Preparation method of SERS substrate based on gold-silver polyhedral alloy nano-frame

Abstract

The invention provides a preparation method of an SERS (Surface Enhanced Raman Scattering) substrate based on a gold-silver polyhedron alloy nano frame. The preparation method comprises the following steps: preparing gold polyhedrons with different sizes through a'three-step 'seed growth method; sequentially adding chloroplatinic acid and chloroauric acid to react to form a hollow platinum framework; further adding chloroplatinic acid, silver nitrate and ascorbic acid to prepare a hollow gold-platinum polyhedral nano material; treating by sodium iodide and chloroplatinic acid to obtain a platinum-gold-platinum alloyed nano material, and removing internal gold by using chloroauric acid to form a new platinum framework; selectively depositing gold or silver on the surface to obtain a platinum-gold or platinum-silver alloyed nano material; the gold and silver alloyed nano-frame material is prepared by mixing the gold and silver alloyed nano-frame material and is applied to detection of nitrophenol. The alloy nano-frame can significantly improve the sensitivity and stability of p-nitrophenol detection, and has a good application prospect.

Description

Technical Field

[0001] This application belongs to the field of SERS substrate preparation technology, specifically relating to a method for preparing a SERS substrate based on a gold-silver polyhedral alloy nanoframework. Background Technology

[0002] Nitrophenol is a class of highly toxic organic pollutants widely found in industrial wastewater and environmental water bodies. It possesses carcinogenic, teratogenic, and mutagenic properties, posing a serious threat to the ecological environment and human health. Therefore, achieving highly sensitive and rapid detection of nitrophenol in water bodies is an important research direction in the field of environmental monitoring.

[0003] Existing methods for detecting nitrophenol compounds in water mainly include liquid chromatography, gas chromatography, and mass spectrometry. While these methods offer a certain level of detection accuracy (detection limits of approximately 0.8–8 nM), they suffer from drawbacks such as time-consuming detection processes and the need for complex sample pretreatment, making it difficult to meet the practical needs of real-time monitoring and rapid on-site detection.

[0004] Raman spectroscopy, as a non-destructive and highly sensitive molecular spectroscopy technique, has significant advantages in material structure identification and trace detection. SERS technology, in particular, leverages the localized plasmon resonance effect on noble metal surfaces to enhance molecular Raman signals by several orders of magnitude, enabling trace detection at the single-molecule level. However, traditional single-component noble metal nanomaterials (such as gold and silver nanoparticles) have significant limitations when used as SERS substrates: gold nanomaterials have limited SERS enhancement effects and high detection limits. For example, the AuNPs@polyimide SERS heating chip prepared in Chinese patent CN202310006741.X has a detection limit of approximately 10⁻⁷ M for 4-ATP, making reliable single-molecule detection difficult. Patent CN202510159888.1 discloses a method for rapid detection of BaP in edible oils using CTAB-modified silver nanomaterials based on LLE-SERS. While this material has high sensitivity, its poor chemical stability leads to a significant degradation in detection performance over storage time. Therefore, developing alloyed nanomaterials that combine high sensitivity and high stability has become a key direction for SERS substrate research.

[0005] Hollow framework nanostructures, also known as noble metal nanostructures, typically refer to a class of hollow, framework-like nanostructures prepared using noble metals (such as gold (Au), silver (Ag), and platinum (Pt). These materials exhibit stronger localized plasmon resonance effects, superior electromagnetic field localization, and more efficient molecular trapping capabilities, making them highly valuable for research and application in fields such as SERS, catalysis, sensing, and biomedicine.

[0006] In the prior art, some researchers have developed some alloy SERS substrates. For example, Chinese patent CN120268997A discloses an AuAgPt ternary alloy nanoframework, its preparation method, and its application in antitumor agents. This method synthesizes AuAgPt ternary alloy nanoframeworks through a four-step process and uses it to study antitumor effects. However, this technology does not involve methods for regulating substrate size and SERS performance, nor has it been applied to the detection of organic pollutants. Summary of the Invention

[0007] This application provides a method for preparing a SERS substrate based on a gold-silver polyhedral alloy nanoframework to solve the above-mentioned technical problems.

[0008] To solve the above-mentioned technical problems, one technical solution adopted in this application is: a method for preparing a SERS substrate based on a gold-silver polyhedral alloy nanoframework, comprising:

[0009] S1. Gold polyhedra of different sizes were prepared by a three-step seed growth method;

[0010] S2. Chloroplatinic acid and chloroauric acid are added sequentially to the gold polyhedron to form a hollowed-out platinum frame;

[0011] S3. Prepare hollowed-out gold@platinum polyhedral nanomaterials by adding chloroplatinic acid, silver nitrate and ascorbic acid to a hollowed-out platinum framework;

[0012] S4. Based on hollowed-out gold@platinum polyhedral nanomaterials, platinum@gold@platinum alloy nanomaterials are obtained by treatment with sodium iodide and chloroplatinic acid, and then the internal gold is removed with chloroauric acid to form a new platinum framework;

[0013] S5. Selectively deposit gold / silver on the surface of the new platinum framework to obtain platinum@gold alloyed nanomaterials and platinum@silver alloyed nanomaterials;

[0014] S6. Platinum@gold alloyed nanomaterials and platinum@silver alloyed nanomaterials are mixed in equal proportions to prepare gold-silver alloyed nanoframework materials.

[0015] Furthermore, the method in step S1 includes:

[0016] S11. Gold nano cubic seeds were obtained by reducing chloroauric acid solution with a mixture of sodium borohydride and hexadecyltrimethylammonium bromide prepared by chilling, and then incubated in an oven at 40°C for 4 hours to prepare a brown seed solution.

[0017] S12. Gently stir the brown seed solution at 30°C for 2 to 5 hours to decompose excess sodium borohydride, then dilute the seed solution by 1 / 100 with ultrapure water to obtain the diluted seed solution.

[0018] S13. Add the diluted seed solution to a mixture of hexadecyltrimethylammonium bromide, chloroauric acid solution, and ascorbic acid; wherein, the brown seed solution should be added to the first mixture immediately after the ascorbic acid is added; keep the first mixture undisturbed at 30 °C overnight; when the solution turns pink, it indicates that the first growth of the gold polyhedron has been formed;

[0019] S14. The gold polyhedron after the first growth is added to a second mixture of hexadecyltrimethylammonium bromide, chloroauric acid solution and ascorbic acid, and the second mixture is kept undisturbed at 30 °C overnight to obtain the gold polyhedron after the second growth;

[0020] S15. The gold polyhedron after the second growth was added to the third mixture of hexadecyltrimethylammonium bromide, chloroauric acid solution and ascorbic acid, and the third mixture was kept undisturbed at 30 °C overnight to obtain the gold polyhedron after the third growth. Then, it was centrifuged at 8000 rpm / min for 10 min. After centrifugation was repeated twice, the solution was redissolved to 15 mL to obtain the gold polyhedron.

[0021] Furthermore, the method in step S2 includes:

[0022] S21. Add the above gold polyhedron solution to a mixture containing hexadecyltrimethylammonium bromide, sodium iodide, silver nitrate and ascorbic acid, and incubate in an oven for 1 hour;

[0023] S22. Add a small amount of hydrochloric acid and chloroplatinic acid to the solution, and then incubate in an oven for 4 hours. This promotes the electrochemical reaction, causing platinum to preferentially grow along the edge direction of the gold polyhedron. Then remove the reactants by centrifugation and washing twice with ultrapure water.

[0024] S23. Dilute the centrifuged solution to 15 mL, mix it with an equal volume of solution containing hexadecyltrimethylammonium bromide and chloroauric acid, and keep it at 50 °C for 1 h to etch away the gold inside the gold@platinum alloy nanomaterial;

[0025] S24. After the reaction is complete, wash the reactants twice with ultrapure water by centrifugation to remove the reactants, and dilute the solution to about 15 mL to obtain a hollowed-out platinum frame.

[0026] Furthermore, the method in step S3 includes:

[0027] S31. Mix the hollowed-out platinum frame with hexadecyltrimethylammonium chloride, chloroauric acid, silver nitrate and ascorbic acid, and incubate in an oven at 50°C for 30 min;

[0028] S32. After incubation, the gold@platinum polyhedral nanomaterials were obtained by washing twice with ultrapure water at 8000 rpm for 10 min each time.

[0029] Furthermore, the method in step S4 includes:

[0030] S41. Add hexadecyltrimethylammonium bromide, sodium iodide, silver nitrate, and ascorbic acid to the gold@platinum nanomaterial solution and incubate in an oven at 70°C for 1 hour;

[0031] S42. After incubation, add hydrochloric acid and chloroplatinic acid and keep at 70°C for 3 hours. Then centrifuge and wash twice, and dilute with ultrapure water to 5 mL.

[0032] S43. Add hexadecyltrimethylammonium bromide and chloroauric acid to the diluted solution, incubate at 50°C for 1 h, and then wash twice with ultrapure water by centrifugation to obtain a new platinum nanoframework material.

[0033] Furthermore, the method in step S5 includes:

[0034] S51. Hexadecyltrimethylammonium chloride, silver nitrate, sodium hydroxide and ascorbic acid were added to the new platinum nanoframework material and incubated at 30°C for 30 min; wherein, the volume of silver nitrate was used to control the thickness of the edges and gaps of the silver nanoframework material;

[0035] S52. After silver was deposited onto the platinum framework, it was centrifuged twice at 10,000 rpm and diluted to 5 mL with ultrapure water to obtain silver nanoframework material.

[0036] S53. Add hexadecyltrimethylammonium chloride, chloroauric acid, silver nitrate and ascorbic acid to the platinum nanoframework material and incubate at 30°C for 30 min;

[0037] S54. After gold was deposited onto the platinum framework, it was centrifuged twice at 10,000 rpm and diluted to 5 mL with ultrapure water to obtain gold@platinum nanoframework materials and silver@platinum nanoframework colloids.

[0038] Furthermore, the method in step S6 includes:

[0039] S61. The gold@platinum nanoframework material and the @platinum nanoframework colloid were mixed sequentially in ratios of 1:1, 1:2, and 1:3, and then washed twice with ultrapure water at 9000 rpm for 10 min.

[0040] S62. Place a cleaned and hydrophilically treated silicon wafer at the bottom of the funnel, close the funnel valve, and pour the prepared colloidal gold / silver@platinum nanoframework material and n-hexane into the funnel in a 1:1 ratio. A clear two-phase interface can be seen.

[0041] S63. Slowly add ethanol dropwise into the funnel. As the interfacial barrier between the two phases decreases, the gold / silver@platinum nanoparticles are gradually captured at the interface, and a nanoparticle film of random size begins to appear.

[0042] S64. Open the valve to allow the liquid level to drop slowly until the scattered nanoparticle films approach each other and form a dense interfacial film, then close the valve.

[0043] S65. After the hexane has completely evaporated, use clean tweezers to lift the silicon wafer from below the funnel film interface to form a gold / silver@platinum nanoframework monolayer film on the silicon wafer surface.

[0044] S66. Immerse the silicon wafer in ethanol for 3 minutes to remove organic matter from the surface, and dry it at room temperature. Add nitrophenol to the silicon wafer in different concentrations in sequence, and measure it with a Raman spectrometer to obtain the gold-silver polyhedral alloy nanoframework SERS substrate.

[0045] The beneficial effects of this application are:

[0046] (1) The SERS substrate based on the gold-silver polyhedral alloy nanoframework of this application combines the high sensitivity of silver nanomaterials with the chemical stability of gold nanomaterials, which significantly improves the reliability and stability of the substrate for long-term detection in complex aquatic environments.

[0047] (2) The SERS substrate of this application, through alloying and polyhedral hollow framework design, can generate a stronger local electromagnetic field "hot spot" effect, which makes the detection limit of nitrophenol significantly lower than that of traditional chromatography, mass spectrometry methods and single-component metal nanomaterials, and can achieve efficient detection of trace or even near single molecule levels.

[0048] (3) Based on the gold polyhedron and using a reasonable three-step synthesis strategy, this invention achieves controllable regulation of the size and morphology of the alloy nanoframework, thereby effectively optimizing its SERS enhancement performance and ensuring the sensitivity and repeatability of detection.

[0049] (4) Compared with traditional detection methods such as liquid chromatography, gas chromatography and mass spectrometry, the SERS substrate detection method of the present invention has a short response time and can achieve rapid, in-situ and on-site detection without complicated pretreatment. It is especially suitable for real-time monitoring of nitrophenol pollution in drinking water and environmental water quality. Attached Figure Description

[0050] Figure 1 This is a flowchart illustrating an embodiment of the cleaning method of the sweeping robot of this application for cleaning an area;

[0051] Figure 2This is the ultraviolet-visible absorption spectrum of the gold octahedron provided in Example 1 of this application;

[0052] Figure 3 This is a TEM image of the gold octahedron after the third step of growth provided in Example 1 of this application;

[0053] Figure 4 This is a TEM topography image of the Pt framework provided in Embodiment 1 of this application;

[0054] Figure 5 This is a scan diagram of the Pt frame elements provided in Embodiment 1 of this application;

[0055] Figure 6 This is a TEM image of the gold@platinum polyhedral nanomaterial provided in Example 1 of this application;

[0056] Figure 7 This is an elemental scan of the gold@platinum polyhedral nanomaterial provided in Example 1 of this application;

[0057] Figure 8 This is a TEM image of the silver@platinum alloy nanomaterial provided in Example 1 of this application;

[0058] Figure 9 This is an elemental scan of the silver@platinum alloy nanomaterial provided in Example 1 of this application;

[0059] Figure 10 This is a TEM image of the gold@platinum alloy nanomaterial provided in Example 1 of this application;

[0060] Figure 11 This is an elemental scan of the gold@platinum alloy nanomaterial provided in Example 1 of this application;

[0061] Figure 12 This is a TEM image of the alloy nanomaterial after mixing silver@platinum alloy nanomaterial and gold@platinum alloy nanomaterial in Example 1 of this application;

[0062] Figure 13 This is an elemental scan of the alloy nanomaterials after mixing silver@platinum alloy nanomaterials and gold@platinum alloy nanomaterials in Example 1 of this application;

[0063] Figure 14 These are SERS spectra of nitrophenol standard solutions of different concentrations provided in Example 2 of this application;

[0064] Figure 15 This is a linear relationship graph of characteristic peak intensity versus nitrophenol concentration in the concentration range of 10⁻⁸ M to 10⁻⁵ M, provided in Example 2 of this application. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments.

[0066] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0067] See Figure 1 This application provides a method for preparing a SERS substrate based on a gold-silver polyhedral alloy nanoframework, comprising:

[0068] S1. Gold polyhedra of different sizes were prepared by a three-step seed growth method;

[0069] S2. Chloroplatinic acid and chloroauric acid are added sequentially to the gold polyhedron to form a hollowed-out platinum frame;

[0070] S3. Prepare hollowed-out gold@platinum polyhedral nanomaterials by adding chloroplatinic acid, silver nitrate and ascorbic acid to a hollowed-out platinum framework;

[0071] S4. Based on hollowed-out gold@platinum polyhedral nanomaterials, platinum@gold@platinum alloy nanomaterials are obtained by treatment with sodium iodide and chloroplatinic acid, and then the internal gold is removed with chloroauric acid to form a new platinum framework;

[0072] S5. Selectively deposit gold / silver on the surface of the new platinum framework to obtain platinum@gold alloyed nanomaterials and platinum@silver alloyed nanomaterials;

[0073] S6. Platinum@gold alloyed nanomaterials and platinum@silver alloyed nanomaterials are mixed in equal proportions to prepare gold-silver alloyed nanoframework materials.

[0074] Example 1: Preparation of SERS substrate using gold-silver polyhedral alloy nanoframeworks

[0075] Step S1: Preparation of the gold polyhedron:

[0076] S11. Prepare 10 mM sodium borohydride solution and 75 mM hexadecyltrimethylammonium bromide solution by chilling. Mix hexadecyltrimethylammonium bromide solution, 20 mM chloroauric acid solution and sodium borohydride solution at a volume ratio of 240:3:2 and stir until homogeneous to obtain gold nanocubic seeds. Incubate the seeds in a 40℃ oven for 4 h to obtain a brown seed solution.

[0077] S12. Transfer the seed solution to a 30°C constant temperature water bath and gently stir for 3 h to decompose excess sodium borohydride. Then dilute the seed solution 100 times with ultrapure water.

[0078] S13. Prepare a mixture of 20 mM hexadecyltrimethylammonium bromide solution, 20 mM chloroauric acid solution and 38.8 mM ascorbic acid. Immediately after adding the ascorbic acid, add the diluted seed solution and stir quickly until homogeneous.

[0079] S14. The mixture was left to stand overnight at 30°C. The solution turned pink, and the gold polyhedron after the first growth was obtained.

[0080] S15. Take the gold polyhedron solution after the first growth and add it to a freshly prepared mixture of hexadecyltrimethylammonium bromide, chloroauric acid and ascorbic acid. Let it stand overnight at 30°C to obtain the gold polyhedron after the second growth.

[0081] S16. Repeat step S15 to obtain the gold polyhedron after the third growth; centrifuge at 8000 rpm for 10 min, repeat twice, and dilute the precipitate with ultrapure water to 15 mL for later use.

[0082] See Figure 2 , Figure 2 The image shows the UV-Vis absorption spectrum of the gold octahedron provided in Example 1. Based on the positions of the absorption peaks, the absorption peak at 540 nm corresponds to a gold octahedron size of 55 nm, the absorption peak at 549 nm corresponds to a gold octahedron size of 75 nm, and the absorption peak at 574 nm corresponds to a gold octahedron size of 100 nm. (See also...) Figure 3 , Figure 3 The image shown is a TEM image of the gold octahedron after the third step of growth provided in Example 1, with an average particle size of 90-100 nm.

[0083] Step S2: Preparation method of the hollowed-out platinum frame:

[0084] S21. Take 5 mL of the gold polyhedron solution obtained in step S1, add it to a mixture containing hexadecyltrimethylammonium bromide, sodium iodide, silver nitrate and ascorbic acid, and incubate it in an oven at 30°C for 1 h.

[0085] S22. Add 0.1 mL of hydrochloric acid and 1 mL of 10 mM chloroplatinic acid solution to the above solution and incubate in an oven at 50 °C for 4 h; then centrifuge at 8000 rpm for 10 min, wash twice with ultrapure water to remove unreacted reagents;

[0086] S23. Dilute the centrifuged precipitate with ultrapure water to 15 mL, mix it with 15 mL of a mixture containing hexadecyltrimethylammonium bromide and chloroauric acid, keep it at 50°C for 1 h, and etch the internal gold.

[0087] S24. After the reaction is complete, centrifuge at 8000 rpm for 10 min, wash twice with ultrapure water, and dilute the precipitate to 15 mL to obtain a hollowed-out platinum frame solution.

[0088] See Figure 4-5 , Figure 4 This is a TEM topography image of the Pt framework provided in Example 1; Figure 5 This is a scan diagram of the Pt frame elements provided in Example 1.

[0089] Step S3: Preparation of gold@platinum polyhedral nanomaterials:

[0090] S31. Take 10 mL of the hollowed-out platinum frame solution obtained in step S2, add hexadecyltrimethylammonium chloride, chloroauric acid, silver nitrate and ascorbic acid, stir well and incubate in a 50℃ oven for 30 min;

[0091] S32. After incubation, centrifuge at 8000 rpm for 10 min, wash twice with ultrapure water to obtain gold@platinum polyhedral nanomaterials, and dilute with ultrapure water to 10 mL for later use.

[0092] See Figure 6-7 , Figure 6 This is a TEM image of the gold@platinum polyhedral nanomaterial provided in Example 1; Figure 7 This is an elemental scan of the gold@platinum polyhedral nanomaterial provided in Example 1.

[0093] Step S4: Preparation of platinum@gold@platinum alloyed nanomaterials:

[0094] S41. Add hexadecyltrimethylammonium bromide, sodium iodide, silver nitrate and ascorbic acid to the gold@platinum polyhedral nanomaterial solution obtained in step S3, and incubate in an oven at 70°C for 1 h;

[0095] S42. Add 0.1 mL of hydrochloric acid and 1 mL of 10 mM chloroplatinic acid solution, incubate at 70℃ for 3 h; after centrifugation and washing twice, dilute with ultrapure water to 5 mL;

[0096] S43. Add hexadecyltrimethylammonium bromide and chloroauric acid to the above solution, incubate at 50°C for 1 h; centrifuge at 8000 rpm for 10 min, wash twice with ultrapure water to obtain a new platinum nanoframework material.

[0097] Step S5: Preparation method of silver@platinum and gold@platinum alloyed nanomaterials:

[0098] S51. Take 2 mL of a fresh platinum nanoframework material solution, add hexadecyltrimethylammonium chloride, silver nitrate, sodium hydroxide and ascorbic acid, and incubate at 30°C for 30 min (silver nitrate volume is 0.2 mL).

[0099] See Figure 8-9 , Figure 8 This is a TEM image of the silver@platinum alloy nanomaterial provided in Example 1; Figure 9 This is an elemental scan of the silver@platinum alloy nanomaterial provided in Example 1.

[0100] S52. Centrifuge at 10000 rpm for 10 min, repeat twice, and dilute with ultrapure water to 5 mL to obtain silver@platinum alloyed nanomaterials;

[0101] S53. Take another 2 mL of fresh platinum nanoframework material solution, add hexadecyltrimethylammonium chloride, chloroauric acid, silver nitrate and ascorbic acid, and incubate at 30°C for 30 min;

[0102] S54. Centrifuge at 10000 rpm for 10 min, repeat twice, and dilute with ultrapure water to 5 mL to obtain gold@platinum alloyed nanomaterials.

[0103] Step S6: Preparation method of SERS substrate:

[0104] S61. Mix gold@platinum alloyed nanomaterials and silver@platinum alloyed nanomaterials at a volume ratio of 1:1, centrifuge at 9000 rpm for 10 min, and wash twice with ultrapure water;

[0105] S62. Take a clean silicon wafer, treat it with hydrophilicity, place it at the bottom of the funnel, and close the valve; pour the mixed colloidal material and n-hexane into the funnel at a volume ratio of 1:1 to form a two-phase interface;

[0106] S63. Ethanol was slowly added dropwise, and nanoparticles were observed to aggregate at the interface to form a thin film.

[0107] S64. Slowly open the valve to allow the liquid level to drop until the film is dense, then close the valve;

[0108] S65. After the hexane has completely evaporated, remove the silicon wafer, immerse it in ethanol for 3 min, and dry it at room temperature to obtain the gold-silver polyhedral alloy nanoframework SERS substrate.

[0109] Figure 10 This is a TEM image of the gold@platinum alloy nanomaterial provided in Example 1. Figure 11 This is an elemental scan of the gold@platinum alloy nanomaterial provided in Example 1.

[0110] Figure 12 This is a TEM image of the alloy nanomaterial after mixing silver@platinum alloy nanomaterials and gold@platinum alloy nanomaterials in Example 1. Figure 8 and Figure 10 The two materials are mixed in equal proportions.

[0111] Figure 13 This is an elemental scan of the alloy nanomaterials obtained by mixing silver@platinum alloy nanomaterials and gold@platinum alloy nanomaterials in Example 1.

[0112] Example 2: Detection of Nitrophenol

[0113] Take nitrophenol standard solutions of different concentrations (10 -5 M, 10 -6 M, 10 -7 M, 10 -8 M, 10 -9 M), 5 μL was added dropwise to the surface of the SERS substrate prepared in Example 1, and allowed to stand at room temperature for 30 min; Raman spectroscopy was performed using a laser wavelength of 785 nm and a scanning range of 400-2000 cm⁻¹. -1 The Raman spectrum signal was recorded by integrating the laser (10 s integration time and 15 mW laser power).

[0114] Figure 14 The different concentrations (10) provided in Example 2 -5 M, 10 -6 M, 10 -7 M, 10 -8 M, 10 -9 SERS spectrum of nitrophenol standard solution (M), where the bottom 10 -9 The SERS spectrum at concentration M was magnified in detail in some areas;

[0115] The results showed that the substrate exhibited the characteristic Raman peak of p-nitrophenol (approximately 1345 cm⁻¹). -1 1590 cm -1 It has a significant enhancement effect, with a detection limit as low as 10. -9 M, and in 10 -8 M-10 -5 Within the M concentration range, the characteristic peak intensity showed a good linear relationship with the nitrophenol concentration (R²=0.996), indicating that the substrate can achieve highly sensitive and quantitative detection of nitrophenol.

[0116] Figure 15 In Example 2, at 10 -8 M-10 -5The linear relationship between the intensity of the characteristic peak within the M concentration range and the concentration of nitrophenol is shown in the graph, where the Raman characteristic peak is located at 1064 cm⁻¹. -1 .

[0117] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for preparing a SERS substrate based on a gold-silver polyhedral alloy nanoframework, characterized in that, include: S1. Gold polyhedra of different sizes were prepared by a three-step seed growth method; S2. Chloroplatinic acid and chloroauric acid are added sequentially to the gold polyhedron to react and form a hollowed-out platinum frame; S3. Add chloroplatinic acid, silver nitrate and ascorbic acid to the hollowed-out platinum frame to prepare hollowed-out gold@platinum polyhedral nanomaterials; S4. Based on the hollowed-out gold@platinum polyhedral nanomaterial, a platinum@gold@platinum alloy nanomaterial is obtained by treatment with sodium iodide and chloroplatinic acid; then, the internal gold is removed by chloroauric acid to form a new platinum framework. S5. Selectively deposit gold / silver on the surface of the new platinum framework to obtain platinum@gold alloyed nanomaterials and platinum@silver alloyed nanomaterials; S6. The platinum@gold alloyed nanomaterial and the platinum@silver alloyed nanomaterial are mixed in equal proportions to obtain a gold-silver alloyed nanoframework material.

2. The method according to claim 1, characterized in that, The method of step S1 includes: S11. Reduce chloroauric acid solution with a mixture of sodium borohydride and hexadecyltrimethylammonium bromide prepared by chilling to obtain gold nano cubic seeds, and then incubate in an oven at 40°C for 4 hours to prepare brown seed solution. S12. The brown seed solution is gently stirred at 30°C for 2 to 5 hours to decompose excess sodium borohydride, and then the seed solution is diluted by 1 / 100 with ultrapure water to obtain a diluted seed solution. S13. Add the diluted seed solution to a mixture of hexadecyltrimethylammonium bromide, chloroauric acid solution, and ascorbic acid, wherein the brown seed solution should be added to the first mixture immediately after the ascorbic acid is added; keep the first mixture undisturbed at 30 °C overnight; when the solution turns pink, it indicates that the first growth of the gold polyhedron has been formed; S14. The gold polyhedron after the first growth is added to a second mixture of hexadecyltrimethylammonium bromide, chloroauric acid solution and ascorbic acid, and the second mixture is kept undisturbed at 30 °C overnight to obtain the gold polyhedron after the second growth; S15. The gold polyhedron after the second growth is added to a third mixture of hexadecyltrimethylammonium bromide, chloroauric acid solution and ascorbic acid, and the third mixture is kept undisturbed at 30 °C overnight to obtain the gold polyhedron after the third growth. Then, it is centrifuged at 8000 rpm for 10 min, and the centrifugation is repeated twice. The solution is then rediluted to 15 mL to obtain the gold polyhedron.

3. The method according to claim 2, characterized in that, The method of step S2 includes: S21. Add the above gold polyhedron solution to a mixture containing hexadecyltrimethylammonium bromide, sodium iodide, silver nitrate and ascorbic acid, and incubate in an oven for 1 hour; S22. Add a small amount of hydrochloric acid and chloroplatinic acid to the solution, and then incubate in an oven for 4 hours. This promotes the electrochemical reaction, causing platinum to preferentially grow along the edge direction of the gold polyhedron. Then remove the reactants by centrifugation and washing twice with ultrapure water. S23. Dilute the centrifuged solution to 15 mL, mix it with an equal volume of solution containing hexadecyltrimethylammonium bromide and chloroauric acid, and keep it at 50 °C for 1 h to etch away the gold inside the gold@platinum alloy nanomaterial; S24. After the reaction is complete, the reactants are removed by centrifugation and washing twice with ultrapure water, and the solution is diluted to about 15 mL to obtain the hollowed-out platinum frame.

4. The method according to claim 3, characterized in that, The method of step S3 includes: S31. The hollowed-out platinum frame is mixed with hexadecyltrimethylammonium chloride, chloroauric acid, silver nitrate and ascorbic acid, and incubated in an oven at 50°C for 30 min; S32. After incubation, the gold@platinum polyhedral nanomaterial was obtained by washing twice with ultrapure water at 8000 rpm for 10 min.

5. The method according to claim 4, characterized in that, The method of step S4 includes: S41. Add hexadecyltrimethylammonium bromide, sodium iodide, silver nitrate and ascorbic acid to the gold@platinum nanomaterial solution and incubate in an oven at 70°C for 1 hour; S42. After incubation, add hydrochloric acid and chloroplatinic acid and keep at 70°C for 3 hours. Then centrifuge and wash twice, and dilute with ultrapure water to 5 mL. S43. Add hexadecyltrimethylammonium bromide and chloroauric acid to the diluted solution, incubate at 50°C for 1 h, and then wash twice with ultrapure water by centrifugation to obtain the new platinum nanoframework material.

6. The method according to claim 5, characterized in that, The method of step S5 includes: S51. Hexadecyltrimethylammonium chloride, silver nitrate, sodium hydroxide and ascorbic acid are added to the new platinum nanoframework material and incubated at 30°C for 30 min; wherein, the volume of silver nitrate is used to control the thickness of the edges and gaps of the silver nanoframework material; S52. After silver was deposited onto the platinum framework, it was centrifuged twice at 10,000 rpm and diluted to 5 mL with ultrapure water to obtain silver nanoframework material. S53. Add hexadecyltrimethylammonium chloride, chloroauric acid, silver nitrate and ascorbic acid to the platinum nanoframework material and incubate at 30°C for 30 min; S54. After gold is deposited onto the platinum framework, it is centrifuged twice at 10,000 rpm and diluted to 5 mL with ultrapure water to obtain gold@platinum nanoframework materials and silver@platinum nanoframework colloids.

7. The method according to claim 6, characterized in that, The method of step S6 includes: S61. The gold@platinum nanoframework material and the @platinum nanoframework colloid are mixed sequentially in ratios of 1:1, 1:2, and 1:3, and then washed twice with ultrapure water at 9000 rpm for 10 min. S62. Place a cleaned and hydrophilically treated silicon wafer at the bottom of the funnel, close the funnel valve, and pour the prepared colloidal gold / silver@platinum nanoframework material and n-hexane into the funnel in a 1:1 ratio. A clear two-phase interface can be seen. S63. Slowly add ethanol dropwise into the funnel. As the interfacial barrier between the two phases decreases, the gold / silver@platinum nanoparticles are gradually captured at the interface, and a nanoparticle film of random size begins to appear. S64. Open the valve to allow the liquid level to drop slowly until the scattered nanoparticle films approach each other and form a dense interfacial film, then close the valve. S65. After the hexane has completely evaporated, use clean tweezers to lift the silicon wafer from below the funnel film interface to form a gold / silver@platinum nanoframework monolayer film on the silicon wafer surface. S66. Immerse the silicon wafer in ethanol for 3 minutes to remove organic matter from the surface, and dry it at room temperature. Add nitrophenol to the silicon wafer in different concentrations in sequence, and measure it with a Raman spectrometer to obtain the gold-silver polyhedral alloy nanoframework SERS substrate.

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