SERS (Surface Enhanced Raman Scattering) rapid detection method for Sudan red illegal additives in hotpot condiment

Abstract

The invention discloses an SERS (Surface Enhanced Raman Scattering) rapid detection method for Sudan red illegal additives in a hotpot condiment. According to the present invention, in the Sudan red-containing hotpot seasoning detection material, the SERS detection is performed by using the simple pretreatment, the large length-diameter ratio gold nanowire / gold nanoparticle enhanced chip and the dried drop sample, such that the SERS signal of the Sudan red can be distinguished from the SERS signal of the matrix so as to achieve the rapid detection and analysis of the Sudan red illegal additives. The method disclosed by the invention has good universality on detection of illegal additives such as Sudan red I, Sudan red II and Sudan red III in the hotpot condiment, and can meet the requirements of actual application detection.

Description

Technical Field

[0001] The invention belongs to the technical field of analysis and detection, and particularly relates to a SERS rapid detection method for Sudan red illegal additives in hot pot soup base. Background Art

[0002] Sudan Red is a type of synthetic azo dye widely used in the leather textile industry, academic research, coatings and cosmetics. The International Agency for Research on Cancer considers Sudan Red to be a Class 3 genotoxic carcinogen and is expressly prohibited from use in food due to its genotoxicity and carcinogenicity. However, due to its strong red color and low price, some criminals illegally use Sudan Red as an additive in hot pot base, chili, curry, palm oil products, frozen meat products and mixed spices.

[0003] At present, the existing detection methods for Sudan Red are: (1) immunoassay strips; (2) atmospheric pressure chemical ionization tandem mass spectrometry; (3) fluorescence spectroscopy; (4) enzyme-linked immunosorbent assay; (5) high performance liquid chromatography. Methods based on mass spectrometry and liquid chromatography have low detection limits and good reproducibility, but often require sophisticated instruments and time-consuming sample pretreatment processes. Immunoassay-based methods are simple, fast, and convenient, but can only detect one target at a time, and antibodies often cannot be stored stably. Methods based on fluorescence spectroscopy are convenient and sensitive, but matrix interference often hinders their application in actual samples.

[0004] The existing standard detection method for Sudan red requires large instruments and professional technicians, has many pre-treatment steps, and uses many types of reagents, which is not suitable for rapid on-site detection and judgment. Methods based on immunity and fluorescence are easily interfered by substances other than the target in the face of complex matrices, and the results are often not accurate enough. Therefore, the development of a rapid detection method for Sudan red has important practical significance. It can not only provide a basis for judgment for on-site law enforcement personnel, provide technical support for combating illegal additives, but also better protect people's food safety and life and health. The surface enhanced Raman scattering (SERS) method has the advantages of no damage to samples, high sensitivity, high resolution and in-situ rapid detection. It can provide precise vibration energy of molecules, provide fingerprint information for detection and identification, and can be used to detect various adsorbed and non-adsorbed molecules to the single molecule level. For SERS detection, the choice of enhanced substrate has a great influence on the detection results. Different enhanced substrate conditions will result in different spectra. But what we are concerned about is whether hot pot base and Sudan red can be clearly and quickly distinguished under the same enhanced substrate conditions. Summary of the invention

[0005] The purpose of the present invention is to provide a surface enhanced Raman spectroscopy (SERS) detection method for Sudan red in hot pot soup base. In the hot pot soup base sample containing Sudan red, a simple pretreatment is used, and aged gold nanowires / gold nanoparticles with a large aspect ratio are used as an enhancement chip. After the drop sample is dried, SERS detection is performed. This method can clearly distinguish the SERS signal of Sudan red from the SERS signal of the hot pot soup base matrix itself, thereby realizing the rapid detection and analysis of Sudan red illegal additives. Specifically, the present invention adopts the following technical solutions:

[0006] A method for rapid SERS detection of illegal Sudan red additives in hot pot soup base, comprising the following steps:

[0007] (1) Take 1-2 mL of hot pot base sample into a centrifuge tube and add 2-4 mL of chloroform solution to dissolve;

[0008] (2) Mix the samples by oscillating for 50-70 seconds and then centrifuging them;

[0009] (3) Take 10 µL of the upper layer solution of the centrifuge tube and drop it onto the aged gold nanowire / gold nanoparticle enhanced chip with a large aspect ratio;

[0010] (4) Place the enhanced chip on a metal table and heat it at 40-50 °C for 1-3 min, then use a portable Raman spectrometer to perform SERS detection.

[0011] For the above-mentioned detection method, preferably, the centrifugation in step (2) refers to centrifugation at 4000-6000 rpm for 1-2 min.

[0012] For the above-mentioned detection method, preferably, the preparation method of aged large aspect ratio gold nanowires / gold nanoparticles in step (3) comprises the following steps:

[0013] (a) Preparation of gold nanowires with large aspect ratio

[0014] Under a constant temperature water bath at 30-35°C, 10 mL of 0.1 M hexadecyltrimethylammonium bromide solution was placed in a conical flask, and 100 μL of 1 wt% chloroauric acid aqueous solution and 600 μL of 0.01 M sodium borohydride aqueous solution were added under magnetic stirring, and then the mixture was allowed to stand for use to obtain a seed solution; under a constant temperature water bath at 30-35°C, 200 mL of 0.1 M hexadecyltrimethylammonium bromide aqueous solution was placed in a conical flask, and 2 mL of 0.01 M silver nitrate aqueous solution, 5 mL of 1 wt% chloroauric acid aqueous solution, 2 mL of 2 M nitric acid solution, 1 mL of 0.1 M ascorbic acid, and 230 μL of seed solution were added under magnetic stirring, and the mixture was mixed and allowed to stand for 45-50 h to obtain gold nanowires with a large aspect ratio;

[0015] (b) Preparation of gold nanoparticles

[0016] Add 150-250 mL of ultrapure water to a conical flask, add 1 mL of 1 wt% chloroauric acid solution under magnetic stirring and heat. After the solution boils, add 2 mL of 1% sodium citrate solution. Stop heating and stirring after 20-40 min, and cool naturally to obtain gold nanoparticles.

[0017] (c) Aging of gold nanowires with large aspect ratio

[0018] Placing the high aspect ratio gold nanowires obtained in step (31) under natural light conditions for more than 1 month to obtain aged high aspect ratio gold nanowires;

[0019] (d) Preparation of aged gold nanowires / gold nanoparticles with large aspect ratio

[0020] The aged gold nanowires with a large aspect ratio obtained in step (c) and the gold nanoparticles obtained in step (b) were respectively placed in centrifuge tubes and centrifuged at a speed of 7000-9000 rpm for 8-12 min, the supernatant was discarded, and the bottom precipitate was mixed to obtain aged gold nanowires with a large aspect ratio / gold nanoparticles.

[0021] For the above-mentioned detection method, preferably, the temperature of the constant temperature water bath in step (a) is 30-32°C.

[0022] For the above-mentioned detection method, preferably, the aspect ratio of the large aspect ratio gold nanowires obtained in step (a) is 30-50:1.

[0023] For step (a), by adjusting the reaction temperature, the amount of reagents, and the reaction time, a small aspect ratio gold nanowire can be obtained. For example, a small aspect ratio gold nanowire with an aspect ratio of 4 to 8:1 can be obtained by the following preparation method: Under a constant temperature water bath condition of 25-28 ° C, 200 mL of 0.1 M hexadecyltrimethylammonium bromide aqueous solution is placed in a conical flask, and under magnetic stirring, 2 mL of 0.008 M silver nitrate aqueous solution, 4 mL of 1 wt% chloroauric acid aqueous solution, 2 mL of 2 M nitric acid solution, 1.2 mL of 0.1 M ascorbic acid, and 240 μL of seed solution are added, and the mixture is mixed and allowed to stand for 24 h to obtain a small aspect ratio gold nanowire.

[0024] For the above-mentioned detection method, preferably, in step (c), the high aspect ratio gold nanowires obtained in step (3a) are placed under natural light conditions for 1-2 months.

[0025] For the above-mentioned detection method, preferably, in step (d), the volume ratio of the aged large aspect ratio gold nanowires to the gold nanoparticles is 3-5:1, preferably 4:1.

[0026] For the above-mentioned detection method, preferably, step (d) is centrifuged at a speed of 8000 rpm for 10 min.

[0027] The present invention uses gold nanowires / gold nanoparticles with a large aspect ratio as an enhanced chip (substrate). The effective hotspot area of ​​gold nanowires / gold nanoparticles with a large aspect ratio is richer, and the gold nanoparticles and gold nanowires are closely arranged, making it easier to detect the target. However, gold nanoparticles as conventional SERS hotspots have greater randomness in detection. Gold nanowires with a large aspect ratio refer to the ratio of the length to the diameter of the gold nanowire, and the aspect ratio is preferably 30 to 50:1. It should be noted that the prepared gold nanowires and gold nanoparticles are both in a sol state, which is well known to SERS detection technicians.

[0028] In the above-mentioned detection method, the aged high aspect ratio gold nanowire / gold nanoparticle enhanced chip in step (3) is an aged high aspect ratio gold nanowire / gold nanoparticle enhanced substrate. During SERS detection, the aged high aspect ratio gold nanowire / gold nanoparticle can be dropped onto a commonly used SERS substrate such as a paper-based substrate, a polymer substrate, or an inorganic material substrate such as a silicon wafer.

[0029] For the above-mentioned detection method, preferably, in step (4), the enhanced chip is placed on a metal table and heated at 45-50°C for 1 min.

[0030] For the detection method described above, preferably, the excitation light wavelength of SERS detection in step (4) is 785 nm, the integration time is 2-4 s, and the laser power is 50-100 mW.

[0031] As a preferred embodiment, the method for rapid SERS detection of illegal Sudan red additives in hot pot soup base may include the following steps:

[0032] (1) Use a disposable dropper to draw 1-2 mL of Sudan Red hot pot base sample into a centrifuge tube and add 2-4 mL of chloroform solution to dissolve;

[0033] (2) Mix the samples by oscillation for 60 seconds and then centrifuge the samples (5000 rpm, 1 min);

[0034] (3) Use a pipette to draw 10 µL of the upper layer solution from the centrifuge tube and drop it onto the aged gold nanowire / gold nanoparticle enhanced chip with a large aspect ratio;

[0035] (4) After the enhanced chip is placed on a metal table and heated at 45-50 °C for 1 min, SERS detection is performed using a portable Raman spectrometer (excitation light wavelength of 785 nm, integration time of 2-4 s, laser power of 50-100 mW).

[0036] For SERS detection, since the selection of the enhanced substrate has a great influence on the detection results, the spectra will be different when the enhanced substrate conditions are different. Therefore, under the enhanced substrate conditions of the present invention, the SERS spectra of Sudan I, Sudan II, and Sudan III obtained have the uniqueness of the present invention. Under the enhanced substrate conditions of the present invention, both the hot pot soup base and Sudan have their unique SERS response signals, and the SERS signals of the hot pot soup base sample and Sudan are significantly different. In other words, the present invention can effectively distinguish the spectral information of Sudan illegal additives in hot pot soup base using the SERS method, thereby realizing the rapid detection and identification of Sudan in complex systems.

[0037] The beneficial effects of the present invention are:

[0038] (1) The present invention is time-saving for the detection of Sudan red in hot pot soup base, and the detection time of a single sample is less than 5 minutes, which is suitable for on-site rapid detection;

[0039] (2) The SERS enhancement chip used in the present invention is an aged gold nanowire / gold nanoparticle enhancement chip with a large aspect ratio, and has a good signal enhancement effect;

[0040] (3) The present invention has good universality for the detection of illegal additives such as Sudan I, Sudan II and Sudan III in hot pot soup base, and can meet the needs of practical application detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a scanning electron microscope image of the gold nanowires / gold nanoparticles with a large aspect ratio in Example 1.

[0042] Figure 2 This is the SERS spectrum of Sudan Red I in the hot pot base of Example 1.

[0043] Figure 3 This is the SERS spectrum of Sudan Red II in the hot pot base of Example 2.

[0044] Figure 4 This is the SERS spectrum of Sudan Red III in the hot pot base of Example 3.

[0045] Figure 5 This is a diagram of the SERS detection results of Comparative Example 1.

[0046] Figure 6 This is a diagram of the SERS detection results of Comparative Example 2.

[0047] Figure 7 This is a diagram of the SERS detection results of Comparative Example 3.

[0048] Figure 8 This is a diagram of the SERS detection results of Comparative Example 4. DETAILED DESCRIPTION

[0049] The following embodiments are further descriptions of the content of the present invention as an explanation of the technical content of the present invention, but the essential content of the present invention is not limited to the following embodiments. Ordinary technicians in this field can and should know that any simple changes or replacements based on the essential spirit of the present invention should fall within the scope of protection required by the present invention.

[0050] The following experimental examples are conducted using the three-five hot pot base purchased from the market that does not contain Sudan red as the basic material (hot pot base heated and melted liquid sampling), where the hot pot base sample containing Sudan red Ⅰ is to add Sudan red Ⅰ to the basic material, the hot pot base sample containing Sudan red Ⅱ is to add Sudan red Ⅱ to the basic material, and the hot pot base sample containing Sudan red Ⅲ is to add Sudan red Ⅲ to the basic material. Among them, 500 μL of 1ppm Sudan red chloroform solution is added to 1mL of the basic material hot pot base to prepare the hot pot base sample containing Sudan red.

[0051] In addition, the aged gold nanowires / gold nanoparticles with a large aspect ratio used in the present invention are prepared by the following preparation method:

[0052] (a) Preparation of gold nanowires with large aspect ratio

[0053] Under a constant temperature water bath at 30°C, take 10 mL of 0.1 M hexadecyltrimethylammonium bromide solution in a conical flask, add 100 μL of 1 wt% chloroauric acid aqueous solution and 600 μL of 0.01 M sodium borohydride aqueous solution under magnetic stirring, and then let stand for use to obtain a seed solution;

[0054] Under the condition of a constant temperature water bath at 30 ℃, 200 mL of 0.1 M hexadecyltrimethylammonium bromide aqueous solution was placed in a conical flask, and under magnetic stirring, 2 mL of 0.01 M silver nitrate aqueous solution, 5 mL of 1 wt% chloroauric acid aqueous solution, 2 mL of 2 M nitric acid solution, 1 mL of 0.1 M ascorbic acid, and 230 μL of seed solution were added, mixed and allowed to stand for 48 h to obtain gold nanowires with a large aspect ratio.

[0055] (b) Preparation of gold nanoparticles

[0056] Add 200 mL of ultrapure water to a conical flask, add 1 mL of 1 wt% chloroauric acid solution under magnetic stirring and heat. After the solution boils, add 2 mL of 1% sodium citrate solution. Stop heating and stirring after 30 min, and cool naturally to obtain gold nanoparticles.

[0057] (c) Aging of gold nanowires with large aspect ratio

[0058] Placing the high aspect ratio gold nanowires obtained in step (31) under natural light conditions for 1 month to obtain aged high aspect ratio gold nanowires;

[0059] (d) Preparation of aged gold nanowires / gold nanoparticles with large aspect ratio

[0060] 800 μL of the aged high aspect ratio gold nanowires obtained in step (c) and 200 μL of the gold nanoparticles obtained in step (d) were respectively placed in centrifuge tubes for centrifugation (8000 rpm, 10 min), the supernatant was discarded, and the precipitate at the bottom was mixed to obtain aged high aspect ratio gold nanowires / gold nanoparticles.

[0061] Example 1

[0062] (1) Use a disposable dropper to draw 1 mL of Sudan Red I hot pot base sample into a centrifuge tube, and use a pipette to add 2 mL of chloroform solution to dissolve the sample;

[0063] (2) Mix the samples by oscillation for 60 seconds and then centrifuge the samples (5000 rpm, 1 min);

[0064] (3) Use a pipette to draw 10 µL of the upper layer of the centrifuge tube solution and drop it onto the aged gold nanowire / gold nanoparticle enhanced chip with a large aspect ratio (aspect ratio of 30-50:1). Figure 1 As shown;

[0065] (4) After the enhanced chip was placed on a metal table and heated at 45 °C for 1 min, SERS detection was performed using a portable Raman spectrometer (excitation wavelength of 785 nm, integration time of 2 s, laser power of 50 mW). The detection results are as follows: Figure 2 shown. Figure 2 The main characteristic peaks of the SERS spectrum measured by Sudan Red I + hot pot base are: 613, 711, 960, 1000, 1148, 1171, 1382, 1568, 1588, 1594 cm -1 The peaks are at 960, 1148, and 1171 cm -1 Belongs to hot pot base, 1000cm -1The peaks at 1382 and 1594 cm -1 Belongs to Sudan Red I.

[0066] Example 2

[0067] (1) Use a disposable dropper to draw 2 mL of Sudan Red II hot pot base sample into a centrifuge tube and add 4 mL of chloroform solution to dissolve;

[0068] (2) Mix the samples by oscillation for 60 seconds and then centrifuge the samples (5000 rpm, 1 min);

[0069] (3) Use a pipette to draw 10 µL of the upper layer solution from the centrifuge tube and drop it onto the aged gold nanowire / gold nanoparticle enhanced chip with a large aspect ratio (aspect ratio of 30-50:1);

[0070] (4) After the enhanced chip was placed on a metal table and heated at 50 °C for 1 min, SERS detection was performed using a portable Raman spectrometer (excitation wavelength of 785 nm, integration time of 4 s, laser power of 100 mW). The detection results are as follows: Figure 3 shown.

[0071] Example 3

[0072] (1) Use a disposable dropper to draw 1.5 mL of Sudan Red III hot pot base sample into a centrifuge tube and add 3 mL of chloroform solution to dissolve;

[0073] (2) Mix the samples by oscillation for 60 seconds and then centrifuge the samples (5000 rpm, 1 min);

[0074] (3) Use a pipette to draw 10 µL of the upper layer solution from the centrifuge tube and drop it onto the aged gold nanowire / gold nanoparticle enhanced chip with a large aspect ratio (aspect ratio of 30-50:1);

[0075] (4) After the enhanced chip was placed on a metal table and heated at 48 °C for 1 min, SERS detection was performed using a portable Raman spectrometer (excitation wavelength of 785 nm, integration time of 3 s, laser power of 80 mW). The detection results are as follows: Figure 4 shown.

[0076] Comparative Example 1

[0077] Compared with Example 1, the hot pot base (basic material) without Sudan red was tested, and no SERS signal of Sudan red was detected, and the obtained signal belongs to the SERS spectrum of the hot pot base. Experimental process:

[0078] (1) Use a disposable dropper to draw 1 mL of hot pot base into a centrifuge tube, and use a pipette to add 2 mL of chloroform solution to dissolve the sample;

[0079] (2) Mix the samples by oscillation for 60 seconds and then centrifuge the samples (5000 rpm, 1 min);

[0080] (3) Use a pipette to draw 10 µL of the upper layer solution from the centrifuge tube and drop it onto the aged gold nanowire / gold nanoparticle enhanced chip with a large aspect ratio (aspect ratio of 30-50:1);

[0081] (4) After the enhanced chip was placed on a metal table and heated at 45 °C for 1 min, SERS detection was performed using a portable Raman spectrometer (excitation wavelength of 785 nm, integration time of 2 s, laser power of 50 mW). The detection results are as follows: Figure 5 shown. Figure 5 The main characteristic peaks of the SERS spectrum of hot pot soup base are: 807, 960, 1000, 1025, 1040, 1148, 1171, 1225, 1280 cm -1 .

[0082] Comparative Example 2

[0083] Compared with Example 1, Sudan Red I was detected and the measured signal was the characteristic signal of Sudan Red I. Test process:

[0084] (1) Use a disposable dropper to draw 1 mL of Sudan I solution (1 ppm chloroform solution) into a centrifuge tube, and use a pipette to add 2 mL of chloroform solution;

[0085] (2) Mix the samples by oscillation for 60 seconds and then centrifuge the samples (5000 rpm, 1 min);

[0086] (3) Use a pipette to draw 10 µL of the upper layer solution from the centrifuge tube and drop it onto the aged gold nanowire / gold nanoparticle enhanced chip with a large aspect ratio (aspect ratio of 30-50:1);

[0087] (4) After the enhanced chip was placed on a metal table and heated at 45 °C for 1 min, SERS detection was performed using a portable Raman spectrometer (excitation wavelength of 785 nm, integration time of 2 s, laser power of 50 mW). The detection results are as follows: Figure 6 shown. Figure 6 (Sudan Red I only) The main characteristic peaks of the SERS spectrum measured are: 587, 725, 983, 1000, 1162, 1228, 1260, 1340, 1382, 1492, 1594 cm -1.

[0088] Comparative Example 3

[0089] The difference from Example 1 is that the unaged high aspect ratio gold nanowire / gold nanoparticle enhanced chip is used for detection, and the other aspects are the same as Example 1. The unaged high aspect ratio gold nanowire / gold nanoparticle enhanced chip is used for SERS detection using a portable Raman spectrometer (excitation light wavelength of 785 nm, integration time of 2 s, laser power of 50 mW). The detection results are as follows: Figure 7 As shown. Found 671 cm -1 A stray peak signal was detected.

[0090] Comparative Example 4

[0091] Different from Example 1, a small aspect ratio gold nanowire / gold nanoparticle enhanced chip with an aspect ratio of 4 to 8:1 is used to detect Sudan Red I in hot pot soup base. The preparation method of the small aspect ratio gold nanowire / gold nanoparticle enhanced chip is as follows: under a constant temperature water bath at 28°C, 200 mL of 0.1 M hexadecyltrimethylammonium bromide aqueous solution is placed in a conical flask, and under magnetic stirring, 2 mL of 0.008 M silver nitrate aqueous solution, 4 mL of 1wt% chloroauric acid aqueous solution, 2 mL of 2 M nitric acid solution, 1.2 mL of 0.1 M ascorbic acid, and 240 μL of seed solution are added, mixed and allowed to stand for 24 h to obtain small aspect ratio gold nanowires. The test results are as follows. Figure 8 As shown, no obvious SERS signal of Sudan Red I was detected.

[0092] It should be noted that the above-mentioned technical contents of the present invention are only for explanation and clarification to enable those skilled in the art to understand the technical essence of the present invention, so the technical contents are not used to limit the substantial protection scope of the present invention. The substantial protection scope of the present invention shall be subject to the claims. Those skilled in the art should know that any modification, equivalent substitution and improvement based on the substantial spirit of the present invention shall be within the substantial protection scope of the present invention.

Claims

1. A SERS rapid detection method for Sudan red illegal additives in hot pot soup base, comprising the following steps: (1) Take 1-2 mL of hot pot base sample into a centrifuge tube and add 2-4 mL of chloroform solution to dissolve; (2) Mix the samples by oscillating for 50-70 seconds and then centrifuging them; (3) Take 10 µL of the upper layer solution of the centrifuge tube and drop it onto the aged gold nanowire / gold nanoparticle enhanced chip with a large aspect ratio; (4) Place the enhanced chip on a metal table and heat it at 40-50 °C for 1-3 min, then use a portable Raman spectrometer to perform SERS detection.

2. The detection method according to claim 1, characterized in that Step (2) centrifugation refers to centrifugation at 4000-6000 rpm for 1-2 min.

3. The detection method according to claim 1, characterized in that The method for preparing the aged gold nanowires / gold nanoparticles with a large aspect ratio comprises the following steps: (a) Preparation of gold nanowires with large aspect ratio Under a constant temperature water bath at 30°C, 10 mL of 0.1 M hexadecyltrimethylammonium bromide solution was placed in a conical flask, and under magnetic stirring, 100 μL of 1 wt% chloroauric acid aqueous solution and 600 μL of 0.01 M sodium borohydride aqueous solution were added, and then the mixture was allowed to stand for use to obtain a seed solution. Under a constant temperature water bath at 30°C, 200 mL of 0.1 M hexadecyltrimethylammonium bromide aqueous solution was placed in a conical flask, and under magnetic stirring, 2 mL of 0.01 M silver nitrate aqueous solution, 5 mL of 1 wt% chloroauric acid aqueous solution, 2 mL of 2M nitric acid solution, 1 mL of 0.1 M ascorbic acid, and 230 μL of seed solution were added, mixed, and allowed to stand for 45-50 h to obtain large aspect ratio gold nanowires with an aspect ratio of 30-50:

1. (b) Preparation of gold nanoparticles Add 200 mL of ultrapure water to a conical flask, add 1 mL of 1 wt% chloroauric acid solution under magnetic stirring and heat. After the solution boils, add 2 mL of 1% sodium citrate solution. Stop heating and stirring after 20-40 min, and cool naturally to obtain gold nanoparticles. (c) Aging of gold nanowires with large aspect ratio Placing the high aspect ratio gold nanowires obtained in step (3a) under natural light conditions for more than 1 month to obtain aged high aspect ratio gold nanowires; (d) Preparation of aged gold nanowires / gold nanoparticles with large aspect ratio The aged gold nanowires with a large aspect ratio obtained in step (c) and the gold nanoparticles obtained in step (b) were respectively placed in centrifuge tubes and centrifuged at a speed of 7000-9000 rpm for 8-12 min, the supernatant was discarded, and the bottom precipitate was mixed to obtain aged gold nanowires with a large aspect ratio / gold nanoparticles.

4. The detection method according to claim 3, characterized in that The aspect ratio of the large aspect ratio gold nanowires obtained in step (a) is 30-50:

1.

5. The detection method according to claim 3, characterized in that: Step (c) placing the large aspect ratio gold nanowires obtained in step (a) under natural light conditions for 1-2 months.

6. The detection method according to claim 3, characterized in that: In step (d), the volume ratio of the aged gold nanowires with a large aspect ratio to the gold nanoparticles is 3-5:

1.

7. The detection method according to claim 6, characterized in that The volume ratio of the aged gold nanowires with a large aspect ratio to the gold nanoparticles is 4:

1.

8. The detection method according to claim 3, characterized in that: Step (d) Centrifuge at 8000 rpm for 10 min.

9. The detection method according to claim 1, characterized in that: Step (4) Place the enhanced chip on a metal table and heat at 45-50°C for 1 min.

10. The detection method according to claim 1, characterized in that: Step (4) The excitation light wavelength of SERS detection is 785 nm, the integration time is 2-4 s, and the laser power is 50-100 mW.

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