A magnetic fluorescent tracer capable of encoding and decoding and a preparation method thereof

Abstract

The present invention relates to the field of tracer technology, and discloses a codable and decodable magnetic fluorescent tracer, comprising a magnetic fluorescent microsphere comprising a core formed by a plurality of fluorescent materials, a polymer coating the core, and a plurality of magnetic microspheres embedded on the surface of the polymer. The tracer has both magnetic and fluorescent functions. When sampling and testing production wells, the tracer can be enriched using a magnetic field, reducing the difficulty of purification from the produced fluid. Compared with direct testing of the original fluid, the error of subsequent analysis and detection after enrichment of the tracer is significantly reduced. The tracer can be prepared in more than 20 different colors and can be decoded using a flow cytometer, increasing the variety of fluorescent tracers.

Description

Technical Field

[0001] The invention belongs to the technical field of tracers, and in particular relates to a magnetic fluorescent tracer capable of encoding and decoding and a preparation method thereof. Background Art

[0002] Oilfield tracer technology is a field production testing technique that involves injecting a tracer into an injection well. Samples are then collected from surrounding production wells according to specific sampling protocols. Monitoring the tracer's evolution over time can guide well design and adjustments in later stages of oilfield development. Oilfield tracers can qualitatively characterize reservoir conditions, such as the direction and velocity of injected fluids, assess volumetric sweep efficiency, fluid obstruction, directional flow trends, reservoir heterogeneity, and determine remaining oil saturation and distribution.

[0003] For a long time, three main types of tracers have been commonly used in oilfields: chemical tracers, isotope tracers, and trace substance tracers. Chemical tracers include soluble inorganic salts, fluorescent dyes, halogenated hydrocarbons, and low-molecular-weight alcohols. Isotope tracers include radioactive isotope tracers and non-radioactive isotope tracers. These tracers all have varying degrees of disadvantages: Chemical tracers, such as inorganic salts, are easy to detect but limited in variety, require large quantities, are costly, and have large detection errors, making them primarily used for interwell testing. Fluorescent dyes have a short shelf life and are susceptible to interference. They experience high absorption and depletion in the formation, easily adsorbing into the formation and becoming unusable after more than five days. Large amounts of halogenated hydrocarbons and low-molecular-weight alcohols can affect subsequent extraction. Isotope tracers require specialized personnel and testing equipment, making them unsuitable for large-scale application. Radioactive isotopes pose certain hazards to humans and the environment, and the testing process is complex. Non-radioactive isotope testing is expensive. Although trace substances are used in small amounts and have high detection accuracy, their types are limited and cannot be used for simultaneous multi-stage detection. In addition, trace substance tracers require the use of high-end analytical equipment such as inductively coupled plasma mass spectrometry.

[0004] In addition, there is a problem with the use of existing common fluorescent tracers. For example, when sampling and testing production wells, the concentration of the fluorescent tracer in the test fluid is low, and further enrichment of the fluorescent tracer is very difficult or the method is relatively complicated, which ultimately leads to large detection errors.

[0005] In view of this, it is necessary to develop a magnetic fluorescent tracer that can be encoded and decoded. The tracer can be extracted from water or oil using a magnet to simplify the tracer collection process and reduce detection costs. It can encode more than 20 different colors, which solves the disadvantage of the limited variety of ordinary fluorescent dyes and has great application potential in the field of tracers. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a magnetic fluorescent tracer that can be encoded and decoded and a preparation method thereof, so as to solve the disadvantage of the limited variety of common fluorescent dyes and enhance their application potential in the field of tracers.

[0007] According to a first aspect of the present invention, there is provided a codable and decodable magnetic fluorescent tracer, comprising magnetic fluorescent microspheres, wherein the magnetic fluorescent microspheres comprise a core aggregated from a plurality of fluorescent materials, a polymer coating the core, and a plurality of magnetic microspheres embedded in the polymer and / or embedded in the polymer, wherein the magnetic microspheres comprise a magnetic material and an inorganic substance coating the magnetic material.

[0008] As a preferred solution of the above-mentioned encodable and decodable magnetic fluorescent tracer, the magnetic material includes metals and metal oxides with superparamagnetism, paramagnetism or ferromagnetism.

[0009] As a preferred embodiment of the above-mentioned encodable and decodable magnetic fluorescent tracer, the inorganic substance is selected from at least one of silicon-containing oxides, aluminum-containing oxides, zirconium-containing oxides, titanium-containing oxides, hafnium-containing oxides or yttrium-containing oxides.

[0010] As a preferred embodiment of the above-mentioned encodable and decodable magnetic fluorescent tracer, the polymer is selected from at least one of melamine resin, urea-formaldehyde resin, polyethylene, polypropylene, polystyrene, polyethylene oxide, polysiloxane, polyphenylene, polythiophene, polyphenylene vinylene, polysilane, polyethylene terephthalate, polyphenylethynyl, polymethyl methacrylate, polydodecyl methacrylate, polycarbonate or epoxy resin.

[0011] As a preferred embodiment of the above-mentioned encodable and decodable magnetic fluorescent tracer, the fluorescent material includes at least one of fluorescent nanoparticles, fluorescein, fluorescent polymers and organic fluorescent molecules.

[0012] As a preferred embodiment of the above-mentioned encodable and decodable magnetic fluorescent tracer, the fluorescent nanoparticles include at least one of quantum dots, nanorods or nanosheets.

[0013] As a preferred embodiment of the above-mentioned encodable and decodable magnetic fluorescent tracer, the size of the magnetic fluorescent microspheres is 1-5 microns.

[0014] According to a second aspect of the present invention, there is provided a method for preparing the above-mentioned encodable and decodable magnetic fluorescent tracer, comprising the steps of:

[0015] S1. preparing magnetic materials;

[0016] S2, coating inorganic substances with magnetic materials to form magnetic microspheres;

[0017] S3, mixing the fluorescent material, the magnetic microspheres and the polymer to prepare a magnetic fluorescent tracer.

[0018] As a preferred embodiment of the above-mentioned preparation method, the specific operation of step S3 is: adding the polymer precursor and the stabilizer to deionized water, adding an alkali agent to adjust the pH value of the reaction system to 8.5 until the reaction system becomes transparent, adding the fluorescent material and the magnetic microspheres in step S2 to react, and finally adding an acid agent to adjust the pH value of the reaction system to 4-5 to obtain a magnetic fluorescent tracer.

[0019] Preferably, the precursors of the polymer include formaldehyde and melamine. The polymer obtained by the reaction of formaldehyde and melamine is melamine formaldehyde resin.

[0020] Specifically, the stabilizer can be PVP (polyvinyl pyrrolidone), PEG (polyethylene glycol), CTAB (cetyltrimethylammonium bromide), SDBS (sodium dodecylbenzenesulfonate), SDS (sodium dodecylsulfonate), and PVP-K60 is preferably used in the present invention. The stabilizer can prevent agglomeration during the polymer coating process and prevent the coated particles from becoming too large.

[0021] Preferably, based on the amount of substances, the ratio of the formaldehyde, melamine, stabilizer, alkaline agent, magnetic microspheres, fluorescent material and acid agent is (1-5): (1-5): (1-5): (0.1-5): (2-6): (0.1-0.001): (0.1-3).

[0022] The reaction temperature of step S3 is preferably 65-100°C.

[0023] As a preferred embodiment of the above-mentioned preparation method, in step S1, the magnetic material is prepared by a co-precipitation method.

[0024] For example, ferroferric oxide can be prepared using the coprecipitation method: appropriate amounts of ferric chloride hexahydrate, sodium acetate, sodium citrate, and ethylene glycol are weighed in a stainless steel reactor and reacted at high temperature for 7-15 hours. After the reaction is complete, the mixture is removed and rinsed several times with deionized water and ethanol to obtain ferroferric oxide. The prepared ferroferric oxide can be stored in deionized water.

[0025] As a preferred embodiment of the above-mentioned preparation method, in step S2, the inorganic substance is coated on the magnetic material by using the Stober method or the microemulsion method.

[0026] Specifically, take appropriate amounts of ferroferric oxide, ethanol, ammonia water and deionized water in a glass reactor, turn on the stirrer, set the speed to 100-300 rpm, and then slowly pour in tetraethyl silicate. After waiting for 3 hours for the reaction to end, pour out the solution, wash it several times with ethanol and deionized water to obtain silicon-coated ferroferric oxide, that is, magnetic microspheres.

[0027] Compared with the prior art, the present invention has at least the following advantages:

[0028] 1. The tracer of the present invention has both magnetic and fluorescent functions, which endows the tracer with multifunctional properties;

[0029] 2. When sampling and testing production wells, the tracer can be enriched using a magnetic field, which reduces the difficulty of purification from the produced fluid. Compared with the method of directly testing the original fluid, the error of the tracer after enrichment and subsequent analysis is significantly reduced;

[0030] 3. The magnetic fluorescent microspheres have a large particle size and can contain fluorescent materials of various colors. The fluorescence intensity and encoding accuracy are high, so that the tracer can be prepared in more than 20 different colors and can be decoded by flow cytometry, which increases the types of fluorescent tracers. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0032] Attachment Figure 1 Schematic diagram of the structure of the magnetic fluorescent microspheres of the present invention;

[0033] Attachment Figure 2 This is a fluorescence microscope image of the magnetic fluorescent tracer of Example 1;

[0034] Attachment Figure 3 This is a fluorescence image of the magnetic fluorescent tracer of Example 1;

[0035] Attachment Figure 4 This is a diagram of the analysis of the magnetic fluorescent tracer of Example 1 using flow cytometry;

[0036] Attachment Figure 5 This is an electron microscope image of the magnetic fluorescent microspheres of Example 1;

[0037] Attachment Figure 6 This is a fluorescence microscope image of the magnetic fluorescent tracer of Example 2;

[0038] Attachment Figure 7 This is a fluorescence image of the magnetic fluorescent tracer of Example 2;

[0039] Attachment Figure 8 This is a diagram showing the analysis of the magnetic fluorescent tracer of Example 2 using flow cytometry;

[0040] Attachment Figure 9 This is an electron microscope image of the magnetic fluorescent microspheres of Example 2;

[0041] Attachment Figure 10 This is a fluorescence microscope image of the magnetic fluorescent tracer of Example 3;

[0042] Attachment Figure 11 This is a fluorescence image of the magnetic fluorescent tracer of Example 3;

[0043] Attachment Figure 12 This is a diagram of the analysis of the magnetic fluorescent tracer of Example 3 using flow cytometry;

[0044] Attachment Figure 13 This is an electron microscope image of the magnetic fluorescent microspheres of Example 3;

[0045] Attachment Figure 14 This is a fluorescence microscope image of the magnetic fluorescent tracer of Example 4;

[0046] Attachment Figure 15 This is a fluorescence image of the magnetic fluorescent tracer of Example 4;

[0047] Attachment Figure 16 This is a diagram showing the analysis of the magnetic fluorescent tracer of Example 4 using flow cytometry;

[0048] Attachment Figure 17 This is an electron microscope image of the magnetic fluorescent microspheres of Example 4;

[0049] Attachment Figure 18 This is a fluorescence microscope image of the magnetic fluorescent tracer of Example 5;

[0050] Attachment Figure 19 This is a fluorescence image of the magnetic fluorescent tracer of Example 5;

[0051] Attachment Figure 20 This is a diagram of the analysis of the magnetic fluorescent tracer of Example 5 using flow cytometry;

[0052] Attachment Figure 21 This is an electron microscope image of the magnetic fluorescent microspheres of Example 5;

[0053] Attachment Figure 22 This is a fluorescence microscope image of the dual-color magnetic fluorescent tracer of Example 6;

[0054] FIG23(a) is a fluorescence image of the dual-color magnetic fluorescent tracer of Example 6 when one color is excited to emit light; FIG23(b) is a fluorescence image of the dual-color magnetic fluorescent tracer of Example 6 when the other color is excited to emit light; FIG23(c) is a fluorescence image of the dual-color magnetic fluorescent tracer of Example 6 when the other color is excited to emit light; Figure 24 This is a diagram showing the analysis of the dual-color magnetic fluorescent tracer of Example 6 using flow cytometry;

[0055] Attachment Figure 25 This is an electron microscope image of the dual-color magnetic fluorescent microspheres of Example 6;

[0056] Attachment Figure 26 This is a fluorescence microscope image of the common fluorescent tracer of Comparative Example 1;

[0057] Attachment Figure 27 This is the fluorescence image of the common fluorescent tracer of Comparative Example 1;

[0058] Attachment Figure 28 This is a diagram of the analysis of the common fluorescent tracer of Comparative Example 1 using a flow cytometer;

[0059] Attachment Figure 29 This is an electron microscope image of the common fluorescent microspheres of Comparative Example 1;

[0060] Attachment Figure 30 is the hysteresis curve of the magnetic fluorescent microspheres of Example 1;

[0061] Attachment Figure 31 is the hysteresis curve of the magnetic fluorescent microspheres of Example 2;

[0062] Attachment Figure 32 is the hysteresis curve of the magnetic fluorescent microspheres of Example 3;

[0063] Attachment Figure 33 is the hysteresis curve of the magnetic fluorescent microspheres of Example 4;

[0064] Attachment Figure 34 is the hysteresis curve of the magnetic fluorescent microspheres of Example 5;

[0065] Attachment Figure 35 is the hysteresis curve of the dual-color magnetic fluorescent microspheres of Example 6;

[0066] Attachment Figure 36 is the hysteresis curve of the ordinary fluorescent microspheres in Comparative Example 1;

[0067] Attachment Figure 37 The magnetic fluorescent microspheres of Example 1 are configured in different proportions and added to petroleum, and then separated and purified by flow cytometry;

[0068] Attachment Figure 38 The flow cytometric fluorescence spectra of the ordinary fluorescent microspheres of Comparative Example 1 after being added to petroleum in different proportions and separated and purified are shown;

[0069] Attachment Figure 39 This is a schematic diagram of the magnetic fluorescent microspheres of Example 1 being added to produced water and adsorbed by a magnet;

[0070] Attachment Figure 40The magnetic fluorescent microspheres of Example 1 were configured in different proportions and added to the produced water, and then separated and purified, and the flow fluorescence spectra were obtained.

[0071] Attachment Figure 41 This is a schematic diagram of the ordinary fluorescent microspheres of Comparative Example 1 added to the produced water and centrifuged;

[0072] Attachment Figure 42 The flow cytometric fluorescence spectra of the ordinary fluorescent microspheres of Comparative Example 1 after being added into produced water in different proportions and separated and purified. DETAILED DESCRIPTION

[0073] The following will describe the technical solutions in the embodiment in detail in conjunction with the embodiments of the present invention. It should be noted that the embodiments are only partial, not complete.

[0074] As used herein, for example, "at least one of" when preceding or following a list of elements modifies the entire list of elements without modifying the individual elements of the list. If not otherwise defined, all terms (including technical and scientific terms) in the specification may be defined as those skilled in the art would normally understand. Terms defined in commonly used dictionaries should be interpreted as being consistent with their meanings in the context of the relevant art and the present disclosure, and should not be interpreted in an ideal manner or too broadly unless clearly defined. In addition, unless explicitly described to the contrary, the phrases "comprise" and "comprising" when used in this specification indicate the presence of the stated features, regions, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, components, and / or sets thereof. Therefore, the above phrases will be understood to mean including the stated elements, but not excluding any other elements.

[0075] As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. The term "or" means "and / or." "Multiple" refers to two or more.

[0076] It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms.

[0077] As used herein, "about" or "approximately" is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" can mean that the deviation from the stated value is within one or more standard deviations, or within ±10%, ±5%.

[0078] Based on the problem mentioned in the background technology that the concentration of existing fluorescent tracers in the liquid to be tested is low, and further enrichment of the fluorescent tracer is very difficult, the present invention develops a magnetic fluorescent tracer that can be encoded and decoded. The tracer can be extracted from water or oil using a magnet, thereby simplifying the tracer collection process and reducing detection costs. It can also encode more than 20 different colors to address the disadvantage of the limited variety of ordinary fluorescent dyes and enhance its application potential in the tracer field.

[0079] In a preferred embodiment of the present invention, a magnetic fluorescent tracer capable of encoding and decoding is provided, including magnetic fluorescent microspheres, such as Figure 1 As shown, the magnetic fluorescent microspheres include a core formed by a plurality of fluorescent materials 10, a polymer 20 coating the core, and a plurality of magnetic microspheres 30 embedded in the polymer 20 and / or embedded in the polymer 20. The magnetic fluorescent microspheres are spherical in shape as a whole and have approximately equal dimensions in three dimensions. The magnetic microspheres composed of this composition have dual functional characteristics of magnetism and fluorescence, so that the tracer has dual functions of magnetism and fluorescence. Magnetism means that under the action of a suitable magnetic field strength, the magnetic fluorescent microspheres have obvious magnetic guidance. For example, after the magnetic fluorescent microspheres are dispersed in a medium, under the action of a magnetic field, the magnetic fluorescent microspheres will move along the direction of the magnetic field, gather in a certain direction, and thus separate from the medium; the fluorescence characteristic means that after the magnetic fluorescent microspheres are irradiated by incident light of a certain wavelength, they emit outgoing light that is inconsistent with the wavelength of the incident light, and the wavelength of the outgoing light is generally larger than that of the incident light. In addition, the size of the magnetic microspheres of this structure can reach 1-5 microns, which can be coated with more fluorescent materials and can prepare more than 20 colors of coded fluorescent tracers, increasing the types of fluorescent tracers; furthermore, the size of the magnetic microspheres of this structure can reach 1-5 microns, which can effectively reduce the phenomenon of sedimentation of magnetic fluorescent microspheres.

[0080] Figure 1 In the figure, Figure A shows the case where the magnetic microspheres 30 are embedded in the polymer 20, Figure B shows the case where some of the magnetic microspheres 30 are embedded in the polymer 20 (protruding from the surface of the polymer 20) and some of the magnetic microspheres 30 are embedded in the polymer 20, and Figure C shows the case where all of the magnetic microspheres 30 are embedded in the polymer 20. In the present invention, the size of the fluorescent material 10 is approximately 10 nm, while the size of the magnetic microspheres 30 is approximately 200 nm. During the polymerization reaction, due to the significant size difference between the magnetic microspheres 30 and the fluorescent material 10, the aforementioned three coating structures appear (the three coating structures appear randomly). The magnetic fluorescent microspheres with these three coating structures can all achieve the effects of fluorescent tracing and magnetic enrichment.

[0081] The magnetic microspheres include a magnetic material 31 and an inorganic substance 32 coating the magnetic material 31. Magnetic materials include, but are not limited to, superparamagnetic, paramagnetic, or ferromagnetic metals and metal oxides, such as, but not limited to, Fe3O4, Fe2O3, CoFe2O4, MnFe2O4, NiFe2O4, compounds of neodymium iron boron, samarium cobalt, metals Fe, Co, Ni, and alloys of Fe2Co and Ni2Fe. Inorganic substances, due to their excellent barrier properties against water and oxygen, protect the magnetic material and reduce damage to it from the external environment. These include, but are not limited to, oxides containing silicon, aluminum, zirconium, titanium, hafnium, or yttrium, specifically silicon dioxide and titanium dioxide.

[0082] The fluorescent material includes at least one of fluorescent nanoparticles, fluorescein, and fluorescent polymers. The fluorescent nanoparticles include quantum dots, nanorods, or nanosheets. Fluorescein includes but is not limited to diphenylethylene, coumarins, fluoranes (xanthenes), benzoxazoles (including imidazoles and thiazoles), naphthalene dicarboxylic acid amides, condensed aromatic hydrocarbons (fluoranthenes), perylene tetracarboximide, phycoerythrin, and polydinium chlorophyll protein. The fluorescent polymer has a functional group that can emit fluorescence in its structure. Common fluorescent emitting groups include but are not limited to diphenylethylene, coumarins, fluoranes (xanthenes), benzoxazoles (including imidazoles and thiazoles), naphthalene dicarboxylic acid amides, condensed aromatic hydrocarbons (fluoranthenes), perylene tetracarboximide, phycoerythrin, and polydinium chlorophyll protein. Amines, condensed ring aromatic hydrocarbons (fluoranthene), perylenetetracarboximide, etc., monomers for synthesizing fluorescent polymers include: fluorescein isothiocyanate, tetramethyl isothiocyanato rhodamine, heme, rhodamine B, 5 (6) -carboxytetramethylrhodamine, rhodamine 6G, rhodamine 123, rhodamine 101, fluorescein, Hoechst fluorescent dye, 4', 6-diamidino-2-phenylindole, copper phthalocyanine disulfonic acid, dihydroxy silicon phthalocyanine, scarlet acid, etc., which have reactive groups such as amino, hydroxyl, thiol, carboxyl, sulfonic acid, isothiocyanate, acyl chloride, sulfonyl chloride, epoxy, etc. These monomers are polymerized with each other or with other monomers that do not contain fluorescence to prepare fluorescent polymers.

[0083] Similarly, polymers are used as carriers for fluorescent materials and magnetic microspheres. In the present invention, the polymer is selected from at least one of melamine resin, urea-formaldehyde resin, polyethylene, polypropylene, polystyrene, polyethylene oxide, polysiloxane, polyphenylene, polythiophene, polyphenylene vinylene, polysilane, polyethylene terephthalate, poly(phenylethynyl), polymethyl methacrylate, polydodecyl methacrylate, polycarbonate, or epoxy resin. In a preferred embodiment of the present invention, the polymer is a melamine resin, i.e., a polymer formed by formaldehyde-melamine dispersion polycondensation.

[0084] Magnetic fluorescent microspheres can be used as oil-soluble, water-soluble, or oil-water partitioning tracers, depending on the application. Common design methods include modifying the surface of the magnetic fluorescent microspheres to enhance their hydrophilicity and hydrophobicity. When sampling production wells, a mixture of oil and water is typically obtained. When using an oil-soluble tracer, the tracer is primarily dispersed in the oil, with the tracer in the oil serving as the primary target for detection. Similarly, when using a water-soluble tracer, the tracer is primarily dispersed in the water, with the tracer in the water serving as the primary target for detection.

[0085] In another preferred embodiment of the present invention, a method for preparing the above-mentioned encodable and decodable magnetic fluorescent tracer is provided, comprising the steps of:

[0086] S1. preparing magnetic materials;

[0087] S2, coating inorganic substances with magnetic materials to form magnetic microspheres;

[0088] S3, mixing the fluorescent material, the magnetic microspheres and the polymer to prepare a magnetic fluorescent tracer.

[0089] In step S1, the present invention uses a coprecipitation method to prepare the magnetic material; in step S2, the inorganic substance can be coated on the magnetic material using a Stober method or a microemulsion method. The specific operation of step S3 is as follows: adding a polymer precursor and a stabilizer to deionized water, adding an alkali agent to adjust the pH of the reaction system to 8.5 until the reaction system becomes transparent, adding a fluorescent material and the magnetic microspheres from step S2 to react, and finally adding an acid agent to adjust the pH of the reaction system to 4-5 to obtain a magnetic fluorescent tracer.

[0090] Specifically, the magnetic fluorescent microspheres of the present invention derive their magnetism from the magnetic microspheres, wherein the magnetic material in the magnetic microspheres is a metal or metal oxide with superparamagnetism, paramagnetism, or ferromagnetism, such as Fe3O4, Fe2O3, CoFe2O4, MnFe2O4, NiFe2O4, compounds of neodymium iron boron, samarium cobalt, metals Fe, Co, Ni, and metal oxides of alloys Fe2Co, Ni2Fe, and the like. When preparing the magnetic microspheres by a coprecipitation method, appropriate amounts of ferric chloride hexahydrate, sodium acetate, sodium citrate, and ethylene glycol are placed in a stainless steel reactor and reacted at high temperature for 7-15 hours. After the reaction is completed, the reactor is removed and washed several times with deionized water and ethanol to obtain ferrosoferric oxide, which is then stored in deionized water. The ratio of ferric chloride hexahydrate, sodium acetate, sodium citrate, and ethylene glycol, measured by amount, is (2-6):(1-4):(1-2):(150-250).

[0091] Inorganic substances can serve as carriers for magnetic microspheres, and the temperature, pH, and salt concentration of underground oilfields place high demands on the stability of magnetic fluorescent microspheres. Inorganic substances can also serve as protective agents for magnetic microspheres. Methods for coating inorganic substances on magnetic microspheres include microemulsion methods. Specifically, a water-in-oil microemulsion is prepared, wherein the water contains multiple magnetic microspheres, and the oil contains a precursor of the inorganic substance. Through microemulsion polymerization, magnetic microspheres coated with the inorganic substance can be obtained. For example, when the inorganic substance is silicon dioxide, the precursor of the inorganic substance can be a silicate compound. In the present invention, appropriate amounts of ferroferric oxide, ethanol, ammonia water, and deionized water are placed in a glass reactor, a stirrer is turned on, and then tetraethyl silicate is slowly poured in. After waiting for 3 hours for the reaction to complete, the solution is poured out and washed several times with ethanol and deionized water to obtain ferroferric oxide coated with silicon dioxide. The ratio of ferroferric oxide to ammonia water is (1-3): (2-6) in terms of the amount of substance.

[0092] The polymer is used as a carrier for the magnetic microspheres and the fluorescent material. The polymer can be any polymer, such as a linear polymer, a hyperbranched polymer, a cross-linked polymer, a star polymer, a dendrimer, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer, and a terpolymer. The polymer includes, but is not limited to, melamine resin, urea-formaldehyde resin, polyethylene, polypropylene, polystyrene, polyethylene oxide, polysiloxane, polyphenylene, polythiophene, poly(phenylene vinylene), polysilane, polyethylene terephthalate and poly(phenylethynyl), polymethyl methacrylate, polydodecyl methacrylate, polycarbonate, epoxy resin, and the like.

[0093] In the present invention, the fluorescent material is dispersed in the polymer when combined with the polymer. In this case, the fluorescent material can be mixed with the precursor of the polymer and then embedded in the polymer during the preparation of the polymer. When the magnetic microspheres are combined with the polymer, a connecting substance exists between the magnetic microspheres and the polymer, such as chemical crosslinking or intermolecular forces, which will cause the magnetic microspheres to be modified on the polymer or embedded in the polymer, or both situations occur simultaneously.

[0094] As a preferred embodiment of the present invention, the polymer is a melamine resin, that is, formed by dispersion polycondensation of the precursor formaldehyde-melamine. Step S3 specifically comprises: adding formaldehyde-melamine and PVP in a certain molar ratio to a certain amount of deionized water, adding sodium hydroxide to adjust the pH to 8.5, reacting and dissolving at 65-100°C until transparent, adding inorganically coated magnetic microspheres and fluorescent material, and continuing to stir. Finally, phosphoric acid is added to adjust the pH to 4-5, thereby obtaining the magnetic fluorescent tracer of the present invention. In the present invention, the molar ratio of formaldehyde-melamine is preferably 3:1, and the reactants are completely consumed without excess. By amount, the ratio of formaldehyde, melamine, PVP, sodium hydroxide, inorganically coated magnetic microspheres, fluorescent material, and phosphoric acid is (1-5):(1-5):(1-5):(0.1-5):(2-6):(0.1-0.001):(0.1-3).

[0095] Some exemplary embodiments of the present invention are described in more detail below; however, exemplary embodiments of the present invention are not limited thereto.

[0096] Example 1

[0097] 1. Synthetic magnetic microspheres

[0098] Calculated by amount, 2 parts of ferric chloride hexahydrate, 1 part of sodium acetate, 1 part of sodium citrate and 150 parts of ethylene glycol were added to a stainless steel reactor and reacted at 200° C. for 12 hours. After the reaction was completed, the reactor was taken out and washed several times with deionized water and ethanol to obtain ferrosoferric oxide.

[0099] 2. Inorganic coating on magnetic microspheres

[0100] According to the order of magnitude of the substance, take 1 part of ferroferric oxide, 2 parts of ammonia water, 100 parts of ethanol, and 100 parts of deionized water into a glass reactor, turn on the stirrer, set the speed to 300 rpm, then slowly pour in 10 parts of tetraethyl silicate, wait for 3 hours for the reaction to end, then pour out the solvent, wash with ethanol and deionized water several times to obtain the silicon-coated ferroferric oxide.

[0101] 3. Polymer coating

[0102] According to the amount of substance, 3 parts of formaldehyde, 1 part of melamine, 1 part of PVP-K60 and 50 parts of deionized water are taken in a three-necked flask, 0.1 part of sodium hydroxide is added to adjust the pH value to 8.5, and the reaction is carried out at 65°C and 150 rpm for half an hour; 2 parts of silicon-coated ferrosoferric oxide and 0.01 part of sodium fluorescein are added, and the temperature and speed are maintained for half an hour. Finally, 0.1 part of phosphoric acid is added to adjust the pH value to 4.5, and the temperature and speed are maintained for two hours. After the reaction, the reaction is centrifuged at 3000 rpm and washed twice with water to obtain a magnetic fluorescent tracer.

[0103] Figure 2 Shown is the fluorescence microscope image of the magnetic fluorescent tracer. Figure 3 is the fluorescence image of the magnetic fluorescent tracer, Figure 4 This is the analysis diagram of the magnetic fluorescent tracer using flow cytometry, which shows that the fluorescence effect is good; Figure 5 This is an electron microscope image of the magnetic fluorescent microspheres. It can be seen that the magnetic fluorescent microspheres have good coating effect and uniform particle size.

[0104] Example 2

[0105] 1. Synthetic magnetic microspheres

[0106] Calculated by amount, 6 parts of ferric chloride hexahydrate, 4 parts of sodium acetate, 2 parts of sodium citrate and 250 parts of ethylene glycol were added to a stainless steel reactor and reacted at 200° C. for 12 hours. After the reaction was completed, the reactor was taken out and washed several times with deionized water and ethanol to obtain ferrosoferric oxide.

[0107] 2. Inorganic coating on magnetic microspheres

[0108] According to the order of magnitude of the substance, take 3 parts of ferroferric oxide, 6 parts of ammonia water, 200 parts of ethanol, and 200 parts of deionized water into a glass reactor, turn on the stirrer, set the speed to 300 rpm, then slowly pour in 100 parts of tetraethyl silicate, wait for 3 hours for the reaction to end, then pour out the solvent, wash with ethanol and deionized water several times to obtain the ferroferric oxide after siliconization.

[0109] 3. Polymer coating

[0110] 3 parts of formaldehyde, 1 part of melamine, 5 parts of PVP-K60, and 150 parts of deionized water were added to a three-necked flask, 5 parts of sodium hydroxide was added to adjust the pH to 8.5, and the reaction was carried out at 65°C and 150 rpm for half an hour. 6 parts of silicon-coated ferrosoferric oxide and 0.01 part of AMC 7-amino-4-methylcoumarin were added, and the temperature and speed were maintained for half an hour. Finally, 3 parts of phosphoric acid were added to adjust the pH to 4.5, and the temperature and speed were maintained for two hours. After the reaction, the reaction was centrifuged at 3000 rpm and washed twice with water to obtain a magnetic fluorescent tracer.

[0111] Figure 6 Shown is the fluorescence microscope image of the magnetic fluorescent tracer. Figure 7 is the fluorescence image of the magnetic fluorescent tracer, Figure 8 This is the analysis diagram of the magnetic fluorescent tracer using flow cytometry, which shows that the fluorescence effect is good; Figure 9 This is an electron microscope image of the magnetic fluorescent microspheres. It can be seen that the magnetic fluorescent microspheres have good coating effect and uniform particle size.

[0112] Example 3

[0113] 1. Synthetic magnetic microspheres

[0114] Calculated by amount, 4 parts of ferric chloride hexahydrate, 3 parts of sodium acetate, 2 parts of sodium citrate and 200 parts of ethylene glycol were added to a stainless steel reactor and reacted at 200° C. for 12 hours. After the reaction was completed, the reactor was taken out and washed several times with deionized water and ethanol to obtain ferrosoferric oxide.

[0115] 2. Inorganic coating on magnetic microspheres

[0116] According to the order of magnitude of the substance, take 2 parts of ferroferric oxide, 4 parts of ammonia water, 150 parts of ethanol, and 150 parts of deionized water into a glass reactor, turn on the stirrer, set the speed to 300 rpm, then slowly pour in 60 parts of tetraethyl silicate, wait for 3 hours for the reaction to end, then pour out the solvent, wash with ethanol and deionized water several times to obtain the ferroferric oxide after siliconization.

[0117] 3. Polymer coating

[0118] According to the amount of substance, 3 parts of formaldehyde, 1 part of melamine, 3 parts of PVP-K60 and 100 parts of deionized water are taken into a three-necked flask, 3 parts of sodium hydroxide are added to adjust the pH value to 8.5, and the reaction is carried out at 65°C and 150 rpm for half an hour; 4 parts of silicon-coated ferrosoferric oxide and 0.01 parts of cadmium selenide quantum dots are added, and the temperature and speed are maintained for half an hour. Finally, 3 parts of phosphoric acid are added to adjust the pH value to 4.5, and the temperature and speed are maintained for two hours. After the reaction, the reaction is centrifuged at 3000 rpm and washed twice with water to obtain a magnetic fluorescent tracer.

[0119] Figure 10 Shown is the fluorescence microscope image of the magnetic fluorescent tracer. Figure 11 is the fluorescence image of the magnetic fluorescent tracer, Figure 12 This is the analysis diagram of the magnetic fluorescent tracer using flow cytometry, which shows that the fluorescence effect is good; Figure 13 This is an electron microscope image of the magnetic fluorescent microspheres. It can be seen that the magnetic fluorescent microspheres have good coating effect and uniform particle size.

[0120] Example 4

[0121] 1. Synthetic magnetic microspheres

[0122] Calculated by amount, 4 parts of ferric chloride hexahydrate, 3 parts of sodium acetate, 2 parts of sodium citrate and 200 parts of ethylene glycol were added to a stainless steel reactor and reacted at 200° C. for 12 hours. After the reaction was completed, the reactor was taken out and washed several times with deionized water and ethanol to obtain ferrosoferric oxide.

[0123] 2. Inorganic coating on magnetic microspheres

[0124] According to the order of magnitude of the substance, take 2 parts of ferroferric oxide, 4 parts of ammonia water, 150 parts of ethanol, and 150 parts of deionized water into a glass reactor, turn on the stirrer, set the speed to 300 rpm, then slowly pour in 60 parts of tetraethyl silicate, wait for 3 hours for the reaction to end, then pour out the solvent, wash with ethanol and deionized water several times to obtain the ferroferric oxide after siliconization.

[0125] 3. Polymer coating

[0126] According to the amount of substance, 3 parts of formaldehyde, 1 part of melamine, 3 parts of PVP-K60 and 100 parts of deionized water are taken in a three-necked flask, 3 parts of sodium hydroxide are added to adjust the pH value to 8.5, and the reaction is carried out at 65°C and 150 rpm for half an hour; 4 parts of silicon-coated ferrosoferric oxide and 0.01 parts of 515 carbon dots (carbon quantum dots with an excitation wavelength of 515 nm) are added, and the temperature and speed are maintained for half an hour. Finally, 3 parts of phosphoric acid are added to adjust the pH value to 4.5, and the temperature and speed are maintained for two hours. After the reaction, the magnetic fluorescent tracer is obtained by centrifugation at 3000 rpm and washing twice with water to obtain a magnetic fluorescent tracer.

[0127] Figure 14 Shown is the fluorescence microscope image of the magnetic fluorescent tracer. Figure 15 is the fluorescence image of the magnetic fluorescent tracer, Figure 16 This is the analysis diagram of the magnetic fluorescent tracer using flow cytometry, which shows that the fluorescence effect is good; Figure 17 This is an electron microscope image of the magnetic fluorescent microspheres. It can be seen that the magnetic fluorescent microspheres have good coating effect and uniform particle size.

[0128] Example 5

[0129] 1. Synthetic magnetic microspheres

[0130] Calculated by amount, 4 parts of ferric chloride hexahydrate, 3 parts of sodium acetate, 2 parts of sodium citrate and 200 parts of ethylene glycol were added to a stainless steel reactor and reacted at 200° C. for 12 hours. After the reaction was completed, the reactor was taken out and washed several times with deionized water and ethanol to obtain ferrosoferric oxide.

[0131] 2. Inorganic coating on magnetic microspheres

[0132] According to the order of magnitude of the substance, take 2 parts of ferroferric oxide, 4 parts of ammonia water, 150 parts of ethanol, and 150 parts of deionized water into a glass reactor, turn on the stirrer, set the speed to 300 rpm, then slowly pour in 60 parts of tetraethyl silicate, wait for 3 hours for the reaction to end, then pour out the solvent, wash with ethanol and deionized water several times to obtain the ferroferric oxide after siliconization.

[0133] 3. Polymer coating

[0134] According to the amount of substance, 3 parts of formaldehyde, 1 part of melamine, 3 parts of PVP-K60 and 100 parts of deionized water are taken in a three-necked flask, 3 parts of sodium hydroxide are added to adjust the pH value to 8.5, and the reaction is carried out at 65°C and 150 rpm for half an hour; 4 parts of silicon-coated ferrosoferric oxide and 0.01 parts of 575 carbon dots (carbon quantum dots with an excitation wavelength of 575 nm) are added, and the temperature and speed are maintained for half an hour. Finally, 3 parts of phosphoric acid are added to adjust the pH value to 4.5, and the temperature and speed are maintained for two hours. After the reaction, the magnetic fluorescent tracer is obtained by centrifugation at 3000 rpm and washing twice with water to obtain a magnetic fluorescent tracer.

[0135] Figure 18 Shown is the fluorescence microscope image of the magnetic fluorescent tracer. Figure 19 is the fluorescence image of the magnetic fluorescent tracer, Figure 20 This is the analysis diagram of the magnetic fluorescent tracer using flow cytometry, which shows that the fluorescence effect is good; Figure 21 This is an electron microscope image of the magnetic fluorescent microspheres. It can be seen that the magnetic fluorescent microspheres have good coating effect and uniform particle size.

[0136] Example 6

[0137] 1. Synthetic magnetic microspheres

[0138] Calculated by amount, 4 parts of ferric chloride hexahydrate, 3 parts of sodium acetate, 2 parts of sodium citrate and 200 parts of ethylene glycol were added to a stainless steel reactor and reacted at 200° C. for 12 hours. After the reaction was completed, the reactor was taken out and washed several times with deionized water and ethanol to obtain ferrosoferric oxide.

[0139] 2. Inorganic coating on magnetic microspheres

[0140] According to the order of magnitude of the substance, take 2 parts of ferroferric oxide, 4 parts of ammonia water, 150 parts of ethanol, and 150 parts of deionized water into a glass reactor, turn on the stirrer, set the speed to 300 rpm, then slowly pour in 60 parts of tetraethyl silicate, wait for 3 hours for the reaction to end, then pour out the solvent, wash with ethanol and deionized water several times to obtain the ferroferric oxide after siliconization.

[0141] 3. Polymer coating

[0142] According to the amount of substance, 3 parts of formaldehyde, 1 part of melamine, 3 parts of PVP-K60 and 100 parts of deionized water are taken into a three-necked flask, 3 parts of sodium hydroxide are added to adjust the pH value to 8.5, and the reaction is carried out at 65°C and 150 rpm for half an hour; 4 parts of silicon-coated ferrosoferric oxide, 0.01 parts of AMC (7-amino-4-methylcoumarin) and 0.01 parts of FITC (fluorescein isothiocyanate) are added, and the temperature and speed are maintained for half an hour. Finally, 3 parts of phosphoric acid are added to adjust the pH value to 4.5, and the temperature and speed are maintained for two hours. After the reaction, the mixture is centrifuged at 3000 rpm and washed twice with water to obtain a dual-color magnetic fluorescent tracer.

[0143] Figure 22 Figure 23(a) and Figure 23(b) show the fluorescence microscopy images of the magnetic fluorescent tracer. Figure 24 This is the analysis diagram of the magnetic fluorescent tracer using flow cytometry, which shows that the fluorescence effect is good; Figure 25 This is an electron microscope image of the magnetic fluorescent microspheres. It can be seen that the magnetic fluorescent microspheres have good coating effect and uniform particle size.

[0144] Comparative Example 1

[0145] According to the amount of substance, 3 parts of formaldehyde, 1 part of melamine, 1 part of PVP-K60 and 100 parts of deionized water are taken into a three-necked flask, 3 parts of sodium hydroxide are added to adjust the pH value to 8.5, and the reaction is carried out at 65°C at a speed of 150 rpm until it dissolves and becomes transparent; 0.01 parts of sodium fluorescein are added, and the temperature and speed are maintained for half an hour. Finally, 0.1 parts of phosphoric acid are added to adjust the pH value to 4.5, and the temperature and speed are maintained for two hours. After the reaction, the reaction is centrifuged at 3000 rpm and washed twice with water to obtain a common fluorescent tracer (i.e., non-magnetic).

[0146] Figure 26 Shown is a fluorescence microscope image of this common fluorescent tracer. Figure 27 This is a fluorescence picture of the common fluorescent tracer, which has a fluorescent effect; Figure 28 The figure is an analysis diagram of the common fluorescent tracer using flow cytometry; Figure 29 This is an electron microscope image of the ordinary fluorescent microsphere.

[0147] Different magnetizing field intensities were applied to the tracers of Examples 1-6 and Comparative Example 1, and their respective magnetic induction intensities were tested. Figures 30-36 From the corresponding hysteresis curves, it can be seen that the magnetic fluorescent tracers prepared in Examples 1-6 of the present invention have good superparamagnetism.

[0148] The magnetic fluorescent tracer of Example 1 and the common fluorescent tracer of Comparative Example 1 were used for detection in petroleum, and the separation and purification effects of the magnetic fluorescent microspheres of the present invention and the common fluorescent microspheres from produced oil were compared.

[0149] 1. Separation and purification test of magnetic fluorescent microspheres in produced oil of Example 1

[0150] First, the magnetic fluorescent tracer of Example 1 was transferred to the oil phase, and 5 mg and 5 × 10 -1 mg, 5×10 -2 mg, 5×10 -3 mg, 5×10 -4 mg, 5×10 -5 The magnetic microspheres after mg transfer to oil phase were added into 5 ml of produced oil and shaken for 20 min to fully disperse them.

[0151] Magnetic fluorescent microspheres separation and purification:

[0152] 1. Use a magnet to absorb the oil for 10 minutes and then take it out. The concentration is too low to be observed with the naked eye.

[0153] 2. Add 5 ml of toluene, ultrasonically wash for 10 minutes, and then adsorb with a magnet for 10 minutes;

[0154] 3. Add 5 ml of acetone, ultrasonically wash for 10 minutes, and then adsorb with a magnet for 10 minutes;

[0155] 4. Add 1 ml of ethanol, wash with ultrasound for 10 minutes, and directly test using flow cytometry.

[0156] like Figure 37 As shown in the figure, the black dotted box is the peak position of the magnetic fluorescent microsphere signal. It can be seen that when the concentration of magnetic fluorescent microspheres is less than 5×10 -3 At mg / ml, effective signals could not be purified by magnetic adsorption.

[0157] 2. Separation and purification test of ordinary fluorescent microspheres in produced oil of comparative example 1

[0158] First, the common fluorescent tracer of Comparative Example 1 was transferred to the oil phase, and 5 mg and 5 × 10 -1 mg, 5×10 -2 mg, 5×10 -3 mg, 5×10 -4 mg, 5×10 -5 The ordinary microspheres after mg conversion to oil phase were added into 5 ml of produced oil and shaken for 20 minutes to fully disperse them.

[0159] Separation and purification of ordinary fluorescent microspheres:

[0160] 1. Ordinary fluorescent microspheres can only be purified by centrifugation. Centrifuge the sample at 10,000 rpm for 5 minutes.

[0161] 2. Add 5 ml of toluene, ultrasonically wash for 10 minutes, and centrifuge at 10,000 rpm for 5 minutes;

[0162] 3. Add 5 ml of acetone, ultrasonically wash for 10 minutes, and centrifuge at 10,000 rpm for 5 minutes;

[0163] 4. Add 1 ml of ethanol, wash with ultrasound for 10 minutes, and directly test using flow cytometry.

[0164] like Figure 38 As shown in the figure, the black dotted box is the peak position of the ordinary fluorescent microsphere signal. It can be seen that when the concentration of ordinary fluorescent microspheres is less than 5×10 -2 When the concentration was 100 mg / ml, the centrifugation washing method could not purify the effective signal.

[0165] In summary, in oil, when the concentration of magnetic fluorescent microspheres is 5×10 -3 The signal was detected at 5×10 mg / ml, but the signal was unstable and the fluorescence intensity was slightly weak. This is because at low concentrations, multiple washings will cause the loss of a large number of magnetic fluorescent microspheres, resulting in unclear fluorescence intensity. -3 The detection limit of the magnetic fluorescent microspheres of the present invention is lower, and they are more suitable for oil tracer detection.

[0166] The magnetic fluorescent tracer of Example 1 and the common fluorescent tracer of Comparative Example 1 were used for detection in underground produced water, and the separation and purification effects of the magnetic fluorescent microspheres of the present invention and the common fluorescent microspheres from produced water were compared.

[0167] 1. Separation and purification test of magnetic fluorescent microspheres in produced water of Example 1

[0168] 5×10 -2 mg, 5×10 -3 mg, 5×10 -4 mg, 5×10 -5 Mg aqueous phase magnetic fluorescent microspheres were added to 5 ml of produced water and shaken for 20 min to fully disperse them.

[0169] Magnetic microsphere separation and purification:

[0170] 1. Such as Figure 39 As shown, directly use the magnet to adsorb for 10 minutes, and then take out the water, you can see the magnetic ball adsorbed on the tube wall (the circled part in the figure);

[0171] 2. Add 5 ml of deionized water, ultrasonically wash for 5 minutes, then adsorb with a magnet for 5 minutes, and repeat the washing three times;

[0172] 3. After dispersion, directly use flow cytometry to test.

[0173] like Figure 40 As shown in the figure, the black dotted box is the peak position of the magnetic fluorescent microsphere signal. It can be seen that when the concentration of magnetic fluorescent microspheres is 5×10 -4 When the concentration is 100 mg / ml, effective signals can still be extracted from the produced water.

[0174] 2. Separation and purification test of magnetic fluorescent microspheres in produced water of comparative example 1

[0175] 5×10 -2 mg, 5×10 -3 mg, 5×10 -4 mg, 5×10 -5 mg of ordinary fluorescent microspheres in aqueous phase were added to 5 ml of produced water and shaken for 20 min to fully disperse them.

[0176] Separation and purification of ordinary fluorescent microspheres:

[0177] 1. Centrifuge the sample at 10000 rpm for 5 min. Figure 41 As shown, the centrifuged material is mainly a mixture of ordinary fluorescent microspheres and impurities in water (the circled part in the figure);

[0178] 2. Add 5 ml of deionized water, ultrasonically wash for 5 minutes, centrifuge at 10,000 rpm for 5 minutes, and repeat the washing three times;

[0179] 3. After dispersion, directly use flow cytometry to test.

[0180] like Figure 42 As shown in the figure, it can be seen that only when the concentration of ordinary fluorescent microspheres is 5×10 -2 A fluorescence signal can be detected at 50 mg / ml, but the signal is very weak. This is because there are many impurities in the produced water and they cannot be removed, resulting in poor detection effect.

[0181] In summary, in produced water, the purification accuracy of the magnetic fluorescent microspheres of the present invention in water is two orders of magnitude higher than that of ordinary fluorescent microspheres, and the detection limit is lower. Moreover, due to the high purification accuracy, the detection error can be greatly reduced, and it is more suitable for tracer detection of groundwater.

[0182] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a magnetic fluorescent tracer capable of encoding and decoding, characterized in that: Including steps: S1. preparing magnetic materials; S2, coating inorganic substances with magnetic materials to form magnetic microspheres; S3. Mixing and reacting the fluorescent material, the magnetic microspheres, the stabilizer, and the precursor of the polymer to prepare magnetic fluorescent microspheres; based on the amount of the substances, the ratio of the stabilizer, the magnetic microspheres, and the fluorescent material is (1-5): (2-6): (0.1-0.001); the magnetic fluorescent microspheres include a core formed by a plurality of fluorescent materials, a polymer coating the core, and a plurality of magnetic microspheres embedded in the polymer and / or embedded in the polymer, wherein the plurality refers to two or more.

2. The method for preparing a codable and decodable magnetic fluorescent tracer according to claim 1, wherein: The magnetic materials include: Fe3O4, Fe2O3, CoFe2O4, MnFe2O4, NiFe2O4, and samarium cobalt.

3. The method for preparing a codable and decodable magnetic fluorescent tracer according to claim 1, wherein: The inorganic substance is selected from at least one of silicon-containing oxides, aluminum-containing oxides, and titanium-containing oxides.

4. The method for preparing a codable and decodable magnetic fluorescent tracer according to claim 1, wherein: The polymer is selected from at least one of melamine resin, urea-formaldehyde resin, polyethylene, polypropylene, polystyrene, polyethylene oxide, polysiloxane, polyphenylene, polythiophene, polyphenylene vinylene, polysilane, polyethylene terephthalate, polyphenylethynyl, polymethyl methacrylate, polydodecyl methacrylate, polycarbonate or epoxy resin.

5. The method for preparing a codable and decodable magnetic fluorescent tracer according to claim 1, wherein: The fluorescent material includes at least one of fluorescent nanoparticles, fluorescent polymers and organic fluorescent molecules.

6. The method for preparing a codable and decodable magnetic fluorescent tracer according to claim 5, characterized in that: The fluorescent nanoparticles include at least one of carbon dots and quantum dots.

7. The method for preparing a codable and decodable magnetic fluorescent tracer according to claim 1, characterized in that: The size of the magnetic fluorescent microspheres is 1-5 microns.

8. The method for preparing a codable and decodable magnetic fluorescent tracer according to claim 1, wherein: The specific operation of step S3 is as follows: adding the polymer precursor and the stabilizer to deionized water, adding an alkali agent to adjust the pH value of the reaction system to 8.5 until the reaction system becomes transparent, adding the fluorescent material and the magnetic microspheres in step S2 to react, and finally adding an acid agent to adjust the pH value of the reaction system to 4-5 to obtain a magnetic fluorescent tracer.

9. The method for preparing a codable and decodable magnetic fluorescent tracer according to claim 8, characterized in that: comprising one or more features selected from the group consisting of: (1) The precursor of the polymer includes formaldehyde and melamine; (2) The stabilizer may be polyvinyl pyrrolidone, polyethylene glycol, hexadecyltrimethylammonium bromide, sodium dodecylbenzenesulfonate, or sodium dodecylsulfonate; (3) Calculated by amount, the ratio of formaldehyde, melamine, alkaline agent and acid agent is (1-5): (1-5): (0.1-5): (0.1-3); (4) The reaction temperature of step S3 is 65-100°C.

10. The method for preparing a codable and decodable magnetic fluorescent tracer according to claim 1, characterized in that: In the step S1, the magnetic material is prepared by a coprecipitation method; in the step S2, the inorganic substance is coated on the magnetic material by a Stober method or a microemulsion method.

11. A codable and decodable magnetic fluorescent tracer, comprising magnetic fluorescent microspheres, characterized in that: The magnetic fluorescent microspheres are obtained by the preparation method according to any one of claims 1 to 10.

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