Preparation method of super-hydrophobic enrichment type SERS (Surface Enhanced Raman Scattering) substrate based on molecular filtration

Abstract

The invention discloses a preparation method of a super-hydrophobic enrichment type SERS (Surface Enhanced Raman Scattering) substrate based on molecular filtration, and belongs to the technical field of Raman spectrum detection. According to the method, the efficient filtering property of molybdenum disulfide is utilized, and rapid preparation of the silver nanoparticle SERS substrate under vacuum filtration is achieved; femtosecond laser is used for ablating the surface of the PTFE adhesive tape, uniform deposition of silver nanoparticles is guaranteed, loss of sample liquid drops is reduced, meanwhile, the hydrophilic difference between PTFE and molybdenum disulfide can generate self-driven longitudinal transfer on the liquid drops, and suction filtration is accelerated; the permeation rate of liquid drops is controlled by changing the use amount of molybdenum disulfide and the negative pressure of vacuum filtration; molybdenum disulfide interlayer spacing is changed through an intercalation method, substances of different sizes can be selectively filtered, and meanwhile the permeation flux of water is improved. The invention provides a new research way for efficiently preparing the SERS substrate in the field of medical detection from the angle of combining two-dimensional material suction filtration with femtosecond laser.

Description

Technical Field

[0001] This invention belongs to the field of Raman spectroscopy detection technology, specifically, it relates to a method for preparing a SERS substrate based on molecular filtration and superhydrophobic enrichment. Background Technology

[0002] The fabrication of surface-enhanced Raman scattering (SERS) substrates stems from the need to enhance Raman scattering signals. Raman scattering is a nonlinear optical phenomenon involving molecular vibrations, resulting in weak signals and limited detection capabilities. Research has found that molecules on the surface of metal nanostructures, particularly noble metals such as gold and silver, can significantly enhance Raman signals, a phenomenon known as the SERS effect. The fabrication of SERS substrates utilizes the local electromagnetic field enhancement effect of metal nanoparticles to improve signal intensity and sensitivity. Currently, commonly used clinical disease detection methods include imaging, antigen-antibody detection, and genetic material detection. Imaging detection procedures are simple, but early detection sensitivity is low; antigen-antibody detection offers good sensitivity and specificity, but performance cannot be balanced, and the procedure is cumbersome; genetic material detection also has high sensitivity and specificity, but is expensive and time-consuming. SERS detection, however, can achieve trace-level specific detection, making it extremely valuable in the field of biomonitoring.

[0003] SERS substrates typically require highly structured metallic surfaces or nanostructures to generate localized electric field enhancement under specific wavelength laser light. Commonly used materials include gold and silver (due to their strong surface plasmon resonance in the visible light region); in addition, composite materials and multifunctional modification methods are also used to improve performance. Various preparation methods are employed, such as chemical reduction, electrochemical deposition, solution methods, and template methods, to optimize morphology, enhance performance, and improve stability, meeting the needs of chemical analysis, environmental monitoring, and biosensing.

[0004] SERS technology commonly employs two approaches. The first is the immersion adsorption method, which involves first preparing a metal nanoarray and then immersing it in an analyte solution, allowing molecules to diffuse to hot spots for detection. Its advantage is good signal uniformity, but it has a long sample preparation time and requires a large sample volume. The second approach, evaporation enrichment, is designed for trace-level, small-sample detection. It constructs an interface with specific wettability to enrich the analyte during droplet evaporation, ultimately achieving detection. This method offers high detection sensitivity and requires less sample volume, meeting the needs of biological sample detection. However, this method faces the challenge of non-uniform detection due to the coffee ring effect.

[0005] Therefore, there is a need to develop new SERS technologies with high sample preparation efficiency, high detection sensitivity, and high detection specificity to meet the higher demands of the field of Raman spectroscopy detection technology. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a SERS substrate based on molecular filtration and superhydrophobic enrichment.

[0007] The objective of this invention can be achieved through the following technical solutions: A method for preparing a SERS substrate based on molecular filtration and superhydrophobic enrichment includes the following steps: S1. The PTFE tape is ultrasonically cleaned with acetone, ethanol and deionized water for 5 minutes in sequence, and then dried with nitrogen to obtain the cleaned PTFE tape. S2. Fix the cleaned PTFE tape on the worktable of the femtosecond laser, turn on the femtosecond laser, focus the laser beam emitted by it on the surface of the PTFE tape, and etch a hole with a diameter of 300μm in the central area of ​​the PTFE tape to obtain a hydrophilic-hydrophobic PTFE tape. S3. Place the PES filter membrane in a vacuum filter and slowly drip the molybdenum disulfide dispersion onto the surface of the PES filter membrane using a pipette. Turn on the vacuum filter and perform initial vacuum filtration. Dry for 30-60 seconds to form a molybdenum disulfide film on the surface of the PES filter membrane, thus obtaining a PES filter membrane containing molybdenum disulfide. S4. Place the hydrophilic-hydrophobic PTFE tape on top of the PES filter membrane containing molybdenum disulfide, aligning the molybdenum disulfide film on the PES filter membrane with the hydrophilic center and pore size of the PTFE tape. After fixing, slowly drop the silver nanoparticle solution onto the central area of ​​the PTFE tape using a pipette. Turn on the vacuum filter and perform a second vacuum filtration. After filtration, dry at room temperature to obtain a SERS substrate based on molecular filtration and superhydrophobic enrichment.

[0008] Furthermore, the thickness of the PTFE tape in step S1 is 0.18-0.20 μm.

[0009] Furthermore, in step S2, the power of the femtosecond laser is 0.5-1.5W; the scanning speed is 100-500mm / s; and the line spacing is 10-50μm.

[0010] Furthermore, in step S3, a PES filter membrane with a pore size of 0.1 μm is selected.

[0011] Furthermore, the amount of molybdenum disulfide dispersion used in step S3 is 1-8 μL.

[0012] Furthermore, in step S3, the initial vacuum filtration time is 2-5 minutes; the negative pressure is -0.08 to -0.1 MPa.

[0013] Furthermore, in step S4, the secondary vacuum filtration time is 2-13 min; the negative pressure is -0.05~-0.08 MPa.

[0014] Furthermore, the amount of silver nanoparticle solution used in step S4 is 1-9 μL.

[0015] In step S2 of this invention, femtosecond laser processing is used to form a superhydrophobic edge and hydrophilic center structure in the PTFE tape, without leaving any residue. In step S3, molybdenum disulfide particles will gradually deposit on the surface of the PES filter membrane to form a molybdenum disulfide film. As a two-dimensional material, molybdenum disulfide has excellent molecular sieving performance, high water flux, and no problems of expansion or decrease in ion repulsion rate when immersed in water for a long time. It has good stability and is suitable for various scenarios in medical testing. In step S4, during the filtration process, the silver nanoparticle droplets are hydrophilic and do not easily diffuse at the hydrophobic edges of PTFE. Therefore, they maintain an approximately spherical shape at the hydrophilic center of PTFE, allowing for uniform deposition and reducing sample droplet loss. Furthermore, under the negative pressure generated by the filtration machine and the capillary force generated by the gradient wettability, the superhydrophobic PTFE surface and the hydrophilic filter membrane exert a downward capillary force on the droplets, driving them through the PTFE micropores. Due to the combined effects of these forces, the droplets can be deposited rapidly, shortening the preparation time.

[0016] Furthermore, the molybdenum disulfide dispersion is prepared by the following steps: Molybdenum disulfide powder was added to N-methylpyrrolidone and ultrasonically treated for 15-30 minutes to uniformly disperse the molybdenum disulfide powder in N-methylpyrrolidone, thus obtaining a molybdenum disulfide dispersion.

[0017] Furthermore, the concentration of the molybdenum disulfide dispersion is 1×10⁻⁶. −7 ~5×10 −7 g / μL.

[0018] Furthermore, the silver nanoparticle solution is prepared through the following steps: A 0.1 mol / L silver nitrate solution was heated until boiling, and then sodium citrate was added to carry out the reaction. When the solution turned yellow-green, it was purified by centrifugation, and the resulting silver nanoparticles were redispersed in deionized water to obtain a silver nanoparticle solution.

[0019] Furthermore, the sodium citrate used accounts for 1% of the total volume of the reaction system.

[0020] Furthermore, the concentration of the silver nanoparticle solution is 1×10⁻⁶. −8 ~5×10 −8 g / μL.

[0021] The beneficial effects of this invention are: This invention utilizes the highly efficient filtration properties of molybdenum disulfide to achieve rapid preparation of silver nanoparticle SERS substrates under vacuum filtration. Femtosecond laser ablation of the PTFE tape surface creates superhydrophobic edges and hydrophilic centers, preventing lateral diffusion of droplets on the PTFE surface, ensuring uniform deposition of silver nanoparticles, and reducing sample droplet loss. Simultaneously, the difference in hydrophilicity between PTFE and molybdenum disulfide induces self-driven longitudinal droplet transfer, accelerating filtration. The droplet permeation rate can be controlled by varying the amount of molybdenum disulfide and the negative pressure of the vacuum filtration. By altering the interlayer spacing of molybdenum disulfide, substances of different sizes can be selectively filtered, while simultaneously increasing water permeation flux. This invention, combining two-dimensional material filtration with femtosecond laser technology, provides a new research approach for the efficient preparation of SERS substrates for medical testing. Attached Figure Description

[0022] The invention will now be further described with reference to the accompanying drawings.

[0023] Figure 1 This is a schematic diagram illustrating the substrate preparation process in an embodiment of the present invention.

[0024] Figure 2 This is a SEM image of the hydrophilic-hydrophobic PTFE tape in Embodiment 3 of the present invention.

[0025] Figure 3 This is a SEM image of the molybdenum disulfide thin film in Embodiment 3 of the present invention.

[0026] Figure 4 This is a SEM image of the substrate after silver nanoparticle deposition in Example 3 of the present invention. Detailed Implementation

[0027] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1 Preparation of molybdenum disulfide dispersion: Molybdenum disulfide powder was added to N-methylpyrrolidone and sonicated for 15 min to uniformly disperse the molybdenum disulfide powder in N-methylpyrrolidone, resulting in a molybdenum disulfide dispersion with a concentration of 1×10⁻⁶. −7 g / μL.

[0029] Example 2 Preparation of silver nanoparticle solution: A 0.1 mol / L silver nitrate solution was heated until boiling, followed by the addition of sodium citrate (1% by mass of the total reaction volume). The reaction proceeded until the solution turned yellow-green, then centrifuged to purify the solution. The resulting silver nanoparticles were redispersed in deionized water to obtain a silver nanoparticle solution with a concentration of 1 × 10⁻⁶. −8 g / μL.

[0030] Example 3 according to Figure 1 The method shown is used to prepare the substrate: S1. The PTFE tape with a thickness of 0.18μm was ultrasonically cleaned with acetone, ethanol and deionized water for 5 minutes in sequence, and then dried with nitrogen to obtain the cleaned PTFE tape. S2. Fix the cleaned PTFE tape onto the stage of the femtosecond laser, turn on the femtosecond laser (power: 0.5W), scan at 100mm / s with a line spacing of 10μm, and focus the emitted laser beam onto the surface of the PTFE tape. Etch a 300μm diameter hole in the central region of the PTFE tape to obtain a hydrophilic-hydrophobic PTFE tape. Obtain a SEM image of the hydrophobic PTFE tape using a scanning electron microscope (SEM), as shown below. Figure 2 As shown; S3. Place a 0.1 μm pore size PES filter membrane in a vacuum filter, and slowly drop 1 μL of the molybdenum disulfide dispersion prepared in Example 1 onto the surface of the PES filter membrane using a pipette. Turn on the vacuum filter and perform initial vacuum filtration for 2 min at a negative pressure of -0.08 MPa. Then dry for 30 s to form a molybdenum disulfide film on the surface of the PES filter membrane, obtaining a PES filter membrane containing molybdenum disulfide. Obtain a SEM image of the molybdenum disulfide film using a scanning electron microscope, as shown below. Figure 3 As shown; S4. Place the hydrophilic-hydrophobic PTFE tape on top of the PES filter membrane containing molybdenum disulfide, aligning the molybdenum disulfide film on the PES filter membrane with the hydrophilic center and pore size of the PTFE tape. After fixing, slowly add 1 μL of the silver nanoparticle solution prepared in Example 2 to the central region of the PTFE tape using a pipette. Turn on the vacuum filter and perform a second vacuum filtration for 2 minutes; the negative pressure is -0.05 MPa. After filtration, dry at room temperature to obtain a SERS substrate based on molecular filtration and superhydrophobic enrichment. Obtain the SEM image of the substrate after silver nanoparticle deposition using scanning electron microscopy, as shown below. Figure 4 As shown.

[0031] Example 4 according to Figure 1 The method shown is used to prepare the substrate: S1. The PTFE tape with a thickness of 0.19μm was ultrasonically cleaned with acetone, ethanol and deionized water for 5 minutes in sequence, and then dried with nitrogen to obtain the cleaned PTFE tape. S2. Fix the cleaned PTFE tape on the worktable of the femtosecond laser, turn on the femtosecond laser with a power of 1.0W, a scanning speed of 300mm / s, and a line spacing of 30μm, so that the emitted laser beam is focused on the surface of the PTFE tape and a hole with a diameter of 300μm is etched in the central area of ​​the PTFE tape to obtain a hydrophilic-hydrophobic PTFE tape. S3. Place the 0.1 μm pore size PES filter membrane in a vacuum filter, and then slowly drop 3 μL of the molybdenum disulfide dispersion prepared in Example 1 onto the surface of the PES filter membrane using a pipette. Turn on the vacuum filter and perform initial vacuum filtration for 3 min with a negative pressure of -0.09 MPa. Then dry for 45 s to form a molybdenum disulfide film on the surface of the PES filter membrane, thus obtaining a PES filter membrane containing molybdenum disulfide. S4. Place the hydrophilic-hydrophobic PTFE tape on top of the PES filter membrane containing molybdenum disulfide, aligning the molybdenum disulfide film on the PES filter membrane with the hydrophilic center and pore size of the PTFE tape. After fixing, slowly add 4 μL of the silver nanoparticle solution prepared in Example 2 to the central region of the PTFE tape using a pipette. Turn on the vacuum filter and perform a second vacuum filtration for 6 min; the negative pressure is -0.06 MPa. After filtration, dry at room temperature to obtain a SERS substrate based on molecular filtration and superhydrophobic enrichment.

[0032] Example 5 according to Figure 1 The method shown is used to prepare the substrate: S1. The PTFE tape with a thickness of 0.20μm was ultrasonically cleaned with acetone, ethanol and deionized water for 5 minutes in sequence, and then dried with nitrogen to obtain the cleaned PTFE tape. S2. Fix the cleaned PTFE tape on the worktable of the femtosecond laser, turn on the femtosecond laser with a power of 1.5W, a scanning speed of 500mm / s and a line spacing of 50μm, so that the emitted laser beam is focused on the surface of the PTFE tape and a hole with a diameter of 300μm is etched in the central area of ​​the PTFE tape to obtain a hydrophilic-hydrophobic PTFE tape. S3. Place the 0.1 μm pore size PES filter membrane in a vacuum filter, and then slowly drop 8 μL of the molybdenum disulfide dispersion prepared in Example 1 onto the surface of the PES filter membrane using a pipette. Turn on the vacuum filter and perform initial vacuum filtration for 5 min with a negative pressure of -0.1 MPa. Then dry for 60 s to form a molybdenum disulfide film on the surface of the PES filter membrane, thus obtaining a PES filter membrane containing molybdenum disulfide. S4. Place the hydrophilic-hydrophobic PTFE tape on top of the PES filter membrane containing molybdenum disulfide, aligning the molybdenum disulfide film on the PES filter membrane with the hydrophilic center and pore size of the PTFE tape. After fixing, slowly add 9 μL of the silver nanoparticle solution prepared in Example 2 to the central area of ​​the PTFE tape using a pipette. Turn on the vacuum filter and perform a second vacuum filtration for 13 min; the negative pressure is -0.08 MPa. After filtration, dry at room temperature to obtain a SERS substrate based on molecular filtration and superhydrophobic enrichment.

[0033] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0034] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for preparing a SERS substrate based on molecular filtration and superhydrophobic enrichment, characterized in that, Includes the following steps: After cleaning the PTFE tape, it was fixed on the worktable of the femtosecond laser, and a hole was etched in the central area of ​​the PTFE tape to obtain a hydrophilic-hydrophobic PTFE tape. The PES filter membrane was placed in a vacuum filter, and then the molybdenum disulfide dispersion was dropped onto the surface of the PES filter membrane. After initial vacuum filtration and drying, a PES filter membrane containing molybdenum disulfide was obtained. Hydrophilic-hydrophobic PTFE tape was stacked on top of a PES filter membrane containing molybdenum disulfide. After adding silver nanoparticle solution, the mixture was vacuum filtered twice and dried to obtain a SERS substrate based on molecular filtration and superhydrophobic enrichment.

2. The method for preparing a SERS substrate based on molecular filtration and superhydrophobic enrichment according to claim 1, characterized in that, The thickness of the PTFE tape is 0.18-0.20 μm.

3. The method for preparing a SERS substrate based on molecular filtration and superhydrophobic enrichment according to claim 1, characterized in that, The femtosecond laser has a power of 0.5-1.5W, a scanning speed of 100-500mm / s, and a line spacing of 10-50μm.

4. The method for preparing a SERS substrate based on molecular filtration and superhydrophobic enrichment according to claim 1, characterized in that, The PES filter membrane is selected with a pore size of 0.1 μm.

5. The method for preparing a SERS substrate based on molecular filtration and superhydrophobic enrichment according to claim 1, characterized in that, The initial vacuum filtration time is 2-5 minutes; the negative pressure is -0.08 to -0.1 MPa.

6. The method for preparing a SERS substrate based on molecular filtration and superhydrophobic enrichment according to claim 1, characterized in that, The secondary vacuum filtration time is 2-13 minutes; the negative pressure is -0.05 to -0.08 MPa.

7. The method for preparing a SERS substrate based on molecular filtration and superhydrophobic enrichment according to claim 1, characterized in that, The amount of the molybdenum disulfide dispersion used is 1-8 μL.

8. The method for preparing a SERS substrate based on molecular filtration and superhydrophobic enrichment according to claim 1, characterized in that, The amount of the silver nanoparticle solution used is 1-9 μL.

9. The method for preparing a SERS substrate based on molecular filtration and superhydrophobic enrichment according to claim 1, characterized in that, The molybdenum disulfide dispersion was prepared by the following steps: Molybdenum disulfide powder was added to N-methylpyrrolidone and ultrasonically treated to uniformly disperse the molybdenum disulfide powder in N-methylpyrrolidone, thus obtaining a molybdenum disulfide dispersion.

10. The method for preparing a SERS substrate based on molecular filtration and superhydrophobic enrichment according to claim 1, characterized in that, The silver nanoparticle solution was prepared by the following steps: The silver nitrate solution was heated until it boiled, and then sodium citrate was added to react. When the solution turned yellow-green, it was centrifuged and purified. The resulting silver nanoparticles were then redispersed in deionized water to obtain a silver nanoparticle solution.

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