Reusable SERS (Surface Enhanced Raman Scattering) substrate of Ag / Ag3PO4 / MXene, preparation method of SERS substrate and application of SERS substrate in degradation / detection of crystal violet

Abstract

The invention relates to the field of wastewater treatment, and provides a reusable SERS (Surface Enhanced Raman Scattering) substrate of Ag / Ag3PO4 / MXene, a preparation method of the SERS substrate and application of the SERS substrate in degradation / detection of crystal violet, and the SERS substrate can be used as a surface enhanced Raman scattering substrate for efficiently detecting organic dyes and has the capability of photocatalytic degradation of organic pollutants. And through the synergistic effect of Ag3PO4 and MXene, the SERS signal of the Ag nanoparticles is obviously improved, and the detection sensitivity to the dye is enhanced. The composite material shows excellent performance in the aspect of photocatalytic degradation, the absorption of visible light is remarkably improved through the Ag nanoparticle plasmon resonance effect, separation and transmission of photo-generated charge carriers are promoted, and the photocatalytic degradation efficiency is improved. As an SERS (Surface Enhanced Raman Scattering) sensor, the detection limit on dye crystal violet is 3.82 * 10 <-11 > M, and the SERS sensor has relatively high sensitivity; the CV degradation rate of the composite material is 83.64% within 90 minutes, and the composite material has good reusability.

Description

Technical Field

[0001] The present invention relates to the field of wastewater treatment and provides a reusable Ag / Ag3PO4 / MXene SERS substrate, its preparation method, and its application in the degradation / detection of crystal violet, which has good environmental friendliness and reusability. Through integrated processing, the present invention combines high-sensitivity detection of organic dyes with efficient degradation, achieving real-time monitoring and pollutant removal in wastewater, significantly improving treatment efficiency and reducing the risk of secondary pollution. Background Art

[0002] Organic dyes in wastewater have attracted widespread attention due to their potential threats to environmental safety and human health. Therefore, it is imperative to develop integrated treatment methods that combine detection and degradation before wastewater is discharged into water bodies. However, current integrated treatment methods primarily rely on different materials for dye detection and removal, which limits the overall efficiency of pollution management. Research on dynamic monitoring and treatment methods in the management of organic pollutants remains relatively limited, and comprehensive solutions for this type of pollutant remain underdeveloped.

[0003] In this context, the application of composite functional materials based on flexible materials in wastewater treatment has attracted widespread attention. In particular, SERS technology has shown great potential in dye detection due to its high sensitivity, non-destructiveness and real-time detection capabilities. Photocatalytic technology has become another important means of environmental pollution control because it can degrade organic pollutants under visible light irradiation. Combining SERS with photocatalytic technology can not only achieve efficient detection of dyes, but also degrade pollutants while detecting, becoming a new type of pollutant treatment technology with dual functions. However, traditional SERS substrates and photocatalysts often need to be designed separately, and the reusability and treatment effect of the materials have not been fully guaranteed. Therefore, the development of a composite material that can combine high-sensitivity detection and efficient degradation capabilities with good reusability is the key to solving this problem.

[0004] Based on this, the present invention successfully prepared a Ag / Ag3PO4 / MXene ternary composite material based on flexible cotton fabric. As a dual-functional and reusable SERS substrate, it can both efficiently detect and degrade organic dyes. Through the synergistic effect of Ag3PO4 and MXene, the SERS signal of AgNPs was significantly improved, and its detection sensitivity for dyes was enhanced. In addition, the composite material showed excellent performance in photocatalytic degradation. The local surface plasmon resonance effect (LSPR) of AgNPs significantly improved the absorption of visible light, promoted the separation and transport of photogenerated charge carriers, and thus improved the photocatalytic degradation efficiency. In addition, this photocatalytic cotton matrix can be used independently for dye degradation in water, effectively avoiding the risk of secondary pollution during the degradation of organic pollutants. Therefore, this high-performance, dual-functional material shows great potential in environmental monitoring and pollution control by providing sensitive SERS detection and efficient degradation of wastewater pollutants. Summary of the Invention

[0005] This paper presents a flexible cotton fabric-based Ag / Ag3PO4 / MXene ternary composite material with dual functionality, enabling highly sensitive detection of organic dyes while also achieving efficient degradation. By combining the synergistic effects of AgNPs, Ag3PO4, and MXene, this composite material significantly enhances the intensity of the SERS signal and the efficiency of photocatalytic degradation of organic dyes. The composite's structure, SERS performance, and photocatalytic degradation of pollutants were characterized. Specifically:

[0006] (1) This paper utilizes electrostatic self-assembly combined with chemical reduction to systematically integrate AgNPs, Ag3PO4, and MXene onto a flexible cotton fabric substrate, successfully fabricating a highly sensitive SERS substrate. SEM, XRD, and XPS experimental results effectively demonstrate the successful preparation of the substrate.

[0007] (2) This paper explores the enhancement effect of the three components in the SERS substrate. The results show that the combination of Ag3PO4 and MXene significantly enhances the SERS signal of AgNPs. The enhancement effect is mainly through the formation of the metal-semiconductor interface to promote charge transfer, thereby significantly enhancing the local electromagnetic field and increasing the intensity of the SERS signal. Furthermore, crystal violet (CV) was selected as the probe molecule to evaluate the sensitivity of the substrate in the detection of crystal violet (CV) molecules.

[0008] (3) The present invention investigates the ability of the substrate to function as a single photocatalyst, and the reasons why the three components synergistically enhance the photocatalytic degradation ability. The LSPR effect of AgNPs can significantly enhance the visible light absorption of Ag3PO4. The two-dimensional layered structure of MXene and its excellent conductivity provide an efficient charge transfer network, significantly promoting the separation and transport of photogenerated charge carriers, thereby improving the efficiency of the photocatalytic reaction.

[0009] (4) The substrate prepared in this invention incorporates a photocatalyst into a flexible cotton fabric substrate, making the composite material not only multifunctional but also easy to operate and perform on-site detection. The flexible substrate can effectively adapt to irregularly shaped samples and is suitable for SERS detection and pollutant degradation in real-world environments.

[0010] The present invention synthesizes an Ag3PO4 / MXene composite material on a cotton fabric substrate through an electrostatically driven self-assembly method, and then grows AgNPs on its surface through a chemical reduction method, successfully preparing an Ag / Ag3PO4 / MXene ternary composite material based on flexible cotton fabric. This material combines the dual functions of SERS detection and photocatalytic degradation, and can efficiently detect organic dyes in water and degrade pollutants under visible light irradiation. The synergistic effect between Ag nanoparticles, Ag3PO4 and MXene enables the composite material to have high-sensitivity detection capabilities at low concentrations and exhibit excellent photocatalytic degradation performance. At the same time, the flexible cotton fabric as a carrier gives the material good mechanical flexibility and operability, making it suitable for long-term repeated use and has broad application prospects in environmental monitoring and wastewater treatment.

[0011] To achieve the above objectives, the technical solution of the present invention is as follows: a reusable Ag / Ag3PO4 / MXene SERS substrate, the preparation method of which is as follows:

[0012] 1) Soak the cotton fabric in alkali solution, treat it at high temperature, rinse it to a neutral state, and freeze-dry it;

[0013] 2) Immersing the treated cotton fabric obtained in step 1) in a MXene dispersion to soak it thoroughly, adding an AgNO3 solution and ultrasonically obtaining a suspension, adding a Na2HPO4 solution and stirring in the dark to obtain a black Ag3PO4 / MXene cotton fabric, which is then rinsed and freeze-dried in a vacuum;

[0014] 3) The Ag3PO4 / MXene cotton fabric was immersed in AgNO3 solution, and NaBH4 solution was added and stirred for reaction. After the reaction was completed, the fabric was rinsed and freeze-dried in vacuum.

[0015] In the above-mentioned reusable Ag / Ag3PO4 / MXene SERS substrate, in step 1), the high-temperature treatment is performed at 130°C for 5 hours.

[0016] The above-mentioned reusable Ag / Ag3PO4 / MXene SERS substrate, in step 2), the preparation method of the MXene dispersion is as follows: LiF is gradually added to HCl, stirred to form an acidic etching solution, MAX phase Ti3AlC2 powder is gradually added, stirred, deionized water is added, centrifuged, the precipitate is washed, and freeze-dried to obtain multilayer Ti3C2 nanosheets, Ti3C2 is suspended in DMSO, stirred, centrifuged, and the obtained black slurry is redispersed in deionized water, and sonicated to obtain a MXene dispersion.

[0017] In the above-mentioned reusable Ag / Ag3PO4 / MXene SERS substrate, in step 2), the stirring is carried out at 35°C for 24 hours.

[0018] In the above-mentioned reusable Ag / Ag3PO4 / MXene SERS substrate, in step 2), the concentration of the MXene dispersion is 0.5 mg / mL.

[0019] In the above-mentioned reusable Ag / Ag3PO4 / MXene SERS substrate, in step 3), the concentration of the AgNO3 solution is 0.05M.

[0020] The above-mentioned reusable Ag / Ag3PO4 / MXene SERS substrate is used in the photocatalytic degradation of crystal violet.

[0021] The above-mentioned application is characterized in that the method is as follows: immersing the Ag / Ag3PO4 / MXene SERS substrate described in any one of claims 1-6 in a crystal violet solution, and degrading the crystal violet under simulated sunlight conditions.

[0022] The above-mentioned reusable Ag / Ag3PO4 / MXene SERS substrate is used for detecting crystal violet.

[0023] The present invention provides a Ag / Ag3PO4 / MXene ternary composite material based on flexible cotton fabric, which has dual functions: it can serve as a surface-enhanced Raman scattering (SERS) substrate for highly sensitive detection of organic dyes, and can also serve as a photocatalyst to efficiently degrade organic dyes under visible light irradiation.

[0024] The above-mentioned Ag / Ag3PO4 / MXene ternary composite material based on flexible cotton fabric, in which the combination of Ag3PO4 and MXene significantly enhances the SERS signal of Ag nanoparticles, is mainly achieved by promoting the charge transfer effect through the formation of the metal-semiconductor interface, thereby significantly enhancing the local electromagnetic field and increasing the intensity of the SERS signal.

[0025] In the aforementioned flexible cotton fabric-based Ag / Ag3PO4 / MXene ternary composite, the localized surface plasmon resonance (LSPR) effect of AgNPs significantly enhances the visible light absorption of Ag3PO4. The two-dimensional layered structure of MXene and its excellent conductivity provide an efficient charge transfer network, significantly promoting the separation and transport of photogenerated charge carriers, thereby improving the efficiency of the photocatalytic reaction.

[0026] The above-mentioned Ag / Ag3PO4 / MXene ternary composite material based on flexible cotton fabric has high SERS sensitivity to crystal violet (CV), and its performance is significantly improved compared with existing SERS substrates.

[0027] The above-mentioned Ag / Ag3PO4 / MXene ternary composite material based on flexible cotton fabric can independently carry out photocatalytic degradation of organic dyes, which can effectively reduce the secondary pollution risk caused by traditional powder photocatalysts.

[0028] The above-mentioned Ag / Ag3PO4 / MXene ternary composite material based on flexible cotton fabric is used for on-site detection and degradation of organic pollutants in wastewater, providing a comprehensive treatment method integrating detection and pollutant removal.

[0029] The present invention has the following beneficial effects

[0030] 1) High efficiency and dual functions: The Ag / Ag3PO4 / MXene ternary composite material of the present invention is used as a SERS substrate with high sensitivity and can effectively detect organic dyes in water. At the same time, through its photocatalytic properties, it can degrade the dyes under visible light irradiation, significantly reducing the content of harmful substances in wastewater.

[0031] 2) Synergistic Effect Enhances Performance: The synergistic effect between Ag nanoparticles, Ag3PO4, and MXene significantly enhances the composite's SERS performance and photocatalytic degradation ability. The localized surface plasmon resonance effect of the Ag nanoparticles enhances the SERS signal, while the excellent conductivity of MXene and its two-dimensional layered structure provide an ideal charge transfer network for the photocatalytic reaction.

[0032] 3) High-sensitivity detection: As a SERS sensor, the composite material can achieve high-sensitivity detection of CV, with a detection limit of 3.82×10 -11 M, which is superior to most existing SERS substrates.

[0033] 4) Efficient photocatalytic degradation: Within 90 minutes, Ag / Ag3PO4 / MXene cotton fabric can achieve a crystal violet degradation rate of up to 83.64% by visible light and can be used as a single photocatalyst.

[0034] 5) Flexibility and practicality: The photocatalyst is combined with a flexible cotton fabric substrate, which has the advantage of being easy to use in practical applications. It can perform real-time SERS detection on site and avoid the risk of secondary pollution caused by traditional powder catalysts by photocatalytic degradation of pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 SEM images of original cotton fabric (a), pretreated cotton fabric (b), Ag3PO4 / MXene cotton fabric (c) and Ag / Ag3PO4 / MXene cotton fabric (d).

[0036] Figure 2 XRD patterns of Ti3AlC2 and MXene (a), XRD of Ag3PO4, Ag3PO4 / MXene, and Ag / Ag3PO4 / MXene cotton fabrics.

[0037] Figure 3 XPS spectra of Ag3PO4, MXene and Ag / Ag3PO4 / MXene cotton fabrics.

[0038] Figure 4 CV powder samples, blank samples of Ag / Ag3PO4 / MXene cotton fabrics, and CV on MXene, Ag3PO4, Ag3PO4 / MXene, and Ag / Ag3PO4 / MXene cotton fabrics (10 -6 SERS spectrum of M) (a), CV at 1618 cm -1 Comparison of the Raman intensities of the peaks (b).

[0039] Figure 5 SERS signals of different concentrations of CV on Ag / Ag3PO4 / MXene cotton fabric substrate (a), the peak of Ag / Ag3PO4 / MXene cotton fabric is at 1618 cm -1 Linear fitting of the peak at and CV concentration (b).

[0040] Figure 6Effect of photocatalytic activity of Ag3PO4, Ag3PO4 / MXene, Ag / Ag3PO4 / MXene cotton fabric and blank sample on CV degradation under visible light irradiation (a), and ln(C0 / C t ) and irradiation time, based on the fitting results of pseudo-first-order reaction kinetics (b).

[0041] Figure 7 Mechanism of photocatalytic degradation of pollutants by Ag / Ag3PO4 / MXene cotton fabric under visible light irradiation.

[0042] Figure 8 Schematic diagram of the integration of SERS technology and photocatalytic degradation on Ag / Ag3PO4 / MXene cotton fabric substrate. DETAILED DESCRIPTION

[0043] In order to better understand the technical solution of the present invention, a specific embodiment is given to further illustrate it in detail, but the solution is not limited thereto.

[0044] Example 1 Preparation and characterization of Ag / Ag3PO4 / MXene cotton fabric

[0045] The specific steps are as follows

[0046] 1. Hydrophilic pretreatment of cotton fabrics

[0047] Approximately 5 grams of cotton fabric was soaked in 28 milliliters of a 12M KOH solution and then placed in a 35-milliliter Teflon-lined autoclave. The fabric was treated at 130°C for 5 hours, resulting in an 80% fill rate. After treatment, the cotton was rinsed with anhydrous ethanol and deionized water until neutral. It was then freeze-dried in a vacuum oven.

[0048] 2. Preparation of 2D layered Ti3C2 MXene

[0049] First, 1.6 g of LiF was gradually added to 20 ml of 9 M HCl and stirred for 15 minutes until the solution turned from milky white to colorless, forming an acidic etching solution. Then, 1 g of MAX phase Ti3AlC2 powder was gradually added and stirred at 35°C for 24 hours. After the reaction, deionized water was added to the reaction mixture and centrifuged at 5000 rpm for 8 minutes. After removing the supernatant, the mixture was repeatedly centrifuged and washed with deionized water until the pH of the supernatant reached approximately 7. The black slurry obtained by centrifugation was then freeze-dried to produce multilayered Ti3C2 nanosheets. 2D layered MXene was further prepared using the DMSO intercalation method. Specifically, 0.05 g of Ti3C2 was suspended in 10 ml of DMSO and stirred at 35°C for 24 hours. The solution was then centrifuged at 8000 rpm for 5 minutes to remove the DMSO. The resulting black slurry was redispersed in 100 ml of deionized water and sonicated for several hours to produce a MXene dispersion with a concentration of approximately 0.5 mg / mL.

[0050] 3. Preparation of Ag3PO4 / MXene cotton fabric

[0051] First, a 2cm×2cm hydrophilic treated cotton fabric was immersed in 2 ml of 0.5 mg / mL MXene dispersion to ensure complete saturation. Subsequently, 2 ml of 0.15M AgNO3 solution was added and sonicated for 30 minutes to obtain a uniform suspension. During this process, the natural pores of the cotton fabric facilitated the effective adsorption of MXene. At the same time, the positively charged silver ions were adsorbed on the negatively charged MXene sheets through electrostatic interaction, forming a stable structure on the cotton surface. Next, 3 ml of 0.05M Na2HPO4 solution was gradually added and stirred in the dark at room temperature for 4 hours to form a black Ag3PO4 / MXene cotton fabric. The cotton was then rinsed with deionized water several times to remove residual particles and finally freeze-dried in vacuum.

[0052] 4. Preparation of Ag / Ag3PO4 / MXene cotton fabric

[0053] First, the Ag3PO4 / MXene cotton fabric precursor was placed in a beaker and immersed in 2 ml of 0.05 M AgNO3 solution for 30 minutes. Subsequently, 1 ml of 0.005 M NaBH4 solution was gradually added and stirred for 10 minutes. After the reaction was complete, the resulting Ag / Ag3PO4 / MXene cotton fabric was thoroughly rinsed with deionized water to remove any residual particles. Finally, the sample was freeze-dried in a vacuum.

[0054] 5. SERS spectroscopy measurement

[0055] In order to evaluate the SERS performance of the composite flexible substrate, different concentrations (10-5 M to 10 -10 M) CV solution and smeared it on a 1 cm × 1 cm piece of APMX cotton. After the solution was allowed to air dry, Raman spectroscopy was performed directly.

[0056] 6. Photocatalytic measurement

[0057] To evaluate the photocatalytic degradation performance of the composite flexible substrate, degradation efficiency experiments were conducted. 2 cm × 2 cm samples of Ag₃PO₄, Ag₃PO₄ / MXene, and Ag / Ag₃PO₄ / MXene cotton fabric were immersed in a 10⁻⁵ M CV solution. The samples were first adsorbed in the dark for 15 minutes and then irradiated under simulated sunlight for 90 minutes. Samples were taken every 15 minutes, and the CV concentration was measured using a UV-visible spectrophotometer. The degradation rate was calculated based on the change in absorbance.

[0058] 7. Preparation and testing of actual samples

[0059] Combining SERS technology with photocatalytic degradation in Ag / Ag3PO4 / MXene cotton fabric substrates provides an effective “detection-degradation integration” solution for real-time monitoring and treatment of wastewater. -5 A 35mL solution of MCV was used as a model water sample. A 40μL droplet of this solution was applied to the surface of an Ag / Ag3PO4 / MXene cotton fabric for SERS analysis. After 15 minutes of simulated sunlight irradiation, the next SERS measurement was performed. Subsequently, the Ag / Ag3PO4 / MXene cotton fabric was placed in a beaker containing the model water sample and subjected to photocatalytic degradation under simulated sunlight. UV-visible spectroscopy was used to record absorbance changes every 15 minutes to verify its degradation performance.

[0060] Figure 1 This is the preparation process of Ag / Ag3PO4 / MXene cotton fabric, and the morphology of the samples was observed by SEM. Figure 1 a is the SEM image of the original cotton fabric, which shows a one-dimensional, tubular, tree-like fiber structure. Figure 1 b depicts cotton fabric after strong alkali treatment, showing that its fiber structure and morphology remain intact. Figure 1 c is Ag3PO4 / MXene cotton fabric synthesized on two-dimensional Ti3C2 MXene sheets by electrostatic self-assembly. The surface of the cotton fabric becomes rough and accumulates spherical silver phosphate particles with a diameter of about 100-200 nm. Figure 1d is the Ag / Ag3PO4 / MXene cotton fabric after in situ reduction with sodium borohydride. In addition to retaining Ag3PO4 microspheres, a large number of Ag NPs of about 20 nm are also formed. These Ag NPs and Ag3PO4 form a stacked cavity structure on the MXene surface.

[0061] Figure 2 a is the XRD pattern of Ti3AlC2 and MXene. As can be seen from the figure, the (002) diffraction peak has shifted and the angle has become smaller. This indicates that Ti3AlC2 has converted into Ti3C2 MXene sheets. Figure 2 b is the XRD pattern of Ag3PO4, Ag3PO4 / MXene, and Ag / Ag3PO4 / MXene cotton fabrics. All samples showed a broad diffraction peak at about 21°, indicating that the cotton fabric has an amorphous structure. In addition, each sample showed a diffraction peak corresponding to the Ag3PO4 phase (JCPDS NO.06-0505), confirming that Ag3PO4 was successfully loaded in the cotton fabric substrate. Due to its low concentration and large dispersibility, XRD did not show the characteristic diffraction peak of MXene. The diffraction peak of metallic Ag (JCPDS NO.04-0783) was observed in Ag3PO4 / MXene and Ag / Ag3PO4 / MXene cotton fabrics, confirming the effective distribution of AgNPs in the photocatalyst.

[0062] Figure 3 The XPS spectra of Ag3PO4, MXene, and Ag / Ag3PO4 / MXene cotton fabric are shown below. The C, O, P, Ti, and Ag elements detected in the Ag / Ag3PO4 / MXene cotton fabric are consistent with the composition of Ag3PO4 and MXene, indicating that the three-component substrate was successfully prepared.

[0063] Example 2 SERS performance evaluation of Ag / Ag3PO4 / MXene cotton fabric substrate

[0064] a. Comparison of SERS signals of substrates with different components

[0065] In order to evaluate the SERS activity of different photocatalysts on flexible cotton fabric substrates, 10 -6 The CV of M was used as a probe molecule. A 40 μL droplet of the probe molecule was applied to a 1 cm × 1 cm Ag / Ag3PO4 / MXene cotton fabric. After the solution was allowed to air dry, Raman spectroscopy was performed directly.

[0066] Figure 4a is the SERS spectra of CV powder sample, blank sample of Ag / Ag3PO4 / MXene cotton fabric, and CV on MXene, Ag3PO4, Ag3PO4 / MXene, and Ag / Ag3PO4 / MXene cotton fabric, Figure 4 b is 1618cm of CV on different substrates -1 The CV powder sample shows five main Raman peaks, located at about 912 cm -1 、1170cm -1 、1370cm -1 、1588cm -1 and 1618cm -1 Specifically, 912cm -1 The peak corresponding to the bending vibration of CNC, 1170cm -1 and 1370cm -1 The peaks at 1588 cm-1 are attributed to the CH plane bending vibration and N-phenyl stretching vibration, respectively, while the peaks at 1588 cm-1 are attributed to the CH plane bending vibration and N-phenyl stretching vibration, respectively. -1 and 1618cm -1 The peak corresponds to the stretching vibration of the benzene ring. After adding CV, the MXene and Ag3PO4 cotton fabric substrates exhibited weak Raman signals similar to those of the CV powder sample. In contrast, the Raman signals of the Ag3PO4 / MXene and Ag / Ag3PO4 / MXene cotton fabric substrates were significantly enhanced. Ag / Ag3PO4 / MXene exhibited the strongest SERS signal.

[0067] b. Sensitivity detection of Ag / Ag3PO4 / MXene cotton fabric substrate

[0068] In order to evaluate the SERS sensitivity of Ag / Ag3PO4 / MXene cotton fabric flexible substrate, the SERS detection results were analyzed under the CV concentration gradient (10 -5 M to 10 -10 M) range was recorded.

[0069] Figure 5 a is the SERS signal of CV with different concentrations on Ag / Ag3PO4 / MXene cotton fabric substrate, 5b is the SERS signal of Ag / Ag3PO4 / MXene cotton fabric peak at 1618 cm -1 The peak at 10 is linearly fitted with the CV concentration. As the CV concentration decreases, the SERS signal intensity of the substrate decreases significantly, but at a concentration as low as 10 -10 The signal can still be detected at 1618cm -1 The intensity of the peak is positively linearly related to its logarithmic concentration, and the linear regression equation is: 1618 cm -1=53561.7+5117.5log C(R 2 =0.993). Under the condition of a signal-to-noise ratio of 3, the detection limit (LOD) of CV was 3.82×10 -11 M, showing the high sensitivity of this substrate in CV detection.

[0070] Example 3 Photocatalytic ability of Ag / Ag3PO4 / MXene cotton fabric substrate

[0071] In order to evaluate the photocatalytic degradation ability of Ag / Ag3PO4 / MXene cotton fabric substrate, a photodegradation experiment was carried out using 10 -5 The prepared samples were immersed in CV solution and incubated in the dark for 15 minutes to establish adsorption-desorption equilibrium. Subsequently, a photocatalytic degradation experiment was carried out under simulated sunlight for 90 minutes using the prepared photocatalytic flexible cotton fabric substrate.

[0072] Figure 6 The photocatalytic activity of Ag3PO4, Ag3PO4 / MXene, Ag / Ag3PO4 / MXene cotton fabric and blank samples on CV degradation under visible light irradiation (a), and ln(C0 / C t ) and irradiation time, based on the fitting results of pseudo-first-order reaction kinetics (b). Under simulated sunlight, the CV degradation rate of Ag / Ag3PO4 / MXene cotton fabric was the highest, indicating that the introduction of MXene enhanced the adsorption capacity and photocatalytic activity of the photocatalyst. In contrast, the excessive amount of silver nanoparticles on the surface of Ag / Ag3PO4 cotton fabric hindered the effective light absorption of Ag3PO4, resulting in low photocatalytic activity. The electron acceptor properties of MXene promoted the electron transfer between Ag3PO4 and silver nanoparticles, effectively separated the photogenerated electron-hole pairs, and improved the photocatalytic efficiency. Therefore, the Ag / Ag3PO4 / MXene cotton fabric substrate exhibited superior photocatalytic performance.

[0073] Figure 7 This is the mechanism of Ag / Ag3PO4 / MXene cotton fabric photocatalytic degradation of pollutants under visible light irradiation. In this photocatalytic system, visible light irradiation can excite Ag3PO4, generate photogenerated electrons that jump to the conduction band, and leave h + , these h + It can oxidize crystal violet dye to produce carbon dioxide, water and other substances. +Not only does it oxidize the dye, it also converts water into OH radicals. 3- The negative charge of the ion, the surface of Ag3PO4 preferentially retains h+, promoting the generation of OH free radicals and destroying the dye molecules. The conduction band potential of Ag3PO4 is lower than that of O2 / ·O2 - The reduction potential of Ag3PO4 is too low to directly reduce O2 molecules. To solve this problem, an APO heterojunction was constructed on MXene, where electrons can be efficiently transferred to AgNPs and MXene, inhibiting the photocorrosion and carrier recombination of Ag3PO4 and promoting the reduction of O2 to generate O2 - The enhanced light absorption capacity of MXene and AgNPs significantly improves photocatalytic activity. This material exhibits excellent performance in environmental pollution control and provides new opportunities for the development of high-performance catalysts.

[0074] Example 4 Actual sample testing of Ag / Ag3PO4 / MXene cotton fabric substrate

[0075] As an excellent photocatalytic material, Ag / Ag3PO4 / MXene cotton fabric exhibits significant photocatalytic degradation ability under visible light conditions, effectively decomposing organic pollutants and harmful substances in polluted water. Combining SERS technology with photocatalytic degradation in Ag / Ag3PO4 / MXene cotton fabric substrates provides an effective "detection-degradation integration" solution for real-time monitoring and treatment of sewage. -5 A 35mL solution of MCV was used as a model water sample. A 40μL droplet of this solution was applied to the surface of an Ag / Ag3PO4 / MXene cotton fabric for SERS analysis. After 15 minutes of simulated sunlight irradiation, the next SERS measurement was performed. Subsequently, the Ag / Ag3PO4 / MXene cotton fabric was placed in a beaker containing the model water sample and subjected to photocatalytic degradation under simulated sunlight. UV-visible spectroscopy was used to record absorbance changes every 15 minutes to verify its degradation performance.

[0076] Figure 8Schematic diagram of the integration of SERS technology and photocatalytic degradation on an Ag / Ag3PO4 / MXene cotton fabric substrate. As shown, 40 μL of this solution was dropwise applied to the Ag / Ag3PO4 / MXene cotton fabric surface, yielding a clear SERS signal. After 15 minutes of simulated sunlight irradiation, SERS measurements were repeated, revealing the disappearance of the signal, further demonstrating the substrate's excellent reusability. Subsequently, the Ag / Ag3PO4 / MXene cotton fabric was placed in a beaker containing a model water sample and subjected to photocatalytic degradation under simulated sunlight. The results demonstrated that the Ag / Ag3PO4 / MXene cotton fabric, acting as a standalone photocatalyst, effectively degraded the sample within 90 minutes. Therefore, this integrated technology not only enables highly sensitive detection of pollutants but also further purifies water through photocatalytic degradation, significantly improving the efficiency and effectiveness of water treatment. This innovative technology platform opens new avenues for applications in environmental monitoring and pollution control, with broad application prospects and potential societal benefits.

Claims

1. A reusable Ag / Ag3PO4 / MXene SERS substrate, characterized in that: The preparation method is as follows, 1) Soak the cotton fabric in alkali solution, treat it at high temperature, rinse it to a neutral state, and freeze-dry it; 2) Immersing the treated cotton fabric obtained in step 1) in a MXene dispersion to soak it thoroughly, adding an AgNO3 solution and ultrasonically obtaining a suspension, adding a Na2HPO4 solution and stirring in the dark to obtain a black Ag3PO4 / MXene cotton fabric, which is then rinsed and freeze-dried in a vacuum; 3) The Ag3PO4 / MXene cotton fabric was immersed in AgNO3 solution, and NaBH4 solution was added and stirred for reaction. After the reaction was completed, the fabric was rinsed and freeze-dried in vacuum.

2. A reusable Ag / Ag3PO4 / MXene SERS substrate according to claim 1, characterized in that: In step 1), the high temperature treatment is performed at 130° C. for 5 hours.

3. The reusable Ag / Ag3PO4 / MXene SERS substrate according to claim 1, characterized in that: In step 2), the preparation method of the MXene dispersion is as follows: LiF is gradually added to HCl, stirred to form an acidic etching solution, MAX phase Ti3AlC2 powder is gradually added, stirred, deionized water is added, centrifuged, the precipitate is washed, and freeze-dried to obtain multilayer Ti3C2 nanosheets, Ti3C2 is suspended in DMSO, stirred, centrifuged, and the obtained black slurry is redispersed in deionized water and sonicated to obtain a MXene dispersion.

4. The reusable Ag / Ag3PO4 / MXene SERS substrate according to claim 3, characterized in that: In step 2), the stirring is carried out at 35° C. for 24 hours.

5. The reusable Ag / Ag3PO4 / MXene SERS substrate according to claim 3, characterized in that: In step 2), the concentration of the MXene dispersion is 0.5 mg / mL.

6. The reusable Ag / Ag3PO4 / MXene SERS substrate according to claim 1, characterized in that: In step 3), the concentration of the AgNO3 solution is 0.05M.

7. Use of a reusable Ag / Ag3PO4 / MXene SERS substrate according to any one of claims 1 to 6 in photocatalytic degradation of crystal violet.

8. The use according to claim 7, characterized in that The method is as follows: immersing the Ag / Ag3PO4 / MXene SERS substrate according to any one of claims 1 to 6 in a crystal violet solution, and degrading the crystal violet under simulated sunlight conditions.

9. Use of a reusable Ag / Ag3PO4 / MXene SERS substrate according to any one of claims 1 to 6 in detecting crystal violet.

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