Heterogeneous double-layer gold / magnetic binary superlattice film SERS (Surface Enhanced Raman Scattering) substrate as well as preparation method and application thereof

Abstract

The invention discloses a heterogeneous double-layer gold / magnetic binary superlattice film SERS (Surface Enhanced Raman Scattering) substrate as well as a preparation method and application thereof. According to the superlattice thin film, gold nanoparticles and ferroferric oxide nanoparticles are used as construction units; the gold nanoparticles are modified by surface ligands and then transferred into an oil phase, and the gold nanoparticles are mixed with ferriferrous oxide nanoparticles and then self-assembled on a gas-liquid interface to form the superlattice film. The heterogeneous double-layer superlattice film prepared by taking gold and ferroferric oxide crystals as basic construction units can be used as a Raman enhanced detection substrate, the SERS signal of the heterogeneous double-layer superlattice film is obviously superior to that of a single layer, and in addition, synergistically enhanced SERS detection can be realized by applying an external magnetic field.

Description

Technical Field

[0001] The present invention belongs to the field of nano synthesis and self-assembly technology, and particularly relates to a preparation method and application of a heterogeneous bilayer gold / magnetic binary superlattice thin film SERS substrate. Background Art

[0002] Binary Nanoparticle Superlattice (BNSL) is composed of two types of nanoparticles, which are co-assembled into an ordered array. Compared with the nanoparticle superlattice with only one type of nanocrystal, the advantage of the binary nanocrystal superlattice is that it not only has the characteristics of a single nanoparticle building unit, but also has collective properties due to the interaction between nanoparticles. The controlled coupling between nanocrystal building units in a highly ordered superlattice generates various novel collective properties, providing unique optical, magnetic, electronic, and catalytic properties. So far, the self-assembly of various inorganic numerical control compounds (such as plasmonic metals, metal oxides, quantum dots, magnetic, and dielectric) has formed single lattices, binary superlattices, and even ternary superlattices with long-range orientation and positional order on a large area. Although a large amount of work has been done to explore the crystal structure and growth mechanism of binary superlattices, the complexity of their self-assembled structure and growth mechanism still needs to be explored, and only a small amount of work has studied the physical properties of binary superlattice thin films. Therefore, further exploring the self-assembled structure of binary superlattice thin films and the application of new properties demonstrated based on synergistic effects remains a difficult problem in this field and has important research value.

[0003] Surface-Enhanced Raman Scattering (SERS) is a powerful spectroscopic analysis technique that can significantly enhance the Raman scattering signal of molecules adsorbed on a rough metal surface or nanostructure, and can even achieve single-molecule detection. The superlattice thin film based on the assembly of plasmonic particles can generate local enhancement hotspots in the particle gaps due to the plasmon coupling between metal ions. In addition, the highly close arrangement of superlattice nanocrystals makes the substrate have high detection sensitivity and ordered hotspots, and provides prospects for the preparation of high-performance SERS substrates. Summary of the Invention

[0004] Object of the Invention: The object of the present invention is to provide a heterogeneous bilayer gold / magnetic binary superlattice thin film SERS substrate; another object of the present invention is to provide a preparation method of a heterogeneous bilayer gold / magnetic binary superlattice thin film SERS substrate; another object of the present invention is to provide an application of a heterogeneous bilayer gold / magnetic binary superlattice thin film SERS substrate.

[0005] Technical solution: The SERS substrate based on the heterogeneous bilayer gold / magnetic binary superlattice film of the present invention is characterized in that the SERS substrate has a bilayer micro-nano array structure, wherein the bottom layer is composed of ordered arrangement of iron oxide nanoparticles, and the upper layer is composed of ordered arrangement of gold nanoparticles.

[0006] Preferably, the particle size of the iron oxide nanoparticles is 14nm - 15nm, and the particle size of the gold nanoparticles is 6.3nm - 7.7nm.

[0007] In the above technical solution, the particle sizes of the gold nanoparticles and the iron oxide nanoparticles affect the structure of the superlattice film. Self-assembly of 15nm iron oxide nanoparticles and 4.0nm gold nanoparticles can form a heterogeneous monolayer superlattice film, but cannot form a heterogeneous bilayer superlattice film; self-assembly of 15nm iron oxide nanoparticles and 6.3nm or 7.7nm gold nanoparticles can form a heterogeneous bilayer superlattice film; the heterogeneous bilayer superlattice film prepared by the present invention is a highly ordered bilayer nanoarray at the micro-nano scale. The ordered gold nanoarray in the upper layer can provide a strong "SERS hot spot". By the combined use of the superlattice film and an external magnetic field, it can be used for the development of practical applications for SERS.

[0008] On the other hand, the present invention provides a preparation method of the above-mentioned SERS substrate based on the heterogeneous bilayer gold / magnetic binary superlattice film, which is characterized in that the water-phase synthesized gold nanoparticles are transferred to the oil phase to modify oleylamine molecules to obtain gold nanoparticles with surface-modified oleylamine molecules; then, the gold nanoparticles with surface-modified oleylamine molecules and the iron oxide particles with surface-modified oleic acid molecules are used as basic building blocks to assemble a bilayer superlattice film at the gas-liquid interface, which is the SERS substrate based on the heterogeneous bilayer gold / magnetic binary superlattice film.

[0009] Further, the preparation method includes the following steps:

[0010] (1) Add the water-phase synthesized gold nanoparticles to a mixed solution containing toluene and oleylamine to obtain a solution of gold nanoparticles with surface-modified oleylamine molecules;

[0011] (2) Add the iron oxide nanoparticles with surface-modified oleic acid molecules to the toluene solution to obtain an iron oxide nano-solution;

[0012] (3) Mix the gold nanoparticle solution prepared in step (1) and the iron oxide nano-solution prepared in step (2) evenly to obtain a mixed solution;

[0013] (4) Drop the mixed solution onto the surface of the diethylene glycol (DEG) solution. After the toluene has completely evaporated, obtain the SERS substrate of the heterogeneous bilayer gold / magnetic binary superlattice film.

[0014] Preferably, step (1) is specifically as follows: Add 1.98 μL of oleylamine and 6 mL of toluene into a 50 mL centrifuge tube and mix well. Subsequently, add 30 mL of 4 nm gold nanoparticle solution, shake vigorously until the lower layer solution becomes transparent, take out the upper layer solution, and then wash it with deionized water multiple times to remove excess sodium citrate molecules. Prepare toluene solutions of 6.3 nm and 7.7 nm gold in the same way.

[0015] Further, in step (1), the gold nanoparticles synthesized in the aqueous phase are used to prepare gold nanoparticles with oleylamine molecules modified on the surface. The method for synthesizing gold nanoparticles in the aqueous phase is as follows: Dilute the gold nanosphere seed solution with a sodium citrate solution, heat it up, and then add an aqueous solution of chloroauric acid and react to obtain gold nanoparticles.

[0016] Further, in step (1), under the conditions of stirring and heating, add a tannic acid solution and a K2CO3 solution to the sodium citrate solution, and then quickly add an aqueous solution of chloroauric acid, and continue to react to prepare a gold nanosphere seed solution.

[0017] Preferably, the method for preparing gold nanoparticles of different sizes includes the following steps:

[0018] (a) 4.0 nm gold nanospheres: Under the conditions of stirring and heating at 70 °C and 500 rpm, add 0.1 mL of 2.5 mM tannic acid solution and 1 mL of 150 mM K2CO3 solution to 150 mL of 2.2 mM sodium citrate solution. After heating up to 70 °C, quickly add 1 mL of 25 mM aqueous chloroauric acid solution, and continue to react for 5 min to prepare a 4.0 nm gold nanosphere solution, which is transparent orange-red. Finally, cool the solution to room temperature naturally and store it in a 4 °C refrigerator.

[0019] (b) 6.3 nm gold nanospheres: Use the 4.0 nm gold nanospheres prepared in (a) as seeds. Take 55 mL of the above seed solution, add 55 mL of 2.2 mM sodium citrate solution to dilute it, heat up to 70 °C, quickly add 1 mL of 25 mM aqueous chloroauric acid solution, and react at 70 °C for 10 min to obtain 6.3 nm gold nanoparticles. Cool to room temperature and store it sealed at 4 °C.

[0020] (c) 7.7 nm gold nanospheres: Use the 6.3 nm gold nanospheres prepared in (b) as seeds. Take 55 mL of the above seed solution, add 55 mL of 2.2 mM sodium citrate solution to dilute it, heat up to 70 °C, quickly add 1 mL of 25 mM aqueous chloroauric acid solution, and react at 70 °C for 10 min to obtain 7.7 nm gold nanoparticles. Cool to room temperature and store it sealed at 4 °C.

[0021] Further, in step (3), in the mixed solution, the concentration of iron oxide nanoparticles is the same as that of gold nanoparticles.

[0022] Further, the preparation method of gold nanoparticles with oleylamine molecules on the surface is as follows: Add oleylamine and toluene and mix them evenly, then add the gold nanoparticle solution to obtain gold nanoparticles with oleylamine molecules on the surface.

[0023] Further, the preparation method of iron oxide particles with oleic acid molecules on the surface is as follows: Mix water, ethanol, n-hexane, sodium oleate and ferric chloride and stir vigorously at room temperature until homogeneous, then heat for reaction to obtain iron oxide particles with oleic acid molecules on the surface.

[0024] Preferably, the preparation method of 15-nm iron oxide nanospheres is as follows:

[0025] Mix 60 mL of deionized water, 80 mL of ethanol, 140 mL of n-hexane, 36.5 g of sodium oleate and 10.8 g of ferric chloride hexahydrate and stir vigorously at room temperature until homogeneous, then heat to 70 °C and maintain for 4 h. After the reaction is completed, wash the upper organic matter 3 times with 30 mL of distilled water and dry it in vacuum to obtain a red-brown waxy iron oleate complex. Weigh 1.6 g of the waxy iron oleate complex and dissolve it in 25 mL of 1-octadecene, add 0.9 g of oleic acid, then heat it to 320 °C at a rate of 3 °C / min and react for 30 min under stirring at 200 rpm. After cooling to room temperature, precipitate, purify and wash with acetone, separate the black solid with a magnet, and dry it in vacuum to obtain a black solid.

[0026] Further, in step (4), after mixing the phase-transfered gold nanoparticle solution and the iron oxide solution, drop the mixture onto the surface of DEG, cover it with a cover glass, and wait for the toluene solution to slowly evaporate completely to obtain a heterostructured bilayer Au / M magnetic superlattice film.

[0027] Preferably, specifically, the operation method for constructing the SERS substrate of the heterostructured bilayer Au / M binary superlattice film is as follows: Dissolve 60 mg of iron oxide nanoparticles in 10 mL of toluene, ultrasonically disperse them evenly to obtain a 6 mg / mL iron oxide solution, dilute it 15 times and mix it evenly with an equal volume of the gold nanoparticle solution phase-transfered to toluene. Take 100 μL of the mixed solution and drop it onto the surface of the DEG solution containing 10% deionized water, cover the mouth of the beaker with a cover glass to control the evaporation rate of toluene. Wait for the toluene to evaporate completely, then pick it up with a 1 cm × 1 cm silicon wafer or glass, and then dry it in a vacuum environment at 150 °C for 1 h to evaporate the excess DEG solution. The prepared substrate is washed several times with absolute ethanol and dried to obtain a SERS substrate of a heterostructured bilayer Au / M binary superlattice film.

[0028] On the other hand, the present invention provides an application of the above-mentioned SERS substrate based on the heterostructured bilayer Au / M binary superlattice film in surface-enhanced Raman spectroscopy detection.

[0029] Furthermore, under the action of an external magnetic field, a surface-enhanced Raman spectroscopy (SERS) detection is carried out using a double-layer gold / magnetic binary superlattice thin film SERS substrate.

[0030] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: (1) The prepared gold nanoparticles do not need to be synthesized by the oil-phase method to obtain gold nanoparticles with surface-modified oleylamine ligands. By synthesizing in the aqueous phase and then performing a phase transfer method, gold nanospheres with different nanosizes can be continuously prepared, with simple operation, environmental friendliness and low cost; (2) Compared with the traditional single-layer binary superlattice thin film, for the prepared heterogeneous double-layer gold / magnetic binary superlattice thin film, the spacing distance of gold nanoparticles is not affected by the nanocrystals of the other component, and the hot spots between particles are stronger; (3) The SERS substrate of the heterogeneous double-layer gold / magnetic binary superlattice thin film provided by the present invention has a significantly better detection signal than the single-layer binary superlattice thin film; (4) The SERS substrate of the heterogeneous double-layer gold / magnetic binary superlattice thin film provided by the present invention has a significantly enhanced detection signal under the action of an external magnetic field. Description of the Drawings

[0031] Figure 1 : The process of preparing a heterogeneous double-layer gold / magnetic binary superlattice thin film at the gas-liquid interface.

[0032] Figure 2 : Transmission electron microscope images of superlattice structures self-assembled by gold nanoparticles of different sizes and magnetite nanoparticles; among them, a is a single-layer superlattice structure formed by 4.0 nm Au and 15 nm Fe3O4, b is a double-layer superlattice structure formed by 6.3 nm Au and 15 nm Fe3O4, c is a double-layer superlattice structure formed by 7.7 nm Au and 15 nm Fe3O4, and the insets d, e, f are schematic diagrams of the corresponding simulated superlattice structures of a, b, c respectively.

[0033] Figure 3 : Performance comparison between the SERS substrate based on the heterogeneous double-layer gold / magnetic binary superlattice thin film and the SERS substrate based on the single-layer gold / magnetic binary superlattice thin film.

[0034] Figure 4 : Application of the SERS substrate based on the heterogeneous double-layer gold / magnetic binary superlattice thin film under an external magnetic field; among them, A is a schematic diagram of the device for Raman detection of the double-layer gold / magnetic binary superlattice thin film SERS substrate under an external magnetic field, and B is the Raman spectra obtained by testing the double-layer gold / magnetic binary superlattice thin film SERS substrate at magnetic field intensities of 0 T, 10 mT, and 25 mT. Detailed Embodiments

[0035] The present invention will be further described below in conjunction with the drawings and embodiments.

[0036] All glassware involved in the present invention was soaked in aqua regia, washed with deionized water, and dried. The water used in each example was deionized water.

[0037] Example 1:

[0038] As Figure 1 shown in the preparation process of the heterogeneous bilayer gold / magnetic binary superlattice film. First, prepare Figure 1 the nanocrystals of the two building blocks of the superlattice film shown in a of

[0039] (1) Preparation of gold nanoparticles of different sizes

[0040] 4.0 nm gold nanospheres: Under the conditions of stirring and heating at 70 °C and 500 rpm, 0.1 mL of 2.5 mM tannic acid solution and 1 mL of 150 mM K2CO3 solution were added to 150 mL of 2.2 mM sodium citrate solution. After heating to 70 °C, 1 mL of 25 mM chloroauric acid aqueous solution was quickly added, and the reaction continued for 5 min to obtain a 4.0 nm gold nanosphere solution, which was transparent orange-red. Finally, the solution was naturally cooled to room temperature and stored in a 4 °C refrigerator.

[0041] 6.3 nm gold nanospheres: The 4.0 nm gold nanospheres prepared in (1) were used as seeds. Take 55 mL of the above seed solution, dilute it with 55 mL of 2.2 mM sodium citrate solution, heat to 70 °C, quickly add 1 mL of 25 mM chloroauric acid aqueous solution, and react at 70 °C for 10 min to obtain 6.3 nm gold nanoparticles. Cool to room temperature and store sealed at 4 °C.

[0042] 7.7 nm gold nanospheres: The 6.3 nm gold nanospheres prepared in (2) were used as seeds. Take 55 mL of the above seed solution, dilute it with 55 mL of 2.2 mM sodium citrate solution, heat to 70 °C, quickly add 1 mL of 25 mM chloroauric acid aqueous solution, and react at 70 °C for 10 min to obtain 7.7 nm gold nanoparticles. Cool to room temperature and store sealed at 4 °C.

[0043] (2) Phase transfer of gold nanoparticles

[0044] Add 1.98 μL of oleylamine and 6 mL of toluene into a 50 mL centrifuge tube and mix well. Subsequently, add 30 mL of the 4 nm gold nanosolution obtained in step (1), and shake vigorously until the lower layer solution becomes transparent. Take out the upper layer solution and wash it with deionized water multiple times to remove the excess sodium citrate molecules. Prepare toluene solutions of 6.3 nm and 7.7 nm gold in the same way.

[0045] (3) Preparation of iron oxide nanoparticles

[0046] 15 nm iron oxide nanospheres: Mix 60 mL of deionized water, 80 mL of ethanol, 140 mL of n-hexane, 36.5 g of sodium oleate, and 10.8 g of ferric chloride hexahydrate, and stir vigorously at room temperature until homogeneous. Heat to 70 °C and maintain for 4 h. After the reaction is completed, wash the upper layer of organic matter 3 times with 30 mL of distilled water, and vacuum dry to obtain a red-brown waxy iron oleate complex. Weigh 1.6 g of the waxy iron oleate complex and dissolve it in 25 mL of 1-octadecene. Add 0.9 g of oleic acid, and then heat to 320 °C at a rate of 3 °C / min and react for 30 min under stirring at 200 rpm. After cooling to room temperature, precipitate and purify with acetone, separate the black solid with a magnet, and vacuum dry to obtain a black solid.

[0047] (4) Construction method of heterogeneous monolayer and bilayer gold / magnetic binary superlattice film SERS substrate:

[0048] First, weigh 60 mg of the iron oxide nanoparticles in step (3), dissolve them in 10 mL of toluene, and obtain a 6 mg / mL iron oxide nanosolution by ultrasonic dispersion. Dilute the 6 mg / mL iron oxide nanosolution 15 times with toluene solution, and then mix it with the gold nanoparticles dissolved in toluene obtained by phase transfer in step (2) at a volume ratio of 1:1 in a 20 mL glass bottle and shake well. Add 25 mL of DEG liquid into a beaker with a diameter of 4 cm, and add 2.5 mL of deionized water to it and mix well. Let it stand until the bubbles in the solution disappear. Then, take out 100 μL of the mixed solution and drop it onto the surface of DEG. Cover the mouth of the beaker with a glass slide and leave a gap in the middle to control the evaporation rate of toluene, as Figure 1 shown. Wait until the toluene evaporates completely, and the superlattice film is prepared. As Figure 2 shown in a of, it is a heterogeneous monolayer superlattice film formed by self-assembly of 4.0 nm gold nanocrystals and 15 nm iron oxide nanoparticles, where the inset d is the superlattice structure; using larger diameter gold nanoparticles, a heterogeneous bilayer superlattice film can be prepared, as Figure 2 shown in b-c of, it is 6.3 nm gold nanocrystals ( Figure 2 shown in b of) and 7.7 nm ( Figure 2In c), gold nanocrystals and 15-nm iron oxide nanoparticles self-assembled to form a heterogeneous bilayer superlattice film, and inserted Figure 2 Figures e and f in it are its superlattice structures respectively. The prepared superlattice film was picked up with a 1 cm × 1 cm silicon wafer or glass, and then dried in a vacuum environment at 150 °C for 1 h to evaporate the excess DEG solution. The prepared substrate was washed with absolute ethanol multiple times and dried to obtain a heterogeneous bilayer gold / magnetic binary superlattice film SERS substrate.

[0049] Example 2:

[0050] The SERS performance of the heterogeneous monolayer and bilayer gold / magnetic binary superlattice film SERS substrates prepared in Example 1 was compared (using 4-MBA as the probe molecule): The substrates prepared in Example 1 were placed in a 10 μM 4-MBA ethanol solution for 6 h. After taking out the silicon wafer and waiting for it to dry naturally, its Raman spectrum was measured. As Figure 3 shown, the obtained spectra were compared in intensity, and the Raman characteristic peak 1586 cm -1 in the spectrum was selected to compare the Raman enhancement detection signal of 4-MBA. It can be seen that the detection signal of the heterogeneous bilayer gold / magnetic binary superlattice film SERS substrate prepared by the present invention is significantly higher than that of the monolayer gold / magnetic binary superlattice film.

[0051] Example 3:

[0052] It is the same as Example 2, except that:

[0053] The prepared bilayer gold / magnetic binary superlattice film SERS substrate was placed under a magnetic field for Raman spectrum measurement. The magnetic field was generated by a toroidal magnet, and the device is as Figure 4 shown in A in it. The distance between the toroidal magnet and the substrate was adjusted to measure at magnetic field intensities of 0 T, 10 mT, and 25 mT. The obtained spectra were compared in intensity, as Figure 4 shown in B in it, and the characteristic peak 1586 cm -1 in the spectrum was selected to compare the Raman enhancement detection signal of 4-MBA. It can be seen that the heterogeneous bilayer gold / magnetic binary superlattice film SERS substrate prepared by the present invention can detect SERS enhancement signals under external magnetic field stimulation.

Claims

1. A surface-enhanced Raman scattering (SERS) substrate based on a heterogeneous bilayer gold / magnetic binary superlattice thin film, characterized in that The SERS substrate has a double-layer micro-nano array structure. Among them, the bottom layer is composed of orderly arranged iron oxide nanoparticles, and the upper layer is composed of orderly arranged gold nanoparticles.

2. The SERS substrate based on the heterogeneous bilayer gold / magnetic binary superlattice thin film according to claim 1, wherein The particle size of the iron oxide nanoparticles is 14nm - 15nm, and the particle size of the gold nanoparticles is 6.3nm - 7.7nm.

3. A preparation method of a SERS substrate based on a heterogeneous bilayer gold / magnetic binary superlattice thin film according to any one of claims 1-2, characterized in that, The water-phase synthesized gold nanoparticles are transferred to the oil phase to modify oleylamine molecules, obtaining gold nanoparticles with surface-modified oleylamine molecules; then, using the gold nanoparticles with surface-modified oleylamine molecules and the iron oxide particles with surface-modified oleic acid molecules as basic building units, a double-layer superlattice film is assembled at the gas-liquid interface, which is the SERS substrate based on the heterogeneous double-layer gold / magnetic binary superlattice film.

4. The preparation method of the SERS substrate based on the heterogeneous bilayer gold / magnetic binary superlattice thin film according to claim 3, characterized in that, The preparation method includes the following steps: (1) Add the water-phase synthesized gold nanoparticles to a mixed solution containing toluene and oleylamine to obtain a gold nanoparticle solution with surface-modified oleylamine molecules; (2) Add the iron oxide nanoparticles with surface-modified oleic acid molecules to the toluene solution to obtain an iron oxide nano-solution; (3) Mix the gold nanoparticle solution prepared in step (1) and the iron oxide nano-solution prepared in step (2) evenly to obtain a mixed solution; (4) Drop the mixed solution onto the surface of the diethylene glycol (DEG) solution. After the toluene has completely evaporated, obtain the SERS substrate of the heterogeneous double-layer gold / magnetic binary superlattice film.

5. The preparation method of the SERS substrate based on the heterogeneous bilayer gold / magnetic binary superlattice thin film according to claim 4, wherein, In step (1), the preparation method of the water-phase synthesized gold nanoparticles is as follows: Dilute the gold nanosphere seed solution with a sodium citrate solution, heat it up, and then add an aqueous chloroauric acid solution to react to obtain gold nanoparticles.

6. The preparation method of the SERS substrate based on the heterogeneous bilayer gold / magnetic binary superlattice thin film according to claim 5, wherein, In step (1), under the conditions of stirring and heating, add a tannic acid solution and a K2CO3 solution to the sodium citrate solution, and then quickly add an aqueous chloroauric acid solution and continue to react to prepare the gold nanosphere seed solution.

7. The preparation method of the SERS substrate based on the heterogeneous bilayer gold / magnetic binary superlattice thin film according to claim 4, wherein In step (3), in the mixed solution, the concentration of the iron oxide nano is the same as the concentration of the gold nanoparticles.

8. The preparation method of the SERS substrate based on the heterogeneous bilayer gold / magnetic binary superlattice thin film according to claim 3, characterized in that, The preparation method of the gold nanoparticles with surface-modified oleylamine molecules is as follows: Add oleylamine and toluene and mix them evenly, and then add the gold nano-solution to obtain the gold nanoparticles with surface-modified oleylamine molecules; And / or, the preparation method of the iron oxide particles with surface-modified oleic acid molecules is as follows: Mix water, ethanol, n-hexane, sodium oleate, and ferric chloride hexahydrate and stir vigorously at room temperature until uniform, heat and react, mix the obtained precursor with oleic acid and 1-octadecene and heat to 320 °C at a rate of 3 °C / min, and perform high-temperature decomposition to obtain the iron oxide particles with surface-modified oleic acid molecules.

9. Application of the SERS substrate based on the heterogeneous double-layer gold / magnetic binary superlattice film according to any one of claims 1 - 2 in surface-enhanced Raman spectroscopy detection.

10. The application according to claim 9, wherein Under the action of an external magnetic field, use the SERS substrate of the double-layer gold / magnetic binary superlattice film for surface-enhanced Raman spectroscopy detection.

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