Magnetic fluorescent composite covert marking ink, preparation method and application thereof

Abstract

The application discloses a kind of magnetic fluorescent composite latent mark inks and preparation method and application thereof, ink contains magnetic nanoparticle and fluorescent marker;Magnetic nanoparticle preparation process is as follows: prepare ferroferric oxide magnetic nanoparticle by coprecipitation method, then modify the surface of magnetic nanoparticle;Magnetic nanoparticle is mixed by mixing trivalent iron salt aqueous solution and divalent iron salt aqueous solution according to the proportion of 7:3, drop into NaOH aqueous solution to adjust pH to set value;After heating, add oleic acid, add tween reagent after reaction, and stop heating, then cool down while stirring, then centrifugal separation is carried out to the surface modified magnetic nanoparticle;Magnetic fluorescent composite mark ink is formed after mixing magnetic nanoparticle and fluorescent solution with fluorescent marker.The latent mark ink of the application has magnetic signal mark and fluorescent color development mark ability simultaneously, and can improve the marking function, marking concealment and anti-fake ability of latent mark ink.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation and chemical reagent technology, specifically to a magnetic fluorescent composite latent labeling ink, its preparation method, and its application. Background Technology

[0002] Hidden marking inks have applications in anti-counterfeiting printing, hidden tracking markings, and the writing of secret letters. Currently, hidden marking inks primarily function as single-function fluorescent markers. Spots marked with fluorescent hidden ink do not appear as distinct colored patterns to the naked eye under visible light. However, when the surface of the spot is illuminated with ultraviolet light, bright colored fluorescent spots become visible to the naked eye. As single-function fluorescent hidden marking inks become more widely known, their function as hidden markers is gradually diminishing. Furthermore, they are easily detected and imitated, leading to a decline in their anti-counterfeiting capabilities.

[0003] In summary, existing hidden marking inks suffer from limited marking functionality, are easily imitated and counterfeited, and thus have reduced anti-counterfeiting capabilities. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a magnetic fluorescent composite latent marking ink, its preparation method, and its application. This addresses the issue that existing latent marking inks have limited marking functions, are easily imitated and counterfeited, leading to a decline in anti-counterfeiting capabilities. The latent marking ink of this invention possesses both magnetic signal marking and fluorescent color-developing marking capabilities, thereby enhancing its marking function, concealment, and anti-counterfeiting effectiveness.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A magnetic fluorescent composite latent marker ink, wherein the ink contains magnetic nanoparticles and fluorescent markers;

[0007] The magnetic nanoparticle preparation process is as follows: magnetic nanoparticles of iron oxide are prepared by co-precipitation, and then the surface of the magnetic nanoparticles is modified; the magnetic nanoparticles are prepared by mixing aqueous solutions of ferric salt and ferrous salt in a volume ratio of 7:3, adding NaOH aqueous solution to adjust the pH to a set value; after heating, oleic acid is added, and after reaction, Tween reagent is added and heating is stopped. Then, the mixture is cooled while stirring, and the surface-modified magnetic nanoparticles are separated by centrifugation.

[0008] Magnetic nanoparticles and fluorescent solutions containing fluorescent markers are mixed to form magnetic fluorescent composite labeling ink.

[0009] Preferably, the fluorescent solution is formed by adding 7-amino-4-methyl coumarin into a solvent of water, ethanol, isopropyl alcohol, and adding lauromercaptoacetate, butylated hydroxyanisole, 4,4'-bis(2-sulfostyryl)-1,1'-biphenyl, citric acid as an auxiliary agent after mixing;

[0010] The raw materials in the fluorescent solution include lauromercaptoacetate 0.1-0.2 parts, butylated hydroxyanisole 0.1-0.3 parts, 7-amino-4-methyl coumarin 0.2-0.3 parts, 4,4'-bis(2-sulfostyryl)-1,1'-biphenyl 0.2-0.4 parts, citric acid 0.2-0.4 parts, isopropyl alcohol 4-8 parts, ethanol 30-45 parts, and water 50-60 parts by weight.

[0011] A preparation method of a magnetic fluorescent composite invisible marking ink, comprising,

[0012] Trivalent iron salt and divalent iron salt are dissolved in water respectively, the trivalent iron salt aqueous solution and the divalent iron salt aqueous solution are stirred at a volume ratio of 7:3, and nitrogen is introduced; NaOH aqueous solution is added dropwise, the solution becomes black after the reaction, and then NaOH aqueous solution is added dropwise to adjust the pH to a set value;

[0013] After heating, oleic acid is added, Tween reagent is added after reaction, heating is stopped, and then the surface modified magnetic nanoparticles are separated by centrifugation while stirring and cooling;

[0014] The surface modified magnetic nanoparticles are added to the fluorescent solution, stirred and mixed to form a magnetic fluorescent composite marking ink.

[0015] Preferably, the trivalent iron salt is a trivalent inorganic iron salt of the same valence, the divalent iron salt is a divalent inorganic iron salt of the same valence, the trivalent iron salt aqueous solution and the divalent iron salt aqueous solution have the same concentration, and the concentration ranges from 0.3M to 0.8M;

[0016] The volume ratio of the trivalent iron salt aqueous solution and the divalent iron salt aqueous solution is 7:3, the trivalent iron salt aqueous solution and the divalent iron salt aqueous solution are mixed, nitrogen is introduced into the solution, and the stirring time is 10-20 minutes.

[0017] Preferably, the concentration of the added NaOH aqueous solution ranges from 2M to 3M, the reaction time after the first dropwise addition is 15-20 minutes, and the pH of the NaOH aqueous solution is adjusted to 10-12.

[0018] Preferably, the volume ratio of the added oleic acid is 0.03-0.06 parts, and the reaction is carried out at 80°C for 30 minutes.

[0019] Preferably, the amount of Tween reagent added is 0.04-0.08 by volume, and stirring is performed for 1-3 hours during the cooling process.

[0020] Preferably, in step 2, the mass ratio of the raw materials is as follows: laurocapram 0.1-0.2 parts, butylated hydroxyanisole 0.1-0.3 parts, 7-amino-4-methylcoumarin 0.2-0.3 parts, 4,4'-bis(2-sulfostyryl)-1,1'-biphenyl 0.2-0.4 parts, citric acid 0.2-0.4 parts, isopropyl alcohol 4-8 parts, ethanol 30-45 parts, dissolved in 50-60 parts of water; the ultrasonic treatment time is 10 minutes, and the stirring time is 2-4 hours, to form a fluorescent solution.

[0021] Preferably, 0.8-1.2 parts by weight of magnetic nanoparticles are added to 100 parts of the fluorescent solution; the ultrasonic treatment time is 10-20 minutes, and the stirring time is 1-2 hours.

[0022] The magnetic fluorescent composite invisible marking ink is applied to paper, cloth, and the surface of skin, to perform magnetic invisible marking and fluorescent invisible marking.

[0023] Compared with the prior art, the present application has the following beneficial technical effects:

[0024] The present application provides a magnetic fluorescent composite invisible marking ink, which has both magnetic invisible marking and fluorescent invisible marking functions by adding magnetic nanoparticles and fluorescent markers, and can be applied to paper, cloth, and the surface of skin, has long-lasting magnetic marking ability, and has firm fluorescent color fastness, and the fluorescent spots do not fade after washing, and has good environmental adaptability and can be used at temperatures of-30℃ to 55℃. The invisible marking ink of the present application has both magnetic marking and fluorescent marking ability, realizes dual magnetic and fluorescent marking, and improves the invisible marking function and performance of the invisible marking ink. The patterns and spots formed by the invisible marking ink of the present application can be identified by irradiating them with an ultraviolet lamp to produce fluorescent spots, and can also be identified by detecting the markers with a magnetic detection instrument. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 A photograph of the magnetic fluorescent composite invisible marking ink and the ink diluted 10 times with water;

[0026] Figure 2 A fluorescent spectrum curve measured after the magnetic fluorescent composite invisible marking ink is diluted 100 times;

[0027] Figure 3The pattern dots formed on the surface of the cloth by the magnetic fluorescent composite hidden marking ink and the fluorescent dots displayed under the ultraviolet lamp. DETAILED DESCRIPTION

[0028] Hereinafter, only certain exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application. Therefore, the drawings and the description are considered to be exemplary in nature rather than limiting.

[0029] In the description of the present application, it needs to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0030] In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0031] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be broadly understood, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected, or it can be communicated; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication or interaction relationship of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0032] In the present application, unless specifically stated and limited otherwise, the "on" or "under" of a first feature to a second feature can include that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the "on", "above" and "over" of a first feature to a second feature includes that the first feature is directly above and obliquely above the second feature, or only means that the first feature is horizontally higher than the second feature. The "under", "below" and "underneath" of a first feature to a second feature includes that the first feature is directly above and obliquely above the second feature, or only means that the first feature is horizontally lower than the second feature.

[0033] It should be understood that the terms "comprises" and "comprising" when used in this specification and the following claims, indicate the presence of the described features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0034] It should also be understood that the terms used in the present application specification are only for the purpose of describing particular embodiments and are not intended to limit the present application. As used in the present application specification and the following claims, the singular forms "a", "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0035] It should be further understood that the term "and / or" used in the present application specification is intended to refer to any combination of one or more of the associated listed items and all possible combinations thereof, and includes these combinations.

[0036] Various structural schematic diagrams of embodiments according to the present application are shown in the accompanying drawings. These diagrams are not drawn to scale, in which certain details are exaggerated for the purpose of clarity and precision, and certain details can be omitted. The shapes of various regions, layers and their relative sizes and positional relationships shown in the drawings are only exemplary, and in actuality can be deviated due to manufacturing tolerances or technical limitations, and regions / layers with different shapes, sizes and relative positions can be additionally designed by those skilled in the art according to actual needs.

[0037] The embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0038] The invisible marking ink has wide application in anti-fake mark, invisible marking of articles, transmission of secret text, etc. The fluorescent invisible marking ink widely used at present has problems of single function, easy to be cracked and identified, etc. In order to improve the anti-fake ability and invisible marking ability of the invisible marking ink, the present application provides an ink with both magnetic invisible marking and fluorescent invisible marking. The pattern or spot marked by the ink can be detected by a magnetic detector to identify the magnetic signal of the invisible marking in addition to the identification by irradiation of ultraviolet light to generate fluorescence.

[0039] The preparation method of the magnetic fluorescent composite invisible marking ink comprises preparation of magnetic nanoparticles, addition of fluorescent markers, addition and proportioning of various additives in the ink.

[0040] The preparation process of the magnetic nanoparticles is as follows: the ferroferric oxide magnetic nanoparticles are prepared by coprecipitation method, and then the surface of the magnetic nanoparticles is modified; the magnetic nanoparticles are prepared by mixing a trivalent iron salt aqueous solution and a divalent iron salt aqueous solution at a volume ratio of (6-8):(2-4), dropping a NaOH aqueous solution to adjust the pH to a set value, adding oleic acid after heating, adding Tween reagent after reaction, and then stopping heating, stirring and cooling, and centrifugally separating the surface-modified magnetic nanoparticles.

[0041] The magnetic fluorescent composite marking ink is formed by mixing the magnetic nanoparticles and the fluorescent solution with the added fluorescent markers.

[0042] The invisible marking ink has both magnetic invisible marking and fluorescent invisible marking functions, and can be applied to the surface of paper, cloth, skin, etc. The magnetic marking ability is durable, the fluorescent color fixing is firm, the fluorescent spot does not fade after washing, and the environmental adaptability is good, and the ink can be used in the temperature range of-30℃ to 55℃. The purpose is to obtain an invisible marking ink with both magnetic marking and fluorescent marking ability, realize the dual marking of magnetism and fluorescence, and improve the invisible marking function and performance of the invisible marking ink.

[0043] The present application discloses a preparation method of a magnetic fluorescent composite invisible marking ink, comprising the following steps: step one, synthesizing and preparing magnetic nanoparticles; the ferroferric oxide magnetic nanoparticles are prepared by coprecipitation method; step two, surface modification of the magnetic nanoparticles; in order to keep the magnetic nanoparticles in the ink stable and dispersed, a surfactant is modified on the surface of the magnetic nanoparticles; step three, configuration of fluorescent reagents and various additive solutions; step four, adding the modified magnetic nanoparticles to form the final magnetic fluorescent composite invisible marking ink.

[0044] Specifically comprising the following steps:

[0045] Step 1: Synthesis of magnetic nanoparticles. A certain amount of ferric salt FeCl3-6H2O and ferrous salt FeSO4-7H2O were weighed and dissolved in water respectively, and then added to the reaction vessel, mechanically stirred, and nitrogen was introduced. After a period of time, NaOH aqueous solution was added dropwise, and after the solution turned black, the reaction was continued for a period of time, then NaOH aqueous solution was added to adjust the pH to 10-12.

[0046] Step 2: Surface modification of magnetic nanoparticles. After step 1, the reaction vessel was heated to 75-85°C, then a certain amount of oleic acid was added, and the reaction was stirred at 80°C for a period of time, then a certain amount of Tween reagent was added, the heating was stopped, and then the stirring was stopped while cooling, after a period of time, the stirring was stopped, and the surface modified magnetic nanoparticles were separated by centrifugation.

[0047] Step 3: Preparation of fluorescent reagent and various auxiliary solution. A certain amount of lauric azone, butyl hydroxy anisole, 7-amino-4-methyl coumarin, 4,4'-bis(2-sulfonic acid styryl)-1,1'-biphenyl, citric acid, ethanol, isopropyl alcohol, etc. were added to a certain amount of water, ultrasonic for a period of time, and then continue to stir for a period of time.

[0048] Step 4: Preparation of magnetic fluorescent composite marking ink. A certain amount of magnetic nanoparticles was added to the mixed solution of fluorescent reagent and auxiliary prepared in step 3, ultrasonic for a period of time, and then mechanically stirred for a period of time,

[0049] In step 1, the ferric salt FeCl3-6H2O and ferrous salt FeSO4-7H2O were dissolved in water to prepare a 0.5M aqueous solution. The ferric salt and ferrous salt can be replaced by other kinds of inorganic iron salts with the same valence, such as Fe(NO3)3, FeCl2, Fe2(SO4)3, etc.

[0050] In step 1, the ferric salt and ferrous salt were dissolved in water to form a ferric salt aqueous solution and a ferrous salt aqueous solution, and the concentrations of the ferric salt aqueous solution and the ferrous salt aqueous solution were the same, ranging from 0.3M to 0.8M. The volume ratio of the ferric salt aqueous solution to the ferrous salt aqueous solution was 7:3, and the total ratio was 10. After the solution was stirred for 10-20 minutes after nitrogen was introduced.

[0051] In step 1, the NaOH aqueous solution used for dropwise addition had a concentration of 2-3M, and the reaction time after the first dropwise addition was 15-20 minutes.

[0052] In step 2, the volume ratio of the oleic acid solution was 0.03-0.06 (calculated by volume), and the reaction was carried out at 75-85°C for 20-30 minutes.

[0053] The amount of Tween 80 added in step 2 is 0.04 to 0.08 parts by volume, and the stirring time is 1 to 3 hours.

[0054] The amounts of the various reagents added in step 3 are, by mass, 0.1 to 0.2 parts of laurocapram, 0.1 to 0.3 parts of butylated hydroxyanisole, 0.2 to 0.3 parts of 7-amino-4-methylcoumarin, 0.2 to 0.4 parts of 4,4'-bis(2-sulfostyryl)-1,1'-biphenyl, 0.2 to 0.4 parts of citric acid, 4 to 8 parts of isopropyl alcohol, and 30 to 45 parts of ethanol, dissolved in 50 to 60 parts of water. The ultrasonic treatment time is 10 minutes, and the stirring time is 2 to 4 hours.

[0055] The 7-amino-4-methylcoumarin is the fluorescent component, the laurocapram and butylated hydroxyanisole are used to adjust the mutual solubility and stability of the solution, the 4,4'-bis(2-sulfostyryl)-1,1'-biphenyl is a fixing agent that ensures that the color spots formed by the ink are not easily washed off, the citric acid is an antioxidant that improves the storage period of the ink, and the isopropyl alcohol and ethanol are cosolvents and antifreezes.

[0056] In step 4, 0.8 to 1.2 parts by mass of magnetic nanoparticles are added to 100 parts of the mixed solution of the fluorescent component and the auxiliary agent. The ultrasonic treatment time is 10 to 20 minutes, and the stirring time is 1 to 2 hours.

[0057] Example 1

[0058] FeCl3-6H2O and FeSO4-7H2O were dissolved in water to form aqueous solutions with a concentration of 0.5 M. 70 ml of the FeCl3aqueous solution and 30 ml of the FeSO4aqueous solution were added to a three-necked flask with a capacity of 200 ml, and the mixture was mechanically stirred and bubbled with nitrogen. After 15 minutes, 3 M aqueous NaOH solution was added dropwise, and the solution was allowed to turn black. After 15 minutes, additional 3 M aqueous NaOH solution was added dropwise to adjust the pH of the reaction solution to about 11. The heating device was turned on, and the temperature of the reaction solution was raised to 80°C. Then, 0.5 ml of oleic acid was added, and the mixture was stirred for 30 minutes. The heating was stopped, 0.8 ml of Tween 80 was added, and the stirring was continued for 2 hours. The cooled solution was centrifuged to separate the magnetic nanoparticles.

[0059] Laurocapram 0.2g, butylated hydroxyanisole 0.2g, 7-amino-4-methylcoumarin 0.2g, 4,4'-bis(2-sulfostyryl)-1,1'-biphenyl 0.3g, citric acid 0.2g, isopropyl alcohol 5g, ethanol 40g were added into a conical flask with a capacity of 200ml. Ultrasonic treatment was performed for 10 minutes. After 53g of water was added, mechanical stirring was performed for 2 hours. 1g of magnetic nanoparticles was added, ultrasonic treatment was performed for 10 minutes, and mechanical stirring was performed for 2 hours. A final magnetic fluorescent composite invisible marking ink was obtained.

[0060] The color and state of the prepared ink and the solution after dilution with water by 10 times are shown in Figure 1 Figure 1 It is mainly illustrated that each component of the ink solution is completely and uniformly dissolved in the solution, and the stability is good. After dilution with water, the ink can be completely miscible with water, and no precipitation occurs. The fluorescence spectrum of the solution after dilution by 100 times is shown in Figure 2

[0061] The ink was dropped onto a cotton cloth without a fluorescent substrate to form two spots with a diameter of about 10mm. After drying, no obvious pattern spots were observed on the surface of the cotton cloth under natural light. When the surface of the cotton cloth was irradiated with an ultraviolet lamp (such as a wavelength of 365nm), clear fluorescent spot patterns were observed, as shown in Figure 3 After being washed with soapy water for 30 minutes, the fluorescent spots on the surface of the cotton cloth were still clearly visible under the ultraviolet lamp. The magnetic signal at the spot on the surface of the cotton cloth could be clearly detected by a magnetic detector.

[0062] After being placed at minus 30°C for 4 hours, the magnetic fluorescent composite invisible marking ink did not freeze and solidify, and could still be used normally. After being placed at 50°C for 4 hours, the magnetic fluorescent composite invisible marking ink did not change obviously, and could still be used normally.

[0063] Example 2

[0064] FeCl3·6H2O and FeSO4·7H2O were respectively dissolved in water to prepare an aqueous solution with a concentration of 0.3M. 70ml of the FeCl3 aqueous solution and 30ml of the FeSO4 aqueous solution were added into a three-necked flask with a capacity of 200ml, mechanical stirring was performed, and nitrogen was introduced. After 10 minutes, 2M NaOH aqueous solution was added dropwise, the solution was turned black, and then 2M NaOH aqueous solution was added dropwise again, so that the PH value of the reaction solution was adjusted to about 11. A heating device was started, the reaction temperature was increased to 75°C, then 0.3ml of oleic acid was added, stirring was performed for 20 minutes, heating was stopped, 0.4ml of Tween reagent was added, and stirring was continued for 1 hour. The cooled solution was centrifuged to separate the magnetic nanoparticles.

[0065] ​​Laurocapram 0.1 g, Butylated hydroxyanisole 0.3 g, 7-amino-4-methylcoumarin 0.3 g, 4,4'-bis(2-sulfonatostyryl)-1,1'-biphenyl 0.4 g, citric acid 0.2 g, isopropyl alcohol 4 g, ethanol 30 g were taken in a conical flask of 200 ml capacity. Sonicated for 10 minutes. Mechanical stirring was carried out for 4 hours after adding 50 g of water. 0.8 g of magnetic nanoparticles were added, sonicated for 20 minutes and mechanically stirred for 2 hours. The final magnetic fluorescent composite stealthy marking ink was obtained.

[0066] Example 3

[0067] FeC13.6H2O and FeSO4.7H2O were dissolved in water separately to make 0.8 M aqueous solution. 70 ml of FeC13aqueous solution and 30 ml of FeSO4aqueous solution were taken in a three necked flask of 200 ml capacity, mechanically stirred and nitrogen gas was bubbled through. After 20 minutes, 2.5 M aqueous solution of NaOH was added drop wise. After the solution turned black, the reaction was continued for another 20 minutes. Then 2.5 M aqueous solution of NaOH was added drop wise to adjust the pH of the reaction solution to 10. Heating was switched on and the temperature of the reaction was raised to 85 °C. Then 0.8 ml of oleic acid was added and stirred for 20 minutes. Heating was switched off and 0.8 ml of Tween reagent was added and stirring was continued for 2 hours. The cooled solution was centrifuged to separate the magnetic nanoparticles.

[0068] Laurocapram 0.1 g, Butylated hydroxyanisole 0.1 g, 7-amino-4-methylcoumarin 0.2 g, 4,4'-bis(2-sulfonatostyryl)-1,1'-biphenyl 0.4 g, citric acid 0.4 g, isopropyl alcohol 8 g, ethanol 45 g were taken in a conical flask of 200 ml capacity. Sonicated for 10 minutes. Mechanical stirring was carried out for 2 hours after adding 55 g of water. 0.8 g of magnetic nanoparticles were added, sonicated for 10 minutes and mechanically stirred for 3 hours. The final magnetic fluorescent composite stealthy marking ink was obtained.

[0069] Example 4

[0070] FeC13-6H2O and FeSO4-7H2O were dissolved in water to make 0.7M aqueous solution. 70ml of FeC13 aqueous solution and 30ml of FeSO4 aqueous solution were added to a 200ml flask, mechanically stirred, and nitrogen was bubbled through. After 15 minutes, 2M aqueous NaOH solution was added dropwise. When the solution turned black, the reaction was continued for 15 minutes, and then 2M aqueous NaOH solution was added dropwise again to adjust the pH of the reaction solution to about 12. The heating device was turned on, and the reaction temperature was raised to 85°C. Then 0.6ml of oleic acid was added, and stirred for 30 minutes. The heating was stopped, 0.7ml of Tween reagent was added, and stirring was continued for 2 hours. The cooled solution was centrifuged to separate the magnetic nanoparticles.

[0071] Laurocapram 0.2g, butylated hydroxyanisole 0.2g, 7-amino-4-methylcoumarin 0.2g, 4,4'-bis(2-sulfostyryl)-1,1'-biphenyl 0.2g, citric acid 0.2g, isopropyl alcohol 4g, ethanol 30g were added to a 200ml flask. Ultrasonic was applied for 10 minutes. After 60g of water was added, mechanical stirring was applied for 2 hours. 1.2g of magnetic nanoparticles was added, ultrasonic was applied for 10 minutes, and mechanical stirring was applied for 2 hours. The final magnetic fluorescent composite invisible marking ink was obtained.

[0072] Example 5

[0073] FeC13-6H2O and FeSO4-7H2O were dissolved in water to make 0.6M aqueous solution. 70ml of FeC13 aqueous solution and 30ml of FeSO4 aqueous solution were added to a 200ml flask, mechanically stirred, and nitrogen was bubbled through. After 15 minutes, 3M aqueous NaOH solution was added dropwise. When the solution turned black, the reaction was continued for 15 minutes, and then 3M aqueous NaOH solution was added dropwise again to adjust the pH of the reaction solution to about 11. The heating device was turned on, and the reaction temperature was raised to 75°C. Then 0.6ml of oleic acid was added, and stirred for 30 minutes. The heating was stopped, 0.8ml of Tween reagent was added, and stirring was continued for 2 hours. The cooled solution was centrifuged to separate the magnetic nanoparticles.

[0074] Laurocapram 0.2g, butylated hydroxyanisole 0.2g, 7-amino-4-methylcoumarin 0.2g, 4,4'-bis(2-sulfostyryl)-1,1'-biphenyl 0.3g, citric acid 0.2g, isopropyl alcohol 5g, ethanol 40g were added to a 200ml flask. Ultrasonic was applied for 10 minutes. After 60g of water was added, mechanical stirring was applied for 2 hours. 1.2g of magnetic nanoparticles was added, ultrasonic was applied for 10 minutes, and mechanical stirring was applied for 2 hours. The final magnetic fluorescent composite invisible marking ink was obtained.

[0075] The foregoing merely illustrates the principles of the application and application of its leading features. This application is not limited to the exact details shown above, and various modifications can be made to the embodiments described without departing from the spirit or scope of the application. Accordingly, no matter from which point of view, the embodiments should be considered as exemplary and non-limiting, and the scope of the application is defined by the claims appended hereto rather than the description above, and all changes falling within the meaning and range of equivalency of the claims are intended to be embraced therein. No reference signs in the claims should be considered as limiting the scope of the claims to the features identified by the reference signs.

[0076] Furthermore, it should be understood that although the description above is based on embodiments, not every embodiment contains only one independent technical solution, and the description above is only for the sake of clarity, and those skilled in the art should consider the description as a whole, and the technical solutions in each embodiment can be properly combined to form other embodiments that those skilled in the art can understand. The above is only to illustrate the technical idea of the application, and cannot limit the protection scope of the application, and any modification made on the basis of the technical solutions according to the application falls within the protection scope of the claims of the application.

Claims

1. A magnetic fluorescent composite covert marking ink, characterized by, The ink contains magnetic nanoparticles and fluorescent markers; The preparation process of the magnetic nanoparticles is as follows: Fe3O4 magnetic nanoparticles are prepared by co-precipitation method, and the surface of the magnetic nanoparticles is modified; the magnetic nanoparticles are prepared by mixing a ferric salt aqueous solution and a ferrous salt aqueous solution in a volume ratio of 7:3, adding NaOH aqueous solution dropwise to adjust the pH to a set value, adding oleic acid after heating, adding Tween reagent after reaction, stopping heating, then stirring and cooling, and then centrifuging to separate the surface-modified magnetic nanoparticles; The magnetic fluorescent composite marker ink is formed by mixing the magnetic nanoparticles and the fluorescent solution with the fluorescent markers added; The fluorescent solution is formed by adding 7-amino-4-methyl coumarin to a solvent of water, ethanol, and isopropyl alcohol, and adding laurazidone, butylated hydroxyanisole, 4,4'-bis(2-sulfostyryl)-1,1'-biphenyl, and citric acid as auxiliary agents; The weight fractions of the raw materials in the fluorescent solution are as follows: laurazidone 0.1-0.2 parts, butylated hydroxyanisole 0.1-0.3 parts, 7-amino-4-methyl coumarin 0.2-0.3 parts, 4,4'-bis(2-sulfostyryl)-1,1'-biphenyl 0.2-0.4 parts, citric acid 0.2-0.4 parts, isopropyl alcohol 4-8 parts, ethanol 30-45 parts, and water 50-60 parts.

2. A method of preparing the magnetic fluorescent composite covert marking ink according to claim 1, characterized by, The ferric salt and the ferrous salt are dissolved in water respectively, the ferric salt aqueous solution and the ferrous salt aqueous solution are stirred in a volume ratio of 7:3, and nitrogen is introduced; NaOH aqueous solution is added dropwise, the solution turns black after the addition, then NaOH aqueous solution is added dropwise to adjust the pH to a set value; After heating, oleic acid is added, Tween reagent is added after reaction, and heating is stopped, then stirring and cooling are performed, and then surface-modified magnetic nanoparticles are separated by centrifugation; The surface-modified magnetic nanoparticles are added to the fluorescent solution, stirred and mixed to form a magnetic fluorescent composite marker ink.

3. The method for preparing a magnetic fluorescent composite latent marker ink according to claim 2, characterized in that, The ferric salt is a trivalent inorganic iron salt with the same valence, and the ferrous salt is a divalent inorganic iron salt with the same valence; the concentrations of the ferric salt aqueous solution and the ferrous salt aqueous solution are the same, and the concentration range is between 0.3M and 0.8M; The volume ratio of the ferric salt aqueous solution to the ferrous salt aqueous solution is 7:3, the ferric salt aqueous solution and the ferrous salt aqueous solution are mixed, and the stirring time after nitrogen is introduced is between 10 minutes and 20 minutes.

4. The method for preparing a magnetic fluorescent composite latent marker ink according to claim 2, characterized in that, The concentration of the added NaOH aqueous solution is between 2M and 3M, the reaction time after the first addition is between 15 minutes and 20 minutes, and the pH adjusted by the NaOH aqueous solution is between 10 and 12.

5. The method for preparing a magnetic fluorescent composite latent marker ink according to claim 2, characterized in that, In step 2, the mass ratio of each raw material is: laurocapram 0.1-0.2 parts, butylated hydroxyanisole 0.1-0.3 parts, 7-amino-4-methyl coumarin 0.2-0.3 parts, 4,4'-bis(2-sulfostyryl)-1,1'-biphenyl 0.2-0.4 parts, citric acid 0.2-0.4 parts, isopropyl alcohol 4-8 parts, ethanol 30-45 parts, dissolved in 50-60 parts of water; the ultrasonic time is 10 minutes, the stirring time is 2-4 hours, and a fluorescent solution is formed.

6. The method for preparing a magnetic fluorescent composite latent marker ink according to claim 2, characterized in that, 100 parts of the fluorescent solution is added with 0.8-1.2 parts of magnetic nanoparticles by weight; ultrasonic for 10-20 minutes, and stirring for 1-2 hours.

7. Use of a magnetic fluorescent composite covert marking ink, characterized in that The magnetic fluorescent composite invisible marking ink of claim 1 is applied to paper, cloth, and the surface of skin for magnetic invisible marking and fluorescent invisible marking.

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