Preparation method and application of composite SERS (Surface Enhanced Raman Scattering) substrate material
By preparing Ag@Au@COF-999 composite nanowires and wrapping Ag@Au nanowires with COF-999 shells, the problem of poor stability of pure noble metal nanoparticles was solved, and highly selective CO2 gas sensing and portable detection were achieved.
Patent Information
- Application Number
- CN202510744114.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-05
- Publication Date
- 2025-09-12
AI Technical Summary
Pure precious metal nanoparticles have poor stability in practical applications, are prone to agglomeration, and their structure and function are affected by changes in the external environment, which affects their long-term storage and processing.
By preparing Ag@Au@COF-999 composite nanowires, the COF-999 shell was used to wrap the Ag@Au nanowires to form a core-shell structure. The porous structure and functional group characteristics of the COF-999 shell were utilized to improve the stability and uniformity of the nanoparticles and enhance the selective sensing performance of CO2 gas.
The high stability and uniformity of Ag@Au@COF-999 composite nanowires were achieved, the selective sensing performance of CO2 gas was enhanced, the practicality of the material and the accuracy of detection were improved, and it was easy to make a portable SERS film.
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Figure CN120629102A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of nanomaterials, and in particular to a preparation method of a composite SERS substrate material and application thereof. Background Art
[0002] In the field of nanomaterial technology, precious metal materials such as gold (Au) and silver (Ag) have become highly sought-after research objects and application materials due to their unique physical and chemical properties. From a physical perspective, Au and Ag nanoparticles exhibit excellent surface plasmon resonance effects, strongly absorbing and scattering light. This characteristic enables highly sensitive detection in sensing and clear optical signals in imaging. In terms of chemical properties, they possess excellent catalytic activity and chemical stability, serving as carriers for photothermal therapy in cancer treatment, participating in the conversion and storage of optical signals in optical data storage, and efficiently catalyzing a variety of chemical reactions in the catalytic field. Based on these advantages, Au and Ag nanoparticles exhibit extremely broad application prospects in numerous fields, including sensing, imaging, cancer treatment, optical data storage, and catalysis.
[0003] However, pure noble metal nanoparticles face significant challenges in practical applications, with poor stability being a key factor limiting their development. Due to their high surface energy, noble metal nanoparticles tend to agglomerate during long-term storage, leading to performance degradation. During processing, environmental fluctuations such as temperature, humidity, and pH can also cause nanoparticles to oxidize and dissolve, affecting their structure and function. These issues severely restrict the long-term storage, processing, and application of pure noble metal nanoparticles.
[0004] To address the poor stability of pure noble metal nanoparticles, a common approach is to encapsulate them in organic or inorganic shells. This core-shell structure, while providing a degree of isolation from the effects of the external environment, remains a challenge. However, significant limitations remain, and the resulting products exhibit poor stability and uniformity. Summary of the Invention
[0005] This invention aims to provide a method for preparing a composite SERS substrate material and its application. Using a simple and gentle method, we fabricate Ag@Au@COF-999 composite nanowires with adjustable shape and size. With the Ag@Au nanowires as the core, the COF-999 shell is uniformly coated on the surface. The composite nanowires exhibit not only high stability and uniformity but also highly selective CO2 sensing performance. This approach addresses the problems encountered in the prior art.
[0006] In order to achieve the above object, the present invention provides the following technical solutions:
[0007] A method for preparing a composite SERS substrate material comprises the following steps:
[0008] S1. Preparation of Ag@Au nanowires: Synthesizing Ag nanowires and depositing Au nanoparticles on their surfaces to form Ag@Au nanowires;
[0009] S2. Preparation of Ag@Au@COF-999-N3 composite nanowires: Ag@Au nanowires, 1,3,5-tris(4-cyanomethylphenyl)benzene, 3,3′-bis[(6-azidohexyl)oxy]-4,4′-biphenyldicarboxaldehyde, Cs2CO3, 1,2-dichlorobenzene, and 1-butanol were placed in a borosilicate glass tube, and the mixture was rapidly frozen in a liquid nitrogen bath, evacuated, flame-sealed, and dried to obtain a yellow solid. The solid was filtered, washed, and dried to obtain Ag@Au@COF-999-N3 composite nanowires.
[0010] S3. Preparation of Ag@Au@COF-999-NH2 composite nanowires: Ag@Au@COF-999-N3, triphenylphosphine and methanol were added to a container, and the mixture was allowed to stand for reaction. The suspension was filtered and washed with methanol to remove excess PPh3. The yellow residue was transferred to another container, and methanol and water were added. After standing, the mixture was filtered and dried, and vacuum degassed to obtain Ag@Au@COF-999-NH2 composite nanowires.
[0011] S4. Preparation of Ag@Au@COF-999 composite nanowires: COF-999-NH2, toluene, acetic acid, and triphenylphosphine were added to a borosilicate glass tube. The mixture was quickly frozen in a liquid nitrogen bath, evacuated, and then flame-sealed. The mixture was heated for reaction and then cooled, centrifuged, washed with methanol and NaOH, and dried in vacuo to obtain yellow solid Ag@Au@COF-999.
[0012] Furthermore, in S1, the synthesizing Ag nanowires and depositing Au nanoparticles on the surface thereof to form Ag@Au nanowires comprises:
[0013] S101, synthesizing an ethanol solution of Ag nanowires with a concentration of 1.2444 mg / ml;
[0014] S102, using a sodium citrate reduction method, heating the HAuCl4 aqueous solution to boiling, rapidly adding the sodium citrate aqueous solution dropwise, and continuing the reaction for 30 minutes to obtain a wine-red Au nanoparticle sol;
[0015] S103. Take the Ag nanowire solution, add the Au nanoparticle sol, and react in a shaker at room temperature for 6 hours to obtain Ag@Au nanowires, which are washed with water and ethanol multiple times for later use; wherein the volume ratio of the Ag nanowire solution to the Au nanoparticle sol is 1:7-9.
[0016] Furthermore, in S2, the weight ratio of Ag@Au nanowires, 1,3,5-tris(4-cyanomethylphenyl)benzene, 3,3′-bis[(6-azidohexyl)oxy]-4,4′-biphenyldicarboxaldehyde, and Cs2CO3 is: 90:8~9:14~15:19~20.
[0017] Further, in S2, the mixture is rapidly frozen in a liquid nitrogen bath, vacuumed, flame-sealed, and dried to obtain a yellow solid, comprising: rapidly freezing the mixture at 77 K in a liquid nitrogen bath, vacuuming until the internal pressure is less than 0.2 mbar, flame-sealing, and after sealing, shortening the length of the glass tube to 10 cm, heating to room temperature, and heating the mixture in an oven at 120° C. for 72 hours to obtain a yellow solid.
[0018] Furthermore, in S3, the ratio of Ag@Au@COF-999-N3, triphenylphosphine, and methanol is 16:20:3 (weight:weight:volume).
[0019] Furthermore, in S4, the ratio of COF-999-NH2, toluene, acetic acid and triphenylphosphine is: 16:400:1:20 (weight: volume: volume: volume).
[0020] Further, in S4, the mixture is rapidly frozen in a liquid nitrogen bath, evacuated, and then flame-sealed, and the mixture is heated for reaction and then cooled, comprising: rapidly freezing the mixture at 77K in a liquid nitrogen bath, evacuating to an internal pressure of less than 0.3mbar, flame-sealing, and after sealing, shortening the length of the glass tube to 10cm, heating to room temperature, heating the reaction mixture at 100°C for 24 hours, and cooling to 25°C.
[0021] Furthermore, in S4, the yellow solid Ag@Au@COF-999 has Ag@Au nanowires as the core and COF-999 as the shell; and the thickness of the COF-999 shell is 1 nm to 50 nm.
[0022] Furthermore, after step S4, the method further includes: loading the Ag@Au@COF-999 composite nanowires onto a filter membrane by filtering, and then drying the Ag@Au@COF-999 composite nanowires in an oven at 40° C. to obtain a portable Ag@Au@COF-999 film.
[0023] The composite SERS substrate material prepared by the above-mentioned preparation method of the composite SERS substrate material is used for selective sensing and detection of CO2 gas.
[0024] The beneficial effects of the technical solution are:
[0025] The present invention provides a preparation method and application of a composite SERS substrate material. The COF-999 shell layer can specifically adsorb CO2 gas molecules, so that the Ag@Au@COF-999 composite nanowires have highly selective sensing performance for CO2 gas; the COF-999 shell layer has a high specific surface area and stability, which can improve the uniformity and stability of the SERS substrate material, making long-term storage and stable and accurate detection possible; through filtration and drying operations, the Ag@Au@COF-999 composite nanowires are made into a portable SERS film, further increasing the practicality of the substrate material.
[0026] Specifically, COF-999 is a covalent organic framework material formed by light elements (C, H, O, N, etc.) connected by covalent bonds. It has a highly ordered porous structure, a large specific surface area and controllable chemical functional groups. Its pore structure and surface functional groups (such as hydroxyl groups, amino groups, etc.) can selectively adsorb target molecules and improve the efficiency of molecular enrichment. The present invention designs and optimizes the preparation process to prepare Ag@Au@COF-999 composite SERS substrate material. With Ag@Au nanowires as the core, a COF-999 shell is uniformly coated on the surface. The COF-999 shell captures the target molecules near the shell through the interaction between the porous structure and functional groups, making them close to the strong electromagnetic field area of the core Ag@Au nanowires, thereby achieving adsorption and enrichment of the target molecules. The COF-999 shell encapsulates the Ag@Au nanowires, preventing them from agglomerating or oxidizing, thereby improving the chemical stability and reusability of the substrate. The porous shell controls the diffusion path of target molecules and optimizes the interaction efficiency between the molecules and the core. After encapsulation, the surface plasmon resonance (SPR) of the Ag@Au nanowires can be adjusted by varying the shell thickness and dielectric environment. A thinner COF-999 shell brings target molecules closer to strong hotspots on the nanowire surface, enhancing the Raman signal. For example, when the COF-999 shell thickness is 1 to 3 nm, the surface-enhanced Raman scattering (SERS) signal of CO2 gas is significantly enhanced, with distinct characteristic peaks. A thicker shell, likely due to its porous structure, increases the amount of molecules adsorbed, balancing signal intensity and loading efficiency. The presence of the shell prevents agglomeration caused by direct contact between the nanowires, maintaining a stable nanogap. Furthermore, through adsorption, the target molecules are evenly distributed around the hotspots, improving signal uniformity. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1Schematic diagram of the process of preparing Ag@Au@COF-999 nanowire substrate and SERS measurement in Example 1 of the present invention;
[0028] Figure 2 The scanning electron microscopy images or high-resolution transmission images of AuNPs, Ag@AuNWs, Ag@Au@COF-999NWs, and Ag@Au@COF-999NWs in Example 1 of the present invention are shown;
[0029] In the figure, (a) is a scanning electron microscopy image of Au NPs, (b) is a scanning electron microscopy image of Ag@AuNWs, (c) is a high-resolution transmission image of Ag@Au@COF-999NWs, and (d) is an optical photograph of the Ag@Au@COF-999NWs film formed by filtration;
[0030] Figure 3 The UV-visible absorption spectra of Ag@Au, Ag@COF-999 and Ag@Au@COF-999 in Example 1 of the present invention are shown;
[0031] Figure 4 This is the full XPS spectrum of Ag@Au@COF-999 in Example 1 of the present invention;
[0032] Figure 5 The CO2 Raman spectrum of the core-shell structure Ag@Au@COF-999NWs substrate material in Example 2 of the present invention is detected at room temperature with CO2 Raman spectra of COF-999 shell thickness of 1nm, 20nm and pure COF-999.
[0033] Figure 6 These are the Raman spectra detection diagrams of CO2, N2 and O2 of the core-shell structured Ag@Au@COF-999NWs with a shell thickness of 1 nm in Example 3 of the present invention. DETAILED DESCRIPTION
[0034] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:
[0035] Example 1
[0036] like Figure 1 FIG. 1 is a flow chart of the preparation of Ag@Au@COF-999 nanowire substrate and SERS measurement, and a method for preparing a composite SERS substrate material, comprising the following steps:
[0037] S1. Preparation of Ag@Au nanowires: Synthesizing Ag nanowires and depositing Au nanoparticles on their surfaces to form Ag@Au nanowires;
[0038] S101. Synthesis of Ag nanowires: First, a 1.2444 mg / mL Ag nanowire ethanol solution was synthesized using a solvothermal method. The specific reaction solution preparation and experimental procedures were as follows: First, a chloride ion solution was prepared (20 mL of ethylene glycol was added to each 40 mL beaker, followed by 0.0324 g of FeCl₃·6H₂O, 0.0205 g of CuCl₂·2H₂O, or 0.0070 g of NaCl, maintaining a Cl⁻ concentration of 0.006 M, and magnetically stirred until dissolved). Then, a PVP solution was prepared (0.8 g of K3000 polyvinylpyrrolidone dissolved in 20 mL of ethylene glycol) and a silver nitrate solution (0.6794 g of AgNO₃ dissolved in 20 mL of ethylene glycol, stirred in the dark for 30 minutes). The silver nitrate solution and PVP solution were mixed, and 2 mL of the chloride ion solution was added. After magnetic stirring, the mixture was transferred to a sealed polytetrafluoroethylene reactor and reacted at a specific temperature for 2.5 hours. After cooling, the product was added with 160 mL of ultrapure water and allowed to stand for 24 h, centrifuged and washed, and finally dispersed in methanol and ultrasonicated for later use. The whole process should be operated in the dark.
[0039] S102. Preparation of Au nanoparticles: Using sodium citrate reduction method, HAuCl4 aqueous solution was heated to boiling, and sodium citrate aqueous solution was rapidly added dropwise. After the reaction was continued for 30 minutes, a wine-red Au nanoparticle sol was obtained; Figure 2 (a) shows the scanning electron microscopy image of Au NPs;
[0040] S103, construction of Ag@Au nanowires: 10 mL of Ag nanowire solution was added to 85 mL of the Au nanosol prepared in advance, and the mixture was reacted in a shaker at room temperature for 6 h to obtain Ag@Au nanowires, which were then washed three times with water and ethanol respectively for later use; Figure 2 (b) shows the scanning electron microscopy image of Ag@Au NWs;
[0041] S2. Preparation of Ag@Au@COF-999-N3 composite nanowires: A borosilicate glass tube with an inner diameter (ID) and outer diameter (OD) of 8 × 10 mm was charged with 180 mg of Ag@Au nanowires, 16.9 mg of 1,3,5-tris(4-cyanomethylphenyl)benzene (TCPB), 29.6 mg of 3,3′-bis[(6-azidohexyl)oxy]-4,4′-biphenyldicarboxaldehyde (BPDA-N3), 39.1 mg of Cs2CO3, 0.5 mL of 1,2-dichlorobenzene, and 0.5 mL of 1-butanol. The mixture was rapidly frozen in a liquid nitrogen bath at 77 K, evacuated to an internal pressure below 0.2 mbar, and then flame-sealed. After sealing, the glass tube was shortened to approximately 10 cm in length. After warming to room temperature, the mixture was heated in an oven at 120°C for 72 hours to yield a yellow solid. The solid was filtered, washed with 30 mL of methanol, and the Ag@Au@COF-999-N3 composite nanowires were dried.
[0042] S3. Preparation of Ag@Au@COF-999-NH2 composite nanowires: To a 100-ml round-bottom flask, add 160 mg of Ag@Au@COF-999-N3, 200 mg of triphenylphosphine (PPh3), and 30 ml of methanol at 25°C. After 24 hours of reaction, the suspension was filtered and washed with methanol to remove excess PPh3. The yellow residue was transferred to another 100-ml round-bottom flask, and 24 ml of methanol and 6 ml of water were added at 25°C. After 24 hours, the mixture was centrifuged, washed, and dried to obtain Ag@Au@COF-999-NH2 composite nanowires.
[0043] S4. Preparation of Ag@Au@COF-999 composite nanowires: Add 80 mg COF-999-NH2, 2 mL toluene, 5 μL acetic acid and 100 μL triphenylphosphine to a borosilicate glass tube with an inner diameter and outer diameter of 8 × 10 mm, and quickly freeze the mixture at 77 K in a liquid nitrogen bath, evacuate to an internal pressure of less than 0.3 mbar, and then flame seal. After sealing, shorten the length of the glass tube to about 10 cm. After warming to room temperature, heat the reaction mixture at 100 ° C for 24 hours. After cooling to 25 ° C, centrifuge, wash with methanol and 1M NaOH, and vacuum dry for 12 hours to obtain yellow solid Ag@Au@COF-999. The prepared yellow solid Ag@Au@COF-999 has Ag@Au nanowires as the core and COF-999 as the shell; the thickness of the COF-999 shell is 1 nm. As Figure 2 (c) and Figure 2 (d) shows the high-resolution transmission image of Ag@Au@COF-999NWs and the optical photograph of the Ag@Au@COF-999NWs filtration film; and the UV-visible absorption light analysis of Ag@Au, Ag@COF-999 and Ag@Au@COF-999 was performed respectively, and the spectra are shown in Figure 3 As shown; the XPS full spectrum of Ag@Au@COF-999 is as follows Figure 4 As shown;
[0044] Through the above steps, Ag@Au@COF-999 composite nanowires with a uniform COF-999 shell layer can be prepared. This material can be used as a SERS substrate and has high selective sensing performance for CO2 gas.
[0045] In step S2, during the preparation of Ag@Au@COF-999-N3 composite nanowires, the COF-999-N3 shell thickness can be precisely controlled by varying the amounts of TCPB, BPDA-N3, and Cs2CO3, as well as the reaction time. For example, increasing the concentration of the precursor solution or extending the reaction time can produce a thicker COF-999 shell.
[0046] Example 2
[0047] SERS performance evaluation: Ag@Au@COF-999 composite nanowires with different COF-999 shell thicknesses were prepared, and their CO2 gas sensing performance was evaluated by SERS detection. The CO2 Raman spectra of the core-shell structure Ag@Au@COF-999NWs substrate material with COF-999 shell thicknesses of 1nm, 20nm and pure COF-999 at room temperature were as follows: Figure 5 By comparing the SERS signal intensities at different shell thicknesses, the optimal COF-999 shell thickness can be determined. When the COF-999 core-shell thickness is 1 nm, the surface-enhanced Raman scattering (SERS) signal of the material to CO2 gas is significantly enhanced.
[0048] Example 3
[0049] In this embodiment, after step S4 of embodiment 1, the Ag@Au@COF-999 composite nanowires are loaded onto a filter membrane by filtration, and then dried in an oven at 40° C. to obtain a portable Ag@Au@COF-999 thin film.
[0050] Sensing performance study: The prepared SERS film is placed in a sealed bottle and filled with the gas to be detected (such as CO2, N2, O2, etc.). After a period of time, SERS detection is performed. The Raman spectrum detection diagram is as follows Figure 6 As shown in the figure. By comparing the SERS signal intensities under different gases, the sensing performance of the Ag@Au@COF-999 composite SERS film was evaluated, showing that the film exhibits highly selective sensing performance for CO2 gas. By fabricating Ag@Au@COF-999 composite nanowires into a SERS film, the practicality and portability of the material were improved, and its sensing performance was further investigated, providing new ideas and methods for the development of highly selective gas sensors.
[0051] In summary, the present invention provides a preparation method and application of a composite SERS substrate material, wherein the COF-999 shell can specifically adsorb CO2 gas molecules, so that the Ag@Au@COF-999 composite nanowires have highly selective sensing performance for CO2 gas; the COF-999 shell has a high specific surface area and stability, which can improve the uniformity and stability of the SERS substrate material, making long-term storage and stable and accurate detection possible; through filtration and drying operations, the Ag@Au@COF-999 composite nanowires are made into a portable SERS film, further increasing the practicality of the substrate material.
[0052] The above is only an embodiment of the present invention, and common knowledge such as the specific technical solutions or characteristics in the solution is not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.
Claims
1. A method for preparing a composite SERS substrate material, characterized in that: The following steps are involved: S1. Preparation of Ag@Au nanowires: Synthesizing Ag nanowires and depositing Au nanoparticles on their surfaces to form Ag@Au nanowires; S2. Preparation of Ag@Au@COF-999-N3 composite nanowires: Ag@Au nanowires, 1,3,5-tris(4-cyanomethylphenyl)benzene, 3,3′-bis[(6-azidohexyl)oxy]-4,4′-biphenyldicarboxaldehyde, Cs2CO3, 1,2-dichlorobenzene, and 1-butanol were placed in a borosilicate glass tube, and the mixture was rapidly frozen in a liquid nitrogen bath, evacuated, flame-sealed, and dried to obtain a yellow solid. The solid was filtered, washed, and dried to obtain Ag@Au@COF-999-N3 composite nanowires. S3. Preparation of Ag@Au@COF-999-NH2 composite nanowires: Ag@Au@COF-999-N3, triphenylphosphine and methanol were added to a container, and the mixture was allowed to stand for reaction. The suspension was filtered and washed with methanol to remove excess PPh3. The yellow residue was transferred to another container, and methanol and water were added. After standing, the mixture was filtered and dried, and vacuum degassed to obtain Ag@Au@COF-999-NH2 composite nanowires. S4. Preparation of Ag@Au@COF-999 composite nanowires: COF-999-NH2, toluene, acetic acid, and triphenylphosphine were added to a borosilicate glass tube. The mixture was quickly frozen in a liquid nitrogen bath, evacuated, and then flame-sealed. The mixture was heated for reaction and then cooled, centrifuged, washed with methanol and NaOH, and dried in vacuo to obtain yellow solid Ag@Au@COF-999.
2. The method for preparing a composite SERS substrate material according to claim 1, wherein: In S1, the step of synthesizing Ag nanowires and depositing Au nanoparticles on the surface of Ag nanowires to form Ag@Au nanowires comprises: S101, synthesizing an ethanol solution of Ag nanowires with a concentration of 1.2444 mg / ml; S102, using a sodium citrate reduction method, heating the HAuCl4 aqueous solution to boiling, rapidly adding the sodium citrate aqueous solution dropwise, and continuing the reaction for 30 minutes to obtain a wine-red Au nanoparticle sol; S103. Take the Ag nanowire solution, add the Au nanoparticle sol, and react in a shaker at room temperature for 6 hours to obtain Ag@Au nanowires, which are washed with water and ethanol multiple times for later use; wherein the volume ratio of the Ag nanowire solution to the Au nanoparticle sol is 1:7-9.
3. The method for preparing a composite SERS substrate material according to claim 1, wherein: In S2, the weight ratio of Ag@Au nanowires, 1,3,5-tris(4-cyanomethylphenyl)benzene, 3,3′-bis[(6-azidohexyl)oxy]-4,4′-biphenyldicarboxaldehyde, and Cs2CO3 is: 90:8~9:14~15:19~20.
4. The method for preparing a composite SERS substrate material according to claim 1, wherein: In S2, the mixture is rapidly frozen in a liquid nitrogen bath, evacuated, flame-sealed, and dried to obtain a yellow solid, comprising: rapidly freezing the mixture in a liquid nitrogen bath at 77 K, evacuating to an internal pressure of less than 0.2 mbar, flame-sealing, and after sealing, shortening the length of the glass tube to 10 cm, heating to room temperature, and heating the mixture in an oven at 120° C. for 72 hours to obtain a yellow solid.
5. The method for preparing a composite SERS substrate material according to claim 1, wherein: In S3, the ratio of Ag@Au@COF-999-N3, triphenylphosphine, and methanol is: 16:20:3 (weight:weight:volume).
6. The method for preparing a composite SERS substrate material according to claim 1, wherein: In S4, the ratio of COF-999-NH2, toluene, acetic acid and triphenylphosphine is: 16:400:1:20 (weight: volume: volume: volume).
7. The method for preparing a composite SERS substrate material according to claim 1, wherein: In S4, the mixture is rapidly frozen in a liquid nitrogen bath, evacuated, and then flame-sealed, and the mixture is heated for reaction and then cooled, comprising: rapidly freezing the mixture in a liquid nitrogen bath at 77 K, evacuating to an internal pressure of less than 0.3 mbar, flame-sealing, and after sealing, shortening the glass tube to 10 cm in length, heating to room temperature, heating the reaction mixture at 100° C. for 24 hours, and cooling to 25° C.
8. The method for preparing a composite SERS substrate material according to claim 1, wherein: In S4, the yellow solid Ag@Au@COF-999 has Ag@Au nanowires as the core and COF-999 as the shell; and the thickness of the COF-999 shell is 1 nm to 50 nm.
9. The method for preparing a composite SERS substrate material according to claim 1, wherein: After step S4, the method further includes: loading the Ag@Au@COF-999 composite nanowires onto a filter membrane by filtering, and then drying the Ag@Au@COF-999 composite nanowires in an oven at 40° C. to obtain a portable Ag@Au@COF-999 film.
10. Use of a composite SERS substrate material prepared by the method for preparing a composite SERS substrate material according to any one of claims 1 to 9, characterized in that: It is used for selective sensing and detection of CO2 gas.