Highly active surface-enhanced raman scattering substrate, preparation method and application thereof

Abstract

The application belongs to the technical field of surface enhanced Raman spectroscopy, and particularly relates to a high-activity surface enhanced Raman scattering substrate, a preparation method and application thereof. The method comprises the following steps: a dichloromethane is added into AuNPs dispersion liquid and mixed uniformly, then a halide salt solution is added and mixed uniformly to form a mixed solution, then n-hexane is added into the mixed solution, and the interface is self-assembled until a gold nanomembrane is formed on the liquid surface, the gold nanomembrane is taken out, and a high-activity surface enhanced Raman scattering substrate is obtained. The application innovatively introduces a halide salt solution in the self-assembly process of AuNPs, significantly changes the assembly arrangement mode of AuNPs, makes the arrangement more compact, enhances the local surface plasmon resonance coupling, and generates more hotspot regions in a unit area, thereby effectively improving the sensitivity of the self-assembled nanometer array SERS substrate.

Description

Technical Field

[0001] This invention belongs to the field of surface-enhanced Raman spectroscopy technology, specifically relating to a highly active surface-enhanced Raman scattering substrate, its preparation method, and its application. Background Technology

[0002] Food hazard detection is a crucial step in ensuring food safety, requiring stringent and comprehensive standards. The scope of detection is broad, encompassing chemical hazards such as pesticide residues, veterinary drug residues, heavy metals, and the misuse of food additives; biological hazards including pathogens, viruses, and parasites; and physical hazards such as plastics. To address such a complex and diverse range of food hazards, detection methods must possess high sensitivity, good specificity, high accuracy, and speed, while also having the capability to detect multiple residues. Currently, commonly used methods for food hazard detection include high-performance liquid chromatography (HPLC), gas chromatography (GC), mass spectrometry (MS), enzyme-linked immunosorbent assay (ELISA), and microbiological detection methods. While these methods each have their advantages, they also have limitations such as complex operation, time-consuming processes, the need for specialized personnel, and expensive equipment.

[0003] In recent years, surface-enhanced Raman scattering (SERS), as a highly sensitive fingerprint vibrational spectroscopy technique, has shown great potential in the detection of food hazards. SERS can provide detailed and specific molecular structural information for various compounds and biological species, possessing significant advantages such as high sensitivity, rapid detection, and label-free detection, demonstrating broad application prospects in analytical chemistry, food science, and biology. However, the low sensitivity of conventional Raman spectroscopy under laser excitation severely limits its in-depth application in the detection of low-concentration food hazard residues. To fully realize the potential of Raman spectroscopy in the rapid detection of food hazard residues, the construction of the SERS substrate is crucial for achieving surface-enhanced Raman scattering.

[0004] Methods for constructing SERS substrates include liquid-liquid interface self-assembly, flexible substrate methods, solid substrate methods, and liquid substrate methods. Compared to other assembly methods, liquid-liquid interface self-assembly has the advantages of precisely controlling the morphology, lateral spacing, and uniformity of nanoparticles, and can form large-area nanoarrays. It has been used to construct various surface-enhanced Raman scattering (SERS) substrates for the rapid detection of various food hazard residues. Although the liquid-liquid interface self-assembly method has certain advantages in constructing SERS substrates, its controllability is significantly insufficient. For example, precise control of nanoparticle spacing is difficult to achieve, and the hot spots per unit area are poor, resulting in relatively high detection limits for the constructed SERS substrates and significantly insufficient sensitivity when detecting trace target molecules. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a highly active surface-enhanced Raman scattering (SERS) substrate, its preparation method, and its applications. By introducing a halide salt solution during the liquid-liquid interface self-assembly process, the assembly arrangement of AuNPs is altered, promoting the formation of a closely packed gold film structure. This reduces the distance between AuNPs, enhances localized surface plasmon resonance coupling, and significantly increases the number of SERS hotspot regions. Consequently, the sensitivity of the liquid-liquid interface self-assembled SERS substrate can be significantly improved using traditional AuNPs.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0007] The first objective of this invention is to provide a method for preparing a highly active surface-enhanced Raman scattering substrate, comprising the following steps:

[0008] Using a three-phase liquid-liquid interface self-assembly method, dichloromethane was added to an AuNPs dispersion and mixed thoroughly. Then, a halide salt solution was added and mixed thoroughly to form a mixed solution. Next, n-hexane was added to the mixed solution, and the interface was allowed to self-assemble until a gold nanofilm formed on the liquid surface. During the self-assembly process, the halide salt solution induced the interfacial aggregation of AuNPs, promoting the close packing of AuNPs and the formation of a gold nanofilm. The gold nanofilm was then retrieved to obtain a highly active surface-enhanced Raman scattering substrate.

[0009] Furthermore, the halide solution is an alkali metal halide solution with a concentration of 0.01 mol / L to 2 mol / L.

[0010] Furthermore, the alkali metal halide is at least one of sodium chloride, potassium chloride, and potassium bromide.

[0011] Furthermore, the volume ratio of the AuNPs dispersion to dichloromethane is 0.5 to 3:2.

[0012] Furthermore, the volume ratio of dichloromethane, halide solution, and n-hexane is 1.5–2.5:1:1.

[0013] Furthermore, the AuNPs dispersion is formed by mixing AuNPs particles and ethanol in a mass-to-volume ratio of 10 mL: 0.5 mL to 3 mL.

[0014] Furthermore, the preparation method of AuNPs particles includes the following steps:

[0015] S1. After mixing the first sodium citrate solution, the first chloroauric acid solution and water, a reduction reaction is carried out to obtain AuNPs seed solution.

[0016] S2. Mix AuNPs seed solution, second sodium citrate solution, first hydroxylamine hydrochloride solution, second chloroauric acid solution and water to form AuNPs intermediate.

[0017] S3. Mix AuNPs intermediate, third sodium citrate solution, second hydroxylamine hydrochloride solution, third chloroauric acid solution and water to obtain AuNPs solution, then wash, concentrate and centrifuge to obtain AuNPs particles.

[0018] Furthermore, the ratio of the first sodium citrate solution to the first chloroauric acid solution is 1 to 1.32:1, and the ratio of the first sodium citrate solution to water is 0.010 to 0.015:1.

[0019] Furthermore, the ratio of sodium citrate to water is 0.010–0.015:1; the ratio of AuNPs seed solution, sodium citrate solution, hydroxylamine hydrochloride solution, chloroauric acid solution, and water is 30–40:10–20:1:1–2:80–90; and the ratio of AuNPs intermediate, sodium citrate solution, hydroxylamine hydrochloride solution, chloroauric acid solution, and water is 5–15:5–10:1–2:1:55–70.

[0020] Furthermore, the mass concentrations of the first sodium citrate solution, the second sodium citrate solution, or the third sodium citrate solution are all 0.8% to 1.2%, the mass concentrations of the first chloroauric acid solution, the second chloroauric acid solution, or the third chloroauric acid solution are all 0.8% to 1.2%, and the concentrations of the first hydroxylamine hydrochloride solution and the second hydroxylamine hydrochloride solution are all 0.005 mol / L to 0.015 mol / L.

[0021] The second objective of this invention is to provide a highly active surface-enhanced Raman scattering substrate, which is prepared using the above-described method.

[0022] A third objective of this invention is to provide the application of a highly active surface-enhanced Raman scattering substrate in the detection of hazardous residues in food, including thiamethoxam, thiram, acid blue, or malachite green.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (2) This invention provides a method for preparing a highly active surface-enhanced Raman scattering (SERS) substrate. The method employs a three-phase liquid-liquid interface self-assembly, wherein the three phases are dichloromethane, a halide solution, and n-hexane in sequence. This invention innovatively introduces a halide solution into the AuNPs self-assembly process. By inducing self-assembly with halide, the surface charge density of gold nanoparticles is regulated. Van der Waals forces are used to achieve more efficient interface aggregation, which significantly changes the assembly arrangement of AuNPs, making them more compact and reducing the distance between AuNPs. This promotes the formation of a tightly packed gold nanofilm structure, enhances local surface plasmon resonance coupling, and generates more hotspot areas per unit area, effectively improving the sensitivity of the self-assembled nanoarray SERS substrate. This method is simple to operate and does not require complex and expensive equipment. It can achieve high-throughput preparation of large batches of high-performance SERS substrates. Compared with the single-layer structure formed by traditional salt-free three-phase interface self-assembly, it can form a dense layered gold film, significantly improving the SERS enhancement performance of the substrate. The prepared highly active self-assembled nanoarray SERS substrate has higher sensitivity than existing self-assembled nanoarray SERS substrates.

[0025] (2) The SERS substrate prepared by the innovative process of this invention exhibits excellent versatility, enabling highly sensitive detection of pesticides, veterinary drugs, and pigments, effectively improving the sensitivity of SERS detection for target molecules. Compared with traditional detection methods based on chromatography and mass spectrometry, the detection speed of this invention is faster and the operation is simpler. Rapid on-site detection can be achieved through handheld Raman spectroscopy, indicating that the SERS substrate of this invention has broad application prospects in the detection of various chemical substances, providing new ideas and methods for the application of surface-enhanced Raman scattering technology in multiple fields such as chemical analysis, environmental monitoring, and food safety testing. Attached Figure Description

[0026] Figure 1 This is a diagram showing the distribution of the three-phase solution in the self-assembly of the three-phase liquid-liquid interface of the present invention.

[0027] Figure 2 These are microstructure diagrams of the SERS substrates prepared in Comparative Example 1 and Example 4 of this invention. Figure 2 In the image, a is a scanning electron microscope (SEM) image of the SERS substrate prepared in Comparative Example 1, and b is a scanning electron microscope (SEM) image of the SERS substrate prepared in Example 4.

[0028] Figure 3 The images show the UV absorption spectra of the SERS substrates prepared in Examples 1 to 5 and Comparative Example 1 of this invention.

[0029] Figure 4The SERS substrates prepared for Comparative Example 1 of this invention were subjected to 1 mg / L thiabendazole, 1 mg / L thiram, 1 mg / L Acid Blue, and 10 mg / L thiabendazole, respectively. -4 Raman spectra of mol / L tetramercaptobenzoic acid and 10 μg / L malachite green.

[0030] Figure 5 The SERS substrates prepared for Examples 1 to 5 and Comparative Example 1 of this invention are 10 -4 Raman spectroscopy for the detection of mol / L tetramercaptobenzoic acid. Figure 5 In this context, 'a' refers to the SERS substrate prepared in Examples 1 to 5 and Comparative Example 1 of this invention. -4 Comparison of Raman spectra for the detection of mol / L tetramercaptobenzoic acid, b is the Raman spectrum of Example 4 and Comparative Example 1.

[0031] Figure 6 Raman spectra of the SERS substrate prepared in Example 4 of this invention at different concentrations of thiabendazole.

[0032] Figure 7 Raman spectra of the SERS substrate prepared in Example 4 of this invention at different concentrations of thiamethoxam.

[0033] Figure 8 The Raman spectra of the SERS substrate prepared in Example 4 of this invention at different concentrations of Acid Blue are shown.

[0034] Figure 9 The graph shows the linear response of the SERS substrate prepared in Example 4 of this invention to different concentrations of thiabendazole, with the Raman peak intensity as a function of the thiabendazole concentration.

[0035] Figure 10 The graph shows the linear response of the SERS substrate prepared in Example 4 of this invention to different concentrations of thiram in Raman peak intensity and thiram concentration.

[0036] Figure 11 The graph shows the linear response of the SERS substrate prepared in Example 4 of this invention to different concentrations of Acid Blue in the detection of Raman peak intensity versus Acid Blue concentration.

[0037] Figure 12 The images show the Raman peak spectra of the SERS substrates prepared in Example 4 and Comparative Example 1 of this invention for the detection of 10 μg / L malachite green.

[0038] Figure 13 This is a comparison of the Raman spectra of the SERS substrates prepared in Example 7 and Comparative Example 1 for the detection of thiabendazole, thiram, acid blue, and malachite green. Figure 13 In the diagram, A represents thiabendazole, B represents thiram, C represents acid blue, and D represents malachite green.

[0039] Figure 14 This is a comparison of the Raman spectra of the SERS substrates prepared in Example 8 and Comparative Example 1 for the detection of thiabendazole, thiram, acid blue, and malachite green. Figure 14 In the diagram, A represents thiabendazole, B represents thiram, C represents acid blue, and D represents malachite green. Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0042] Currently, the liquid-liquid interface self-assembly method has certain advantages in constructing SERS substrates. However, this method still faces many challenges in practical applications. First, the SERS substrates constructed using this method have poor stability and are easily affected by external environmental factors such as temperature and humidity, leading to structural damage or deformation. Second, the uniformity of the substrate is difficult to control precisely, with uneven distribution of hot spots and significant differences in surface smoothness, which greatly affects the accuracy and reliability of the detection results. Furthermore, the controllability of the liquid-liquid interface self-assembly process is significantly insufficient. Many key parameters, including nanoparticle concentration, interfacial tension, and assembly time, are difficult to precisely control, especially the precise control of nanoparticle spacing, resulting in a significant reduction in the reproducibility of substrate preparation and substantial performance differences between different batches. More seriously, the SERS substrates constructed using this method have relatively high detection limits, showing insufficient sensitivity when detecting trace target molecules. Moreover, in the detection of complex samples, signal overlap and interference frequently occur, severely hindering the accurate identification and quantitative analysis of target molecules. To address the aforementioned problems, this invention provides a method for preparing a highly active surface-enhanced Raman scattering (SERS) substrate, thereby solving the issue of low sensitivity in liquid-liquid interface self-assembly methods for constructing SERS substrates. The method includes the following steps:

[0043] Using a three-phase liquid-liquid interface self-assembly method, dichloromethane was added to an AuNPs dispersion and mixed thoroughly. Then, a halide salt solution was added and mixed thoroughly to form a mixed solution. Next, n-hexane was added to the mixed solution, and the mixture was allowed to stand for interface self-assembly until a gold nanofilm formed on the liquid surface. The three-phase solution distribution diagram is shown below when preparing the gold film using this method. Figure 1 As shown, during the static self-assembly process, the halide solution induces the interfacial aggregation of AuNPs, promoting the close arrangement of AuNPs to form a gold nanofilm. The gold nanofilm is then retrieved to obtain a highly active surface-enhanced Raman scattering substrate.

[0044] This invention provides a method for preparing a highly active surface-enhanced Raman scattering substrate, which employs a three-phase liquid-liquid interface self-assembly method, wherein the three phases are dichloromethane, a halide salt solution, and n-hexane in sequence. This invention innovatively introduces a halide salt solution into the self-assembly process of gold nanoparticles (AuNPs) and utilizes a salt-induced assisted self-assembly method to form a tightly packed gold particle film. More specifically, a halide solution is introduced during the self-assembly of AuNPs. By inducing self-assembly with halide, the surface charge density of gold nanoparticles is regulated. Van der Waals forces are used to achieve more efficient interfacial aggregation, significantly altering the assembly arrangement of AuNPs and making them more compact. This reduces the distance between AuNPs, promoting the formation of a tightly packed gold nanofilm structure, enhancing local surface plasmon resonance coupling, and generating more hotspot areas per unit area. This effectively improves the sensitivity of the self-assembled nanoarray SERS substrate. This method is simple to operate, requires no complex and expensive equipment, and can achieve high-throughput preparation of large batches of high-performance SERS substrates. Compared with the monolayer structure formed by traditional salt-free three-phase interface self-assembly, it can form a dense layered gold film, significantly improving the SERS enhancement performance of the substrate. The prepared highly active self-assembled nanoarray SERS substrate has higher sensitivity than existing self-assembled nanoarray SERS substrates.

[0045] In a specific embodiment, the halide solution is an alkali metal halide solution with a concentration of 0.01 mol / L to 2 mol / L. More preferably, the halide solution is a metal halide, and the metal halide is at least one of sodium chloride, potassium chloride, and potassium bromide. In this invention, the metal halide includes, but is not limited to, sodium chloride, potassium chloride, potassium bromide, and combinations of multiple halide salts. By introducing the halide solution, this invention significantly alters the assembly arrangement of AuNPs, making them more compact, thereby reducing the distance between AuNPs, enhancing local surface plasmon resonance coupling, and generating more hotspot areas per unit area. This effectively improves the sensitivity of the self-assembled nanoarray SERS substrate. However, excessively high halide solution concentrations can cause gold particles to aggregate before assembly, preventing the formation of a gold film. Concentrations below this range, while forming a gold nanofilm, reduce the detection efficiency of the target analyte.

[0046] In a specific embodiment, the volume ratio of the AuNPs dispersion to dichloromethane is 0.5–3:2. The volume ratio of dichloromethane, halide solution, and n-hexane is 1.5–2.5:1:1. It should be noted that this invention employs a three-phase liquid-liquid interface self-assembly method, wherein the three phases are dichloromethane, halide solution, and n-hexane in sequence. The volume ratio of dichloromethane, halide solution, and n-hexane affects the stability and formation rate of the interface, thereby affecting the morphology and size of the material, and consequently the uniformity and density of the gold nanofilm, as well as the thickness and coverage area of ​​the gold film.

[0047] In a specific embodiment, the AuNPs dispersion is formed by mixing AuNPs particles and ethanol in a mass-to-volume ratio of 10 mL: 0.5 mL to 3 mL.

[0048] In a specific embodiment, the method for preparing AuNPs particles includes the following steps:

[0049] S1. After mixing the first sodium citrate solution, the first chloroauric acid solution and water, a reduction reaction is carried out to obtain AuNPs seed solution.

[0050] S2. Mix AuNPs seed solution, second sodium citrate solution, first hydroxylamine hydrochloride solution, second chloroauric acid solution and water to form AuNPs intermediate.

[0051] S3. Mix AuNPs intermediate, third sodium citrate solution, second hydroxylamine hydrochloride solution, third chloroauric acid solution and water to obtain AuNPs solution, then wash, concentrate and centrifuge to obtain AuNPs particles.

[0052] In this invention, the particle size of AuNPs seed liquid is 25 nm to 40 nm, the particle size of AuNPs intermediate is 60 nm to 80 nm, and the particle size of AuNPs particles is 100 nm to 200 nm.

[0053] This invention uses a conventional sodium citrate reduction method to prepare AuNPs seed solution, then adds sodium citrate solution, hydroxylamine hydrochloride solution, and chloroauric acid solution. Through the reduction effect of hydroxylamine hydrochloride, gold ions are reduced to the surface of AuNPs seeds, promoting particle growth. The reduction rate is adjusted through the synergistic effect of sodium citrate and hydroxylamine hydrochloride, and sodium citrate acts as a stabilizer to control particle growth and prevent aggregation, thereby regulating the particle size of AuNPs. In this invention, gold nanofilms are prepared by preparing large-sized gold particles (100 nm to 200 nm), which is beneficial to improving the sensitivity of the self-assembled nanoarray SERS substrate. Relatively small-sized gold particles, such as 25 nm to 80 nm, will reduce the sensitivity of the self-assembled nanoarray SERS substrate and reduce the detection effect of the target.

[0054] The concentration and centrifugation method involves adding 100 nm–200 nm AuNPs to sodium dodecyl sulfate (0.08%–0.2% by mass) and Tween 20 (0.008%–0.02% by mass), mixing thoroughly, and then centrifuging at 3000–4500 rpm for 5–10 min. The ratio of AuNPs, sodium dodecyl sulfate, and Tween 20 is 10:1:1.

[0055] In a specific embodiment, the ratio of the first sodium citrate solution to the first chloroauric acid solution is 1–1.32:1; the ratio of the first sodium citrate solution to water is 0.010–0.015:1; the ratio of AuNPs seed solution, the second sodium citrate solution, the first hydroxylamine hydrochloride solution, the second chloroauric acid solution, and water is 30–40:10–20:1:1–2:80–90; and the ratio of AuNPs intermediate, the third sodium citrate solution, the second hydroxylamine hydrochloride solution, the third chloroauric acid solution, and water is 5–15:5–10:1–2:1:55–70. The mass concentrations of the first, second, and third sodium citrate solutions are all 0.8%–1.2%, the mass concentrations of the first, second, and third chloroauric acid solutions are all 0.8%–1.2%, and the concentrations of the first and second hydroxylamine hydrochloride solutions are both 0.005%. mol / L~0.015mol / L.

[0056] In addition, the present invention also provides a highly active surface-enhanced Raman scattering substrate, which is obtained by the above preparation method.

[0057] Furthermore, this invention also provides the application of a highly active surface-enhanced Raman scattering (SERS) substrate in the detection of hazardous residues in food, including thiabendazole, thiram, acid blue, or malachite green. The SERS substrate prepared by this invention using an innovative process exhibits excellent versatility, enabling highly sensitive detection of pesticides, veterinary drugs, and pigments, effectively improving the sensitivity of SERS detection for target molecules. Compared to traditional detection methods based on chromatography and mass spectrometry, this invention offers faster detection speeds and simpler operation, allowing for rapid on-site detection using handheld Raman spectroscopy. This demonstrates the broad application prospects of the SERS substrate in the detection of various chemical substances, providing new ideas and methods for the application of surface-enhanced Raman scattering technology in chemical analysis, environmental monitoring, food safety testing, and other fields.

[0058] The following specific examples will provide further explanation.

[0059] Example 1

[0060] A method for preparing a highly active surface-enhanced Raman scattering substrate includes the following steps:

[0061] The preparation method of S1 and AuNPs particle dispersion includes the following steps:

[0062] Sodium citrate (1% by mass), chloroauric acid (1% by mass), and ultrapure water were mixed and stirred to carry out a reduction reaction, resulting in AuNPs seed solution with a particle size of 30 nm.

[0063] AuNPs seed culture with a particle size of 30 nm, sodium citrate with a mass percentage of 1%, hydroxylamine hydrochloride solution with a concentration of 0.01 mol / L, chloroauric acid with a mass percentage of 1%, and water were mixed in a volume ratio of 33:1.6:14:1:83 and stirred to obtain AuNPs intermediate with a particle size of 70 nm.

[0064] A 70 nm AuNPs intermediate, 1% sodium citrate, 0.01 mol / L hydroxylamine hydrochloride solution, 1% chloroauric acid and water were mixed in a volume ratio of 10:1:6.25:1.5:62.5 and stirred to obtain a 140 nm AuNPs solution.

[0065] Take a 140 nm AuNPs solution, add 0.1% sodium dodecyl sulfate and 0.01% Tween 20 (volume ratio of AuNPs solution, sodium dodecyl sulfate, and Tween 20) to it, and mix thoroughly. Centrifuge at 4000 rpm for 6 min to obtain AuNPs particles. Add 1.8 mL of anhydrous ethanol to disperse the precipitate and obtain an AuNPs particle dispersion, which is then stored for later use.

[0066] S2. Add 2 mL of dichloromethane to the AuNPs particle dispersion prepared in S1 and mix thoroughly. Then add 1 mL of 0.01 mol / L sodium chloride solution and mix thoroughly to form a mixed solution.

[0067] S3. Slowly pour the mixed solution system obtained in S2 into a plastic measuring cup, add 1.5 mL of n-hexane, and let it stand until the interface self-assembles until a gold nanofilm forms on the liquid surface.

[0068] S4. The gold nanofilm obtained in S3 is lifted off the silicon wafer and dried to obtain the SERS substrate.

[0069] Example 2

[0070] A method for preparing a highly active surface-enhanced Raman scattering substrate includes the following steps:

[0071] Sodium citrate (1% by mass), chloroauric acid (1% by mass), and ultrapure water were mixed and stirred to carry out a reduction reaction, resulting in AuNPs seed solution with a particle size of 30 nm.

[0072] AuNPs seed culture with a particle size of 30 nm, sodium citrate with a mass percentage of 1%, hydroxylamine hydrochloride solution with a concentration of 0.01 mol / L, chloroauric acid with a mass percentage of 1%, and water were mixed in a volume ratio of 33:1.6:14:1:83 and stirred to obtain AuNPs intermediate with a particle size of 70 nm.

[0073] A 70 nm AuNPs intermediate, 1% sodium citrate, 0.01 mol / L hydroxylamine hydrochloride solution, 1% chloroauric acid and water were mixed in a volume ratio of 10:1:6.25:1.5:62.5 and stirred to obtain a 140 nm AuNPs solution.

[0074] Take an AuNPs solution with a particle size of 140 nm, add sodium dodecyl sulfate (0.1% by mass) and Tween 20 (0.01% by mass), with a volume ratio of AuNPs solution, sodium dodecyl sulfate, and Tween 20 of 10:1:1. After thorough mixing, centrifuge at 4000 rpm for 6 min to obtain AuNPs particles. Add 1.8 mL of anhydrous ethanol to disperse the precipitate and obtain an AuNPs particle dispersion, which is then stored for later use.

[0075] S2. Add 2 mL of dichloromethane to the AuNPs particle dispersion prepared in S1 and mix thoroughly. Then add 1 mL of 0.05 mol / L sodium chloride solution and mix thoroughly to form a mixed solution.

[0076] S3. Slowly pour the mixed solution system obtained in S2 into a plastic measuring cup, add 1.5 mL of n-hexane, and let it stand until the interface self-assembles until a gold nanofilm forms on the liquid surface.

[0077] S4. The gold nanofilm obtained in S3 is lifted off the silicon wafer and dried to obtain the SERS substrate.

[0078] Example 3

[0079] A method for preparing a highly active surface-enhanced Raman scattering substrate includes the following steps:

[0080] Sodium citrate (1% by mass), chloroauric acid (1% by mass), and ultrapure water were mixed and stirred to carry out a reduction reaction, resulting in AuNPs seed solution with a particle size of 30 nm.

[0081] AuNPs seed culture with a particle size of 30 nm, sodium citrate with a mass percentage of 1%, hydroxylamine hydrochloride solution with a concentration of 0.01 mol / L, chloroauric acid with a mass percentage of 1%, and water were mixed in a volume ratio of 33:1.6:14:1:83 and stirred to obtain AuNPs intermediate with a particle size of 70 nm.

[0082] A 70 nm AuNPs intermediate, 1% sodium citrate, 0.01 mol / L hydroxylamine hydrochloride solution, 1% chloroauric acid and water were mixed in a volume ratio of 10:1:6.25:1.5:62.5 and stirred to obtain a 140 nm AuNPs solution.

[0083] Take a 140 nm AuNPs solution, add 0.1% sodium dodecyl sulfate and 0.01% Tween 20 (volume ratio of AuNPs, sodium dodecyl sulfate, and Tween 20) to it, and mix thoroughly. Centrifuge at 4000 rpm for 6 min to obtain AuNPs particles. Add 1.8 mL of anhydrous ethanol to disperse the precipitate and obtain an AuNPs particle dispersion, which is then stored for later use.

[0084] S2. Add 2 mL of dichloromethane to the AuNPs particle dispersion prepared in S1 and mix thoroughly. Then add 1 mL of 0.1 mol / L sodium chloride solution and mix thoroughly to form a mixed solution.

[0085] S3. Slowly pour the mixed solution system obtained in S2 into a plastic measuring cup, add 1.5 mL of n-hexane, and let it stand until the interface self-assembles until a gold nanofilm forms on the liquid surface.

[0086] S4. The gold nanofilm obtained in S3 is lifted off the silicon wafer and dried to obtain the SERS substrate.

[0087] Example 4

[0088] A method for preparing a highly active surface-enhanced Raman scattering substrate includes the following steps:

[0089] The preparation method of S1 and AuNPs particle dispersion includes the following steps:

[0090] Sodium citrate (1% by mass), chloroauric acid (1% by mass), and ultrapure water were mixed and stirred to carry out a reduction reaction, resulting in AuNPs seed solution with a particle size of 30 nm.

[0091] AuNPs seed culture with a particle size of 30 nm, sodium citrate with a mass percentage of 1%, hydroxylamine hydrochloride solution with a concentration of 0.01 mol / L, chloroauric acid with a mass percentage of 1%, and water were mixed in a volume ratio of 33:1.6:14:1:83 and stirred to obtain AuNPs intermediate with a particle size of 70 nm.

[0092] A 70 nm AuNPs intermediate, 1% sodium citrate, 0.01 mol / L hydroxylamine hydrochloride solution, 1% chloroauric acid and water were mixed in a volume ratio of 10:1:6.25:1.5:62.5 and stirred to obtain a 140 nm AuNPs solution.

[0093] Take a 140 nm AuNPs solution, add 0.1% sodium dodecyl sulfate and 0.01% Tween 20 (volume ratio of AuNPs solution, sodium dodecyl sulfate, and Tween 20) to it, and mix thoroughly. Centrifuge at 4000 rpm for 6 min to obtain AuNPs particles. Add 1.8 mL of anhydrous ethanol to disperse the precipitate and obtain an AuNPs particle dispersion, which is then stored for later use.

[0094] S2. Add 2 mL of dichloromethane to the AuNPs particle dispersion prepared in S1 and mix thoroughly. Then add 1 mL of 0.5 mol / L sodium chloride solution and mix thoroughly to form a mixed solution.

[0095] S3. Slowly pour the mixed solution system obtained in S2 into a plastic measuring cup, add 1.5 mL of n-hexane, and let it stand until the interface self-assembles until a gold nanofilm forms on the liquid surface.

[0096] S4. The gold nanofilm obtained in S3 is lifted off the silicon wafer and dried to obtain the SERS substrate.

[0097] Example 5

[0098] A method for preparing a highly active surface-enhanced Raman scattering substrate includes the following steps:

[0099] The preparation method of S1 and AuNPs particle dispersion includes the following steps:

[0100] Sodium citrate (1% by mass), chloroauric acid (1% by mass), and ultrapure water were mixed and stirred to carry out a reduction reaction, resulting in AuNPs seed solution with a particle size of 30 nm.

[0101] AuNPs seed culture with a particle size of 30 nm, sodium citrate with a mass percentage of 1%, hydroxylamine hydrochloride solution with a concentration of 0.01 mol / L, chloroauric acid with a mass percentage of 1%, and water were mixed in a volume ratio of 33:1.6:14:1:83 and stirred to obtain AuNPs intermediate with a particle size of 70 nm.

[0102] A 70 nm AuNPs intermediate, 1% sodium citrate, 0.01 mol / L hydroxylamine hydrochloride solution, 1% chloroauric acid and water were mixed in a volume ratio of 10:1:6.25:1.5:62.5 and stirred to obtain a 140 nm AuNPs solution.

[0103] Take a 140 nm AuNPs solution, add 0.1% sodium dodecyl sulfate and 0.01% Tween 20 (volume ratio of AuNPs solution, sodium dodecyl sulfate, and Tween 20) to it, and mix thoroughly. Centrifuge at 4000 rpm for 6 min to obtain AuNPs particles. Add 1.8 mL of anhydrous ethanol to disperse the precipitate and obtain an AuNPs particle dispersion, which is then stored for later use.

[0104] S2. Add 2 mL of dichloromethane to the AuNPs particle dispersion prepared in S1 and mix thoroughly. Then add 1 mL of 1 mol / L sodium chloride solution and mix thoroughly to form a mixed solution.

[0105] S3. Slowly pour the mixed solution system obtained in S2 into a plastic measuring cup, add 1.5 mL of n-hexane, and let it stand until the interface self-assembles until a gold nanofilm forms on the liquid surface.

[0106] S4. The gold nanofilm obtained in S3 is lifted off the silicon wafer and dried to obtain the SERS substrate.

[0107] Example 6

[0108] A method for preparing a highly active surface-enhanced Raman scattering substrate includes the following steps:

[0109] The preparation method of S1 and AuNPs particle dispersion includes the following steps:

[0110] Sodium citrate (1% by mass), chloroauric acid (1% by mass), and ultrapure water were mixed and stirred to carry out a reduction reaction, resulting in AuNPs seed solution with a particle size of 30 nm.

[0111] AuNPs seed culture with a particle size of 30 nm, sodium citrate with a mass percentage of 1%, hydroxylamine hydrochloride solution with a concentration of 0.01 mol / L, chloroauric acid with a mass percentage of 1%, and water were mixed in a volume ratio of 33:1.6:14:1:83 and stirred to obtain AuNPs intermediate with a particle size of 70 nm.

[0112] A 70 nm AuNPs intermediate, 1% sodium citrate, 0.01 mol / L hydroxylamine hydrochloride solution, 1% chloroauric acid and water were mixed in a volume ratio of 10:1:6.25:1.5:62.5 and stirred to obtain a 140 nm AuNPs solution.

[0113] Take a 140 nm AuNPs solution, add 0.1% sodium dodecyl sulfate and 0.01% Tween 20 (volume ratio of AuNPs solution, sodium dodecyl sulfate, and Tween 20) to it, and mix thoroughly. Centrifuge at 4000 rpm for 6 min to obtain AuNPs particles. Add 1.8 mL of anhydrous ethanol to disperse the precipitate and obtain an AuNPs particle dispersion, which is then stored for later use.

[0114] S2. Add 2 mL of dichloromethane to the AuNPs particle dispersion prepared in S1 and mix thoroughly. Then add 1 mL of potassium chloride solution with a concentration of 0.5 mol / L and mix thoroughly to form a mixed solution.

[0115] S3. Slowly pour the mixed solution system obtained in S2 into a plastic measuring cup, add 1.5 mL of n-hexane, and let it stand until the interface self-assembles until a gold nanofilm forms on the liquid surface.

[0116] S4. The gold nanofilm obtained in S3 is lifted off the silicon wafer and dried to obtain the SERS substrate.

[0117] Example 7

[0118] A method for preparing a highly active surface-enhanced Raman scattering substrate includes the following steps:

[0119] The preparation method of S1 and AuNPs particle dispersion includes the following steps:

[0120] Sodium citrate (1% by mass), chloroauric acid (1% by mass), and ultrapure water were mixed and stirred to carry out a reduction reaction, resulting in AuNPs seed solution with a particle size of 30 nm.

[0121] AuNPs seed culture with a particle size of 30 nm, sodium citrate with a mass percentage of 1%, hydroxylamine hydrochloride solution with a concentration of 0.01 mol / L, chloroauric acid with a mass percentage of 1%, and water were mixed in a volume ratio of 33:1.6:14:1:83 and stirred to obtain AuNPs intermediate with a particle size of 70 nm.

[0122] A 70 nm AuNPs intermediate, 1% sodium citrate, 0.01 mol / L hydroxylamine hydrochloride solution, 1% chloroauric acid and water were mixed in a volume ratio of 10:1:6.25:1.5:62.5 and stirred to obtain a 140 nm AuNPs solution.

[0123] Take an AuNPs solution with a particle size of 140 nm, add sodium dodecyl sulfate (0.1% by mass) and Tween 20 (0.01% by mass), with a volume ratio of AuNPs solution, sodium dodecyl sulfate, and Tween 20 of 10:1:1. After thorough mixing, centrifuge at 4000 rpm for 6 min to obtain AuNPs particles. Add 1.8 mL of anhydrous ethanol to disperse the precipitate and obtain an AuNPs particle dispersion, which is then stored for later use.

[0124] S2. Add 2 mL of dichloromethane to the AuNPs particle dispersion prepared in S1 and mix thoroughly. Then add 1 mL of potassium bromide solution with a concentration of 0.5 mol / L and mix thoroughly to form a mixed solution.

[0125] S3. Slowly pour the mixed solution system obtained in S2 into a plastic measuring cup, add 1.5 mL of n-hexane, and let it stand until the interface self-assembles until a gold nanofilm forms on the liquid surface.

[0126] S4. The gold nanofilm obtained in S3 is lifted off the silicon wafer and dried to obtain the SERS substrate.

[0127] Comparative Example 1

[0128] A method for preparing a Raman scattering substrate includes the following steps:

[0129] The preparation method of S1 and AuNPs particle dispersion includes the following steps:

[0130] Sodium citrate (1% by mass), chloroauric acid (1% by mass), and ultrapure water were mixed and stirred to carry out a reduction reaction, resulting in AuNPs seed solution with a particle size of 30 nm.

[0131] AuNPs seed culture with a particle size of 30 nm, sodium citrate with a mass percentage of 1%, hydroxylamine hydrochloride solution with a concentration of 0.01 mol / L, chloroauric acid with a mass percentage of 1%, and water were mixed in a volume ratio of 33:1.6:14:1:83 and stirred to obtain AuNPs intermediate with a particle size of 70 nm.

[0132] A 70 nm AuNPs intermediate, 1% sodium citrate, 0.01 mol / L hydroxylamine hydrochloride solution, 1% chloroauric acid and water were mixed in a volume ratio of 10:1:6.25:1.5:62.5 and stirred to obtain a 140 nm AuNPs solution.

[0133] Take a 140 nm AuNPs solution, add 0.1% sodium dodecyl sulfate and 0.01% Tween 20 (volume ratio of AuNPs solution, sodium dodecyl sulfate, and Tween 20) to it, and mix thoroughly. Centrifuge at 4000 rpm for 6 min to obtain AuNPs particles. Add 1.8 mL of anhydrous ethanol to disperse the precipitate and obtain an AuNPs particle dispersion, which is then stored for later use.

[0134] S2. Add 2 mL of dichloromethane to the AuNPs particle dispersion prepared in S1 and mix thoroughly. Then add 1 mL of ultrapure water and mix thoroughly to form a mixed solution.

[0135] S3. Slowly pour the mixed solution system obtained in S2 into a plastic measuring cup, add 1.5 mL of n-hexane, and let it stand until the interface self-assembles until a gold nanofilm forms on the liquid surface.

[0136] S4. The gold nanofilm obtained in S3 is lifted off the silicon wafer and dried to obtain the SERS substrate.

[0137] Figure 2 These are microstructure diagrams of the SERS substrates prepared in Example 4 and Comparative Example 1 of this invention. Figure 2 In the diagram, 'a' is a scanning electron microscope (SEM) image of the SERS substrate in Comparative Example 1, and 'b' is a scanning electron microscope (SEM) image of the SERS substrate in Example 4. Figure 2 As shown, observations revealed that, compared to the SERS substrate without sodium chloride solution in the comparative example, the gaps between AuNPs in the SERS substrate with added sodium chloride solution were significantly reduced, thereby enhancing the local surface plasmon resonance coupling effect, forming more SERS "hot spots," and thus improving the SERS enhancement signal of the material, providing strong technical support for high-sensitivity detection.

[0138] The SERS substrates prepared in Examples 1-5 and Comparative Example 1 were used to detect hazardous residues in food. The process included the following steps: the SERS substrates prepared in Examples 1-5 and Comparative Example 1 were each immersed in 500 μL of target analyte solution, dried, and then subjected to SERS detection. The target analyte solution contained 1 mg / L thiabendazole, 1 mg / L thiram, 1 mg / L acid blue, and 10 mg / L thiabendazole, respectively. -4 mol / L tetramercaptobenzoic acid (MBA), 10 μg / L malachite green. Results are as follows:

[0139] Figure 3 The images show the UV absorption spectra of the SERS substrates prepared in Examples 1 to 5 and Comparative Example 1 of this invention. Figure 3As shown, the SERS substrates prepared in Examples 1 to 5 and Comparative Example 1 all contain gold nanofilms. Therefore, their ultraviolet absorption overlaps, and all have obvious ultraviolet absorption peaks at 596 nm.

[0140] Figure 4 The SERS substrates prepared for Comparative Example 1 of this invention were subjected to 1 mg / L thiabendazole, 1 mg / L thiram, 1 mg / L Acid Blue, and 10 mg / L thiabendazole, respectively. -4 Raman spectra of mol / L tetramercaptobenzoic acid and 10 μg / L malachite green. (Example) Figure 4 As shown, at 1008 cm⁻¹ in the Raman spectrum -1 1375 cm -1 1216 cm -1 1074 cm -1 and 1615 cm -1 Raman characteristic peaks of thiabendazole, thiram, acid blue, tetramercaptobenzoic acid and malachite green can be observed at the respective locations.

[0141] Figure 5 The SERS substrates prepared for Examples 1 to 5 and Comparative Example 1 of this invention are 10 -4 Raman spectroscopy for the detection of mol / L tetramercaptobenzoic acid. Figure 5 In this context, 'a' refers to the SERS substrate prepared in Examples 1 to 5 and Comparative Example 1 of this invention. -4 Comparison of Raman spectra for the detection of mol / L tetramercaptobenzoic acid, b is the Raman spectrum of Example 4 and Comparative Example 1. Figure 5 As shown in Figure a, the Raman signal of tetramercaptobenzoic acid detected by the self-assembled SERS substrate showed an increasing trend with the gradual increase of sodium chloride concentration. The Raman signal reached its maximum value when the added sodium chloride concentration was 0.5 mol / L. Figure 5 As shown in b, compared with the substrate without added sodium chloride (Comparative Example 1), the Raman signal enhancement ratio for detecting tetramercaptobenzoic acid under this condition reached 615.43%.

[0142] To demonstrate the detection efficacy of the highly active SERS substrate prepared by the innovative process of this invention against food hazards, the SERS substrate prepared in Example 4 was used to detect thiabendazole, thiram, acid blue, and malachite green. The specific steps included:

[0143] Step 1: Accurately weigh thiabendazole and prepare a 100 ppm solution, then dilute to 0.2 ppm to 10 ppm. Accurately weigh thiram and prepare a 100 ppm solution, then dilute to 0.1 ppm to 10 ppm. Accurately weigh acid blue and prepare a 100 ppm solution, then dilute to 0.05 ppm to 5 ppm.

[0144] Step 2: Weigh 500 μL of the above solutions of thiabendazole, thiram and acid blue at different concentration gradients respectively, and immerse the SERS substrate prepared in Example 4 in the above solutions of thiabendazole, thiram and acid blue at different concentration gradients respectively. After 30 min, take it out and dry it. Use a handheld Raman spectrometer to detect the Raman signal. The excitation wavelength is 785 nm, the excitation power is 60 mW and the excitation time is 2 s. Point the Raman probe at the substrate surface and collect the Raman intensity.

[0145] Thiamethoxam 1008 cm -1 Fu Mei Shuang 1375 cm -1 Acid Blue 1216 cm -1 With Raman intensity as the ordinate and target concentration as the abscissa, standard curves were established for thiabendazole, thiram, and acid blue, respectively.

[0146] Figure 6 The images show the Raman spectra of the SERS substrate prepared in Example 4 of this invention at different concentrations of thiabendazole. Figure 6 As shown, within the thiabendazole concentration range of 0.2 ppm to 10 ppm, as the target analyte concentration increases, 1008 cm⁻¹ -1 The intensity of the Raman vibration peak also gradually increases.

[0147] Figure 7 The images show the Raman spectra of the SERS substrate prepared in Example 4 of this invention at different concentrations of thiamethoxam. Figure 7 As shown, within the concentration range of thiram (0.1 ppm to 10 ppm), the concentration of the target analyte increases with increasing concentration (1375 cm⁻¹). -1 The intensity of the Raman vibration peak also gradually increases.

[0148] Figure 8 The images show the Raman spectra of the SERS substrate prepared in Example 4 of this invention at different concentrations of Acid Blue. Figure 8 As shown, within the acid blue concentration range of 0.05 ppm to 5 ppm, as the concentration of the target analyte increases, 1216 cm⁻¹ -1 The Raman intensity also gradually increases.

[0149] Based on the Raman peak intensity changes of the SERS substrate prepared in Example 4 for different concentrations of thiabendazole, thiram, and acid blue, linear response relationships between the Raman absorption spectrum intensity and different concentrations of thiabendazole, thiram, and acid blue were constructed. Fitting curves of Raman spectrum intensity and thiabendazole concentration, Raman spectrum intensity and thiram concentration, and Raman spectrum intensity and acid blue were plotted. The curves with the highest fitting degree were selected as the detection standard curves for thiabendazole, thiram, and acid blue, respectively.

[0150] Figure 9 This is a graph showing the linear response of the SERS substrate prepared in Example 4 of this invention to different concentrations of thiabendazole, as well as the Raman peak intensity versus the concentration of thiabendazole. Figure 9 As shown, the characteristic peak of thiabendazole is at 1008 cm⁻¹. -1 The Raman signal intensity at the target concentration showed a good linear relationship in the concentration range of 0.2 ppm to 10 ppm, with a linear regression equation of y1 = 3.419 + 0.316x1, where y1 is the logarithm of the Raman signal intensity and x1 is the logarithm of the thiabendazole concentration. R1 2 The value was 0.998, and the limit of detection (LOD) was 7.59 × 10⁻⁶. -3 ppm.

[0151] Figure 10 This is a graph showing the linear response of the SERS substrate prepared in Example 4 of this invention to different concentrations of thiram, with respect to the Raman peak intensity and thiram concentration. Figure 10 As shown, the characteristic peak of Fumei is at 1375 cm⁻¹. -1 The Raman signal intensity at the concentration point showed a good linear relationship in the concentration range of 0.1 ppm to 10 ppm, with a linear regression equation of y2 = 3.605 + 0.490x2, where y2 is the logarithm of the Raman signal intensity, x2 is the logarithm of the thiamethoxam concentration, and R2. 2 The value is 0.998, and the LOD is 9.27 × 10. -3 ppm.

[0152] Figure 11 This is a linear response graph showing the Raman peak intensity of the SERS substrate prepared in Example 4 of this invention to different concentrations of thiram and the concentration of acid blue. Figure 11 As shown, the characteristic peak of Acid Blue is at 1216 cm⁻¹. -1 The Raman signal intensity at the concentration showed a good linear relationship in the concentration range of 0.05 ppm to 5 ppm, and the linear regression equation was y3 = 462.173 + 7985.244x3, where y3 is the Raman signal intensity, x3 is the thiabendazole concentration, and R3 is the concentration of thiabendazole. 2 The value was 0.997, and the LOD was 0.039 ppm.

[0153] Figure 12 The images show the Raman peak spectra of the SERS substrates prepared in Example 4 and Comparative Example 1 of this invention for the detection of 10 μg / L malachite green. Figure 12 As shown, compared with Comparative Example 1, the SERS substrate prepared in Example 4 also showed a very significant enhancement effect on the detection of malachite green.

[0154] In summary, this invention, when used with a portable Raman spectrometer, can detect food hazards such as thiabendazole, thiram, acid blue, and malachite green. It also features high sensitivity, simple operation, and eliminates the need for large instruments, enabling rapid on-site detection.

[0155] SERS substrates were prepared using different alkali metal halide solutions, as in Examples 6 and 7. The SERS substrates prepared in Examples 6 and 7 were tested for thiabendazole, thiram, acid blue, and malachite green, and the results are as follows.

[0156] The SERS substrates prepared in Example 6 were immersed in 500 μL of solutions containing 1 mg / L thiabendazole, 1 mg / L thiram, 1 mg / L acid blue, and 10 μg / L malachite green, respectively. Figure 13 This is a comparison of the Raman spectra of the SERS substrates prepared in Example 6 and Comparative Example 1 for the detection of thiabendazole, thiram, acid blue, and malachite green. Figure 13 In the diagram, 'a' represents thiabendazole, 'b' represents thiram, 'c' represents acid blue, and 'd' represents malachite green. For example... Figure 13 As shown, compared with Comparative Example 1, the SERS substrate prepared in Example 6 also showed a very significant enhancement effect on the detection of thiabendazole, thiram, acid blue and malachite green.

[0157] The SERS substrates prepared in Example 7 were immersed in 500 μL of solutions containing 1 mg / L thiabendazole, 1 mg / L thiram, 1 mg / L acid blue, and 10 μg / L malachite green, respectively. Figure 14 This is a comparison of the Raman spectra of the SERS substrates prepared in Example 7 and Comparative Example 1 for the detection of thiabendazole, thiram, acid blue, and malachite green. Figure 14 In the diagram, 'a' represents thiabendazole, 'b' represents thiram, 'c' represents acid blue, and 'd' represents malachite green. For example... Figure 14 As shown, compared to the comparative example, the SERS substrate prepared in Example 7 also showed a very significant enhancement effect on the detection of thiabendazole, thiram, acid blue and malachite green.

[0158] In summary, this invention proposes an innovative preparation process that, for the first time, incorporates a halide solution into the self-assembly of AuNPs to construct a self-assembled SERS substrate. This significantly alters the assembly arrangement of AuNPs, making them more compact and reducing the distance between them. This enhances localized surface plasmon resonance coupling and results in more SERS "hot spots." This improvement also effectively increases the sensitivity of the self-assembled nanoarray SERS substrate for target analyte detection. The method of this invention is simple to operate, requiring no complex or expensive equipment, enabling high-throughput preparation of large quantities of high-performance SERS substrates. Combined with handheld Raman spectroscopy, it allows for rapid on-site detection. Furthermore, the halide solution used in this innovative process is a metal halide, including but not limited to sodium chloride, potassium chloride, potassium bromide, and combinations of various halide salts, demonstrating a degree of versatility. Moreover, the SERS substrate prepared by this invention has broad application prospects in the detection of various food hazards, providing new ideas and methods for the application of surface-enhanced Raman scattering technology in chemical analysis, environmental monitoring, food safety testing, and other fields.

[0159] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0160] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a highly active surface-enhanced Raman scattering substrate, characterized in that, Includes the following steps: Using a three-phase liquid-liquid interface self-assembly method, dichloromethane was added to an AuNPs dispersion and mixed thoroughly. Then, a halide salt solution was added and mixed thoroughly to form a mixed solution. Next, n-hexane was added to the mixed solution, and the interface was allowed to self-assemble until a gold nanofilm was formed on the liquid surface. During the self-assembly process, the halide salt solution induced the interface aggregation of AuNPs, promoting the close packing of AuNPs and the formation of a gold nanofilm. The gold nanofilm was then retrieved to obtain a highly active surface-enhanced Raman scattering substrate. The halide solution is an alkali metal halide solution with a concentration of 0.01 mol / L to 1 mol / L. The alkali metal halide is at least one of sodium chloride, potassium chloride, and potassium bromide.

2. The method for preparing a highly active surface-enhanced Raman scattering substrate according to claim 1, characterized in that, The volume ratio of the AuNPs dispersion to dichloromethane is 0.5 to 3:

2.

3. The method for preparing a highly active surface-enhanced Raman scattering substrate according to claim 1, characterized in that, The volume ratio of dichloromethane, halide solution, and n-hexane is 1.5–2.5:1:

1.

4. The method for preparing a highly active surface-enhanced Raman scattering substrate according to claim 1, characterized in that, The AuNPs dispersion was formed by mixing AuNPs particles and ethanol in a mass-to-volume ratio of 10 mL: 0.5 mL to 3 mL.

5. The method for preparing a highly active surface-enhanced Raman scattering substrate according to claim 4, characterized in that, The method for preparing AuNPs particles includes the following steps: The first sodium citrate solution, the first chloroauric acid solution and water were mixed and a reduction reaction was carried out to obtain AuNPs seed solution; AuNPs seed solution, second sodium citrate solution, first hydroxylamine hydrochloride solution, second chloroauric acid solution and water are mixed to form AuNPs intermediate; AuNPs intermediate, third sodium citrate solution, second hydroxylamine hydrochloride solution, third chloroauric acid solution and water were mixed to obtain AuNPs solution, which was then washed, concentrated and centrifuged to obtain AuNPs particles.

6. The method for preparing a highly active surface-enhanced Raman scattering substrate according to claim 5, characterized in that, The ratio of the first sodium citrate solution to the first chloroauric acid solution is 1–1.32:1; the ratio of the first sodium citrate solution to water is 0.010–0.015:1; the ratio of the first sodium citrate solution to water is 0.010–0.015:1; the ratio of AuNPs seed solution, second sodium citrate solution, first hydroxylamine hydrochloride solution, second chloroauric acid solution to water is 30–40:10–20:1:1–2:80–90; the ratio of AuNPs intermediate, third sodium citrate solution, second hydroxylamine hydrochloride solution, third chloroauric acid solution to water is 5–15:5–10:1–2:1:55–70. The mass concentrations of the first, second, or third sodium citrate solutions are all 0.8% to 1.2%, the mass concentrations of the first, second, or third chloroauric acid solutions are all 0.8% to 1.2%, and the concentrations of the first and second hydroxylamine hydrochloride solutions are all 0.005 mol / L to 0.015 mol / L.

7. A highly active surface-enhanced Raman scattering substrate, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 6.

8. The application of the highly active surface-enhanced Raman scattering substrate of claim 7 in the detection of hazardous residues in food, characterized in that, The hazardous residues are thiabendazole, thiram, acid blue, or malachite green.

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