Cicada wing-Au-Ag flexible nano SERS (Surface Enhanced Raman Scattering) array material, preparation method thereof and application of cicada wing-Au-Ag flexible nano SERS array material in aging state evaluation of No.45 transformer oil

Abstract

The invention discloses a cicada wing-Au-Ag flexible nano SERS (Surface Enhanced Raman Scattering) array material, a preparation method thereof and application of the cicada wing-Au-Ag flexible nano SERS array material in evaluation of the aging state of No.45 transformer oil, and relates to the technical field of Raman spectra. The preparation method of the cicada wing-Au-Ag flexible nano SERS array material comprises the following steps: taking a pretreated cicada wing as a substrate template, and uniformly loading gold nanoparticles on the surface of the substrate template through electron beam evaporation; immersing the cicada wing-Au nano film into an AgNO3 solution, stirring and controlling the temperature, slowly adding a sodium citrate solution, and reacting to obtain a cicada wing-Au-Ag array; and immersing the cicada wing-Au-Ag array into a PBS (Phosphate Buffer Solution) of 4-sulfydryl-N-(4-sulfydryl phenyl) pyrrolidine amide, and incubating in a dark place, so as to prepare the cicada wing-Au-Ag flexible nano SERS array material. The cicada wing-Au-Ag flexible SERS substrate prepared by the invention can realize extraction-free high-sensitivity detection of furfural in No.45 transformer oil.

Description

Technical Field

[0001] The present invention relates to the field of Raman spectroscopy technology, and particularly relates to a cicada wing-Au-Ag flexible nano SERS array material, a preparation method thereof, and an application in the aging state evaluation of No. 45 transformer oil. Background Art

[0002] As one of the important indicators for the aging of oil-paper insulation, furfural plays a key role in evaluating the aging state of transformers. The detection of furfural content has gradually become an effective method to replace the degree of polymerization.

[0003] Surface-enhanced Raman scattering (SERS) is a highly sensitive vibrational spectroscopy technology widely used in the detection of trace substances. By regulating the microscopic morphology of noble metal nanostructures, SERS technology can effectively detect the vibrational spectral information of target molecules. In recent years, the research on using SERS technology for furfural in mineral oil / transformer oil in substations has been gradually promoted. However, due to the relatively complex Raman spectral information of No. 45 transformer oil itself, when a small amount of furfural diffuses from insulating paper into No. 45 transformer oil, its signal will almost be covered by the Raman signal of No. 45 transformer oil. Therefore, conventional Raman spectroscopy technology needs to extract the furfural in No. 45 transformer oil and then perform Raman detection, which not only results in low detection sensitivity of furfural, but also the cumbersome operation process can only apply this detection technology to laboratory operations.

[0004] However, the traditional SERS substrate preparation process is relatively complex, and currently, no extraction-free SERS substrate suitable for furfural in No. 45 transformer oil has been developed on the market. Aiming at the problems of the existing furfural detection methods, such as cumbersome steps, high detection limit, and poor detection consistency, the present application proposes an innovative solution, providing a new detection method for the rapid and highly sensitive detection of dissolved furfural in No. 45 transformer oil, which has important theoretical significance and practical application value. Summary of the Invention

[0005] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a cicada wing-Au-Ag flexible nano SERS array material, a preparation method thereof, and an application in the aging state evaluation of No. 45 transformer oil.

[0006] To achieve the above purpose, the present invention is realized through the following technical solutions: A preparation method of a cicada wing-Au-Ag flexible nano SERS array material, comprising the following steps: S1: Using the pretreated cicada wing as a substrate template, uniformly loading gold nanoparticles on its surface by electron beam evaporation to form a cicada wing-Au nano film; S2: Add the PVP solution to the AgNO3 solution, stir, then immerse the cicada wing-Au nanomembrane, stir, control the temperature at 80 - 95 °C, then slowly add the sodium citrate solution, react for 40 - 60 min, and obtain the cicada wing-Au-Ag array after post-treatment; S3: Immerse the cicada wing-Au-Ag array into the PBS buffer solution of 4-mercapto-N-(4-mercaptophenyl)pyrrolidone amide, stir, incubate in the dark on a constant temperature shaker, and obtain the cicada wing-Au-Ag flexible nano SERS array material after post-treatment.

[0007] In step S1, the thickness of the cicada wing-Au nanomembrane is 8 - 12 nm.

[0008] In step S2, the concentration of the AgNO3 solution is 0.05 - 2 mM, the concentration of the sodium citrate solution is 0.5 - 2 w / v%, and the concentration of the PVP solution is 0.1 - 0.4 wt%.

[0009] The feeding volume ratio of the AgNO3 solution, the sodium citrate solution, and the PVP solution is 4:(0.8 - 1.2):(0.8 - 1.2).

[0010] In step S3, the concentration of 4-mercapto-N-(4-mercaptophenyl)pyrrolidone amide in the PBS buffer solution of 4-mercapto-N-(4-mercaptophenyl)pyrrolidone amide is 0.1 - 0.15 mM, and the pH of the PBS buffer solution = 7.4.

[0011] The pre-treatment steps of the cicada wing in step S1 are as follows: Cut the cicada wing into 1×1 cm squares with sterile scissors, and place them in beakers of acetone, absolute ethanol, and deionized water for ultrasonic cleaning in sequence; transfer the cleaned cicada wing to a glass petri dish, and place it in a sterile vacuum drying oven. The vacuum chamber is evacuated to remove the water molecules and gases adsorbed on the surface.

[0012] In step S1, the cicada wing is the hind wing of an adult cicada.

[0013] In step S1, the parameters of electron beam evaporation are: the target material is 99.999% high-purity gold, the evaporation deposition rate is 0.1 - 0.3 Å / s, and the sample stage rotation speed is 5 - 10 rpm.

[0014] The present invention also provides a cicada wing-Au-Ag flexible nano SERS array material prepared by the above preparation method.

[0015] The present invention also provides an application of the cicada wing-Au-Ag flexible nano SERS array material in the evaluation of the aging state of No. 45 transformer oil.

[0016] Due to the above technical solutions, the beneficial effects of the present invention include: (1) As a low-cost, green, and biodegradable biomaterial, cicada wings can produce a localized surface plasmon resonance effect after the attachment of precious metals to their nanoscale array structure, which can not only promote the amplification of SERS signals, but also promote the uniformity of the molecules adsorbed on their surface, which helps to obtain stable SERS signals. The surface of cicada wings modified with precious metal nanoparticles was functionalized by coupling 4-mercapto-N-(4-mercaptophenyl)pyrrolidinoamide, with a short incubation time (only 40-60 minutes of incubation is required), and the prepared SERS array has high detection sensitivity.

[0017] (2) The present invention solves the problem of poor consistency of traditional SERS substrates. Natural cicada wings are used as templates. Their excellent array structure provides a stable space gap for the subsequent attachment of gold and silver nanoparticles, forming a SERS substrate with good consistency and uniform Raman "hot spots". The particle size of the synthesized silver nanoparticles can be controlled at 10 nm (±2 nm).

[0018] (3) The cicada wing-Au-Ag flexible SERS substrate prepared by the present invention can realize extraction-free high-sensitivity detection of furfural in No. 45 transformer oil, and the minimum detection limit (LOD) reaches 0.01 mg / L, which meets the detection requirements of furfural when the transformer insulation paper is slightly aged. In addition, the consistency index of the substrate is systematically evaluated: the relative standard deviation (RSD) is 3.54%, which has good consistency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the preparation flow chart of cicada wing-Au-Ag flexible nano SERS array material.

[0020] Figure 2 is a scanning electron microscope photograph of the cicada wing-Au-Ag flexible nano SERS array material prepared in Example 3, wherein: Figure 2 The scale bar in (a) is 500 nm. Figure 2 The scale bar in (b) is 300 nm. Figure 2 The scale bar in (c) is 200 nm. Figure 2 The scale bar in (d) is 100 nm.

[0021] Figure 3 This is the SERS spectrum of the cicada wing-Au-Ag flexible nano SERS array material used for trace detection of furfural in No. 45 transformer oil.

[0022] Figure 4 When the cicada wing-Au-Ag flexible nano SERS array material detects 1 mg / L furfural in 45# transformer oil at different positions, furfural is located at 1658 cm -1 Corresponding Raman intensity histogram within the wavenumber range.

[0023] Figure 5 It is the equal division diagram of the cicada wing-Au-Ag flexible nano SERS array material. Specific embodiments

[0024] The following is further described in conjunction with embodiments, but the present invention is not limited to these embodiments.

[0025] Example 1 Preparation of 4-mercapto-N-(4-mercaptophenyl)pyrrolidone: Under nitrogen protection and ice bath conditions, dissolve 4-mercaptopyridine-2-carboxylic acid (1.0 mmol, 155 mg) in 10 mL of anhydrous DMF, and successively add EDC·HCl (1.2 mmol, 230 mg) and NHS (1.2 mmol, 138 mg). After stirring and activating for 30 minutes, raise the temperature to room temperature and continue the reaction for 2 h; then slowly add dropwise a 5 mL DMF solution containing 4-aminobenzenethiol (1.1 mmol, 139 mg), add dropwise for 5 min, and add triethylamine (2.0 mmol, 280 μL). After stirring in the dark at room temperature (25°C) for 12 h, adjust the pH to neutral with 0.25 M HCl, precipitate the crude product in an ice-water bath, and after suction filtration, purify by silica gel column chromatography (gradient elution with DCM / methanol = 20:1 → 10:1) to obtain a white solid product, which is 4-mercapto-N-(4-mercaptophenyl)pyrrolidone. The 1H NMR data is as follows: 1 H NMR (500 MHz, DMSO- d 6) δ 9.12 (s, 1H), 8.64 (d, J = 4.2 Hz, 1H), 7.74(d, J = 2.1 Hz, 1H), 7.54 – 7.48 (m, 2H), 7.40 – 7.34 (m, 2H), 7.25 (dd, J =4.2, 2.2 Hz, 1H), 4.77 (s, 1H), 4.14 (s, 1H). The reaction equation for the preparation of 4-mercapto-N-(4-mercaptophenyl)pyrrolidone is as follows:

[0026] Example 2 Preparation of cicada wing-Au-Ag flexible nano SERS array material: S1: Using the pretreated 1×1 cm cicada wing as the substrate template, through electron beam evaporation (vacuum degree 2×10 -6Torr, the target material is 99.999% high-purity gold, the evaporation deposition rate is 0.1 Å / s, and the sample stage rotation speed is 10 rpm), uniformly load gold nanoparticles on its surface to form a cicada wing-Au nanofilm, and the thickness of the cicada wing-Au nanofilm is 8 nm; S2: Add 8 ml of 0.1 wt% PVP solution to 40 ml of 0.5 mM AgNO3 solution, stir, then immerse the cicada wing-Au nanofilm, stir, control the temperature at 80 °C, then slowly add 8 ml of 2 w / v% sodium citrate solution dropwise over 8 min, react for 60 min, take out the cicada wing and rinse it with 15 ml of ice water, dry it with nitrogen and then vacuum dry (40 °C, 2 h) to obtain a cicada wing-Au-Ag array; S3: Immerse the cicada wing-Au-Ag array in 35 ml of PBS buffer solution (pH = 7.4) containing 0.1 mM 4-mercapto-N-(4-mercaptophenyl)pyrrolidone amide, stir, incubate in the dark at 200 rpm on a constant temperature shaker at 25 °C for 40 min, take out the cicada wing and rinse it successively with 15 ml of absolute ethanol and 15 ml of deionized water, dry it with nitrogen and then vacuum dry (25 °C, 1 h) to prepare a cicada wing-Au-Ag flexible nano SERS array material.

[0027] Example 3 Preparation of a cicada wing-Au-Ag flexible nano SERS array material: S1: Using the pretreated 1×1 cm cicada wing as a substrate template, through electron beam evaporation (vacuum degree 1×10 -6 Torr, the target material is 99.999% high-purity gold, the evaporation deposition rate is 0.2 Å / s, and the sample stage rotation speed is 8 rpm), uniformly load gold nanoparticles on its surface to form a cicada wing-Au nanofilm, and the thickness of the cicada wing-Au nanofilm is 10 nm; S2: Add 10 ml of 0.25 wt% PVP solution to 40 ml of 1 mM AgNO3 solution, stir, then immerse the cicada wing-Au nanofilm, stir, control the temperature at 90 °C, then slowly add 10 ml of 1 w / v% sodium citrate solution dropwise over 10 min, react for 50 min, take out the cicada wing and rinse it with 15 ml of ice water, dry it with nitrogen and then vacuum dry (40 °C, 2 h) to obtain a cicada wing-Au-Ag array; S3: Immerse the cicada wing-Au-Ag array in 35 ml of PBS buffer solution (pH = 7.4) containing 0.12 mM 4-mercapto-N-(4-mercaptophenyl)pyrrolidone amide, stir, incubate in the dark at 200 rpm on a constant temperature shaker at 25 °C for 50 min, take out the cicada wing and rinse it successively with 15 ml of absolute ethanol and 15 ml of deionized water, dry it with nitrogen and then vacuum dry (25 °C, 1 h) to prepare a cicada wing-Au-Ag flexible nano SERS array material.

[0028] Example 4 Preparation of Cicada Wing-Au-Ag Flexible Nano SERS Array Material: S1: Using the pretreated 1×1 cm cicada wing as the substrate template, uniformly load gold nanoparticles on its surface by electron beam evaporation (vacuum degree lower than 2×10 - 6 Torr, the target material is 99.999% high-purity gold, the evaporation deposition rate is 0.3 Å / s, and the sample stage rotation speed is 5 rpm) to form a cicada wing-Au nanomembrane with a thickness of 12 nm; S2: Add 12 ml of 0.4 wt% PVP solution to 40 ml of 2 mM AgNO3 solution, stir, then immerse the cicada wing-Au nanomembrane, stir, control the temperature at 95 °C, then slowly add 12 ml of 0.5 w / v% sodium citrate solution dropwise for 10 min, react for 40 min, take out the cicada wing and rinse it with 15 ml of ice water, dry it with nitrogen and then vacuum dry (40 °C, 2 h) to obtain a cicada wing-Au-Ag array; S3: Immerse the cicada wing-Au-Ag array in 30 ml of 0.15 mM PBS buffer solution (pH = 7.4) of 4-mercapto-N-(4-mercaptophenyl)pyrrolidone amide, stir, incubate in the dark at 25 °C in a constant temperature shaker at 250 rpm for 60 min, take out the cicada wing and rinse it successively with 15 ml of absolute ethanol and 15 ml of deionized water, dry it with nitrogen and then vacuum dry (25 °C, 1 h) to prepare the cicada wing-Au-Ag flexible nano SERS array material.

[0029] The pretreatment steps of the cicada wing in Examples 2-4 are as follows: Cut the hind wings of adult cicadas into 1×1 cm squares with sterile scissors, and ultrasonically clean them in 50 ml of acetone, 50 ml of absolute ethanol, and 50 ml of deionized water in turn at 25 °C for 5 min; transfer the cleaned cicada wings to a glass petri dish and place them in a sterile vacuum drying oven, vacuum dry (30 °C, -0.095 MPa, 2 h) to remove the adsorbed water molecules and gases on the surface.

[0030] Comparative Example 1 Preparation of Cicada Wing-Au-Ag Flexible Nano SERS Array Material: The preparation method of the SERS array in this comparative example is basically the same as that in Example 3, the difference is that 35 ml of 0.12 mM PBS buffer solution of 4-aminothiophenol is used to replace 35 ml of 0.12 mM PBS buffer solution of 4-mercapto-N-(4-mercaptophenyl)pyrrolidone amide in step S3.

[0031] Comparative Example 2 Preparation of Cicada Wing-Au-Ag Flexible Nano SERS Array Material: The preparation method of the SERS array in this comparative example is basically the same as that in Example 3, except that in step S3, 35 ml of 0.12 mM PBS buffer solution of 4-mercapto-N-(4-mercaptophenyl)pyrrolidone amide is replaced with 35 ml of 0.12 mM PBS buffer solution of 3-mercapto-N-(4-mercaptophenyl)pyrrolidone amide.

[0032] The preparation method of 3-mercapto-N-(4-mercaptophenyl)pyrrolidone amide is basically the same as that in Example 1, except that 1.0 mmol of 4-mercaptopyridine-2-carboxylic acid is replaced with an equimolar amount of 3-mercaptopyridine-2-carboxylic acid.

[0033] Preparation of the cicada wing-Au-Ag flexible nano SERS array material in Comparative Example 3: The preparation method of the SERS array in this comparative example is basically the same as that in Example 3, except that in step S3, 35 ml of 0.12 mM PBS buffer solution of 4-mercapto-N-(4-mercaptophenyl)pyrrolidone amide is replaced with 35 ml of 0.12 mM PBS buffer solution of 6-mercapto-N-(4-mercaptophenyl)pyrrolidone amide.

[0034] The preparation method of 3-mercapto-N-(4-mercaptophenyl)pyrrolidone amide is basically the same as that in Example 1, except that 1.0 mmol of 4-mercaptopyridine-2-carboxylic acid is replaced with an equimolar amount of 6-mercaptopyridine-3-carboxylic acid.

[0035] Application example Application of the cicada wing-Au-Ag flexible nano SERS array material in the evaluation of the aging state of No. 45 transformer oil: (1) Standard solution preparation: Add furfural to No. 45 transformer oil and ultrasonicate for 20 min to prepare standard solutions of 0.01 mg / L, 0.1 mg / L, and 1 mg / L respectively; (2) Transfer the cicada wing-Au-Ag flexible nano SERS array materials prepared in Examples 2-4 and Comparative Examples 1-3 into the 1 mg / L standard solution respectively, and incubate in an incubator at 60 °C for 20 min to obtain the test samples, which are labeled as Example 2, Example 3-1, Example 4, Comparative Example 1, Comparative Example 2, and Comparative Example 3 respectively; Transfer the cicada wing-Au-Ag flexible nano SERS array material prepared in Example 3 into the 0.01 and 0.1 mg / L standard solutions respectively, and incubate in an incubator at 60 °C for 20 min to obtain the test samples, which are labeled as Example 3-0.01 and Example 3-0.1 respectively; (3) Raman spectroscopy test was carried out using an ATR-3000 portable Raman spectrometer (excitation light wavelength is 532 nm, laser power is 30 mW, integration time is 1 s, integration times is 10 times, slit width is 10 μm, and 1200 nm type grating is selected) to obtain furfural signal information.

[0036] Figure 1 This is the flow chart for preparing the cicada wing-Au-Ag flexible nano SERS array material in Examples 2-4 of this application.

[0037] Figure 2 It is the scanning electron microscope photo of the cicada wing-Au-Ag flexible nano SERS array material prepared in Example 3. Among them, Figure 2 (a) The scale bar is 500 nm, Figure 2 (b) The scale bar is 300 nm, Figure 2 (c) The scale bar is 200 nm, Figure 2 (d) The scale bar is 100 nm; from Figure 2 the four SEM pictures with different magnification factors, it can be seen that the surface of the cicada wing is covered with nano-hills with an average height of about 100 nm ( Figure 2 (b) is the SEM photo taken at an angle of 45°, and the overall height of the "hills" on the surface of the cicada wing is about 100 nm). There is an ordered microscopic array structure, that is, nano-hills. The "hills" show a structure feature of being narrow at the upper end and wide at the lower end, and the diameter at the widest part is about 100 nm. The nano-gaps between the arrays are between 30 - 100 nm. This closely arranged nano-array structure with specific sizes has a super large specific surface area, which is more conducive to the attachment of noble metal nano-materials and increases the distribution range of the Raman active sites of the substrate; secondly, the natural nano-gaps formed between the hills can provide an effective enrichment space for the molecules to be detected, making the adsorption of molecules on its surface more stable and uniform. From Figure 2 (b-d), it can be seen that AgNPs with a particle size of about 10 nm (the fine particles (showing a furry state) on the surface of the small hills, with a size of about 10 nm) are in-situ grown on the surface of the cicada wing-Au. It can be observed from the figure that the AgNPs with consistent particle sizes are evenly and densely attached to the surface of the cicada wing-Au, forming a highly ordered and closely arranged nano-structure. The uniform distribution of these AgNPs and the cicada wing-Au substrate are conducive to generating a strong synergistic effect, greatly enhancing the local electromagnetic field, and further improving the SERS activity.

[0038] As Figure 3 shown, in Examples 2-4 of this application, when the furfural concentration is 1 mg / L, the characteristic peak intensity of furfural at 1658 cm -1 is relatively high; when the furfural concentration is 0.1 mg / L, at 1658 cm -1There are still obvious characteristic peaks; when the furfural concentration is 0.01 mg / L, the Raman signal corresponding to furfural can still be observed near the wavenumber of 1658 cm -1 . The intensity of the furfural signal is about 2642.45 a.u., the corresponding noise signal is about 818.30 a.u., and the signal-to-noise ratio is about 3.23, meeting the 3-fold signal-to-noise ratio relationship, so this signal is a valid signal. When using an array obtained by coupling other compounds with cicada wing-Au-Ag for furfural detection in No. 45 transformer oil, the intensity of the characteristic peak is much lower than that of the present application.

[0039] Figure 4 Figure is the bar chart of the Raman intensity corresponding to furfural in the wavenumber range of 1658 cm -1 when detecting 1 mg / L furfural in No. 45 transformer oil at different positions of the cicada wing-Au-Ag array. During the test, the cicada wing-Au-Ag substrate (1×1 cm) was evenly divided into 16 regions according to the Figure 5 style, and then 8 regions ( Figure 5 the 8 regions numbered) were selected. One set of furfural signals was tested in each region to obtain the signal intensity of furfural at the wavenumber of 1658 cm -1 . The signal intensities measured in the 8 regions were plotted as a bar chart, as Figure 4 shown. It can be seen that the signal reproducibility of furfural is good, and its relative standard deviation is RSD = 3.54%.

[0040] The above are only the preferred embodiments of the present invention and are not used to limit the present invention; however, for those of ordinary skill in the art, within the scope of the technical solution of the present invention, any slight changes, modifications, and equivalent variations made using the above-disclosed technical content are all equivalent embodiments of the present invention; at the same time, any equivalent changes, modifications, and variations made to the above embodiments based on the essential technology of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A preparation method of a cicada wing-Au-Ag flexible nano SERS array material, characterized in that, It includes the following steps: S1: Using the pretreated cicada wing as a base template, uniformly load gold nanoparticles on its surface by electron beam evaporation to form a cicada wing-Au nanofilm; S2: Add the PVP solution to the AgNO3 solution, stir, then immerse the cicada wing-Au nanofilm, stir, control the temperature at 80 - 95 °C, then slowly add the sodium citrate solution, react for 40 - 60 min, and obtain the cicada wing-Au-Ag array after post-treatment; S3: Immerse the cicada wing-Au-Ag array in the PBS buffer solution of 4-mercapto-N-(4-mercaptophenyl)pyrrolidone amide, stir, incubate in the dark on a constant temperature shaker, and obtain the cicada wing-Au-Ag flexible nano-SERS array material after post-treatment.

2. The preparation method according to claim 1, characterized in that, In step S1, the thickness of the cicada wing-Au nanofilm is 8 - 12 nm.

3. The preparation method according to claim 1, characterized in that, In step S2, the concentration of the AgNO3 solution is 0.5 - 2 mM, the concentration of the sodium citrate solution is 0.5 - 2 w / v%, and the concentration of the PVP solution is 0.1 - 0.4 wt%.

4. The preparation method according to claim 3, wherein, The feeding volume ratio of the AgNO3 solution, sodium citrate solution, and PVP solution is 4:(0.8 - 1.2):(0.8 - 1.2).

5. The preparation method according to claim 1, wherein In step S3, the concentration of 4-mercapto-N-(4-mercaptophenyl)pyrrolidone amide in the PBS buffer solution of 4-mercapto-N-(4-mercaptophenyl)pyrrolidone amide is 0.1 - 0.15 mM, and the pH of the PBS buffer solution is 7.

4.

6. The preparation method according to claim 1, characterized in that The pretreatment steps of the cicada wing in step S1 are as follows: Cut the cicada wing into 1×1 cm squares with sterile scissors, and sequentially place them in beakers of acetone, absolute ethanol, and deionized water for ultrasonic cleaning; transfer the cleaned cicada wing to a glass petri dish and place it in a sterile vacuum drying oven, evacuate the vacuum chamber to remove the water molecules and gases adsorbed on the surface.

7. The preparation method according to claim 1, characterized in that, In step S1, the cicada wing is the hind wing of an adult cicada.

8. The preparation method according to claim 1, characterized in that, In step S1, the parameters of electron beam evaporation are: the target is 99.999% high-purity gold, the evaporation deposition rate is 0.1–0.3 Å / s, and the sample stage rotation speed is 5 - 10 rpm.

9. A cicada wing-Au-Ag flexible nano SERS array material, characterized in that, Prepared by the preparation method described in any one of claims 1 - 8.

10. Application of the cicada wing-Au-Ag flexible nano-SERS array material described in claim 9 in the evaluation of the aging state of No. 45 transformer oil.

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