Magnetic nanoparticles for flavonoid enrichment and preparation method and application thereof

Abstract

The application discloses a magnetic nanoparticle for enriching flavonoids and a preparation method and application thereof, wherein the magnetic nanoparticle comprises a magnetic core formed by ferroferric oxide and a nanoshell covering at least part of the surface of the magnetic core, wherein the nanoshell is composed of repeated polybasic ring units, and the polybasic ring unit has the following formula (I). The magnetic nanoparticle can be used for rapid and efficient purification and enrichment of flavonoids in food, and has the advantages of high efficiency, small dosage, good stability, large adsorption capacity, easy separation and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemistry, in particular to magnetic nanoparticles and a method for preparing and using the same. BACKGROUND

[0002] Magnetic solid phase extraction (MSPE) is a kind of dispersed solid phase extraction technology with magnetic or magnetizable material as adsorbent. The difference between MSPE and traditional solid phase extraction technology is that the adsorbent does not need to be filled into a solid phase extraction column, but is directly dispersed into a sample solution. The sample and the extraction material are fully contacted by means of stirring, vortexing or shaking, so that the target substance is adsorbed onto the surface of the magnetic solid phase extraction material. With the help of an external magnetic field, the magnetic solid phase extraction material and the sample are separated, and then an organic solvent is used for elution, so as to realize the separation and enrichment of the target substance. MSPE has the characteristics of high extraction efficiency, simple operation steps and wide application range, and as a new and effective sample pretreatment method, it has obtained wide attention.

[0003] Flavonoids are one of the main bioactive components in many foods and traditional Chinese medicines, and have various pharmacological and biochemical effects such as antioxidant, antibacterial, anti-vascular disease, anti-inflammatory, etc. Due to these pharmacological effects, more and more researchers have begun to pay attention to the separation and enrichment of active flavonoids from natural medicines. However, considering the complexity of natural medicine extracts, it is crucial to develop efficient and selective adsorbents.

[0004] Therefore, the adsorbents for extracting flavonoids in different sample matrices need to be further studied. SUMMARY

[0005] The present application aims to solve at least one of the technical problems existing in the prior art. To this end, one object of the present application is to propose a kind of magnetic nanoparticles, which has the advantages of good stability, large adsorption capacity and easy adsorption and separation, and is especially suitable for the adsorption and enrichment of flavonoids in complex matrices, such as foods.

[0006] Covalent organic polymers (COPs) are a class of porous organic polymers based on light elements such as C, H, N, O, which have a wide range of applications in pretreatment, catalysis, sensing, drug delivery, energy collection and other fields. In addition, magnetic materials provide a simpler and more effective alternative to traditional SPE adsorbents, eliminating the need for packaging and sample loading, enabling rapid separation of target substances in complex samples, and making up for the shortcomings of covalent organic framework materials in separation and recovery. The inventors coated a covalent organic polymer on the surface of a magnetic Fe3O4 to form an organic nanoshell with a porous structure, and used the magnetic nanoparticles to efficiently enrich flavonoids in complex samples, with strong adsorption capacity and fast adsorption speed.

[0007] Thus, according to one aspect of the present application, a magnetic nanoparticle is provided. According to an embodiment of the present application, the magnetic nanoparticle comprises: a magnetic core formed of magnetite;

[0008] a nanoshell coated on at least part of the surface of the magnetic core, the nanoshell being composed of repeated polybasic ring units, the polybasic ring units having the following formula (I).

[0009]

[0010] The magnetic nanoparticle according to the embodiment of the present application has a magnetic core of magnetite, is magnetic, and is easy to adsorb and separate, thereby solving the problems of covalent organic polymers, such as inconvenient use and difficult recycling. The nanoshell is formed of a covalent organic polymer material, has a large specific surface area and good stability, can specifically adsorb flavonoids, and is particularly suitable for adsorbing and enriching flavonoids in complex matrices, such as food and traditional Chinese medicine.

[0011] In addition, the magnetic nanoparticle according to the above-mentioned embodiment of the present application can also have the following additional technical features:

[0012] According to an embodiment of the present application, the nanoshell has a porous structure.

[0013] According to an embodiment of the present application, the nanoshell has an average pore size of 20-25 nm and a thickness of 40-50 nm.

[0014] According to an embodiment of the present application, in the X-ray powder diffraction data of the magnetic nanoparticle, the proportions of C, N, O and Fe atoms on the surface of the magnetic nanoparticle are 70-75: 10-15: 10-15: 0-5.

[0015] According to an embodiment of the present application, the particle size of the magnetic core is 50-100 nm.

[0016] According to an embodiment of the present application, the saturation adsorption capacity of the magnetic nanoparticles for flavonoids is 190-260 mg·g -1 .

[0017] According to an embodiment of the present application, the adsorption equilibrium time of the magnetic nanoparticles for flavonoids is 20 minutes.

[0018] According to an embodiment of the present application, the flavonoids are at least one selected from matricaria, oxymatricaria, xanthohumol, isoxanthohumol, hesperetin, naringenin, daidzein, glycyrrhizin, pinocembrin and formononetin.

[0019] According to another aspect of the present application, the present application provides a method for preparing the aforementioned magnetic nanoparticles. According to an embodiment of the present application, the method comprises: providing a deep eutectic solvent; and placing an aldehyde group-containing monomer, an amino group-containing monomer and a ferroferric oxide nanoparticle into the deep eutectic solvent, adding a catalyst and mixing to obtain the magnetic nanoparticles.

[0020] According to the preparation method of the embodiment of the present application, the nanoshell synthesized by the amino group-containing monomer and the aldehyde group-containing monomer is coated on the surface of the magnetic ferroferric oxide nanoparticles to form a magnetic covalent organic polymer, and the prepared magnetic nanoparticles have high yield, mild reaction conditions, simple operation, low requirement for instruments and equipment, and are easy to popularize and apply, and are suitable for industrial production.

[0021] According to an embodiment of the present application, the aldehyde group-containing monomer is 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (TFPT).

[0022] According to an embodiment of the present application, the amino group-containing monomer is 1,3,5-triaminobenzene (TAB).

[0023] According to an embodiment of the present application, the molar ratio of the amino group-containing monomer to the aldehyde group-containing monomer is 1:0.8-1.2, preferably 1:1.

[0024] According to an embodiment of the present application, the catalyst is acetic acid.

[0025] According to an embodiment of the present application, the reaction solvent is a deep eutectic solvent.

[0026] According to an embodiment of the present application, the deep eutectic solvent is formed by eutectic crystallization of a first compound and a second compound, wherein the first compound is tetrabutylammonium bromide, and the second compound is ethylene glycol, glycerol or n-butanol, preferably ethylene glycol.

[0027] According to an embodiment of the present application, the molar ratio of the tetrabutylammonium bromide to the ethylene glycol is 1:1.5-2.5, preferably 1:2.

[0028] According to an embodiment of the present application, the temperature of the stirring is room temperature, and the rotating speed is 400-1000 rpm, preferably 500-600 rpm.

[0029] According to an embodiment of the present application, the reaction temperature of the co-crystallization is 60-100℃, preferably 70-80℃.

[0030] According to an embodiment of the present application, the co-crystallization is carried out under stirring, and the stirring speed is 400-1000 rpm, preferably 500-600 rpm.

[0031] According to another aspect of the present application, the present application provides a method for adsorbing flavonoids. According to an embodiment of the present application, the method is carried out by using the aforementioned magnetic nanoparticles. Thus, the magnetic nanoparticles according to the embodiments of the present application can quickly and efficiently extract flavonoids from complex samples, and have large adsorption capacity, fast adsorption speed, and easy adsorption and separation; in addition, the pretreatment time is short, and only a small amount of organic reagent is needed to complete the adsorption and desorption of flavonoids within a few minutes, and the method has the advantages of simple operation, time saving, high efficiency, green environmental protection, etc.

[0032] According to an embodiment of the present application, the saturated adsorption capacity of the magnetic nanoparticles is 190-260 mg·g -1 .

[0033] According to an embodiment of the present application, the adsorption equilibrium time of the magnetic nanoparticles for flavonoids is 20 minutes.

[0034] According to an embodiment of the present application, the flavonoids are at least one of matatabi ketone, nor-matatabi ketone, xanthohumol, isoxanthohumol, hesperetin, naringenin, daidzein, glycyrrhizin, pinocembrin, and formononetin.

[0035] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0036] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the appended drawings.

[0037] Figure 1A and B are SEM images of Fe3O4 and Fe3O4@TAB-TFPT respectively; C and D are TEM images of Fe3O4 and Fe3O4@TAB-TFPT respectively; E is FT-IR spectrum; F is nitrogen adsorption-desorption isotherm; G is energy dispersive spectrum; H is X-ray photoelectron spectrum; I is X-ray C1 spectrum; J is thermogravimetric analysis; K is hysteresis loop; L is contact angle;

[0038] Figure 2 A is static adsorption graph, B is Freundlich model data fitting curve, C is Langmuir model data fitting curve, D is dynamic adsorption graph, E is pseudo-first-order model fitting curve, F is pseudo-second-order model fitting curve;

[0039] Figure 3 A is static adsorption graph, B is Freundlich model data fitting curve, C is Langmuir model data fitting curve, D is dynamic adsorption graph, E is pseudo-first-order model fitting curve, F is pseudo-second-order model fitting curve;

[0040] Figure 4 A is static adsorption graph, B is Freundlich model data fitting curve, C is Langmuir model data fitting curve, D is dynamic adsorption graph, E is pseudo-first-order model fitting curve, F is pseudo-second-order model fitting curve; DETAILED DESCRIPTION

[0041] Embodiments of the present application are described in detail below with reference to the attached drawings. The embodiments described below are examples of the present application and are not intended to limit the present application.

[0042] It should be noted that the terms "first", "second" are used 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. Further, in the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0043] According to one aspect of the present application, the present application provides a magnetic nanoparticle. According to an embodiment of the present application, the magnetic nanoparticle comprises: a magnetic core formed of magnetite; a nanoshell covering at least part of the surface of the magnetic core, which is composed of a repeating polybasic ring unit, and the structure of the polybasic ring unit is as follows formula (I).

[0044] It should be noted that the terms "first", "second" are used 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. Further, in the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0045] The magnetic nanoparticle according to the embodiment of the present application has magnetism and is easy to adsorb and separate by using ferroferric oxide as a magnetic core, thereby solving the problems of the covalent organic polymer, such as inconvenient operation and difficult recycling.

[0046] The nanoshell according to the embodiment of the present application has a porous network structure, and the greater the thickness, the more the layers between the repeating units of the nanoshell material, and the greater the adsorption capacity. According to the embodiment of the present application, the average pore size of the nanoshell is 20-25 nm, and the thickness is 40-50 nm. Thus, the nanoshell has a good adsorption effect on flavonoids, and the average pore size of the nanoshell is 20-25 nm, which is greater than the diameter of the target molecules, so that the spatial embedding effect can be formed between the nanoshell and the target molecules, and the flavonoids are easy to be adsorbed.

[0047] According to the embodiment of the present application, the particle size of the core is 50-100 nm. Thus, the specific surface area of the magnetic nanoparticle is large, and the adsorption capacity is strong.

[0048] According to the embodiment of the present application, in the X-ray powder diffraction data of the magnetic nanoparticle, the composition ratio of C, N, O and Fe atoms on the surface of the magnetic nanoparticle is 70-75: 10-15: 10-15: 0-5, and the surface of the magnetic nanoparticle refers to the surface of the magnetic nanoparticle that can be detected by X-ray powder diffraction.

[0049] According to the embodiment of the present application, the saturation adsorption capacity of the magnetic nanoparticle for flavonoids is 190-260 mg·g -1 Thus, the adsorption capacity of the magnetic nanoparticle is strong, and the flavonoids in the complex sample can be efficiently extracted.

[0050] According to the embodiment of the present application, the adsorption equilibrium time of the magnetic nanoparticle for flavonoids is 20 minutes. Thus, the adsorption rate of the magnetic nanoparticle is high, and the flavonoids in the complex sample can be quickly extracted.

[0051] According to the embodiment of the present application, the flavonoids are at least one selected from the group consisting of matrine, nor-matrine, xanthohumol, isoxanthohumol, hesperetin, naringenin, daidzein, glycyrrhizin, pinocembrin, and formononetin.

[0052] According to another aspect of the present application, the present application provides a method for preparing the aforementioned magnetic nanoparticles. According to the method for preparing the magnetic nanoparticles according to the embodiments of the present application, the surface of the magnetic ferroferric oxide nanoparticles is coated with a nanoshell synthesized from an amino monomer and an aldehyde monomer to form a magnetic covalent organic polymer, and the magnetic nanoparticles prepared thereby have a high yield, in some embodiments, the yield is more than 90%, and the reaction conditions are mild, the operation is simple, the equipment requirement is low, the method is easy to popularize and apply, and is suitable for industrial production.

[0053] In order to facilitate the understanding of the method for preparing the aforementioned magnetic nanoparticles, the method is explained as follows. According to the embodiments of the present application, the method comprises the following steps:

[0054] S100 providing a deep eutectic solvent

[0055] According to the embodiments of the present application, the deep eutectic solvent is provided. Due to the characteristics of the deep eutectic solvent, such as chemical inertness to water, non-toxicity, environmental protection, easy preparation, high efficiency of extracting flavonoids, and the like, the deep eutectic solvent becomes a new type of green solvent which can replace traditional organic solvents.

[0056] According to the embodiments of the present application, the deep eutectic solvent is formed by eutectic of a first compound and a second compound, wherein the first compound is a hydrogen bond acceptor, and the second compound is a hydrogen bond donor. The inventors have investigated the combination of several hydrogen bond donors (polyols, urea) and hydrogen bond acceptors (quaternary ammonium salts, such as choline chloride, tetrabutylammonium bromide). It is found that the combination of tetrabutylammonium bromide and the three alcohols is more suitable for the subsequent synthesis of magnetic nanoparticles as a solvent. According to some specific embodiments of the present application, the first compound is tetrabutylammonium bromide, and the second compound is ethylene glycol, glycerol or n-butanol, preferably ethylene glycol. Thus, the extraction effect of the magnetic nanoparticles prepared by using the aforementioned deep eutectic solvent is good, and the effect is better when the second compound is ethylene glycol.

[0057] The inventors have found that when the molar ratio of tetrabutylammonium bromide to ethylene glycol is less than 1:1.5, the eutectic reaction is too viscous, and when the molar ratio is higher than 1:2.5, the reaction is too dilute. According to the embodiments of the present application, the molar ratio of tetrabutylammonium bromide to ethylene glycol is 1:1.5-2.5, preferably 1:2. Thus, the concentration of the reaction solution of the eutectic reaction is appropriate, and the reaction efficiency is high.

[0058] According to the embodiments of the present application, the reaction temperature of the eutectic reaction is 60-100℃, preferably 70-80℃.

[0059] According to the embodiments of the present application, the eutectic reaction is carried out under stirring, and the stirring speed is 400-1000rpm, preferably 500-600rpm.

[0060] S200 mixing reaction

[0061] According to the embodiment of the present application, the aldehyde group-containing monomer, the amino monomer and the ferroferric oxide nanoparticles are placed in the deep eutectic solvent, a catalyst is added and a mixing reaction is carried out so as to obtain the magnetic nanoparticles. In this way, the aldehyde group-containing monomer and the amino monomer form imine group covalent bonds under the action of the catalyst.

[0062] According to the embodiment of the present application, the aldehyde group-containing monomer is 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (TFPT). According to the embodiment of the present application, the amino monomer is 1,3,5-triaminobenzene (TAB). The inventors compared a plurality of aldehyde group-containing monomers and amino monomers, and the polymer formed by the above aldehyde group-containing monomer and amino monomer has good adsorption effect on flavones and high recovery rate.

[0063] According to the embodiment of the present application, the molar ratio of the amino monomer to the aldehyde group-containing monomer is 1:0.8-1.2, preferably 1:1, according to the number of aldehyde groups (3) in the molecular formula of the aldehyde group-containing monomer and the number of amino groups (3) in the molecular formula of the amino monomer. In this way, the two monomers participating in the reaction can be reacted completely to the maximum extent under this ratio.

[0064] According to the embodiment of the present application, the catalyst is acetic acid. In this way, the catalytic effect is good and the reaction rate is fast. According to some embodiments of the present application, the amount of acetic acid added is 1-2 mL, preferably 1.5 mL, based on 30 mL of reaction solution. In this way, the catalytic reaction efficiency is high.

[0065] According to the embodiment of the present application, the mixing reaction is carried out under stirring.

[0066] According to the embodiment of the present application, the temperature of the stirring is room temperature and the rotation speed is 400-1000 rpm, preferably 500-600 rpm.

[0067] According to another aspect of the present application, the present application provides a method for adsorbing flavones. According to the embodiment of the present application, the method is carried out by using the aforementioned magnetic nanoparticles. In this way, the magnetic nanoparticles of the embodiment of the present application can quickly and efficiently extract flavones from complex samples, and have large adsorption capacity, fast adsorption speed and easy adsorption and separation; in addition, the pretreatment time is short, and only a small amount of organic reagent is needed to complete the adsorption and desorption of flavones in a few minutes, which has the advantages of simple operation, time saving, high efficiency, green environmental protection and the like.

[0068] According to the embodiment of the present application, the saturated adsorption capacity of the magnetic nanoparticles for flavones is 190-260 mg·g -1 . In this way, the magnetic nanoparticles have strong adsorption capacity and can efficiently extract flavones from complex samples.

[0069] According to the embodiment of the present application, the adsorption equilibrium time of the magnetic nanoparticles to flavonoids is 20 minutes. Thus, the adsorption rate of the magnetic nanoparticles is high, and flavonoids in complex samples can be quickly extracted.

[0070] According to the embodiment of the present application, the flavonoids are at least one selected from the group consisting of matrine, nor-matrine, xanthohumol, isoxanthohumol, hesperetin, naringenin, daidzein, glycyrrhizin, pinocembrin, and formononetin.

[0071] The present application will be described below with reference to specific examples, and it should be noted that these examples are merely illustrative and should not be construed as limiting the present application.

[0072] The solutions of the present application will be explained below with reference to examples. Those skilled in the art will understand that the following examples are only for illustrating the present application, and should not be considered as limiting the scope of the present application. If the specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art or according to the product manual are used. If the reagents or instruments are not specified by the manufacturer, they are all conventional products that can be purchased, for example, from Sigma.

[0073] Example 1

[0074] In this example, 1,3,5-triaminobenzene was used as an amino monomer, and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine was used as an aldehyde monomer to prepare magnetic nanoparticles, and the specific method is as follows:

[0075] (1) Tetra-n-butylammonium bromide and ethylene glycol (DESs-1: TBAB / EG), tetra-n-butylammonium bromide and glycerol (DESs-2: TBAB / DG), and tetra-n-butylammonium bromide and n-butanol (DESs-3: TBAB / CA) were respectively added to round-bottom flasks, heated in a constant-temperature water bath at 80°C, and mechanically stirred at 500 rpm for 30 min until a uniform transparent liquid was formed. Finally, the three solutions were dried at 60°C for 12 h.

[0076] (2) Fe3O4 (0.43 mmol, 100 mg), 1,3,5-triaminobenzene (0.2 mmol, 24.6 mg), and 2,4,6-tris(4-formylphenyl)-1,3,5-triazine (0.2 mmol, 78.6 mg) in a double-necked round-bottom flask (100 mL) were respectively dispersed or dissolved in 15 mL of the three deep eutectic solvents prepared in step (1) to obtain three uniform solutions.

[0077] (3) 1.5 mL of acetic acid was added as a catalyst to accelerate the reaction in each of the three flasks obtained in step 2, and mechanical stirring was performed at room temperature at a rotation speed of 500 rpm for 10 h.

[0078] (4) With the help of an external magnet, the magnetic ink green precipitate obtained in each flask was washed with MeOH and ACN alternately until the supernatant was clear.

[0079] (5) The three bottles of precipitate were dried in an oven at 60°C for 12 h (yield ≥ 90%) to obtain the magnetic black-green powder particles Fe3O4@TAB-TFPT, as shown in the reaction formula Figure 4 .

[0080] Example 2

[0081] This example is directed to the characterization of the magnetic nanoparticles (Fe3O4@TAB-TFPT) prepared in Example 1 using tetrabutylammonium bromide and ethylene glycol (DESs-1: TBAB / EG) deep eutectic solvents to demonstrate the successful preparation of the magnetic nanoparticles and their excellent physical and chemical properties. The specific content is as follows:

[0082] 1. The morphology and internal structure of Fe3O4 nanoparticles and magnetic COPs were observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the results are shown in Figure 1 A and Figure 1 B, and the structure of Fe3O4 nanoparticles and magnetic COPs is regular.

[0083] In addition, the diameter of the Fe3O4 nanoparticles is about 50-100 nm, and in comparison, the diameter of the magnetic COPs is increased by about 50 nm. As can be seen from Figure 1 D, Fe3O4@COPs has a clear core-shell structure, with the internal black solid as the magnetic core, indicating that the adsorbent has good magnetism. The outer light gray coating is the COPs coating, and compared with Figure 1 C, the core-shell thickness of the magnetic COPs is about 50 nm, indicating that the COPs modification on the magnetic core is successful, which is also the key to ensuring that the adsorbent can adsorb the target.

[0084] 2. The chemical structure and composition of Fe3O4 and magnetic nanoparticles Fe3O4@TAB-TFPT were analyzed by Fourier transform infrared spectroscopy, and the results are shown in Figure 1 E, and the transmittance of the particles was measured in the range of 4000 to 500 cm -1 -1. The FT-IR result (curve 4) of the new material shows a characteristic absorption band at 576 cm -1 -1 attributed to Fe-O-Fe vibration of Fe3O4 nanoparticles (curve 1). At the same time, in the range of 1580 cm -1A new absorption peak was observed, which can be attributed to C=N stretching vibration, indicating the conversion of C=O (TFPT, curve 3) and N-H (TAB, curve 2) to C=N groups. In addition, the two characteristic peaks of TFPT at 2730 cm -1 and 2850 cm -1 were attributed to C-H stretching vibration of -CHO groups, which were not present in the new material Fe3O4@TAB-TFPT, indicating the successful synthesis of the material.

[0085] 3、The gas adsorption isotherms were studied by nitrogen adsorption-desorption experiments, and the results are shown in Figure 1 F, Fe3O4@TAB-TFPT is a typical type IV isotherm with mesoporous characteristics. The calculated BET specific surface area and pore volume of Fe3O4@TAB-TFPT are 12.77 m 2 / g and 0.023 cm 3 / g, respectively. The average pore size of M-COPs is 23.54 nm.

[0086] 4、As shown in Figure 1 G and H, the chemical composition of the generated M-COPs was evaluated by EDS and XPS analysis, and the data obtained by the two methods were compared (Table 1), which showed that the content of Fe atoms was low, further confirming that the surface of Fe3O4 was coated with a new material. The XPS (C1s) spectrum Figure 1 I) had peaks at 284.8 eV related to C=C bonds, 287.0 eV for C-C bonds, 290.8 eV for N-C=N bonds, and 291.1 eV for C=N-C bonds, confirming the successful synthesis of Fe3O4@TAB-TFPT.

[0087] Table 1 Elemental analysis results of M-COPs

[0088]

[0089] 5、The thermal stability of M-COPs at 30-800℃ was studied by thermogravimetric analysis and differential thermal analysis Figure 1 J): at 196.26℃, solvent volatilization resulted in a weight loss of 9.917%; at 390.77℃, the weight loss rate was 4.894%, at 474.83℃, the weight loss rate was 7.40%, and at 668.17℃, the weight loss rate was 8.67%, corresponding to three upward peaks on the DTA curve, which may be due to the thermal decomposition of abnormal structures; when the temperature was in the range of 700-800℃, the TGA curve showed a weight loss of 20.01%, which matched the upward exothermic peak on the DTA curve. It is speculated that this phenomenon is due to the degradation and carbonization of the material.

[0090] 6. The magnetic properties of the prepared Fe3O4 nanoparticles and M-COPs were characterized using a vibrating sample magnetometer: the saturation magnetization values ​​of Fe3O4 and Fe3O4@TAB-TFPT were 84.8 and 41.6 emu / g, respectively. Figure 1 With the aid of an external magnet, the phase separation of M-COPs from the solution can be completed within 30 seconds, meeting the requirements for rapid sample preparation.

[0091] 7. The hydrophobicity of the M-COPs surface was studied using a video optical contact angle meter: the water contact angle was 23.1°. Figure 1 L) indicates that the material can be well dispersed in the sample solution.

[0092] Example 3

[0093] The feasibility of adsorption and extraction of four flavonoids using the magnetic nanoparticles (Fe3O4@TAB-TFPT) prepared in Example 1 was investigated, as detailed below:

[0094] Experiments confirmed that Fe3O4@TAB-TFPT can be used as an adsorbent for extracting flavonoids. The adsorption performance of this material for different concentrations of flavonoids at different times was investigated. The high adsorption capacity of these compounds can be attributed to van der Waals forces and the strong interaction between COPs and the target analytes. This example studies the adsorption of flavonoids on the Fe3O4@TAB-TFPT adsorbent.

[0095] For the adsorption isotherm experiment, 1 mg of Fe3O4@TAB-TFPT was added to 5 mL of four flavonoid compounds (0-80 μg·mL). -1 The sample was placed in a container and shaken. The maximum adsorption capacity of Fe3O4@TAB-TFPT for four flavonoids was calculated.

[0096] Experimental results are as follows Figure 2 As shown in Figure A, when the amount of adsorbent is 1.0 mg, the adsorption capacity of the magnetic adsorbent for flavonoids ranges from 0 to 80 μg·mL. -1 Within the concentration range, the adsorption capacity increases with increasing concentration. Experiments showed that the saturated adsorption capacity of the material for matrine, oxymatrine, fulvicol, and isoflavone reached 194.75, 240.75, 253.00, and 243.83 mg·g, respectively. -1 The adsorption isotherms were determined using both the Freundlich and Langmuir models.

[0097] Figure 2 B and C are two simulated curves of the adsorption process of these four flavonoids. The parameters of the model adsorption isotherms are shown in Table 2. The results show that the Freundlich model (R) 2 (≥0.983) is more suitable than the Langmuir model (R2 The results show that the adsorption sites on the surface of the adsorbent are heterogeneous, and the adsorption process involves a multilayer adsorption mechanism.

[0098] Table 2 Correlation parameters of Langmuir model and Freundlich model

[0099]

[0100] Example 4

[0101] Kinetics is to study the concentration of adsorbate molecules involved in the adsorption process on the adsorption rate, and the kinetic model is an equation used to describe the adsorption process on the basis of kinetics and actual situation. In the process of solid-liquid adsorption, the equations commonly used to describe the adsorption rate are pseudo-first-order kinetic equation and pseudo-second-order kinetic equation.

[0102] According to the R 2 It can be compared that the linear correlation coefficient (R 2 ≥0.9998) of the pseudo-second-order adsorption kinetic model is closer to 1 than the linear correlation coefficient (R 2 ≤0.986) of the pseudo-first-order adsorption kinetic model, and the equilibrium adsorption capacity measured in the experiment is closer to the equilibrium adsorption capacity calculated by the pseudo-second-order adsorption kinetic model. Therefore, the adsorption process of the magnetic COPs adsorbent to flavonoids can be described by the pseudo-second-order kinetic model, which indicates that there are double-bonding sites on the surface of the adsorbent, and emphasizes that the adsorption process is not only affected by material transport, but also by chemical adsorption.

[0103] Table 3 Correlation parameters of pseudo-first-order kinetic model and pseudo-second-order kinetic model

[0104]

[0105] Example 5

[0106] In this embodiment, the recovery rate of the magnetic nanoparticles prepared in Example 1 is compared, and the method is as follows:

[0107] (1) 5 mg of each of the three kinds of magnetic nanoparticles prepared based on three different deep eutectic solvents in Example 1 was weighed, and was placed in a 40 mL transparent glass vial together with 5 mL of a sample solution with a standard addition, and then was rapidly oscillated at a speed of 2000 rpm for 10 min.

[0108] (2) The magnetic nanoparticles were adsorbed under the magnetic force of an external strong magnet, and the supernatant was discarded.

[0109] (3) The target analyte was desorbed for 3 min using 3 mL of 75% ethanol under sonication.

[0110] (4) 1 mL of the supernatant was filtered through a 0.22 μιη filter and analyzed using HPLC-MS / MS.

[0111] It was detected that the extraction recovery rates of the materials synthesized by DESs-1, DESs-2, and DESs-3 for the four flavones were 89.13-93.37%, 64.4-90.3%, and 63.4-92.4%, respectively, as shown in Table 2. Figure 3 The results show that the Fe3O4@TAB-TFPT nanoparticles prepared by using DESs-1 (TBAB / EG) have better extraction effect.

[0112] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0113] Although the embodiments of the present application have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made thereto without departing from the principles and spirit of the present application, and the scope of the present application is defined by the claims and their equivalents.

Claims

1. A magnetic nanoparticle, characterized in that, Comprise: a magnetic core formed of ferroferric oxide; a nanoshell covering at least a part of a surface of the magnetic core, the nanoshell being composed of a repeating polybasic ring unit, the polybasic ring unit having a structural formula of Formula (I); the nanoshell has a porous structure, the nanoshell has an average pore diameter of 20-25 nm and a thickness of 40-50 nm; The saturation adsorption amount of the magnetic nanoparticle for flavonoids is 190-260 mg·g -1 ; a method for preparing the magnetic nanoparticle comprises: providing a deep eutectic solvent; and placing an aldehyde group-containing monomer, an amino group-containing monomer, and a ferroferric oxide nanoparticle in the deep eutectic solvent, adding a catalyst, and performing a mixing reaction to obtain the magnetic nanoparticle; the aldehyde group-containing monomer is 2,4,6-tris(4-aldehyde phenyl)-1,3,5-triazine (TFPT), the amino group-containing monomer is 1,3,5-triaminobenzene (TAB), a molar ratio of the amino group-containing monomer to the aldehyde group-containing monomer is 1:0.8-1.2; the deep eutectic solvent is formed of a first compound and a second compound, wherein the first compound is tetrabutylammonium bromide, and the second compound is ethylene glycol, glycerol, or n-butanol; the catalyst is acetic acid; the mixing reaction is performed under stirring at a temperature of room temperature and a rotation speed of 400-1000 rpm; the flavonoid compound is at least one selected from the group consisting of matrine, oxymatrine, xanthohumol, isoxanthohumol, hesperetin, naringenin, daidzein, glycyrrhizin, pinocembrin, and formononetin.

2. The magnetic nanoparticle of claim 1, wherein, In X-ray powder diffraction data, the magnetic nanoparticle has a composition ratio of C, N, O, and Fe atoms on the surface of the magnetic nanoparticle of 70-75:10-15:10-15:0-5.

3. The magnetic nanoparticles according to claim 1, characterized in that, The magnetic core has a particle size of 50-100 nm.

4. The magnetic nanoparticle of claim 1, wherein the adsorption equilibrium time of the magnetic nanoparticle for the flavonoid compound is 20 minutes.

5. The magnetic nanoparticles according to claim 1, characterized in that, The molar ratio of the amino group-containing monomer to the aldehyde group-containing monomer is 1:

1.

6. The magnetic nanoparticle of claim 1, wherein, The rotation speed is 500-600 rpm.

7. The magnetic nanoparticle of claim 1, wherein the first compound is tetrabutylammonium bromide, and the second compound is ethylene glycol, a molar ratio of the tetrabutylammonium bromide to the ethylene glycol is 1:1.5-2.

5.

8. The magnetic nanoparticle of claim 1, wherein, The molar ratio of the tetrabutylammonium bromide to the ethylene glycol is 1:

2.

9. A method of adsorbing flavonoids, characterized by, The method is performed using the magnetic nanoparticle of any one of claims 1-8, The saturation adsorption amount of the magnetic nanoparticle is 190-260 mg·g -1 , the adsorption equilibrium time of the magnetic nanoparticle for the flavonoid compound is 20 minutes, the flavonoid compound is at least one selected from the group consisting of matrine, oxymatrine, xanthohumol, isoxanthohumol, hesperetin, naringenin, daidzein, glycyrrhizin, pinocembrin, and formononetin.

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