Preparation method of flexible polymer PVP / ZIF-67 composite SERS (Surface Enhanced Raman Scattering) chip and application of flexible polymer PVP / ZIF-67 composite SERS chip in poison detection

Abstract

The invention discloses a preparation method of a flexible polymer PVP / ZIF-67 composite SERS (Surface Enhanced Raman Scattering) chip and application of the flexible polymer PVP / ZIF-67 composite SERS chip in poison detection, and the preparation method is characterized by comprising the following steps: uniformly dripping 10-20 L of PVP solution on a silicon wafer with the size of 5-15 mm < 2 >, placing the silicon wafer on a spin coater, controlling the rotation speed to be 3000-4000 r / min and the spin-coating time to be 10-20 s, transferring the silicon wafer spin-coated with a PVP film into a drying oven at 70-80 DEG C, and drying to obtain the flexible polymer PVP / ZIF-67 composite SERS chip. After drying is conducted for 2-3 h, the silicon wafer is soaked in a ZIF-67 precursor solution at the temperature of 36.5-37.5 DEG C to be cultured for 1-3 h, then the silicon wafer is taken out and placed in the drying oven at the temperature of 70-80 DEG C to be dried for 10-15 min, and the flexible polymer PVP / ZIF-67 composite SERS chip is obtained. The flexible polymer PVP / ZIF-67 composite SERS chip has the advantages of being good in repeatability, low in detection limit, capable of being applied to poison detection and identifying poison, high in speed and good in stability.

Description

Technical Field

[0001] The present invention relates to a SERS chip, in particular to a preparation method of a flexible polymer PVP / ZIF-67 composite SERS chip and its application in poison detection. Background Art

[0002] With the widespread distribution of microcystin-LR (abbreviated as MC-LR) in the water environment, its threat to public health and the ecological environment is increasing day by day, seriously endangering aquatic organisms, human health and drinking water safety. Microcystin has multiple toxic effects, and long-term low-dose exposure may lead to chronic diseases and even induce cancer. Therefore, it is urgent to strengthen the monitoring and control of microcystin in water bodies, and exploring rapid, sensitive and accurate detection technologies can provide strong technical support for the safety assessment and treatment of water environment.

[0003] Traditional microcystin detection methods include high performance liquid chromatography (HPLC), enzyme-linked immunosorbent assay (ELISA), mass spectrometry (MS), etc. Although HPLC has high separation and quantification capabilities, the instrument is expensive, the operation is complex, the sample pretreatment is cumbersome, and professional technical personnel are required. Although ELISA is relatively easy to operate, it is prone to false positive or false negative results due to being affected, and its sensitivity and specificity are limited. These traditional methods often fail to meet the requirements of rapid response and real-time monitoring in the face of large-scale water body monitoring and sudden water pollution incidents.

[0004] Surface-Enhanced Raman Spectroscopy (SERS) technology, with its unique advantages such as rapidity, non-destructiveness, obvious fingerprint characteristics and high sensitivity, shows great application potential in the fields of biomolecule detection, environmental pollutant analysis, etc. It has been found that the SERS effect is closely related to the performance of the substrate material, and developing a SERS substrate with a high enhancement factor, good reproducibility and stability is the key to promoting the practical application of this technology. In recent years, SERS substrate materials based on flexible polymers have received extensive attention. Polyvinylpyrrolidone (abbreviated as PVP) thin films are widely used in the medical field due to their good flexibility and processability, such as preparing medical dressings, wound plasters or drug delivery systems. At present, there are no relevant research reports on flexible polymer PVP / ZIF-67 composite SERS chips and their application in poison detection on the market. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a preparation method of a flexible polymer PVP / ZIF-67 composite SERS chip with good repeatability and low detection limit and its application in poison detection.

[0006] The technical solution adopted by the present invention to solve the above technical problems is as follows: A preparation method of a flexible polymer PVP / ZIF-67 composite SERS chip, comprising the following steps: uniformly dropping a PVP solution on a silicon wafer, placing the silicon wafer on a spin coater for spin coating, and then transferring the silicon wafer coated with a PVP film to an oven for drying; soaking the dried silicon wafer in a ZIF-67 precursor solution for cultivation, taking out the silicon wafer and placing it in the oven for drying again to obtain a flexible polymer PVP / ZIF-67 composite SERS chip.

[0007] Further, 10 - 20 μL of the PVP solution is uniformly dropped on a silicon wafer with a size of 5 - 15 mm 2 The silicon wafer is placed on a spin coater, the rotation speed is controlled to be 3000 - 4000 r / min, and the spin coating time is 10 - 20 s. Then, the silicon wafer coated with a PVP film is transferred to an oven at 70 - 80 °C and dried for 2 - 3 h to remove the solvent and enhance the stability of the film; the dried silicon wafer is soaked in a ZIF-67 precursor solution at 36.5 - 37.5 °C for 1 - 3 h to allow ZIF-67 to grow uniformly on the surface of the PVP film; after the cultivation is completed, the silicon wafer is taken out and placed in an oven at 70 - 80 °C again for drying for 10 - 15 min to remove the residual solvent, and a flexible polymer PVP / ZIF-67 composite SERS chip is obtained.

[0008] Further, the preparation method of the PVP solution is as follows: Add 1000 - 1500 mg of PVP powder to 30 - 40 mL of deionized water, control the temperature at 60 - 90 °C, heat and stir for 1 - 2 hours until the PVP powder is completely dissolved, and filter with filter paper to obtain the PVP solution.

[0009] Further, the preparation method of the ZIF-67 solution is as follows: Dissolve 410 - 420 mg of dimethylimidazole in 25 - 30 mL of methanol and stir until completely dissolved to obtain a dimethylimidazole methanol solution; dissolve 730 - 735 mg of cobalt nitrate hexahydrate solid in 30 - 35 mL of methanol to form a uniform cobalt nitrate hexahydrate methanol solution; mix the dimethylimidazole methanol solution and the cobalt nitrate hexahydrate methanol solution in a volume ratio of 1:3 and stir evenly to obtain a ZIF-67 precursor solution.

[0010] The present invention also provides the application of the flexible polymer PVP / ZIF-67 composite SERS chip prepared by the above method in toxin detection. The detection method steps are as follows: Drop 10 - 20 μL of the test solution containing MC-LR toxin onto the flexible polymer PVP / ZIF-67 composite SERS chip, and after natural drying, measure at 1507 cm using a Raman spectrometer -1The Raman signal intensity at a specific wavelength, based on the linear relationship between the peak intensity of the SERS signal of MC-LR toxin at 1507 cm −1 and its logarithmic concentration, is used to calculate the concentration of MC-LR toxin in the test solution.

[0011] Compared with the prior art, the advantages of the present invention are as follows: The present invention discloses a preparation method of a flexible polymer PVP / ZIF-67 composite SERS chip and its application in poison detection. For the first time, it is proposed to use the composite of PVP and ZIF-67 for the preparation of SERS chips. This composite chip combines the excellent film-forming property of PVP and the high specific surface area and porosity of ZIF-67, has a uniform PVP film and a uniformly grown ZIF-67 layer, and the ZIF-67 layer has a highly ordered porous structure and abundant active sites, significantly improving the intensity and uniformity of the SERS signal. The preparation method is simple, low-cost, has good reproducibility and the potential for large-scale production. The Raman signal enhancement factor of the SERS chip is ≥10 6 and has good reproducibility and uniformity, enabling large-area SERS imaging and quantitative detection. The SERS chip prepared by the present invention can detect MC-LR molecular concentration as low as 10⁻ 6 M, showing high detection sensitivity, and also showing good reproducibility in multiple detections, which is used to achieve rapid and highly sensitive detection of target molecules, providing strong support for trace analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is the scanning electron microscope (SEM) photograph of the PVP / ZIF-67 composite SERS chip prepared in Example 1; Figure 2 is the SERS spectrum of detecting MC-LR using the PVP / ZIF-67 composite SERS chip prepared in Example 1: Figure 3 is the repeatability test result graph of the PVP / ZIF-67 composite SERS chip prepared in Example 1; Figure 4 is the SERS detection limit test result graph of detecting different concentrations of MC-LR using the PVP / ZIF-67 composite SERS chip prepared in Example 1; Figure 5 is the scanning electron microscope (SEM) photograph of the PVP / ZIF-67 composite SERS chip prepared in Example 2; Figure 6 is the SERS spectrum of detecting MC-LR using the PVP / ZIF-67 composite SERS chip prepared in Example 2: Figure 7SEM photograph of the PVP / ZIF-67 composite SERS chip prepared in Example 3; Figure 8 SERS spectrum of detecting MC-LR by using the PVP / ZIF-67 composite SERS chip prepared in Example 3. Detailed implementation manners

[0013] The present invention will be further described in detail below in conjunction with the embodiments with reference to the accompanying drawings.

[0014] The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art, and the raw materials used are all commercially available products. The Raman spectrometer BWS415 used in the embodiments is purchased from B&W Tek Inc., USA.

[0015] Example 1. A preparation method of a flexible polymer PVP / ZIF-67 composite SERS chip, comprising the following steps: Step 1. Preparation of polyvinylpyrrolidone (PVP) solution: After adding 1200 mg of PVP powder into 35 mL of deionized water, controlling the temperature at 75 °C, heating and stirring for 1.5 hours until the PVP powder is completely dissolved, and filtering with filter paper to obtain a PVP solution. The appearance of the solution is uniform and transparent, without obvious particles or turbidity.

[0016] Step 2. Preparation of ZIF-67 solution: Dissolve 417.9 mg of dimethylimidazole in 29.85 mL of methanol and stir until completely dissolved to obtain a dimethylimidazole methanol solution with a concentration of 14.00 mg / mL (1.5×10 -1 M); dissolve 731.9 mg of cobalt nitrate hexahydrate solid in 34.95 mL of methanol to form a uniform cobalt nitrate hexahydrate methanol solution with a concentration of 21.00 mg / mL (7.2×10 -2 M); mix the dimethylimidazole methanol solution and the cobalt nitrate hexahydrate methanol solution in a volume ratio of 1:3 and stir evenly to obtain a ZIF-67 precursor solution.

[0017] Step 3. Preparation of the PVP / ZIF-67 composite SERS chip: Drop 15 μL of the PVP solution evenly on 10 mm 2On a silicon wafer of a certain size, the silicon wafer was placed on a spin coater. The rotation speed was controlled at 3500 r / min, and the spin coating time was 15 s to ensure uniform coverage of the PVP film. The silicon wafer with the spin-coated PVP film was transferred to an oven at 75 °C and dried for 2.5 h to remove the solvent and enhance the stability of the film. The dried silicon wafer was immersed in a ZIF-67 precursor solution at 37 °C for 2 h to allow ZIF-67 to grow uniformly on the surface of the PVP film. After the cultivation, the silicon wafer was taken out and placed in the oven at 75 °C again for 12 min to remove the residual solvent, obtaining a flexible polymer PVP / ZIF-67 composite SERS chip. Figure 1 This is the scanning electron microscope (SEM) photograph of the PVP / ZIF-67 composite chip prepared in this example. As Figure 1 shown, the PVP / ZIF-67 composite chip prepared in this example presents a unique uniform two-dimensional network structure.

[0018] As Figure 1 shown, the SERS chip presents unique microstructural features. On the two-dimensional network structure substrate, flower-like nanostructures with three-dimensional characteristics grow uniformly. The formation of this structure not only enriches the surface morphology of the chip but also brings significant effects on the physical and chemical properties of the chip. The two-dimensional network substrate provides a stable support platform for the growth of the flower-like structure, while the three-dimensional flower-like structure further increases the specific surface area and provides more active sites, thus significantly enhancing the adsorption ability of the chip for target molecules.

[0019] 10 μL of the MC-LR molecular solution was dropped onto the SERS chip and then naturally dried in a dust-free environment. After drying, the SERS activity was evaluated by Raman spectroscopy. The excitation wavelength of the Raman spectrometer was 532 nm, the laser power was 1 mW, and the acquisition time was 10 s. Raman spectra were measured on the SERS chip to observe several Raman signal characteristic peaks of the MC-LR molecule, and the minimum trace detection limit of the SERS chip was obtained. The results are as Figure 2 shown. The SERS spectrum shows that the intensity of the MC-LR solution with a detection concentration of 1×10 -4 M at 1507 wavenumbers on the PVP / ZIF-67 composite SERS chip is 807.3.

[0020] Figure 3 This is the repeatability test result graph of the PVP / ZIF-67 composite SERS chip. As Figure 3As shown, through multiple Raman spectroscopy detections of MC-LR molecular solutions with the same concentration, the results show that the intensities of the Raman characteristic peaks remain highly consistent in multiple measurements, indicating that the SERS chip has good repeatability and stability. This repeatability is particularly important for achieving large-area SERS imaging and quantitative detection, ensuring the reliability and reproducibility of the detection results.

[0021] Figure 4 This is the test result of the detection limit of the PVP / ZIF-67 composite SERS chip. Figure 4 It shows the change in Raman signal intensity of MC-LR molecular solutions with different concentrations on this SERS chip. By analyzing the relationship between the intensity of the Raman characteristic peak and the concentration of MC-LR molecules, the detection limit of this SERS chip for MC-LR molecules was determined. The results show that this chip can detect MC-LR molecular concentrations as low as 10⁻ 6 M, showing high detection sensitivity and providing strong support for trace analysis.

[0022] Example 2 is the same as Example 1 above, with the difference being: Step 1, Preparation of PVP solution: After adding 1000 mg of PVP powder to 30 mL of deionized water, control the temperature at 60 °C and heat and stir for 2 hours.

[0023] Step 2, Preparation of ZIF-67 solution: Dissolve 410 mg of dimethylimidazole in 20 mL of methanol and stir until completely dissolved to obtain a dimethylimidazole methanol solution; dissolve 730 mg of cobalt nitrate hexahydrate solid in 30 mL of methanol to form a uniform cobalt nitrate hexahydrate methanol solution.

[0024] Step 3, Preparation of PVP / ZIF-67 composite SERS chip: Drop 10 μL of PVP solution evenly on a silicon wafer with a size of 10 mm 2 After that, place the silicon wafer on a spin coater, control the rotation speed at 3000 r / min, and after a spin coating time of 20 s, transfer the silicon wafer with the spin-coated PVP film to an oven at 70 °C and dry it for 3 h; Immerse the dried silicon wafer in the ZIF-67 precursor solution at 36.5 °C for 3 h, then take out the silicon wafer and place it in an oven at 70 °C again and dry it for 15 min to obtain a flexible polymer PVP / ZIF-67 composite SERS chip. Figure 5 This is the scanning electron microscope (SEM) photo of the PVP / ZIF-67 composite chip prepared in this example. As Figure 5 shown, the PVP / ZIF-67 composite chip prepared in this example presents a unique uniform two-dimensional network structure.

[0025] Drop 10 μL of the MC-LR molecular solution onto the SERS chip, and then let it dry naturally in a dust-free environment. After drying, evaluate the SERS activity by Raman spectroscopy. The excitation wavelength of the Raman spectrometer is 532 nm, the laser power is 1 mW, and the acquisition time is 10 s. Test the Raman spectrum on the SERS chip, observe several Raman signal characteristic peaks of the MC-LR molecule, and obtain the minimum trace detection limit of this SERS chip. The results are as Figure 6 shown. The SERS spectrum shows that the intensity of the MC-LR solution with a detection concentration of 1×10 -4 M at 1507 wavenumbers on the PVP / ZIF-67 composite SERS chip is 1235.2.

[0026] Example 3: The same as Example 1 above, the difference is as follows: Step 1, preparation of the PVP solution: Add 1500 mg of PVP powder to 40 mL of deionized water, control the temperature at 90 °C, and heat and stir for 1 hour.

[0027] Step 2, preparation of the ZIF-67 solution: Dissolve 420 mg of dimethylimidazole in 30 mL of methanol and stir until completely dissolved to obtain a dimethylimidazole methanol solution; dissolve 735 mg of cobalt nitrate hexahydrate solid in 35 mL of methanol to form a uniform cobalt nitrate hexahydrate methanol solution; mix the dimethylimidazole methanol solution and the cobalt nitrate hexahydrate methanol solution in a volume ratio of 1:3 and stir evenly to obtain a ZIF-67 precursor solution.

[0028] Step 3, preparation of the PVP / ZIF-67 composite SERS chip: Drop 20 μL of the PVP solution evenly on a silicon wafer with a size of 10 mm 2 . Place the silicon wafer on a spin coater, control the rotation speed at 4000 r / min, and after a spin coating time of 10 s, transfer the silicon wafer coated with the PVP film to an oven at 80 °C and dry for 2 h. Immerse the dried silicon wafer in the ZIF-67 precursor solution at 37.5 °C for 1 h, then take out the silicon wafer and place it in the oven at 80 °C again to dry for 10 min to obtain a flexible polymer PVP / ZIF-67 composite SERS chip. Figure 7 is the scanning electron microscope (SEM) photograph of the PVP / ZIF-67 composite chip. As Figure 7 shown, the PVP / ZIF-67 composite chip prepared in this example presents a unique uniform two-dimensional network structure.

[0029] 10 μL of the MC-LR molecular solution was dropped onto the SERS chip and then naturally dried in a dust-free environment. After drying, the SERS activity was evaluated by Raman spectroscopy. The excitation wavelength of the Raman spectrometer was 532 nm, the laser power was 1 mW, and the acquisition time was 10 s. The Raman spectrum was tested on the SERS chip to observe several Raman signal characteristic peak values of the MC-LR molecule, and the minimum trace detection limit of the SERS chip was obtained. The results are as Figure 8 shown. The SERS spectrum shows that the intensity of the MC-LR solution with a detection concentration of 1×10 -4 M at 1507 wavenumbers is 1028.6.

[0030] In summary, the flexible polymer PVP / ZIF-67 composite SERS chip prepared by the method of the present invention is not only applicable to the detection of MC-LR molecules, but also can be used to detect a variety of other poisons, including but not limited to environmental poisons such as heavy metal ions, organophosphorus pesticides, and polycyclic aromatic hydrocarbons, as well as special poisons such as biological toxins and chemical warfare agents. The detection limits can all reach the nanomolar to picomolar level, meeting the high-sensitivity detection requirements for trace poisons.

[0031] The above description is not a limitation of the present invention, nor is the present invention limited to the above examples. Changes, modifications, additions, or substitutions made by those of ordinary skill in the art within the scope of the essence of the present invention shall also fall within the protection scope of the present invention.

Claims

1. Preparation method of a flexible polymer PVP / ZIF-67 composite SERS chip, characterized in that Including the following steps: Drop the PVP solution evenly on the silicon wafer. After spin-coating the silicon wafer on a spin coater, transfer the silicon wafer spin-coated with the PVP film to an oven for drying; soak the dried silicon wafer in the ZIF-67 precursor solution for cultivation, then take out the silicon wafer and place it in the oven for drying again to obtain a flexible polymer PVP / ZIF-67 composite SERS chip.

2. The preparation method of a flexible polymer PVP / ZIF-67 composite SERS chip according to claim 1, characterized in that The specific steps are as follows: uniformly drop 10 - 20 µL of PVP solution on a silicon wafer with a size of 5 - 15 mm 2 ; place the silicon wafer on a spin coater, control the rotation speed at 3000 - 4000 r / min, after spin coating for 10 - 20 s, transfer the silicon wafer spin-coated with PVP film to an oven at 70 - 80 °C and dry for 2 - 3 h; immerse the dried silicon wafer in a ZIF-67 precursor solution at 36.5 - 37.5 °C and incubate for 1 - 3 h; after the incubation, take out the silicon wafer and place it in the oven at 70 - 80 °C again to dry for 10 - 15 min to obtain a flexible polymer PVP / ZIF-67 composite SERS chip.

3. The preparation method of a flexible polymer PVP / ZIF-67 composite SERS chip according to claim 2, characterized in that The preparation method of the PVP solution is as follows: add 1000-1500 mg of PVP powder to 30-40 mL of deionized water, control the temperature at 60-90 °C, heat and stir for 1-2 hours until the PVP powder is completely dissolved, and filter with filter paper to obtain the PVP solution.

4. The preparation method of a flexible polymer PVP / ZIF-67 composite SERS chip according to claim 2, characterized in that The preparation method of the ZIF-67 precursor solution is as follows: dissolve 410-420 mg of dimethylimidazole in 25-30 mL of methanol and stir until completely dissolved to obtain a dimethylimidazole methanol solution; dissolve 730-735 mg of cobalt nitrate hexahydrate solid in 30-35 mL of methanol to form a uniform cobalt nitrate hexahydrate methanol solution; mix the dimethylimidazole methanol solution and the cobalt nitrate hexahydrate methanol solution in a volume ratio of 1:3 and stir evenly to obtain the ZIF-67 precursor solution.

5. Use of the flexible polymer PVP / ZIF-67 composite SERS chip prepared by the method according to any one of claims 1-4 in the detection of poisons, characterized in that The detection method steps are as follows: Drop 10 - 20 µL of the test sample containing MC-LR toxin onto the flexible polymer PVP / ZIF-67 composite SERS chip. After natural drying, use a Raman spectrometer to measure the Raman signal intensity at a wavelength of 1507 cm -1 , and calculate the concentration of MC-LR toxin in the test solution according to the linear relationship between the peak intensity of the SERS signal of MC-LR toxin at 1507 cm -1 and its logarithmic concentration.

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