CN113552111A

CN113552111A - Magnetic Au-MOF material and preparation method and application thereof

Info

Publication number: CN113552111A
Application number: CN202110823938.3A
Authority: CN
Inventors: 孙振丽; 王宁; 葛宏伟; 李雪
Original assignee: North China Electric Power University
Current assignee: North China Electric Power University
Priority date: 2021-07-21
Filing date: 2021-07-21
Publication date: 2021-10-26
Anticipated expiration: 2041-07-21
Also published as: CN113552111B

Abstract

The invention relates to the technical field of uranium detection, in particular to a magnetic Au-MOF material and a preparation method and application thereof, wherein the magnetic Au-MOF material is of a shell-core structure, takes magnetic iron oxide as a material core layer, and is coated with a gold enhancement layer and an MOF adsorption layer in sequence on the surface; the magnetic iron oxide material is used as a core, gold is used as an SERS enhancement layer, and the MOF is a core-shell structure nano particle of a uranium adsorption layer, so that the magnetic iron oxide material is a new choice for the SERS active substrate due to the characteristics of superparamagnetism, easy separation and easy modification of the gold surface.

Description

Magnetic Au-MOF material and preparation method and application thereof

Technical Field

The invention relates to the technical field of uranium detection, and particularly relates to a magnetic Au-MOF material and a preparation method and application thereof.

Background

Uranium is a radioactive element and is used in the fields of nuclear energy and military affairs, however, nuclear waste thereof can cause serious harm to human health and environment. Of all the valence states of uranium, uranyl is one of the most stable forms of existence and has attracted considerable attention. The analysis and monitoring of the uranium content in water and other media has important significance for protecting the environment and improving the human life quality. The commonly used uranium detection methods at present include atomic absorption spectrometry, mass spectrometry and ionizationA sub-chromatography, an ultraviolet-visible spectrophotometry, a neutron activation analysis, and the like. These methods can accurately detect UO of low concentration₂ ²⁺However, some devices are expensive, the detection process is long, and a complex sample pretreatment process is required. Other detection methods, such as Surface Enhanced Raman Scattering (SERS), have received much attention because of their cost effectiveness, high sensitivity, fast detection speed, and lack of complex pre-treatment processes.

Surface Enhanced Raman Spectroscopy (SERS) is widely used in the fields of analysis, catalysis, sensing, etc., as a nondestructive, rapid, ultrasensitive molecular detection technique. Generally, molecules need to be close to the surface of a plasma (<5nm) to greatly enhance self raman signals, the molecules are generally adsorbed on the surface of a metal nanoparticle substrate (Au, Ag, Cu and the like) through chemical or physical actions, and good molecule SERS signals can be obtained under excitation light with specific wavelength due to the surface plasmon resonance effect (SPR). Therefore, a high-activity substrate capable of being used as a SERS for detecting uranium is needed to realize enrichment and separation of uranyl in an actual water sample and realize SERS detection of uranyl ions.

Disclosure of Invention

Based on the content, the invention provides a magnetic Au-MOF material and a preparation method and application thereof; the magnetic iron oxide material is used as a core, gold is used as an SERS enhancement layer, and the MOF is a core-shell structure nano particle of a uranium adsorption layer, so that the magnetic iron oxide material becomes a new choice of an SERS active substrate due to the characteristics of superparamagnetism, easy separation and easy modification of the gold surface.

According to one technical scheme, the magnetic Au-MOF material is of a shell-core structure, magnetic iron oxide is used as a material core layer, and a gold enhancement layer and an MOF adsorption layer are sequentially coated on the surface of the material core layer.

The agglomeration of metal nano particles is inevitable in a complex environment, and the magnetic satellite component Fe₃O₄/SiO₂The application of the alloy can not only effectively prevent the gold nanoparticles from agglomerating, but also prevent Fe₃O₄/SiO₂The gold nano particles on the surface of the spherical structure are arranged to form a surface between the gold nano particlesMore hot spots are shown, and the distance between the gold nanoparticles is reduced, so that the SERS activity is enhanced, and strong electromagnetic field enhancement is generated. Meanwhile, because the concentration of some target detection objects in an environmental sample is very low, the high-sensitivity and selective detection can be realized through enrichment and separation. Fe₃O₄/SiO₂The material has a super-paramagnetic property, and can be recycled. The magnetic Au-MOF material can be specifically combined with a target detection object in the environment, and is easy to enrich and separate from the complex environment, so that further SERS detection is carried out. The magnetic Au-MOF material has magnetism, the plasma characteristic of noble metal nanoparticles and the adsorption performance of a ZIF material, and is a good SERS substrate for detecting uranyl.

Due to Fe₃O₄The particles have large surface area and high surface energy, and dipolar interaction exists among the particles, so that agglomeration and sedimentation easily occur in the dispersion liquid. In Fe₃O₄SiO with inert material coated on the outer layer₂The dispersion stability of the particles can be improved. Due to SiO₂The gold nanoparticles are negatively charged with the shell layer of the gold nanoparticles, which is not beneficial to the modification of the gold nanoparticles, so that the gold nanoparticles are modified in the magnetic Fe through the electrostatic adsorption effect by using PDDA strong cationic polyelectrolyte₃O₄/SiO₂Preparing a satellite-shaped magnetic Au substrate on the surface of the microsphere.

Further, the magnetic iron oxide is PDDA modified Fe₃O₄/SiO₂Magnetic particles, the MOF being a metal organic framework ZIF 8. ZIF porous structure is beneficial to adsorption of uranyl and Fe₃O₄@SiO₂@ Au surface transfer.

Further, SiO₂In Fe₃O₄The coating thickness of the surface is 2-5nm, and Au is in Fe₃O₄@SiO₂The density of the ZIF8 coating layer is about 3-7nm in terms of distance between Au layers, and the coating thickness of the ZIF8 coating layer on the Au layer is 2-5 nm.

Further, the PDDA modified Fe₃O₄/SiO₂The preparation method of the magnetic particles comprises the following steps:

mixing Fe₃O₄/SiO₂Dispersing magnetic particles in a PDDA modification solution, and stirring for reaction to obtain PDDA modified Fe₃O₄/SiO₂Magnetic particles.

Further, said Fe₃O₄/SiO₂The magnetic particles are Fe with the particle diameter of 200-400nm₃O₄The particles and the tetraethyl silicate are prepared by hydrolysis method;

further, the preparation method of the PDDA modification solution comprises the following steps: adding deionized water, sodium citrate and sodium chloride into a PDDA solution with the mass fraction of 20% and mixing to obtain a PDDA modified solution, wherein the mass-volume ratio of the PDDA solution to the deionized water to the sodium citrate to the sodium chloride is 10 mL: 90mL of: 88 mg: 12 mg;

further, said Fe₃O₄/SiO₂The mass-to-volume ratio of the magnetic particles to the PDDA modification solution was 1 mg: 1mL, stirring the reaction time for 20 min.

In the second technical scheme of the invention, the preparation method of the magnetic Au-MOF material comprises the following steps:

(1) dispersing the magnetic iron oxide in the gold nanoparticle sol to react to obtain a product magnetic Au particle;

(2) dissolving magnetic Au particles and zinc salt in an organic solvent to obtain a mixed solution A, mixing a methylimidazole solution and CTAB to obtain a mixture, adding the mixture into the mixed solution A, standing for reaction to obtain a product magnetic Au-MOF material, and dispersing the magnetic Au-MOF material in 1.5mL of water for storage.

Further, the preparation method of the gold nanoparticle sol comprises the following steps: to preheated HAuCl₄Adding sodium citrate aqueous solution into the solution, and heating and reacting under the stirring condition to obtain the gold nanoparticle sol.

Further, the HAuCl₄HAuCl in solution₄The concentration of (A) is 0.1-0.5mg/mL, the concentration of the sodium citrate aqueous solution is 50mg/mL, and the HAuCl is₄The volume ratio of the solution to the sodium citrate aqueous solution is 24: 1; the heating reaction conditions under the stirring condition are as follows: 1800 ℃ 2200r/min, 100 ℃ 150 ℃ and 15-25 min.

Further, in the step (1):

the mass-volume ratio of the magnetic iron oxide dispersed in the gold nanoparticle sol is 0.03 g: 200mL, wherein the reaction is specifically carried out for 20-30min at normal temperature;

in the step (2):

the organic solvent is methanol, and the solvent of the methylimidazole solution is methanol;

the concentration of the magnetic Au particles in the mixed solution A is 7-12mg/mL, and the concentration of the zinc salt is 6-10 mmol/mL;

the concentration of the methylimidazole in the methylimidazole solution is 50mg/mL, and the mixing ratio of the methylimidazole solution to CTAB is 1.8 mL: 1 mM;

the mixing volume ratio of the mixture to the mixed solution A is (3-4): 2;

standing for 3 h.

In the fourth technical scheme of the invention, the magnetic Au-MOF material is applied to enrichment of uranyl.

The invention provides a fifth technical scheme, and a uranyl detection method comprises the following steps: and (3) mixing the magnetic Au-MOF material with the uranyl solution, collecting the magnetic particles by using an external magnetic field, and collecting signals by using a Raman spectrometer to obtain the SERS spectrum of the uranyl.

Further, the mixing ratio of the magnetic Au-MOF material to the uranyl solution is 20 mu L: 5 mL.

The mixing time was 20 min.

The laser wavelength of the Raman spectrometer is 785nm, and the integration time is 3-8 s.

Compared with the prior art, the invention has the beneficial effects that:

the magnetic Au-MOF material prepared by the invention has large specific surface area and is beneficial to adsorption and capture of uranyl, and Fe₃O₄The magnetic property of the material is beneficial to the separation of the material, thereby overcoming the problem of difficult uranyl enrichment.

The gold nano material has good stability and biocompatibility, and has a lower detection limit due to the existence of an electron transfer mechanism when being used as an enhancement layer of SERS, so that the sensitive detection of uranyl can be realized.

Drawings

FIG. 1 shows Fe used in step (1) of example 1 of the present invention₃O₄Scanning electron micrographs of magnetic particles;

FIG. 2 shows Fe used in step (1) of example 1 of the present invention₃O₄/SiO₂Scanning electron micrographs of magnetic particles;

FIG. 3 shows Fe prepared in step (5) of example 1 of the present invention₃O₄/SiO₂Scanning electron microscope images of/Au magnetic particles;

FIG. 4 is a scanning electron micrograph of FA @ ZIF8 prepared in step (6) of example 1 of the present invention;

FIG. 5 is a graph showing the results of Raman spectrum analysis of FA obtained in step (5) and FA @ ZIF8 obtained in step (6) in example 1;

FIG. 6 is a graph showing the results of Raman spectroscopy analysis of Crystal Violet (CV), 4-mercaptopyridine (4-MPY), rhodamine (R6G) and uranyl groups detected on the FA @ ZIF8 substrate in step (7) of example 1 of the present invention;

FIG. 7 is a diagram showing step (9) of FA @ ZIF8 substrate pair 10 according to example 1 of the present invention^-4、10^-5、10^-6Raman spectrograms for detecting uranyl ions with different concentrations of M;

FIG. 8 shows Fe obtained in step (5) of example 1 of the present invention₃O₄/SiO₂Au and Fe produced in step (6)₃O₄/SiO₂Raman analysis comparison result spectrum of uranyl detection by Au/ZIF 8;

FIG. 9 shows Fe in inventive example 2₃O₄/SiO₂A Raman spectrum analysis result chart of Crystal Violet (CV), 4-mercaptopyridine (4-MPY) and uranyl detected by an Au substrate;

FIG. 10 shows Fe synthesized in aqueous environment in inventive example 4₃O₄/SiO₂Scanning electron micrographs of/Au/ZIF 8;

FIG. 11 shows Fe synthesized in inventive examples 1 and 4₃O₄/SiO₂Au/ZIF 8 pair 10^-5And a Raman spectrum analysis result chart of M uranyl detection.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The specification and examples are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

Example 1

(1) Magnetic Fe₃O₄And (3) particle: dispersing 0.118g of sodium citrate, 0.65g of ferric chloride hexahydrate and 1.2g of sodium acetate in 20mL of ethylene glycol, mixing and magnetically stirring for 0.5h, putting into a polytetrafluoroethylene reaction kettle for reaction at 200 DEG CAnd (5) 10 h. Cooling to room temperature after heating, cleaning with ethanol and ultrapure water, and vacuum drying at 60 deg.C for 2 hr to obtain Fe₃O₄Magnetic nanoparticles, scanning electron microscopy results are shown in figure 1.

(2)Fe₃O₄/SiO₂Magnetic particles: 0.2g of Fe₃O₄Dispersing in concentrated nitric acid solution, ultrasonic cleaning for 10min, and cleaning with ultrapure water several times. Dispersing in 20mL of ethanol, 4mL of ammonia water and 40mL of deionized water, performing ultrasonic treatment for 10min, transferring into a three-neck round-bottom flask, adding 3.2mL of tetraethyl silicate (TEOS) while mechanically stirring, and reacting for 3 h. Washing the precipitate with ethanol and ultrapure water, and vacuum drying at 60 deg.C for 2 hr to obtain Fe₃O₄/SiO₂The magnetic particles, the scanning electron microscope results are shown in figure 2.

(3) PDDA modified Fe₃O₄/SiO₂Magnetic particles: mixing 30mg of Fe₃O₄/SiO₂Dispersing magnetic particles in 30mL of 2% poly (diallyldimethylammonium chloride) (PDDA) solution, reacting for 20min under mechanical stirring, washing the generated precipitate with deionized water to obtain PDDA modified Fe₃O₄/SiO₂The magnetic particles, wherein the preparation method of the PDDA solution comprises the following steps: to 10mL of PDDA (20%) solution was added 90mL of deionized water, 88mg of sodium citrate, 12mg of sodium chloride, and the solution was shaken to dissolve.

(4) Au nanoparticle sol: 8mL of 2% HAuCl₄The solution was added to 184mL of deionized water, the vessel was sealed, and the solution was heated with magnetic stirring. Adding 8mL of aqueous solution containing 400mg of anhydrous sodium citrate into the solution, reacting for 20min, stopping heating, continuously stirring the product, and cooling to room temperature to obtain Au nanoparticle sol, wherein the heating specifically comprises the following steps: the heating temperature is 130 ℃, the stirring speed is 2000r/min, and the stirring time is 20 min.

(5)Fe₃O₄/SiO₂Preparation of Au magnetic particles: 0.03g of PDDA-modified Fe obtained in step (3)₃O₄/SiO₂Dispersing magnetic particles in 200mL of Au nanoparticle sol prepared in the step (4), putting the Au nanoparticle sol into a shaking table, reacting for 20min at normal temperature, and using deionized water to react the productWashing to obtain Fe₃O₄/SiO₂Au magnetic particles (FA). Scanning electron microscope analysis of the prepared FA showed that the result is shown in FIG. 3, and FIG. 3 shows Fe at 370nm₃O₄/SiO₂The surface is evenly coated with 20nm Au nano particles.

(6) Preparation of FA @ ZIF 8: respectively dissolving 30mg of FA prepared in the step (5) in 3mL of methanol, dissolving 45mg of zinc nitrate hexahydrate in 0.75mL of methanol, adding the solution into the solution of FA, and slowly and mechanically stirring at room temperature for 5 min; dissolving 90mg of methylimidazole in 1.8mL of methanol, mixing 0.12mL of CTAB (1mM) with the methylimidazole solution to obtain a mixture, adding the mixture to the previously prepared mixture of FA and zinc nitrate, and standing at room temperature for reaction for 3 hours; the resulting product was isolated with a magnet, washed with methanol, and then dissolved in 1.5mL of ultrapure water to give FA @ ZIF 8. The prepared FA @ ZIF8 is analyzed by a scanning electron microscope, and the result is shown in figure 4, and figure 4 shows that a ZIF material is modified on FA magnetic particles. And (3) carrying out Raman spectrum analysis on the FA prepared in the step (5) and the FA @ ZIF8 prepared in the step (6), wherein the result is shown in figure 5, and the detection result shows that the ZIF8 is successfully modified on the surface of the FA and the shape of the FA is not changed.

(7) Taking 20 mu L of FA @ ZIF8 substrate dispersed in water, and respectively mixing with 10^-4Mixing 5mL of M Crystal Violet (CV), 4-mercaptopyridine (4-MPY), rhodamine (R6G) and uranyl solution in a 10mL centrifuge tube, enriching by using a magnet after 20min, removing 10mL of supernatant, taking 4 mu L of residual precipitate on a silicon chip, and detecting Raman spectrum.

The result is shown in FIG. 6, and the detection result shows that the synthesized FA @ ZIF8 substrate has good SERS effect on various probe molecules.

(8) Enrichment of uranium: the FA @ ZIF8 magnetic substrate dispersed in water was mixed at 20. mu.L with 5mL of 10^-4、10^-5、10^-6Respectively mixing the uranyl solutions of M into 10mL centrifuge tubes for 20min, and recovering the magnetic material enriched with uranyl by using an external magnetic field;

(9) detection of uranium: taking 4 mu L of magnetic material enriched with uranyl on a silicon chip, and collecting signals by using a portable Raman spectrometer, wherein the laser wavelength is 785nm, and the integration time is 3 s; FA @ ZIF8 groupBottom pair 10^-4、10^-5、10^-6The Raman spectrogram for detecting the uranyl ions with different concentrations of M is shown in figure 7, and the detection result shows that the FA @ ZIF8 obtained by the invention has better detection limit on the uranyl ions and can detect the uranyl ions with the concentration of 1 multiplied by 10^-6The signal of the uranyl ion in the uranyl solution of M has good detection limit.

(10) Using synthetic FA and FA @ ZIF8 material pairs 10 respectively^-4The uranyl of M is detected, the signal of the uranyl cannot be detected by single FA, the signal of the uranyl can be effectively detected by the FA/ZIF 8 material, and the enhancement factor reaches 1.04 multiplied by 10⁴. The results are shown in FIG. 8.

(11) Respectively taking 20 mu L of synthesized FA and FA @ ZIF8 materials and the concentration of the materials is 10^-4M、10^-55mL of uranyl group M was mixed for 20 min. And enriching the magnetic materials FA and FA @ ZIF8 by using an external magnetic field, recovering the removed supernatant, and detecting the absorbance of the supernatant. The results are shown in Table 1 for FA @ ZIF8 vs. 10^-4M、10^-5The uranyl solution of M has good adsorption effect, and the adsorption effect of FA on the uranyl solution is greatly reduced compared with FA @ ZIF 8.

TABLE 1

Example 2

The difference from example 1 is that step (1) is omitted and Fe is used directly₃O₄/SiO₂The magnetic particles and the Au nano-particle sol prepared in the step (2) are used as raw materials to carry out the reaction in the step (3) to prepare Fe₃O₄/SiO₂Au magnetic particles; the prepared material is used for enrichment and Raman spectrum detection of uranium ions in the uranyl solution.

The results show that: fe₃O₄/SiO₂The SERS effect of the Au magnetic particles can detect Raman spectra of CV and 4-MPY, but cannot detect the signal of uranyl, and the result is shown in FIG. 9.

Example 3

The difference from example 1 is that step (3) is omitted and Fe is used directly₃O₄The magnetic particles and the Au nano-particle sol prepared in the step (4) are used as raw materials to carry out the reaction in the step (5) to prepare Fe₃O₄Au magnetic particles; the prepared material is used for enrichment and Raman spectrum detection of uranium ions in the uranyl solution.

The results show that: fe₃O₄the/Au magnetic particles have plasma characteristics, and can detect Raman spectra of CV and 4-MPY, but cannot detect Raman spectra of uranyl. And due to Fe₃O₄The nano particles have larger surface area and higher surface energy, and simultaneously, the influence of dipolar mutual attraction exists between the particles, so that the Fe is enabled to be contained₃O₄The Au particles are easy to agglomerate and settle in the dispersion liquid, and the stability of the material is reduced.

Example 4

The difference from example 1 is that in step (6), Fe synthesized in step (5) is used₃O₄/SiO₂When the ZIF8 is coated by the Au magnetic particles, the reaction is carried out in a water environment. The method comprises the following specific steps: 6mL of 25mM Zn (NO) was added under magnetic stirring at room temperature₃)₂·6H₂O aqueous solution was added to 6mL of 25mM 2-methylimidazole (2-MI, 99%) aqueous solution. To this solution was added rapidly 6mL of 5X 10^-4M cetyltrimethylammonium bromide (CTAB, 97%) in water. After stirring for 2min, the solution was allowed to stand at room temperature for 2 h. And centrifuging and washing the product, and dispersing the product in ultrapure water to obtain a precursor solution. 30mg of FA was added to 18mL of the ZIF8 precursor solution and allowed to stand at room temperature for 40min, whereupon the solution turned from cloudy white to blue. And magnetically recovering the product, and dispersing the product in 3mL of ultrapure water after cleaning to obtain FA @ ZIF 8.

Scanning electron microscope analysis is carried out on FA @ ZIF8 prepared in a water environment, the result is shown in figure 10, and figure 10 shows that a ZIF8 material is modified on FA magnetic particles. FA @ ZIF8 prepared in methanol environment in step (6) and FA @ ZIF8 prepared in water environment in example 4 are detected by 10^-4The uranyl of M is shown in the figure 11, and the detection result shows that the characteristic peak of uranyl detected by FA @ ZIF8 synthesized in a methanol environment is obvious, and the intensity is nearly 2 times higher.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included therein.

Claims

1. The magnetic Au-MOF material is characterized by being of a shell-core structure, taking magnetic iron oxide as a material core layer, and sequentially coating a gold enhancement layer and an MOF adsorption layer on the surface.

2. The magnetic Au-MOF material of claim 1, wherein the magnetic iron oxide is PDDA modified Fe₃O₄/SiO₂Magnetic particles.

3. The magnetic Au-MOF material of claim 2, wherein the PDDA modified Fe₃O₄/SiO₂The preparation method of the magnetic particles comprises the following steps:

4. The magnetic Au-MOF material of claim 3,

said Fe₃O₄/SiO₂The magnetic particles are Fe with the particle diameter of 200-400nm₃O₄The particles and the tetraethyl silicate are prepared by hydrolysis method;

the preparation method of the PDDA modification solution comprises the following steps: adding deionized water, sodium citrate and sodium chloride into a PDDA solution with the mass fraction of 20% and mixing to obtain a PDDA modified solution, wherein the mixing ratio of the PDDA solution to the deionized water to the sodium citrate to the sodium chloride is 10 mL: 90mL of: 88 mg: 12 mg;

said Fe₃O₄/SiO₂The mixing ratio of the magnetic particles and the PDDA modification solution was 1 mg: 1mL, stirring the reaction time for 20 min.

5. A method of preparing a magnetic Au-MOF material according to any one of claims 1 to 4, comprising the steps of:

(2) dissolving magnetic Au particles and zinc salt in an organic solvent to obtain a mixed solution A, mixing a methylimidazole solution and CTAB to obtain a mixture, adding the mixture into the mixed solution A, and standing for reaction to obtain the product, namely the magnetic Au-MOF material.

6. The method for preparing a magnetic Au-MOF material according to claim 5, wherein the method for preparing the gold nanoparticle sol comprises the following steps: to preheated HAuCl₄Adding sodium citrate aqueous solution into the solution, and heating and reacting under the stirring condition to obtain the gold nanoparticle sol.

7. Method for the preparation of a magnetic Au-MOF material according to claim 6, wherein the HAuCl is₄HAuCl in solution₄The concentration of (A) is 0.1-0.5mg/mL, the concentration of the sodium citrate aqueous solution is 50mg/mL, and the HAuCl is₄The mixing volume ratio of the solution to the sodium citrate aqueous solution is 24: 1; the heating reaction conditions under the stirring condition are as follows: 1800 ℃ 2200r/min, 100 ℃ 150 ℃ and 15-25 min.

8. A method of preparing a magnetic Au-MOF material according to claim 5, wherein in the step (1):

in the step (2):

the mixing ratio of the mixture to the mixed solution A is (3-4): 2;

standing for 3 h.

9. Use of a magnetic Au-MOF material according to any one of claims 1 to 4 for the enrichment of uranyl.

10. A uranyl detection method is characterized by comprising the following steps: mixing the magnetic Au-MOF material of any one of claims 1-4 with a uranyl solution, collecting the magnetic particles by using an external magnetic field, and collecting signals by using a Raman spectrometer to obtain an SERS spectrum of the uranyl.