A dioxin SERS sensing analysis method and device based on fluorine-functionalized MOF

Abstract

The application is suitable for the technical field of environmental pollutant detection, and provides a dioxin SERS sensing analysis method and device based on fluorine functionalized MOF.The method synthesizes a zirconium-based-MOF or iron-based-MOF carrier through a solvothermal method, loads a noble metal nano structure unit in situ after fluorine functionalization modification, and prepares a fluorine functionalized MOF composite material;after surfactant dispersion pretreatment of a to-be-detected sample, 2,3,7,8-TCDD is captured through the synergistic effect of the 'F to Cl halogen bond + pi-pi stacking' of the composite material, and SERS is combined to realize ultratrace sensing analysis.The application solves the problems of low sensitivity, complex operation and insufficient stability in the prior art, and is suitable for ultratrace sensing analysis of 2,3,7,8-TCDD in food, water, soil and other sample matrices.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of environmental pollutant detection, and particularly relates to a dioxin SERS sensing analysis method and device based on fluorine-functionalized MOF. BACKGROUND

[0002] Dioxin (2,3,7,8-TCDD) is one of the most toxic persistent organic pollutants (POPs) with a toxicity equivalent (TEQ) of 1, and has strong carcinogenicity, teratogenicity and endocrine disrupting properties. Even at ultra-trace concentration levels, it still causes serious harm to the ecological environment and human health. 2,3,7,8-TCDD is mainly derived from processes such as waste incineration, chemical production and metal smelting, and is easily enriched in food, soil, water and sediments, and is difficult to degrade naturally. Therefore, it is of great practical significance to establish a rapid, highly sensitive and highly specific detection method. The existing detection methods for 2,3,7,8-TCDD mainly include high-resolution gas chromatography-high-resolution mass spectrometry, two-dimensional gas chromatography combined with time-of-flight mass spectrometry, etc. They have extremely high sensitivity, but the sample pretreatment is complex (involving extraction, multiple purification, concentration and other multi-step operations), the analysis period is as long as 3-4 days / sample, the instrument is expensive and depends on professional operators, and it is difficult to realize on-site rapid detection.

[0003] In recent years, the SERS sensing technology developed has attracted much attention in pollutant detection due to its fingerprint identification characteristics, fast detection speed, high sensitivity and other advantages, but the SERS detection of 2,3,7,8-TCDD still faces the following core problems:

[0004] (1) 2,3,7,8-TCDD is extremely hydrophobic and difficult to effectively contact with the SERS substrate;

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

[0006] (3) The existing SERS substrate (such as simple noble metal nanoparticles and ordinary MOF composite materials) has no specific structure design, and cannot realize specific enrichment and signal enhancement of 2,3,7,8-TCDD.

[0007] In the prior art, fluorine-modified MOF materials are mainly used in the fields of gas separation and electrolyte membrane preparation, and are not involved in the analysis and sensing of dioxin. The research on the combination of MOF and SERS technology is mainly aimed at PCB-77, agricultural and veterinary drug residues and other compounds, and there is no specific design for 2,3,7,8-TCDD. Therefore, in view of the above status, it is urgent to provide a dioxin SERS sensing analysis method and device based on fluorine-functionalized MOF to overcome the deficiencies in current practical applications. SUMMARY

[0008] The application aims to provide a dioxin SERS sensing analysis method and device based on fluorine-functionalized MOF, which effectively solves the problems in the background art.

[0009] The application is implemented as follows: a dioxin SERS sensing analysis method based on fluorine-functionalized MOF, which comprises the following steps:

[0010] S1, fluorine-functionalized MOF composite material preparation:

[0011] S1.1, precise preparation of MOF carrier framework: taking zirconium-based MOF (Zr-MOF-BDC-NH2) or iron-based MOF (Fe-MOF-TA) as the carrier framework, solvent thermal synthesis is adopted;

[0012] S1.2, post-processing: the synthesis product is sequentially washed with DMF and ethanol under ultrasonic, and vacuum dried to obtain pure MOF carrier;

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

[0014] S1.4, in-situ loading of noble metal nanostructure: in-situ reduction and loading of noble metal nanostructure in the pores of the MOF through metal node coordination guidance;

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

[0016] S2.1, pretreatment: adding a surfactant to the sample to be detected and ultrasonic dispersion;

[0017] S2.2, capture and pre-enrichment: mixing the composite material prepared in S1 with the pretreated sample and stirring, and realizing specific capture of 2,3,7,8-TCDD through the formation of "F→Cl" type linear halogen bond between the fluorine-containing functional groups and the aromatic ring-Cl atoms in the 2,3,7,8-TCDD molecules, and the synergistic π-π stacking effect of the MOF ligand aromatic ring and the 2,3,7,8-TCDD aromatic ring;

[0018] S3, SERS analysis:

[0019] The signal is collected by a Raman spectrometer, the characteristic Raman absorption shift of 2,3,7,8-TCDD is taken as the qualitative identification basis, and the standard curve constructed by the characteristic peak intensity and the 2,3,7,8-TCDD concentration realizes quantitative analysis.

[0020] As a further scheme of the application: in S1.1, the synthesis conditions of the Zr-MOF-BDC-NH2 are as follows:

[0021] The synthesis conditions of the Fe-MOF-TA are as follows: N,N-dimethylformamide is used as a solvent, acetic acid is used as an adjusting agent, the molar ratio of 2-amino terephthalic acid to zirconium chloride is 1:(1.2-1.5), the reaction temperature is 120-140 DEG C, and the reaction time is 24-36 hours.

[0022] The synthesis conditions of the Fe-MOF-TA are as follows: N,N-dimethylformamide is used as a solvent, acetic acid is used as an adjusting agent, the molar ratio of 2-amino terephthalic acid to zirconium chloride is 1:(1.2-1.5), the reaction temperature is 120-140 DEG C, and the reaction time is 24-36 hours.

[0023] The synthesis conditions of the Fe-MOF-TA are as follows: N,N-dimethylformamide is used as a solvent, acetic acid is used as an adjusting agent, the molar ratio of 2-amino terephthalic acid to zirconium chloride is 1:(1.2-1.5), the reaction temperature is 120-140 DEG C, and the reaction time is 24-36 hours.

[0024] As a further scheme of the application, in S1.3, the fluorine-containing functional group is a perfluoroalkyl chain modified amine compound, specifically:

[0025] For Zr-MOF-BDC-NH2, the amino group in the 2-amino terephthalic acid ligand is acylated with 3,3,3-trifluoropropylamine to form a "-NH-CO-CH2-CH2-CF3" structure.

[0026] For Fe-MOF-TA, the carboxyl group in the trimesic acid ligand is modified by esterification with perfluorohexylamine.

[0027] As a further scheme of the application, in S1.4, the noble metal nanostructure particle size is 30-60 nm, the surface is modified with mercaptoacetic acid, and a hydrogen bond is formed between the mercapto group and the amino group of the MOF ligand to stabilize it.

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

[0029] As a further scheme of the application, in S2.2, the stirring conditions are as follows: pH=5-7, and the stirring temperature is 25-30 DEG C.

[0030] As a further scheme of the application, in S2.2, the composite material dosage is 0.3-0.8 g / L, the stirring speed is 150-200 rpm, and the time is 20-30 min.

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

[0032] As a further scheme of the present application: 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 vibration 1350-1550 cm -1 and C-Cl bond vibration 500-550 cm -1 ; the detection limit is 0.1-0.2 ppt.

[0033] The present application also provides a fluorine-functionalized MOF-based dioxin SERS sensing and analysis device for realizing the above method, comprising:

[0034] (1) Fluorine-functionalized MOF composite substrate: made of fluorine-functionalized MOF composite material, the substrate is array-shaped, each unit is provided with a plurality of interconnected porous channels inside, 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: emitting 633 nm or 785 nm wavelength laser, the spot diameter is adjustable within the range of 5-20 μm;

[0037] (4) Signal acquisition and intelligent analysis module: for acquiring characteristic Raman shift and performing intelligent analysis.

[0038] As a further scheme of the present application: the array surface of the fluorine-functionalized MOF composite substrate is provided with a polydimethylsiloxane microchannel, the microchannel width is 100-200 μm, the depth is 50-100 μm, and the flow rate of the sample after pretreatment is controlled to be 0.05-0.5 mL / min;

[0039] The signal acquisition and intelligent analysis module is built-in with a deep learning algorithm model based on CNN convolutional neural network, for noise reduction processing and feature peak identification.

[0040] Compared with the prior art, the present application has the following beneficial effects:

[0041] 1. Capture mechanism innovation, high specificity: for the first time, "fluorine-containing functional groups and dioxin aromatic ring-Cl F→Cl halogen bond" and "MOF ligand aromatic ring and dioxin π-π stacking" are combined, and the specific capture of 2,3,7,8-TCDD is realized by van der Waals force, effectively avoiding the influence of interference substances such as polychlorinated biphenyls, and solving the problem of poor specificity in the prior art;

[0042] 2. High detection sensitivity: through the high specific surface area (1500-2500 m 2g) The pre-enrichment of 2,3,7,8-TCDD and the "hot spot" enhancement effect of noble metal nanostructures are combined to achieve a detection limit as low as 0.1-0.2 ppt, 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 has a stable structure in the pH range of 5-7, the metal ion dissolution amount is less than or equal to 0.01 mg / L, the performance does not obviously attenuate after being stored at room temperature for 1 month, and the signal intensity still remains more than 92% of the initial value after being repeatedly used for 5 times, thus solving the problem of poor stability of the antibody labeling method;

[0044] 4. Simple and rapid detection process: sample pretreatment only needs 5-10 min, the whole process of capture and detection is less than or equal to 2 h, no complex extraction and purification steps are needed, and the device has a high degree of integration, so that on-site rapid detection can be realized;

[0045] 5. Controllable cost: no expensive antibody or large and precise instrument is needed, the preparation process of the composite material is simple and can be mass-produced, and the detection cost is much lower than that of traditional mass spectrometry detection methods such as high-resolution gas chromatography and high-resolution mass spectrometry. BRIEF DESCRIPTION OF DRAWINGS

[0046] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. Obviously, the drawings described below are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0047] Figure 1 The flowchart of the present application. DETAILED DESCRIPTION

[0048] The technical solutions of the present application will be described below in conjunction with the drawings. Obviously, the described embodiments are some embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0049] The present application will be further explained and described below in conjunction with specific embodiments.

[0050] Please refer to Figure 1 The dioxin SERS sensing and analysis method based on the fluorine-functionalized MOF provided by the embodiments of the present application includes the following steps:

[0051] S1, preparation of fluorine-functionalized MOF composite material

[0052] S1.1, Precise preparation of MOF carrier framework: Zirconium-based MOF (Zr-MOF-BDC-NH2) or iron-based MOF (Fe-MOF-TA) is used as the carrier framework, and is synthesized by a solvothermal method. The specific conditions are as follows:

[0053] a: Zr-MOF-BDC-NH2: N,N-dimethylformamide (DMF) is used as the solvent, acetic acid (AA) is used as the adjusting agent (DMF: AA = 10: 1 (V: V)), the molar ratio of 2-amino terephthalic acid to zirconium chloride (ZrCl4) is 1: (1.2-1.5), the reaction temperature is 120-140°C, the reaction time is 24-36h, and the reaction pressure is 0.1-0.3MPa. After synthesis, the pore size is precisely controlled to be 1.8-2.2nm, with an error of ±0.2nm from the dynamic diameter of 2,3,7,8-TCDD molecules (~1.8nm).

[0054] b: Fe-MOF-TA: A mixture of deionized water and DMF (V: V = 1: 2) is used as the solvent, formic acid (FA) is used as the adjusting agent (FA: mixed solvent = 1: 15 (V: V)), the molar ratio of trimesic acid to iron nitrate (Fe(NO3)3·9H2O) is 1: (2.5-3.0), the reaction temperature is 100-120°C, 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-processing: The synthesis product is sequentially washed with DMF and ethanol for 3 times (15min each time), and is vacuum dried (80-100°C, 12-24h) to obtain a pure MOF carrier with a specific surface area of 1500-2500m 2 / g and a porosity of ≥80%;

[0056] S1.3, Fluorine functionalization: A fluorine-containing functional group is modified at the amino or carboxyl sites of the MOF ligand by covalent grafting. The fluorine-containing functional group is an amine compound modified with a perfluoroalkyl chain, and specifically:

[0057] a: In the 2-amino terephthalic acid ligand of Zr-MOF-BDC-NH2, the amino group reacts with 3,3,3-trifluoropropylamine through an amidation reaction to form a “-NH-CO-CH2-CH2-CF3” structure. Dichloromethane is used as the solvent, EDC is used as the condensing agent, the reaction is carried out at a temperature of 25-30°C for 8-12h, and the grafting density is 0.8-1.2mmol / 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 ≥0.99) to achieve quantitative analysis, and the detection limit is 0.1-0.2 ppt.

[0065] In a more specific example, the Zeta potential of the fluorine-functionalized MOF composite prepared in step one is-10 mV to +5 mV, the structure is stable in the pH range of 5-7, and the metal ion leaching amount is ≤0.01 mg / L; the fluorine-functionalized Zr-MOF-BDC-NH2 composite material is characterized by XRD, and the characteristic diffraction peak is 2θ=7.3°, 8.5°, 25.8°, and the characteristic diffraction peak of the fluorine-functionalized Fe-MOF-TA composite material is 2θ=9.1°, 10.3°, 18.5°.

[0066] The embodiment of the application also provides a fluorine-functionalized MOF-based dioxin SERS sensing analysis device for realizing the above method, characterized by comprising:

[0067] (1) Fluorine-functionalized MOF composite substrate: made of the above-mentioned composite material, the substrate is array-shaped (array unit size is 50-100 μm), each unit is provided with a plurality of interconnected porous channels consistent with the pore size of the MOF inside, and is fixed on the surface of a quartz sheet by a sol-gel method (the thickness of the fixed layer is 20-50 μm, and the adhesion is ≥1.5 MPa);

[0068] (2) Pretreatment module: dispersing the sample to be detected by using a surfactant, and internally provided with an ultrasonic dispersion unit (power is 150-200 W, dispersion time is 5-10 min) and a concentration control unit (controlling the addition amount of Tween-80 to be 0.01-0.1%);

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

[0070] (4) Signal acquisition and intelligent analysis module: collecting the characteristic Raman shift of 2,3,7,8-TCDD, internally provided with a deep learning algorithm model based on CNN convolutional neural network, and realizing qualitative and quantitative analysis through noise reduction processing and characteristic peak identification (the characteristic peak region is located at 1350-1550 cm -1 and 500-550 cm -1 ).

[0071] In a more specific example, the array surface of the fluorine-functionalized MOF composite substrate is provided with a polydimethylsiloxane (PDMS) microchannel with a width of 100-200 pm and a depth of 50-100 pm, and the flow rate of the sample after pretreatment is controlled at 0.05-0.5 mL / min, thereby prolonging the contact time of 2,3,7,8-TCDD with the composite substrate and promoting the synergistic capture effect of "F→Cl halogen bond + π-π stacking".

[0072] Example 1: 2,3,7,8-TCDD SERS sensing analysis based on Zr-MOF-BDC-NH2

[0073] 1.1 Materials and instruments

[0074] 1.1.1 Reagents: 2-amino terephthalic acid (purity ≥ 98%), zirconium chloride (ZrCl4, purity ≥ 99%), N,N-dimethylformamide (DMF, analytical pure), glacial acetic acid (analytical pure), 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 pure), 2,3,7,8-TCDD standard (purity ≥ 99.5%), ultrapure water (resistivity ≥ 18.2 MΩ·cm).

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

[0076] 1.2 Preparation of fluorine-containing functionalized Zr-MOF-BDC-NH2 composite material

[0077] 1.2.1 Synthesis of Zr-MOF-BDC-NH2 carrier 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 relationships. Subsequently, a 24 mmol / L NaBH4 solution (Au) was prepared. 3+The gold nanostar was reduced in situ and loaded by adding 0.005 g of NaBH4(molar ratio of 1:3) into the above mixture at room temperature, stirring for 2 h. After the reaction, the product was collected by centrifugation, washed with ultrapure water for 3 times, and dried at 60 °C under vacuum for 8 h. TEM characterization showed that the gold nanostar was 45 nm in size, uniformly dispersed in the pores and on the surface of the fluorine-functionalized Zr-MOF-BDC-NH2, and no obvious agglomeration was observed. XPS characterization confirmed that the mercaptoacetic acid formed a hydrogen bond with the amino group of the Zr-MOF-BDC-NH2 ligand through the mercapto group, and the loading amount was 10 wt%.

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

[0084] 1.3.1 Sample pretreatment

[0085] 10 mL of the water sample to be tested (containing 2,3,7,8-TCDD) was taken, 0.005 g of Tween-80 (mass-volume ratio 0.05%) was added, and ultrasonic dispersion was performed at 180 W power for 8 min to uniformly disperse the 2,3,7,8-TCDD molecules and avoid agglomeration.

[0086] 1.3.2 Capture and pre-enrichment

[0087] 0.005 g of fluorine-functionalized Zr-MOF-BDC-NH2 composite material (dosage 0.5 g / L) was added to the pretreated sample, the solution pH was adjusted to 6.0, and magnetic stirring was performed at 28 °C and 180 rpm for 25 min. During this period, the composite material formed a bond angle of 175° and an interaction strength of 12 kJ / mol "F→Cl" type linear halogen bond between the lone pair electrons of the fluorine functional group and the 2,3,7,8-TCDD aromatic ring-Cl, and cooperated with the π-π stacking action of the Zr-MOF-BDC-NH2 ligand aromatic ring and 2,3,7,8-TCDD to achieve specific capture and pre-enrichment of 2,3,7,8-TCDD. After the reaction, the composite material was collected by centrifugation (8000 rpm for 5 min), washed with ultrapure water for 2 times, and the un-captured impurities were removed.

[0088] 1.4 SERS analysis

[0089] The composite material after capturing 2,3,7,8-TCDD was evenly spread on a quartz piece, dried, and placed on the sample table of the Raman spectrometer. A 785 nm excitation wavelength was used, the laser power was 20 mW, the integration time was 15 s, and the SERS spectrum was collected. The results showed that the C-Cl bond characteristic vibration peak of 2,3,7,8-TCDD appeared at 520 cm -1 and 1450 cm -1The characteristic peaks of aromatic ring skeleton vibration appeared, and there was no obvious background interference. The standard curve was constructed with the concentration of 2, 3, 7, 8-TCDD standard (0.1 ppt, 0.5 ppt, 1 ppt, 5 ppt, 10 ppt) as the abscissa and the characteristic Raman absorption displacement (1450 cm -1 ) intensity as the ordinate, and the fitting degree R 2 = 0.996. The detection results of the water sample to be detected showed that its concentration was 0.3 ppt, which was consistent with the verification results of high-resolution gas chromatography and high-resolution mass spectrometry, and the detection limit was as low as 0.1 ppt.

[0090] 1.5 Performance verification

[0091] 1.5.1 Specificity: Add the same concentration of interference substances such as polychlorinated biphenyl (PCB-77) and phenol to the water sample containing 2, 3, 7, 8-TCDD (0.5 ppt), and detect according to the above method. Only target characteristic peaks appear at 520 cm -1 and 1450 cm -1 , and there is no obvious signal response of interference substances, which proves that the method has good specificity.

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

[0093] Example 2: 2, 3, 7, 8-TCDD SERS sensing analysis based on iron-based MOF (Fe-MOF-TA)

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

[0095] 1.1 Synthesis of Fe-MOF-TA carrier framework

[0096] According to the molar ratio 1:2.8, trimesic acid (0.5 mmol, 0.126 g) and Fe(NO3)3·9H2O (1.4 mmol, 0.651 g) were weighed into a 50 mL reactor liner, 15 mL of a mixed solvent of deionized water and DMF (volume ratio 1:2) was added, and 3 mL of formic acid (volume ratio 1:15 with the mixed solvent) was added as a regulator, and ultrasonic dispersion was performed for 15 min. The reactor was sealed and placed in an oven, and reacted at 110°C for 21 h (pressure 0.15 MPa). After the reaction was completed, it was cooled to room temperature, centrifuged to collect the precipitate, and washed with DMF, ethanol for 3 times respectively, and vacuum dried at 100°C for 20 h to obtain pure Fe-MOF-TA carrier. The BET characterization showed that the specific surface area was ~2000 m 2 / g, porosity 82%, pore size 2.8 nm.

[0097] 1.2 Fluorine-functionalized modification

[0098] 0.2 g Fe-MOF-TA support was weighed and dispersed in 25 mL toluene, 0.4 mmol perfluorohexylamine and 0.3 mmol p-toluenesulfonic acid catalyst were added, and the reaction was carried out at 115°C under reflux for 14 h. After the reaction was completed, the product was collected by centrifugation, washed with toluene for 3 times, and dried at 90°C under vacuum for 14 h to obtain fluorine-functionalized Fe-MOF-TA, with a fluorine-functional group grafting density of 1.3 mmol / g.

[0099] 1.3 In-situ loading of silver nanocubes

[0100] A 6 mmol / L silver nitrate solution was prepared, and 6 mL was added dropwise into 20 mL of fluorine-functionalized Fe-MOF-TA dispersion (concentration 10 mg / mL) at a rate of 0.6 mL / min, and stirred for 40 min to make Ag + coordination with Fe 3+ metal nodes of Fe-MOF-TA. A 24 mmol / L NaBH4 solution (molar ratio of Ag + to NaBH4 1:4) was prepared and added to the mixed solution, and the reaction was carried out at room temperature for 2.5 h to realize in-situ loading of silver nanocubes. TEM characterization showed that the particle size of the silver nanocubes was 50 nm, the loading amount was 12 wt%, and the silver nanocubes were uniformly dispersed in the pores of the fluorine-functionalized Fe-MOF-TA composite material.

[0101] 2. Capture and SERS analysis

[0102] 2.1 Sample pretreatment: 0.008 g of Tween-80 (mass-volume ratio 0.08%) was added to 10 mL of water sample to be detected, and ultrasonic dispersion was carried out at 190 W for 7 min.

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

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

[0105] Comparative experiment: set 3 groups of comparative experiments, verify the innovation and superiority of the application:

[0106] 1. Comparative group 1 (Zr-MOF-BDC-NH2 without fluorine modification): using Zr-MOF-BDC-NH2@ gold nanostar composite material without modified fluorine functional group, detecting 0.5 ppt 2,3,7,8-TCDD according to the method of example 1, the characteristic peak intensity is only 35% of example 1, and the capture time is extended to 60 min, which proves that the "F→Cl" halogen bond of fluorine functional group can improve the capture efficiency.

[0107] 2. Comparative group 2 (without noble metal nanostructure loading): using fluorine functionalized Zr-MOF-BDC-NH2 (without gold nanostar loading), detecting 0.5 ppt 2,3,7,8-TCDD, no obvious characteristic peak is detected, which proves that the LSPR enhancement effect of gold nanostar is the key to signal detection.

[0108] 3. Comparative group 3 (prior art: antibody labeled SERS detection): using magnetic microbeads + 2,3,7,8-TCDD antibody labeled silver nanoprobe, detecting 0.5 ppt 2,3,7,8-TCDD, the detection limit is 5 ppt, and the activity of antibody decreases by 50% after 1 week of storage at room temperature, while the performance of the composite material of the application does not decrease significantly after 1 month of storage at room temperature, which proves the advantages of the application in sensitivity and stability.

[0109] Finally, it should be pointed out that: the above embodiments are only used to illustrate the technical solutions of the application, but not to limit it; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A dioxin SERS sensing analysis method based on fluorine-functionalized MOF, characterized in that, The method comprises the following steps: S1, fluorine functionalized MOF composite material preparation: S1.1, accurate preparation of MOF carrier framework: taking Zr-MOF-BDC-NH2 or Fe-MOF-TA as the carrier framework, and adopting solvothermal synthesis; S1.2, post-processing: the synthesis product is sequentially washed with DMF and ethanol under ultrasonic, and vacuum dried to obtain pure MOF carrier; S1.3, fluorine functionalization: modifying fluorine functional groups at the amino or carboxyl sites of the MOF ligand through covalent grafting; S1.4, in-situ loading of noble metal nanostructure: in-situ reduction and loading of noble metal nanostructure in the pores of the MOF through metal node coordination guidance; S2, 2, 3, 7, 8-TCDD specific capture: S2.1, pretreatment: adding a surfactant to the sample to be detected and ultrasonic dispersion; S2.2, capture and pre-enrichment: mixing the composite material prepared in S1 with the pretreated sample and stirring, and realizing specific capture of 2, 3, 7, 8-TCDD through the formation of "F→Cl" type linear halogen bond between the fluorine functional groups and the aromatic ring-Cl atoms in the 2, 3, 7, 8-TCDD molecules, and the synergistic π-π stacking effect of the MOF ligand aromatic ring and the 2, 3, 7, 8-TCDD aromatic ring; S3, SERS analysis: The signal is collected by a Raman spectrometer, the characteristic Raman absorption shift of 2, 3, 7, 8-TCDD is taken as the qualitative identification basis, and the standard curve constructed by the characteristic peak intensity and the 2, 3, 7, 8-TCDD concentration is used for quantitative analysis.

2. The method of claim 1, wherein, In S1.1, the synthesis conditions of the Zr-MOF-BDC-NH2 are as follows: N,N-dimethylformamide is used as the solvent, acetic acid is used as the adjusting agent, the molar ratio of 2-amino terephthalic acid to zirconium chloride is 1:(1.2-1.5), the reaction temperature is 120-140℃, the reaction time is 24-36h, and the pore size after synthesis is 1.8-2.2nm; The synthesis conditions of the Fe-MOF-TA are as follows: Deionized water and DMF mixed solution are used as the solvent, formic acid is used as the adjusting agent, the molar ratio of trimesic acid to ferric nitrate is 1:(2.5-3.0), the reaction temperature is 100-120℃, the reaction time is 18-24h, and the pore size after synthesis is 2.5-3.0nm.

3. The method of claim 1, wherein, In S1.3, the fluorine functional group is a perfluoroalkyl chain modified amine compound, specifically: For Zr-MOF-BDC-NH2, the amino group in the 2-amino terephthalic acid ligand is modified into "-NH-CO-CH2-CH2-CF3" structure through amidation reaction with 3, 3, 3-trifluoropropylamine; For Fe-MOF-TA, the carboxyl group in the trimesic acid ligand is modified through esterification reaction with perfluorohexylamine.

4. The method of claim 1, wherein, In S1.4, the noble metal nanostructure has a particle size of 30-60nm, is surface modified with mercaptoacetic acid, and is stabilized through hydrogen bonding between the mercapto group and the amino group of the MOF ligand.

5. The method of claim 1, wherein, In S2.1, the mass / volume ratio of the surfactant is 0.01-0.1%, the ultrasonic dispersion power is 150-200W, and the time is 5-10min.

6. The method of claim 1, wherein, In S2.2, the stirring conditions are: pH = 5-7, stirring temperature is 25-30℃.

7. The method of claim 1, wherein, In S2.2, the composite material is added in an amount of 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 8-15 kJ / mol.

8. The method of claim 1, wherein, 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 displacement includes aromatic ring skeleton vibration 1350-1550 cm -1 and C-Cl bond vibration 500-550 cm -1 ; the detection limit is 0.1-0.2 ppt.

9. A fluorine-functionalized MOF-based dioxin SERS sensing device for implementing the method of any one of claims 1-8, characterized in that, Comprise: (1) Fluorine-functionalized MOF composite substrate: made of fluorine-functionalized MOF composite material, the substrate is arrayed, each unit is provided with a plurality of interconnected porous channels inside, and is fixed on the surface of a quartz sheet; (2) Pretreatment module: built-in ultrasonic dispersion unit and surfactant concentration control unit; (3) SERS detection module: emitting 633 nm or 785 nm wavelength laser, the spot diameter is adjustable in the range of 5-20 μm; (4) Signal acquisition and intelligent analysis module: for collecting characteristic Raman shift and performing intelligent analysis.

10. The apparatus of claim 9, wherein, The array surface of the fluorine-functionalized MOF composite substrate is provided with a polydimethylsiloxane microchannel, the microchannel width is 100-200 μm, the depth is 50-100 μm, and the flow rate of the sample after pretreatment is controlled to be 0.05-0.5 mL / min; The signal acquisition and intelligent analysis module is built-in with a deep learning algorithm model based on CNN convolutional neural network, for noise reduction processing and feature peak identification.

Images