Composite SERS (Surface Enhanced Raman Scattering) substrate based on needle tip silicon wafer and preparation method and application thereof

Abstract

The invention relates to the technical field of surface enhanced Raman spectroscopy detection, in particular to a composite SERS (Surface Enhanced Raman Scattering) substrate based on a needle tip silicon wafer as well as a preparation method and application thereof, and the preparation method comprises the following steps: adding S powder into a mixed solution of octylamine and ethanol to obtain a mixed solution; (NH4) 6Mo7O24. 4H2O is added into the mixed solution, and a reaction solution is obtained; transferring the reaction liquid into a reaction kettle, adding a silicon wafer with a periodic needle tip structure into the reaction kettle, completely immersing the silicon wafer into the reaction liquid, sealing the reaction kettle, and putting the reaction kettle into a drying oven for hydrothermal reaction; and after the hydrothermal reaction is finished, taking out a product, cleaning, and drying in a drying oven to obtain the composite SERS substrate based on the needle tip silicon wafer. The composite SERS substrate with excellent performance is prepared, the Raman enhancement effect is effectively improved, and meanwhile the method has the advantages that the preparation process is simple, the substrate is easy to store, and the requirement for preparation equipment is low.

Description

Technical Field

[0001] The present invention relates to the technical field of surface-enhanced Raman spectroscopy detection, and particularly to a composite SERS substrate based on a tip wafer, a preparation method thereof, and an application thereof. Background Art

[0002] Surface-enhanced Raman scattering (SERS) detection technology, with its excellent ability to detect trace molecules, has shown great application potential in many fields such as biomedicine, environmental monitoring, food safety, and security. It can achieve in-situ, non-destructive, and real-time fingerprint detection, which makes it a research hotspot in the field of analytical chemistry. However, current mainstream SERS substrates face many challenges in practical applications, restricting the further development and wide application of this technology.

[0003] Currently, the mainstream SERS enhancement mechanisms are mainly divided into physical enhancement and chemical enhancement, and the corresponding substrates are mainly noble metal substrates and two-dimensional material substrates. Noble metal substrates mainly rely on the local surface plasmon resonance effect to multiply the intensity of incident light, thereby increasing the intensity of Raman scattered light, and are widely used. For example, in Patent CN202110929800.1, a SERS substrate modified with gold nanorods was prepared, and high-sensitivity detection of specific molecules was achieved using the unique optical properties of gold nanorods. However, such noble metal substrates have obvious defects. Their preparation process is complex, and the storage conditions are demanding, resulting in high costs. During the preparation process, reaction conditions such as temperature, concentration, and reaction time often need to be precisely controlled. Any deviation in any link may affect the performance of the substrate, making large-scale production difficult. Moreover, during storage, an oxygen-free environment is required to prevent oxidation, which increases the usage cost and difficulty.

[0004] Two-dimensional material substrates include graphene, sulfides, black phosphorus, MXenes, and emerging two-dimensional materials, etc., and have the advantages of anti-fluorescence background, high biocompatibility of biomolecules, and easy preservation. The SERS substrate based on MXenes disclosed in Patent CN201710554489.0 shows good performance in biological detection. However, the enhancement factor of such substrates is still not ideal compared with noble metal substrates. In practical applications, for the detection of some trace substances, its detection sensitivity is difficult to meet the requirements, restricting the application of two-dimensional material substrates in scenarios with higher detection accuracy requirements.

[0005] To address the deficiencies of existing technologies, composite SERS substrates have become a key research focus in recent years. For example, Patent CN202410366191.7 discloses a SERS substrate based on the composite of metal-organic framework (MOF) and noble metal nanoparticles. By combining the high adsorption of MOF and the strong enhancement effect of noble metal nanoparticles, the detection performance of the substrate is improved. However, the preparation process of this composite substrate involves multiple complex reactions, requiring precise control of the reaction conditions for each step, which increases the preparation difficulty and cost. Moreover, the stability of MOF materials in certain environments needs to be improved, which may affect the long-term use performance of the substrate.

[0006] In summary, it is urgent to develop a new type of SERS substrate. This substrate needs to integrate the advantages of physical enhancement and chemical enhancement, possess higher detection sensitivity and selectivity, while reducing the preparation cost, simplifying the preparation process, improving the stability of the substrate and its compatibility with actual samples to meet the growing detection needs in different fields. Summary of the Invention

[0007] The object of the present invention is to provide a composite SERS substrate based on a tip silicon wafer, its preparation method and application, to prepare a composite SERS substrate with excellent performance, effectively improving the Raman enhancement effect, while having the advantages of simple preparation process, easy preservation of the substrate, and low requirements for preparation equipment.

[0008] To achieve the above object, the present invention provides a preparation method of a composite SERS substrate based on a tip silicon wafer, comprising the following steps:

[0009] S1. Add S powder to the mixed solution of octylamine and ethanol, and stir with a magnetic stirrer until completely dissolved to obtain a mixed solution;

[0010] S2. Add (NH4)6Mo7O 24 ·4H2O to the mixed solution of S1, and continue to stir to completely dissolve (NH4)6Mo7O 24 ·4H2O to obtain a reaction solution;

[0011] S3. Transfer the reaction solution of S2 to a reaction kettle, add a 1 cm × 1 cm silicon wafer with a periodic tip structure to the reaction kettle, completely immerse the silicon wafer in the reaction solution, seal the reaction kettle, and place it in an oven for hydrothermal reaction;

[0012] S4. After the hydrothermal reaction is completed, wait for the reaction kettle to cool naturally to room temperature, take out the product for cleaning, and then place it in an oven for drying to obtain a composite SERS substrate based on a tip silicon wafer.

[0013] Preferably, in S1, the dosage of S powder is 0.15 mmol - 0.6 mmol, the dosage of octylamine is 6 - 8 mL, the dosage of ethanol is 3 - 7 mL, and the stirring time is 30 min.

[0014] Preferably, in S2, the dosage of (NH4)6Mo4O 24 ·4H2O is 0.0095 mmol - 0.038 mmol, and the stirring time is 30 min.

[0015] Preferably, in S3, the temperature of the hydrothermal reaction is 180°C - 220°C, and the reaction time is 12 h - 24 h.

[0016] Preferably, in S4, the cleaning is first rinsing with deionized water and then rinsing with ethanol.

[0017] Preferably, in S4, the drying temperature is 50°C.

[0018] A composite SERS substrate based on a tip - silicon wafer is prepared by the above - mentioned preparation method of the composite SERS substrate based on a tip - silicon wafer.

[0019] An application of a composite SERS substrate based on a tip - silicon wafer, which is applied to the detection of biological samples, environmental water samples, and food detection.

[0020] The beneficial effects of the present invention:

[0021] (1) The preparation process of the present invention is simple. The synthesis can be completed by a one - step hydrothermal method without complex multi - step operations.

[0022] (2) The composite SERS substrate based on a tip - silicon wafer of the present invention is easy to store. Different from the commonly used noble metal substrates that need to be stored in an anaerobic environment, the composite SERS substrate based on a tip - silicon wafer of the present invention has strong antioxidant properties and can be stored in a daily environment.

[0023] (3) The present invention has low requirements for preparation equipment. It does not require complex equipment such as magnetron sputtering or chemical vapor deposition, and the operation is simple, reducing the preparation cost and technical threshold.

[0024] (4) The composite SERS substrate based on a tip - silicon wafer of the present invention has good enhancement factors and detection limits, good uniformity, and does not require secondary spin - coating or two - dimensional material transfer. It comprehensively utilizes the physical enhancement mechanism (silicon wafer with a periodic tip structure on the surface) and the chemical enhancement mechanism (MoS2), and shows high - sensitivity detection capabilities for rhodamine R6G, methylene blue, and crystal violet, etc.

[0025] The technical solutions of the present invention will be further described in detail below through the drawings and embodiments. Description of the Drawings

[0026] Figure 1 SEM image of the silicon wafer with a periodic tip structure in Example 1 of the present invention;

[0027] Figure 2 TEM image of MoS2 in Example 1 of the present invention;

[0028] Figure 3 SEM image of the silicon-based @MoS2 composite substrate in Example 1 of the present invention;

[0029] Figure 4 Detection result graph of the silicon-based @MoS2 composite substrate in Example 1 of the present invention for crystal violet molecules with different concentrations;

[0030] Figure 5 Detection result graph of the silicon-based @MoS2 composite substrate in Example 1 of the present invention for rhodamine 6G (R6G) molecules with different concentrations;

[0031] Figure 6 Detection comparison graph of rhodamine R6G (R6G) molecules between Example 1 of the present invention and Comparative Examples 1-2; Detailed implementation manners

[0032] The present invention will be further described below in conjunction with the drawings and embodiments. Unless otherwise defined, the technical terms or scientific terms used in the present invention should have the ordinary meaning understood by those of ordinary skill in the field to which the present invention belongs. The above-mentioned features mentioned in the present invention or the features mentioned in the specific examples can be combined arbitrarily. These specific embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0033] The present invention provides a preparation method for a composite SERS substrate based on a tip silicon wafer, including the following steps,

[0034] S1. Add S powder into the mixed solution of octylamine and ethanol, and stir with a magnetic stirrer until completely dissolved to obtain a mixed solution;

[0035] S2. Add (NH4)6Mo7O 24 ·4H2O into the mixed solution of S1, and continue to stir to completely dissolve (NH4)6Mo7O 24 ·4H2O to obtain a reaction solution;

[0036] S3. Transfer the reaction solution of S2 to a reaction kettle, add a 1 cm × 1 cm silicon wafer with a periodic tip structure into the reaction kettle, completely immerse the silicon wafer in the reaction solution, seal the reaction kettle, and then put it into an oven for hydrothermal reaction;

[0037] S4. After the hydrothermal reaction is completed, wait for the reaction kettle to cool naturally to room temperature. Take out the product for cleaning, and then place it in an oven for drying to obtain a composite SERS substrate based on a needle-tip silicon wafer.

[0038] Preferably, in S1, the dosage of S powder is 0.15 mmol - 0.6 mmol, the dosage of octylamine is 6 - 8 mL, the dosage of ethanol is 3 - 7 mL, and the stirring time is 30 min.

[0039] In some embodiments of the present invention, the dosage of S powder is 0.3 mmol, the dosage of octylamine is 7 mL, and the dosage of ethanol is 6.5 mL.

[0040] Preferably, in S2, the dosage of (NH4)6Mo7O 24 ·4H2O is 0.0095 mmol - 0.038 mmol, and the stirring time is 30 min.

[0041] In some embodiments of the present invention, the dosage of (NH4)6Mo7O 24 ·4H2O is 0.019 mmol.

[0042] Stirring in S2 can ensure that (NH4)6Mo7O 24 ·4H2O is completely dissolved in the solution, so that it is fully mixed with the previously dissolved S powder, preparing for the subsequent reaction under hydrothermal conditions;

[0043] Preferably, in S3, the temperature of the hydrothermal reaction is 180°C - 220°C, and the reaction time is 12 h - 24 h.

[0044] In some embodiments of the present invention, the temperature of the hydrothermal reaction is 220°C, and the reaction time is 12 h.

[0045] In some embodiments of the present invention, in S3, MoS2 gradually grows and adheres to the surface of the silicon wafer during the hydrothermal reaction.

[0046] Preferably, in S4, the cleaning is first rinsing with deionized water and then rinsing with ethanol. In the present invention, the purpose of cleaning is to remove the residual reaction solution and impurities on the surface. Therefore, the dosages of deionized water and ethanol are not limited, and those skilled in the art can select according to needs.

[0047] Preferably, in S4, the drying temperature is 50°C.

[0048] A composite SERS substrate based on a needle-tip silicon wafer is prepared by the preparation method of the above-mentioned composite SERS substrate based on a needle-tip silicon wafer.

[0049] Application of a composite SERS substrate based on a needle tip silicon wafer, applied to biological sample detection, environmental water sample detection, and food detection.

[0050] Example 1

[0051] The present invention provides a preparation method of a composite SERS substrate based on a needle tip silicon wafer, comprising the following steps:

[0052] S1. Accurately weigh 0.3 mmol of S powder, measure 7 mL of octylamine and 6.5 mL of ethanol. Add the weighed S powder into the mixed solution of octylamine and ethanol, and stir with a magnetic stirrer for 30 min. The purpose is to fully dissolve the S powder in the mixed solution to form a uniform mixed system, obtaining a mixed solution.

[0053] S2. In the uniformly stirred mixed solution of S1, add 0.019 mmol of (NH4)6Mo7O 24 ·4H2O, and continue to stir for 30 min to obtain a reaction solution.

[0054] S3. Transfer the reaction solution of S2 to a 20 mL reaction kettle, put a 1 cm × 1 cm silicon wafer with a periodic needle tip structure into the reaction kettle, and the silicon wafer is completely immersed in the reaction solution. Subsequently, seal the reaction kettle and place it in an oven for hydrothermal reaction in the temperature range of 220 °C, and control the reaction time to 12 h.

[0055] S4. After the hydrothermal reaction is completed, wait for the reaction kettle to cool naturally to room temperature, take out the product, first rinse the surface with deionized water to remove the residual reaction solution on the surface, then rinse with ethanol to further remove the residual impurities, and finally place it in an oven and dry at 50 °C to obtain a composite SERS substrate based on a needle tip silicon wafer with MoS2 grown thereon (denoted as silicon-based @MoS2 composite substrate).

[0056] Example 2

[0057] The difference from Example 1 is that the dosage of S powder in S1 is 0.15 mmol, and the dosage of (NH4)6Mo7O 24 ·4H2O in S2 is 0.0095 mmol, and the others are the same as in Example 1.

[0058] Example 3

[0059] The difference from Example 1 is that the dosage of S powder in S1 is 0.6 mmol, and the dosage of (NH4)6Mo7O 24 ·4H2O in S2 is 0.038 mmol, and the others are the same as in Example 1.

[0060] Example 4

[0061] The difference from Example 1 is that the dosage of octylamine in S1 is 6 mL, the dosage of ethanol is 3 mL, and the others are the same as in Example 1.

[0062] Example 5

[0063] The difference from Example 1 is that the dosage of octylamine in S1 is 8 mL, the dosage of ethanol is 7 mL, and the others are the same as in Example 1.

[0064] Example 6

[0065] The difference from Example 1 is that the temperature of the hydrothermal reaction in S3 is 180 °C, and the others are the same as in Example 1.

[0066] Example 7

[0067] The difference from Example 1 is that the temperature of the hydrothermal reaction in S3 is 200 °C, and the others are the same as in Example 1.

[0068] Example 8

[0069] The difference from Example 1 is that the time of the hydrothermal reaction in S3 is 18 h, and the others are the same as in Example 1.

[0070] Example 9

[0071] The difference from Example 1 is that the time of the hydrothermal reaction in S3 is 24 h, and the others are the same as in Example 1.

[0072] Comparative Example 1

[0073] A silicon wafer with a periodic tip structure is directly used as the SERS substrate.

[0074] Comparative Example 2

[0075] MoS2 is directly used as the SERS substrate.

[0076] Application Example 1

[0077] The present invention provides an application of a composite SERS substrate based on a tip silicon wafer, which is applied to the detection of biological samples, including the following process:

[0078] Collect an appropriate amount of blood sample, and after pretreatment steps such as centrifugation, separate the serum. Dilute the serum with physiological saline by a certain multiple as the sample to be detected.

[0079] Detection process: Take 10 μL of the diluted serum sample and drop it on the surface of the silicon-based @MoS2 composite substrate prepared in Example 1, and let it dry naturally at room temperature for more than 2 hours. Place the dried substrate on the stage of a micro-Raman spectrometer. After focusing under a common light source, select appropriate sites for Raman signal collection. By comparing with the Raman characteristic peaks of known biomarkers, detect whether the target biomarker exists in the serum sample.

[0080] Application Example 2

[0081] The present invention provides an application of a composite SERS substrate based on a tip silicon wafer, which is applied to the detection of environmental water samples, including the following process:

[0082] Collect water samples near the wastewater discharge outlet, filter the water samples through a 0.45 μm filter membrane to remove the suspended particulate matter therein. Take a certain volume of the filtered water sample and concentrate it to an appropriate volume using a rotary evaporator as the water sample to be detected.

[0083] Detection process: Take 10 μL of the concentrated water sample and drop it on the surface of the silicon-based @MoS2 composite substrate prepared in Example 1, and let it dry naturally at room temperature for more than 2 hours. Place the substrate on the stage of the Raman spectrometer and collect Raman signals according to the set test conditions (laser light source 532 nm, power intensity 5 mW, spot diameter 2 μm, integration time 20 seconds). By comparing with the Raman spectrum database of standard organic pollutants, analyze the types and concentrations of trace organic pollutants in the water sample.

[0084] Application Example 3

[0085] The present invention provides an application of a composite SERS substrate based on a tip silicon wafer, which is applied to the detection of pesticide residues in food, including the following process:

[0086] Select a certain vegetable sample. After chopping the vegetable, add an appropriate amount of acetonitrile for ultrasonic extraction. After the extract goes through steps such as centrifugation and filtration, it is dried with nitrogen and then fixed to a certain volume with methanol as the sample solution to be detected.

[0087] Detection process: Take 10 μL of the sample solution to be detected and drop it on the surface of the silicon-based @MoS2 composite substrate prepared in Example 1, and let it dry naturally at room temperature for more than 2 hours. Place the substrate on the Raman spectrometer and collect Raman signals according to appropriate test parameters (laser light source 532 nm, power intensity 3 mW, spot diameter 2 μm, integration time 15 seconds). By comparing with the Raman spectrum of the pesticide standard product, judge whether there are pesticide residues in the food and the residue amount.

[0088] Performance Test

[0089] Figure 1SEM image of the silicon wafer with a periodic tip structure in Example 1 of the present invention. Figure 2 TEM image of MoS2 in Example 1 of the present invention. Figure 3 SEM image of the silicon@MoS2 composite substrate in Example 1 of the present invention. It can be seen from Figures 1-3 that the surface of the silicon wafer presents a periodically arranged regular tip structure. In the silicon@MoS2 composite substrate prepared by the present invention, MoS2 crystals grow uniformly on the surface of the silicon wafer, combining the physical enhancement characteristics of the silicon substrate and the chemical enhancement characteristics of MoS2, making the composite substrate have good SERS performance.

[0090] The SERS performance of Example 1 was tested using a Raman spectrometer. Under the same test conditions (laser light source 532 nm, power intensity 5 mW, spot diameter 2 μm, integration time 20 seconds), the Raman enhancement effects of crystal violet and rhodamine R6G were tested.

[0091] 10 μL of alcohol solutions of rhodamine R6G and crystal violet with different concentrations were respectively drop-coated on the surfaces of different substrates. After drying at room temperature, they were placed on the stage of a microscopic Raman spectrometer. First, they were focused under a normal light source, and then appropriate sites were selected for Raman signal collection.

[0092] The concentrations of the crystal violet alcohol solution were 10 -7 M and 10 -8 M. The test results are as shown in Figure 4 . The Raman characteristic peaks of crystal violet molecules are 805 cm -1 , 1175 cm -1 , 1380 cm -1 , 1536 cm -1 , 1587 cm -1 and 1620 cm -1 . It shows that the Raman signals of crystal violet molecules can be effectively detected on the silicon@MoS2 composite substrate prepared by the present invention, and crystal violet molecules with a concentration as low as 10 - 8 M can be detected. That is, the lowest detection limit of the silicon@MoS2 composite substrate for crystal violet molecules reaches 10 -8 M, having a high detection sensitivity.

[0093] The concentrations of the rhodamine R6G alcohol solution were 10 -4 M, 10 -5 M, 10 -6 M, 10 -7 M, 10 -8 M and 10 -9 M. The test results are as shown in Figure 5 . The Raman characteristic peak of R6G molecules is 612 cm -1, 773 cm -1 , 1183 cm -1 , 1362 cm -1 , 1505 cm -1 , 1573 cm -1 and 1646 cm -1 . It shows that the characteristic Raman signal of R6G molecules can be effectively detected on the silicon-based @MoS2 composite substrate prepared in the present invention, and R6G molecules with a concentration as low as 10 -9 M can be detected. That is, the lowest detection limit of the silicon-based @MoS2 composite substrate for R6G molecules reaches 10 -9 M, indicating that it has a high detection sensitivity for R6G molecules.

[0094] The SERS performance of Example 1 and Comparative Examples 1-2 was tested using a 10 -4 M rhodamine R6G alcohol solution. The test conditions were the same as above, and the test results are as Figure 6 shown. The Raman enhancement effect of the silicon-based @MoS2 composite substrate in Example 1 on the 10 -4 M R6G probe molecule is significantly better than that of the silicon substrate with a periodic tip structure in Comparative Example 1 and the MoS2 substrate in Comparative Example 2. Through the synergistic effect of physical and chemical enhancement mechanisms, the silicon-based @MoS2 composite substrate can not only significantly enhance the Raman scattering signal of R6G molecules but also effectively suppress the fluorescence effect of the probe molecules.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method of a composite SERS substrate based on a tip silicon wafer, characterized in that: It includes the following steps: S1. Add S powder into the mixed solution of octylamine and ethanol, and stir with a magnetic stirrer until it is completely dissolved to obtain a mixed solution; S2. Add (NH4)6Mo7O 24 ·4H2O to the mixed solution of S1, and continue stirring to completely dissolve (NH4)6Mo7O 24 ·4H2O to obtain a reaction solution; S3. Transfer the reaction solution of S2 to a reaction kettle, add a silicon wafer with a periodic tip structure of 1 cm × 1 cm into the reaction kettle, the silicon wafer is completely immersed in the reaction solution, seal the reaction kettle, and then put it into an oven for hydrothermal reaction; S4. After the hydrothermal reaction is completed, wait for the reaction kettle to cool naturally to room temperature, take out the product for cleaning, and then place it in an oven for drying to obtain a composite SERS substrate based on the tip silicon wafer.

2. The preparation method of a composite SERS substrate based on a needle tip silicon wafer according to claim 1, characterized in that: In S1, the dosage of S powder is 0.15 mmol - 0.6 mmol, the dosage of octylamine is 6 - 8 mL, the dosage of ethanol is 3 - 7 mL, and the stirring time is 30 min.

3. The preparation method of a composite SERS substrate based on a needle tip silicon wafer according to claim 1, wherein: In S2, the dosage of (NH4)6Mo7O 24 ·4H2O is 0.0095 mmol - 0.038 mmol, and the stirring time is 30 min.

4. The preparation method of a composite SERS substrate based on a tip silicon wafer according to claim 1, wherein: In S3, the temperature of the hydrothermal reaction is 180°C - 220°C, and the reaction time is 12 h - 24 h.

5. The preparation method of a composite SERS substrate based on a tip silicon wafer according to claim 1, characterized in that: In S4, the cleaning is to first rinse with deionized water and then rinse with ethanol.

6. The preparation method of a composite SERS substrate based on a needle tip silicon wafer according to claim 1, characterized in that: In S4, the drying temperature is 50°C.

7. A composite SERS substrate based on a needle tip silicon wafer, characterized in that: It is prepared by the preparation method of the composite SERS substrate based on the tip silicon wafer according to any one of claims 1 - 6.

8. The application of the composite SERS substrate based on a needle tip silicon wafer according to claim 7, characterized in that: It is applied to biological sample detection, environmental water sample detection, and food detection.

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