A highly sensitive surface-enhanced Raman scattering substrate and a preparation method thereof

Abstract

The present invention discloses a highly sensitive surface enhanced Raman scattering substrate and a preparation method thereof, belonging to the technical fields of functional nanomaterials and analytical detection. The present invention uses a closely packed monolayer of nanospheres as a template, introduces centrifugal potential energy to metal atoms during the deposition process. Under the influence of the centrifugal potential energy, the metal atoms will change their subsequent growth state by changing their nucleation density on the substrate, and under the action of the centrifugal potential energy, the subsequently deposited metal atoms will spontaneously form a gold nanostructure with a gap of less than 5 nm. Using the periodic gap nanostructure prepared by the method of the present invention, as a surface enhanced Raman scattering substrate, the gain for common detection markers reaches 7.9×10 9 , and the lowest detectable concentration limit can reach 10 ‑12 M, reaching the detection level of single molecules, which has important value for the application of surface enhanced Raman scattering substrates in molecular detection technologies such as biopharmaceuticals and clinical medicine that require single molecule levels.

Description

Technical Field

[0001] The present invention belongs to the technical fields of functional nanomaterials and analytical detection, and more specifically, relates to a highly sensitive surface-enhanced Raman scattering substrate and a preparation method thereof. Background Art

[0002] Because the excitation light of Raman scattering spectroscopy is visible light to near-infrared light, it not only has the characteristics of fast detection speed and little influence on the activity of biomolecules, but also can achieve rapid detection in various complex environments, especially in the cellular environment. More importantly, because Raman spectroscopy identifies the "fingerprint" mode of the vibration of the detected molecule, it has extremely strong molecular specificity, showing great advantages in the detection of biological samples and providing the possibility for the combined detection of multiple cancer markers. However, the Raman scattering signal is weak and the sensitivity is low, and the limit concentration for detecting biomolecules is only 10 -1 -10 -2 mol / L, while the content of early cancer markers in blood is much lower than the Raman detection limit, severely limiting its clinical application in the detection of early cancer markers. In recent years, in order to solve the problem of weak Raman scattering signal, surface-enhanced Raman scattering (SERS) technology has developed rapidly. By combining the excellent molecular specificity of Raman scattering spectroscopy with the optical properties of local surface plasmon resonance (LSPR) nanostructures, ultra-high-sensitivity Raman detection has been achieved. Using SERS technology, the limit detection level of biomolecules can even reach the single-molecule level. It has not only become a research hotspot for new detection technologies of biomolecules, but also shown great application potential in medical clinical detection.

[0003] The gain of the SERS signal depends on the nanostructure that enhances its signal. In order to detect low-concentration markers, the prepared SERS substrate needs to have high gain, which requires the preparation of optical coupling nanostructures with a gap size less than 5 nm to generate a high-intensity local electromagnetic field to form "hot spots". However, in the actual application process, the SERS substrate needs to generate reliable and reproducible Raman signals at the same time. Traditional methods for assembling nano-gap junctions rely on chemical synthesis processes, such as the aggregation of silver particles in solution. The maximum enhancement of silver nanoparticles in the "hot spot" region can reach nearly 10 12 , but the chemical instability and irreproducibility of this method seriously hinder its applicability in the actual application process. Some alternative SERS substrates, such as two-dimensional materials based on chemical enhancement mechanisms, can perform Raman enhancement through charge transfer between the substrate and the detected substance, which solves the problems of signal reproducibility and instability to a certain extent. Unfortunately, the enhancement of CM is only on the order of 10 2 -10 3 magnitude, seriously affecting its detection sensitivity as a Raman scattering substrate.

[0004] Fabricating a periodic array of metal nanostructures with a gap size less than 5 nanometers provides a solution to the above problems because each nanostructure unit in the long-range ordered nanoarray has the same "hot spot", while ensuring high gain and uniformity of the substrate. By controlling the size, shape, and surface topography of the designed nanostructures to adjust the plasmon resonance, the fabricated "hot spot" structures can meet the application requirements of different needs. Combining electron beam lithography or focused ion beam technology with metal deposition and etching is very advantageous in fabricating controllable metal structures. However, limited by its low resolution and high manufacturing process cost during the fabrication process, it is extremely difficult and costly to fabricate a large-area SERS substrate with a gap size less than 10 nm using this method. Therefore, it is difficult to meet the industrial production requirements for SERS substrates with both high gain and uniform and stable characteristics. Summary of the Invention

[0005] In view of the above defects or improvement requirements of the prior art, the present invention provides a highly sensitive surface-enhanced Raman scattering substrate and a preparation method thereof, aiming to solve the technical problem that it is difficult to fabricate a Raman scattering substrate that simultaneously satisfies high uniformity and high gain by the existing nanostructure preparation technology.

[0006] To achieve the above object, the present invention provides a highly sensitive surface-enhanced Raman scattering substrate, on which a long-range ordered periodic nanostructure is distributed, and each nanostructure unit has a nano-gap capable of generating a Raman gain exceeding 10 9 The average size of the nano-gap is less than 5 nm.

[0007] The present invention also provides a preparation method of the above highly sensitive surface-enhanced Raman scattering substrate, including:

[0008] S1. Evaporating and depositing a metal atom film on a substrate covered with a monolayer of closely packed nano-sphere array, and keeping the substrate rotating at a constant angular velocity during the film deposition process;

[0009] S2. Stripping the nano-sphere array from the coated substrate to obtain a surface-enhanced Raman scattering substrate.

[0010] Preferably, the rotation speed of the substrate during the film deposition process is 12° / s - 300° / s.

[0011] Preferably, the evaporation rate of the metal atoms during the film deposition process is 0.01 nm - 0.5 nm.

[0012] Preferably, the diameter of the nano-spheres is 350 nm.

[0013] Preferably, before step S1, the method further includes: preparing a monolayer of closely packed nano - microsphere arrays on a silicon wafer and transferring the nano - microsphere arrays onto a glass substrate.

[0014] Preferably, transferring the nano - microsphere arrays onto a glass substrate specifically includes:

[0015] Placing the glass substrate obliquely below the liquid surface in a container filled with deionized water;

[0016] Inserting the silicon wafer covered with a monolayer of closely packed nano - microsphere arrays into the deionized water and dropping 5 μl of a 1% sodium dodecyl sulfate solution into the deionized water;

[0017] Lowering the liquid level of the deionized water in the container so that the nano - microspheres fall onto the glass substrate.

[0018] Preferably, a monolayer of closely packed nano - microsphere arrays is prepared by the air - water interface method.

[0019] Generally speaking, compared with the prior art, the above - mentioned technical solution conceived by the present invention can achieve the following beneficial effects.

[0020] The present invention uses closely packed monolayer polystyrene nano - microspheres as templates. During the evaporation process, by rotating the fixture, centrifugal potential energy is introduced to the metal atoms during deposition. Under the influence of the centrifugal potential energy, the metal atoms will change the subsequent growth state by changing their nucleation density on the substrate. And under the action of the centrifugal potential energy, the subsequently deposited metal atoms will spontaneously form a gold nanostructure with a gap of less than 5 nm. After template stripping, this structure has a long - range ordered periodic arrangement. Each individual metal nanostructure in the periodic array has exposed nano - gaps that can effectively adsorb analyte molecules, and the analyte molecules can be distributed in the high - gain "hot spot" regions with a higher probability.

[0021] Using the method of the present invention, a long - range ordered periodic gap nanostructure is successfully prepared. As a surface - enhanced Raman scattering substrate, its gain for common detection markers reaches 7.9×10 9 , and the lowest detectable concentration can reach 10 -12 M, reaching the detection level of single - molecule level. This has important value for the application of surface - enhanced Raman scattering substrates in molecular detection technologies such as biopharmaceuticals and clinical medicine that require single - molecule level. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flowchart of a method for preparing a high - sensitivity surface - enhanced Raman scattering substrate provided by the present invention;

[0023] Figure 2It is a characterization diagram of the microscopic surface morphology of the surface-enhanced Raman scattering substrate provided in Embodiments 1-3 of the present invention, where (a)-(c) respectively represent the SEM images of the nanoarrays obtained in Embodiments 1-3 at different rotational angular velocities. The inset is an enlarged view of a single structure, and (d)-(f) in the figure are the statistical distribution histograms of the gap sizes in the nanostructures;

[0024] Figure 3 It is the SEM image of the microscopic surface morphology of the surface-enhanced Raman scattering substrate provided in Comparative Examples 1-3 of the present invention, where (a)-(c) respectively represent the triangular prism nanostructure arrays formed in Comparative Examples 1-3 at different evaporation rates. The inset is an enlarged view of its morphology;

[0025] Figure 4 It is the atomic force microscope test diagram of Embodiment 1 of the present invention and Comparative Example 2 and the schematic diagram of its side undulation. Among them, Figure (a) is the triangular prism structure of Comparative Example 2 and its side height distribution diagram, and Figure (b) is the gap structure diagram of Embodiment 1 and its side height distribution diagram;

[0026] Figure 5 It is the optical characterization and Raman enhancement spectrum diagram of the gap nanostructure surface-enhanced Raman scattering substrate provided in Embodiments 1-3 of the present invention. Among them, the detected substance is R6G, and its concentration is 10 -5 , and the laser wavelength used is 532 nm; Figure 5 Among them, (a)-(c) are the optical absorption spectra of Embodiments 1-3, Figure 5 Among them, (d) is the Raman enhancement spectrum of the nanostructures obtained in Embodiments 1-3 at different rotational angular velocities, where the glass slide is used as a comparison to calculate the gain; Figure 5 Among them, (e) is the Raman peak intensity and the corresponding Raman gain of R6G at the main modes 613 cm -1 and 1650 cm -1 ;

[0027] Figure 6 It is the optical characterization and Raman enhancement spectrum diagram of the triangular prism nanostructures in Comparative Examples 1-3 of the present invention, Figure 6 Among them, (a)-(c) are the optical absorption spectra of Comparative Examples 1-3, Figure 6 Among them, (d) is the Raman enhancement spectrum of the triangular prism nanostructures obtained in Comparative Examples 1-3 at different evaporation rates, Figure 6 Among them, (e) is the Raman gain factor of different vibration modes obtained by calculating the Raman peak intensity in (d) of Figure 6 ; Detailed implementation manners

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] Referring to Figure 1 , a method for preparing a highly sensitive surface-enhanced Raman scattering substrate provided by the present invention includes:

[0030] S1. Evaporating and depositing a metal atom film on a substrate covered with a monolayer of closely packed nano-microsphere arrays, and keeping the substrate rotating at a constant angular velocity during the film deposition process;

[0031] Specifically, in the embodiment of the present invention, the air-water interface method is used to first prepare a closely packed nano-microsphere array on a silicon wafer, and then transfer the nano-microsphere array from the silicon wafer to a glass substrate; compared with various other methods for preparing closely packed single-layer nano-sphere arrays such as drop coating, dip coating, spin coating, electrophoretic deposition, etc., the air-water interface method is easier to obtain a closely packed high-quality template in preparing a single-layer nano-sphere template because it uses the surface tension and capillary force of the air-water interface as the growth driving force. More importantly, this method has an irreplaceable advantage in large-area preparation. Combining the transfer technology of the template on the liquid surface can further improve the quality of the nano-array prepared by the air-water interface method, and the required array template can be transferred to any substrate.

[0032] The detailed process of preparing the nano-microsphere array is as follows: First, the silicon wafer is hydrophilized, that is, concentrated sulfuric acid and hydrogen peroxide are mixed at a volume ratio of 3:1, and then the silicon wafer ultrasonically treated with deionized water is placed in the mixture and heated on a heating plate at 80°C for 1 hour. 100 μl - 400 μl of deionized water is dropped on the hydrophilized substrate to form an air-water interface. Subsequently, the polystyrene microsphere solution and alcohol are mixed at a ratio of 1:1, and the mixed solution is dropped on the air-water interface, and the polystyrene microspheres will spontaneously form a closely packed array.

[0033] The specific process of transferring the nano-microsphere array is as follows: The glass substrate is placed below the liquid surface in a container filled with deionized water, the silicon wafer with the formed closely packed nano-microsphere array is inserted into the deionized water, and 5 μl of a 1% sodium dodecyl sulfate solution is dropped into the deionized water. The closely packed single-layer polystyrene nano-microsphere array will first be transferred from the silicon wafer to the deionized water interface, and then by lowering the liquid level of the deionized water in the container, the polystyrene nano-microspheres will fall on the glass substrate.

[0034] Next, during the metal coating process, the rotation speed of the substrate is set to 12° / s - 300° / s. Due to the influence of the centrifugal potential energy in the rotating coordinate system, the nucleation density of metal atoms during the nucleation process on the substrate surface will change, thus changing the subsequent crystallization state of metal atoms. Eventually, the prepared nanostructures will spontaneously transform from the originally directly formed triangular prisms into island-like structures with a larger lateral area and a lower longitudinal height. Gaps will form between the islands, and these gaps are affected by the nucleation density, that is, the rotation speed of the substrate set in the experiment. During the coating process, the evaporation rate of metal atoms is 0.01nm - 0.5nm, and the diameter of the nanospheres is 350nm. The diameter of the nanospheres determines the lateral area of each unit of the prepared metal nanostructures. For different excitation lights, different polystyrene nanospheres can be selected to regulate the size of the units to form resonances for different excitation lights;

[0035] S2. Peel the nanosphere array from the coated substrate to obtain a surface-enhanced Raman scattering substrate. The surface-enhanced Raman scattering substrate is distributed with a periodic nanostructure array, and each nanostructure has a nano-gap with an average width of less than 5nm.

[0036] Specifically, place a glass substrate with a monolayer of closely packed polystyrene nanospheres in a metal evaporation coating instrument. By rotating the fixture that holds the glass substrate, the metal atoms are in a rotating coordinate system during the evaporation coating process. The evaporated gold atoms spontaneously form nano-gaps with a size of about 3 - 5nm due to the influence of the centrifugal potential energy, and a gain factor as high as 1.56×10 10 can be achieved for the commonly used rhodamine 6G marker, and the detection limit of the solution concentration can reach 10 -12 M, with the ability to detect at the single-molecule level.

[0037] To verify the effectiveness of the method of the present invention, the following examples are provided

[0038] Example 1

[0039] (1) Preparation and transfer of the monolayer nanosphere template:

[0040] Drop 100ul - 400ul of deionized water on the substrate that has been hydrophilized to form an air-water interface. Subsequently, mix the polystyrene microsphere solution and alcohol in a ratio of 1:1, and drop the mixed solution on the air-water interface. The polystyrene microspheres will spontaneously form a closely packed monolayer template. Insert a silicon wafer into a container filled with deionized water, place the glass substrate at the bottom of the container, and transfer the monolayer nanosphere template to the glass substrate by lowering the liquid level.

[0041] (2) Preparation of the nano-gap array structure under rotating evaporation coating conditions:

[0042] A glass substrate with closely packed polystyrene nanospheres was placed in a resistive evaporation coater for the deposition of a gold film. During the deposition process, the vacuum degree of the chamber was maintained at 1×10 -4 Torr, the evaporation rate was 0.1 nm / s, and the rotational angular velocity of the substrate was 12° / s. After evaporation, the obtained substrate was placed in toluene solution and left standing for 10 min. The obtained nanostructure is an array structure with nanogaps, which can achieve a high-sensitivity surface Raman scattering enhancement effect. The experimental results are as Figure 2 shown in (a) therein. It can be seen that the entire substrate has a long-range ordered periodic metal nanostructure array, and each nanostructure in the array is an island structure. The statistical distribution of its nanogaps is as Figure 2 shown in (d) therein, and its average size is 4.26 nm.

[0043] Example 2

[0044] (1) Prepared with the same method as in (1) of Example 1 to obtain a polystyrene monolayer template and transferred it to a glass substrate;

[0045] (2) Rotational deposition of gold film:

[0046] A glass substrate with closely packed polystyrene nanospheres was placed in a resistive evaporation coater for the deposition of a gold film. During the deposition process, the vacuum degree of the chamber was maintained at 1×10 -4 Torr, the evaporation rate was 0.1 nm / s, and the rotational angular velocity of the substrate was 60° / s. After evaporation, the obtained substrate was placed in toluene solution and left standing for 10 min. The experimental results are as Figure 2 shown in (b) therein. It can be seen that the periodic arrangement of Example 2 is exactly the same as that of Example 1. The difference is that the self-growth of a single nanostructure has a change of dense growth due to different rotation speeds. Its nanogap is Figure 2 shown in (e) therein and is 4.424 nm, which is increased compared with Example 1.

[0047] Example 3

[0048] (1) Prepared with the same method as in (1) of Example 1 to obtain a polystyrene monolayer template and transferred it to a glass substrate;

[0049] (2) Rotational deposition of gold film:

[0050] A glass substrate with closely packed polystyrene nanospheres was placed in a resistive evaporation coater for the deposition of a gold film. During the deposition process, the vacuum degree of the chamber was maintained at 1×10 -4Torr, the evaporation rate is 0.1nm / s, and the rotation angular velocity of the substrate is 300° / s. After the evaporation is completed, the obtained substrate is placed in a toluene solution and allowed to stand for 10 minutes. The experimental results are as follows Figure 2 As shown in (c), it can be seen that Example 3 has the same periodic arrangement as Example 1, but the nano-gaps in a single structure are reduced. This is due to the denser core density causing the island structure to be swallowed up during the growth process. Compared with Example 2, the gap size is almost the same. Figure 2 The statistical gap data in (f) show that the average gap size is about 4.416.

[0051] After the substrate is rotated, a gap nanostructure completely different from the triangular prism nanostructure obtained by traditional direct evaporation is obtained. Figure 4 From the height distribution and morphology obtained by atomic force microscopy, it can be seen that the metal atoms in the rotating coordinate system change the nucleation density under the action of centrifugal potential energy, so in the subsequent growth process, the traditional triangular prism will be transformed into a nanostructure with gaps, and the total height will be changed from 60nm, which is almost the same as the deposition amount, to 10nm, which means that the longitudinal growth of low-density nucleation has been transformed into the lateral growth of high-density nucleation. In order to verify that the multi-slit structure has stronger gain under rotary evaporation, the following comparative example is set to supplement its improvement of Raman gain performance.

[0052] Comparative Example 1

[0053] (1) preparing a template with a single polystyrene layer by the same method as in Example 1 (1) and transferring the template to a glass substrate;

[0054] (2) Spin deposition of gold film:

[0055] The glass substrate with densely packed polystyrene nanospheres was placed in a resistive evaporation coating apparatus for deposition of gold thin film. During the deposition process, the vacuum degree of the chamber was maintained at 1×10 -4 Torr, the evaporation rate is 0.01nm / s, and the rotation angular velocity of the substrate is 0° / s. After the evaporation is completed, the obtained substrate is placed in the toluene solution and allowed to stand for 10 minutes. The experimental results are as follows Figure 3 As shown in (a), it can be seen that the nanostructure is a triangular prism, and at a lower evaporation rate, the nucleation density is denser, the triangle size is smaller, and there are fewer particles dispersed around it.

[0056] Comparative Example 2

[0057] (1) preparing a template with a single polystyrene layer by the same method as in Example 1 (1) and transferring the template to a glass substrate;

[0058] (2) Spin deposition of gold film:

[0059] A glass substrate with closely packed polystyrene nanospheres was placed in a resistive evaporation coater for the deposition of a gold film. During the deposition process, the vacuum degree of the chamber was maintained at 1×10 -4 Torr, the evaporation rate was 0.1 nm / s, and the rotational angular velocity of the substrate was 0° / s. After evaporation, the obtained substrate was placed in toluene solution and allowed to stand for 10 min. The experimental results are as shown in Figure 3 (b) below. It can be seen that after increasing the evaporation rate, the size of the triangular prism of the formed nanostructure further increases, indicating that the nucleation density decreases at a high evaporation rate. The number of individual metal particles dispersed around also increases.

[0060] Comparative Example 3

[0061] (1) Prepared with a polystyrene monolayer template in the same method as in (1) of Example 1 and transferred to a glass substrate;

[0062] (2) Rotational deposition of a gold film:

[0063] A glass substrate with closely packed polystyrene nanospheres was placed in a resistive evaporation coater for the deposition of a gold film. During the deposition process, the vacuum degree of the chamber was maintained at 1×10 -4 Torr, the evaporation rate was 0.5 nm / s, and the rotational angular velocity of the substrate was 0° / s. After evaporation, the obtained substrate was placed in toluene solution and allowed to stand for 10 min. The experimental results are as shown in Figure 3 (c) below. It can be seen that when a certain evaporation rate is reached, the size of the formed triangular prism structure remains almost unchanged, but the number of individual particles scattered around will still increase.

[0064] Table 1 Main performance parameters of the samples

[0065]

[0066]

[0067] According to the main performance parameters and Figure 2-5 it can be known that the high-sensitivity surface-enhanced Raman scattering substrate of the present invention mainly has the following characteristics:

[0068] (1) Through comprehensive analysis Figure 2 、 Figure 3 it is known that after introducing rotational evaporation coating, the nanostructure array will form a nanostructure with gaps, and its total structural area increases, providing more "hot spots" for Raman scattering enhancement, and the Raman enhancement generated by the optical coupling of the nanogaps greatly increases its gain factor.

[0069] (2) Figure 4Figures (a)-(b) are the atomic force microscope surface topography and side undulation data diagrams provided by Example 1 of the present invention and Comparative Example 2. Analysis Figure 4 It can be seen that after introducing the rotary evaporation process, the prepared nanostructured substrate will change from the original triangular prism nanostructure without the rotation condition to a nanostructure with multiple gaps, and its height changes from 60 nm, which was originally equal to the deposition amount, to 10 nm. This structure has both nanogaps and a relatively low thickness, which can greatly increase the probability of detecting molecules adsorbed at the "hot spot" positions, thus being more conducive to its single-molecule detection. On the other hand, the reduction in thickness will weaken the non-uniform electromagnetic field gain in the longitudinal direction, further improving the uniformity and reproducibility of the substrate.

[0070] (3) Figure 5 Figures (a)-(e) in Figure 6 Figures (a)-(e) are the SERS enhanced Raman spectra of the surface-enhanced Raman scattering substrate for the common Raman marker R6G and the optical absorption spectra of the plasmon resonance caused by light excitation of its nanostructure provided by Example 1-Example 3 of the present invention and Comparative Example 1-Comparative Example 3. Comprehensive analysis Figure 5 、 Figure 6 shows that the local surface plasmon resonance generated by the nanogap structure and the traditional triangular prism nanostructure under light excitation is different. As shown in Figures (a)-(c) in Figure 5 , the optical absorption spectrum generated by the nanogap structure shows the resonance peak splitting phenomenon due to optical coupling, indicating that light is more strongly coupled in the nanogap structure, while Figure 6 Figures (a)-(c) in are traditional single-peak resonances. The corresponding Raman gain data shows that the nanogap structure will have stronger gain. Compared with the periodic array structure formed without rotary evaporation, its gain factor is enhanced by an order of magnitude, and the highest can reach 7.9×10 9 .

[0071] It is easy for those skilled in the art to understand that the above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a high-sensitivity surface-enhanced Raman scattering substrate, characterized in that, Including: S1. Evaporate and deposit a metal atom coating on a substrate covered with a monolayer of closely packed nano - microsphere arrays, and keep the substrate rotating at a constant angular velocity during the coating process; the rotation speed of the substrate during the coating process is 12° / s - 300° / s; the evaporation speed of metal atoms during the coating process is 0.01nm - 0.5nm; the diameter of the nano - microspheres is 350nm; S2. Peel the nano-microsphere array from the coated substrate to obtain a highly sensitive surface-enhanced Raman scattering substrate; wherein, the surface-enhanced Raman scattering substrate is distributed with long-range ordered periodic nanostructures, and each nanostructure unit has a nano-gap capable of generating more than 10 9 Raman gain, and the average size of the nano-gap is less than 5 nm.

2. The preparation method according to claim 1, characterized in that, Before step S1, the method further includes: preparing a monolayer of closely packed nano - microsphere arrays on a silicon wafer and transferring the nano - microsphere arrays to a glass substrate.

3. The preparation method according to claim 2, characterized in that, Transferring the nano - microsphere arrays to the glass substrate specifically includes: Placing the glass substrate obliquely below the liquid level in a container filled with deionized water; Inserting the silicon wafer covered with a monolayer of closely packed nano - microsphere arrays into the deionized water and dropping 5ul of a 1% sodium dodecyl sulfate solution into the deionized water; Lowering the liquid level of the deionized water in the container so that the nano - microspheres fall onto the glass substrate.

4. The preparation method of a highly sensitive surface-enhanced Raman scattering substrate according to claim 2, wherein Preparing a monolayer of closely packed nano - microsphere arrays by the air - water interface method.

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