Three-dimensional porous SERS (Surface Enhanced Raman Scattering) substrate based on MXene / GO non-woven fabric loaded AgNPs and preparation method

Abstract

The invention discloses a three-dimensional porous SERS (Surface Enhanced Raman Scattering) substrate based on MXene / GO non-woven fabric loaded AgNPs and a preparation method, and relates to the technical field of functional materials. The method comprises the following steps: respectively preparing a single-layer GO colloidal solution and an MXene colloidal solution; the preparation method comprises the following steps: uniformly mixing a single-layer GO colloidal solution and an MXene colloidal solution to prepare a spinning solution, sequentially carrying out continuous wet spinning and coagulating bath ion exchange curing on the spinning solution to obtain MXene / GO composite fibers, and sequentially carrying out fiber shearing, vacuum-assisted suction filtration, vacuum heat treatment and freeze drying to obtain the MXene / GO non-woven fabric with a three-dimensional structure, the MXene / GO non-woven fabric is soaked in a silver nitrate solution, and the three-dimensional porous SERS substrate based on the MXene / GO non-woven fabric loaded with the AgNPs is obtained. The three-dimensional SERS substrate with flexibility, high porosity and high detection sensitivity is obtained by constructing the three-dimensional porous composite carrier and carrying AgNPs through in-situ reduction, and the three-dimensional SERS substrate is suitable for detection of trace substances such as biomolecules, organic pollutants and harmful additives.

Description

Technical Field

[0001] This invention relates to the field of functional materials technology, specifically to a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs and its preparation method. Background Technology

[0002] Surface-enhanced Raman scattering (SERS) technology has shown broad application prospects in environmental monitoring, food safety, and biomedicine due to its advantages such as high sensitivity, non-destructive detection, and fingerprint recognition characteristics. The core of SERS technology lies in the performance of the SERS substrate. An ideal SERS substrate should have characteristics such as high enhancement factor, good signal repeatability, excellent stability, and ease of preparation.

[0003] Among common SERS materials, noble metal nanoparticles and two-dimensional materials have attracted much attention. Based on the localized surface plasmon resonance (LSPR) effect, noble metal nanoparticles can generate a significant electromagnetic enhancement (EM) effect, making them effective materials for constructing SERS "hotspot" regions. Two-dimensional materials, on the other hand, have promising applications in the field of SERS substrates due to their excellent specific surface area, abundant electronic valence states, tunable functional bond physicochemical properties, and uniform active sites. As a member of the two-dimensional materials family, MXene materials have excellent charge transfer efficiency and tunable electronic band structure. At the same time, the abundant functional groups on the surface can realize the adsorption and binding of analyte molecules. However, it is difficult for them to generate ionic resonance effects with visible light excitation light. The main way to achieve enhancement is through chemical enhancement (CM) effect generated by electron transfer between them and probe molecules. When two-dimensional materials and noble metal particles are used to form doped composite materials, it can not only effectively alleviate the problems of easy aggregation and oxidation of noble metal nanoparticles and provide a stable macroscopic support structure, but also combine EM and CM enhancement. However, the resulting two-dimensional doped colloidal SERS substrate is prone to aggregation and loss of active sites, making it difficult to maintain a stable enhancement signal.

[0004] Based on differences in substrate structure, SERS substrates can be classified into zero-dimensional (e.g., noble metal nanoparticle colloids, quantum dots), one-dimensional (e.g., nanowires, nanotubes, nanofibers), two-dimensional (e.g., thin films, layered materials), and three-dimensional (e.g., ordered nanoarrays, porous frameworks) SERS substrates. Since the laser confocal volume in a Raman spectrometer is a three-dimensional space, zero-dimensional, one-dimensional, and two-dimensional SERS substrates are difficult to fully collect and utilize Raman signals. Existing three-dimensional SERS substrates are mainly based on rigid three-dimensional arrays, whose rigid structure and high fabrication cost hinder further development and application. Therefore, developing a three-dimensional SERS substrate with stable structure, strong enhancement effect, low cost, and scalable fabrication methods is a key requirement for the practical application of SERS technology.

[0005] Nonwoven fabrics, as flexible materials with a three-dimensional network structure, are a promising load material with broad application prospects. Using colloidal solutions of two-dimensional materials as raw materials, nonwoven fabrics with uniform fiber diameter and controllable pore size can be prepared through continuous wet spinning and vacuum-assisted filtration. Their high porosity and large specific surface area are beneficial for the adsorption and diffusion of target molecules. Existing technology discloses an MXene fiber nonwoven fabric and its preparation method. Through wet spinning and wet assembly, a low-density, high-porosity, and high-specific-surface-area MXene nonwoven fabric was obtained and used as electrode and membrane materials in catalysis and energy fields. However, there are currently no patent reports on SERS substrates based on two-dimensional material nonwoven fabrics. SERS substrates based on polymer fiber nonwoven fabrics or bio-fiber nonwoven fabrics suffer from poor conductivity, weak bonding between noble metal nanoparticles and the carrier, and a single reinforcement mechanism, resulting in insufficient reinforcement performance and stability of the substrate. Summary of the Invention

[0006] To address the shortcomings of the aforementioned background technologies, this invention primarily solves the problems of low signal utilization in existing zero-dimensional, one-dimensional, and two-dimensional SERS substrates, and the poor flexibility, high cost, and complex fabrication processes of three-dimensional metal arrays. This invention provides a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs and its preparation method. This method constructs a three-dimensional porous composite carrier and in-situ reduces the loaded AgNPs (loaded silver nanoparticles) to obtain a three-dimensional SERS substrate with flexibility, high porosity, and high detection sensitivity, suitable for the detection of trace substances such as biomolecules, organic pollutants, and harmful additives. The MXene / GO nonwoven fabric is a novel functional material composed of graphene oxide (GO) and MXene.

[0007] The first objective of this invention is to provide a method for preparing a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs, comprising the following steps: Monolayer GO colloidal solutions and MXene colloidal solutions were prepared separately. After uniformly mixing a single-layer GO colloidal solution and an MXene colloidal solution, a spinning solution is prepared. The spinning solution is then subjected to continuous wet spinning and ion exchange curing in a coagulation bath to obtain MXene / GO composite fibers. The fibers are then subjected to fiber shearing, vacuum-assisted filtration, vacuum heat treatment, and freeze drying to obtain MXene / GO nonwoven fabric with a three-dimensional structure. MXene / GO nonwoven fabric was immersed in silver nitrate solution to carry out in-situ reduction growth of AgNPs, thus obtaining a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs.

[0008] Preferably, the monolayer GO colloidal solution is prepared according to the following steps: Weigh 0.5-5 g K2S2O8, 1-20 mL H3PO4, 5-50 mL H2SO4, and 2-10 g flake graphite, mix them, heat to 60-100℃ and stir for 3-6 h, then dilute to 200-1500 mL; subsequently filter to separate the solid material, wash with water until pH=6-7.5, and heat-treat in an oven at 40-80℃ until dry to obtain pre-oxidized graphite; Take 50-150 mL of H2SO4, add pre-oxidized graphite, stir at -10 to -3℃ for 0.5-2 h, add 5-20 g of KMnO4, 150-400 mL of deionized water, and 10-30 mL of H2O2 solution, and stir thoroughly for 3-10 h; then add 100-500 mL of 1-10 wt% HCl solution, let stand overnight, pour off the supernatant, and wash repeatedly with deionized water until pH=6-7.5 to obtain a monolayer GO colloidal solution.

[0009] Preferably, the MXene colloidal solution is prepared according to the following steps: Weigh 3-15 mL of HCl and 0.5-1.5 g of LiF, and stir at 20-50℃ for 10-30 min to obtain the etching agent; Weigh 0.5~2.0 g of MAX phase raw material and add it to the etching agent. Continue the reaction for 12~48 h. After etching, use HCl to acid wash the reaction solution and wash it with deionized water 3~10 times until the pH=6~7.5. Then sonicate for 10~60 min to obtain MXene colloidal solution.

[0010] Preferably, the MXene in the MXene colloidal solution is Ti3C2T. x or TiNbCT x .

[0011] Preferably, the mass ratio of GO in the monolayer GO colloidal solution to MXene in the MXene colloidal solution is 1:0.2~5.

[0012] Preferably, the diameter of the MXene / GO composite fiber is 10~100 μm; The concentration of the spinning solution is 5~25 mg / mL; The coagulation bath is an aqueous ethanol solution containing 2-8 wt% CaCl2, wherein the volume ratio of ethanol to water in the aqueous ethanol solution is 1:0.5-5.

[0013] Preferably, the three-dimensional MXene / GO nonwoven fabric is prepared according to the following steps: MXene / GO composite fibers were cut into short fibers with a length of 1~10 mm, and a fiber membrane precursor was prepared by vacuum-assisted filtration. The fibers were partially fused by vacuum heat treatment, and then freeze-dried for 6~36 h to obtain MXene / GO nonwoven fabric. The vacuum heat treatment conditions are: temperature 40~70℃, vacuum degree -0.06~-0.1 MPa, and drying time 1~8 h.

[0014] Preferably, the concentration of the silver nitrate solution is 0.01~0.2 mol / L; and the in-situ reduction growth time of AgNPs is 0.5~6 h.

[0015] The second objective of this invention is to provide a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs. In this substrate, silver nanoparticles are uniformly loaded on the fiber surface and internal pores of the nonwoven fabric, with a particle size of 10~120nm and a loading amount of 3~20 wt%.

[0016] The third objective of this invention is to provide an application of a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs in trace detection.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs and its preparation method. By constructing MXene / GO nonwoven fabric loaded with AgNPs, this invention maximizes the synergistic effect of each component. GO can improve structural stability and adsorption capacity of analytes, while MXene enhances conductivity and acts as a reducing agent to achieve in-situ reduction and growth of AgNPs on the fiber surface, providing a significant electromagnetic enhancement effect for the hot spot region of AgNP construction. The preparation method is based on continuous wet spinning, vacuum-assisted filtration, and in-situ reduction, which is simple to operate, mild under mild conditions, and can achieve continuous production, making it suitable for large-scale applications.

[0018] The three-dimensional porous network structure constructed in this invention has a porosity of 60-95%, providing an ultra-large specific surface area for efficient capture of target molecules. MXene acts as a reducing agent in the in-situ reduction growth of AgNPs, greatly improving the binding stability between the support and the noble metal nanostructure. The uniform distribution of AgNPs in three-dimensional space significantly improves the efficiency of Raman signal acquisition and utilization compared to existing one-dimensional or two-dimensional SERS substrates. The detection limit of the substrate for probe molecules is as low as 10. -11 mol / L, with an enhancement factor of 10 7 The above achieves highly sensitive detection of the analyte.

[0019] Unlike existing rigid SERS substrates, the three-dimensional SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs provided by this invention has both flexibility and structural stability. It can be cut into different shapes according to actual testing needs and is suitable for the detection of various forms of samples such as liquids and solids. It has wide applicability in different trace detection scenarios in the fields of environment, food, and biology. Attached Figure Description

[0020] Figure 1 The Ti3C2T prepared in this invention x SEM images.

[0021] Figure 2 This is a SEM image of GO prepared in this invention.

[0022] Figure 3 The Ti3C2T prepared in this invention x SEM image of / GO fiber.

[0023] Figure 4 The Ti3C2T prepared in this invention x SERS performance test results of / GO fiber.

[0024] Figure 5 The Ti3C2T prepared in this invention x SERS performance test results of / GO nonwoven fabric.

[0025] Figure 6 The Ti3C2T prepared in this invention x SEM images and EDS mappings of Ag on SERS substrates loaded with AgNPs on nonwoven fabrics.

[0026] Figure 7 The Ti3C2T prepared in this invention x SERS performance test results of / GO nonwoven fabric loaded with AgNPs on SERS substrate.

[0027] Figure 8 Different proportions of TiNbCT prepared in this invention x The SERS strength of / GO fibers varies with GO content. Detailed Implementation

[0028] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0029] This invention addresses the limitations of existing three-dimensional SERS substrates, which are primarily based on rigid three-dimensional arrays. Their rigid structure and high fabrication costs hinder further development and application. Furthermore, it addresses the issues of low signal utilization in existing zero-dimensional, one-dimensional, and two-dimensional SERS substrates, and the poor flexibility, high cost, and complex fabrication processes of three-dimensional metal arrays. The purpose of this invention is to provide a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs and its fabrication method. By constructing a three-dimensional porous composite carrier and in-situ reducing the AgNP load, a three-dimensional SERS substrate with flexibility, high porosity, and high detection sensitivity is obtained, suitable for the detection of trace substances such as biomolecules, organic pollutants, and harmful additives.

[0030] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs, comprising the following steps: Monolayer GO colloidal solutions and MXene colloidal solutions were prepared separately. After uniformly mixing a single-layer GO colloidal solution and an MXene colloidal solution, a spinning solution is prepared. The spinning solution is then subjected to continuous wet spinning and ion exchange curing in a coagulation bath to obtain MXene / GO composite fibers. The fibers are then subjected to fiber shearing, vacuum-assisted filtration, vacuum heat treatment, and freeze drying to obtain MXene / GO nonwoven fabric with a three-dimensional structure. MXene / GO nonwoven fabric was immersed in silver nitrate solution to carry out in-situ reduction growth of AgNPs, thus obtaining a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs.

[0031] This invention involves immersing MXene / GO nonwoven fabric in a silver nitrate solution, utilizing the strong reducing properties of MXene to achieve in-situ reduction and growth of AgNPs, thereby obtaining a three-dimensional SERS substrate of MXene / GO nonwoven fabric loaded with AgNPs.

[0032] The mass ratio of GO in the monolayer GO colloidal solution to MXene in the MXene colloidal solution is 1:0.2~5. The concentration of the silver nitrate solution is 0.01~0.2 mol / L; the in-situ reduction growth time of AgNPs is 0.5~6 h.

[0033] Specifically, the monolayer GO colloidal solution is prepared according to the following steps: Weigh 0.5-5 g K2S2O8, 1-20 mL H3PO4, 5-50 mL H2SO4, and 2-10 g flake graphite, mix them, heat to 60-100℃ and stir for 3-6 h, then dilute to 200-1500 mL; subsequently filter to separate the solid material, wash with water until pH=6-7.5, and heat-treat in an oven at 40-80℃ until dry to obtain pre-oxidized graphite; Take 50-150 mL of H2SO4, add pre-oxidized graphite, stir at -10 to -3℃ for 0.5-2 h, add 5-20 g of KMnO4, 150-400 mL of deionized water, and 10-30 mL of H2O2 solution, and stir thoroughly for 3-10 h; then add 100-500 mL of 1-10 wt% HCl solution, let stand overnight, pour off the supernatant, and wash repeatedly with deionized water until pH=6-7.5 to obtain a monolayer GO colloidal solution.

[0034] The MXene colloidal solution was prepared according to the following steps: Weigh 3-15 mL of HCl and 0.5-1.5 g of LiF, and stir at 20-50℃ for 10-30 min to obtain the etching agent; Weigh 0.5~2.0 g of MAX phase raw material and add it to the etching agent. Continue the reaction for 12~48 h. After etching, use HCl to acid wash the reaction solution and wash it with deionized water 3~10 times until the pH=6~7.5. Then sonicate for 10~60 min to obtain MXene colloidal solution. The MAX phase raw material is Ti3AlC2 or TiNbAlC.

[0035] The MXene in the MXene colloidal solution is Ti3C2T x or TiNbCT x .

[0036] For example, the preparation steps of MXene / GO composite fibers are as follows: GO and MXene colloidal solutions were mixed at a mass ratio of 1:0.2 to 1:5, stirred, and centrifuged to form a homogeneous spinning solution. This solution was then continuously and uniformly injected into a coagulation bath using a syringe. MXene / GO composite fibers were obtained through ion exchange solidification in the coagulation bath. The centrifugation speed for forming the homogeneous spinning solution was 6000–13000 rpm, and the time was 10–50 min.

[0037] The concentration of the spinning solution is 5~25 mg / mL; the coagulation bath is an aqueous ethanol solution containing 2~8 wt% CaCl2, wherein the volume ratio of ethanol to water in the aqueous ethanol solution is 1:0.5~5.

[0038] The diameter of MXene / GO composite fibers is 10~100 μm.

[0039] The three-dimensional MXene / GO nonwoven fabric is prepared according to the following steps: MXene / GO composite fibers were cut into short fibers with a length of 1~10 mm, and a fiber membrane precursor was prepared by vacuum-assisted filtration. The fibers were partially fused by vacuum heat treatment, and then freeze-dried for 6~36 h to obtain MXene / GO nonwoven fabric. The vacuum heat treatment conditions are: temperature 40~70℃, vacuum degree -0.06~-0.1 MPa, and drying time 1~8 h.

[0040] The second aspect of the present invention provides a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs, wherein silver nanoparticles are uniformly loaded on the fiber surface and internal pores of the nonwoven fabric, with a particle size of 10~120 nm and a loading amount of 3~20 wt%.

[0041] A third aspect of this invention provides an application of a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs in trace detection. The application includes the detection of organic pollutants, harmful additives, biomolecules, etc.

[0042] It should be noted that, unless otherwise specified, the experimental methods used in this invention are all conventional methods; and the reagents and materials used, unless otherwise specified, are all commercially available.

[0043] Example 1 Ti3C2T x Preparation and SERS performance testing of / GO fibers Step 1, Ti3C2T x Preparation of colloidal solution: Ti3AlC2 powder was etched using the HCl-LiF etching method. Specifically, 8 mL of HCl and 1 g of LiF were weighed and stirred at 35 °C for 20 min to obtain the etching agent; 1.2 g of Ti3AlC2 raw material was weighed and slowly added to the etching agent, and the reaction was continued for 24 h; after etching, the reaction solution was transferred to a centrifuge tube, acid-washed with HCl, and washed several times with deionized water until pH=7 to obtain multilayer Ti3C2T x Its SEM image is as follows Figure 1 As shown, the typical accordion-like structure of multilayer MXene can be observed, indicating that multilayer Ti3C2T has been successfully etched and fabricated. x After ultrasonic treatment for 30 minutes, few-layer or monolayer Ti3C2T was obtained. x Colloidal solution.

[0044] Step 2, Preparation of GO colloidal solution: A modified Hummers method was used to prepare the GO colloidal solution. Specifically, 2 g K₂S₂O₈, 10 mL H₃PO₄, 25 mL H₂SO₄, and 5 g flake graphite were weighed, stirred evenly, heated to 80 ℃ and stirred for 4 h, and diluted to 800 mL. The solid matter was separated by filtration, washed with water until pH=7, and heat-treated in an oven at 60 ℃ until dry to obtain pre-oxidized graphite. 100 mL H₂SO₄ was measured, and the pre-oxidized graphite was added. The mixture was stirred at -5 ℃ for 1 h, and 10 g KMnO₄, 250 mL deionized water, and 20 mL H₂O₂ solution were slowly added. The mixture was stirred thoroughly for 6 h. 300 mL of 5 wt% HCl solution was added, and the mixture was allowed to stand overnight. The supernatant was discarded, and the mixture was repeatedly washed with deionized water until pH=7 to obtain the GO colloidal solution. Its SEM image is shown below. Figure 2 As shown, a distinct layered structure can be observed, indicating the successful preparation of the GO colloidal solution.

[0045] Step 3, preparation of coagulation bath: Mix deionized water and ethanol at a volume ratio of 2:1, add 4 wt% CaCl2, and mix evenly to obtain the desired spinning solution.

[0046] Step 4, continuous wet spinning: Ti3C2T x The colloidal solution was mixed with the GO colloidal solution, wherein GO accounted for 30 wt% of the total mass of the mixture. The mixture was thoroughly stirred and centrifuged to concentrate it, forming 20 mL of homogeneous spinning solution. This solution was then continuously and uniformly injected into the coagulation bath obtained in step three using a syringe to obtain Ti3C2T. x / GO fiber, its SEM image is as follows Figure 3 As shown, this proves that Ti3C2T x Successful preparation of / GO fiber.

[0047] Step 5, SERS test: The Ti3C2T... x / GO fibers were fixed on a glass slide, and 20 μl of a 10% concentration was added. -4 The R6G solution of M was dried with nitrogen to remove residual liquid from the surface. Raman spectroscopy was performed using a spectrometer (excitation wavelength 532 nm, laser power 0.1 mW, integration time 15 s). The results are as follows: Figure 4 As shown; calculations show that the SERS substrate has an enhancement factor of 1.01 × 10⁻⁶ for R6G molecules. 2 .

[0048] Example 2 Based on Ti3C2T x Preparation and SERS performance testing of / GO nonwoven fabric Step 1, Ti3C2T xPreparation of / GO fibers: Following the procedure in Example 1, Ti3C2T fibers were prepared respectively. x Ti3C2T was prepared by continuously wet spinning in a prepared spinning solution after uniformly mixing with GO colloidal solution. x / GO fiber.

[0049] Step 2, Ti3C2T x Preparation of / GO nonwoven fabric: Ti3C2T x / GO fibers are cut into short fibers with a length of no more than 1 cm and subjected to vacuum-assisted filtration. During the process, Ti3C2T x / GO fibers fuse together based on their self-fluxing properties to form a cross-linked porous network fiber membrane. The thickness and porosity were controlled by varying the parameters of vacuum drying, followed by freeze-drying for 18 h to obtain Ti3C2T. x / GO nonwoven fabric.

[0050] Step 3, SERS test: Referring to the operation in Example 1, Ti3C2T x / GO nonwoven fabric was adhered to a glass slide to prepare a SERS sample, and SERS testing was performed. The results are as follows: Figure 5 As shown; calculations show that the SERS substrate has an enhancement factor of 2.34 × 10⁻⁶ for R6G molecules. 2 Example 2 differs from Example 1 only in that the fibers are assembled into a nonwoven fabric, while all other conditions remain the same. The results show that the SERS performance of Example 2 is improved, and the fluorescence quenching effect is significant, demonstrating the advantages of nonwoven fabric in SERS substrates. Specifically, its three-dimensional porous structure can not only enhance the SERS signal by adsorbing probe molecules, but also strengthen the fluorescence quenching effect through mechanisms such as interface enhancement and light scattering path extension.

[0051] Example 3 Based on Ti3C2T x Preparation and SERS performance testing of / GO nonwoven fabric-loaded AgNPs SERS substrate Step 1, Ti3C2T x Preparation of / GO fibers: Following the procedure in Example 1, Ti3C2T was prepared. x / GO fiber.

[0052] Step 2, Ti3C2T x Preparation of / GO nonwoven fabric: Following the procedure in Example 2, Ti3C2T was prepared. x / GO nonwoven fabric.

[0053] Step 3, in-situ loading of AgNPs: The nonwoven fabric was immersed in a 0.05 mol / L silver nitrate solution, and vacuum-assisted wetting was used to ensure full contact and reaction for 1 h; after the reaction, it was rinsed 3 times each with deionized water and anhydrous ethanol, and vacuum dried at 50 ℃ for 2 h to obtain Ti3C2T x / GO nonwoven fabric loaded with AgNPs SERS substrate, its SEM image is as follows Figure 6 As shown in (a), its Ag EDS mapping is as follows Figure 6 As shown in (b), the uniform distribution of Ag and the successful preparation of the composite SERS substrate are demonstrated.

[0054] Step 4, SERS test: Referring to the operation in Example 1, Ti3C2T x A SERS substrate loaded with AgNPs on GO nonwoven fabric was adhered to a glass slide to prepare SERS samples, which were then tested. The results are as follows: Figure 7 As shown; calculations show that the SERS substrate has an enhancement factor of 1.21 × 10⁻⁶ for the R6G molecule. 6 Compared to Example 2, Example 3 only involved in-situ loading of AgNPs onto the surface of the nonwoven fabric, while all other conditions remained the same. The results showed a significant improvement in SERS performance in Example 3, demonstrating that the local surface plasmon resonance (LSPR) effect of AgNPs can provide electromagnetic enhancement, thereby greatly improving the SERS performance of the substrate.

[0055] Example 4 TiNbCT x / GO fiber parameter optimization Step 1, TiNbCT x Preparation of colloidal solution: TiNbAlC powder was etched using the HCl-LiF etching method. Specifically, 18 mL of HCl and 2 g of LiF were weighed and stirred at 50 °C for 20 min to obtain the etchant; 1.2 g of TiNbAlC raw material was weighed and slowly added to the etchant, and the reaction was continued for 40 h; after etching, the reaction solution was transferred to a centrifuge tube, acid-washed with HCl, and washed several times with deionized water until pH=6.5, and then sonicated for 30 min to obtain TiNbCT. x Colloidal solution.

[0056] Step 2, Preparation of GO colloidal solution: Following the procedure in Example 1, a GO colloidal solution was prepared.

[0057] Step 3, Preparation of the coagulation bath: Prepare the coagulation bath according to the operation in Example 1.

[0058] Step 4, Preparation of spinning solutions with different proportions: TiNbCT x Colloidal solutions and GO colloidal solutions were mixed in different proportions, with GO mass percentages of 10 wt%, 20 wt%, 30 wt%, 40 wt%, and 50 wt%, respectively. The mixtures were thoroughly stirred and centrifuged to concentrate the solution, forming 20 mL of uniform spinning solution. This solution was then continuously and uniformly injected into the coagulation bath obtained in step three using a syringe to obtain TiNbCT solutions with different proportions. x / GO fibers, labeled as TiNbCT according to GO content. x / GO-10, TiNbCT x / GO-20、TiNbCT x / GO-30、TiNbCT x / GO-40 and TiNbCT x / GO-50. Following the procedure in Example 1, TiNbCT... x GO fibers were fixed on a glass slide to prepare SERS samples, and SERS tests were performed. The change in SERS intensity with GO content was statistically analyzed. The results are as follows: Figure 8 As shown: When the GO content is low, the SERS intensity increases significantly with increasing GO content, which is due to the stronger chemical enhancement effect provided by the construction of the MXene / GO heterojunction; when the GO content is high, the SERS intensity does not change significantly with GO content, and the signal stability deteriorates sharply. This is because the GO-covered area on the fiber surface hinders the contact and charge transfer between the probe molecules and the MXene substrate. Therefore, TiNbCT x The optimal GO content in GO fiber should be 20-30 wt%.

[0059] Example 5 Based on TiNbCT x Preparation and SERS performance testing of / GO nonwoven fabric-loaded AgNPs SERS substrate Step 1, TiNbCT x Preparation of GO fibers: Following the procedures in Example 4, GO and TiNbCT fibers were prepared respectively. x The colloidal solutions were mixed, with GO comprising 30% of the total mass of the mixture. The mixture was then stirred, centrifuged, and concentrated to form 20 mL of a homogeneous spinning solution. The spinning solution was then extruded into a prepared coagulation bath to prepare TiNbCT. x / GO fiber.

[0060] Step 2, TiNbCT x Preparation of / GO nonwoven fabric: Following the procedure in Example 2, TiNbCT was prepared. x / GO nonwoven fabric.

[0061] Step 3, in-situ loading of AgNPs: Following the procedure in Example 3, TiNbCT was prepared. x / GO nonwoven fabric loaded with AgNPs SERS substrate.

[0062] Step 4, SERS test: Referring to the operation in Example 1, TiNbCT... x A SERS substrate containing AgNPs loaded with / GO nonwoven fabric was fixed on a glass slide to prepare SERS samples and perform SERS tests. Calculations showed that the SERS substrate had an enhancement factor of 10 for R6G molecules. 6 .

[0063] Comparative Example 1 A method for preparing a silver nanoparticle aggregate SERS substrate This comparative example refers to a typical silver nanoparticle aggregate SERS substrate disclosed in Chinese Patent Publication No. CN115855912A, and the specific steps are as follows: Step 1: Prepare an aqueous solution of silver nanoparticles using the seed growth method.

[0064] Step 2: Add the aqueous solution of silver nanoparticles to the toluene solution and let it stand to form a liquid-liquid two-phase interface.

[0065] Step 3: Inject an ethanol solution into the interface to promote the self-assembly of silver nanoparticles into a monolayer film at the interface.

[0066] Step four: Add the toluene solution of polymethyl methacrylate to the external toluene phase of the system, and after the reaction, wash to obtain silver nanoparticle aggregates.

[0067] The silver nanoparticle aggregates prepared in Comparative Example 1 exhibit a dense structure and demonstrate good sensitivity in SERS detection. However, this substrate is a discrete powder material, requiring additional fixation steps during use, and the preparation process involves multiple precise liquid-phase operations and organic solvent interface assembly, making the process relatively complex. In contrast, this invention constructs an MXene / GO three-dimensional heterostructure nonwoven fabric and directly loads AgNPs, obtaining a one-piece, self-supporting flexible SERS substrate. This avoids complex interface assembly and subsequent fixation steps, significantly improving preparation efficiency and practical application convenience while maintaining detection performance.

[0068] Comparative Example 2 A noble metal-semiconductor SERS substrate based on MXene / Ag / PDMS and its fabrication method This comparative example refers to a flexible SERS substrate disclosed in Chinese Patent Publication No. CN115046982A, and the specific steps are as follows: Step 1: Mix sylgard 184 siloxane elastomer base material and curing agent at a volume ratio of 10:1, stir to remove bubbles, spin coat onto silicon wafer, cure at 80 ℃, and then peel off to obtain PDMS flexible film. Step 2: Ascorbic acid, sodium citrate and silver nitrate solution are added sequentially to the surface of the PDMS membrane and incubated for 5 minutes to generate AgNPs in situ through external chemical reduction. Step 3: Immerse the obtained sample in MXene solution for 2 hours to allow MXene to cover the surface of AgNPs and form a protective layer.

[0069] Comparative Example 2 utilizes PDMS as a flexible support, constructing AgNPs@MXene structures on its surface through multi-step chemical modification. While this method achieves the preparation of a flexible SERS substrate, the formation of its silver nanoparticles entirely depends on an external reducing agent, and the PDMS matrix itself lacks conductivity and reducing properties, resulting in limited binding force with the active components. In contrast, this invention, by introducing GO into the MXene system to construct a three-dimensional heterojunction nonwoven fabric, has the following advantages: Firstly, GO improves the fiber-forming properties of the material, giving the substrate excellent self-supporting performance; secondly, the heterojunction formed by GO and MXene promotes electron transfer, not only enhancing the chemical reinforcement (CM) effect but also facilitating the formation of Ag... + In-situ reduction allows for stable loading of AgNPs without the need for additional reducing agents. This integrated material design simplifies the preparation process while ensuring a high density and uniform distribution of SERS active sites.

[0070] In summary, this invention provides a three-dimensional SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs and its preparation method. The method includes preparing a colloidal solution containing monolayer GO and MXene using a modified Hummers method and HCl-LiF etching; mixing the GO and MXene colloidal solution and solidifying it through a coagulation bath ion exchange process using continuous wet spinning to obtain MXene / GO composite fibers; and forming a three-dimensional MXene / GO nonwoven fabric through fiber shearing, vacuum-assisted filtration, vacuum heat treatment, and freeze-drying; and in-situ reduction growth of silver nanoparticles (AgNPs) on and within the nonwoven fabric carrier to form a three-dimensional porous network structure of MXene / GO / AgNPs SERS substrate. The SERS substrate prepared by this invention achieves a synergistic effect of electromagnetic and chemical enhancement. Its three-dimensional porous structure can efficiently adsorb analyte molecules and support multifunctional detection, while also possessing excellent detection sensitivity. It can be widely applied in fields such as environmental pollutant detection, food safety analysis, and trace biomolecule detection.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs, characterized in that, Includes the following steps: Monolayer GO colloidal solutions and MXene colloidal solutions were prepared separately. After uniformly mixing a single-layer GO colloidal solution and an MXene colloidal solution, a spinning solution is prepared. The spinning solution is then subjected to continuous wet spinning and ion exchange curing in a coagulation bath to obtain MXene / GO composite fibers. The fibers are then subjected to fiber shearing, vacuum-assisted filtration, vacuum heat treatment, and freeze drying to obtain MXene / GO nonwoven fabric with a three-dimensional structure. MXene / GO nonwoven fabric was immersed in silver nitrate solution to carry out in-situ reduction growth of AgNPs, thus obtaining a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs.

2. The method for preparing a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs according to claim 1, characterized in that, The monolayer GO colloidal solution was prepared according to the following steps: Weigh 0.5-5 g K2S2O8, 1-20 mL H3PO4, 5-50 mL H2SO4, and 2-10 g flake graphite, mix them, heat to 60-100℃ and stir for 3-6 h, then dilute to 200-1500 mL; subsequently filter to separate the solid material, wash with water until pH=6-7.5, and heat-treat in an oven at 40-80℃ until dry to obtain pre-oxidized graphite; Take 50-150 mL of H2SO4, add pre-oxidized graphite, stir at -10 to -3℃ for 0.5-2 h, add 5-20 g of KMnO4, 150-400 mL of deionized water, and 10-30 mL of H2O2 solution, and stir thoroughly for 3-10 h; then add 100-500 mL of 1-10 wt% HCl solution, let stand overnight, pour off the supernatant, and wash repeatedly with deionized water until pH=6-7.5 to obtain a monolayer GO colloidal solution.

3. The method for preparing a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs according to claim 1, characterized in that, The MXene colloidal solution was prepared according to the following steps: Weigh 3-15 mL of HCl and 0.5-1.5 g of LiF, and stir at 20-50℃ for 10-30 min to obtain the etching agent; Weigh 0.5~2.0 g of MAX phase raw material and add it to the etching agent. Continue the reaction for 12~48 h. After etching, use HCl to acid wash the reaction solution and wash it with deionized water 3~10 times until the pH=6~7.

5. Then sonicate for 10~60 min to obtain MXene colloidal solution.

4. The method for preparing a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs according to claim 3, characterized in that, The MXene in the MXene colloidal solution is Ti3C2T x or TiNbCT x .

5. The method for preparing a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs according to claim 1, characterized in that, The mass ratio of GO in a monolayer GO colloidal solution to MXene in an MXene colloidal solution is 1:0.2~5.

6. The method for preparing a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs according to claim 1, characterized in that, The diameter of MXene / GO composite fibers is 10~100 μm; The concentration of the spinning solution is 5~25 mg / mL; The coagulation bath is an aqueous ethanol solution containing 2-8 wt% CaCl2, wherein the volume ratio of ethanol to water in the aqueous ethanol solution is 1:0.5-5.

7. The method for preparing a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs according to claim 1, characterized in that, The three-dimensional MXene / GO nonwoven fabric is prepared according to the following steps: MXene / GO composite fibers were cut into short fibers with a length of 1~10 mm, and a fiber membrane precursor was prepared by vacuum-assisted filtration. The fibers were partially fused by vacuum heat treatment, and then freeze-dried for 6~36 h to obtain MXene / GO nonwoven fabric. The vacuum heat treatment conditions are: temperature 40~70℃, vacuum degree -0.06~-0.1 MPa, and drying time 1~8 h.

8. The method for preparing a three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs according to claim 1, characterized in that, The concentration of the silver nitrate solution is 0.01~0.2 mol / L; the in-situ reduction growth time of AgNPs is 0.5~6 h.

9. A three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs, prepared by the method according to any one of claims 1 to 8, characterized in that, In this substrate, silver nanoparticles are uniformly loaded on the fiber surface and internal pores of the nonwoven fabric, with a particle size of 10~120 nm and a loading amount of 3~20 wt%.

10. The application of the three-dimensional porous SERS substrate based on MXene / GO nonwoven fabric loaded with AgNPs as described in claim 9 in trace detection.

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