A molecular imprinting ratio fluorescence sensor and a preparation method and application thereof

Abstract

The application discloses a molecular imprinting ratio fluorescent sensor and a preparation method and application thereof, and comprises the following steps: coating SiO2 on blue fluorescent carbon quantum dots CQDs to obtain CQD@SiO2; coating mesoporous silica on the surface of the CQD@SiO2 to obtain mesoporous silica nanoparticles; performing surface modification on the mesoporous silica nanoparticles to obtain double-bond modified mesoporous silica nanoparticles; uniformly mixing a template molecule, a functional monomer and an organic fluorescent monomer, adding the double-bond modified mesoporous silica carrier, a crosslinking agent and an initiator, initiating a polymerization reaction, and obtaining a mesoporous silica-based molecular imprinting fluorescent polymer; and removing the template molecule to obtain the molecular imprinting ratio fluorescent sensor; the molecular imprinting ratio fluorescent sensor is rich in recognition sites, the mass transfer rate of the template molecule is fast, efficient detection can be performed, the detection result is not affected by environmental factors, and the purpose of visual detection can be achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of molecular imprinting fluorescent sensors, and particularly relates to a molecular imprinting ratio fluorescent sensor and a preparation method and application thereof. BACKGROUND

[0002] Tetrabromobisphenol A as a persistent organic pollutant, has a serious impact on the health and safety of human and other aquatic organisms; at present, most of the traditional detection methods are based on chromatography and chromatography-mass spectrometry combined technology, for example: high performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (HPLC-MS); among them, high performance liquid chromatography (HPLC) and gas chromatography-mass spectrometry (GC-MS) are the most commonly used detection technologies, but the shortcomings of chromatographic detection are increasingly prominent, which not only needs complicated sample pretreatment, expensive instruments, but also requires professional operators; the fluorescent sensor is widely used in the detection of pollutants due to its inherent advantages of high sensitivity, low cost and simple operation, but the existing single fluorescent sensor has poor selectivity, the detection result is easily affected by environmental factors, and the purpose of visual detection cannot be achieved. SUMMARY

[0003] In view of the technical problems existing in the prior art, the application provides a molecular imprinting ratio fluorescent sensor and a preparation method and application thereof, so as to solve the technical problems that the selectivity of the single fluorescent sensor is poor in the traditional tetrabromobisphenol A detection process, the detection result is easily affected by environmental factors, and the purpose of visual detection cannot be achieved.

[0004] To achieve the above-mentioned purposes, the technical scheme adopted by the application is as follows:

[0005] The application provides a preparation method of a molecular imprinting ratio fluorescent sensor, comprising the following steps:

[0006] Step 1, SiO2 is coated on blue fluorescent carbon quantum dots CQDs to obtain CQD@SiO2;

[0007] Step 2, mesoporous silica is coated on the surface of the CQD@SiO2 by using an oil-water two-phase coating method to obtain mesoporous silica nanoparticles;

[0008] Step 3, the mesoporous silica nanoparticles are surface-modified to obtain double bond-modified mesoporous silica nanoparticles;

[0009] Step 4, a template molecule, a functional monomer and a pre-synthesized organic fluorescent monomer are uniformly mixed, then the double bond-modified mesoporous silica carrier, a crosslinking agent and an initiator are added, and a polymerization reaction is initiated to obtain a mesoporous silica-based molecular imprinting fluorescent polymer;

[0010] Step 5, removing the template molecules of the mesoporous silica-based molecularly imprinted fluorescent polymer to obtain the molecularly imprinted ratiometric fluorescent sensor.

[0011] Further, in step 1, the blue fluorescent carbon quantum dots CQDs are prepared by a hydrothermal method.

[0012] The process of preparing the blue fluorescent carbon quantum dots CQDs by the hydrothermal method is as follows:

[0013] The citric acid and the polyethyleneimine solution are dispersed in ultrapure water, mixed uniformly, and then subjected to a hydrothermal reaction to obtain a hydrothermal reaction product.

[0014] The hydrothermal reaction product is naturally cooled to room temperature, centrifuged to remove impurities, dialyzed, and freeze-dried to obtain the blue fluorescent carbon quantum dots CQDs.

[0015] Further, in step 1, the blue fluorescent carbon quantum dots CQDs are coated with SiO2 by a reverse microemulsion method to obtain CQD@SiO2.

[0016] The coating process is as follows:

[0017] Cyclohexane, n-hexanol, triton X-100, and ultrapure water are mixed to form a microemulsion by vigorous stirring.

[0018] Carbon quantum dot solution and PEI solution are added to the microemulsion and ultrasonically stirred to obtain a mixed solution.

[0019] Tetraethyl orthosilicate and ammonia are added to the mixed solution and reacted, after which acetone is added to break the emulsion, and the mixture is centrifuged, washed, and vacuum dried to obtain CQD@SiO2.

[0020] Further, in step 2, the surface of the CQD@SiO2 is coated with mesoporous silica by an oil-water two-phase coating method to obtain mesoporous silica nanoparticles, and the process is as follows:

[0021] The CQD@SiO2, ultrapure water, cetyltrimethylammonium chloride, and triethanolamine are mixed and dispersed uniformly, refluxed, and maintained for a predetermined period of time to obtain a mixed system A.

[0022] A mixed solution of cyclohexane and tetraethyl orthosilicate is added dropwise to the mixed system A, and after the dropwise addition is complete, the reaction is carried out in the dark to obtain a dark reaction product; the dark reaction product is washed with ethanol and water alternately, centrifuged, and vacuum dried to obtain a treated product.

[0023] The processed product is added into a solvent, and after refluxing for a preset time, the mesoporous silica nanoparticles are obtained by washing with ethanol, centrifugation and drying; wherein, during the refluxing process, the solvent is replaced once; and the solvent is a mixed solution containing ammonium nitrate and anhydrous ethanol.

[0024] Further, in step 3, the mesoporous silica nanoparticles are surface-modified to obtain the process of obtaining the double-bond-modified mesoporous silica nanoparticles, which is specifically as follows:

[0025] The mesoporous silica nanoparticles and KH570 are dispersed in anhydrous toluene, and ultrasonic stirring is performed to uniformly disperse them, and the reaction is performed under the condition of nitrogen protection; after the reaction is completed, the product is collected by centrifugation, and is washed with anhydrous ethanol, centrifuged and vacuum dried to obtain the double-bond-modified mesoporous silica nanoparticles.

[0026] Further, the preparation process of the pre-synthesized organic fluorescent monomer is specifically as follows:

[0027] 4-bromo-1,8-naphthalic anhydride, allylamine hydrochloride and triethylamine are added into a three-necked flask containing anhydrous ethanol to obtain a reaction mixture;

[0028] The reaction mixture is refluxed at a temperature of 80°C for 8h under the protection of nitrogen; and then naturally cooled to room temperature, and the solvent is removed by rotary evaporation to obtain a crude product;

[0029] The crude product is purified by column chromatography to obtain N-allyl-1,8-naphthalimide in the form of white solid;

[0030] The white solid N-allyl-1,8-naphthalimide, ethylenediamine and ethylene glycol monomethyl ether are added into a three-necked flask, and the reaction is performed at a temperature of 110°C for 6-8h under the protection of nitrogen; after the reaction, the reaction system is naturally cooled to room temperature, and recrystallization is performed to obtain the pre-synthesized organic fluorescent monomer.

[0031] Further, in step 4, the template molecule, the functional monomer and the pre-synthesized fluorescent monomer are uniformly mixed, and then the double-bond-modified mesoporous silica carrier, the crosslinking agent and the initiator are added to initiate the polymerization reaction to obtain the process of obtaining the mesoporous silica-based molecularly imprinted fluorescent polymer, which is specifically as follows:

[0032] The template molecule, the functional monomer and the fluorescent monomer are dissolved in anhydrous toluene, and mechanical stirring is performed for 6h under the protection of nitrogen to obtain a mixed system B;

[0033] In the mixed system B, the double-bond-modified mesoporous silica carrier is added, and after ultrasonic dispersion, the crosslinking agent and the initiator are added, and the polymerization reaction is performed under the protection of nitrogen to obtain the mesoporous silica-based molecularly imprinted fluorescent polymer.

[0034] Further, the template molecule is tetrabromobisphenol A, the functional monomer is methacrylic acid, the crosslinking agent is ethylene glycol dimethacrylate, and the initiator is azobisisobutyronitrile.

[0035] The application further provides a molecular imprinting ratio fluorescent sensor prepared by the preparation method of the molecular imprinting ratio fluorescent sensor.

[0036] The application further provides an application of the molecular imprinting ratio fluorescent sensor, which is used for visual identification and detection of tetrabromobisphenol A in an environmental system.

[0037] Compared with the prior art, the application has the following beneficial effects:

[0038] The application provides a molecular imprinting ratio fluorescent sensor, a preparation method and an application thereof, wherein SiO2 is coated on blue fluorescent carbon quantum dots CQDs, so that the CQDs are protected by the silicon layer in CQD@SiO2, and contact with the outside world is avoided, so that a stable fluorescent reference signal can be provided; mesoporous silica nanoparticles are introduced, so that the recognition sites are more abundant, and the subsequent modification is simpler due to the presence of a large number of hydroxyl groups on the surface of the mesoporous silicon layer; due to the presence of the imprinting layer, specific recognition of the target to be detected is realized, combined with a fluorescent analysis method, analysis and determination of the target to be detected in the sample to be measured are realized, visual detection can be realized, and the detection result has high precision; in the application, the molecular imprinting ratio fluorescent sensor has abundant recognition sites, the mass transfer rate of the template molecule is fast, tetrabromobisphenol A in the sample to be measured can be efficiently detected, the principle is simple, the cost of raw materials is low, and the detection process does not require any large instrument, so that rapid, efficient and visual detection of tetrabromobisphenol A in the sample to be measured can be realized.

[0039] Further, mesoporous silica modified with a double bond is used as an imprinting carrier, tetrabromobisphenol A is used as a template molecule, methacrylic acid is used as a functional monomer, ethylene glycol dimethacrylate is used as a crosslinking agent, and azobisisobutyronitrile is used as an initiator to prepare a surface molecular imprinting product, so that the obtained molecular imprinting fluorescent polymer has specific recognition function for tetrabromobisphenol A; the molecular imprinting ratio fluorescent sensor is used, combined with a fluorescent analysis method, to analyze and determine tetrabromobisphenol A in a sample, so that a new idea and method are provided for preparation of the molecular imprinting ratio fluorescent sensor and detection of target substances in a complex sample. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 A flowchart of the preparation method of the molecular imprinting ratio fluorescent sensor is shown in the application.

[0041] Figure 2Transmission electron microscopy (TEM) images of CQD@SiO2, mesoporous silica nanoparticles CQD@mSiO2, and the molecularly imprinted fluorescent polymer (MIP) based on mesoporous silica from Example 1; wherein, Figure 2 a is a transmission electron microscope image of CQD@SiO2; Figure 2 b is a transmission electron microscope image of mesoporous silica nanoparticles CQD@mSiO2; Figure 2 c is a transmission electron microscope image of the molecularly imprinted fluorescent polymer (MIP) based on mesoporous silica;

[0042] Figure 3 The infrared spectra of blue fluorescent carbon quantum dots CQDs (a), CQD@SiO2 (b), double bond modified mesoporous silica nanoparticles CQD@mSiO2-KH570 (c), and molecularly imprinted fluorescent polymer MIP based on mesoporous silica (d) in Example 1 are shown.

[0043] Figure 4 The X-ray diffraction patterns of blue fluorescent carbon quantum dots (CQDs) (a), CQD@SiO2 (b), mesoporous silica nanoparticles (CQD@mSiO2) (c), and molecularly imprinted fluorescent polymer (MIP) based on mesoporous silica (d) in Example 1 are shown.

[0044] Figure 5 This is a graph showing the relationship between the fluorescence intensity of the molecularly imprinted ratio fluorescence sensor and the concentration of tetrabromobisphenol A in Example 1.

[0045] Figure 6 This is a graph showing the linear relationship between the fluorescence intensity of the molecularly imprinted ratio fluorescence sensor and the concentration of tetrabromobisphenol A in Example 1.

[0046] Figure 7 This is a selectivity diagram of the molecularly imprinted ratio fluorescence sensor in Example 1 for tetrabromobisphenol A and its analogues under the same concentration conditions. Detailed Implementation

[0047] To make the technical problems solved by the present invention, the technical solutions, and the beneficial effects clearer, the following specific embodiments provide a further detailed description of the present invention. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.

[0048] As attached Figure 1 As shown, this invention provides a method for preparing a molecularly imprinted ratiometric fluorescence sensor, comprising the following steps:

[0049] Step 1: Blue fluorescent carbon quantum dots (CQDs) are prepared using a hydrothermal method; the specific preparation process of the blue fluorescent carbon quantum dots (CQDs) is as follows:

[0050] The citric acid and polyethylene imine solution is dispersed in ultrapure water, mixed uniformly, and then subjected to a hydrothermal reaction at 200°C for 2h to obtain a hydrothermal reaction product; the hydrothermal reaction product is naturally cooled to room temperature, centrifuged to remove impurities, and subjected to dialysis treatment for 48h using dialysis tape, and then freeze-dried to obtain the blue fluorescent carbon quantum dots CQDs.

[0051] Step 2: The blue fluorescent carbon quantum dots CQDs are coated with SiO2 by using a reverse microemulsion method to obtain CQD@SiO2; wherein the coating process is as follows:

[0052] Cyclohexane, n-hexanol, triton X-100, and ultrapure water are mixed to form a microemulsion; carbon quantum dot solution and PEI solution are added to the microemulsion and ultrasonically stirred to obtain a mixed solution; tetraethyl orthosilicate and ammonia are added to the mixed solution and reacted in the dark for 24h; after the reaction is completed, acetone is added to break the emulsion, and then centrifuged, washed, and vacuum dried to obtain CQD@SiO2.

[0053] Step 3: The surface of the CQD@SiO2 is coated with mesoporous silica by using an oil-water two-phase coating method to obtain mesoporous silica nanoparticles CQD@mSiO2; wherein the preparation process of the mesoporous silica nanoparticles CQD@mSiO2 is as follows:

[0054] The CQD@SiO2, ultrapure water, cetyltrimethylammonium chloride, and triethanolamine are mixed and dispersed uniformly, refluxed, and maintained for a preset period of time to obtain a mixed system A; a mixed solution of cyclohexane and tetraethyl orthosilicate is added dropwise to the mixed system A, and after the dropwise addition is completed, the reaction is carried out in the dark to obtain a dark reaction product; the dark reaction product is washed with ethanol and water alternately, centrifuged, and vacuum dried to obtain a treated product; the treated product is added to a solvent, refluxed for a preset time, and then washed with ethanol, centrifuged, and dried to obtain the mesoporous silica nanoparticles CQD@mSiO2; wherein the solvent is replaced once during the refluxing process; the solvent is a mixed solution containing ammonium nitrate and anhydrous ethanol.

[0055] Step 4: The mesoporous silica nanoparticles CQD@mSiO2 are surface-modified to obtain double-bond-modified mesoporous silica nanoparticles CQD@mSiO2-KH570; wherein the surface modification process is as follows:

[0056] The mesoporous silica nanoparticles CQD@mSiO2 and KH570 are dispersed in anhydrous toluene, ultrasonic stirring is performed to uniformly disperse them, and under the protection of nitrogen, the reaction is carried out at a temperature of 110°C for 12-24h; after the reaction is completed, the product is collected by centrifugation, and is washed with anhydrous ethanol, centrifuged, and vacuum dried to obtain the double bond modified mesoporous silica nanoparticles CQD@mSiO2-KH570.

[0057] Step 5, synthesis of an organic fluorescent monomer to obtain a pre-synthesized organic fluorescent monomer; wherein the preparation process of the pre-synthesized organic fluorescent monomer is specifically as follows:

[0058] 4-bromo-1,8-naphthalic anhydride, allylamine hydrochloride and triethylamine are added to a three-necked flask containing anhydrous ethanol to obtain a reaction mixture; under the protection of nitrogen, the reaction mixture is refluxed at a temperature of 80°C for 8h; then it is naturally cooled to room temperature, and the solvent is removed by rotary evaporation to obtain a crude product; the crude product is purified by column chromatography to obtain N-allyl-1,8-naphthalimide in the form of white solid; wherein the column chromatography adopts dichloromethane / methanol 100:1; the white solid N-allyl-1,8-naphthalimide, ethylenediamine and ethylene glycol monomethyl ether are added to a three-necked flask, and under the protection of nitrogen, the reaction is carried out at a temperature of 110°C for 6-8h; after the reaction, it is naturally cooled to room temperature, and recrystallized to obtain the pre-synthesized organic fluorescent monomer.

[0059] Step 6, the template molecule, the functional monomer and the pre-synthesized organic fluorescent monomer are uniformly mixed, then the double bond modified mesoporous silica nanoparticles CQD@mSiO2-KH570, the crosslinking agent and the initiator are added to initiate the polymerization reaction to obtain the mesoporous silica-based molecularly imprinted fluorescent polymer MIP; wherein the specific process is as follows:

[0060] The template molecule, the functional monomer and the pre-synthesized organic fluorescent monomer are dissolved in anhydrous toluene, and under the protection of nitrogen, mechanical stirring is performed for 6h to obtain a mixed system B; in the mixed system B, the double bond modified mesoporous silica nanoparticles CQD@mSiO2-KH570 are added, the crosslinking agent and the initiator are added after ultrasonic dispersion, and the polymerization reaction is carried out under the protection of nitrogen at a temperature of 60°C for 24h to obtain the mesoporous silica-based molecularly imprinted fluorescent polymer MIP; wherein the template molecule is tetrabromobisphenol A, the functional monomer is methacrylic acid, the crosslinking agent is ethylene glycol dimethacrylate, and the initiator is azobisisobutyronitrile; wherein the molar ratio among the template molecule, the functional monomer and the crosslinking agent is 1:(4-8):(10-20).

[0061] Step 7, removing the template molecules of the mesoporous silica-based molecular imprinting fluorescent polymer to obtain the molecular imprinting ratio fluorescent sensor; wherein the removing process is specifically as follows:

[0062] After removing the template molecules in the molecular imprinting fluorescent polymer with methanol / acetic acid mixed solvent as an eluent, the molecular imprinting ratio fluorescent sensor is obtained by washing with ethanol for several times and vacuum drying treatment; wherein the eluent is obtained by mixing methanol and acetic acid in a volume ratio of 9:1.

[0063] Preparation principle:

[0064] The preparation method of the molecular imprinting ratio fluorescent sensor provided by the application adopts a hydrothermal method to prepare blue fluorescent carbon quantum dots CQDs, adopts a reverse microemulsion method to coat the blue fluorescent carbon quantum dots CQDs to obtain CQD@SiO2, the CQDs are protected by the silicon layer in the CQD@SiO2, avoiding contact with the outside world, so that a stable fluorescent reference signal can be provided; then, an oil-water two-phase layered coating technology is adopted to coat mesoporous silica on the surface of the CQD@SiO2, and after solvent extraction treatment, mesoporous silica nanoparticles CQD@mSiO2 are obtained; the introduction of the mesoporous silica layer makes the recognition sites more abundant, and the existence of a large number of hydroxyl groups on the surface of the mesoporous silica layer makes subsequent modification simpler; the mesoporous silica nanoparticles CQD@mSiO2 are modified with double bonds to obtain double bond modified mesoporous silica nanoparticles CQD@mSiO2-KH570, and then an organic fluorescent monomer is introduced into the imprinting layer to obtain a mesoporous silica-based molecular imprinting fluorescent polymer MIP; the mesoporous silica-based molecular imprinting fluorescent polymer is eluted to obtain the molecular imprinting ratio fluorescent sensor; the preparation process is relatively simple, and the raw material cost is low.

[0065] The application further provides a molecular imprinting ratio fluorescent sensor, wherein due to the existence of the imprinting layer, specific recognition function of the to-be-detected target is realized, combined with a fluorescent analysis method, analysis and determination of the to-be-detected target in the to-be-measured sample are realized, visual detection can be realized, and the detection result precision is high; the recognition sites of the molecular imprinting ratio fluorescent sensor are rich, the template molecule mass transfer rate is high, the to-be-measured sample can be efficiently detected, the principle is simple, the raw material cost is low, and the detection process does not need any large instrument, so that rapid and efficient detection of the tetrabromobisphenol A in the to-be-measured sample can be realized.

[0066] The application further provides application of the molecular imprinting ratio fluorescent sensor, namely visual identification and detection of tetrabromobisphenol A in an environmental system by using the molecular imprinting ratio fluorescent sensor; specifically, blue fluorescent carbon quantum dots CQDs are used as a fluorescent reference signal, green fluorescent monomers N-allyl-4-ethylenediamine-1,8-naphthalimide are used as a fluorescent response signal, and a fluorescence spectrophotometer is used to analyze and detect tetrabromobisphenol A (TBBPA) in an environmental system.

[0067] The molecular imprinting ratio fluorescent sensor, the preparation method and the application thereof have the following advantages.

[0068] Embodiment 1

[0069] The preparation method of the molecular imprinting ratio fluorescent sensor provided in this embodiment 1 comprises the following steps.

[0070] Step 1, blue fluorescent carbon quantum dots CQDs are prepared by using a hydrothermal method; wherein the preparation process of the blue fluorescent carbon quantum dots CQDs is specifically as follows.

[0071] 1.0 g of citric acid was ultrasonically dissolved in 10 mL of ultrapure water, then 5 mL of polyethyleneimine solution was added, and ultrasonic dispersion was performed for 30 min to obtain a uniform mixed solution; the uniform mixed solution was transferred to a 50 mL hydrothermal kettle, and hydrothermal reaction was performed at 200°C for 2 h to obtain a hydrothermal reaction product; the hydrothermal reaction product was naturally cooled to room temperature, centrifuged to remove impurities, and treated with a 1 kDa dialysis bag for 48 h to obtain a dialysis-treated product; during the dialysis treatment, the water was changed every 6-8 h; finally, the dialysis-treated product was freeze-dried to obtain the blue fluorescent carbon quantum dots CQDs.

[0072] Step 2, SiO2-coated CQDs were prepared by coating the blue fluorescent carbon quantum dots CQDs with SiO2 using a reverse microemulsion method; the specific process is as follows:

[0073] 60 mL of cyclohexane, 14.4 mL of n-hexanol, 14.4 mL of triton X-100, and 2 mL of ultrapure water were mixed and vigorously stirred for 30 min to form a microemulsion; 500 μL of carbon quantum dot solution and 500 μL of polyethyleneimine solution were added to the microemulsion and ultrasonically stirred to obtain a mixed solution; 550 μL of tetraethyl orthosilicate and 400 μL of ammonia water were added to the mixed solution, and the reaction was carried out at room temperature and in the dark for 24 h; after the reaction was completed, 20 mL of acetone was added and ultrasonically stirred for 30 min to break the emulsion and centrifuged, washed, and vacuum dried to obtain the CQD@SiO2; the washing process is as follows: ethanol was used to wash twice, and deionized water was used to wash 3 times; the vacuum drying temperature was 60°C, and the vacuum drying time was 7 h.

[0074] Step 3, mesoporous silica nanoparticles CQD@mSiO2 were obtained by coating mesoporous silica on the surface of the CQD@SiO2 using an oil-water two-phase coating method, followed by centrifugal separation, washing, drying, and solvent extraction treatment; the specific process is as follows:

[0075] The 0.3 g of CQD@SiO2 is added to a three-neck flask containing 100 mL of ultrapure water, ultrasonic stirring for 30 min, then 10.5 g of cetyltrimethylammonium chloride is added and stirred to disperse uniformly, then 135 μL of triethanolamine is added, and the temperature is raised to 60°C for 1 h, then a mixed solution of 15 mL of cyclohexane and 3 mL of TEOS is added dropwise, after the dropwise addition is completed, the reaction is carried out at 60°C in the dark for 12 h to obtain a dark reaction product; the dark reaction product is washed with ethanol and water alternately for 2 times, centrifuged and collected, and vacuum dried at 50°C for 10 h to obtain a treated product; in order to remove cetyltrimethylammonium chloride in the treated product, the treated product is added to a three-neck flask containing 1.8 g of ammonium nitrate and 300 mL of anhydrous ethanol, and ultrasonic stirring is performed for 30 min to disperse uniformly, then reflux treatment is carried out at 60°C for 12 h with stirring; during the reflux treatment, the solvent is replaced once; then washed with ethanol for 3 times, centrifuged and collected to obtain the mesoporous silica nanoparticles CQD@mSiO2.

[0076] Step 4, the mesoporous silica nanoparticles CQD@mSiO2 are modified with a double bond to obtain double bond modified mesoporous silica nanoparticles CQD@mSiO2-KH570; wherein the specific process is as follows:

[0077] The 0.25 g of mesoporous silica nanoparticles CQD@mSiO2 is added to a three-neck flask containing 50 mL of anhydrous toluene, ultrasonic stirring for 1 h to disperse uniformly, then 1.5 mL of KH570 is slowly added; the reaction is carried out at a temperature of 110°C for 12-24 h under nitrogen protection; after the reaction is completed, the product is centrifuged and collected, and washed with anhydrous ethanol for 3 times; finally, vacuum drying is carried out at 40°C overnight to obtain double bond modified mesoporous silica nanoparticles CQD@mSiO2-KH570.

[0078] Step 5, synthesis of organic fluorescent monomers to obtain pre-synthesized organic fluorescent monomers; wherein the preparation process of the pre-synthesized organic fluorescent monomers is as follows:

[0079] Under magnetic stirring, 0.831 g of 4-bromo-1,8-naphthalene anhydride, 0.281 g of allylamine hydrochloride and 416 μL of triethylamine were added into a three-necked flask containing 40 mL of anhydrous ethanol to obtain a reaction mixture; the reaction mixture was refluxed at 80°C for 8 h under nitrogen protection; then it was naturally cooled to room temperature; the solvent was removed by rotary evaporation to obtain a crude product; the crude product was purified by column chromatography to obtain N-allyl-1,8-naphthalimide in the form of white solid; wherein, the column chromatography used dichloromethane / methanol 100:1; 314 mg of N-allyl-1,8-naphthalimide in the form of white solid, 3 mL of ethylenediamine and 30 mL of ethylene glycol monomethyl ether were added into a 100 mL three-necked flask, deoxygenated by nitrogen for 30 min, then heated to 110°C for 6-8 h, after reaction, naturally cooled to room temperature, and purified by recrystallization to obtain the pre-synthesized organic fluorescent monomer.

[0080] Step 6, the template molecule, functional monomer and pre-synthesized organic fluorescent monomer were uniformly mixed, then the double bond modified mesoporous silica nanoparticles CQD@mSiO2-KH570, crosslinking agent and initiator were added to initiate polymerization to obtain the mesoporous silica-based molecularly imprinted fluorescent polymer MIP; wherein, the specific process is as follows:

[0081] 86 mg of methacrylic acid and 10 mg of pre-synthesized organic fluorescent monomer and tetrabromobisphenol A were dissolved in 50 mL of anhydrous toluene, mechanically stirred for 6 h under nitrogen protection; then 50 mg of double bond modified mesoporous silica nanoparticles CQD@mSiO2-KH570 was added, ultrasonic stirring for 30 min, finally 0.99 g of EGDMA and 20 mg of AIBN were added to form a mixed solution, which was reacted at 60°C for 24 h under nitrogen atmosphere in the dark; then the product was washed with ethanol and vacuum dried to obtain the mesoporous silica-based molecularly imprinted fluorescent polymer MIP; wherein, the washing was performed with ethanol for 3 times; the temperature of vacuum drying was 60°C, and the time of vacuum drying was 12 h.

[0082] Step 7, the mesoporous silica-based molecularly imprinted fluorescent polymer MIP was subjected to elution treatment to obtain a molecularly imprinted ratio fluorescent sensor; wherein, the specific process is as follows:

[0083] The template molecule in the mesoporous silica-based molecularly imprinted fluorescent polymer MIP was removed by Soxhlet extraction using 150 mL of a methanol-acetic acid mixed solvent until no template molecule TBBPA was detected in the supernatant by ultraviolet-visible spectrophotometer, then washed with ethanol for 3 times and dried in a vacuum drying oven to obtain the molecularly imprinted ratio fluorescent sensor; wherein, the preparation process of the methanol-acetic acid mixed solvent is as follows: methanol and acetic acid were mixed in a volume ratio of 9:1 to obtain the mixed solvent.

[0084] As shown in the accompanying Figure 2 , the accompanying Figure 2 Figures show transmission electron micrographs of CQD@SiO2, mesoporous silica nanoparticles CQD@mSiO2 and molecularly imprinted fluorescent polymer MIP based on mesoporous silica in Example 1; wherein, Figure 2 a is a transmission electron micrograph of CQD@SiO2; from the accompanying Figure 2 a, it can be seen that the CQD@SiO2 has good dispersibility, uniform particle size, and presents a regular spherical shape; Figure 2 b is a transmission electron micrograph of mesoporous silica nanoparticles CQD@mSiO2; from the accompanying Figure 2 b, it can be seen that the mesoporous silica nanoparticles CQD@mSiO2 have further increased particle size, and the mesoporous structure can be clearly seen; Figure 2 c is a transmission electron micrograph of a molecularly imprinted fluorescent polymer MIP based on mesoporous silica; from the accompanying Figure 2 c, it can be seen that the mesoporous surface is obviously coated with a polymer layer, i.e. the generation of an imprinting layer; the polymer layer on the surface of the mesoporous carrier is conducive to rapid mass transfer during template binding and removal.

[0085] As shown in the accompanying Figure 3 , the accompanying Figure 3 Figures show infrared spectra of blue fluorescent carbon quantum dots CQDs (a), CQD@SiO2 (b), double bond modified mesoporous silica nanoparticles CQD@mSiO2-KH570 (c) and molecularly imprinted fluorescent polymer MIP (d) based on mesoporous silica in Example 1; from the accompanying Figure 3 curve (a) in Figure 1650 cm -1 is an absorption peak of C=O stretching vibration, 3417 cm -1 is a broad peak of O-H stretching vibration, 1555 cm -1 is a characteristic peak of -NH2, which indicates the successful preparation of blue fluorescent carbon quantum dots CQDs; from the accompanying Figure 3 curve (b) 1099 cm -1 is a stretching vibration peak of Si-O-Si, 800 cm -1 and 470 cm -1 are absorption peaks of Si-O bending vibration and symmetric stretching vibration, respectively, which indicates the successful preparation of CQD@SiO2; from the accompanying Figure 3 curve (c) 1711 cm -1 is a characteristic peak of C=O, 2961 cm -1The presence of a -CH2 peak indicates successful modification of KH570, namely the successful preparation of double-bond modified mesoporous silica nanoparticles CQD@mSiO2-KH570; (See attached image) Figure 3 In curve (d), 1715cm -1 1206cm -1 and 1155cm -1 The peaks at the positions are the stretching vibration peak of C=O, the stretching vibration peak of CO, and the bending vibration peak, respectively, indicating that the polymerization of MAA and EGDMA was successful, and that the molecularly imprinted fluorescent polymer (MIP) based on mesoporous silica was successfully prepared.

[0086] As attached Figure 4 As shown, attached Figure 4 The X-ray diffraction patterns of blue fluorescent carbon quantum dots (CQDs) (a), CQD@SiO2 (b), mesoporous silica nanoparticles (CQD@mSiO2) (c), and the molecularly imprinted fluorescent polymer (MIP) based on mesoporous silica (d) in Example 1 are shown in the attached figure. Figure 4 The curve (a) shows a broad peak centered at 2θ = 23°, which is attributed to the highly disordered carbon atoms; from the attached... Figure 4 As can be seen from curves (b), (c) and (d), the diffraction peaks correspond to the diffraction peaks of carbon quantum dots (CQDs), and the intensity does not change significantly, indicating that subsequent modifications will not affect the structure of carbon quantum dots (CQDs).

[0087] Comparative Example 1

[0088] The steps of the molecularly imprinted ratio fluorescence sensor preparation method described in Comparative Example 1 and Example 1 are basically the same, except that a blank template molecule is added in step 6, that is, tetrabromobisphenol A is not added in step 6, and the final product is denoted as non-imprinted fluorescent polymer NIP.

[0089] Example 2

[0090] This embodiment 2 provides a method for preparing a molecularly imprinted ratio fluorescence sensor, which is basically the same as the method for preparing a molecularly imprinted ratio fluorescence sensor described in embodiment 1. The difference is that the fluorescence intensity of the molecularly imprinted ratio fluorescence sensor is detected by using phosphate buffer solutions with different pH values ​​to obtain the optimal pH value of the phosphate buffer solution.

[0091] The specific process is as follows:

[0092] Prepare phosphate buffer solutions with pH values ​​of 4.0, 5.0, 6.0, 7.0, 8.0, and 9.0 respectively.

[0093] 4.0, 5.0, 6.0, 7.0, 8.0 and 9.0 phosphate buffer solution as detection test solution;

[0094] An equal amount of the mesoporous silica-based molecularly imprinted fluorescent polymer MIP is added to each of the above phosphate buffer solutions, and is uniformly dispersed by ultrasonic, the fluorescence intensity is detected, and the fluorescence intensity ratio is calculated to determine the optimal pH value of the phosphate buffer solution; wherein the fluorescence intensity ratio is best when the pH of the phosphate buffer solution is 7, that is, the optimal pH value of the phosphate buffer solution is 7.

[0095] Example 3

[0096] The present embodiment 3 provides an application of a molecularly imprinted ratio fluorescent sensor; specifically, the incubation time of the molecularly imprinted ratio fluorescent sensor in the to-be-detected solution is 0 min, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min and 8 min; the results of detection by a fluorescence spectrophotometer show that: with the increase of the incubation time, the fluorescence intensity of the green fluorescent monomer N-allyl-4-ethylenediamine-1, 8-naphthalimide as a response signal gradually decreases, while the fluorescence intensity of the blue fluorescent carbon quantum dots CQDs as a reference signal remains unchanged, and the fluorescence intensity ratio basically no longer changes after 6 min, because the existence of imprinting cavities on the surface of the molecularly imprinted fluorescent polymer promotes the combination of TBBPA, resulting in the weakening of the fluorescence intensity of N-allyl-4-ethylenediamine-1, 8-naphthalimide; therefore, 6 min is selected as the optimal incubation time.

[0097] Example 4

[0098] The present embodiment 4 is basically the same as the steps of the embodiment 1, except that the molar ratio of the functional monomer and the crosslinking agent in step 6 is different; specifically, in step 6, 86 mg of methacrylic acid and 10 mg of a pre-synthesized organic fluorescent monomer and tetrabromobisphenol A are dissolved in 50 mL of anhydrous toluene, and mechanical stirring is performed for 6 h under the protection of nitrogen; then 50 mg of double bond modified mesoporous silica nanoparticles CQD@mSiO2-KH570 is added, and ultrasonic stirring is performed for 30 min, finally a mixed solution of 0.495 g of EGDMA and 20 mg of AIBN is added, and the reaction is carried out at 60°C under the protection of nitrogen for 24 h in the dark; then the product is washed with ethanol, and vacuum dried to obtain the mesoporous silica-based molecularly imprinted fluorescent polymer MIP; wherein the washing is performed with ethanol for 3 times; the temperature of vacuum drying is 60°C, and the time of vacuum drying is 12 h.

[0099] In Example 4, the molar ratio of template molecule, functional monomer and crosslinking agent is 1:4:10. The molecularly imprinted fluorescent polymer (MIP) prepared in Example 4 was evaluated by fluorescence testing, and the imprinting factor of the obtained sensor was found to be 6.5. Therefore, the imprinted polymers obtained at different ratios showed different binding abilities to TBBPA.

[0100] Example 5

[0101] Example 5 is largely the same as Example 1 except that the molar ratio of the functional monomer and crosslinking agent is different in step 6. Specifically, in step 6, 172 mg of methacrylic acid, 10 mg of the pre-synthesized organic fluorescent monomer, and tetrabromobisphenol A are dissolved in 50 mL of anhydrous toluene and mechanically stirred for 6 h under nitrogen protection. Then, 50 mg of double-bond modified mesoporous silica nanoparticles CQD@mSiO2-KH570 are added and ultrasonically stirred for 30 min. Finally, a mixed solution of 0.99 g of EGDMA and 20 mg of AIBN is added, and the reaction is carried out at 60 °C in the dark for 24 h under a nitrogen atmosphere. The product is then washed with ethanol and vacuum dried to obtain the molecularly imprinted fluorescent polymer (MIP) based on mesoporous silica. The washing process involves three washes with ethanol. The vacuum drying temperature is 60 °C and the vacuum drying time is 12 h.

[0102] In Example 5, the molar ratio of the template molecule, functional monomer, and crosslinking agent is 1:8:20. The molecularly imprinted fluorescent polymer (MIP) prepared in Example 5 was evaluated by fluorescence testing, and the imprinting factor of the obtained sensor was found to be 8.3. Therefore, the imprinted polymers obtained at different ratios exhibit different binding abilities to TBBPA.

[0103] Fluorescence sensitivity detection test:

[0104] As attached Figure 5 As shown, Figure 5 A graph showing the relationship between the fluorescence intensity of the molecularly imprinted ratiometric fluorescence sensor and the concentration of tetrabromobisphenol A in Example 1 is provided. In the fluorescence sensitivity detection experiment, ten TBBPA solutions with concentrations of 0 μM, 0.1 μM, 0.5 μM, 1.0 μM, 1.5 μM, 2.0 μM, 3.0 μM, 5.0 μM, 7.0 μM and 10 μM were prepared. The prepared ratiometric fluorescence sensor was added to each solution and incubated in the solution for 6 min. Then, the fluorescence intensity of the ten solutions was detected by a fluorescence spectrophotometer.

[0105] As attached Figure 6 As shown, Figure 6 The figure shows a linear relationship between the fluorescence intensity of the molecularly imprinted ratio fluorescence sensor in Example 1 and the concentration of tetrabromobisphenol A; from the appendix... Figure 6As can be seen, the fluorescence intensity ratio of the molecularly imprinted ratio fluorescence sensor exhibits a good linear relationship with the TBBPA concentration; wherein, the expression for the linear regression equation of the fluorescence intensity ratio of the molecularly imprinted ratio fluorescence sensor with the TBBPA concentration is:

[0106] The linear relationship is y = 0.4237x + 0.9457 (R²). 2 =0.9951)

[0107] The detection limit for TBBPA concentration is 2.5 nM.

[0108] Furthermore, as the concentration of TBBPA increases, the fluorescence intensity of the blue fluorescent carbon quantum dots (CQDs), which serve as the fluorescence reference signal, remains constant, while the fluorescence intensity of the green fluorescent monomer N-allyl-4-ethylenediamine-1,8-naphthalimide, which serves as the response signal, gradually decreases. This change in fluorescence intensity ratio causes the fluorescence color to change from green to blue, enabling visual detection. Therefore, the molecularly imprinted ratio fluorescence sensor has a low detection limit, demonstrating that it can achieve visual detection of trace pollutants in complex environments.

[0109] Fluorescence specificity detection assay:

[0110] As attached Figure 7 As shown, Figure 7 This is a selectivity diagram of the molecularly imprinted ratiometric fluorescence sensor in Example 1 for tetrabromobisphenol A and its analogues under the same concentration conditions. Specifically, structural analogues of TBBPA, such as bisphenol A (BPA), p-tert-butylphenol (BP), and 4,4-biphenyl (BIP), were selected to study the selectivity of the molecularly imprinted ratiometric fluorescence sensor. 5.0 μM solutions of TBBPA, BPA, BP, and BIP were taken, and the molecularly imprinted fluorescent polymer (MIP) solution was added to each. The fluorescence intensity was detected using a fluorescence spectrophotometer under the same conditions.

[0111] The results showed that the molecularly imprinted ratio fluorescence sensor only had a good recognition effect on TBBPA, but a very weak response to its structural analogues. The reason is that the specific recognition cavity generated on the surface of the molecularly imprinted fluorescent polymer (MIP) is perfectly matched with the shape, size and spatial arrangement of TBBPA. However, BPA, BP and BIP are not complementary to the recognition site, so they do not bind specifically. This indicates that the molecularly imprinted ratio fluorescence sensor can specifically recognize TBBPA in complex environments.

[0112] The molecular imprinting ratio fluorescence sensor, and a preparation method and application thereof, are prepared by using double-bond modified mesoporous silica as an imprinting carrier, using tetrabromobisphenol A as a template molecule, using methacrylic acid as a functional monomer, using ethylene glycol dimethacrylic acid ester as a crosslinking agent, using azobisdimethyl isobutyronitrile as an initiator, and performing surface molecular imprinting to obtain a molecular imprinting fluorescence polymer MIP; the molecular imprinting fluorescence polymer is subjected to elution treatment to obtain the molecular imprinting ratio fluorescence sensor; the molecular imprinting ratio fluorescence sensor has rich recognition sites, a fast template molecule mass transfer rate, can quickly and accurately detect tetrabromobisphenol A in a sample to be measured, has a simple principle, low material cost, and does not require any large instrument in the detection process, and realizes high sensitivity and visual detection of tetrabromobisphenol A in the sample to be measured.

[0113] The above examples are only one of the implementation manners of the technical scheme of the present application, and the scope of the present application is not limited to the above examples, but also includes any changes, substitutions and other implementation manners easily thought of by those skilled in the art within the technical scope disclosed by the present application.

Claims

1. A method for preparing a molecularly imprinted ratiometric fluorescence sensor, characterized in that, Includes the following steps: Step 1: Coat blue fluorescent carbon quantum dots (CQDs) with SiO2 to obtain CQD@SiO2; Step 2: Using an oil-water two-phase coating method, mesoporous silica is coated onto the surface of CQD@SiO2 to obtain mesoporous silica nanoparticles; Step 3: Surface modification of the mesoporous silica nanoparticles to obtain double bond modified mesoporous silica nanoparticles; Step 4: Mix the template molecule, functional monomer and pre-synthesized organic fluorescent monomer evenly, then add the double bond modified mesoporous silica support, crosslinking agent and initiator to initiate the polymerization reaction and obtain a molecularly imprinted fluorescent polymer based on mesoporous silica. Step 5: Remove the template molecules of the molecularly imprinted fluorescent polymer based on mesoporous silica to obtain the molecularly imprinted ratio fluorescence sensor. In step 2, the oil-water two-phase coating method is used to coat the surface of CQD@SiO2 with mesoporous silica to obtain mesoporous silica nanoparticles. The specific process is as follows: The CQD@SiO2, ultrapure water, hexadecyltrimethylammonium chloride and triethanolamine are mixed and dispersed evenly, refluxed and maintained for a preset time period to obtain mixed system A; A mixed solution of cyclohexane and tetraethyl orthosilicate was added dropwise to the mixed system A. After the addition was complete, the mixture was reacted under light-protected conditions to obtain a light-protected reaction product. The light-protected reaction product was washed alternately with ethanol and water, centrifuged, and vacuum dried to obtain the treated product. The treated product is added to a solvent, refluxed for a preset time, washed with ethanol, centrifuged, and dried to obtain the mesoporous silica nanoparticles; wherein, the solvent is replaced once during the reflux process; the solvent is a mixed solution containing ammonium nitrate and anhydrous ethanol. The preparation process of the pre-synthesized organic fluorescent monomer is as follows: 4-Bromo-1,8-naphthoic anhydride, allylamine hydrochloride and triethylamine were added to a three-necked flask containing anhydrous ethanol to obtain a reaction mixture; Under nitrogen protection, the reaction mixture was refluxed at 80°C for 8 hours; then naturally cooled to room temperature, and the solvent was removed by rotary evaporation to obtain the crude product. The crude product was purified by column chromatography to obtain N-allyl-1,8-naphthalimide as a white solid. White solid N-allyl-1,8-naphthalimide, ethylenediamine, and ethylene glycol monomethyl ether were added to a three-necked flask and reacted at 110°C for 6-8 hours under nitrogen protection. After the reaction, the mixture was allowed to cool naturally to room temperature and recrystallized to obtain the pre-synthesized organic fluorescent monomer. Step 3 involves surface modification of the mesoporous silica nanoparticles to obtain double-bond modified mesoporous silica nanoparticles, as detailed below: The mesoporous silica nanoparticles and KH570 were dispersed in anhydrous toluene, ultrasonically stirred to ensure uniform dispersion, and reacted under nitrogen protection. After the reaction was completed, the product was collected by centrifugation, washed with anhydrous ethanol, centrifuged, and vacuum dried to obtain double bond modified mesoporous silica nanoparticles. In step 4, the template molecule, functional monomer, and pre-synthesized fluorescent monomer are mixed evenly, and then the double-bond modified mesoporous silica support, crosslinking agent, and initiator are added to initiate the polymerization reaction, thereby obtaining the molecularly imprinted fluorescent polymer based on mesoporous silica. The specific process is as follows: The template molecule, functional monomer, and fluorescent monomer were dissolved in anhydrous toluene and mechanically stirred for 6 hours under nitrogen protection to obtain mixed system B. In the mixed system B, a double-bond modified mesoporous silica support is added, ultrasonically dispersed, and then a crosslinking agent and an initiator are added. The polymerization reaction is carried out under a nitrogen atmosphere to obtain a molecularly imprinted fluorescent polymer based on mesoporous silica.

2. The method for preparing a molecularly imprinted ratiometric fluorescence sensor according to claim 1, characterized in that, In step 1, the blue fluorescent carbon quantum dots (CQDs) are prepared using a hydrothermal method. The process of preparing the blue fluorescent carbon quantum dots (CQDs) using a hydrothermal method is as follows: Citric acid and polyethyleneimine solutions were dispersed in ultrapure water, mixed evenly, and then subjected to a hydrothermal reaction to obtain the hydrothermal reaction product. The hydrothermal reaction product was naturally cooled to room temperature, centrifuged to remove impurities, dialyzed, and freeze-dried to obtain the blue fluorescent carbon quantum dots (CQDs).

3. The method for preparing a molecularly imprinted ratiometric fluorescence sensor according to claim 1, characterized in that, In step 1, the blue fluorescent carbon quantum dots (CQDs) are coated with SiO2 using the reverse microemulsion method to obtain CQD@SiO2. The coating process is detailed below: Cyclohexane, n-hexanol, Triton X-100 and ultrapure water were mixed and vigorously stirred to form a microemulsion. A carbon quantum dot solution and a PEI solution were added to the microemulsion and ultrasonically stirred to obtain a mixture; Tetraethyl orthosilicate and ammonia were added to the mixture to carry out the reaction. After the reaction was completed, acetone was added to break the emulsion and the mixture was centrifuged, washed, and vacuum dried to obtain CQD@SiO2.

4. The method for preparing a molecularly imprinted ratiometric fluorescence sensor according to claim 1, characterized in that, The template molecule is tetrabromobisphenol A, the functional monomer is methacrylic acid, the crosslinking agent is ethylene glycol dimethacrylate, and the initiator is azobisisobutyronitrile.

5. A molecularly imprinted ratio fluorescence sensor, characterized in that, The molecularly imprinted ratio fluorescence sensor is prepared using the method described in any one of claims 1-4.

6. The application of the molecularly imprinted ratio fluorescence sensor as described in claim 5, characterized in that, The aforementioned molecularly imprinted ratio fluorescence sensor was used for the visual identification and detection of tetrabromobisphenol A in an environmental system.

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