CnTsAg@AuNPsSiO2 combined sers substrate, preparation method and pesticide detection method

Abstract

The application discloses a CNTsAg@AuNPsSiO2 combined SERS substrate, CNTsAg@AuNPs solution is dropped on a silica glass sheet, and after drying, a CNTsAg@AuNPsSiO2 combined SERS substrate is formed; the mass percentage of each component of CNTsAg@AuNPs in the CNTsAg@AuNPs solution is 20-80% of gold in a gold shell, 16-76% of silver in a silver core and 3-25% of a multi-walled carbon nanotube. The application can realize large-area uniform construction of a SERS substrate with a complex structure at low cost and simply.

Description

Technical Field

[0001] This invention relates to the field of pesticide residue analysis and detection technology, specifically to a CNTsAg@AuNPsSiO2 combined SERS substrate (a composite SERS substrate of multi-walled carbon nanotubes with gold shell and silver core nanoparticles and silica material), its preparation method, and a pesticide detection method. Background Technology

[0002] With the development of agricultural technology, the use of pesticides to treat crops is a common method to ensure that agricultural products meet expected standards. However, pesticide residues still remain on crops after they mature. When the amount of residue exceeds a certain standard, it can cause irreversible damage to the human body. Therefore, it is necessary to test for pesticide residues on the surface of crops after they mature.

[0003] Currently, many pesticide detection methods have been proposed, such as thin-layer chromatography, gas chromatography, high-performance liquid chromatography, supercritical fluid chromatography, gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, and high-performance capillary electrophoresis. While these traditional methods are stable, reliable, and reproducible, they involve complex sample pretreatment, long detection times, and delayed results, making them unsuitable for on-site detection. Therefore, researching rapid and efficient pesticide residue detection methods is of significant practical importance. Surface-enhanced Raman spectroscopy (SERS) offers advantages such as high sensitivity, strong anti-interference capabilities, and fluorescence quenching. Furthermore, SERS can generally enhance the signal by 10... -5 ~10 -6 It has been increased several times, reaching the standard for practical application, and therefore has great advantages and application potential in the rapid detection of pesticide residues in agricultural and sideline products.

[0004] To perform analysis and testing using Raman spectroscopy, it is necessary to select a suitable Raman substrate and detect analytes through the surface-enhanced Raman effect of the substrate. Currently, domestic and international research on surface-enhanced Raman spectroscopy focuses on two enhancement mechanisms: electromagnetic field enhancement (EM) and chemical enhancement (CM). Among these, the preparation of surface-enhanced Raman substrates has received considerable attention. However, most existing substrate preparation processes are complex, with limited and demanding preparation conditions, making large-scale production difficult, applications relatively limited, and costs somewhat high. Therefore, there is a need to seek more economical and reliable methods for preparing highly active SERS substrates. Summary of the Invention

[0005] The purpose of this invention is to provide a CNTsAg@AuNPsSiO2-bonded SERS substrate, its preparation method, and a pesticide detection method. This invention can achieve large-area uniform construction of complex SERS substrates at low cost and with relatively simple methods.

[0006] To achieve this objective, the present invention designs a CNTsAg@AuNPsSiO2-bonded SERS substrate, characterized in that: a CNTsAg@AuNPs solution is dropped onto a silica glass slide, and after drying, a CNTsAg@AuNPsSiO2-bonded SERS substrate is formed. The mass percentage of each component of CNTsAg@AuNPs in the CNTsAg@AuNPs solution is as follows: gold in the surface gold shell 20-80%, silver in the core silver core 16-76%, and multi-walled carbon nanotubes 3-25%.

[0007] A method for preparing the above-mentioned CNTsAg@AuNPsSiO2-bonded SERS substrate, characterized in that it includes the following steps:

[0008] Step 1: Add AgNO3 standard solution to deionized water;

[0009] Step 2: Add multi-walled carbon nanotube dispersion to the solution obtained in Step 1 and mix to obtain a mixed solution;

[0010] Step 3: Use an oil bath to magnetically stir and heat the above mixture;

[0011] Step 4: Add sodium citrate solution to the solution after magnetic stirring and heating in Step 3, continue heating, and then remove and cool to room temperature;

[0012] Step 5: Centrifuge the cooled sample from Step 4, then disperse the centrifuged product in deionized water and store it at room temperature for later use to obtain the silver in the gold shell and silver core structure.

[0013] Step 6: Prepare a gold growth solution using hypochlorous acid solution, sodium hydroxide solution, Na2SO3 solution and water for subsequent use;

[0014] Step 7: Mix deionized water, polyvinylpyrrolidone (PVP) solution, ascorbic acid solution, NaOH solution, Na2SO3 solution and gold growth solution to obtain the gold in the gold-shell-silver-core structure;

[0015] Step 8: The sample solutions prepared in Step 5 and Step 7 are allowed to stand at room temperature to generate CNTs / Ag@AuNPs solution. At this time, the gold shell and silver core are adsorbed on the multi-walled carbon nanotubes. The mass percentage of each component of CNTsAg@AuNPs in the CNTsAg@AuNPs solution is 20-80% gold in the surface gold shell, 16-76% silver in the core silver core, and 3-25% multi-walled carbon nanotubes.

[0016] Step 9: Add the CNTs / Ag@AuNPs solution generated in Step 8 to deionized water, and after ultrasonic cleaning, centrifuge. Take out the bottom mixture collected after centrifugation, add 5ml of deionized water, ultrasonically clean, and store at room temperature for later use to prepare the CNTs / Ag@AuNPs substrate.

[0017] Step 10: Drop the prepared sample solution from step 9 onto a silica glass slide and let it air dry naturally to obtain a CNTsAg@AuNPs SiO2-bonded SERS substrate.

[0018] In step 1 of the above technical solution, AgNO3 standard solution is added to deionized water and stirred to dilute 0.01-1 mol / L AgNO3 to the range of 0.001-0.01 mol / L. The volume ratio of deionized water to AgNO3 standard solution is 57-95:3-5.

[0019] In step 2 of the above technical solution, the mixed solution obtained in step 2 is stirred with a glass rod for 5 to 15 minutes, covered with plastic wrap (to prevent evaporation) and left to stand for 20 to 40 minutes to allow Ag ions to fully contact and absorb the surface of multi-walled carbon nanotubes.

[0020] In step 2, the volume ratio of the solution after stirring in step 1 to the multi-walled carbon nanotube solution is 50-100:0.25-0.5.

[0021] In step 3 of the above technical solution, the above mixed solution is magnetically stirred and heated to 90-100°C using an oil bath with a rotation speed of 100-200 r / min. This oil bath method ensures constant temperature conditions, thereby reducing the influence of temperature fluctuations on the chemical reaction.

[0022] In step 4 of the above technical solution, a sodium citrate solution with a mass fraction of 0.5-1% is added, and the volume ratio of the mixed solution in step 2 to the sodium citrate solution is 96-201:2-4.

[0023] In step 4, after heating at 90-100°C for 30-45 minutes, the sample is removed and cooled to room temperature. At this time, the strong reducing power of sodium citrate solution in high-temperature water reduces the Ag ions in AgNO3 into Ag nanoparticles.

[0024] In step 5 of the above technical solution, the centrifugation process involves centrifuging at a speed of 4000-4800 r / min for 80-100 minutes using a centrifuge. The centrifuged product is then dispersed in 5 mL of deionized water. Selecting centrifugation can greatly shorten the separation time.

[0025] In step 6 of the above technical solution, the volume ratio of hypochlorous acid solution to water is 0.11-0.33:2.27-6.81, the volume ratio of sodium hydroxide solution to water is 0.01-0.05:1.14-5.68, and the volume ratio of Na2SO3 solution to water is 2-5:3.03-7.57.

[0026] The mass percentage of hypochlorous acid in the hypochlorous acid solution ranges from 1% to 3%.

[0027] The concentration range of sodium hydroxide solution is 0.1–0.5 mol / L;

[0028] The concentration range of Na2SO3 solution is 0.01–0.05 mol / L.

[0029] In step 7 of the above technical solution, the volume ratio of deionized water to gold growth solution is 2-4:3-4.71, the volume ratio of polyvinylpyrrolidone solution to gold growth solution is 0.5-3:2-12, the volume ratio of ascorbic acid solution to gold growth solution is 0.1-0.5:2-10, the volume ratio of NaOH solution to gold growth solution is 0.1-0.5:2-10, and the volume ratio of Na2SO3 solution to gold growth solution is 0.01-0.1:0.8-8.

[0030] The polyvinylpyrrolidone solution is a polyvinylpyrrolidone solution with a mass fraction of 2-5% and a relative molecular mass of 40,000;

[0031] The concentration range of ascorbic acid solution is 0.1–1 mol / L;

[0032] The concentration range of the NaOH solution is 0.1–1 mol / L;

[0033] The concentration range of Na2SO3 solution is 0.1–1 mol / L.

[0034] In step 9 of the above technical solution, CNTs / Ag@AuNPs are removed by centrifuging the CNTs / Ag@AuNPs sample solution. The centrifugation speed is selected as 4500 r / min, and the centrifugation is performed 5 times, 10 minutes each time.

[0035] A method for pesticide spectral detection using the CNTsAg@AuNPsSiO2-bound SERS substrate, wherein the detection method involves dropping the probe molecule rhodamine and the pesticide onto the CNTsAg@AuNPsSiO2-bound SERS substrate, allowing it to stand and air dry naturally, and then performing Raman detection to obtain the Raman spectrum of the pesticide, wherein the pesticide is thiram or diquat.

[0036] Compared with the prior art, the present invention improves the structure and preparation, and has the following technical effects:

[0037] 1. Structurally, the operation methods in steps 5 and 7 are used to obtain core-shell structured nanoparticles composed of gold and silver with strong electromagnetic enhancement capabilities, which are then combined with carbon nanotubes. The charge transfer of semiconductors is used to further enhance the Raman signal, which can greatly enhance the Raman signal and ultimately improve the detection limit. Good results are obtained with a simple structure.

[0038] 2. Since the preparation steps can all be completed at room temperature, and the operation is simple and the preparation time is short, the gold shell and silver core structure can be prepared in a short time. Therefore, the preparation method is simple, requires little time, is low in cost, and is easy to replicate.

[0039] 3. Because the preparation process yields core-shell structured nanoparticles composed of gold and silver with strong electromagnetic enhancement capabilities, the Raman signal is greatly enhanced. Furthermore, combined with multi-walled carbon nanotubes, it can detect low concentrations of thiram in applications with strong uniformity and stability. Attached Figure Description

[0040] Figure 1 Flowchart of CNTs / Ag@AuNPs / SiO2 SERS substrate fabrication;

[0041] Figure 2 TEM image of CNTs / Ag@AuNPs / SiO2 SERS substrate;

[0042] Figure 3 Image of a CNTs / Ag@AuNPs / SiO2 SERS substrate;

[0043] Figure 4 Raman spectroscopy pattern of rhodamine as a probe molecule for CNTs / Ag@AuNPs / SiO2 SERS substrate;

[0044] Figure 5a Raman spectroscopy results for the stability of CNTs / Ag@AuNPs / SiO2 SERS substrate;

[0045] Figure 5b Raman spectroscopy results for uniformity of CNTs / Ag@AuNPs / SiO2 SERS substrate;

[0046] Figure 6 Raman spectroscopy results for CNTs / Ag@AuNPs / SiO2 SERS substrates using the pesticide thiram; Detailed Implementation

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0048] Example 1

[0049] A CNTsAg@AuNPsSiO2-bonded SERS substrate is formed by dropping a CNTsAg@AuNPs solution onto a silica glass slide and drying it. The mass percentage of each component of CNTsAg@AuNPs in the CNTsAg@AuNPs solution is as follows: gold in the gold shell, silver in the silver core, and multi-walled carbon nanotubes, totaling 42.1%;

[0050] The method for preparing CNTsAg@AuNPsSiO2-bonded SERS substrates includes the following steps:

[0051] Step 1: Add 5 ml of AgNO3 standard solution to 95 ml of deionized water and stir for 10 minutes. At this time, the solution is colorless.

[0052] Step 2: Add 0.5 ml of multi-walled carbon nanotubes to the above colorless solution, mix them, and stir for 5 minutes. At this time, the solution changes from colorless to black.

[0053] Step 3: Use an oil bath at 200 r / min to magnetically stir the above black solution and heat it to 95°C;

[0054] Step 4: After heating to 95°C, add 2 mL of 1% sodium citrate solution to the black solution, maintain the temperature at 95°C and heat and stir for 40 minutes. After 40 minutes, remove it and cool it to room temperature.

[0055] Step 5: Centrifuge the black solution sample that has been cooled to room temperature at a speed of 4500 r / min for 90 minutes. After centrifugation, disperse the centrifuged product in 5 mL of deionized water and store it at room temperature for later use.

[0056] Step 6: Add 4.54 ml of deionized water to a 20 ml glass bottle, then add 220 μl of hypochlorous acid (2% by mass), then add 40 μl of sodium hydroxide (0.2 mol / L), and finally add 3 ml of Na2SO3 to obtain a colorless gold growth solution.

[0057] Step 7: Add 2.55 mL of deionized water to a 25 mL glass bottle, add 1 mL of polyvinylpyrrolidone (5 wt%, Mw 40000), then add 200 μL of ascorbic acid (0.5 mol / L), then add 200 μL of NaOH (0.5 mol / L), then add 50 μL of Na2SO3 (0.1 mol / L), and finally add 4 mL of gold growth solution.

[0058] Step 8: Let the sample solutions prepared in Step 5 and Step 7 stand at room temperature to generate CNTs / Ag@AuNPs;

[0059] Step 9: Add the CNTs / Ag@AuNPs solution generated in Step 8 to deionized water, and after ultrasonic cleaning, centrifuge at 4500 r / min for 5 times, 10 minutes each time. After centrifugation, take out the bottom mixture and add 5 mL of deionized water. Use an ultrasonic cleaner to ultrasonically vibrate for 10 minutes and store at room temperature for later use. The ultrasonic frequency is 45 Hz.

[0060] Step 10: Drop the prepared sample solution from step 9 onto a silica glass slide and let it air dry naturally to obtain a CNTsAg@AuNPs SiO2-bonded SERS substrate. Figure 2 The image shows a TEM image of the CNTs / Ag@AuNPs / SiO2 SERS substrate. As can be seen from the image, gold-shelled silver-core nanoparticles are adsorbed onto multi-walled carbon nanotubes, which indicates that the preparation of this substrate structure is entirely feasible and has good results. Figure 3 This is a photo of the base after it has dried.

[0061] Step 11: The SERS substrate with CNTsAg@AuNPs SiO2 bound in Step 10 was placed for 1 day, 7 days, 15 days, 30 days, and 45 days, respectively. Then, the SERS substrate was measured at days 1, 7, 15, 30, and 45. -8 The results for rhodamine at a concentration of mol / L are as follows: Figure 5a As shown, rhodamine can still be detected well even after the substrate has been placed for a relatively long period of 45 days, which proves that the substrate has good stability.

[0062] Step 12: Perform Raman spectroscopy on the SERS substrate bound to CNTsAg@AuNPs SiO2 from Step 10, randomly selecting 5 test points, such as... Figure 5b As shown in the figure, the signals at the five randomly selected points are good, indicating that the substrate has good uniformity.

[0063] Example 2:

[0064] A CNTsAg@AuNPsSiO2-bonded SERS substrate is formed by dropping a CNTsAg@AuNPs solution onto a silica glass slide and drying it. The mass percentage of each component of CNTsAg@AuNPs in the CNTsAg@AuNPs solution is as follows: gold in the gold shell, silver in the silver core, and multi-walled carbon nanotubes, totaling 41.1%.

[0065] The method for preparing CNTsAg@AuNPsSiO2-bonded SERS substrates includes the following steps:

[0066] Step 1: Add 4 ml of AgNO3 standard solution to 95 ml of deionized water and stir for 10 minutes. At this time, the solution is colorless.

[0067] Step 2: Add 0.3 ml of multi-walled carbon nanotubes to the above colorless solution, mix them, and stir for 15 minutes. At this time, the solution changes from colorless to black.

[0068] Step 3: Use an oil bath at 100 r / min to magnetically stir the above black solution and heat it to 100°C;

[0069] Step 4: After heating to 100℃, add 4mL of 0.5% sodium citrate solution to the black solution, maintain the temperature at 100℃ and heat and stir for 35 minutes. After 35 minutes, remove it and cool it to room temperature.

[0070] Step 5: Centrifuge the black solution sample that has been cooled to room temperature at a speed of 4600 r / min for 85 minutes. After centrifugation, disperse the centrifuged product in 6 mL of deionized water and store it at room temperature for later use.

[0071] Step 6: Add 4 ml of deionized water to a 20 ml glass bottle, then add 200 μl of hypochlorous acid (2% by mass), then add 50 μl of sodium hydroxide (0.2 mol / L), and finally add 5 ml of Na2SO3 to obtain a colorless gold growth solution.

[0072] Step 7: Add 2 mL of deionized water to a 25 mL glass bottle, add 1.5 mL of polyvinylpyrrolidone (5 wt%, Mw 40000), then add 220 μL of ascorbic acid (0.5 mol / L), then add 220 μL of NaOH (0.5 mol / L), then add 40 μL of Na2SO3 (0.1 mol / L), and finally add 3 mL of gold growth solution.

[0073] Step 8: Let the sample solutions prepared in Step 5 and Step 7 stand at room temperature to generate CNTs / Ag@AuNPs;

[0074] Step 9: Add the CNTs / Ag@AuNPs solution generated in Step 8 to deionized water, and after ultrasonic cleaning, centrifuge at 4500 r / min for 5 times, 10 minutes each time. After centrifugation, take out the bottom mixture and add 5 mL of deionized water. Use an ultrasonic cleaner to ultrasonically vibrate for 10 minutes and store at room temperature for later use. The ultrasonic frequency is 45 Hz.

[0075] Step 10: Drop the prepared sample solution from step 9 onto a silica glass slide and let it air dry naturally to obtain a CNTsAg@AuNPs SiO2-bonded SERS substrate.

[0076] Step 11: The SERS substrate with CNTsAg@AuNPs SiO2 bound in Step 10 was placed for 1 day, 7 days, 15 days, 30 days, and 45 days, respectively. Then, the SERS substrate was measured at days 1, 7, 15, 30, and 45. -8 The stability of the substrate was investigated using rhodamine at a concentration of mol / L.

[0077] Step 12: Raman spectroscopy was performed on the SERS substrate with CNTsAg@AuNPs SiO2 bound in Step 10. Five test points were randomly selected to investigate the uniformity of the substrate.

[0078] Test Example 1:

[0079] To prepare a rhodamine solution, 0.0479 g of rhodamine red solid powder was weighed using an electronic balance and added to 100 mL of deionized water, yielding 10... -3 1 mL of mol / L R6G stock solution. -3 A mol / L R6G stock solution was added to a centrifuge tube, followed by the addition of deionized water to bring the volume to 10 mL, yielding 10 mol / L. -4 Dilute the R6G solution to 1 mol / L (i.e., 1 ml R6G + 9 ml deionized water) and so on to a concentration of 10 mol / L. -12 mol / L.

[0080] Different concentrations of Rhodamine solutions were dropped onto the silica glass slide of Example 7, and then left to air dry naturally. After air drying, Raman spectroscopy was performed. Figure 4 Raman spectra of the CNTs / Ag@AuNPs / SiO2-bound SERS substrate obtained in Example 1 were obtained using different concentrations of the probe molecule rhodamine. Figure 4 It can be seen that the probe molecule rhodamine at a low concentration of 10 -11 It can still be detected at mol / L, indicating that the substrate has good detection performance.

[0081] Test Example 2:

[0082] Preparation of thiram solution:

[0083] 10 mg / L thiram diethanol solution: Weigh 0.01 g of thiram powder using an electronic balance, add it to 100 mL of ethanol, and sonicate for 2 min to prepare a 10 mg / L thiram diethanol solution;

[0084] 5 mg / L thiram diethanol solution: Take 5 mL of 10 mg / L thiram diethanol solution with a dropper and add 5 mL of ethanol to form a 5 mg / L thiram diethanol solution;

[0085] 1 mg / L thiram diethanol solution: Take 1 mL of 10 mg / L thiram diethanol solution with a dropper and add 9 mL of ethanol to form a 1 mg / L thiram diethanol solution;

[0086] 0.1 mg / L thiram diethanol solution: Take 1 mL of 1 mg / L thiram diethanol solution with a dropper and add 9 mL of ethanol to form a 0.1 mg / L thiram diethanol solution.

[0087] Then, convert them into thiram solutions of different concentrations and let them stand at room temperature for later use.

[0088] Different concentrations of thiram solutions were dropped onto the silica glass slide of Example 7, and then left to air dry naturally. After air drying, Raman spectroscopy was performed. Figure 6 Raman spectroscopy images of CNTs / Ag@AuNPs / SiO2 bound SERS substrates using different concentrations of the pesticide thiram, by [the following text is incomplete and likely refers to a different topic] Figure 6 It can be seen that the pesticide thiram can still be detected at a low concentration of 0.01 mg / L, indicating that the substrate has good detection performance and high sensitivity, making it suitable for the detection of thiram residues.

[0089] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A dual-spectral detection method for the pesticide thiram using a SERS substrate bound to CNTsAg@AuNPsSiO2, characterized in that: The CNTsAg@AuNPsSiO2-bonded SERS substrate is formed by dropping a CNTsAg@AuNPs solution onto a silica glass slide and drying it. The mass percentage of each component of CNTsAg@AuNPs in the CNTsAg@AuNPs solution is as follows: gold in the gold shell on the surface, silver in the silver core on the core, and multi-walled carbon nanotubes, which are 20-80% by mass. The method for preparing a SERS substrate bound to CNTsAg@AuNPsSiO2 includes the following steps: Step 1: Add AgNO3 standard solution to deionized water; the volume ratio of deionized water to AgNO3 standard solution is 57~95:3~5; Step 2: Add multi-walled carbon nanotube dispersion to the solution obtained in Step 1 and mix to obtain a mixed solution; Step 3: Use an oil bath to magnetically stir and heat the above mixture; Step 4: Add sodium citrate solution to the solution after magnetic stirring and heating in Step 3, continue heating, and then remove and cool to room temperature; the volume ratio of the mixed solution to the sodium citrate solution is 96~201:2~4; Step 5: Centrifuge the cooled sample from Step 4, then disperse the centrifuged product in deionized water and store it at room temperature for later use to obtain silver in the gold shell and silver core structure. Step 6: Prepare a gold growth solution using chloroauric acid solution, sodium hydroxide solution, Na2SO3 solution, and water; Step 7: Mix deionized water, polyvinylpyrrolidone solution, ascorbic acid solution, NaOH solution, Na2SO3 solution and gold growth solution for later use to obtain the gold in the gold shell and silver core structure; Step 8: Let the sample solutions prepared in Step 5 and Step 7 stand at room temperature to generate a CNTs / Ag@AuNPs solution. The mass percentage of each component of CNTs / Ag@AuNPs in the CNTs / Ag@AuNPs solution is as follows: gold in the gold shell 20-80%, silver in the silver core 16-76%, and multi-walled carbon nanotubes 3-25%. Step 9: Add the CNTs / Ag@AuNPs solution generated in Step 8 to deionized water, and after ultrasonic cleaning, centrifuge. Take out the bottom mixture collected after centrifugation, add deionized water and ultrasonic cleaning, and store at room temperature for later use. Step 10: Drop the prepared sample solution from step 9 onto a silica glass slide and let it air dry. In step 2, the mixed solution obtained in step 2 is stirred with a glass rod for 5 to 15 minutes and then left to stand for 20 to 40 minutes to allow Ag ions to fully contact and absorb the surface of multi-walled carbon nanotubes. In step 2, the volume ratio of the solution after stirring in step 1 to the multi-walled carbon nanotube solution is 50~100 : 0.25~0.5; In step 6, the volume ratio of chloroauric acid solution to water is 0.11~0.33 : 2.27~6.81, the volume ratio of sodium hydroxide solution to water is 0.01~0.05 : 1.14~5.68, and the volume ratio of Na2SO3 solution to water is 2~5 : 3.03~7.57; The method for pesticide spectral detection using a CNTsAg@AuNPsSiO2-bound SERS substrate is as follows: the pesticide thiram is dropped onto the CNTsAg@AuNPsSiO2-bound SERS substrate, and then left to air dry naturally. After air drying, Raman detection is performed to obtain the Raman spectrum of the pesticide thiram.

2. The method for dual-spectral detection of the pesticide thiram according to claim 1, characterized in that: In step 1, AgNO3 standard solution is added to deionized water and stirred to dilute 0.01~1 mol / L AgNO3 to the range of 0.001~0.01 mol / L.

3. The method for dual-spectral detection of the pesticide thiram according to claim 1, characterized in that: In step 3, the above mixed solution is magnetically stirred and heated to 90-100°C using an oil bath with a rotation speed of 100-200 r / min.

4. The method for dual-spectral detection of the pesticide thiram according to claim 1, characterized in that: In step 4, a sodium citrate solution with a mass fraction of 0.5-1% is added; In step 4, continue heating at 90~100℃ for 30~45 minutes, then remove and cool to room temperature.

5. The method for dual-spectral detection of the pesticide thiram according to claim 1, characterized in that: In step 5, the centrifugation process involves centrifuging at a speed of 4000~4800 r / min for 80~100 minutes using a centrifuge, and the centrifuged product is dispersed in deionized water.

6. The method for dual-spectral detection of the pesticide thiram according to claim 1, characterized in that: The mass percentage of chloroauric acid in a chloroauric acid solution ranges from 1% to 3%. The concentration range of sodium hydroxide solution is 0.1~0.5 mol / L; The concentration range of the Na2SO3 solution is 0.01~0.05 mol / L.

7. The method for dual-spectral detection of the pesticide thiram according to claim 1, characterized in that: In step 7, the volume ratio of deionized water to gold growth solution is 2~4:3~4.71, the volume ratio of polyvinylpyrrolidone solution to gold growth solution is 0.5~3:2~12, the volume ratio of ascorbic acid solution to gold growth solution is 0.1~0.5:2~10, the volume ratio of NaOH solution to gold growth solution is 0.1~0.5:2~10, and the volume ratio of Na2SO3 solution to gold growth solution is 0.01~0.1:0.8~8. The polyvinylpyrrolidone solution is a polyvinylpyrrolidone solution with a mass fraction of 2-5% and a relative molecular mass of 40,000; The concentration range of ascorbic acid solution is 0.1~1 mol / L; The concentration range of the NaOH solution is 0.1~1 mol / L; The concentration range of Na2SO3 solution is 0.1~1 mol / L.

Images