Preparation method of gold nanoparticle / pdms flexible substrate, product and application thereof

Abstract

This invention discloses a method for preparing a flexible gold nanoparticle / PDMS substrate. The method is simple, convenient, widely applicable, has low overall preparation cost and short preparation time, requires no other large or expensive equipment, can be mass-produced, and has significant potential commercial value. It is also safer and more environmentally friendly; the particles can firmly and uniformly bond to the PDMS surface; and it can be reused multiple times while effectively ensuring the substrate's enhancement performance. This invention also discloses a flexible gold nanoparticle / PDMS substrate prepared by the method. This flexible substrate requires no additional storage requirements, and its Raman enhancement performance remains unchanged for 30 days. Furthermore, this invention discloses the application of this flexible gold nanoparticle / PDMS substrate in the quantitative detection of pesticides. The detection limit of this application is far lower than the lowest detection limit reported by general methods and related literature, reaching 0.01 ppm.

Description

Technical Field

[0001] This invention relates to a method for detecting pesticide residues, and more particularly to a method for preparing a gold nanoparticle / PDMS flexible substrate, its products, and applications, belonging to the field of pesticide detection. Background Technology

[0002] Thiram (chemical formula C6H) 12 N2S4 is a novel pesticide with broad-spectrum therapeutic effects against fruit tree diseases and pests. Due to its excellent insecticidal and control effects, it is widely used for pest and disease control in apple trees. While the extensive use of thiram pesticides can effectively control diseases and pests and increase fruit yield, it inevitably leads to excessive thiram residues in apples and various apple-based derivatives. Apple juice is one of the most consumed fruit juice beverages in daily life. Traditional methods for detecting pesticide residues in apple juice, such as chromatography, mass spectrometry, thin-layer chromatography, liquid chromatography-mass spectrometry, and immunoassay, all suffer from drawbacks such as complex pretreatment, numerous operational steps, and long detection times. These problems result in low detection efficiency and low sensitivity for food pesticide residues. Therefore, developing efficient and convenient methods for detecting food pesticide residues is particularly important. Developing novel detection methods for thiram residues in apple juice is therefore significant and meaningful.

[0003] Methyl chlorpyrifos (molecular formula C7H7Cl3NO3PS) is a broad-spectrum organophosphorus insecticide, effective through contact, stomach poison, and fumigation. It is non-systemic and used to control pests in stored grains and various leafy crops. It can also be used to control adult mosquitoes, flies, aquatic larvae, and sanitary pests. It has no persistence in soil. While the extensive use of methyl chlorpyrifos increases crop yields, it inevitably leads to excessive residues in the environment. Humans can develop various diseases, including cancer, from ingesting food with excessive methyl chlorpyrifos residues. Traditional methods for detecting methyl chlorpyrifos residues, such as capillary electrophoresis, fluorescence detection, biosensor methods, gas chromatography, and liquid chromatography-mass spectrometry, suffer from drawbacks such as long detection times, cumbersome procedures, narrow detection ranges, and poor data reproducibility. In particular, traditional methods require complex pretreatment procedures, placing high demands on operators and experimental equipment. Therefore, developing rapid detection methods for chlorpyrifos is necessary and meaningful.

[0004] The discovery of surface-enhanced Raman scattering (SERS) has provided a novel approach for pesticide residue detection. Because it can obtain material structure information that is difficult to obtain using traditional Raman detection methods, it has greatly broadened the development and application of Raman detection. Currently, SERS technology is widely used in biochemical analysis, catalysis research, and environmental monitoring. Compared to traditional pesticide residue detection methods, SERS can amplify the Raman signal of molecules by millions of times, and the process is simple and rapid. It overcomes the shortcomings of traditional pesticide residue detection methods, such as low sensitivity, complex processing steps, long detection time, and high requirements for experimental personnel. In recent years, SERS technology has been applied to the qualitative and quantitative detection of pesticide residues in food due to its advantages such as convenient operation, small detection volume, high detection sensitivity, and fast detection process. Furthermore, the development and use of portable Raman instruments has made direct on-site detection possible. However, traditional SERS technology requires complex pretreatment of the PDMS substrate. For example, Ma Wenzhe et al. (Preparation and Characterization of AuNPs-PDMS Composite Thin Films Based on Chemical Method, 2014) first reacted the prepared PDMS with a piranha solution (a mixture of concentrated sulfuric acid and 30% hydrogen peroxide (volume ratio 7:3)). Piranha solution is a highly corrosive and dangerous reagent, making the preparation process risky. Furthermore, it requires controlling the solution temperature and the reaction time between PDMS and the piranha solution, making the process complex, dangerous, time-consuming, and inefficient. Mei Yongsong et al. (Study on PDMS Surface Modification under Microwave Plasma and its Application in SERS Substrates, 2020) modified the surface of PDMS using an oxygen plasma machine. However, this method requires a plasma etching machine, which is expensive, involves cumbersome steps, and is difficult to promote. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a method for preparing a flexible gold nanoparticle / PDMS substrate with the advantages of simple preparation process, convenient operation, wide applicability, low overall preparation cost and short time consumption, no need for other large or expensive equipment, large-scale preparation, great potential commercial value, overall safety and environmental protection, strong and uniform bonding of particles to PDMS surface, and repeated use while effectively ensuring the substrate enhancement performance.

[0006] Another technical problem to be solved by the present invention is to provide a flexible gold nanoparticle / PDMS substrate prepared by the method, wherein the flexible substrate does not require any other additional storage requirements and the Raman enhancement performance of the substrate remains unchanged for 30 days.

[0007] Another technical problem to be solved by the present invention is to provide an application of the gold nanoparticle / PDMS flexible substrate prepared by the method in the quantitative detection of pesticides.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0009] This invention provides a method for preparing a flexible gold nanoparticle / PDMS substrate, comprising the following steps:

[0010] 1) Mix PDMS with dibutyltin dilaurate, stir evenly, vacuum pump, heat, and then ultrasonically clean in acetone, ethanol, and deionized water in sequence, and dry with nitrogen to obtain cleaned PDMS.

[0011] 2) Place the washed PDMS into APTES ethanol solution, incubate, rinse with deionized water and dry with nitrogen to obtain a flexible PDMS substrate;

[0012] 3) Immerse the PDMS flexible substrate in the nano-gold star ethanol solution, shake to react, rinse with deionized water and dry with nitrogen to obtain gold nanoparticles / PDMS flexible substrate.

[0013] In step 1), the mass ratio of PDMS to dibutyltin dilaurate is 9-15:1.

[0014] The ultrasonic cleaning time in step 1) is 10-20 mins.

[0015] In step 2), the volume ratio of triethoxysilane to ethanol in the APTES ethanol solution is 1:9-20.

[0016] The incubation time in step 2) is 3-15 hours.

[0017] In step 3), the concentration of the nano-gold particles in the nano-gold ethanol solution is 0.005-0.1 nM.

[0018] Preferably, the concentration of the gold nanoparticles in the gold nanoparticle ethanol solution in step 3) is 0.125 nM, and the gold nanoparticles have good dispersion on the substrate.

[0019] The present invention also provides a flexible gold nanoparticle / PDMS substrate prepared by the method.

[0020] The present invention also provides an application of the gold nanoparticle / PDMS flexible substrate prepared by the method in the quantitative detection of pesticides. The application includes immersing the gold nanoparticle / PDMS flexible substrate in a test solution containing pesticides, adsorbing the pesticides, rinsing with deionized water and drying with nitrogen, and then performing Raman signal detection. The pesticides are thiram or methyl chlorpyrifos.

[0021] When the pesticide is thiram, the linear relationship between thiram concentration and Raman signal intensity is given by the equation: I = 28121.60011 + 10816.24831 × lg C Where I is at 1371cm -1 The Raman peak intensity at the specified location, where C represents the concentration of thiram, and the concentration of thiram is 0.01-100 ppm, with a detection limit of 0.01 ppm.

[0022] When the pesticide is methyl chlorpyrifos, the characteristic is that the linear relationship equation between methyl chlorpyrifos and the Raman signal intensity is I = 19364.24781 + 6675.00279 × lgC, where I is the value at 1269 cm⁻¹. -1 The Raman peak intensity at the specified location, where C represents the concentration of methyl chlorpyrifos, and the concentration of methyl chlorpyrifos is 0.01-100 ppm, with a detection limit of 0.01 ppm.

[0023] Working Principle: This invention achieves rapid detection of substances through surface-enhanced Raman spectroscopy (SERS). First, negatively charged gold nanoparticles and amination-modified PDMS bind tightly together under electrostatic forces to form a flexible gold nanoparticle / PDMS substrate. Then, the substrate is mixed with the analyte for adsorption. The analyte enriched on the substrate experiences a significant enhancement of its Raman signal under the SERS effect of the gold nanoparticle / PDMS substrate, thus enabling substance detection. Furthermore, this invention modifies the electronegativity of the gold nanoparticles by adjusting the amount of sodium dodecyl sulfate (SDS), ensuring that the final gold nanoparticles bind tightly to the PDMS, thereby obtaining the final substrate.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0025] (1) The flexible substrate preparation process in this invention is simple, convenient to operate, widely applicable, has low overall preparation cost and short time consumption, does not require other large or expensive equipment, can be prepared on a large scale, and has great potential commercial value.

[0026] (2) It does not require the use of dangerous chemicals such as piranha solution, making it safer and more environmentally friendly overall;

[0027] (3) Gold nanostar particles are fixed on the surface of PDMS after amination by electrostatic force, and the particles can be firmly and uniformly bonded to the PDMS surface.

[0028] (4) It can be reused multiple times while effectively ensuring the substrate reinforcement performance;

[0029] (5) The Raman-enhanced substrate itself has the characteristics of low background noise, strong enhancement performance and stable enhancement performance; at room temperature, without any other additional storage requirements, the Raman enhancement performance of the substrate remains unchanged for 30 days.

[0030] (6) The detection limit of methyl chlorpyrifos is much lower than the lowest detection limit reported by general methods and related literature, reaching 0.01 ppm;

[0031] (7) The detection limit of thiamethoxam is much lower than the lowest detection limit reported by general methods and related literature, reaching 0.01 ppm;

[0032] (8) It can not only qualitatively detect and identify pesticides, but also quantitatively analyze the specific content of pesticide residues. Attached Figure Description

[0033] Figure 1 A is a transmission electron microscopy (TEM) image of the nano-Venus particles. Figure 1 B is the ultraviolet absorption spectrum of the nano-Venus particles. Figure 1 C is the statistical distribution of the hydrated particle size of the nano-Venus particles. Figure 1 D is a statistical distribution diagram of the gold nucleus diameter of nano-Venus particles;

[0034] Figure 2 The fabrication process for flexible Raman substrates;

[0035] Figure 3 A shows the substrate electron microscopy characterization of the nano-Venus particles at a concentration of 0.1 nM. Figure 3 B is an electron microscopy image of the substrate containing nano-Venus particles at a concentration of 0.05 nM. Figure 3 C is the electron microscopy image of the substrate containing nano-Venus particles at a concentration of 0.0125 nM. Figure 3 D is an electron microscopy image of the substrate containing nano-Venus particles at a concentration of 0.01 nM. Figure 3 E is an electron microscopy image of the substrate containing nano-Venus particles at a concentration of 0.0067 nM. Figure 3 F is an electron microscopy image of the substrate containing nano-gold particles at a concentration of 0.005 nM;

[0036] Figure 4 A is the Raman spectrum of thiophanate-methyl at two concentration gradients. Figure 4 B is a logarithmic graph of the concentrations of thiophanate-methyl in a dual gradient.

[0037] Figure 5 A is the Raman spectrum of the concentration gradient of methyl chlorpyrifos. Figure 5 B is a logarithmic graph of methyl chlorpyrifos concentration;

[0038] Figure 6 A is the test substrate detection double reproducibility diagram of thiophanate-methyl. Figure 6B is the Raman spectrum of the test substrate for detecting thiamethoxam. Figure 6 C represents the Raman spectra of thiamethoxam on the same substrate at different times. Figure 6 D is a graph showing the change in the intensity of the characteristic peak of thiram on the same substrate over time. Detailed Implementation

[0039] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0040] Silver nitrate, ascorbic acid, sodium citrate, sodium dodecyl sulfate, chloroauric acid (HAuCl4), polydimethylsiloxane (PDMS), and triethoxysilane (APTES) were purchased from Maclean's (Shanghai, China); hydrochloric acid, acetone, and ethanol were purchased from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China); dibutyltin dilaurate (Dow Corning 184, Shanghai, China); methyl chlorpyrifos and thiram were obtained from the Criminal Investigation Technology Research Institute of Nanjing Municipal Public Security Bureau (Nanjing, China); the apples used in the experiment were purchased from a supermarket near the school (Nanjing, China); and the apple juice was commercially available (Nanjing, China).

[0041] Confocal Raman microscope (Renishaw, Shanghai, China); Field emission scanning electron microscope (Frequency Electronics, Shanghai, China); Transmission electron microscope (Frequency Electronics, Shanghai, China); Mixer (Icarus, Suzhou, China); Refrigerated centrifuge (Thermo Fisher Scientific, Shanghai, China).

[0042] Example 1: Synthesis of Nano Venus Particles

[0043] 1. Synthesis and characterization of star-shaped gold nanoparticles (i.e., gold nanoparticles) by seed growth method.

[0044] First, spherical gold nanoparticles with a diameter of 13 nm were synthesized: 50 mL of a 0.25 mM HAuCl4 solution was added to a flask; the solution was initially pale yellow. The flask was then heated and stirred using a magnetic stirrer. Once the solution reached complete boiling, 7.5 mL of a 1% sodium citrate aqueous solution was immediately added. After reacting for 15 minutes, heating was stopped, yielding a spherical gold nanoparticle solution, which was then wine-red in color. The flask was removed, and the spherical gold nanoparticle solution was allowed to cool naturally to room temperature before use.

[0045] Next, the gold nanoparticles were synthesized: 50 mL of 0.25 mM HAuCl4 solution and 50 μL of 1 M hydrochloric acid were added to a flask and stirred for 3 min. Then, 0.5 mL of newly synthesized spherical gold nanoparticles with a diameter of 13 nm were added to the flask and stirred for another 3 min. Then, 1 mL of 0.75 mM silver nitrate solution and 0.25 mL of 0.1 M ascorbic acid solution were added to the solution. After reacting for 30 s, 0.75 mL of 0.01 M sodium dodecyl sulfate solution was added. The solution was centrifuged and washed for 15 min at 4500 RCF using a refrigerated centrifuge. After removing the supernatant, the solution was dispersed in 5 mL of ethanol to obtain a 0.1 nM gold nanoparticle ethanol solution.

[0046] The centrifuged and washed gold nanoparticles were first characterized using transmission electron microscopy to observe whether the morphology of the synthesized material met the requirements. For example... Figure 1 As shown in Figure A, transmission electron microscopy results indicate that the synthesized gold nanospheres possess a distinct star-shaped morphology and a clearly defined multi-branched structure; Figure 1 As shown in B, ultraviolet testing shows that the nano-gold particles have an absorption peak at 806 nm, which further confirms the successful synthesis of nano-gold particles. Figure 1 C indicates that the synthesized nano-Venus particles have a symmetrical size distribution and good uniformity; Figure 1 D indicates that the diameter distribution of the gold nanoparticles is symmetrical and has excellent normalization. These test results all show that the synthesized gold nanoparticles have uniform morphology and good dispersibility.

[0047] Example 2: Preparation and Detection of Nano-Venus Particles / PDMS Composite Substrate

[0048] like Figure 2 The method shown is used to prepare a nano-gold star particle / PDMS composite substrate.

[0049] 1. Preparation of PDMS flexible substrate: First, weigh 4.5g of PDMS and 0.5g of curing agent dibutyltin dilaurate, mix them, and mechanically stir for 10 minutes. After uniform mixing, place the mixture in a vacuum desiccator and vacuum-degas for 30 minutes to eliminate any residual air bubbles. Then, pour the PDMS mixture into a sterile petri dish and heat it at 80℃ for 30 minutes. After drying and curing, remove and cool to obtain the cured PDMS. Cut the cured PDMS into 0.5×0.5cm pieces. -2The PDMS sheets were then sonicated in acetone, ethanol, and deionized water for 15 minutes in sequence to remove surface impurities and dried with nitrogen to obtain cleaned PDMS sheets. Next, the cleaned PDMS sheets were placed in a 5% APTES ethanol solution and incubated at 70°C for 3 hours for amination. Finally, after the amination reaction was completed, the sheets were removed, rinsed with deionized water, and dried with nitrogen to obtain a flexible PDMS substrate.

[0050] 2. Preparation and detection of nano-gold particle / PDMS composite substrate

[0051] The area is 0.5 × 0.5 cm. -2 Square-shaped PDMS flexible substrates were immersed in 1 ml of 0.1 nM, 0.05 nM, 0.0125 nM, 0.01 nM, 0.0067 nM, and 0.005 nM nano-gold nanoparticle ethanol solutions (diluted from 0.1 nM nano-gold nanoparticle ethanol solution) at concentrations of 0.1 nM, 0.01 nM, 0.0067 nM, and 0.005 nM, respectively. After shaking and reacting at room temperature for 12 h, the substrates were rinsed with deionized water and dried under nitrogen to obtain gold nanoparticle / PDMS flexible substrates with surface Raman enhancement effects. The prepared substrates were characterized by scanning electron microscopy (SEM). SEM results (…). Figure 3 The results show that the dispersibility of gold nanoparticles on the substrate gradually improves as the concentration of the gold nanoparticle solution decreases. However, when the concentration is too low, there are too few gold nanoparticles loaded on the substrate, and the large spacing between the nanoparticles is not conducive to Raman enhancement. Therefore, a flexible substrate prepared with a gold nanoparticle concentration of 0.125 nM was ultimately selected.

[0052] Example 3: Preparation of nano-gold asteroid particles / PDMS composite substrates under different conditions

[0053] First, weigh out 5g and 7.5g of PDMS and two 0.5g portions of dibutyltin dilaurate, respectively, and mix them separately. Stir mechanically for 10 minutes until homogeneous. Then, place the mixture in a vacuum desiccator and evacuate for 30 minutes to eliminate any remaining air bubbles. Next, pour the PDMS mixture (PDMS to dibutyltin dilaurate mass ratios of 10:1 and 15:1, respectively) into a sterile petri dish and heat at 80℃ for 30 minutes. After drying and curing, remove and cool to obtain cured PDMS. Cut the cured PDMS into 0.5×0.5cm pieces. -2The PDMS sheets were then sonicated in acetone, ethanol, and deionized water for 10 min and 20 min respectively to remove surface impurities, and then dried with nitrogen to obtain cleaned PDMS sheets. Next, the cleaned PDMS sheets were placed in 6.6% and 11% APTES ethanol solutions and incubated at 70°C for 10 h and 15 h respectively for amination. Finally, after the amination reaction was completed, the sheets were removed, rinsed with deionized water, and dried with nitrogen to obtain a flexible PDMS substrate.

[0054] The resulting area is 0.5 × 0.5 cm. -2 The square-shaped PDMS flexible substrates were immersed in 1 ml of 0.0125 nM gold nanoparticle ethanol solution, and reacted with shaking at room temperature for 12 h. After rinsing with deionized water and drying with nitrogen, gold nanoparticle / PDMS flexible substrates with surface Raman enhancement effect were obtained. The prepared substrates were characterized by scanning electron microscopy, and the results were the same as in Example 1.

[0055] Example 4: Detection of thiram in standard samples using a nano-gold asteroid / PDMS composite substrate

[0056] Thiram was dissolved in a 20% (v / v) methanol aqueous solution to prepare thiram solutions with concentrations of 0.01 ppm, 0.05 ppm, 0.1 ppm, 1 ppm, 5 ppm, 10 ppm, 25 ppm, 50 ppm, and 100 ppm. The prepared nano-gold asteroid / PDMS composite substrates were immersed in these thiram solutions for 30 mins, then removed, rinsed with deionized water, and dried with nitrogen gas. The substrates were then subjected to an induction atmosphere at 1371 cm⁻¹. -1 The detection was performed at the peak intensity at a given location. The main instrument parameters were: Raman excitation source wavelength of 785 nm, integration time of 10 s, and laser power of 10%. Each test result was performed in triplicate and independently. Figure 4 As shown, the thiram bimolecule was placed at 1371 cm⁻¹. -1 Linear fitting was performed on the peak intensity at that point, yielding the normalized equation I = 28121.60011 + 10816.24831 × lg C Where I represents the concentration of the thiamethoxam bimolecule at 1371 cm⁻¹ -1 The Raman peak intensity is shown at [value], where C represents the concentration of the pesticide thiram. Test results indicate that this method has a good detection range for thiram, capable of detecting thiram in concentrations ranging from 0.01 ppm to 100 ppm, with a minimum detectable concentration of 0.01 ppm. The detection process takes only 10 seconds to obtain the Raman spectrum of thiram and yield the final data.

[0057] Example 5 verifies the reproducibility and stability of detection using the nano-gold asteroid / PDMS composite substrate.

[0058] Three batches of thiram at a concentration of 25 ppm, prepared from the same batch, were tested on a nano-golden star particle / PDMS composite substrate to verify the reproducibility of the substrate. The operating procedures and conditions were as described in Example 4. Five regions were randomly selected from each substrate for testing, resulting in a total of 15 test points for three parallel samples. The relative standard deviation was calculated by measuring the thiram molecule at 1371 cm⁻¹. -1 The Raman characteristic peak intensity is calculated. Stability is determined by testing the change in Raman characteristic peak intensity of a single substrate over time. For example... Figure 6 As shown in A and 6B, the test results for the three parallel samples indicate that the relative standard deviation of the overall data is 3.80%, demonstrating that this substrate has advantages such as a small error range, good data reproducibility, and high data reliability. Figure 6 As shown in Figure C, the absorption intensity of the characteristic peaks of thiram did not change significantly at different time intervals. Even after a 30-day interval, the signal intensity of thiram remained unchanged. Figure 6 As shown in D, the signal intensity of thiamethoxam can still reach 94% of the signal intensity on the first day after a 30-day interval. This indicates that the prepared substrate can maintain its enhancement performance for a long time, has good stability, and good reproducibility.

[0059] Example 6 verifies the spiked recovery rate of real samples using a nano-gold asteroid / PDMS composite substrate.

[0060] A thiram solution with concentrations of 0.01 ppm, 0.05 ppm, 0.1 ppm, 1 ppm, 5 ppm, 10 ppm, 25 ppm, 50 ppm, and 100 ppm, prepared in Example 4, was added to apple juice to obtain apple juice containing different concentrations of thiram. The prepared nano-gold asteroid / PDMS composite substrate was directly immersed in the above-mentioned apple juice containing thiram and adsorbed at room temperature for 30 mins. After removal, it was rinsed with deionized water and dried with nitrogen. Then, flexible Raman spectroscopy was performed according to the steps and conditions of Example 4, and the spiked recovery rate was calculated. As shown in Table 1, we selected three order of magnitudes (0.1 ppm, 1.0 ppm, and 10 ppm) for the spiked recovery of actual samples. The test results showed that the final recovery rate was in the range of 97.05%-106.00%, and the relative standard deviation was between 3.26%-9.35%. The good recovery rate and high data reliability indicate that this method can be used for the detection of actual samples.

[0061] Table 1

[0062] Serial Number Formizumab concentration (ppm) Recovery concentration (ppm) Recovery rate (%) 1 0.1 0.1060 106.00％±9.35％ 2 1.0 0.9705 97.05％±4.95％ 3 10 9.825 98.25％±3.26％

[0063] Example 7: Detection of methyl chlorpyrifos in standard samples using a nano-gold asteroid particle / PDMS composite substrate.

[0064] Methyl chlorpyrifos was dissolved in a 20% (v / v) methanol aqueous solution to prepare methyl chlorpyrifos solutions with concentrations of 0.01 ppm, 0.05 ppm, 0.1 ppm, 0.5 ppm, 1 ppm, 10 ppm, 50 ppm, and 100 ppm. The prepared nano-gold asteroid particle / PDMS composite substrates were immersed in these methyl chlorpyrifos solutions for 30 mins, then removed, rinsed with deionized water, and dried with nitrogen gas. The substrates were then subjected to an induction atmosphere at 1269 cm⁻¹. -1 The detection was performed at the peak intensity at a given location. The main instrument parameters were: Raman excitation source wavelength of 785 nm, integration time of 10 s, and laser power of 10%. Each test result was performed in triplicate and independently. Figure 5 As shown, methyl chlorpyrifos molecules were placed at 1269 cm⁻¹. -1 Linear fitting was performed on the peak intensity at 1269 cm⁻¹. The normalized equation is I = 28121.60011 + 10816.24831 × lgC. Where I represents the peak intensity of methyl chlorpyrifos at 1269 cm⁻¹. -1 The Raman peak intensity is shown at [value], where C represents the concentration of methyl chlorpyrifos. Test results indicate that this method has a good detection range for methyl chlorpyrifos, capable of detecting it within a concentration range of 0.01 ppm to 100 ppm, with a detection limit of 0.01 ppm. The detection process takes only 10 seconds to obtain the Raman spectrum of methyl chlorpyrifos, yielding the final data.

[0065] Comparative Example 1: Difference in effectiveness between conventional detection methods and the detection method of this invention in detecting thiamethoxam.

[0066] The method of this invention (No. 7) was compared with that of Liu Huanying et al. (Rapid detection of thiram based on SERS paper discs coupled with three-dimensional dendritic gold nanomaterials and sea urchin-shaped nanoparticles, 2022) (No. 1), Zhang Chunhong et al. (Small and pointed triangular silver nanoplates synthesized using micro-triangular nuclei and their excellent SERS activity and selectivity for the detection of thiram residues in soil, 2022) (No. 2), Zhao Hang (Preparation of solid SERS substrate and its study on the detection of pesticide residues on fruit surface, 2019) (No. 3), Huang Zhibin (Preparation of 2D substrate based on Au@Ag nanorods and its application in surface-enhanced Raman detection of thiram in apples, 2020) (No. 4), Chang Linghao (Study on the detection of three toxic residues in agricultural products based on SERS technology, 2018) (No. 5), and Duan Junli (Preparation of paper SERS substrate and its application in the detection of pesticide residues in fruits, 2021) (No. 6). The results are shown in Table 2.

[0067] Table 2

[0068]

[0069] As shown in Table 2, the detection process of this invention is fast and simple, with a wide linear range. Compared with similar detection methods, this invention has the advantages of a wider concentration range and a lower detection limit; it can detect substances in a wider concentration range, and the overall detection process is more efficient.

[0070] Comparative Example 2: Difference in effectiveness between conventional detection methods and the detection method of this invention in detecting methyl chlorpyrifos

[0071] The method of this invention (No. 6) was compared with those of Li Hongxia et al. (Detection of methyl chlorpyrifos content in rice by gas chromatography-mass spectrometry, 2018) (No. 1), Su Meiling et al. (Determination of methyl chlorpyrifos residue in soybean by gas chromatography, 2018) (No. 2), Yang Xi et al. (Uncertainty assessment of determination of methyl chlorpyrifos pesticide residue in head cabbage by QuEchERS-gas chromatography-tandem mass spectrometry, 2021) (No. 3), Hu Xiao et al. (Application of two-dimensional correlation spectroscopy in the selection of characteristic variables of methyl chlorpyrifos in rice, 2019) (No. 4), and Gong Xuechun et al. (Study on rapid detection method of pesticide residue in Nanfeng tangerine by surface-enhanced Raman spectroscopy) (No. 5). The results are shown in Table 3.

[0072] Table 3

[0073] Serial Number method Detection range Detection limit Detection time 1 Gas chromatography-mass spectrometry 0.05~0.50μg / ml 0.005μg / ml 17.94 mins 2 Gas chromatography 0.15~25μg / ml 0.01μg / ml 80mins 3 Gas chromatography-tandem mass spectrometry 0.005~0.5μg / ml - 38mins 4 Surface-enhanced Raman spectroscopy 0.1~76mg / L - 10s 5 Surface-enhanced Raman spectroscopy 1~45mg / L - - 6 Method of the present invention 0.01~100ppm 0.01ppm 10s

[0074] As shown in Table 3, the detection process of this invention is rapid and simple, with a wide linear range. Compared with traditional detection methods, the detection process of this invention is shorter and more efficient. Compared with similar detection methods, this invention has advantages such as a wider concentration range and a lower detection limit, enabling the detection of substances over a wider concentration range, and the overall detection process is more efficient.

Claims

1. Application of gold nanoparticles / PDMS flexible substrate in quantitative detection of pesticides, characterized in that, The application comprises immersing the gold nanoparticle / PDMS flexible substrate in a solution containing a pesticide to be tested, adsorbing, rinsing with deionized water and blowing dry with nitrogen, and then detecting the Raman signal, wherein the pesticide is thiram or methidathion; and the preparation method of the gold nanoparticle / PDMS flexible substrate comprises the following steps: 1) mixing PDMS with dibutyltin dilaurate, stirring uniformly, vacuum pumping, heating, ultrasonic cleaning in acetone, ethanol and deionized water solution in sequence and blowing dry with nitrogen to obtain cleaned PDMS; 2) placing the cleaned PDMS into an APTES ethanol solution, incubating, rinsing with deionized water and blowing dry with nitrogen to obtain a PDMS flexible substrate; 3) immersing the PDMS flexible substrate into a gold nanoparticle star ethanol solution, oscillating reaction, rinsing with deionized water and blowing dry with nitrogen to obtain a gold nanoparticle / PDMS flexible substrate.

2. Use according to claim 1, characterized in that, When the pesticide is thiram, the linear relationship equation between the thiram concentration and the Raman signal intensity is I = 28121.60011 + 10816.24831D lg C , wherein I is the Raman peak intensity at 1371 cm -1 , and C represents the concentration of thiram, and the concentration of the thiram is 0.01-100 ppm.

3. Use according to claim 1, characterized in that, When the pesticide is methoxychlor, it is characterized in that the linear relationship equation between methoxychlor and Raman signal intensity is I = 19364.24781 + 6675.00279DlogC, wherein I is the Raman peak intensity at 1269 cm -1 -1, and C represents the concentration of methoxychlor, which is 0.01-100 ppm.

4. The use according to claim 1, characterized in that, In step 1), the mass ratio of PDMS to dibutyltin dilaurate is 9-15:

1.

5. The use according to claim 1, characterized in that, In step 1), the ultrasonic cleaning time is 10-20 mins.

6. The use according to claim 1, characterized in that, In step 2), the volume ratio of triethoxysilane to ethanol in the APTES ethanol solution is 1:9-20.

7. Use according to claim 1, characterized in that, In step 2), the incubation time is 3-15 h.

8. The use according to claim 1, characterized in that, In step 3), the concentration of gold nanoparticle star in the gold nanoparticle star ethanol solution is 0.005-0.1 nM.

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