Dioxin SERS (Surface Enhanced Raman Scattering) sensing analysis method and device based on fluorine functionalized MOF (Metal Organic Framework)

Abstract

The invention is applicable to the technical field of environmental pollutant detection, and provides a dioxin SERS (Surface Enhanced Raman Scattering) sensing analysis method and device based on fluorine-functionalized MOFs (Metal Organic Frames.The method comprises the following steps: synthesizing a zirconium-based-MOF or iron-based-MOF carrier through a solvothermal method, carrying out fluorine-containing functional modification, loading a noble metal nanostructure unit in situ, and preparing a fluorine-containing functionalized MOF composite material; after a to-be-detected sample is subjected to surfactant dispersion pretreatment, 2, 3, 7, 8-TCDD is captured through the synergistic effect of F-Cl halogen bonds and pi-pi accumulation of the composite material, and ultra-trace sensing analysis is achieved in combination with SERS. The invention solves the problems of low sensitivity, complex operation and insufficient stability in the prior art, and is suitable for ultra-trace sensing analysis of 2, 3, 7, 8-TCDD in sample matrixes such as food, water, soil and the like.

Description

Technical Field

[0001] This invention relates to the field of environmental pollutant detection technology, specifically a dioxin SERS sensing and analysis method and device based on fluorinated functionalized MOFs. Background Technology

[0002] Dioxins (2,3,7,8-TCDD) are among the most toxic persistent organic pollutants (POPs), with a toxicity equivalent (TEQ) of 1. They are highly carcinogenic, teratogenic, and endocrine disruptive, posing serious threats to the environment and human health even at trace concentrations. 2,3,7,8-TCDD primarily originates from waste incineration, chemical production, and metal smelting processes. It easily accumulates in food, soil, water bodies, and sediments and is difficult to degrade naturally. Therefore, establishing rapid, highly sensitive, and highly specific detection methods is of significant practical importance. Existing detection methods for 2,3,7,8-TCDD mainly include high-resolution gas chromatography-high-resolution magnetic mass spectrometry (HPLC-HPLC-MS / MS) and two-dimensional gas chromatography combined with time-of-flight mass spectrometry (TOF-MS). While these methods offer extremely high sensitivity, they involve complex sample pretreatment (involving multiple steps such as extraction, multiple purification, and concentration), analysis cycles of 3-4 days per sample, expensive instruments, and reliance on specialized operators, making rapid on-site detection difficult.

[0003] In recent years, SERS sensing technology has attracted much attention in pollutant detection due to its advantages such as fingerprint recognition characteristics, fast detection speed, and high sensitivity. However, SERS detection of 2,3,7,8-TCDD still faces core challenges:

[0004] (1) 2,3,7,8-TCDD is extremely hydrophobic and has difficulty in effectively contacting SERS substrates;

[0005] (2) The Raman scattering cross section of the 2,3,7,8-TCDD molecule is small, making it difficult to specifically capture, resulting in low enhanced sensitivity and poor anti-interference ability;

[0006] (3) Existing SERS substrates (such as pure noble metal nanoparticles and ordinary MOF composites) lack targeted structural design and cannot achieve specific enrichment and signal enhancement of 2,3,7,8-TCDD.

[0007] In existing technologies, fluorine-modified MOF materials are mainly used in gas separation and electrolyte membrane preparation, without addressing dioxin analysis and sensing. Furthermore, research combining MOFs with SERS technology primarily targets compounds such as PCB-77 and pesticide / veterinary drug residues, lacking specific designs for 2,3,7,8-TCDD. Therefore, there is an urgent need to provide a dioxin SERS sensing and analysis method and device based on fluorine-functionalized MOFs to overcome the shortcomings in current practical applications. Summary of the Invention

[0008] The purpose of this invention is to provide a dioxin SERS sensing and analysis method and device based on fluorinated functionalized MOFs, which effectively solves the problems in the background art.

[0009] This invention is implemented as follows: a dioxin SERS sensing and analysis method based on fluorine-functionalized MOFs, the method comprising the following steps:

[0010] Preparation of S1, fluorine-functionalized MOF composite materials:

[0011] S1.1 Precise preparation of MOF support framework: Zirconium-based MOF (Zr-MOF-BDC-NH2) or iron-based MOF (Fe-MOF-TA) is used as support framework and synthesized by solvothermal method;

[0012] S1.2 Post-processing: The synthesized product was ultrasonically washed with DMF and ethanol in sequence, and then vacuum dried to obtain a pure MOF support;

[0013] S1.3 Fluorine functionalization: Fluorine-containing functional groups are modified at the amino or carboxyl sites of MOF ligands through covalent grafting;

[0014] S1.4 In-situ loading of noble metal nanostructures: In-situ reduction and loading of noble metal nanostructures are guided by metal node coordination within the pores of MOF.

[0015] S2, 2,3,7,8-TCDD specific capture:

[0016] S2.1 Pretreatment: Add surfactant to the sample to be tested and disperse ultrasonically;

[0017] S2.2, Capture and Pre-enrichment: The composite material prepared in S1 is mixed with the pretreated sample and stirred. Through the "F→Cl" type linear halogen bond formed by the fluorine-containing functional group and the aromatic ring-Cl atom in the 2,3,7,8-TCDD molecule, the π-π stacking effect of the MOF ligand aromatic ring and the 2,3,7,8-TCDD aromatic ring is coordinated to achieve specific capture of 2,3,7,8-TCDD.

[0018] S3 and SERS analysis:

[0019] Signals were acquired using a Raman spectrometer. The characteristic Raman absorption shift of 2,3,7,8-TCDD was used as the basis for qualitative identification, and a standard curve constructed by the characteristic peak intensity and the concentration of 2,3,7,8-TCDD was used for quantitative analysis.

[0020] As a further aspect of the present invention: In S1.1, the synthesis conditions for Zr-MOF-BDC-NH2 are as follows:

[0021] Using N,N-dimethylformamide as solvent and acetic acid as regulator, the molar ratio of 2-aminoterephthalic acid to zirconium chloride was 1:(1.2~1.5), the reaction temperature was 120-140℃, the reaction time was 24-36h, and the pore size after synthesis was 1.8-2.2nm.

[0022] The synthesis conditions for Fe-MOF-TA are as follows:

[0023] Using a mixture of deionized water and DMF as solvent, formic acid as regulator, the molar ratio of trimesic acid to ferric nitrate was 1:(2.5~3.0), the reaction temperature was 100~120℃, the reaction time was 18~24h, and the pore size after synthesis was 2.5~3.0nm.

[0024] As a further aspect of the present invention: In S1.3, the fluorine-containing functional group is an amine compound modified with a perfluoroalkyl chain, specifically:

[0025] For Zr-MOF-BDC-NH2, the amino group in its 2-aminoterephthalic acid ligand reacts with 3,3,3-trifluoropropylamine via an amidation reaction to form the "-NH-CO-CH2-CH2-CF3" structure.

[0026] For Fe-MOF-TA, the carboxyl group in its pyromellitic acid ligand is modified by perfluorohexylamine via an esterification reaction.

[0027] As a further aspect of the present invention: in S1.4, the noble metal nanostructure has a particle size of 30~60nm, and its surface is modified with mercaptoacetic acid and stabilized by hydrogen bonding between the mercapto group and the amino group of the MOF ligand.

[0028] As a further aspect of the present invention: in S2.1, the mass-volume ratio of the added surfactant is 0.01~0.1%, the ultrasonic dispersion power is 150~200W, and the time is 5~10min.

[0029] As a further aspect of the present invention: in S2.2, the stirring conditions are: pH=5~7 and stirring temperature is 25~30℃.

[0030] As a further aspect of the present invention: in S2.2, the amount of the composite material added is 0.3~0.8g / L, the stirring speed is 150-200rpm, and the time is 20~30min;

[0031] The bond angle of the “F→Cl” type linear halogen bond is 170°~180°, and the interaction strength is 8-15kJ / mol.

[0032] As a further aspect of the present invention: In S3, the excitation wavelength of the Raman spectrometer is 633 nm or 785 nm, the power is 10~30 mW, and the integration time is 10~20 s; the characteristic Raman absorption shift includes aromatic ring skeleton vibrations of 1350~1550 cm⁻¹. -1 The C-Cl bond vibrates at 500~550 cm. -1 The detection limit is 0.1~0.2ppt.

[0033] The present invention also provides a dioxin SERS sensing and analysis device based on fluorine-functionalized MOF to implement the above method, comprising:

[0034] (1) Fluorine-functionalized MOF composite substrate: made of fluorine-functionalized MOF composite material, the substrate is arrayed, each unit has interconnected porous channels, and is fixed to the surface of a quartz sheet;

[0035] (2) Pretreatment module: Built-in ultrasonic dispersion unit and surfactant concentration control unit;

[0036] (3) SERS detection module: emits 633nm or 785nm wavelength laser, and the spot diameter is adjustable in the range of 5~20μm;

[0037] (4) Signal acquisition and intelligent analysis module: used to acquire characteristic Raman shifts and perform intelligent analysis.

[0038] As a further aspect of the present invention: the array surface of the fluorinated MOF composite substrate is provided with polydimethylsiloxane microchannels, the microchannels having a width of 100~200μm and a depth of 50~100μm, for controlling the flow rate of the pretreated sample to be 0.05~0.5mL / min;

[0039] The signal acquisition and intelligent analysis module incorporates a deep learning algorithm model based on CNN convolutional neural networks for noise reduction and feature peak identification.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. Innovative capture mechanism with high specificity: For the first time, the "F→Cl halogen bond between fluorine-containing functional groups and dioxin aromatic ring-Cl" is combined with "π-π stacking of MOF ligand aromatic ring and dioxin", which synergistically achieves specific capture of 2,3,7,8-TCDD by van der Waals forces, effectively avoiding the influence of interfering substances such as polychlorinated biphenyls and solving the problem of poor specificity of existing technologies;

[0042] 2. High detection sensitivity: Detection is achieved through the high specific surface area of ​​MOFs (1500-2500 m²). 2 / g) to achieve pre-enrichment of 2,3,7,8-TCDD, combined with the "hot spot" enhancement effect of noble metal nanostructures, the detection limit is as low as 0.1-0.2ppt, far exceeding the existing ELISA method (ppb concentration level) and some SERS detection methods (ppm concentration level).

[0043] 3. Excellent stability: The fluorine-functionalized MOF composite material is structurally stable in the pH range of 5 to 7, with metal ion leaching amount ≤0.01mg / L. After being stored at room temperature for 1 month, its performance does not show significant degradation. After being reused 5 times, the signal intensity still maintains more than 92% of the initial value, which solves the problem of poor stability of antibody labeling methods.

[0044] 4. Simple and fast detection process: Sample pretreatment only takes 5-10 minutes, and the entire capture and detection process takes ≤2 hours. There is no need for complicated extraction and purification steps. Moreover, the device is highly integrated and can realize rapid on-site detection.

[0045] 5. Controllable cost: No expensive antibodies or large precision instruments are required. The composite material preparation process is simple and can be mass-produced. The detection cost is far lower than traditional mass spectrometry detection methods such as high-resolution gas chromatography and high-resolution magnetic mass spectrometry. Attached Figure Description

[0046] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0047] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0048] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0049] The present invention will be further explained below with reference to specific embodiments.

[0050] Please see Figure 1 This invention provides a dioxin SERS sensing and analysis method based on fluorine-functionalized MOFs, which includes the following steps:

[0051] Preparation of S1 and fluorine-functionalized MOF composite materials

[0052] S1.1 Precise preparation of MOF support framework: Using zirconium-based MOF (Zr-MOF-BDC-NH2) or iron-based MOF (Fe-MOF-TA) as support framework, it was synthesized by solvothermal method under the following conditions:

[0053] a:Zr-MOF-BDC-NH2: Using N,N-dimethylformamide (DMF) as solvent and acetic acid (AA) as regulator (DMF:AA = 10:1 (V:V)), the molar ratio of 2-aminoterephthalic acid to zirconium chloride (ZrCl4) was 1:(1.2~1.5). The reaction temperature was 120-140℃, the reaction time was 24-36h, and the reaction pressure was 0.1-0.3MPa. After synthesis, the pore size was precisely controlled to 1.8-2.2nm, with an error of ±0.2nm compared to the molecular dynamic diameter of 2,3,7,8-TCDD (~1.8nm).

[0054] b: Fe-MOF-TA: Using a mixture of deionized water and DMF (V:V=1:2) as solvent, formic acid (FA) as regulator (FA:mixed solvent=1:15(V:V)), the molar ratio of trimesic acid to ferric nitrate (Fe(NO3)3·9H2O) is 1:(2.5~3.0), the reaction temperature is 100~120℃, the reaction time is 18~24h, the reaction pressure is 0.1~0.2MPa, and the pore size after synthesis is 2.5~3.0nm.

[0055] S1.2 Post-treatment: The synthesized product was ultrasonically washed three times (15 min each time) with DMF and ethanol, and then vacuum dried (80-100℃, 12-24 h) to obtain a specific surface area of ​​1500-2500 m². 2 / g, pure MOF support with a porosity ≥80%;

[0056] S1.3 Fluorine functionalization: Fluorine-containing functional groups are covalently grafted onto the amino or carboxyl sites of the MOF ligand. These fluorine-containing functional groups are amine compounds modified with perfluoroalkyl chains, specifically:

[0057] In the 2-aminoterephthalic acid ligand of a:Zr-MOF-BDC-NH2, the amino group reacts with 3,3,3-trifluoropropylamine via an amidation reaction to form a "-NH-CO-CH2-CH2-CF3" structure. Using dichloromethane as solvent and EDC as condensing agent, the reaction is carried out at 25-30℃ for 8-12 hours, with a grafting density of 0.8-1.2 mmol / g.

[0058] b: In the pyromellitic acid ligand of Fe-MOF-TA, the carboxyl group is modified with perfluorohexylamine via esterification reaction. The reaction conditions are toluene as solvent, p-toluenesulfonic acid as catalyst, reflux at 110~120℃ for 12~16h, and the grafting density is 1.0-1.5mmol / g.

[0059] S1.4 In-situ loading of noble metal nanostructures: Noble metal nanostructures are in-situ reduced and loaded within the pores of the MOF through coordination at metal nodes. The noble metal nanostructures (such as nanostars or silver nanocubes) have a particle size of 30–60 nm and are surface-modified with thioglycolic acid, which is stabilized by hydrogen bonds formed between the thiol groups and the amino groups of the MOF ligands. During this process, a noble metal ion solution (5–10 mmol / L) is added to the MOF dispersion (dropping rate 0.5–1 mL / min), and the molar ratio of the reducing agent (such as sodium borohydride) to the noble metal ions is controlled at (3–5):1, with a loading amount of 5–15 wt%.

[0060] S2, 2,3,7,8-TCDD specific capture

[0061] S2.1 Add a surfactant (such as Tween-80) at a mass-volume ratio of 0.01~0.1% to the sample to be tested, and ultrasonically disperse it at a power of 150~200W for 5~10min to promote the uniform dispersion of 2,3,7,8-TCDD molecules.

[0062] S2.2. The composite material prepared in step one is mixed with the pretreated sample and stirred magnetically at 150-200 rpm for 20-30 min at pH 5-7 and 25-30℃ (the amount of composite material added is 0.3-0.8 g / L). The lone pair electrons of the fluorine-containing functional group form a linear halogen bond of type "F→Cl" with a bond angle of 170°-180° and an interaction strength of 8-15 kJ / mol with the aromatic ring-Cl atom in the 2,3,7,8-TCDD molecule. This synergistic effect of the π-π stacking of the MOF ligand aromatic ring and the 2,3,7,8-TCDD aromatic ring and the van der Waals forces achieves the specific capture of 2,3,7,8-TCDD. The synergistic effect of the halogen bond and the π-π stacking is the core mechanism of specific recognition.

[0063] S3 and SERS analysis

[0064] The Raman spectrometer used an excitation wavelength of 633 nm or 785 nm, a power of 10–30 mW, and an integration time of 10–20 s. The characteristic Raman absorption shift of 2,3,7,8-TCDD (aromatic ring skeleton vibration 1350–1550 cm⁻¹) was observed. -1 The C-Cl bond vibration is 500~550 cm⁻¹ -1 Using characteristic peak intensity and 2,3,7,8-TCDD concentration as the basis for qualitative identification, a standard curve (R0) was constructed.2 Quantitative analysis can be achieved with a detection limit of 0.1~0.2 ppt (≥0.99).

[0065] In a more specific example, the fluorinated MOF composite material prepared in step one has a zeta potential of -10mV to +5mV, is structurally stable in the pH range of 5-7, and has a metal ion dissolution rate of ≤0.01mg / L. XRD characterization shows that the characteristic diffraction peaks of the fluorinated Zr-MOF-BDC-NH2 composite material are 2θ=7.3°, 8.5°, and 25.8°, and the characteristic diffraction peaks of the fluorinated Fe-MOF-TA composite material are 2θ=9.1°, 10.3°, and 18.5°.

[0066] This invention also provides a dioxin SERS sensing and analysis device based on fluorine-functionalized MOFs to implement the above method, characterized in that it includes:

[0067] (1) Fluorine-functionalized MOF composite substrate: made of the above-mentioned composite material, the substrate is arrayed (array unit size is 50~100μm), each unit has interconnected porous channels with the same size as MOF pores, and is fixed to the surface of quartz sheet by sol-gel method (fixed layer thickness is 20~50μm, adhesion ≥1.5MPa).

[0068] (2) Pretreatment module: The surfactant is used to disperse the sample to be tested. It has an built-in ultrasonic dispersion unit (power of 150~200W, dispersion time of 5~10min) and a concentration control unit (controlling the amount of Tween-80 added to 0.01~0.1%).

[0069] (3) SERS detection module: excited by 633nm or 785nm laser, with the spot diameter adjustable in the range of 5~20μm;

[0070] (4) Signal Acquisition and Intelligent Analysis Module: Acquires characteristic Raman shifts of 2, 3, 7, 8-TCDD, incorporates a deep learning algorithm model based on CNN convolutional neural network, and performs noise reduction and characteristic peak identification (characteristic peak region is located at 1350-1550cm). -1 and 500-550cm -1 This enables qualitative and quantitative analysis.

[0071] In a more specific example, the array surface of the fluorinated MOF composite substrate is provided with polydimethylsiloxane (PDMS) microchannels, with a width of 100~200μm and a depth of 50~100μm, to control the flow rate of the pretreated sample to 0.05~0.5mL / min, prolong the contact time between 2,3,7,8-TCDD and the composite substrate, and promote the synergistic capture effect of "F→Cl halogen bond + π-π stacking".

[0072] Example 1: 2,3,7,8-TCDDSERS Sensing Analysis Based on Zr-MOF-BDC-NH2

[0073] 1.1 Materials and Instruments

[0074] 1.1.1 Reagents: 2-Aminoterephthalic acid (purity ≥98%), zirconium chloride (ZrCl4, purity ≥99%), N,N-dimethylformamide (DMF, analytical grade), glacial acetic acid (analytical grade), 3,3,3-trifluoropropylamine (purity ≥97%), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC, purity ≥98%), chloroauric acid (HAuCl4·4H2O, purity ≥99%), sodium borohydride (NaBH4, purity ≥98%), mercaptoacetic acid (purity ≥98%), Tween-80 (analytical grade), 2,3,7,8-TCDD standard (purity ≥99.5%), ultrapure water (resistivity ≥18.2 MΩ·cm).

[0075] 1.1.2 Instruments: Solvent thermal reactor (50mL, PTFE liner), vacuum drying oven, ultrasonic cleaner, magnetic stirrer, transmission electron microscope (TEM), X-ray diffractometer (XRD), surface area and porosity analyzer (BET), Zeta potentiometer, Raman spectrometer (excitation wavelength 633nm / 785nm), electronic balance (accuracy 0.0001g).

[0076] 1.2 Preparation of Fluorine-Functionalized Zr-MOF-BDC-NH2 Composite Materials

[0077] 1.2.1 Synthesis of Zr-MOF-BDC-NH2 support framework

[0078] Weigh 0.5 mmol (0.087 g) of 2-aminoterephthalic acid and 0.65 mmol (0.152 g) at a molar ratio of 1:1.3, add them to the lining of a 50 mL reaction vessel, add 20 mL of DMF as solvent, and then add 2 mL of glacial acetic acid (1:10 volume ratio with DMF) as a regulator. Sonicate the mixture for 10 min to ensure complete dissolution of the raw materials. Seal the reaction vessel and place it in an oven at 130 °C for 30 h (reaction pressure 0.2 MPa). After the reaction, allow it to cool naturally to room temperature, centrifuge to collect the precipitate, and wash it three times each with DMF and ethanol (15 min each time) ultrasonically to remove unreacted raw materials and impurities. Then dry it in a vacuum drying oven at 90 °C for 18 h to obtain pure Zr-MOF-BDC-NH2 support. BET characterization showed that the specific surface area of ​​this support was 2200 m². 2 / g, porosity 85%, pore size 1.9nm (0.1nm error compared to the molecular dynamic diameter of 2,3,7,8-TCDD ~1.8nm); XRD characterization showed characteristic diffraction peaks at 2θ=7.3°, 8.5°, and 25.8°.

[0079] 1.2.2 Fluorine functionalization modification

[0080] 0.2 g of Zr-MOF-BDC-NH2 support was dispersed in 20 mL of dichloromethane. 0.3 mmol of 3,3,3-trifluoropropylamine and 0.4 mmol of EDC condensing agent were added, and the mixture was magnetically stirred at 28 °C for 10 h. After the reaction, the product was collected by centrifugation, washed three times with dichloromethane to remove ungrafted fluorinated reagents and condensing agents, and dried under vacuum at 80 °C for 12 h to obtain fluorinated Zr-MOF-BDC-NH2. Elemental analysis showed that the grafting density of fluorinated functional groups was 1.0 mmol / g, and the modified material retained the crystalline structure of Zr-MOF-BDC-NH2 (no significant shift in XRD characteristic peaks).

[0081] 1.2.3 In-situ loading of nanostars

[0082] Prepare an 8 mmol / L chloroauric acid solution. Take 5 mL of this solution and add it dropwise to 20 mL of fluorinated Zr-MOF-BDC-NH2 dispersion (concentration 10 mg / mL) at a rate of 0.8 mL / min. Stir for 30 min to allow Au to settle. 3+ Zr with fluorinated Zr-MOF-BDC-NH2 4+ Metal nodes form coordination interactions. Subsequently, a 24 mmol / L NaBH4 solution (Au) was prepared. 3+A 1:3 molar ratio of gold nanostars to NaBH4 was rapidly added to the above mixture, and the mixture was stirred at room temperature for 2 h to achieve in-situ reduction loading of gold nanostars. After the reaction, the product was collected by centrifugation, washed three times with ultrapure water, and dried under vacuum at 60 °C for 8 h. TEM characterization showed that the gold nanostars had a particle size of 45 nm and were uniformly dispersed in the pores and surface of fluorinated Zr-MOF-BDC-NH2 without obvious agglomeration. XPS characterization confirmed that thioglycolic acid formed hydrogen bonds with the amino groups of the Zr-MOF-BDC-NH2 ligand through the thiol groups, with a loading of 10 wt%.

[0083] 1.32,3,7,8-TCDD-specific capture

[0084] 1.3.1 Sample Pretreatment

[0085] Take 10 mL of the water sample to be tested (containing 2,3,7,8-TCDD), add 0.005 g of Tween-80 (0.05% by volume), and ultrasonically disperse at 180 W for 8 min to ensure uniform dispersion of 2,3,7,8-TCDD molecules and avoid aggregation.

[0086] 1.3.2 Capture and Pre-enrichment

[0087] 0.005 g of fluorinated Zr-MOF-BDC-NH2 composite material (0.5 g / L) was added to the pretreated sample, and the pH of the solution was adjusted to 6.0. The mixture was then magnetically stirred at 180 rpm for 25 min at 28 °C. During the reaction, the composite material formed a linear halogen bond of type "F→Cl" with a bond angle of 175° and an interaction strength of 12 kJ / mol with the -Cl of the fluorinated functional group. This synergistic effect with the π-π stacking of the Zr-MOF-BDC-NH2 ligand and 2,3,7,8-TCDD achieved specific capture and pre-enrichment of 2,3,7,8-TCDD. After the reaction, the composite material was collected by centrifugation (8000 rpm, 5 min) and washed twice with ultrapure water to remove uncaptured impurities.

[0088] 1.4 SERS Analysis

[0089] The composite material after capturing 2,3,7,8-TCDD was uniformly coated onto a quartz slide, dried, and then placed on the sample stage of a Raman spectrometer. SERS spectra were acquired using an excitation wavelength of 785 nm, a laser power of 20 mW, and an integration time of 15 s. The results showed that at 520 cm⁻¹... -1 Characteristic vibrational peaks of C-Cl bonds of 2,3,7,8-TCDD appear at 1450 cm⁻¹. -1A characteristic peak of aromatic ring skeletal vibration appeared at [location], with no obvious background interference. Plotting the concentrations of 2,3,7,8-TCDD standards (0.1 ppt, 0.5 ppt, 1 ppt, 5 ppt, 10 ppt) on the x-axis, the characteristic Raman absorption shift (1450 cm⁻¹) was [value]. -1 Using intensity as the ordinate, construct a standard curve and calculate the goodness of fit R. 2 =0.996. The test results for the water sample showed a concentration of 0.3 ppt, consistent with the results of high-resolution gas chromatography-high-resolution magnetic mass spectrometry verification, with a detection limit as low as 0.1 ppt.

[0090] 1.5 Performance Verification

[0091] 1.5.1 Specificity: Adding equal concentrations of polychlorinated biphenyls (PCB-77) and phenol to a water sample containing 2,3,7,8-TCDD (0.5 ppt) and detecting it using the method described above, the specificity was only observed at a depth of 520 cm³. -1 and 1450cm -1 The presence of the target characteristic peak at the location and the absence of obvious signal response from interfering substances demonstrate the good specificity of this method.

[0092] 1.5.2 Stability: After soaking in the fluorine-functionalized Zr-MOF-BDC-NH2 composite material for 72 h in the pH range of 5-7, the XRD characteristic peaks did not change, the metal ion dissolution was 0.008 mg / L, and after repeated use 5 times, the detection signal intensity still maintained 92% of the initial value, showing excellent stability.

[0093] Example 2: 2,3,7,8-TCDDSERS Sensing Analysis Based on Iron-based MOF (Fe-MOF-TA)

[0094] 1. Preparation of Fe-MOF-TA composite materials

[0095] 1.1 Synthesis of Fe-MOF-TA Support Framework

[0096] Weigh out 0.5 mmol (0.126 g) of trimesic acid and 1.4 mmol (0.651 g) of Fe(NO3)3·9H2O at a molar ratio of 1:2.8, add them to the lining of a 50 mL reaction vessel, add 15 mL of a mixed solvent of deionized water and 30 mL of DMF (volume ratio 1:2), and then add 3 mL of formic acid (volume ratio 1:15 with the mixed solvent) as a regulator. Disperse the mixture ultrasonically for 15 min. Seal the reaction vessel and place it in an oven at 110 °C for 21 h (pressure 0.15 MPa). After the reaction, cool to room temperature, centrifuge to collect the precipitate, wash three times successively with DMF and ethanol, and dry under vacuum at 100 °C for 20 h to obtain pure Fe-MOF-TA support. BET characterization showed a specific surface area of ​​~2000 m². 2 / g, porosity 82%, pore size 2.8nm.

[0097] 1.2 Fluorine functionalization modification

[0098] 0.2 g of Fe-MOF-TA support was dispersed in 25 mL of toluene, and 0.4 mmol of perfluorohexylamine and 0.3 mmol of p-toluenesulfonic acid catalyst were added. The mixture was refluxed at 115 °C for 14 h. After the reaction was completed, the product was collected by centrifugation, washed three times with toluene, and dried under vacuum at 90 °C for 14 h to obtain fluorinated Fe-MOF-TA with a fluorinated functional group grafting density of 1.3 mmol / g.

[0099] 1.3 In-situ loading of silver nanocubes

[0100] Prepare a 6 mmol / L silver nitrate solution. Take 6 mL of the solution and add it dropwise to 20 mL of fluorinated Fe-MOF-TA dispersion (concentration 10 mg / mL) at a rate of 0.6 mL / min. Stir for 40 min to allow the Ag to dissolve. + Fe with Fe-MOF-TA 3+ Metal node coordination. Preparation of 24 mmol / L NaBH4 solution (Ag) + Silver nanocubes were added to a mixture at a molar ratio of 1:4 with NaBH4 and reacted at room temperature for 2.5 h to achieve in-situ loading. TEM characterization showed that the silver nanocubes had a particle size of 50 nm, a loading of 12 wt%, and were uniformly dispersed within the pores of the fluorine-functionalized Fe-MOF-TA composite material.

[0101] 2. Capture and SERS Analysis

[0102] 2.1 Sample pretreatment: Add 0.008 g Tween-80 (0.08% by mass / volume) to 10 mL of the water sample to be tested, and disperse by ultrasonication at 190 W for 7 min.

[0103] 2.2 Capture and pre-enrichment: Add 0.006 g of fluorine-functionalized Fe-MOF-TA composite material (dosage 0.6 g / L), adjust pH to 5.5, and stir at 170 rpm for 22 min at 27 °C.

[0104] 2.3 SERS Detection: A 633 nm excitation wavelength, 15 mW laser power, and 12 s integration time were used to acquire the spectrum. The results showed that the C-Cl bond in 2,3,7,8-TCDD (at 530 cm⁻¹) was... -1 ) and aromatic ring skeleton vibration (1420cm) -1 The characteristic peaks are clear, and the standard curve fit is good (R). 2 =0.994, detection limit as low as 0.2ppt, specificity and stability are comparable to those of Example 1.

[0105] Comparative experiments: Three sets of comparative experiments were set up to verify the innovativeness and superiority of the present invention:

[0106] 1. Comparative Group 1 (Zr-MOF-BDC-NH2 without fluorine modification): Zr-MOF-BDC-NH2@gold nanostar composite material without fluorine functional groups was used. The 0.5ppt 2,3,7,8-TCDD was detected according to the method of Example 1. The characteristic peak intensity was only 35% of that of Example 1, and the capture time was extended to 60 min, which proves that the "F→Cl" halogen bond of the fluorine functional group has the effect of improving the capture efficiency.

[0107] 2. Comparative Group 2 (without noble metal nanostructure loading): Fluorine-functionalized Zr-MOF-BDC-NH2 (without gold nanostar loading) was used. 0.5ppt2,3,7,8-TCDD was detected, and no obvious characteristic peak was detected, proving that the LSPR enhancement effect of gold nanostars is the key to signal detection.

[0108] 3. Comparison Group 3 (Prior Technology: Antibody-labeled SERS Detection): Using magnetic microbeads + silver nanoprobes labeled with 2,3,7,8-TCDD antibody, the detection limit of 0.5 ppt 2,3,7,8-TCDD was 5 ppt. The antibody activity decreased by 50% after being stored at room temperature for 1 week, while the composite material of the present invention showed no significant performance degradation after being stored at room temperature for 1 month, demonstrating the advantages of the present invention in terms of sensitivity and stability.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dioxin SERS sensing and analysis method based on fluorine-functionalized MOFs, characterized in that, The method includes the following steps: Preparation of S1, fluorine-functionalized MOF composite materials: S1.1 Precise preparation of MOF support framework: Zirconium-based MOF (Zr-MOF-BDC-NH2) or iron-based MOF (Fe-MOF-TA) is used as support framework and synthesized by solvothermal method; S1.2 Post-processing: The synthesized product was ultrasonically washed with DMF and ethanol in sequence, and then vacuum dried to obtain a pure MOF support; S1.3 Fluorine functionalization: Fluorine-containing functional groups are modified at the amino or carboxyl sites of MOF ligands through covalent grafting; S1.4 In-situ loading of noble metal nanostructures: In-situ reduction and loading of noble metal nanostructures are guided by metal node coordination within the pores of MOF. S2, 2,3,7,8-TCDD specific capture: S2.1 Pretreatment: Add surfactant to the sample to be tested and disperse ultrasonically; S2.2, Capture and Pre-enrichment: The composite material prepared in S1 is mixed with the pretreated sample and stirred. Through the "F→Cl" type linear halogen bond formed by the fluorine-containing functional group and the aromatic ring-Cl atom in the 2,3,7,8-TCDD molecule, the π-π stacking effect of the MOF ligand aromatic ring and the 2,3,7,8-TCDD aromatic ring is coordinated to achieve specific capture of 2,3,7,8-TCDD. S3 and SERS analysis: Signals were acquired using a Raman spectrometer. The characteristic Raman absorption shift of 2,3,7,8-TCDD was used as the basis for qualitative identification, and a standard curve constructed by the characteristic peak intensity and the concentration of 2,3,7,8-TCDD was used for quantitative analysis.

2. The method according to claim 1, characterized in that, In S1.1, the synthesis conditions for Zr-MOF-BDC-NH2 are as follows: Using N,N-dimethylformamide as solvent and acetic acid as regulator, the molar ratio of 2-aminoterephthalic acid to zirconium chloride was 1:(1.2~1.5), the reaction temperature was 120-140℃, the reaction time was 24-36h, and the pore size after synthesis was 1.8-2.2nm. The synthesis conditions for Fe-MOF-TA are as follows: Using a mixture of deionized water and DMF as solvent, formic acid as regulator, the molar ratio of trimesic acid to ferric nitrate was 1:(2.5~3.0), the reaction temperature was 100~120℃, the reaction time was 18~24h, and the pore size after synthesis was 2.5~3.0nm.

3. The method according to claim 1, characterized in that, In S1.3, the fluorine-containing functional group is an amine compound modified with a perfluoroalkyl chain, specifically: For Zr-MOF-BDC-NH2, the amino group in its 2-aminoterephthalic acid ligand reacts with 3,3,3-trifluoropropylamine via an amidation reaction to form the "-NH-CO-CH2-CH2-CF3" structure. For Fe-MOF-TA, the carboxyl group in its pyromellitic acid ligand is modified by perfluorohexylamine via an esterification reaction.

4. The method according to claim 1, characterized in that, In S1.4, the noble metal nanostructure has a particle size of 30~60nm, and its surface is modified with mercaptoacetic acid and stabilized by hydrogen bonds formed between the mercapto groups and the amino groups of the MOF ligand.

5. The method according to claim 1, characterized in that, In S2.1, the surfactant is added at a mass-volume ratio of 0.01~0.1%, the ultrasonic dispersion power is 150~200W, and the time is 5~10min.

6. The method according to claim 1, characterized in that, In S2.2, the stirring conditions are: pH=5~7 and stirring temperature=25~30℃.

7. The method according to claim 1, characterized in that, In step S2.2, the amount of the composite material added is 0.3~0.8 g / L, the stirring speed is 150-200 rpm, and the time is 20~30 min; The bond angle of the "F→Cl" type linear halogen bond is 170°~180°, and the interaction strength is 8-15kJ / mol.

8. The method according to claim 1, characterized in that, In S3, the excitation wavelength of the Raman spectrometer is 633 nm or 785 nm, the power is 10~30 mW, and the integration time is 10~20 s; the characteristic Raman absorption shift includes aromatic ring skeleton vibrations of 1350~1550 cm⁻¹. -1 The C-Cl bond vibrates at 500~550 cm. -1 The detection limit is 0.1~0.2ppt.

9. A dioxin SERS sensing and analysis device based on fluorine-functionalized MOF that implements the method of any one of claims 1-8, characterized in that, include: (1) Fluorine-functionalized MOF composite substrate: made of fluorine-functionalized MOF composite material, the substrate is arrayed, each unit has interconnected porous channels, and is fixed to the surface of a quartz sheet; (2) Pretreatment module: Built-in ultrasonic dispersion unit and surfactant concentration control unit; (3) SERS detection module: emits 633nm or 785nm wavelength laser, and the spot diameter is adjustable in the range of 5~20μm; (4) Signal acquisition and intelligent analysis module: used to acquire characteristic Raman shifts and perform intelligent analysis.

10. The apparatus according to claim 9, characterized in that, The array surface of the fluorinated MOF composite substrate is provided with polydimethylsiloxane microchannels, the width of which is 100~200μm and the depth is 50~100μm, which are used to control the flow rate of the pretreated sample to be 0.05~0.5mL / min. The signal acquisition and intelligent analysis module incorporates a deep learning algorithm model based on CNN convolutional neural networks for noise reduction and feature peak identification.

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