Preparation and application of pyraclostrobin nanocapsules

Abstract

The present invention relates to the technical field of pesticides, and in particular to the preparation and application of a pyraclostrobin nano-microcapsule. The present invention first uses an emulsifier and deionized water to prepare an aqueous phase, then divides the first aqueous phase and the second aqueous phase into equal mass, then adds pyraclostrobin and isophorone diisocyanate to an organic solvent to prepare an oil phase, then drops the oil phase into the first aqueous phase to prepare an oil-in-water emulsion, disperses modified carbon nanotubes in the second aqueous phase, obtains a modified liquid, and finally adds polyethylene glycol, 1,4-butanediol, a modified liquid and dodecylamine to the oil-in-water emulsion to obtain pyraclostrobin nano-microcapsules. The pyraclostrobin nano-microcapsules prepared by the present invention have efficient drug loading capacity, excellent encapsulation effect, and have excellent adhesion to leaves, and have broad application prospects and economic value.

Description

Technical Field

[0001] The invention relates to the technical field of pesticides, and in particular to the preparation and application of pyraclostrobin nano-microcapsules. Background Art

[0002] As a broad-spectrum fungicide, pyraclostrobin has the effect of inhibiting the growth and reproduction of pathogenic fungi. However, traditional formulations face multiple problems in practical applications. For example, the efficacy of the drug is easily affected by environmental conditions (such as rainfall and light), which leads to the loss of active ingredients and reduced efficacy. In addition, traditional spraying and spreading methods usually make it difficult to evenly distribute the drug on the crop leaves and improve the efficiency of drug utilization.

[0003] Microencapsulation technology is a technology that encapsulates active ingredients in micron or nanoparticles. It is widely used in many fields such as agriculture, medicine and food. Through this technology, pesticides can be effectively protected from the direct influence of environmental factors while achieving quantitative release. This not only prolongs the duration of the efficacy, but also reduces the total amount and frequency of agricultural applications. However, traditional microcapsules lack sufficient surface activity, resulting in insufficient adhesion to the wax layer of leaves. Secondly, the particle size and morphology of microcapsules are not ideal. The larger particle size and irregular morphology affect their adhesion and stability. As a result, they are easy to fall off the surface of the leaves after application, especially when encountering natural environmental factors such as wind and rain. This phenomenon is more obvious. This not only reduces the efficiency of pesticide use, but may also increase the frequency of application, leading to rising costs and increased environmental burdens. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a preparation method and application of pyraclostrobin nano-microcapsules to solve the problems of poor adhesion and poor resistance to rain erosion of traditional pyraclostrobin nano-microcapsules.

[0005] Based on the above purpose, the present invention provides a preparation method of pyraclostrobin nanocapsules, comprising the following steps:

[0006] (1) adding an emulsifier to deionized water, and then dividing the water into two equal parts by weight to obtain a first aqueous phase and a second aqueous phase;

[0007] (2) dissolving pyraclostrobin and isophorone diisocyanate in an organic solvent to obtain an oil phase;

[0008] (3) High-speed shearing of the first aqueous phase at 10,000-14,000 rpm and dropwise addition of the oil phase, stirring at room temperature for 20-40 minutes after the dropwise addition is completed, to obtain an oil-in-water emulsion;

[0009] (4) using polyethylene glycol monomethyl ether triethoxysilane and 3-aminopropyl triethoxysilane to modify carbon nanotubes to obtain modified carbon nanotubes;

[0010] (5) dispersing the modified carbon nanotubes in the second aqueous phase to obtain a modified liquid;

[0011] (6) Add polyethylene glycol to the oil-in-water emulsion, stir at room temperature for 20-40 minutes, then heat to 35-45°C, continue stirring for 0.5-2 hours, then continue to heat to 55-65°C, add 1,4-butanediol dropwise, continue stirring for 1 hour after the addition is complete, then add the modified liquid, continue stirring for 1 hour, and finally add dodecylamine, continue stirring for 0.5-2 hours to obtain pyraclostrobin nanocapsules.

[0012] Preferably, the emulsifier in step (1) is a mixture of Tween-80 and Span-80 in a weight ratio of 7:3.

[0013] Preferably, in step (1), the weight ratio of the emulsifier to the deionized water is 1:50.

[0014] Preferably, in step (2), the weight ratio of pyraclostrobin, isophorone diisocyanate and organic solvent is 2:1.2:5.

[0015] Preferably, the organic solvent in step (2) is one of n-butyl acetate, isobutyl acetate and n-propyl acetate.

[0016] Preferably, in step (3), the weight ratio of the first water phase to the oil phase is 25.5:8.2.

[0017] Preferably, in step (4), the outer diameter of the carbon nanotubes is 10-20 nm and the length is 0.5-2 μm.

[0018] Preferably, in step (4), the weight ratio of polyethylene glycol monomethyl ether triethoxysilane, 3-aminopropyl triethoxysilane and carbon nanotubes is 0.2-0.4:0.05-0.2:5.

[0019] Preferably, the weight average molecular weight of polyethylene glycol monomethyl ether triethoxysilane in step (4) is 1000.

[0020] Preferably, in step (6), the weight ratio of polyethylene glycol, isophorone diisocyanate in the oil-in-water emulsion, 1,4-butanediol, modified carbon nanotubes and dodecylamine in the modification liquid is 0.7:1.2:0.3:0.1-0.3:0.1-0.5.

[0021] Preferably, the weight average molecular weight of the polyethylene glycol in step (6) is 400.

[0022] Furthermore, the present invention also provides the use of the pyraclostrobin nanocapsules for preventing and controlling diseases caused by fungi on crops.

[0023] Beneficial effects of the present invention:

[0024] The present invention obtains pyraclostrobin nano-microcapsules with nano-scale particle sizes through a sophisticated preparation process. This feature not only improves the stable loading capacity of the drug, but also significantly improves the drug loading amount and encapsulation rate. The nano-microcapsules provided by the present invention can be quickly started at the initial stage of release and achieve stable release after 48 hours. The cumulative release rate of 96 hours reaches 65.8%, which helps to achieve a lasting protective effect.

[0025] After the pyraclostrobin nano-microcapsules prepared by the present invention are washed by rainwater, the residual rate of pyraclostrobin on rice leaves is as high as 75.3%, which shows that the pyraclostrobin nano-microcapsules have excellent adhesion performance and anti-rainwater washing ability, ensuring the continuity and stability of the drug effect. This performance improvement is mainly attributed to the surface modification of carbon nanotubes. By introducing polyethylene glycol monomethyl ether triethoxysilane and 3-aminopropyl triethoxysilane, these modifiers work synergistically to promote the uniform distribution and arrangement of carbon nanotubes on the surface of microcapsules, thereby enhancing the adhesion to rice leaves.

[0026] The dodecylamine introduced in the present invention further improves the rainwater erosion resistance of the nano-microcapsules. Dodecylamine contains a relatively long alkyl chain and has a significant hydrophobic effect, which enables it to be well combined with the lipid layer of rice leaves and penetrate into the lipid layer, thereby enhancing the adhesion. This intermolecular interaction not only improves the adhesion of the drug, but also enhances its stability in harsh environments.

[0027] In summary, the pyraclostrobin nanocapsules provided by the present invention have shown significant advantages in agricultural applications. Their efficient drug loading capacity, excellent encapsulation effect, sustained drug release characteristics and excellent adhesion properties enable them to significantly improve the use efficiency and effect of pyraclostrobin. This not only helps to reduce the use of pesticides and reduce environmental burdens, but also improves the protection effect of crops, and has broad application prospects and economic value. DETAILED DESCRIPTION

[0028] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments.

[0029] Carbon nanotubes were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. with the product number C579013, a diameter of 20-30 nm, and a length of 0.5-2 μm.

[0030] Example 1: (1) 0.7 g of Tween-80 and 0.3 g of Span-80 were added to 50 g of deionized water, stirred for 20 min, and then divided into two equal parts to obtain a first aqueous phase and a second aqueous phase;

[0031] (2) dissolving 2 g of pyraclostrobin and 1.2 g of isophorone diisocyanate in n-butyl acetate and stirring for 20 min to obtain an oil phase;

[0032] (3) The first aqueous phase was sheared at 10,000 rpm and the oil phase was added dropwise. After the addition was completed, stirring was continued at room temperature for 20 minutes to form a stable oil-in-water emulsion;

[0033] (4) Add 0.5 g of carbon nanotubes to a mixture of 1 g of deionized water and 9 g of anhydrous ethanol, ultrasonicate for 20 min, then add 0.02 g of polyethylene glycol monomethyl ether triethoxysilane with a weight average molecular weight of 1000 and 0.005 g of 3-aminopropyl triethoxysilane, stir at room temperature for 6 h, wash, and dry to obtain modified carbon nanotubes;

[0034] (5) The second aqueous phase was stirred at 300 rpm and 0.1 g of modified carbon nanotubes was added, followed by ultrasonic treatment for 20 min to obtain a modified solution;

[0035] (6) 0.7 g of polyethylene glycol with a weight average molecular weight of 400 was added to the water-in-oil emulsion, stirred at room temperature for 20 min, then heated to 35 °C and stirred for 0.5 h, then heated to 55 °C, 0.3 g of 1,4-butanediol was added dropwise, and after the addition was complete, stirring was continued for 1 h. The modified liquid was then added and stirred for 1 h. Finally, 0.1 g of dodecylamine was added and stirred for 0.5 h. The mixture was cooled to room temperature to obtain pyraclostrobin nanocapsules.

[0036] Example 2: (1) 0.7 g of Tween-80 and 0.3 g of Span-80 were added to 50 g of deionized water, stirred for 20 min, and then divided into two equal parts to obtain a first aqueous phase and a second aqueous phase;

[0037] (2) dissolving 2 g of pyraclostrobin and 1.2 g of isophorone diisocyanate in n-butyl acetate and stirring for 20 min to obtain an oil phase;

[0038] (3) The first aqueous phase was sheared at 12000 rpm and the oil phase was added dropwise. After the addition was completed, stirring was continued at room temperature for 30 minutes to form a stable oil-in-water emulsion;

[0039] (4) adding 0.5 g of carbon nanotubes to a mixture of 1 g of deionized water and 9 g of anhydrous ethanol, ultrasonicating for 20 min, then adding 0.03 g of polyethylene glycol monomethyl ether triethoxysilane with a weight average molecular weight of 1000 and 0.01 g of 3-aminopropyl triethoxysilane, stirring at room temperature for 6 h, washing, and drying to obtain modified carbon nanotubes;

[0040] (5) The second aqueous phase was stirred at 300 rpm and 0.2 g of modified carbon nanotubes was added, and ultrasonicated for 20 min to obtain a modified solution;

[0041] (6) 0.7 g of polyethylene glycol with a weight average molecular weight of 400 was added to the water-in-oil emulsion, stirred at room temperature for 30 min, then heated to 40 °C and stirred for 1 h, then heated to 60 °C, 0.3 g of 1,4-butanediol was added dropwise, and after the addition was complete, stirring was continued for 1 h, then the modified liquid was added and stirred for 1 h, and finally 0.2 g of dodecylamine was added and stirred for 1 h, and then cooled to room temperature to obtain pyraclostrobin nanocapsules.

[0042] Example 3: (1) 0.7 g of Tween-80 and 0.3 g of Span-80 were added to 50 g of deionized water, stirred for 20 min, and then divided into two equal parts to obtain a first aqueous phase and a second aqueous phase;

[0043] (2) dissolving 2 g of pyraclostrobin and 1.2 g of isophorone diisocyanate in n-butyl acetate and stirring for 20 min to obtain an oil phase;

[0044] (3) The first aqueous phase was sheared at 14000 rpm and the oil phase was added dropwise. After the addition was completed, stirring was continued at room temperature for 40 minutes to form a stable oil-in-water emulsion;

[0045] (4) Add 0.5 g of carbon nanotubes to a mixture of 1 g of deionized water and 9 g of anhydrous ethanol, ultrasonicate for 20 min, then add 0.04 g of polyethylene glycol monomethyl ether triethoxysilane with a weight average molecular weight of 1000 and 0.02 g of 3-aminopropyl triethoxysilane, stir at room temperature for 6 h, wash, and dry to obtain modified carbon nanotubes;

[0046] (5) The second aqueous phase was stirred at 300 rpm and 0.3 g of modified carbon nanotubes was added, and ultrasonicated for 20 min to obtain a modified solution;

[0047] (6) 0.7 g of polyethylene glycol with a weight average molecular weight of 400 was added to the water-in-oil emulsion, stirred at room temperature for 40 min, then heated to 45 °C and stirred for 2 h, then heated to 65 °C, 0.3 g of 1,4-butanediol was added dropwise, and after the addition was complete, stirring was continued for 1 h. The modified liquid was then added and stirred for 1 h. Finally, 0.5 g of dodecylamine was added and stirred for 2 h. The mixture was cooled to room temperature to obtain pyraclostrobin nanocapsules.

[0048] Comparative Example 1:

[0049] The difference between Comparative Example 1 and Example 2 is that: the carbon nanotubes are not modified;

[0050] The specific steps are as follows:

[0051] (1) Add 0.7 g of Tween-80 and 0.3 g of Span-80 to 50 g of deionized water, stir for 20 min, and then divide into two equal parts to obtain a first aqueous phase and a second aqueous phase;

[0052] (2) dissolving 2 g of pyraclostrobin and 1.2 g of isophorone diisocyanate in n-butyl acetate and stirring for 20 min to obtain an oil phase;

[0053] (3) The first aqueous phase was sheared at 12000 rpm and the oil phase was added dropwise. After the addition was completed, stirring was continued at room temperature for 30 minutes to form a stable oil-in-water emulsion;

[0054] (4) The second aqueous phase was stirred at 300 rpm and 0.2 g of carbon nanotubes was added, followed by ultrasonic treatment for 20 min to obtain a modified solution;

[0055] (5) 0.7 g of polyethylene glycol with a weight average molecular weight of 400 was added to the water-in-oil emulsion, stirred at room temperature for 30 min, then heated to 40 °C and stirred for 1 h, then heated to 60 °C, 0.3 g of 1,4-butanediol was added dropwise, and after the addition was complete, stirring was continued for 1 h, then the modified liquid was added and stirred for 1 h, and finally 0.2 g of dodecylamine was added and stirred for 1 h, and then cooled to room temperature to obtain pyraclostrobin nanocapsules.

[0056] Comparative Example 2:

[0057] The difference between Comparative Example 2 and Example 2 is that the carbon nanotubes are modified only with polyethylene glycol monomethyl ether triethoxysilane;

[0058] The specific steps are as follows:

[0059] (1) Add 0.7 g of Tween-80 and 0.3 g of Span-80 to 50 g of deionized water, stir for 20 min, and then divide into two equal parts to obtain a first aqueous phase and a second aqueous phase;

[0060] (2) dissolving 2 g of pyraclostrobin and 1.2 g of isophorone diisocyanate in n-butyl acetate and stirring for 20 min to obtain an oil phase;

[0061] (3) The first aqueous phase was sheared at 12000 rpm and the oil phase was added dropwise. After the addition was completed, stirring was continued at room temperature for 30 minutes to form a stable oil-in-water emulsion;

[0062] (4) adding 0.5 g of carbon nanotubes to a mixture of 1 g of deionized water and 9 g of anhydrous ethanol, ultrasonicating for 20 min, then adding 0.04 g of polyethylene glycol monomethyl ether triethoxysilane with a weight average molecular weight of 1000, stirring at room temperature for 6 h, washing, and drying to obtain modified carbon nanotubes;

[0063] (5) The second aqueous phase was stirred at 300 rpm and 0.2 g of modified carbon nanotubes was added, and ultrasonicated for 20 min to obtain a modified solution;

[0064] (6) 0.7 g of polyethylene glycol with a weight average molecular weight of 400 was added to the water-in-oil emulsion, stirred at room temperature for 30 min, then heated to 40 °C and stirred for 1 h, then heated to 60 °C, 0.3 g of 1,4-butanediol was added dropwise, and after the addition was complete, stirring was continued for 1 h, then the modified liquid was added and stirred for 1 h, and finally 0.2 g of dodecylamine was added and stirred for 1 h, and then cooled to room temperature to obtain pyraclostrobin nanocapsules.

[0065] Comparative Example 3:

[0066] The difference between Comparative Example 3 and Example 2 is that the carbon nanotubes are modified only with 3-aminopropyltriethoxysilane;

[0067] The specific steps are as follows:

[0068] (1) Add 0.7 g of Tween-80 and 0.3 g of Span-80 to 50 g of deionized water, stir for 20 min, and then divide into two equal parts to obtain a first aqueous phase and a second aqueous phase;

[0069] (2) dissolving 2 g of pyraclostrobin and 1.2 g of isophorone diisocyanate in n-butyl acetate and stirring for 20 min to obtain an oil phase;

[0070] (3) The first aqueous phase was sheared at 12000 rpm and the oil phase was added dropwise. After the addition was completed, stirring was continued at room temperature for 30 minutes to form a stable oil-in-water emulsion;

[0071] (4) adding 0.5 g of carbon nanotubes to a mixture of 1 g of deionized water and 9 g of anhydrous ethanol, ultrasonicating for 20 min, then adding 0.04 g of 3-aminopropyltriethoxysilane, stirring at room temperature for 6 h, washing, and drying to obtain modified carbon nanotubes;

[0072] (5) The second aqueous phase was stirred at 300 rpm and 0.2 g of modified carbon nanotubes was added, and ultrasonicated for 20 min to obtain a modified solution;

[0073] (6) 0.7 g of polyethylene glycol with a weight average molecular weight of 400 was added to the water-in-oil emulsion, stirred at room temperature for 30 min, then heated to 40 °C and stirred for 1 h, then heated to 60 °C, 0.3 g of 1,4-butanediol was added dropwise, and after the addition was complete, stirring was continued for 1 h, then the modified liquid was added and stirred for 1 h, and finally 0.2 g of dodecylamine was added and stirred for 1 h, and then cooled to room temperature to obtain pyraclostrobin nanocapsules.

[0074] Comparative Example 4:

[0075] The difference between Comparative Example 4 and Example 2 is that no dodecylamine is added;

[0076] The specific steps are as follows:

[0077] (1) Add 0.7 g of Tween-80 and 0.3 g of Span-80 to 50 g of deionized water, stir for 20 min, and then divide into two equal parts to obtain a first aqueous phase and a second aqueous phase;

[0078] (2) dissolving 2 g of pyraclostrobin and 1.2 g of isophorone diisocyanate in n-butyl acetate and stirring for 20 min to obtain an oil phase;

[0079] (3) The first aqueous phase was sheared at 12000 rpm and the oil phase was added dropwise. After the addition was completed, stirring was continued at room temperature for 30 minutes to form a stable oil-in-water emulsion;

[0080] (4) adding 0.5 g of carbon nanotubes to a mixture of 1 g of deionized water and 9 g of anhydrous ethanol, ultrasonicating for 20 min, then adding 0.03 g of polyethylene glycol monomethyl ether triethoxysilane with a weight average molecular weight of 1000 and 0.01 g of 3-aminopropyl triethoxysilane, stirring at room temperature for 6 h, washing, and drying to obtain modified carbon nanotubes;

[0081] (5) The second aqueous phase was stirred at 300 rpm and 0.2 g of modified carbon nanotubes was added, and ultrasonicated for 20 min to obtain a modified solution;

[0082] (6) 0.7 g of polyethylene glycol with a weight average molecular weight of 400 was added to the water-in-oil emulsion, stirred at room temperature for 30 min, then heated to 40 °C and stirred for 1 h, then heated to 60 °C, 0.3 g of 1,4-butanediol was added dropwise, and after the addition was complete, the stirring was continued for 1 h. The modified liquid was then added and stirred for 2 h. The mixture was cooled to room temperature to obtain pyraclostrobin nanocapsules.

[0083] Performance Test:

[0084] Drug loading and encapsulation efficiency: By UV spectrophotometer testing, a standard curve of pyraclostrobin was first drawn, and then the mass of pyraclostrobin was calculated using the standard curve method, and the drug loading and encapsulation efficiency were calculated. The results are shown in Table 1.

[0085] Cumulative release amount: The cumulative release amount was tested by dialysis method. The release medium was a mixture of 70 mL of deionized water, 30 mL of anhydrous ethanol and 0.5 g of Tween-80. The results are shown in Table 1.

[0086] Adhesion test: After the rice leaves sprayed with pyraclostrobin nanocapsules were dried naturally in the air, the leaves were divided into two pieces of 1 cm × 3 cm, one of which was used as the control group, and the control group was not washed with simulated rain water. The other piece was slowly washed with 10 mL of distilled water at a 60° angle to simulate rain water washing. After the end, the two groups of leaves were placed in 100 mL of methanol solution, and all the pyraclostrobin on the leaves were extracted by ultrasound. The concentration of pyraclostrobin was measured at 274 nm with an ultraviolet spectrophotometer, and the amount of residual pyraclostrobin was calculated, where the control group was the initial concentration. The results are shown in Table 1.

[0087]

[0088] Data Analysis:

[0089] From the data of Examples 1-3 in Table 1, it can be seen that the pyraclostrobin nano-microcapsules prepared by the present invention have nano-scale particle size, drug loading up to 28.1%, encapsulation efficiency not less than 88%, good encapsulation effect, and rapid release in the initial release, stable release after 48h, and cumulative release rate of 96h reached 65.8%, which shows that this nano-microcapsule can provide continuous drug effect for a long time, which is conducive to lasting protective effect. Most importantly, after scouring, the residual rate of pyraclostrobin on rice leaves is as high as 75.3%, indicating that it has excellent adhesion to rice leaves, which is conducive to anti-rainwater scouring and ensures the continuity and stability of drug effect. Overall, these characteristics make the application of the nano-microcapsules in agriculture very advantageous, and can significantly improve the efficiency and effect of the use of pyraclostrobin.

[0090] From the data of Example 2 and Comparative Example 1 in Table 1, it can be seen that the surface modification of carbon nanotubes helps to reduce the particle size of nano-microcapsules, increase the drug loading and encapsulation efficiency, increase the cumulative release rate, and greatly improve the rain resistance. This is mainly due to the synergistic effect of the ether chain in polyethylene glycol monomethyl ether triethoxysilane and the amino group in 3-aminopropyl triethoxysilane.

[0091] From the data of Example 2 and Comparative Example 2 in Table 1, it can be seen that 3-aminopropyltriethoxysilane is crucial to the modification of carbon nanotubes, which helps to significantly improve the rain erosion resistance. This is mainly because 3-aminopropyltriethoxysilane promotes the dispersion of carbon nanotubes on the surface of microcapsules, so that the tiny carbon nanotubes can be inserted into the gaps of the lipid layer on the surface of rice leaves, thereby improving the adhesion to the rice leaves.

[0092] From the data of Example 2 and Comparative Example 3 in Table 1, it can be seen that polyethylene glycol monomethyl ether triethoxysilane can significantly reduce the particle size of nano-microcapsules and improve the drug loading rate and encapsulation rate. This is mainly due to the surface activity of the ether chain of polyethylene glycol monomethyl ether triethoxysilane. In addition, polyethylene glycol monomethyl ether triethoxysilane can further improve the rain erosion resistance, which is mainly because polyethylene glycol monomethyl ether triethoxysilane and 3-aminopropyl triethoxysilane synergistically promote the arrangement of carbon nanotubes on the surface of nano-microcapsules.

[0093] From the data of Example 2 and Comparative Example 4 in Table 1, it can be seen that dodecylamine can further improve the rain erosion resistance of the nanocapsules. This is mainly because dodecylamine contains a longer alkyl chain and has a significant hydrophobic effect. In addition, the alkyl chain of dodecylamine has good compatibility with the lipid layer of rice leaves and can penetrate into the lipid layer, thereby improving the adhesion to the rice leaves.

[0094] Those skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

Claims

1. A preparation method of pyraclostrobin nanocapsules, characterized in that: The following steps are involved: (1) adding an emulsifier to deionized water, and then dividing the water into two equal parts by weight to obtain a first aqueous phase and a second aqueous phase; (2) dissolving pyraclostrobin and isophorone diisocyanate in an organic solvent to obtain an oil phase; (3) High-speed shearing of the first aqueous phase at 10,000-14,000 rpm and dropwise addition of the oil phase, stirring at room temperature for 20-40 minutes after the dropwise addition is completed, to obtain an oil-in-water emulsion; (4) using polyethylene glycol monomethyl ether triethoxysilane and 3-aminopropyl triethoxysilane to modify carbon nanotubes to obtain modified carbon nanotubes; (5) dispersing the modified carbon nanotubes in the second aqueous phase to obtain a modified liquid; (6) Add polyethylene glycol to the oil-in-water emulsion, stir at room temperature for 20-40 minutes, then heat to 35-45°C, continue stirring for 0.5-2 hours, then continue heating to 55-65°C, add 1,4-butanediol dropwise, continue stirring for 1 hour after the addition is complete, then add the modified liquid, continue stirring for 1 hour, and finally add dodecylamine, continue stirring for 0.5-2 hours to obtain pyraclostrobin nanocapsules; In the step (4), the weight ratio of polyethylene glycol monomethyl ether triethoxysilane, 3-aminopropyl triethoxysilane and carbon nanotubes is 0.2-0.4:0.05-0.2:5; The weight average molecular weight of polyethylene glycol monomethyl ether triethoxysilane in step (4) is 1000; In the step (6), the weight ratio of polyethylene glycol, isophorone diisocyanate in the oil-in-water emulsion, 1,4-butanediol, modified carbon nanotubes and dodecylamine in the modified liquid is 0.7:1.2:0.3:0.1-0.3:0.1-0.

5.

2. The preparation of pyraclostrobin nanocapsules according to claim 1, characterized in that: The emulsifier in step (1) is a mixture of Tween-80 and Span-80 in a weight ratio of 7:

3.

3. The preparation of pyraclostrobin nanocapsules according to claim 1, characterized in that: The weight ratio of the emulsifier to the deionized water in the step (1) is 1:

50.

4. The preparation of pyraclostrobin nanocapsules according to claim 1, characterized in that: In the step (2), the weight ratio of pyraclostrobin, isophorone diisocyanate and organic solvent is 2:1.2:

5.

5. The preparation of pyraclostrobin nanocapsules according to claim 1, characterized in that: The organic solvent in step (2) is one of n-butyl acetate, isobutyl acetate and n-propyl acetate.

6. The preparation of pyraclostrobin nanocapsules according to claim 1, characterized in that: In the step (3), the weight ratio of the first water phase to the oil phase is 25.5:8.

2.

7. The preparation of pyraclostrobin nanocapsules according to claim 1, characterized in that: In the step (4), the outer diameter of the carbon nanotubes is 10-20 nm and the length is 0.5-2 μm.

8. The preparation of pyraclostrobin nanocapsules according to claim 1, characterized in that: The weight average molecular weight of the polyethylene glycol in step (6) is 400.

9. An application of pyraclostrobin nanocapsules prepared according to any one of claims 1 to 8, characterized in that: Used to prevent and control fungal diseases on crops.

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