An alkali metal-covalent organic framework-based surface-enhanced raman scattering active substrate and a preparation method and application thereof

Abstract

The application relates to an alkali metal-covalent organic framework-based surface-enhanced Raman scattering active substrate and a preparation method and application thereof, and belongs to the technical field of functional materials. The preparation method comprises the following steps: dissolving TAPT-Tp-COF powder in an organic solvent to obtain a TAPT-Tp-COF solution; dissolving alkali metal salt powder in deionized water to obtain an alkali metal salt solution; dropping the alkali metal salt solution into the TAPT-Tp-COF solution, ultrasonicating, drying, then placing in a microwave oven for reaction, and finally performing washing, centrifugation, drying treatment to obtain the alkali metal-covalent organic framework-based surface-enhanced Raman scattering active substrate. The application solves the problems of poor uniformity of a traditional surface-enhanced Raman scattering active substrate and low enhancement factor of a COF surface-enhanced Raman scattering active substrate, and has high practical application value.

Description

Technical Field

[0001] This invention belongs to the field of functional materials technology, specifically relating to a surface-enhanced Raman scattering active substrate based on an alkali metal-covalent organic framework, its preparation method, and its application. Background Technology

[0002] Surface-enhanced Raman scattering (SERS) is a spectroscopic analysis method that primarily achieves accurate detection of analytes by adsorbing target molecules onto the surface of materials to enhance the Raman signal. It has been applied in fields such as reaction monitoring, food safety monitoring, and environmental pollutant analysis.

[0003] Existing SERS enhancement mechanisms mainly fall into two categories: electromagnetic enhancement and chemical enhancement. Electromagnetic enhancement primarily relies on the localized surface plasmon resonance effect of noble metal nanomaterials to generate hotspot regions, thereby enhancing the Raman signal of the analyte. Chemical enhancement mainly depends on the transfer of electrons between the molecule and the substrate, and currently, semiconductors are the primary enhancing materials. The SERS substrate needs to possess both high enhancement performance and good stability and reproducibility.

[0004] Chinese patent "CN118028733A A Surface Enhanced Raman Substrate with Titanium Dioxide Nanofilm Grown on Aluminum Substrate and Its Preparation Method and Application" provides a surface enhanced Raman substrate with titanium dioxide nanofilm grown on an aluminum substrate, its preparation method and application. It utilizes the large number of oxygen vacancy defects in the titanium dioxide nanofilm to transfer electrons, thereby achieving Raman enhancement. It interacts with the dense alumina film naturally formed on the surface of the metallic aluminum substrate to obtain a highly reproducible Raman signal.

[0005] Covalent organic framework (COF) materials are a class of highly ordered porous materials formed by organic monomers through covalent bonds. Due to their advantages such as high porosity, high specific surface area, and chemical stability, they have been widely used in molecular adsorption, catalysis, and sensing.

[0006] Chinese patent "CN121203110A A Raman beacon COF nanoflower and its preparation method and application" provides a method for preparing Raman beacon covalent organic framework nanoflowers and its application. It loads AgNO3 on TpDBD-COF to ensure signal reproducibility and stability while obtaining extremely high enhancement factor.

[0007] Electromagnetic enhancement using noble metals relies on hotspot regions between nanoparticles, thus suffering from hotspot inhomogeneity. Furthermore, noble metal substrates are expensive; semiconductor materials based on charge transfer enhancement mechanisms have limited charge transfer efficiency and low enhancement factors, making it difficult to achieve highly sensitive detection. Summary of the Invention

[0008] To address the aforementioned issues of poor uniformity, high cost, and poor enhancement effect, this invention proposes a method for preparing a surface-enhanced Raman scattering active substrate based on an alkali metal-covalent organic framework. Methylene blue (MB) is used as a signal probe molecule to detect its application performance. The surface-enhanced Raman scattering active substrate provided by this invention features simple preparation, low cost, good enhancement effect, and good uniformity.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing a surface-enhanced Raman scattering active substrate based on an alkali metal-covalent organic framework includes the following steps: (1) Dissolve TAPT-Tp-COF powder in an organic solvent and disperse it by ultrasonication to obtain TAPT-Tp-COF solution.

[0010] (2) Dissolve the alkali metal salt powder in deionized water and disperse it by ultrasonication to obtain an alkali metal salt solution.

[0011] (3) The alkali metal salt solution obtained in step (2) is added dropwise to the TAPT-Tp-COF solution obtained in step (1) and ultrasonically dispersed to obtain a TAPT-Tp-COF solution doped with alkali metal ions.

[0012] (4) Dry the TAPT-Tp-COF solution doped with alkali metal ions obtained in step (3) to obtain TAPT-Tp-COF powder doped with alkali metal ions.

[0013] (5) Place the TAPT-Tp-COF powder doped with alkali metal ions obtained in step (4) in a microwave oven to react and obtain TAPT-Tp-COF powder loaded with alkali metal ions.

[0014] (6) The TAPT-Tp-COF powder loaded with alkali metal ions obtained in step (5) is washed, centrifuged and dried to obtain a surface-enhanced Raman scattering active substrate material based on alkali metal-TAPT-Tp-COF.

[0015] The TAPT-Tp-COF powder mentioned in step (1) is the TAPT-Tp described in the literature (Yuan XM, Xiao DMF, Zhao CL, et al. Enhancing Photocatalytic CO2RR by Modulating the Active Sites of COF‐Based Catalysts[J]. Small, 2025, 21(10): 2411316.). The TAPT-Tp-COF powder is prepared according to the preparation method of the TAPT-Tp.

[0016] In step (1), the mass-to-volume ratio of TAPT-Tp-COF powder to organic solvent is (8 mg~12 mg): (0.5 mL~2 mL); the ultrasonic dispersion time is 5 min~10 min.

[0017] The organic solvents in step (1) include N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

[0018] In step (2), the alkali metal salt is lithium carbonate, sodium carbonate, or potassium carbonate; wherein the molar concentration of the alkali metal salt solution is (0.2 mmol~0.5 mmol): (0.8 mL~1.2 mL); and the ultrasonic dispersion time is 5 min~10 min.

[0019] The ultrasonic dispersion time in step (3) is 15 min to 45 min.

[0020] In step (4), the drying temperature is 40℃~80℃ and the drying time is 8 h~20 h.

[0021] In step (5), the microwave power in the microwave oven reaction is 600 W to 1000 W, and the microwave time is 5 min to 10 min.

[0022] The solvents used in step (6) for washing include water, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide. The centrifugation speed is 8000 rpm to 12000 rpm, the centrifugation time is 5 min to 10 min, and the number of centrifugations is 3 to 6. The oven temperature is 40℃ to 80℃, and the reaction time is 12 h to 36 h.

[0023] This invention also provides the application of the alkali metal-covalent organic framework material surface-enhanced Raman scattering active substrate as a detection analyte.

[0024] The beneficial effects of this invention are as follows: This invention provides a surface-enhanced Raman scattering (SERS) active substrate based on an alkali metal-covalent organic framework, which is simple to prepare and low in cost. The SERS-enhanced Raman scattering active substrate based on the alkali metal-covalent organic framework exhibits a Raman enhancement factor of 0.57 × 10⁻⁶ for methylene blue. 7 Furthermore, it exhibits good uniformity. This solves the problems of poor uniformity in traditional surface-enhanced Raman scattering active substrates and low enhancement factor in COF surface-enhanced Raman scattering active substrates, thus possessing high practical application value. Attached Figure Description

[0025] Figure 1The preparation process of alkali metal-covalent organic framework Raman-enhanced substrates; Figure 2 The image is a scanning electron microscope (SEM) image of K-TAPT-Tp-COF. Figure 3 X-ray diffraction (XRD) patterns of TAPT-Tp-COF and K-TAPT-Tp-COF; Figure 4 Fourier transform infrared (FT-IR) spectra of TAPT, Tp, TAPT-Tp-COF, and K-TAPT-Tp-COF; Figure 5 X-ray photoelectron spectra (XPS) of TAPT-Tp-COF and K-TAPT-Tp-COF; Figure 6 Raman spectra of MB, MB@TAPT-Tp-COF, and MB@K-TAPT-Tp-COF; Figure 7 The results show the uniformity test results of K-TAPT-Tp-COF as a Raman-enhanced substrate. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and should not be construed as limiting the scope of protection of this invention. In the embodiments, all original reagents are commercially available.

[0027] Example 1 A method for preparing a surface-enhanced Raman scattering active substrate based on an alkali metal-covalent organic framework, such as... Figure 1 As shown, the specific steps include: (1) 32 mg of 2,4,6-trihydroxy-1,3,5-benzenetrialdehyde (Tp) was dissolved in a mixed solvent of mesitylene (1.5 mL) and 1,4-dioxane (1.5 mL), followed by the addition of 53 mg of 4,4′,4″-(1,3,5-triazine-2,4,6-triyl)triphenylamine (TAPT). The mixture was sonicated for 5 min, and then 0.6 mL of 6 M acetic acid solution was added. The resulting mixture was transferred to a Pyrex tube, which was then subjected to a three-cycle degassing process of freezing-evacuation-thawing in a liquid nitrogen bath. The Pyrex tube was then sealed and heated at 120 °C for 72 h. After the reaction was completed, the precipitate was collected by centrifugation and washed sequentially with tetrahydrofuran and acetone by centrifugation. The precipitate was dried under vacuum at 60 °C for 12 h to obtain TAPT-Tp-COF powder.

[0028] (2) Dissolve 10 mg of TAPT-Tp-COF powder in 1 mL of N,N-dimethylformamide and disperse by ultrasonication for 5 min to obtain TAPT-Tp-COF solution.

[0029] (3) Dissolve 42 mg of potassium carbonate powder in 1 mL of water and sonicate for 5 min to obtain potassium carbonate solution.

[0030] (4) The potassium carbonate solution obtained in step (3) is added dropwise to the solution obtained in step (1), and ultrasonically dispersed for 30 min to obtain a K-doped TAPT-Tp-COF solution.

[0031] (5) The mixed solution obtained in step (4) was placed in a vacuum oven at 60°C and dried for 12 h to obtain K-doped TAPT-Tp-COF powder.

[0032] (6) Then the K-doped TAPT-Tp-COF powder obtained in step (5) was placed in a microwave oven and reacted for 5 min at a power of 800W.

[0033] (7) The K-loaded TAPT-Tp-COF powder obtained in step (6) was washed with water and N,N-dimethylformamide three times, respectively, and centrifuged at 10,000 rpm for 5 min. Then it was placed in a vacuum oven at 60℃ and dried for 12 hours. The K-TAPT-Tp-COF surface-enhanced Raman scattering active substrate was obtained.

[0034] The product K-TAPT-Tp-COF prepared above was characterized by scanning electron microscopy, X-ray diffraction, infrared spectroscopy, and X-ray photoelectron spectroscopy. The results are as follows: Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown. By Figure 2 It can be seen that the synthesized K-TAPT-Tp-COF has a coral-like morphology. From... Figure 3 It can be seen that both TAPT-Tp-COF and K-TAPT-Tp-COF have similar diffraction peaks, proving that both have ordered crystal structures, and the introduction of K does not affect the crystal structure of COF. Figure 4 It can be seen that the infrared spectrum of K-TAPT-Tp-COF is similar to that of TAPT-Tp-COF, proving that the introduction of K does not destroy the chemical structure of COF. Figure 5 It can be seen that TAPT-Tp-COF contains only three elements: C, N, and O, while K-TAPT-Tp-COF contains four elements: C, N, O, and K, proving the successful synthesis of K-TAPT-Tp-COF.

[0035] Example 2 The application of a K-TAPT-Tp-COF surface-enhanced Raman scattering active substrate material in the detection of MB is as follows: (1) Take 1 mg of K-TAPT-Tp-COF prepared in Example 1 and dissolve it in 1 mL of deionized water.

[0036] (2) Take 10 μL of the solution obtained in step (1) and 10 μL of MB solution (1×10 -5 The mixture (mol / L) was incubated for 3 h and then dropped onto a 5 mm × 5 mm silicon wafer. After drying, Raman spectroscopy was performed. The laser wavelength was 633 nm, the laser power was attenuated to 0.05%, the exposure time was 10 s, and the number of acquisitions was 3. The measured Raman spectra are as follows: Figure 6 As shown in the figure. The results indicate that the K-TAPT-Tp-COF Raman enhancement substrate can significantly enhance the MB signal.

[0037] (3) Calculate the enhancement factor according to formula (1), where The Raman signal intensity is based on K-TAPT-Tp-COF. For the signal strength of a standard Raman test, at 1624 cm⁻¹ -1 The signal strength at that location is calculated. To determine the concentration of MB during Raman spectroscopy using K-TAPT-Tp-COF as a substrate, This represents the concentration of MB during a standard Raman spectroscopy test. The calculated enhancement factor is 0.57 × 10⁻⁶. 7 .

[0038] (1) Example 3 Uniformity of a prepared K-TAPT-Tp-COF surface-enhanced Raman scattering active substrate in the detection of MB.

[0039] The specific process is similar to that in Example 2, except that 20 points are randomly selected from the same sample for uniformity measurement.

[0040] The results are as follows Figure 7 As shown, the RSD of 20 measurements was only 2.13%, which proves that the surface-enhanced Raman scattering active substrate based on K-TAPT-Tp-COF has good uniformity.

[0041] Comparative Example An application of TAPT-Tp-COF surface-enhanced Raman scattering active substrate in the detection of MB.

[0042] (1) Take 1 mg TAPT-Tp-COF and dissolve it in 1 mL of deionized water.

[0043] (2) Take 10 μL of the solution obtained in step (1) and mix it with 10 μL of MB (1×10 -5 The mixture was prepared by mixing (mol / L) and incubating for 3 h, then dropped onto a 5 mm × 5 mm silicon wafer. After drying, Raman spectroscopy was performed. The laser wavelength was 633 nm, the laser power was attenuated to 0.05%, the exposure time was 10 s, and the number of acquisitions was 3.

[0044] Figure 6 The Raman spectra obtained in Example 2 and the comparative example show that the signal peak positions of TAPT-Tp-COF and K-TAPT-Tp-COF are basically the same when detecting MB, but the signal intensity obtained by TAPT-Tp-COF is significantly lower than that of K-TAPT-Tp-COF, proving that the surface-enhanced Raman effect of K-TAPT-Tp-COF proposed in this invention is stronger.

[0045] The above description is a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a surface-enhanced Raman scattering active substrate based on an alkali metal-covalent organic framework, characterized in that, It includes the following steps: (1) Dissolve TAPT-Tp-COF powder in an organic solvent and disperse it by ultrasonication to obtain TAPT-Tp-COF solution; (2) Dissolve the alkali metal salt powder in deionized water and disperse it by ultrasonication to obtain an alkali metal salt solution; (3) The alkali metal salt solution obtained in step (2) is added dropwise to the TAPT-Tp-COF solution obtained in step (1) and ultrasonically dispersed to obtain a TAPT-Tp-COF solution doped with alkali metal ions; (4) Dry the TAPT-Tp-COF solution doped with alkali metal ions obtained in step (3) to obtain TAPT-Tp-COF powder doped with alkali metal ions; (5) Place the TAPT-Tp-COF powder doped with alkali metal ions obtained in step (4) in a microwave oven to react and obtain TAPT-Tp-COF powder loaded with alkali metal ions. (6) The TAPT-Tp-COF powder loaded with alkali metal ions obtained in step (5) is washed, centrifuged and dried to obtain a surface-enhanced Raman scattering active substrate material based on alkali metal-TAPT-Tp-COF.

2. The method for preparing a surface-enhanced Raman scattering active substrate based on an alkali metal-covalent organic framework according to claim 1, characterized in that, In step (1), the mass-to-volume ratio of TAPT-Tp-COF powder to organic solvent is (8 mg~12 mg): (0.5 mL~2 mL); the ultrasonic dispersion time is 5 min~10 min; the organic solvent includes N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

3. The method for preparing a surface-enhanced Raman scattering active substrate based on an alkali metal-covalent organic framework according to claim 1, characterized in that, In step (2), the alkali metal salt is lithium carbonate, sodium carbonate, or potassium carbonate; wherein the molar concentration of the alkali metal salt solution is (0.2 mmol~0.5 mmol): (0.8 mL~1.2 mL); and the ultrasonic dispersion time is 5 min~10 min.

4. The method for preparing a surface-enhanced Raman scattering active substrate based on an alkali metal-covalent organic framework according to claim 1, characterized in that, The ultrasonic dispersion time in step (3) is 15 min to 45 min; the drying temperature in step (4) is 40℃ to 80℃ and the time is 8 h to 20 h; the microwave power in the microwave oven reaction in step (5) is 600 W to 1000 W and the microwave time is 5 min to 10 min.

5. The method for preparing a surface-enhanced Raman scattering active substrate based on an alkali metal-covalent organic framework according to claim 1, characterized in that, The solvents used in the washing process in step (6) include water, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide. The centrifugation speed is 8000 rpm to 12000 rpm, the time is 5 min to 10 min, and the number of times is 3 to 6. The drying temperature is 40℃ to 80℃, and the time is 12 h to 36 h.

6. A surface-enhanced Raman scattering active substrate based on an alkali metal-covalent organic framework, characterized in that, It is prepared by the preparation method described in any one of claims 1-5.

7. The application of the surface-enhanced Raman scattering active substrate based on an alkali metal-covalent organic framework as described in claim 6 as a detection analyte.

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