CN107384367B

CN107384367B - Method for preparing melamine molecular imprinting fluorescence sensor MEL-MIP by using ZnO quantum dot/porous silicon fluorescent material

Info

Publication number: CN107384367B
Application number: CN201710465106.2A
Authority: CN
Inventors: 刘燕; 仇建; 胡肖; 倪良; 刘占超
Original assignee: Jiangsu University
Current assignee: Jiangsu University
Priority date: 2017-06-19
Filing date: 2017-06-19
Publication date: 2020-06-09
Anticipated expiration: 2037-06-19
Also published as: CN107384367A

Abstract

The invention belongs to the technical field of functional material preparation, and uses SiO₂The @ ZnO QDs is a fluorescent substrate material, and the porous silicon surface molecularly imprinted fluorescent sensor is synthesized by a free radical polymerization method. The invention utilizes the gel sol method to package ZnO QDs to porous SiO₂In the method, the stability problem of the quantum dots is solved, and the service life of the quantum dots is prolonged; also prepares porous SiO by adding pore-foaming agent₂The problem of excessively deep embedding of the quantum dots is solved, the specific surface area is increased, and the application range of the quantum dots is widened. The method is combined with the surface molecular imprinting technology, improves the identification capability and response speed of the fluorescent sensor to the substances to be detected, and lays a solid theoretical and practical foundation for rapid and selective identification and detection of trace melamine in the dairy products.

Description

Method for preparing melamine molecular imprinting fluorescence sensor MEL-MIP by using ZnO quantum dot/porous silicon fluorescent material

Technical Field

The invention belongs to the technical field of functional material preparation, and relates to a method for preparing a melamine molecular imprinting fluorescent sensor by using a ZnO quantum/porous silicon fluorescent material.

Background

Melamine is a chemical raw material and widely used in the industries of plastics, kitchenware, adhesives and the like. Melamine can cause serious health problems in children and adolescents such as kidney stones, renal failure, bladder cancer, and the like. It is therefore necessary to monitor the melamine content of the food product to prevent its illegal addition.

The traditional methods for detecting melamine comprise High Performance Liquid Chromatography (HPLC), gas-mass spectrometry (GC-MS), liquid-mass spectrometry (LC-MS), Capillary Electrophoresis (CE) and the like, and the detection methods are expensive in instruments and complex and complicated in operation, and limit the application of the detection methods in rapid detection. With the development of nanotechnology, a series of novel methods for detecting melamine in food have been developed. The Quantum Dots (QDs) have the characteristics of wide excitation spectrum, narrow emission spectrum, excellent optical stability and the like, and replace the traditional organic fluorescent dye for detecting pollutants. The QDs prepared by the method of doping metal elements generally have larger Stokes shift, but also cause the increase of surface defects thereof and reduce the fluorescence stability thereof. No heavy metal ion is used in the preparation process of ZnO QDs, the cost is low, and the preparation method is emptyGood stability in air, and the like, and becomes an ideal green fluorescence detection material. ZnOQDs are easy to grow up and agglomerate due to high surface energy; the Ostwald Ripening phenomenon is easy to generate so that the fluorescence emission peak disappears. In order to prevent agglomeration in the preparation and curing processes of ZnO QDs, organic surface modifiers are added in the traditional method, but the modifiers are easy to fall off in the using process, so that the using reliability of the modifiers is reduced. The silicon dioxide has the characteristics of good chemical stability, decomposition resistance, optical transparency and the like, so that the silicon dioxide becomes an ideal QDs (quantum dots) coating material. Coating QDs by a sol-gel method, and adding a template agent to prepare porous SiO₂The fluorescent material effectively improves the stability of the QDs, increases the specific surface area of the QDs and reduces the over-deep embedding of the QDs. In addition, SiO₂Because the surface is easy to be functionalized, the method lays a foundation for further application of QDs.

The melamine content in food is generally low and the environment of the substrate is complex, and a pre-enrichment treatment is required before the detection of the melamine content. Molecular imprinting techniques (MIPs) are a common separation and enrichment method for selective recognition of specific molecules. The MIPs have the characteristics of simple preparation, good stability, low cost, high selectivity and the like, and are widely used as solid-phase extraction adsorbents. The traditional molecular imprinting has the defects of deep imprinting site embedding, difficult elution, slow mass transfer rate and the like, and researchers develop a surface molecular imprinting technology for overcoming the defects. Porous SiO₂The surface of the material is easy to modify, the specific surface area is large, the mass transfer is fast, and the like, so the material is a good surface imprinting substrate. The fluorescent sensor capable of having fluorescent response capability to melamine is prepared by combining surface molecular imprinting selective recognition and quantum dot fluorescent detection technology, and can be applied to detection of melamine in dairy products.

Disclosure of Invention

The invention aims to overcome the defects of complex operation, low sensitivity, poor anti-interference capability and the like of the existing melamine detection, and provides a preparation method and application of a ZnO QDs/porous silicon surface molecular imprinting fluorescent sensor. Synthesizing a template molecule by adopting a free radical polymerization method and taking Melamine (MEL) as a molecularly imprinted polymer and taking Acrylic Acid (AA) as a functional unitBulk, zinc oxide quantum dots/porous Silicon (SiO)₂@ ZnO QDs) is used as a matrix material, Ethylene Glycol Dimethacrylate (EGDMA) is used as a cross-linking agent, Azobisisobutyronitrile (AIBN) is used as an initiator, and an ethanol/water mixed solution is used as a solvent to synthesize a surface molecular imprinting fluorescence sensor (MEL-MIP) with selective recognition characteristics on melamine, and the MEL-MIP is used for detecting the melamine in dairy products.

A preparation method of a ZnO quantum dot/porous silicon fluorescent material comprises the following steps:

(1) weighing zinc acetate dihydrate ZnAc₂·2H₂Adding O into the single-neck flask, adding ethanol for ultrasonic treatment, transferring the dispersed mixed solution into an oil bath pot, and refluxing to obtain a colorless transparent solution; wherein, in order to prevent the water vapor from entering, the top end of the reflux pipe should be added with calcium chloride (CaCl)₂) A drying tube;

(2) transferring the zinc acetate solution prepared in the step (1), adding lithium hydroxide, and ultrasonically shaking and stirring in an ice-water bath to prepare colorless and transparent ZnO quantum dot sol; adding gamma-mercaptopropyltrimethoxysilane KH-590 ethanol solution, stirring for modification, washing with n-hexane anti-solvent, adding ethanol for dissolution, repeating the above operations for several times, freeze-drying the finally obtained ZnO QDs, and grinding into powder for later use;

(3) dissolving P123 in ethanol, adding SiO₂Mixing hydrosol, stirring, weighing prepared quantum dots, dissolving in the above mixture, stirring, adding HCl to catalyze TEOS hydrolysis, dark reacting overnight, washing off surfactant with ethanol, centrifuging with centrifuge, vacuum drying, grinding, and finally N₂Burning in airflow to remove pore-forming agent P123 to form porous SiO₂@ ZnO QDs fluorescent materials.

In the step (1), the dosage ratio of the zinc acetate/ethanol solution is 1mmol:10 mL; the ultrasonic treatment time is 30 min; and (3) refluxing and dissolving the zinc acetate in the ethanol solution at the reflux temperature of 80-85 ℃ for 30-180 min.

In the step (2), the ratio of the zinc acetate to the lithium hydroxide to the KH-590 substance is 1: 1-3 mol: 5-10 mmol; the volume of n-hexane was 20 mL.

In the step (3), the P123, the ethanol and the SiO₂The dosage proportion of the hydrosol is 0.5-2 g: 30mL of: 5-20 mL, and the addition amount of ZnO QDs is 50-200 mg; the volume of the hydrochloric acid is 200 mu L; the centrifugation speed is 12000 rpm/min; n is a radical of₂The ignition temperature in the gas stream was 550 ℃.

In the step (3), the SiO₂In the hydrosol, the volume ratio of water to ethanol to TEOS is 2:1: 2.

The ZnO quantum dot/porous silicon fluorescent material prepared by the preparation method is provided.

The ZnO quantum dot/porous silicon fluorescent material prepared by the invention is used for preparing a molecular imprinting fluorescent sensor.

The ZnO quantum dot/porous silicon fluorescent material prepared by the invention is used for preparing a melamine molecular imprinting fluorescence sensor MEL-MIP.

The method for preparing the MEL-MIP of the melamine molecular imprinting fluorescence sensor by utilizing the ZnO quantum dot/porous silicon fluorescent material comprises the following steps:

in a three-neck flask, melamine MEL is weighed and added into an ethanol/water mixed solution, acrylic acid is added, and prepared SiO₂The method comprises the following steps of self-assembling the @ ZnO QDs matrix material, stirring overnight, transferring the mixed solution into a water bath kettle, adding ethylene glycol dimethacrylate EGDMA and azobisisobutyronitrile AIBN, starting polymerization under nitrogen atmosphere, finally washing with ethanol and water, carrying out vacuum drying and grinding, carrying out Soxhlet extraction washing with a methanol/acetic acid mixed solution, and carrying out vacuum drying to obtain the melamine surface molecularly imprinted fluorescence sensor MEL-MIP.

The melamine MEL, the acrylic acid and the SiO₂The dosage ratio of the @ ZnO QDs matrix material, the EGDMA and the AIBN is 0.5 mmol: 0.3-0.6 mL: 20-100 mg: 0.12 mL: 10 mg;

in the ethanol/water mixed solution, the volume ratio of ethanol to water is 1-4: 1;

the polymerization temperature is 55-65 ℃;

in the methanol/acetic acid mixed solution, the volume ratio of methanol to acetic acid is 4:1, the extraction time is 72h, and the process is repeated for 3 times.

The preparation method of the melamine surface non-imprinted fluorescence sensor (MEL-NIP) is the same as the preparation method of MEL-MIP, but the template molecule MEL is not added.

The invention has the technical advantages that:

with SiO₂The @ ZnO QDs is a fluorescent substrate material, and the porous silicon surface molecularly imprinted fluorescent sensor is synthesized by a free radical polymerization method. The invention utilizes the gel sol method to package ZnO QDs to porous SiO₂In the method, the stability problem of the quantum dots is solved, and the service life of the quantum dots is prolonged; also prepares porous SiO by adding pore-foaming agent₂The problem of excessively deep embedding of the quantum dots is solved, the specific surface area is increased, and the application range of the quantum dots is widened. The method is combined with the surface molecular imprinting technology, improves the identification capability and response speed of the fluorescent sensor to the substances to be detected, and lays a solid theoretical and practical foundation for rapid and selective identification and detection of trace melamine in the dairy products.

Drawings

FIG. 1 is SiO₂The IR spectra of @ ZnO QDs (a) and MEL-MIP (b).

FIG. 2 shows ZnO QDs (a) and SiO₂XRD patterns of @ ZnO QDs (b).

FIG. 3 is SiO₂Fluorescence spectrograms of @ ZnO QDs (a), MEL-NIP (b), and MEL-MIP (c).

Detailed Description

The invention is further described with reference to the drawings and the detailed description.

Example 1

(1) Silicon dioxide/zinc oxide quantum dot fluorescent material (SiO)₂@ ZnO QDs) synthesis

Accurately weighing 10mmol ZnAc₂·2H₂O is put into a 250mL single-neck flask, and 100mL ethanol is added for 30min of ultrasonic treatment. Transferring the dispersed mixed solution into an oil bath kettle, and refluxing at 82 ℃ for 45min to obtain a colorless transparent solution. Wherein, in order to prevent the water vapor from entering, CaCl should be added to the top end of the return pipe₂And (7) drying the tube. And (3) transferring 20mL of zinc acetate solution, adding 3mmol of LiOH, and ultrasonically shaking and stirring in an ice-water bath to obtain the colorless and transparent ZnO quantum dot sol. Adding 6mmol KH-590, stirring, and adding 20mL n-hexane as anti-solventWashing, adding ethanol for dissolving, and repeating the above steps for 3 times. The ZnO QDs are freeze-dried and ground into powder for later use.

0.6g P123 was dissolved in 30mL of ethanol, and 10mL of SiO was added₂The hydrosol (water: ethanol: TEOS ═ 2:1:2, v: v: v) was mixed and stirred for 2 h. And weighing 60mg of prepared quantum dots, dissolving the quantum dots into the mixed solution, and stirring for 6 hours. After stirring, 200 mul HCl is added to catalyze TEOS hydrolysis, dark reaction is carried out for 12h, the surfactant is washed away by ethanol, centrifugation is carried out at 12000rpm/min, and grinding is carried out after vacuum drying. Finally, 550 ℃ C.N₂Burning in airflow to remove pore-forming agent P123 to form porous SiO₂@ ZnO QDs fluorescent materials.

(2) Preparation of melamine fluorescence molecular imprinting sensor (MEL-MIP)

100mL three-necked flask, 0.5mmol MEL was weighed and put into 20mL ethanol/water (1:1, v: v) mixed solution, 0.4mL acrylic acid, 30mg prepared SiO₂The @ ZnO QDs matrix material was self-assembled and stirred overnight. The mixed solution was transferred to a water bath, 0.12mL of EGDMA and 10mg of AIBN were added, and polymerization was started under a nitrogen atmosphere at 56 ℃. And finally, washing the melamine surface molecularly imprinted fluorescence sensor (MEL-MIP) for 3 times by using ethanol and water, drying and grinding the melamine surface molecularly imprinted fluorescence sensor in vacuum, and performing Soxhlet extraction washing on the melamine surface molecularly imprinted fluorescence sensor by using a methanol/acetic acid (v: v, 4:1) mixed solution.

Example 2

Accurately weighing 10mmol ZnAc₂·2H₂O is put into a 250mL single-neck flask, and 100mL ethanol is added for 30min of ultrasonic treatment. Transferring the dispersed mixed solution into an oil bath kettle, and refluxing at 83 ℃ for 60min to obtain a colorless transparent solution. Wherein, in order to prevent the water vapor from entering, CaCl should be added to the top end of the return pipe₂And (7) drying the tube. And (3) transferring 20mL of zinc acetate solution, adding 4mmol of LiOH, and ultrasonically shaking and stirring in an ice-water bath to obtain the colorless and transparent ZnO quantum dot sol. Adding 7mmol KH-590, stirring and modifyingWashing with 20mL of n-hexane anti-solvent, adding ethanol for dissolving, and repeating the above operations for 3 times. The ZnO QDs are freeze-dried and ground into powder for later use.

1.0g P123 was dissolved in 30mL of ethanol, and 12mL of SiO was added₂The hydrosol (water: ethanol: TEOS ═ 2:1:2, v: v: v) was mixed and stirred for 2 h. And weighing 70mg of prepared quantum dots, dissolving the quantum dots into the mixed solution, and stirring for 6 hours. After stirring, 200 mul HCl is added to catalyze TEOS hydrolysis, dark reaction is carried out for 12h, the surfactant is washed away by ethanol, centrifugation is carried out at 12000rpm/min, and grinding is carried out after vacuum drying. Final 550 ℃ N₂Burning in airflow to remove pore-forming agent P123 to form porous SiO₂@ ZnO QDs fluorescent materials.

(2) Preparation of melamine fluorescence molecular imprinting sensor (MEL-MIP)

100mL three-necked flask, 0.5mmol MEL was weighed and put into 20mL ethanol/water (2:1, v: v) mixed solution, 0.5mL acrylic acid, 40mg prepared SiO₂The @ ZnO QDs matrix material was self-assembled and stirred overnight. The mixed solution was transferred to a water bath, 0.12mL of EGDMA and 10mg of AIBN were added, and polymerization was started under a nitrogen atmosphere at 58 ℃. And finally, washing the melamine surface molecularly imprinted fluorescence sensor (MEL-MIP) for 3 times by using ethanol and water, drying and grinding the melamine surface molecularly imprinted fluorescence sensor in vacuum, and performing Soxhlet extraction washing on the melamine surface molecularly imprinted fluorescence sensor by using a methanol/acetic acid (v: v, 4:1) mixed solution.

Example 3

Accurately weighing 10mmol ZnAc₂·2H₂O is put into a 250mL single-neck flask, and 100mL ethanol is added for 30min of ultrasonic treatment. Transferring the dispersed mixed solution into an oil bath pan, and refluxing at 85 ℃ for 90min to obtain a colorless transparent solution. Wherein, in order to prevent the water vapor from entering, CaCl should be added to the top end of the return pipe₂And (7) drying the tube. And (3) transferring 20mL of zinc acetate solution, adding 5mmol of LiOH, and ultrasonically shaking and stirring in an ice-water bath to obtain the colorless and transparent ZnO quantum dot sol. AddingAdding 8mmol KH-590, stirring, modifying, washing with 20mL n-hexane antisolvent, adding ethanol for dissolving, and repeating the above steps for 3 times. The ZnO QDs are freeze-dried and ground into powder for later use.

1.5g P123 was dissolved in 30mL of ethanol, and 15mL of SiO was added₂The hydrosol (water: ethanol: TEOS ═ 2:1:2, v: v: v) was mixed and stirred for 2 h. And weighing 80mg of prepared quantum dots, dissolving the quantum dots into the mixed solution, and stirring for 6 hours. After stirring, 200 mul HCl is added to catalyze TEOS hydrolysis, dark reaction is carried out for 12h, the surfactant is washed away by ethanol, centrifugation is carried out at 12000rpm/min, and grinding is carried out after vacuum drying. Final 550 ℃ N₂Burning in airflow to remove pore-forming agent P123 to form porous SiO₂@ ZnO QDs fluorescent materials.

(2) Preparation of melamine fluorescence molecular imprinting sensor (MEL-MIP)

100mL three-necked flask, 0.5mmol MEL was weighed and put into 20mL ethanol/water (3:1, v: v) mixed solution, 0.55mL acrylic acid, 50mg prepared SiO₂The @ ZnO QDs matrix material was self-assembled and stirred overnight. The mixed solution was transferred to a water bath, 0.12mL of EGDMA and 10mg of AIBN were added, and polymerization was started under a nitrogen atmosphere at 58 ℃. And finally, washing the melamine surface molecularly imprinted fluorescence sensor (MEL-MIP) for 3 times by using ethanol and water, drying and grinding the melamine surface molecularly imprinted fluorescence sensor in vacuum, and performing Soxhlet extraction washing on the melamine surface molecularly imprinted fluorescence sensor by using a methanol/acetic acid (v: v, 4:1) mixed solution.

The identification response and detection performance evaluation in the embodiment of the invention are carried out according to the following methods: weighing a certain amount of MEL-MIP/MEL-NIP to prepare an aqueous solution. Adding a series of target substance solutions with known concentrations into a colorimetric tube, adding MEL-MIP/MEL-NIP aqueous solution, fixing the volume to a scale mark, oscillating at room temperature, standing for 1h, and detecting the fluorescence intensity of the solution by using a molecular fluorescence photometer measuring system. According to Stern-Volmer equilibrium (F)₀/F＝1+K_sv[c]) In the concentration of [ c ]]As abscissa, relative fluorescence intensity (F)₀and/F) is the ordinate to plot the fluorescence response curve. Selecting several structures andmelamine-like substances, as comparative substances, were involved in the study of MEL-MIP/MEL-NIP selectivity.

In experiments of influence of pH on MEL-MIP fluorescence intensity, the prepared MEL-MIP has good stability. MEL-MIP/MEL-NIP was formulated as a 500mg/L aqueous solution and the target was formulated as a 1mmol/L aqueous solution. And adding 10mL of LMEL-MIP/MEL-NIP solution and a certain amount of melamine solution to be detected into a 25mL colorimetric tube, fixing the volume by using distilled water, oscillating at room temperature and standing for 1 h. The concentration of melamine in the colorimetric tube test solution is respectively 0, 10, 15, 20, 30 and 40 mu M/L, the influence of melamine with different concentrations on MEL-MIP/MEL-NIP fluorescence intensity is detected, the fluorescence intensity is weakened along with the increase of the concentration of the melamine, and then the fluorescence intensity of the solution is detected by a fluorescence spectrophotometer. According to Stern-Volmer equilibrium (F)₀/F＝1+K_sv[c]) In the concentration of [ c ]]As abscissa, relative fluorescence intensity (F)₀/F) is used as a longitudinal coordinate to draw a fluorescence response curve to obtain a correlation coefficient R²0.9979. MEL-MIP has a very good capacity for fluorescence detection of melamine.

Selecting three targets of cyanuric acid, dicyandiamide and melamine, respectively preparing 500 mu M/L aqueous solution of the substances, adding 10mL of prepared MEL-MIP aqueous solution and 1mL of aqueous solution of substances with similar structures into a colorimetric tube, fixing the volume to 25mL by using distilled water, oscillating at room temperature, standing for 1h, and detecting the fluorescence intensity of the solution by using a fluorescence spectrophotometer. The quenching of MEL-MIP by melamine is far more than that of other two structurally similar substances, which indicates that the MEL-MIP has the specific recognition capability on the target melamine. The results show that MEL-MIP prepared by the invention has sensitive fluorescence response capability to melamine.

FIG. 1 is SiO₂Infrared spectra of @ ZnO QDs and MEL-MIP. From the figure, SiO can be seen₂@ ZnO QDs at 2956cm^-1Has weak infrared absorption, which shows-CH₃and-CH₂The presence of-groups, proving that KH-590 is successfully modified in SiO₂The surface of @ ZnO QDs; at 1060cm^-1The presence of an absorption peak indicates the presence of a Si-O group. MEL-MIP infrared spectrum at 1456cm^-1The appearance of an absorption peak indicates that O ═A C-O group; 2956cm^-1The absorption peaks at the left and right parts are obviously enhanced, which shows that-CH₃and-CH₂-an increase in groups; 1718cm^-1The absorption peak indicates the presence of a C ═ O group; these absorption peaks indicate successful imprinting of acrylic acid on SiO₂@ ZnO QDs surface.

FIG. 2 shows ZnO QDs and SiO₂XRD patterns of @ ZnO QDs. The XRD curve of the ZnO QDs has 7 diffraction peaks which are respectively positioned at 31.7, 34.5, 36.5, 47.7, 56.5, 63.0 and 67.9, and the diffraction crystal faces of the ZnO on the JCPDS card corresponding to (100), (002), (101), (102), (110), (103) and (112) are consistent, so that the prepared ZnO QDs are considered to still have a perfect hexagonal wurtzite structure after being modified by KH-590. Adding SiO₂No obvious ZnO QDs diffraction peak appears after coating ZnO QDs, which is caused by SiO₂The coating layer (B) is thicker and covers the diffraction peak of ZnO QDs, so that SiO₂The XRD pattern of @ ZnO QDs shows only porous SiO₂Diffraction peaks of the cladding layer.

FIG. 3 is SiO₂Fluorescence spectrograms for @ ZnO QDs, MEL-NIP and MEL-MIP SiO when excited at 320nm₂The fluorescence emission peak of @ ZnO QDs is at 510 nm; after the surface is covered with the imprinting layer, MEL-MIP and MEL-NIP are red-shifted due to the size increase, and the emission peak is at 528 nm. Although the fluorescence emission peak is weakened due to the coating of the imprinting layer, the imprinting layer still has good fluorescence performance.

Claims

1. The method for preparing the melamine molecular imprinting fluorescence sensor MEL-MIP by using the ZnO quantum dot/porous silicon fluorescent material is characterized by comprising the following steps of:

(1) weighing zinc acetate dihydrate ZnAc₂·2H₂Adding O into the single-neck flask, adding ethanol for ultrasonic treatment, transferring the dispersed mixed solution into an oil bath pot, and refluxing to obtain a colorless transparent solution; wherein, in order to prevent the water vapor from entering, a calcium chloride drying tube is added at the top end of the return tube; the dosage ratio of the zinc acetate dihydrate to the ethanol solution is 1mmol:10 mL; the ultrasonic treatment time is 30 min; refluxing and dissolving zinc acetate dihydrate in an ethanol solution at the reflux temperature of 80-85 ℃ for 30-180 min;

(2) transferring the zinc acetate solution prepared in the step (1), adding lithium hydroxide, and ultrasonically shaking and stirring in an ice-water bath to prepare colorless and transparent ZnO quantum dot sol; adding gamma-mercaptopropyltrimethoxysilane KH-590 ethanol solution, stirring for modification, washing with n-hexane anti-solvent, adding ethanol for dissolution, repeating the above operations for several times, freeze-drying the finally obtained ZnO QDs, and grinding into powder for later use; the ratio of the zinc acetate to the lithium hydroxide to the KH-590 substance is 1: 1-3 mol: 5-10 mmol; the volume of n-hexane is 20 mL;

(3) dissolving P123 in ethanol, adding SiO₂Mixing hydrosol, stirring, weighing prepared quantum dots, dissolving in the above mixture, stirring, adding HCl to catalyze TEOS hydrolysis, dark reacting overnight, washing off surfactant with ethanol, centrifuging with centrifuge, vacuum drying, grinding, and finally N₂Burning in airflow to remove pore-forming agent P123 to form porous SiO₂@ ZnO QDs fluorescent materials;

the P123, the ethanol and the SiO₂The dosage proportion of the hydrosol is 0.5-2 g: 30mL of: 5-20 mL, and the addition amount of ZnO QDs is 50-200 mg; the volume of the hydrochloric acid is 200 mu L; the centrifugation speed is 12000 rpm/min; n is a radical of₂The ignition temperature in the air flow is 550 ℃;

the SiO₂In the hydrosol, the volume ratio of water to ethanol to TEOS is 2:1: 2;

(4) in a three-neck flask, melamine MEL is weighed and added into an ethanol/water mixed solution, acrylic acid is added, and prepared SiO₂The method comprises the following steps of self-assembling the @ ZnO QDs matrix material, stirring overnight, transferring the mixed solution into a water bath kettle, adding ethylene glycol dimethacrylate EGDMA and azobisisobutyronitrile AIBN, starting polymerization under nitrogen atmosphere, finally washing with ethanol and water, carrying out vacuum drying and grinding, carrying out Soxhlet extraction washing with a methanol/acetic acid mixed solution, and carrying out vacuum drying to obtain the melamine surface molecularly imprinted fluorescence sensor MEL-MIP.

2. The method according to claim 1, wherein in the step (4), the melamine MEL, acrylic acid, SiO₂The dosage ratio of the @ ZnO QDs matrix material, the EGDMA and the AIBN is 0.5 mmol: 0.3-0.6 mL: 20-100 mg: 0.12 mL: 10 mg;

the polymerization temperature is 55-65 ℃;