Piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate and preparation method thereof

Abstract

The invention discloses a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate and a preparation method thereof, the surface enhanced Raman substrate comprises a substrate and a composite micron wire, the composite micron wire is bent, two ends of the composite micron wire are fixed on the substrate, and the composite micron wire is a ZnO micron wire with silver nanoparticles sputtered on the surface. The preparation method comprises the following steps: selecting ZnO microwires with good crystal quality and a perfect echo wall cavity structure; placing the selected ZnO microwires on a clean substrate; applying mechanical stress to bend the ZnO microwire, and fixing two ends of the ZnO microwire on the substrate; and placing the obtained product on a magnetron sputtering instrument sample table, and sputtering silver nanoparticles on the surface of the ZnO microwire. According to the SERS substrate of the piezoelectric enhanced ZnO-Ag composite microcavity structure, the detection sensitivity of the substrate is greatly improved, the measurement precision can be greatly improved, data analysis is simplified, and the like.

Description

Technical Field

[0001] The invention relates to a Raman detection substrate and a preparation method thereof, in particular to a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate and a preparation method thereof. Background Art

[0002] Surface enhanced Raman scattering (SERS) technology is a fast and non-destructive spectral analysis technology with significant advantages and broad prospects. However, the traditional SERS technology has shortcomings such as complex assembly methods and high costs, which greatly limits its application. In order to solve the above problems, many new substrate configurations and physical effects are used to prepare SERS substrates.

[0003] The patent with publication number CN107356584A discloses a method for preparing a surface-enhanced Raman substrate of a zinc oxide-silver composite microcavity structure, which uses the high localization of the optical microcavity to increase the interaction between light and matter, and cooperates with the local electromagnetic field enhancement effect of the plasmon resonance effect to achieve ultra-sensitive detection of rhodamine 6G molecules. Although the above preparation method has the advantages of simplicity, high efficiency, and flexibility, its detection sensitivity still has room for further improvement. Summary of the invention

[0004] Purpose of the invention: In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate that enhances the interaction between light and detection molecules and improves the sensitivity of Raman signal detection. Another purpose of the present invention is to provide a simple, convenient and precisely controlled method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate.

[0005] Technical solution: The piezoelectrically enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate described in the present invention includes a substrate and a composite microwire. The composite microwire is bent and both ends are fixed on the substrate. The composite microwire is a ZnO microwire with silver nanoparticles sputtered on the surface.

[0006] Furthermore, the ZnO microwires have good crystal quality, a perfect whispering gallery cavity structure, and a diameter of 2 to 6 μm.

[0007] Furthermore, the substrate is a quartz substrate.

[0008] The method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate of the present invention comprises the following steps:

[0009] Step 1: Select ZnO micron wires with good crystal quality and perfect whispering gallery cavity structure;

[0010] Step 2, placing the ZnO microwires selected in step 1 on a clean substrate;

[0011] Step 3, after applying mechanical stress to bend the ZnO micron wire, two ends of the ZnO micron wire are fixed on the substrate;

[0012] Step 4: placing the product obtained in step 3 on a sample stage of a magnetron sputtering instrument, and sputtering silver nanoparticles on the surface of the ZnO micron wires to obtain a piezoelectrically enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate.

[0013] ZnO microwires with natural microcavity structures have become ideal candidate materials for biosensors due to their high isoelectric point and biocompatibility. In addition, ZnO also has excellent piezoelectric properties. Due to the asymmetry of the crystal structure, external stress will cause the redistribution of its internal electric dipoles, the separation of positive and negative charge centers, and the generation of polarized charges. The electrostatic field caused will attract surrounding polar molecules or charged particles, greatly increasing the molecular coverage of the material surface, thereby improving the sensing sensitivity. In view of this, the present invention introduces the piezoelectric effect and regulates the ability of the microwire to enrich molecules on its surface by changing the degree of curvature of the microwire, thereby constructing an ultra-sensitive piezoelectric enhanced SERS substrate.

[0014] Furthermore, in step 1, the selection is performed using pointed tweezers under an optical microscope. The diameter of the ZnO microwire is 2 to 6 μm. The perfect whispering gallery cavity structure means that the hexagonal cross-section cavity of the material itself is a whispering gallery structure.

[0015] Furthermore, in step 3, mechanical stress is applied through a tungsten steel probe, and the angle between the tungsten steel probe and the table is 30 to 45 degrees to avoid the phenomenon that the ZnO micron wire is no longer close to the substrate but warps upward. The strain of the ZnO micron wire bending is 0.018% to 0.232%. The diameter of the tungsten steel probe is about 1 μm.

[0016] Furthermore, in step three, the fixing is performed by contacting the two ends of the ZnO micrometer wire with a thin copper wire dipped in PMMA under a microscope to make it adhere to the substrate.

[0017] Furthermore, in step 4, the specific steps of sputtering are: adjusting the target position to the metal silver target, evacuating the sample chamber, and introducing argon gas to adjust the pressure in the chamber to 5×10 -3 Pa or less, and then set the sputtering time to 5 to 60s and the sputtering current power to 70 to 80W for sputtering.

[0018] Working principle: The optical microcavity has an extremely high quality factor and a small mode volume, allowing resonant photons to circulate in the cavity for a long time. This feature greatly increases the chance of light interacting with matter; the localized surface plasmon resonance effect of metal nanoparticles can achieve significant enhancement of molecular signals through electromagnetic field enhancement; due to the asymmetry of the ZnO crystal structure, the applied stress will cause its internal electric dipoles to redistribute, the positive and negative charge centers to separate, and generate polarized charges. In the absence of strain release, these polarized charges cannot be reorganized and accumulate on the surface of the material, forming an internal piezoelectric field. In particular, these polarized charges attract nearby tiny molecules from the dilute solution to the surface of the material through electrostatic adsorption, greatly increasing the molecular coverage and thus improving the sensing sensitivity. Combining the ZnO microcavity whispering gallery mode effect, the metal Ag localized surface plasmon resonance effect, and the piezoelectric effect of the ZnO material, the three synergistically enhance the interaction between light and the detection molecules and improve the sensitivity of Raman signal detection.

[0019] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0020] 1. A piezoelectrically enhanced SERS substrate of ZnO-Ag composite microcavity structure was prepared, which utilized the synergistic effect of localized surface plasmons and WGM mode, and introduced the piezoelectric effect to increase the molecular adsorption on the surface of the material, greatly improving the detection sensitivity of the substrate;

[0021] 2. Taking advantage of the low cost and low toxicity of ZnO materials, the high cost and complexity of SERS substrate preparation were solved;

[0022] 3. By utilizing the excellent flexibility of ZnO microwires, the piezoelectric field intensity can be adjusted over a wide range to enhance the detection performance of the SERS substrate. The bending degree of the ZnO microwires has a good linear relationship with the signal intensity, which can greatly improve the measurement accuracy and simplify data analysis.

[0023] 4. The preparation method is efficient, simple, sensitive and widely applicable, has good prospects for practical detection applications, and can determine the degree of curvature of the micrometer wire according to the required accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the preparation principle diagram of the present invention;

[0025] Figure 2 is a scanning electron microscope image of a hexagonal cross section of a ZnO microwire of the present invention;

[0026] Figure 3 is the stimulated emission spectrum of the ZnO perfect whispering gallery cavity structure selected in Example 1 of the present invention under optical pumping conditions;

[0027] Figure 4 is a scanning electron microscope image of the product obtained in Example 1 of the present invention;

[0028] Figure 5 is a scanning electron microscope image of the metallic silver nanoparticles of Example 1 of the present invention;

[0029] Figure 6 is a graph showing the relationship between the piezoelectric field intensity and the strain degree obtained by evaluating the present invention using the finite element analysis method;

[0030] Figure 7 This is an optical picture of the product obtained in Example 1 of the present invention;

[0031] Figure 8 The E2 of six points on the ZnO micrometer line in Example 1 of the present invention high Normalized Raman spectra of the mode characteristic peaks;

[0032] Fig. 9 The concentration of 5×10 -8 mol / L Raman spectrum of R6G;

[0033] Fig.10 is a linear fitting relationship diagram between Raman signal intensity and strain value of the present invention;

[0034] Fig.11 is an optical performance test chart of the present invention;

[0035] Fig.12 The concentration of 5×10 -8 mol / L Raman spectrum of Rhodamine 6G. DETAILED DESCRIPTION

[0036] Unless otherwise specified, the materials, reagents, instruments, etc. used in the following examples can be obtained from commercial sources. Experimental methods without specific conditions in the examples are usually carried out under conventional conditions or under conditions recommended by the manufacturer.

[0037] Example 1

[0038] like Figure 1 , a method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate, comprising the following steps:

[0039] (1) Using tweezers under an optical microscope, select a 4 μm diameter ZnO microwire with a perfect whispering gallery cavity structure from the ZnO microwire array. Figures 2-3 As shown, it was transferred to a 1 cm×1 cm quartz glass substrate.

[0040] (2) Under a stereo microscope, a thin copper wire with PMMA attached to it was used to contact one end of the selected ZnO microwire so that it was bonded to the quartz glass substrate, while the other end was in a free state.

[0041] (3) Under a stereo microscope, the tip of a tungsten steel probe with a diameter of 1 μm was used to contact the unfixed end of the ZnO microwire, and stress was applied to push the ZnO microwire to make it bend to a certain extent. Then, an appropriate amount of PMMA was applied to fix the free end of the ZnO microwire.

[0042] (4) The strain value of the ZnO microwire at the position of maximum strain (point 3) is calculated to be 0.232% by the formula.

[0043] The strain values ​​of different regions on the bent ZnO microwire can be calculated using the corresponding formula.

[0044] Specifically, the formula is: Δω is E2 high The peak displacement of the mode, a and b are the phonon deformation potential parameters, C 33 and C 13 is the elastic constant, ε cc is the strain value.

[0045] Specifically, E2 high The mode is a typical characteristic peak in the Raman spectrum of ZnO, located at 438 cm -1 about.

[0046] Specifically, the value in brackets is determined to be (527 ± 25) cm -1 For convenience, the slope is taken as 527cm -1 To calculate the strain value at each point of the bent ZnO microwire.

[0047] (5) The quartz substrate with the bent ZnO microwire fixed was placed on the sample stage of the magnetron sputtering instrument, and then the surfaces of the bent ZnO microwire and the substrate were modified with metallic silver nanoparticles (Ag NPs) with controllable morphology, size and uniform density distribution. The sputtering current was 20 mA and the chamber pressure was 5×10 -3 Pa, the sputtering time is 10s, such as Figure 4 , and obtain a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate. Figure 5 , the diameter of Ag NPs is 15-30 nm, and the interparticle gap is 5-10 nm.

[0048] Simulation of piezoelectric field: The relationship between the piezoelectric field strength and the strain degree was evaluated using the finite element analysis (FEA) method, such as Figure 6The simulation results show that when the applied stress causes the bending degree of the microwire to gradually increase, the potential difference between the two ends increases accordingly.

[0049] Spectral collection and analysis:

[0050] Step 1: The original Raman spectra of ZnO at six points on the curved ZnO micrometer line are collected by the MStarter 100 micro-spectral scanning test system, with an excitation light wavelength of 532 nm and an integration time of 8 seconds. The Raman spectra are then processed to obtain standardized Raman spectra that meet certain conditions, such as Figures 7-8 Data processing refers to the Gaussian fitting of the original Raman spectrum data of ZnO after deducting the baseline in the Origin drawing software to facilitate the estimation of E2 high The peak position of the mode is in the spectral range of 410-470 cm -1 .

[0051] Step 2: Read E2 of each point high The peak position of the mode is then calculated, and the peak displacement Δω is calculated. The strain value is calculated according to the formula in step (4). Table 1 shows the strain values ​​at the six points. The peak displacement Δω refers to the displacement relative to E2 in the unstrained state. high The peak position ω0 is offset, ω0 is 438.287 cm -1 .

[0052] Table 1 E2 caused by strain values ​​in different regions on the bent ZnO microwire high Phonon Raman peak shift and the corresponding signal intensity at 1364 wavenumbers

[0053]

[0054] The data given in Table 1 show that bending occurs by 0.232% and 0.214% respectively along the moving direction of micrometer line point 3 to point 6 and point 3 to point 1. Point 3 is the position with the maximum strain value, which is 0.232%. Point 6 is in a state of no strain.

[0055] Step 3: Dissolve powdered R6G in deionized water and mix them quantitatively to obtain a concentration of 5×10 -8 mol / L R6G solution. The substrate was soaked in the R6G solution for one hour, then taken out and dried with nitrogen. The Raman spectrum of R6G was obtained by FinderOne Raman microspectrometer, with an excitation wavelength of 532nm and an integration time of 5 seconds. The Raman spectra of R6G at the six points in step 1 were collected, and the Raman spectra were processed to obtain standardized Raman spectra that met certain conditions, such as Fig. 9Data processing refers to the process of deducting the baseline from the original Raman spectrum data of R6G and plotting it into a y-axis offset stacking diagram in the Origin drawing software to facilitate the comparison of the intensity of the R6G Raman signal collected at different positions. The spectral range is 570-1750cm -1 .

[0056] Step 4: Select 1364cm of R6G -1 The Raman characteristic peaks were analyzed to obtain the relationship between the strain value and the Raman signal intensity at different positions, as shown in Table 1. Since the signal intensity of the characteristic peak 1364 is significant and very stable under different conditions, 1364 was selected as the iconic Raman characteristic peak of R6G for analysis. Data processing was performed to prove that the two have a good linear relationship, such as Fig.10 As shown. Data processing refers to setting the strain value and Raman signal intensity as x-axis and y-axis parameters in the Origin drawing software, and performing linear fitting. Taking the strain value as an absolute value facilitates the analysis of the amplitude of signal change. The relationship is Y = 18115.3X + 5752.5, R 2 =0.9, indicating that the two have a good linear relationship. The molecular signal obtained at point 3 with the maximum strain value is the strongest, reaching 10062. The signal intensity collected at the position with a slightly lower strain value than point 3 is reduced until the molecular signal intensity at point 6 is reduced to the weakest.

[0057] The optical performance of the piezoelectric enhanced ZnO-Ag composite microcavity structure surface enhanced Raman substrate constructed in Example 1 of the present invention was tested using a Raman spectrometer. The research results are as follows Fig.11 As shown in Figure 2, the minimum detection limit of the SERS substrate for R6G molecules reached 10 -13 The Raman enhancement factor is as high as 1.05×10 11 .

[0058] Example 2

[0059] A method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate comprises the following steps:

[0060] (1) Under an optical microscope, a ZnO microwire with a diameter of 2 μm and a perfect whispering gallery cavity structure was selected from the ZnO microwire array using tweezers and transferred to a 1 cm × 1 cm quartz glass substrate.

[0061] (2) Under a stereo microscope, a thin copper wire with PMMA attached to it was used to contact one end of the selected ZnO microwire so that it was bonded to the quartz glass substrate, while the other end was in a free state.

[0062] (3) Under a stereo microscope, the tip of a tungsten steel probe with a diameter of 1 μm was used to contact the unfixed end of the ZnO microwire, and stress was applied to push the ZnO microwire to make it bend to a certain extent. Then, an appropriate amount of PMMA was applied to fix the free end of the ZnO microwire.

[0063] (4) The strain value at the position where the maximum strain occurs in the ZnO microwire is calculated by the formula to be 0.187%.

[0064] (5) The quartz substrate with the bent ZnO microwire fixed was placed on the sample stage of the magnetron sputtering instrument, and then the surfaces of the bent ZnO microwire and the substrate were modified with metallic silver nanoparticles (Ag NPs) with controllable morphology, size and uniform density distribution. The sputtering power was 70 W and the chamber pressure was 5×10 -3 Pa, the sputtering time was 5s, and a piezoelectrically enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate was obtained.

[0065] Example 3

[0066] A method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate comprises the following steps:

[0067] (1) Under an optical microscope, a ZnO microwire with a diameter of 3 μm and a perfect whispering gallery cavity structure was selected from the ZnO microwire array using tweezers and transferred to a 1 cm × 1 cm quartz glass substrate.

[0068] (2) Under a stereo microscope, a thin copper wire with PMMA attached to it was used to contact one end of the selected ZnO microwire so that it was bonded to the quartz glass substrate, while the other end was in a free state.

[0069] (3) Under a stereo microscope, the tip of a tungsten steel probe with a diameter of 1 μm was used to contact the unfixed end of the ZnO microwire, and stress was applied to push the ZnO microwire to make it bend to a certain extent. Then, an appropriate amount of PMMA was applied to fix the free end of the ZnO microwire.

[0070] (4) The strain value at the position where the maximum strain occurs in the ZnO microwire is calculated by the formula to be 0.111%.

[0071] (5) The quartz substrate with the bent ZnO microwire fixed was placed on the sample stage of the magnetron sputtering instrument, and then the surfaces of the bent ZnO microwire and the substrate were modified with metallic silver nanoparticles (Ag NPs) with controllable morphology, size and uniform density distribution. The sputtering power was 70 W and the chamber pressure was 5×10 -3 Pa, the sputtering time was 20s, and a piezoelectrically enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate was obtained.

[0072] Example 4

[0073] A method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate comprises the following steps:

[0074] (1) Under an optical microscope, a ZnO microwire with a diameter of 3.5 μm and a perfect whispering gallery cavity structure was selected from the ZnO microwire array using tweezers and transferred to a 1 cm × 1 cm silicon wafer.

[0075] (2) Under a stereo microscope, a thin copper wire with PMMA attached to it is used to contact one end of the selected ZnO microwire so that it adheres to the silicon wafer, while the other end is free.

[0076] (3) Under a stereo microscope, the tip of a tungsten steel probe with a diameter of 1 μm was used to contact the unfixed end of the ZnO microwire, and stress was applied to push the ZnO microwire to make it bend to a certain extent. Then, an appropriate amount of PMMA was applied to fix the free end of the ZnO microwire.

[0077] (4) The strain value at the position where the maximum strain occurs in the ZnO micron wire is calculated by the formula to be 0.1%.

[0078] (5) The quartz substrate with the bent ZnO microwire fixed was placed on the sample stage of the magnetron sputtering instrument, and then the surfaces of the bent ZnO microwire and the substrate were modified with metallic silver nanoparticles (Ag NPs) with controllable morphology, size and uniform density distribution. The sputtering power was 70 W and the chamber pressure was 5×10 -3 Pa, the sputtering time was 40s, and a piezoelectrically enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate was obtained.

[0079] Example 5

[0080] A method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate comprises the following steps:

[0081] (1) Under an optical microscope, a ZnO microwire with a diameter of 5 μm and a perfect whispering gallery cavity structure was selected from the ZnO microwire array using tweezers and transferred to a 1 cm × 1 cm glass slide.

[0082] (2) Under a stereo microscope, a thin copper wire with PMMA attached to it was used to contact one end of the selected ZnO microwire so that it adhered to a glass slide and the other end was free.

[0083] (3) Under a stereo microscope, the tip of a tungsten steel probe with a diameter of 1 μm was used to contact the unfixed end of the ZnO microwire, and stress was applied to push the ZnO microwire to make it bend to a certain extent. Then, an appropriate amount of PMMA was applied to fix the free end of the ZnO microwire.

[0084] (4) The strain value at the position where the maximum strain occurs in the ZnO micron wire is calculated by the formula to be 0.039%.

[0085] (5) The quartz substrate with the bent ZnO microwire fixed was placed on the sample stage of the magnetron sputtering instrument, and then the surfaces of the bent ZnO microwire and the substrate were modified with metallic silver nanoparticles (Ag NPs) with controllable morphology, size and uniform density distribution. The sputtering power was 80 W and the chamber pressure was 5×10 -3 Pa, the sputtering time was 60s, and a piezoelectrically enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate was obtained.

[0086] Among the above embodiments, embodiment 1 is the best embodiment.

[0087] Comparative Example 1

[0088] The remaining steps of this comparative example are the same as those of Example 1, except that the measurement position is changed to point 6. Fig.12 As shown, the results show that the 1364cm -1 The signal intensity of the Raman characteristic peak is 4947, which is reduced to half of the signal intensity collected at point 3. This phenomenon can be attributed to the fact that point 6 is in a strain-free state, so it lacks the enhancement of the piezoelectric effect compared to point 3.

[0089] Comparative Example 2

[0090] The remaining steps of this comparative example are the same as those of Example 1, except that the measurement position is changed to point 7. Fig.12 As shown, the results show that the 1364cm -1 The signal intensity of the Raman characteristic peak is 706, which is reduced to one seventh of the signal intensity collected at point 6. This phenomenon can be attributed to the fact that point 7 only introduces the plasmon resonance effect of Ag NPs.

Claims

1. A piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate, characterized in that: The invention comprises a substrate and a composite micron wire. The composite micron wire is bent and two ends of the composite micron wire are fixed on the substrate. The composite micron wire is a ZnO micron wire with silver nanoparticles sputtered on the surface.

2. The piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate according to claim 1, characterized in that: The ZnO micron wire has good crystal quality, a perfect whispering gallery cavity structure, and a diameter of 2 to 6 μm.

3. The piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate according to claim 1, characterized in that: The substrate is a quartz glass substrate, a glass slide or a silicon wafer.

4. A method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate, characterized in that: The following steps are involved: Step 1: Select ZnO micron wires with good crystal quality and perfect whispering gallery cavity structure; Step 2, placing the ZnO microwires selected in step 1 on a clean substrate; Step 3, after applying mechanical stress to bend the ZnO micron wire, two ends of the ZnO micron wire are fixed on the substrate; Step 4: placing the product obtained in step 3 on a sample stage of a magnetron sputtering instrument, and sputtering silver nanoparticles on the surface of the ZnO micron wires to obtain a piezoelectrically enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate.

5. The method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate according to claim 4, characterized in that: In the step 1, the selection is performed using pointed tweezers under an optical microscope.

6. The method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate according to claim 4, characterized in that: In the step 1, the diameter of the ZnO micron wire is 2-6 μm.

7. The method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate according to claim 4, characterized in that: In the step three, the mechanical stress is applied by a tungsten steel probe, and the angle between the tungsten steel probe and the desktop is 30 to 45 degrees.

8. The method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate according to claim 4, characterized in that: In the step 3, the strain of the ZnO micron wire bending is 0.018% to 0.232%.

9. The method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate according to claim 4, characterized in that: In the step three, the fixing is performed by contacting the two ends of the ZnO micrometer wire with a thin copper wire dipped in PMMA under a microscope to make it adhere to the substrate.

10. The method for preparing a piezoelectric enhanced zinc oxide-silver composite microcavity structure surface enhanced Raman substrate according to claim 4, characterized in that: In step 4, the specific steps of sputtering are: adjusting the target position to the metal silver target, evacuating the sample chamber, introducing argon gas to adjust the pressure in the chamber to 5×10 -3 Pa or less, and then set the sputtering time to 5 to 60 s and the sputtering power to 70 to 80 W for sputtering.

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