A composite SERS substrate based on needle tip silicon wafer and its preparation method and application

Abstract

The present application relates to the technical field of surface enhanced Raman spectroscopy detection, and particularly relates to a composite SERS substrate based on a needle tip silicon wafer and a preparation method and application thereof, comprising the following steps: adding S powder into a mixed solution of octylamine and ethanol to obtain a mixed solution; adding (NH4)6Mo7O 24 ·4H2O into the mixed solution to obtain a reaction solution; transferring the reaction solution into a reaction kettle, adding a silicon wafer with a periodic needle tip structure into the reaction kettle, and completely immersing the silicon wafer in the reaction solution; after sealing the reaction kettle, placing the reaction kettle in an oven to perform a hydrothermal reaction; after the hydrothermal reaction is completed, taking out the product to perform cleaning, and then placing the product in the oven to dry, to obtain the composite SERS substrate based on the needle tip silicon wafer. The present application prepares the composite SERS substrate with excellent performance, effectively improves the Raman enhancement effect, and simultaneously has the advantages of a simple preparation process, easy storage of the substrate, and low requirement on the preparation equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of surface-enhanced Raman spectroscopy detection technology, in particular to a composite SERS substrate based on a needle tip silicon wafer and a preparation method and application thereof. BACKGROUND

[0002] Surface-enhanced Raman scattering (SERS) detection technology has shown great application potential in many fields such as biological medicine, environmental monitoring, food safety and security, etc. due to its excellent ability to detect trace molecules. It can realize in-situ, non-destructive and real-time fingerprint detection, which has become a research hotspot in analytical chemistry. However, the current mainstream SERS substrate faces many challenges in practical application, which limits the further development and wide application of the technology.

[0003] Currently, the main SERS enhancement mechanisms are mainly physical enhancement and chemical enhancement, and the corresponding substrates are mainly noble metal substrates and two-dimensional material substrates. The noble metal substrate mainly relies on the localized surface plasmon resonance effect to multiply the intensity of incident light, thereby improving the intensity of Raman scattering light, and is widely used. For example, in the patent CN202110929800.1, a gold nanorod modified SERS substrate is prepared, which realizes high sensitivity detection of specific molecules by using the unique optical properties of gold nanorods. However, this kind of noble metal substrate has obvious defects, its preparation process is complex, and it has strict requirements on storage conditions, resulting in high cost. In the preparation process, it is often necessary to accurately control the reaction conditions such as temperature, concentration and reaction time, and any deviation in any link may affect the performance of the substrate, which makes it difficult for large-scale production. Moreover, in the storage process, an oxygen-free environment is required to prevent oxidation, which increases the cost and difficulty of use.

[0004] Two-dimensional material substrates include graphene, sulfide, black phosphorus, MXenes and emerging two-dimensional materials, etc., which have the advantages of anti-fluorescence background, high biological molecule compatibility and easy storage. The SERS substrate based on MXenes disclosed in the patent CN201710554489.0 shows good performance in biological detection. However, the enhancement factor of this kind of substrate is still not ideal compared with noble metal substrates. In practical application, for the detection of some trace substances, the detection sensitivity is difficult to meet the demand, which limits the application of two-dimensional material substrates in scenes with high detection accuracy requirements.

[0005] To solve the problems in the prior art, in recent years, composite SERS substrates have become a focus of research. For example, patent CN202410366191.7 discloses a SERS substrate based on a combination of metal-organic frameworks (MOF) and noble metal nanoparticles. The high adsorption of MOF and the strong enhancement effect of noble metal nanoparticles are combined to improve the detection performance of the substrate. However, the preparation process of the composite substrate involves multiple complex reactions, which need to be accurately controlled, increasing the difficulty and cost of preparation. Moreover, the stability of MOF materials in some 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. Such a substrate needs to combine the advantages of physical enhancement and chemical enhancement, have higher detection sensitivity and selectivity, reduce the preparation cost, simplify the preparation process, improve the stability of the substrate and the compatibility with actual samples, so as to meet the growing detection needs in different fields. SUMMARY

[0007] The purpose of the present application is to provide a composite SERS substrate based on a needle tip silicon wafer and its preparation method and application, to prepare a composite SERS substrate with excellent performance, effectively improve the Raman enhancement effect, and at the same time have the advantages of simple preparation process, easy storage of the substrate, and low requirement for preparation equipment.

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

[0009] S1, adding S powder into a mixed solution of octylamine and ethanol, stirring with a magnetic stirrer until completely dissolved, to obtain a mixed solution;

[0010] S2, adding (NH4)6Mo7O 24 ·4H2O into the mixed solution of S1, continuing to stir until (NH4)6Mo7O 24 ·4H2O is completely dissolved, to obtain a reaction solution;

[0011] S3, transferring the reaction solution of S2 into a reaction kettle, adding a 1cm×1cm silicon wafer with a periodic needle tip structure into the reaction kettle, immersing the silicon wafer in the reaction solution, sealing the reaction kettle, and then placing it in an oven to perform a hydrothermal reaction;

[0012] S4, after the hydrothermal reaction is completed, naturally cooling the reaction kettle to room temperature, taking out the product for cleaning, and then placing it in an oven for drying, to obtain a composite SERS substrate based on a needle tip silicon wafer.

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

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

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

[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℃.

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

[0019] The application of the composite SERS substrate based on the needle tip silicon wafer is applied to biological sample detection, environmental water sample detection, and food detection.

[0020] The beneficial effects of the present application are as follows:

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

[0022] (2) The composite SERS substrate based on the needle tip silicon wafer of the present application is easy to store, and is different from the noble metal substrate which needs to be stored in an oxygen-free environment. The composite SERS substrate based on the needle tip silicon wafer of the present application has strong oxidation resistance and can be stored in the daily environment.

[0023] (3) The present application has low requirements for preparation equipment, does not need complex equipment such as magnetron sputtering or vapor deposition, is simple to operate, and reduces the preparation cost and technical threshold.

[0024] (4) The composite SERS substrate based on the needle tip silicon wafer of the present application has good enhancement factor and detection limit, good uniformity, does not need secondary spin coating or two-dimensional material transfer, and comprehensively utilizes the physical enhancement mechanism (the silicon wafer with periodic needle tip structure on the surface) and the chemical enhancement mechanism (MoS2), and exhibits high sensitive detection capability for rhodamine R6G, methyl blue and crystal violet.

[0025] The technical solutions of the present application will be further described in detail below by means of the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 This is a SEM image of the silicon wafer with a periodic needle-tip structure in Embodiment 1 of the present invention;

[0027] Figure 2 This is a TEM image of MoS2 in Embodiment 1 of the present invention;

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

[0029] Figure 4 The image shows the detection results of different concentrations of crystal violet molecules on the silicon-based @MoS2 composite substrate in Example 1 of this invention.

[0030] Figure 5 The image shows the detection results of different concentrations of Rhodamine 6G (R6G) molecules on the silicon-based @MoS2 composite substrate in Example 1 of this invention.

[0031] Figure 6 This is a comparison chart of the detection of Rhodamine R6G (R6G) molecules between Example 1 and Comparative Examples 1-2 of the present invention. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should be understood in their ordinary sense by those skilled in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0033] This invention provides a method for fabricating a composite SERS substrate based on a pin-tip silicon wafer, comprising the following steps:

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

[0035] S2, (NH4)6Mo7O 24 ·4H2O was added to the mixed solution of S1, and stirring was continued to make (NH4)6Mo7O 24 ·4H2O completely dissolves the substance, yielding a reaction solution;

[0036] S3. Transfer the reaction solution from S2 to the reaction vessel. Add a 1cm×1cm silicon wafer with a periodic needle-like structure to the reaction vessel. The silicon wafer should be completely immersed in the reaction solution. After sealing the reaction vessel, place it in an oven for hydrothermal reaction.

[0037] S4, after the hydrothermal reaction, the reactor is naturally cooled to room temperature, the product is taken out for cleaning, and then placed in an oven for drying to obtain a composite SERS substrate based on a needle-shaped silicon wafer.

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

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

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

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

[0042] The stirring in S2 ensures that (NH4)6Mo7O 24 ·4H2O is completely dissolved in the solution, and 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 180-220℃, and the reaction time is 12-24 h.

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

[0045] In some embodiments of the present application, 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 application, the purpose of cleaning is to remove the residual reaction solution and impurities on the surface, and therefore, the amount of deionized water and ethanol is not limited, and can be selected by a person skilled in the art as needed.

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

[0048] A composite SERS substrate based on a needle-shaped silicon wafer is prepared by the above method for preparing a composite SERS substrate based on a needle-shaped silicon wafer.

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

[0050] Example 1

[0051] The application provides a preparation method of a composite SERS substrate based on a needle tip silicon wafer, which comprises the following steps:

[0052] S1, 0.3 mmol of S powder is accurately weighed, 7 mL of octylamine and 6.5 mL of ethanol are measured. The weighed S powder is added to the mixed solution of octylamine and ethanol, and a magnetic stirrer is used for stirring for 30 min, so that the S powder is fully dissolved in the mixed solution to form a uniform mixed system, and a mixed solution is obtained.

[0053] S2, 0.019 mmol of (NH4)6Mo7O 24 ·4H2O is added to the mixed solution stirred uniformly in S1, and stirring is continued for 30 min, so that a reaction solution is obtained.

[0054] S3, the reaction solution in S2 is transferred to a 20 mL reaction kettle, a 1 cm*1 cm silicon wafer with a periodic needle tip structure is placed in the reaction kettle, and the silicon wafer is completely immersed in the reaction solution. Subsequently, the reaction kettle is sealed and placed in an oven, and a hydrothermal reaction is carried out at a temperature interval of 220 DEG C, and the reaction time is controlled to be 12 h.

[0055] S4, after the hydrothermal reaction is completed, the reaction kettle is naturally cooled to room temperature, the product is taken out, the surface is washed with deionized water to remove the residual reaction solution on the surface, then the surface is washed with ethanol to further remove the residual impurities, and finally the product is placed in an oven and dried at 50 DEG C, so that a composite SERS substrate based on a needle tip silicon wafer on which MoS2 is grown (denoted as silicon-based@MoS2 composite substrate) is obtained.

[0056] Example 2

[0057] The difference from example 1 is that the amount of S powder in S1 is 0.15 mmol, the amount 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 amount of S powder in S1 is 0.6 mmol, the amount 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 amount of octylamine in S1 is 6 mL, the amount of ethanol is 3 mL, and the others are the same as example 1.

[0062] Example 5

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

[0064] Example 6

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

[0066] Example 7

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

[0068] Example 8

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

[0070] Example 9

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

[0072] Comparative example 1

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

[0074] Comparative example 2

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

[0076] Application example 1

[0077] The application provides an application of a composite SERS substrate based on a needle silicon wafer, which is applied to biological sample detection and includes the following processes:

[0078] An appropriate amount of blood sample is collected, pretreated by centrifugation, and serum is separated. The serum is diluted with physiological saline to a certain multiple to serve as a 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 naturally dry it at room temperature for more than 2 hours. After drying, place the substrate on the sample stage of the Raman spectrometer, focus under ordinary light, and select an appropriate site for Raman signal collection. By comparing with the Raman characteristic peaks of known biomarkers, it can be determined whether the target biomarker exists in the serum sample.

[0080] Application Example 2

[0081] The application provides an application of a composite SERS substrate based on a needle tip silicon wafer, which is applied to environmental water sample detection, and includes 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 suspended particulate matter. Take a certain volume of the filtered water sample, concentrate it to an appropriate volume using a rotary evaporator, and use it as a 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 naturally dry it at room temperature for more than 2 hours. Place the substrate on the sample 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, the types and concentrations of trace organic pollutants in the water sample can be analyzed.

[0084] Application Example 3

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

[0086] Select a certain vegetable sample, chop the vegetable, add an appropriate amount of acetonitrile for ultrasonic extraction, and then centrifuge, filter, and dry the extract with nitrogen. Then, make up the volume to a certain volume with methanol, and use it as a 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 naturally dry it at room temperature for more than 2 hours. Place the substrate on the Raman spectrometer, and collect Raman signals according to the 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, it can be determined whether there are pesticide residues in the food and the amount of the residues.

[0088] Performance test

[0089] Figure 1The SEM image of the silicon wafer with periodic needle tip structure in Example 1 of the present application, Figure 2 The TEM image of MoS2 in Example 1 of the present application, Figure 3 The SEM image of the silicon substrate@MoS2 composite substrate in Example 1 of the present application, Figures 1-3 It can be seen that the surface of the silicon wafer presents a regular arrangement of periodic needle tip structure, and the MoS2 crystals in the silicon substrate@MoS2 composite substrate prepared by the present application grow uniformly on the surface of the silicon wafer, which comprehensively combines the physical enhancement characteristics of the silicon substrate and the chemical enhancement characteristics of MoS2, so that the composite substrate has good SERS performance.

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

[0091] 10 μL of alcohol solutions of rhodamine R6G and crystal violet with different concentrations were respectively dropped on the surfaces of different substrates, and after drying at room temperature, they were placed on the sample stage of the micro-Raman spectrometer. First, focusing was performed under ordinary light, and then appropriate sites were selected for Raman signal collection.

[0092] The concentrations of the alcohol solutions of crystal violet were 10 -7 M and 10 -8 M, and the test results are shown in Table 1. Figure 4 The Raman characteristic peaks of crystal violet molecules were 805 cm -1 , 1175 cm -1 , 1380 cm -1 , 1536 cm -1 , 1587 cm -1 and 1620 cm -1 . It shows that the Raman signal of crystal violet molecules can be effectively detected on the silicon substrate@MoS2 composite substrate prepared by the present application, 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 substrate@MoS2 composite substrate for crystal violet molecules reaches 10 -8 M, which has high detection sensitivity.

[0093] The concentrations of the alcohol solutions of rhodamine R6G were 10 -4 M, 10 -5 M, 10 -6 M, 10 -7 M, 10 -8 M and 10 -9 M, and the test results are shown in Table 2. Figure 5 The Raman characteristic peaks of R6G molecules were 612 cm -1, 773 cm -1 , 1183 cm -1 , 1362 cm -1 , 1505 cm -1 , 1573 cm -1 and 1646 cm -1 . It is shown that the characteristic Raman signal of R6G molecules can be effectively detected on the silicon-based MoS2 composite substrate prepared in the application, and R6G molecules as low as 10 -9 M in concentration can be detected, that is, the minimum detection limit of the silicon-based MoS2 composite substrate for R6G molecules reaches 10 -9 M, which shows that it has 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, and the test conditions were the same as above. The test results are shown in Table 2. Figure 6 The Raman enhancement effect of the silicon-based MoS2 composite substrate of Example 1 on 10 -4 M R6G probe molecules is obviously better than that of the silicon substrate with a periodic needle structure of Comparative Example 1 and the MoS2 substrate of Comparative Example 2. The silicon-based MoS2 composite substrate can not only significantly enhance the Raman scattering signal of R6G molecules through the synergistic effect of physical and chemical enhancement mechanisms, but also effectively suppress the fluorescence effect of the probe molecules.

[0095] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the application and not to limit it. Although the application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the application can still be modified or replaced by equivalents, and these modifications or replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the application.

Claims

1. A method for fabricating a composite SERS substrate based on a pin-tip silicon wafer, characterized in that: Includes the following steps: S1. Add S powder to a mixed solution of octylamine and ethanol, and stir with a magnetic stirrer until completely dissolved to obtain a mixed solution; S2, (NH4)6Mo7O 24 • Add 4H2O to the mixed solution of S1 and continue stirring to make (NH4)6Mo7O 24 • The solution completely dissolves in 4H2O, yielding a reaction solution; S3. Transfer the reaction solution from S2 to a reaction vessel. Add a 1cm×1cm silicon wafer with a nanoscale periodic needle-like structure to the reaction vessel. The silicon wafer should be completely immersed in the reaction solution. After sealing the reaction vessel, place it in an oven for hydrothermal reaction. The hydrothermal reaction temperature is 180℃-220℃, and the reaction time is 12h-24h. S4. After the hydrothermal reaction is completed, the reactor is allowed to cool naturally to room temperature. The product is then removed, cleaned, and placed in an oven to dry, thus obtaining a composite SERS substrate based on a pinhead silicon wafer. The drying temperature is 50°C. The aforementioned composite SERS substrate is used for biological sample testing, environmental water sample testing, and food testing.

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

3. The method for preparing a composite SERS substrate based on a pin-tip silicon wafer according to claim 1, characterized in that: In S2, (NH4)6Mo7O 24 • The amount of 4H2O used is 0.0095mmol-0.038mmol, and the stirring time is 30min.

4. The method for preparing a composite SERS substrate based on a pin-tip silicon wafer according to claim 1, characterized in that: In S4, the cleaning process involves first rinsing with deionized water, followed by rinsing with ethanol.

5. A composite SERS substrate based on a pin-tip silicon wafer, characterized in that: It is prepared by the method for preparing a composite SERS substrate based on a pinhead silicon wafer as described in any one of claims 1-4.

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