Molecularly imprinted electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline as well as preparation method and application of molecularly imprinted electrochemical-photoelectrochemical dual-mode sensor

Abstract

The invention provides a molecularly imprinted electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline as well as a preparation method and application of the molecularly imprinted electrochemical-photoelectrochemical dual-mode sensor, and relates to the technical field of detection. According to the molecularly imprinted electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline, provided by the invention, the tetracycline is accurately detected by utilizing a quenching effect of a steric hindrance effect caused by specific binding of tetracycline and an imprinted cavity on electrochemical and photoelectric signals, and the molecularly imprinted electrochemical-photoelectrochemical dual-mode sensor has the advantages of wide detection range, high sensitivity and high accuracy. Wherein the electrochemical detection linear range is 5.010 <-14 > to 1.010 <-9 > mol / L, and the detection limit is 2.110 to 14 mol / L; the linear range of photoelectrochemical detection is 5.010 <-12 >-5.010 <-6 > mol / L, the detection limit is 2.710 <-13 > mol / L, and the method is successfully used for detecting the content of tetracycline in water around livestock and poultry farms and has good analysis performance.

Description

Technical Field

[0001] The invention relates to the field of detection technology, and in particular to a molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline, and a preparation method and application thereof. Background Art

[0002] Tetracycline (TC) is a typical tetracycline antibiotic. Due to its broad spectrum and low price, it is widely used as a veterinary drug and growth promoter in livestock and poultry farming. However, more than 75% of unabsorbed TC is directly discharged into the environment in the form of urine and feces, which accumulates continuously and causes serious pollution. In recent years, high concentrations of TC have been detected in surface water and groundwater in many places, posing a serious threat to the ecological environment and human health. Therefore, it is very necessary to develop accurate and sensitive detection methods for TC.

[0003] Various high-sensing nanomaterials and signal amplification strategies have been introduced into sensors to meet the requirements of high-sensitivity detection of TC, but a single detection mode often leads to result deviation. Therefore, in order to meet the requirements of detection sensitivity, it is an inevitable trend in biological tissue research and genetic testing to develop a multi-mode joint method to output multiple signals through mutual verification of multiple sets of data, eliminate abnormal diagnostic results of a single mode, and ensure the accuracy of detection. Summary of the invention

[0004] In order to solve the problem of insufficient reliability and sensitivity of most detection methods in the prior art, the present invention discloses a molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline, and a preparation method and application thereof. The dual-mode combination of molecular imprinting electrochemistry and photoelectrochemistry realizes the complementary advantages and mutual synergy of the two modes, avoids the diagnostic abnormality of a single mode, obtains more and richer detection information, and outputs more accurate, complete and reliable detection results.

[0005] The technical solution adopted by the present invention to solve its technical problem is: A method for preparing a molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline comprises the following steps: S11: adding molecular imprinting polymer solution to the surface of CDs / COFs / MB electrode, and then curing the solution under thermal polymerization conditions to form a molecular imprinting film; S12: Methanol and acetic acid are mixed in a specific ratio to obtain an eluent, the electrode interface is immersed in the eluent to elute the TC template molecules, and a sensor is obtained after drying, which is marked as CDs / COFs / MB / MIP.

[0006] Optionally, in step S11, the amount of the molecular imprinting polymer solution added is 10-15 μL; the thermal polymerization temperature is 60-65° C.; and the polymerization time is 3-5 min.

[0007] Optionally, the volume ratio of methanol to acetic acid in the eluent in step S12 is 7-9:1; and the elution time is 15-20 min.

[0008] Optionally, the molecular imprinting polymer solution is prepared as follows: tetracycline, methacrylic acid (MAA), azobisisobutyronitrile (AIBN) and ethylene glycol dimethacrylate (EGDMA) are dissolved in methanol, an inert gas is introduced to obtain the molecular imprinting polymer solution, and the solution is stored in the dark.

[0009] Optionally, the usage ratio of methanol, tetracycline, methacrylic acid (MAA), azobisisobutyronitrile (AIBN) and ethylene glycol dimethacrylate (EGDMA) is 2~5 mL: 25~27 mg: 340~345 μL: 80~83 mg: 290~295 μL.

[0010] Optionally, the CDs / COFs / MB electrode is prepared according to the following method: S21: Boil the ITO electrode in 1 M NaOH solution for 20-30 min, clean it with ultrasonic and then dry it for later use; S22: Dissolve ethylenediamine and citric acid in water, transfer to a high-pressure reactor after fully dissolving; react at 200-220°C for 5-6 h, cool to room temperature and filter to obtain a yellow CDs solution; S23: ethanol, trimethylbenzene and acetic acid are mixed in proportion and used as solvents to dissolve the ligand 2,6-dialdehyde-1,5-dihydroxynaphthalene and tris-4 (aminophenyl) amine respectively to obtain a 2,6-dialdehyde-1,5-dihydroxynaphthalene solution and a tris-4 (aminophenyl) amine solution; S24: dispersing the CDs solution in ethanol to obtain an ethanol dispersion of carbon dots, premixing the dispersion with a tris-4(aminophenyl)amine solution, and then adding a 2,6-dialdehyde-1,5-dihydroxynaphthalene solution to obtain a mixed solution; S25: taking a certain volume of the mixed solution to quickly modify the surface of the ITO electrode, sealing and storing it at a specific temperature and humidity, and then immersing the electrode in a dichloromethane solution to obtain a CDs / COFs electrode; S26: Dissolve methylene blue (MB) in a mixed solvent of ethanol and water to obtain a MB solution; take a certain volume of the MB solution and drop it on the surface of the CDs / COFs electrode prepared above, and obtain a CDs / COFs / MB electrode after drying.

[0011] Optionally, the dosage ratio of citric acid, ethylenediamine and water in step S22 is: (0.35 g~0.42 g):(0.5~0.6):(10~15) mL; the volume ratio of ethanol, trimethylbenzene and acetic acid in step S23 is (5~6):(5~6):1; the concentration of ligand 2,6-dialdehyde-1,5-dihydroxynaphthalene and tri-4(aminophenyl)amine is 1~2 mg / mL.

[0012] Optionally, the concentration of the carbon dot ethanol dispersion in step S24 is 0.5-1 mg / mL; the concentration of the MB solution in step S26 is 80-100 μg / mL.

[0013] Another object of the present invention is to provide a method for preparing the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline as described above, and the prepared sensor.

[0014] Another object of the present invention is to provide an application of the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline as described above, wherein the detection method comprises the following steps: S31: The preparation concentration range is 5.0 × 10 -6 ~5.0 × 10 -14 mol / L TC solution; S32: soaking the prepared sensor in the above solution and incubating for 20-30 min, and drying naturally to obtain a modified electrode; S33: Electrochemical and photoelectrochemical signal testing: Ⅰ Electrochemical signal test: The modified electrode was used as the working electrode, the saturated Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode. The EC signal was recorded by CHI 750E in 0.1 mol / L PBS (pH=7.0). The linear relationship between the EC signal and the logarithmic value of TC concentration (lg C) was obtained, and a standard curve was drawn. Ⅱ Photoelectric signal test: The modified electrode was used as the working electrode, the saturated Ag / AgCl electrode was used as the reference electrode, the platinum wire electrode was used as the counter electrode, and the light source was BBZM-Ⅲ (350 W). The PEC signal was recorded by CHI 750E in 0.1 mol / L PBS (pH=7.0). The linear relationship between the PEC signal and the logarithmic value of TC concentration (lg C) was obtained, and a standard curve was drawn; S34: Sample detection: According to the change values ​​of the EC signal and the PEC signal, the concentration of TC in the sample is calculated with reference to the standard curve in step S33.

[0015] The present invention has the following beneficial effects: (1) The present invention prepares CDs / COFs electrodes by an in-situ growth method at room temperature, which has improved electrochemical and photoelectric properties compared to the electrodes with COFs modified alone. MB is introduced as an electrochemical probe to form a stable modification layer at the electrode interface, which not only retains the original two-dimensional structure of CDs / COFs but also effectively provides electrochemical signals. On this basis, the molecular imprinting technology (MIP), known as "artificial antibody", is further combined to make the constructed dual-signal sensor have more accurate detection results and can realize sensitive detection of TC in actual samples. (2) The present invention combines molecular imprinting technology with electrochemical and photoelectrochemical analysis methods. On the one hand, the selectivity of the sensor is improved. On the other hand, the formation of the film protects the electrode interface, making the generated electrical and photoelectric signals more stable. (3) The present invention adopts a thermal polymerization method to prepare molecular imprinting film, which can realize the in-situ rapid synthesis of the recognition element MIP, and the polymerization time is short, only 3 minutes; the sensor is simple to construct and has a fast signal response; (4) In the detection process of the present invention, no external bias voltage is applied, and no redox substances are added to the PBS solution, thereby avoiding the interference of multiple factors on the electrical signal and the photoelectric signal; (5) The molecular imprinting electrochemical-photoelectrochemical dual-mode sensor constructed in the present invention is used for the detection of TC, and has high sensitivity, good stability, high accuracy, and a wide linear range. The linear range of electrochemical detection is 5.0 × 10 -14 ~1.0 × 10 -9 mol / L, the detection limit was 2.1 × 10 -14 mol / L; the linear range of photoelectrochemical detection is 5.0 × 10 -12 ~ 5.0 × 10 -6 mol / L, the detection limit was 2.7 × 10 -13 mol / L; (6) The molecular imprinting electrochemical-photoelectrochemical dual-mode sensor constructed in the present invention can be used for actual sample detection and verified using the national standard method. In addition, the design ideas proposed in the present invention can be used to develop sensing methods for detecting other targets, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the construction and detection process of the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor of the present invention; Figure 2(A) Transmission electron microscopy (TEM) of CDs; (B) High-resolution transmission electron microscopy (HRTEM) image of CDs / COFs; (C) High-resolution transmission electron microscopy (HRTEM) image of CDs / COFs and lattice spacing; Figure 3 (A) Surface and (B) cross-sectional scanning electron microscopy images (SEM) of CDs / COFs modified on ITO; (C) Surface and (D) cross-sectional scanning electron microscopy images (SEM) of CDs / COFs / MB modified on ITO; (E) Surface and (F) cross-sectional scanning electron microscopy images (SEM) of CDs / COFs / MB / MIP modified on ITO; (G) Surface and (H) cross-sectional scanning electron microscopy images (SEM) of CDs / COFs / MB / MIP modified on ITO after elution of template molecules; Figure 4 The electron transfer mechanism diagram between COFs and carbon dots under photoexcitation (A), the signal comparison diagram of COFs and CDs / COFs; Figure 5 Comparison of photoelectric signals generated by electrodes constructed by drop coating and in-situ growth under light excitation; Figure 6 Comparison of electrochemical signal (A) and photoelectric signal (B) before and after adding MB; Figure 7 (A) EC response corresponding to different TC concentrations; (B) Linear relationship between the logarithm of different TC concentrations and its EC response change value; Figure 8 (A) PEC response corresponding to different TC concentrations; (B) Linear relationship between the logarithm of different TC concentrations and their PEC response change values; Fig. 9 The selectivity and anti-interference of the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor in the present invention, where the TC concentration is 1 × 10 -11 mol / L, the concentration of the interfering substance was 1 × 10 -10 mol / L; Fig.10 The reproducibility and long-term stability of the molecular imprinted electrochemical-photoelectrochemical dual-mode sensor in the present invention, where the TC concentration is 1 × 10 -11 mol / L. DETAILED DESCRIPTION

[0017] The present invention is now further described in detail. The embodiments described below are exemplary and intended to be used to explain the present invention, but cannot be understood as limiting the present invention. All other embodiments obtained by ordinary technicians in this field without creative work based on the embodiments of the present invention belong to the scope of protection of the present invention.

[0018] The key to sensor analysis performance lies in sensitivity and accuracy; at the same time, how to avoid interference caused by complex components in the environment and achieve selective and specific response to the target TC is also the key to complete detection. Compared with traditional detection methods such as high performance liquid chromatography-mass spectrometry, capillary electrophoresis, spectrophotometry, etc., electrochemical (EC) and photoelectrochemical (PEC) detection methods have the advantages of high sensitivity, high economic benefits, simple operation, and easy miniaturization, making them more promising in practical applications.

[0019] Covalent organic frameworks (COFs), as a new type of crystalline organic semiconductor material, have received increasing attention in the field of PEC sensors. Two-dimensional COFs have covalent bonding and a planar ordered columnar π-conjugated structure, which ensures their high chemical stability and remarkable photoelectric properties. At the same time, the cathodic PEC activity of COFs can effectively avoid photocorrosion and coexistence interference, and is suitable for building high-performance PEC sensors. Molecular imprinting technology is a new technology for creating artificial recognition sites in synthetic polymers. The molecular imprinted polymers (MIPs) synthesized by this technology can be combined with target molecules through covalent bonds, semi-covalent bonds, and non-covalent bonds, and have the ability to specifically recognize and selectively adsorb target molecules. They have the advantages of low preparation cost, good stability, and repeatability.

[0020] Based on this, in order to solve the problem of insufficient reliability and sensitivity of most detection methods in the prior art, the present invention provides a method for preparing a molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline, comprising the following steps: S11: dripping 10-15 μL of molecular imprinting polymerization liquid on the surface of CDs / COFs / MB electrode, and then curing at a thermal polymerization temperature of 60-65°C to form a molecular imprinting film, and the polymerization time is 3-5 min; S12: Methanol and acetic acid are mixed in a volume ratio of 7 to 9:1 to obtain an eluent, and the electrode interface is immersed in the eluent to elute the TC template molecules. The elution time is 15 to 20 min. After drying, a sensor is obtained, which is marked as CDs / COFs / MB / MIP.

[0021] Furthermore, preferably, in step S11, the amount of the molecular imprinting polymerization solution added is 10 μL; the thermal polymerization temperature is 60° C.; the polymerization time is 3 min; By eluting the target molecules on the molecular imprinting film, recognition sites that can specifically bind to the target are formed; further, the volume ratio of methanol to acetic acid in the mixed solution in step S12 is preferably 9:1; preferably, the elution is accompanied by stirring at 150 rpm to achieve a better removal effect; the elution time is preferably 15 min; after the elution is completed, it is dried in the dark at room temperature for further detection.

[0022] The preferred molecular imprinting polymerization solution of the present invention is prepared according to the following method: 25-27 mg of the detection target tetracycline, 340-345 μL of the functional monomer methacrylic acid (MAA), 80-83 mg of the initiator azobisisobutyronitrile (AIBN) and 290-295 μL of the cross-linking agent ethylene glycol dimethacrylate (EGDMA) are dissolved in 2-5 mL of methanol, N2 is introduced for a period of time, and the dissolved oxygen in the solution is removed to obtain the molecular imprinting polymerization solution, which is then stored in the dark.

[0023] Furthermore, the preferred usage ratio of methanol, tetracycline, methacrylic acid (MAA), azobisisobutyronitrile (AIBN) and ethylene glycol dimethacrylate (EGDMA) is 2 mL:26.7 mg:340 μL:82.1 mg:291 μL.

[0024] The CDs / COFs / MB electrode of the present invention uses citric acid (CA) and ethylenediamine (EDA) as the synthesis raw materials of carbon dots, uses 2,6-dialdehyde-1,5-dihydroxynaphthalene and tri-4 (aminophenyl) amine as the synthesis precursors of COFs, combines the carbon dots with amino groups with COFs monomers through aldehyde-amine condensation, and then modifies the MB solution layer by layer, specifically comprising the following steps: S21: Boil an ITO electrode with a size of 2 × 1 cm in 1 M NaOH solution for 20-30 min, then ultrasonically clean it in ethanol and water in turn, and dry it for later use; S22: Dissolve 0.5-0.6 mL of ethylenediamine and 0.35-0.42 g of citric acid in 10-15 mL of water, transfer to a high-pressure reactor after fully dissolving; react at 200-220°C for 5-6 h, cool to room temperature, and filter using a 0.22 μm aqueous filter membrane to obtain a yellow CDs solution; Furthermore, the preferred ratio of citric acid, ethylenediamine and water is 0.42 g:0.536 mL:10 mL; the preferred temperature is 200°C and the reaction time is 5 h; S23: ethanol, trimethylbenzene, and acetic acid are mixed in a volume ratio of (5-6):(5-6):1 and used as a solvent to dissolve the ligand 2,6-dialdehyde-1,5-dihydroxynaphthalene and tris-4 (aminophenyl)amine, respectively, to obtain a 2,6-dialdehyde-1,5-dihydroxynaphthalene solution and a tris-4 (aminophenyl)amine solution with a concentration of 1-2 mg / mL; Furthermore, the volume ratio of ethanol, trimethylbenzene and acetic acid is preferably 5:5:1; the concentrations of the ligands 2,6-dialdehyde-1,5-dihydroxynaphthalene and tris-4 (aminophenyl)amine are both 1 mg / mL; S24: dispersing the CDs solution in ethanol to obtain an ethanol dispersion of carbon dots with a concentration of 0.5-1 mg / mL, premixing with a tris-4(aminophenyl)amine solution, and then adding a 2,6-dialdehyde-1,5-dihydroxynaphthalene solution to obtain a mixed solution; Furthermore, the concentration of the carbon dot ethanol dispersion is preferably 0.5 mg / mL; the amount ratio of the carbon dot ethanol dispersion, tri-4 (aminophenyl) amine solution and 2,6-dialdehyde-1,5-dihydroxynaphthalene solution in the mixed solution is 1:3:3; S25: Take 10~20 μL of the mixed solution to modify the surface of the ITO electrode treated by the plasma cleaner, seal and store at a specific temperature and humidity, and then immerse the electrode in a dichloromethane solution to obtain a CDs / COFs electrode; Furthermore, the present invention preferably uses a plasma cleaner for 10 s of treatment time, preferably a modified area of ​​1×1 cm, and preferably seals and stores for 10 min at a humidity of about 55% to wait for the two ligands to form COFs through aldehyde amine condensation; preferably, the immersion time in the dichloromethane solution is 5 min to remove unreacted ligands; S26: dissolving methylene blue (MB) in a mixed solvent of ethanol and water in a volume ratio of 1:1 to obtain a MB solution with a concentration of 80-100 μg / mL; applying 20-40 μL of the MB solution dropwise on the surface of the CDs / COFs electrode prepared above, and obtaining a CDs / COFs / MB electrode after drying; Furthermore, in the present invention, the concentration of the MB solution is preferably 100 μg / mL, and the modified volume of the MB solution is 20 μL.

[0025] Another object of the present invention is to provide a method for preparing the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline as described above, and the prepared sensor.

[0026] Another object of the present invention is to provide an application of the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline as described above, wherein the detection method comprises the following steps: S31: Prepare a TC solution of a certain concentration and then dilute it step by step to 5.0 × 10 -14 , 1 × 10 -13 , 5.0× 10 -13 , 1.0 × 10 -12 , 5.0 × 10 -12 , 1.0 × 10 -11 , 5.0 × 10 -11 , 1.0 × 10 -10 , 5.0 × 10 -10 , 1.0 × 10 -9 , 5.0 × 10 -9 , 1.0 × 10 -8 , 5.0 × 10 -8 , 1.0 × 10 -7 , 5.0 × 10 -7 , 1.0× 10 -6 , 5.0 × 10 -6 mol / L TC solution; S32: soaking the prepared sensor in the above solution and incubating for 20-30 min, and drying naturally to obtain a modified electrode; Furthermore, the preferred incubation time of the present invention is 20 min; S33: Electrochemical and photoelectrochemical signal testing: Ⅰ Electrochemical signal test: The modified electrode was used as the working electrode, the saturated Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode. The EC signal was recorded by CHI 750E in 0.1 mol / L PBS (pH=7.0). The linear relationship between the EC signal and the logarithmic value of TC concentration (lg C) was obtained, and a standard curve was drawn. Ⅱ Photoelectric signal test: The modified electrode was used as the working electrode, the saturated Ag / AgCl electrode was used as the reference electrode, the platinum wire electrode was used as the counter electrode, and the light source was BBZM-Ⅲ (350 W). The PEC signal was recorded by CHI 750E in 0.1 mol / L PBS (pH=7.0). The linear relationship between the PEC signal and the logarithmic value of TC concentration (lg C) was obtained, and a standard curve was drawn; S34: Sample detection: Calculate the concentration of TC in the sample according to the change values ​​of the EC signal and the PEC signal and refer to the standard curve in step S33; In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below.

[0027] Example 1: Preparation of COFs electrode by in-situ growth method The CDs / COFs / MB electrode was replaced with a COFs electrode. The preparation method of the COFs electrode was as follows: The ITO electrode with a size of 2 × 1 cm was boiled in 1 M NaOH solution for 20 min, then ultrasonically cleaned in ethanol and water in turn, and dried for later use; Ethanol, trimethylbenzene and acetic acid were mixed in a volume ratio of 5:5:1 as a solvent to dissolve the ligand 2,6-dialdehyde-1,5-dihydroxynaphthalene and tris-4 (aminophenyl) amine respectively to obtain a 2,6-dialdehyde-1,5-dihydroxynaphthalene solution and a tris-4 (aminophenyl) amine solution with a concentration of 1 mg / mL; 30 μL of tris-4(aminophenyl)amine solution was mixed with 30 μL of 2,6-dialdehyde-1,5-dihydroxynaphthalene solution to obtain a mixed solution; 13 μL of the mixed solution was taken to modify the surface of the ITO electrode treated by a plasma cleaner, and the electrode was sealed and stored at a humidity of about 55% for 10 min. The electrode was then immersed in a dichloromethane solution for 5 min to obtain a COFs electrode.

[0028] Example 2: Preparation of CDs / COFs Electrode by In-situ Growth Method The ITO electrode with a size of 2 × 1 cm was boiled in 1 M NaOH solution for 20 min, then ultrasonically cleaned in ethanol and water in turn, and dried for later use; Dissolve 0.536 mL of ethylenediamine and 0.42 g of citric acid in 10 mL of water, transfer to a high-pressure reactor after fully dissolving; heat to 200°C for 5 h, cool to room temperature, and filter using a 0.22 μm aqueous filter membrane to obtain a yellow CDs solution; Ethanol, trimethylbenzene and acetic acid were mixed in a volume ratio of 5:5:1 as a solvent to dissolve the ligand 2,6-dialdehyde-1,5-dihydroxynaphthalene and tris-4 (aminophenyl) amine respectively to obtain a 2,6-dialdehyde-1,5-dihydroxynaphthalene solution and a tris-4 (aminophenyl) amine solution with a concentration of 1 mg / mL; The CDs solution was dispersed in ethanol to obtain an ethanol dispersion of carbon dots with a concentration of 0.5 mg / mL, and then 10 μL of the ethanol dispersion of carbon dots was pre-mixed with 30 μL of tri-4(aminophenyl)amine solution, and then 30 μL of 2,6-dialdehyde-1,5-dihydroxynaphthalene solution was added to obtain a mixed solution; 13 μL of the mixed solution was taken to modify the surface of the ITO electrode treated by a plasma cleaner, and the electrode was sealed and stored at a humidity of about 55% for 10 min. The electrode was then immersed in a dichloromethane solution for 5 min to obtain a CDs / COFs electrode.

[0029] Example 3: Preparation of CDs / COFs electrodes by drop coating S21: Boil an ITO electrode with a size of 2 × 1 cm in 1 M NaOH solution for 20 min, then ultrasonically clean it in ethanol and water in turn, and dry it for later use; S22: Dissolve 0.536 mL of ethylenediamine and 0.42 g of citric acid in 10 mL of water, transfer to a high-pressure reactor after fully dissolving; heat to 200 °C for 5 h, cool to room temperature, and filter using a 0.22 μm aqueous filter membrane to obtain a yellow CDs solution; S23: ethanol, trimethylbenzene and acetic acid were mixed in a volume ratio of 5:5:1 as a solvent to dissolve the ligand 2,6-dialdehyde-1,5-dihydroxynaphthalene and tris-4 (aminophenyl) amine respectively to obtain a 2,6-dialdehyde-1,5-dihydroxynaphthalene solution and a tris-4 (aminophenyl) amine solution with a concentration of 1 mg / mL; S24: The CDs solution was dispersed in ethanol to obtain an ethanol dispersion of carbon dots with a concentration of 0.5 mg / mL, and then 10 μL of the ethanol dispersion of carbon dots was pre-mixed with 30 μL of tri-4(aminophenyl)amine solution, and then 30 μL of 2,6-dialdehyde-1,5-dihydroxynaphthalene solution was added to obtain a mixed solution; S25: The mixed solution was sealed and stored at a humidity of about 55% for 10 min. After centrifugation, a purple solid was obtained. The purple solid was immersed in a dichloromethane solution and shaken for 5 min. The solid was centrifuged and dried to obtain CDs / COFs. S26: CDs / COFs was prepared into an aqueous solution with a concentration of 2 mg / mL, 13 μL was taken to modify the surface of the ITO electrode treated by a plasma cleaner, and the CDs / COFs electrode was obtained after drying; S27: Methylene blue (MB) was dissolved in a mixed solvent of ethanol and water in a volume ratio of 1:1 to obtain a MB solution with a concentration of 100 μg / mL; 20 μL of the MB solution was drop-coated on the surface of the CDs / COFs electrode prepared above, and a CDs / COFs / MB electrode was obtained after drying.

[0030] Example 4: Preparation of CDs / COFs / MB electrode by in-situ growth method S21: Boil an ITO electrode with a size of 2 × 1 cm in 1 M NaOH solution for 20 min, then ultrasonically clean it in ethanol and water in turn, and dry it for later use; S22: Dissolve 0.536 mL of ethylenediamine and 0.42 g of citric acid in 10 mL of water, transfer to a high-pressure reactor after fully dissolving; heat to 200 °C for 5 h, cool to room temperature, and filter using a 0.22 μm aqueous filter membrane to obtain a yellow CDs solution; S23: ethanol, trimethylbenzene and acetic acid were mixed in a volume ratio of 5:5:1 as a solvent to dissolve the ligand 2,6-dialdehyde-1,5-dihydroxynaphthalene and tris-4 (aminophenyl) amine respectively to obtain a 2,6-dialdehyde-1,5-dihydroxynaphthalene solution and a tris-4 (aminophenyl) amine solution with a concentration of 1 mg / mL; S24: The CDs solution was dispersed in ethanol to obtain an ethanol dispersion of carbon dots with a concentration of 0.5 mg / mL, and then 10 μL of the ethanol dispersion of carbon dots was pre-mixed with 30 μL of tri-4(aminophenyl)amine solution, and then 30 μL of 2,6-dialdehyde-1,5-dihydroxynaphthalene solution was added to obtain a mixed solution; S25: Take 13 μL of the mixed solution to modify the surface of the ITO electrode treated by the plasma cleaner, seal and store it at a humidity of about 55% for 10 min, and then soak the electrode in a dichloromethane solution for 5 min to obtain a CDs / COFs electrode; S26: Methylene blue (MB) was dissolved in a mixed solvent of ethanol and water in a volume ratio of 1:1 to obtain a MB solution with a concentration of 100 μg / mL; 20 μL of the MB solution was drop-coated on the surface of the CDs / COFs electrode prepared above, and a CDs / COFs / MB electrode was obtained after drying.

[0031] Example 5: Photoelectrochemical signal test 1 The COFs electrode and CDs / COFs electrode prepared in Example 1 and Example 2 were used as working electrodes, saturated Ag / AgCl electrode was used as reference electrode, platinum wire electrode was used as counter electrode, BBZM-Ⅲ type (350 W) light source was used, and PEC signal was recorded by CHI 750E in 0.1 mol / L PBS (pH=7.0). The test results are shown in FIG. Figure 4 As shown; Depend on Figure 4 A shows that due to the matching energy levels, CDs and COFs successfully construct a type II heterojunction. Under light excitation, the photogenerated electrons and holes generated by CDs and COFs are separated, and the photogenerated electrons on the COFs conduction band are transferred to the CDs conduction band; at the same time, the photogenerated holes in the CDs valence band are transferred to the COFs valence band with the transfer of electrons. Due to the synergistic effect of the heterojunction and the good interface energy level matching, the effective separation of photogenerated carriers is achieved. Figure 4 As shown in B, the cathode photocurrent signal of CDs / COFs is 1.6 times that of single COFs.

[0032] Example 6: Photoelectrochemical signal test 2 The CDs / COFs electrodes prepared in Examples 2 and 3 were used as working electrodes, saturated Ag / AgCl electrodes were used as reference electrodes, platinum wire electrodes were used as counter electrodes, and the light source was BBZM-III (350 W). The PEC signals were recorded using CHI 750E in 0.1 mol / L PBS (pH=7.0). The test results are shown in Figure 2. Figure 5 As shown; Depend on Figure 5 It can be seen that compared with the drop-coated electrodes, the electrodes that are rapidly grown in situ at room temperature can simultaneously complete material synthesis and electrode preparation, simplifying the sensor construction process. In addition, due to the closer bonding between the in situ grown materials and ITO, the transfer efficiency of photogenerated carriers is effectively improved, and the photoelectric signal is effectively amplified by 7.5 times.

[0033] Example 7: Electrochemical and photoelectric signal test 1 Ⅰ Electrochemical signal test: The electrodes prepared in the above-mentioned Examples 2 and 4 were used as working electrodes, saturated Ag / AgCl electrodes were used as reference electrodes, and platinum wire electrodes were used as counter electrodes. EC signals were recorded using CHI 750E in 0.1 mol / L PBS (pH=7.0). The test results are shown in FIG. Figure 6 As shown in A; II Photoelectric signal test: The electrodes prepared in the above Examples 2 and 4 were used as working electrodes, saturated Ag / AgCl electrodes were used as reference electrodes, platinum wire electrodes were used as counter electrodes, and the light source was BBZM-III (350 W). The PEC signals were recorded using CHI 750E in 0.1 mol / L PBS (pH=7.0). The test results are shown in Figure 2. Figure 6 As shown in B; Depend on Figure 6 It can be seen that since MB exhibits a highly reversible single electron transfer process in the solution, after introducing MB as an electrochemical probe, the sensor can effectively obtain electrochemical signals at -0.2 V, which can be mutually verified with the PEC signal, thereby improving the detection accuracy of the sensor.

[0034] Example 8: Construction of sensor S10: 26.7 mg of tetracycline, 340 μL of methacrylic acid (MAA), 82.1 mg of azobisisobutyronitrile (AIBN) and 291 μL of ethylene glycol dimethacrylate (EGDMA) were dissolved in 2 mL of methanol, and an inert gas was introduced to obtain the molecular imprinting polymerization solution, which was then stored in the dark. S11: 10 μL of molecular imprinting polymerization solution was added dropwise onto the surface of CDs / COFs / MB electrode, and then thermally polymerized at 60 °C for 3 min to form a molecular imprinting film; S12: Methanol and acetic acid were mixed in a volume ratio of 9:1 to obtain an eluent, the electrode interface was immersed in the eluent and stirred for 15 min, and a sensor was obtained after drying, which was marked as CDs / COFs / MB / MIP.

[0035] Example 9: Construction of standard curve S31: Take a certain amount of deionized water, prepare a TC solution of a certain concentration, and then dilute it step by step to 5.0× 10 -14 , 1 × 10 -13 , 5.0 × 10 -13 , 1.0 × 10 -12 , 5.0 × 10 -12 , 1.0 × 10 -11 , 5.0 × 10 -11 , 1.0 × 10 -10 , 5.0 × 10 -10 , 1.0 × 10 -9 , 5.0 × 10 -9 , 1.0 × 10 -8 , 5.0 × 10 -8 , 1.0× 10 -7 , 5.0 × 10 -7 , 1.0 × 10 -6 , 5.0 × 10 -6 mol / L TC solution; S32: soaking the prepared sensor in the above solution and incubating for 20 min, and drying naturally to obtain a modified electrode; S33: Electrochemical and photoelectrochemical signal test 2: Ⅰ Electrochemical signal test: The modified electrode was used as the working electrode, the saturated Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode. The EC signal was recorded by CHI 750E in 0.1 mol / L PBS (pH=7.0). The linear relationship between the EC signal and the logarithmic value of TC concentration (lg C) was obtained, and a standard curve was drawn. Ⅱ Photoelectric signal test: The modified electrode was used as the working electrode, the saturated Ag / AgCl electrode was used as the reference electrode, the platinum wire electrode was used as the counter electrode, and the light source was BBZM-Ⅲ (350 W). The PEC signal was recorded by CHI 750E in 0.1 mol / L PBS (pH=7.0). The linear relationship between the PEC signal and the logarithmic value of TC concentration (lg C) was obtained, and a standard curve was drawn; When the prepared sensor is not incubated in the above solution, the electrochemical signal response of the working electrode is measured and recorded as I 10, the photocurrent signal response is recorded as I 11 At this time, due to the presence of a large number of imprinted cavities on the membrane, the photogenerated electrons can be transferred to the electrolyte solution, so the electrochemical response and photocurrent response are large; after the prepared sensor is incubated and immersed in the above solution for 20 min, the electrochemical signal response measured at this time is recorded as I 20 , the photocurrent response is recorded as I 21 At this time, the target blocked the imprinting cavity on the molecular imprinting membrane, resulting in the obstruction of electron transfer, so both the electrochemical signal and the photocurrent signal decreased; In electrochemical detection mode, the linear range of the sensor is 5.0 × 10 -14 ~ 1.0 × 10 -9 mol / L, the detection limit was 2.1 × 10 -14 mol / L( Figure 7 In the photoelectrochemical detection mode, the linear range of the sensor is 5.0 × 10 -12 ~ 5.0 × 10 -6 mol / L, the detection limit was 2.7 × 10 -13 mol / L( Figure 8 ).

[0036] Example 10: The sensor of the present invention is used for TC detection S31: Select lake water samples around the farm, filter it with a 0.22 μm water filter membrane, and add 0 and 8×10 -11 , 6×10 -10 , 5×10 -9 mol / L tetracycline aqueous solution; S32: soaking the prepared sensor in the above solution and incubating for 20 min, and drying naturally to obtain a modified electrode; S33: Electrochemical and photoelectrochemical signal test 3: Ⅰ Electrochemical signal test: The modified electrode was used as the working electrode, the saturated Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode. The EC signal was recorded using CHI 750E in 0.1 mol / L PBS (pH=7.0). Ⅱ Photoelectric signal test: The modified electrode was used as the working electrode, the saturated Ag / AgCl electrode was used as the reference electrode, the platinum wire electrode was used as the counter electrode, the light source was BBZM-Ⅲ (350 W), and the PEC signal was recorded by CHI 750E in 0.1 mol / L PBS (pH=7.0); S34: Sample detection: According to the EC signal and the PEC signal value, the concentration of TC in the sample is calculated with reference to the standard curve in step S33 of Example 9.

[0037] Example 11: The samples were tested according to the national standard method LC-MS / MS, and the detected amount and recovery rate were recorded.

[0038] The test results of Example 10 and Example 11 are shown in Table 1: As shown in Table 1, the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor constructed in the present invention has better detection performance than the prior art, and can detect TC simply and quickly. The electrochemical detection recovery rate is between 97-106%, and the RSD is less than 2.81%. The photoelectrochemical detection recovery rate is between 97-104%, and the RSD is less than 1.95%, which is comparable to the national standard detection method.

[0039] In addition, in the detection of unknown TC concentration in water samples, such as Fig. 9 As shown, the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor constructed by the invention can avoid the interference of complex components in the actual sample and realize the selective detection of TC; and the sensor has good reproducibility and long-term stability ( Fig.10 ); in addition, the dual signals verify each other, and accurate detection of TC can be achieved within the linear range of the sensor; and the idea provided by the present invention can be used to develop sensing methods for detecting other targets, which has a good application prospect.

[0040] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing a molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline, characterized in that: The steps include: S11: adding molecular imprinting polymer solution to the surface of CDs / COFs / MB electrode, and then curing the solution under thermal polymerization conditions to form a molecular imprinting film; S12: Methanol and acetic acid are mixed in a specific ratio to obtain an eluent, the electrode interface is immersed in the eluent to elute the TC template molecules, and a sensor is obtained after drying, which is marked as CDs / COFs / MB / MIP.

2. The method for preparing the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline according to claim 1, characterized in that: In step S11, the amount of the molecular imprinting polymer solution added is 10-15 μL; the thermal polymerization temperature is 60-65° C.; and the polymerization time is 3-5 min.

3. The method for preparing the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline according to claim 1, characterized in that: The volume ratio of methanol to acetic acid in the eluent in step S12 is 7-9:1; and the elution time is 15-20 min.

4. The method for preparing the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline according to claim 2, characterized in that: The molecular imprinting polymerization solution is prepared according to the following method: tetracycline (TC), methacrylic acid (MAA), azobisisobutyronitrile (AIBN) and ethylene glycol dimethacrylate (EGDMA) are dissolved in methanol, an inert gas is introduced to obtain the molecular imprinting polymerization solution, and the solution is stored in the dark.

5. The method for preparing the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline according to claim 4, characterized in that: The dosage ratio of tetracycline, methacrylic acid (MAA), azobisisobutyronitrile (AIBN), ethylene glycol dimethacrylate (EGDMA) and methanol is 25-27 mg: 340-345 μL: 80-83 mg: 290-295 μL: 2-5 mL.

6. The method for preparing the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline according to claim 1, characterized in that: The CDs / COFs / MB electrode was prepared as follows: S21: Boil the ITO electrode in 1 M NaOH solution for 20-30 min, clean it with ultrasonic and then dry it for later use; S22: Dissolve ethylenediamine and citric acid in water, transfer to a high-pressure reactor after fully dissolving; react at 200-220°C for 5-6 h, cool to room temperature and filter to obtain a yellow CDs solution; S23: ethanol, trimethylbenzene and acetic acid are mixed in proportion and used as solvents to dissolve the ligand 2,6-dialdehyde-1,5-dihydroxynaphthalene and tris-4 (aminophenyl) amine respectively to obtain a 2,6-dialdehyde-1,5-dihydroxynaphthalene solution and a tris-4 (aminophenyl) amine solution; S24: dispersing the CDs solution in ethanol to obtain an ethanol dispersion of carbon dots, premixing the dispersion with a tris-4(aminophenyl)amine solution, and then adding a 2,6-dialdehyde-1,5-dihydroxynaphthalene solution to obtain a mixed solution; S25: taking a certain volume of the mixed solution to modify the surface of the ITO electrode, sealing and storing it at a specific temperature and humidity, and then immersing the electrode in a dichloromethane solution to obtain a CDs / COFs electrode; S26: Dissolve methylene blue (MB) in a mixed solvent of ethanol and water to obtain a MB solution; take a certain volume of the MB solution and drop it on the surface of the CDs / COFs electrode prepared above, and obtain a CDs / COFs / MB electrode after drying.

7. The method for preparing the molecularly imprinted electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline according to claim 6, characterized in that: The dosage ratio of citric acid, ethylenediamine and water in step S22 is: (0.35g~0.42 g):(0.5~0.6):(10~15) mL; the volume ratio of ethanol, trimethylbenzene and acetic acid in step S23 is (5~6):(5~6):1; the concentration of ligand 2,6-dialdehyde-1,5-dihydroxynaphthalene and tris-4(aminophenyl)amine is 1~2 mg / mL.

8. The method for preparing the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline according to claim 6, characterized in that: The concentration of the carbon dot ethanol dispersion in step S24 is 0.5-1 mg / mL; the concentration of the MB solution in step S26 is 80-100 μg / mL.

9. A method for preparing a molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline according to any one of claims 1 to 8, and the sensor prepared.

10. The use of the molecular imprinting electrochemical-photoelectrochemical dual-mode sensor for detecting tetracycline according to claim 9, characterized in that: The detection method comprises the following steps: S31: The preparation concentration range is 5.0 × 10 -6 ~5.0 × 10 -14 mol / L TC solution; S32: soaking the prepared sensor in the above solution and incubating for 20-30 min, and drying naturally to obtain a modified electrode; S33: Electrochemical and photoelectrochemical signal testing: Ⅰ Electrochemical signal test: The modified electrode was used as the working electrode, the saturated Ag / AgCl electrode was used as the reference electrode, and the platinum wire electrode was used as the counter electrode. The EC signal was recorded by CHI 750E in 0.1 mol / L PBS (pH=7.0). The linear relationship between the EC signal and the logarithmic value of TC concentration (lg C) was obtained, and a standard curve was drawn. Ⅱ Photoelectric signal test: The modified electrode was used as the working electrode, the saturated Ag / AgCl electrode was used as the reference electrode, the platinum wire electrode was used as the counter electrode, and the light source was BBZM-Ⅲ (350 W). The PEC signal was recorded by CHI750E in 0.1 mol / L PBS (pH=7.0). The linear relationship between the PEC signal and the logarithmic value of TC concentration (lg C) was obtained, and a standard curve was drawn; S34: Sample detection: According to the change values ​​of the EC signal and the PEC signal, the concentration of TC in the sample is calculated with reference to the standard curve in step S33.

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