Preparation method of a flexible polymer PVP / ZIF-67 composite SERS chip and its application in poison detection

Abstract

The present invention discloses a preparation method of a flexible polymer PVP / ZIF-67 composite SERS chip and its application in poison detection, which is characterized by comprising the following steps: dropping 10-20 μL of PVP solution evenly on a 5-15 mm 2 The silicon wafer was placed on a spin coater with a rotation speed of 3000-4000 r / min and a spin coating time of 10-20 s. The silicon wafer with the PVP film was transferred to a 70-80°C oven and dried for 2-3 h. The silicon wafer was immersed in a 36.5-37.5°C ZIF-67 precursor solution and incubated for 1-3 h. The silicon wafer was taken out and placed in a 70-80°C oven for drying for 10-15 min to obtain a flexible polymer PVP / ZIF-67 composite SERS chip. The advantages of the chip are good repeatability and low detection limit. It can be used in poison detection to identify poisons with high speed and good 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 application thereof in poison detection. Background Art

[0002] The widespread distribution of microcystin-LR (MC-LR) in aquatic environments poses an increasing threat to public health and the ecological environment, seriously endangering aquatic life, human health, and drinking water safety. Microcystins have multiple toxic effects, and long-term low-dose exposure may cause chronic diseases and even cancer. Therefore, strengthening the monitoring and control of microcystins in water bodies is urgent. Exploring rapid, sensitive, and accurate detection technologies can provide strong technical support for water environment safety assessment and management.

[0003] Traditional methods for detecting microcystins include high-performance liquid chromatography (HPLC), enzyme-linked immunosorbent assay (ELISA), and mass spectrometry (MS). While HPLC offers high separation and quantitative capabilities, it is expensive, complex, and requires specialized technicians for sample pretreatment. While relatively simple to use, ELISA is susceptible to false positives and negatives, and has limited sensitivity and specificity. These traditional methods often struggle to meet the demands of rapid response and real-time monitoring for large-scale water monitoring and sudden water pollution incidents.

[0004] Surface-enhanced Raman spectroscopy (SERS) technology, with its unique advantages such as rapidity, non-destructiveness, distinct fingerprint characteristics, and high sensitivity, has shown great application potential in fields such as biomolecule detection and environmental pollutant analysis. Studies have found that the SERS effect is closely related to the properties of the substrate material. Developing a SERS substrate with a high enhancement factor, good reproducibility, and stability is key to promoting the practical application of this technology. In recent years, flexible polymer-based SERS substrates have garnered widespread attention. Polyvinylpyrrolidone (PVP) films, due to their excellent flexibility and processability, are widely used in the medical field, such as in the preparation of medical dressings, wound dressings, and drug delivery systems. Currently, there are no reports on commercially available research on flexible polymer PVP / ZIF-67 composite SERS chips and their application in toxicant detection. 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: a method for preparing a flexible polymer PVP / ZIF-67 composite SERS chip, comprising the following steps: evenly 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 the PVP film to an oven for drying; immersing the dried silicon wafer in a ZIF-67 precursor solution for incubation, taking out the silicon wafer and placing it in an oven for drying again to obtain a flexible polymer PVP / ZIF-67 composite SERS chip.

[0007] Furthermore, 10-20 μL of PVP solution was evenly dropped on 5-15 mm 2 The silicon wafer was placed on a spin coater with a rotation speed of 3000-4000 r / min and a spin coating time of 10-20 s. The silicon wafer with the PVP film was then transferred to a 70-80 ℃ oven and dried for 2-3 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 36.5-37.5 ℃ and incubated for 1-3 h to allow ZIF-67 to grow evenly on the surface of the PVP film. After the incubation period, the silicon wafer was taken out and placed in a 70-80 ℃ oven for drying for 10-15 min to remove the residual solvent, thereby obtaining a flexible polymer PVP / ZIF-67 composite SERS chip.

[0008] Furthermore, the preparation method of the PVP solution is as follows: after adding 1000-1500 mg of PVP powder to 30-40 mL of deionized water, controlling the temperature to 60-90° C., heating and stirring for 1-2 hours until the PVP powder is completely dissolved, and filtering with filter paper to obtain a PVP solution.

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

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

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

[0012] Figure 1 This is a scanning electron microscope (SEM) photograph of the PVP / ZIF-67 composite SERS chip prepared in Example 1;

[0013] Figure 2 The SERS spectrum of MC-LR was detected using the PVP / ZIF-67 composite SERS chip prepared in Example 1:

[0014] Figure 3 Graph showing the repeatability test results of the PVP / ZIF-67 composite SERS chip prepared in Example 1;

[0015] Figure 4 Graph showing the SERS detection limit test results of the PVP / ZIF-67 composite SERS chip prepared in Example 1 for detecting MC-LR at different concentrations;

[0016] Figure 5 This is a scanning electron microscope (SEM) photograph of the PVP / ZIF-67 composite SERS chip prepared in Example 2;

[0017] Figure 6The SERS spectrum of MC-LR was detected using the PVP / ZIF-67 composite SERS chip prepared in Example 2:

[0018] Figure 7 This is a scanning electron microscope (SEM) photograph of the PVP / ZIF-67 composite SERS chip prepared in Example 3;

[0019] Figure 8 The SERS spectrum of MC-LR was detected using the PVP / ZIF-67 composite SERS chip prepared in Example 3. DETAILED DESCRIPTION

[0020] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0021] The following examples illustrate the present invention but are not intended to limit its scope. Unless otherwise specified, the techniques used in these examples are conventional techniques known to those skilled in the art, and all raw materials used are commercially available products. The Raman spectrometer BWS415 used in these examples was purchased from B&W Tek Inc., USA.

[0022] Example 1: A method for preparing a flexible polymer PVP / ZIF-67 composite SERS chip, comprising the following steps:

[0023] Step 1: Preparation of polyvinylpyrrolidone (PVP) solution:

[0024] After adding 1200 mg of PVP powder to 35 mL of deionized water, the temperature was controlled at 75°C and heated with stirring for 1.5 hours until the PVP powder was completely dissolved. The PVP solution was obtained after filtering with filter paper. The solution had a uniform and transparent appearance without obvious particles or turbidity.

[0025] Step 2, preparation of ZIF-67 solution:

[0026] Dissolve 417.9 mg of dimethylimidazole in 29.85 mL of methanol and stir until completely dissolved to obtain a concentration of 14.00 mg / mL (1.5×10 -1 M) dimethylimidazole methanol solution; 731.9 mg of cobalt nitrate hexahydrate solid was dissolved in 34.95 mL of methanol to form a uniform concentration of 21.00 mg / mL (7.2×10 -2 M) hexahydrate cobalt nitrate methanol solution; the dimethylimidazole methanol solution and the hexahydrate cobalt nitrate methanol solution are mixed and stirred at a volume ratio of 1:3 to obtain a ZIF-67 precursor solution.

[0027] Step 3: Preparation of PVP / ZIF-67 composite SERS chip:

[0028] 15 μL of PVP solution was evenly dropped on a 10 mm 2 The silicon wafer was placed on a spin coater with a rotation speed of 3500 r / min and a spin coating time of 15 s to ensure uniform coverage of the PVP film. The silicon wafer with the PVP film was transferred to a 75 ℃ oven 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 37 ℃ ZIF-67 precursor solution and incubated for 2 h to allow ZIF-67 to grow evenly on the surface of the PVP film. After the incubation period, the silicon wafer was removed and placed in a 75 ℃ oven for drying for 12 min to remove the residual solvent to obtain a flexible polymer PVP / ZIF-67 composite SERS chip. Figure 1 This is a scanning electron microscope (SEM) photograph of the PVP / ZIF-67 composite chip prepared in this example. Figure 1 As shown, the PVP / ZIF-67 composite chip prepared in this example exhibits a unique uniform two-dimensional network structure.

[0029] like Figure 1 As shown in the figure, the SERS chip exhibits unique microstructural features. Flower-like nanostructures with three-dimensional characteristics are uniformly grown on a two-dimensional mesh substrate. The formation of this structure not only enriches the chip's surface morphology but also significantly influences its physical and chemical properties. The two-dimensional mesh substrate provides a stable support platform for the growth of the flower-like structures, while the three-dimensional flower-like structures further increase the specific surface area and provide more active sites, significantly enhancing the chip's adsorption capacity for target molecules.

[0030] A 10 µL droplet of MC-LR molecule solution was added to the SERS chip and then dried naturally in a dust-free environment. After drying, SERS activity was evaluated using Raman spectroscopy. The Raman spectrometer was operated at an excitation wavelength of 532 nm, a laser power of 1 mW, and an acquisition time of 10 s. The Raman spectrum was measured on the SERS chip, observing several characteristic Raman signal peaks of the MC-LR molecule. The minimum trace detection limit of the SERS chip was obtained, as shown in the following figure. Figure 2 As shown, the SERS spectrum shows that the detection concentration of PVP / ZIF-67 composite SERS chip is 1×10 -4 The intensity of the MC-LR solution of M at 1507 wavenumber is 807.3.

[0031] Figure 3 The figure shows the repeatability test results of the PVP / ZIF-67 composite SERS chip. Figure 3As shown in the figure, multiple Raman spectroscopy measurements of the same MC-LR molecular solution showed that the intensity of the Raman characteristic peak remained highly consistent across multiple measurements, demonstrating the SERS chip's excellent repeatability and stability. This repeatability is particularly important for achieving large-area SERS imaging and quantitative detection, ensuring the reliability and repeatability of the detection results.

[0032] Figure 4 This is the detection limit test result of the PVP / ZIF-67 composite SERS chip. Figure 4 The Raman signal intensity changes of MC-LR molecule solutions with different concentrations on the SERS chip were demonstrated. By analyzing the relationship between the intensity of the Raman characteristic peak and the concentration of MC-LR molecules, the detection limit of the SERS chip for MC-LR molecules was determined. The results showed that the chip can detect as low as 10⁻ 6 The MC-LR molecular concentration of M showed high detection sensitivity, providing strong support for trace analysis.

[0033] Example 2 is the same as Example 1, except that: Step 1, preparation of PVP solution: 1000 mg of PVP powder was added to 30 mL of deionized water, the temperature was controlled at 60° C., and heated with stirring for 2 hours.

[0034] 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.

[0035] Step 3, Preparation of PVP / ZIF-67 Composite SERS Chip: 10 μL of PVP solution was evenly dropped on a 10 mm 2 The silicon wafer was placed on a spin coater with a rotation speed of 3000 r / min and a spin coating time of 20 s. The silicon wafer with the PVP film was then transferred to a 70°C oven and dried for 3 h. The dried silicon wafer was immersed in a 36.5°C ZIF-67 precursor solution for 3 h, then taken out and placed in a 70°C oven for drying for 15 min to obtain a flexible polymer PVP / ZIF-67 composite SERS chip. Figure 5 This is a scanning electron microscope (SEM) photograph of the PVP / ZIF-67 composite chip prepared in this example. Figure 5 As shown, the PVP / ZIF-67 composite chip prepared in this example exhibits a unique uniform two-dimensional network structure.

[0036] A 10 µL droplet of MC-LR molecule solution was added to the SERS chip and then dried naturally in a dust-free environment. After drying, SERS activity was evaluated using Raman spectroscopy. The Raman spectrometer was operated at an excitation wavelength of 532 nm, a laser power of 1 mW, and an acquisition time of 10 s. The Raman spectrum was measured on the SERS chip, observing several characteristic Raman signal peaks of the MC-LR molecule. The minimum trace detection limit of the SERS chip was obtained, as shown in the following figure. Figure 6 As shown, the SERS spectrum shows that the detection concentration of PVP / ZIF-67 composite SERS chip is 1×10 -4 The intensity of the MC-LR solution of M at 1507 wavenumber is 1235.2.

[0037] Example 3 is the same as Example 1, except that: Step 1, preparation of PVP solution: 1500 mg of PVP powder was added to 40 mL of deionized water, the temperature was controlled at 90° C., and heated with stirring for 1 hour.

[0038] Step 2. Preparation of 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.

[0039] Step 3: Preparation of PVP / ZIF-67 composite SERS chip: 20 μL of PVP solution was evenly dropped on a 10 mm 2 The silicon wafer was placed on a spin coater with a rotation speed of 4000 r / min and a spin coating time of 10 s. The silicon wafer with the PVP film was then transferred to an 80 ℃ oven and dried for 2 h. The dried silicon wafer was immersed in a 37.5 ℃ ZIF-67 precursor solution and incubated for 1 h. The silicon wafer was taken out and placed in an 80 ℃ oven for drying for 10 min to obtain a flexible polymer PVP / ZIF-67 composite SERS chip. Figure 7 This is a scanning electron microscope (SEM) photograph of the PVP / ZIF-67 composite chip. Figure 7 As shown, the PVP / ZIF-67 composite chip prepared in this example exhibits a unique uniform two-dimensional network structure.

[0040] A 10 µL droplet of MC-LR molecule solution was added to the SERS chip and then dried naturally in a dust-free environment. After drying, SERS activity was evaluated using Raman spectroscopy. The Raman spectrometer was operated at an excitation wavelength of 532 nm, a laser power of 1 mW, and an acquisition time of 10 s. The Raman spectrum was measured on the SERS chip, observing several characteristic Raman signal peaks of the MC-LR molecule. The minimum trace detection limit of the SERS chip was obtained, as shown in the following figure. Figure 8 As shown, the SERS spectrum shows that the detection concentration of PVP / ZIF-67 composite SERS chip is 1×10 -4 The intensity of the MC-LR solution of M at 1507 wavenumber is 1028.6.

[0041] In summary, the flexible polymer PVP / ZIF-67 composite SERS chip prepared by the method of the present invention is not only suitable for the detection of MC-LR molecules, but can also be used to detect a variety of other poisons, including but not limited to environmental poisons such as heavy metal ions, organophosphorus pesticides, polycyclic aromatic hydrocarbons, as well as special poisons such as biological toxins and chemical warfare agents. The detection limits can reach the nanomolar to picomolar level, meeting the needs of high-sensitivity detection of trace poisons.

[0042] The above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by persons of ordinary skill in the art within the spirit and scope of the present invention shall also fall within the scope of protection of the present invention.

Claims

1. A method for preparing a flexible polymer PVP / ZIF-67 composite SERS chip, characterized in that The following steps are involved: The PVP solution was evenly dropped on the silicon wafer, and the silicon wafer was placed on a spin coater for spin coating. The silicon wafer with the PVP film was then transferred to an oven for drying. The dried silicon wafer was immersed in a ZIF-67 precursor solution for incubation, and then the silicon wafer was taken out and placed in an oven for drying again to obtain a flexible polymer PVP / ZIF-67 composite SERS chip.

2. The method for preparing a flexible polymer PVP / ZIF-67 composite SERS chip according to claim 1, characterized in that The specific steps are as follows: 10-20 μL of PVP solution is evenly dropped on 5-15 mm 2 The silicon wafer was placed on a spin coater with a rotation speed of 3000-4000 r / min and a spin coating time of 10-20 s. The silicon wafer with the PVP film was then transferred to an oven at 70-80°C and dried for 2-3 h. The dried silicon wafer was immersed in a ZIF-67 precursor solution at 36.5-37.5°C and incubated for 1-3 h. After the incubation period, the silicon wafer was taken out and placed in an oven at 70-80°C for drying for 10-15 min to obtain a flexible polymer PVP / ZIF-67 composite SERS chip.

3. The method for preparing 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: after adding 1000-1500 mg of PVP powder to 30-40 mL of deionized water, controlling the temperature to 60-90° C., heating and stirring for 1-2 hours until the PVP powder is completely dissolved, and filtering with filter paper to obtain a PVP solution.

4. The method for preparing 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: 410-420 mg of dimethylimidazole is dissolved in 25-30 mL of methanol and stirred until completely dissolved to obtain a dimethylimidazole methanol solution; 730-735 mg of cobalt nitrate hexahydrate solid is dissolved in 30-35 mL of methanol to form a uniform cobalt nitrate hexahydrate methanol solution; the dimethylimidazole methanol solution and the cobalt nitrate hexahydrate methanol solution are mixed and stirred in a volume ratio of 1:3 to obtain a ZIF-67 precursor solution.

5. Application of a flexible polymer PVP / ZIF-67 composite SERS chip prepared by the method according to any one of claims 1 to 4 in poison detection, characterized in that The detection method is as follows: 10-20 μL of the sample containing MC-LR toxin is dropped onto the flexible polymer PVP / ZIF-67 composite SERS chip, and after natural drying, the Raman spectrometer is used to measure the 1507 cm -1 The Raman signal intensity at the wavelength of 1507 cm was calculated based on the MC-LR toxin. -1 The concentration of MC-LR toxin in the test solution was calculated based on the linear relationship between the SERS signal peak intensity and its logarithmic concentration.

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