Fluorescent complex for marking soil microplastification and preparation method thereof

Abstract

The invention discloses a fluorescent complex for marking soil microplastification and a preparation method of the fluorescent complex. The fluorescent complex is prepared from the following components in parts by weight: 20 to 50 parts of Ni composite fluorescent complex carrier, 3 to 8 parts of rhodamine B and 10 to 20 parts of (3-aminopropyl) triethoxysilane, the preparation method comprises the following steps: preparing a rhodamine B ethanol solution and a fluorescent mixed solution, then dropwise adding a (3-aminopropyl) triethoxysilane solution into the fluorescent mixed solution, and carrying out magnetic stirring, filtering and vacuum drying to obtain a fluorescent complex; according to the method, rhodamine B is adsorbed and fixed in a magnetic fluorescent complex carrier formed by biochar and ferroferric oxide, the rhodamine B is adsorbed with micro-plastic in the soil under the hydrophobic action force of the surface of a fluorescent complex, and catalase in plastic gaps on the surface of the micro-plastic is subjected to fluorescence labeling, so that the inter-field effect range in the soil is determined.

Description

Technical Field

[0001] The present invention belongs to the technical field of microplastic detection, and particularly relates to a fluorescent complex for labeling the soil microplastic sphere and a preparation method thereof. Background Art

[0002] Plastic fragments with a particle size less than 5 mm are called "microplastics". Plastic fragments in the natural environment can provide an ideal specific ecological niche for microorganisms, form biofilms, and become an effective matrix for microbial colonization. A biofilm is a dynamic biological system composed of complex and diverse microorganisms such as bacteria, fungi, algae, and protozoa, which are assembled in the matrix of extracellular polymers; the microbial community on plastic fragments is called the "plastisphere".

[0003] As a gathering place for microplastics, terrestrial systems such as soil are more vulnerable to plastic pollution. Therefore, a fluorescent complex capable of fluorescently labeling the microplastic sphere in soil is needed to monitor the scope of the microplastic sphere effect in soil.

[0004] Patent CN108587102A discloses a metal-organic fluorescent complex-labeled environmental microplastic and a preparation method and application thereof. An organic solvent is used to dissolve the metal-organic fluorescent complex, and the microplastic is soaked in the metal-organic fluorescent complex solution, separated, and dried to obtain fluorescent microplastics; however, this scheme is to prepare fluorescent plastics and cannot detect the scope of the sphere effect for the soil environment where the sphere effect has already occurred.

[0005] Patent CN112798780A discloses a method for directly competitive fluorescence immunoassay of catalase labeled with quantum dots. CdSe / ZnS quantum dots are used to label catalase to form a catalase-quantum dot fluorescence probe (QDs-CAT) complex; however, this scheme is to detect the concentration value of catalase in a test sample through the fluorescence intensity of an antibody-antigen immune complex, and the generation of the antibody-antigen immune complex is affected by factors such as temperature and pH, resulting in inaccurate detection results.

[0006] Therefore, there is no fluorescent complex that can directly label the catalase on the surface of microplastics in soil and determine the scope of the microplastic sphere effect in soil by detecting the content of catalase on the surface of microplastics. Summary of the Invention

[0007] The purpose of the present invention is to solve the problem of how to adsorb microplastics in soil and label the catalase on the surface of microplastics to produce fluorescence.

[0008] The present invention synthesizes a magnetic fluorescent complex carrier from biochar and magnetite, adsorbs microplastics in soil, and labels them with the fluorescent complex inside the fluorescent complex carrier.

[0009] The object of the present invention can be achieved by the following technical solutions:

[0010] A fluorescent complex for labeling the soil microplastic rhizosphere, comprising the following components by weight:

[0011] 20-50 parts of Ni composite fluorescent complex carrier, 3-8 parts of rhodamine B, and 10-20 parts of (3-aminopropyl)triethoxysilane.

[0012] Furthermore, the preparation method of the Ni composite fluorescent complex carrier is as follows:

[0013] React a nickel nitrate solution and a magnetic fluorescent complex carrier in a reaction kettle at 70-80 °C for 24 h. After the product is washed to neutrality and dried, the Ni composite fluorescent complex carrier is obtained.

[0014] Furthermore, the nickel nitrate solution is prepared through the following steps:

[0015] Dissolve nickel nitrate hexahydrate powder in deionized water in a reaction kettle, stir and disperse it, and then stir with 30 wt% hydrogen peroxide solution. The nickel nitrate solution is obtained. The dosage ratio of nickel nitrate hexahydrate, deionized water, and hydrogen peroxide solution is: 2-2.3 g: 250-300 mL: 50 mL - 60 mL.

[0016] Furthermore, the preparation method of the magnetic fluorescent complex carrier is as follows:

[0017] Mix the fluorescent complex carrier and ethylene glycol in a reaction kettle and ultrasonically disperse them. Then, successively add ferric chloride hexahydrate, anhydrous sodium acetate, and 1,6-hexanediamine and continue to ultrasonically disperse. React at 180-200 °C in the reaction kettle for 3.5-4.5 h. Use a magnet to collect the solid product, wash and dry it to obtain the magnetic fluorescent complex carrier.

[0018] Furthermore, the dosage ratio of the fluorescent complex carrier, ethylene glycol, ferric chloride hexahydrate, anhydrous sodium acetate, and 1,6-hexanediamine is: 3-4 g: 1 L: 10-12 g: 30-36 g: 90-100 g.

[0019] Furthermore, the preparation method of the fluorescent complex carrier is as follows:

[0020] Mix the crushed and dried corn straw with a 30 g / L calcium chloride solution in a reaction kettle, filter and dry it. Then, place it in a muffle furnace under nitrogen conditions at 550-600 °C for pyrolysis for 1 h. Wash the solid reactant with dilute hydrochloric acid to neutrality, dry and grind it, and pass through a 60-mesh sieve to obtain the fluorescent complex carrier; the dosage ratio of corn straw and calcium chloride solution is: 8-10 g: 150-200 mL.

[0021] A preparation method of a fluorescent complex for labeling the soil microplastic rhizosphere, comprising the following steps:

[0022] S101. Mix rhodamine B with absolute ethanol in a reaction kettle to prepare a rhodamine B ethanol solution with a concentration of 0.1 - 0.15 g / L.

[0023] S102. Mix the rhodamine ethanol solution with the Ni composite fluorescent complex in a reaction kettle and ultrasonically vibrate for 30 - 40 min to obtain a fluorescent mixture. The dosage ratio of the rhodamine ethanol solution to the Ni composite fluorescent complex is 1 L : 5 - 6 g.

[0024] S103. Mix (3 - aminopropyl)triethoxysilane with deionized water in a reaction kettle to prepare a (3 - aminopropyl)triethoxysilane solution with a concentration of 2 - 2.5 wt%.

[0025] S104. Drop the (3 - aminopropyl)triethoxysilane solution into the fluorescent mixture in the reaction kettle at a volume ratio of 1:10 - 15 while magnetically stirring during the dropping process. After the dropping is completed, continue stirring for 30 min, then filter and vacuum dry at 60°C to obtain the fluorescent complex.

[0026] The usage method of the present invention is as follows: Add the soil sample to be detected and the fluorescent complex of the present invention into deionized water, stir for 15 min to mix evenly, then separate the fluorescent complex with a strong magnet. After reacting with the hydrogen peroxide matrix solution in the fluorescent complex for 15 min, add dilute sulfuric acid solution and potassium iodide solution, stir and react for 15 min, then make up the volume with distilled water and measure the fluorescence intensity with a fluorescence spectrophotometer to obtain the intensity of the interphase effect in the soil sample, and monitor the range of the soil interphase effect according to soil samples from different regions and depths.

[0027] The beneficial effects of the present invention:

[0028] (1) By adsorbing and fixing rhodamine B in the magnetic fluorescent complex carrier formed by biochar and magnetite, the present invention can identify catalase and produce fluorescence labeling, and adsorb with microplastics in the soil under the hydrophobic interaction on the surface of the fluorescent complex, and fluorescently label the catalase in the plastisphere on the surface of the microplastics, thereby measuring the range of the interphase effect in the soil.

[0029] (2) By modifying biochar with calcium ions, the adsorption capacity of the fluorescent complex carrier for the fluorescent agent rhodamine B is enhanced. Due to the magnetite in the magnetic fluorescent complex carrier, the present invention can be magnetically separated after measurement, is easy to detect, easy to separate, and can be reused.

[0030] (3) By loading nickel ions onto the magnetite of the magnetic fluorescent complex carrier in the present invention, the groups on the catalase are chelated by the present invention, so that the catalase on the plastisphere is adsorbed by the present invention and labeled with rhodamine B fluorescence, improving the accuracy of detection. Detailed implementation manners

[0031] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0032] Example 1

[0033] A fluorescent complex for labeling the soil plastisphere comprises the following components by weight:

[0034] 20 parts of Ni composite fluorescent complex carrier, 3 parts of rhodamine B and 10 parts of (3-aminopropyl) triethoxysilane;

[0035] The preparation method of the Ni composite fluorescent complex carrier is as follows:

[0036] Dissolve 2 g of nickel nitrate hexahydrate powder in 250 mL of deionized water in a reaction kettle, stir evenly, then add 50 mL of 30 wt% hydrogen peroxide solution to the reaction kettle to obtain a nickel nitrate solution. Put the nickel nitrate solution and 5 g of magnetic fluorescent complex carrier into a high-pressure reaction kettle and carry out hydrothermal reaction at 70 °C for 24 h. Wash the precipitate with water and absolute ethanol until the last washing solution is neutral, and then dry it in vacuum at 60 °C to obtain the Ni composite fluorescent complex carrier.

[0037] By hydrothermal reaction, nickel ions are loaded onto the magnetite of the magnetic fluorescent complex carrier. Nickel ions are positively charged and catalase is negatively charged, making them more likely to bind. Moreover, there is a metal chelation effect between nickel ions and the His imidazole group on catalase, enabling the fluorescent complex carrier to effectively bind to the catalase in the plastisphere and increasing the adsorption capacity of the fluorescent complex.

[0038] The preparation method of the magnetic fluorescent complex carrier is as follows:

[0039] In a reaction kettle, 3 g of the fluorescent complex carrier and 1 L of ethylene glycol were mixed and ultrasonically dispersed evenly. Then, 10 g of ferric chloride hexahydrate, 30 g of anhydrous sodium acetate, and 90 g of 1,6 - hexanediamine were successively added to the reaction kettle and dispersed under ultrasonic treatment for 20 min to obtain a mixture. The mixture was placed in a high - pressure reaction kettle and subjected to a mixing reaction at 180 °C for 3.5 h. After the reactants were cooled, the solid product was collected with a magnet. The solid product was washed with water and absolute ethanol until the last washing liquid was neutral, and then dried at 30 °C to obtain the magnetic fluorescent complex carrier.

[0040] The magnetic fluorescent complex carrier was synthesized by the solvent co - heating method with the fluorescent complex carrier and magnetite, enabling the carrier to be magnetically separated and reused.

[0041] The preparation method of the fluorescent complex carrier is as follows:

[0042] The dried corn straw was ground and crushed to a particle size of 1 mm. In a reaction kettle, 8 g of the crushed corn straw was added to 150 mL of a calcium chloride solution with a concentration of 30 g / L, stirred and mixed for 24 h, then filtered and dried at room temperature for 24 h; under nitrogen conditions, the crushed corn straw was pyrolyzed in a muffle furnace for 1 h at a pyrolysis temperature of 550 °C to obtain crude biochar. 0.1 M hydrochloric acid solution was added to the crude biochar for washing to remove impurities, the supernatant was centrifuged, and the precipitate was washed with deionized water until the last washing liquid was neutral, and then dried, ground, and passed through a 60 - mesh sieve to obtain the fluorescent complex carrier.

[0043] By preparing calcium - ion - modified biochar, the adsorption capacity of the fluorescent complex carrier for the fluorescent agent rhodamine was enhanced. Under the condition of 550 - 600 °C, the generated biochar had more carboxyl functional groups and stronger hydrophobicity, enabling the fluorescent complex carrier to bind to microplastics under the action of hydrophobic partitioning force and enhancing the adsorption capacity of the fluorescent complex carrier for microplastics.

[0044] The preparation steps of the fluorescent complex are as follows:

[0045] S101: 0.1 g of rhodamine B was mixed with 1 L of absolute ethanol in a reaction kettle to prepare a 0.1 g / L rhodamine B ethanol solution;

[0046] S102: 1 L of the rhodamine ethanol solution was mixed with 5 g of the Ni composite fluorescent complex in a reaction kettle and ultrasonically oscillated for 30 min to obtain a fluorescent mixture;

[0047] S103: 2.1 mL of (3 - aminopropyl)triethoxysilane was mixed with 100 mL of deionized water in a reaction kettle to prepare a 2 wt% (3 - aminopropyl)triethoxysilane solution;

[0048] S104. Add 100 mL of 2 wt% (3-aminopropyl)triethoxysilane solution dropwise to 1 L of the fluorescent mixture in a reaction kettle. Stir magnetically during the dropping process. After the dropping is completed, continue stirring for 30 min, then filter and dry in vacuum at 60 °C to obtain the fluorescent complex.

[0049] After adding the Ni composite fluorescent complex carrier to the rhodamine B solution, rhodamine B is adsorbed by the Ni composite fluorescent complex carrier and fixed in the pores of the carrier under the cross-linking action of (3-aminopropyl)triethoxysilane; when the fluorescent complex adsorbs to microplastics, the catalase in the biofilm on the surface of the microplastics will be labeled by rhodamine B and produce fluorescence, thereby measuring the range of the actual effect of the microplastics.

[0050] Calcium chloride, hydrochloric acid, ethylene glycol, ferric chloride hexahydrate, anhydrous sodium acetate, 1,6-hexanediamine, hydrogen peroxide, rhodamine B, nickel nitrate hexahydrate, and (3-aminopropyl)triethoxysilane were all purchased from Sigma-Aldrich.

[0051] The usage method of the present invention is as follows: Add the soil sample to be detected and the fluorescent complex of the present invention to deionized water, stir for 15 min to mix evenly, then separate the fluorescent complex with a strong magnet. After reacting with the hydrogen peroxide matrix solution in the fluorescent complex for 15 min, add dilute sulfuric acid solution and potassium iodide solution, stir and react for 15 min, then make up the volume with distilled water and measure the fluorescence intensity with a fluorescence spectrophotometer, thereby obtaining the intensity of the actual effect in the soil sample, and monitoring the range of the soil actual effect according to soil samples from different regions and depths.

[0052] Example 2

[0053] A fluorescent complex for labeling the rhizosphere of soil microplastics, comprising the following components by weight:

[0054] 35 parts of Ni composite fluorescent complex carrier, 5 parts of rhodamine B, and 15 parts of (3-aminopropyl)triethoxysilane;

[0055] The preparation method of the Ni composite fluorescent complex carrier is as follows:

[0056] Dissolve 2.15 g of nickel nitrate hexahydrate powder in 275 mL of deionized water in a reaction kettle, stir evenly, then add 55 mL of 30 wt% hydrogen peroxide solution to the reaction kettle to obtain a nickel nitrate solution. Put the nickel nitrate solution and 5.5 g of magnetic fluorescent complex carrier into a high-pressure reaction kettle and carry out hydrothermal reaction at 75 °C for 24 h. Wash the product with water and anhydrous ethanol until the last washing liquid is neutral, and then dry in vacuum at 60 °C to obtain the Ni composite fluorescent complex carrier.

[0057] The preparation method of the magnetic fluorescent complex carrier is as follows:

[0058] Mix 3.5 g of the fluorescent complex carrier and 1 L of ethylene glycol in a reaction kettle, and ultrasonically disperse them evenly. Then, sequentially add 11 g of ferric chloride hexahydrate, 33 g of anhydrous sodium acetate, and 95 g of 1,6 - hexanediamine to the reaction kettle, and disperse for 25 min under ultrasonic treatment to obtain a mixture. Put the mixture into a high - pressure reaction kettle and carry out a mixing reaction at 190 °C for 4 h. After the reactants are cooled, collect the solid product with a magnet, wash the solid product with water and absolute ethanol until the last washing liquid is neutral, and then dry at 40 °C to obtain the magnetic fluorescent complex carrier.

[0059] The preparation method of the fluorescent complex carrier is as follows:

[0060] Grind the dried corn straw to a particle size of 1.5 mm. Add 9 g of the ground corn straw to 175 mL of a calcium chloride solution with a concentration of 30 g / L in a reaction kettle, stir and mix for 24 h, then filter and dry at room temperature for 24 h. Pyrolyze the ground corn straw in a muffle furnace for 1 h under nitrogen conditions at a pyrolysis temperature of 575 °C to obtain crude biochar. Add 0.1 M hydrochloric acid solution to the crude biochar for washing to remove impurities, then centrifuge to separate the supernatant, wash the precipitate with deionized water until the last washing liquid is neutral, and then dry and grind at 98 °C, and pass through a 60 - mesh sieve to obtain the fluorescent complex carrier.

[0061] The preparation steps of the fluorescent complex are as follows:

[0062] S101: Mix 0.125 g of rhodamine B and 1 L of absolute ethanol in a reaction kettle to prepare a 0.125 g / L rhodamine B ethanol solution;

[0063] S102: Mix 1 L of the rhodamine ethanol solution and 5.5 g of Ni composite fluorescent complex in a reaction kettle and ultrasonically oscillate for 35 min to obtain a fluorescent mixture;

[0064] S103: Mix 2.4 mL of (3 - aminopropyl)triethoxysilane and 100 mL of deionized water in a reaction kettle to prepare a 2.25 wt% (3 - aminopropyl)triethoxysilane solution;

[0065] S104: Drop 100 mL of the 2.25 wt% (3 - aminopropyl)triethoxysilane solution into 1 L of the fluorescent mixture in a reaction kettle, stir magnetically during the dropping process, continue to stir for 30 min after the dropping is completed, then filter, and dry in vacuum at 60 °C to obtain the fluorescent complex.

[0066] Example 3

[0067] A fluorescent complex for labeling the soil micro - plastic rhizosphere, comprising the following components by weight:

[0068] 50 parts of Ni composite fluorescent complex carrier, 8 parts of rhodamine B, and 20 parts of (3-aminopropyl)triethoxysilane;

[0069] The preparation method of the Ni composite fluorescent complex carrier is as follows:

[0070] Dissolve 2.3 g of nickel nitrate hexahydrate powder in 300 mL of deionized water in a reaction kettle, stir evenly, then add 60 mL of 30 wt% hydrogen peroxide solution to the reaction kettle to obtain a nickel nitrate solution. Put the nickel nitrate solution and 6 g of magnetic fluorescent complex carrier into a high-pressure reaction kettle and carry out hydrothermal reaction at 80 °C for 24 h. Wash the product with water and absolute ethanol until the last washing liquid is neutral, and then dry it in vacuum at 60 °C to obtain the Ni composite fluorescent complex carrier.

[0071] The preparation method of the magnetic fluorescent complex carrier is as follows:

[0072] Mix 4 g of fluorescent complex carrier and 1 L of ethylene glycol in a reaction kettle and disperse them evenly by ultrasonic treatment. Then, sequentially add 12 g of ferric chloride hexahydrate, 36 g of anhydrous sodium acetate, and 100 g of 1,6-hexanediamine to the reaction kettle, and disperse them for 30 min under ultrasonic treatment to obtain a mixture. Put the mixture into a high-pressure reaction kettle and carry out a mixing reaction at 200 °C for 4.5 h. After the reactants are cooled, collect the solid product with a magnet. Wash the solid product with water and absolute ethanol until the last washing liquid is neutral, and then dry it at 50 °C to obtain the magnetic fluorescent complex carrier.

[0073] The preparation method of the fluorescent complex carrier is as follows:

[0074] Grind and crush the dried corn straw to a particle size of 2 mm. Add 10 g of crushed corn straw to 200 mL of calcium chloride solution with a concentration of 30 g / L in a reaction kettle, stir and mix for 24 h, then filter and dry at room temperature for 24 h. Pyrolyze the crushed corn straw in a muffle furnace for 1 h under nitrogen conditions at a pyrolysis temperature of 600 °C to obtain crude biochar. Add 0.1 M hydrochloric acid solution to the crude biochar to wash away impurities, then centrifuge to separate the supernatant, wash the precipitate with deionized water until the last washing liquid is neutral, and then dry, grind, and pass through a 60-mesh sieve to obtain the fluorescent complex carrier.

[0075] The preparation steps of the fluorescent complex are as follows:

[0076] S101. Mix 0.15 g of rhodamine B with 1 L of absolute ethanol in a reaction kettle to prepare a 0.15 g / L rhodamine B ethanol solution;

[0077] S102. Mix 1 L of rhodamine ethanol solution with 6 g of Ni composite fluorescent complex in a reaction kettle and ultrasonically oscillate for 40 min to obtain a fluorescent mixture;

[0078] S103. Mix 2.65 mL of (3-aminopropyl)triethoxysilane with 100 mL of deionized water in a reaction kettle to prepare a 0.25 wt% (3-aminopropyl)triethoxysilane solution;

[0079] S104. Drop 100 mL of a 2.25 wt% (3-aminopropyl)triethoxysilane solution into 1 L of a fluorescent mixture in a reaction kettle. Stir magnetically during the dropping process. After the dropping is completed, continue stirring for 30 min, then filter, and dry in vacuum at 60 °C to obtain a fluorescent complex.

[0080] Comparative Example 1

[0081] The difference from Example 1 is that the preparation method of the fluorescent complex carrier is as follows:

[0082] Grind and crush the dry corn straw to a particle size of 1 mm. Take 8 g of the crushed corn straw and pyrolyze it in a muffle furnace for 1 hour under nitrogen conditions at a pyrolysis temperature of 550 °C to obtain crude biochar. Add 0.1 M hydrochloric acid solution to the crude biochar for washing to remove impurities, then centrifuge to separate the supernatant. Wash the precipitate with deionized water until the last washing solution is neutral, then dry and grind at 95 °C, and pass through a 60-mesh sieve to obtain the fluorescent complex carrier.

[0083] Comparative Example 2

[0084] The difference from Example 1 is that the steps for preparing the fluorescent complex are as follows: Mix 0.1 g of rhodamine B with 1 L of absolute ethanol in a reaction kettle to prepare a 0.1 g / L rhodamine B ethanol solution. Mix 1 L of the rhodamine ethanol solution with 5 g of Ni composite fluorescent complex in a reaction kettle and ultrasonically vibrate for 30 min to obtain a fluorescent mixture, filter, and dry in vacuum at 60 °C to obtain the fluorescent complex.

[0085] Comparative Example 3

[0086] The difference from Example 1 is that in the steps for preparing the fluorescent complex, S103 is: Mix 4.2 mL of (3-aminopropyl)triethoxysilane with 100 mL of deionized water in a reaction kettle to prepare a 4 wt% (3-aminopropyl)triethoxysilane solution.

[0087] Comparative Example 4

[0088] The difference from Example 1 is that in the steps for preparing the fluorescent complex, S103 is: Mix 1.05 mL of (3-aminopropyl)triethoxysilane with 100 mL of deionized water in a reaction kettle to prepare a 1 wt% (3-aminopropyl)triethoxysilane solution.

[0089] The content of rhodamine B in the filtrate obtained by filtration in step S104 of Examples 1-3 and Comparative Examples 1-4 was detected using a fluorescence spectrophotometer. With 365 nm as the excitation wavelength, the fluorescence intensity of the solution at 585 nm was detected, and the adsorption rates of rhodamine B by Examples 1-3 and Comparative Examples 1-3 were calculated based on the fluorescence intensity. The adsorption rates are shown in Table 1:

[0090] Table 1

[0091]

[0092] From the data in Table 1, it can be seen that Examples 1-3 of the present invention have a high adsorption capacity for rhodamine B, and the adsorption rate of rhodamine B can reach more than 85%; in Comparative Example 1, since no calcium chloride solution was added, there were no calcium ions on the surface of the obtained biochar, so the adsorption capacity for rhodamine B was weak; in Comparative Example 2, since no coupling agent was added, some rhodamine B was lost on the surface of the complex during filtration, so the adsorption rate was slightly lower than that of Examples 1-3; in Comparative Example 3, since the amount of coupling agent added was too much, the pores of the complex were blocked, resulting in a low adsorption rate of rhodamine B; in Comparative Example 4, since the amount of coupling agent added was small, the adsorption rate of rhodamine B was slightly lower than that of Examples 1-3;

[0093] Examples 1-3 and Comparative Examples 1-4 were respectively treated with inactivated soil according to the usage method of the present invention, and a fluorescence spectrophotometer was used to detect the fluorescence intensity of the solution at 585 nm with 365 nm as the excitation wavelength. The measurement results are shown in Table 2:

[0094] Table 2

[0095]

[0096] From the data in Table 2, it can be seen that in Comparative Example 1, since the content of adsorbed rhodamine B was low, the fluorescence intensity was lower than that of Examples 1-3; in Comparative Example 2, since no coupling agent was added, part of the rhodamine B was dissolved and lost in the solution during the treatment, resulting in a low fluorescence intensity; in Comparative Example 3, since the coupling agent blocked the pores of the complex and the adsorption amount of rhodamine B was low, the fluorescence intensity was low; in Comparative Example 4, since the amount of coupling agent added was small, a small amount of rhodamine B was dissolved and lost in the solution during the treatment, resulting in a lower fluorescence intensity than that of Examples 1-3.

[0097] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0098] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A fluorescent complex for labeling the soil microplastic rhizosphere, characterized in that, It includes the following components by weight parts: 20 - 50 parts of Ni composite fluorescent complex carrier, 3 - 8 parts of rhodamine B, and 10 - 20 parts of (3 - aminopropyl)triethoxysilane.

2. The fluorescent complex for labeling the soil microplastic rhizosphere according to claim 1, wherein, The preparation method of the Ni composite fluorescent complex carrier is as follows: React nickel nitrate solution and magnetic fluorescent complex carrier in a reaction kettle at 70 - 80 °C for 24 h. After the product is washed to neutrality and dried, the Ni composite fluorescent complex carrier is obtained.

3. A fluorescent complex for labeling soil microplastic rhizospheres according to claim 2, characterized in that, The nickel nitrate solution is prepared through the following steps: Dissolve nickel nitrate hexahydrate powder in deionized water in a reaction kettle, stir and disperse, and then stir with 30 wt% hydrogen peroxide solution. The dosage ratio of nickel nitrate hexahydrate, deionized water, and hydrogen peroxide solution is: 2 - 2.3 g : 250 - 300 mL : 50 mL - 60 mL.

4. A fluorescent complex for labeling the soil microplastic rhizosphere according to claim 2, characterized in that, The preparation method of the magnetic fluorescent complex carrier is as follows: Mix the fluorescent complex carrier and ethylene glycol in a reaction kettle and ultrasonically disperse them. Then, successively add ferric chloride hexahydrate, sodium acetate anhydrous, and 1,6 - hexanediamine and continue ultrasonically dispersing. React at 180 - 200 °C in the reaction kettle for 3.5 - 4.5 h. Collect the solid product with a magnet, wash and dry it to obtain the magnetic fluorescent complex carrier.

5. A fluorescent complex for labeling the soil microplastic rhizosphere according to claim 4, characterized in that, The dosage ratio of the fluorescent complex carrier, ethylene glycol, ferric chloride hexahydrate, sodium acetate anhydrous, and 1,6 - hexanediamine is: 3 - 4 g : 1 L : 10 - 12 g : 30 - 36 g : 90 - 100 g.

6. A fluorescent complex for labeling the soil microplastic rhizosphere according to claim 5, characterized in that, The preparation method of the fluorescent complex carrier is as follows: Mix the crushed and dried corn straw with 30 g / L calcium chloride solution in a reaction kettle, filter and dry, then put it into a muffle furnace under nitrogen condition at 550 - 600 °C for pyrolysis for 1 h. Wash the solid reactant with dilute hydrochloric acid to neutrality, dry and grind, and pass through a 60 - mesh sieve to obtain the fluorescent complex carrier; The dosage ratio of corn straw and calcium chloride solution is: 8 - 10 g : 150 - 200 mL.

7. A method for preparing a fluorescent complex for labeling the soil microplastic rhizosphere according to any one of claims 1-6, characterized in that, It includes the following steps: S101. Mix rhodamine B and absolute ethanol in a reaction kettle to prepare a 0.1 - 0.15 g / L rhodamine B ethanol solution; S102. Mix the rhodamine ethanol solution and the Ni composite fluorescent complex in a reaction kettle and ultrasonically oscillate for 30 - 40 min to obtain a fluorescent mixture. The dosage ratio of the rhodamine ethanol solution and the Ni composite fluorescent complex is: 1 L : 5 - 6 g; S103. Mix (3 - aminopropyl)triethoxysilane and deionized water in a reaction kettle to prepare a 2 - 2.5 wt% (3 - aminopropyl)triethoxysilane solution; S104. Drop the (3 - aminopropyl)triethoxysilane solution into the fluorescent mixture in a reaction kettle at a volume ratio of 1:10 - 15. Stir magnetically during the dropping process. After the dropping is completed, continue stirring for 30 min, then filter and vacuum - dry at 60 °C to obtain the fluorescent complex.

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