Bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification and preparation method thereof

Abstract

The present invention provides a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification and a preparation method thereof, belonging to the technical field of coordination complexes. The present invention obtains a bispyridine bisamide organic ligand by using chlorinated 4,4'-stilbene dicarboxylic acid and a halogen-containing pyridine compound and introducing mercaptosulfur quantum dots, which can effectively reduce soil nitrate reductase while increasing soil urease activity.

Description

Technical Field

[0001] The present invention belongs to the technical field of coordination complexes, and particularly relates to a bipyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification and a preparation method thereof. Background Art

[0002] Coordination polymers (which can be called complexes or coordination compounds) are inorganic-organic hybrid materials obtained by self-assembling transition metals such as Co, Zn, Cu, etc., and organic ligands. Due to this special composition method, complexes not only combine the advantages of inorganic materials such as high fire resistance, light weight, and environmental protection, but also have the characteristics of organic materials, such as porosity and good designability. Ligands (abbreviated as ligands) are divided into monodentate and polydentate according to the number of coordinating atoms. Monodentate ligands have one coordinating atom and can directly coordinate with the central atom; polydentate ligands have two or more coordinating atoms and can form various coordination modes with the central atom, such as chelating coordination.

[0003] Chinese Patent (Publication No. CN103724365A) discloses a transition metal complex based on a semi-rigid bipyridine bisamide organic ligand and terephthalic acid, a synthesis method and an application thereof. The invention uses the semi-rigid bipyridine bisamide ligand N,N'-bis(3-pyridinecarboxamido)-1,2-cyclohexane as a neutral organic amine ligand. Not only do the pyridine nitrogen atoms coordinate with metal ions, but also the amide oxygen atoms are potential coordination sites. And due to the introduction of the amide group, the hydrophilicity of the ligand is increased, the crystallization process during the synthesis of the transition metal complex is accelerated, the synthesis cycle is shortened, the constant temperature time is shortened, and the power consumption is reduced. However, this patented technology still fails to solve the problem that when the bipyridine bisamide organic ligand is applied to soil fertilizers, it cannot effectively regulate soil urease activity and inhibit nitrification, thus restricting the use of the bipyridine bisamide organic ligand.

[0004] Therefore, there is an urgent need for a bipyridine bisamide organic ligand that, by functionalizing the raw material components and introducing modified components, can effectively reduce soil nitrate reductase while increasing soil urease activity. Summary of the Invention

[0005] The purpose of the present invention is to provide a bipyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification and a preparation method thereof. By using chlorinated 4,4'-stilbenedicarboxylic acid and halogen-containing pyridine compounds, and introducing thiol-containing sulfur quantum dots, a bipyridine bisamide organic ligand is obtained, which can effectively reduce soil nitrate reductase while increasing soil urease activity.

[0006] To achieve the above purpose, the present invention provides the following technical solutions:

[0007] The first aspect of the present invention provides a preparation method of a dipyridyl bisamide organic ligand for regulating soil urease activity and inhibiting nitrification, comprising the following steps:

[0008] Step S1: By weight, add 20 - 25 parts of 4,4'-stilbenedicarboxylic acid and 12 - 15 parts of N-chlorosuccinimide to 40 - 50 parts of dichloromethane, stir for 10 - 20 min, then add 2 - 4 parts of trifluoroacetic acid and stir to react for 12 - 24 h to obtain a reaction mixture. Pour the reaction mixture into ice water, extract with an organic solvent, dry, concentrate, and recrystallize to obtain chlorinated 4,4'-stilbenedicarboxylic acid;

[0009] Step S2: By weight, add 6 - 8 parts of the chlorinated 4,4'-stilbenedicarboxylic acid, 4 - 6 parts of a pyridine compound, and 0.2 - 0.5 parts of a quantum dot material to 60 - 70 parts of pyridine, stir for 30 - 60 min, then add 14 - 16 parts of triphenyl phosphite, heat to 110 - 120 °C, reflux for 10 - 12 h, then cool, let stand, filter to collect the solid, wash with absolute ethanol, and dry to obtain a dipyridyl bisamide organic ligand for regulating soil urease activity and inhibiting nitrification.

[0010] Chlorinated 4,4'-stilbenedicarboxylic acid can provide chlorine elements for microorganisms, promote the growth and metabolism of microorganisms, and indirectly increase urease activity by enhancing the activity of microorganisms; at the same time, chlorine elements can form soluble complexes with metal ions in the soil, increase the bioavailability of these metal ions, and ensure that metal ions can serve as important cofactors for urease activity.

[0011] As a preferred scheme, the organic solvent in step S1 is ether or ethyl acetate.

[0012] As a preferred scheme, the pyridine compound in step S2 is a halogen-containing pyridine compound.

[0013] As a preferred scheme, the halogen-containing pyridine compound is 2-fluoro-3-amino-4-methylpyridine and 2-bromo-3-amino-4-methylpyridine.

[0014] As a preferred scheme, the mass ratio of 2-fluoro-3-amino-4-methylpyridine to 2-bromo-3-amino-4-methylpyridine is (1 - 2):1.

[0015] The halogen in the pyridine compound can bind to the key amino acid residues of nitrifying enzymes, interfere with the active sites of the enzymes, thereby reducing the activity of nitrifying enzymes; at the same time, the halogen can also interfere with the cell membrane structure and function of nitrifying bacteria, inhibit their growth and metabolism, and comprehensively affect the activity of nitrifying bacteria and inhibit nitrification.

[0016] As a preferred solution, the quantum dot material in step S2 is a mercapto sulfur quantum dot.

[0017] As a preferred solution, the preparation method of the mercapto sulfur quantum dot includes: by weight, dispersing 5-10 parts of sulfur quantum dots in 40-50 parts of deionized water to obtain a sulfur quantum dot mixture, then performing plasma treatment on the sulfur quantum dot mixture, and after the plasma treatment is completed, adding 1-3 parts of mercaptoacetic acid and 0.2-0.5 parts of 1-hydroxybenzotriazole to the sulfur quantum dot mixture, stirring and reacting for 2-4 h, centrifuging, washing, and drying after the reaction is completed to obtain the mercapto sulfur quantum dot.

[0018] As a preferred solution, the preparation method of the sulfur quantum dot includes: by weight, adding 4-6 parts of sodium hydroxide and 3-5 parts of polyethylene glycol to 40-50 parts of deionized water, stirring evenly and then adding 1-2 parts of sulfur powder, stirring at 70-75 °C for 2-4 h to obtain an orange-red solution; using a peristaltic pump to introduce air into the orange-red solution and continuing to react for 20-24 h, after the reaction is completed, adding 10-12 parts of a 35% hydrogen peroxide solution by mass concentration and reacting for 40-60 min, cooling to room temperature after the reaction is completed to obtain a light yellow solution, dialyzing, rotary evaporating, and freeze-drying to obtain the sulfur quantum dot.

[0019] As a preferred solution, the average particle size of the sulfur powder is 0.5 μm.

[0020] The charge on the surface of the mercapto sulfur quantum dot can form a complex with the positively charged metal ions in the soil through electrostatic attraction, and improve the utilization rate of metal ions by soil urease in the form of a complex, thereby improving the activity of soil urease.

[0021] The second aspect of the present invention provides a bipyridyl bisamide organic ligand for regulating soil urease activity and inhibiting nitrification prepared by the preparation method described in the first aspect.

[0022] Compared with the prior art, the advantages and beneficial effects of the present invention are:

[0023] 1. The mercapto group of the sulfur quantum dot of the present invention forms a covalent bond with the key amino acid residues of nitrifying enzyme, interfering with the active site of nitrifying enzyme, while the halogen in the pyridine compound can bind to the active site of nitrifying enzyme, further reducing the activity of nitrifying enzyme, thereby inhibiting nitrification.

[0024] 2. The chlorinated 4,4'-stilbenedicarboxylic acid of the present invention can provide chlorine elements for microorganisms, promote the growth and metabolism of microorganisms, and indirectly increase the urease activity by enhancing the microbial activity; meanwhile, the chlorine elements can form soluble complexes with metal ions in the soil, increase the bioavailability of these metal ions, and ensure that the metal ions can serve as important cofactors for urease activity.

[0025] 3. The halogen in the pyridine compound of the present invention can bind to the key amino acid residues of nitrase, interfere with the active site of the enzyme, and thus reduce the activity of nitrase; meanwhile, the halogen can also interfere with the cell membrane structure and function of nitrifying bacteria, inhibit their growth and metabolism, and comprehensively affect the activity of nitrifying bacteria and inhibit nitrification.

[0026] 4. The charge on the surface of the mercapto sulfur quantum dots of the present invention can form a complex with the positively charged metal ions in the soil through electrostatic attraction, and improve the utilization rate of metal ions by soil urease in the form of the complex, thereby increasing the activity of soil urease. Detailed implementation manners

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative efforts shall fall within the protection scope of the present invention.

[0028] The sources of some components in the examples and comparative examples are as follows:

[0029] 4,4'-stilbenedicarboxylic acid, CAS No. 100-31-2, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0030] 3-amino-4-methylpyridine, CAS No. 3430-27-1, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0031] Pyridine, CAS No. 110-86-1, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0032] Triphenyl phosphite, CAS No. 101-02-0, purchased from Nantong Runzhou Chemical Co., Ltd.;

[0033] N-chlorosuccinimide, CAS No. 128-09-6, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0034] Dichloromethane, CAS No. 75-09-2, purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0035] Trifluoroacetic acid, CAS No. 76-05-1, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0036] Absolute ethanol, CAS No. 64-17-5, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0037] Ethyl acetate, CAS No. 141-78-6, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0038] Diethyl ether, CAS No. 60-29-7, was purchased from Sinopharm Chemical Reagent Co., Ltd.;

[0039] 2-Fluoro-3-amino-4-methylpyridine, CAS No. 173435-32-0, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0040] 2-Bromo-3-amino-4-methylpyridine, CAS No. 126325-50-6, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0041] Polyethylene glycol, product number 202398-250G, was purchased from Sigma-Aldrich;

[0042] Sulfur powder I, with an average particle size of 0.5 μm, was purchased from Anngene (Shanghai) Pharmaceutical Chemistry Co., Ltd.;

[0043] Sulfur powder II, with an average particle size of 45 μm, was purchased from Sigma-Aldrich;

[0044] Hydrogen peroxide solution, product number H433859-250ml, with a mass concentration of 35%, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0045] Mercaptoacetic acid, CAS No. 68-11-1, was purchased from Shandong Jinghao Chemical Co., Ltd.;

[0046] 1-Hydroxybenzotriazole, CAS No. 2592-95-2, was purchased from Shanghai Anngene Chemical Reagent Co., Ltd.

[0047] Example 1

[0048] This example provides a preparation method of a dipyridyl diamide organic ligand for regulating soil urease activity and inhibiting nitrification, including the following steps:

[0049] Preparation of mercapto-containing sulfur quantum dots: (1) By weight, add 6 parts of sodium hydroxide and 5 parts of polyethylene glycol to 50 parts of deionized water. After stirring evenly, add 2 parts of sulfur powder (sulfur powder I, with an average particle size of 0.5 μm), and stir at 75 °C for 2 h to obtain an orange-red solution; use a peristaltic pump to introduce air into the orange-red solution and continue the reaction for 24 h. After the reaction is completed, add 12 parts of a 35% hydrogen peroxide solution by mass and react for 60 min. After the reaction is completed, cool to room temperature to obtain a light yellow solution, dialyze, rotary evaporate, and freeze-dry to obtain sulfur quantum dots. (2) By weight, disperse 10 parts of sulfur quantum dots in 50 parts of deionized water to obtain a sulfur quantum dot mixture, and then perform plasma treatment on the sulfur quantum dot mixture. After the plasma treatment is completed, add 3 parts of mercaptoacetic acid and 0.5 part of 1-hydroxybenzotriazole to the sulfur quantum dot mixture, stir and react for 4 h. After the reaction is completed, centrifuge, wash, and dry to obtain mercapto-containing sulfur quantum dots.

[0050] Step S1: By weight, add 25 parts of 4,4'-stilbenedicarboxylic acid and 15 parts of N-chlorosuccinimide to 50 parts of dichloromethane, stir for 20 min, then add 4 parts of trifluoroacetic acid and stir and react for 24 h to obtain a reaction mixture. Pour the reaction mixture into ice water, extract with ethyl acetate, dry, concentrate, and recrystallize to obtain chlorinated 4,4'-stilbenedicarboxylic acid.

[0051] Step S2: By weight, add 8 parts of the chlorinated 4,4'-stilbenedicarboxylic acid, 4 parts of 2-fluoro-3-amino-4-methylpyridine, 2 parts of 2-bromo-3-amino-4-methylpyridine, and 0.5 part of mercapto-containing sulfur quantum dots to 70 parts of pyridine, stir for 60 min, then add 16 parts of triphenyl phosphite, heat to 120 °C, reflux for 10 h, then cool, stand, filter to collect the solid, wash with absolute ethanol, and dry to obtain a bipyridyl diamide organic ligand for regulating soil urease activity and inhibiting nitrification.

[0052] Example 2

[0053] This example provides a preparation method of a bipyridyl diamide organic ligand for regulating soil urease activity and inhibiting nitrification, including the following steps:

[0054] Preparation of mercapto-containing sulfur quantum dots: (1) By weight, add 4 parts of sodium hydroxide and 3 parts of polyethylene glycol to 40 parts of deionized water. After stirring evenly, add 1 part of sulfur powder (sulfur powder I, with an average particle size of 0.5 μm), and stir at 70 °C for 4 h to obtain an orange-red solution; use a peristaltic pump to introduce air into the orange-red solution and continue the reaction for 20 h. After the reaction is completed, add 10 parts of a 35% hydrogen peroxide solution by mass and react for 40 min. After the reaction is completed, cool to room temperature to obtain a light yellow solution, dialyze, rotary evaporate, and freeze-dry to obtain sulfur quantum dots. (2) By weight, disperse 5 parts of sulfur quantum dots in 40 parts of deionized water to obtain a sulfur quantum dot mixture, and then perform plasma treatment on the sulfur quantum dot mixture. After the plasma treatment is completed, add 1 part of mercaptoacetic acid and 0.2 part of 1-hydroxybenzotriazole to the sulfur quantum dot mixture, stir and react for 2 h. After the reaction is completed, centrifuge, wash, and dry to obtain mercapto-containing sulfur quantum dots.

[0055] Step S1: By weight, add 20 parts of 4,4'-stilbenedicarboxylic acid and 12 parts of N-chlorosuccinimide to 40 parts of dichloromethane, stir for 10 min, then add 2 parts of trifluoroacetic acid and stir and react for 12 h to obtain a reaction mixture. Pour the reaction mixture into ice water, extract with ether, dry, concentrate, and recrystallize to obtain chlorinated 4,4'-stilbenedicarboxylic acid.

[0056] Step S2: By weight, add 6 parts of the chlorinated 4,4'-stilbenedicarboxylic acid, 2 parts of 2-fluoro-3-amino-4-methylpyridine, 2 parts of 2-bromo-3-amino-4-methylpyridine, and 0.2 part of mercapto-containing sulfur quantum dots to 60 parts of pyridine, stir for 30 min, then add 14 parts of triphenyl phosphite, heat up to 110 °C, reflux for 12 h, then cool, let stand, filter to collect the solid, wash with absolute ethanol, and dry to obtain a bipyridyl diamide organic ligand for regulating soil urease activity and inhibiting nitrification.

[0057] Example 3

[0058] This example provides a preparation method of a bipyridyl diamide organic ligand for regulating soil urease activity and inhibiting nitrification, including the following steps:

[0059] Preparation of mercapto-containing sulfur quantum dots: (1) By weight, 5 parts of sodium hydroxide and 4 parts of polyethylene glycol are added to 45 parts of deionized water. After stirring evenly, 2 parts of sulfur powder (sulfur powder I, with an average particle size of 0.5 μm) are added, and the mixture is stirred at 72 °C for 3 h to obtain an orange-red solution. Air is introduced into the orange-red solution using a peristaltic pump and the reaction continues for 22 h. After the reaction, 11 parts of a 35% hydrogen peroxide solution by mass concentration are added and reacted for 50 min. After the reaction is completed, it is cooled to room temperature to obtain a light yellow solution, which is dialyzed, rotary evaporated, and freeze-dried to obtain sulfur quantum dots. (2) By weight, 8 parts of sulfur quantum dots are dispersed in 45 parts of deionized water to obtain a sulfur quantum dot mixture. Then, the sulfur quantum dot mixture is subjected to plasma treatment. After the plasma treatment is completed, 2 parts of mercaptoacetic acid and 0.4 part of 1-hydroxybenzotriazole are added to the sulfur quantum dot mixture, and the mixture is stirred and reacted for 3 h. After the reaction is completed, it is centrifuged, washed, and dried to obtain mercapto-containing sulfur quantum dots.

[0060] Step S1: By weight, 24 parts of 4,4'-stilbenedicarboxylic acid and 14 parts of N-chlorosuccinimide are added to 45 parts of dichloromethane, stirred for 15 min, and then 3 parts of trifluoroacetic acid are added and reacted for 20 h to obtain a reaction mixture. The reaction mixture is poured into ice water, extracted with ethyl acetate, dried, concentrated, and recrystallized to obtain chlorinated 4,4'-stilbenedicarboxylic acid.

[0061] Step S2: By weight, 7 parts of the chlorinated 4,4'-stilbenedicarboxylic acid, 3 parts of 2-fluoro-3-amino-4-methylpyridine, 2 parts of 2-bromo-3-amino-4-methylpyridine, and 0.4 part of mercapto-containing sulfur quantum dots are added to 65 parts of pyridine, stirred for 50 min, and then 15 parts of triphenyl phosphite are added. The temperature is raised to 115 °C, refluxed for 11 h, cooled, allowed to stand, and the solid is collected by suction filtration, washed with absolute ethanol, and dried to obtain a bipyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification.

[0062] Comparative Example 1

[0063] This comparative example provides a method for preparing a bipyridine bisamide organic ligand, which includes the following steps: By weight, 8 parts of 4,4'-stilbenedicarboxylic acid and 6 parts of 3-amino-4-methylpyridine are added to 70 parts of pyridine, stirred for 60 min, and then 16 parts of triphenyl phosphite are added. The temperature is raised to 120 °C, refluxed for 10 h, cooled, allowed to stand, and the solid is collected by suction filtration, washed with absolute ethanol, and dried to obtain a bipyridine bisamide organic ligand.

[0064] Comparative Example 2

[0065] This comparative example provides a method for preparing a bipyridine bisamide organic ligand. The difference between this comparative example and Comparative Example 1 is that chlorinated 4,4'-stilbenedicarboxylic acid is used instead of 4,4'-stilbenedicarboxylic acid.

[0066] Comparative Example 3

[0067] This comparative example provides a method for preparing a bipyridine bisamide organic ligand. The difference between this comparative example and Comparative Example 1 is that 4 parts of 2-fluoro-3-amino-4-methylpyridine and 2 parts of 2-bromo-3-amino-4-methylpyridine are used instead of 6 parts of 3-amino-4-methylpyridine.

[0068] Comparative Example 4

[0069] This comparative example provides a method for preparing a bipyridine bisamide organic ligand. The difference between this comparative example and Comparative Example 3 is that the amount of 2-bromo-3-amino-4-methylpyridine is changed from 2 parts to 1 part.

[0070] Comparative Example 5

[0071] This comparative example provides a method for preparing a bipyridine bisamide organic ligand. The difference between this comparative example and Comparative Example 3 is that the amount of 2-fluoro-3-amino-4-methylpyridine is changed from 4 parts to 1 part, and the amount of 2-bromo-3-amino-4-methylpyridine is changed from 2 parts to 4 parts.

[0072] Comparative Example 6

[0073] This comparative example provides a method for preparing a bipyridine bisamide organic ligand. The difference between this comparative example and Comparative Example 1 is that 0.5 part of mercapto-functionalized sulfur quantum dots is added.

[0074] Comparative Example 7

[0075] This comparative example provides a method for preparing a bipyridine bisamide organic ligand. The difference between this comparative example and Comparative Example 6 is that sulfur powder II (average particle size of 45 μm) is used instead of sulfur powder I (average particle size of 0.5 μm) to prepare mercapto-functionalized sulfur quantum dots.

[0076] Performance Test

[0077] The bipyridine bisamide organic ligands prepared in the above examples and comparative examples were subjected to the following tests: The soil urease was tested according to the requirements of "TNAIA 011-2020 Determination of Soil Urease Activity - Sodium Phenolate-Sodium Hypochlorite Colorimetric Method"; the soil nitrate reductase was determined by the phenoldisulfonic acid colorimetric method. The test results are shown in Table 1.

[0078] Table 1 Performance Test Results

[0079]

[0080] From the above performance test results, it can be seen that the comprehensive performance of the dipyridyl diamide organic ligands in Examples 1-3 is the most prominent. The soil urease tested is 156.97-158.82 IU / g, and the soil nitrate reductase is 2.66-2.78 IU / g. This is mainly because by using chlorinated 4,4'-stilbenedicarboxylic acid and halogen-containing pyridine compounds and introducing mercapto-functionalized sulfur quantum dots, while improving the soil urease activity, the soil nitrate reductase is effectively reduced.

[0081] In Comparative Example 1, since the necessary technical solutions were not adopted, its performance in the corresponding performance tests was significantly worse than that of the examples. The soil urease tested was 134.06 IU / g, and the soil nitrate reductase was 4.23 IU / g. Compared with Comparative Example 1, in Comparative Example 2, chlorinated 4,4'-stilbenedicarboxylic acid was used to replace 4,4'-stilbenedicarboxylic acid, and the soil urease increased. Compared with Comparative Example 1, in Comparative Example 3, 4 parts of 2-fluoro-3-amino-4-methylpyridine and 2 parts of 2-bromo-3-amino-4-methylpyridine were used to replace 6 parts of 3-amino-4-methylpyridine, and the soil nitrate reductase decreased. Compared with Comparative Example 3, in Comparative Example 4, the amount of 2-bromo-3-amino-4-methylpyridine was changed from 2 parts to 1 part, that is, the mass ratio of 2-fluoro-3-amino-4-methylpyridine to 2-bromo-3-amino-4-methylpyridine was greater than 2. Due to the excessive amount of 2-fluoro-3-amino-4-methylpyridine resulting in poor composite effect, the soil nitrate reductase increased. Compared with Comparative Example 1, in Comparative Example 5, the amount of 2-fluoro-3-amino-4-methylpyridine was changed from 4 parts to 1 part, and the amount of 2-bromo-3-amino-4-methylpyridine was changed from 2 parts to 4 parts, that is, the mass ratio of 2-fluoro-3-amino-4-methylpyridine to 2-bromo-3-amino-4-methylpyridine was less than 1. Due to the insufficient amount of 2-fluoro-3-amino-4-methylpyridine resulting in poor composite effect, the soil nitrate reductase increased. Compared with Comparative Example 1, in Comparative Example 6, 0.5 part of mercapto-functionalized sulfur quantum dots was added, and the soil urease increased. Compared with Comparative Example 6, in Comparative Example 7, sulfur powder II (particle size of 45 μm, purchased from Sigma-Aldrich) was used to replace sulfur powder I (particle size of 0.5 μm, purchased from Aladdin) to prepare mercapto-functionalized sulfur quantum dots. Due to the too large particle size of sulfur powder II resulting in poor preparation effect of sulfur quantum dots, the soil urease decreased. The above experimental results further prove the importance of the technical solutions defined in the present invention for its technical effects.

[0082] The above is the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification, characterized in that: include: Step S1: adding 20-25 parts of 4,4'-stilbene dicarboxylic acid and 12-15 parts of N-chlorosuccinimide to 40-50 parts of dichloromethane by weight, stirring for 10-20 minutes, adding 2-4 parts of trifluoroacetic acid, stirring for 12-24 hours to obtain a reaction mixture, pouring the reaction mixture into ice water, extracting with an organic solvent, drying, concentrating, and recrystallizing to obtain chlorinated 4,4'-stilbene dicarboxylic acid; Step S2: adding 6-8 parts of chlorinated 4,4'-stilbene dicarboxylic acid, 4-6 parts of pyridine compounds and 0.2-0.5 parts of quantum dot materials to 60-70 parts of pyridine by weight, stirring for 30-60 minutes, adding 14-16 parts of triphenyl phosphite, heating to 110-120° C., refluxing for 10-12 hours, cooling, standing, collecting solids by suction filtration, washing with anhydrous ethanol, and drying to obtain a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification; The pyridine compound is composed of 2-fluoro-3-amino-4-methylpyridine and 2-bromo-3-amino-4-methylpyridine in a mass ratio of (1-2):1; The quantum dot material is a thiol-containing sulfur quantum dot, and the preparation method thereof comprises: dispersing 5 to 10 parts of sulfur quantum dots in 40 to 50 parts of deionized water to obtain a sulfur quantum dot mixed solution, and then plasma treating the mixed solution, adding 1 to 3 parts of thioglycolic acid and 0.2 to 0.5 parts of 1-hydroxybenzotriazole to the sulfur quantum dot mixed solution after the plasma treatment, stirring the reaction for 2 to 4 hours, centrifuging, washing, and drying to obtain the thiol-containing sulfur quantum dots; The preparation method of sulfur quantum dots comprises: adding 4 to 6 parts of sodium hydroxide and 3 to 5 parts of polyethylene glycol to 40 to 50 parts of deionized water by weight, stirring evenly, adding 1 to 2 parts of sulfur powder, stirring at 70 to 75° C. for 2 to 4 hours to obtain an orange-red solution; using a peristaltic pump to introduce air into the orange-red solution for reaction for 20 to 24 hours, adding 10 to 12 parts of a 35% mass concentration hydrogen peroxide solution dropwise for reaction for 40 to 60 minutes after the reaction is completed, cooling to room temperature to obtain a light yellow solution, dialysis, rotary evaporation, and freeze-drying to obtain sulfur quantum dots; The average particle size of the sulfur powder is 0.5 μm.

2. A method for preparing a bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification according to claim 1, characterized in that: In step S1, the organic solvent is ether or ethyl acetate.

3. A bispyridine bisamide organic ligand for regulating soil urease activity and inhibiting nitrification, characterized in that: Prepared according to any one of the preparation methods of claims 1 to 2.

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