Photonic crystal-plasmon superlattice composite superstructure and preparation method and application thereof

Abstract

The invention discloses a photonic crystal-plasmon superlattice composite superstructure and a preparation method and application thereof, and belongs to the technical field of nanometers.The method comprises the steps that 1, monodisperse silicon dioxide nano colloidal particles are self-assembled in a medium to form liquid colloidal crystals, the surface of a base material is coated with the liquid colloidal crystals, and the liquid colloidal crystals are formed; volatilizing the solvent to form a silicon dioxide photonic crystal three-dimensional array; (2) modifying the gold nanoparticles by using sulfydryl polystyrene and 1, 8-octyldithiol in sequence, and forming a film on a liquid interface, so as to obtain a gold nano superlattice ordered two-dimensional single-layer film; and (3) transferring the gold nano superlattice ordered two-dimensional single-layer film to the silicon dioxide photonic crystal three-dimensional array to prepare the photonic crystal-plasmon superlattice composite superstructure. When the photonic crystal is used as an SERS substrate, the photonic crystal light gap characteristic and the plasmon local plasma near-field coupling characteristic can be fully utilized, the interaction between light and substances is synergistically enhanced, and the Raman enhancement effect is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of surface enhanced Raman scattering spectrum detection elements, and in particular to a photonic crystal-plasmon superlattice composite superstructure and a preparation method and application thereof. Background Art

[0002] Surface-Enhanced Raman Scattering (SERS) is a highly sensitive spectral analysis technique that can detect low or extremely low concentrations of molecules and is widely used in biomedicine, food science and environmental analysis. The SERS effect is mainly achieved through two mechanisms: electromagnetic enhancement (EM) and chemical enhancement (CM), among which the electromagnetic enhancement mechanism is the most important contributor. The electromagnetic enhancement mechanism mainly originates from the localized surface plasmon resonance (LSPR) effect of noble metal nanostructures. When excitation light at a specific wavelength is irradiated on the surface of the noble metal nanostructure, due to the LSPR effect, the light is focused on the edge, tip or gap of the nanomaterial, thereby generating a strong electromagnetic field enhancement, which can further significantly amplify the molecular signals in the field.

[0003] Photonic crystals are a class of materials with periodic dielectric constant distribution and unique optical bandgap characteristics, which can significantly affect the propagation of light. The slow light effect of photonic crystals can significantly extend the propagation path of light in the material, thereby enhancing the interaction between light and matter. Silica photonic crystals have been used in the design of SERS substrates to improve detection sensitivity and selectivity. By combining precious metal nanostructures with photonic crystals, the SERS effect can be further enhanced and the detection sensitivity can be improved.

[0004] For example, the Chinese patent document with publication number CN107132212A discloses a method for preparing a surface enhanced Raman scattering sensor device based on the band edge effect of photonic crystals. The invention uses an amino modification liquid containing 3-aminopropyltriethoxysilane to carry out an amino modification reaction on monodisperse SiO2 microspheres to obtain amino modified SiO2 microspheres; uses sodium citrate reduction method to prepare a gold nanoparticle solution; prepares an amino modified SiO2 microsphere-ethanol suspension, inserts a glass slide vertically into the suspension, and obtains regularly arranged SiO2 opal structure photonic crystals on the glass slide; cyclically drips the gold nanoparticle solution onto the surface of the photonic crystal to obtain a surface enhanced Raman scattering sensor device based on the opal structure photonic crystal. The invention uses the periodic ordered structure of the photonic crystal to achieve an ordered distribution of gold nanoparticles, and the obtained sensor device has high sensitivity.

[0005] The Chinese patent document with publication number CN103257134A discloses a method for preparing a capillary-based surface enhanced Raman scattering substrate, which includes: preparing a three-dimensional porous ordered SiO2 inverse opal structure photonic crystal in the capillary; loading gold nanoparticles in the three-dimensional porous ordered SiO2 inverse opal structure by in-situ reduction or electrostatic adsorption. The invention uses a capillary as a substrate so that the analyte is restricted to flow in the pipeline, increasing its initiative to contact the SERS binding hotspot.

[0006] Although the above invention has combined photonic crystals and noble metal nanostructures for the preparation of SERS substrates, the upper noble metal nanoparticles are mostly disorderly dispersed or stacked structures, and there are problems such as low coupling efficiency between photonic crystals and noble metal nanostructures, and easy loss of structural stability in long-term use, resulting in unsatisfactory SERS enhancement effects. The multi-level ordered array composite structure of plasmon superlattice array and photonic crystal superstructure array has not been reported yet. Summary of the invention

[0007] In order to address the deficiencies in the above-mentioned prior art, the present invention provides a method for preparing a photonic crystal-plasmon superlattice composite superstructure, by effectively coupling a three-dimensional array of silicon dioxide photonic crystals with an ordered two-dimensional monolayer film of a gold nanosuperlattice, and utilizing the synergistic effect of the two to enhance the interaction between light and matter, thereby obtaining better coupling effect and electromagnetic enhancement characteristics, thereby improving SERS performance.

[0008] The specific technical solutions adopted are as follows:

[0009] A method for preparing a photonic crystal-plasmon superlattice composite superstructure comprises:

[0010] (1) self-assembling monodisperse silica nanoparticles with a particle size of 100 to 400 nm in a medium to form liquid colloidal crystals, coating the liquid colloidal crystals on the surface of a substrate, and allowing the solvent to evaporate to form a three-dimensional array of silica photonic crystals;

[0011] (2) preparing gold nanoparticles with a particle size of 10 to 60 nm, modifying the gold nanoparticles with mercapto polystyrene and 1,8-octanedithiol in sequence, and forming a film at the liquid interface to obtain a gold nanosuperlattice ordered two-dimensional monolayer film;

[0012] (3) The ordered two-dimensional monolayer film of the gold nano-superlattice is transferred to the three-dimensional array of silicon dioxide photonic crystals to couple the double-layer ordered structures and prepare the photonic crystal-plasmon superlattice composite superstructure.

[0013] The present invention prepares a multi-level ordered superstructure film by effectively coupling a gold nano superlattice ordered two-dimensional monolayer film with a silicon dioxide photonic crystal three-dimensional array. The gold nano superlattice ordered two-dimensional monolayer film has significant near-field plasmon coupling characteristics compared to monodisperse or disordered gold nanoparticles to enhance the electromagnetic field intensity; further, the reflected light bandgap wavelength of the lower silicon dioxide photonic crystal three-dimensional array is regulated to match the wavelength band edge of the upper superlattice plasmon structure, so that the photonic crystal bandgap characteristics are further coupled with the localized surface plasmon resonance, and the synergistic effect of the two is fully utilized to enhance the interaction between light and matter, thereby obtaining a better coupling effect and electromagnetic enhancement characteristics, and then applied to the SERS substrate to improve the Raman enhancement performance.

[0014] The optical bandgap wavelength of the lower layer of silica photonic crystal three-dimensional array can be adjusted to match the main LSPR peak of the upper layer of gold nanosuperlattice ordered two-dimensional monolayer film. The final composite multi-level ordered superstructure can make full use of the synergistic effect of the two.

[0015] Preferably, in step (1), the monodisperse silica nanoparticles are prepared by a seed growth method; first, tetraethyl silicate is used as a raw material and arginine is used as a catalyst to synthesize silica nanoparticles; then, ammonia water is used in the system to catalyze the hydrolysis reaction of tetraethyl silicate so that the silica nanoparticles are further grown to obtain monodisperse silica nanoparticles. By changing the amount of seeds used, monodisperse silica nanoparticles with different particle sizes can be prepared.

[0016] Specifically, in step (1), the medium includes at least one of ethanol, ethylene glycol, diethylene glycol, propylene carbonate, dimethylformamide, and dimethyl sulfoxide; and the volume fraction of the monodisperse silica nanoparticles in the medium is 15% to 40%.

[0017] The substrate includes, but is not limited to, silicon wafer, glass, polyimide, polyethylene terephthalate, polydimethylsiloxane, ceramic or metal substrate.

[0018] Preferably, the solvent is volatilized by heating to form a three-dimensional array of silicon dioxide photonic crystals, and the heating conditions are 30-100° C. for 1.5-2 hours.

[0019] Preferably, the gold nanoparticles are prepared by a seed growth method, using chloroauric acid, sodium borohydride and cetyltrimethylammonium bromide (CTAB) as raw materials to prepare a nanogold seed solution, and then using the nanogold seed solution, ascorbic acid, cetyltrimethylammonium chloride (CTAC) and chloroauric acid as raw materials to further grow the nanogold seeds to prepare a gold nanoparticle solution.

[0020] Mercaptopolystyrene and 1,8-octanedithiol can be connected to gold nanoparticles through gold-sulfur bonds, thereby grafting and modifying them at the molecular level.

[0021] Preferably, the average molecular weight of mercapto polystyrene PSSH is 5000-20000 g / mol; -6 ~10 -4 mol / L mercapto polystyrene solution reacts with the gold nanoparticle solution to complete the modification of mercapto polystyrene.

[0022] Preferably, the concentration is 5.0×10 -6 ~1.5×10 -5 The 1,8-octanedithiol solution of 3.5 mol / L reacts with the solution of the gold nanoparticles modified with mercapto polystyrene to complete the modification of 1,8-octanedithiol.

[0023] Furthermore, the gold nanoparticles modified with mercaptopolystyrene and 1,8-octanedithiol were dispersed in toluene and then transferred to the diethylene glycol subphase. After the toluene was completely evaporated, a gold nanosuperlattice monolayer was obtained on the diethylene glycol interface.

[0024] The present invention also provides a photonic crystal-plasmon superlattice composite superstructure prepared by the preparation method of the photonic crystal-plasmon superlattice composite superstructure.

[0025] The photonic crystal-plasmon superlattice composite superstructure comprises, from bottom to top, a substrate, a three-dimensional array of silicon dioxide photonic crystals and an ordered two-dimensional single-layer film of gold nano superlattice.

[0026] The present invention also provides a SERS substrate, comprising the photonic crystal-plasmon superlattice composite superstructure. The photonic crystal-plasmon superlattice composite superstructure is applied to the SERS substrate to enhance Raman signals and improve detection sensitivity.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention prepares photonic crystal-plasmon superlattice composite superstructures through simple chemical synthesis and physical deposition methods, without the need for complex equipment and expensive reagents. Traditional composite superstructure preparation methods usually require expensive equipment, such as electron beam lithography (EBL) and focused ion beam etching (FIB). The method of the present invention only requires basic laboratory equipment, which reduces the preparation cost, has low energy consumption, and low equipment requirements. By adjusting the seed dosage and reaction conditions, the particle size of the silica nanoparticles and the photonic crystal optical bandgap wavelength can be accurately controlled, and the superstructure substrate can be customized according to different detection requirements. By regulating the superlattice spacing of the gold nanoparticles, the surface localized plasma resonance effect of the gold nanoparticle superlattice can be accurately controlled, further optimizing the electromagnetic field enhancement effect.

[0029] (2) The slow light effect of the silica photonic crystal significantly prolongs the propagation path of light in the material, enhances the interaction between light and matter, and thus increases the intensity of the SERS signal. The LSPR effect and near-field coupling characteristics of the gold nanoparticle superlattice produce strong electromagnetic field enhancement at specific wavelengths, further improving the sensitivity of the SERS signal. The synergistic enhancement of these two effects enables the multi-level ordered superstructure of the present invention to maximize the interaction between light and matter, thereby increasing the electromagnetic field intensity, and has a significant Raman enhancement effect.

[0030] (3) The preparation method of the present invention has a high degree of controllability and stability, ensuring the repeatability of the SERS substrate between batches and samples, and improving the consistency of the detection results. The gold nano-superlattice ordered two-dimensional monolayer film is fixed on the surface of the three-dimensional array of silicon dioxide photonic crystals by physical transfer, ensuring the structural stability of the SERS substrate, and maintaining good performance even in long-term use. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the preparation of photonic crystal-plasmonic superlattice composite superstructure.

[0032] Figure 2 a is a scanning electron microscope image of the three-dimensional array of silica photonic crystals in Example 1; b is a reflection spectrum of the silica photonic crystals in Example 1, and the inset is a real picture; c is a scanning electron microscope image of the ordered two-dimensional monolayer film of the gold nanosuperlattice in Example 1; d is an absorption spectrum of the ordered two-dimensional monolayer film of the gold nanosuperlattice in Example 1; e is a scanning electron microscope image of the photonic crystal-plasmon superlattice composite superstructure SERS substrate in Example 1.

[0033] Figure 3 a is the reflection spectrum of the silicon dioxide photonic crystal in Example 4, and the inset is the actual picture; b is the reflection spectrum of the photonic crystal-plasmon superlattice composite superstructure SERS substrate in Example 4.

[0034] Figure 4 a in Example 4 is the detection of different SERS substrates 10 -5 M is the Raman spectrum of methylene blue molecule; b is the Raman spectrum at 1622cm -1 Raman intensity histogram at . DETAILED DESCRIPTION

[0035] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the following is a detailed description through specific embodiments. In the following description, many specific details are set forth in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below. The technical features in each embodiment of the present invention can be combined accordingly without conflicting with each other.

[0036] The operating methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. The contents not described in detail in this specification belong to the prior art known to professionals in the field. The experimental materials used in the following examples, unless otherwise specified, can be purchased from conventional biochemical reagent companies.

[0037] In the embodiment, the preparation process flow chart of the photonic crystal-plasmon superlattice composite superstructure is as follows: Figure 1 shown.

[0038] Example 1

[0039] (1) Preparation of monodisperse silica nanoparticles:

[0040] S1: 0.087 g of L-arginine was dissolved in 87 mL of water, and 5.55 mL of tetraethyl silicate was added after stirring for 10 min. The temperature was raised to 70° C. and hydrolyzed for 24 h to obtain a silica nanoparticle solution with a particle size of about 20 nm as a seed solution.

[0041] S2: Take 200 μL of seed solution and add it to 14 mL of water, and then add it to a solution of 200 mL of ethanol and 8 mL of ammonia water. After thorough stirring and mixing, inject 16 mL of tetraethyl silicate at a rate of 4 mL / h using a syringe pump, stir magnetically for 12 hours, and wash it by centrifugation with anhydrous ethanol for 3 times (8000 rpm, 5 min) to finally obtain monodisperse silica nanoparticles with a particle size of 200 nm.

[0042] (2) Assembly of silica photonic crystals:

[0043] The prepared silica nanoparticles were uniformly dispersed in propylene carbonate to induce volatilization and self-assembly to obtain liquid colloidal crystals with a volume fraction of 30%, which were then coated on a silicon wafer substrate and subsequently heated at 60°C for 0.5h to form a three-dimensional array of silica photonic crystals.

[0044] (3) Preparation of gold nanoparticles:

[0045] S1: The newly prepared NaBH4 solution (600 μL, 0.010 mol / L) was quickly injected into a mixed solution of CTAB (9.9 mL, 0.10 mol / L) and HAuCl4 (0.0250 mol / L). After stirring at 300 r / min for 3 h, the reaction mixture was placed in a water bath at 30 °C for 3 h to obtain a nanogold seed solution.

[0046] S2: 500 μL of gold nanoparticle seed solution (gold seeds stabilized with CTAB) was mixed with ascorbic acid AA (15.0 mL, 0.10 mol / L) and CTAC (20.0 mL, 0.20 mol / L), stirred at 600 r / min for 1 min, and then HAuCl4 (20 mL, 0.000050 mol / L) was injected. After continuous stirring for 15 min (300 rpm), 15 mL of the solution after the first growth was collected, initially purified by centrifugation (16000 r / min × 20 min), and the gold nanoparticles were redispersed in CTAC (2.5 mL, 0.020 mol / L) solution.

[0047] S3: CTAC (20 mL, 0.10 mol / L) and gold nanoparticles (750 μL, purified and dispersed in 0.020 mol / L CTAC) were mixed and ultrasonicated for 10 min. The mixture was then stirred in a 30 °C water bath (400 r / min), and then AA (1.3 mL, 0.010 mol / L) was added and stirred for 1 min. Then, HAuCl4 (50 mL, 0.00050 mol / L) was dripped into it at a concentration of 20 mL / h using a syringe pump. Finally, the mixture was stirred at 30 °C for another 5 minutes (400 r / min) and then refrigerated to obtain the final gold nanoparticle solution (containing Au NP@CTAC, the concentration of the gold nanoparticle solution was 7.69×10 -10 mol / L, particle size is 30nm).

[0048] (4) Modification of gold nanoparticles:

[0049] S1: Centrifuge 10 ml of the gold nanoparticle solution obtained in the above step twice to remove excess CTAC. After the second round of centrifugation, reduce the volume of the solution to <100 μL, and then add the concentrated solution dropwise to a vigorously stirred (1000 rpm) THF solution of PSSH ligand (2 ml, 5.0×10 -6mol / L) (the average molecular weight of PSSH is 12000 g / mol, and the molar ratio of PSSH to gold nanoparticles is 1300:1). The resulting mixture was stirred at 300 rpm for at least 24 hours so that PSSH completely replaced CTAC to obtain mercapto polystyrene-modified gold nanoparticles Au NP@PSSH, and the Au NP@PSSH solution was centrifuged, the supernatant was removed, and the volume of the solution was reduced to <100 μL.

[0050] S2: The Au NP@PSSH solution was centrifuged, the supernatant was removed, and the volume of the solution was reduced to <100 μL. Then, the concentrated Au NP@PSSH solution was added dropwise to the 1,8-octanedithiol OCT solution (THF, 2 mL, 1.0 × 10 -5 mol / L) (the molar ratio of 1,8-octanedithiol to gold nanoparticles in Au NP@PSSH is 2600:1). The resulting mixture was further mixed for at least 24 h to allow sufficient interaction between OCT and the residual active sites on the gold nanoparticles to obtain a gold nanoparticle solution modified with mercapto polystyrene and 1,8-octanedithiol dual ligands.

[0051] (5) Preparation of ordered two-dimensional monolayer films of gold nanosuperlattice:

[0052] S1: The dual-ligand modified gold nanoparticle solution was centrifuged three times, the solution was concentrated, and redispersed in 1 mL of toluene under ultrasonic treatment. Then, equal volumes of water and ethanol were added to form a 1:1:1 mixture with the toluene solution, the upper toluene solution was extracted and the washing and extraction process was repeated to obtain Au NP@PSSH@OCT.

[0053] S2: The Au NP@PSSH@OCT in 1 mL of toluene was slowly transferred into a polytetrafluoroethylene test tube (~2 cm inner diameter, maximum volume of 30.0 mL) containing 20 mL of diethylene glycol (DEG). The mouth of the test tube was covered with a glass petri dish to control the evaporation rate of toluene. After the toluene evaporated, an ordered two-dimensional monolayer film of gold nanosuperlattice was formed on the surface of the DEG phase.

[0054] (6) Construction of photonic crystal-plasmon superlattice composite superstructure:

[0055] The prepared gold nano-superlattice ordered two-dimensional monolayer film is transferred to the surface of the three-dimensional array of silicon dioxide photonic crystals in step (2) to couple the double-layer ordered structures and prepare the photonic crystal-plasmon superlattice composite superstructure.

[0056] like Figure 2 As shown in a in Figure 1, the three-dimensional array of silicon dioxide photonic crystals has a long-range ordered structure. Figure 2As shown in b, the optical bandgap of the silica photonic crystal is located at 407nm, and the inset shows that the silica photonic crystal is macroscopically blue. Figure 2 Figure c is a scanning electron microscope image of a gold nanosuperlattice ordered two-dimensional monolayer film, which is assembled from dual-ligand modified gold nanoparticles with a diameter of 30 nm. The gold nanoparticles have uniform particle size and a regular hexagonal close-packed structure, verifying the formation of its superlattice ordered array. Figure 2 Figure d shows the absorption spectrum of the gold nanoparticles with a diameter of 30nm after being assembled into an ordered two-dimensional monolayer of gold nano-superlattice, with an absorption peak at 658nm and an absorbance of 1.003. The prepared photonic crystal-plasmonic superlattice composite superstructure was further characterized. Figure 2 As shown in (e), both the upper layer of gold nanoparticles and the lower layer of silica maintain a highly ordered structure, and the gold nanoparticles are evenly distributed on the surface of the silica photonic crystal array and present a mulberry-like multi-level ordered composite structure.

[0057] Example 2

[0058] The difference between this embodiment and embodiment 1 is that when preparing monodisperse silica nanoparticles, the amount of seed solution added is 150 μL, monodisperse silica nanoparticles with a particle size of 233 nm are prepared, and the silica photonic crystal three-dimensional array is assembled, and the other parameters and conditions are the same as those in embodiment 1. The reflection peak of the prepared silica photonic crystal is located at 487 nm. After compounding with the ordered two-dimensional monolayer film of the gold nanosuperlattice, the photonic crystal-plasmon superlattice composite superstructure can be prepared.

[0059] Example 3

[0060] The difference between this embodiment and embodiment 1 is that when preparing monodisperse silica nanoparticles, the amount of seed solution added is 100 μL, monodisperse silica nanoparticles with a particle size of 255 nm are prepared, and the silica photonic crystal three-dimensional array is assembled, and the other parameters and conditions are the same as those in embodiment 1. The reflection peak of the prepared silica photonic crystal is located at 527 nm. After compounding with the ordered two-dimensional monolayer film of the gold nanosuperlattice, the photonic crystal-plasmon superlattice composite superstructure can be prepared.

[0061] Example 4

[0062] The difference between this embodiment and embodiment 1 is that when preparing monodisperse silica nanoparticles, the amount of seed solution added is 50 μL, monodisperse silica nanoparticles with a particle size of 300 nm are prepared, and the three-dimensional array of silica photonic crystals is obtained by assembling. The other parameters and conditions are the same as those in embodiment 1. The reflection peak of the prepared silica photonic crystals is located at 623 nm. Figure 3 As shown in a in FIG. After being combined with a gold nano superlattice ordered two-dimensional monolayer film, the photonic crystal-plasmon superlattice composite superstructure can be prepared. The reflection spectrum of the composite superstructure is shown in FIG. Figure 3 As shown in b.

[0063] Application Example 1

[0064] The photonic crystal-plasmon superlattice composite superstructure prepared in Example 4 was used as a SERS substrate to verify its Raman enhancement effect. Figure 4 As shown in a, a three-dimensional array of silicon dioxide photonic crystals, an ordered two-dimensional monolayer of gold nano-superlattice, and a composite superstructure of photonic crystal-plasmon superlattice prepared under the same parameter conditions were used as SERS substrates to detect 10 -5 The Raman spectrum of the methylene blue molecule was used to evaluate the SERS enhancement performance of the composite superstructure. The Raman spectrum signal obtained can clearly identify the characteristic peak of the methylene blue molecule (1395cm -1 and 1622cm -1 ). Compared with the single silicon dioxide photonic crystal three-dimensional array substrate and the gold nano-superlattice ordered two-dimensional monolayer film substrate, the Raman signal of the photonic crystal-plasmon superlattice composite superstructure has a significant enhancement. Figure 4 Middle b shows different substrate detection 10 -5 The molecular wavelength of methylene blue is 1622 cm -1 The results show that the Raman intensity of the silicon dioxide photonic crystal three-dimensional array substrate is only 9.67, the Raman characteristic peak intensity of the gold nano-superlattice ordered two-dimensional monolayer film substrate is 4468.41 due to the electromagnetic field enhancement provided by the plasmon nanoparticles, and the Raman intensity of the photonic crystal-plasmon superlattice composite superstructure is as high as 14508.67, which is 3.25 times that of the gold nano-superlattice ordered two-dimensional monolayer film substrate and 1500 times that of the silicon dioxide photonic crystal three-dimensional array substrate. The excellent effect of the photonic crystal-plasmon superlattice composite superstructure in the Raman spectrum enhancement of the present invention is verified.

[0065] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a photonic crystal-plasmon superlattice composite superstructure, characterized in that: include: (1) self-assembling monodisperse silica nanoparticles with a particle size of 100 to 400 nm in a medium to form liquid colloidal crystals, coating the liquid colloidal crystals on the surface of a substrate, and allowing the solvent to evaporate to form a three-dimensional array of silica photonic crystals; (2) preparing gold nanoparticles with a particle size of 10 to 60 nm, modifying the gold nanoparticles with mercapto polystyrene and 1,8-octanedithiol in sequence, and forming a film at the liquid interface to obtain a gold nanosuperlattice ordered two-dimensional monolayer film; (3) The ordered two-dimensional monolayer film of the gold nano-superlattice is transferred to the three-dimensional array of silicon dioxide photonic crystals to couple the double-layer ordered structures and prepare the photonic crystal-plasmon superlattice composite superstructure.

2. The method for preparing a photonic crystal-plasmon superlattice composite superstructure according to claim 1, characterized in that: In step (1), monodisperse silica nanoparticles are prepared by a seed growth method; first, tetraethyl silicate is used as a raw material and arginine is used as a catalyst to synthesize silica nanoseeds; then, ammonia water is used in the system to catalyze the hydrolysis reaction of tetraethyl silicate to further grow the silica nanoseeds to obtain monodisperse silica nanoparticles.

3. The method for preparing a photonic crystal-plasmon superlattice composite superstructure according to claim 1, characterized in that: In step (1), the medium includes at least one of ethanol, ethylene glycol, diethylene glycol, propylene carbonate, dimethylformamide, and dimethyl sulfoxide; and / or the substrate includes a silicon wafer, glass, polyimide, polyethylene terephthalate, polydimethylsiloxane, a ceramic or metal substrate.

4. The method for preparing a photonic crystal-plasmon superlattice composite superstructure according to claim 1, characterized in that: In step (1), the solvent is volatilized by heating to form a three-dimensional array of silicon dioxide photonic crystals, and the heating conditions are 30-100° C. for 1.5-2 hours.

5. The method for preparing a photonic crystal-plasmon superlattice composite superstructure according to claim 1, characterized in that: In step (2), the gold nanoparticles are prepared by a seed growth method; mercapto polystyrene and 1,8-octanedithiol are connected to the gold nanoparticles via gold-sulfur bonds.

6. The method for preparing a photonic crystal-plasmon superlattice composite superstructure according to claim 1, characterized in that: In step (2), The average molecular weight of mercapto polystyrene PSSH is 5000-20000 g / mol; the concentration is 10 -6 ~10 -4 mol / L mercapto polystyrene solution reacts with the gold nanoparticle solution to complete the modification of mercapto polystyrene; and / or, using a concentration of 5.0×10 -6 ~1.5×10 -5 The 1,8-octanedithiol solution of 3.5 mol / L reacts with the solution of the gold nanoparticles modified with mercapto polystyrene to complete the modification of 1,8-octanedithiol.

7. The method for preparing a photonic crystal-plasmon superlattice composite superstructure according to claim 1, characterized in that: In step (2), Gold nanoparticles modified with mercapto polystyrene and 1,8-octanedithiol were dispersed in toluene and then transferred to the diethylene glycol subphase. After the toluene was completely evaporated, an ordered two-dimensional monolayer film of gold nanosuperlattice was obtained on the diethylene glycol interface.

8. A photonic crystal-plasmon superlattice composite superstructure prepared according to the method for preparing a photonic crystal-plasmon superlattice composite superstructure according to any one of claims 1 to 7.

9. The photonic crystal-plasmon superlattice composite superstructure according to claim 8, characterized in that: The structure from bottom to top includes a substrate, a three-dimensional array of silica photonic crystals, and an ordered two-dimensional monolayer film of gold nanosuperlattice.

10. A SERS substrate, characterized in that: It comprises the photonic crystal-plasmon superlattice composite superstructure as described in claim 8 or 9.

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