A method for preparing a wettable multi-level nanoarray structure SERS substrate

Abstract

The invention discloses a preparation method of a wettable multi-level nano-array structure SERS substrate, which belongs to the field of micro-nano processing, surface interface regulation and electrochemical synthesis cross technology. The method comprises the following steps: firstly, a gas-liquid interface self-assembly method is used on a silicon oxide wafer in combination with a reactive ion etching process to obtain a regular and non-densely packed PS ball mask; then, silicon oxide and silicon are sequentially etched to obtain a large-area silicon column structure; and a metal film is coated on the surface of the obtained silicon column structure, and the substrate is immersed in a thiol molecule solution for hydrophobicity regulation; finally, a pine-branch-shaped Au nano-array structure is prepared on the hydrophobic silicon substrate by an electrochemical deposition technology, so as to obtain a SERS substrate with flexible and adjustable nano-array structure gap, large area, low cost, high repeatability, large active heat enrichment and high sensitivity.

Description

Technical Field

[0001] The invention belongs to the cross-technical field of micro-nano processing, surface interface regulation and electrochemical synthesis, and in particular relates to a method for preparing a wettable multi-level nano-array structure SERS substrate. Background Art

[0002] The surface enhanced Raman scattering effect (SERS) was discovered in the mid-1970s. This effect causes the Raman signal of molecules adsorbed on a SERS-active metal surface to be up to 10 times larger than the Raman signal of the same number of molecules in solution. 6 The huge enhancement of 100 times makes SERS technology have extremely high detection sensitivity and selectivity for surface species, and can capture the "fingerprint" information of various substances on the interface at the molecular level. With its advantages, SERS has been widely used in research fields such as labeled and label-free detection, materials science, biochemistry, biomedicine, electrochemistry and molecular imaging.

[0003] Through systematic research, it was found that the SERS phenomenon mainly comes from the electromagnetic field enhancement caused by surface plasmon resonance (SPR), and it was found that the SERS activity of the substrate is directly related to the properties, scale and shape of the nanoparticles or nanostructures. This clearly reveals that SERS is not only a combination of surface science and Raman spectroscopy, but also an important part of nanoscience. The rapid development of nanotechnology has led to some major breakthroughs in SERS research. For example, by optimizing the size, shape and aggregation state of silver and gold nanoparticles, SERS enhancement factors of up to 14 orders of magnitude can be obtained.

[0004] Micro-nano manufacturing technology is the main method for processing silicon-based materials in the field of microelectronics. Patterned etching, coating and other process technologies can be used to obtain large-area, uniformly structured and controllable silicon-based array structures. Some micro-nano structure SERS substrates prepared by this method have shown certain application value. For example, patent CN 112499581 A first combines dry and wet etching to obtain an inverted pyramid silicon structure, and then obtains a precious metal pyramid SERS substrate carrying graphene by coating stripping. The substrate shows a relatively excellent SERS effect in the test of methylene blue. Patents CN 108046211 A and CN 111122543 A directly etch silicon cones or rough silicon column structures through one or two PS ball masks, and finally deposit a layer of Au film as a SERS substrate. The preparation process is very simple and convenient, which can reduce the manufacturing cost. However, the hotspot material prepared by this method has a single structure, a low specific surface area, and a fixed number of hotspots, which may be limited to a certain extent in the detection of trace substances. The hydrophilic and hydrophobic properties of the substrate significantly change the distribution state of the liquid on its surface. The hydrophobic substrate can increase the contact angle of the solution on its surface, effectively concentrate and enrich the analyte, and enhance the Raman signal of the molecule to be measured. Patent CN 109358032 A sputtered Au film as an electrode on a nano-level flat insulator, semiconductor, and conductor, and prepared leaf-shaped and needle-shaped Au nanostructures by electrodeposition. Although the structure has a large number of active hotspots, the structural uniformity is not good enough, which may eventually lead to poor repeatability of SERS substrate signal measurement. The repeatability of SERS signals is also a major problem that needs to be solved urgently. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a method for preparing a wettable multi-level nanoarray structure SERS substrate, the method comprising the following steps:

[0006] 1) Using a silicon wafer containing a silicon oxide layer as a substrate, a densely packed single layer of polystyrene (PS) spheres are deposited on the surface of the silicon oxide layer; etching the polystyrene spheres to reduce the diameter of the spheres, thereby obtaining polystyrene nanospheres that are not densely packed with equal spacing;

[0007] 2) using the polystyrene nanospheres as a mask to etch the silicon oxide to form a polystyrene-silicon oxide column array structure;

[0008] 3) Using the polystyrene-silicon oxide pillars as a mask, the silicon wafer is further etched to obtain a primary nanostructure of a silicon oxide pillar-silicon pillar array;

[0009] 4) coating the surface of the primary nanostructure of silicon oxide pillar-silicon pillar array with metal materials and regulating the hydrophobicity by using mercapto-containing molecules;

[0010] 5) Using the material treated in step 4) as the working electrode, an electrochemical workstation is used to electrodeposit a gold nano-pine branch-like secondary nanostructure on the silicon oxide column-silicon column array primary nanostructure to obtain a multi-level nanoarray structure SERS substrate.

[0011] During the magnetron sputtering process of depositing the metal layer, the top position of the primary nanostructure of the silicon oxide column-silicon column array has better conductivity and nucleation sites. Therefore, during the electrodeposition process, nucleation will preferentially form at the top of the column and then grow the Au nanostructure.

[0012] The method adopts a microelectronic micro-nano manufacturing process, obtains silicon oxide columns by etching with a polystyrene nanosphere mask, and obtains a nano silicon column array structure by etching with a polystyrene-silicon oxide column as a mask. The introduction of the silicon oxide column overcomes the influence of the collapse of the polystyrene balls caused by excessive temperature during the etching process on the morphology of the silicon columns.

[0013] A conductive layer is formed by sputtering a metal layer on the silicon oxide column-silicon column array structure and in the gaps between the silicon columns, and the hydrophobicity is adjusted. Then, a pine-branch-shaped Au secondary nanostructure is prepared by an electrochemical deposition method. This greatly increases the specific surface area of ​​the SERS substrate, that is, increases the SERS hotspots, and ultimately obtains a SERS substrate with a large number of hotspot enrichments, uniform and controllable morphology, and high signal repeatability.

[0014] The step 4) controls the hydrophobicity by immersion or drop coating;

[0015] Furthermore, after the hydrophobicity is regulated, the contact angle of the material surface is 90°-120°;

[0016] Furthermore, the mercapto-containing molecules include mercaptosilane or thiol, the solution concentration is 0.01-1 mM, the immersion time is 30-600 s, or the drop amount is 30-100 μL.

[0017] The silicon substrate is a single-sided or double-sided polished wafer with different sizes and oxide layer thickness;

[0018] The sphere size of close-packed monolayer polystyrene (PS) spheres is 200-500nm;

[0019] The diameter of the equally spaced and non-closely packed polystyrene nanospheres is 150-450 nm;

[0020] The height of the silicon oxide pillars is 100-300 nm;

[0021] The height of the silicon pillars is 50-700 nm.

[0022] Furthermore, the total height of the etched silicon oxide column-silicon column is controlled to be 300-1000 nm, and the column gap is controlled to be 10-100 nm.

[0023] Furthermore, the total height of the silicon oxide column-silicon column after etching is controlled at 700nm, and the column gap is controlled at 50nm; the study found that the total height of the silicon oxide column-silicon column and the column gap affect the test performance of the final SERS substrate. Through finite time-domain difference method (FDTD) simulation, the electromagnetic enhancement effect is strongest when the total height of the silicon oxide column-silicon column is controlled at 700nm and the column gap is around 50nm, that is, it has excellent Raman signal amplification capability.

[0024] The preparation method of the densely packed single-layer polystyrene spheres in step 1) is as follows: using a polished silicon oxide wafer as a substrate, using a device with a function of limiting the movement of the silicon wafer and controllable liquid level sinking, sequentially adding water, sodium dodecyl sulfate (SDS), and PS ethanol suspension, and letting it stand, and obtaining densely packed single-layer polystyrene spheres by adjusting the amount of SDS and ethanol added.

[0025] The step 1) is to obtain polystyrene nanospheres with medium spacing and non-tight arrangement by the following steps: using ICP-RIE equipment or a plasma degumming machine, adjusting the oxygen (O2) flow rate, reaction pressure, power, and reaction time to etch the above-obtained tightly arranged PS ball mask layer to obtain polystyrene nanospheres with equal spacing and non-tight arrangement; further, using ICP-RIE etching power of 10-50W, O2 flow rate of 10-60sccm, and etching time of 20-90s; using plasma degumming reaction power of 500-800W, O2 flow rate of 500-900sccm, and etching time of 30-180s.

[0026] Polystyrene balls can react and shrink quickly in an oxygen environment. The morphology retention and uniformity of polystyrene balls during the shrinking process are affected by temperature and power. In order to avoid the collapse of polystyrene balls at high temperatures, the reaction time should be strictly controlled.

[0027] The polystyrene-silicon oxide column array structure in step 2) is obtained by the following steps: using RIE equipment, using polystyrene nanospheres as a mask layer, first introducing CF4 reactive etching gas, and etching by adjusting the reaction pressure, power, reaction gas flow rate, and reaction time to obtain a polystyrene-silicon oxide column array structure;

[0028] Because the required silicon column is relatively long, the reaction needs to be carried out for a long time. Compared with polystyrene, the silicon oxide column has stronger corrosion resistance. Therefore, the silicon is etched with the polystyrene-silicon oxide column array structure as a mask, and then SF6 and O2 reaction etching gas are introduced. The reaction pressure, power, reaction gas flow rate, and reaction time are adjusted to etch to obtain a silicon oxide column-silicon column array primary nanostructure. The introduction of O2 in this step can effectively remove organic matter such as polystyrene that is deposited on the silicon column and other structures during the reaction process and hinders etching.

[0029] Further, the reaction gas used in the etching process of the polystyrene-silicon oxide column array structure is CF4, the gas flow rate is 30-60sccm, the reaction pressure is 0.5-5Pa, the etching power is 100-400W, and the etching time is 180-360s;

[0030] The reaction gases used in the etching process of the silicon oxide column-silicon column array primary nanostructure in step 3) are SF6 and O2, with gas flow rates of 30-80sccm and 5-20sccm respectively, a reaction pressure of 1-10Pa, an etching power of 100-400W, and an etching time of 240-420s.

[0031] The metal-coated silicon pillar substrate structure in step 4) is obtained by the following steps: using thermal evaporation, magnetron sputtering or chemical bonding coupling technology to adjust the metal deposition rate and content to obtain a silicon pillar substrate coated with a dense metal layer;

[0032] Furthermore, during magnetron sputtering deposition of the metal layer, the pressure is 1.5-2Pa, the power is 10-30W, and the time is 10-50s; during thermal evaporation deposition of the metal layer, the current is 100-150A, and the time is 2-10min; and in chemical coupling, the silicon column structure substrate is first amino-ated, and then the gold nanoparticles are coupled.

[0033] The metal coated in step 4) is Au or Pt, and the thickness of the metal film is at least 50 nm.

[0034] The Au pine-branch structure in step 5) is prepared by the following steps: using an electrochemical workstation, with a Pt sheet or a carbon rod as a counter electrode, a saturated calomel or silver-silver chloride electrode as a reference electrode, a hydrophobic silicon column substrate as a working electrode, and a mixed solution of chloroauric acid and potassium nitrate as an electrolyte, and by adjusting the deposition potential, electrolyte concentration, reaction temperature, and electrochemical deposition time, a multi-level nano-array structure SERS substrate with high specific surface area, uniform structure, and controllable structure is obtained;

[0035] Furthermore, the reaction temperature is 20-50°C, and the reaction time is 10-50min.

[0036] An application of a wettable multi-level nano-array structure SERS substrate is to match the multi-level nano-array structure SERS substrate with a Raman spectrometer to analyze and detect pesticide residues, food additives or trace substances for classification and identification of traditional Chinese medicine.

[0037] The beneficial effects of the present invention are:

[0038] 1. The present invention relates to a method for preparing a multi-level nano-array structure SERS substrate with high specific surface area and high repeatability. The present invention adopts a micro-nano manufacturing process and uses a nano-sized mask to overcome the problem of photolithography process accuracy and thus achieves efficient etching of nano-scale silicon pillars. The operation method is simple, the structure size is controllable, and large-area preparation can be achieved. While effectively controlling the manufacturing cost, the high uniformity and consistency of the micro-nano structure can be ensured, thereby solving the problem of SERS signal repeatability.

[0039] 2. The present invention changes the wetting characteristics exhibited by the inherent SERS chip structure by regulating the surface wettability of the SERS chip, enriches the functionality of the SERS chip, strengthens the control degree of the SERS chip over the molecules to be detected, and provides a new research direction and idea for the development of high-sensitivity SERS chips;

[0040] 3. The present invention adopts electrochemical synthesis technology to prepare high specific surface area pine-branch Au nanostructures, which increase the active hot spots of the SERS substrate, thereby improving the detection sensitivity and enhancement factor of the SERS substrate;

[0041] 4. The present invention firstly carried out a preliminary Raman enhanced analysis test on the Raman indicator R6G molecule, demonstrating high sensitivity and uniformity. Based on this, the detection range was expanded to pesticide residues, additives, antibiotics, etc. in food, and a multi-faceted trace substance detection system combining food safety with SERS technology was established, demonstrating significant application innovation. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The process flow chart for preparing SERS substrate with multi-level nano-array structure;

[0043] Figure 2 The SEM image of the multi-level nano-array structure SERS substrate;

[0044] Figure 3 The results of the detection of the sensitivity of the multi-level nano-array structure SERS substrate to R6G molecules;

[0045] Figure 4 This is the detection result of R6G molecular consistency using multi-level nanoarray structure SERS substrate. DETAILED DESCRIPTION

[0046] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0047] A method for preparing a wettable multi-level nanoarray structure SERS substrate, such as Figure 1 As shown, the method comprises the following steps:

[0048] 1) polishing a silicon wafer containing a silicon oxide layer, cleaning it, and then using a gas-liquid interface self-assembly method to deposit a single layer of polystyrene (PS) balls tightly arranged in a hexagonal shape on the silicon oxide surface as a subsequent etching mask; using low-temperature inductively coupled plasma enhanced reactive ion etching (ICP-RIE) or plasma stripping technology to etch the obtained single layer of PS film tightly arranged in a hexagonal shape, and each small ball is uniformly reduced to a specific size, so as to obtain a mask layer of PS nanospheres with equal spacing and non-tight arrangement;

[0049] 2) using reactive ion etching (RIE) technology, the polystyrene nanospheres are used as a mask to etch silicon oxide, forming a large-area orderly arranged polystyrene-silicon oxide column array structure;

[0050] 3) Using the polystyrene-silicon oxide pillars as a mask, the silicon wafer is further etched to obtain a primary nanostructure of a silicon oxide pillar-silicon pillar array;

[0051] 4) using physical methods such as thermal evaporation or magnetron sputtering or chemical methods using metal nanoparticle coupling to coat the surface of the primary nanostructure substrate of the silicon oxide column-silicon column array with a metal material as a conductive layer of the working electrode; modifying dodecyl mercaptan molecules on the treated substrate by an immersion method or a drop coating method to obtain a hydrophobic silicon column structure;

[0052] 5) Then, an electrochemical workstation is used to electrodeposit gold nano-pine branch-like secondary nanostructures on the wettable silicon pillar substrate in step 4), thereby finally obtaining a multi-level nano-array structure SERS substrate that integrates a large number of active hotspots, novel structure, and flexible adjustability.

[0053] Example 1

[0054] 1) Use a 4-inch single-sided polished silicon wafer with a 300nm silicon oxide layer as the substrate, prepare a concentrated H2SO4:H2O2 mixed cleaning solution, immerse the silicon wafer substrate in it, boil it at 120℃ for 2h to remove oil and other pollutants on the surface of the silicon wafer, and finally rinse it with ultrapure water and blow dry it with N2 for later use;

[0055] Place the cleaned silicon wafer in the device mentioned in the work reported by our group (doi:10.1109 / NEMS51815.2021.9451289), add deionized water until the silicon wafer is completely immersed, then add 6mL of 20mM SDS solution along the glass slide and let it stand for 10min, then add 550μL of 300nm diameter PS suspension (volume ratio, alcohol:PS=3:2) to the above solution very slowly along the glass slide with a micro syringe, let it stand for 1h, and finally add water to transfer the PS monolayer film floating on the air-liquid interface to the oxidized silicon wafer, and the sphere size of the densely packed monolayer polystyrene spheres is 300nm;

[0056] The self-assembled and closely arranged PS spheres were etched by ICP-RIE, with an etching power of 20 W, an O2 flow rate of 30 sccm, and an etching time of 40 s. After etching, the size of the PS spheres was reduced to 250 nm to obtain a single-layer mask of non-closely arranged PS nanospheres.

[0057] 2) RIE technology was used to etch silicon oxide with a PS nanosphere mask. The reaction gas used for silicon oxide etching was CF4, the gas flow rate was 40 sccm, the reaction pressure was 1 Pa, the etching power was 300 W, the etching time was 300 s, and the silicon oxide etching depth was 300 nm.

[0058] 3) Then, the silicon is etched using the silicon oxide column as a mask. The reaction gases used for silicon etching are SF6 and O2, with gas flow rates of 60 sccm and 10 sccm respectively, a reaction pressure of 5 Pa, an etching power of 300 W, an etching time of 360 s, and a silicon etching depth of 400 nm.

[0059] 4) using magnetron sputtering technology, under the conditions of pressure of 1.5 Pa, power of 20 W and reaction time of 50 s, a 50 nm thick Au film was deposited on the silicon pillar substrate obtained above; the substrate was immersed in 0.01 mM dodecyl mercaptan solution for 60 s to obtain a wettable silicon pillar structure substrate; the contact angle of the material surface after the hydrophobicity was adjusted was 100°;

[0060] 5) Using the constant potential mode in the Shanghai Chenhua electrochemical workstation, with a Pt sheet as the counter electrode, a saturated calomel electrode as the reference electrode, the hydrophobic 50 nm thick Au film obtained above as the working electrode, the electrolyte was a mixed solution of HAuCl4 and KNO3, wherein the concentration of HAuCl4 was 3 mM and the concentration of KNO3 was 0.1 M, the deposition potential was set to -0.3 V, the electrolyte temperature was 40 ° C, the electrodeposition time was 30 min, and a pine branch-like Au nanoarray structure was obtained. The SEM image of the multi-level nanoarray structure SERS substrate is shown in Figure 2 .

[0061] Using micro-Raman, 10 μL of R6G solution was dropped onto the SERS substrate (5×5 mm) prepared above and dried, and then Raman testing was performed.

[0062] like Figure 3 As shown, based on the SERS substrate prepared above, Raman enhanced detection was performed on R6G molecules with concentrations of 0.001 μg / mL, 0.01 μg / mL, and 0.1 μg / mL. At a higher concentration of 0.1 μg / mL, the R6G molecules were detected at 771 cm -1 、1190cm -1 、1310cm -1 、1358cm-1 、1506cm -1 、1645cm -1 When the concentration of R6G molecules was as low as 0.001 μg / mL, there was still a clear R6G molecular characteristic peak at 1358 cm -1 The SERS substrate has high sensitivity and is expected to be applied in the field of trace rapid detection. R6G molecules with a concentration of 1 μg / mL were added to the above SERS substrate, and then 8 groups of Raman enhancement data of R6G molecules were measured at 8 different points on the same substrate to characterize the repeatability of the SERS substrate. Figure 4 As shown, the relative standard deviation (RSD) obtained by analysis was 2.48%-10.28%, indicating that the SERS substrate has excellent repeatability.

[0063] Example 2

[0064] The preparation method of the wettable multi-level nanoarray structure SERS substrate of Example 2 is the same as that of Example 1, except that: in step 1) of Example 1, the selected silicon oxide thickness is 100nm, and the reaction gas used for silicon oxide etching in step 2) is CF4, the gas flow rate is 40sccm, the reaction pressure is 1Pa, the etching power is 300W, the etching time is 180s, and the silicon oxide etching depth is 100nm; in step 3), the reaction gases used for silicon etching are SF6 and O2, the gas flow rates are 60sccm and 10sccm respectively, the reaction pressure is 5Pa, the etching power is 300W, the etching time is 420s, and the silicon etching depth is 600nm; in step 4), a layer of gold nanoparticles is loaded on the nano silicon column by a chemical coupling method.

Claims

1. A method for preparing a wettable multi-level nanoarray structure SERS substrate, characterized in that: The method comprises the following steps: 1) Using a silicon wafer containing a silicon oxide layer as a substrate, depositing a densely packed single layer of polystyrene spheres on the surface of the silicon oxide layer; etching the polystyrene spheres to reduce the diameter of the spheres, thereby obtaining polystyrene nanospheres that are not densely packed and are equally spaced; 2) using the polystyrene nanospheres as a mask to etch the silicon oxide to form a polystyrene-silicon oxide column array structure; 3) Using the polystyrene-silicon oxide pillars as a mask, the silicon wafer is further etched to obtain a primary nanostructure of a silicon oxide pillar-silicon pillar array; 4) coating the surface of the primary nanostructure of silicon oxide pillar-silicon pillar array with metal materials and regulating the hydrophobicity by using mercapto-containing molecules; 5) using the material treated in step 4) as a working electrode, using an electrochemical workstation to electrodeposit a gold nano-pine branch-like secondary nanostructure on the silicon oxide pillar-silicon pillar array primary nanostructure to obtain a multi-level nanoarray structure SERS substrate; The diameter of the close-packed monolayer polystyrene spheres is 200-500 nm; The diameter of the equally spaced and non-closely packed polystyrene nanospheres is 150-450 nm; The height of the silicon oxide pillars is 100-300 nm; The height of the silicon pillars is 300-1000nm; The total height of the etched silicon oxide column-silicon column is controlled to be 300-1000 nm, and the column gap is controlled to be 10-100 nm.

2. The method for preparing a wettable multi-level nanoarray structure SERS substrate according to claim 1, characterized in that: The step 4) controls the hydrophobicity by immersion or drop coating; Furthermore, after the hydrophobicity is regulated, the contact angle of the material surface is 90°-120°; Furthermore, the mercapto-containing molecules include mercaptosilane or thiol, and the solution concentration is 0.01-1 mM; the immersion time is 30-600 s or the drop coating volume is controlled to be 30 μL-100 μL.

3. The method for preparing a wettable multi-level nanoarray structure SERS substrate according to claim 1, characterized in that: The step 1) is to obtain medium-spaced non-tightly arranged polystyrene nanospheres by the following steps: using ICP-RIE equipment or a plasma degumming machine, adjusting the oxygen flow rate, reaction pressure, power, and reaction time to etch the above-obtained tightly arranged PS ball mask layer to obtain equally spaced non-tightly arranged polystyrene nanospheres; further, using ICP-RIE etching power of 10-50W, O2 flow rate of 10-60sccm, and etching time of 20-90s; using plasma degumming reaction power of 500-800W, O2 flow rate of 500-900sccm, and etching time of 30-180s.

4. The method for preparing a wettable multi-level nanoarray structure SERS substrate according to claim 1, characterized in that: In the step 2), the polystyrene-silicon oxide column array structure is obtained by the following steps: using RIE equipment, taking polystyrene nanospheres as a mask layer, first introducing CF4 reaction etching gas, and etching by adjusting the reaction pressure, power, reaction gas flow rate, and reaction time to obtain the polystyrene-silicon oxide column array structure; further, the reaction gas used in the etching process of the polystyrene-silicon oxide column array structure is CF4, the gas flow rate is 30-60sccm, the reaction pressure is 0.5-5Pa, the etching power is 100-400W, and the etching time is 180-360s; The reaction gases used in the etching process of the silicon oxide column-silicon column array primary nanostructure in step 3) are SF6 and O2, with gas flow rates of 30-80sccm and 5-20sccm respectively, a reaction pressure of 1-10Pa, an etching power of 100-400W, and an etching time of 240-420s.

5. The method for preparing a wettable multi-level nanoarray structure SERS substrate according to claim 1, characterized in that: The metal-coated silicon pillar substrate structure in step 4) is obtained by the following steps: using thermal evaporation, magnetron sputtering or chemical bonding coupling technology to adjust the metal deposition rate and content to obtain a silicon pillar substrate coated with a dense metal layer; Furthermore, during magnetron sputtering deposition of the metal layer, the pressure is 1.5-2Pa, the power is 10-30W, and the time is 10-50s; during thermal evaporation deposition of the metal layer, the current is 100-150A, and the time is 2-10min; and in chemical coupling, the silicon column structure substrate is first amino-ated, and then the gold nanoparticles are coupled.

6. The method for preparing a multi-level nanoarray structure SERS substrate according to claim 1, characterized in that: The metal coated in step 4) is Au or Pt, and the thickness of the metal film is at least 50 nm.

7. The method for preparing a wettable multi-level nanoarray structure SERS substrate according to claim 1, characterized in that: The Au pine-branch structure in step 5) is prepared by the following steps: using an electrochemical workstation, a Pt sheet or a carbon rod as a counter electrode, a saturated calomel or silver-silver chloride electrode as a reference electrode, a hydrophobic silicon column substrate as a working electrode, a mixed solution of chloroauric acid and potassium nitrate as an electrolyte, adjusting the electrochemical deposition temperature to 20-50° C., and the electrochemical deposition time to 10-50 min, to obtain a high specific surface area, uniformly structured and controllable multi-level nanoarray structure SERS substrate.

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