Controllable preparation method of SERS (Surface Enhanced Raman Scattering) internal standard magnetic nanoparticles

Abstract

The invention discloses a ferroferric oxide, gold, internal label and gold core-shell nanoparticle and a preparation method thereof. Ferroferric oxide is used as a main body, nano-particles which take 16-20 nm gold nano-particles as cores, take sulfydryl molecules with benzene rings as internal standards and have the gold shell thickness of 35-40 nm are adsorbed on the surface of the ferroferric oxide, the overall particle size of the ferroferric oxide nano-particles is 200-460 nm, and the particle size of ferroferric oxide balls is 160-400 nm; the method comprises the following steps: uniformly dissolving ferric chloride, sodium acetate and polyethylene glycol in ethylene glycol according to a mass ratio of (1-2.7): (0.15-0.72): (0.5-2.3), heating to 200 DEG C, keeping the temperature for 8-72 hours, and naturally cooling to room temperature; and putting the product into a drying box, and drying at 60 DEG C. The method comprises the following steps: firstly, preparing Fe3O4 nano-particles, then carrying out surface modification on the Fe3O4 nano-particles, adsorbing 16nm gold seeds to the surfaces of the Fe3O4 nano-particles, adding internal standard molecules, and finally adding ascorbic acid and chloroauric acid to realize gold shell growth on the surfaces of the 16nm gold seeds. The material has the advantages of magnetic aggregation, easiness in separation and the like, and can be applied to the fields of pesticide residue detection, catalytic degradation, environment detection and analysis and the like based on an SERS (Surface Enhanced Raman Scattering) technology.

Description

Technical Field

[0001] The present invention relates to a core-shell nanoparticle and a preparation method thereof, in particular to a Fe3O4@Au@(-SH)@Au nanoparticle and a preparation method thereof. Technical Background

[0002] In recent years, due to their unique magnetic, optical and biocompatible properties, core-shell structured gold-ferroferric oxide (Fe3O4 / Au) nanocomposites have shown broad application prospects in the fields of biomedicine, catalysis, environmental governance, etc. However, there are still the following key problems to be solved in the prior art: Fe3O4 nanoparticles are prone to aggregation due to their high specific surface area in neutral physiological environments, which affects their targeting and dispersibility in vivo. Although the gold shell can improve chemical stability, surface modifiers (such as citric acid) used in traditional methods may limit subsequent biofunctionalization. For example, although thiol (-SH) modification can achieve directional modification through Au-S bonds, the thiol modification step in the prior art is complex, and the binding strength between the gold shell and the Fe3O4 core is insufficient, making it easy to peel off. For example, Patent CN110211758A proposes to mix Fe3O4 and gold nanorods by ultrasonic dispersion method, which simplifies the process, but does not solve the problems of weak core-shell interface binding force and surface functionalization. Another patent CN101773810A uses the microwave method to synthesize the Fe3O4 core and coats the gold shell by the seed method, but still requires multiple repeated reduction steps, resulting in low yield and high cost. The present invention uses modified positively charged ferroferric oxide, which electrostatically adsorbs with negatively charged Au, replacing the problem of insufficient binding strength of thiol groups. Moreover, this structure not only endows the substrate with good magnetic responsiveness, facilitating rapid separation and enrichment through an external magnetic field, but also significantly increases the plasmonic hot spot regions due to the aggregated multi-layer structure. It also has advantages such as simple synthesis method, high yield, good repeatability, and good Raman signal enhancement performance. Summary of the Invention

[0003] To solve the above problems, the present invention proposes a Fe3O4@Au@(-SH)@Au nanoparticle and a preparation method thereof. The polyethyleneimine modified on the surface of ferroferric oxide not only acts as a protective agent to prevent aggregation, but also facilitates the adsorption of gold nanoparticles on the surface of ferroferric oxide through electrostatic interaction, finally forming a core-shell nanostructure with gold-coated ferroferric oxide. Through the strong coordination effect of the thiol (-SH) of the internal standard molecule with Fe3O4 and Au, the core-shell binding strength is enhanced, a stable interface layer is formed, and the gold shell peeling is avoided; the preparation process is simplified, and the gold shell is coated by a one-step method, reducing the reduction steps, and improving the yield and reproducibility.

[0004] The present invention aims to solve the above existing technical problems and provides a preparation method of the above-mentioned Fe3O4@Au@(-SH)@Au nanoparticle.

[0005] To solve the technical problems of the present invention, the technical solution adopted is: magnetite@gold@internal standard@gold nanoparticles. In particular,

[0006] The magnetite@gold@internal standard@gold nanoparticles have a core-shell structure with magnetite as the main body, gold nanoparticles as the core, thiol molecules with benzene rings as the internal standard molecules, and gold as the shell. The overall particle size is 200 - 460 nm;

[0007] The magnetite is magnetite nanospheres with a particle size of 160 - 400 nm;

[0008] The gold@internal standard@gold is a gold sphere with a core-shell structure, where the gold core is 16 - 20 nm, the gold shell is 35 - 40 nm thick, and the gold@internal standard@gold core-shell structure is 50 - 60 nm.

[0009] The preparation method of the above magnetite@gold@internal standard@gold nanoparticles adopts the hydrothermal method. Specifically, the steps are as follows:

[0010] Step 1. First, dissolve ferric chloride in ethylene glycol according to the mass ratio of ferric chloride: sodium acetate: polyethylene glycol of 1 - 2.7: 0.15 - 0.72: 0.5 - 2.3. After stirring evenly, add sodium acetate and polyethylene glycol to the mixed solution and stir for at least 20 min to obtain a precursor solution;

[0011] Step 2. Place the precursor solution in a sealed state and react at 200 °C for 8 - 72 h to obtain a precipitate of magnetite nanoparticles;

[0012] Step 3. Modify the surface of the magnetite nanoparticles. Weigh 80 - 100 mg of magnetite powder and add it to an aqueous solution of sodium polystyrene sulfonate with a concentration of 2 - 5 mg / mL and containing 0.05 M NaCl for surface modification. Then disperse it into an aqueous solution of polyethyleneimine with a concentration of 2 - 5 mg / mL and containing 0.05 M NaCl, and then perform alternating modification of sodium polystyrene sulfonate and polyethyleneimine. Repeat the above steps, collect by magnetic absorption to obtain a precipitate, and disperse it in 20 mL of deionized water;

[0013] Step 4. Add 200 mL of deionized water and 2.42 mL of chloroauric acid solution with a mass fraction of 1% to the flask, then heat to boiling, quickly add 6 mL of CA aqueous solution with a mass fraction of 50%, continue heating and stirring vigorously for about 2 - 5 minutes, keep the solution in a slightly boiling state and continue to react for 20 - 30 min. After cooling to room temperature, gold nanoparticles with an average particle size of about 16 nm are obtained;

[0014] Step 5. Add 100 - 300 μL of the synthesized gold nanoparticles in Step 4 into 0.5 mL of Fe3O4 colloidal solution. Collect the product with a magnet, wash the product to remove the excess gold nanoparticles, redisperse the composite product in 20 mM CTAC solution, and adsorb for 0.5 - 1 h;

[0015] Step 6. Add 0.5 - 1 ml of a thiol internal standard molecule solution with a benzene ring into the composite product synthesized in Step 5. Shake and incubate the above mixture for 20 - 40 min, centrifuge three times, remove the supernatant after each centrifugation, and make up the precipitate to 10 mL with 20 mM CTAC solution;

[0016] Step 7. Add 10 mL of 0.1 M CTAC solution into a flask, place the flask in a water bath at 30 - 40 °C, then add 500 μL of the internal standard molecule - modified gold - seeded composite iron oxide solution and 500 μL of 0.04 M ascorbic acid solution. After stirring evenly, slowly add 500 μL of HAuCI4 solution. Finally, gold@internal standard@gold nanospheres with a particle size of about 60 nm are coated on the surface of the iron oxide particles, and the overall particle size is 200 - 460 nm.

[0017] As a further improvement of the preparation method of iron oxide@gold@internal standard@gold nanoparticles, the precipitate is washed, separated, and dried; the washing treatment is to alternately wash with ethanol and deionized water 3 - 4 times; the separation treatment is to use a magnet for separation; the drying treatment is to dry at 60 °C for 6 h; the alternating modification requires at least two times.

[0018] The beneficial effects compared with the prior art are as follows. First, the obtained target product was detected by scanning electron microscopy, transmission electron microscopy and Raman spectroscopy respectively. From the results, it can be seen that the target product is a large number of nanoparticles with uniform size and good dispersion. Its overall particle size is 200 - 460 nm, and it is composed of a core of magnetite with a particle size of 160 - 400 nm and a shell composed of a gold particle-like substance with a thickness of 35 - 40 nm coated on the outside. Among them, for the magnetite@gold@internal standard@gold nanoparticles detected by transmission electron microscopy, the results show that magnetite nanospheres are distributed in the central part, and gold nanocore-shell particles are attached to the edge, proving that the core of the core-shell nanoparticles is magnetite and the shell is a gold@gold nanostructure. Second, for the obtained target product detected by Raman spectroscopy, the characteristic peaks of the internal standard molecules can be significantly detected with relatively high Raman signal intensity, proving its good Raman signal enhancement performance. Third, the preparation method is scientific and effective. It has prepared core-shell nanoparticles with magnetite as the core and gold@internal standard@gold as the shell. This structure not only endows the substrate with good magnetic responsiveness, facilitating rapid separation and enrichment through an external magnetic field, but also significantly increases the plasmon hot spot regions due to the aggregated multi-layer structure. The synthesis method is simple, with a high yield and good repeatability, and can be applied to fields such as pesticide residue detection, catalytic degradation and environmental detection analysis based on SERS technology. Brief Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions in the present invention, the accompanying drawings of the examples will be briefly introduced below.

[0020] Figure 1 It is the result of characterizing the obtained target product Fe3O4 by scanning electron microscopy (SEM). It can be seen that the Fe3O4 nanoparticles are mainly spherical, and their particle size is about 160 - 400 nm. Figure 1 The scale bar is 200 nm.

[0021] Figure 2 It is the result of characterizing the obtained target product Fe3O4@Au by scanning electron microscopy (SEM). It can be seen that the surface of the Fe3O4 nanoparticles is coated with 200 uL Au particles, and the particle size of the Au nanoparticles is about 16 nm. Figure 2 The scale bar is 200 nm.

[0022] Figure 3 It is the result of characterizing the obtained target product Fe3O4@Au@1,4-BDT@Au by scanning electron microscopy (SEM). It can be seen that the surface of the Fe3O4 nanoparticles is coated with Au@1,4-BDT@Au particles. The particle size of the Au@1,4-BDT@Au nanoparticles is about 50 - 60 nm, and the particle size of the final product Fe3O4@Au@1,4-BDT@Au nanoparticles is about 200 - 460 nm.Figure 3 The scale bar is 200 nm.

[0023] Figure 4 This is the result of characterizing the target product Fe3O4@Au@1,4-BDT@Au prepared in (5) using a transmission electron microscope (TEM). It shows an obvious difference between the center and the edge of the product. The inset in the lower right corner is a high-magnification TEM image, from which it can be seen that a core-shell structure of Au@1,4-BDT@Au is formed on the surface of the iron oxide. Figure 4 The scale bar is 200 nm, and the scale bar of the inset in the lower right corner is 10 nm.

[0024] Figure 5 This is the result of detecting the target product Fe3O4@Au@1.4-BDT@Au prepared in (5) using a Raman spectrometer. Characteristic peaks of 1.4-BDT molecules at 1055 cm -1 and 1555 cm -1 have relatively high Raman signal intensities, demonstrating that this substrate has good performance in enhancing Raman signals. Detailed implementation manners

[0025] First, obtain or purchase from the market using conventional methods:

[0026] Ferric chloride; polyethylene glycol; ethylene glycol; sodium acetate; sodium polystyrene sulfonate; polyethyleneimine; CA; 1,4-BDT; ethanol; CTAC; ascorbic acid; chloroauric acid.

[0027] In the implementation examples of the present invention, 1,4-BDT is used as the internal standard molecule.

[0028] The specific preparation steps are as follows:

[0029] Example 1

[0030] (1) Synthesis of iron oxide nanoparticles

[0031] First, dissolve ferric chloride in ethylene glycol according to the mass ratio of ferric chloride: sodium acetate: polyethylene glycol of 1 - 2.7: 0.15 - 0.72: 0.5 - 2.3. After stirring evenly, add sodium acetate and polyethylene glycol to the mixture and stir for at least 20 min to obtain a precursor solution;

[0032] Place the precursor solution in a sealed state and react at 200 °C for 72 h to obtain a precipitate of iron oxide nanoparticles, as shown in Figure 1 shown.

[0033] Surface modification of Fe₃O₄ nanoparticles: Weigh 80 - 100 mg of Fe₃O₄ powder and add it to an aqueous solution of sodium polystyrene sulfonate with a concentration of 2 mg / mL and containing 0.05 M NaCl for surface modification. Subsequently, disperse it into an aqueous solution of polyethyleneimine with a concentration of 2 mg / mL and containing 0.05 M NaCl, and then perform alternating modification of sodium polystyrene sulfonate and polyethyleneimine. Repeat the above steps, collect the precipitate by magnetic absorption, and finally disperse it in 20 mL of deionized water.

[0034] (2) Synthesis of 16 nm gold nanoparticles

[0035] Add 200 mL of ultrapure water and 2.42 mL of chloroauric acid solution with a mass fraction of 1% to the flask, then heat to boiling, quickly add 6 mL of CA aqueous solution with a mass fraction of 50%, continue heating and stir vigorously for about 2 min, keep the solution in a slightly boiling state and continue the reaction for 30 min. After cooling to room temperature, finally obtain gold nanoparticles with an average particle size of about 16 nm.

[0036] (3) Synthesis of Fe₃O₄@Au nanoparticles

[0037] Add 100 μL of the gold nanoparticles synthesized in (2) to 0.5 mL of Fe₃O₄ colloidal solution, collect the product with a magnet, wash the product to remove excess gold nanoparticles, redisperse the composite product in 20 mM CTAC solution, and adsorb for 1 h to obtain Fe₃O₄ coated with about 16 nm Au nanoparticles as shown in Figure 2 shown.

[0038] (4) Fe₃O₄@Au modified internal standard molecule

[0039] Add 1 mL of 1,4 - BDT ethanol solution with a concentration of 1 mM to the product synthesized in (3), shake and incubate the above mixture for 20 minutes, centrifuge three times, remove the supernatant after each centrifugation, and make up the volume of the precipitate to 10 mL with 20 mM CTAC solution.

[0040] (5) Synthesis of Fe₃O₄@Au@1,4 - BDT@Au nanoparticles

[0041] Add 10 mL of 0.1 M CTAC solution to the flask, place the flask in a 30 °C water bath, add 500 μL of thiol - modified gold seed composite Fe₃O₄ solution and 500 μL of ascorbic acid solution with a concentration of 0.04 M, stir evenly, and then slowly add 500 μL of HAuCI₄ solution. Finally, obtain gold@1,4 - BDT@gold core - shell nanoparticles with a particle size of about 60 nm coated on the surface of Fe₃O₄ particles, and prepare as shown in Figure 3The surface of the magnetite nanoparticles is coated with a nanostructure of Au@1,4-BDT@Au with a particle size of approximately 60 nm.

[0042] Example 2

[0043] (1) Synthesis of magnetite nanoparticles

[0044] First, dissolve ferric chloride in ethylene glycol according to the mass ratio of ferric chloride: sodium acetate: polyethylene glycol of 1-2.7: 0.15-0.72: 0.5-2.3. After stirring evenly, add sodium acetate and polyethylene glycol to the mixed solution and stir for at least 20 min to obtain a precursor solution.

[0045] Place the precursor solution in a sealed state and react at 200 °C for 72 h to obtain a precipitate of magnetite nanoparticles, as shown in Figure 1 shown.

[0046] Modify the surface of the magnetite nanoparticles. Weigh 80-100 mg of magnetite powder and add it to an aqueous solution of sodium polystyrene sulfonate with a concentration of 2 mg / mL and containing 0.05 M NaCl for surface modification. Subsequently, disperse it into an aqueous solution of polyethyleneimine with a concentration of 2 mg / mL and containing 0.05 M NaCl, and then perform alternating modification of sodium polystyrene sulfonate and polyethyleneimine. Repeat the above steps, collect the precipitate by magnetic absorption, and finally disperse it in 20 mL of deionized water.

[0047] (2) Synthesis of 16 nm gold nanoparticles

[0048] Add 200 mL of ultrapure water and 2.42 mL of chloroauric acid solution with a mass fraction of 1% to the flask, then heat to boiling, quickly add 6 mL of CA aqueous solution with a mass fraction of 50%, continue heating and stirring vigorously for about 2 min, keep the solution in a slightly boiling state and continue to react for 30 min. After cooling to room temperature, finally obtain gold nanoparticles with an average particle size of about 16 nm.

[0049] (3) Synthesis of magnetite@gold nanoparticles

[0050] Add 150 μL of the gold nanoparticles synthesized in (2) to 0.5 mL of Fe3O4 colloidal solution, collect the product with a magnet, wash the product to remove excess gold nanoparticles, redisperse the composite product in 20 mM CTAC solution, and adsorb for 1 h to obtain magnetite coated with approximately 16 nm Au nanoparticles, as shown in Figure 2 shown.

[0051] (4) Magnetite@gold modified internal standard molecule

[0052] Add 1 mL of a 1 mM 1,4-BDT ethanol solution to the product synthesized in (3). Incubate the above mixture with shaking for 20 minutes, centrifuge three times, remove the supernatant after each centrifugation, and dilute the precipitate to 10 mL with a 20 mM CTAC solution.

[0053] (5) Synthesis of Fe₃O₄@Au@1,4-BDT@Au nanoparticles

[0054] Add 10 mL of a 0.1 M CTAC solution to a flask. Place the flask in a 30 °C water bath, add 500 μL of a thiol-modified gold seed composite Fe₃O₄ solution and 500 μL of a 0.04 M ascorbic acid solution. After stirring evenly, slowly add 500 μL of HAuCI₄ solution. Finally, gold@1,4-BDT@Au core-shell nanoparticles with a particle size of about 60 nm are obtained and coated on the surface of the Fe₃O₄ particles, preparing Fe₃O₄ nanoparticles with a nanostructure of Au@1,4-BDT@Au with a particle size of about 60 nm coated on their surface as described in Figure 3 in.

[0055] Example 3

[0056] (1) Synthesis of Fe₃O₄ nanoparticles

[0057] First, dissolve ferric chloride in ethylene glycol according to the mass ratio of ferric chloride: sodium acetate: polyethylene glycol of 1 - 2.7: 0.15 - 0.72: 0.5 - 2.3. After stirring evenly, add sodium acetate and polyethylene glycol to the mixture and stir for at least 20 min to obtain a precursor solution;

[0058] Keep the precursor solution in a closed state and react at 200 °C for 72 h to obtain a precipitate of Fe₃O₄ nanoparticles, as prepared in Figure 1 shown.

[0059] Surface modification of the Fe₃O₄ nanoparticles: Weigh 80 - 100 mg of Fe₃O₄ powder, add it to an aqueous solution of sodium polystyrene sulfonate with a concentration of 2 mg / mL and containing 0.05 M NaCl for surface modification, and then disperse it into an aqueous solution of polyethyleneimine with a concentration of 2 mg / mL and containing 0.05 M NaCl. Then, perform alternating modifications of sodium polystyrene sulfonate and polyethyleneimine. Repeat the above steps, collect the precipitate by magnetic absorption, and finally disperse it in 20 mL of deionized water.

[0060] (2) Synthesis of 16 nm gold spheres

[0061] Add 200 mL of ultrapure water and 2.42 mL of chloroauric acid solution with a mass fraction of 1% into a flask, then heat to boiling, quickly add 6 mL of CA aqueous solution with a mass fraction of 50%, continue heating and stir vigorously for about 2 min, keep the solution in a slightly boiling state and continue the reaction for 30 min. After cooling to room temperature, finally obtain gold nanoparticles with an average particle size of about 16 nm.

[0062] (3) Synthesis of Fe₃O₄@Au nanoparticles

[0063] Add 200 μL of the gold nanoparticles synthesized in (2) into 0.5 mL of Fe₃O₄ colloidal solution, collect the product with a magnet, wash the product to remove the excess gold nanoparticles, redisperse the composite product in 20 mM CTAC solution, and adsorb for 1 h to obtain the Fe₃O₄ coated with about 16 nm Au nanoparticles as Figure 2 shown.

[0064] (4) Fe₃O₄@Au modified internal standard molecule

[0065] Add 1 mL of 1,4 - BDT ethanol solution with a concentration of 1 mM to the product synthesized in (3), incubate the above mixture by shaking for 20 minutes, centrifuge three times, remove the supernatant after each centrifugation, and make the precipitate up to 10 mL with 20 mM CTAC solution.

[0066] (5) Synthesis of Fe₃O₄@Au@1,4 - BDT@Au nanoparticles

[0067] Add 10 mL of CTAC solution with a concentration of 0.1 M into a flask, place the flask in a 30 °C water bath, add 500 μL of thiol - modified gold seed composite Fe₃O₄ solution and 500 μL of ascorbic acid solution with a concentration of 0.04 M, stir evenly, and then slowly add 500 μL of HAuCI₄ solution. Finally, obtain gold@1,4 - BDT@Au core - shell nanoparticles with a particle size of about 60 nm coated on the surface of Fe₃O₄ particles, and prepare the Fe₃O₄ nanoparticles with a nanostructure of Au@1,4 - BDT@Au with a particle size of about 60 nm coated on the surface as Figure 3 shown.

[0068] If a target product with higher purity and quality is to be obtained, the obtained precipitate can be further washed, separated and dried; among them, the washing treatment is to alternately wash with ethanol and deionized water 3 - 4 times, the separation treatment is to use a magnet for separation, and the drying treatment is to dry at 60 °C for 6 h.

[0069] As described above, the above are only specific embodiments of the present invention. Those skilled in the art can make various changes or substitutions to the magnetite@gold@internal standard@gold particles of the present invention and its preparation method, and all should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims described above.

Claims

1. A Fe₃O₄@Au@Internal Standard@Au nanoparticle, characterized in that: The Fe₃O₄@Au@Internal Standard@Au nanoparticle has a core-shell structure with Fe₃O₄ as the main body, on the surface of which Au nanoparticles are adsorbed as the core, and mercapto molecules with benzene rings are used as internal standard molecules, and Au as the shell. Its overall particle size is 200 - 460 nm; The Fe₃O₄ is a Fe₃O₄ nanosphere with a particle size of 160 - 400 nm; The Au is a gold sphere, where the gold core is 16 - 20 nm, the gold shell is 35 - 40 nm thick, and the Au@Internal Standard@Au core-shell structure is 50 - 60 nm.

2. The preparation method of the magnetite@gold@internal standard@gold nanoparticles described in claim 1 adopts the hydrothermal method, characterized in that The steps are as follows: Step 1. First, dissolve ferric chloride in ethylene glycol according to the mass ratio of ferric chloride: sodium acetate: polyethylene glycol of 1 - 2.7: 0.15 - 0.72: 0.5 - 2.

3. After stirring evenly, add sodium acetate and polyethylene glycol to the mixed solution and stir for at least 20 min to obtain a precursor solution; Step 2. Place the precursor solution in a closed state and react at 200 °C for 8 - 72 h to obtain a precipitate of Fe₃O₄ nanoparticles; Step 3. Modify the surface of the Fe₃O₄ nanoparticles. Weigh 80 - 100 mg of Fe₃O₄ powder and add it to an aqueous solution of sodium polystyrene sulfonate with a concentration of 2 - 5 mg / mL and containing 0.05 M NaCl for surface modification. Then disperse it into an aqueous solution of polyethyleneimine with a concentration of 2 - 5 mg / mL and containing 0.05 M NaCl, and then perform alternating modification of sodium polystyrene sulfonate and polyethyleneimine. Repeat the above steps, collect the precipitate by magnetic absorption, and finally disperse it in 20 mL of deionized water; Step 4. Add 200 mL of ultrapure water and 2.42 mL of chloroauric acid solution with a mass fraction of 1% to the flask, heat to boiling, quickly add 6 mL of CA aqueous solution with a mass fraction of 50%, continue heating and stir vigorously for about 2 - 5 min, keep the solution in a slightly boiling state and continue to react for 20 - 30 min, and cool to room temperature to finally obtain gold nanoparticles with an average particle size of about 16 nm; Step 5. Add 100 - 300 μL of the gold nanoparticles synthesized in Step 4 to 0.5 - 1 mL of Fe₃O₄ colloidal solution, collect the product with a magnet, wash the product to remove excess gold nanoparticles, redisperse the composite product in 20 mM CTAC solution, and adsorb for 0.5 - 1 h; Step 6. Add 0.5 - 1 mL of a mercapto internal standard molecule solution with a benzene ring to the composite product synthesized in Step 5, shake and incubate the above mixture for 20 - 40 min, centrifuge three times, remove the supernatant after each centrifugation, and make the precipitate up to 10 mL with 20 mM CTAC solution; Step 7. Add 5 - 10 mL of 0.1 M CTAC solution into a flask. Place the flask in a water bath at 30 - 40 °C. Add 500 μL of the gold seed solution modified with the inner standard molecule on the surface of iron oxide and 300 - 500 μL of ascorbic acid solution. After stirring evenly, slowly add 300 - 500 μL of HAuCI4 solution to finally obtain iron oxide@gold@inner standard@gold nanoparticles with a particle size of about 200 - 460 nm.

3. The preparation method of the magnetite @ gold @ internal standard @ gold nanoparticles according to claim 2, characterized in that For the precursor solution in Step 2, the mass ratio of ferric chloride: sodium acetate: polyethylene glycol is 1 - 2.7: 0.15 - 0.72: 0.5 - 2.

3.

4. The preparation method of the magnetite@gold@internal standard@gold nanoparticles according to claim 2, characterized in that Wash, separate, and dry the precipitate in Step 2.

5. The preparation method of the Fe₃O₄@Au@internal standard@gold nanoparticles according to claim 3, characterized in that Wash with ethanol and deionized water alternately for 3 - 4 times.

6. The preparation method of the magnetite @ gold @ internal standard @ gold nanoparticles according to claim 3, characterized in that The separation process is carried out using a magnet.

7. The preparation method of the magnetite @ gold @ internal standard @ gold nanoparticles according to claim 3, characterized in that The drying process is to dry at 60 °C for 6 h.

8. The preparation method of the magnetite @ gold @ internal standard @ gold nanoparticles according to claim 2, characterized in that Modify at least 2 times alternately in Step 3.

9. The preparation method of the magnetite @ gold @ internal standard @ gold nanoparticles according to claim 2, characterized in that The volume of gold nanoparticles added in Step 5 is 100 - 300 uL.

10. The preparation method of the Fe₃O₄@Au@internal standard@gold nanoparticles according to claim 2, wherein In Step 6, the inner standard molecule is a thiol molecule with a benzene ring.

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