A method for detecting isoprene using surface-enhanced Raman spectroscopy

Abstract

This invention provides a method for detecting isoprene using surface-enhanced Raman spectroscopy. The method includes the following steps: (1) reacting Au nanoparticles with probe molecules to obtain a detection substrate; (2) oxidizing the isoprene to be tested to obtain an oxidation product, and incubating the detection substrate with the oxidation product to obtain a sample to be tested; (3) performing Raman spectroscopy on the sample to be tested to obtain the characteristic spectrum, and qualitatively determining the isoprene based on the characteristic spectrum. The Au nanoparticles prepared by this invention have surface plasmon resonance properties and surface-enhanced Raman spectroscopy. The detection substrate of this invention can react with the oxidation product of isoprene, thereby enhancing the surface-enhanced Raman substrate's ability to grasp isoprene and improving detection sensitivity. The surface-enhanced Raman spectroscopy method for detecting isoprene provided by this invention is simple to operate, low in cost, and short in time, and is of great significance for the detection of isoprene.

Description

Technical Field

[0001] This invention belongs to the field of chemical detection technology, specifically relating to a method for detecting isoprene using surface-enhanced Raman spectroscopy. Background Technology

[0002] Volatile organic compounds (VOCs) generally refer to a class of organic compounds with boiling points between 50 and 260°C that exhibit volatility. Isoprene is a major VOC in the atmosphere, primarily emitted by terrestrial vegetation. It plays a crucial role in determining the troposphere's oxidizing capacity and the formation of secondary organic aerosols. The main sources of atmospheric isoprene are terrestrial plants, including some mosses, ferns, gymnosperms, and angiosperms. Furthermore, isoprene in exhaled human breath can serve as a universal biomarker for diagnosing blood cholesterol and chronic liver disease. Isoprene is a toxic VOC harmful to humans; excessive inhalation can lead to chest tightness, difficulty breathing, and even fainting. Therefore, isoprene detection is crucial.

[0003] Common methods for detecting isoprene include gas chromatography-mass spectrometry (GC-MS), chemiluminescence immunoassay (CTEM), and infrared photoacoustic assay (IRAS). GC-MS is relatively inexpensive and simple to operate; however, it requires adsorption of the test sample, resulting in a limited range of adsorbed substances and necessitating repeated tests. Chemielectric sensing has made some progress in isoprene detection, but improvements are still needed in selectivity for interfering gases, detection limits, and operating temperatures. These methods also require lengthy gas sampling and pretreatment steps.

[0004] CN111707770A discloses a gas chromatography internal standard method for determining the isoprene content in butyl rubber latex. The method involves directly weighing 1g of the latex sample into a 10mL volumetric flask, adding a certain amount of internal standard solution, diluting with tetrahydrofuran, filtering the sample, and then detecting the isoprene. The internal standard method is used to quantitatively analyze the isoprene in the latex, ensuring complete separation of isoprene from the internal standard, and thus detecting the isoprene content.

[0005] Traditional methods for isoprene detection are complex, requiring lengthy gas sampling and pretreatment steps, and still need improvement in terms of selectivity, detection limit, and operating temperature in the face of mixed interfering gases.

[0006] Surface-enhanced Raman spectroscopy (SERS) utilizes the strong surface plasmon resonance effect generated by the interaction of nanostructured materials such as gold, silver, and copper. This significantly enhances the Raman signal of molecules adsorbed on the nanostructure surface, enabling ultrasensitive acquisition of rich fingerprint spectra of the sample itself or Raman probe molecules. This technique boasts advantages such as high sensitivity, fast response speed, non-destructive operation, low sample consumption, and immunity to water molecule interference, and has been widely applied to trace detection of various pollutants and molecules.

[0007] CN110426386A discloses a surface-enhanced Raman spectroscopy method for drug detection, comprising the following steps: 1) collecting a biological sample of the target, placing the biological sample in a fusion solution for pretreatment of the biological sample to form a sample to be processed; 2) filtering the sample to be processed using a filter to obtain a filtered sample with impurities removed; by first collecting the biological sample, then placing the biological sample in the fusion solution for pretreatment, filtration separation, extraction and pre-concentration, and placing it in a gel to obtain the sample to be detected, after transferring the sample to be detected into a carrier, when the sample to be detected is irradiated by a laser, the surface of the sample to be detected will undergo a surface-enhanced Raman effect, the surface-enhanced Raman effect includes scattered radiation, and by collecting and analyzing the scattered radiation using a spectroscopic analysis instrument, it can be determined whether the sample to be detected contains a drug, thereby determining whether the biological sample contains a drug.

[0008] Traditional methods for isoprene detection are complex, requiring lengthy gas sampling and pretreatment steps. Further improvements are needed in terms of selectivity, detection limit, and operating temperature in the face of interfering gases. Currently, methods for detecting isoprene based on surface-enhanced Raman spectroscopy (SERS) present certain technical challenges, primarily due to the following issues: (1) isoprene is difficult to capture and readily adsorbs onto SERS substrates; (2) isoprene detection sensitivity is low.

[0009] Therefore, developing a method for detecting isoprene using surface-enhanced Raman spectroscopy, which is characterized by high sensitivity and short processing time, is a key research focus in this field. Summary of the Invention

[0010] To address the shortcomings of existing technologies, the present invention aims to provide a method for detecting isoprene using surface-enhanced Raman spectroscopy, which can detect isoprene rapidly and efficiently with high sensitivity.

[0011] To achieve this objective, the present invention employs the following technical solution:

[0012] In a first aspect, the present invention provides a method for detecting isoprene using surface-enhanced Raman spectroscopy, the method comprising the following steps:

[0013] (1) React Au nanoparticles with probe molecules to obtain a detection substrate;

[0014] (2) The isoprene to be tested is oxidized to obtain an oxidation product, and the detection substrate is incubated with the oxidation product to obtain the sample to be tested;

[0015] (3) The sample to be tested is subjected to Raman spectroscopy to obtain the characteristic spectrum, and isoprene is qualitatively determined based on the characteristic spectrum.

[0016] This invention involves oxidizing isoprene under low nitrogen oxide conditions and incubating the oxidation product with a detection substrate. This effectively combines the oxidized isoprene with the detection substrate, thereby enhancing the detection capability of the surface-enhanced Raman substrate for isoprene and improving detection sensitivity.

[0017] Preferably, the Au nanoparticles are prepared by the following method, which includes reacting chloroauric acid with sodium citrate to obtain the Au nanoparticles.

[0018] Preferably, the Au nanoparticles have a particle size of 40-65 nm, such as 45 nm, 48 nm, 50 nm, 55 nm, 60 nm, 62 nm or 64 nm.

[0019] Preferably, the reaction is carried out in the presence of a solvent.

[0020] Preferably, the solvent is water.

[0021] Preferably, the water is deionized water.

[0022] Preferably, the reaction temperature is 130-150℃, for example, 135℃, 140℃ or 145℃, and the time is 20-40min, for example, 25min, 30min or 35min.

[0023] Preferably, the reaction further includes centrifugation, washing, and dispersion steps.

[0024] Preferably, the centrifugation speed is 7000-9000 rpm, for example, 7500 rpm, 8000 rpm or 8500 rpm, and the time is 4-6 min, for example, 4.5 min, 5 min or 5.5 min.

[0025] Preferably, the detergent used for washing is deionized water.

[0026] Preferably, the washing is repeated twice.

[0027] Preferably, the dispersant is deionized water.

[0028] Preferably, the volume ratio of Au nanoparticles to deionized water is 1:(8-10), for example, it can be 1:8.5, 1:9 or 1:9.5, etc., preferably 1:9.

[0029] Preferably, the Au nanoparticle solution is stored at 3-5°C, for example, at 3.5°C, 4°C, or 4.5°C.

[0030] Preferably, the Au nanoparticles are prepared by the following method: adding 245 μL of 0.5 M chloroauric acid to 50 mL of deionized water, and after a slight boil, adding 350 μL of 38.8 mM sodium citrate solution, maintaining a slight boil for 30 min. Under the condition that the concentration of chloroauric acid, the amount added, and the concentration of sodium citrate remain constant, the amount of sodium citrate added is 940 μL-300 μL, for example, 900 μL, 850 μL, 850 μL, 750 μL, 700 μL, 600 μL, 500 μL, 450 μL, 400 μL, or 350 μL, preferably 550-300 μL.

[0031] All other specific point values ​​within the above numerical ranges can be selected, and will not be elaborated on here.

[0032] Preferably, the probe molecule contains thiol and sulfonic acid groups.

[0033] Preferably, the probe molecule is sodium mercaptoethanesulfonate.

[0034] Preferably, the molar concentration of the probe molecules in the reaction described in step (1) is 1 × 10⁻⁶. -5 ~1×10 -3 mol / L, for example, 5 × 10 -5 mol / L, 1×10 -4 mol / L or 5×10 -4 mol / L, etc., preferably 1×10 -4 mol / L.

[0035] Preferably, the reaction temperature in step (1) is 15-30°C, for example, 18°C, 20°C or 25°C, and the time is 13-15h, for example, 13.5h, 14h or 14.5h.

[0036] Taking sodium mercaptoethanesulfonate as the probe molecule as an example, the reaction route between Au nanoparticles and the probe molecule is shown below:

[0037]

[0038] Preferably, the reaction in step (1) further includes centrifugation, washing, and dispersion steps.

[0039] Preferably, the centrifugation speed is 7000-9000 rpm, for example, 7500 rpm, 8000 rpm or 8500 rpm, and the time is 2-4 min, for example, 2.5 min, 3 min or 3.5 min.

[0040] Preferably, the detergent used for washing is deionized water.

[0041] Preferably, the dispersant is deionized water.

[0042] Preferably, the volume ratio of the dispersant to the Au nanoparticle solution is (0.5-1):1, for example, it can be 0.6:1, 0.7:1, 0.8:1 or 0.9:1, etc.

[0043] All other specific point values ​​within the above numerical ranges can be selected, and will not be elaborated on here.

[0044] Preferably, the oxidation reaction is carried out under ultraviolet light irradiation.

[0045] Preferably, the wavelength of the ultraviolet light is 350-360nm, for example, it can be 352nm, 355nm or 358nm, and preferably 355nm.

[0046] Preferably, the oxidation reaction is carried out under closed conditions.

[0047] Preferably, the volume of the sealed environment is 2000-2500 times the volume of isoprene, for example, 2200 times, 2300 times, or 2400 times.

[0048] Preferably, an oxidizing agent is added during the oxidation reaction.

[0049] Preferably, the oxidant is hydrogen peroxide.

[0050] Preferably, the hydrogen peroxide content in the hydrogen peroxide solution is 20-40% by mass, for example, it can be 24%, 28%, 30%, 32% or 38%, etc.

[0051] The reaction pathway for the oxidation of isoprene is as follows:

[0052]

[0053] Preferably, the incubation temperature is 15-30℃, such as 18℃, 20℃ or 25℃, and the incubation time is 2-3h, such as 2.2h, 2.5h or 2.8h.

[0054] Taking sodium mercaptoethanesulfonate as the probe molecule as an example, the detection substrate is incubated with the oxidation product, and the reaction route is shown below:

[0055]

[0056] Preferably, the conditions for Raman spectroscopy detection include: an excitation wavelength of 500-800 nm, such as 550 nm, 600 nm, 650 nm, 700 nm or 750 nm, an integration time of 9-11 s, such as 9.5 s, 10 s or 10.5 s, preferably 10 s, and an accumulation number of 1-2 times, such as once or twice, preferably once.

[0057] Preferably, the excitation wavelength is 780-790nm, for example, it can be 782nm, 785nm or 788nm, and is preferably 785nm.

[0058] Preferably, the excitation wavelength is 630-640nm, for example, it can be 632nm, 635nm or 638nm, and more preferably 633nm.

[0059] Preferably, the excitation wavelength is 510-520nm, for example, it can be 512nm, 515nm or 518nm, and more preferably 514nm.

[0060] All other specific point values ​​within the above numerical ranges can be selected, and will not be elaborated on here.

[0061] Preferably, the method includes the following steps:

[0062] (1) Chloroauric acid and sodium citrate were reacted in water at 130-150℃ for 20-40 min, then centrifuged, washed and dispersed to obtain the Au nanoparticles;

[0063] The Au nanoparticles have a particle size of 40-65 nm;

[0064] Au nanoparticles were reacted with sodium mercaptoethanesulfonate at 15-30℃ for 13-15 h, followed by centrifugation, washing, and dispersion to obtain the detection substrate;

[0065] The molar concentration of sodium mercaptoethanesulfonate in the reaction is 1 × 10⁻⁶. -5 ~1×10 -3 mol / L;

[0066] (2) The isoprene to be tested is irradiated with 350-360nm ultraviolet light and oxidized with hydrogen peroxide under closed conditions to obtain an oxidation product. The detection substrate and the oxidation product are incubated at 15-30℃ for 2-3 hours to obtain the sample to be tested.

[0067] The hydrogen peroxide in the hydrogen peroxide solution has a mass percentage content of 20-40%;

[0068] (3) The sample to be tested is subjected to Raman spectroscopy detection at an excitation wavelength of 780-790nm, 630-640nm or 510-520nm, the integral is 9-11s, the number of accumulations is 1-2 times, and the characteristic spectrum is obtained. Isoprene is qualitatively determined based on the characteristic spectrum.

[0069] Secondly, the present invention provides a Raman spectrum obtained by the method provided in the first aspect, wherein the Raman shift of the isoprene characteristic peak in the Raman spectrum is 920-940 cm⁻¹. -1 For example, it can be 925cm -1 930cm -1 Or 935cm -1 wait.

[0070] All other specific point values ​​within the above numerical ranges can be selected, and will not be elaborated on here.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] (1) The present invention uses sodium citrate reduction method to prepare Au nanoparticles, which have surface plasmon resonance properties and surface-enhanced Raman spectroscopy.

[0073] (2) The surface-enhanced Raman detection substrate of Au-mercaptoethanesulfonate in this invention can react with the oxidation products of isoprene, thereby enhancing the detection capability of the surface-enhanced Raman substrate for isoprene and improving the detection sensitivity.

[0074] (3) The surface-enhanced Raman spectroscopy method for detecting isoprene provided by the present invention is simple to operate, low in cost and short in time, and is of great significance for the detection of isoprene. Attached Figure Description

[0075] Figure 1 SEM image of the Au nanoparticles obtained in Example 1;

[0076] Figure 2 SEM image of the Au nanoparticles obtained in Example 2;

[0077] Figure 3 SEM image of the Au nanoparticles obtained in Example 3;

[0078] Figure 4 SEM image of the Au nanoparticles obtained in Example 4;

[0079] Figure 5 SEM image of the Au nanoparticles obtained in Example 5;

[0080] Figure 6 Raman spectra of different excitation wavelengths for test example 1;

[0081] Figure 7 Raman spectra detected for different Au nanoparticle sizes in Test Example 2;

[0082] Figure 8 Raman spectra obtained from the detection substrates with different concentrations of sodium thiosulfate solution in Test Example 3;

[0083] Figure 9 The images shown are the Raman spectra obtained from Example 1 and the control example. Detailed Implementation

[0084] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0085] The terms “comprising,” “including,” “having,” “containing,” or any other variations thereof, as used herein, are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not limited to those elements and may also include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0086] "Optional" or "any one" means that the matter or event described thereafter may or may not occur, and the description includes both the possibility that the event may occur and the possibility that the event may not occur.

[0087] The indefinite articles “a” and “an” preceding an element or component of this invention do not impose any limitation on the quantity (i.e., number of times) of the element or component. Therefore, “an” or “a” should be interpreted as including one or at least one, and the singular form of an element or component also includes the plural form, unless the quantity clearly refers only to the singular form.

[0088] The terms "one embodiment," "some embodiments," "exemplary," "specific example," or "some examples," etc., used in this invention refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this document, the illustrative expressions of the above terms are not necessarily directed at the same embodiment or example.

[0089] Preparation Example 1

[0090] This preparation example provides an Au nanoparticle solution, and the preparation method of the Au nanoparticle solution is as follows:

[0091] 245 μL of 0.1 M chloroauric acid solution was diluted to 50 mL with deionized water and placed in a 100 mL round-bottom flask. The flask was heated to 140 °C in an oil bath and brought to a gentle boil. 0.350 mL of 38.8 mM sodium citrate solution was quickly added, and the mixture was kept at a gentle boil for 30 min. The solution was then cooled to room temperature and centrifuged at 8000 r / min for 5 min. The flask was washed twice with deionized water, and then dispersed with 9 times its volume of deionized water to obtain the Au nanoparticle solution. The solution was stored at 4 °C. The particle size of the Au nanoparticles was determined to be 50 nm. The Au nanoparticles were then analyzed using a scanning electron microscope (SEM, Hitachi-SU8220). The obtained SEM images are shown below. Figure 1 As shown.

[0092] Preparation Example 2

[0093] This preparation example provides an Au nanoparticle solution, and the preparation method of the Au nanoparticle solution is as follows:

[0094] The only difference between this preparation and Preparation Example 1 is that the amount of chloroauric acid solution used is 245 μL, and the amount of sodium citrate solution used is 940 μL. All other raw materials, amounts, and preparation methods are the same as in Preparation Example 1. The particle size of the Au nanoparticles was measured to be 22 nm. The Au nanoparticles were scanned by electron microscopy, and the resulting SEM image is shown below. Figure 2 As shown.

[0095] Preparation Example 3

[0096] This preparation example provides an Au nanoparticle solution, and the preparation method of the Au nanoparticle solution is as follows:

[0097] The only difference between this preparation and Preparation Example 1 is that the amount of chloroauric acid solution used is 245 μL, and the amount of sodium citrate solution used is 700 μL. All other raw materials, amounts, and preparation methods are the same as in Preparation Example 1. The Au nanoparticles were found to have a particle size of 30 nm. The Au nanoparticles were scanned by electron microscopy, and the resulting SEM image is shown below. Figure 3 As shown.

[0098] Preparation Example 4

[0099] This preparation example provides an Au nanoparticle solution, and the preparation method of the Au nanoparticle solution is as follows:

[0100] The only difference between this preparation and Preparation Example 1 is that the amount of chloroauric acid solution used is 245 μL, and the amount of sodium citrate solution used is 550 μL. All other raw materials, amounts, and preparation methods are the same as in Preparation Example 1. The Au nanoparticles were found to have a particle size of 40 nm. The Au nanoparticles were scanned by electron microscopy, and the resulting SEM image is shown below. Figure 4 As shown.

[0101] Preparation Example 5

[0102] This preparation example provides an Au nanoparticle solution, and the preparation method of the Au nanoparticle solution is as follows:

[0103] The only difference between this preparation and Preparation Example 1 is that the amount of chloroauric acid solution used is 245 μL, and the amount of sodium citrate solution used is 300 μL. All other raw materials, amounts, and preparation methods are the same as in Preparation Example 1. The particle size of the Au nanoparticles was measured to be 62 nm. The Au nanoparticles were scanned by electron microscopy, and the resulting SEM image is shown below. Figure 5 As shown.

[0104] Test Example 1

[0105] Selection of excitation wavelength

[0106] The Au nanoparticle solution obtained in Preparation Example 1 was subjected to Raman spectroscopy. The integration time was 10 s, the number of accumulations was 1, and the excitation wavelengths were 514 nm, 785 nm, and 633 nm, respectively. The obtained Raman spectra are as follows: Figure 6 As shown in the figure, when the excitation wavelength is 514nm, 785nm and 633nm, characteristic spectra with excellent peak shape can be obtained. When the excitation wavelength is 785nm, the Raman performance is the best.

[0107] Test Example 2

[0108] Screening Au nanoparticle size

[0109] Preparation 10 -5 Rhodamine B (M) was used. 10 μL of Rhodamine B was incubated with 100 μL of Au nanoparticles obtained in Preparation Examples 1-5 at room temperature for 6 hours. Then, 10 μL of the incubated solution was dropped onto a silicon wafer, dried, and used for Raman spectroscopy. The excitation wavelength of the Raman spectrometer was 785 nm, the integration time was 10 s, and the number of accumulations was 1. The Raman spectra obtained from Au nanoparticles of different sizes are shown below. Figure 7 As shown in the figure, the signal intensity of the surface-enhanced Raman spectroscopy obtained when the particle size is 40-65 nm is high.

[0110] Preparation Example 6

[0111] This preparation example provides an Au-mercaptoethanesulfonate sodium detection substrate, and the preparation method of the Au-mercaptoethanesulfonate sodium detection substrate is as follows:

[0112] 100 μL of the Au nanoparticle solution obtained in Example 1 and 100 μL of a 10% concentration were prepared. -4The sodium mercaptoethanesulfonate solution of M was mixed at room temperature and incubated for 14 h. Finally, it was centrifuged at 8000 r / min for 3 min, washed once with deionized water, and then 100 μL of deionized water was added to disperse it. 10 μL was dropped onto a silicon wafer and dried to obtain the Au-mercaptoethanesulfonate detection substrate.

[0113] Preparation Examples 7-8

[0114] This preparation example provides an Au-mercaptoethanesulfonate sodium detection substrate, and the preparation method of the Au-mercaptoethanesulfonate sodium detection substrate is as follows:

[0115] The only difference between this and Preparation Example 6 is that the concentration of the sodium mercaptoethanesulfonate solution is replaced with 10. -3 M and 10 -5 M, the other raw materials, dosages and preparation methods are the same as those in Preparation Example 6.

[0116] Test Example 3

[0117] Screening the concentration of sodium mercaptoethanesulfonate solution

[0118] The Au-mercaptoethanesulfonate detection substrates obtained in Preparation Examples 6-8 were subjected to Raman spectroscopy. The excitation wavelength of the Raman spectrometer was 785 nm, the integration time was 10 s, and the number of accumulations was 1. The detected surface-enhanced Raman spectra are as follows: Figure 8 As shown in the figure. It can be seen from the figure that when the concentration of sodium mercaptoethanesulfonate is 10... -4 The surface-enhanced Raman detection substrate with the best performance is obtained when M is selected.

[0119] Example 1

[0120] This embodiment provides a method for detecting isoprene using surface-enhanced Raman spectroscopy, the method comprising the following steps:

[0121] In a 25 mL sealed conical flask, 30 μL of 30% hydrogen peroxide solution was sprayed using a spray bottle. Then, the Au-mercaptoethanesulfonate detection substrate obtained in Example 1 was added to the flask, followed by 20 μL of isoprene liquid. The reaction was carried out at room temperature for 2.5 h. The surface-enhanced Raman substrate was then removed for Raman spectroscopy detection. The excitation wavelength of the Raman spectrometer was 785 nm, the integration time was 10 s, and the number of accumulations was 1. The detected surface-enhanced Raman spectrum is shown below. Figure 9 As shown.

[0122] Comparison Example

[0123] This comparative example provides a surface-enhanced Raman spectroscopy detection method, which includes the following steps:

[0124] The only difference between this example and Example 1 is that the isoprene liquid is replaced with an equal amount of deionized water; all other raw materials, amounts, reaction time, and testing methods are the same as in Example 1. The detected surface-enhanced Raman spectrum is as follows: Figure 9 As shown.

[0125] according to Figure 9 It can be seen that when the Au-mercaptoethanesulfonate detection substrate did not react with isoprene, the characteristic peak shift in the detected Raman spectrum was 800 cm⁻¹. -1 1074cm -1 When the Au-mercaptoethanesulfonate detection substrate reacted with isoprene, the characteristic peak shift in the detected Raman spectrum was 868 cm⁻¹. -1 932cm -1 1020cm -1 These three characteristic peaks represent the vibrations of RO-SO3, CH2&CH3, and SO3, respectively, indicating that the surface-enhanced Raman spectroscopy detection method provided by this invention can effectively detect isoprene qualitatively.

[0126] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for detecting isoprene using surface-enhanced Raman spectroscopy, characterized in that, The method includes the following steps: (1) Au nanoparticles are reacted with probe molecules to obtain a detection substrate; (2) The isoprene to be tested is oxidized with hydrogen peroxide under ultraviolet light irradiation and sealed conditions to obtain an oxidation product. The detection substrate is then incubated with the oxidation product to obtain the sample to be tested. (3) The sample to be tested is subjected to Raman spectroscopy to obtain a characteristic spectrum, and isoprene is qualitatively determined based on the characteristic spectrum; The probe molecule is sodium mercaptoethanesulfonate.

2. The method according to claim 1, characterized in that, The Au nanoparticles are prepared by the following method: reacting chloroauric acid with sodium citrate to obtain the Au nanoparticles.

3. The method according to claim 2, characterized in that, The Au nanoparticles have a particle size of 40-65 nm.

4. The method according to claim 2, characterized in that, The reaction between chloroauric acid and sodium citrate is carried out in the presence of a solvent.

5. The method according to claim 4, characterized in that, The solvent is water.

6. The method according to claim 2, characterized in that, The reaction is carried out at a temperature of 130-150℃ for a time of 20-40 min.

7. The method according to claim 2, characterized in that, The reaction is followed by centrifugation, washing, and dispersion steps.

8. The method according to claim 1, characterized in that, In step (1), the molar concentration of the probe molecules in the reaction is 1 × 10⁻⁶. -5 ~1×10 -3 mol / L.

9. The method according to claim 1, characterized in that, The reaction in step (1) is carried out at a temperature of 15-30℃ for 13-15 h.

10. The method according to claim 1, characterized in that, Step (1) includes centrifugation, washing, and dispersion steps after the reaction.

11. The method according to claim 1, characterized in that, The wavelength of the ultraviolet light is 350-360 nm.

12. The method according to claim 1, characterized in that, The hydrogen peroxide in the hydrogen peroxide solution has a mass percentage content of 20-40%.

13. The method according to claim 1, characterized in that, The incubation temperature is 15-30℃, and the time is 2-3 hours.

14. The method according to claim 1, characterized in that, The conditions for the Raman spectroscopy detection include: The excitation wavelength is 500-800 nm, the integration time is 9-11 s, and the number of accumulations is 1-2.

15. The method according to claim 14, characterized in that, The excitation wavelength is 780-790 nm.

16. The method according to claim 14, characterized in that, The excitation wavelength is 630-640 nm.

17. The method according to claim 14, characterized in that, The excitation wavelength is 510-520 nm.

18. The method according to claim 1, characterized in that, The method includes the following steps: (1) Chloroauric acid and sodium citrate were reacted in water at 130-150℃ for 20-40 min, then centrifuged, washed and dispersed to obtain the Au nanoparticles; The Au nanoparticles have a particle size of 40-65 nm; Au nanoparticles were reacted with sodium mercaptoethanesulfonate at 15-30℃ for 13-15 h, followed by centrifugation, washing, and dispersion to obtain the detection substrate; The molar concentration of sodium mercaptoethanesulfonate in the reaction is 1 × 10⁻⁶. -5 ~1×10 -3 mol / L; (2) The isoprene to be tested is irradiated with 350-360 nm ultraviolet light and oxidized with hydrogen peroxide under closed conditions to obtain oxidation products. The detection substrate and the oxidation products are incubated at 15-30℃ for 2-3 h to obtain the sample to be tested. The hydrogen peroxide content in the hydrogen peroxide solution is 20-40% by mass. (3) The sample to be tested is subjected to Raman spectroscopy detection at an excitation wavelength of 780-790 nm, 630-640 nm or 510-520 nm, the integral is 9-11 s, the number of accumulations is 1-2 times, and the characteristic spectrum is obtained. Isoprene is qualitatively determined based on the characteristic spectrum.

19. A method according to any one of claims 1-18, characterized in that, The Raman shift of the isoprene characteristic peak in the Raman spectrum obtained by the method is 920-940 cm⁻¹. -1 .

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