Carboxylate rare earth complexes, composites, and methods of making and using the same

Abstract

The application discloses a carboxylic acid rare earth complex, a composite material, and a preparation method and application thereof. The carboxylic acid rare earth complex is formed by complexing a carboxylic acid shown in formula (I) with a rare earth element. The composite material prepared by combining the carboxylic acid rare earth complex with a silane coupling agent and silicon dioxide can sensitively detect polychlorinated biphenyl.

Description

Technical Field

[0001] This invention relates to a rare earth carboxylic acid complex, a composite material, its preparation method, and its uses. Background Technology

[0002] Polychlorinated biphenyls (PCBs) are chlorobiphenyl compounds formed by replacing hydrogen atoms in biphenyl with varying numbers of chlorine atoms. Due to their stable physicochemical properties, they are widely used as insulating oils, heat transfer fluids, and lubricants, and also as additives in various industrial products (such as resins, rubbers, binders, coatings, carbon paper, ceramic glazes, fire retardants, pesticide retardants, and dye dispersants). PCBs are widely present in the atmosphere, soil, and water, and can accumulate in organisms through the food chain. Because of their toxicity and carcinogenicity, PCBs pose a significant threat to biological health. Therefore, monitoring and controlling PCBs in the environment is extremely important.

[0003] Currently, PCB inspection is mostly performed using testing instruments. However, these instruments are often expensive, require professional operators, involve complex procedures and high costs, and their sensitivity needs improvement. Therefore, developing a simple yet highly sensitive PCB inspection method is of great significance.

[0004] Rare earth elements, due to their unique 4f electron shell structure, exhibit abundant separated energy levels and long-lived excited states, resulting in exceptionally strong absorption and transfer capabilities for radiation. Therefore, rare earth elements can be used as various spectroluminescent and laser materials. Rare earth complexes possess advantages such as narrow spectral bands, high color purity, and stable physicochemical properties, and are frequently used as fluorescent probe materials. The luminescence principle of rare earth complexes involves the absorption of energy by organic ligands, followed by intramolecular energy transfer to rare earth ions, sensitizing them to emit light. This method is known as the "antenna effect."

[0005] CN106432295A discloses a method that can be used for Eu 3+ A sensitized luminescent metal-organic framework. This luminescent metal-organic framework is prepared by a solvothermal method using a cadmium salt and a 2,5-bis-(3,5-dicarboxyphenyl)thiophene dicarboxamide (H4L) ligand. The luminescent metal-organic framework itself does not contain rare earth elements and is used for sensitization of rare earth elements.

[0006] CN106190103A discloses an oleophilic silica rare-earth fluorescent nanomaterial. This fluorescent material is prepared by coordinating rare-earth ions with alkyl / carboxyl-modified nano-silica as ligands and adding small organic molecules as co-ligands in an organic solvent. The alkyl / carboxyl-modified nano-silica is prepared by modifying nano-silica with aminosilane coupling agents and alkylsilane coupling agents, followed by reaction with aromatic carboxylic acids or their derivatives. This oleophilic silica rare-earth fluorescent nanomaterial is mainly used in fluorescent anti-counterfeiting inks.

[0007] CN101735216A discloses a europium complex silica fluorescent nanoparticle. This fluorescent nanoparticle uses a europium rare-earth fluorescent complex as its core, with amino-containing silica coating the complex to form a core-shell fluorescent nanoparticle structure. The use of 4,7-diphenyl-1,10-phenanthroline-2,9-dicarboxylic acid as a ligand to encapsulate silica in this core-shell structure easily leads to particle inhomogeneity and agglomeration.

[0008] Existing rare earth complexes often have drawbacks such as large size and easy agglomeration, which affect their stability in applications. Summary of the Invention

[0009] In view of this, one object of the present invention is to provide a rare earth carboxylate complex, which, together with a silane coupling agent and silica, forms a composite material with a detection limit of up to 12 μM for polychlorinated biphenyls (PCBs), which can be used for sensitive detection of PCBs. Another object of the present invention is to provide a method for preparing the above-mentioned rare earth carboxylate complex. A further object of the present invention is to provide a composite material. Yet another object of the present invention is to provide a method for preparing the above-mentioned composite material. Still another object of the present invention is to provide a use for the above-mentioned composite material.

[0010] The present invention achieves the above objectives using the following technical solutions.

[0011] On the one hand, the present invention provides a rare earth carboxylic acid complex, which is formed by complexing carboxylic acid with rare earth element ions; wherein,

[0012] The carboxylic acid has a structure as shown in formula (I):

[0013]

[0014] R1, R2, R3, and R4 are each independently selected from hydrogen or C1 to C6 alkyl groups.

[0015] According to the rare earth carboxylic acid complex of the present invention, preferably, the rare earth element ion is selected from La. 3+ Ce 3+ 、Sm3 + Eu 3+ Gd 3+ 、Tb 3+ Dy 3+ Y 3+ At least one of them.

[0016] According to the rare earth carboxylic acid complex of the present invention, preferably, the rare earth carboxylic acid complex is obtained by reacting the carboxylic acid of formula (I) with a compound containing rare earth elements; wherein, the molar ratio of the carboxylic acid of formula (I) to the rare earth elements in the compound containing rare earth elements is 1:(1-6).

[0017] On the other hand, the present invention also provides a method for preparing the above-mentioned rare earth carboxylic acid complex, comprising the following steps:

[0018] The carboxylic acid shown in formula (I) is reacted with a compound containing rare earth elements under solvent and acidic conditions to prepare a rare earth carboxylic acid complex.

[0019] The rare earth element-containing compound is selected from at least one of rare earth element oxides and rare earth element inorganic salts.

[0020] The solvent includes solvent A and solvent B; solvent A is selected from at least one of acetonitrile, tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; solvent B is selected from at least one of water and C1-C5 alkyl alcohols.

[0021] The reaction temperature is 80–150℃.

[0022] According to the preparation method of the present invention, preferably, the preparation method of the carboxylic acid represented by formula (I) includes the following steps:

[0023] 1) Add titanium chloride, reducing agent, and compound (II) to the first solvent and mix to allow the compound (II) to undergo a McMurry coupling reaction to obtain intermediate product A.

[0024]

[0025] R1 and R2 are each independently selected from hydrogen or C1 to C6 alkyl groups; R5 and R6 are each independently selected from C1 to C6 alkyl groups.

[0026] The first solvent is selected from at least one of acetonitrile, tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide;

[0027] 2) Intermediate product A and boron halide are added to a second solvent to react and obtain intermediate product B;

[0028] The second solvent is selected from at least one of haloalkanes;

[0029] 3) Add the alkali metal alkoxide to the third solvent to carry out the first reaction; then add intermediate product B to carry out the second reaction; then add the compound shown in formula (III) to carry out the third reaction to obtain intermediate product C;

[0030]

[0031] R3 and R4 are each independently selected from hydrogen or C1-C6 alkyl groups; R7 is selected from C1-C6 alkyl groups; X1 is a halogen;

[0032] The third solvent is selected from at least one of acetonitrile, tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide;

[0033] 4) The alkali metal hydroxide and intermediate product C are added to the fourth solvent to react. After the reaction, the organic solvent is removed and acid is added to prepare the carboxylic acid shown in formula (I).

[0034] The fourth solvent includes solvent C, solvent D, and solvent E; solvent C is selected from at least one of acetonitrile, tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; solvent D is selected from at least one of C1 to C5 alkyl alcohols; and solvent E is water.

[0035] In another aspect, the present invention also provides a composite material, which is formed by coating the above-mentioned rare earth carboxylic acid complex onto the surface of silicon dioxide with a silane coupling agent.

[0036] In the composite material according to the present invention, preferably, the silane coupling agent is selected from at least one of N-(β-aminoethyl-γ-aminopropyl)methyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, vinyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, and γ-mercaptopropyltriethoxysilane.

[0037] In another aspect, the present invention also provides a method for preparing the above-mentioned composite material, comprising the following steps:

[0038] A) Immerse silica in a weakly alkaline aqueous solution and let it stand for 1–12 hours, then filter, wash and dry the silica; wherein the weakly alkaline aqueous solution is selected from at least one of ammonia, alkali metal carbonate aqueous solution and alkali metal bicarbonate aqueous solution.

[0039] B) Place the dried silica and silane coupling agent from step A) into a C1-C5 alkyl alcohol and react at 50-120°C to obtain silica with a surface coated by the silane coupling agent.

[0040] C) The silica with a surface coated with silane coupling agent obtained in step B) and the above-mentioned rare earth carboxylic acid complex are placed in a C1-C5 alkyl alcohol and reacted at 50-120°C to obtain a composite material.

[0041] According to the preparation method of the present invention, preferably, in step C), the reaction is carried out under conditions of pH 6 to 8.

[0042] In another aspect, the present invention also provides the use of the above-mentioned composite material in the detection of polychlorinated biphenyls.

[0043] This invention involves complexing the polypodylic acid shown in Formula (I) with rare earth elements to form carboxylic acid rare earth complexes. The coordination bonds formed between the polypodylic acid shown in Formula (I) and the rare earth center are strong and diverse, allowing for the synthesis of various carboxylic acid rare earth complexes with large pore sizes and multidimensional structures. The composite material prepared by combining this carboxylic acid rare earth complex with a silane coupling agent and silica exhibits a detection limit of up to 12 μM for polychlorinated biphenyls (PCBs), enabling sensitive detection of PCBs. Furthermore, the prepared composite material demonstrates good stability and recyclability. Attached Figure Description

[0044] Figure 1 The preparation route for tetra-(4-carboxy-1-methyleneoxy-(1,1-biphenyl))ethylene (H4L) in Example 1 is shown in the diagram.

[0045] Figure 2 This is a flowchart illustrating the preparation process of the composite material (SiO2@WD-53@L-Eu) in Example 1.

[0046] Figure 3 The XPS spectra of the composite material SiO2@WD-53@L-Eu in Experimental Example 1 are shown below; where a is the total spectrum, b is the C1s spectrum, c is the O1s spectrum, and d is the Eu3d spectrum.

[0047] Figure 4 The images are TEM images of the composite material SiO2@WD-53@L-Eu in Experiment Example 1 at different magnifications; where a is the TEM image at a 500 nm scale, b is the TEM image at a 100 nm scale, c is the TEM image at a 50 nm scale, and d is the core-shell structure schematic diagram of the TEM image at a 50 nm scale.

[0048] Figure 5The image shows the TEM elemental mapping of the composite material SiO2@WD-53@L-Eu in Experimental Example 1 on an 80 nm scale; where e is the mapping image of the composite material SiO2@WD-53@L-Eu, f is the mapping image of element Si, g is the mapping image of element O, h is the mapping image of element C, i is the mapping image of element N, and j is the mapping image of element Eu.

[0049] Figure 6 The image shown is the infrared spectrum from Experiment Example 1.

[0050] Figure 7 The fluorescence spectra of the composite material SiO2@WD-53@L-Eu after adding different amounts of 2,2',5-trichlorobiphenyl solution in Experiment Example 2 are shown.

[0051] Figure 8 The fluorescence spectra of the composite material SiO2@WD-53@L-Eu after adding different amounts of 2,2',5,5'-tetrachlorobiphenyl solution in Experimental Example 2 are shown.

[0052] Figure 9 The fluorescence spectra of the composite material SiO2@WD-53@L-Eu after adding different amounts of 2,2',4,4',5,5'-hexachlorobiphenyl solution in Experimental Example 2 are shown.

[0053] Figure 10 The fluorescence intensity of the composite material SiO2@WD-53@L-Eu in Experiment Example 3 at an emission wavelength of 616 nm during four fluorescence quenching experiments. Detailed Implementation

[0054] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0055] <Rare Earth Carboxylic Acid Complexes>

[0056] The rare earth carboxylic acid complex provided by this invention is formed by the complexation of carboxylic acid with rare earth element ions; wherein...

[0057] The carboxylic acid has a structure as shown in formula (I):

[0058]

[0059] In formula (I), R1, R2, R3, and R4 can be independently selected from hydrogen or C1-C6 alkyl groups; preferably hydrogen or C1-C3 alkyl groups; more preferably hydrogen or C1-C3 n-alkyl groups. Most preferably, R1, R2, R3, and R4 are all hydrogen.

[0060] According to a specific embodiment of the present invention, the carboxylic acid represented by formula (I) has the following structure:

[0061]

[0062] In this invention, the C1 to C6 alkyl groups may include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, methylbutyl, ethylpropyl, hexyl, methylpentyl, dimethylbutyl, and ethylbutylene.

[0063] According to one embodiment of the present invention, rare earth element ions may be selected from La 3+ Ce 3+ 、Sm 3+ Eu 3+ Gd 3+ 、Tb 3 + Dy 3+ Y 3+ At least one of the following; preferably Ce 3+ 、Sm 3+ Eu 3+ Gd 3+ 、Tb 3+ Dy 3+ At least one of them; more preferably Sm 3 + Eu 3+ 、Tb 3+ Dy 3+ At least one of them.

[0064] According to one embodiment of the present invention, the carboxylic acid rare earth complex is obtained by reacting the carboxylic acid represented by formula (I) with a rare earth-containing compound.

[0065] The molar ratio of the carboxylic acid shown in formula (I) to the rare earth element in the rare earth compound can be 1:(1-6); preferably 1:(1-5); more preferably 1:(2-5).

[0066] The rare earth element compound can be selected from at least one of rare earth element oxides and rare earth element inorganic salts; preferably, it is at least one of rare earth element nitrates, sulfates, phosphates, acetates, carbonates, halides, and oxides; more preferably, it is at least one of rare earth element nitrates, acetates, halides, and oxides. The rare earth element inorganic salt of the present invention can be either anhydrous or hydrated.

[0067] A reasonable carboxylic acid structure and a reasonable ratio of carboxylic acid to rare earth elements are more conducive to the formation of structurally stable carboxylic acid rare earth complexes.

[0068] <Preparation Methods of Carboxylic Acid Rare Earth Complexes>

[0069] This invention also provides a method for preparing the carboxylic acid rare earth complex as described above, comprising reacting a carboxylic acid of formula (I) with a rare earth element compound under solvent and acidic conditions to obtain the carboxylic acid rare earth complex. It also includes a preparation step of the carboxylic acid of formula (I). A detailed description follows.

[0070] According to one embodiment of the present invention, the solvent includes solvent A and solvent B.

[0071] Solvent A may be selected from at least one of acetonitrile, tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; preferably at least one of tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; more preferably at least one of tetrahydrofuran, dimethylformamide, and dimethylacetamide.

[0072] Solvent B may be selected from at least one of water and C1 to C5 alkyl alcohols; preferably at least one of water and C1 to C3 alkyl alcohols; more preferably at least one of water and C1 to C3 n-alkyl alcohols. Examples of C1 to C5 alkyl alcohols include, but are not limited to, methanol, ethanol, isopropanol, n-butanol, 1-pentanol, and 2-pentanol.

[0073] The volume ratio of solvent A to solvent B can be (1-5):1, preferably (1-3):1, and more preferably (1.5-3):1.

[0074] According to one embodiment of the present invention, the molar ratio of the carboxylic acid shown in formula (I) to the rare earth element in the compound can be 1:(1-6); preferably 1:(1-5); more preferably 1:(2-5).

[0075] According to one embodiment of the present invention, the reaction temperature can be 80–150°C; preferably 90–140°C; more preferably 95–140°C.

[0076] According to another embodiment of the present invention, the reaction time can be 1 to 12 hours; preferably 2 to 10 hours; more preferably 3 to 10 hours.

[0077] The reaction can be carried out in any high-temperature reaction equipment known in the art, preferably in a high-temperature reactor with a polytetrafluoroethylene liner.

[0078] In this invention, the pH value of the acidic condition can be 1 to 6; preferably 2 to 6; more preferably 3 to 5. This invention can use any type of acid solution to adjust the pH value, and no particular limitation is made herein. For example, it can be at least one selected from hydrochloric acid solution, nitric acid solution, acetic acid solution, phosphoric acid solution, sulfuric acid solution, and carbonic acid solution; preferably at least one selected from hydrochloric acid solution, nitric acid solution, and sulfuric acid solution; more preferably at least one selected from hydrochloric acid solution with a concentration of 0.1 to 2 mol / L, nitric acid solution with a concentration of 0.1 to 2 mol / L, and sulfuric acid solution with a concentration of 0.1 to 2 mol / L.

[0079] According to one embodiment of the present invention, the method for preparing the carboxylic acid represented by formula (I) includes a step for preparing intermediate product A, a step for preparing intermediate product B, a step for preparing intermediate product C, and a step for preparing the carboxylic acid. These are described in detail below.

[0080] Preparation steps of intermediate product A

[0081] Titanium chloride, a reducing agent, and the compound shown in formula (II) are added to a first solvent and mixed to allow the compound shown in formula (II) to undergo a McMurry coupling reaction, thereby obtaining intermediate product A.

[0082]

[0083] In formula (II), R1 and R2 can be independently selected from hydrogen or C1 to C6 alkyl groups; preferably hydrogen or C1 to C3 alkyl groups; more preferably hydrogen or C1 to C3 n-alkyl groups. R5 and R6 can be independently selected from C1 to C6 alkyl groups; preferably C1 to C3 alkyl groups; more preferably C1 to C3 n-alkyl groups.

[0084] The C1 to C6 alkyl groups may include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, methylbutyl, ethylpropyl, hexyl, methylpentyl, dimethylbutyl, ethylbutylene, etc.

[0085] The first solvent may be selected from at least one of acetonitrile, tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; preferably at least one of tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; more preferably at least one of tetrahydrofuran and dimethyl sulfoxide.

[0086] According to one embodiment of the present invention, the titanium chloride may be selected from at least one of TiCl3 (titanium trichloride) and TiCl4 (titanium trichloride); preferably TiCl3 or TiCl4.

[0087] The reducing agent can be selected from at least one of Li (lithium), Na (sodium), K (potassium), Zn (zinc), Mg (magnesium), Al (aluminum), Pd (palladium), platinum (Pt), and LiAlH4 (lithium aluminum hydride); preferably at least one of Li, K, Zn, Mg, Al, Pd, and LiAlH4; more preferably at least one of K, Zn, Mg, and LiAlH4.

[0088] In this invention, based on 1g of the compound represented by formula (II), the amount of titanium chloride used can be 0.1 to 0.5 mL; preferably 0.15 to 0.45 mL; more preferably 0.2 to 0.4 mL.

[0089] Based on 1 mL of titanium chloride, the amount of reducing agent can be 0.5–5 g; preferably 1–5 g; more preferably 1–4 g.

[0090] In this invention, the McMurry coupling reaction is carried out under heating conditions, with heating until the reactants are refluxed. The reaction temperature can be 50–200°C; preferably 50–180°C; more preferably 60–150°C.

[0091] The reaction time can be 12 to 48 hours; preferably 12 to 36 hours; more preferably 24 to 36 hours.

[0092] In this invention, the McMurry coupling reaction is carried out in a protective gas. The protective gas can be selected from at least one of nitrogen (N2) and an inert gas, including helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe); preferably, the protective gas is selected from at least one of nitrogen, helium, neon, and argon; more preferably, the protective gas is selected from at least one of nitrogen, helium, and argon.

[0093] According to a preferred embodiment of the present invention, a first solvent is first added to a container under a protective gas atmosphere and stirred for 1 to 10 minutes, preferably 1 to 8 minutes, more preferably 2 to 8 minutes. Then a reducing agent is added, and the mixture is cooled to -10 to 5°C, preferably -5 to 5°C, more preferably -5 to 0°C. Next, titanium chloride is added and heated to temperature a, and stirred at temperature a. Temperature a can be 10 to 30°C, preferably 15 to 30°C, more preferably 20 to 30°C, and the stirring time can be 0.1 to 5 hours, preferably 0.1 to 3 hours, more preferably 0.2 to 2 hours. Then, heating continues to reflux, and stirring is performed under reflux for 0.1 to 5 hours, preferably 0.1 to 3 hours, more preferably 0.2 to 2 hours. After stirring is complete, the mixture is cooled again to -10 to 5°C, preferably -5 to 5°C, more preferably -5 to 0°C. Then, the compound shown in formula (II) is added, heated to reflux, and a McMurry coupling reaction is carried out under reflux to generate a precipitate. After the reaction is complete, an aqueous solution of an alkali metal carbonate or an aqueous solution of an alkali metal bicarbonate is added to quench the reaction. The precipitate is then filtered and recrystallized in the first recrystallization solvent to obtain intermediate product A.

[0094] The alkali metal carbonate is preferably at least one of Li, Na, and K carbonates; more preferably at least one of Na₂CO₃ and K₂CO₃.

[0095] The alkali metal bicarbonate is preferably at least one of Li, Na, and K bicarbonates; more preferably at least one of NaHCO3 and KHCO3.

[0096] The mass concentration of the aqueous solution of alkali metal carbonate or alkali metal bicarbonate can be 1–20 wt%; preferably 2–18 wt%; more preferably 5–15 wt%.

[0097] The first recrystallization solvent includes first recrystallization solvent A and first recrystallization solvent B. First recrystallization solvent A may be selected from at least one chloroalkane; preferably at least one of dichloromethane, chloroform, and carbon tetrachloride; more preferably dichloromethane or chloroform. First recrystallization solvent B is selected from at least one of C1-C5 alkyl alcohols; preferably at least one of C1-C3 alkyl alcohols; more preferably methanol or ethanol.

[0098] The volume ratio of the first recrystallization solvent A to the first recrystallization solvent B can be 1:(0.2-5), preferably 1:(0.5-5), and more preferably 1:(1-3).

[0099] Limiting the reaction conditions to the above range is beneficial for the formation of intermediate product A and increases the yield of intermediate product A.

[0100] Preparation steps of intermediate product B

[0101] Intermediate product A and boron halide were added to a second solvent to react and obtain intermediate product B.

[0102] According to one embodiment of the present invention, the second solvent may be selected from at least one of haloalkanes; preferably at least one of chloroalkanes; more preferably at least one of dichloromethane, chloroform, and carbon tetrachloride.

[0103] Boron halide can be selected from at least one of BF3, BBr3, BCl3, and BI3; preferably at least one of BBr3 and BCl3; more preferably BBr3 or BCl3.

[0104] In this invention, based on 1g of intermediate product A, the amount of boron halide can be 0.1-5mL; preferably 0.2-4mL; more preferably 0.5-2mL.

[0105] Based on 1g of intermediate product A, the amount of the second solvent can be 5 to 100 mL; preferably 10 to 80 mL; more preferably 10 to 60 mL.

[0106] In this invention, the reaction temperature for obtaining intermediate product B can be 10–50°C; preferably 15–45°C; more preferably 20–40°C. The reaction time for obtaining intermediate product B can be 5–24 h; preferably 10–24 h; more preferably 12–20 h.

[0107] According to a preferred embodiment of the present invention, the second solvent and intermediate product A are first added to a container at -10 to 5°C, preferably -5 to 5°C, more preferably -5 to 0°C, and then stirred for 1 to 5 hours, preferably 1 to 3 hours, more preferably 2 to 3 hours. The temperature is then raised to the reaction temperature for obtaining intermediate product B, and the reaction is carried out with stirring at this temperature to generate a precipitate. After the reaction is complete, water is added at -10 to 5°C, preferably -5 to 5°C, more preferably -5 to 0°C, to quench the reaction, and then the precipitate is filtered and washed. The precipitate is then recrystallized in a second recrystallization solvent to obtain intermediate product B.

[0108] In this invention, the water used for quenching can be selected from at least one of deionized water and ultrapure water; preferably, it is deionized water.

[0109] In this invention, the water used for washing can be selected from at least one of deionized water and ultrapure water; preferably, it is deionized water. The number of washing cycles can be 1 to 5 times; preferably 2 to 5 times; more preferably 2 to 4 times.

[0110] The second recrystallization solvent includes second recrystallization solvent A and second recrystallization solvent B. Second recrystallization solvent A can be selected from at least one chloroalkane; preferably at least one of dichloromethane, chloroform, and carbon tetrachloride; more preferably dichloromethane or chloroform. Second recrystallization solvent B is water. The water used can be selected from at least one of deionized water and ultrapure water; preferably deionized water.

[0111] The volume ratio of the second recrystallization solvent A to the second recrystallization solvent B can be 1:(0.2-5), preferably 1:(0.5-5), and more preferably 1:(1-3).

[0112] Limiting the reaction conditions to the above range is beneficial for the formation of intermediate product B and increases the yield of intermediate product B.

[0113] Preparation steps of intermediate product C

[0114] An alkali metal alkoxide was added to a third solvent to carry out the first reaction; then intermediate B was added to carry out the second reaction; then the compound shown in formula (III) was added to carry out the third reaction to obtain intermediate C.

[0115]

[0116] In formula (III), R3 and R4 can be independently selected from hydrogen or C1-C6 alkyl groups; preferably hydrogen or C1-C3 alkyl groups; more preferably hydrogen or C1-C3 n-alkyl groups. R7 can be selected from C1-C6 alkyl groups; preferably C1-C3 alkyl groups; more preferably C1-C3 n-alkyl groups. X1 is a halogen; preferably one of F, Cl, Br, and I; more preferably Cl or Br.

[0117] In this invention, alkyl groups may include, but are not limited to, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, methylbutyl, ethylpropyl, hexyl, methylpentyl, dimethylbutyl, ethylbutylene, heptyl, and octyl.

[0118] The third solvent is selected from at least one of acetonitrile, tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; preferably at least one of tetrahydrofuran, dimethylformamide, and dimethyl sulfoxide; more preferably at least one of tetrahydrofuran and dimethyl sulfoxide.

[0119] According to one embodiment of the present invention, the alkali metal alkoxide may be selected from at least one of the C1 to C5 alkyl alkoxides of Li, Na, and K; preferably at least one of the C1 to C3 alkyl alkoxides of Li, Na, and K; more preferably at least one of the C1 to C3 alkyl alkoxides of Na and K; and most preferably sodium tert-butoxide or potassium tert-butoxide.

[0120] In this invention, based on 1g of intermediate product B, the amount of alkali metal alkoxide can be 0.1-1g; preferably 0.2-0.8g; more preferably 0.2-0.6g.

[0121] Based on 1g of intermediate product B, the amount of the second solvent can be 1 to 50 mL; preferably 5 to 30 mL; more preferably 10 to 30 mL.

[0122] According to one embodiment of the present invention, the temperature of the first reaction can be 10–50°C; preferably 20–50°C; more preferably 30–45°C. The time of the first reaction can be 0.1–5 h; preferably 0.2–3 h; more preferably 0.5–2 h.

[0123] The temperature of the second reaction can be 10–80°C; preferably 20–60°C; more preferably 30–60°C. The time of the second reaction can be 0.1–5 h; preferably 0.2–3 h; more preferably 0.5–2 h.

[0124] The temperature of the third reaction can be 30–90°C; preferably 35–85°C; more preferably 40–80°C. The time of the third reaction can be 2–12 hours; preferably 3–10 hours; more preferably 5–10 hours.

[0125] In this invention, after the reaction is completed, the reaction can be quenched with water. The water used for quenching can be selected from at least one of deionized water and ultrapure water; preferably, it is deionized water.

[0126] According to a preferred embodiment of the present invention, the reaction product can be extracted after the quenching reaction. The extractant used can be selected from at least one of chloroalkanes; preferably at least one of dichloromethane, chloroform, and carbon tetrachloride; more preferably dichloromethane or chloroform.

[0127] According to a preferred embodiment of the present invention, after extraction, the extractant is removed by evaporation of the extract to obtain the extract product. The extract product is then recrystallized in a third recrystallization solvent to obtain intermediate product C.

[0128] The third recrystallization solvent includes third recrystallization solvent A and third recrystallization solvent B. Third recrystallization solvent A may be selected from at least one chloroalkane; preferably at least one of dichloromethane, chloroform, and carbon tetrachloride; more preferably dichloromethane or chloroform. Third recrystallization solvent B may be selected from at least one of C1 to C5 alkyl alcohols; preferably at least one of C1 to C3 alkyl alcohols; more preferably methanol or ethanol.

[0129] The volume ratio of the third recrystallization solvent A to the third recrystallization solvent B can be 1:(0.2-5), preferably 1:(0.5-5), and more preferably 1:(1-3).

[0130] In this invention, the step of obtaining intermediate product C is carried out in a protective gas. The protective gas may be selected from at least one of nitrogen (N2) and an inert gas, including helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe); preferably, the protective gas is selected from at least one of nitrogen, helium, neon, and argon; more preferably, the protective gas is selected from at least one of nitrogen, helium, and argon.

[0131] Limiting the reaction conditions to the above range is beneficial for the formation of intermediate product C and increases the yield of intermediate product C.

[0132] Carboxylic acid preparation steps

[0133] An alkali metal hydroxide and intermediate product C are added to a fourth solvent for reaction. After the reaction, the organic solvent is removed, and acid is added to prepare the carboxylic acid shown in formula (I).

[0134] According to one embodiment of the present invention, the fourth solvent comprises solvent C, solvent D, and solvent E. Solvent C is selected from at least one of acetonitrile, tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; preferably at least one of tetrahydrofuran, dimethylformamide, and dimethyl sulfoxide; more preferably at least one of tetrahydrofuran and dimethyl sulfoxide. Solvent D is selected from at least one of C1 to C5 alkyl alcohols; preferably at least one of C1 to C3 alkyl alcohols; more preferably methanol or ethanol. Solvent E is water; preferably deionized water or ultrapure water.

[0135] The volume ratio of solvent C, solvent D and solvent E can be (1-5):(1-5):1, preferably (1-4):(1-4):1, and more preferably (2-4):(2-4):1.

[0136] The alkali metal hydroxide in this invention can be selected from at least one of LiOH, NaOH, and KOH; preferably at least one of NaOH and KOH; more preferably NaOH or KOH.

[0137] In this invention, based on 1g of intermediate product C, the amount of alkali metal hydroxide can be 0.1-1g; preferably 0.2-0.8g; more preferably 0.3-0.8g.

[0138] Based on 1g of intermediate product C, the amount of the fourth solvent can be 5 to 100 mL; preferably 10 to 80 mL; more preferably 10 to 70 mL.

[0139] According to one embodiment of the present invention, the reaction is carried out under reflux. The reaction time can be 1 to 12 hours; preferably 2 to 10 hours; more preferably 3 to 8 hours.

[0140] According to one embodiment of the present invention, after the reaction is completed, the organic solvent is removed, and acid is added to the remaining aqueous phase to obtain a precipitate. The precipitate is filtered, washed, and dried to obtain the carboxylic acid shown in formula (I).

[0141] In this invention, the added acid can be selected from at least one of hydrochloric acid solution, nitric acid solution, phosphoric acid solution, and sulfuric acid solution; preferably at least one of hydrochloric acid solution, nitric acid solution, and sulfuric acid solution; more preferably at least one of hydrochloric acid solution with a concentration of 10-12 mol / L, nitric acid solution with a concentration of 8-12 mol / L, and sulfuric acid solution with a concentration of 10-20 mol / L.

[0142] The filtration, washing, and drying processes in this invention are all implemented using any method known in the art, and are not particularly limited herein. The water used for washing is preferably deionized water.

[0143] Limiting the reaction conditions to the above range is beneficial for forming rare earth carboxylate complexes and increasing the yield of rare earth carboxylate complexes.

[0144] <Composite Materials>

[0145] The present invention also provides a composite material formed by coating the above-mentioned rare earth carboxylic acid complex onto the surface of silicon dioxide with a silane coupling agent.

[0146] According to one embodiment of the present invention, the silane coupling agent is selected from at least one of N-(β-aminoethyl-γ-aminopropyl)methyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, vinyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, and γ-mercaptopropyltriethoxysilane; preferably N-(β-aminoethyl-γ-aminopropyltrimethoxysilane) At least one of N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, vinyltrimethoxysilane, and γ-(methacryloyloxy)propyltrimethoxysilane; more preferably at least one of N-(β-aminoethyl)-γ-aminopropyl)methyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, and γ-aminopropyltrimethoxysilane.

[0147] This invention involves coating rare earth carboxylic acid complexes onto the surface of silica using a silane coupling agent, resulting in a composite material that is less prone to agglomeration and exhibits better dispersibility and stability.

[0148] <Preparation methods of composite materials>

[0149] The present invention also provides a method for preparing the composite material as described above, comprising a silica activation step, a silane coupling agent coating step, and a carboxylic acid rare earth complex coating step. This is described in detail below.

[0150] Silica activation steps

[0151] Immerse the silica in a weakly alkaline aqueous solution and let it stand for 1–12 hours, then filter, wash and dry the silica.

[0152] According to one embodiment of the present invention, the weakly alkaline aqueous solution may be selected from at least one of ammonia water, alkali metal carbonate aqueous solution, and alkali metal bicarbonate aqueous solution; preferably at least one of ammonia water, sodium carbonate aqueous solution, sodium bicarbonate aqueous solution, potassium carbonate aqueous solution, and potassium bicarbonate aqueous solution; more preferably at least one of ammonia water, sodium carbonate aqueous solution, and potassium carbonate aqueous solution.

[0153] The settling time can be 1 to 12 hours; preferably 2 to 10 hours; more preferably 3 to 9 hours.

[0154] The filtration, washing, and drying processes in this invention can all be implemented using any method known in the art, and are not particularly limited herein. The water used for washing is preferably deionized.

[0155] Reasonable activation conditions are beneficial to activating the hydroxyl groups on the surface of SiO2 and improving the binding ability of SiO2 with silane coupling agents.

[0156] Silane coupling agent coating steps

[0157] Dry silica and silane coupling agent are placed in C1-C5 alkyl alcohols and reacted at 50-120°C to obtain silica with a surface coated by silane coupling agent.

[0158] According to one embodiment of the present invention, the C1 to C5 alkyl alcohols can be C1 to C3 alkyl alcohols; preferably C1 to C3 n-alkyl alcohols; more preferably methanol or ethanol.

[0159] According to one embodiment of the present invention, based on 1g of silicon dioxide, the amount of silane coupling agent can be 1 to 10g; preferably 1 to 8g; more preferably 2 to 8g.

[0160] Based on 1g of silica coated with silane coupling agent, the amount of C1-C5 alkyl alcohol can be 1-10mL; preferably 1-8mL; more preferably 2-6mL.

[0161] According to one embodiment of the present invention, the reaction temperature can be 50–120°C; preferably 60–110°C; more preferably 65–100°C.

[0162] The reaction time can be 1 to 20 hours; preferably 2 to 18 hours; more preferably 3 to 15 hours.

[0163] According to a preferred embodiment of the present invention, the prepared silica coated with silane coupling agent can also be filtered, washed and dried.

[0164] Filtration, washing, and drying can all be carried out using any method known in the art, and no particular limitation is made herein. The water used for washing is preferably deionized water.

[0165] Limiting the reaction conditions to the above range is beneficial to the stable bonding of silane coupling agent and silica, resulting in silica with a stable structure coated with silane coupling agent.

[0166] Steps for coating rare earth carboxylic acid complexes

[0167] A composite material is prepared by reacting silica coated with a silane coupling agent with a rare earth carboxylic acid complex in a C1-C5 alkyl alcohol at 50-120°C.

[0168] According to one embodiment of the present invention, the pH value for carrying out the reaction can be 6 to 8, preferably 6.5 to 7.5, and more preferably 7. The pH value can be adjusted using any alkaline solution, such as, but not limited to, at least one of ammonia, alkali metal hydroxide solution, and alkali gold carbonate solution; preferably at least one of ammonia, sodium hydroxide aqueous solution, and sodium carbonate aqueous solution; more preferably ammonia.

[0169] According to one embodiment of the present invention, based on 1g of silicon dioxide coated with silane coupling agent, the amount of rare earth carboxylic acid complex can be 1-5g; preferably 1-4g; more preferably 1.5-3.5g.

[0170] Based on 1g of silica coated with silane coupling agent, the amount of C1-C5 alkyl alcohol can be 1-10mL; preferably 2-10mL; more preferably 2-8mL.

[0171] The C1 to C5 alkyl alcohols can be C1 to C3 alkyl alcohols; preferably C1 to C3 n-alkyl alcohols; more preferably methanol or ethanol.

[0172] According to one embodiment of the present invention, the reaction temperature can be 50–120°C; preferably 60–110°C; more preferably 65–100°C.

[0173] The reaction time can be 1 to 20 hours; preferably 2 to 18 hours; more preferably 3 to 15 hours.

[0174] Limiting the reaction conditions to the above range is beneficial for the stable combination of silica coated with silane coupling agent and rare earth carboxylic acid complex to form composite material; it can ensure that the prepared composite material has good stability and recyclability, and is more conducive to improving the sensitivity of the composite material to the detection of polychlorinated biphenyls.

[0175] The raw materials used in this invention can be commercially available products or prepared by existing methods, and are not particularly limited herein. The purity of the raw materials in this invention is at least industrial grade (99.9 wt%).

[0176] <Application>

[0177] The present invention also provides the use of the above-described composite material in the detection of polychlorinated biphenyls.

[0178] According to a preferred embodiment of the present invention, the composite material can be used to detect polychlorinated biphenyls in water.

[0179] According to one embodiment of the present invention, the detection limit of the composite material for polychlorinated biphenyls is at most 8 μM, preferably at most 7 μM, and more preferably at most 6.8 μM.

[0180] According to one embodiment of the present invention, the polychlorinated biphenyl (PCB) can be at least one of trichlorobiphenyl to decachlorobiphenyl; preferably at least one of trichlorobiphenyl to octachlorobiphenyl; more preferably at least one of trichlorobiphenyl to hexachlorobiphenyl; and even more preferably at least one of 2,2',5-trichlorobiphenyl, 2,2',5,5'-tetrachlorobiphenyl, and 2,2',4,4',5,5'-hexachlorobiphenyl.

[0181] <Testing Methods>

[0182] Fluorescence excitation and emission spectroscopy determination: Detection was performed using a Horiba FL-3 fluorescence spectrometer.

[0183] Infrared spectroscopy determination: Thermo Fisher Scientific Nicolet iS20 infrared spectrometer was used for detection.

[0184] X-ray photoelectron spectroscopy (XPS) was performed using a Thermo Scientific ESCALAB QXi X-ray photoelectron spectrometer.

[0185] Transmission electron microscopy (TEM) measurements: Thermo Fisher Talos F200i (USA) was used for the measurements.

[0186] <Ingredient Description>

[0187] Unless otherwise specified, all raw materials used in the following examples are commercially available products.

[0188] Europium oxide, 4,4'-dimethylbenzophenone, tetra(4-methoxyphenyl), methyl 4-(bromomethyl)benzoate, potassium hydroxide, tetrahydrofuran, and dichloromethane were purchased from Shanghai Aladdin Reagent Co., Ltd. Hydrochloric acid was purchased from Fuchen Chemical Reagent Co., Ltd. All other reagents were purchased from Maclean's Biochemical Technology Co., Ltd.

[0189] Preparation Example 1

[0190] The preparation route for tetra-(4-carboxy-1-methyleneoxy-(1,1-biphenyl))ethylene (H4L) is as follows: Figure 1 As shown.

[0191] Under nitrogen (N2) protection, 40 mL of tetrahydrofuran (THF) was added to a container and stirred at room temperature for 5 min. Then, 6.5 g of zinc powder was added, and after cooling to 0 °C, 5.5 mL of titanium tetrachloride was slowly added using a syringe to form a suspension. The suspension was heated to room temperature (25 °C below) and stirred at room temperature for 0.5 h, then heated to reflux and stirred for 1.5 h. The system was then cooled to 0 °C again. 20 g of 4,4'-dimethoxybenzophenone was added, and the reaction was carried out under reflux for 24 h. After the reaction was completed, 50 mL of 10 wt% K2CO3 aqueous solution was added to quench the reaction. The precipitate formed by the reaction was filtered, and the precipitate was recrystallized in 20 mL of dichloromethane in methanol solution (CH2Cl2 to CH3OH volume ratio of 1:1) to obtain pale yellow crystals, which was intermediate product A (tetra(4-methoxyphenyl)ethylene), with a yield of 63 wt%.

[0192] At 0°C, 5 g of intermediate product A and 100 mL of anhydrous dichloromethane (DCM) were added to a container, followed by the addition of 4.2 mL of BBr3 via a syringe. The mixture was stirred at 0°C for 2 h to form a mixture. The mixture was then stirred at room temperature for 16 h to generate a precipitate. The reaction was then quenched with 100 mL of deionized water at -5°C. The precipitate was filtered and washed with deionized water. The washed precipitate was recrystallized from 20 mL of an aqueous ethanol solution (CH3CH2OH to H2O in a 1:1 volume ratio) to obtain a pink solid, which was intermediate product B (methyl 4-(bromomethyl)benzoate), in a yield of 47 wt%.

[0193] Under nitrogen protection, 1.83 g of potassium tert-butoxide (KTB) and 50 mL of dimethyl sulfoxide (DMSO) were added to a container and reacted at 35 °C for 0.5 h. Then, 5 g of intermediate product B was added, and the reaction was continued at 45 °C for another 0.5 h. Next, 14.5 g of methyl 4-(bromomethyl)benzoate was added, and the reaction was further carried out at 60 °C for 8 h. The reaction was then quenched by adding 100 mL of deionized water. The reaction product was then extracted three times with 40 mL of dichloromethane each time, and the dichloromethane was evaporated after extraction. The extracted reaction product was recrystallized in 15 mL of CH2Cl2 / CH3OH (V / V = 1:2) solution to obtain pale yellow crystals, which was intermediate product C, with a yield of 41%.

[0194] 3 g of intermediate product C and 2.04 g of potassium hydroxide were added to a container, along with 35 mL of an aqueous solution of tetrahydrofuran and ethanol (THF, CH3CH2OH, and H2O in a volume ratio of 3:3:1). The mixture was heated to reflux and reacted under reflux for 6 h. After the reaction, the organic phase was removed by separation. Concentrated hydrochloric acid (18.4 mol / L) was added to the aqueous phase to adjust the pH to 1, resulting in a precipitate. The precipitate was filtered, washed, and dried to obtain a pale pink product, tetra-(4-carboxy-1-methyleneoxy-(1,1-biphenyl))ethylene (denoted as H4L), with a yield of 34 wt%.

[0195] Example 1

[0196] The preparation route for the composite material (SiO2@WD-53@L-Eu) is as follows: Figure 2 As shown.

[0197] 5 mL of N,N-dimethylformamide and 3 mL of water were added to the liner of a polytetrafluoroethylene reactor. Then, 0.01 mmol of H4L and 0.01 mmol of Eu2O3 were added. The pH of the reaction system was adjusted to 5 with dilute nitric acid solution (concentration of 1 mol / L). The reaction was then carried out at 130 °C for 8 h to obtain europium carboxylate complex (denoted as L-Eu).

[0198] 5g of SiO2 powder was immersed in 0.1mol / L ammonia water and allowed to stand for 6 hours to activate the hydroxyl groups on the surface of SiO2. The activated SiO2 was then filtered, washed, and dried, and placed in a container. 10g of N-(β-aminoethyl-γ-aminopropyl)methyldimethoxysilane (WD-53) and 10mL of anhydrous ethanol were added, and the reaction system was allowed to react at 80℃ for 8 hours. The mixture was then filtered, washed, and dried to obtain SiO2 with a surface coated with a silane coupling agent (denoted as SiO2@WD-53).

[0199] 1g of SiO2@WD-53 was added to a container, followed by 1.5g of L-Eu and 5mL of anhydrous ethanol. The pH of the reaction system was adjusted to 7 with ammonia (0.1mol / L). The reaction was then carried out at 80℃ for 12h to obtain the composite material (denoted as SiO2@WD-53@L-Eu).

[0200] Experimental Example 1

[0201] The chemical bonds in the composite material SiO2@WD-53@L-Eu prepared in Example 1 were further analyzed by measuring the XPS energy spectrum of 30 mg of the composite material. The results are as follows: Figure 3 As shown. (Through) Figure 3 As can be seen in the total spectrum (a) of the composite material SiO2@WD-53@L-Eu, peaks of Si2p, O1s, C1s, N1s, and Eu3d can be identified, proving that the europium carboxylate complex L-Eu, coupling agent WD-53, and SiO2 combine to form the composite material SiO2@WD-53@L-Eu. In the C1s spectrum (b), the binding energies of C-Si (284.1 eV), CC / C=C (284.7 eV), CN (285.3 eV), CO (286.1 eV), and C=O (288.5 eV) bonds can be observed. In the O1s spectrum (c), three peaks of Si-O-Si (532.5 eV), CO (532.5 eV), and C=O (31.6 eV) can be observed, which proves that the ligand binds to Eu through the carboxylic acid. 3+ Coordination and coupling agent WD-53 are linked to SiO2 via Si-O-Si bonds. Eu3d3 / 2 (1164.9 eV), Eu3d5 / 2 (1135.4 eV), and a satellite peak at 1156.6 eV were observed in the Eu3d energy spectrum (d), further indicating that europium is involved in the process of energy transfer. 3+ The composite material SiO2@WD-53@L-Eu exists in the form of coupling agent WD-53 and europium carboxylate complex L-Eu coated on SiO2. The XPS energy dispersive spectroscopy results proved that the composite material SiO2@WD-53@L-Eu is a composite material formed by coupling agent WD-53 and europium carboxylate complex L-Eu coated on SiO2.

[0202] To further understand the morphological characteristics of the SiO2@WD-53@L-Eu composite material prepared in Example 1, TEM (transmission electron microscopy) tests were performed on it, and the results are as follows: Figure 4 and 5 As shown. From Figure 4 A thin film of WD-53@L-Eu with a thickness of 11.07 nm (d) was clearly observed on the outer layer of SiO2. Figure 5 It can be seen that the composite material SiO2@WD-53@L-Eu is a core-shell material, and the elements are evenly distributed.

[0203] The infrared spectra of 10 mg of H4L from Preparation Example 1, L-Eu, SiO2, SiO2@WD-53 from Example 1, and the composite material SiO2@WD-53@L-Eu were measured respectively, and the results are as follows: Figure 6 As shown, a focal length of 3449.18 cm⁻¹ can be observed in the infrared spectrum of H4L. -1 The broad absorption peak at 1640 cm⁻¹ is due to the stretching vibration of the -OH group on the carboxyl group. -1 The stretching vibration at this point is C=O. In the L-Eu infrared spectrum, a decrease in the intensity of the absorption peak of the -OH stretching vibration on the carboxyl group can be observed, decreasing from 1640 cm⁻¹. -1 Moved to 3444.07cm -1 The C=O stretching vibration absorbed by 1640.04 cm -1 Moved to 1634.33cm -1 This indicates that Eu 3+ It coordinates with carboxylic acid H4L. The SiO2 infrared spectral data shows a value at 3660.84 cm⁻¹. -1 The broad absorption peak at 1635.76 cm⁻¹ is due to the -OH stretching vibration. -1 814.31cm -1 The peaks at this location represent the stretching and bending vibrations of the Si-O-Si bond. In the infrared spectra of SiO2@WD-53 and SiO2@WD-53@L-Eu, the -OH stretching vibration on SiO2@WD-53 and SiO2@WD-53@L-Eu shifts to 3663.69 cm⁻¹. -1 and 3439.80cm -1 At this point, the stretching vibration absorption peak of the Si-O-Si bond shifts to 1612.94 cm⁻¹. -1 and 1624.34cm -1 At this point, the absorption peak of the bending vibration of the Si-O-Si bond shifts to 811.46 cm⁻¹. -1 and 807.18cm -1 This indicates that SiO2 is coated with WD-53 and L-Eu.

[0204] Experimental Example 2

[0205] 0.002 g of the composite material SiO2@WD-53@L-Eu prepared in Example 1 was dispersed in 2 mL of anhydrous ethanol and sonicated for 15 min to prepare a dispersion with a concentration of 1 mg / mL for later use. 2,2',5-trichlorobiphenyl was weighed and dissolved in 1 mL of anhydrous ethanol to prepare a dispersion with a concentration of 1 × 10⁻⁶ mg / mL. -2 mol·L -1Similarly, solutions of 2,2',5'-tetrachlorobiphenyl and 2,2',4,4',5,5'-hexachlorobiphenyl of the same concentration were prepared. Different volumes of the above 2,2',5-trichlorobiphenyl solution were added to the dispersion of the composite material SiO2@WD-53@L-Eu, and the fluorescence emission spectra of the dispersions were detected. The results are as follows: Figure 7 As shown in the figure, the fluorescence emission intensity of SiO2@WD-53@L-Eu gradually decreased with the increasing content of 2,2',5-trichlorobiphenyl in the dispersion. When the volume of 2,2',5-trichlorobiphenyl added to the dispersion reached 500 μL, the fluorescence emission spectrum of SiO2@WD-53@L-Eu was almost completely quenched. The fluorescence quenching effect of 2,2',5,5'-tetrachlorobiphenyl solution and 2,2',4,4',5,5'-hexachlorobiphenyl solution on the dispersion of the composite material SiO2@WD-53@L-Eu was detected using the same method, and the results are shown in the figure. Figure 8 and Figure 9 As shown. The fluorescence quenching constants of 2,2',5-trichlorobiphenyl, 2,2',5,5'-tetrachlorobiphenyl, and 2,2',4,4',5,5'-hexachlorobiphenyl, obtained by fitting, are 4.446 × 10⁻⁶. 3 M -1 4.819×10 3 M -1 5.261×10 3 M -1 Further calculations showed that the limits of detection for the three substances were 6.748 μM, 6.225 μM, and 5.752 μM, respectively.

[0206] Experimental Example 3

[0207] Take 500 μL of the 1 mg / mL SiO2@WD-53@L-Eu dispersion prepared in Example 2 and detect its fluorescence spectrum. Then, add 2,2',5-trichlorobiphenyl solution to quench the fluorescence of the composite material, and detect the fluorescence spectrum of the solution again. Then, wash the SiO2@WD-53@L-Eu composite material with anhydrous ethanol. Repeat the above fluorescence quenching experiment four times, and compare the fluorescence intensity at the emission wavelength of 616 nm in the five quenching experiments. The results are as follows. Figure 10 As shown in the figure, although the fluorescence intensity of the SiO2@WD-53@L-Eu composite dispersion decreased by 19% after three fluorescence quenching experiments compared to before the experiment, its fluorescence quenching efficiency in the fourth experiment still reached 89%. This fully demonstrates that the SiO2@WD-53@L-Eu composite material of the present invention has good recyclability when detecting polychlorinated biphenyls in solution.

[0208] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A rare earth carboxylic acid complex, characterized in that, The carboxylic acid rare earth complex is formed by the complexation of carboxylic acid and rare earth element ions; wherein... The carboxylic acid has a structure as shown in formula (I): R1, R2, R3, and R4 are each independently selected from hydrogen; the rare earth element ion is Eu. 3+ .

2. The rare earth carboxylic acid complex according to claim 1, characterized in that, The carboxylic acid rare earth complex is obtained by reacting the carboxylic acid of formula (I) with a compound containing rare earth elements; wherein the molar ratio of the carboxylic acid of formula (I) to the rare earth elements in the compound containing rare earth elements is 1:(1-6).

3. A method for preparing the rare earth carboxylic acid complex according to claim 1 or 2, comprising the following steps: The carboxylic acid shown in formula (I) is reacted with a compound containing rare earth elements under solvent and acidic conditions to prepare a rare earth carboxylic acid complex. The rare earth element-containing compound is selected from at least one of rare earth element oxides and rare earth element inorganic salts. The solvent includes solvent A and solvent B; solvent A is selected from at least one of acetonitrile, tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; solvent B is selected from at least one of water and C1-C5 alkyl alcohols. The reaction temperature is 80–150℃.

4. The preparation method according to claim 3, characterized in that, The method for preparing the carboxylic acid represented by formula (I) includes the following steps: 1) Add titanium chloride, reducing agent, and compound (II) to the first solvent and mix to allow the compound (II) to undergo a McMurry coupling reaction to obtain intermediate product A. R1 and R2 are each independently selected from hydrogen; R5 and R6 are each independently selected from C1 to C6 alkyl groups. The first solvent is selected from at least one of acetonitrile, tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; 2) Add intermediate product A and boron halide to the second solution and mix to react and obtain intermediate product B; The second solvent is selected from at least one of haloalkanes; 3) Add the alkali metal alkoxide to the third solvent to carry out the first reaction; then add intermediate product B to carry out the second reaction; then add the compound shown in formula (III) to carry out the third reaction to obtain intermediate product C; R3 and R4 are each independently selected from hydrogen; R7 is selected from C1 to C6 alkyl groups; X1 is a halogen; The third solvent is selected from at least one of acetonitrile, tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; 4) The alkali metal hydroxide and intermediate product C are added to the fourth solvent to react. After the reaction, the organic solvent is removed and acid is added to prepare the carboxylic acid shown in formula (I). The fourth solvent includes solvent C, solvent D, and solvent E; solvent C is selected from at least one of acetonitrile, tetrahydrofuran, dimethylformamide, dimethylacetamide, and dimethyl sulfoxide; solvent D is selected from at least one of C1 to C5 alkyl alcohols; and solvent E is water.

5. A composite material, characterized in that, The composite material is formed by coating the rare earth carboxylic acid complex of claim 1 or 2 onto the surface of silicon dioxide with a silane coupling agent.

6. The composite material according to claim 5, characterized in that, The silane coupling agent is selected from at least one of N-(β-aminoethyl-γ-aminopropyl)methyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, vinyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane, γ-(methacryloyloxy)propyltrimethoxysilane, and γ-mercaptopropyltriethoxysilane.

7. A method for preparing the composite material according to claim 5 or 6, comprising the following steps: A) Immerse silica in a weakly alkaline aqueous solution and let it stand for 1–12 hours, then filter, wash and dry the silica; wherein the weakly alkaline aqueous solution is selected from at least one of ammonia, alkali metal carbonate aqueous solution and alkali metal bicarbonate aqueous solution. B) Place the dried silica and silane coupling agent from step A) into a C1-C5 alkyl alcohol and react at 50-120°C to obtain silica with a surface coated by the silane coupling agent. C) The silica with a surface coated with a silane coupling agent obtained in step B) and the rare earth carboxylic acid complex according to claim 1 or 2 are placed in a C1-C5 alkyl alcohol and reacted at 50-120°C to obtain a composite material.

8. The preparation method according to claim 7, characterized in that, In step C), the reaction is carried out under conditions of pH 6 to 8.

9. Use of the composite material according to any one of claims 5 or 6 in the detection of polychlorinated biphenyls.

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