A composite nanofiber membrane, a preparation method thereof and application thereof in agricultural pest control

Abstract

The application provides a composite nanofiber membrane containing difluorocyclopropane compounds and a preparation method and application thereof, and through screening, it is found that two difluorocyclopropanes containing pyridyl and methoxy have obvious fungistasis activity on banana fusarium wilt fungi, then a polyvinyl butyral ester nanofiber membrane containing difluorocyclopropane is prepared through a high-pressure electrostatic spinning method, and the nanofiber membrane is applied to disease prevention and control of banana fusarium wilt fungi and agricultural insect repellent application. The application effectively combines the chemical fungicide and the nanofiber membrane, can not only block the close-range transmission of banana fusarium wilt fungi caused by irrigation water, rainwater and nematodes in a disease area, but also can help other plants to effectively prevent diseases and insect pests.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of agricultural protection, and particularly relates to a composite nanofiber film containing difluorocyclopropane compounds and a preparation method thereof and application thereof in the prevention and control of agricultural diseases and pests. BACKGROUND

[0002] Banana industry is one of the agricultural pillar industries in tropical and subtropical regions of China, and has made important contributions to the growth of the national economy. However, the spread of banana wilt in major banana producing areas such as Guangdong and Guangxi has seriously hampered the healthy and sustainable development of the banana industry. Banana wilt is a devastating fungal disease caused by the infection of Fusarium oxysporum f. sp. cubense (Foc). Foc has rich genetic diversity, and can be divided into four physiological races according to the type of banana varieties it infects. The most dangerous one is banana wilt pathogen tropical race 4 (Foc TR4), which can infect almost all banana cultivars. At present, the main means of comprehensive prevention and control are to cultivate resistant varieties, biological control, chemical control, etc. Among them, the promotion of disease-resistant varieties is playing a key role in the prevention and control of banana wilt, but in recent years, the diversification of physiological races of the pathogen has accelerated the loss of disease resistance of varieties. Biological control needs a long time to take effect and the process is complex, and is still in the research and development stage in disease control. Chemical sterilization has the advantages of high efficiency, quick effect, convenience, and economic benefits, and plays an important role in integrated pest control. tropical race 4,Foc TR4), which can infect almost all banana cultivars. At present, the main means of comprehensive prevention and control are to cultivate resistant varieties, biological control, chemical control, etc. Among them, the promotion of disease-resistant varieties is playing a key role in the prevention and control of banana wilt, but in recent years, the diversification of physiological races of the pathogen has accelerated the loss of disease resistance of varieties. Biological control needs a long time to take effect and the process is complex, and is still in the research and development stage in disease control. Chemical sterilization has the advantages of high efficiency, quick effect, convenience, and economic benefits, and plays an important role in integrated pest control.

[0003] Polyvinyl butyral (PVB) is a solvent type resin, and there are three chemical functional groups in its chemical structure, including butyraldehyde group, alcohol hydroxyl group and acetate group. The alcohol hydroxyl group and the acetate group are obtained by hydrolysis of polyvinyl acetate. The excellent properties of PVB material are mainly due to its chemical structure. The alcohol hydroxyl group makes PVB have strong tear resistance, and the film made has high adhesion; the butyraldehyde group is a six-membered ring molecular structure, which has strong stability, improves the adhesion and strength of the entire molecular chain, and exhibits good non-crystalline performance. Because the material molecule has a long branch, it not only has structural stability, but also has good flexibility. SUMMARY

[0004] The application provides a composite nanofiber film containing difluorocyclopropane compounds, which can be applied to the disease prevention and control of banana wilt and crop pest control.

[0005] To achieve the above object, the application provides the following technical scheme:

[0006] A preparation method of a composite nanofiber membrane, comprising the following steps:

[0007] (1) A certain amount of triphenylphosphonium bromide and potassium tert-butoxide are added to a reactor, nitrogen is filled, and tetrahydrofuran and aldehyde are added under ice bath conditions, and the reaction is carried out (for 12-24 hours at room temperature); after the reaction, the olefin compound is obtained by purification (extraction, drying and filtration, evaporation under reduced pressure, and silica gel column chromatography purification);

[0008] The aldehyde is one of anisaldehyde and 4-(2-pyridyl)-benzaldehyde.

[0009] The molar ratio of the triphenylphosphonium bromide, potassium tert-butoxide and aldehyde is (1.0-1.5):(1.0-1.5):1, and tetrahydrofuran is used as the reaction solvent, and the amount of the solvent is sufficient to submerge the reactants.

[0010] (2) Sodium iodide is added to a reactor, nitrogen is filled, and a certain amount of tetrahydrofuran, trifluoromethyltrimethylsilane (TMSCF3) and the olefin compound are added, and the reaction is carried out (for 12-18 hours at 65-70°C); after the reaction, the difluorocyclopropane compound is obtained by purification (extraction, drying and filtration, evaporation under reduced pressure, and silica gel column chromatography purification);

[0011] The molar ratio of the sodium iodide, TMSCF3 and the olefin compound is (0.8-1.2):(2.0-3.0):1, and tetrahydrofuran is used as the reaction solvent, and the amount of the solvent is sufficient to submerge the reactants.

[0012] (3) A certain amount of PVB powder is taken, dissolved in a solvent, and then a certain amount of the difluorocyclopropane compound is added, and the spinning solution is obtained after uniform dispersion;

[0013] The solvent is one or both of anhydrous ethanol and ethyl acetate, or a mixed solution of the above-mentioned solvent and water.

[0014] The amount of the added difluorocyclopropane compound accounts for 0.1%-0.5% of the mass of PVB; and the amount of the solvent used is sufficient to make the PVB concentration reach 10-12% w / v.

[0015] (4) The obtained spinning solution is used to prepare a composite nanofiber membrane by using an electrospinning technology.

[0016] The parameters of the electrospinning are as follows: voltage: 10-11 kV, flow rate: 0.1-1.5 mL / h, receiving distance: 5-10 cm, and injection needle: 15-24 gauge; more preferably, the flow rate is 0.8 mL / h, the receiving distance is 5-7 cm, and the injection needle is 20 gauge.

[0017] The composite nanofiber membrane provided by the application can be applied to the disease prevention and control of banana fusarium wilt and agricultural pest control.

[0018] The application has the following positive beneficial effects: the composite nanofiber membrane containing difluorocyclopropane compounds prepared based on the high-voltage electrospinning method has stable structure, uniform particle size and good dispersity, can not only maintain the high-efficiency antibacterial and pest control performance of the drug, but also can be spun on site as needed, flexibly adjust the size of the material, and will not cause resource waste; meanwhile, the composite nanofiber membrane can be easily adsorbed on the surface of plants to form firm adhesion and has good water resistance and acid resistance. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to further illustrate the advantages and purposes of the technical scheme of the application, the related drawings in the examples will be briefly introduced below.

[0020] Figure 1 SEM electron microscope photos of the composite nanofiber membrane obtained in Example 1 of the application;

[0021] Figure 2 Inhibition effect diagram of the composite nanofiber membranes with different drug addition amounts obtained by the application on banana fusarium wilt colonies;

[0022] Figure 3 Mycelial morphology diagram of the composite nanofiber membrane obtained in Example 1 of the application after the action on banana fusarium wilt;

[0023] Figure 4 On-site effect diagram of the composite nanofiber membrane obtained by the application by using a handheld electrospinning machine for tomato leaf pest control. DETAILED DESCRIPTION

[0024] The application will be further described below in combination with the drawings and examples, but the examples of the application are not limited thereto.

[0025] Example 1: A preparation method of a composite nanofiber membrane, comprising the following steps:

[0026] (1) 18.57 g (52 mmol) of triphenylphosphine bromide was weighed in a two-necked flask, 5.84 g (52 mmol) of potassium tert-butoxide was added, nitrogen was filled into the flask, 40 mL of tetrahydrofuran and 5.44 mL (40 mmol) of anisaldehyde were added under ice bath conditions, and then the mixture was reacted at room temperature for 12 h. After extraction, drying, filtration, reduced pressure evaporation and silica gel column chromatography purification, the corresponding olefin compound was obtained;

[0027] (2) 5.25 g (35 mmol) of sodium iodide was weighed into a two-necked flask, nitrogen was filled into the flask, 40 mL of anhydrous tetrahydrofuran, 12.45 mL (87.5 mmol) of TMSCF3 and 4.70 mL (35 mmol) of the olefin compound obtained in (1) were injected into the flask by using a syringe, and then the mixture was reacted at 65°C for 12 h. After the reaction time was reached, the reaction was taken out, extracted, dried, filtered, evaporated under reduced pressure, purified by silica gel column chromatography, and then connected to a vacuum pump to remove a small amount of residual solvent under vacuum to obtain a methoxy group difluoro cyclopropane (MGDC) compound, which was stored at low temperature and used later;

[0028] (3) 1.65 g (11%) of PVB was weighed into 15 mL of anhydrous ethanol, stirred until the PVB was completely dissolved, 3.3 μL (0.2 wt%) of MGDC was added, and then the mixture was stirred again to obtain a composite nanofiber membrane solution, which was used later.

[0029] (4) The composite nanofiber membrane solution obtained above was spun by using a handheld electrospinning machine, the amount was 3 mL, the voltage was 10-11 kV, the flow rate was 0.8 mL / h, the receiving distance was 5-7 cm, and the injection needle was No. 20. After spinning, a composite nanofiber membrane was obtained.

[0030] Example 2 A method for preparing a composite nanofiber membrane, comprising the following steps:

[0031] (1) 18.57 g (52 mmol) of triphenylphosphine bromide was weighed into a two-necked flask, 5.84 g (52 mmol) of potassium tert-butoxide and 7.3 g (40 mmol) of 4-(2-pyridyl)-benzaldehyde were added, nitrogen was filled into the flask, 40 mL of tetrahydrofuran was added under ice bath conditions, and then the mixture was reacted at room temperature for 12 h. After extraction, drying, filtration, evaporation under reduced pressure, and purification by silica gel column chromatography, a corresponding olefin compound was obtained;

[0032] (2) 5.25 g (35 mmol) of sodium iodide was weighed into a two-necked flask, nitrogen was filled into the flask, 40 mL of anhydrous tetrahydrofuran, 12.45 mL (87.5 mmol) of TMSCF3 and 6.34 g (35 mmol) of the olefin compound obtained in (1) were injected into the flask by using a syringe, and then the mixture was reacted at 65°C for 12 h. After the reaction time was reached, the reaction was taken out, extracted, dried, filtered, evaporated under reduced pressure, purified by silica gel column chromatography, and then connected to a vacuum pump to remove a small amount of residual solvent under vacuum to obtain a pyridyl-based difluoro cyclopropane (PBDC) compound, which was stored at low temperature and used later;

[0033] (3) Weigh 1.65g (11%) PVB, add 15mL of anhydrous ethanol, stir until PVB is completely dissolved, add 3.3mg (0.2wt%) PBDC, stir again until homogeneous to obtain composite nanofiber membrane solution, and set aside for use.

[0034] (4) The above-obtained composite nanofiber membrane solution was spun using a handheld electrospinning machine. The volume was 3 mL, the voltage was 10-11 kV, the flow rate was 0.8 mL / h, the receiving distance was 5-7 cm, and the jetting needle was No. 20. The composite nanofiber membrane was obtained after spinning.

[0035] Experimental method: The SEM image of the composite nanofiber membrane obtained in Example 1 of this invention is shown below. Figure 1 As shown. In Figure 1 In this case, the magnification is 4000x. Figure 1 As can be seen, the nanofibers are interlaced and uniform in diameter in the membrane, with smooth surfaces and good morphology. The images show that adding difluorocyclopropane to the spinning membrane has little effect on the spinning process of the microfiber membrane, preserving not only the physical properties of the microfiber membrane itself, but also ensuring the stability of the material.

[0036] The antibacterial results of the composite nanofiber membrane obtained in this invention against *Fusarium wilt* fungus at different drug concentrations are shown in the figure below. Figure 2 As shown. The antibacterial activity of two composite nanofiber membranes against FocTR4 at different drug concentrations was determined using the mycelial growth rate method. Potato dextrose agar (PDA) medium was heated until completely melted, and then cooled to 40–50 °C. Different drug concentrations of the two composite nanofiber membranes were added to the membranes at concentrations of 0.025 wt%, 0.05 wt%, 0.1 wt%, and 0.2 wt%, respectively. Mycelial cakes with a diameter of 5 mm were punched at the edge of the colony using a sterilized puncher and inoculated upside down onto PDA plates cooled to room temperature. The plates were sealed with sealing film and incubated upside down in a 28 °C incubator. An equal volume of DMSO was added as a control. After 7 days of incubation, the growth diameter of colonies on each plate was measured using the cross-cross method, and the inhibition rate of each concentration of difluorocyclopropane was calculated. The formula for calculating the mycelial growth inhibition rate is as follows:

[0037] Mycelial growth inhibition rate (%) = (Coronary growth diameter of control group - Colony growth diameter of treatment group) / Colony growth diameter of control group × 100.

[0038] The composite nanofiber membrane obtained in Example 1 of this invention achieved an antibacterial rate of 77% when the addition amount was 0.2wt%, indicating that the composite nanofiber membrane obtained in this invention has a good antibacterial effect against Foc TR4.

[0039] The mycelium morphology chart after the composite nanofiber membrane obtained by the embodiment 1 of the present application acts on the banana fusarium wilt is shown in Figure 3 As shown in Figure 3 It can be seen that the mycelium of the control group is smooth, and the growth is uniform in thickness, and the branches are normal; while the mycelium of the treatment group presents irregular branches, uneven growth in thickness and other deformities. Further observation by scanning electron microscope shows that the treatment of the composite nanofiber membrane obtained by the present application can cause the Foc TR4 mycelium to appear surface shrinkage, depression and flattening.

[0040] The on-site effect chart of the composite nanofiber membrane obtained by the present application for tomato leaf insect repellent is shown in Figure 4 As shown in Figure 4 It can be seen that the composite nanofiber membrane obtained by the present application can be well attached to the surface of the tomato leaf, and can be spun on site according to the actual size of the object by using the handheld electrospinning machine, and is not easy to slip off, break, and will not cause resource waste. The composite nanofiber membrane obtained by the present application not only can effectively prevent the occurrence of various diseases and pests, but also can isolate the action object from the pollutants and pesticides in the air, and can also avoid rainwater pollution of the plant surface when encountering rainy weather; compared with the ordinary bagging technology, the present application does not cause the phenomenon of damaged leaf stalk or fruit stalk due to improper force during bag sealing, and the subsequent infection of the damaged part by the pathogen and the rotting of the fruit.

[0041] The claims indicate the scope of the present application, and the above description does not indicate the scope of the present application, therefore, any change within the meaning and scope equivalent to the claims of the present application should be considered as included in the scope of the claims of the present application.

Claims

1. A method for preparing a composite nanofiber membrane, characterized in that, Includes the following steps: (1) A certain amount of triphenylphosphine bromide and potassium tert-butoxide were added to the reactor, nitrogen gas was introduced, and tetrahydrofuran and aldehyde were added under ice bath conditions to carry out the reaction; after the reaction, the olefin compound was obtained by purification. (2) Sodium iodide was added to the reactor, nitrogen gas was introduced, tetrahydrofuran, trifluoromethyltrimethylsilane and the olefin compound were added, and the reaction was carried out; after the reaction, the difluorocyclopropane compound was obtained by silica gel column chromatography. (3) Take a certain amount of PVB powder, add a solvent to dissolve it, then add a certain amount of the difluorocyclopropane compound, and disperse it evenly to obtain the spinning solution; (4) The obtained spinning solution is electrospun to form a composite nanofiber membrane.

2. The preparation method according to claim 1, characterized in that: The aldehyde mentioned in step (1) is one of anisaldehyde or 4-(2-pyridyl)-benzaldehyde.

3. The preparation method according to claim 1, characterized in that: The molar ratio between triphenylphosphine bromide, potassium tert-butoxide and aldehyde in step (1) is (1.0-1.5):(1.0-1.5):

1.

4. The preparation method according to claim 1, characterized in that: Step (1) reaction is carried out at room temperature for 12-24 hours; Step (2) reaction is carried out at 65-70℃ for 12-18 hours.

5. The preparation method according to claim 1, characterized in that: The purification process described in step (1) or step (2) is extraction, drying and filtration, vacuum evaporation, and silica gel column chromatography purification.

6. The preparation method according to claim 1, characterized in that: The molar ratio of sodium iodide, TMSCF3 and olefin compound in step (2) is (0.8-1.2):(2.0-3.0):

1.

7. The preparation method according to claim 1, characterized in that: The solvent in step (3) is one or both of anhydrous ethanol and ethyl acetate, or a mixture of the above with water.

8. The preparation method according to claim 1, characterized in that: In step (3), the difluorocyclopropane compound used accounts for 0.1%-0.5% of the mass of PVB; the amount of solvent used is such that the PVB concentration reaches 10-12% w / v.

9. The composite nanofiber membrane obtained by the preparation method according to any one of claims 1-8.

10. The application of the composite nanofiber membrane according to claim 9 in the prevention and control of banana wilt pathogen and in agricultural pest control.

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