Surface-enhanced Raman fiber as well as preparation method and application thereof

Abstract

The invention provides a surface-enhanced Raman optical fiber and a preparation method and application thereof. The surface-enhanced Raman optical fiber comprises an optical fiber of which the surface is modified with a gold-silver composite nano material, the gold-silver composite nano material is in the shape of a nano square block; the gold-silver composite nano material is of a core-shell structure and comprises a silver nano core and a gold nano shell, the modified optical fiber with charges on the surface and the gold-silver composite nano material with opposite charges on the surface are adsorbed through electrostatic interaction, so that stable combination can be formed, and uniform distribution and stable combination of Ag (at) Au NCs with different sizes on the surface of the optical fiber are realized. Surfactants in synthetic raw materials of the gold-silver composite nano material and the silver nano material comprise PVP, multi-step negative charge modification is formed, and uniform distribution and stable combination of Ag-coated Au NCs of different sizes on the surface of the optical fiber are achieved. The SERS optical fiber disclosed by the invention has high sensitivity, high stability and good batch-to-batch reproducibility, and is suitable for in-situ detection of various samples.

Description

Technical Field

[0001] This invention belongs to the field of enhanced Raman materials technology, specifically relating to a surface-enhanced Raman optical fiber, its preparation method, and its application. Background Technology

[0002] Fiber optic Raman spectroscopy utilizes optical fibers to conduct laser excitation of samples and collect their Raman scattered light. The molecular fingerprint information of the substance is then analyzed using a spectrometer. Its main applications include industrial process monitoring (such as real-time monitoring of chemical reactions), hazardous environment detection (such as chemical pipeline leaks), and clinical in vivo detection (such as endoscopy combined with Raman spectroscopy). While optical fibers, as the light transmission medium, enable remote and flexible detection with advantages such as non-destructive operation and long-distance manipulation, conventional fiber optic Raman signals are relatively weak, limiting their ability to detect trace amounts of substances.

[0003] Surface-enhanced Raman spectroscopy (SERS) is a highly effective tool for probing intermolecular interactions, characterizing surface molecular adsorption behavior, and identifying molecular structures. It offers advantages such as high detection sensitivity, simple sample pretreatment, fast analysis speed, low detection cost, and the ability to perform real-time in-situ detection. It has been used for the rapid detection of food additives and pesticide residues in food and agricultural products. SERS fiber Raman detection technology utilizes the SERS effect by modifying the end face or side face of an optical fiber with metallic nanostructures to amplify the signal by 10⁻¹⁰. 6 -10 14 It can be multiplied by 10 times, greatly improving detection sensitivity. It is mainly used in biomedicine such as early cancer screening (such as the detection of tumor markers in blood), rapid detection of pathogens (such as viruses and bacteria), security detection such as trace analysis of drugs and explosives, and environmental monitoring such as the detection of heavy metals and organic pollutants in water.

[0004] The fabrication strategies for SERS probes include "top-down" and "bottom-up" methods. Specifically, "top-down" refers to decomposing materials into nanostructures through macroscopic processing methods, such as using focused ion beam milling to create plasma structures on the surface of fiber optic probes. This allows for precise design of the shape, size, and arrangement of nanostructures, but suffers from drawbacks such as reliance on precision equipment, high processing costs, and difficulty in large-scale production. "Bottom-up" refers to constructing nanostructures at the atomic / molecular level through chemical synthesis or self-assembly, such as combining them to the surface of fiber optic probes via plasma nanomaterial deposition. This method offers advantages such as flexibility, simplicity, speed, and high throughput. In recent years, various plasma nanomaterials have been developed for "bottom-up" SERS probe fabrication, such as nanospheres, nanorods, nanocubes, and nanostars. However, current "bottom-up" SERS probe fabrication still faces challenges such as poor uniformity (difficulty in controlling particle size and distribution), poor stability (e.g., easy oxidation of metals), and poor reproducibility.

[0005] Therefore, the preparation of a SERS probe that combines sensitivity and reliability is of great significance for SERS detection. Summary of the Invention

[0006] To overcome the problems existing in the prior art, one objective of this invention is to provide a surface-enhanced Raman fiber. A second objective is to provide a method for preparing the aforementioned surface-enhanced Raman fiber. A third objective is to provide applications of the aforementioned surface-enhanced Raman fiber. A fourth objective is to provide a Raman spectroscopy detection device.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a surface-enhanced Raman optical fiber, comprising an optical fiber with a surface modified with a gold-silver composite nanomaterial; the gold-silver composite nanomaterial is in the shape of a nanocube; the gold-silver composite nanomaterial has a core-shell structure, comprising a silver nanocore and a gold nanoshell; the optical fiber modified with a surface charge and the gold-silver composite nanomaterial with an opposite surface charge are adsorbed by electrostatic interaction.

[0008] 785 nm near-infrared lasers are widely used in Raman spectrometers. Their low photon energy effectively suppresses autofluorescence interference from biological samples, achieving an optimal balance between fluorescence suppression, penetration depth, and detection sensitivity in conventional Raman detection. Compared to traditional 532 nm and 633 nm lasers, they are an ideal choice for fields such as biomedicine and materials science. However, existing technologies (especially those using reverse charge adsorption / assembly methods) exhibit poor enhancement performance and stability under 785 nm laser light. Silver on the surface of silver cubes (Ag NCs), silver nanoparticles (Ag NPs), and silver-coated gold nanorods (Au@Ag NRs) is easily oxidized (4Ag + O2 → 2Ag2O), which weakens the surface Raman enhancement performance. The LSPR wavelength of silver cubes (Ag NCs) and silver nanoparticles (Ag NPs) with a size of 5-100 nm is 390-500 nm, which is suitable for 532 nm lasers. The surface Raman enhancement factor of gold nanoparticles (Au NPs) is usually lower than that of silver nanomaterials. Gold nanorods (Au NRs) and gold nanostars (Au NSs) have strong photothermal effects. Strong local photothermal effects can cause distortion of Raman characteristic peaks and may also cause baseline drift in the Raman spectrum.

[0009] To address the shortcomings of the above materials, this invention prepares gold-coated silver nanocubes (Ag@Au NCs) that can be used as core materials for SERS and plasma optics applications. These nanocubes have significant advantages such as high sensitivity (high SERS activity of the silver core), high stability (effective protection by the gold shell), and tunability to the near-infrared (tunable silver core size and gold layer thickness). Furthermore, SERS optical fibers can be mass-produced using a simple and low-cost modification method.

[0010] Preferably, the side length of the gold-silver composite nanomaterial is 40-120 nm.

[0011] More preferably, the side length of the gold-silver composite nanomaterial is 100-120 nm.

[0012] Preferably, the thickness of the gold nanoshell is 0.5-3 nm.

[0013] More preferably, the thickness of the gold nanoshell is 0.5-1 nm.

[0014] Preferably, the shape of the silver nanonucleus is a nanocube.

[0015] Preferably, the side length of the silver nanonucleus is 40-115 nm.

[0016] More preferably, the side length of the silver nanonucleus is 100-115 nm.

[0017] Preferably, the surface of the gold-silver composite nanomaterial carries a negative charge.

[0018] More preferably, the raw materials for preparing the gold-silver composite nanomaterial include silver nano cubes, a gold source, and a surfactant; the raw materials for preparing the silver nanomaterial include a silver source and a surfactant; and the surfactant includes polyvinylpyrrolidone.

[0019] More preferably, the method for preparing silver nanocubes with a side length of 40-50 nm includes the following steps: The silver nanocubes were prepared by reacting a silver source, sodium sulfide, and a surfactant in an organic solvent.

[0020] More preferably, the silver source includes silver nitrate.

[0021] More preferably, the process includes the following steps: dissolving the silver source, sodium sulfide, and surfactant in ethylene glycol to prepare corresponding solutions; adding the surfactant solution to the sodium sulfide solution; and finally adding the silver source solution to react and obtain the silver nanocube with a side length of 40-50 nm.

[0022] More preferably, the mass ratio of the silver source to the surfactant is 1:(1-1.5).

[0023] More preferably, the mass ratio of the silver source to sodium sulfide is 1:(10) -3 -10 -4 ).

[0024] More preferably, the reaction is carried out at room temperature.

[0025] More preferably, the reaction time is 5-30 min.

[0026] More preferably, the reaction time is 7-20 min.

[0027] More preferably, the reaction temperature is 145-155 °C.

[0028] More preferably, the reaction temperature is 148-152 °C.

[0029] More preferably, the method for preparing silver nanocubes with side lengths of 70 nm-110 nm includes the following steps: The silver nanocubes with a side length of 40-50 nm, a silver source, and a surfactant were reacted in an organic solvent to prepare the silver nanocubes.

[0030] More preferably, the reaction temperature is 145-155 min.

[0031] More preferably, the reaction temperature is 148-152 °C.

[0032] More preferably, the preparation method of the gold-silver composite nanomaterial includes the following steps: The gold-silver composite nanomaterial is prepared by reacting silver nanoblocks, gold source, reducing agent and surfactant in a solvent.

[0033] More preferably, the reducing agent includes ascorbic acid.

[0034] Further, the gold source is selected in a more favorable location, including tetrachloroauric acid.

[0035] More preferably, the molar ratio of the gold source to the surfactant is 1:(600-1000).

[0036] Further, the molar ratio of the gold source to the reducing agent is 1:(1500-2500).

[0037] More preferably, sodium hydroxide is also added to react together.

[0038] Preferably, the positively charged optical fiber is an aminated optical fiber.

[0039] More preferably, the preparation method of the aminated optical fiber includes the following steps: placing the hydroxylated optical fiber in an alcohol solution containing 3-aminopropyltriethoxysilane to carry out an amination reaction to obtain the aminated optical fiber.

[0040] More preferably, the method for preparing the hydroxylated optical fiber includes the following steps: placing the optical fiber in a piranha solution to carry out a hydroxylation reaction, thereby obtaining the hydroxylated optical fiber.

[0041] The piranha solution, also known as piranha etching solution, is a mixture of concentrated sulfuric acid and 30% hydrogen peroxide (7:3).

[0042] A second aspect of the present invention provides a method for fabricating the surface-enhanced Raman fiber described in the first aspect, comprising the following steps: The surface-enhanced Raman fiber is obtained by placing a positively charged optical fiber in a dispersion containing gold and silver composite nanomaterials for modification.

[0043] Preferably, the modification reaction takes 20-40 minutes.

[0044] More preferably, the modification reaction takes 25-30 minutes.

[0045] Preferably, the modification reaction is performed at room temperature.

[0046] The third aspect of this invention provides for the application of the surface-enhanced Raman fiber described in the first aspect in any of the following aspects: a) Detect the spectrum of the sample; b) Prepare a Raman spectroscopy detection device.

[0047] Preferably, the sample is a dye molecule.

[0048] More preferably, the dye molecule is rhodamine.

[0049] Preferably, the sample is an organic pollutant in water.

[0050] A fourth aspect of the present invention provides a Raman spectroscopy detection device, comprising an optical fiber Raman spectrometer and the surface-enhanced Raman fiber described in the first aspect.

[0051] The beneficial effects of this invention are: This invention proposes a surface-enhanced Raman fiber, comprising an optical fiber with a surface modified with gold-silver composite nanomaterials; the gold-silver composite nanomaterials are in the shape of nanocubes; the gold-silver composite nanomaterials have a core-shell structure, including a silver nanocore and a gold nanoshell; the modified optical fiber with a surface charge and the gold-silver composite nanomaterials with opposite surface charges are adsorbed by electrostatic interaction, especially when the negatively charged gold-silver composite nanomaterials are connected to amino groups on the optical fiber, a stable bond can be formed, achieving uniform distribution and stable bonding of Ag@Au NCs of different sizes on the surface of the optical fiber.

[0052] This invention also proposes a method for preparing the gold-silver composite nanomaterials of the aforementioned surface-enhanced Raman optical fiber. Both methods utilize polyvinylpyrrolidone (PVP) as a surface activator in their raw materials. During the reaction, the hydroxyl groups of PVP are converted to carboxyl groups, thereby ionizing H+. + The negatively charged carboxylate radicals are exposed, thus the resulting silver nanomaterials and gold-silver composite nanomaterials plasma nanostructures with silane are negatively charged, forming a multi-step negative charge modification. This not only eliminates the need for additional charge modification, but also makes the surface-modified molecules inherent in the synthesis process more stable than those with subsequent charge modifications. The SERS fiber of this invention has high sensitivity, high stability, and good batch-to-batch reproducibility, making it suitable for in-situ detection of various samples. Attached Figure Description

[0053] Figure 1 Methods for fabricating Ag@Au NCs optical fibers; Figure 2 The UV-Vis absorption spectrum of Ag@Au NCs at 50 nm is shown. Figure 3 Scanning electron microscope (SEM) image of 50 nm Ag@Au NCs; Figure 4 High-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) image of 50 nm Ag@Au NCs; Figure 5 UV-Vis of 80 nm Ag@Au NCs; Figure 6 SEM image of 80 nm Ag@Au NCs; Figure 7 High-angle annular dark-field scanning transmission electron microscopy (HAADF STEM) image of 80 nm Ag@Au NCs; Figure 8 For the corresponding Figure 7 Element marker; Figure 9 UV-Vis of 110 nm Ag@Au NCs; Figure 10 SEM image of 110 nm Ag@Au NCs; Figure 11 High-angle annular dark-field scanning transmission electron microscopy (HAADFSTEM) image of 100 nm Ag@Au NCs; Figure 12 For the corresponding Figure 11 Element marker; Figure 13 SEM image of 80 nm Ag NCs; Figure 14 SEM images of 80 nm Ag NCs stored in deionized water after one month; Figure 15 SEM images of 80 nm Ag@Au NCs stored in deionized water after one month; Figure 16 SEM image of the surface of a 50 nm Ag@Au NCs optical fiber; Figure 17 SEM images of the surface of a 50 nm Ag@Au NCs optical fiber at different magnifications; Figure 18 SEM image of the surface of an 80 nm Ag@Au NCs optical fiber; Figure 19 SEM images of the surface of an 80 nm Ag@Au NCs optical fiber at different magnifications; Figure 20 SEM image of the surface of a 110 nm Ag@Au NCs optical fiber; Figure 21 SEM images of the surface of 110 nm Ag@Au NCs optical fiber at different magnifications; Figure 22 Procedure for measuring sample spectra using an Ag@Au NCs fiber-coupled fiber Raman spectrometer; Figure 23 The spectra of Rhodamine 6G (R6G) samples were detected using a 50 nm Ag@Au NCs fiber-coupled fiber Raman spectrometer. Figure 24 For the corresponding Figure 23 Linear fitting of spectral data; Figure 25 The spectra of Rhodamine 6G (R6G) samples were detected using an 80 nm Ag@Au NCs fiber-coupled fiber Raman spectrometer. Figure 26 For the corresponding Figure 25 Linear fitting of spectral data; Figure 27The spectra of Rhodamine 6G (R6G) samples were detected using a 110 nm Ag@Au NCs fiber-coupled fiber Raman spectrometer. Figure 28 For the corresponding Figure 27 Linear fitting of spectral data; Figure 29 The spectrum of R6G sample was detected using a 90 nm Au NPs fiber-coupled fiber Raman spectrometer. Figure 30 SEM image of the surface of a 90 nm Au NPs optical fiber; Figure 31 The results are reproducibility experiments for 50 nm Ag@Au NCs optical fibers. Figure 32 The reproducibility experimental Raman spectrum of a 50 nm Ag@Au NCs fiber; Figure 33 The reproducibility test results are for 80 nm Ag@Au NCs optical fiber; Figure 34 Reproducible Raman spectra of 80 nm Ag@Au NCs optical fiber; Figure 35 The results are reproducibility experiments for 110 nm Ag@Au NCs optical fibers. Figure 36 The reproducibility experimental Raman spectrum of a 110 nm Ag@Au NCs fiber. Detailed Implementation

[0054] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials used in the following embodiments can be obtained from conventional commercial channels or prepared and isolated through simple synthesis; unless otherwise specified, the processes employed are conventional processes in the art.

[0055] Example 1 This embodiment provides a surface-enhanced Raman fiber. The fabrication steps of the Ag@Au NCs fiber are described below. Figure 1 The specific preparation method is as follows: 1. Synthesis of Ag NCs with side length of 40-50 nm 1) Add 6 mL of ethylene glycol (EG) to the reaction glass bottle and stir and heat at 150 °C for 1 hour. Continue to maintain the temperature at 150 °C in subsequent step 3) until the reaction is complete.

[0056] 2) Dissolve 0.03 g of polyvinylpyrrolidone (PVP) in 1.5 mL of EG to prepare 1 mL of approximately 3 mM sodium sulfide Na2S EG solution, and dissolve 0.072 g of AgNO3 in 1.5 mL of EG.

[0057] 3) Add 70-100 μL (preferably 80 μL) of the above Na2S solution to the reaction flask, wait for 8-9 minutes for the reaction to proceed, then add 1.5 mL of the above PVP solution to the reaction flask, and finally immediately add 0.5-1.5 mL of the above AgNO3 solution to the reaction flask, wait for 7-20 minutes, observe that the meniscus turns deep red and the reaction medium turns greenish-ochre, and quench the reaction in cold water.

[0058] 4) Transfer the contents of each vial to the corresponding 50 mL centrifuge tube. Rinse the reaction flask with acetone and transfer the washings to the corresponding centrifuge tube for centrifugation. Redisperse the precipitate with deionized water and centrifuge 3-4 times for purification. Redisperse in deionized water and store at 4 °C. The product material is designated as 50 nm Ag NCs.

[0059] 2. Synthesis of Ag@Au NCs 1) Add 2 mL of 1 mM PVP solution, 0.5 mL of 10 mM ascorbic acid (AA) solution, 0.1 mL of 0.2 M sodium hydroxide (NaOH) solution and 0.1 mL of 0.5 mg / mL AgNCs solution to the reaction flask in sequence, with water as the solvent for all solutions.

[0060] 2) Inject 0.2 mL of 12.5 μM HAuCl4 solution at a rate of 0.02 mL / min, and then stir the reaction for 10 minutes.

[0061] 3) After separating the product, redisperse it with deionized water, then centrifuge and purify it 2-3 times, and finally redisperse it in deionized water. The product material is denoted as 50 nm Ag@Au NCs.

[0062] 3. Fabrication of surface-enhanced Raman fibers After removing the coating from the optical fiber, it was first sonicated in anhydrous ethanol, then hydroxylated in a piranha solution, and finally cleaned with deionized water. The cleaned fiber was then aminated in an ethanol solution containing APTES, followed by drying in a drying oven. Finally, the dried fiber was immersed in a 10 mg / mL Ag@Au NCs dispersion for 30 minutes to allow Ag@Au NCs to adsorb onto the fiber surface. By changing the concentration of the Ag@Au NCs dispersion, the density of noble metal nanoparticles on the fiber surface could be controlled. The fiber was designated as a 50 nm Ag@Au NCs fiber.

[0063] Example 2 This embodiment provides a surface-enhanced Raman fiber. The fabrication steps of the Ag@Au NCs fiber are described below. Figure 1The specific preparation method is as follows: 1. Synthesis of Ag NCs with side lengths of 70-110 nm 1) Transfer 1.25 mL of EG into a vial and heat in an oil bath at 150 °C with magnetic stirring. Continue at 150 °C in subsequent step 3) until the reaction is complete.

[0064] 2) After 2 minutes, add 0.3 mL of PVP solution (20 mg / mL dissolved in EG) to the vial.

[0065] 3) The 50 nm Ag NCs (50 µL, 5 mg / mL, dissolved in EG) prepared in Example 1 were added to a vial as seed, followed by a transfer of 200 µL AgNO3 solution (282 mM, dissolved in EG) into the vial. Ag NCs with side lengths of 80 nm and 110 nm were collected at 12 minutes and 40 minutes of reaction, respectively. The reaction was quenched in cold water.

[0066] 4) Transfer the contents of each vial to the corresponding 50 mL centrifuge tube. Rinse the reaction flask with acetone and transfer the washings to the corresponding centrifuge tube for centrifugation. Redisperse the precipitate with deionized water and centrifuge 3-4 times for purification. Redisperse in deionized water and store at 4 °C. The product materials are designated as 80 nm Ag NCs and 110 nm Ag NCs.

[0067] 2. Synthesis of Ag@Au NCs 1) Add 2 mL of 1 mM PVP, 0.5 mL of 10 mM ascorbic acid (AA), 0.1 mL of 0.2 M sodium hydroxide (NaOH) and 0.1 mL of AgNCs to the reaction flask in sequence.

[0068] 2) Inject 0.2 mL of 12.5 μM HAuCl4 solution at a rate of 0.02 mL / min, and then stir the reaction for 10 minutes.

[0069] 3) After separating the product, redisperse it with deionized water, then centrifuge and purify it 2-3 times, finally redispersing it in deionized water. The product materials are designated as 80 nm Ag@Au NCs and 80 nm Ag@Au NCs. 3. Fabrication of surface-enhanced Raman fibers After removing the coating from the optical fiber, it is first sonicated in anhydrous ethanol, then hydroxylated in a piranha solution, and then cleaned with deionized water. The cleaned optical fiber is then placed in an ethanol solution containing APTES for amination, and then dried in a drying oven. Finally, the dried optical fiber is placed in an Ag@Au NCs dispersion to allow Ag@Au NCs to adsorb onto the fiber surface. By changing the concentration of the Ag@Au NCs dispersion, the density of noble metal nanoparticles on the fiber surface can be controlled.

[0070] Comparative Example 1 This comparative example provides a surface-enhanced Raman fiber, specifically an Au NPs fiber, and the specific fabrication method is as follows: 90 nm gold polyhedra (AuNPs, with cetyltrimethylammonium bromide as the surface activator) were prepared using the classic seed growth method. Fibers were prepared using 10 mg / mL AuNPs, following the same steps and methods as Ag@Au NCs, except that APTES was replaced with sodium carboxyethylsilanetriol (CEOS).

[0071] Ag@Au NCs material characterization The gold-silver composite nanomaterials of Examples 1 and 2 were characterized using ultraviolet-visible absorption spectroscopy (UV-Vis) and scanning electron microscopy (SEM) images, wherein... Figure 2 , 5 9 are the UV-Vis absorption spectra of Ag@Au NCs at 50, 80 and 110 nm, respectively. Figure 3 , 6 Scanning electron microscope (SEM) images of Ag@Au NCs at 50, 80, and 110 nm, respectively; Figure 4 , 6 Images of Ag@Au NCs at 50, 80, and 110 nm, respectively, obtained by high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM). Figure 8 and 12 For the corresponding Figure 6 and Figure 10 The elemental labeling; as shown in the above figures, the main UV-Vis absorption peaks of Ag@Au NCs synthesized using the method of this invention are all redshifted compared to the absorption peaks of AgNCs, and the SEM images all show a relatively obvious cubic shape with uniform size, with side lengths of 50, 80, and 110 nm, respectively. HAADF-STEM images and elemental labeling show that the Au layer has completely encapsulated the Ag core, and the thickness of the gold nanoshell is 1-3 nm (see Figure 8 and 12 ).

[0072] Figure 13 SEM image of 80 nm Ag NCs; Figure 14 SEM images of 80 nm Ag NCs stored in deionized water after one month; Figure 15 The image shows SEM images of 80 nm Ag@Au NCs stored in deionized water for one month. As can be seen from the image, Ag@Au NCs have good stability. Ag NCs have obvious rounded corners after being stored in deionized water for one month. The hot spots of the nanocubes are distributed at the eight cubic corners of the cube. Rounded corners will reduce the number of effective hot spots that can be generated, resulting in a decrease in SERS activity. Ag@Au NCs, on the other hand, still maintains the cubic shape.

[0073] Ag@Au NCs fiber characterization The distribution and morphology of noble metal nanoparticles modified on the surface of optical fibers were characterized using field emission scanning electron microscopy.

[0074] Depend on Figure 16-21 It can be seen that Ag@Au NCs fibers are uniformly distributed, mostly densely packed, with uniform morphology and high hotspot density.

[0075] Raman characterization Ag@Au NCs optical fibers can be coupled to fiber optic Raman spectrometers for measuring sample spectra. Figure 22 The procedure for measuring the sample spectrum using an Ag@Au NCs fiber-coupled fiber Raman spectrometer is as follows: all sample detection parameters are set as follows: 785 nm excitation, laser intensity 20 mw, exposure time 500 ms, and 20 averages.

[0076] Depend on Figure 23-28 It is known that Ag@Au NCs optical fibers possess high sensitivity, with a detection limit (LOD) as low as the pM level. Combined with... Figures 29-30 It can be seen that under the same conditions, 10 are detected. -6 The signal intensity detected by MR6G solution in Ag@Au NCs fiber is 4 to 6 times that in 90 nm Au NPs fiber.

[0077] Depend on Figures 31-36It is evident that the Ag@Au NCs fiber fabrication technology in this invention exhibits excellent reproducibility. In contrast, Wuhan University of Technology developed a gold-plated nanobipyramidal SERS fiber probe, its fabrication method, and its application in 2023. In that probe, a negatively charged modified gold nanobipyramidal layer is applied to the end face of the fiber body via a positively charged layer (the principle and method are similar to this invention, but the modification time in this prior art is as long as 12 hours), but its stability is poor; the SERS fiber fabricated by that patent showed a signal strength decrease of more than two times on the second day of use. The SERS fiber fabricated in this invention exhibits high sensitivity, high stability, and good batch-to-batch reproducibility, making it suitable for in-situ detection of various samples.

[0078] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A surface-enhanced Raman fiber, characterized in that, The optical fiber includes a surface-modified gold-silver composite nanomaterial; the gold-silver composite nanomaterial is in the shape of a nanocube; the gold-silver composite nanomaterial has a core-shell structure, including a silver nanocore and a gold nanoshell; the optical fiber modified with a surface charge adsorbs the gold-silver composite nanomaterial with an opposite surface charge through electrostatic interaction.

2. The surface-enhanced Raman fiber according to claim 1, characterized in that, The gold-silver composite nanomaterial has a side length of 40-120 nm; And / or, the thickness of the gold nanoshell is 0.5-3 nm.

3. The surface-enhanced Raman fiber according to claim 1, characterized in that, The surface of the gold-silver composite nanomaterial carries a negative charge. Preferably, the raw materials for preparing the gold-silver composite nanomaterial include silver nanomaterials, a gold source, and a surfactant; the raw materials for preparing the silver nanomaterials include a silver source and a surfactant; and the surfactant includes polyvinylpyrrolidone.

4. The surface-enhanced Raman fiber according to claim 3, characterized in that, The preparation method of the gold-silver composite nanomaterial includes the following steps: reacting silver nano cubes, gold source, reducing agent and surfactant in a solvent to obtain the gold-silver composite nanomaterial. And / or, the method for preparing the silver nanocubes includes the following steps: reacting a silver source, sodium sulfide and a surfactant in an organic solvent to obtain the silver nanocubes.

5. The surface-enhanced Raman fiber according to claim 4, characterized in that, The reducing agent includes ascorbic acid; And / or, the gold source includes tetrachloroauric acid.

6. The surface-enhanced Raman fiber according to claim 1, characterized in that, The surface-charged optical fiber is an aminated optical fiber; Preferably, the preparation method of the aminated optical fiber includes the following steps: placing the hydroxylated optical fiber in an alcohol solution containing 3-aminopropyltriethoxysilane to carry out an amination reaction to obtain the aminated optical fiber.

7. The surface-enhanced Raman fiber according to claim 6, characterized in that, The preparation method of the hydroxylated optical fiber includes the following steps: placing the optical fiber in a piranha solution to carry out a hydroxylation reaction, thereby obtaining the hydroxylated optical fiber.

8. The method for preparing the surface-enhanced Raman fiber according to any one of claims 1-7, characterized in that, Includes the following steps: The surface-charged optical fiber was placed in a dispersion containing gold and silver composite nanomaterials for modification reaction to obtain the surface-enhanced Raman optical fiber.

9. The application of the surface-enhanced Raman fiber according to any one of claims 1-7 in any of the following aspects: a) Detect the spectrum of the sample; b) Prepare a Raman spectroscopy detection device.

10. A Raman spectroscopy detection device, characterized in that, Includes fiber Raman spectrometer and surface-enhanced Raman fiber as described in any one of claims 1-7.

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