A pH-light dual response nano-pesticide and a preparation process thereof

Abstract

This application relates to the field of pesticides and insecticides, specifically disclosing a pH-light dual-responsive nano-insecticide and its preparation process. The preparation method of the pH-light dual-responsive nano-insecticide comprises the following steps: polyethylene glycol, castor oil polyoxyethylene ether, and sodium lignosulfonate are added to water to form an aqueous phase; lambda-cyhalothrin technical is mixed with xylene, and diisocyanate is added to form an oil phase; the oil phase is added to the aqueous phase, and ethylenediamine, YUS-SC3A, glycerol, xanthan gum, magnesium aluminum silicate, and benzoic acid are added to obtain a lambda-cyhalothrin microcapsule suspension; YUS-SC3A is mixed with water, and thiamethoxam technical, glycerol, xanthan gum, magnesium aluminum silicate, AF205, and benzoic acid are added to obtain a thiamethoxam suspension; the two agents are mixed to obtain the nano-insecticide, a composite dispersant is added, followed by a pre-gelling agent, azobisisobutyronitrile (AIBN), inert gas purging, and Kathon. This application aims to improve the insecticidal effect and avoid the development of drug resistance by preparing a pH-photoresponsive nano-insecticide, thereby achieving efficient control of wheat aphids.

Description

Technical Field

[0001] This application relates to the field of pesticides and insecticides, and more specifically, to a pH-photoresponsive nanoparticle insecticide and its preparation process. Background Technology

[0002] The warm and humid climate and high crop density in the Huang-Huai-Hai agricultural region provide ideal conditions for the breeding and reproduction of wheat aphids, leading to frequent and severe outbreaks. In practice, there are problems with indiscriminate pesticide selection and long-term use of a single type of pesticide, resulting in a rapid increase in resistance to commonly used pesticides and a significant decrease in their effectiveness. Furthermore, conventional insecticides are mostly released immediately after spraying, and their active ingredients are easily washed away by rainwater, further reducing their effectiveness. Rainwater runoff also increases the frequency of pesticide application, further exacerbating the resistance problem.

[0003] Therefore, there is an urgent need to provide an insecticide that features precise and slow release, delaying the development of aphid resistance and achieving efficient and green control of wheat aphids. Summary of the Invention

[0004] To achieve efficient control of wheat aphids, this application provides a pH-photoresponsive nano-insecticide and its preparation process.

[0005] Firstly, this application provides a pH-photoresponsive dual-response nano-insecticide, which adopts the following technical solution:

[0006] A method for preparing a pH-photoresponsive nano-insecticide includes the following steps:

[0007] (1) Polyethylene glycol, castor oil polyoxyethylene ether and sodium lignosulfonate were added to water and sheared and stirred at 27-30℃ to obtain an aqueous phase; at 50-55℃, high-efficiency cyhalothrin technical and xylene were mixed evenly, diisocyanate was added and stirred evenly to obtain an oil phase; the oil phase was slowly poured into the aqueous phase and sheared at 27-30℃ for 3-5 min to obtain a primary emulsion; at 29-31℃, ethylenediamine was added, the temperature was raised to 55-60℃ and stirred for 4.5-5.5 h to obtain an emulsion; YUS-SC3A, glycerol, xanthan gum, magnesium aluminum silicate and benzoic acid were added to the emulsion and sheared and stirred to obtain high-efficiency cyhalothrin microcapsule suspension;

[0008] (2) Add YUS-SC3A to water, mix well, add thiamethoxam technical, stir well, add glycerin, xanthan gum, magnesium aluminum silicate, AF205 and benzoic acid, shear and stir to obtain thiamethoxam suspension;

[0009] (3) Mix the high-efficiency cyhalothrin microcapsule suspension and thiamethoxam suspension, stir evenly, grind and homogenize to obtain nano insecticide;

[0010] (4) Add a composite dispersant to the nano insecticide, disperse it by ultrasonication, slowly add it to the pregel, stir it evenly, add azobisisobutyronitrile, purge with inert gas, heat at 60-65℃ for 10-12h, add Kathon, stir evenly, and obtain pH-photo-responsive nano insecticide.

[0011] The method for preparing the pregel includes the following steps:

[0012] (a) Add azobenzene acrylate to DMSO and stir until homogeneous to obtain azobenzene acrylate solution;

[0013] (b) Add HEMA, PEGDA600 and MBAA to water and stir until homogeneous to obtain a mixture;

[0014] (c) Add the acrylate azobenzene solution dropwise into the mixture and stir until homogeneous to obtain a pregel.

[0015] By employing the above technical solutions, lambda-cyhalothrin, while lacking systemic activity, possesses extremely strong contact toxicity. It acts on sodium ion channels in the nerve cell membranes of wheat aphids, inhibiting sodium ion outflow, leading to abnormal nerve excitation, muscle spasms, and paralysis that kills the aphids. Thiamethoxam, with its strong systemic activity, acts on acetylcholinesterase receptors on the postsynaptic membrane of wheat aphid nerves, competitively inhibiting acetylcholine binding, blocking nerve conduction, and causing paralysis and death in the aphids. Lamda-cyhalothrin disrupts ion channel signal transduction, while thiamethoxam blocks neurotransmitter signal transmission; the synergistic effect of both achieves a dual blockade of the nerve conduction pathway, leading to the complete collapse of the aphid's nervous system. The aphid is unable to regulate its own nervous system (e.g., through ion regulation). (Channel repair and enhanced neurotransmitter metabolism) mitigate toxicity, avoid drug resistance, and improve control efficacy; high-efficiency cyhalothrin acts on the peripheral nerves through surface contact, while thiamethoxam acts on the central nervous system through feeding. The systemic nature of thiamethoxam allows the pesticide to enter the aphid's body, forming a dual toxicity of cyhalothrin and cyhalothrin, reducing the risk of drug resistance; the stability of cyhalothrin and thiamethoxam is improved by preparing microcapsule suspensions. After the microcapsules are ground and homogenized into nanodroplets, they are added to the pregel, cross-linking to form a three-dimensional network internal structure. The hydrogel encapsulates the active ingredients, enabling precise release of the active ingredients according to the external environment, further avoiding the development of drug resistance and achieving efficient and green treatment.

[0016] During the pre-gel preparation process, the acrylate groups of azobenzene acrylate can undergo free radical copolymerization with the double bonds of HEMA, PEGDA600, and MBAA, covalently embedding the photoresponsive unit into the three-dimensional gel network. HEMA molecules contain hydroxyl groups, and the network structure formed after polymerization has good hydrophilicity, which can accommodate the suspension and release of nano-insecticides. Its hydrophilicity can improve the wettability and adhesion of the gel on the surface of wheat leaves. In addition, the hydroxyl groups of HEMA can form hydrogen bonds with the dispersant of nano-insecticides, further fixing the nanoparticles and reducing leakage during storage and release. Under light-free conditions, azobenzene acrylate is in a trans conformation, and the dense three-dimensional network structure precisely traps the nano-insecticides, avoiding ineffective release in non-target environments. Under ultraviolet light irradiation, azobenzene acrylate undergoes trans-cis isomerization. The change in molecular conformation drives the relaxation of the gel network and the expansion of pores, releasing the nano-insecticides, inhibiting the feeding and reproductive behavior of wheat aphids, and improving the control effect.

[0017] Optionally, the mass ratio of the high-efficiency cyhalothrin technical and the thiamethoxam technical is 1:1-1.1.

[0018] Optionally, the mass ratio of the high-efficiency cyhalothrin technical material to the composite dispersant is 1:0.1-0.15, and the composite dispersant includes polyvinylpyrrolidone and sulfosuccinate anionic dispersants in a mass ratio of 1:1-2.

[0019] By employing the above technical solutions, sulfosuccinate anionic dispersants, as suspension additives, significantly improve the dispersion uniformity and system stability of nanoparticles and inhibit the aggregation of active ingredients through interfacial tension regulation, charge repulsion, and steric hindrance. Polyvinylpyrrolidone (PVP) physically isolates monomers from free radical erosion by forming a dense adsorption film, while simultaneously capturing free radicals to reduce oxidative damage. PPVP molecules form dynamic and reversible hydrogen bonds with the gel network, locking nanoparticles to prevent burst drug release and ensuring precise drug release. The two work synergistically to form a double-layer protective structure, effectively ensuring the precise release of pH-light dual-response nano-insecticides and further improving the control effect.

[0020] Optionally, the mass ratio of the high-efficiency cyhalothrin technical material to the pregel is 1:0.3-0.5.

[0021] Optionally, in step (a), after adding azobenzene acrylate to DMSO, a pH-responsive component is added, wherein the pH-responsive component comprises acrylic acid and methacrylic acid in a mass ratio of 1:1-2.

[0022] By employing the above technical solution, the hydrogen ion concentration in the natural field environment is low, the carboxyl groups exist in a protonated state, there is no obvious electrostatic repulsion between chain segments, and the hydrophobicity of the carboxyl groups causes the chain segments to approach each other through hydrophobic interactions. The hydrogel network is in a contracted state with small pores, thus preserving the nano-insecticide within the hydrogel. Acrylic acid and methacrylic acid, as unsaturated carboxylic acid monomers, rapidly ionize their carboxyl groups into negatively charged -COO⁻ groups when the environment is acidic. Electrostatic repulsion drives the swelling of the hydrogel network, expanding the pores and rapidly releasing the nano-insecticide. Simultaneously, the short carbon chain structure of acrylic acid enhances the swelling flexibility of the hydrogel network. The methyl substituents in methacrylic acid increase the release rate of the drug. They enhance the segmental rigidity and network stability of the hydrogel, thereby increasing its adhesion to wheat leaf surfaces. Furthermore, the combination of acrylic acid and methacrylic acid, with their negative logarithmic difference in dissociation constants, forms a synergistic pH response system. This broadens the acidic response range of the hydrogel, covering the acidic microenvironment generated by honeydew microorganisms on the surface of wheat aphids and the acidic environment in their midgut. This avoids the narrow response range of acrylic acid and the insufficient response sensitivity of methacrylic acid, improving the release precision of the nano-insecticide, further reducing the risk of drug resistance, and enhancing the control effect.

[0023] Optionally, the mass ratio of the acrylate azobenzene to the pH-responsive component is 1:2-3.

[0024] In summary, this application has the following beneficial effects:

[0025] 1. This application preferably uses light-pH responsive hydrogel to encapsulate nano-insecticides to avoid the development of resistance due to direct application of insecticides; the nano-insecticide is a combination of highly effective contact insecticide cyhalothrin and systemic thiamethoxam, which work synergistically to block nerve conduction pathways, causing the aphid's nervous system to collapse completely, quickly killing wheat aphids, and further preventing the development of resistance.

[0026] 2. This application uses sulfosuccinate anions to improve the dispersibility of nano-insecticides, and polyvinylpyrrolidone can prevent nano-insecticides from being eroded. The two are used together to form a double-layer protection mechanism to prevent the aggregation and loss of nano-insecticides, increase drug utilization, and improve the control effect.

[0027] 3. This application prepares a light-pH responsive release hydrogel by adding light-responsive azobenzene acrylate and pH-responsive acrylic acid and methacrylic acid to the hydrogel. When wheat aphids forage during the day, the light-pH responsive hydrogel releases nano-insecticides that precisely target the acidic surface of the wheat aphids, achieving efficient and green control. Detailed Implementation

[0028] The following embodiments provide a further detailed description of this application.

[0029] Example of pregel preparation

[0030] 4-Amino-4'-methacrylate-based azobenzene was purchased from Jiangsu Renhe Environmental Protection Technology Co., Ltd.; HEMA was purchased from Nantong Zhonghe Chemical New Materials Co., Ltd.; PEGDA was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., model number P131592; and MABA was purchased from Nanjing Dulai Biotechnology Co., Ltd., model number I0003.

[0031] Preparation Example 1

[0032] (1) Add 2 kg of 4-amino-4'-methacrylate azobenzene, 2 kg of acrylic acid and 4 kg of methacrylic acid to 8 kg of DMSO and stir evenly to obtain an acrylate azobenzene solution;

[0033] (2) Add 10kg HEMA, 1.5kg PEGDA 600 and 0.3kg MBAA to 75kg water, stir well to obtain a mixture;

[0034] (3) The acrylate azobenzene solution obtained in step (1) is added dropwise to the mixture obtained in step (2), and stirred evenly to obtain a pregel.

[0035] Preparation Example 2

[0036] (1) Add 2 kg of 4-amino-4'-methacrylate azobenzene, 2 kg of acrylic acid and 2 kg of methacrylic acid to 8 kg of DMSO and stir until homogeneous to obtain an acrylate azobenzene solution;

[0037] (2) Add 10kg HEMA, 1.5kg PEGDA 600 and 0.3kg MBAA to 75kg water, stir well to obtain a mixture;

[0038] (3) The acrylate azobenzene solution obtained in step (1) is added dropwise to the mixture obtained in step (2), and stirred evenly to obtain a pregel.

[0039] Preparation Example 3

[0040] The difference from Preparation Example 1 is that acrylic acid is replaced by an equal amount of methacrylic acid.

[0041] Preparation Example 4

[0042] The difference from Preparation Example 1 is that methacrylic acid is replaced by an equal amount of acrylic acid.

[0043] Preparation Example 5

[0044] (1) Add 2 kg of 4-amino-4'-methacrylate azobenzene to 8 kg of DMSO and stir until homogeneous to obtain an acrylate azobenzene solution;

[0045] (2) Add 10kg HEMA, 1.5kg PEGDA 600 and 0.3kg MBAA to 75kg water, stir well to obtain a mixture;

[0046] (3) The acrylate azobenzene solution obtained in step (1) is added dropwise to the mixture obtained in step (2), and stirred evenly to obtain a pregel.

[0047] Example

[0048] In the following examples, sodium lignosulfonate was purchased from Shandong Ailiwan Chemical Technology Co., Ltd., model BL1; lambda-cyhalothrin technical grade was purchased from Nanjing Bermuda Biotechnology Co., Ltd., with a purity of 95%; diisocyanate was purchased from Covestro AG, model TDI-80; sodium diisooctyl sulfosuccinate was purchased from Xinxiang Huashun Chemical Co., Ltd., model OT-75; xanthan gum was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number S30551-100g; YUS-SC3A was purchased from Takemoto Oils & Fats Co., Ltd., Japan; thiamethoxam technical grade was purchased from Hubei Jiahuixingcheng Biotechnology Co., Ltd., product number JHXL-15; and azobisisobutyronitrile was purchased from Shandong Weijin Chemical Technology Co., Ltd., with a purity of 99%.

[0049] Example 1: A method for preparing a pH-photoresponsive nano-insecticide, wherein the pregel is prepared by the method in Example 1; the sulfosuccinate salt anionic dispersant is sodium diisooctyl sulfosuccinate.

[0050] The preparation method of the above-mentioned pH-photoresponsive nano-insecticide includes the following steps:

[0051] (1) Add 4.5 kg polyethylene glycol, 22.3 kg castor oil polyoxyethylene ether and 13.4 kg sodium lignosulfonate to 50 kg water, and shear and stir at 30 °C to obtain an aqueous phase; mix 250 kg of high-efficiency cyhalothrin technical and 134 kg xylene at 55 °C, add 33.50 kg diisocyanate, and stir evenly to obtain an oil phase; slowly pour the oil phase into the aqueous phase at a speed of 130 mL / s, shear at 30 °C for 5 min to obtain a primary emulsion; add 3.4 kg ethylenediamine at 31 °C, raise the temperature to 60 °C, and stir for 5.5 h to obtain an emulsion; add 40 kg YUS-SC3A, 30 kg glycerol, 0.5 kg xanthan gum, 5 kg magnesium aluminum silicate and 5 kg benzoic acid to the emulsion, shear and stir to obtain a high-efficiency cyhalothrin microcapsule suspension;

[0052] (2) Add 60kg YUS-SC3A to 400kg water and mix evenly. Add 275kg thiamethoxam technical and stir evenly. Add 30kg glycerin, 1kg xanthan gum, 10kg magnesium aluminum silicate, 8kg AF205 and 2kg benzoic acid. Shear and stir to obtain thiamethoxam suspension.

[0053] (3) The high-efficiency cyhalothrin microcapsule suspension prepared in step (1) and the thiamethoxam suspension prepared in step (2) are mixed, stirred evenly, and ground and homogenized for 6 hours to obtain nano insecticide.

[0054] (4) Add 12.5 kg of polyvinylpyrrolidone and 25 kg of sulfosuccinate anionic dispersant to the nano insecticide, disperse by ultrasonication, slowly add to 125 kg of pregel at a speed of 150 mL / s, stir evenly, add 3 kg of azobisisobutyronitrile, purge with nitrogen for 30 min, heat at 65℃ for 12 h, add 0.1 kg of Kathon, stir evenly, and obtain the nano insecticide.

[0055] Example 2: A method for preparing a pH-photoresponsive nano-insecticide, wherein the pregel is prepared by the method in Example 2; the sulfosuccinate salt anionic dispersant is sodium diisooctyl sulfosuccinate.

[0056] The preparation method of the above-mentioned pH-photoresponsive nano-insecticide includes the following steps:

[0057] (1) Add 4.5 kg polyethylene glycol, 22.3 kg castor oil polyoxyethylene ether and 13.4 kg sodium lignosulfonate to 50 kg water, and shear and stir at 27 °C to obtain an aqueous phase; mix 250 kg of high-efficiency cyhalothrin technical and 134 kg xylene at 50 °C, add 33.50 kg diisocyanate, and stir evenly to obtain an oil phase; slowly pour the oil phase into the aqueous phase at a speed of 130 mL / s, shear at 27 °C for 5 min to obtain a primary emulsion; add 3.4 kg ethylenediamine at 29 °C, raise the temperature to 55 °C, and stir for 4.5 h to obtain an emulsion; add 40 kg YUS-SC3A, 30 kg glycerol, 0.5 kg xanthan gum, 5 kg magnesium aluminum silicate and 5 kg benzoic acid to the emulsion, shear and stir to obtain a high-efficiency cyhalothrin microcapsule suspension;

[0058] (2) Add 60kg YUS-SC3A to 400kg water and mix evenly. Add 250kg thiamethoxam technical and stir evenly. Add 30kg glycerol, 1kg xanthan gum, 10kg magnesium aluminum silicate, 8kg AF205 and 2kg benzoic acid. Shear and stir to obtain thiamethoxam suspension.

[0059] (3) The high-efficiency cyhalothrin microcapsule suspension prepared in step (1) and the thiamethoxam suspension prepared in step (2) are mixed, stirred evenly, and ground and homogenized for 6 hours to obtain nano insecticide.

[0060] (4) Add 12.5 kg of polyvinylpyrrolidone and 12.5 kg of sulfosuccinate anionic dispersant to the nano insecticide, disperse by ultrasonication, slowly add to 75 kg of pregel at a speed of 150 mL / s, stir evenly, add 3 kg of azobisisobutyronitrile, purge with nitrogen for 30 min, heat at 60℃ for 10 h, add 0.1 kg of Kathon, and obtain the nano insecticide.

[0061] Example 3: A method for preparing a pH-photoresponsive nano-insecticide, the difference from Example 1 is that the pregel is prepared using the method in Example 3.

[0062] Example 4: A method for preparing a pH-photoresponsive nano-insecticide, the difference from Example 1 is that the pregel is prepared using the method in Example 4.

[0063] Example 5: A method for preparing a pH-photoresponsive nano-insecticide, the difference from Example 1 is that the pregel is prepared using the method in Example 5.

[0064] Example 6: A method for preparing a pH-photoresponsive nano-insecticide, the difference from Example 1 is that polyvinylpyrrolidone is replaced by an equal amount of sulfosuccinate anionic dispersant.

[0065] Example 7: A method for preparing a pH-photoresponsive nano-insecticide, the difference from Example 1 is that the sulfosuccinate anionic dispersant is replaced by an equal amount of polyvinylpyrrolidone.

[0066] Comparative Example

[0067] Comparative Example 1: The pH-light dual-response nano insecticide was replaced by an equal amount of 2.5% high-efficiency cyhalothrin; the 2.5% high-efficiency cyhalothrin was purchased from Adomai Huifeng Co., Ltd.

[0068] Comparative Example 2: The pH-light dual-response nano insecticide was replaced by an equal amount of 50% thiamethoxam water-dispersible granules; the 50% thiamethoxam water-dispersible granules were purchased from Jinan Lvba Pesticide Co., Ltd.

[0069] Comparative Example 3: A method for preparing a pH-light dual-response nano insecticide, which differs from Example 1 in that no pre-gel is added in step (4). The specific preparation method is as follows: 12.5 kg of polyvinylpyrrolidone and 25 kg of sulfosuccinate anionic dispersant are added to the nano insecticide, ultrasonically dispersed, 0.1 kg of Kathon is added, and the mixture is stirred evenly to obtain the insecticide.

[0070] Comparative Example 4: A preparation method of a pH-light dual-responsive nano-pesticide, which is different from Example 1 in that no composite dispersant is added.

[0071] Performance detection test

[0072] Prepare the pH-light dual-responsive nano-pesticide according to the methods in the examples and comparative examples, and perform performance detection according to the following methods. Record the detection results in Table 1.

[0073] 1. Stability: The thermal storage stability is detected according to GB / T 19136-2021 "Determination Method for Thermal Storage Stability of Pesticides". Experimental steps: Seal the test sample in a glass bottle, store it in a constant temperature oven at 54±2°C for 14 days, take it out, put it in a desiccator, and cool it to room temperature; complete the determination of specified items such as the mass fraction of the active ingredient within 24 hours, or directly use the original commercial package for the thermal storage test. If the relative decomposition rate of the active ingredient content is less than 5.0%, and the pH value and dilution stability still meet the standard requirements, it is qualified; the low-temperature stability is detected according to GB / T 19137 "Determination Method for Low-Temperature Stability of Pesticides". Experimental steps: Pipette 100 mL of the sample into a centrifuge tube, cool it to (0±2)°C in a refrigerator, keep the centrifuge tube and its contents at (0±2)°C for 1 hour, and stir it every 15 minutes for 15 seconds each time. Check and record whether there is precipitation of solid or oily substances. Put the centrifuge tube back into the refrigerator and continue to place it at (0±2)°C for 7 days. After 7 days, take out the centrifuge tube, let it stand at room temperature (not exceeding 20°C) for 3 hours, centrifuge for 15 minutes (the relative centrifugal force at the top of the tube is 500g - 600g, g is the acceleration of gravity), and record the volume of the separated matter at the bottom of the tube (accurate to 0.05 mL). If the volume of the separated matter does not exceed 0.3 mL, it is qualified; for the dilution stability, pipette 5 mL of the liquid agent with a pipette, place it in a 100 mL graduated cylinder, dilute it to the scale with standard hard water, mix well, put this graduated cylinder into a constant temperature water bath at 30°C±1°C, and let it stand for 1 hour. If the diluted solution is uniform and there is no precipitation, it is qualified; determine the stability test results according to the following three situations:

[0074] (1) If the low-temperature stability and dilution stability are qualified, but the thermal storage stability is unqualified, it is considered that the thermal storage stability is unqualified;

[0075] (2) If the thermal storage stability and dilution stability are qualified, but the low-temperature stability is unqualified, it is considered that the low-temperature stability is unqualified;

[0076] (3) If the low-temperature stability and thermal storage stability are qualified, but the dilution stability is unqualified, it is considered that the dilution stability is unqualified.

[0077] 2. Field Trial: The field trials were conducted in accordance with GB / T 17980.79-2004 "Guidelines for Field Efficacy Trials of Pesticides (II) Part 79: Insecticides for the Control of Wheat Aphids". The total experimental area was 480 m². 2 It is approximately 60m long and 8m wide, with each unit measuring approximately 2m (width) × 10m (length) = 20m. 2 There are a total of 24 blocks, with 4 replicates for each treatment. The examples, comparative examples, and blank control treatments are arranged in randomized blocks.

[0078] The experimental target was wheat aphids, primarily the wheat long-tubed aphid. The experimental crop was wheat, variety Taimai 198. The pesticide was prepared using a dilution method: the weighed pesticide was placed in a beaker with water and stirred thoroughly with a glass rod to ensure a homogeneous solution. The solution was then transferred to a sprayer and sprayed evenly over the entire plant. The blank control plot was sprayed with clean water first, followed by the control and comparative treatment plots. The treatment plots were sprayed evenly, progressing from low to high concentrations. The sprayer was rinsed with clean water before each pesticide treatment. The pesticide solution volume per plot was 2250 ml, and the formulation dosage was 0.23 g, including 2.5% high-efficiency chlorofluorocyanuric acid in the comparative example. The dosage of pyrethroid formulation was 2.3g; five sampling points were taken in each plot, with 10 plants at each point and two leaves per plant. The control effect was investigated and recorded 1 day, 3 days and 7 days after the first application; the control effect was calculated as follows: insect population reduction rate = ((number of insects before application - number of insects after application) / number of insects before application) × 100; control effect (%) = ((PT-CK) / (100-CK)) × 100; PT is the insect population reduction rate in the pesticide-treated area and CK is the insect population reduction rate in the blank control area; the weather at the test site on the day of application was foggy turning cloudy, with a temperature of 13-20℃ and a wind speed of 0.2-0.4m / s during the application period.

[0079] Table 1. Results of pH-light dual-response nano-insecticide tests in the examples and comparative cases.

[0080]

[0081] As shown in Table 1, the pH-photoresponsive nano-insecticides prepared in Examples 1-2 of this application exhibit good stability and control efficacy. Comparing Examples 3-4 with Example 1, it is evident that adding only one of acrylic acid and methacrylic acid slightly reduces the control efficacy. This may be due to a weakened synergistic effect between acrylic acid and methacrylic acid, thus narrowing the pH response range. Comparing Example 5 with Example 1, it is evident that without the addition of acrylic acid and methacrylic acid, the control efficacy in field trials is lower than in Example 1. This may be due to the lack of pH-responsive components affecting the insecticide release pathway. The reasons are as follows: Example 6, compared with Example 1, shows that without the addition of polyvinylpyrrolidone, the control effect in the field trial was significantly reduced. This may be because the protective effect of the dense adsorption membrane on the insecticide was destroyed, thus reducing the effective concentration. Example 7, compared with Example 1, shows that without the addition of sulfosuccinate anionic dispersants, the dilution stability of the insecticide was unqualified. This may be because the lack of interfacial tension regulation, charge repulsion, and steric hindrance weakened the dispersing effect on lambda-cyhalothrin and thiamethoxam, failing to effectively inhibit their aggregation and precipitation, ultimately leading to unqualified dilution stability.

[0082] Comparing Comparative Examples 1-2 with Example 1, it can be seen that when the insecticide was replaced by equal amounts of 2.5% high-efficiency cyhalothrin and 50% thiamethoxam water-dispersible granules, the control effect of the insecticide was slightly lower than that of the pH-light dual-response nano-insecticide. This may be because the single use of high-efficiency cyhalothrin and thiamethoxam only has contact and systemic insecticidal effects, and aphids may avoid the toxicity through self-regulation, thus affecting the control effect. Comparing Comparative Example 3 with Comparative Example 1, it can be seen that without the addition of pre-gel, the control effect was improved 1 day after the first application, but decreased 3 and 5 days after the first application. This may be because the insecticide was not encapsulated by the cross-linked hydrogel, and the insecticide was fully exposed in the early stage of spraying. In the later stage, the insecticide could not maintain an effective insecticidal concentration due to loss or degradation. Comparative Example 4 with Comparative Example 1, it can be seen that without the addition of a compound dispersant, the dispersing effect of high-efficiency cyhalothrin and thiamethoxam was weakened, and the active ingredients agglomerated, resulting in substandard dilution stability.

[0083] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing a pH-photoresponsive nano-insecticide, characterized in that, Includes the following steps: (1) Polyethylene glycol, castor oil polyoxyethylene ether and sodium lignosulfonate were added to water and sheared and stirred at 27-30℃ to obtain an aqueous phase; at 50-55℃, high-efficiency cyhalothrin technical and xylene were mixed evenly, diisocyanate was added and stirred evenly to obtain an oil phase; the oil phase was slowly poured into the aqueous phase and sheared at 27-30℃ for 3-5 min to obtain a primary emulsion; at 29-31℃, ethylenediamine was added, the temperature was raised to 55-60℃ and stirred for 4.5-5.5 h to obtain an emulsion; YUS-SC3A, glycerol, xanthan gum, magnesium aluminum silicate and benzoic acid were added to the emulsion and sheared and stirred to obtain high-efficiency cyhalothrin microcapsule suspension; (2) Add YUS-SC3A to water, mix well, add thiamethoxam technical, stir well, add glycerin, xanthan gum, magnesium aluminum silicate, AF205 and benzoic acid, shear and stir to obtain thiamethoxam suspension; (3) Mix the high-efficiency cyhalothrin microcapsule suspension and thiamethoxam suspension, stir evenly, grind and homogenize to obtain nano insecticide; (4) Add a composite dispersant to the nano insecticide, disperse it by ultrasonication, slowly add it to the pregel, stir it evenly, add azobisisobutyronitrile, purge with inert gas, heat at 60-65℃ for 10-12h, add Kathon, stir evenly, and obtain pH-photo-responsive nano insecticide. The method for preparing the pregel includes the following steps: (a) Add azobenzene acrylate to DMSO and stir until homogeneous to obtain azobenzene acrylate solution; (b) Add HEMA, PEGDA600 and MBAA to water and stir until homogeneous to obtain a mixture; (c) Add the acrylate azobenzene solution dropwise into the mixture and stir until homogeneous to obtain a pregel; The mass ratio of the high-efficiency cyhalothrin technical material to the composite dispersant is 1:0.1-0.15, and the composite dispersant includes polyvinylpyrrolidone and sulfosuccinate anionic dispersants in a mass ratio of 1:1-2. In step (a), after adding azobenzene acrylate to DMSO, a pH-responsive component is added, which includes acrylic acid and methacrylic acid in a mass ratio of 1:1-2.

2. The method for preparing a pH-photoresponsive nano-insecticide according to claim 1, characterized in that, The mass ratio of the high-efficiency cyhalothrin technical and the thiamethoxam technical is 1:1-1.

1.

3. The method for preparing a pH-photoresponsive nano-insecticide according to claim 1, characterized in that, The mass ratio of the high-efficiency cyhalothrin technical material to the pregel is 1:0.3-0.

5.

4. The method for preparing a pH-photoresponsive nano-insecticide according to claim 1, characterized in that, The mass ratio of the acrylate azobenzene to the pH-responsive component is 1:2-3.

5. A pH-photoresponsive nano-insecticide, characterized in that, It is prepared by the preparation method described in any one of claims 1-4.

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