A terbium modified zinc-based metal organic framework surface molecular imprinting fluorescent material, a preparation method of a Tb@Zn-MOF@MIPs fluorescent film and a detection method of benz[a]pyrene

Abstract

The application provides a terbium modified zinc-based metal organic framework surface molecular imprinting fluorescent material, a preparation method of a Tb@Zn-MOF@MIPs fluorescent film and a detection method of benz[a]pyrene. 3+ As the second light emitting center, the dual-emission fluorescent material has ligand blue emission and Tb 3+ Green characteristic emission; again, a B[a]P is used as a template molecule, phenyltriethoxysilane is used as a functional monomer, tetraethyl orthosilicate is used as a crosslinking agent, and a molecular imprinting thin layer is formed on the surface of the fluorescent material; after the template molecule is eluted, the surface of the material forms a recognition cavity matched with the B[a]P, so that selective enrichment of the B[a]P is realized, and a target recognition process is converted into fluorescence intensity and comprehensive color change; the application can realize rapid, visual and portable detection of the benz[a]pyrene, and dependence of a detection process on large instruments is reduced.

Description

Technical Field

[0001] This invention relates to the field of benzo[a]pyrene detection technology, and particularly to a terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material, a method for preparing Tb@Zn-MOF@MIPs fluorescent thin films, and a method for detecting benzo[a]pyrene. Background Technology

[0002] Benzo[a]pyrene (B[a]P, chemical formula C) 20 H 12 B[a]P is a common polycyclic aromatic hydrocarbon (PAH) contaminant in food and is widely considered one of the world's most potent carcinogens. Due to its strong hydrophobicity, environmental persistence, and bioaccumulation, B[a]P easily accumulates in edible oils, grains, and their processed products, and may enter the human body through the food chain, posing a potential threat to food safety and human health. Therefore, establishing a highly sensitive, selective, rapid, and portable method for detecting B[a]P suitable for complex grain and oil samples is of great significance.

[0003] Currently, the main detection methods for B[a]P include high-performance liquid chromatography (HPLC), gas chromatography-mass spectrometry (GC-MS), liquid chromatography-mass spectrometry (LC-MS), fluorescence analysis, immunoassay, and surface-enhanced Raman spectroscopy (SMR). Among these, chromatographic and mass spectrometric methods typically rely on large analytical instruments, have complex sample pretreatment and detection procedures, consume large amounts of solvent, and incur high equipment and operating costs, making them difficult to meet the needs of rapid on-site screening and immediate identification. Ordinary fluorescent sensing materials often lack specific recognition sites that match the molecular structure of B[a]P, making them susceptible to interference from food matrices and structural analogs such as anthracene and phenanthrene. Furthermore, single-emission fluorescent probes rely primarily on changes in single fluorescence intensity for quantification, and the detection results are easily affected by factors such as probe concentration, excitation light intensity, environmental conditions, and image acquisition parameters. Since B[a]P is an approximately planar, rigid, hydrophobic molecule lacking typical hydrogen-bonded functional groups, its selective recognition mainly relies on hydrophobic interactions, π-π interactions, and pore size and spatial configuration matching. Ordinary adsorbent materials struggle to simultaneously achieve recognition selectivity, response sensitivity, and detection speed. In addition, some recognition sites of traditional bulk molecular imprinted materials are located inside the polymer, and the target molecule mass transfer path is long and the site accessibility is low, which also limits their rapid detection performance.

[0004] Given the current deficiencies in the detection of benzo[a]pyrene, it is necessary to improve it. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a method for preparing terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent materials, Tb@Zn-MOF@MIPs fluorescent thin films, and a method for detecting benzo[a]pyrene. This invention uses a zinc-based metal-organic framework with stable fluorescence properties and tunable pore structure as the main body, and introduces Tb through a post-modification method. 3+ As a secondary luminescent center, it constructs a structure that simultaneously exhibits ligand blue emission and Tb emission. 3+ A dual-emission fluorescent material exhibiting green characteristic emission is further developed. Using B[a]P as a template molecule, phenyltriethoxysilane as a functional monomer, and tetraethyl orthosilicate as a crosslinking agent, a molecularly imprinted thin layer is formed on the surface of the fluorescent material via a sol-gel method. After the template molecule is eluted, recognition pores matching B[a]P in terms of molecular size, shape, aromatic framework, hydrophobic microenvironment, and spatial configuration are formed on the material surface. This allows for selective enrichment of B[a]P through surface imprinting sites, hydrophobic interactions, and π-π interactions, transforming the target analyte recognition process into fluorescence intensity and overall color change. Furthermore, this invention prepares the material as a flexible fluorescent thin film, combining image acquisition and RGB parameter analysis to achieve rapid, visualized, and portable quantitative detection of B[a]P, addressing the problems of insufficient selectivity, strong instrument dependence, complex detection procedures, and inconvenience for on-site application in existing technologies.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material, comprising the following steps:

[0008] Preparation of zinc-based metal-organic framework materials;

[0009] The zinc-based metal-organic framework material and terbium salt were added to the first solvent and reacted to obtain the Tb@Zn-MOF dual-emission fluorescent material.

[0010] Benzo[a]pyrene and phenyltriethoxysilane were dissolved in a second solvent, stirred, and then Tb@Zn-MOF dual-emission fluorescent material was added to obtain a pre-assembled solution.

[0011] Tetraethyl orthosilicate is dissolved in ethanol, and then water and ammonia are added to obtain a crosslinking agent solution;

[0012] The crosslinking agent solution was added to the pre-assembled solution, stirred and reacted, washed and dried to obtain Tb@Zn-MOF@MIPs molecularly imprinted dual-emission fluorescent material, which is a terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material.

[0013] Preferably, zinc iodide, 4,4'-(1H-1,2,4-triazol-3,5-diyl)bisbenzoic acid, and acetic acid are added to a third solvent, reacted, washed, and dried to obtain Zn-MOF, which is a zinc-based metal-organic framework material.

[0014] Preferably, the zinc-based metal-organic framework material and terbium salt are added to the first solvent and reacted at 120~130℃ for 10~15h. After washing and drying, Tb@Zn-MOF dual-emission fluorescent material is obtained.

[0015] Preferably, the crosslinking agent solution is added to the pre-assembled solution, and the mixture is stirred at 20-25°C for 12-15 hours, then allowed to stand for 2-4 hours, washed, and dried to obtain Tb@Zn-MOF@MIPs molecularly imprinted dual-emission fluorescent material.

[0016] Preferably, the mass-to-volume ratio of the zinc-based metal-organic framework material, the terbium salt, and the first solvent is (100~120) mg:(100~120) mg:(4~6) mL;

[0017] The mass-to-volume ratio of the benzo[a]pyrene, Tb@Zn-MOF dual-emission fluorescent material, phenyltriethoxysilane, second solvent, tetraethyl orthosilicate, ethanol, water, and ammonia is (25~30) mg:(100~110) mg:(97~107) μL:(50~60) mL:(210~220) μL:(2~5) mL:(100~110) μL:(30~40) μL, and the mass fraction of the ammonia is 25~28%.

[0018] The terbium salt includes at least one of terbium nitrate hexahydrate, terbium nitrate, terbium chloride, and terbium chloride trihydrate;

[0019] The first solvent includes at least one of N,N-dimethylformamide and N,N-dimethylacetamide;

[0020] The second solvent includes at least one of ethanol, n-propanol, and isopropanol.

[0021] Preferably, zinc iodide, 4,4'-(1H-1,2,4-triazol-3,5-diyl)bisbenzoic acid and acetic acid are added to a third solvent and reacted at 80-90°C for 60-72 h. After washing and drying, Zn-MOF is obtained.

[0022] The third solvent includes N,N-dimethylformamide and ethanol;

[0023] The mass-to-volume ratio of zinc iodide, 4,4'-(1H-1,2,4-triazol-3,5-diyl)bisbenzoic acid, acetic acid, N,N-dimethylformamide and ethanol is (160~170) mg:(75~85) mg:(150~160) μL:(15~25) mL:(5~15) mL.

[0024] Secondly, the present invention also provides a method for preparing Tb@Zn-MOF@MIPs fluorescent thin films, comprising the following steps: adding the terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material prepared by the above preparation method to a polymer solution to obtain a mixture;

[0025] Add the mixture into the mold;

[0026] A polyvinyl alcohol solution was added to the surface of the mixture to form a gel, and the solvent was evaporated by heating to obtain a flexible fluorescent film of Tb@Zn-MOF@MIPs.

[0027] The polymer solution comprises a polymer and an organic solvent, wherein the polymer comprises at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinylidene fluoride-trifluorochloroethylene copolymer.

[0028] The organic solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0029] Thirdly, the present invention also provides the application of the terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material prepared by the preparation method described above or the Tb@Zn-MOF@MIPs fluorescent thin film prepared by the preparation method described above in the detection of benzo[a]pyrene.

[0030] Fourthly, the present invention also provides a method for detecting benzo[a]pyrene, comprising the following steps:

[0031] The terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material prepared by the above preparation method was dispersed in ethanol, and a benzo[a]pyrene test solution was added. The fluorescence emission spectrum was measured at an excitation wavelength of 306 nm, and the fluorescence intensity at 390 nm was recorded. The benzo[a]pyrene content was detected based on the fluorescence intensity.

[0032] Fifthly, the present invention also provides a method for detecting benzo[a]pyrene, comprising the following steps:

[0033] The Tb@Zn-MOF@MIPs fluorescent film prepared by the above method was placed in a dark-box ultraviolet analyzer. The benzo[a]pyrene test solution was dropped onto the surface of the fluorescent film. Under 254 nm ultraviolet light irradiation, the film produced a fluorescent color change. The fluorescence image was collected, and the benzo[a]pyrene content was detected based on the fluorescence image.

[0034] The terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material, the preparation method of Tb@Zn-MOF@MIPs fluorescent thin film, and the detection method of benzo[a]pyrene of the present invention have the following advantages over the prior art:

[0035] 1. The method for preparing terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent materials of the present invention uses a zinc-based metal-organic framework with stable fluorescence properties and tunable pore structure as the main body, and introduces Tb through post-modification. 3+ As a secondary luminescent center, it constructs a structure that simultaneously exhibits ligand blue emission and Tb emission. 3+ A dual-emission fluorescent material exhibiting green characteristic emission; further, using B[a]P as a template molecule, phenyltriethoxysilane as a functional monomer, and tetraethyl orthosilicate as a crosslinking agent, a molecularly imprinted thin layer is formed on the surface of the fluorescent material using a sol-gel method; after the template molecule is eluted, recognition pores matching B[a]P in terms of molecular size, shape, aromatic skeleton, hydrophobic microenvironment, and spatial configuration are formed on the material surface, thereby achieving selective enrichment of B[a]P through surface imprinting sites, hydrophobic interactions, and π-π interactions, and transforming the target recognition process into fluorescence intensity and comprehensive color changes;

[0036] 2. This invention uses molecularly imprinted fluorescent materials to form Tb@Zn-MOF@MIPs fluorescent films, and combines smartphone image acquisition and color parameter analysis to achieve rapid, visualized, and portable detection of benzo[a]pyrene. This reduces the dependence on large instruments in the detection process and provides a new technical solution for on-site screening of benzo[a]pyrene in complex grain and oil samples. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of the preparation method of the terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material of the present invention;

[0039] Figure 2Transmission electron microscope images and EDS elemental distribution maps of Zn-MOF, Tb@Zn-MOF, Tb@Zn-MOF@MIPs and Tb@Zn-MOF@NIPs prepared in Examples 1-3 and Comparative Example 1;

[0040] Figure 3 The images show scanning electron microscope (SEM) images and EDS elemental distribution maps of the Tb@Zn-MOF@MIPs fluorescent thin films prepared in Example 4.

[0041] Figure 4 The fluorescence spectra of Tb@Zn-MOF@MIPs for different concentrations of B[a]P in Example 5 are shown.

[0042] Figure 5 The fluorescence color change of the Tb@Zn-MOF@MIPs film in Example 6 after adding different concentrations of B[a]P. Detailed Implementation

[0043] The present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] To better understand the invention and not to limit its scope, all figures indicating amounts, percentages, and other numerical values ​​used in this application should, in all cases, be understood to be modified by the word "approximately." Therefore, unless specifically stated otherwise, the numerical parameters listed in the specification and appended claims are approximate values ​​and may vary depending on the desired properties being sought. Each numerical parameter should at least be considered as obtained based on reported significant figures and through conventional rounding methods.

[0045] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0046] This invention provides a method for preparing terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent materials, comprising the following steps:

[0047] S1. Preparation of zinc-based metal-organic framework materials;

[0048] S2. Add zinc-based metal-organic framework material and terbium salt to the first solvent and react to obtain Tb@Zn-MOF dual-emission fluorescent material;

[0049] S3, Benzo[a]pyrene (CAS No. 50-32-8, chemical formula C) 20 H 12 ), phenyltriethoxysilane (CAS No. 780-69-8, molecular formula C 12 H 20 O3Si) is dissolved in a second solvent, stirred, and then Tb@Zn-MOF dual-emission fluorescent material is added to obtain a pre-assembled solution;

[0050] S4. Dissolve tetraethyl orthosilicate in ethanol, then add water and ammonia to obtain a crosslinking agent solution;

[0051] S5. Add the crosslinking agent solution to the pre-assembly solution, stir to react, wash, and dry to obtain Tb@Zn-MOF@MIPs molecularly imprinted dual-emission fluorescent material, which is a terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material.

[0052] The present invention provides a method for preparing terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent materials. The method uses a zinc-based metal-organic framework with stable fluorescence properties and tunable pore structure as the main body, and introduces Tb through a post-modification approach. 3+ As a secondary luminescent center, it constructs a structure that simultaneously exhibits ligand blue emission and Tb emission. 3+A dual-emission fluorescent material exhibiting green characteristic emission is further developed. Using B[a]P as a template molecule, phenyltriethoxysilane as a functional monomer, and tetraethyl orthosilicate as a crosslinking agent, a molecularly imprinted thin layer is formed on the surface of the fluorescent material using a sol-gel method. After the template molecule is eluted, recognition pores matching B[a]P in terms of molecular size, shape, aromatic skeleton, hydrophobic microenvironment, and spatial configuration are formed on the material surface. This allows for the selective enrichment of B[a]P through surface imprinting sites, hydrophobic interactions, and π-π interactions, transforming the target recognition process into fluorescence intensity and overall color change.

[0053] In some embodiments, zinc iodide and 4,4'-(1H-1,2,4-triazol-3,5-diyl)bisbenzoic acid (CAS No.: 65697-90-7, chemical formula: C 16 H 11 N3O4 (TDA) and acetic acid are added to a third solvent, reacted, washed, and dried to obtain Zn-MOF, which is a zinc-based metal-organic framework material.

[0054] In some embodiments, zinc-based metal-organic framework materials and terbium salts are added to a first solvent and ultrasonically dispersed (ultrasonic frequency 40-50 kHz, ultrasonic power 50-100 W) for 3-5 min, and then reacted at 120-130 °C for 10-15 h to allow Tb to form. 3+ After the reaction was completed, the product was centrifuged, washed three times with N,N-dimethylformamide, and vacuum dried at 80-100℃ for 10-12 h to obtain Tb@Zn-MOF dual-emission fluorescent material.

[0055] In some embodiments, benzo[a]pyrene and phenyltriethoxysilane are dissolved in a second solvent and stirred at 20-25°C for 30-40 min. Then, Tb@Zn-MOF dual-emission fluorescent material is added and ultrasonically dispersed (ultrasonic frequency of 40-50 kHz and ultrasonic power of 50-100 W) for 30-40 min to obtain a pre-assembled solution.

[0056] In some embodiments, a crosslinking agent solution is added to a pre-assembled solution containing Tb@Zn-MOF, and the mixture is stirred at 20-25°C for 12-15 hours and then allowed to stand for 2-4 hours to allow phenyltriethoxysilane to undergo hydrolysis and condensation reactions, forming a molecularly imprinted layer on the surface of Tb@Zn-MOF. After the reaction is complete, the product is centrifuged and washed with acetonitrile until no benzo[a]pyrene template residue is detected in the washing solution. The obtained product is dried at 60-80°C for 10-12 hours to obtain Tb@Zn-MOF@MIPs molecularly imprinted dual-emission fluorescent material.

[0057] In some embodiments, the mass-to-volume ratio of the zinc-based metal-organic framework material, the terbium salt, and the first solvent is (100~120) mg:(100~120) mg:(4~6) mL;

[0058] The mass-to-volume ratio of benzo[a]pyrene, Tb@Zn-MOF dual-emission fluorescent material, phenyltriethoxysilane, second solvent, tetraethyl orthosilicate, ethanol, water, and ammonia is (25~30) mg:(100~110) mg:(97~107) μL:(50~60) mL:(210~220) μL:(2~5) mL:(100~110) μL:(30~40) μL, and the mass fraction of ammonia is 25~28%.

[0059] Terbium salts include at least one of terbium nitrate hexahydrate, terbium nitrate, terbium chloride, and terbium chloride trihydrate;

[0060] The first solvent includes at least one of N,N-dimethylformamide and N,N-dimethylacetamide;

[0061] The second solvent includes at least one of ethanol, n-propanol, and isopropanol.

[0062] In some embodiments, zinc iodide, 4,4'-(1H-1,2,4-triazol-3,5-diyl)bisbenzoic acid, and acetic acid are added to a third solvent and reacted at 80-90°C for 60-72 h to obtain a light white transparent blocky product. After the reaction is completed, the product is centrifuged, washed three times with N,N-dimethylformamide, and dried at 60-80°C for 10-12 h to obtain a white powdery Zn-MOF.

[0063] The third solvent includes N,N-dimethylformamide and ethanol;

[0064] The mass-to-volume ratio of zinc iodide, 4,4'-(1H-1,2,4-triazol-3,5-dimethyl)bisbenzoic acid, acetic acid, N,N-dimethylformamide and ethanol was (160~170) mg:(75~85) mg:(150~160) μL:(15~25) mL:(5~15) mL.

[0065] Further reference Figure 1 As shown, it is a schematic diagram of the preparation process of the Tb@Zn-MOF@MIPs molecularly imprinted dual-emission fluorescent material of the present invention; specifically, using Zn 2+ Zn-MOF was synthesized by coordination with TDA (4,4'-(1H-1,2,4-triazol-3,5-diyl)bisbenzoic acid) ligand via Tb 3+Post-modification yielded a blue-green dual-emission Tb@Zn-MOF. Using B[a]P as a template, PTES (phenyltriethoxysilane) as a functional monomer, and TEOS (tetraethyl orthosilicate) as a crosslinking agent, a molecularly imprinted silicon layer was coated onto the surface of Tb@Zn-MOF using a sol-gel method. After template elution, Tb@Zn-MOF@MIPs fluorescent sensing material was obtained. This material can specifically recognize and bind B[a]P, generating a fluorescence quenching response. It can be regenerated for detection after template elution with organic solvents. Specifically, during detection, B[a]P in the test solution enters the imprinted cavity and is specifically adsorbed through π-π stacking and hydrophobic interactions, resulting in fluorescence quenching. 3+ The green fluorescence intensity decreases, and quantification is achieved by relying on the I0 / I ratio; organic solvent washing desorbs B[a]P, the imprinted sites return to a blank state, the fluorescence signal is restored, and the material can be regenerated and reused for detection.

[0066] Based on the same inventive concept, this invention also provides a method for preparing Tb@Zn-MOF@MIPs fluorescent thin films, comprising the following steps:

[0067] The terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material was added to the polymer solution to obtain a mixture;

[0068] Add the mixture into the mold;

[0069] A polyvinyl alcohol solution was added to the surface of the mixture to form a gel, and the solvent was evaporated by heating to obtain a flexible fluorescent film of Tb@Zn-MOF@MIPs.

[0070] The polymer solution includes a polymer and an organic solvent, wherein the polymer includes at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinylidene fluoride-trifluorochloroethylene copolymer;

[0071] The organic solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

[0072] In some embodiments, the polymer is dissolved in an organic solvent to obtain a polymer solution; polyvinyl alcohol is added to water and heated at 90-100°C for 30-40 minutes to obtain a polyvinyl alcohol solution.

[0073] In some embodiments, the above-mentioned terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material Tb@Zn-MOF@MIPs is added to a polymer solution and ultrasonically dispersed (ultrasonic frequency of 40~50kHz, ultrasonic power of 50~100W) for 10~20min to obtain a mixture;

[0074] The mixture was added to a polytetrafluoroethylene mold, and a polyvinyl alcohol solution was added to the surface of the mixture to form a gel. The resulting gel was heated at 60-80℃ for 4-5 hours to evaporate the solvent. After the solvent was completely removed, a Tb@Zn-MOF@MIPs flexible fluorescent film was obtained.

[0075] In some embodiments, the mass-volume ratio of Tb@Zn-MOF@MIPs, polymer, polyvinyl alcohol, organic solvent, and water is (5~10)mg:(100~110)mg:(10~20)mg:(2~5)mL:(1~5)mL.

[0076] Based on the same inventive concept, the present invention also provides the application of terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material prepared by the above preparation method or Tb@Zn-MOF@MIPs fluorescent thin film prepared by the above preparation method in the detection of benzo[a]pyrene.

[0077] Based on the same inventive concept, the present invention also provides a method for detecting benzo[a]pyrene, comprising the following steps:

[0078] The terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material Tb@Zn-MOF@MIPs was dispersed in ethanol and ultrasonically dispersed (ultrasonic frequency 40~50kHz, ultrasonic power 50~100W) for 30~40min. The benzo[a]pyrene test solution was added, and after mixing and incubation for 5~10min, it was transferred to a quartz cuvette. The fluorescence emission spectrum was measured at an excitation wavelength of 306 nm using a fluorescence spectrophotometer, and the fluorescence intensity at 390 nm was recorded. The benzo[a]pyrene content was detected based on the fluorescence intensity.

[0079] Specifically, if the test solution does not contain benzo[a]pyrene, the measured fluorescence intensity is I0. If the test solution contains benzo[a]pyrene, the measured fluorescence intensity is I. The content of benzo[a]pyrene in the test solution is quantitatively detected by using the I0 / I ratio.

[0080] In some embodiments, the present invention also provides a method for detecting benzo[a]pyrene, comprising the following steps:

[0081] The Tb@Zn-MOF@MIPs fluorescent film prepared by the above method was placed in a dark-box ultraviolet analyzer. The benzo[a]pyrene test solution was dropped onto the surface of the fluorescent film. Under 254 nm ultraviolet light irradiation, the film produced a fluorescent color change. Fluorescence images were acquired using a smartphone under fixed shooting position, angle, background and exposure conditions. The benzo[a]pyrene content was detected based on the fluorescence images. Specifically, after acquiring the fluorescence images, the R, G, and B channel values ​​were extracted, the G / B ratio was calculated, and the visual quantitative detection of benzo[a]pyrene in the test solution was realized according to the standard equation between the G / B ratio and the benzo[a]pyrene concentration.

[0082] This invention uses a zinc-based metal-organic framework as the fluorescent host and introduces Tb through a post-modification method. 3+ This invention constructs a fluorescent material with dual emission characteristics. Further, by combining surface molecular imprinting technology, recognition cavities matching the size, shape, aromatic skeleton, and spatial configuration of benzo[a]pyrene molecules are formed on the surface of the fluorescent material. This allows the material to selectively enrich benzo[a]pyrene through hydrophobic interactions, π-π interactions, and spatial matching, converting the target molecule recognition process into fluorescence intensity and color changes. Furthermore, the prepared molecularly imprinted fluorescent material is fabricated into a flexible thin film and combined with smartphone image acquisition and color parameter analysis to achieve rapid, visualized, and portable detection of benzo[a]pyrene. This reduces the dependence on large instruments and provides a new technical solution for on-site screening of benzo[a]pyrene in complex grain and oil samples.

[0083] Specifically, this invention combines dual-emission fluorescence with molecular imprinting: This invention uses Zn-MOF as the fluorescent host and introduces Tb... 3+ A dual-emission system was constructed, and a molecular imprinted layer was formed on its surface, enabling the material to simultaneously possess the functions of selective recognition of benzo[a]pyrene and fluorescence signal output;

[0084] Surface imprinting improves selectivity and response speed: This invention constructs molecular imprinted sites on the surface of Tb@Zn-MOF, which can shorten the mass transfer path of target molecules, improve site utilization and response speed, and reduce interference from structural analogs and complex matrices.

[0085] This invention enhances target recognition through multiple functions: the spatial matching of molecular imprinted cavities, the hydrophobic environment of the material surface, and the interaction between aromatic structures work together to allow benzo[a]pyrene to preferentially accumulate on the surface of the sensing material. After the target molecule enters the imprinted layer and approaches the fluorescent host, it can change the energy and electron transfer process inside the material, thereby causing a significant fluorescence response and improving the sensitivity and recognition ability of the detection.

[0086] The Tb@Zn-MOF@MIPs fluorescent film of the present invention improves the convenience of detection: The present invention makes a flexible film from molecularly imprinted fluorescent material and combines it with smartphone image acquisition and color parameter analysis to realize the visualization and portable quantitative detection of benzo[a]pyrene, reduce the dependence on large instruments, and is suitable for rapid screening and auxiliary detection of benzo[a]pyrene in grain and oil samples.

[0087] The following specific embodiments further illustrate the preparation method of the terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material, the Tb@Zn-MOF@MIPs fluorescent thin film, and the detection method of benzo[a]pyrene according to the present invention. This section further illustrates the content of the present invention in conjunction with specific embodiments, but should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0088] Example 1

[0089] This embodiment provides a method for preparing zinc-based metal-organic framework materials (Zn-MOFs), including the following steps:

[0090] 160 mg of zinc iodide, 75 mg of 4,4'-(1H-1,2,4-triazol-3,5-diyl)bisbenzoic acid, and 150 μL of acetic acid were added to a mixed solvent (i.e., the third solvent) consisting of 15 mL of N,N-dimethylformamide and 5 mL of anhydrous ethanol. The mixture was reacted at 80 °C for 72 h to obtain a light white transparent blocky product. After the reaction was completed, the product was centrifuged, washed three times with N,N-dimethylformamide, and dried at 80 °C for 12 h to obtain a white powdery Zn-MOF, which is the zinc-based metal-organic framework material Zn-MOF.

[0091] Example 2

[0092] This embodiment provides a method for preparing Tb@Zn-MOF dual-emission fluorescent materials, including the following steps:

[0093] 100 mg of Zn-MOF prepared in Example 1 and 100 mg of Tb(NO3)3·6H2O were added to 4 mL of N,N-dimethylformamide and ultrasonically dispersed (ultrasonic frequency 50 kHz, ultrasonic power 100 W) for 3 min. Then the reaction was carried out at 120 °C for 10 h. The reaction product was collected by centrifugation, washed three times with N,N-dimethylformamide, and vacuum dried at 80 °C for 10 h to obtain Tb@Zn-MOF dual-emission fluorescent material.

[0094] Example 3

[0095] This embodiment provides a method for preparing terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent materials, including the following steps:

[0096] S1. Dissolve 25 mg of benzo[a]pyrene and 97 μL of phenyltriethoxysilane in 50 mL of ethanol, stir at 25 °C for 30 min, then add 100 mg of Tb@Zn-MOF dual-emission fluorescent material prepared in Example 2, and ultrasonically disperse (ultrasonic frequency 50 kHz, ultrasonic power 100 W) for 30 min to obtain a pre-assembled solution.

[0097] S2. Dissolve 210 μL of tetraethyl orthosilicate in 2 mL of ethanol, then add 100 μL of water and 30 μL of 28% ammonia solution, stir for 10 min to obtain a crosslinking agent solution.

[0098] S3. Add the crosslinking agent solution from S2 to the pre-assembled solution from S1. Stir the reaction at 25°C for 12 hours, let it stand for 2 hours, collect the product by centrifugation, wash with acetonitrile until no B[a]P residue is detected in the washing solution, and dry under vacuum at 60°C for 12 hours to obtain Tb@Zn-MOF@MIPs, which is a terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material.

[0099] Example 4

[0100] This embodiment provides a method for preparing Tb@Zn-MOF@MIPs fluorescent thin films, including the following steps:

[0101] S1. Dissolve 100 mg of polyvinylidene fluoride (PVDF) in 2 mL of N,N-dimethylformamide to obtain a polymer solution;

[0102] S2. Add 5 mg of Tb@Zn-MOF@MIPs prepared in Example 3 to the polymer solution in S1, and disperse by ultrasonication (ultrasonic frequency 50 kHz, ultrasonic power 100 W) for 10 min to obtain a mixture.

[0103] S3. Add 10 mg of polyvinyl alcohol to 1 mL of water and heat at 100 °C for 30 min to obtain a polyvinyl alcohol solution;

[0104] S4. Add the S2 mixture to the polytetrafluoroethylene mold, add the polyvinyl alcohol solution from S3 to the surface of the mixture to form a gel, heat the resulting gel at 80°C for 4 hours to evaporate the solvent, and after the solvent is completely removed, obtain the Tb@Zn-MOF@MIPs flexible fluorescent film.

[0105] Example 5

[0106] This embodiment provides a method for detecting benzo[a]pyrene, including the following steps:

[0107] S1. Add 5 mg of Tb@Zn-MOF@MIPs prepared in Example 3 to 100 mL of ethanol and disperse by ultrasonication (ultrasonic frequency 50 kHz, ultrasonic power 100 W) for 30 min to obtain Tb@Zn-MOF@MIPs solution.

[0108] S2. Mix 1.9 mL of Tb@Zn-MOF@MIPs solution with 0.1 mL of benzo[a]pyrene test solution, incubate for 5 min, then transfer to a quartz cuvette. Use a fluorescence spectrophotometer to measure the fluorescence emission spectrum of the solution at an excitation wavelength of 306 nm and record the fluorescence intensity at 390 nm.

[0109] If the test solution does not contain benzo[a]pyrene, the measured fluorescence intensity is I0. If the test solution contains benzo[a]pyrene, the measured fluorescence intensity is I. The content of benzo[a]pyrene in the test solution is quantitatively detected by using the I0 / I ratio.

[0110] Example 6

[0111] This embodiment provides a method for detecting benzo[a]pyrene, including the following steps:

[0112] The Tb@Zn-MOF@MIPs fluorescent film prepared in Example 5 was placed in a dark-box ultraviolet analyzer;

[0113] 0.02 mL of benzo[a]pyrene test solution was dropped onto the surface of a fluorescent film. Under 254 nm ultraviolet light irradiation, the film produced a fluorescent color change. Fluorescence images were acquired using a smartphone under fixed shooting position, angle, background and exposure conditions. The R, G and B channel values ​​were extracted, the G / B ratio was calculated, and the visual quantitative detection of benzo[a]pyrene in the test solution was realized according to the standard equation between the G / B ratio and the concentration of benzo[a]pyrene.

[0114] Comparative Example 1

[0115] This comparative example provides a method for preparing Tb@Zn-MOF@NIPs, which is the same as in Example 3, except that benzo[a]pyrene is not added, and the rest of the process is the same as in Example 3.

[0116] Performance testing

[0117] Figure 2 Transmission electron microscope (TEM) images and EDS elemental distribution maps of Zn-MOF, Tb@Zn-MOF, Tb@Zn-MOF@MIPs, and Tb@Zn-MOF@NIPs prepared in Examples 1-3 and Comparative Example 1 are shown. In the figures, A is Zn-MOF, B is Tb@Zn-MOF, C is Tb@Zn-MOF@MIPs, and D is Tb@Zn-MOF@NIPs.

[0118] Figure 2 The results showed that Zn-MOF exhibited a regular, nearly rhomboid blocky structure with uniform elemental distribution; the introduction of Tb... 3+ Afterwards, the material morphology remained basically unchanged, and the Tb element was uniformly distributed, indicating that Tb... 3+ Successful modification; after coating with the imprint layer, the material surface is more dense and a uniform Si element signal appears, proving that the silicon-based imprint layer was successfully formed; Tb@Zn-MOF@MIPs and Tb@Zn-MOF@NIPs have similar overall morphology and elemental composition, the main difference being whether they have benzo[a]pyrene imprint recognition sites.

[0119] Figure 3 The images shown are scanning electron microscope (SEM) images and EDS elemental distribution maps of the Tb@Zn-MOF@MIPs fluorescent thin films prepared in Example 4; where A is the SEM image of the film surface, B is the SEM image of the film edge, C is the EDS mapping image of the total elemental distribution, D is the C elemental distribution map, E is the N elemental distribution map, F is the O elemental distribution map, G is the Zn elemental distribution map, H is the Tb elemental distribution map, and I is the Si elemental distribution map.

[0120] from Figure 3 As can be seen, the surface of the Tb@Zn-MOF@MIPs film is generally smooth and continuous, without obvious cracks or collapses, and possesses a rich microporous structure. The film edge contour is clear, and the film layer is continuous and has a relatively uniform thickness. EDS results show that C, N, O, Zn, Tb, and Si elements are uniformly distributed within the film region, indicating that Tb@Zn-MOF@MIPs are well dispersed in the film and no obvious agglomeration occurs.

[0121] Following the method described in Example 5 above, benzo[a]pyrene test solutions of different concentrations (0.005~20 μmol / L, specifically 0.005 μmol / L, 0.01 μmol / L, 0.1 μmol / L, 0.2 μmol / L, 0.5 μmol / L, 1 μmol / L, 1.5 μmol / L, 2 μmol / L, 5 μmol / L, 10 μmol / L, 15 μmol / L, and 20 μmol / L) were prepared, and the fluorescence emission spectra of the solutions were measured; the results are as follows. Figure 4 As shown, the fluorescence intensity gradually decreased with increasing B[a]P concentration; it exhibited good linearity in the range of 0.005–2 μmol / L, with a detection limit of 0.43 μg / L and a quantitation limit of 1.41 μg / L, respectively.

[0122] Following the method described in Example 6 above, benzo[a]pyrene test solutions of different concentrations (0 μmol / L, 0.1 μmol / L, 0.2 μmol / L, 1 μmol / L, 5 μmol / L, 10 μmol / L, 20 μmol / L, 50 μmol / L, 100 μmol / L, and 200 μmol / L) were prepared. 0.02 mL of the benzo[a]pyrene test solution was dropped onto the surface of the fluorescent film. Under 254 nm ultraviolet light irradiation, the film exhibited a fluorescence color change. Fluorescence images were acquired, and G and B values ​​were extracted for quantitative analysis. The results are as follows: Figure 5 As shown; from Figure 5 As can be seen, with the increase of B[a]P concentration, the fluorescence color of the film gradually changes from yellow-green to blue, and the G / B value decreases accordingly. In the low concentration range of 0.10–20 μmol / L, the G / B value shows a good linear relationship with the B[a]P concentration, and the fitting equation is y = -0.0288x + 1.5619, R0. 2 =0.9906, where y represents the G / B value and x represents the B[a]P concentration; the detection limit and quantitation limit are 8.32 μg / L and 27.72 μg / L, respectively, indicating that this method can achieve rapid, visual and portable quantitative detection of B[a]P.

[0123] It is understood that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0124] The above are merely preferred embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.

Claims

1. A method for preparing a terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material, characterized in that, Includes the following steps: Preparation of zinc-based metal-organic framework materials; The zinc-based metal-organic framework material and terbium salt were added to the first solvent and reacted to obtain the Tb@Zn-MOF dual-emission fluorescent material. Benzo[a]pyrene and phenyltriethoxysilane were dissolved in a second solvent, stirred, and then Tb@Zn-MOF dual-emission fluorescent material was added to obtain a pre-assembled solution. Tetraethyl orthosilicate is dissolved in ethanol, and then water and ammonia are added to obtain a crosslinking agent solution; The crosslinking agent solution was added to the pre-assembled solution, stirred and reacted, washed and dried to obtain Tb@Zn-MOF@MIPs molecularly imprinted dual-emission fluorescent material, which is a terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material.

2. The method for preparing terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent materials as described in claim 1, characterized in that, Zinc iodide, 4,4'-(1H-1,2,4-triazol-3,5-diyl)bisbenzoic acid, and acetic acid were added to a third solvent, reacted, washed, and dried to obtain Zn-MOF, which is a zinc-based metal-organic framework material.

3. The method for preparing terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent materials as described in claim 1, characterized in that, The zinc-based metal-organic framework material and terbium salt were added to the first solvent and reacted at 120-130°C for 10-15 hours. After washing and drying, Tb@Zn-MOF dual-emission fluorescent material was obtained.

4. The method for preparing terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent materials as described in claim 1, characterized in that, The crosslinking agent solution was added to the pre-assembled solution, and the mixture was stirred at 20-25°C for 12-15 hours. After standing for 2-4 hours, the mixture was washed and dried to obtain Tb@Zn-MOF@MIPs molecularly imprinted dual-emission fluorescent material.

5. The method for preparing terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent materials as described in claim 1, characterized in that, The mass-to-volume ratio of the zinc-based metal-organic framework material, the terbium salt, and the first solvent is (100~120) mg:(100~120) mg:(4~6) mL; The mass-to-volume ratio of the benzo[a]pyrene, Tb@Zn-MOF dual-emission fluorescent material, phenyltriethoxysilane, second solvent, tetraethyl orthosilicate, ethanol, water, and ammonia is (25~30) mg:(100~110) mg:(97~107) μL:(50~60) mL:(210~220) μL:(2~5) mL:(100~110) μL:(30~40) μL, and the mass fraction of the ammonia is 25~28%. The terbium salt includes at least one of terbium nitrate hexahydrate, terbium nitrate, terbium chloride, and terbium chloride trihydrate; The first solvent includes at least one of N,N-dimethylformamide and N,N-dimethylacetamide; The second solvent includes at least one of ethanol, n-propanol, and isopropanol.

6. The method for preparing terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material as described in claim 2, characterized in that, Zinc iodide, 4,4'-(1H-1,2,4-triazol-3,5-diyl)bisbenzoic acid, and acetic acid were added to a third solvent and reacted at 80-90℃ for 60-72 h. The mixture was then washed and dried to obtain Zn-MOF. The third solvent includes N,N-dimethylformamide and ethanol; The mass-to-volume ratio of zinc iodide, 4,4'-(1H-1,2,4-triazol-3,5-diyl)bisbenzoic acid, acetic acid, N,N-dimethylformamide and ethanol is (160~170) mg:(75~85) mg:(150~160) μL:(15~25) mL:(5~15) mL.

7. A method for preparing a Tb@Zn-MOF@MIPs fluorescent thin film, characterized in that, Includes the following steps: The terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material prepared by any of the preparation methods described in claims 1 to 6 is added to a polymer solution to obtain a mixture; Add the mixture into the mold; A polyvinyl alcohol solution was added to the surface of the mixture to form a gel, and the solvent was evaporated by heating to obtain a flexible fluorescent film of Tb@Zn-MOF@MIPs. The polymer solution comprises a polymer and an organic solvent, wherein the polymer comprises at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, and polyvinylidene fluoride-trifluorochloroethylene copolymer. The organic solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone.

8. The application of a terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material prepared by any of the preparation methods described in claims 1 to 6, or a Tb@Zn-MOF@MIPs fluorescent film prepared by the preparation method described in claim 7, in the detection of benzo[a]pyrene.

9. A method for detecting benzo[a]pyrene, characterized in that, Includes the following steps: The terbium-modified zinc-based metal-organic framework surface molecularly imprinted fluorescent material prepared by any of the preparation methods described in claims 1 to 6 is dispersed in ethanol, and a benzo[a]pyrene test solution is added. The fluorescence emission spectrum is measured at an excitation wavelength of 306 nm, and the fluorescence intensity at 390 nm is recorded. The benzo[a]pyrene content is detected based on the fluorescence intensity.

10. A method for detecting benzo[a]pyrene, characterized in that, Includes the following steps: The Tb@Zn-MOF@MIPs fluorescent film prepared by the preparation method described in claim 7 was placed in a dark-box ultraviolet analyzer. The benzo[a]pyrene test solution was dropped onto the surface of the fluorescent film. Under 254 nm ultraviolet light irradiation, the film produced a fluorescent color change. The fluorescence image was collected, and the benzo[a]pyrene content was detected based on the fluorescence image.

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