An ultrahydrophobic SERS substrate for detecting surface contaminants of fish bodies and a preparation method thereof

Abstract

A superhydrophobic SERS substrate for detecting contaminants on fish surfaces and its preparation method belong to the field of Raman spectroscopy technology. The steps are as follows: PET fabric is cleaned and dried; polydimethylsiloxane prepolymer and curing agent are dissolved in an organic solvent to obtain solution A; octadecylamine is dissolved in an organic solvent to obtain solution B; solutions A and B are mixed and stirred to obtain a coating solution; the treated PET fabric is immersed in the coating solution, removed, and dried, allowing polydimethylsiloxane and octadecylamine to self-assemble on the PET fabric surface to form a micro / nano composite structure coating; an Ag layer is deposited on the coated PET fabric surface to obtain the superhydrophobic SERS substrate. This invention utilizes the self-assembly of octadecylamine and polydimethylsiloxane on the surface of PET fabric to form a micro / nano secondary structure, preparing a SERS substrate with high sensitivity and superhydrophobicity for trace and in-situ wiping detection of target molecules.

Description

Technical Field

[0001] This invention belongs to the field of Raman spectroscopy technology, specifically relating to a superhydrophobic SERS substrate for detecting pollutants on the surface of fish and its preparation method. Background Technology

[0002] During aquaculture and storage, pollutants and pesticide residues (such as malachite green and tricyclazole) in the water can easily accumulate on the surface of fish, posing a serious food safety hazard. These residues can not only cause acute poisoning, but long-term ingestion can also lead to chronic toxicity accumulation, directly threatening public health. Therefore, establishing an analytical technique capable of highly sensitive and rapid detection of trace harmful substances on fish surfaces is of significant practical importance for ensuring the quality and safety of aquatic products and improving risk assessment systems.

[0003] Surface-enhanced Raman spectroscopy (SERS) technology, due to its unique fingerprint recognition capabilities and extremely high sensitivity, has great application potential in the analysis and detection of trace harmful substances such as pesticide residues. Traditional rigid substrates (such as silicon wafers and glass), while possessing excellent mechanical stability, are inherently brittle and difficult to conformally adhere to the irregular curved surfaces, scale gaps, and soft muscle tissue of fish bodies. During physical wiping or adhesive sampling, this rigid contact easily leads to the loss or missed detection of target residues. Furthermore, extraction methods often involve cumbersome pretreatment steps, making them unsuitable for rapid on-site detection.

[0004] Flexible SERS substrates, with their excellent flexibility, can achieve good conformal adhesion, thus significantly improving sampling efficiency and detection sensitivity, providing a more convenient and reliable technical solution for rapid on-site screening of contaminants on fish surfaces. Among many flexible materials, polymer films have smooth surfaces that make it difficult to enrich analytes; sponges have excessive pores and insufficient mechanical strength, easily leading to substrate damage; filter paper has poor encapsulation stability and is prone to swelling and deformation on damp surfaces, affecting reproducibility. In addition, the mucus on the fish surface easily spreads and adheres to the substrate surface, forming a non-specific adsorption layer. This not only masks the SERS activity "hot spots" on the substrate surface but also hinders effective contact between the analyte molecules and the substrate, resulting in decreased detection sensitivity. Summary of the Invention

[0005] Technical Problem Solved: Addressing the problems existing in the prior art, this invention proposes a superhydrophobic SERS substrate for detecting pollutants on fish surfaces and its preparation method. Using environmentally friendly and economical PET (commonly known as polyester) fabric as the substrate, a densely interwoven, sheet-like "floral" structure is formed on its surface through the self-assembly of low surface energy ODA and PDMS, endowing the substrate with excellent superhydrophobic properties. This effectively reduces mucus adhesion during fish surface wiping and detection, and facilitates the enrichment of target molecules, achieving rapid and highly sensitive detection. The prepared substrate has a minimum detection concentration of crystal violet (CV) as low as 10⁻⁶. -11 M, with an enhancement factor (EF) as high as 1.32 × 10 9 Furthermore, it exhibits excellent uniformity and reproducibility (RSD of only 6.75%). The SERS substrate prepared by this invention not only possesses excellent in-situ detection capabilities but also maintains stable and reliable detection performance after five cycles of use. This substrate provides an innovative solution for developing SERS substrates that combine flexibility, high sensitivity, high stability, low cost, and good practicality.

[0006] Technical solution: The first objective of this invention is to provide a method for preparing a superhydrophobic SERS substrate for detecting contaminants on the surface of fish, characterized by the following steps:

[0007] Step 1: Clean and dry the PET fabric;

[0008] Step 2: Dissolve the polydimethylsiloxane prepolymer and curing agent in an organic solvent to obtain solution A; dissolve octadecylamine in an organic solvent to obtain solution B; mix solution A and solution B and stir to obtain coating solution;

[0009] Step 3: Immerse the PET fabric treated in Step 1 into the coating solution obtained in Step 2, remove it and dry it, so that polydimethylsiloxane and octadecylamine self-assemble on the surface of the PET fabric to form a micro-nano composite structure coating.

[0010] Step 4: Deposit an Ag layer on the coated PET fabric obtained in Step 3 to obtain a superhydrophobic SERS substrate.

[0011] Preferably, in step one, the cleaning conditions are as follows: ultrasonic cleaning by sequentially immersing in acetone, anhydrous ethanol, and deionized water.

[0012] Preferably, in step one, the drying conditions are as follows: drying with nitrogen gas.

[0013] Preferably, in step two, the organic solvent is tetrahydrofuran.

[0014] Preferably, in step two, the ratio of polydimethylsiloxane prepolymer, curing agent and organic solvent in solution A is 1 g: 0.1 g: 48.9 g; the ratio of octadecylamine and organic solvent in solution B is 3-4 g: 47-48 g; solution B is prepared by heating to 45-60°C; and the mass ratio of solution A to solution B is 1:1.

[0015] Preferably, in step two, solution A and solution B are mixed and stirred at 40-50°C for 50-60 minutes to obtain a coating solution.

[0016] Preferably, in step three, the immersion time is 2-3 minutes, and the drying conditions are: vacuum drying at 40-50°C for 50-60 minutes.

[0017] Preferably, in step four, the method for depositing the Ag layer is vapor deposition, with a deposition rate of 0.3-1.0 Å / s and a deposition time of 18-60 min.

[0018] The second objective of this invention is to provide a superhydrophobic SERS substrate for detecting contaminants on the surface of fish, prepared by the above-described method.

[0019] The second objective of this invention is to provide the application of the superhydrophobic SERS substrate for detecting contaminants on the surface of fish in the detection of contaminants on the surface of fish.

[0020] Beneficial effects:

[0021] 1. This invention employs a convenient one-step wet chemical coating technology, which eliminates the need for complex templates and expensive equipment. It enables the construction of micro-nano structures on economical PET fabrics. The process is simple, requires no expensive equipment or complex steps, has low cost, and is pollution-free.

[0022] 2. This invention successfully generated flower-like micro-nano structures on the surface of PET fabric using PDMS and ODA. This structure not only endows the substrate with excellent superhydrophobicity (contact angle >150°), effectively resisting the contamination of fish surface mucus and enriching the target molecules, but also provides an ideal "skeleton" for the subsequent deposition of Ag nanoparticles, forming a large number of uniform SERS "hot spots".

[0023] 3. The substrate provided by this invention has a minimum detection concentration of crystal violet (CV) as low as 10. -11 M, with an enhancement factor (EF) as high as 1.32 × 10 9 It exhibits excellent uniformity and reproducibility (RSD of only 6.75%), and its sensitivity far exceeds that of similar flexible SERS substrates.

[0024] 4. Meanwhile, the micro-nano structure on the substrate surface provided by this invention has good mechanical stability. It can still maintain excellent SERS performance after experiencing friction and bending, and can be reused multiple times, effectively reducing the detection cost. It has good reusability, is economical and environmentally friendly.

[0025] 5. The substrate provided by this invention possesses excellent flexibility and superhydrophobicity. Its superhydrophobic properties facilitate the enrichment of target analytes and anti-contamination detection, enabling trace detection of contaminants on fish surfaces via wiping, eliminating the need for complex sample processing steps such as extraction. Therefore, this substrate is quick, convenient, and suitable for detection on various curved surfaces. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the preparation and detection process of the Ag-PDMS-ODA-PET substrate in Example 1 of the present invention;

[0027] Figure 2 The images shown are: (A) SEM image of untreated PET fabric, (B) a partial enlarged view of (A), (C) SEM image of modified PET fabric, and (D) a partial enlarged view of (C) in Embodiment 1 of the present invention.

[0028] Figure 3 SEM images of substrates prepared by depositing Ag on the surface of (A) raw PET, (B) PDMS-modified only, (C) ODA-modified only, and (D) PDMS and ODA co-modified PET fabrics for 60 min; (E) static contact angle of Ag-PDMS-ODA-PET substrate; (F) 10° angle of Ag on the four substrates. -5 SERS spectrum of M CV;

[0029] Figure 4 Different concentrations (10) were measured on the surface of the Ag-PDMS-ODA-PET substrate in Example 1 of this invention. -7 -10 -11 Raman spectra of M)CV;

[0030] Figure 5 The concentration measured on the surface of the Ag-PDMS-ODA-PET substrate in Example 1 of this invention was 10. -10 The CV of M is compared with the concentration of 10 measured on the silicon wafer surface. -2 Raman spectrum of M CV;

[0031] Figure 6 This is a characterization diagram of the SERS signal uniformity and reproducibility of the Ag-PDMS-ODA-PET substrate in Example 1 of the present invention. In the figure, (A) shows the SERS signal uniformity and reproducibility of the Ag-PDMS-ODA-PET substrate collected at 50 random locations on 5 batches of Ag-PDMS-ODA-PET substrates.-9 Raman spectral intensity mapping of M CV; (B) is 1162 cm⁻¹ -1 (C) shows the intensity distribution of the characteristic peak; (D) is the Raman image of the 1.0 mm × 1.0 mm region.

[0032] Figure 7 This is a SEM image of the Ag-PDMS-ODA-PET substrate prepared with an ODA concentration of 4 g in Example 2 of the present invention.

[0033] Figure 8 This is a SEM image of the Ag-PDMS-ODA-PET substrate prepared when the ODA concentration was 2 g in Comparative Example 1 of this invention.

[0034] Figure 9 This is a SEM image of the Ag-PDMS-ODA-PET substrate prepared by reacting in solution for 3 min in Example 3 of the present invention.

[0035] Figure 10 This is a SEM image of the Ag-PDMS-ODA-PET substrate prepared by reacting in solution for 1 min in Comparative Example 2 of this invention.

[0036] Figure 11 In Application Example 1 of this invention, Ag-PDMS-ODA-PET substrate was used to detect different concentrations (10) on the surface of fish using a wiping method. -7 -10 -10 (A) SERS spectrum of MMG and (B) corresponding linear correlation curve;

[0037] Figure 12 This is a test graph showing the reusability of the Ag-PDMS-ODA-PET substrate in Example 4 of the present invention. In the graph, (A) shows the test result after one reuse. -9 (B) SERS spectrum of M MG; (C) 1175 cm⁻¹ during 5 cycles. -1 The intensity change of the characteristic peak;

[0038] Figure 13 The figures show the mechanical stability test results of the Ag-PDMS-ODA-PET substrate in Example 5 of this invention. In the figures, (A) is a schematic diagram of friction on sandpaper; (B) is a schematic diagram of one peel; (C) is a SEM image after 80 cm friction; (D) is a SEM image after 20 peels; (E) is a SEM image after 80 cm friction; and (F) is a SEM image after 20 peels using the Ag-PDMS-ODA-PET substrate. -10 M CV at 1162cm -1 The intensity change of the characteristic peak;

[0039] Figure 14To investigate the SERS spectra and corresponding linear correlation curves obtained by detecting (A, B) malachite green, (C, D) thiabendazole, (E, F) hydrogen peroxide, and (G, H) tricyclazole using an Ag-PDMS-ODA-PET substrate. Detailed Implementation

[0040] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Instruments used, unless otherwise specified, are all commercially available conventional products.

[0041] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available products. The PET fabric is polyester fabric, purchased from a local supermarket. The octadecylamine (ODA) has a purity of 99%, and the polydimethylsiloxane (PDMS) prepolymer and its curing agent are Dow Corning Sylgard 184, purchased from Nantong Feiyu Biotechnology Co., Ltd. The organic solvent is tetrahydrofuran (THF) with a purity of 99%.

[0042] Example 1

[0043] This embodiment provides a method for preparing an Ag-PDMS-ODA-PET superhydrophobic SERS substrate, see [link to documentation]. Figure 1 The steps are as follows:

[0044] (1) Cleaning and drying PET fabric: Soak 1cm×1cm PET fabric in acetone, anhydrous ethanol and deionized water in sequence for ultrasonic cleaning for 5 min, and then blow dry with nitrogen.

[0045] (2) Dissolve 1 g of PDMS prepolymer and 0.1 g of curing agent in 48.9 g of THF, and obtain solution A after ultrasonic treatment for 15 min; dissolve 3 g of ODA in 47 g of THF, and form solution B by heating in a 60°C water bath. Mix solution A and solution B together and stir in a 45°C water bath for 60 min to obtain coating solution;

[0046] (3) Immerse the PET fabric treated in step (1) into the coating solution prepared in step (2) for 2 min, take it out and vacuum dry it at 40°C for 60 min, so that ODA and PDMS self-assemble on the surface of the PET fabric to obtain a PET fabric with PDMS-ODA coating.

[0047] (4) Using a vacuum evaporation apparatus, Ag was deposited on the surface of a PET fabric with a PDMS-ODA coating by vacuum evaporation using 99.99% silver particles as raw material. The evaporation rate was set to 0.3 Å / s and the time was 60 min to obtain a highly sensitive Ag-PDMS-ODA-PET substrate.

[0048] The properties of the prepared Ag-PDMS-ODA-PET substrate were characterized, and the results are as follows:

[0049] The substrate morphology was characterized using scanning electron microscopy (SEM), such as... Figure 2 As shown, the untreated PET fabrics (A, B) have smooth surfaces. After PDMS-ODA modification (C, D), the PET fabric surfaces self-assemble to form micro-nano-scale "flower cluster"-like composite structures. This is because during solvent evaporation, ODA begins to crystallize, forming sheet-like crystals with nanometer-thickness. As the solvent further evaporates, the ODA sheets continue to grow and interlock, eventually forming a three-dimensional "flower cluster" morphology. During this process, there are interactions (such as hydrogen bonds or van der Waals forces) between the PDMS polymer chains and ODA molecules. When the solvent evaporates, the PDMS polymer chains effectively restrict the free diffusion of ODA molecules through this interaction, thereby slowing down the crystallization rate of ODA and making its crystal size more uniform. Therefore, ODA no longer forms large and brittle sheets, but transforms into smaller, denser, and interlocking sheet clusters, ultimately co-constructing a stable and uniform micro-nano hierarchical structure with PDMS.

[0050] Figure 3 (AD) shows SEM images of samples obtained by depositing silver for 60 min on PET surfaces treated with different methods (original PET, PDMS-only modified (same as steps (1)-(3), except that the coating solution is only solution A), ODA-only modified (same as steps (1)-(3), except that the coating solution is only solution B), and PDMS and ODA-co-modified (steps (1)-(3))). Compared with the experimental surfaces, the untreated PET fabric (original PET fabric) has a smooth surface; after PDMS coating, the surface morphology does not change significantly; after ODA coating, the PET surface forms a sparse interwoven sheet structure; after adding ODA and PDMS at the same time, the PET fabric surface forms a dense flower cluster interwoven structure.

[0051] Figure 3 (E) shows the hydrophobic angle test results for the Ag-PDMS-ODA-PET substrate. The figure shows that the water contact angle of this substrate reaches 155°, exhibiting superhydrophobic properties. 10 μL of water was dropped onto the surfaces of the four substrates. -5After the MCV was allowed to dry naturally, the SERS spectrum was measured using a Raman spectrometer (Advantage 785, DeltaNu). The laser wavelength was 785 nm, and the integration time was 10 s. The results are as follows: Figure 3 As shown in (F), the Ag-PDMS-ODA-PET substrate obtained through co-modification exhibits the best reinforcing properties.

[0052] Figure 4 10 was measured on the surface of Ag-PDMS-ODA-PET substrate. -7 -10 -11 The Raman spectrum of M CV shows that the minimum detectable concentration of this substrate can reach 10. -11 M.

[0053] Figure 5 The SERS substrate surface concentration is 10. -10 M and silicon wafer surface concentration are 10 -2 Raman spectra of M CV. According to the formula enhancement factor EF=(I SERS *C 0) / (I0*C SERS ) Calculate the enhancement factor, where I SERS I0 and I0 represent the CV measured on Ag-PDMS-ODA-PET substrate and silicon wafer, respectively. -1 Peak intensity, C SERS C0 represents the corresponding CV concentration. The calculated enhancement factor of this Ag-PDMS-ODA-PET substrate reaches 1.32 × 10⁻⁶. 9 .

[0054] Uniformity and reproducibility tests were performed on the Ag-PDMS-ODA-PET substrate, and the results are as follows: Figure 6 As shown, Figure 6 (A) In a base of 5 batches (two samples per batch), 10 samples were collected from 5 randomly selected locations on each base. -9 Intensity mapping of M CV Raman spectra Figure 6 (B) corresponds to 1162 cm -1 Peak intensity distribution. The calculated relative standard deviation is 6.75%, confirming that the substrate has good reproducibility. Figure 6 (C) shows Raman imaging results within a 1.0 mm × 1.0 mm area, confirming the excellent homogeneity of the Ag-PDMS-ODA-PET substrate.

[0055] Example 2

[0056] Same as Example 1, except that in step (2), 4 g of ODA is dissolved in 46 g of THF and heated in a 60°C water bath to form solution B. Figure 7 The high-concentration ODA is stacked in multiple disordered layers, and the release of internal stress forms wrinkles.

[0057] Comparative Example 1

[0058] Same as Example 1, except that in step (2), 2g of ODA is dissolved in 48g of THF and heated in a 60°C water bath to form solution B. Figure 8 As shown, continuous coverage is not possible due to insufficient ODA content.

[0059] Example 3

[0060] Similar to Example 1, except that in step (3), the PET fabric treated in step (1) is immersed in the coating solution prepared in step (2) for 3 minutes. Figure 9 The density of the flower cluster structure shown is reduced, and sparse lamellar distribution appears in some areas.

[0061] Comparative Example 2

[0062] Similar to Example 1, except that in step (3), the PET fabric treated in step (1) is immersed in the coating solution prepared in step (2) for 1 min. Figure 10 As shown, insufficient soaking time limited the growth of ODA crystals, and only low lamellar protrusions were observed, without the formation of interlocking flower clusters.

[0063] Example 4

[0064] The Ag-PDMS-ODA-PET substrate prepared in Example 1 was used to detect 10 -9 After applying malachite green (MG), the substrate was immersed in ethanol and ultrasonically cleaned for 15 min to remove the detection molecules from the surface. After drying with nitrogen, it was reused to detect MG solutions of the same concentration. The detection and cleaning process was repeated five times. Results are shown below. Figure 12 . Figure 12 (A) shows that ultrasonic cleaning of the used Ag-PDMS-ODA-PET substrate with ethanol can completely remove the detection molecules on the surface and make it usable for the next detection. Figure 12 (B) 10 -9 M MG is located at 1175 cm -1 The changes in the intensity of the characteristic peaks show that although the enhancement performance of the substrate gradually decreases with the increase of the number of uses, its performance only decreases by 27.7% after 5 cycles of use, which proves that the SERS substrate prepared in Example 1 has good chemical stability and reusability, which is beneficial to reducing detection costs.

[0065] Example 5

[0066] The Ag-PDMS-ODA-PET substrate prepared in Example 1 was subjected to friction and peel tests to evaluate its mechanical stability.

[0067] Friction test: Place a 50 g weight on the substrate, with the test surface (silver-plated side) facing down and in close contact with the sandpaper surface. Hold one end of the substrate with tweezers and drag it along the sandpaper surface under the pressure of the weight, for a total drag length of 80 cm. During the dragging process, set a measurement point every 20 cm (i.e., 0 cm, 20 cm, 40 cm, 60 cm, and 80 cm), remove the substrate from the sandpaper, and use a Raman spectrometer to collect the SERS signal at each point.

[0068] Peel test: Smoothly apply the tape to the coated surface of the substrate (i.e., the silver-plated test surface), press evenly with your fingers to ensure full contact between the tape and the coating without air bubbles. Quickly and evenly peel the tape off the coating surface at a 90° or 180° angle.

[0069] The results are as follows Figure 13 As shown, the Ag-PDMS-ODA-PET substrate exhibits excellent mechanical stability. Figure 13 (A) and (B) show the friction and peel tests performed on them, respectively. Figure 13 (C) and (D) show that the microstructure of the substrate surface remained unchanged after rubbing 80 cm under a 50 g weight and after five peeling treatments. (Detection 10) -10 M CV at 1162 cm -1 The peak intensity at the point shows that the signal decreased by 22.5% after rubbing for 80 cm, and the RSD of the signal intensity change was only 6.5% during the process of 20 peels.

[0070] Application Example 1: Actual Detection of Pollutants on Fish Surfaces

[0071] The Ag-PDMS-ODA-PET substrate prepared in Example 1 was used for the detection of malachite green (MG) on the surface of fish using a wiping method. The fish used in the experiment were purchased from the market. The specific steps are as follows:

[0072] After cleaning the fish surface with ethanol and deionized water, malachite green solutions of different concentrations were drop-coated onto the fish surface. After drying, the contaminated areas were directly wiped with a substrate. The wiped substrate was then placed in a Raman spectrometer to acquire SERS signals. Results are shown below. Figure 11 , Figure 11 (A) The Ag-PDMS-ODA-PET substrate shows that 10 -10 M's MG. Figure 11 (B) 1175 cm-1 The good linear relationship between the characteristic peak intensity and the logarithm of the concentration, and the linear fitting equation y=449x+4715 (where y is the SERS intensity in arbitrary units and x is the logarithm of the MG concentration), R²=0.964, proves that this substrate can be used for the quantitative analysis of trace pollutants in complex real samples.

[0073] Application Example 2: Universal Detection of Multiple Pollutants

[0074] Referring to the method in Application Example 1, the Ag-PDMS-ODA-PET substrate prepared in Example 1 was used to detect residual malachite green, thiabendazole, hydrogen peroxide, and tricyclazole on the surface of fish using a wiping method. The results are as follows: Figure 14 As shown, this substrate can detect 10 on the surface of the fish. -9 M's malachite green, thiabendazole, hydrogen peroxide, and tricyclazole effectively overcome the bottleneck of complex fish surface curvature and difficult sampling, achieving in-situ, non-destructive, and highly sensitive rapid screening. This not only curbs illegal additives at the source and prevents harmful substances from endangering health through the food chain, but also has significant meaning and important application value for maintaining consumer health and industry reputation.

[0075] 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 foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a superhydrophobic SERS substrate for detecting contaminants on the surface of fish, characterized in that, The steps are as follows: Step 1: Clean and dry the PET fabric; Step 2: Dissolve the polydimethylsiloxane prepolymer and curing agent in an organic solvent to obtain solution A; dissolve octadecylamine in an organic solvent to obtain solution B; mix solution A and solution B and stir to obtain coating solution; Step 3: Immerse the PET fabric treated in Step 1 into the coating solution obtained in Step 2, remove it and dry it, so that polydimethylsiloxane and octadecylamine self-assemble on the surface of the PET fabric to form a micro-nano composite structure coating. Step 4: Deposit an Ag layer on the coated PET fabric obtained in Step 3 to obtain a superhydrophobic SERS substrate.

2. The method for preparing a superhydrophobic SERS substrate for detecting pollutants on the surface of fish according to claim 1, characterized in that, In step one, the cleaning conditions are as follows: ultrasonic cleaning by sequentially immersing in acetone, anhydrous ethanol, and deionized water.

3. The method for preparing a superhydrophobic SERS substrate for detecting contaminants on the surface of fish according to claim 1, characterized in that, In step one, the drying conditions are as follows: dry with nitrogen gas.

4. The method for preparing a superhydrophobic SERS substrate for detecting contaminants on the surface of fish according to claim 1, characterized in that, In step two, the organic solvent is tetrahydrofuran.

5. The method for preparing a superhydrophobic SERS substrate for detecting contaminants on the surface of fish according to claim 1, characterized in that, In step two, the ratio of polydimethylsiloxane prepolymer, curing agent and organic solvent in solution A is 1 g: 0.1 g: 48.9 g; the ratio of octadecylamine and organic solvent in solution B is 3-4 g: 47-48 g; when preparing solution B, heat to 45-60℃; the mass ratio of solution A to solution B is 1:

1.

6. The method for preparing a superhydrophobic SERS substrate for detecting contaminants on the surface of fish according to claim 1, characterized in that, In step two, solution A and solution B are mixed and stirred at 40-50°C for 50-60 minutes to obtain a coating solution.

7. The method for preparing a superhydrophobic SERS substrate for detecting contaminants on the surface of fish according to claim 1, characterized in that, In step three, the immersion time is 2-3 minutes, and the drying conditions are: vacuum drying at 40-50℃ for 50-60 minutes.

8. The method for preparing a superhydrophobic SERS substrate for detecting contaminants on the surface of fish according to claim 1, characterized in that, In step four, the Ag layer is deposited by vapor deposition, with a deposition rate of 0.3-1.0 Å / s and a deposition time of 18-60 min.

9. A superhydrophobic SERS substrate for detecting contaminants on the surface of fish, prepared by the method according to any one of claims 1-8.

10. The application of the superhydrophobic SERS substrate for detecting contaminants on the surface of fish as described in claim 9 in the detection of contaminants on the surface of fish.

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