A standard micro-nano plastic containing a polymerizable rare earth complex and preparation and application thereof

Abstract

The present application relates to the technical field of microplastic, and provides a standard micro-nano plastic containing a polymerizable rare earth complex and a preparation method and application thereof, the standard micro-nano plastic comprising: polymer microspheres with a particle size of 50 nm to 900 nm, a monodispersity coefficient of less than 0.4, and a molecular chain skeleton bonded with a ternary rare earth complex containing a cage structure; and the preparation method comprising: preparing the standard micro-nano plastic by one-step emulsion polymerization of a ternary rare earth complex containing a cage structure and an unsaturated carboxylic acid ligand and polymer monomers. The standard micro-nano plastic prepared by the present application can realize accurate quantitative detection and visual analysis in complex environments and biological media, and the method of the present application can be realized by only one-step polymerization reaction, is relatively more environmentally friendly, reduces cost and saves time.

Description

Technical Field

[0001] This invention relates to the field of microplastics technology, and more particularly to a standard micro / nanoplastics copolymerized with polymerizable rare earth complexes, its preparation and application. Background Technology

[0002] Microplastics refer to plastic pollutants with a diameter of less than 5 mm. Their small particle size, high specific surface area, and strong hydrophobicity make them ideal carriers of persistent organic pollutants and heavy metals. Microplastics can have toxic effects on environmental organisms, posing serious ecological risks, and can also enter the human body through the food chain, threatening human health. The small size of microplastics and their carbon-based material properties make their detection in complex environments and biological media challenging. Accurate quantitative analysis of microplastics is of great significance for studying their environmental behavior and biotoxicity.

[0003] Methods for quantitative analysis of microplastics in the environment mainly include visual inspection, spectroscopic analysis, and thermal analysis. However, these methods are affected by complex environmental backgrounds and have relatively low accuracy. Traditional fluorescent labeling suffers from fluorescent dye leakage and interference from the autofluorescence of biological tissues.

[0004] Therefore, this invention is proposed. Summary of the Invention

[0005] This invention provides a standard micro / nanoplastics copolymerized with polymerizable rare earth complexes, and its preparation and application, to address the shortcomings of existing technologies in the accurate quantitative analysis of microplastics in complex media. By using polymer microspheres with a particle size of 50–900 nm, a monodispersity index (PDI) of less than 0.4, and ternary rare earth complexes with cage-like structures bonded in their molecular chain backbone as standard micro / nanoplastics, accurate quantitative detection and visual analysis of microplastics in complex environments and biological media can be achieved.

[0006] Specifically, the present invention provides a standard micro / nanoplastics comprising: polymer microspheres with a particle size of 50 nm to 900 nm, a monodispersity index (PDI) of less than 0.4, and a ternary rare earth complex containing a cage-like structure bonded in the molecular chain backbone.

[0007] Although rare earth organic complexes have certain application potential in luminescent biolabeling materials due to their unique advantages such as high luminescence efficiency, high color purity, and high stability, research on using rare earth organic complexes for the quantitative detection of micro / nanoplastics in complex environments has not been reported. Classic rare earth fluorescent microspheres are mainly prepared by swelling or doping methods; however, these methods cannot guarantee particle dispersion, easily leading to adhesion, and there is also a certain possibility of leakage. This invention constructs polymer microspheres with a monodispersity index (PDI) below 0.4, and chemically bonds ternary rare earth complexes containing cage-like structures to their molecular chain backbone. On the one hand, the excellent fluorescence intensity of the ternary rare earth complexes is brought into play through chemical bonding, and the polymer microspheres exhibit good chemical stability (Zeta potential of ~±40mV), possessing a long fluorescence lifetime not found in conventional fluorescent dyes (meaning that time-resolved fluorescence technology can significantly reduce background interference from biological tissues), chemical stability, and low leakage resistance. On the other hand, since the ternary rare earth complexes are chemically bonded to the molecular chain backbone of the polymer microspheres, the resulting polymer microspheres have a smooth and clean surface, and the size and monodispersity of the polymer microspheres are effectively controlled. This further enables the polymer microspheres to be used as metal-labeled polymer microspheres (i.e., standard micro / nanoplastics) for research, and when qualitative and quantitative analysis is performed using inductively coupled plasma mass spectrometry (ICP-MS), they have advantages such as high sensitivity, low background interference, fast analysis speed, and good selectivity. In this invention, standard micro-nano plastics refer to plastic particles with a size of less than 5 mm and a narrow particle size distribution.

[0008] Preferably, the standard micro-nanoplastics are polystyrene polymer microspheres with a particle size of 50-500 nm and a monodispersity index (PDI) of less than 0.4; more preferably, the standard micro-nanoplastics are polymer microspheres with a particle size of 50-100 nm and a monodispersity index (PDI) of less than 0.06.

[0009] According to the standard micro-nanoplastics provided by the present invention, the ion dissolution rate of the standard micro-nanoplastics in the artificial simulation medium is less than 3%, preferably less than 2.2%; wherein, the artificial simulation medium is whole culture serum, Hoagland culture medium, artificial simulated intestinal fluid, artificial simulated gastric fluid, rhizosphere simulated fluid, or artificial cerebrospinal fluid.

[0010] According to the standard micro-nano plastic provided by the present invention, the content of rare earth elements in the standard micro-nano plastic is less than 3‰.

[0011] The complex used in this invention is a ternary rare earth complex containing a cage-like structure. Its content in the obtained standard micro-nano plastic is low. Correspondingly, the content of rare earth elements in the standard micro-nano plastic is also low. However, according to the experiment, the fluorescence performance of the standard micro-nano plastic was not affected. This shows that the method of this invention can maximize the fluorescence characteristics of rare earth complexes while reducing the adverse effects of ion dissolution on the application.

[0012] The present invention also provides a method for preparing the standard micro / nano plastics as described above, comprising: preparing the standard micro / nano plastics in one step by emulsion polymerization of a ternary rare earth complex containing a cage-like structure and an unsaturated carboxylic acid ligand and a polymeric monomer.

[0013] Compared to other existing methods for preparing polymer microspheres, such as:

[0014] Adsorption methods primarily rely on molecular forces between the carrier and the fluorescent substance. The advantages are simple operation and a mature methodology. The disadvantages are that the fluorescent substance mainly interacts with the microspheres through its surface, making it highly susceptible to external environmental and media influences; the fluorescent substance adhering to the surface may occupy functional groups and active sites on the microsphere surface, interfering with the binding of biomolecules in vivo; and the relatively weak intermolecular forces may lead to detachment.

[0015] The encapsulation method involves uniformly dispersing fluorescent substances in a medium and preparing microspheres using polymerization reactions, microencapsulation, or molecular self-assembly. These microspheres typically exhibit a distinct core-shell structure. The advantage is good chemical stability, but the disadvantages are relatively complex procedures and higher costs.

[0016] Chemical grafting typically involves reacting microspheres with functional or modified surfaces with fluorescent molecules carrying active groups, resulting in the growth of fluorescent substances on the surface of the microspheres. The advantage is that the microspheres produced are more robust than those obtained through adsorption. However, the disadvantages are similar to adsorption methods: they are significantly affected by the environmental medium, carry a risk of detachment, and the occupation of surface active sites may alter the original chemical activity.

[0017] The swelling method utilizes the swelling of polymer microspheres in a good solvent, allowing fluorescent molecules to penetrate into the microspheres. After the solvent is removed by rotary evaporation, the microspheres shrink back, preserving the fluorescent material inside. Advantages include the ability to add higher doses of fluorescent material, the ability to dope real plastics, and minimal particle size change before and after swelling. Disadvantages include the relatively environmentally unfriendly use of swelling agents and the potential for particle adhesion after swelling.

[0018] Copolymerization is a process in which rare-earth complexes with polymerizable functional groups are polymerized with organic monomers possessing polymerizable functional groups to produce polymeric microspheres. The main polymerization methods are suspension polymerization, emulsion polymerization, dispersion polymerization, and microemulsion polymerization. Advantages include uniform distribution of fluorescent substances, greater stability due to growth on a polymer backbone, and less susceptibility to environmental influences. Disadvantages include the potential impact of complex addition on particle morphology and dispersibility, particularly leading to poor monodispersity.

[0019] The present invention also found through a large number of experiments that, compared with the absence of ternary rare earth complexes, when ternary rare earth complexes containing cage-like structures are chemically bonded to the molecular chain backbone of polymer microspheres, the particle size, monodispersity and stability of the resulting polymer microspheres are almost unaffected.

[0020] According to the method for preparing standard micro / nanoplastics provided by the present invention, the polymer monomer includes one or more of styrene, methyl methacrylate, acrylic acid, glycidyl methacrylate, acrylonitrile, ethyl acrylate, acrylamide, and divinylbenzene; the ternary rare earth complex is formed by coordination of a rare earth element with a first ligand and an unsaturated carboxylic acid ligand.

[0021] The rare earth elements include one or more of the following: europium (Eu), terbium (Tb), samarium (Sm), holmium (Ho), gadolinium (Gd), yttrium (Y), lanthanum (La), dysprosium (Dy), lutetium (Lu), ytterbium (Yb), and thulium (Tm);

[0022] And / or, the first ligand comprises: 2,2'-bipyridine and / or 1,10-o-phenanthroline;

[0023] And / or, the unsaturated carboxylic acid ligands include one or more of the following: oleic acid, undecenoic acid, maleic acid, itaconic acid, linoleic acid, acrylic acid, methacrylic acid, butenoic acid, acetylacetone, and acrylonitrile.

[0024] This invention employs a ternary complex formed by a combination of unsaturated carboxylic acid ligands and rigid ligands. Firstly, the unsaturated carboxylic acid ligands provide active groups for polymerization reactions, allowing the complex to bond to the backbone of the polymer chain. Secondly, the addition of the first ligand, such as o-phenanthroline, can significantly improve the luminescence intensity of the material because o-phenanthroline undergoes a π→π reaction. * Absorption involves a singlet-to-singlet (S0→S) electronic transition followed by intersystem crossing to the triplet T1 state, and then energy transfer from the lowest excited triplet T1 state to the vibrational energy level of the rare earth ion. In addition, the synthesized complex has a cage-like structure, and the rare earth ions do not easily aggregate to form ion clusters in the center of the cage, thus making it difficult for fluorescence quenching to occur.

[0025] According to the standard micro / nano plastic preparation method provided by the present invention, when the rare earth element in the ternary rare earth complex is europium (Eu), terbium (Tb), samarium (Sm), thulium (Tm), lutetium (Lu), or holmium (Ho), the first ligand in the ternary rare earth complex is o-phenanthroline, the unsaturated carboxylic acid ligand is methacrylic acid or acrylic acid, and the polymer monomer is styrene or methyl methacrylate.

[0026] According to the preparation method of standard micro-nano plastics provided by the present invention, the process of obtaining the standard micro-nano plastics in one step by emulsion polymerization includes: firstly, adding surfactant, polymeric monomer and the ternary rare earth complex sequentially to ultrapure water, then emulsifying (e.g., emulsifying for 20-40 min using an ultrasonic cleaner), and then adding an aqueous initiator to the obtained emulsion at 60-85°C for 6-24 h.

[0027] The initiator is added in the form of an aqueous solution of the initiator;

[0028] The process of adding the initiator at 60-85℃ can be as follows: after the emulsion is put into a 250mL three-necked flask, nitrogen gas is introduced for 15min to remove the oxygen, the temperature is raised to 60-85℃, and magnetic stirring is performed at 200-600rpm / min. After adding the aqueous solution of the initiator, the polymerization reaction is continued for 6-24h.

[0029] The surfactant may be one or more of the following: sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, potassium dodecyl phosphate, polyvinylpyrrolidone, Tween-20, Span-20, polyvinyl alcohol, octadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and hexadecyltrimethylammonium bromide.

[0030] And / or, the aqueous phase initiator is one or more of azobisisobutylamidine hydrochloride, potassium persulfate, ammonium persulfate and sodium thiosulfate;

[0031] In existing technologies, polymer microspheres are generally only negatively charged. This invention, through experiments, has discovered that standard micro / nanoplastics with either positive or negative charges can be obtained by adjusting the types of surfactants and initiators. For example, when synthesizing negatively charged microspheres, the surfactant is sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, or potassium dodecyl phosphate, and the aqueous initiator is one or more of potassium persulfate, ammonium persulfate, and sodium thiosulfate. When synthesizing positively charged microspheres, the surfactant is hexadecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, or octadecyltrimethylammonium chloride, and the aqueous initiator is azobisisobutylammonium hydrochloride V50. The microspheres with different charges obtained by this invention, including both positive and negative charges, are of great significance for the research of nanotoxicology and micro / nanoplastics.

[0032] The mass ratio of the aqueous initiator to the mass of ultrapure water is 0.1% to 0.25%.

[0033] Ultrapure water is distilled water that has been filtered through an ultrapure water system.

[0034] The preparation process of the ternary rare earth complex includes: adding a rare earth ion salt solution to a ligand solution consisting of a first ligand and the unsaturated carboxylic acid ligand; wherein the rare earth ion salt solution and the ligand solution use the same organic solvent; preferably, the organic solvent includes one or more of the following: dichloromethane, chloroform, dimethyl sulfoxide, N,N-dimethylformamide, anhydrous ethanol, acetone, and acetonitrile;

[0035] More preferably, the molar ratio of the first ligand to the unsaturated carboxylic acid ligand is 1:3 to 1:5.

[0036] Further, the preparation process of the rare earth ion salt solution includes: dissolving anhydrous chloride in the organic solvent; more preferably, the molar ratio of rare earth elements in the rare earth ion salt solution to the volume ratio of the organic solvent in the rare earth ion salt solution is 0.1 mmol / mL to 0.5 mmol / mL;

[0037] The anhydrous chloride can be obtained by thoroughly mixing rare earth oxide powder with excess concentrated hydrochloric acid (e.g., concentration 37%) (volume ratio 1:2), heating to dissolve, filtering to remove insoluble matter, and evaporating to dryness.

[0038] The preparation process of the ligand solution includes: dissolving the first ligand and the unsaturated carboxylic acid ligand in the organic solvent according to the molar ratio, and adjusting the pH value to 5-8 (generally using ammonia water for adjustment); the total molar number of the first ligand and the unsaturated carboxylic acid ligand and the volume ratio of the organic solvent in the ligand solution are 0.4 mmol / mL to 0.8 mmol / mL;

[0039] The volume ratio of the rare earth ion salt solution to the ligand solution is 1:1 to 1:1.5;

[0040] The reaction temperature between the rare earth ion salt solution and the ligand solution is 50–90°C, and the reaction time is 8–12 h.

[0041] The preparation process of the ternary rare earth complex also includes post-processing, which can be as follows: after the reaction product of the rare earth ion solution and the ligand solution precipitates, it is allowed to stand for aging for 12-24 hours, the solid product is collected by filtration, washed several times with anhydrous ethanol, and then the solid powder product is transferred to a vacuum oven and dried at 50°C for 72 hours before being sealed for later use.

[0042] The experiment revealed that the particle size and monodispersity of the micro-nanoplastics could be controlled by adjusting the monomer ratio, reaction time, and surfactant concentration.

[0043] According to the method for preparing standard micro / nano plastics provided by the present invention, the volume ratio of the polymeric monomer to the ultrapure water is 1:5 to 1:20; the mass ratio of the ternary rare earth complex to the polymeric monomer is 0.5% to 1.5%; and the mass ratio of the surfactant to the ultrapure water is 0.2 mg / mL to 2 mg / mL.

[0044] To obtain micro / nanoplastics with a particle size of less than 100 nm and a monodispersity index (PDI) of less than 0.06, preferably, the volume ratio of the polymeric monomer to the ultrapure water is 1:8 to 1:20; the mass ratio of the ternary rare earth complex to the polymeric monomer is 0.5% to 1%; and the mass ratio of the surfactant to the ultrapure water is 1 mg / mL to 2 mg / mL.

[0045] The present invention also provides applications of the standard micro / nanoplastics described above.

[0046] According to the application of the standard micro-nanoplastics provided by the present invention, the standard micro-nanoplastics are used as microplastics for visualization and accurate quantitative analysis in biological organisms or artificial simulated media.

[0047] When the standard micro-nanoplastics in this invention are accurately quantified using ICP-MS technology, they can also be used in conjunction with radioactive tracer technology and time-resolved fluorescence technology.

[0048] The present invention provides standard micro / nanoplastics containing polymerizable rare earth complex copolymers, their preparation and application. By using polymer microspheres with a particle size of 50-900 nm, a monodispersity index (PDI) of less than 0.4 and ternary rare earth complexes with cage-like structures bonded in their molecular chain backbone as standard micro / nanoplastics, accurate quantitative detection and visual analysis of them in complex environments and biological media can be achieved.

[0049] This invention binds polymerizable rare earth complexes to a polymer backbone, which has relatively stable chemical properties, excellent compatibility with acid and alkali media, and low ion dissolution rate, making it suitable as a tool for metal-labeled polymer microspheres.

[0050] The method of the present invention can be applied to different emulsion formulation systems. By replacing and mixing the types of central metal atoms and ligands, the variety of rare earth-doped polymer microspheres can be greatly enriched. In particular, the polymer microspheres prepared by the present invention can have a particle size of less than 100 nm, and have excellent monodispersity and good stability.

[0051] The method of the present invention can be achieved through a single polymerization reaction, which is more environmentally friendly, reduces costs, and saves time. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0053] Figure 1 The ultraviolet absorption spectrum of the complex prepared by Preparation Example 1 of the present invention; wherein, ligand a is methacrylic acid and ligand b is o-phenanthroline;

[0054] Figure 2 The present invention provides fluorescence spectra of the complex prepared in Preparation Example 1 under different media; wherein, solution A is a 1 mol / L HCl solution and solution B is a 1 mol / L sodium hydroxide solution;

[0055] Figure 3 SEM image of the microspheres prepared in Example 1 of this invention;

[0056] Figure 4 The present invention provides fluorescence spectra of the microspheres prepared in Example 1 under different media;

[0057] Figure 5 SEM images of the polystyrene microspheres prepared in Example 2 are provided for the present invention.

[0058] Figure 6 SEM images of the polystyrene microspheres prepared in Example 3 are provided for the present invention.

[0059] Figure 7 SEM images of the polystyrene microspheres prepared in Example 5 are provided for the present invention.

[0060] Figure 8 Transmission electron microscope image of the microspheres prepared in Example 5 of this invention;

[0061] Figure 9 EDS energy spectrum of microspheres prepared in Example 5 of this invention;

[0062] Figure 10 SEM images of the polystyrene microspheres prepared in Example 6 are provided for the present invention.

[0063] Figure 11 This invention provides a laser confocal image of the microspheres prepared in Example 6 before immersion in strong acid for 72 hours;

[0064] Figure 12 This invention provides a laser confocal image of the microspheres prepared in Example 6 after immersion in strong acid for 72 hours;

[0065] Figure 13 SEM image of the microspheres prepared in Comparative Example 1 provided by the present invention. Detailed Implementation

[0066] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0067] The following is combined Figures 1-13 This invention describes standard micro / nanoplastics copolymerized with polymerizable rare earth complexes, their preparation, and applications.

[0068] Preparation of the complex in Example 1

[0069] A method for preparing a coordination compound, comprising the following steps:

[0070] (1) Dissolve rare earth europium oxide in excess concentrated hydrochloric acid (37%) (volume ratio 1:2), filter to remove insoluble matter, evaporate to dryness to form anhydrous chloride, and then disperse in an organic solvent to obtain a rare earth ion solution.

[0071] (2) Dissolve 1,10-o-phenanthroline and acrylic acid in the same organic solvent at a molar ratio of 1:3. Adjust the pH of the ligand solution to 7 by adding concentrated ammonia dropwise, and add rare earth ion solution dropwise while stirring continuously. Reflux at 60°C overnight. After the product precipitates, allow it to stand for 20 hours to collect the solid product, filter it, wash it several times with anhydrous ethanol, transfer the product to a vacuum oven, dry it at 50°C for 72 hours, and then seal it for later use.

[0072] The ultraviolet absorption spectra of the above complexes were analyzed, and the results are as follows: Figure 1 As shown in the figure, the complex exhibits absorption peaks for both ligands, indicating that the ligands and the central ion form a stable chelate.

[0073] The fluorescence properties of the above complexes in different media were analyzed, and the results are as follows: Figure 2 As shown in the figure, it can be seen that the complex itself undergoes fluorescence quenching in strong acid or strong base media.

[0074] Preparation of the complex in Example 2

[0075] A method for preparing a coordination compound, comprising the following steps:

[0076] (1) Dissolve rare earth europium oxide in excess concentrated hydrochloric acid (37%) (volume ratio 1:2), filter to remove insoluble matter, evaporate to dryness to form anhydrous chloride, and then disperse in an organic solvent to obtain a rare earth ion solution.

[0077] (2) Dissolve 2,2'-bipyridine and acrylic acid in the same organic solvent at a molar ratio of 1:4. Adjust the pH of the ligand solution to 7 by adding concentrated ammonia dropwise, and add rare earth ion solution dropwise while stirring continuously. Reflux overnight at 65°C. After the product precipitates, allow it to stand for 24 hours to collect the solid product, filter it, wash it several times with anhydrous ethanol, transfer the product to a vacuum oven, dry it at 50°C for 72 hours, and then seal it for later use.

[0078] Preparation of the complex in Example 3

[0079] A method for preparing a coordination compound, comprising the following steps:

[0080] (1) Dissolve rare earth terbium oxide in excess concentrated hydrochloric acid (37%) (volume ratio 1:2), filter to remove insoluble matter, evaporate to dryness to form anhydrous chloride, and then disperse in an organic solvent to obtain a rare earth ion solution.

[0081] (2) Dissolve 1,10-o-phenanthroline and acrylic acid in the same organic solvent at a molar ratio of 1:3. Adjust the pH of the ligand solution to 6.5 by adding concentrated ammonia dropwise, and add rare earth ion solution dropwise while stirring continuously. Reflux at 80°C overnight. After the product precipitates, allow it to stand for 18 hours to collect the solid product, filter it, wash it several times with anhydrous ethanol, transfer the product to a vacuum oven, dry it at 50°C for 72 hours, and then seal it for later use.

[0082] Preparation of Complex 4

[0083] A method for preparing a coordination compound, comprising the following steps:

[0084] (1) Dissolve rare europium oxide in excess concentrated hydrochloric acid (37%) (volume ratio 1:2), filter to remove insoluble matter, evaporate to dryness to form anhydrous chloride, and then disperse in an organic solvent to obtain a rare earth ion solution.

[0085] (2) Dissolve 1,10-o-phenanthroline and methacrylic acid in the same organic solvent at a molar ratio of 1:4. Adjust the pH of the ligand solution to 8 by adding concentrated ammonia dropwise, and add rare earth ion solution dropwise while stirring continuously. Reflux overnight at 70°C. After the product precipitates, allow it to stand for 12 hours to collect the solid product, filter it, wash it several times with anhydrous ethanol, transfer the product to a vacuum oven, dry it at 50°C for 72 hours, and then seal it for later use.

[0086] Example 1: Standard Micro / Nano Plastics

[0087] A method for preparing standard micro / nanoplastics, comprising the following steps:

[0088] (1) Sodium dodecyl sulfate was dissolved in ultrapure water (mass ratio 0.12%), and then a complex (prepared in Preparation Example 1) of 1% relative to the monomer mass was mixed with styrene monomer (monomer to ultrapure water volume 1:20) and transferred to an aqueous solution. The mixture was then ultrasonically emulsified for 30 min to obtain an emulsion.

[0089] (2) The emulsion obtained in step (1) was transferred into a reactor, N2 was introduced to remove oxygen from the system, and then heated to 70°C. 2 mL (25 mg / mL) of potassium persulfate aqueous solution was added, and the reaction was continued for 24 h under magnetic stirring at 300 rpm / min.

[0090] (3) The emulsion after polymerization in step (2) is washed several times by centrifugation with ethanol / ultrapure water to remove dispersant, oligomers and residual monomers. Then, it is re-dispersed in ultrapure water by ultrasonication to obtain negatively charged polymer microspheres.

[0091] The above polymer microspheres were tested, and the test results are as follows: Figures 3-4 As shown in the figure: Figure 3It can be concluded that the particle size is very uniform, distributed at around 53nm; Figure 4 This demonstrates that the microspheres exhibit stable fluorescence properties between pH 0 and 14, and are not quenched by strong acid or alkaline media, with the complex being stably encapsulated inside the microspheres.

[0092] Example 2: Standard Micro / Nano Plastics

[0093] A method for preparing standard micro / nanoplastics is provided, with steps essentially the same as in Example 1, except that sodium dodecyl sulfate is dissolved in ultrapure water (0.03% by mass) to obtain negatively charged polymer microspheres. These polymer microspheres are then tested, and the results are as follows: Figure 5 As shown in the figure, the particle size is very uniform, distributed at around 100nm.

[0094] Example 3 Standard Micro / Nano Plastics

[0095] A method for preparing standard micro / nanoplastics is provided, the steps of which are basically the same as in Example 1, except that sodium dodecyl sulfate is replaced with an equal mass of hexadecyltrimethylammonium bromide to obtain positively charged polymer microspheres. The polymer microspheres are then tested, and the test results are as follows: Figure 6 As shown in the figure, the particle size is very uniform, distributed at around 50nm.

[0096] Example 4: Standard Micro / Nano Plastics

[0097] A method for preparing standard micro / nanoplastics is basically the same as that in Example 3, except that the volume ratio of monomer to ultrapure water is replaced with 1:8 to obtain positively charged polymer microspheres.

[0098] Example 5: Standard Micro / Nano Plastics

[0099] A method for preparing standard micro / nanoplastics is presented, with conditions and steps essentially the same as in Example 2, except that the volume ratio of monomer to ultrapure water is replaced with 1:5. The resulting polymer microspheres are then tested, and the results are as follows: Figure 7 As shown in the figure, the particle size is very uniform, distributed at around 300nm.

[0100] Example 6 Standard Micro / Nano Plastics

[0101] A method for preparing standard micro / nanoplastics is provided, the steps of which are basically the same as in Example 1, except that the surfactant sodium dodecyl sulfate is not added. The resulting polymer microspheres are then tested, and the test results are as follows. Figure 10 As shown in the figure, the particle size distribution is around 800nm.

[0102] Example 7 Standard Micro / Nano Plastics

[0103] A method for preparing a standard micro / nanoplastics is basically the same as that in Example 1, except that the complex is replaced with the complex obtained in Preparation Example 2.

[0104] Example 8: Standard Micro / Nano Plastics

[0105] A method for preparing a standard micro / nanoplastics is basically the same as that in Example 1, except that the complex is replaced with the complex obtained in Preparation Example 3.

[0106] Example 9 Standard Micro / Nano Plastics

[0107] A method for preparing a standard micro / nanoplastics is basically the same as that in Example 1, except that the complex is replaced with the complex obtained in Preparation Example 4.

[0108] Example 10

[0109] A method for preparing micro / nanoplastics is basically the same as that in Example 1, except that the ultrapure water solvent is replaced with a mixture of water and ethanol, and sodium hexadecyl sulfate is replaced with polyvinylpyrrolidone (K-30).

[0110] Comparative Example 1

[0111] A method for preparing micro / nanoplastics is provided, the steps of which are basically the same as in Example 1, except that no complexing agent is added, while the other conditions and methods remain unchanged. The obtained polymer microspheres are tested, and the test results are as follows. Figure 13 As shown in the figure, the particle size is very uniform, distributed at around 50nm.

[0112] The average particle size and PdI of the polymer microspheres prepared in Examples 1-4 were tested using a Malvern Zetasizer Nano ZS90 particle size analyzer. The test results are as follows:

[0113]

[0114]

[0115] As can be seen from the table above, the rare earth complex fluorescent microspheres obtained by the preparation method provided by the present invention have a wide controllable size range and good monodispersity.

[0116] To investigate the ion dissolution rate of the polymer microspheres prepared in this invention in different simulated biological media, the polymer microspheres prepared in Examples 1-4 were tested using the following media (all commercially available products), and the test results are as follows:

[0117] Media type Example 1 Example 2 Example 3 Example 4 Whole culture serum 1.71％ 0.850％ 1.91％ 0.907％ Modified Hoagland medium 0.252％ 0.219％ 0.183％ 0.0039％ Artificial intestinal fluid 0.610％ 0.444％ 1.00％ 0.765％ Artificial gastric juice 1.82％ 1.187％ 1.36％ 2.12％ Rhizosphere Simulation Solution 0.140％ 1.43％ 0.362％ 2.12％ Artificial cerebrospinal fluid 0.0297％ 0.0056％ 0.034％ 0.0487％ Ultrapure water 0.765％ 1.088％ 1.32％ 0.967％

[0118] The test method for ion dissolution rate, using artificial cerebrospinal fluid as an example, is explained as follows:

[0119] 20 mg of microplastic emulsion was weighed and dispersed in 40 mL of artificial cerebrospinal fluid to obtain a final concentration of 500 μg / mL. The solution was then incubated in a shaker at 37 °C and 200 rpm for 168 h. After incubation, the solution was centrifuged three times using a Himac CP80NX ultra-high-speed centrifuge (Japan) at 40,000 rpm for 1 h. The supernatant was then filtered through a 0.22 μm pore size filter membrane.

[0120] A certain amount of supernatant was taken, and 5 mL of concentrated nitric acid was added for pre-digestion overnight. Then, the mixture was heated on a hot plate according to a programmed temperature increase: 120℃ for 10 min, 160℃ for 10 min, and 200℃ for 30 min, with hydrogen peroxide continuously added to ensure complete oxidation. After digestion, the acid was removed by hot plate treatment at 100℃ for 30 min, and the volume was brought to 10 mL. The ion dissolution rate was measured using a Thermo-X7 high-performance liquid chromatography-inductively coupled plasma mass spectrometer.

[0121] As can be seen from the table above, the standard micro-nanoplastics of this invention exhibit low ion dissolution rates (0.1% to 2.12%) in different artificial simulated media, indicating that their polymerization remains stable on the polymer backbone and that the vast majority of complexes are fully encapsulated inside the microspheres.

[0122] This also demonstrates that the standard micro / nanoplastics containing polymerizable rare earth complex copolymers in this invention have important value for quantitative analysis in biological organisms and complex environmental media, and can exist stably in strongly acidic media and complex salt solutions while maintaining a low ion dissolution rate.

[0123] Application Example 1

[0124] A quantitative analysis method for micro / nanoplastics in plants, the process of which is as follows:

[0125] Cucumber seeds were sterilized with a 1% sodium hypochlorite solution and then germinated in the dark for 4 days in an artificial climate chamber at 25°C, 60% humidity, and a photoperiod of 16h / 9h. Seeds with similar growth stages were then selected for further cultivation. Seedlings were transplanted and cultivated for 21 days in an artificial climate chamber at 25°C, 60% humidity, and a photoperiod of 16h / 9h, using 1 / 4 strength Hoagland medium, with the nutrient solution being changed regularly. When the plants developed their second true leaf, they were exposed to 10 mg / L 50 nm negatively charged Eu-PS microspheres (Example 1 microspheres) for 4 days. After harvesting, the plant roots were washed multiple times and dried in a vacuum oven at 75°C for 72h, then ground into powder for later use.

[0126] Specific masses of root and aerial powder were taken separately, and 5 mL of concentrated nitric acid was added for pre-digestion overnight. Then, the mixture was heated on a hot plate according to a programmed temperature increase: 120℃ for 10 min, 160℃ for 10 min, and 200℃ for 30 min, with hydrogen peroxide continuously added to ensure complete oxidation. After digestion, the acid was removed by hot plate treatment at 100℃ for 30 min, and the volume was adjusted to 10 mL. The dissolution rate was measured using a Thermo-X7 high-performance liquid chromatography-inductively coupled plasma mass spectrometry (HPLC-ICP-MS).

[0127]

[0128]

[0129] The Eu content in the microspheres prepared in Example 1 was 2.13‰. After deducting the elemental content of the background group, the nanoplastic content in the aboveground parts of the exposed group was 32.6476 μg, and the internalization amount in the aboveground parts of the exposed group was 6.53%. The nanoplastic content in the roots of the exposed group was 153.0442 μg, and the internalization amount in the roots of the exposed group was 30.61%. It can be seen that 37.14% of the negatively charged nanoplastics prepared in Example 1 at 10 mg / L were transferred to the cucumber plants.

[0130] This further confirms that the standard micro / nanoplastics copolymerized with polymerizable rare earth complexes in this invention are of great value for studying the migration of micro / nanoplastics in organisms and even more complex environmental media.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An application of a standard micro / nanoplastics, characterized in that, The standard micro-nanoplastics are used as microplastics for visualization and accurate quantitative analysis in biological or artificial simulated media; The artificial simulation medium is whole culture serum, Hoagland medium, artificial intestinal fluid, artificial gastric fluid, rhizosphere simulation medium, or artificial cerebrospinal fluid; The standard micro-nanoplastics are polymer microspheres with a rare earth element content of less than 3‰, which are obtained by emulsion polymerization of a ternary rare earth complex containing a cage-like structure and an unsaturated carboxylic acid ligand and a polymer monomer. The polymer microspheres have a particle size of 50~900nm, a monodispersity coefficient of less than 0.4, and a ternary rare earth complex containing a cage-like structure is bonded in their molecular chain skeleton. The polymeric monomers include one or more of the following: styrene, methyl methacrylate, acrylic acid, glycidyl methacrylate, acrylonitrile, ethyl acrylate, acrylamide, and divinylbenzene; The ternary rare earth complex is formed by coordination of rare earth elements with a first ligand and an unsaturated carboxylic acid ligand. The rare earth elements include one or more of europium, terbium, samarium, holmium, gadolinium, yttrium, lanthanum, dysprosium, lutetium, ytterbium, and thulium; The first ligand comprises: 2,2'-bipyridine and / or 1,10-o-phenanthroline; The unsaturated carboxylic acid ligands include one or more of maleic acid, itaconic acid, acrylic acid, methacrylic acid, and butenoic acid.

2. The application of the standard micro / nanoplastics according to claim 1, characterized in that, The standard micro-nanoplastics exhibit an ion dissolution rate of less than 3% in the artificial simulated medium.

3. The application of the standard micro / nanoplastics according to claim 1, characterized in that, The standard micro / nanoplastics exhibit an ion dissolution rate of less than 2.2% in the artificial simulated medium.

4. The application of the standard micro / nanoplastics according to any one of claims 1 to 3, characterized in that, The method for preparing the standard micro / nano plastic includes: preparing the standard micro / nano plastic in one step by emulsion polymerization of a ternary rare earth complex containing a cage-like structure and an unsaturated carboxylic acid ligand and a polymeric monomer.

5. The application of the standard micro / nanoplastics according to claim 4, characterized in that, When the rare earth element in the ternary rare earth complex is europium, terbium, samarium, thulium, lutetium, or holmium, the first ligand in the ternary rare earth complex is o-phenanthroline, the unsaturated carboxylic acid ligand is methacrylic acid or acrylic acid, and the polymer monomer is styrene or methyl methacrylate.

6. The application of the standard micro / nanoplastics according to claim 5, characterized in that, The process of preparing the standard micro-nano plastics by emulsion polymerization in one step includes: firstly, adding surfactant, polymeric monomer and the ternary rare earth complex sequentially to ultrapure water, then emulsifying, and then adding an aqueous initiator to the resulting emulsion at 60~85℃ for 6~24h. The surfactant is one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, potassium dodecyl phosphate, polyvinylpyrrolidone, Tween-20, Span-20, polyvinyl alcohol, octadecyltrimethylammonium bromide, dodecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, and hexadecyltrimethylammonium bromide. And / or, the aqueous initiator is one or more of azobisisobutylamidine hydrochloride, potassium persulfate, and ammonium persulfate.

7. The application of the standard micro / nanoplastics according to claim 6, characterized in that, The volume ratio of the polymeric monomer to the ultrapure water is 1:5 to 1:20; the mass ratio of the ternary rare earth complex to the polymeric monomer is 0.5% to 1.5%; and the mass ratio of the surfactant to the ultrapure water is 0.2 mg / mL to 2 mg / mL.

8. The application of the standard micro / nanoplastics according to claim 7, characterized in that, The volume ratio of the polymeric monomer to the ultrapure water is 1:10 to 1:20; the mass ratio of the ternary rare earth complex to the polymeric monomer is 0.5% to 1%; and the mass ratio of the surfactant to the ultrapure water is 1 mg / mL to 2 mg / mL.

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