed, and ultrasonically cleaned in ultrapure water and anhydrous ethanol, respectively, and dried with nitrogen. The electrode was then electrochemically activated in 0.5 mol / L H2SO4 to achieve optimal electrode conditions. The electrode was then removed, rinsed with ultrapure water, and dried with nitrogen to obtain a pretreated glassy carbon electrode.

[0115] Step 8.2, dispersing reduced graphene oxide rGO in ultrapure water to obtain dispersion system 1; dispersing the magnetic molecularly imprinted polymer Fe3O4@UiO-66@MIP after removing the template molecules in ultrapure water to obtain dispersion system 2;

[0116] Step 8.3: The dispersion system 1 and the dispersion system 2 were sequentially drop-coated on a glassy carbon electrode, dried at room temperature, and then incubated in a phosphate buffer solution for 200 seconds. Cyclic voltammetry was performed until a symmetrical and reversible redox peak appeared with a peak potential difference of less than 85 mV, thereby obtaining an electrochemical sensor of the molecularly imprinted polymer; wherein the phosphate buffer solution contained 1 mol / L KCl and 5 mmol / L [Fe(CN)6] 3- / 4- pH = 7 phosphate buffer solution; by differential pulse voltammetry, the current response of the sensor is 0.2193 mA in the range of -0.1V to 0.5V.

[0117] As attached Figure 2 As shown, attached Figure 2 The transmission electron microscopy images of the magnetic molecularly imprinted polymer Fe3O4@UiO-66@MIP (a) and thermally reduced graphene oxide (b) in Example 1 are given in the attached figure. Figure 2 (a) shows the transmission electron microscopy image of the magnetic molecularly imprinted polymer prepared in Example 1. Figure 2 (b) shows the transmission electron microscopy image of thermally reduced graphene oxide; Figure 2 As can be seen from (a), the magnetic molecular imprinted polymer prepared in Example 1 exhibits good dispersion and uniform size and has an obvious multi-layer core-shell structure; the innermost layer is Fe3O4 nanoparticles with a diameter of about 250-300nm; the first layer is a uniformly coated SiO2 layer with a thickness of about 25-30nm; the second layer is a uniformly coated polydopamine layer with a thickness of about 22-30nm; the third layer is a MOFs layer uniformly coated by a solvent thermal method with a thickness of about 50-60nm; the outermost layer is a polymer layer; the polymer layer is located on the surface of the carrier, which is conducive to the rapid binding of template molecules and rapid mass transfer during the test process; from the attached Figure 2 In (b), obvious wrinkle morphology of reduced graphene oxide can be observed, which also proves the successful preparation of thermally reduced graphene oxide.

[0118] As attached Figure 3 As shown, attached Figure 3 The infrared spectra of the polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA (a), the MOFs-coated magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2 (b), and the magnetic molecularly imprinted polymer Fe3O4@UiO-66@MIP (c) without template molecules prepared in Example 1 are given in the figure. Figure 3 As can be seen in (a), 473cm -1 The peak at 1158 cm can be attributed to the characteristic absorption peak of Fe-O. -1 The absorption peak near 1603 cm can be attributed to the stretching vibration peak of Si-O-Si. -1 The absorption peak near the surface of the polydopamine can be attributed to the C=C stretching vibration absorption peak of the aromatic group, indicating that the Fe3O4@SiO2@PDA nanospheres have been successfully synthesized. Figure 3 (b) shows that at 1640 cm -1 There is a characteristic peak of stretching vibration of the carboxyl group of 2-aminoterephthalic acid, which shows that the MOFs material has been successfully coated; Figure 3 In (c), it can be seen that at 1721 and 1637 cm -1 The peaks are the characteristic peaks of C=O and OH in the magnetic molecular imprinted polymer Fe3O4@UiO-66@MIP, which further proves that the magnetic MOFs molecular imprinted polymer has been successfully synthesized.

[0119] As attached Figure 4 As shown, attached Figure 4 The X-ray diffraction spectra of the magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2 (a) and the magnetic molecular imprinted polymer Fe3O4@UiO-66@MIP (b) with the template molecules removed are given in Example 1; Figure 4 (a) It can be seen that the diffraction peaks at 7.4°, 8.6°, 26.3°, 7.4° and 30.1° in the diffraction spectrum of the magnetic MOFs nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2 correspond to the (111), (002), (224) and (046) crystal planes of the UiO-66 particles, respectively; it can also be seen that the diffraction peaks at 30.0°, 35.2°, 43.3°, 57° and 62.9° correspond to the (220), (311), (400), (440) and (533) crystal planes of the Fe3O4 nanoparticles, respectively; Figure 4It can be seen from (b) that after ATRP polymerization, the diffraction spectrum has no obvious change, indicating that the crystal structure of the magnetic core and UiO-66 is not affected during the preparation of the magnetic molecularly imprinted polymer Fe3O4@UiO-66@MIP.

[0120] As attached Figure 5 As shown, attached Figure 5 The electrochemical cyclic voltammetry curves of the glassy carbon electrode GCE (a), the reduced graphene oxide modified glassy carbon electrode rGO / GCE (b), the MIP / rGO / GCE obtained by drop-coating a magnetic molecularly imprinted polymer on rGO / GCE (c), and the NIP / rGO / GCE obtained by drop-coating a magnetic non-molecularly imprinted polymer on rGO / GCE (d) are given in Example 1; wherein, from the attached Figure 5 As shown in (a), the cyclic voltammetry curve of the bare glassy carbon electrode at 0.25 V is about [Fe(CN)6] 3- / 4- The anodic peak of oxidation, on its reverse scan, the reduction peak at 0.15V corresponds to the reduction of the previously formed oxide; the highest current response it produces is 95μA; Figure 5 As shown in (b), the current response of the electrode modified with reduced graphene oxide is increased to 130 μA, which is mainly due to the large specific surface area and high conductivity of reduced graphene oxide. Figure 5 As shown in (c), after modification with magnetic molecular imprinted polymer, the current response is 112 μA. Compared with the electrode modified with reduced graphene oxide, the current is reduced. This is mainly due to the non-conductivity of the polymer film. In addition, the prepared magnetic molecular imprinted polymer has a special cavity, which also provides certain conditions for electron transfer in the electrolyte. Figure 5 As shown in (d), after the glassy carbon electrode was modified with the non-molecularly imprinted polymer, the current response suddenly dropped to 67 μA. This is because the non-conductive nature of the polymer blocked the [Fe(CN)6] 3- / 4- The transfer process of probe ions.

[0121] As attached Figure 6 As shown, attached Figure 6 The electrochemical impedance spectra of the electrodes modified with different materials prepared in Example 1 are given in the figure, including the electrochemical impedance spectra of the glassy carbon electrode GCE, the reduced graphene oxide modified glassy carbon electrode rGO / GCE, the MIP / rGO / GCE obtained by drop-coating a magnetic molecularly imprinted polymer on rGO / GCE, and the NIP / rGO / GCE obtained by drop-coating a magnetic non-molecularly imprinted polymer on rGO / GCE; Figure 6 As can be seen from the electrochemical impedance spectrum, the resistance generated on the basis of various modified electrodes can be seen. In addition, the test results of the electrochemical impedance spectrum correspond to the results of the electrochemical cyclic voltammetry spectrum. Figure 6It can be seen that the radius of the Nyquist loop of the NIP / rGO / GCE electrode is the largest, the resistance is the largest, and the corresponding current response is also the lowest; the radius of the Nyquist loop of the rGO / GCE electrode is the smallest, the resistance is also the smallest, and the current response it produces is the highest. Figure 5 The results of the cyclic voltammetry spectra were consistent with those of the

[0122] Example 2

[0123] The steps and principles of Example 2 are basically the same as those of Example 1 above; the difference lies in the changes in the masses of the polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA, zirconium chloride, and 2-aminoterephthalic acid in Step 4.

[0124] Specifically, 50 mg of polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA were dispersed in 40 mL of N,N-dimethylformamide, 1165 mg of zirconium chloride and 905 mg of 2-aminoterephthalic acid were added, ultrasonically mixed, transferred to a stainless steel hydrothermal autoclave, and reacted at 120°C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain magnetic porous nanospheres coated with UiO-66-NH2. The magnetic porous nanospheres coated with UiO-66-NH2 were magnetically separated, washed, and vacuum dried to obtain MOFs material-coated magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2. The washing process was performed by washing with ethanol and deionized water several times in sequence. The vacuum drying temperature was 60°C and the vacuum drying time was 6 hours.

[0125] The molecularly imprinted electrochemical sensor prepared in Example 2 had a current response of 0.1817 mA in differential pulse voltammetry detection.

[0126] Example 3

[0127] The steps and principles of this embodiment 3 are basically the same as those of the above embodiment 1; the difference is that in step 4, the mass changes of the polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA, zirconium chloride and 2-aminoterephthalic acid are observed.

[0128] Specifically, 50 mg of polydopamine-coated magnetic nanospheres Fe3O4@SiO2@PDA were dispersed in 40 mL of N,N-dimethylformamide, 466 mg of zirconium chloride and 362 mg of 2-aminoterephthalic acid were added, ultrasonically mixed, transferred to a stainless steel hydrothermal autoclave, and reacted at 120°C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature to obtain magnetic porous nanospheres coated with UiO-66-NH2. The magnetic porous nanospheres coated with UiO-66-NH2 were magnetically separated, washed, and vacuum dried to obtain MOFs material-coated magnetic porous nanospheres Fe3O4@SiO2@PDA@UiO-66-NH2. The washing process was performed by washing with ethanol and deionized water several times in sequence. The vacuum drying temperature was 60°C and the vacuum drying time was 6 hours.

[0129] In this Example 3, the prepared molecularly imprinted electrochemical sensor had a current response of 0.2037 mA in the detection of differential pulse voltammetry.

[0130] Example 4

[0131] The steps and principles of this embodiment 4 are basically the same as those of the above embodiment 1; the difference is: the difference lies in the pH value of the phosphate buffer solution in step 8.

[0132] Specifically, in step 8, the phosphate buffer solution is 1 mol / L KCl and 5 mmol / L [Fe(CN)6] 3- / 4- The pH of the phosphate buffer solution was 4, and the concentration of the SDZ solution was fixed at 2×10 -6 mol / L; by differential pulse voltammetry, the current response of the sensor was 0.1197 mA in the range of -0.1V to 0.5V.

[0133] Example 5

[0134] The steps and principles of this embodiment 5 are basically the same as those of the above embodiment 1; the difference is: the pH value of the phosphate buffer solution in step 8.

[0135] Specifically, in step 8, the phosphate buffer solution is 1 mol / L KCl and 5 mmol / L [Fe(CN)6] 3- / 4- The pH of the phosphate buffer solution was 5, and the concentration of the SDZ solution was fixed at 2×10 -6 mol / L; by differential pulse voltammetry, the current response of the sensor was 0.1432 mA in the range of -0.1V to 0.5V.

[0136] Example 6

[0137] The steps and principles of this embodiment 6 are basically the same as those of the above embodiment 1; the difference is: the pH value of the phosphate buffer solution in step 8.

[0138] Specifically, in step 8, the phosphate buffer solution is 1 mol / L KCl and 5 mmol / L [Fe(CN)6] 3- / 4- The pH of the phosphate buffer solution was 6, and the concentration of the SDZ solution was fixed at 2×10 -6 mol / L; by differential pulse voltammetry, the current response of the sensor was 0.1943 mA in the range of -0.1V to 0.5V.

[0139] Example 7

[0140] The steps and principles of this embodiment 7 are basically the same as those of the above embodiment 1; the difference is: the pH value of the phosphate buffer solution in step 8.

[0141] Specifically, in step 8, the phosphate buffer solution is 1 mol / L KCl and 5 mmol / L [Fe(CN)6] 3- / 4- The pH of the phosphate buffer solution was 8, and the concentration of the SDZ solution was fixed at 2×10 -6 mol / L; by differential pulse voltammetry, the current response of the sensor was 0.2014 mA in the range of -0.1V to 0.5V.

[0142] Example 8

[0143] The steps and principles of this embodiment 8 are basically the same as those of the above embodiment 1; the difference is: the pH value of the phosphate buffer solution in step 8.

[0144] Specifically, in step 8, the phosphate buffer solution is 1 mol / L KCl and 5 mmol / L [Fe(CN)6] 3- / 4- The pH of the phosphate buffer solution was 8, and the concentration of the SDZ solution was fixed at 2×10 -6 mol / L; by differential pulse voltammetry, the current response of the sensor was 0.1972 mA in the range of -0.1V to 0.5V.

[0145] Example 9-Example 17

[0146] The steps and principles of Examples 9-17 are basically the same as those of Example 1 above; the difference lies in the time in which the electrode is placed in the solution to be tested in Step 8.

[0147] Specifically, the optimal electrode incubation time is selected. The time for placing the electrode in a phosphate buffer solution with a pH of 7 is divided into eight types, corresponding to Examples 9 to 17, specifically 0s, 40s, 80s, 120s, 160s, 200s, 240s, 280s, and 320s. In differential pulse voltammetry detection, among the above ten incubation times, 80s begins to stabilize, 120s is in the stable current stage, and 200s is the optimal incubation time.

[0148] Comparative Example 1

[0149] Comparative Example 1 is substantially the same as Example 1 except for the amount of sulfadiazine added in step 6. Without adding sulfadiazine, a non-molecularly imprinted polymer was prepared, and a comparative experiment with and without the imprinted cavity was conducted.

[0150] Electrodes modified with non-molecularly imprinted polymer (NIP) were fabricated by the same procedure except that SDZ was added during polymerization. These electrodes were named NIP / rGO / GCE, while the electrodes modified with molecularly imprinted polymer were named MIP / rGO / GCE. Two electrolytes containing different concentrations of SDZ (1 mol / L KCl and 5 mmol / L [Fe(CN)6] 3- / 4- , pH = 7), the concentrations were 2 × 10 -8 mol / L, 1×10 -7 mol / L. The NIP / rGO / GCE and MIP / rGO / GCE electrodes were tested in two solutions with different concentrations, and the effects of MIP and NIP on the test results at the same concentration were obtained. - 8 mol / L SDZ electrolyte, the current response of NIP / rGO / GCE is 7.54×10 -6 A, the current response of MIP / rGO / GCE is 2.25×10 -4 A. In the presence of 1×10 -7 mol / L SDZ electrolyte, the current response of NIP / rGO / GCE is 8.03×10 -6 A, the current response of MIP / rGO / GCE is 2.11×10 -4 A. It can be seen from this that the recognition ability of the magnetic molecularly imprinted polymer modified electrochemical sensor of the present invention for SDZ is significantly higher than that of the non-molecularly imprinted polymer modified electrochemical sensor under the same conditions. Therefore, the magnetic molecularly imprinted polymer modified electrochemical sensor of the present invention has a better affinity for SDZ than the non-molecularly imprinted polymer modified electrochemical sensor.

[0151] Test Example 1

[0152] This test example 1 uses the product of Example 1 and changes the concentration of sulfadiazine during electrochemical detection to test the sensitivity of the sensor.

[0153] In the electrochemical sensitivity test, eight groups of sulfadiazine solutions with different concentrations were prepared, namely 0 mol / L, 2×10 -8 mol / L, 2.2×10 -7 mol / L, 4.2×10 -7 mol / L, 2.36×10 -6 mol / L, 2.52×10 -5 mol / L, 2.81×10 -5 mol / L and 3×10 -5 mol / L (maintaining the pH value of the electrolyte at 7). The prepared magnetic molecularly imprinted polymer modified electrode was first incubated in the solution for 200s, and then tested using differential pulse voltammetry in eight groups of solutions. Different current responses were obtained, which were 2.41×10 -4 A. 2.25×10 -4 A. 2.23×10 -4 A. 2.20×10 -4 A. 2.18×10 -4 A. 2.16×10 -4 A. 2.14×10 -4 A and 2.10×10 -4 A.

[0154] It was also found that with the increase of SDZ concentration, the current response gradually decreased. Based on this feature, a standard curve of concentration and current response was drawn, and the minimum detection limit was calculated to be 5.97×10 -8 mol / L. It can be seen that the molecular imprinting electrochemical sensor has a strong specific recognition ability for sulfadiazine and a low detection limit, which also shows that the molecular imprinting electrochemical sensor of the present invention can realize trace detection of SDZ in complex environments.

[0155] Test Example 2

[0156] This Test Example 2 uses the product of Example 1 and structural analogs of sulfadiazine, such as sulfanilamide, sulfamethoxazole, and sulfamethazine, to study the selectivity of the imprinted polymer.

[0157] Specifically, three electrolytes containing different sulfadiazine structural analogs were prepared, namely, 2×10 - 7 mol / L sulfadiazine and 2×10 -6mol / L sulfonamide structural analogue electrolyte, containing 2×10 -7 mol / L sulfadiazine and 2×10 -6 mol / L sulfamethoxazole structural analogue electrolyte, containing 2×10 -7 mol / L sulfadiazine and 2×10 - 6 mol / L sulfamethazine structural analogues. In these three electrolytes, detection was performed by differential pulse voltammetry using modified electrodes of the same structure. In addition, a modified electrode containing only 2×10 -7 mol / L sulfadiazine electrolyte was used as a comparison; it can be seen that the magnetic molecularly imprinted polymer has a high selectivity for sulfadiazine, and the recognition efficiency for the other three structural analogs is relatively low, indicating that the polymer has a strong anti-interference ability, and also shows that the molecularly imprinted electrochemical sensor of the magnetic MOFs material described in the present invention can specifically recognize sulfadiazine in a complex environment.

[0158] The present invention uses molecular imprinting technology to overcome the shortcomings of poor selectivity in previous detection. At the same time, it uses electrochemical sensors for real-time monitoring, overcoming the defects of traditional detection technology that cannot detect in real time. The prepared molecular imprinting polymer is used as a recognition element. Through its specific recognition performance of the template molecule, it affects the transfer of electrons in the conversion element (electrode). At the same time, the experimental processing and data recording are carried out with the help of an electrochemical workstation, thereby achieving the effect of real-time detection of the template molecule. In addition, due to the low cost and portability of the electrochemical workstation, it can achieve real-time trace detection in the field of food and environment, overcoming the defects of traditional detection pre-processing that is complicated and time-consuming.

[0159] The present invention describes a molecularly imprinted electrochemical sensor and its preparation method. A magnetic molecularly imprinted polymer is prepared using MOFs-coated magnetic porous nanospheres, Fe3O4@SiO2@PDA@UiO-66-NH2, as a carrier for imprinted polymerization. The prepared imprinted material is capable of specifically recognizing SDZ in a short period of time. The presence of the magnetic core allows the polymer to be rapidly separated under an external magnetic field. The porous skeleton structure increases the binding sites of the imprinted material, making the imprinted sites easily accessible, thereby achieving the effect of rapidly recognizing SDZ. The magnetic molecularly imprinted polymer is modified on the electrode. Once the imprinted cavity is filled with SDZ molecules, the redox process of the probe ion is hindered, and the current response will fluctuate to a certain extent. Combining the highly selective recognition of the molecularly imprinted polymer with the highly sensitive detection of the electrochemical test, the sensor is expected to be able to realize the recognition and detection of SDZ in complex environments in practical applications.

[0160] The above embodiment is only one of the implementation methods that can realize the technical solution of the present invention. The scope of protection claimed by the present invention is not limited only to this embodiment, but also includes changes, replacements and other implementation methods that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention.

Claims

1. A method for preparing a molecularly imprinted electrochemical sensor, characterized in that: Using magnetic MOFs material as a carrier, ATRP polymerization is performed to obtain a magnetic molecularly imprinted polymer; the magnetic molecularly imprinted polymer is modified onto the electrode surface to obtain the molecularly imprinted electrochemical sensor; The following steps are involved: Step 1: Using Fe3O4 magnetic nanoparticles as cores, silica-coated magnetic nanoparticles are prepared; Step 2: using the silica-coated magnetic nanoparticles as cores to prepare polydopamine-coated magnetic nanospheres; Step 3: Using the polydopamine-coated magnetic nanospheres as carriers, preparing MOFs-coated magnetic porous nanospheres; Step 4, modifying the MOFs-coated magnetic porous nanospheres with 2-bromoisobutyryl bromide to obtain modified magnetic porous nanospheres; Step 5: After the template molecule and the functional monomer are evenly mixed, a cross-linking agent, CuBr, pentamethyldiethylenetriamine and the modified magnetic porous nanospheres are added to initiate a polymerization reaction to obtain a magnetic molecularly imprinted polymer; Step 6, removing the template molecule from the magnetic molecularly imprinted polymer to obtain a magnetic molecularly imprinted polymer after the template molecule is removed; Step 7, modifying the magnetic molecularly imprinted polymer after removing the template molecule onto a glassy carbon electrode to obtain the molecularly imprinted electrochemical sensor; In step 4, the process of modifying the MOFs-coated magnetic porous nanospheres with 2-bromoisobutyryl bromide to obtain the modified magnetic porous nanospheres is as follows: Step 4.1, dissolving the MOFs-coated magnetic porous nanospheres in a mixed solution of anhydrous tetrahydrofuran and triethylamine, adding 2-bromoisobutyryl bromide, stirring, and reacting to obtain a reaction product B; Step 4.2, washing the reaction product B until the supernatant is clear, and vacuum drying to obtain the modified magnetic porous nanospheres; In step 5, the template molecule is sulfadiazine, the functional monomer is methacrylic acid, and the cross-linking agent is ethylene glycol dimethacrylate.

2. The method for preparing a molecularly imprinted electrochemical sensor according to claim 1, wherein: In step 1, the process of preparing silica-coated magnetic nanoparticles using Fe3O4 magnetic nanoparticles as cores specifically includes the following steps: Step 1.1, ultrasonically dispersing Fe3O4 magnetic nanoparticles in a mixed solvent of anhydrous ethanol and water, adding ammonia water, and continuing ultrasonic dispersion to obtain a uniform dispersion system; Step 1.2: adding ethyl orthosilicate to the uniformly dispersed system, performing magnetic separation after the reaction, washing, and vacuum drying to obtain the silica-coated magnetic nanoparticles.

3. The method for preparing a molecularly imprinted electrochemical sensor according to claim 1, wherein: In step 2, the process of preparing polydopamine-coated magnetic nanoparticles using the silica-coated magnetic nanoparticles as cores is as follows: Step 2.1, dispersing dopamine hydrochloride in Tris-HCl buffer, adding the silica-coated magnetic nanoparticles, and stirring to react to obtain a reaction product A; Step 2.2: Wash the reaction product A until the supernatant is clear, and vacuum dry it to obtain the polydopamine-coated magnetic nanoparticles.

4. The method for preparing a molecularly imprinted electrochemical sensor according to claim 1, wherein: In step 3, the process of preparing MOFs material-coated magnetic porous nanospheres using the polydopamine-coated magnetic nanospheres as carriers is as follows: Step 3.1, dispersing the polydopamine-coated magnetic nanospheres in N,N-dimethylformamide, adding zirconium chloride and 2-aminoterephthalic acid, ultrasonically mixing, reacting, and cooling to obtain magnetic porous nanospheres coated with UiO-66-NH2; Step 3.2: The magnetic porous nanospheres coated with UiO-66-NH2 are subjected to magnetic separation, washing, and vacuum drying to obtain the magnetic porous nanospheres coated with the MOFs material.

5. The method for preparing a molecularly imprinted electrochemical sensor according to claim 1, wherein: In step 6, the process of removing the template molecule from the magnetic molecularly imprinted polymer to obtain the magnetic molecularly imprinted polymer after the template molecule is removed is as follows: extracting the magnetic molecularly imprinted polymer with a methanol-acetic acid solution to obtain a magnetic molecularly imprinted polymer with the template molecule removed; In step 7, the process of modifying the magnetic molecularly imprinted polymer after removing the template molecule onto a glassy carbon electrode to obtain the molecularly imprinted electrochemical sensor is as follows: Dispersing the reduced graphene oxide in ultrapure water to obtain a dispersion system 1; dispersing the magnetic molecularly imprinted polymer after removing the template molecules in ultrapure water to obtain a dispersion system 2; The dispersion system 1 and the dispersion system 2 are sequentially drop-coated on a glassy carbon electrode, dried, and placed in a buffer solution. Cyclic voltammetry is performed until a symmetrical and reversible redox peak appears and the peak potential difference is less than 85 mV, thereby obtaining the molecularly imprinted electrochemical sensor.

6. A molecularly imprinted electrochemical sensor, characterized in that The molecularly imprinted electrochemical sensor is prepared by the method for preparing a molecularly imprinted electrochemical sensor according to any one of claims 1 to 5.

7. Use of the molecularly imprinted electrochemical sensor according to claim 6 in the specific recognition and detection of sulfadiazine.

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