Preparation method and application of self-calibration and self-cleaning SERS sensing platform based on intelligent hydrogel

Abstract

The application discloses a preparation method and application of a self-calibration and self-cleaning SERS sensing platform based on intelligent hydrogel, and relates to the field of new functional materials and analytical sensing technology. The application takes sodium alginate hydrogel as a basic structure framework, introduces Ag@PB as a Raman active probe in the network structure, corrects signal fluctuation in the detection process by using the internal standard peak of PB, and realizes accurate quantitative analysis. Meanwhile, the photo-Fenton and photocatalytic synergistic activity generated by the MIL100(Fe) / GO heterostructure is used to degrade the target molecules in situ after detection, so that the platform is self-cleaning. The multifunctional hydrogel sensing platform prepared by the application can be used for detection and degradation of organic pollutants such as polar molecules methylene blue and non-polar molecules thiram, and provides a new way for trace detection and environmental protection removal of organic pollutants in water / food.

Description

Technical Field

[0001] This invention relates to the field of novel functional materials and analytical sensing technology, and in particular to a method for preparing and applying a self-calibrating and self-cleaning SERS sensing platform based on smart hydrogels. Background Technology

[0002] Surface-enhanced Raman scattering (SERS) utilizes the localized surface plasmon resonance effect of metal nanostructures to amplify the weak Raman signal of the material by several orders of magnitude. While noble metal nanoparticles (NPs) such as gold and silver exhibit excellent SERS enhancement, their susceptibility to oxidation and aggregation leads to rapid SERS performance degradation. Furthermore, highly reactive noble metal NPs are highly sensitive to subtle changes in local structure and interparticle coupling, resulting in poor signal stability. To address these issues, researchers have proposed various substrate design strategies to protect noble metal materials, such as nanohybridization strategies, which introduce at least one functional component to protect, support, and stabilize the active metal; and nanoimmobilization strategies, which deposit metal films or active NPs on solid substrates and achieve an ordered and uniform distribution of nanostructures through controlled assembly, thereby improving the uniformity and long-term stability of the SERS signal. However, traditional rigid solid substrates suffer from high preparation costs and complex processes, making them unsuitable for complex scenarios such as liquid environments and curved samples. Moreover, their flat surfaces do not allow for sufficient contact between the substrate and target molecules, limiting the detection sensitivity of such heterogeneous systems.

[0003] To address the aforementioned shortcomings, emerging hydrogel substrates combine the advantages of colloidal and rigid SERS substrates. Hydrogels are cross-linked polymers whose stable three-dimensional cross-linked network structure can effectively immobilize and encapsulate noble metal nanomaterials, inhibiting the spontaneous aggregation and oxidation of nanoparticles (NPs). Furthermore, the abundant hydrophobic and hydrophilic sites in hydrogels can efficiently enrich target molecules, further enhancing SERS detection sensitivity. Combining active noble metals with a hydrogel matrix can simultaneously achieve long-term sensor stability and sensitive SERS response. However, due to the strong adsorption behavior of target molecules on the substrate surface, almost all hydrogel substrates can only be used once. Not only is it necessary to repeatedly synthesize large quantities of substrate material during use, but batch-to-batch variations can also reduce spectral reproducibility and affect the accuracy of quantitative analysis. In addition, detection waste loaded with toxic and hazardous substances can easily cause secondary pollution. Therefore, developing a sensitive, stable, and reusable hydrogel sensing platform is of great value in promoting the practical application of SERS technology in food safety detection. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing and applying a self-calibrating and self-cleaning SERS sensing platform based on intelligent hydrogels, thereby solving the problems existing in the prior art. This invention addresses the problems of poor signal sensitivity and stability, difficulty in reusability, insufficient quantitative analysis accuracy, and susceptibility to secondary contamination in existing SERS sensing platforms by constructing a multifunctional hydrogel SERS sensing platform integrating self-calibration and self-cleaning; combining visible light-driven photocatalytic degradation function with a hydrogel SERS substrate, relying on MIL100... The (Fe) / GO heterostructure exhibits synergistic photo-Fenton and photocatalytic activity, enabling in-situ photodegradation of target molecules and substrate self-cleaning after detection. This effectively addresses the issues of signal attenuation and poor spectral reproducibility in noble metal SERS substrates, while avoiding secondary pollution from detection waste, thus forming a closed-loop "detection-degradation" application model. The metal-organic framework MIL100(Fe) possesses a high specific surface area, abundant pores, and binding sites, effectively enriching target molecules and enhancing the SERS signal response. When combined with graphene oxide (GO) to form a heterostructure, it significantly improves carrier mobility, strengthens photocatalytic and photo-Fenton degradation efficiency, and avoids the limitation of the metal-organic framework's photocatalytic activity by its own low photosensitivity. Furthermore, GO, as a nanofiller in the hydrogel network, can interact with polymer chains at the interface, enhancing the stability of the hydrogel. Additionally, to overcome the limitations imposed by the substrate itself and the detection environment... To address the limitations of signal fluctuations and quantitative accuracy caused by complex matrix effects during repeated use, Prussian blue (PB) is introduced as an intrinsic standard. Its C≡N group exhibits a stable and significant characteristic peak in the Raman silent region, which can be ratio-calibrated with the target molecule signal, reducing bias caused by signal fluctuations and improving quantitative accuracy. Simultaneously, the mixed valence iron present in PB endows it with excellent Fenton catalytic activity, further enhancing the substrate's self-cleaning ability. Based on the above design concept, this invention uses sodium alginate hydrogel as a framework, combined with MIL100(Fe) / GO and Ag@PB composite nanomaterials, ultimately obtaining a self-calibrating and self-cleaning SERS sensing platform that is sensitive and stable, reusable, quantitatively accurate, and also possesses pollutant degradation capabilities. This provides a novel technical pathway for the precise trace detection and green removal of organic pollutants such as pesticides and veterinary drugs in water and food.

[0005] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention is a method for preparing a self-calibrating and self-cleaning SERS sensing platform based on smart hydrogel, comprising the following steps: Ag NPs solution (i.e., Ag nanoparticle solution), K3Fe(CN)6 solution (i.e., potassium ferricyanide solution), FeCl3 solution and K4Fe(CN)6 solution (i.e., potassium ferrocyanide solution) were mixed and reacted. The reaction product was dispersed in water to obtain Ag@PB NPs (i.e., Ag@Prussian blue core-shell nanoparticles) dispersion. Fe 2+ The solution and GO solution (i.e., graphene oxide solution) were mixed to obtain Fe. 2+ -GO solution; dissolve H3BTC (1,3,5-pyromellitic acid) and NaOH in water to obtain Na3BTC solution; the Fe 2+ - The GO solution and the Na3BTC solution are mixed and reacted. The reaction product is dispersed in water to obtain MIL100(Fe) / GO dispersion. The Ag@PB NPs dispersion, the MIL100(Fe) / GO dispersion, and sodium alginate (SA) solution were mixed and then crosslinked and cured with calcium ion solution to obtain MIL100(Fe) / GO / Ag@PB hydrogel (i.e., MIL100(Fe) / GO / Ag@PB-Gel), which is the self-calibrating and self-cleaning SERS sensing platform based on smart hydrogel.

[0006] This invention uses sodium alginate hydrogel as the base structural framework and introduces Ag@PB as a Raman-active probe into its network structure. The stable internal standard peak of PB is used to correct signal fluctuations during detection, achieving accurate quantitative analysis. Simultaneously, the photo-Fenton and photocatalytic synergistic activity generated by the MIL100(Fe) / GO heterostructure is utilized to degrade target molecules in situ after detection, achieving platform self-cleaning. The multifunctional hydrogel sensing platform prepared by this invention can be used for the detection and degradation of organic pollutants such as polar molecules like methylene blue and non-polar molecules like thiram, providing a new approach for trace detection and environmentally friendly removal of organic pollutants in water and food.

[0007] Furthermore, the preparation steps of the Ag NPs solution include: mixing the silver source solution, water and reducing agent, reacting them to obtain the Ag NPs solution.

[0008] Furthermore, the silver source solution includes an AgNO3 solution with a concentration of 20 mg / mL. -1 .

[0009] Furthermore, the reducing agent comprises a trisodium citrate dihydrate solution, wherein the concentration of the trisodium citrate dihydrate solution is 1 wt%.

[0010] Furthermore, the volume ratio of the silver source solution, water, and reducing agent is 1:100:3.

[0011] Furthermore, the reaction temperature is 100 °C and the time is 30 min.

[0012] Furthermore, the concentration of the K3Fe(CN)6 solution is 5 mmol / L. -1 .

[0013] Furthermore, the concentration of the FeCl3 solution is 1 mmol / L. -1 .

[0014] Furthermore, the concentration of the K4Fe(CN)6 solution is 1 mmol / L. -1 .

[0015] Furthermore, the volume ratio of the Ag NPs solution, K3Fe(CN)6 solution, FeCl3 solution and K4Fe(CN)6 solution is 50:1:20:20.

[0016] Furthermore, the Ag NPs solution, K3Fe(CN)6 solution, FeCl3 solution and K4Fe(CN)6 solution were mixed and reacted at 25 °C for 3 h.

[0017] Furthermore, the Fe 2+ The solution was prepared by mixing FeSO4·7H2O and water in a ratio of 0.28 g: 15.5 mL.

[0018] Furthermore, the concentration of the GO solution is 5 mg / mL. -1 .

[0019] Furthermore, the mass of GO in the GO solution is equal to the mass of Fe. 2+ 5% of the mass of FeSO4·7H2O in the solution.

[0020] Furthermore, the ratio of H3BTC, NaOH, and water is 0.18 g:0.1 g:15.5 mL.

[0021] Furthermore, the Fe 2+ The volume ratio of the -GO solution to the Na3BTC solution is 1:1.

[0022] Further, the Fe 2+ The -GO solution and the Na3BTC solution were mixed and reacted at a temperature of 25 °C for 15 h.

[0023] Furthermore, the Ag NPs solution, K3Fe(CN)6 solution, FeCl3 solution and K4Fe(CN)6 solution are mixed, and the reaction product is washed with water after the reaction. The washed product is then redispersed in water to obtain Ag@PBNPs dispersion. The volume ratio of water used to prepare Ag@PBNPs dispersion to the volume of Ag NPs solution added to the reaction system is 1:10.

[0024] Further, the Fe 2+ The reaction involves mixing the GO solution and the Na3BTC solution, followed by centrifugation, washing, and drying to obtain MIL100(Fe) / GO powder. The MIL100(Fe) / GO powder is then redispersed in water to obtain a MIL100(Fe) / GO dispersion.

[0025] Furthermore, the concentration of the MIL100(Fe) / GO dispersion is 20 mg / mL. -1 .

[0026] Furthermore, the concentration of the sodium alginate solution is 2 wt%.

[0027] Furthermore, the calcium ion solution includes a CaCl2 solution with a concentration of 2 wt%.

[0028] Furthermore, the volume ratio of the Ag@PB NPs dispersion, the MIL100(Fe) / GO dispersion, and the sodium alginate solution is 3:2:4.

[0029] Furthermore, the sum of the volumes of the Ag@PB NPs dispersion, the MIL100(Fe) / GO dispersion, and the sodium alginate solution (i.e., the volume of the gel precursor solution obtained by mixing) is in a 1:1 ratio to the volume of the calcium ion solution.

[0030] Furthermore, the cross-linking curing temperature is 25 °C and the time is 10 min.

[0031] The second technical solution of the present invention: a self-calibrating and self-cleaning SERS sensing platform based on smart hydrogel prepared by the above-described method.

[0032] This invention relates to a self-calibrating and self-cleaning SERS sensing platform based on a smart hydrogel. The platform uses a hydrogel formed by the cross-linking of sodium alginate polymer chains and calcium ions as a carrier, and loads MIL100(Fe) / GO and Ag@PB composite nanomaterials, making it a multifunctional hydrogel sensing platform. This self-calibrating and self-cleaning SERS sensing platform based on a smart hydrogel can achieve efficient detection and photocatalytic degradation of organic pollutants, such as methylene blue (used as a veterinary drug) and thiram (used as a pesticide).

[0033] The third technical solution of the present invention: an application of the above-mentioned self-calibrating and self-cleaning SERS sensing platform based on smart hydrogel in the detection of organic pollutants.

[0034] The fourth technical solution of the present invention: a method for cyclically detecting organic pollutants using a self-calibrating and self-cleaning SERS sensing platform based on smart hydrogels, comprising the following steps: Standard solutions of organic pollutants of different concentrations were dropped onto the self-calibrating and self-cleaning SERS sensing platform based on the smart hydrogel. After the droplets had completely penetrated, the SERS ratio signal (specifically referring to the organic pollutant to be measured, i.e., the characteristic peak of the target analyte) was recorded. I 目标物 ) and PB peak ( I PB ， The ratio of the intensity of the internal standard peak (i.e., the ratio of the internal standard peak to the internal standard peak). I 目标物 / I PB ), and plot the standard curve of organic pollutant concentration versus SERS ratio signal; The test solution containing organic pollutants was dropped onto the self-calibrating and self-cleaning SERS sensing platform based on the smart hydrogel. After the droplet had completely penetrated, the SERS ratio signal was recorded and substituted into the standard curve to obtain the concentration of organic pollutants. Organic pollutants adsorbed in a smart hydrogel-based self-calibrating and self-cleaning SERS sensing platform are removed by photodegradation, followed by cyclic detection of organic pollutants.

[0035] Furthermore, the infiltration time is 2 minutes, and the infiltration is carried out at 25 °C.

[0036] Furthermore, the detection conditions for the SERS ratio signal include: an excitation wavelength of 785 nm, an integration time of 3000 ms, and an excitation power of 200 mW.

[0037] Furthermore, the photodegradation step includes: immersing the smart hydrogel-based self-calibrating and self-cleaning SERS sensing platform, which has been detected and adsorbed with organic pollutants, in an H2O2 solution and irradiating it with light for 60 min.

[0038] Furthermore, the concentration of the H2O2 solution is 1.5 mmol / L. -1 .

[0039] Furthermore, the illumination is provided by a 150 W xenon lamp.

[0040] Furthermore, all organic pollutants include organic pesticides and veterinary drugs, such as methylene blue or thiram.

[0041] This invention uses methylene blue and thiram as model molecules for organic pesticides and veterinary drugs, and proposes a self-calibrating and self-cleaning SERS sensing platform based on a smart hydrogel, along with a method for detecting and degrading organic pollutants using this platform. This self-calibrating and self-cleaning SERS sensing platform uses sodium alginate hydrogel as its structural framework and Ag@PB as the Raman responsive substrate. Its stable IS (internal standard) peak (i.e., I PB This technology can correct signal fluctuations during the detection process, enabling precise quantitative analysis. Simultaneously, the synergistic activity of photo-Fenton and photocatalysis generated by the MIL100(Fe) / GO heterostructure achieves in-situ degradation of adsorbates, endowing the sensing platform with self-cleaning capabilities. Rational material design promotes a significant increase in signal intensity through synergistic enhancement effects of electromagnetic and charge transfer among the components; the band structure interweaving among the composite gel components effectively promotes the separation and transfer of electron-hole pairs. Under the synergistic effects of photo-Fenton reaction, photocatalytic oxidation, and electron transfer, reactive oxygen species are continuously generated, achieving efficient oxidative degradation of organic pollutants.

[0042] The present invention discloses the following technical effects: This invention constructs a novel self-calibrating and self-cleaning SERS sensing platform that synergistically leverages the functions of different components to achieve accurate detection and efficient degradation of organic pollutants such as methylene blue and thiram. The organic pollutant detection based on this SERS sensing platform features high sensitivity, good stability, and repeatable signals.

[0043] Based on the efficient enrichment and hotspot regulation of hydrogel networks, the electromagnetic enhancement effect and charge transfer process of Ag@PB NPs, and the signal correction function of PB, this invention successfully achieves the amplification and stabilization of Raman signals. This composite material provides a new approach for the detection of organic pollutants in food / environment.

[0044] Based on the photo-Fenton and photocatalytic synergistic activity generated by the MIL100(Fe) / GO heterostructure, this invention has successfully achieved the environmentally friendly removal of organic pollutants and has good application prospects in the prevention and control of organic pollutants in food and the environment. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a TEM image of Ag NPs synthesized by citric acid reduction in Example 1.

[0047] Figure 2 This is a TEM image of Ag@PB NPs prepared by the dual precursor synthesis method in Example 1.

[0048] Figure 3 This is a TEM image of MIL100(Fe) / GO prepared in Example 1.

[0049] Figure 4 The images show SEM images of MIL100(Fe) / GO / Ag@PB-Gel prepared in Example 1 at different magnifications.

[0050] Figure 5 The elemental mapping diagram is shown for MIL100(Fe) / GO / Ag@PB-Gel prepared in Example 1.

[0051] Figure 6 The images show the UV-vis images of MIL100(Fe) / GO (i.e., MIL / GO) and Ag@PB NPs (i.e., Ag@PB) prepared in Example 1.

[0052] Figure 7 Raman spectra of MIL100(Fe) / GO / Ag@PB-Gel (hereinafter referred to as MGAP-Gel) and its intermediate products MIL100(Fe) / GO, Ag@PB NPs (i.e. Ag@PB), and Gel prepared in Example 1.

[0053] Figure 8 XPS full spectra of MIL100(Fe) / GO / Ag@PB-Gel and MIL100(Fe) / GO prepared in Example 1.

[0054] Figure 9 The MIL100(Fe) / GO / Ag@PB-Gel (MGAP-Gel) and its intermediates or comparative samples MIL100 / AP, GO / AP, MG / Ag, and MG prepared in Example 1 were reacted with 1 mg L -1 Methylene blue (A) and 100 mg L -1Comparison of SERS spectra and intensity signal values ​​of selected characteristic peaks determined by the reaction of thiram (B).

[0055] Figure 10 MIL100(Fe) / GO / Ag@PB-Gel prepared in Example 1 was used to detect 1 mg L -1 The intensity of different peak positions and ratio signals of methylene blue.

[0056] Figure 11 The SERS response spectra of different concentrations of methylene blue are shown.

[0057] Figure 12 For methylene blue solution concentration of 10 -2 -10 3 mg L -1 The linear relationship between the ratio signal and the range.

[0058] Figure 13 The variation of SERS response spectra of different concentrations of thiram.

[0059] Figure 14 For the concentration of thiram solution at 10 -5 -10 3 mg L -1 The linear relationship between the ratio signal and the range.

[0060] Figure 15 The SERS spectral changes of methylene blue during photodegradation are shown.

[0061] Figure 16 The degradation rate curves of methylene blue under xenon lamp illumination and in darkness are shown.

[0062] Figure 17 The SERS spectral changes of thiamethoxam during photodegradation.

[0063] Figure 18 The degradation rate curves of thiram under xenon lamp irradiation and darkness are shown.

[0064] Figure 19 The SERS spectral changes for methylene blue during eight detection-degradation cycles.

[0065] Figure 20 The ratio signal changes for eight detection-degradation cycles of methylene blue.

[0066] Figure 21 The SERS spectral changes of Fumei Shuang during eight detection-degradation cycles.

[0067] Figure 22 The ratio signal change of the eight detection-degradation cycles of Fumei. Detailed Implementation

[0068] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0069] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0070] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0071] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0072] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0073] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0074] Unless otherwise specified, the room temperature mentioned in the following embodiments of the present invention refers to 20-30 ℃.

[0075] All raw materials used in the following embodiments of the present invention are commercially available products, and unless otherwise specified, all solutions refer to aqueous solutions.

[0076] Example 1 The fabrication of a self-calibrating and self-cleaning SERS sensing platform based on smart hydrogels is as follows: (1) Synthesis of Ag NPs: Ag NPs were prepared by citric acid reduction. AgNO3 solution (20 mg / mL) was used to prepare Ag NPs. -1 Add 1 mL of the solution to 100 mL of boiling water and heat at 100 °C for 10 min. Then quickly inject 3 mL of trisodium citrate dihydrate solution and maintain boiling for 30 min. As Ag NPs are synthesized, the solution eventually turns pale yellow, yielding an Ag NPs solution, which is then cooled to 25 °C for later use.

[0077] (2) Synthesis of Ag@PB NPs: Ag@PB NPs were prepared using a dual precursor synthesis method. K3Fe(CN)6 solution (5 mmol / L) was stirred. -1 200 μL), FeCl3 solution (1 mmol L -1 4 mL), K4Fe(CN)6 solution (1 mmol L -1 4 mL was added sequentially to the Ag NPs solution (10 mL) prepared in step (1), and stirred continuously at 25 °C for 3 h. Then it was washed three times with deionized water and redispersed in 1 mL of water to obtain the Ag@PB NPs dispersion, which was stored at 4 °C for later use.

[0078] (3) Preparation of MIL100(Fe) / GO: 0.28 g FeSO4·7H2O was dissolved in 15.5 mL of water to form a homogeneous Fe... 2+ The solution was prepared by adding GO solution (2.8 mL, 5 mg / mL). -1 Then sonicate for 15 minutes to ensure full dispersion and formation of Fe. 2+ - GO solution, with GO added at 5% of the mass of FeSO4·7H2O. Dissolve 0.18 g H3BTC and 0.1 g NaOH in 15.5 mL of water and sonicate to prepare a Na3BTC solution. Under continuous mechanical stirring, react the Na3BTC solution with Fe... 2+ The GO solution was thoroughly mixed at a 1:1 volume ratio and stirred at 25 °C for 15 h (stirring speed 200 rpm). The solid complex was collected by centrifugation, washed three times with water and ethanol respectively, and dried at 70 °C to obtain MIL100(Fe) / GO powder. 0.2 g of the powder was weighed and redispersed in 10 mL of deionized water to obtain MIL100(Fe) / GO dispersion (concentration 20 mg / mL). -1 ), store for later use.

[0079] (4) Preparation of MIL100(Fe) / GO / Ag@PB-Gel (abbreviated as MGAP-Gel): The composite hydrogel was prepared by ionic crosslinking. 1 g CaCl2 was dissolved in 50 mL of water to prepare a 2wt% CaCl2 solution as a crosslinking agent. 1 g SA powder was added to 50 mL of water and stirred until completely dissolved to obtain a 2wt% SA solution. At 25 °C, the previously prepared Ag@PB NPs dispersion and MIL100(Fe) / GO dispersion were incorporated into the SA solution at a volume ratio of 3:2:4 (i.e., Ag@PB NPs dispersion: MIL100(Fe) / GO dispersion: SA solution = 3:2:4). The mixture was vortexed for 10 min to achieve complete homogeneity, forming a gel precursor solution. 150 μL of the precursor solution was injected into a 48-well plate. 150 μL of CaCl2 solution was then slowly injected along the container wall into the precursor solution using a syringe. A gel film formed on the surface upon contact with the droplet. The solution was allowed to stand and solidify at 25 °C for 10 min to ensure sufficient cross-linking. The gel was rinsed with deionized water to remove excess ions. The resulting gel sheets (approximately 10 mm in diameter) were stored in a petri dish covered with plastic wrap in the dark at 4 °C for later use. This constitutes the self-calibrating and self-cleaning SERS sensing platform based on intelligent hydrogels.

[0080] Figure 1 The image shows a TEM image of Ag NPs synthesized by citric acid reduction in Example 1. It can be seen that the Ag NPs are uniform in size and have a diameter of about 60 nm. Figure 2 The image shows a TEM image of Ag@PB NPs prepared by the dual precursor synthesis method in Example 1, which clearly shows its core-shell structure. Figure 3 The image shows a TEM image of the MIL100(Fe) / GO composite prepared in Example 1. It can be seen that the polyhedral crystals MIL100(Fe) are uniformly dispersed on the GO wrinkles. Figure 4 SEM images of MIL100(Fe) / GO / Ag@PB-Gel prepared in Example 1 at different magnifications show that the gel surface is rough and contains obvious particles. Under high magnification, a large number of nanomaterials are densely embedded in the gel layers. Figure 5 The elemental mapping diagram of MIL100(Fe) / GO / Ag@PB-Gel prepared in Example 1 shows that multiple elements such as C, Fe, O, Ag, N, Na, and Ca are uniformly distributed within the scanning area. Figure 6The UV-vis images of MIL100(Fe) / GO (i.e., MIL / GO in the figure) and Ag@PB NPs (i.e., Ag@PB in the figure) prepared in Example 1 show that the complex Ag@PB has absorption peaks belonging to Ag and PB (PB is prepared in the same way as step (2) of Example 1, except that the use of Ag NPs solution is omitted) and both peaks are blue shifted and broadened. Figure 7 The Raman spectra of MIL100(Fe) / GO / Ag@PB-Gel (hereinafter referred to as MGAP-Gel) and its intermediate products MIL100(Fe) / GO, Ag@PB NPs (i.e. Ag@PB) and Gel (the preparation method of Gel is the same as step (4) of Example 1, the only difference being that the use of Ag@PB NPs dispersion and MIL100(Fe) / GO dispersion is omitted) prepared in Example 1 can be seen. It can be seen that the D peak and G peak of MIL100(Fe) / GO and the strong C≡N peak of Ag@PB NPs appear simultaneously in the spectrum of the composite hydrogel. Figure 8 The XPS full spectrum of MIL100(Fe) / GO / Ag@PB-Gel and MIL100(Fe) / GO prepared in Example 1 shows the successful incorporation of Fe, O, N, Ag and C elements, proving the successful synthesis of MIL100(Fe) / GO / Ag@PB-Gel.

[0081] Example 2 A self-calibrating and self-cleaning SERS sensing platform based on smart hydrogels was used for the detection of methylene blue (MB) and thiram (TMTD). The steps are as follows: 10 μL of the test solution was dropped onto the self-calibrating and self-cleaning SERS sensing platform (MIL100(Fe) / GO / Ag@PB-Gel) based on smart hydrogel prepared in Example 1, the intermediate product, or the control sample, and allowed to permeate at 25 °C for 2 min. Subsequently, the SERS spectra of the composite hydrogel, intermediate product, or control sample (a composition of one or more components) were acquired using a portable Raman spectrometer under fixed conditions (excitation wavelength of 785 nm, integration time of 3000 ms, and excitation power of 200 mW).

[0082] The specific details of the intermediate product or control sample are as follows: MIL100 / AP (i.e., MIL100(Fe) / Ag@PB) is prepared as follows: 0.28 g of FeSO4·7H2O is dissolved in 15.5 mL of water to form a homogeneous Fe... 2+ Solution preparation: Dissolve 0.18 g H3BTC and 0.1 g NaOH in 15.5 mL of water, and sonicate to prepare a Na3BTC solution. Under continuous mechanical stirring, react the Na3BTC solution with Fe...2+ The solutions were thoroughly mixed at a 1:1 volume ratio and stirred at 25 °C for 15 h (stirring speed 200 rpm). The solid complex was collected by centrifugation, washed three times with water and ethanol respectively, and dried at 70 °C to obtain MIL100(Fe) powder. 0.2 g of the powder was weighed and redispersed in 10 mL of deionized water to obtain a MIL100(Fe) dispersion (concentration 20 mg / mL). -1 The MIL100(Fe) dispersion was mixed with the Ag@PBNPs dispersion in step (2) of Example 1 at a volume ratio of 1:1 to obtain the MIL100 / AP dispersion. 10 μL was taken as the MIL100 / AP sample to be tested.

[0083] GO / AP (i.e., GO / Ag@PB) is prepared as follows: Mix 2.8 mL of GO solution with 5 mg of phosphate (PbAg, phosphate, and phosphate). -1 The Ag@PB NPs dispersion from step (2) of Example 1 was mixed at a volume ratio of 1:1 to obtain the GO / AP dispersion. 10 μL was taken as the GO / AP sample to be tested.

[0084] The preparation method of MG / Ag (i.e. MIL100(Fe) / GO / Ag) is as follows: the Ag NPs solution in step (1) of Example 1 and the MIL100(Fe) / GO dispersion in step (3) of Example 1 are mixed at a volume ratio of 1:1 to obtain the MG / Ag dispersion, and 10 μL is taken as the MG / Ag sample to be tested.

[0085] MG (i.e., the intermediate product MIL100(Fe) / GO in Example 1): Take 10 μL of the MIL100(Fe) / GO dispersion in step (3) of Example 1 as the MG sample to be tested.

[0086] Figure 9 The MIL100(Fe) / GO / Ag@PB-Gel (MGAP-Gel) and its intermediates or comparative samples MIL100 / AP, GO / AP, MG / Ag, and MG prepared in Example 1 were reacted with 1 mg L -1 Methylene blue (A) and 100 mg L -1 Comparison of SERS spectra and intensity signal values ​​of selected characteristic peaks determined by the thiram (B) reaction (IS in the figure represents PB at 2080 cm⁻¹). -1 The internal standard peak at (A) is 1621 cm. -1 The peak at (B) is a characteristic peak of MB, and MB power represents MB powder standard; 1380 cm⁻¹ -1The peak at this point represents a characteristic peak of TMTD (TMTD power represents TMTD powder standard). It can be seen that the prepared MIL100(Fe) / GO / Ag@PB-Gel exhibits the best enhancement effect, with multiple obvious Raman characteristic peaks appearing for both methylene blue and thiram.

[0087] To eliminate the influence of signal fluctuations caused by changes in detection conditions, the 2080 cm -1 The PB characteristic peak appearing at the point is used as an internal standard, and a ratio signal is established with the intensity of the SERS characteristic peak of the detected molecule.

[0088] Figure 10 MIL100(Fe) / GO / Ag@PB-Gel prepared in Example 1 was used to detect 1 mg L -1 By analyzing the different peak positions of methylene blue and the intensity of the ratio signal, it can be seen that the fluctuation trend of the PB peak is highly consistent with that of the characteristic peak of the detected molecule, and the RSD of both peaks is relatively high. After calibrating the two together, the RSD of the ratio signal is significantly reduced.

[0089] Example 3 A self-calibrating and self-cleaning SERS sensing platform based on smart hydrogels was used for the detection of methylene blue, and the steps are as follows: (1) Take 10 μL of methylene blue solutions of different concentrations (10 -2 -10 3 mg L -1 The sample was dropped onto the self-calibrating and self-cleaning SERS sensing platform based on the smart hydrogel prepared in Example 1 and allowed to permeate at 25 °C for 2 min. Subsequently, the SERS spectra and ratio signals of different concentrations of methylene blue were recorded at a fixed excitation wavelength of 785 nm (integration time of 3000 ms and excitation power of 200 mW).

[0090] (2) Based on the recorded ratio signals of different concentrations of methylene blue, plot a linear curve of methylene blue concentration versus ratio signal.

[0091] Figure 11 The variation of SERS response spectra of methylene blue at different concentrations, from Figure 11 The results show that the SERS response of methylene blue increases with increasing concentration.

[0092] Figure 12 For methylene blue solution concentration of 10 -2 -10 3 mg L -1 The linear relationship between the ratio signal and the detection limit is 3.23 × 10⁻⁶. -3 mg L -1 .

[0093] Example 4 A self-calibrating and self-cleaning SERS sensing platform based on smart hydrogels was used for the detection of thiamethoxam. The steps are as follows: (1) Take 10 μL of different concentrations of thiram solution (10 -5 -10 3 mg L -1 The sample was dropped onto the self-calibrating and self-cleaning SERS sensing platform based on the smart hydrogel prepared in Example 1 and allowed to permeate at 25 °C for 2 min. Subsequently, the SERS spectra and ratio signals of different concentrations of thiram were recorded at a fixed excitation wavelength of 785 nm (integration time of 3000 ms and excitation power of 200 mW).

[0094] (2) Based on the recorded ratio signals of different concentrations of thiram, plot a linear curve of thiram concentration versus ratio signal.

[0095] Figure 13 The changes in the SERS response spectra of different concentrations of thiram were observed from... Figure 13 The results show that the SERS response of thiamethoxam increases with increasing concentration.

[0096] Figure 14 For the concentration of thiram solution at 10 -5 -10 3 mg L -1 The linear relationship between the ratio signal and the detection limit is 7.06 × 10⁻⁶. -6 mg L -1 .

[0097] Example 5 A self-calibrating and self-cleaning SERS sensing platform based on smart hydrogels was used for the photodegradation of methylene blue, and the steps are as follows: (1) The MIL100(Fe) / GO / Ag@PB-Gel prepared in Example 1 was soaked in a methylene blue solution (10 mg / L). -1 In a solution of 5 mL H₂O₂, shaken in the dark for 30 min to reach adsorption-desorption equilibrium. -1 After 250 μL, the sample was subjected to photodegradation under continuous irradiation with a 150 W xenon lamp (with degradation under dark conditions as a control).

[0098] (2) Record the SERS spectrum changes of methylene blue during photodegradation, calculate the degradation rate constant k using the first-order reaction kinetic equation, and plot the degradation rate curve of methylene blue.

[0099] Figure 15The SERS spectrum changes of methylene blue during the photodegradation process show that the concentration of methylene blue continuously decreases over time within 1 hour.

[0100] Figure 16 The graphs show the degradation rate of methylene blue under xenon lamp illumination and in darkness. It can be seen that light illumination greatly promotes the degradation of methylene blue.

[0101] Example 6 A self-calibrating and self-cleaning SERS sensing platform based on smart hydrogels was used for the photodegradation of thiamethoxam, and the steps are as follows: (1) The MIL100(Fe) / GO / Ag@PB-Gel prepared in Example 1 was soaked in thiram solution (10 mg / L). -1 Add 5 mL of H₂O₂ solution to the reaction mixture and shake in the dark for 30 min to reach adsorption-desorption equilibrium. -1 After 250 μL, the sample was subjected to photodegradation under continuous irradiation with a 150 W xenon lamp (with degradation under dark conditions as a control).

[0102] (2) Record the SERS spectrum changes of thiram during photodegradation, calculate the degradation rate constant k using the first-order reaction kinetic equation, and plot the degradation rate curve of thiram.

[0103] Figure 17 The SERS spectrum changes of thiram during photodegradation show that the concentration of thiram continuously decreases over time within 1 hour.

[0104] Figure 18 The degradation rate curves of thiram under xenon lamp irradiation and darkness show that light irradiation greatly promotes the degradation of thiram.

[0105] Example 7 A self-calibrating and self-cleaning SERS sensing platform based on smart hydrogels was used for the detection-degradation cycle of methylene blue, with the following steps: (1) Take 10 μL of methylene blue solution (concentration of 10 mg / L) -1 The methylene blue was dropped onto the self-calibrating and self-cleaning SERS sensing platform based on the smart hydrogel prepared in Example 1 and allowed to permeate at 25 °C for 2 min. Subsequently, the SERS spectrum and ratio signal of methylene blue were recorded at a fixed excitation wavelength of 785 nm (integration time of 3000 ms and excitation power of 200 mW).

[0106] (2) After completing the SERS detection by adding methylene blue solution, immerse the contaminated SERS sensing platform in H2O2 solution (1.5 mmol L). -1The sample was placed in a 1 mL xenon lamp and exposed to a 150 W xenon lamp for 60 min. The SERS spectrum of the SERS sensing platform was recorded. Then, the same volume and concentration of methylene blue solution were added to the SERS sensing platform for repeated detection.

[0107] Figure 19 The SERS spectrum changes of methylene blue during eight detection-degradation cycles show that the characteristic peaks of methylene blue disappear after photodegradation, and a response spectrum is obtained again after further addition of methylene blue.

[0108] Figure 20 The ratio signal changes of methylene blue over eight detection-degradation cycles show that the ratio signal disappears and approaches 0 after the SERS sensing platform self-cleansing. Continuing to add methylene blue again yields a signal with consistent intensity. The signal changes over eight cycles are within an acceptable range.

[0109] Example 8 A self-calibrating and self-cleaning SERS sensing platform based on smart hydrogels was used for the detection-degradation cycle of thiamethoxam, with the following steps: (1) Take 10 μL of thiram solution (concentration of 10 mg / L) -1 The sample was dropped onto the self-calibrating and self-cleaning SERS sensing platform based on the smart hydrogel prepared in Example 1 and allowed to permeate at 25 °C for 2 min. Subsequently, the SERS spectrum and ratio signal of thiamethoxam were recorded at a fixed excitation wavelength of 785 nm (integration time of 3000 ms and excitation power of 200 mW).

[0110] (2) After completing the SERS detection by adding thiram solution, immerse the contaminated SERS sensing platform in H2O2 solution (1.5 mmol L). -1 The sample was placed in a 1 mL solution and exposed to a 150 W xenon lamp for 60 min. The SERS spectrum of the SERS sensing platform was recorded. Then, the same volume and concentration of thiram solution were added to the SERS sensing platform for repeated detection.

[0111] Figure 21 The SERS spectrum changes of thiram after eight detection-degradation cycles show that the characteristic peaks of thiram disappear after photodegradation, and the response spectrum can be obtained again after thiram is added again.

[0112] Figure 22 The ratio signal changes of thiram over eight detection-degradation cycles show that the ratio signal disappears after the SERS sensing platform self-cleansing and approaches 0. Continuing to add thiram again yields a signal with consistent intensity. The signal changes over eight cycles are within an acceptable range.

[0113] In summary, this invention provides a self-calibrating and self-cleaning SERS sensing platform based on smart hydrogels and its application in the accurate detection and green degradation of organic pollutants. Under optimal detection conditions, the methylene blue concentration is 10... -2 -10 3 mg L -1 The changes in the ratio signal within the range are shown in the figure. Figure 12 The detection limit is as low as 3.23×10⁻⁶. -3 mg L -1 ; the concentration of thiamethoxam is at 10 -5 -10 3 mg L -1 The changes in the ratio signal within the range are shown in the figure. Figure 14 The detection limit is as low as 7.06×10⁻⁶. -6 mg L -1 Following detection, the SERS sensing platform demonstrated the photodegradation behavior of the adsorbate. Figure 16 and Figure 18 The SERS sensing platform can be reused for eight cycles.

[0114] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing a self-calibrating and self-cleaning SERS sensing platform based on smart hydrogels, characterized in that, Includes the following steps: Ag NPs solution, K3Fe(CN)6 solution, FeCl3 solution and K4Fe(CN)6 solution were mixed and reacted. The reaction product was dispersed in water to obtain Ag@PB NPs dispersion. Fe 2+ The solution and GO solution were mixed to obtain Fe. 2+ -GO solution; dissolve H3BTC and NaOH in water to obtain Na3BTC solution; add the Fe 2+ - The GO solution and the Na3BTC solution are mixed and reacted. The reaction product is dispersed in water to obtain MIL100(Fe) / GO dispersion. The Ag@PB NPs dispersion, the MIL100(Fe) / GO dispersion, and sodium alginate solution were mixed and then crosslinked and cured with calcium ion solution to obtain MIL100(Fe) / GO / Ag@PB hydrogel, which is the self-calibration and self-cleaning SERS sensing platform based on smart hydrogel.

2. The method for preparing the self-calibrating and self-cleaning SERS sensing platform based on smart hydrogel as described in claim 1, characterized in that, The preparation steps of the Ag NPs solution include: mixing silver source solution, water and reducing agent, reacting to obtain the Ag NPs solution.

3. The method for preparing the self-calibrating and self-cleaning SERS sensing platform based on smart hydrogel as described in claim 2, characterized in that, The silver source solution includes an AgNO3 solution with a concentration of 20 mg / mL. -1 ; And / or, the reducing agent comprises a trisodium citrate dihydrate solution, wherein the concentration of the trisodium citrate dihydrate solution is 1 wt%; And / or, the volume ratio of the silver source solution, water and reducing agent is 1:100:3; And / or, the reaction is carried out at a temperature of 100 °C for a time of 30 min.

4. The method for preparing the self-calibrating and self-cleaning SERS sensing platform based on smart hydrogel as described in claim 1, characterized in that, The concentration of the K3Fe(CN)6 solution was 5 mmol / L. -1 ; And / or, the concentration of the FeCl3 solution is 1 mmol L. -1 ; And / or, the concentration of the K4Fe(CN)6 solution is 1 mmol / L. -1 ; And / or, the volume ratio of the Ag NPs solution, K3Fe(CN)6 solution, FeCl3 solution and K4Fe(CN)6 solution is 50:1:20:20; And / or, after mixing Ag NPs solution, K3Fe(CN)6 solution, FeCl3 solution and K4Fe(CN)6 solution, the reaction temperature is 25 °C and the time is 3 h.

5. The method for preparing the self-calibrating and self-cleaning SERS sensing platform based on smart hydrogel as described in claim 1, characterized in that, The Fe 2+ The solution was prepared by mixing FeSO4·7H2O and water in a ratio of 0.28 g: 15.5 mL. And / or, the concentration of the GO solution is 5 mg / mL. -1 ; And / or, the mass of GO in the GO solution is equal to the mass of Fe. 2+ 5% of the mass of FeSO4·7H2O in the solution; And / or, the ratio of H3BTC, NaOH and water is 0.18 g:0.1 g:15.5 mL; And / or, the Fe 2+ The volume ratio of the -GO solution to the Na3BTC solution is 1:1; And / or, the Fe 2+ The -GO solution and the Na3BTC solution were mixed and reacted at a temperature of 25 °C for 15 h.

6. The method for preparing the self-calibrating and self-cleaning SERS sensing platform based on smart hydrogel as described in claim 1, characterized in that, The concentration of the MIL100(Fe) / GO dispersion was 20 mg / mL. -1 ; And / or, the concentration of the sodium alginate solution is 2 wt%; And / or, the calcium ion solution comprises a CaCl2 solution with a concentration of 2 wt%; And / or, the volume ratio of the Ag@PB NPs dispersion, the MIL100(Fe) / GO dispersion and the sodium alginate solution is 3:2:4; And / or, the sum of the volumes of the Ag@PB NPs dispersion, the MIL100(Fe) / GO dispersion, and the sodium alginate solution is in a 1:1 ratio to the volume of the calcium ion solution. And / or, the cross-linking curing temperature is 25 °C and the time is 10 min.

7. A self-calibrating and self-cleaning SERS sensing platform based on smart hydrogel, prepared by the method described in any one of claims 1-6.

8. The application of the self-calibrating and self-cleaning SERS sensing platform based on smart hydrogel as described in claim 7 in the detection of organic pollutants.

9. A method for cyclically detecting organic pollutants using a self-calibrating and self-cleaning SERS sensing platform based on smart hydrogels, characterized in that... Includes the following steps: Different concentrations of standard solutions of organic pollutants are dropped onto the self-calibrating and self-cleaning SERS sensing platform based on smart hydrogel as described in claim 7. After the droplets have completely penetrated, the SERS ratio signal is recorded, and a standard curve of organic pollutant concentration versus SERS ratio signal is plotted. The test solution containing organic pollutants is dropped onto the self-calibrating and self-cleaning SERS sensing platform based on smart hydrogel as described in claim 7. After the droplets have completely penetrated, the SERS ratio signal is recorded and substituted into the standard curve to obtain the concentration of organic pollutants. Organic pollutants adsorbed in a smart hydrogel-based self-calibrating and self-cleaning SERS sensing platform are removed by photodegradation, followed by cyclic detection of organic pollutants.

10. The method as described in claim 9, characterized in that, The photodegradation step includes immersing the smart hydrogel-based self-calibrating and self-cleaning SERS sensing platform, which has been detected and adsorbed with organic pollutants, in an H2O2 solution and irradiating it with light for 60 minutes.

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