A method for preparing an elastic self-healing surface-enhanced raman substrate

Abstract

This invention provides a method for preparing an elastic self-healing surface-enhanced Raman (SERS) substrate, belonging to the field of SERS substrate preparation technology. The method employs a composite precursor constructed from dynamic covalent self-healing units, an elastomer matrix, carbon-based reinforcing fillers, noble metal nanoparticles, inorganic microspheres, and pore-regulating components. Solvent evaporation induces phase separation, followed by hot-pressing curing, to obtain an elastic self-healing SERS substrate with a predetermined porosity. This allows the SERS substrate to maintain high analyte enrichment capacity and Raman enhancement response even after damage repair. This method achieves a synergistic balance between improved detection efficiency, preserved self-healing performance, and long-term stability.

Description

Technical Field

[0001] This invention belongs to the field of surface-enhanced Raman (SERS) substrate preparation technology, specifically relating to a method for preparing an elastic self-healing surface-enhanced Raman substrate. Background Technology

[0002] Surface-enhanced Raman scattering (SERS) is a highly sensitive detection technique based on the localized electromagnetic field enhancement effect of noble metal nanostructures. SERS substrates typically incorporate noble metal nanoparticles, nanorods, nanoislands, or composite nanostructures, such as gold or silver, to create numerous electromagnetic enhancement hotspots on or near the substrate surface, thereby increasing the Raman scattering signal intensity of the analyte molecule. Due to its advantages such as high sensitivity, fast detection speed, and ability to perform molecular fingerprinting, SERS substrates have significant application value in fields such as environmental pollutant detection, food safety screening, biological sample analysis, forensic evidence detection, and rapid on-site detection.

[0003] Traditional surface-enhanced Raman spectroscopy (SERS) substrates typically employ rigid sheet-like substrates or hard nanostructures, such as silicon wafers, glass sheets, metal sheets, or rigid inorganic nanoarrays. While these substrates offer advantages for detecting samples on flat surfaces, they often struggle to achieve adequate adhesion to curved, irregular, rough, flexible, or complex contamination interfaces. This reduces the contact efficiency between the analyte and the Raman enhancement hotspot, consequently affecting detection sensitivity and repeatability. Therefore, flexible or elastic SERS substrates have gained increasing attention. By introducing noble metal nanoparticles into flexible polymer or elastomer matrices, the substrate can acquire bending, stretching, and adhesion capabilities, thereby improving its adaptability to complex detection scenarios. However, flexible or elastic SERS substrates still face damage and failure issues during practical use. During attachment, peeling, bending, stretching, friction, cutting, or repeated use, the substrate may develop cracks, scratches, localized fractures, or interface damage. This alters the distribution of noble metal nanoparticles, the hotspot structure, and the analyte transport path, leading to reduced Raman signal intensity, decreased signal uniformity, and reduced reusability. Therefore, for surface-enhanced Raman spectroscopy substrates that require on-site testing, complex surface testing, or repeated use, flexibility or elasticity alone is insufficient; they also need to possess a certain degree of self-healing capability in order to restore the continuity of the substrate structure and the stability of the testing function after damage.

[0004] Existing self-healing elastic materials typically achieve crack closure and mechanical property recovery through dynamic covalent bonds, hydrogen bonds, metal coordination, ionic interactions, microcapsule release of repair agents, or multiphase composite structures. Among these, self-healing systems based on the formation of dynamic imine bonds between amino-modified polysiloxanes and aldehyde compounds exhibit mild reaction conditions, good network reversibility, and high elasticity and compliance, making them suitable for constructing self-healing elastic matrices. However, current research on self-healing elastic materials largely focuses on crack closure, interfacial rebonding, and mechanical property recovery within the material bulk, while insufficient attention is paid to the spatial distribution of noble metal nanoparticles, surface micro / nano rough structures, pore channels, and analyte enrichment pathways required for their use as surface-enhanced Raman spectroscopy (SERS) substrates. In other words, the ability of the material bulk to achieve macroscopic self-healing does not necessarily imply that its SERS-detected interface can be simultaneously restored.

[0005] For surface-enhanced Raman spectroscopy (SERS) substrates, detection performance depends not only on the presence of noble metal nanoparticles, but also on whether these nanoparticles can form stable, uniform, and reusable hotspot regions, and whether analytes can effectively enter and accumulate near these hotspots. Existing elastic SERS substrates typically suffer from problems such as noble metal nanoparticle aggregation or uneven distribution, relatively dense substrate surface structures, and limited analyte diffusion and adsorption channels, leading to insufficient utilization of effective hotspots and low signal response efficiency. Especially after introducing self-healing networks, if only crack closure is considered without synergistic design of pore and hotspot structures, problems such as localized structural densification, blocked pore channels, changes in the spacing between noble metal nanoparticles, or insufficient hotspot exposure may occur during the repair process, thus affecting the detection sensitivity and signal repeatability after repair. Appropriate pore structures can increase the substrate's specific surface area, shorten the migration path of analytes to the hotspot region, promote analyte adsorption and accumulation near noble metal nanoparticles, and increase the number of effective hotspots utilized. However, higher porosity is not always better. When the porosity is too low, the substrate tends to be dense, which is not conducive to the entry and enrichment of analytes. When the porosity is too high, the continuity of the elastic network and the stability of the pore walls decrease, which may reduce the mechanical stability, self-healing quality and fixation stability of the substrate and noble metal nanoparticles.

[0006] Therefore, there is an urgent need to provide a method for preparing composite substrates that combine elasticity, self-healing ability, controllable porosity, and stable surface-enhanced Raman detection performance, so that the substrate can not only restore the material structure after damage, but also maintain the analyte transport channels, noble metal hot spot structure, and Raman signal response capability as much as possible. Summary of the Invention

[0007] To address the problems existing in the background technology, the present invention aims to provide a method for preparing an elastic self-healing surface-enhanced Raman spectroscopy (SERS) substrate. This method employs a composite precursor constructed from dynamic covalent self-healing units, an elastomer matrix, carbon-based reinforcing fillers, noble metal nanoparticles, inorganic microspheres, and pore-regulating components. Solvent evaporation induces phase separation, followed by hot-pressing curing, to obtain an elastic self-healing SERS substrate with a predetermined porosity. This allows the SERS substrate to maintain high analyte enrichment capacity and Raman enhancement response after damage repair. This method achieves a synergistic balance between improved detection efficiency, preserved self-healing performance, and long-term stability.

[0008] To achieve the above objectives, the technical solution of the present invention is as follows:

[0009] A method for preparing an elastic self-healing surface-enhanced Raman substrate includes the following steps:

[0010] Step 1. Prepare the self-healing monomer solution: Add pyromellitic methyl ether to the main solvent and stir until the pyromellitic methyl ether is completely dissolved to obtain the self-healing monomer solution;

[0011] Step 2. Preparation of elastic matrix mixture: Mix carbon-based reinforced filler, elastomer matrix, pore-forming component and main solvent, then ultrasonically stir to mix and disperse, forming elastic matrix mixture;

[0012] Step 3. Preparation of composite precursor: Under continuous stirring, the self-healing monomer solution is added dropwise to the elastic matrix mixture, and noble metal nanoparticle dispersion and inorganic microsphere dispersion are added. The composite precursor is obtained by ultrasonic dispersion and mechanical stirring.

[0013] Step 4. Solvent Evaporation: Pour the composite precursor into a mold of a pre-designed shape, and let it stand to allow the main solvent to evaporate completely, forming a preform.

[0014] Step 5. Hot pressing curing: The preformed blank is subjected to hot pressing treatment. The hot pressing parameters are: hot pressing temperature is 80-100℃, pressure is 10-25 MPa, and holding time is 20-40 min. After hot pressing, an elastic self-healing surface-enhanced Raman substrate is obtained.

[0015] Furthermore, the main solvent mentioned in step 1 can be selected from one or more of toluene, xylene, tetrahydrofuran, and chloroform; the mass concentration of pyromellitic aldehyde in the self-healing monomer solution is 0.02–0.04 g / mL.

[0016] Further, in step 2, the mass ratio of the amount of carbon-based reinforced filler added to the elastic matrix mixture to the mass ratio of the elastomer matrix is ​​(0.025-0.125):1; the amount of pore-forming component added to the elastic matrix mixture is 0.04-0.38 mL / g.

[0017] Further, in step 2, the carbon-based reinforcing filler is preferably aminated multi-walled carbon nanotubes, carbon nanotubes, graphene oxide, carbon nanofibers, conductive carbon black, or mesoporous carbon; the elastomer matrix is ​​an amino-containing elastomer matrix, preferably amino-terminated polydimethylsiloxane, side-chain aminated polydimethylsiloxane, aminated polysiloxane, aminated silicone rubber, aminated polyurethane, aminated polyether, or aminated polyacrylate; the pore-forming component is preferably a weak solvent, non-solvent, volatile co-solvent, or pore-forming agent capable of inducing microphase separation during solvent evaporation.

[0018] Furthermore, the pore-forming component may be selected from one or more of ethanol, isopropanol, water / lower alcohol mixture, polyethylene glycol, polyvinylpyrrolidone, ethyl acetate, acetone, n-hexane, cyclohexane, and petroleum ether.

[0019] Further, in step 3, the inorganic microspheres are preferably silica microspheres, titanium dioxide microspheres, polystyrene microspheres, zinc oxide microspheres, alumina microspheres, etc.; the noble metal nanoparticles are preferably gold nanoparticles, gold nanorods, silver nanoparticles, gold nanospheres, gold-silver bimetallic nanoparticles, etc.

[0020] Furthermore, the concentration of the gold nanoparticle dispersion is 0.01–0.10 g / mL, and the mass ratio of silica microspheres to gold nanoparticles is 1:(2–6).

[0021] Furthermore, the volume porosity of the elastic self-healing surface-reinforced Raman substrate is 20%–35%, more preferably 20%–30%.

[0022] The mechanism of this invention is as follows:

[0023] Non-porous elastic substrates can also load noble metal nanoparticles and generate surface-enhanced Raman signals, and can also achieve material self-healing through dynamic covalent bond networks. However, in such dense structures, noble metal nanoparticles are mainly distributed on the outer surface of the substrate, limiting the diffusion, adsorption, and enrichment pathways of analyte molecules to near-surface hotspot regions, resulting in relatively insufficient utilization of effective hotspots. Furthermore, during bending, friction, cutting, or repair processes, the surface-loaded noble metal nanoparticles are more susceptible to interfacial deformation, leading to localized spacing changes, migration, or detachment, thus affecting signal stability and the retention of detection performance after repair. Therefore, porosity is a crucial component of self-healing elastic Raman substrates.

[0024] The influence of porosity on the performance of surface-enhanced Raman spectroscopy (SERS) substrates is mainly reflected in three aspects: First, appropriate porosity can increase the specific surface area and provide multi-level rough interfaces, making it easier for analytes to enter the substrate surface and near-surface region, and increasing the number of contactable active sites per unit area; Second, interconnected pores can shorten the migration and diffusion path of analytes to hotspot regions, promoting the enrichment of analytes near noble metal nanoparticles, thereby improving the utilization rate of effective hotspots; Third, the pore structure can, to a certain extent, restrict the disordered large-scale aggregation of noble metal nanoparticles, making it easier for them to maintain nanoscale gaps and a more stable local electromagnetic field distribution, thereby improving the intensity and repeatability of SERS signal response.

[0025] However, higher porosity is not always better. When porosity is too low, the substrate surface tends to be dense, making it difficult for analytes to quickly penetrate and accumulate near hot spots, resulting in slow response speed and limited effective enhancement sites. When porosity is too high, the continuous phase of elastic polymer decreases, the pore wall thickness and support capacity decrease, and the polymer coating, interfacial adsorption, and mechanical confinement of noble metal nanoparticles weaken. During bending, damage, or repair, they are more prone to positional changes, local aggregation, or detachment, thereby reducing the stability of the hot spot structure and the reproducibility of the Raman signal after repair. Therefore, this invention emphasizes controlling the porosity within a range that promotes analyte enrichment and hot spot construction without significantly impairing the integrity of the self-healing network, in order to achieve a synergistic balance between improved detection efficiency, maintained self-healing performance, and long-term stability.

[0026] In the preparation of the surface-enhanced Raman substrate of this invention, the precursor system does not simply form a dense film during the solvent evaporation stage, but rather undergoes a transformation from a homogeneous system to a microphase-separated system. As the main solvent gradually evaporates, the polymer concentration in the system increases, and the local solvation capacity decreases. If weak solvents, non-solvents, or removable pore-forming components are present simultaneously, polymer-enriched phases and polymer-depleted phases will be induced. The polymer-enriched phase forms a continuous elastic framework during subsequent hot pressing and dynamic crosslinking, while the space occupied by the polymer-depleted phase and / or the removed components is transformed into pores. Simultaneously, the crosslinking density of the dynamic imine bond network also affects the stabilization process of the pore structure. At higher crosslinking densities, the network forms faster, the pore walls are more easily fixed, the overall porosity tends to decrease, but the structural stability is enhanced; at lower crosslinking densities, the system fluidity is maintained for a longer time, the pores are more easily expanded and interconnected, and the porosity is correspondingly increased. Inorganic microspheres and carbon-based reinforcing fillers can serve as structural support points and interfacial heterogeneous nucleation sites, influencing pore nucleus formation and pore wall stability. Furthermore, they can improve the mechanical support capacity of the composite network, mitigating pore wall collapse or embrittlement under high porosity conditions. Noble metal nanoparticles are distributed on the pore walls, in rough surface regions, and around the inorganic microspheres, and under appropriate porosity conditions, they more easily form spatially uniform and appropriately spaced electromagnetically reinforcing hotspot regions. Therefore, this invention, through formulation design, achieves porosity regulation through the combined effects of phase separation behavior, cross-linking curing rate, and the interfacial interaction of the composite filler.

[0027] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0028] 1. The elastic self-healing surface-enhanced Raman spectroscopy (SERS) substrate obtained in this invention exhibits a clear self-healing capability. After the substrate is completely cut, the fracture surfaces are rejoined and placed at room temperature or subjected to moderate pressure. After 3 hours, the fracture surfaces can recombine, surface cracks are significantly reduced or essentially disappear, and the substrate restores its continuous and intact morphology. The repaired substrate can still be bent or attached. 2. The substrate obtained in this invention maintains a high level of surface-enhanced Raman response after repair. Using toluidine blue as the analyte, at its 1623 cm⁻¹... -1 Detection was performed at the characteristic peak, and the Raman signal retention rate of the repaired substrate still reached 93%–95%. This indicates that after the substrate is repaired, it can still maintain the hot spot structure of noble metal nanoparticles and the contact interface with the analyte, avoiding the problem of significant decline in detection performance due to only macroscopic repair. 3. This invention significantly improves the detection efficiency of the substrate through porosity control. Compared with the non-porous control, the substrate with porosity controlled in the range of 20%–35% can detect the same concentration of toluidine blue at a 1623 cm⁻¹. -1The characteristic peak intensity can be increased by up to 2.5 times, indicating that an appropriate pore structure can improve the penetration, adsorption and local enrichment of analytes, increase the number of hot spots that can be enhanced by noble metals, and thus improve the intensity of surface-enhanced Raman signal response.

[0029] 4. The substrate obtained by this invention has good applicability for trace detection. When using toluidine blue of different concentrations as analytes for detection, the substrate can withstand 10... -3 mol / L~10 -7 It produces identifiable Raman characteristic peak responses within a concentration range of mol / L, with the lowest detectable concentration reaching 10. -7 mol / L; as the concentration of the analyte decreases, the substrate still maintains the distinguishability of the target characteristic peak, indicating that the substrate of the present invention is suitable for trace molecule detection scenarios. Attached Figure Description

[0030] Figure 1 This is a physical image of the self-healing process of the elastic self-healing surface-enhanced Raman substrate of the present invention.

[0031] Figure 2 To detect toluidine blue at 1623 cm⁻¹ under different porosity conditions -1 Comparison of surface-enhanced Raman signals.

[0032] Figure 3 This is a comparison of surface-enhanced Raman signals before and after substrate damage and repair.

[0033] Figure 4 The gradient map of different toluidine blue concentrations was obtained for the substrate.

[0034] Figure 5 SEM characterization image of the elastic self-healing surface-enhanced Raman substrate prepared in this invention. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0036] Example 1

[0037] A method for preparing an elastic self-healing surface-enhanced Raman substrate includes the following steps:

[0038] Step 1. Prepare self-healing monomer solution: Weigh 0.3 g of pyromellitic aldehyde and add it to 12 mL of toluene. Stir at 500 r / min for 20 min until completely dissolved to obtain a clear and transparent self-healing monomer solution.

[0039] Step 2. Preparation of elastic matrix mixture: Weigh 10 g of aminated polydimethylsiloxane, add 0.7 g of aminated multi-walled carbon nanotube powder, then add 12 mL of toluene and 1.5 mL of isopropanol, and treat with a combination of ultrasonic dispersion and mechanical stirring to obtain a uniformly dispersed mixture, forming an elastic matrix mixture.

[0040] Step 3. Preparation of composite precursor: Under continuous stirring, the self-healing monomer solution obtained in step 1 is added dropwise to the elastic matrix mixture, and gold nanoparticle dispersion and silica microsphere dispersion are added, wherein the concentration of gold nanoparticle dispersion is 0.05 g / mL, and the mass ratio of silica microspheres to gold nanoparticles is 1:4. The mixture is sonicated for 15 min and stirred for 10 min to obtain the composite precursor.

[0041] Step 4. Solvent evaporation: Pour the composite precursor obtained in step 3 into an acrylic mold of a pre-designed shape, place it in a fume hood and let it stand for 10 h to allow the toluene solvent to evaporate completely. The system gradually undergoes solvent evaporation-induced phase separation, forming a polymer-enriched phase and a polymer-depleted phase, which are then transformed into a continuous skeleton and porous structure during the subsequent curing process to form a preform.

[0042] Step 5. Hot pressing curing: The preformed blank is subjected to hot pressing treatment. The hot pressing parameters are: hot pressing temperature of 90℃, pressure of 20 MPa, and holding time of 30 min. During the hot pressing process, dynamic imine bond crosslinking occurs between pyromellitic trimethylolpropionate and amino-modified polydimethylsiloxane to form a self-healing elastic network. At the same time, gold nanoparticles and silica microspheres are fixed to the pore walls and substrate surface. After hot pressing, an elastic self-healing surface-reinforced Raman substrate with 25% porosity is obtained.

[0043] Example 2

[0044] Elastic self-healing surface-enhanced Raman substrates were prepared according to the steps of Example 1, except that the amount of isopropanol, the pore-regulating component in step 2, was adjusted in a gradient manner. All other steps and process parameters were the same as in Example 1. Elastic self-healing surface-enhanced Raman substrates with volume porosities of 20%, 30%, and 35% were prepared respectively.

[0045] Comparative Example 1

[0046] The elastic self-healing surface-enhanced Raman substrate was prepared according to the steps of Example 1, except that: in step 2, isopropanol, which is a pore-forming component, was not added, and the isopropanol was replaced with an equal volume of toluene to keep the total liquid volume of the system basically the same; the other conditions remained unchanged.

[0047] Specifically, in step 2, 10 g of aminated polydimethylsiloxane was weighed, and 0.7 g of aminated multi-walled carbon nanotube powder was added. Then, 13.5 mL of toluene was added, without adding isopropanol. After ultrasonic dispersion and mechanical stirring, an elastic matrix mixture was obtained. Subsequently, following step 3 of Example 1, a self-healing monomer solution, a gold nanoparticle dispersion, and a silica microsphere dispersion were added. After solvent evaporation and hot-press curing, a non-porous elastic self-healing surface-enhanced Raman substrate was obtained.

[0048] Comparative Example 2

[0049] Elastic self-healing surface-enhanced Raman substrates were prepared according to the steps of Example 1, except that the amount of isopropanol, the pore-regulating component in step 2, was adjusted in a gradient manner. All other steps and process parameters were the same as in Example 1. Elastic self-healing surface-enhanced Raman substrates with volume porosities of 10%, 15%, 40%, 45%, and 50% were prepared respectively.

[0050] Using toluidine blue solution of the same concentration as in Example 1 as the analyte, and under the same Raman testing conditions, the porous substrate obtained in Example 1 and the non-porous substrate obtained in Comparative Example 1 were tested at 1623 cm⁻¹. -1 The surface-enhanced Raman (SERS) characteristic peak intensity was measured. The results show that although the non-porous substrate obtained in Comparative Example 1 can generate SERS signals and achieve material self-healing through a dynamic imine bond network, its SERS characteristic peak intensity is significantly lower than that of the porous substrate obtained in Example 1. This is because the noble metal nanoparticles in the non-porous substrate are mainly distributed or exposed on the outer surface of the substrate, limiting the channels for the diffusion, adsorption, and enrichment of analyte molecules into the near-surface region of the substrate, resulting in a smaller number of effective hot spots. In contrast, the porous substrate obtained in Example 1, with its appropriate pore structure, can increase the specific surface area of ​​the substrate, providing transport channels for analyte molecules to enter the near-surface region. This makes it easier for analyte molecules to contact the pore walls, the area around the silica microspheres, and the enhanced hot spots near the gold nanoparticles, thus exhibiting a higher SERS response intensity.

[0051] Furthermore, after cutting the non-porosity substrate obtained in Comparative Example 1 and performing cross-sectional repair, although the substrate itself could still undergo a certain degree of self-repair, the SERS signal retention rate after repair was lower than that of the porous substrate obtained in Example 1. This indicates that for surface-enhanced Raman substrates, the self-repair capability of the material itself does not necessarily mean that the detection interface can be fully restored. Appropriate porosity helps maintain the transport path of the analyte molecules, the accessibility of the noble metal nanoparticle hotspots, and the stability of the repaired Raman signal.

[0052] Table 1. Comparison of SERS performance before and after repair of porous and non-porosity substrates.

[0053] sample Volume porosity / % SERS characteristic peak intensity at 1623 cm⁻¹ / au Signal retention rate after repair / % Comparative Example 1: Porosity-free substrate 0 5200 69.2 Example 1: Porous substrate 25 11300 94.3

[0054] Compared to the non-porosity substrate obtained in Comparative Example 1, the porous substrate with a volumetric porosity of approximately 25% obtained in Example 1 has a lower porosity at 1623 cm⁻¹. -1 The intensity of the SERS characteristic peak at the analyte increased from approximately 5200 au to approximately 11300 au, an increase of approximately 2.17 times, indicating that an appropriate porous structure can significantly improve the enrichment capacity of analyte molecules and the utilization rate of effective hotspots. The characteristic Raman peak of toluidine blue was still detectable on the non-porosity substrate obtained in Comparative Example 1 after repair, but its intensity decreased to 1623 cm⁻¹. -1 The peak intensity decreased from approximately 5200 a.u. before repair to approximately 3600 au, with a signal retention rate of approximately 69.2%. The peak intensity of the porous substrate obtained in Example 1 after repair decreased from approximately 11300 au to approximately 10655 au, with a signal retention rate of approximately 94.3%. These results demonstrate that the porous structure not only improves the initial SERS response intensity but also helps maintain detection performance after repair.

[0055] Figure 1 This is a photograph of the self-healing process of the elastic self-healing surface-enhanced Raman spectroscopy substrate of the present invention. The elastic self-healing surface-enhanced Raman spectroscopy substrate prepared in Example 1 was cut into strips and then cut from the middle, completely fracturing the substrate into two segments, forming a clearly visible fracture interface. The two segments were then aligned and bonded together, and allowed to stand at room temperature for healing without the addition of any additional adhesive or repair agent. Figure 1 As shown, immediately after cutting, the substrate cross-section is completely separated, and the fracture interface is clearly visible. After the cross-sections are put back together, the fracture interface gradually closes as the placement time increases, and the gap at the cross-section gradually decreases. After being placed at room temperature for 3 hours, the substrate macroscopically recovers to a continuous whole, and no obvious cracks or through gaps are observed at the fracture interface with the naked eye. When held with tweezers or slightly bent, the repaired interface does not separate naturally again, indicating that the substrate obtained in Example 1 has good self-healing ability.

[0056] Figure 2 Toluidine blue was tested at 1623 cm⁻¹ under different volumetric porosity conditions in Examples 1, 2, and 2. -1 Comparison of surface-enhanced Raman signals. (From...) Figure 2It can be seen that as the substrate volume porosity increases from 10% to 25%, the SERS characteristic peak intensity gradually increases from approximately 6100 au to approximately 11300 au, indicating that an appropriate pore structure can improve the substrate specific surface area and analyte transport and enrichment capacity, making it easier for toluidine blue molecules to approach the enhanced hotspots formed by noble metal nanoparticles. When the porosity continues to increase to 30%–50%, the SERS characteristic peak intensity gradually decreases, indicating that excessively high porosity weakens the stability of the elastic polymer continuous phase and pore wall support, affecting the fixation of noble metal nanoparticles and the stability of the hotspot structure. Therefore, porosity has a significant impact on the detection performance of elastic self-healing surface-enhanced Raman substrates. The preferred substrate volume porosity of this invention is 20%–35%, more preferably 20%–30%.

[0057] Figure 3 This is a comparison of the surface-enhanced Raman spectra obtained from toluidine blue detection of the elastic self-healing surface-enhanced Raman substrate prepared in Example 1 before and after damage. The red curve represents the detection result before substrate damage, and the blue curve represents the detection result after the substrate was cut, damaged, and repaired. Figure 3 It can be seen that the undamaged substrate exhibits a significant surface-enhanced Raman response to toluidine blue, with the 1623 cm⁻¹ being the most effective. -1 The most prominent characteristic peaks are found in the vicinity. After the substrate was cut and damaged, and the cross-sections were repaired by face-to-face bonding at room temperature, toluidine blue characteristic peaks, essentially identical to those before the damage, could still be detected, and the positions of the main characteristic peaks did not shift significantly. This indicates that the repaired substrate can still maintain its Raman fingerprint recognition capability for toluidine blue molecules. From 1623 cm⁻¹ -1 The nearby main characteristic peaks indicate that the repaired substrate still maintains a high surface-enhanced Raman response intensity. This result demonstrates that the substrate obtained in Example 1, after being damaged, can not only restore the structural continuity of the elastic matrix through a dynamic imine bond network, but also maintain the effectiveness of the noble metal nanoparticle hotspot structure and the analyte contact interface after repair, thus avoiding the problem of significant loss of detection performance due to only macroscopic repair. Therefore, the elastic self-healing surface-enhanced Raman substrate obtained in this invention has excellent post-repair detection performance retention capability and is suitable for surface-enhanced Raman detection scenarios requiring bending, attachment, damage repair, or reuse.

[0058] Figure 4 The images show surface-enhanced Raman spectra obtained by detecting toluidine blue solutions of different concentrations on the elastic self-healing surface-enhanced Raman substrate prepared in Example 1. Figure 4 It can be seen that samples of different concentrations of toluidine blue can all be obtained at approximately 1623 cm⁻¹. -1A distinct characteristic Raman peak was observed. Even at low concentrations, the main characteristic peak of toluidine blue was still observed, indicating that the substrate has good trace detection capability. This result suggests that the porous structure in the substrate facilitates the entry of analyte molecules into the near-surface region and their enrichment near the hotspots of noble metal nanoparticles, thereby improving the sensitivity of surface-enhanced Raman detection.

[0059] The prepared substrate was subjected to Raman spectroscopy using toluidine blue, rhodamine 6G, or other trace analytes. Compared to dense substrates with no porosity, substrates with appropriate porosity provide stronger adsorption of target molecules and higher hotspot utilization, resulting in higher characteristic peak response intensity, faster signal establishment speed, and better detection repeatability. In this invention, porosity was quantified using SEM image statistics or density methods.

[0060] Figure 5 This is a SEM image of the elastic self-healing surface-enhanced Raman substrate prepared in Example 1. Figure 5 As can be seen, the obtained substrate surface exhibits a distinctly rough and undulating morphology, with locally open pores and recessed areas observed, indicating that the substrate is not a dense, flat structure, but rather a porous, rough structure formed within an elastic matrix. The pore walls surrounding the pores are interconnected with the continuous elastic framework, which helps maintain the overall structural integrity of the substrate. Simultaneously, the rough pore walls and surface granular structure facilitate the dispersion and fixation of noble metal nanoparticles and inorganic microspheres. The above SEM results demonstrate that this invention, by introducing pore-regulating components and combining solvent evaporation-induced phase separation and hot-pressing curing processes, can effectively construct a porous, elastic, self-healing surface-enhanced Raman substrate. This porous structure helps improve the substrate's specific surface area and analyte transport and enrichment capacity, thereby enhancing the effective utilization rate of noble metal-enhanced hotspots and the Raman detection response capability.

[0061] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A method for preparing an elastic self-healing surface-enhanced Raman substrate, characterized in that, Includes the following steps: Step 1. Prepare the self-healing monomer solution: Add pyromellitic methyl ether to the main solvent and stir until the pyromellitic methyl ether is completely dissolved to obtain the self-healing monomer solution; Step 2. Preparation of elastic matrix mixture: Mix carbon-based reinforced filler, elastomer matrix, pore-forming component and main solvent, then ultrasonically stir to mix and disperse, forming elastic matrix mixture; Step 3. Preparation of composite precursor: Under continuous stirring, the self-healing monomer solution is added dropwise to the elastic matrix mixture, and noble metal nanoparticle dispersion and inorganic microsphere dispersion are added. The composite precursor is obtained by ultrasonic dispersion and mechanical stirring. Step 4. Solvent Evaporation: Pour the composite precursor into a mold of a pre-designed shape, and let it stand to allow the main solvent to evaporate completely, forming a preform. Step 5. Hot pressing curing: The preformed blank is subjected to hot pressing treatment. The hot pressing parameters are: hot pressing temperature is 80-100℃, pressure is 10-25 MPa, and holding time is 20-40 min. After hot pressing, an elastic self-healing surface-enhanced Raman substrate is obtained.

2. The preparation method according to claim 1, characterized in that, The main solvent mentioned in step 1 is selected from one or more of toluene, xylene, tetrahydrofuran, and chloroform; the mass concentration of pyromellitic aldehyde in the self-healing monomer solution is 0.02-0.04 g / mL.

3. The preparation method according to claim 1, characterized in that, In step 2, the mass ratio of carbon-based reinforced filler to elastomer matrix is ​​(0.025-0.125):1; the amount of pore-forming component added to the elastomer matrix mixture is 0.04-0.38 mL / g.

4. The preparation method according to claim 1, characterized in that, In step 2, the carbon-based reinforcing filler is aminated multi-walled carbon nanotubes, carbon nanotubes, graphene oxide, carbon nanofibers, conductive carbon black, or mesoporous carbon; the elastomer matrix is ​​an amino-containing elastomer matrix; and the pore-forming component is a weak solvent, non-solvent, volatile co-solvent, or pore-forming agent that can induce microphase separation during solvent evaporation.

5. The preparation method according to claim 4, characterized in that, The amino-containing elastomer matrix is ​​amino-terminated polydimethylsiloxane, side-chain amino-modified polydimethylsiloxane, amino-modified polysiloxane, amino-modified silicone rubber, amino-modified polyurethane, amino-modified polyether, or amino-modified polyacrylate; the pore-forming component is selected from one or more of ethanol, isopropanol, water / lower alcohol mixture, polyethylene glycol, polyvinylpyrrolidone, ethyl acetate, acetone, n-hexane, cyclohexane, and petroleum ether.

6. The method of claim 1, wherein the step of forming the first and second layers is performed by a method selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. In step 3, the inorganic microspheres are silica microspheres, titanium dioxide microspheres, polystyrene microspheres, zinc oxide microspheres, or alumina microspheres; the noble metal nanoparticles are gold nanoparticles, gold nanorods, silver nanoparticles, gold nanospheres, or gold-silver bimetallic nanoparticles.

7. The preparation method according to claim 1, characterized in that, The concentration of the gold nanoparticle dispersion was 0.01–0.10 g / mL, and the mass ratio of silica microspheres to gold nanoparticles was 1:(2–6).

8. The preparation method according to claim 1, characterized in that, The volume porosity of the elastic self-healing surface-enhanced Raman substrate is 20%–35%.

9. The preparation method according to claim 8, characterized in that, The volume porosity of the elastic self-healing surface-enhanced Raman substrate is 20%–30%.

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