1. An electrochemical sensor for detecting chloramphenicol by molecular imprinting is characterized in that: the preparation method comprises Uio-66-CDs/GCE modified electrodes, and chloramphenicol molecularly imprinted polymer films formed on the surfaces of Uio-66-CDs/GCE modified electrodes after functional monomers and template molecules, namely chloramphenicol CAP, are electropolymerized and then washed to remove CAP molecules, wherein the Uio-66-CDs/GCE modified electrodes comprise glassy carbon electrodes and composites of metal organic frameworks Uio-66 and carbon quantum dots CDs coated on the surfaces of the glassy carbon electrodes; the mass ratio of Uio-66 to carbon quantum dots CDs is 1-2: 1-4.

2. The electrochemical sensor for detecting chloramphenicol by molecular imprinting according to claim 1, characterized in that: Uio-66-CDs/GCE modified electrode is prepared by the following method: uio-66 and CDs were mixed in DMF and sonicated until a homogeneous suspension was formed, which was dropped onto the surface of a glassy carbon electrode and dried at room temperature to give the Uio-66-CDs/GCE modified electrode.

3. The electrochemical sensor for detecting chloramphenicol by molecular imprinting according to claim 1, characterized in that: the concentration of the Uio-66 and CDs suspension is 1.0-2.5 mg/mL.

4. The electrochemical sensor for detecting chloramphenicol by molecular imprinting according to claim 1, characterized in that: what is needed isThe preparation method of Uio-66 comprises the following steps: reacting ZrCl₄Dissolving terephthalic acid in DMF, transferring the mixture into an autoclave lined with Teflon, heating at 120 ℃ for 48h, cooling to room temperature, centrifugally collecting a solid product, washing with methanol, and drying in vacuum for 24h at 120 ℃;

and/or the preparation method of the CDs comprises the following steps: dissolving citric acid and ethylenediamine in ultrapure water, stirring to form a uniform transparent solution, transferring into a polytetrafluoroethylene autoclave for reaction at 200 ℃ for 5h, cooling to room temperature after the reaction is finished, transferring the liquid in the autoclave to a dialysis membrane, dialyzing in the ultrapure water, centrifuging the liquid in the membrane, and freeze-drying.

5. The method for preparing an electrochemical sensor for detecting chloramphenicol by molecular imprinting according to any one of claims 1 to 4, characterized in that: the method comprises the following steps: soaking Uio-66-CDs/GCE modified electrode in PBS buffer solution containing functional monomer and CAP, electropolymerizing the functional monomer and template molecule CAP to Uio-66-CDs/GCE modified electrode surface under a three-electrode system to form a functional polymer-chloramphenicol film, removing chloramphenicol in the functional polymer-chloramphenicol film by using eluent to obtain a chloramphenicol molecularly imprinted polymer film, and obtaining the electrochemical sensor for imprinting and detecting chloramphenicol.

6. The method for preparing the electrochemical sensor for detecting chloramphenicol by molecular imprinting according to claim 5, characterized in that: the eluent is a mixed solution of methanol and acetic acid.

7. The method for preparing the electrochemical sensor for detecting chloramphenicol by molecular imprinting according to claim 5, characterized in that: the functional monomer is any one of pyrrole (Py), o-phenylenediamine, aniline or methacrylic acid.

8. The method for preparing the electrochemical sensor for detecting chloramphenicol by molecular imprinting according to claim 5, characterized in that: the functional monomer is pyrrole (Py), and PBS buffer containing Py and CAPThe concentration of Py in the solution was 1X 10^-4mol/L, CAP concentration of 1X 10^-3mol/L。

9. Use of the electrochemical sensor for the molecular imprinting detection of chloramphenicol according to any of claims 1 to 4, characterized in that: the method is used for detecting the CAP content in water solution and comprises the following steps:

Ppy-Mip/Uio-66-CDs/GCE is used as a working electrode of the molecularly imprinted electrochemical sensor, a platinum electrode is used as an auxiliary electrode, Ag/AgCl is used as a reference electrode, and a three-electrode system is formed for electrochemically detecting chloramphenicol.

10. Use of an electrochemical sensor for the molecular imprinting detection of chloramphenicol according to claim 9, characterized in that: the method for detecting the CAP content in water solution further comprises the following steps:

step A1. preparation of standard solutions containing CAP with different concentrations:

chloramphenicol was prepared in 1.0X 10 phosphate buffer (pH 7.0)^-4Diluting the solution into a series of standard chloramphenicol solutions with different concentrations (1.0 × 10)^-13mol/L～1.0×10^-10mol/L；

Step A2, drawing a standard curve:

taking a modified electrode Ppy-Mip/Uio-66-CDs/GCE as a working electrode, a platinum electrode as an auxiliary electrode, Ag/AgCl as a reference electrode to form a three-electrode system, putting the three-electrode system into a series of chloramphenicol standard solutions with different concentrations prepared in the step A2, recombining for a certain time, taking a potassium ferricyanide solution containing potassium chloride as an electrochemical cyclic voltammetry probe, scanning at the speed of 0.1V/s within the electrochemical window range of-0.2-0.6V, performing cyclic voltammetry scanning, and recording a potential-current curve. Meanwhile, potassium ferricyanide solution containing potassium chloride is used as a probe of electrochemical cyclic voltammetry, and the probe has the voltage of 0.2V, the amplitude of 10mV and the frequency of 0.1-10⁵Electrochemical impedance scanning was performed under Hz conditions. Fitting the resistance value data by using ZSIM Demo software, and establishing a linear relation between the difference value of the resistance Rct before and after adding chloramphenicol and the logarithm value of the chloramphenicol concentration to obtain the corresponding resistanceThe linear regression equation of (1);

step A3, sample detection:

and (3) pretreating the sample, testing according to the same molecular imprinting test conditions as those in the step A3, and calculating the concentration of chloramphenicol in the sample to be tested by using a linear regression equation corresponding to the standard curve obtained in the step A3 after fitting the resistance value.

Background

Chloramphenicol (CAP) is a bacteriostatic broad-spectrum antibiotic, has inhibitory effects on gram-positive and gram-negative bacteria, and is commonly used for treating infection of typhoid bacillus, Escherichia coli and the like. As chloramphenicol has the characteristics of low cost, high efficacy, strong activity, easy acquisition and the like, chloramphenicol is widely applied to the treatment of animal diseases. The use of chloramphenicol may result in residual chloramphenicol drug in animal derived foods. In addition, chloramphenicol can bind to human mitochondria, inhibiting protein synthesis by human mitochondria. Chloramphenicol was listed in 2019 as a prohibited drug use in food animals and a list of other compounds. The detection means of chloramphenicol generally includes gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry/mass spectrometry, etc., which can perform detection accurately and efficiently, but often requires time-consuming pretreatment, expensive equipment, skilled operators, etc. The electrochemical method has the characteristics of easy operation, low price, high selectivity, convenient carrying and the like, can be used for detecting drugs, pesticides, mould fungi and the like, and attracts the wide attention of people.

Molecular imprinting techniques have attracted considerable attention in recent years due to their good selectivity and chemical stability. The electrochemical sensor based on molecular imprinting can selectively identify and detect target compounds, is simple to manufacture, high in sensitivity, low in price and convenient to carry, and is more and more widely applied to aspects of clinical diagnosis, food analysis and the like.

Disclosure of Invention

In order to overcome the problems in the prior art, a first object of the present invention is to provide an electrochemical sensor for detecting chloramphenicol by molecular imprinting and a method for preparing the same, wherein elution of a template CAP and formation of a cavity are achieved based on formation and breakage of hydrogen bonds between Ppy molecules and CAP molecules of a Ppy-Mip/Uio-66-CDs/GCE sensor, quantitative detection of chloramphenicol is achieved, and the electrochemical sensor has the advantages of high detection sensitivity, high detection speed and convenience in use.

The technical purpose of the invention is realized by the following technical scheme: an electrochemical sensor for detecting chloramphenicol by molecular imprinting comprises Uio-66-CDs/GCE modified electrodes, and chloramphenicol molecular imprinting polymer films formed on the surfaces of Uio-66-CDs/GCE modified electrodes after CAP (chloramphenicol) is electropolymerized by functional monomers and template molecules and then washed to remove CAP molecules, wherein the Uio-66-CDs/GCE modified electrodes comprise glassy carbon electrodes and compounds of metal organic frameworks Uio-66 and carbon quantum dots CDs coated on the surfaces of the glassy carbon electrodes; the mass ratio of Uio-66 to carbon quantum dots CDs is 1-2: 1-4. Uio-66 has high void ratio, high specific surface area and strong adsorption of other MOF materials, Uio-66 is in regular octahedral structure and is very stable, and forms a compound with CDs, which can improve the agglomeration effect of CDs and increase the effective binding point number of the sensor, meanwhile, Uio-66 has double signal amplification effect in cooperation with CDs, so that the electrochemical sensor obtains higher sensitivity.

Preferably, the Uio-66-CDs/GCE modified electrode is prepared by the following method: uio-66 and CDs were mixed in DMF and sonicated until a homogeneous suspension was formed, which was dropped onto the surface of a glassy carbon electrode and dried at room temperature to give the Uio-66-CDs/GCE modified electrode. The Uio-66-CDs/GCE modified electrode is obtained by dissolving Uio-66 and CDs according to a set mass ratio, performing ultrasonic treatment to form a suspension, dripping the suspension onto the surface of a glassy carbon electrode, and drying at room temperature, and the method is simple and guarantees high detection sensitivity of chloramphenicol.

Further, the concentration of the Uio-66 and CDs suspension is 1.0-2.5 mg/mL;

further defines the preparation method of Uio-66: reacting ZrCl₄Terephthalic acid was dissolved in DMF and the mixture was transferred to a teflon lined autoclave, heated at 120 ℃ for 48h, cooled to room temperature, centrifuged to collect the solid product, washed with methanol, dried under vacuum for 24h at 120 ℃.

Further defines the preparation method of CDs: dissolving citric acid and ethylenediamine in ultrapure water, stirring to form a uniform transparent solution, transferring into a polytetrafluoroethylene autoclave for reaction at 200 ℃ for 5h, cooling to room temperature after the reaction is finished, transferring the liquid in the autoclave to a dialysis membrane, dialyzing in the ultrapure water, centrifuging the liquid in the membrane, and freeze-drying.

The preparation method of the electrochemical sensor for detecting chloramphenicol by molecular imprinting comprises the following steps: soaking Uio-66-CDs/GCE modified electrode in PBS buffer solution containing functional monomer and CAP, electropolymerizing the functional monomer and template molecule CAP to the surface of Uio-66-CDs/GCE modified electrode under a three-electrode system to form a functional polymer-chloramphenicol film, removing chloramphenicol in the functional polymer-chloramphenicol film by using eluent (preferably mixed solution of methanol and acetic acid) to obtain a chloramphenicol molecularly imprinted polymer film, and obtaining the electrochemical sensor for detecting chloramphenicol by imprinting.

Specifically, the functional monomer can be pyrrole, o-phenylenediamine, aniline, methacrylic acid and the like, pyrrole is preferred in the application, and when the functional monomer is pyrrole, the functional polymer-chloramphenicol film is named as Ppy-chloramphenicol film, and the electrochemical sensor for detecting chloramphenicol by imprinting is named as Ppy-Mip/Uio-66-CDs/GCE.

Further, the concentration of Py in the PBS buffer solution containing Py and CAP is 1X 10^-4mol/L, CAP concentration of 1X 10^-3mol/L。

The second purpose of the invention is to provide an application method of the electrochemical sensor for detecting chloramphenicol by molecular imprinting, which comprises the following steps:

Ppy-Mip/Uio-66-CDs/GCE is used as a working electrode of the molecularly imprinted electrochemical sensor, a platinum electrode is used as an auxiliary electrode, Ag/AgCl is used as a reference electrode, and a three-electrode system is formed for electrochemically detecting chloramphenicol.

Preferably, the method comprises the following steps:

step A1. preparation of standard solutions containing CAP with different concentrations:

chloramphenicol was prepared in 1.0X 10 phosphate buffer (pH 7.0)^-4Diluting the solution into a series of standard chloramphenicol solutions with different concentrations (1.0 × 10)^-13mol/L～1.0×10^-10mol/L；

Step A2, drawing a standard curve:

taking a modified electrode Ppy-Mip/Uio-66-CDs/GCE as a working electrode, a platinum electrode as an auxiliary electrode, AAnd g/AgCl is used as a reference electrode to form a three-electrode system, the three-electrode system is placed in a series of chloramphenicol standard solutions with different concentrations prepared in the step A2 to be recombined for a certain time, potassium ferricyanide solution containing potassium chloride is used as an electrochemical cyclic voltammetry probe, cyclic voltammetry scanning is carried out at a sweep rate of 0.1V/s within an electrochemical window range of-0.2-0.6V, and a potential-current curve is recorded. Meanwhile, potassium ferricyanide solution containing potassium chloride is used as a probe of electrochemical cyclic voltammetry, and the probe has the voltage of 0.2V, the amplitude of 10mV and the frequency of 0.1-10⁵Electrochemical impedance scanning was performed under Hz conditions. Fitting the resistance value data by using ZSIM Demo software, and establishing a linear relation between the difference value of the resistance Rct before and after adding chloramphenicol and the logarithm value of the chloramphenicol concentration to obtain a corresponding linear regression equation;

step A3, sample detection:

the sample was pretreated and tested under the same conditions as in step A3. And (4) calculating the concentration of the chloramphenicol in the sample to be detected by using the fitted resistance value and a linear regression equation corresponding to the standard curve obtained in the step A3.

Compared with the prior art, the invention has the following beneficial effects:

the sensor has the advantages of high detection sensitivity, high detection speed, strong specificity, wide linear range and convenient use.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:

FIG. 1 is a schematic flow chart of the preparation of the molecularly imprinted electrochemical sensor Ppy-Mip/Uio-66-CDs/GCE and the detection of chloramphenicol according to the present invention;

FIG. 2 is a resistance variation curve of the molecularly imprinted electrochemical sensor Ppy-Mip/Uio-66-CDs/GCE of example 1 in different preparation stages, wherein a corresponds to the resistance variation curve of GCE, b corresponds to the resistance variation curve of the Uio-66-CDs/GCE modified electrode prepared in step (2) of example 1, and c corresponds to the resistance variation curve of the example1 step 2 resistance change curve of the product (Ppy-chloramphenicol film) after electropolymerization, d corresponds to the resistance change curve of the sensor prepared in step 2 of example 1, and e corresponds to the resistance change curve of the sensor prepared in example 1 after electrochemical detection of chloramphenicol, i.e., after adsorption of CAP molecules (corresponding to a chloramphenicol solution concentration of 10)^-10mol/L), f corresponds to the resistance change curve of the pyrrole polymer Ppy film, g corresponds to the resistance change curve of the sensor prepared in the comparative example 2, and h corresponds to the resistance change curve of the sensor prepared in the comparative example 2 after electrochemical detection of chloramphenicol, namely after adsorption and combination of CAP molecules; as can be seen from fig. 2: after electropolymerization, a layer of Ppy-CAP film is formed on the surface of the electrode, which hinders the electron transfer of potassium ferricyanide and increases the resistance. The change curve of the resistance value around 6000 shows that CAP molecules are recombined, the resistance value after CAP is eluted is reduced, the potassium ferricyanide probe can reach the surface of the electrode again, and the surface of the electrode forms a CAP cavity. The resistance value increased after elution of CAP, indicating that the potassium ferricyanide probe was difficult to reach the electrode surface due to specific binding to CAP.

FIG. 3 is a cyclic voltammogram of a Uio-66-CDs/GCE modified electrode at different mass ratios (1: 4; 1: 2; 1: 1; 2: 1; 4:1) of Uio-66 and CDs prepared in inventive examples 1 to 4 and comparative example 1;

FIG. 4 is a graph showing the resistance change of the sensor prepared in the previous and subsequent examples before and after chloramphenicol of different concentrations of 10^-10～10^-13mol/L；

FIG. 5 is a calibration curve showing the resistance change of the sensor prepared in the example before and after the addition of chloramphenicol at various concentrations.

Detailed Description

The present invention is not limited to the following embodiments, and those skilled in the art can implement the present invention in other embodiments according to the disclosure of the present invention, or make simple changes or modifications on the design structure and idea of the present invention, and fall into the protection scope of the present invention. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.

The invention is described in more detail below with reference to the following examples:

example 1:

preparation and application methods of electrochemical sensor for detecting chloramphenicol by molecular imprinting

A preparation method of an electrochemical sensor for detecting chloramphenicol by molecular imprinting comprises the following steps:

(1) Uio-66-CDs, preparation method:

s1, ZrCl₄Terephthalic acid was dissolved in DMF, the mixture was transferred to an autoclave lined with 100mL teflon, heated at 120 ℃ for 48h, cooled to room temperature, centrifuged to collect the solid product, washed with methanol, dried under vacuum for 24h, 120 ℃;

s2, dissolving citric acid and ethylenediamine in 10mL of ultrapure water, and stirring for 10 minutes to form a uniform transparent solution. Then transferred to a 50mL polytetrafluoroethylene autoclave for reaction at 200 ℃ for 5 h. After completion of the reaction, the reaction mixture was cooled to room temperature, and the liquid in the autoclave was transferred to a dialysis membrane and dialyzed in ultrapure water. Centrifuging the liquid in the membrane, and freeze-drying;

s3, mixing 1mg of Uio-66 and 1mg of CDs in 2mL of DMF, and carrying out ultrasonic treatment until a uniform suspension is formed to obtain Uio-66-CDs;

s4: taking 25mL of the prepared PBS, transferring 7.0 mu L of Py by using a micro-injector, accurately weighing 0.8mg of CAP, mixing the three, and ultrasonically stirring for 10 minutes to prepare the PBS containing 1 multiplied by 10^-4mol/L Py and 1X 10^-3mol/L CAP phosphate buffer.

(2) The preparation method of the Ppy-Mip/Uio-66-CDs/GCE electrochemical sensor comprises the following steps:

polishing a glassy carbon electrode, sequentially performing ultrasonic treatment on the glassy carbon electrode by using nitric acid, absolute ethyl alcohol and deionized water respectively, transferring a DMF solution of Uio-66-CDs onto the surface of the glassy carbon electrode by using a microsyringe, and drying the solution at room temperature to obtain a Uio-66-CDs/GCE modified electrode; the Uio-66-CDs/GCE surface is recombined in PBS containing Py and CAP, and a functional monomer Py and a template molecule CAP are electropolymerized on the electrode surface to form a Ppy-chloramphenicol film under a traditional three-electrode system; and then eluting the template in a methanol-acetic acid mixed solution to form a Ppy-Mip/Uio-66-CDs/GCE sensor, wherein the Ppy-Mip/Uio-66-CDs/GCE sensor electrode after eluting the template can be specifically combined with CAP molecules through hydrogen bonds.

The invention provides an application method of an electrochemical sensor for detecting chloramphenicol by molecular imprinting, which comprises the following steps:

Ppy-Mip/Uio-66-CDs/GCE is used as a working electrode of the molecularly imprinted electrochemical sensor, a platinum electrode is used as an auxiliary electrode, Ag/AgCl is used as a reference electrode, and a three-electrode system is formed for electrochemically detecting chloramphenicol.

Preferably, the method comprises the following steps:

A1. preparing standard solutions containing different concentrations of CAP:

chloramphenicol was prepared in 1.0X 10 phosphate buffer (pH 7.0)^-4Diluting the solution into a series of standard chloramphenicol solutions with different concentrations (1.0 × 10)^-13mol/L～1.0×10^-10mol/L；

A2. Drawing a standard curve:

and forming a three-electrode system by using the modified electrode Ppy-Mip/Uio-66-CDs/GCE as a working electrode, a platinum electrode as an auxiliary electrode and Ag/AgCl as a reference electrode. And (3) putting the three-electrode system into a series of chloramphenicol standard solutions with different concentrations prepared in the step A2, recombining for a certain time, taking potassium ferricyanide solution containing potassium chloride as an electrochemical cyclic voltammetry probe, performing cyclic voltammetry scanning at a sweep rate of 0.1V/s within an electrochemical window range of-0.2-0.6V, and recording a potential-current curve. Meanwhile, potassium ferricyanide solution containing potassium chloride is used as a probe of electrochemical cyclic voltammetry, and the probe has the voltage of 0.2V, the amplitude of 10mV and the frequency of 0.1-10⁵Electrochemical impedance scanning was performed under Hz conditions. Fitting the resistance value data by using ZSIM Demo software, and establishing a linear relation between the difference value of the resistance Rct before and after adding chloramphenicol and the logarithm value of the chloramphenicol concentration to obtain a corresponding linear regression equation;

the three-electrode system was placed in a range of chloramphenicol concentrations (1.0X 10)^-13mol/L、5.0×10^-12mol/L、1.0×10^-12mol/L、5.0×10^-11mol/L、1.0×10^-11mol/L、5.0×10^-10mol/L、1.0×10^-10mol/L) in 0.1mol/L PBS. Taking potassium ferricyanide solution containing potassium chloride as probe of electrochemical cyclic voltammetry, under the condition of voltage of 0.2V, amplitude of 10mV and frequency of 0.1-10⁵Electrochemical impedance scanning was performed under Hz conditions. Establishing a linear relation between the resistance value (Rct) difference before and after adding the chloramphenicol and the log value of the chloramphenicol concentration to obtain a corresponding linear regression equation as follows: 1174.9x +16341.2, and R is the correlation coefficient (R)²0.9959. The detection range of the linear regression equation is 10^-13-10^-10mol/L, the lowest detection limit of CAP is 6.2X 10^-14mol/L。

A3. Sample detection:

the sample was pretreated and tested under the same conditions as in step A3. And (4) calculating the concentration of the chloramphenicol in the sample to be detected by using the fitted resistance value and a linear regression equation corresponding to the standard curve obtained in the step A3.

Example 2

S1, the specific operation is the same as S1 in example 1, specifically: reacting ZrCl₄Terephthalic acid was dissolved in DMF, the mixture was transferred to an autoclave lined with 100mL teflon, heated at 120 ℃ for 48h, cooled to room temperature, centrifuged to collect the solid product, washed with methanol, dried under vacuum for 24h, 120 ℃;

s2. the specific operation is the same as S2 in example 1, specifically: citric acid and ethylenediamine were dissolved in 10mL of ultrapure water and stirred for 10 minutes to form a uniform transparent solution. Then transferred to a 50mL polytetrafluoroethylene autoclave for reaction at 200 ℃ for 5 h. After completion of the reaction, the reaction mixture was cooled to room temperature, and the liquid in the autoclave was transferred to a dialysis membrane and dialyzed in ultrapure water. Centrifuging the liquid in the membrane, and freeze-drying;

s3. 2mg of Uio-66 and 1mg of CDs were mixed in 2mL of DMF and sonicated until a homogeneous suspension was formed, giving the Uio-66-CDs.

Example 3

Uio-66-CDs, preparation method:

s1, the specific operation is the same as S1 in example 1, specifically: reacting ZrCl₄Terephthalic acid was dissolved in DMF and the mixture was transferred to high pressure lined with 100mL TeflonHeating in a kettle at 120 ℃ for 48h, cooling to room temperature, centrifuging to collect a solid product, washing with methanol, and vacuum-drying for 24h at 120 ℃;

s2. the specific operation is the same as S2 in example 1, specifically: citric acid and ethylenediamine were dissolved in 10mL of ultrapure water and stirred for 10 minutes to form a uniform transparent solution. Then transferred to a 50mL polytetrafluoroethylene autoclave for reaction at 200 ℃ for 5 h. After completion of the reaction, the reaction mixture was cooled to room temperature, and the liquid in the autoclave was transferred to a dialysis membrane and dialyzed in ultrapure water. Centrifuging the liquid in the membrane, and freeze-drying;

s3. 1mg of Uio-66 and 2mg of CDs were mixed in 2mL of DMF and sonicated until a homogeneous suspension was formed, giving the Uio-66-CDs.

Example 3

Uio-66-CDs, preparation method:

s1, the specific operation is the same as S1 in example 1, specifically: reacting ZrCl₄Terephthalic acid was dissolved in DMF, the mixture was transferred to an autoclave lined with 100mL teflon, heated at 120 ℃ for 48h, cooled to room temperature, centrifuged to collect the solid product, washed with methanol, dried under vacuum for 24h, 120 ℃;

s2. the specific operation is the same as S2 in example 1, specifically: citric acid and ethylenediamine were dissolved in 10mL of ultrapure water and stirred for 10 minutes to form a uniform transparent solution. Then transferred to a 50mL polytetrafluoroethylene autoclave for reaction at 200 ℃ for 5 h. After completion of the reaction, the reaction mixture was cooled to room temperature, and the liquid in the autoclave was transferred to a dialysis membrane and dialyzed in ultrapure water. Centrifuging the liquid in the membrane, and freeze-drying;

s3. 1mg of Uio-66 and 4mg of CDs were mixed in 2mL of DMF and sonicated until a homogeneous suspension was formed, giving the Uio-66-CDs.

Comparative example 1

Uio-66-CDs, preparation method:

s1, the specific operation is the same as S1 in example 1, specifically: reacting ZrCl₄Terephthalic acid was dissolved in DMF, the mixture was transferred to an autoclave lined with 100mL teflon, heated at 120 ℃ for 48h, cooled to room temperature, centrifuged to collect the solid product, washed with methanol, dried under vacuum for 24h, 120 ℃;

s2. the specific operation is the same as S2 in example 1, specifically: citric acid and ethylenediamine were dissolved in 10mL of ultrapure water and stirred for 10 minutes to form a uniform transparent solution. Then transferred to a 50mL polytetrafluoroethylene autoclave for reaction at 200 ℃ for 5 h. After completion of the reaction, the reaction mixture was cooled to room temperature, and the liquid in the autoclave was transferred to a dialysis membrane and dialyzed in ultrapure water. Centrifuging the liquid in the membrane, and freeze-drying;

s3, mixing 4mg of Uio-66 and 1mg of CDs in 2mL of DMF, and carrying out ultrasonic treatment until a uniform suspension is formed to obtain Uio-66-CDs;

the prepared Uio-66-CDs composite material 5 μ L was dropped on the surface of a glassy carbon electrode by a microsyringe, and the cyclic voltammetry performance of Uio-66-CDs/GCE modified electrode (0.5 mol/L K containing 0.5mol/L KCl) was tested under CH660 (electrochemical workstation)₃[Fe(CN)₆]/K₄[Fe(CN)₆]Cyclic voltammogram in solution (pH 7.0).

The results obtained are shown in FIG. 3, which illustrates that when Uio-66: CDs in the range of 0.25 to 2 are suitable for this system. When Uio-66: when the CDs is 4, the cyclic voltammetry performance is obviously reduced, and the amplification effect of the sensor is not obvious.

Comparative example 2

A preparation method of an electrochemical sensor for non-imprinting detection of chloramphenicol comprises the following steps:

(1) Uio-66-CDs, preparation method:

s1, ZrCl₄Terephthalic acid was dissolved in DMF, the mixture was transferred to an autoclave lined with 100mL teflon, heated at 120 ℃ for 48h, cooled to room temperature, centrifuged to collect the solid product, washed with methanol, dried under vacuum for 24h, 120 ℃;

s2, dissolving citric acid and ethylenediamine in 10mL of ultrapure water, and stirring for 10 minutes to form a uniform transparent solution. Then transferred to a 50mL polytetrafluoroethylene autoclave for reaction at 200 ℃ for 5 h. After completion of the reaction, the reaction mixture was cooled to room temperature, and the liquid in the autoclave was transferred to a dialysis membrane and dialyzed in ultrapure water. Centrifuging the liquid in the membrane, and freeze-drying;

s3, mixing 1.0mg of Uio-66 and 1.0mg of CDs in 2mL of DMF and carrying out ultrasonic treatment until a uniform suspension is formed, so as to obtain Uio-66-CDs;

s4: 25mL of the prepared PBS was sampled and 7.0. mu.L of Py was transferred by a microsyringe, and the three were mixed and ultrasonically stirred for 10 minutes to prepare a PBS containing 1X 10^-4mol/L Py phosphate buffer solution.

(3) The preparation method of the Ppy-Nip/Uio-66-CDs/GCE electrochemical sensor comprises the following steps:

polishing a glassy carbon electrode, sequentially performing ultrasonic treatment on the glassy carbon electrode by using nitric acid, absolute ethyl alcohol and deionized water respectively, transferring a DMF solution of Uio-66-CDs onto the surface of the glassy carbon electrode by using a microsyringe, and drying the solution at room temperature to obtain a Uio-66-CDs/GCE modified electrode; the Uio-66-CDs/GCE surface is recombined in PBS containing Py, and the functional monomer Py is electropolymerized to the electrode surface under the traditional three-electrode system to form Ppy-Nip/Uio-66-CDs/GCE (without CAP).

Ppy-Nip/Uio-66-CDs/GCE is used as a working electrode of a non-imprinted electrochemical sensor, a platinum electrode is used as an auxiliary electrode, Ag/AgCl is used as a reference electrode, and a three-electrode system is formed for electrochemical detection of chloramphenicol.

In addition, experiments have verified that when Uio-66 and CDs suspensions are prepared, the solvents of water, ethanol and DMF are tried, but the results show that a sensor with higher sensitivity can be obtained only when DMF is used as the solvent.

The functional monomer is pyrrole, o-phenylenediamine, aniline or methacrylic acid, and can be specifically combined with CAP, but the optimal pyrrole is used, and the preparation and application method of the electrochemical sensor for detecting chloramphenicol by pyrrole-based molecular imprinting is characterized in that a hydrogen bond exists between the functional monomer Py and the CAP, and due to the interaction of the hydrogen bond, a layer of imprinted membrane of Ppy and CAP is formed on the surface of an electrode through electropolymerization, so that the potassium ferricyanide probe is prevented from reaching the surface of the electrode, and the conductivity of the surface of the electrode is reduced. After the CAP molecules on the surface of the electrode are washed by methanol-acetic acid mixed liquor, hydrogen bonds between Ppy and CAP are broken and a specific imprinting cavity is formed, at the moment, a potassium ferricyanide probe can reach the surface of the electrode through the cavity, so that the conductivity is obviously improved and the CAP molecules can be specifically combined, the quantitative detection of the CAP is realized, meanwhile, the Ppy has conductivity and can be used for further enhancing the detection sensitivity in cooperation with Uio-66-CDs/GCE modified electrodes, and the minimum detection limit of chloramphenicol can reach 6.210^-14mol/L。

Although the present invention has been described with reference to a preferred embodiment, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.