Detection substrates for surface-enhanced Raman detection, their preparation methods, and applications.

Abstract

This invention discloses a detection substrate for surface-enhanced Raman spectroscopy (SERS), its preparation method, and its applications. The preparation method includes mixing silver nitrate, ethylene glycol, and polyvinylpyrrolidone to prepare a mixture; heating the mixture to prepare a seed solution; mixing the seed solution, tetrachloroauric acid, and a preservative; centrifuging; separating the solid to prepare gold-silver alloy nanoparticles; dispersing the gold-silver alloy nanoparticles in a buffer solution to prepare a nano-gold-silver buffer solution; mixing the nano-gold-silver buffer solution and CsPbBr3@MSNs to prepare a composite suspension; and adding the composite suspension to a silicon wafer and heating it. The detection substrate has a high specific surface area, promoting the formation of more adsorption sites on the surface, improving the adsorption capacity of the analyte, and increasing the intensity of characteristic peaks in SERS detection. The substrate surface can also improve the signal intensity in the detection and analysis of trace amounts of furfural dissolved in transformer oil, improving the accuracy of furfural content detection.

Description

Technical Field

[0001] This invention relates to the field of detection technology, and in particular to a detection substrate for surface-enhanced Raman detection, its preparation method, and its application. Background Technology

[0002] In the operation of power systems, large power transformers serve as crucial equipment, and their stable operation is essential for ensuring high-quality power supply. The internal insulation of transformers is primarily composed of composite insulation made of mineral oil and insulating paperboard. During long-term operation, the insulating materials, such as insulating oil and insulating paper, decompose under the influence of electricity and heat, producing substances that reflect the nature of the fault and insulation performance, such as furans, alcohols, acids, esters, and ketones. These substances dissolve in the oil, and their concentration can be used as a chemical indicator to evaluate the degree of insulation aging. Testing the degree of polymerization of paper insulation in transformer oil, as well as the content of characteristic aging products such as furfural, CO, and CO2 dissolved in the oil, are the main methods for judging the aging state of transformer insulation. While the dissolved gas and furfural content in transformer oil can objectively reflect the aging condition of the transformer's internal insulation, it is difficult to accurately determine the degree of insulation aging due to the easy diffusion of gases in the oil and the easy adsorption of furfural.

[0003] Furfural, as one of the aging properties of oil-paper insulation, is used to accurately assess the aging state of the insulating paper and the remaining life of transformers. Currently, the determination of dissolved furfural in oil typically employs high-performance liquid chromatography (HPLC), ultraviolet spectrophotometry (UV spectrophotometry), and electrochemical methods. These methods possess high specificity and sensitivity, but their practical application is hindered by the complexity of chemical operations, the high cost of equipment, and the time-consuming nature of the process, limiting their use to offline analysis in the laboratory. Compared to traditional methods, laser Raman spectroscopy can simultaneously detect any mixture and achieve in-situ detection without damaging the sample's molecular structure.

[0004] In recent years, with the development of laser and CCD detection technologies, Raman spectroscopy has been widely applied in the detection and analysis of trace solid and liquid materials. Compared with traditional detection techniques, Raman spectroscopy has advantages such as fast detection speed, high sensitivity, and simple operation, and can determine the type and concentration of substances. Therefore, laser Raman spectroscopy can be used to detect trace amounts of furfural dissolved in transformer oil. However, the Raman scattering signal intensity is generally only 1 × 10⁻⁶ times the intensity of the incident light. -10 Furthermore, the small number of molecules at the interface results in a weak Raman scattering signal. Additionally, the complex composition of transformer oil and its low content of dissolved furfural mean that current Raman spectroscopy techniques cannot meet the practical engineering requirements for detecting aging characteristic substances in transformer oil. While surface-enhanced Raman spectroscopy offers stronger detection capabilities, the lack of a suitable detection substrate prevents reliable quantitative detection and analysis of trace amounts of dissolved furfural in transformer oil. Summary of the Invention

[0005] Therefore, in order to improve the signal intensity in surface-enhanced Raman spectroscopy (SERS) analysis of trace amounts of furfural dissolved in transformer oil and to quantitatively analyze the furfural content in transformer oil, it is necessary to provide a detection substrate for SERS, its preparation method, and its application.

[0006] This invention provides a method for preparing a detection substrate for surface-enhanced Raman detection, comprising the following steps:

[0007] Step S10: Mix silver nitrate, sodium sulfide, ethylene glycol and polyvinylpyrrolidone to prepare a mixture, heat the mixture to prepare a seed solution, the seed solution containing elemental silver nanoparticles;

[0008] Step S20: Mix the seed solution, tetrachloroauric acid and protective agent, centrifuge, separate the solid, prepare gold-silver alloy nanoparticles, disperse the gold-silver alloy nanoparticles in buffer solution, and prepare nano gold-silver buffer solution;

[0009] Step S30: Mix the gold-silver nanoparticle buffer solution and CsPbBr3@MSNs to prepare a composite suspension. Add the composite suspension to the substrate and heat.

[0010] In one embodiment, step S10 satisfies one or more of the following characteristics:

[0011] (1) The ratio of silver nitrate, sodium sulfide, ethylene glycol, and polyvinylpyrrolidone is (100~140) mg: (9×10 -4 ~1.2×10 -3 )mmol: (30~50)mL: (130~180)mg;

[0012] (2) The heating conditions include: in an inert gas environment, the heating temperature is 120℃~180℃ and the heating time is 0.2h~1h.

[0013] In one embodiment, step S20 satisfies one or more of the following characteristics:

[0014] (1) The mixing step includes: adding the seed solution to the protectant at a temperature of 80℃~120℃, and then adding tetrachloroauric acid after 1 minute to 5 minutes;

[0015] (2) The ratio of the protective agent, the seed solution, and tetrachloroauric acid is (10:10). -3 ~10 -1 )g:(0.1~1)mL:(10 -4 ~10 -3 ) mmol;

[0016] (3) Before dispersing the gold-silver alloy nanoparticles in the buffer solution, the steps of dispersing the gold-silver alloy nanoparticles in water and filtering out the solids are also included;

[0017] (4) The buffer solution is selected from one or more of potassium carbonate solution, potassium phosphate solution, sodium citrate solution and potassium hydrogen phthalate solution;

[0018] (5) The gold-silver alloy nanoparticles generate a surface plasmon resonance effect when irradiated with light of wavelengths from 450 nm to 700 nm.

[0019] In one embodiment, the preparation method of the CsPbBr3@MSNs includes the following steps:

[0020] Monodisperse mesoporous silica nanoparticles were prepared by mixing hexadecyltrimethylammonium p-toluenesulfonate, triethanolamine, polyolefin thermoplastic elastomer and water, and calcining.

[0021] A precursor solution was prepared by mixing cesium bromide, lead bromide, and an organic solvent.

[0022] The monodisperse mesoporous silica nanoparticles were immersed in the precursor solution and dried to prepare the CsPbBr3@MSNs.

[0023] In one embodiment, the method for preparing the CsPbBr3@MSNs satisfies one or more of the following characteristics:

[0024] (1) The ratio of hexadecyltrimethylammonium p-toluenesulfonate, triethanolamine, polyolefin thermoplastic elastomer and water is (0.8~1.2)g:(0.1~0.3)g:(5~10)mL:(30~80)mL;

[0025] (2) The calcination conditions include: calcination temperature of 450℃~650℃ and calcination time of 4h~8h;

[0026] (3) The ratio of cesium bromide, lead bromide and the organic solvent is (3-5) mg: (5-10) mL: (100-300) μL;

[0027] (4) The organic solvent is selected from one or more of dimethyl sulfoxide, vinyl sulfite, propylene sulfite, dimethyl sulfite, and diethyl sulfite;

[0028] (5) The drying conditions include: drying temperature of 100℃~200℃ and drying time of 15 minutes~45 minutes.

[0029] In one embodiment, the ratio of the gold-silver nanoparticle buffer to the CsPbBr3@MSNs is (1-10) mL:(5-15) mg.

[0030] Furthermore, the present invention provides a detection substrate prepared by the method described above.

[0031] The present invention also provides the application of the above-described detection substrate in the detection of furfural in transformer oil.

[0032] Furthermore, the present invention provides a method for detecting furfural in transformer oil, comprising the following steps: mixing the detection substrate, transformer oil and extractant as described above to prepare a test solution;

[0033] The test liquid was subjected to surface-enhanced Raman spectroscopy with a frequency shift of 900 cm⁻¹. -1 The peak area at that location is used as x1 and the frequency shift is 1675 cm⁻¹. -1 The peak area corresponding to the point is taken as x2, and the furfural content y in the transformer oil satisfies: y = 1.983x1 + 0.07722x2 - 65.98658, where the unit of y is mg / L.

[0034] In one embodiment, the extractant is selected from one or more of methanol, water, and acetonitrile.

[0035] The above-mentioned detection substrate surface forms gold and silver nanoparticles that are combined with CsPbBr3@MSNs, which effectively increases the specific surface area of ​​the detection substrate, promotes the formation of more adsorption sites on the surface of the detection substrate, further improves the adsorption capacity of the analyte, and increases the intensity of the characteristic peak in surface-enhanced Raman detection.

[0036] Furthermore, the aforementioned detection substrate surface can enhance the signal intensity present in the detection and analysis of trace amounts of furfural dissolved in transformer oil, thereby improving the accuracy of detecting the content of trace amounts of furfural dissolved in transformer oil. Attached Figure Description

[0037] Figure 1 SEM image of the detection substrate provided for the embodiment;

[0038] Figure 2 For this example, the surface-enhanced Raman spectrum of the substrate characterizing R6G was detected;

[0039] Figure 3 To utilize the surface-enhanced Raman spectrum of dissolved furfural in transformer oil after methanol extraction;

[0040] Figure 4 The surface-enhanced Raman spectra of oil samples No. 1 to No. 6 with different concentrations were characterized using the detection substrate of the embodiment. Detailed Implementation

[0041] This invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this invention. Of course, they are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different instances. Such repetition is for the purpose of simplicity and clarity and does not in itself indicate a relationship between the various embodiments and / or settings discussed.

[0042] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of the invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified. In the description of the present invention, "a number" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0043] Unless otherwise specified, all percentages, fractions, and ratios are calculated based on the total mass of the compositions of the present invention. Unless otherwise specified, all masses of the listed ingredients give an amount of active substance and therefore do not include solvents or byproducts that may be present in commercially available materials. The term "percentage by mass" may be expressed by the symbol "%".

[0044] The terms “comprising,” “including,” “containing,” “having,” “comprising,” or other variations thereof are intended to cover non-closed inclusion, and no distinction is made between these terms. The term “comprising” means that other steps and ingredients may be added without affecting the final result. The term “comprising” also includes the terms “consisting of” and “substantially composed of.” The compositions and methods / processes of the present invention comprise, consist of, and substantially consist of the essential elements and limitations described herein, as well as any additional or optional ingredients, components, steps, or limitations described herein. No distinction is made between the terms “efficacy,” “performance,” “effect,” and “potency” herein.

[0045] The terms "preferred," "more preferably," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0046] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0048] This invention provides a method for preparing a detection substrate for surface-enhanced Raman detection, comprising the following steps:

[0049] Step S10: Mix silver nitrate, sodium sulfide, ethylene glycol and polyvinylpyrrolidone to prepare a mixture, heat the mixture to prepare a seed solution, wherein the seed solution contains elemental silver nanoparticles;

[0050] Step S20: Mix the seed solution, tetrachloroauric acid and protective agent, centrifuge, separate the solid, prepare gold-silver alloy nanoparticles, disperse the gold-silver alloy nanoparticles in buffer solution, and prepare nano gold-silver buffer solution.

[0051] Step S30: Mix the gold-silver nanoparticle buffer and CsPbBr3@MSNs to prepare a composite suspension. Add the composite suspension to the substrate and heat.

[0052] Understandably, the role of ethylene glycol is to reduce Ag. + To silver single ore.

[0053] In a specific example, in step S10, the ratio of silver nitrate, sodium sulfide, ethylene glycol, and polyvinylpyrrolidone is (100–140) mg: (9 × 10⁻⁶ mg / mg ≤ ... -4 ~1.2×10 -3 )mmol:(30~50)mL:(130~180)mg. In the presence of polyvinylpyrrolidone (PVP), silver nitrate was reduced with ethylene glycol to obtain silver nanoparticles with uniform morphology.

[0054] Furthermore, the ratio of silver nitrate, sodium sulfide, ethylene glycol, and polyvinylpyrrolidone is (110–130) mg: (1 × 10⁻⁶ mg / mL). -3 ~1.1×10 -3)mmol: (35~45)mL: (140~160)mg.

[0055] In a specific example, in step S10, the heating conditions include: in an inert gas environment, the heating temperature is 120℃~180℃, and the heating time is 0.2h~1h.

[0056] Furthermore, the heating time may be, but is not limited to, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or 180°C, and the heating time may be, but is not limited to, 0.2h, 0.3h, 0.4h, 0.5h, 0.6h, 0.7h, 0.8h, 0.9h, or 1h.

[0057] Understandably, step S20 involves preparing gold-silver alloy nanoparticles via an electric current displacement method.

[0058] In a specific example, the mixing step in step S20 includes: adding seed solution to the protectant at a temperature of 80°C to 120°C, and then adding tetrachloroauric acid after 1 to 5 minutes.

[0059] Understandably, the tetrachloroauric acid was added within 15 minutes.

[0060] Furthermore, the temperature in the above mixture can be, but is not limited to, 80°C, 90°C, 100°C, 110°C, or 120°C.

[0061] In a specific example, the ratio of the protectant, seed solution, and tetrachloroauric acid in step S20 is (10) -3 ~10 -1 )g:(0.1~1)mL:(10 -4 ~10 -3 )mmol.

[0062] Furthermore, the ratio of the protectant, seed solution, and tetrachloroauric acid is (5 × 10⁻⁶). -3 ~5×10 -2 )g:(0.1~0.4)mL:(10 -4 ~10 -3 )mmol.

[0063] In one specific example, step S20 further includes dispersing the gold-silver alloy nanoparticles in water and filtering out the solids before dispersing the gold-silver alloy nanoparticles in the buffer solution.

[0064] In one specific example, in step S20, the buffer solution may be, but is not limited to, one or more selected from potassium carbonate solution, potassium phosphate solution, sodium citrate solution, and potassium hydrogen phthalate solution.

[0065] Furthermore, the concentration of the buffer solution is 1 mmol / L to 3 mmol / L.

[0066] In a specific example, in step S20, the gold-silver alloy nanoparticles generate a surface plasmon resonance effect under light irradiation with wavelengths of 450 nm to 700 nm.

[0067] Furthermore, the centrifugation time in step S20 is 5 min to 20 min. It can be understood that the centrifugation time can be, but is not limited to, 5 min, 10 min, 15 min or 20 min.

[0068] In a specific example, the preparation method of CsPbBr3@MSNs includes the following steps:

[0069] Monodisperse mesoporous silica nanoparticles were prepared by mixing hexadecyltrimethylammonium p-toluenesulfonate, triethanolamine, polyolefin thermoplastic elastomer and water, and calcining.

[0070] A precursor solution was prepared by mixing cesium bromide, lead bromide, and an organic solvent.

[0071] CsPbBr3@MSNs were prepared by impregnating monodisperse mesoporous silica nanoparticles in a precursor solution and drying them.

[0072] In a specific example, the ratio of hexadecyltrimethylammonium p-toluenesulfonate, triethanolamine, polyolefin thermoplastic elastomer, and water is (0.8–1.2) g: (0.1–0.3) g: (5–10) mL: (30–80) mL.

[0073] Furthermore, the ratio of hexadecyltrimethylammonium p-toluenesulfonate, triethanolamine, polyolefin thermoplastic elastomer, and water is (0.9–1) g: (0.12–0.2) g: (6–9) mL: (40–60) mL.

[0074] Understandably, the above-mentioned hexadecyltrimethyl p-toluenesulfonate ammonium and triethanolamine are added to water and stirred at 70℃~90℃ for 0.5h~1.5h, and polyolefin thermoplastic elastomer is added and stirred at 70℃~90℃ for 1.5h~2.5h to prepare monodisperse mesoporous silica nanoparticles.

[0075] In a specific example, the calcination conditions include: a calcination temperature of 450℃ to 650℃ and a calcination time of 4h to 8h.

[0076] Furthermore, the calcination temperature may be, but is not limited to, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃, or 650℃.

[0077] The calcination time can be, but is not limited to, 4h, 5h, 6h, 7h or 8h.

[0078] In a specific example, the ratio of cesium bromide, lead bromide, and organic solvent is (3-5) mg: (5-10) mL: (100-300) μL.

[0079] Furthermore, the ratio of cesium bromide, lead bromide, and organic solvent is (3.5–4.5) mg: (6–9) mL: (150–250) μL.

[0080] In one specific example, the organic solvent is selected from one or more of dimethyl sulfoxide, vinyl sulfite, propylene sulfite, dimethyl sulfite, and diethyl sulfite.

[0081] In a specific example, the drying conditions include a drying temperature of 100℃ to 200℃ and a drying time of 15 minutes to 45 minutes.

[0082] Understandably, the above drying temperature may be, but is not limited to, 100°C, 120°C, 140°C, 160°C, 180°C or 200°C, and the drying time may be, but is not limited to, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes or 45 minutes.

[0083] In one specific example, the ratio of gold-silver nanoparticle buffer to CsPbBr3@MSNs was (1–10) mL: (5–15) mg.

[0084] Further, 20 mg to 30 mg of monodisperse mesoporous silica nanoparticles were impregnated in the precursor solution.

[0085] In a specific example, in step S30, the substrate is selected from a silicon wafer or a gold film.

[0086] Furthermore, in step S30, the heating temperature is 50°C to 70°C.

[0087] Furthermore, the present invention provides a detection substrate prepared by the method described above.

[0088] The present invention also provides the application of the above-described detection substrate in the detection of furfural in transformer oil.

[0089] Furthermore, the present invention provides a method for detecting furfural in transformer oil, comprising the following steps: mixing the detection substrate, transformer oil and extractant as described above to prepare a test solution;

[0090] Surface-enhanced Raman spectroscopy was performed on the test liquid with a frequency shift of 900 cm⁻¹. -1 The peak area at that location is used as x1 and the frequency shift is 1675 cm⁻¹. -1 The peak area corresponding to the given location is taken as x2. The furfural content y in the transformer oil satisfies: y = 1.983x1 + 0.07722x2 - 65.98658, where the unit of y is mg / L.

[0091] Furthermore, the conditions for the Raman detection mentioned above include a 560nm wavelength laser, a laser power of 500±100mW, an integration time of 0.001±0.0005s, 100±50 integration times, a slit width of 500±100μm, and the use of a 1200 / 500nm type grating.

[0092] In one specific example, the extractant is selected from one or more of methanol, water, and acetonitrile.

[0093] The above-mentioned detection substrate surface forms gold and silver nanoparticles that are combined with CsPbBr3@MSNs, which effectively increases the specific surface area of ​​the detection substrate, promotes the formation of more adsorption sites on the surface of the detection substrate, further improves the adsorption capacity of the analyte, and increases the intensity of the characteristic peak in surface-enhanced Raman detection.

[0094] Furthermore, the aforementioned detection substrate surface can enhance the signal intensity present in the detection and analysis of trace amounts of furfural dissolved in transformer oil, thereby improving the accuracy of detecting the content of trace amounts of furfural dissolved in transformer oil.

[0095] The following detailed description, with reference to specific embodiments, illustrates the detection substrate for surface-enhanced Raman detection and its preparation method according to the present invention. Unless otherwise specified, all raw materials used in the following embodiments are commercially available.

[0096] This embodiment provides a detection substrate for surface-enhanced Raman detection, the preparation method of which includes the following steps:

[0097] Step S10: Add 120 mg silver nitrate, 150 mg polyvinylpyrrolidone, and 0.35 mL of 3 mmol / L sodium sulfide solution to 40 mL ethylene glycol. Heat the solution at 150 °C for 30 min under argon atmosphere to prepare a seed solution containing elemental silver nanoparticles.

[0098] Step S20: 10 mL of polyvinylpyrrolidone aqueous solution (1 g / L) was heated at 100 °C with magnetic stirring, and 0.2 mL of the prepared seed solution was added by injection. After three minutes, a specified amount (0.1–1 mL) of 1 mmol / L tetrachloroauric acid (HAuCl4) solution was added dropwise over 10 minutes. The suspension was purified by centrifugation for 10 minutes to obtain gold-silver alloy nanoparticles that exhibit surface plasmon resonance under light irradiation at wavelengths of 450 nm–700 nm. The gold-silver alloy nanoparticles were then redispersed in pure water. Finally, the prepared gold-silver alloy nanoparticles were redispersed again in 5 mL of 2 mmol / L potassium carbonate buffer to prepare a nano-gold-silver buffer solution.

[0099] Step S30: 10 mg of CsPbBr3@MSNs and 5 mL of nano-gold-silver buffer solution were stirred at 100 °C and 800 r / min for 2 h. After cooling, a composite suspension was obtained. The composite suspension was dropped onto a silicon wafer and heated on a hot plate at 60 °C until the liquid completely evaporated, thus obtaining the detection substrate.

[0100] The steps for synthesizing CsPbBr3@MSNs include:

[0101] 0.96 g of cetyltrimethyl-p-toluenesulfonate (CTATOs) and 0.16 g of triethanolamine (TEAH3) were added to 50 mL of deionized water and stirred at 80 °C for 1 h. After the powder was completely dissolved within 1 h, 7.8 mL of polyolefin thermoplastic elastomer (TEO) was injected, and the mixture was stirred at 80 °C for another 2 h to synthesize monodisperse mesoporous silica nanoparticles (MSNs). After the reaction, the synthesized MSNs were washed and calcined at 550 °C for 6 h. A precursor solution was prepared by dissolving 4.2 mg of CsBr and 7.4 mg of PbBr2 in 200 μL of dimethyl sulfoxide. Then, 25 mg of MSNs were impregnated with the precursor solution. The moistened MSNs were dried at 150 °C for 30 min to obtain the green luminescent material CsPbBr3@MSNs.

[0102] The enhancement factor of the detection substrate in the above embodiments is detected:

[0103] 1. Prepare Rhodamine 6G (R6g) probe solution:

[0104] (1) Dissolve 0.12 g of Rhodamine 6G in water and make up to 2500 mL of the solution. Stir the solution with a magnetic stirrer to obtain the first concentration of R6G solution of 10. -3 mol / L.

[0105] (2) Add 0.1 mL of 10 -3A mol / L L6G solution was mixed with 99.9 mL of water and stirred with a magnetic stirrer to obtain a solution with a concentration of 10. -6 mg / L R6G solution;

[0106] (3) Add 10 mL of 10 -6 A mol / L L6G solution was mixed with 90 mL of water and stirred with a magnetic stirrer to obtain a concentration of 10. -7 mg / L R6G solution;

[0107] (4) Add 10 mL of 10 -7 A mol / L L6G solution was mixed with 90 mL of water and stirred with a magnetic stirrer to obtain a concentration of 10. -8 mg / L R6G solution;

[0108] (5) Add 10 mL of 10 -8 A mol / L L6G solution was mixed with 90 mL of water and stirred with a magnetic stirrer to obtain a concentration of 10. -9 mg / L R6G solution;

[0109] (6) Add 10 mL of 10 -9 A mol / L L6G solution was mixed with 90 mL of water and stirred with a magnetic stirrer to obtain a concentration of 10. -10 mg / L R6G solution;

[0110] Each equipped with 10 -6 10 -7 10 -8 10 -9 10 -10 A mol / L R6G solution was used as a molecular probe to evaluate the enhancement effect of surface-enhanced substrates, such as... Figure 2 The image shows the Raman spectrum of R6G detected using this detection substrate, which can detect 10... - 10 mol / L.

[0111] 2. Calculate the enhancement factor

[0112] By comparing the Raman characteristic peak areas of furfural without and with a substrate, the enhancement factor EF was calculated.

[0113]

[0114] In the formula, I SERS Indicates the effective intensity of the characteristic peaks in the SERS spectrum of the sample under test; I NR C represents the effective intensity of the Raman peak corresponding to the SERS characteristic peak in the ordinary Raman spectrum of the sample under test; SERSC represents the concentration of the sample to be tested in surface-enhanced Raman spectroscopy. NR This represents the concentration of the sample to be tested in conventional Raman spectroscopy.

[0115] Select 1650cm -1 As the Raman characteristic peak of R6G, the area of ​​the Raman characteristic peak is equal to the intensity I, 10 - 6 mol / L I SERS =1025682,10 -6 mol / L unbased I NR =124, and the calculated enhancement factor is 8271.6, indicating that the detection substrate has a good enhancement effect.

[0116] Preparation of furfural gradient solution in transformer oil

[0117] (1) Dissolve 1 mL of furfural solution in transformer oil, make up to 200 mL of mixed solution, and stir with a magnetic stirrer to obtain the first furfural solution with a concentration of 5800 mg / L, and label it as oil sample No. 1.

[0118] (2) Mix 100 mL of oil sample No. 1 with 100 mL of transformer oil and stir with a magnetic stirrer to obtain oil sample No. 2 with a concentration of 2900 mg / L.

[0119] (3) Take 100 mL of oil sample II and mix it with 100 mL of transformer oil. After stirring with a magnetic stirrer, oil sample No. 3 with a concentration of 1450 mg / L is obtained.

[0120] (4) Take 100 mL of No. Ⅲ oil sample and mix it with 100 mL of transformer oil. After stirring with a magnetic stirrer, No. 4 oil sample with a concentration of 725 mg / L is obtained.

[0121] (5) Take 100 mL of No. IV oil sample and mix it with 100 mL of transformer oil. After stirring with a magnetic stirrer, No. 5 oil sample with a concentration of 362.5 mg / L is obtained.

[0122] (6) Take 100 mL of transformer oil as oil sample No. 6 with a concentration of 0 mg / L.

[0123] Due to the complexity of substances in the oil, the measurement results were difficult to distinguish. Therefore, methanol was used to extract the furfural gradient solutions (oil samples 1 to 6) in the above-mentioned transformer oil, labeled as Extract-1, Extract-2, Extract-3, Extract-4, Extract-5, and Extract-6. Samples 1-6 were placed in quartz cuvettes, and six prepared test substrates were immersed in these samples for light protection. After 24 hours of immersion, the quartz cuvettes were placed on the stage of a confocal Raman detection platform, and the Raman spectra of the extracted gradient solutions were acquired. A 560nm wavelength laser with a power of 500mW, an integration time of 0.001s, 100 integration times, a slit width of 500μm, and a 1200 / 500nm grating were used to focus the laser on the oil samples, acquiring the Raman spectra of the gradient solutions. The Raman spectrum of dissolved furfural in the extracted transformer oil is shown below. Figure 3 As shown, the Raman spectral data of oil samples No. 1 to No. 6 obtained by measurement were preprocessed using methods such as peak identification based on derivative spectroscopy, peak removal based on cubic curves, and smoothing and denoising based on the median of three-point cyclic fast Fourier transform to eliminate interference from cosmic rays, fluorescence background, and instrument noise.

[0124] Select the Raman characteristic peaks of furfural in solution

[0125] Comparison of Raman spectra of transformer oil, furfural, and oil samples No. 1-6 revealed that the dissolved furfural in the methanol-extracted transformer oil sample was at 900 cm⁻¹. -1 and 1675cm -1 The Raman signal at 900 cm⁻¹ is significantly enhanced. This is due to the superposition of Raman signals from furfural molecules; therefore, 900 cm⁻¹ is selected. -1 and 1675cm -1 As a Raman characteristic peak of furfural molecules, such as Figure 4 The image shows the Raman spectra of oil samples No. 1 to No. 6 at different concentrations.

[0126] Establish a quantitative analysis model for furfural

[0127] The characteristic peak area of ​​furfural was calculated using Gaussian peak analysis in Origin software, and the relative Raman intensity of furfural was calculated as equal to the characteristic peak area of ​​furfural. Using the content of dissolved furfural in the oil as the independent variable and the characteristic peak area of ​​furfural as the dependent variable, multiple linear regression was applied to obtain a quantitative calibration curve for the furfural concentration in transformer oil, yielding a 900 cm⁻¹ curve. -1 and 1675cm -1 The relationship between the Raman peak area of ​​furfural in the methanol extract and the furfural content in the oil, 900 cm⁻¹ -1 The area of ​​Raman Peak is x1, 1675 cm² -1 The area of ​​the Raman peak is x2, and the multiple linear regression equation is:

[0128] y=1.983x1+0.07722x2-65.98658, (1.1)

[0129] The goodness of fit is R 2 =0.98975.

[0130] Equation (1.1) can be used to determine the furfural concentration in the Raman spectroscopy detection experiment of furfural in transformer oil based on methanol as the extractant. This shows that the peak area of ​​the Raman characteristic peak of the methanol extract of furfural in the standard oil sample has a good linear relationship with the furfural content in the oil.

[0131] The prepared detection substrate was used as a surface-reinforced substrate for in-situ detection of furfural in transformer oil. The R6g probe molecule demonstrated that the surface-reinforced substrate had a good reinforcing effect. The relationship between furfural solutions of different concentrations and the characteristic peak area of ​​furfural was measured. A quantitative analysis model for furfural concentration in transformer oil was established based on the least squares method, which can be used for the quantitative detection of furfural concentration in transformer oil.

[0132] This invention utilizes surface-enhanced Raman spectroscopy. This highly sensitive and repeatable structure has significant application value for the in-situ detection of trace amounts of furfural dissolved in transformer oil. It provides technical support for the future use of surface-enhanced substrates for Raman spectroscopy detection in transformer oil and can be widely applied in fields such as energy and power.

[0133] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0134] The embodiments described above are merely illustrative of several implementations of the present invention, designed to facilitate a detailed understanding of the technical solutions of the present invention, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided by the present invention through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this invention patent should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for preparing a detection substrate for surface-enhanced Raman spectroscopy (SERS) of furfural in transformer oil, characterized in that, Includes the following steps: step S10: Prepare a mixture by mixing silver nitrate, sodium sulfide, ethylene glycol, and polyvinylpyrrolidone, and heat the mixture to prepare a seed solution containing elemental silver nanoparticles; Step S20: Mix the seed solution, tetrachloroauric acid and protective agent, centrifuge, separate the solid, prepare gold-silver alloy nanoparticles, disperse the gold-silver alloy nanoparticles in buffer solution, and prepare nano gold-silver buffer solution; Step S30: Mix the gold-silver nanoparticle buffer solution and CsPbBr3@MSNs to prepare a composite suspension. Add the composite suspension to the substrate and heat.

2. The method for preparing the detection substrate as described in claim 1, characterized in that, Step S10 satisfies one or more of the following characteristics: (1) The ratio of silver nitrate, sodium sulfide, ethylene glycol, and polyvinylpyrrolidone is (100~140) mg : (9×10 -4 ~1.2×10 -3 )mmol : (30~50) mL : (130~180) mg; (2) The heating conditions include: in an inert gas environment, the heating temperature is 120℃~180℃ and the heating time is 0.2h~1h.

3. The method for preparing the detection substrate as described in claim 1, characterized in that, Step S20 satisfies one or more of the following characteristics: （ 1) The mixing step includes: adding the seed solution to the protectant at a temperature of 80℃~120℃, and then adding tetrachloroauric acid after 1 minute to 5 minutes; (2) The ratio of the protective agent, the seed solution, and tetrachloroauric acid is (10:10). -3 ~10 -1 )g : (0.1~1)mL :(10 -4 ~10 -3 ) mmol; (3) The process further includes dispersing the gold-silver alloy nanoparticles in water and filtering out the solids before dispersing the gold-silver alloy nanoparticles in the buffer solution; (4) The buffer solution is selected from one or more of potassium carbonate solution, potassium phosphate solution, sodium citrate solution and potassium hydrogen phthalate solution; (5) The gold-silver alloy nanoparticles generate a surface plasmon resonance effect when irradiated with light of wavelengths of 450 nm to 700 nm.

4. The method for preparing the detection substrate as described in claim 1, characterized in that, The preparation method of the CsPbBr3@MSNs includes the following steps: Monodisperse mesoporous silica nanoparticles were prepared by mixing hexadecyltrimethylammonium p-toluenesulfonate, triethanolamine, polyolefin thermoplastic elastomer and water, and calcining. A precursor solution was prepared by mixing cesium bromide, lead bromide, and an organic solvent. The monodisperse mesoporous silica nanoparticles were immersed in the precursor solution and dried to prepare the CsPbBr3@MSNs.

5. The method for preparing the detection substrate as described in claim 4, characterized in that, The preparation method of the CsPbBr3@MSNs satisfies one or more of the following characteristics: (1) The ratio of hexadecyltrimethylammonium p-toluenesulfonate, triethanolamine, polyolefin thermoplastic elastomer and water is (0.8~1.2) g : (0.1~0.3) g : (5~10) mL : (30~80) mL; (2) The calcination conditions include: calcination temperature of 450℃~650℃ and calcination time of 4h~8h; (3) The ratio of cesium bromide, lead bromide and the organic solvent is (3~5) mg : (5~10) mL : (100~300) μL; (4) The organic solvent is selected from one or more of dimethyl sulfoxide, vinyl sulfite, and propylene sulfite; (5) The drying conditions include: drying temperature of 100℃~200℃ and drying time of 15 minutes~45 minutes.

6. The method for preparing the detection substrate as described in claim 1, characterized in that, The ratio of the nano-gold-silver buffer solution to the CsPbBr3@MSNs is (1~10) mL : (5~15) mg.

7. A detection substrate, characterized in that, It is prepared by the method according to any one of claims 1 to 6.

8. A method for detecting furfural in transformer oil, characterized in that, Includes the following steps: The test solution is prepared by mixing the detection substrate, transformer oil, and extractant as described in claim 7; The test liquid was subjected to surface-enhanced Raman spectroscopy with a frequency shift of 900 cm⁻¹. -1 The peak area at that location is used as x1 and the frequency shift is 1675 cm⁻¹. -1 The peak area corresponding to the point is taken as x2, and the furfural content y in the transformer oil satisfies: y=1.983x1+0.07722x2-65.98658, where the unit of y is mg / L.

9. The detection method as described in claim 8, characterized in that, The extractant is selected from one or more of methanol, water, and acetonitrile.

Images