Enrichment enhanced bifunctional filter membrane SERS substrate and preparation method and application thereof

Abstract

The invention provides an enrichment-enhanced bifunctional filter membrane SERS (Surface Enhanced Raman Scattering) substrate as well as a preparation method and application thereof. The preparation method comprises the following steps: preparing Ag nano-particles and functionalizing the Ag nano-particles; the method comprises the following steps: self-assembling functionalized Ag nano-particles and a nano-carbon material, so that the Ag nano-particles are loaded on the surface of the nano-carbon material to form a hybrid structure; anchoring the hybrid structure by using a matrix with a fibrous structure to obtain an SERS solution system with a composite nanostructure; and filtering the SERS solution system onto a glass fiber filter membrane to form the SERS substrate with the enriched and enhanced bifunctional filter membrane. According to the filter membrane SERS substrate prepared through the method, rapid enrichment and detection of PAHs in the water environment can be achieved through simple filtering operation, the detection sensitivity and efficiency are remarkably improved, and the filter membrane SERS substrate has wide application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of spectral analysis, and in particular to an enrichment enhanced dual-function filter membrane SERS substrate and a preparation method and application thereof. Background Art

[0002] Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds composed of two or more benzene rings, usually derived from petroleum combustion, chemical production and vehicle exhaust emissions, and can enter the water environment through natural circulation. Some PAHs have strong carcinogenic, teratogenic and mutagenic properties, and are therefore listed as persistent organic pollutants for priority control by many countries. Therefore, rapid and sensitive detection of PAHs is crucial. Although traditional high-performance liquid chromatography and gas chromatography-mass spectrometry methods are sensitive, they are more suitable for laboratory detection and are difficult to meet the needs of rapid on-site detection. Surface Enhanced Raman Scattering (SERS) technology has become a potential method for detecting PAHs due to its high sensitivity, molecular specificity and rapid response. At present, SERS detection research on PAHs mainly focuses on the pretreatment methods of PAHs in complex environments, the construction of SERS active substrates, and the functionalization of substrates.

[0003] When detecting PAHs in complex environments, sample pretreatment is usually required to remove interfering substances and enrich the analytes to improve detection sensitivity and accuracy. Current methods mostly use extraction-volatilization-elution and other operation steps. The pretreatment process is complex and time-consuming, and relies on organic solvents and the fine skills of the operator. These requirements greatly limit its application potential in rapid on-site detection. At the same time, SERS activity strongly depends on the electromagnetic field enhancement effect generated by metal nanostructures or the chemical enhancement effect generated by charge transfer between metals and the molecules to be detected. For this reason, researchers have done a lot of work in substrate structure design. At present, a variety of SERS substrates based on new materials such as Au / Ag nanostructures and graphene have been developed. These substrates improve detection sensitivity through electromagnetic field enhancement and chemical enhancement effects. However, the specific surface energy of these nanostructures is generally large, and they are prone to agglomeration, which makes the distribution of electromagnetic hotspots difficult to control, ultimately affecting the stability and reproducibility of the Raman signal of the analyte.

[0004] In recent years, filter membranes have attracted much attention as SERS substrates constructed as supporting matrices due to their unique advantages such as high mechanical strength, diverse components, and adjustable pore size. This substrate not only demonstrates the high sensitivity of SERS technology, but also has the functions of sample pretreatment and enrichment, which can effectively reduce the detection sensitivity and improve the efficiency and accuracy of sample analysis. Wang Juyong's team used filtering devices and filtering materials to adsorb PAHs in water bodies, and then eluted them with organic solvents, and used Ag NPs sol as SERS substrates to detect the eluent. One detection took about 30 minutes, and the detection and analysis of 16 PAHs in water environments was achieved. However, due to the strong hydrophobicity of PAHs, their binding force with metal nanoparticles is weak, and it is difficult to spontaneously aggregate within the effective enhancement range of the substrate. In order to enrich the target analytes near the metal nanoparticles, researchers have also conducted extensive research on the functionalization of the substrate. Various functional groups or ligands, such as thiols, alkyl chains, cup aromatics, and cyclodextrin derivatives, have been shown to enhance the interaction between metals and analytes. These research results show that the SERS-based PAHs rapid detection method has great potential and application prospects. However, most of them are still in the laboratory prototype stage and cannot meet the needs of rapid on-site detection. It is urgent to develop an enrichment-enhanced integrated SERS filter membrane substrate that does not require pretreatment and can achieve rapid measurement of PAHs for rapid enrichment detection of persistent organic pollutants in complex environmental systems. Summary of the invention

[0005] In view of the defects in the prior art, the purpose of the present invention is to provide an enrichment enhanced dual-function filter membrane SERS substrate and a preparation method and application thereof.

[0006] The present invention is achieved through the following technical solutions:

[0007] According to a first aspect of the present invention, a method for preparing an enrichment enhanced dual-function filter membrane SERS substrate is provided, the method comprising:

[0008] preparing Ag nanoparticles;

[0009] Functionalizing the Ag nanoparticles;

[0010] Self-assembling the functionalized Ag nanoparticles and the nanocarbon material so that the functionalized Ag nanoparticles are loaded on the surface of the nanocarbon material to form a hybrid structure;

[0011] Anchoring the hybrid structure with a matrix having a fibrous structure to form a SERS solution system of a composite nanostructure;

[0012] The SERS solution system of the composite nanostructure is filtered onto a glass fiber filter membrane to obtain an enriched and enhanced dual-function filter membrane SERS substrate.

[0013] Optionally, the preparation of Ag nanoparticles comprises:

[0014] Adding the silver nitrate aqueous solution dropwise into the mixed solution of hydroxylamine hydrochloride and sodium hydroxide;

[0015] After magnetic stirring, yellow-grey silver colloid is obtained, which is Ag nanoparticles.

[0016] Optionally, the Ag nanoparticles are functionalized, including: functionalizing the Ag nanoparticles with a macrocyclic compound having an inner hydrophobic property and an outer hydrophilic property.

[0017] Optionally, the macrocyclic compound is any one of cyclodextrin, calixarene and cucurbituril.

[0018] Optionally, the functionalized Ag nanoparticles are self-assembled with nano-carbon materials, wherein the nano-carbon material is any one of graphene, graphene oxide, reduced graphene oxide nanosheets and carbon nanotubes.

[0019] Optionally, the hybrid structure is anchored by using a matrix with a fibrous structure to form a composite nanostructured SERS solution system, wherein: the matrix with a fibrous structure is any one of nanocellulose, chitosan and sepiolite.

[0020] Optionally, filtering the composite nanostructured SERS solution system onto a glass fiber filter membrane comprises: slowly filtering the nanostructured SERS solution system onto a microporous glass fiber filter membrane by a vacuum filtration device, and vacuum-sealing and storing the prepared filter membrane SERS substrate.

[0021] Optionally, the SERS solution system of the composite nanostructure is filtered onto a glass fiber filter membrane, wherein the pore size of the glass fiber filter membrane is determined according to the size of the composite nanostructure.

[0022] According to a second aspect of the present invention, there is provided an enrichment enhanced dual-function filter membrane SERS substrate, which is prepared by the preparation method of the enrichment enhanced dual-function filter membrane SERS substrate of the first aspect.

[0023] According to a third aspect of the present invention, there is provided an application of the filter membrane SERS substrate prepared by the method of the first aspect or the filter membrane SERS substrate of the second aspect in detecting PAHs in a water environment, the application comprising:

[0024] Provide water samples to be tested;

[0025] After filtering the water sample to be tested once using a filtration platform, PAHs in the water sample are enriched on the filter membrane SERS substrate;

[0026] The filter membrane SERS substrate is taken out and Raman spectrum is directly collected to achieve rapid detection of PAHs in water samples.

[0027] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0028] The filter membrane SERS substrate provided by the present invention loads functionalized Ag nanoparticles on the surface of nanocarbon materials to construct a hybrid structure, and uses a fibrous matrix to firmly anchor the structure to obtain a SERS solution system with a composite nanostructure, and then filters the SERS solution system onto the filter membrane, so that the filter membrane has the dual functions of sample pre-enrichment and signal enhancement, which significantly improves the efficiency and accuracy of sample analysis. For PAHs water samples to be tested, no complicated pretreatment is required, and efficient enrichment and detection can be achieved through only one simple filtration. The present invention overcomes the problems of complicated and time-consuming water sample pretreatment, low detection efficiency, and poor stability of the SERS substrate in the prior art. Combined with a portable Raman spectrometer, it is helpful to carry out on-site SERS rapid detection applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0030] Figure 1 Schematic diagram of the preparation of Ag-HP-β-CD / rGO / NCF filter membrane SERS substrate and its detection method in one embodiment of the present invention;

[0031] Figure 2 The SEM characterization results of different materials in one embodiment of the present invention, wherein: (a) is a statistical diagram of Ag nanoparticles and their particle size distribution, (b) is rGO, and (c) is NCF;

[0032] Figure 3 The Raman spectra of pyrene obtained under different concentration gradients are detected by using the enrichment-enhanced dual-function filter membrane SERS substrate in the embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0034] In order to achieve rapid enrichment and detection of PAHs in a water environment, an embodiment of the present invention provides a method for preparing an enrichment enhanced dual-function filter membrane SERS substrate, which can be applied to the rapid detection of persistent organic pollutants in a water environment. The method comprises the following steps:

[0035] S1. preparing Ag nanoparticles;

[0036] S2, functionalizing Ag nanoparticles;

[0037] S3, self-assembling the functionalized Ag nanoparticles with the nanocarbon material having a large specific surface area, so that the functionalized Ag nanoparticles are loaded on the surface of the nanocarbon material to form a hybrid structure;

[0038] S4, using a matrix with a fibrous structure to anchor the hybrid structure to obtain a SERS solution system with a composite nanostructure;

[0039] S5. The composite nanostructured SERS solution system is filtered onto a glass fiber filter membrane by a filtration method to obtain an integrated enrichment-enhanced dual-functional filter membrane SERS substrate, thereby realizing rapid enrichment and detection of PAHs.

[0040] In some embodiments, in step S1, Ag nanoparticles are synthesized as metal plasma to enhance the Raman signal of the molecule to be detected. -2 M) was added dropwise to hydroxylamine hydrochloride (90 mL, 1.67×10 -3 M) and sodium hydroxide (300 μL, 1 M) in a mixed solution; after magnetic stirring for 30 min, a yellow-grey silver colloid was obtained, which was Ag nanoparticles (Ag nanoparticle sol).

[0041] In some embodiments, in step S2, Ag nanoparticles are functionalized with a macrocyclic compound having an inner hydrophobic structure and an outer hydrophilic structure to enhance the affinity between the Ag nanoparticles and the hydrophobic PAHs molecules, so that the molecules to be tested can be close to the electromagnetic hotspots of the Ag nanoparticles.

[0042] Illustratively, the macrocyclic compound is any one of macrocyclic compounds such as cyclodextrin, calixarene and cucurbituril.

[0043] Taking cyclodextrin as an example, the process of functionalizing Ag nanoparticles includes: preparing a cyclodextrin aqueous solution and fully stirring and mixing it with the Ag nanoparticle solution so that the Ag nanoparticles are combined with the cyclodextrin to improve the interaction between the Ag nanoparticles and the hydrophobic organic pollutant molecules.

[0044] In some embodiments, in step S3, the nanocarbon material is any one of graphene, graphene oxide, reduced graphene oxide nanosheets and carbon nanotubes. Nanocarbon materials have a large specific surface area and can provide abundant loading sites for metal nanoparticles, thereby indirectly regulating the spacing of metal nanoparticles and constructing high-density electromagnetic hotspots. In addition, nanocarbon materials can also contribute additional chemical enhancement effects.

[0045] Through the self-assembly process, the functionalized Ag nanoparticles are hybridized with nanocarbon materials, so that the Ag nanoparticles are evenly distributed on the surface of the nanocarbon materials, achieving the synergistic effect of electromagnetic enhancement and chemical enhancement. In addition, the nanocarbon materials can also effectively adsorb the aromatic ring molecules to be tested through π-π interactions, thereby further improving the detection sensitivity and selectivity of the SERS substrate.

[0046] In step S4, a fibrous matrix is ​​used as a supporting material, and the fibrous matrix is ​​fully mixed with the hybrid structure so that the hybrid structure is firmly anchored in the fiber skeleton to form a SERS solution system of a composite nanostructure. The fiber skeleton not only enhances the stability of the hybrid structure, but also provides good controllability in the subsequent preparation process of the filter membrane substrate, thereby helping to improve the repeatability of the Raman signal of the object to be tested. In some embodiments, the matrix of the fibrous structure is any one of nanocellulose, chitosan and sepiolite, which are easy to obtain and have good compatibility. They not only have a specific fibrous microstructure, which can provide a stable and effective support for the hybrid structure of Ag / nanocarbon, but also have no obvious Raman spectral signal itself, thereby avoiding the introduction of interference during the detection process.

[0047] In some embodiments, in step S5, the SERS solution system of the composite nanostructure is slowly filtered onto a microporous glass fiber filter membrane through a vacuum filtration device. The pore size of the glass fiber filter membrane is determined according to the size of the composite nanostructure and should be smaller than the minimum size of the composite nanostructure. It is generally recommended to select a filter membrane pore size that is 20%-30% smaller than the minimum diameter of the composite nanostructure, which can ensure that the composite nanostructure can be effectively retained during the filtration process to prevent it from penetrating the membrane material, and ensure that even if there are some size fluctuations or uneven particles, it can still be effectively retained, and the prepared filter membrane SERS substrate is vacuum sealed and stored.

[0048] The method in the above embodiment of the present invention hybridizes functionalized Ag nanoparticles with nanocarbon materials with a large specific surface area, so that the Ag nanoparticles are loaded on the surface of nanocarbon materials, thereby indirectly regulating the gaps between metal nanoparticles and constructing high-density SERS hotspots; then the above hybrid structure is mixed with a matrix with a fibrous structure so that it can be firmly anchored in the fiber skeleton, thereby enhancing the stability of the substrate and the signal uniformity; finally, the SERS solution system of the composite nanostructure is filtered onto a glass fiber filter membrane to obtain a filter membrane type SERS substrate with both enrichment and enhancement functions. This integrated enrichment and enhancement dual-function filter membrane SERS substrate does not require complex sample pretreatment steps, and can achieve rapid enrichment and detection of PAHs in water bodies through simple filtration operations. The entire detection process can be completed within 15 minutes, with high sensitivity and accuracy, and is suitable for rapid detection of persistent organic pollutants in water environments.

[0049] Another embodiment of the present invention provides an enrichment-enhanced dual-function filter membrane SERS substrate, which is prepared using the above-mentioned preparation method of the enrichment-enhanced dual-function filter membrane SERS substrate. The filter membrane SERS substrate can be used to directly measure persistent organic pollutants in aquatic environments, achieve efficient sample enrichment and Raman signal enhancement, and thus quickly detect PAHs in aquatic environments.

[0050] Another embodiment of the present invention provides an application of the above-mentioned filter membrane SERS substrate in detecting PAHs in a water environment, including: providing a water sample to be tested; using a filtration platform to filter the water sample to be tested once, and enriching the PAHs in the water sample into the filter membrane SERS substrate; taking out the filter membrane SERS substrate, and directly collecting Raman spectra to achieve rapid detection of PAHs in the water sample.

[0051] The detection method provided in the embodiment of the present invention uses a filtration platform and can achieve rapid enrichment of PAHs in a water environment with only one filtration. Combined with a portable Raman spectrometer, the entire enrichment and measurement process can be completed within 15 minutes.

[0052] The scheme of the present application will be explained below in conjunction with specific embodiments. It will be appreciated by those skilled in the art that the following embodiments are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific techniques or conditions are not indicated in the embodiments, the techniques or conditions described in the documents in this area or the product specifications are carried out. The reagents used or the instruments that do not indicate the manufacturer are all conventional products that can be obtained through commercial channels.

[0053] The enrichment enhanced dual-function filter membrane SERS substrate provided in this embodiment is specifically an Ag-2-hydroxypropyl-β-cyclodextrin / reduced graphene oxide / nanocellulose (Ag-HP-β-CD / rGO / NCF) filter membrane SERS substrate, refer to Figure 1 , and its preparation method comprises the following steps:

[0054] Step 1: Synthesize Ag nanoparticle sol.

[0055] Silver nitrate aqueous solution (10 mL, 10 -2 M) was added dropwise to hydroxylamine hydrochloride (90 mL, 1.67×10 -3 M) and sodium hydroxide (300 μL, 1 M) in a mixed solution. After magnetic stirring for 30 min, a yellow-grey Ag colloid was obtained. Figure 2 As shown in (a), the prepared Ag nanoparticles are approximately spherical. In order to further understand their particle size distribution, 100 nanoparticles were randomly selected for statistical analysis. The results show that the particle size distribution of the Ag nanoparticles synthesized by this method is relatively uniform, mainly concentrated between 20-40nm, and the average size is about 29.55nm, which can ensure the reliability and repeatability of the experimental results. In other embodiments, the size of the Ag nanoparticles can also be optimized to enhance the SERS signal intensity.

[0056] Step 2: Functionalization of Ag NPs.

[0057] Based on the Ag NPs sol prepared in step 1, it was mixed with a concentration of 10 -2 The HP-β-CD aqueous solution of Ag and HP-β-CD was mixed in a volume ratio of 10: 1. Subsequently, the mixture was stirred overnight to promote the combination of Ag and HP-β-CD to prepare a functionalized Ag-HP-β-CD nanoparticle solution.

[0058] Step 3: Hybridization of Ag-HP-β-CD and rGO.

[0059] After 5 min of ultrasonic treatment, the rGO powder was completely dispersed in the aqueous solution to obtain a rGO solution with a concentration of 0.1 mg / mL. Figure 2 As shown in (b), rGO exhibits a unique wrinkled structure, which can provide abundant loading sites for the Ag-HP-β-CD structure, thereby indirectly regulating the spacing of Ag-HP-β-CD metal nanoparticles and forming high-density electromagnetic hotspots. The functionalized Ag-HP-β-CD nanoparticle solution prepared in step 2 was mixed with the rGO solution in a ratio of 3:2 and ultrasonically treated for 5 min to form an Ag-HP-β-CD / rGO hybrid solution.

[0060] Step 4: Composite of Ag-HP-β-CD / rGO and NCF.

[0061] After the NCF gel (2.5 wt%) is fully stirred, an appropriate amount is taken out and diluted to 0.0125 wt% with deionized water, and ultrasonic stirring is performed to ensure uniform dispersion. Then, the diluted nanocellulose solution is fully mixed with the Ag-HP-β-CD / rGO solution prepared in step 3 to obtain the Ag-HP-β-CD / rGO / NCF composite nanostructure SERS solution system. This system uses the complex fiber skeleton of NCF to fix the Ag-HP-β-CD / rGO hybrid structure. Figure 2 (c) is the SEM characterization image, which clearly shows the stability of the fiber structure.

[0062] Step 5. Preparation and characterization of Ag-HP-β-CD / rGO / NCF filter membrane substrate.

[0063] A 0.1um glass fiber filter membrane was selected as the matrix. Under the action of a vacuum filtration device, 10mL of the Ag-HP-β-CD / rGO / NCF composite nanostructured SERS solution system prepared in step 4 was slowly filtered onto a glass cellulose filter membrane (0.1um, 25mm) to obtain a Ag-HP-β-CD / rGO / NCF portable filter membrane SERS substrate, which was then stored in a vacuum packaging bag.

[0064] Continue to refer to Figure 1 The typical PAHs pollutant pyrene in the water environment was measured using the prepared enrichment enhanced dual-functional filter membrane SERS substrate. The specific process is as follows:

[0065] Take 1 mL of simulated water sample, filter it once, remove the filter membrane and directly collect Raman spectra. Figure 3 The different concentrations (20-10 5 The average SERS spectra of pyrene at 410, 597, 1073, 1243, 1599 and 1627 cm -1 . It is worth noting that even at a concentration as low as 20 μg / L, the characteristic peaks of pyrene are still clearly discernible. This indicates that the Ag-HP-β-CD / rGO / NCF filter membrane SERS substrate has great potential in detecting PAHs pollutants. This method shows application prospects for rapid detection and early risk warning in water and soil environments in key pollution areas such as coking plants and urban sewage treatment plants.

[0066] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various modifications or variations within the scope of the claims, which does not affect the essence of the present invention. The above preferred features can be used in any combination without conflicting with each other.

Claims

1. A method for preparing an enrichment enhanced dual-function filter membrane SERS substrate, characterized in that: include: preparing Ag nanoparticles; Functionalizing the Ag nanoparticles; Self-assembling the functionalized Ag nanoparticles and the nanocarbon material, so that the functionalized Ag nanoparticles are loaded on the surface of the nanocarbon material to obtain a hybrid structure; Anchoring the hybrid structure with a matrix having a fibrous structure to obtain a SERS solution system of a composite nanostructure; The SERS solution system of the composite nanostructure is filtered onto a glass fiber filter membrane to obtain an enriched and enhanced dual-function filter membrane SERS substrate.

2. The method for preparing the enrichment enhanced dual-function filter membrane SERS substrate according to claim 1, characterized in that: The preparation of Ag nanoparticles comprises: Adding the silver nitrate aqueous solution dropwise into the mixed solution of hydroxylamine hydrochloride and sodium hydroxide; After magnetic stirring, yellow-grey silver colloid is obtained, which is Ag nanoparticles.

3. The method for preparing the enrichment enhanced dual-function filter membrane SERS substrate according to claim 1, characterized in that: Functionalizing the Ag nanoparticles comprises: functionalizing the Ag nanoparticles with a macrocyclic compound having inner hydrophobicity and outer hydrophilicity.

4. The method for preparing the enrichment enhanced dual-function filter membrane SERS substrate according to claim 3, characterized in that: The macrocyclic compound is any one of cyclodextrin, calixarene and cucurbituril.

5. The method for preparing the enrichment enhanced dual-function filter membrane SERS substrate according to claim 1, characterized in that: The functionalized Ag nanoparticles are self-assembled with nano-carbon materials, wherein the nano-carbon material is any one of graphene, graphene oxide, reduced graphene oxide nanosheets and carbon nanotubes.

6. The method for preparing the enrichment enhanced dual-function filter membrane SERS substrate according to claim 1, characterized in that: The hybrid structure is anchored by using a matrix with a fibrous structure to form a SERS solution system with a composite nanostructure, wherein: the matrix with a fibrous structure is any one of nanocellulose, chitosan and sepiolite.

7. The method for preparing the enrichment enhanced dual-function filter membrane SERS substrate according to claim 1, characterized in that: The composite nanostructured SERS solution system is filtered onto a glass fiber filter membrane, comprising: slowly filtering the composite nanostructured SERS solution system onto a microporous glass fiber filter membrane through a vacuum filtration device, and vacuum-sealing and storing the prepared filter membrane SERS substrate.

8. The method for preparing the enrichment enhanced dual-function filter membrane SERS substrate according to claim 1, characterized in that: The SERS solution system of the composite nanostructure is filtered onto a glass fiber filter membrane, wherein the pore size of the glass fiber filter membrane is determined according to the size of the composite nanostructure.

9. An enrichment enhanced dual-function filter membrane SERS substrate, characterized in that: The SERS substrate is prepared by the method for preparing the enrichment enhanced dual-functional filter membrane SERS substrate according to any one of claims 1 to 8.

10. Use of a filter membrane SERS substrate prepared by the method according to any one of claims 1 to 8 or the filter membrane SERS substrate according to claim 9 in detecting PAHs in a water environment, characterized in that: include: Provide water samples to be tested; After filtering the water sample to be tested once using a filtration platform, PAHs in the water sample are enriched on the filter membrane SERS substrate; The filter membrane SERS substrate is taken out and Raman spectrum is directly collected to achieve rapid detection of PAHs in water samples.

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