Silver nanoparticle functionalized covalent organic framework microspheres and their preparation and application

Abstract

The present invention discloses a silver nanoparticle functionalized covalent organic framework microsphere and its enrichment, extraction and colorimetric detection application. The microsphere uses an imine-type covalent organic framework as a matrix, utilizes its surface thiol or amino groups to capture silver ions and adopts an in-situ reduction method to achieve silver nanoparticle functionalization. The prepared silver nanoparticle functionalized covalent organic framework microsphere is used as a dispersed solid phase extraction adsorbent or an in-tube solid phase microextraction adsorbent, and utilizes the charge transfer effect and π-π stacking effect between the microsphere and the unsaturated analyte to achieve selective enrichment analysis of trace unsaturated analytes in complex samples. In addition, the microsphere also has strong oxidase-like activity and high affinity for the substrate 3,3',5,5'-tetramethylbenzidine. Based on this, a simple and rapid colorimetric detection method is constructed using the microsphere as a probe and a UV-visible spectrophotometer as a readout device to achieve efficient colorimetric detection of trace dopamine in actual biological fluid samples.

Description

Technical Field

[0001] The present invention belongs to the technical field of synthesis and application of covalent organic framework composite materials, and particularly relates to a silver nanoparticle functionalized covalent organic framework microsphere, a preparation method thereof, and application in enrichment, extraction and colorimetric detection. Background Art

[0002] Covalent organic frameworks (COFs) are a class of crystalline porous polymers composed entirely of light elements through strong covalent bonds. They possess advantages such as extremely high specific surface area, well-defined, regular pores, tunable functionality, and excellent stability in harsh media. They have attracted widespread attention in fields such as energy storage, catalysis, sensing, drug analysis, and sample pretreatment. Combining COFs with materials such as metal nanoparticles (MNPs), metal oxides (MOS), metal-organic frameworks (MOFs), and bioenzymes to prepare COF-based composites can further leverage the unique properties of COFs and expand their application potential in various scenarios.

[0003] Leveraging the open porous structure and excellent stability of COFs, metal nanoparticles (CNPs) have been combined with COFs to prepare metal nanoparticle-functionalized COFs composites. These composites combine the outstanding catalytic activity of metal nanoparticles with the robust stability of COFs, attracting widespread attention in sample pretreatment and catalysis. By leveraging the charge transfer interaction between silver nanoparticles (AgNPs) and unsaturated C=C double bonds, as well as the π-π stacking interaction between the COF matrix and the unsaturated C=C double bonds, they are expected to achieve selective enrichment and extraction of unsaturated analytes in complex samples, demonstrating the unique sample pretreatment capabilities of AgNP-functionalized COFs. Furthermore, AgNP-functionalized COFs, possessing the catalytic activity of metallic silver nanoparticles, can be used as nanozymes for colorimetric detection. This color-change-based direct detection of analytes holds promise as an ideal rapid detection technology. Therefore, AgNP-functionalized covalent organic frameworks (COFs) have significant research implications and broad application prospects, potentially enabling applications in diverse fields, such as enzyme-mimicking catalysis and selective enrichment and detection. Summary of the Invention

[0004] The present invention aims to provide silver nanoparticle-functionalized covalent organic framework microspheres. These microspheres can be used as both selective enrichment and extraction adsorbents and as nanozymes for colorimetric detection. The present invention utilizes a post-synthesis in situ reduction method to load silver nanoparticles onto the covalent organic framework microspheres to achieve the preparation of silver nanoparticle-functionalized covalent organic framework microspheres. This method utilizes charge transfer between the AgNPs and unsaturated C=C double bonds on the microspheres, as well as π-π stacking interactions between the covalent organic framework and the unsaturated C=C double bonds, to achieve selective enrichment and analysis of trace unsaturated analytes in complex samples. Furthermore, the silver nanoparticle-functionalized covalent organic framework microspheres exhibit excellent oxidase-like activity. In the presence of oxygen, they can oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to blue oxTMB. Adding dopamine reduces the amount of oxTMB produced, resulting in a decrease in absorbance measured by a UV spectrophotometer, thereby enabling rapid and visual detection of dopamine. The present invention demonstrates the multiple properties of silver nanoparticle-functionalized covalent organic framework microspheres, further expanding the application of covalent organic framework materials in different fields.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] Silver nanoparticle-functionalized covalent organic framework microspheres are characterized in that: the microspheres are loaded with silver nanoparticles on the matrix covalent organic framework microspheres by in-situ reduction after synthesis to achieve the preparation of the silver nanoparticle-functionalized covalent organic framework microspheres; the matrix covalent organic framework microspheres are prepared by a Schiff base reaction between covalent organic framework preparation ligands at room temperature; the preparation process uses the matrix covalent organic framework microspheres as carriers to capture silver ions in the solution, and then uses an in-situ reduction reaction to reduce the silver ions captured on the covalent organic framework microspheres to generate silver nanoparticles, thereby achieving the preparation of the silver nanoparticle-functionalized covalent organic framework microspheres.

[0007] The method for preparing the silver nanoparticle functionalized covalent organic framework microspheres comprises the following steps:

[0008] 1) Preparation of matrix covalent organic framework microspheres: 1,3,5-tris(4-aminophenyl)benzene was used as amino ligand, 2,5-divinyl-1,4-benzenedicarboxaldehyde, terephthalaldehyde or 2,5-dimethoxybenzene-1,4-dicarboxaldehyde was used as aldehyde ligand, wherein the molar ratio of amino ligand to aldehyde ligand was 2:3, 5 mL of acetonitrile was used as solvent, ultrasonic dispersion was performed and dissolved, 0.3 mL to 1.5 mL of 12 mol / L acetic acid was added as catalyst, the reaction was carried out at room temperature for 72 hours, and the precipitate obtained by centrifugation was washed with tetrahydrofuran and ethanol three times respectively, and dried in a vacuum drying oven at 60°C for 24 hours to obtain matrix covalent organic framework microspheres COF-V and COF-V, respectively. TAPB-TPA and COFTAPB-DMTP .

[0009] 2) Preparation of silver nanoparticle-functionalized covalent organic framework microspheres by three reduction methods

[0010] S1: Preparation of AgNPs@COF-V-SH microspheres:

[0011] (1) Preparation of thiol-functionalized covalent organic framework microspheres: The COF-V microspheres synthesized above and 2 mg of azobisisobutyronitrile were placed in a flask, 4 mL of 1,2-ethanedithiol was added, and stirred at room temperature for 48 hours to obtain a uniform yellow-brown suspension. The centrifuged product was washed three times with acetone and dried in a vacuum drying oven at 60°C for 24 hours to obtain thiol-functionalized covalent organic framework microspheres COF-V-SH.

[0012] (2) Preparation of AgNPs@COF-V-SH microspheres: The above-mentioned thiol-functionalized covalent organic framework microspheres were dispersed in 44.6 mL of secondary water. At room temperature, 10 mL of silver nitrate solution was slowly added to the above solution at a flow rate of 4-7 mL / h. The mixture was stirred for 24 hours. The centrifuged precipitate was washed with secondary water and ethanol three times each, and dried in a vacuum drying oven at 60°C for 24 hours to obtain AgNPs@COF-V-SH microspheres.

[0013] S2: Preparation of AgNPs@COF TAPB-TPA Microspheres: 100 mg of the COF prepared above TAPB-TPA The microspheres were dispersed in 20 mL of ethanol and ultrasonicated for 1 hour. 70 mg of silver nitrate was dissolved in 5 mL of dimethyl sulfoxide and added to the above dispersion, and ultrasonicated for another 30 minutes. The mixture was then heated in an oil bath for 24 hours. Finally, it was washed with N,N-dimethylformamide and ethanol to remove unreacted impurities. The resulting powder was dried in a vacuum drying oven at 60 °C for 24 hours to obtain AgNPs@COF. TAPB-TPA microspheres.

[0014] S3: Preparation of AgNPs@COF TAPB-DMTP Microspheres: Take 10 mg of the COF prepared above TAPB-DMTP Dispersed in 5 mL of ethanol, ultrasonicated for 1 hour, then added 30 mg of polyvinyl pyrrolidone, 4.5 mL of secondary water and 0.5 mL of silver nitrate solution, and ultrasonicated for another 1 hour. After the ultrasonication, 0.5 mL of sodium citrate solution was added to the above solution and stirred for 10 minutes. Under vigorous stirring, 0.5 mL of glucose solution was slowly added to the solution, and then stirred at room temperature for 15 hours. Finally, the centrifuged precipitate was washed 3 times with a mixture of ethanol and water, and dried in a vacuum drying oven at 60 ° C for 24 hours to obtain AgNPs@COF TAPB-DMTP microspheres.

[0015] Silver nanoparticle functionalized covalent organic framework microspheres in multiple fields:

[0016] 1) As a dispersed solid-phase extraction adsorbent: Using silver nanoparticle-functionalized covalent organic framework microspheres (AgNPs@COF-V-SH) as a selective adsorbent, dispersed solid-phase extraction is used to purify, extract, and enrich unsaturated analytes in complex samples. Finally, combined with a high-performance liquid chromatography system, efficient detection of the enriched analytes is achieved. The specific steps are as follows:

[0017] ① Dispersive solid-phase extraction: Prepare a sample solution with a methanol / water solution at a volume ratio of 1:1. Take 1 mL of this solution in a centrifuge tube, add 0.5 mg of AgNPs@COF-V-SH microspheres, disperse evenly with ultrasound, place in a constant temperature mixer, and perform dispersive solid-phase extraction at room temperature for 3 minutes. After that, centrifuge and remove the supernatant.

[0018] ② Desorption: Add 1 mL of acetonitrile-saturated n-hexane to the centrifuge tube and perform ultrasonic desorption for 5 minutes. Then, centrifuge rapidly, collect the desorbed liquid, and filter it with a syringe filter. Blow the desorbed liquid dry with nitrogen and re-dissolve it with 0.2 mL of mobile phase to prepare the test solution.

[0019] ③ High performance liquid chromatography system detection: The test solution is directly injected into the high performance liquid chromatography (HPLC) system for detection.

[0020] 2) As an in-tube solid phase microextraction adsorbent: AgNPs@COF functionalized covalent organic framework microspheres TAPB-TPA ) was used as an in-tube solid phase microextraction adsorbent to construct an on-line in-tube AgNPs-SPME-Ag + -HPLC) to achieve online extraction and efficient analysis of unsaturated analytes in complex samples. The specific steps are as follows:

[0021] ① Preparation of AgNPs@COF TAPB-TPA Filling solid phase microextraction column: 60 mg AgNPs@COF TAPB-TPA The microspheres were filled into a stainless steel column, and then a high-pressure infusion pump was used to flush the filled solid phase microextraction (SPME) column with n-hexane as the mobile phase at a flow rate of 0.08 mL / min for 1 hour to obtain AgNPs@COF TAPB-TPA Pack the SPME column.

[0022] ② Combined system construction: AgNPs@COF TAPB-TPAThe SPME column was filled as a selective adsorbent, and a silver nanoparticle in-tube microextraction-silver ion high performance liquid chromatography online coupling system was constructed using a "six-way valve + ten-way valve" method.

[0023] ③ Online enrichment and elution: After the SPME column and the chromatographic analysis column are stable, the sample to be tested is injected into the 0.5 mL quantitative loop through the injector; then, the sample solution in the quantitative loop is brought into the AgNPs@COF through the loading phase. TAPB-TPA Fill the SPME column and completely pass the sample to be tested into the SPME column for online enrichment; then, replace the loading phase with the elution phase (n-hexane / dichloromethane = 99.2% / 0.8%, v / v), and elute the analytes extracted from the SPME column through pump A at a flow rate of 0.1 mL / min.

[0024] ④Online detection: After the elution program is completed, adjust the ten-way valve to the INJECT state. At this time, the mobile phase pushes the eluate collected in the quantitative loop into the chromatographic analysis column for analysis and detection through pump B at a flow rate of 1.0 mL / min.

[0025] 3) Colorimetric detection as nanozymes: AgNPs@COF microspheres functionalized with silver nanoparticles TAPB-DMTP ) is an enzyme-mimicking material, combined with UV-spectrophotometer, to achieve colorimetric detection of analytes in complex samples through color changes. The specific steps are as follows: 300 μL of AgNPs@COF TAPB-DMTP The dispersion (final concentration of 40 μg / mL) and 600 μL of TMB solution (final concentration of 0.6 mM) were added to 1.5 mL of HAC-NaAC solution (0.2 M, pH 4.0), mixed well, and reacted at room temperature for 5 minutes. Then, dopamine (DA) standard solutions of different concentrations (0-100 μM) were added to the above mixture, mixed well, and reacted at room temperature. The absorption spectrum of the reaction solution was then measured using a UV-visible absorption spectrometer, and the absorbance value at a wavelength of 657 nm was recorded.

[0026] The beneficial effects of the present invention are that, compared with traditional composite materials, the silver nanoparticle-functionalized covalent organic framework microspheres provided by the present invention can not only serve as selective adsorbents to achieve dispersed solid-phase extraction and in-tube solid-phase microextraction of unsaturated compounds, but can also serve as a nanoenzyme to achieve efficient colorimetric detection of trace targets in complex biological fluid samples. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Transmission electron microscopy (TEM) image of the silver nanoparticle functionalized covalent organic framework microspheres (AgNPs@COF-V-SH) prepared in the present invention ( Figure 1a) and XPS characterization diagram ( Figure 1 b).

[0028] Figure 2 The silver nanoparticles functionalized covalent organic framework microspheres (AgNPs@COF TAPB-TPA ) transmission electron microscope (TEM) image ( Figure 2 a) and XPS characterization diagram ( Figure 2 b).

[0029] Figure 3 The silver nanoparticles functionalized covalent organic framework microspheres (AgNPs@COF TAPB-DMTP ) transmission electron microscope (TEM) image ( Figure 3 a) and XPS characterization diagram ( Figure 3 b).

[0030] Figure 4 The following are HPLC chromatograms. a is a chromatogram of direct detection of milk powder spiked with 0.5 μg / mL eicosatetraenoic acid methyl ester (ARAME) and docosahexaenoic acid methyl ester (DHAME); b is a chromatogram of blank milk powder after HPLC detection using the silver nanoparticle functionalized covalent organic framework (AgNPs@COF-V-SH) prepared by the present invention as a dispersed solid phase extraction adsorbent; c is a chromatogram of milk powder spiked with 0.5 μg / mL ARAME and DHAME after HPLC detection using AgNPs@COF-V-SH microspheres as dispersed solid phase extraction; d is a chromatogram of 5.0 μg / mL ARAME and DHAME standards. Peak identification: (1) DHAME; (2) ARAME.

[0031] Figure 5 is a HPLC chromatogram. a is an in-tube Ag NPs-SPME-Ag + -HPLC analysis of spiked milk tea samples; b is in-tube Ag NPs-SPME-Ag + -HPLC analysis of blank milk tea samples; c is conventional silver ion liquid chromatography (Ag + -HPLC) analysis of spiked milk tea samples. Peak identification: (1) 9t-C18:1; (2) 9t,12t-C18:2; (3) 9c-C18:1; (4) 9c,12c-C18:2.

[0032] Figure 6 The silver nanoparticle functionalized covalent organic framework (AgNPs@COF TAPB-DMTP ) Photographs and absorption spectra of the nanozyme for colorimetric detection of dopamine solutions with different concentrations.

[0033] Figure 7 The silver nanoparticle functionalized covalent organic framework (AgNPs@COF TAPB-DMTP ) as the linear calibration curve for colorimetric detection of dopamine solutions with different concentrations by nanozymes. DETAILED DESCRIPTION

[0034] In order to make the contents of the present invention easier to understand, the technical solutions of the present invention are clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0035] Example 1

[0036] Silver nanoparticle functionalized covalent organic framework microspheres and their enrichment and extraction applications include the following steps:

[0037] (1) Preparation of matrix covalent organic framework: 1,3,5-tris(4-aminophenyl)benzene and 2,5-divinyl-1,4-benzenedicarboxaldehyde in a molar ratio of 2:3 were added to 5 mL of acetonitrile, ultrasonically dispersed and dissolved, 0.35 mL of 12 mol / L acetic acid was added as a catalyst, and the reaction was carried out at room temperature for 72 hours. The precipitate obtained by centrifugation was washed three times with tetrahydrofuran and ethanol respectively, and dried in a vacuum drying oven at 60°C for 24 hours to obtain matrix covalent organic framework microspheres COF-V.

[0038] (2) Preparation of thiol-functionalized covalent organic framework: 20 mg of the COF-V microspheres synthesized above and 2 mg of azobisisobutyronitrile were placed in a flask, 4 mL of 1,2-ethanedithiol was added, and stirred at room temperature for 48 hours to obtain a uniform yellow-brown suspension. The centrifuged product was washed three times with acetone and dried in a vacuum drying oven at 60°C for 24 hours to obtain thiol-functionalized covalent organic framework microspheres COF-V-SH.

[0039] (3) Preparation of AgNPs@COF-V-SH: 223 mg of the above-mentioned thiol-functionalized covalent organic framework microspheres were dispersed in 44.6 mL of secondary water. At room temperature, 10 mL of silver nitrate solution was slowly added to the above solution at a flow rate of 6 mL / h. The mixture was stirred for 24 hours. The centrifuged precipitate was washed with secondary water and ethanol three times each, and dried in a vacuum drying oven at 60°C for 24 hours to obtain the final product, AgNPs@COF-V-SH microspheres.

[0040] (4) Enrichment detection: Prepare the sample solution prepared with a methanol / water solution at a volume ratio of 1:1, take 1 mL of the solution into a centrifuge tube, add 0.5 mg of AgNPs@COF-V-SH microspheres, disperse evenly with ultrasound, place in a constant temperature mixer, and perform solid phase extraction at room temperature for 3 minutes, then centrifuge to remove the supernatant; add 1 mL of acetonitrile-saturated n-hexane into the centrifuge tube, ultrasonically desorb for 5 minutes, then quickly centrifuge, collect the desorbed liquid, and filter it with a syringe filter; blow the desorbed liquid dry with nitrogen, and then redissolve it with 0.2 mL of mobile phase to prepare the test solution; the test solution is directly injected into the high performance liquid chromatography (HPLC) system for detection, and the mobile phase used for detection is acetonitrile, the mobile phase flow rate is 1.0 mL / min, the detection wavelength is 221 nm, and the column temperature is 40°C.

[0041] The silver nanoparticle functionalized covalent organic framework microspheres (AgNPs@COF-V-SH) prepared in Example 1 were characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Figure 1 In a, a large number of black dots that the electron beam cannot penetrate can be found. These are all AgNPs particles, which are evenly distributed on the surface of AgNPs@COF-V-SH microspheres. Figure 1 As shown in (b), the five element signals of C, N, O, S, and Ag can be clearly seen in the full-band XPS spectrum of the material, proving that AgNPs are successfully loaded on the COF-V-SH microspheres.

[0042] The silver nanoparticle functionalized covalent organic framework microspheres (AgNPs@COF-V-SH) prepared in Example 1 were used as a dispersed solid phase extraction adsorbent and combined with a high performance liquid chromatography system (HPLC) to analyze polyunsaturated fatty acid methyl esters in milk powder samples. Figure 4 As shown, when a standard mixture of unsaturated fatty acid methyl esters is directly analyzed by HPLC, the corresponding peaks are attributed to docosahexaenoic acid methyl ester (DHAME) and eicosatetraenoic acid methyl ester (ARAME) (curve d). However, when the sample is directly analyzed using an HPLC system, the milk powder matrix interferes severely, resulting in broad peaks and difficulty in separating and identifying the analytes (curve a). However, using silver nanoparticle-functionalized covalent organic frameworks (AgNPs@COF-V-SH) as a dispersive solid-phase extraction adsorbent, the matrix interference in the milk powder sample is significantly reduced, with no interfering substances present near the chromatographic peaks of the analytes (curve b). Using this method, a milk powder sample spiked with ARAME and DHAME (concentration 0.5 μg / mL) is subjected to dispersive solid-phase extraction (curve c). Clear chromatographic peaks for ARAME and DHAME are visible, demonstrating that the dispersive solid-phase extraction method using AgNPs@COF-V-SH microspheres as an adsorbent can efficiently enrich and extract trace amounts of ARAME and DHAME in milk powder samples.

[0043] Example 2

[0044] Silver nanoparticle functionalized covalent organic framework microspheres and their enrichment and extraction applications include the following steps:

[0045] (1) Preparation of matrix covalent organic framework: 1,3,5-tris(4-aminophenyl)benzene and terephthalaldehyde in a molar ratio of 2:3 were added to 5 mL of acetonitrile, ultrasonically dispersed and dissolved, 1.0 mL of 12 mol / L acetic acid was added as a catalyst, and the reaction was carried out at room temperature for 72 hours. The precipitate obtained by centrifugation was washed three times with tetrahydrofuran and ethanol respectively, and dried in a vacuum drying oven at 60°C for 24 hours to obtain matrix covalent organic framework microspheres COF. TAPB-TPA .

[0046] (2) Preparation of AgNPs@COF TAPB-TPA : 100 mg of the COF prepared above TAPB-TPA The microspheres were dispersed in 20 mL of ethanol and ultrasonicated for 1 hour. 70 mg of silver nitrate was dissolved in 5 mL of dimethyl sulfoxide and added to the above dispersion, and ultrasonicated for another 30 minutes. The mixture was then heated in an 80°C oil bath for 24 hours. Finally, it was washed with N,N-dimethylformamide and ethanol to remove unreacted impurities. The resulting powder was dried in a vacuum drying oven at 60°C for 24 hours to obtain AgNPs@COF. TAPB-TPA microspheres.

[0047] (3) Preparation of AgNPs@COF TAPB-TPA Filling SPME: 60 mg of AgNPs@COF was homogenized TAPB-TPA The microspheres were filled into a stainless steel column, and then a high-pressure infusion pump was used to flush the filled SPME column with n-hexane as the mobile phase at a flow rate of 0.08 mL / min for 1 hour to obtain AgNPs@COF TAPB-TPA Pack the solid phase microextraction column.

[0048] (4) Combined system construction: AgNPs@COF TAPB-TPA The SPME column was filled as a selective adsorbent, and a silver nanoparticle in-tube microextraction-silver ion high performance liquid chromatography online coupling system was constructed using a "six-way valve + ten-way valve" method.

[0049] (5) Online detection: After the SPME column and the chromatographic analysis column are stable, the sample to be tested is injected into a 0.5 mL quantitative loop through the injector; then, the sample solution in the quantitative loop is brought into the AgNPs@COF through the loading phase. TAPB-TPAFill the SPME column and completely pass the sample to be tested into the SPME column for online enrichment; then, replace the loading phase with the elution phase (n-hexane / dichloromethane = 99.2% / 0.8%, v / v), and elute the sample extracted on the SPME column through pump A at a flow rate of 0.1 mL / min; after the elution program is completed, adjust the ten-way valve to the INJECT state, and at this time, the mobile phase pushes the eluate collected in the quantitative loop into the chromatographic analysis column through pump B at a flow rate of 1.0 mL / min for analysis and detection.

[0050] Silver nanoparticle functionalized covalent organic framework microspheres (AgNPs@COF TAPB-TPA ), and the samples were characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Figure 2 AgNPs@COF can be seen in a TAPB-TPA The microspheres have a uniform spherical structure and many opaque small particles are evenly distributed on the surface, which are AgNPs. Figure 2 As shown in b, AgNPs@COF TAPB-TPA The full-band energy spectrum of the microspheres shows that the prepared AgNPs@COF TAPB-TPA The microspheres are mainly composed of C, N, O, and Ag elements. This result further confirms that AgNPs are successfully reduced to COF TAPB-TPA On microspheres.

[0051] The silver nanoparticles functionalized covalent organic framework microspheres (AgNPs@COF TAPB-TPA ) as an in-tube solid phase extraction adsorbent to construct in-tube AgNPs-SPME-Ag + -HPLC online coupling system, analyze the cis-trans mono- and di-unsaturated fatty acid methyl esters in milk tea samples. Figure 5 As shown, when the spiked milk tea samples were treated with conventional Ag + -HPLC system in direct injection analysis mode (curve c), the matrix in the milk tea sample caused strong interference with the analyte, and the absorption chromatographic peak overlapped with the analyte. + -HPLC online coupled system for analysis (curve a), the interference signal of the sample matrix decreased significantly, reducing the impact on the identification and detection of the analyte, and the signal peak of the analyte was clearly visible, which proved that AgNPs@COF TAPB-TPA The microspheres not only have good enrichment ability, but also have satisfactory impurity removal ability. +-Analysis of the blank milk tea sample by the HPLC system (curve b) shows that there is a very small amount of cis-unsaturated fatty acid methyl ester in the actual milk tea sample.

[0052] Example 3

[0053] Silver nanoparticle-functionalized covalent organic framework microspheres and their colorimetric detection applications include the following steps:

[0054] (1) Preparation of matrix covalent organic framework: 1,3,5-tris(4-aminophenyl)benzene and 2,5-dimethoxybenzene-1,4-dicarboxaldehyde in a molar ratio of 2:3 were added to 5 mL of acetonitrile, ultrasonically dispersed and dissolved, 1.5 mL of 12 mol / L acetic acid was added as a catalyst, and the reaction was carried out at room temperature for 72 hours. The precipitate obtained by centrifugation was washed three times with tetrahydrofuran and ethanol respectively, and dried in a vacuum drying oven at 60°C for 24 hours to obtain matrix covalent organic framework microspheres COF. TAPB-DMTP .

[0055] (2) Preparation of AgNPs@COF TAPB-DMTP : Take 10 mg of the COF prepared above TAPB-DMTP Add to 5 mL of ethanol, ultrasonicate for 1 hour, then add 30 mg of polyvinyl pyrrolidone, 4.5 mL of secondary water and 0.5 mL of silver nitrate solution, and then ultrasonicate for 1 hour. Add 0.5 mL of sodium citrate solution to the above solution and stir on a magnetic stirrer for 10 minutes. Under vigorous stirring, slowly add 0.5 mL of glucose solution to the solution, then stir at room temperature for 15 hours. Finally, the centrifugal precipitate is washed 3 times with a mixture of ethanol and water, and dried in a vacuum drying oven at 60 ° C for 24 hours to obtain AgNPs@COF TAPB-DMTP microspheres.

[0056] (3) Colorimetric detection: 300 μL of AgNPs@COF TAPB-DMTP The dispersion (final concentration of 40 μg / mL) and 600 μL of TMB solution (final concentration of 0.6 mM) were added to 1.5 mL of HAC-NaAC solution (0.2 M, pH 4.0), mixed well, and reacted at room temperature for 5 minutes. Then, dopamine standard solutions of different concentrations (0-100 μM) were added to the above mixture, mixed well, and reacted at room temperature. The absorption spectrum of the reaction solution was then measured using a UV-visible absorption spectrometer, and the absorbance value at a wavelength of 657 nm was recorded.

[0057] Silver nanoparticle functionalized covalent organic framework microspheres (AgNPs@COF TAPB-DMTP ), and the samples were characterized by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Figure 3a It can be seen intuitively that AgNPs@COF TAPB-DMTP The uniform flower-like spherical shape and the many opaque small particles distributed on the surface indicate that AgNPs are successfully deposited on COF. TAPB-TPA The surface of the microspheres is reduced. Figure 3 As shown in b, AgNPs@COF TAPB-DMTP The XPS images of the microspheres mainly show signals of four elements: C, N, O, and Ag, which once again proves that AgNPs are successfully loaded on the matrix covalent organic framework.

[0058] Silver nanoparticle functionalized covalent organic framework microspheres (AgNPs@COF TAPB-DMTP ) as nanozymes to construct AgNPs@COF TAPB-DMTP A simple and rapid colorimetric method using microspheres as probes and a UV-visible spectrophotometer as a readout enables quantitative detection of dopamine in real samples. The silver nanoparticle-functionalized covalent organic framework microspheres exhibit strong oxidase-like activity and high affinity for the substrate 3,3',5,5'-tetramethylbenzidine (TMB). The amount of oxTMB produced by the oxidase-like reaction mediated by the microspheres is significantly reduced upon addition of dopamine. Figure 6 The following are photos and absorption spectra of colorimetric detection of dopamine solutions at different concentrations. It can be seen that as the dopamine concentration increases, the color of the solution gradually becomes lighter, and the corresponding UV-visible absorption spectrum shows a gradual decrease in absorbance at 657 nm. Figure 7 is the linear relationship diagram of UV-visible absorbance of different concentrations of dopamine, and the linear equations are Δ 657 nm =0.01004 C DA +0.04410(R 2 =0.999) and Δ 657 nm =0.00362 C DA +0.19928(R 2 =0.983). The above results show that the silver nanoparticle-functionalized covalent organic framework microspheres provided by the present invention can be used as nanozymes and have good application prospects in the field of colorimetric detection.

[0059] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. A method for preparing silver nanoparticle-functionalized covalent organic framework microspheres, characterized by: The following steps are involved: 1) Preparation of matrix covalent organic framework microspheres: 1,3,5-tris(4-aminophenyl)benzene was used as amino ligand, 2,5-divinyl-1,4-benzenedicarboxaldehyde, terephthalaldehyde or 2,5-dimethoxybenzene-1,4-dicarboxaldehyde was used as aldehyde ligand, wherein the molar ratio of amino ligand to aldehyde ligand was 2:3, acetonitrile was used as solvent, ultrasonic dispersion and dissolution were carried out, and 12 mol / L acetic acid was added as catalyst, and the reaction was carried out at room temperature for 72 hours; centrifugation was carried out, and the precipitate was washed with tetrahydrofuran and ethanol three times each, and dried in vacuum at 60℃ for 24 hours to obtain matrix covalent organic framework microspheres COF-V and COF TAPB-TPA or COF TAPB-DMTP ; 2) Preparation of silver nanoparticle-functionalized covalent organic framework microspheres by in situ reduction S1: Preparation of AgNPs@COF-V-SH microspheres: 20 mg COF-V, 2 mg azobisisobutyronitrile and 4 mL 1,2-ethanedithiol were mixed, stirred at room temperature for 48 hours, centrifuged, washed with acetone three times, and dried in vacuum at 60°C for 24 hours to obtain thiol-functionalized covalent organic framework microspheres COF-V-SH; COF-V-SH was dispersed in 44.6 mL secondary water, 10 mL silver nitrate solution was slowly added at room temperature at a flow rate of 4-7 mL / h, stirred for 24 hours, centrifuged, and the precipitate was washed with secondary water and ethanol three times each, and dried in vacuum at 60°C for 24 hours to obtain AgNPs@COF-V-SH microspheres; S2: Preparation of AgNPs@COF TAPB-TPA Microspheres: 100 mg COF TAPB-TPA Dispersed in 20 mL of ethanol, ultrasonicated for 1 hour, 70 mg of silver nitrate was dissolved in 5 mL of dimethyl sulfoxide and added to the dispersion, ultrasonicated for 30 minutes, heated in an oil bath for 24 hours, washed with N,N-dimethylformamide and ethanol, and dried in a vacuum at 60 ° C for 24 hours to obtain AgNPs@COF TAPB-TPA microspheres; S3: Preparation of AgNPs@COF TAPB-DMTP Microspheres: 10 mg COF TAPB-DMTP Dispersed in 5 mL of ethanol, ultrasonicated for 1 hour, 30 mg of polyvinyl pyrrolidone, 4.5 mL of secondary water and 0.5 mL of silver nitrate solution were added, ultrasonicated for another 1 hour, 0.5 mL of sodium citrate solution was added, stirred for 10 minutes, and 0.5 mL of glucose solution was slowly added under vigorous stirring. Stirred at room temperature for 15 hours, centrifuged, and the precipitate was washed three times with ethanol solution and dried in vacuum at 60 ° C for 24 hours to obtain AgNPs@COF TAPB-DMTP microspheres.

2. Silver nanoparticle functionalized covalent organic framework microspheres prepared by the method according to claim 1.

3. An application of silver nanoparticle-functionalized covalent organic framework microspheres prepared by the method of claim 1, characterized in that: Silver nanoparticle-functionalized covalent organic framework microspheres AgNPs@COF-V-SH were used as dispersed solid phase extraction adsorbents to achieve selective enrichment and efficient analysis of trace unsaturated fatty acid methyl esters in complex samples.

4. A use of silver nanoparticle-functionalized covalent organic framework microspheres prepared by the method of claim 1, characterized in that: Silver nanoparticle-functionalized covalent organic framework microspheres AgNPs@COF TAPB-TPA As an online in-tube solid-phase microextraction adsorbent, it can achieve selective enrichment and efficient detection of trace unsaturated fatty acid methyl esters in complex samples.

5. An application of silver nanoparticle-functionalized covalent organic framework microspheres prepared by the method of claim 1, characterized in that: Silver nanoparticle-functionalized covalent organic framework microspheres AgNPs@COF TAPB-DMTP As a nanozyme with oxidase-like activity, it can realize the colorimetric detection of trace dopamine in biological fluids for non-disease diagnosis and treatment purposes.

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