A mesoporous silica as carrier of nanometer herbicide and its preparation method

Abstract

The application relates to the technical field of pesticide preparation, and specifically discloses a mesoporous silica as carrier nano-herbicide and a preparation method thereof, a preparation method of the mesoporous silica as carrier nano-herbicide, which comprises the following steps: dissolving a template agent in water, dropping a silicon source and a catalyst, stirring to obtain a suspension, centrifuging, washing, removing the template agent, and obtaining MSNs; the MSNs are subjected to three-step modification of amination, aldehyde group modification and acetalization to obtain acetal bond grafted MSNs; the acetal bond grafted MSNs are dispersed in an organic solvent, dimethenamid technical agent is added, stirring, filtering, washing, spraying a coating solution, and vacuum drying to obtain the mesoporous silica as carrier nano-herbicide. The nano-herbicide provided by the application can prolong the pesticide persistence period, reduce the pesticide application frequency, improve the pesticide efficacy and utilization rate, and reduce the pressure on the environment.

Description

Technical Field

[0001] This application relates to the field of pesticide formulation technology, and more specifically, to a nano-herbicide using mesoporous silica as a carrier and its preparation method. Background Technology

[0002] In agricultural production, weeds compete with crops for sunlight, water, and nutrients, which is one of the core factors leading to reduced crop yields. Herbicides have advantages such as high efficiency, speed, economy, simple operation, and low labor intensity in controlling crop weeds, and play an irreplaceable and important role in integrated pest management. In 2016, China's chemical pesticide production reached 3.778 million tons, and its usage reached 1.8 million tons, mainly conventional pesticide formulations such as emulsifiable concentrates, wettable powders, and water-in-oil emulsions.

[0003] Because the active ingredients in traditional pesticide formulations are easily affected by external environmental factors such as sunlight, high temperatures, and rain erosion, their efficacy typically decreases significantly after 1-2 weeks of application, requiring multiple reapplications to control weed growth. Therefore, the development of a highly stable nano-pesticide slow-release agent is of significant practical importance for improving pesticide utilization, extending pesticide effectiveness, maintaining ecological balance, and promoting the development of green agriculture. Summary of the Invention

[0004] To address the problem that traditional herbicides are susceptible to environmental factors, resulting in reduced efficacy and the need for repeated reapplication, this application provides a nano-herbicide using mesoporous silica as a carrier and its preparation method.

[0005] Firstly, this application provides a technical solution using mesoporous silica as a carrier, employing the following approach: The template agent is dissolved in water, and a silicon source and catalyst are added dropwise. After stirring, a suspension is obtained. The suspension is centrifuged, washed, and the template agent is removed to obtain MSNs. MSNs were dispersed in toluene, APTES was added, and the mixture was refluxed at 60-80℃ for 12-24 h under nitrogen protection. After centrifugation, washing, and drying, MSNs-NH2 was obtained. MSNs-NH2 was dispersed in ethanol, glutaraldehyde was added, and the mixture was stirred at 23-27℃ for 4-6 h. After centrifugation, washing, and drying, MSNs-CHO was obtained. MSNs-CHO was dispersed in ethanol, ethylene glycol and p-toluenesulfonic acid were added, and the mixture was stirred at 35-40℃ for 12-24 h. After centrifugation, washing, and drying, acetal-grafted MSNs were obtained. The mass ratio of MSNs, APTES, glutaraldehyde, ethylene glycol, and p-toluenesulfonic acid was 1-1.2:0.2-0.3:0.5:0.3:0.01-0.02. The acetal-grafted MSNs were dispersed in an organic solvent, and pendimethalin technical was added. The mixture was stirred for 4-6 hours, filtered, washed, coated with a coating solution, and vacuum dried to obtain a nano-herbicide with mesoporous silica as the carrier. The preparation method of the coating solution includes the following steps: Cellulose is added to a buffer solution and sonicated to obtain a cellulose solution. PVA is added to water and heated to 70-80℃ and stirred to obtain a PVA solution. The PVA solution and AKD are added to the cellulose solution to obtain a coating solution. The mass ratio of cellulose, buffer solution, PVA and AKD is 1:40-60:0.3-0.5:0.2-0.3.

[0006] By employing the above-mentioned technical solution, this preparation method first synthesizes mesoporous silica nanoparticles (MSNs), then sequentially modifies the surface of the MSNs through three steps: amylation, aldehyde modification, and acetalization, constructing pH-responsive acetal bonds to obtain MSNs with acetal bonds on their surface. Next, the MSNs with acetal bonds are dispersed in an organic solvent, and pendimethalin technical grade is added for loading. After filtration and washing, a coating solution is sprayed on and vacuum dried to obtain the nano-herbicide. The coating solution is composed of cellulose, polyvinyl alcohol, and alkyl ketone dimer (AKD). The specific cleavage of acetal bonds in the acidic microenvironment of weed rhizosphere enables precise release of the herbicide. Simultaneously, the cellulose-PVA-AKD composite coating layer imparts excellent hydrophobic properties to the particles, significantly enhancing their resistance to rain erosion and reducing environmental loss of the herbicide due to rainwater leaching. This invention integrates a dual mechanism of pH-responsive precise release and rain-resistant physical protection, and has the advantages of high drug loading capacity, controllable release, and environmental friendliness, providing a new technical solution for reducing the dosage and increasing the efficiency of herbicides.

[0007] This coating solution preparation scheme achieves excellent film-forming and hydrophobic properties through stepwise processing and component synergy. Polyvinyl alcohol solution and alkyl ketone dimer are added together to the cellulose solution, forming a synergistic effect. Cellulose nanofibers construct a dense nanofiber network as the coating framework, polyvinyl alcohol fills the fiber gaps, improving film continuity and flexibility and preventing cracking after drying. The alkyl ketone dimer adsorbs onto the carboxyl sites on the cellulose surface via electrostatic interactions, forming stable ester bonds after subsequent curing, thus endowing the coating layer with durable hydrophobic properties. The coating solution prepared by this scheme exhibits good spray adaptability and film uniformity. When applied to the particle surface, it significantly improves resistance to rain erosion. Simultaneously, the coating layer does not alter the pH response characteristics of the core, thus not affecting the precise release of the drug in the acidic environment of the weed rhizosphere.

[0008] Optionally, the raw materials used in the nano herbicide with mesoporous silica as a carrier are as follows by weight: 1-3 parts silicon source, 0.2-0.5 parts template agent, 0.1-0.4 parts pendimethalin technical, 100-120 parts deionized water, 5-10 parts organic solvent, and 1.4-1.8 parts catalyst.

[0009] By adopting the above technical solution, the silicon source forms a silica shell under the guidance of the template agent, and the catalyst provides hydroxide ions to accelerate the hydrolysis and condensation of the silicon source, ensuring that silicic acid molecules uniformly encapsulate micelles, ultimately forming a mesoporous carrier with a large specific surface area and multiple pore sizes, providing sufficient loading sites for pendimethalin technical. Deionized water, as a dispersion medium, can dilute the concentration of each raw material and avoid local aggregation of the silicon source. Organic solvents can fully dissolve the hydrophobic pendimethalin technical, solving the problem of pesticides being highly hydrophobic and prone to aggregation, and improving loading efficiency.

[0010] Optionally, the mass ratio of the silicon source, pendimethalin technical material, and organic solvent is 1:0.1-0.3:5-8.

[0011] By adopting the above technical solution, pendimethalin technical material, being a hydrophobic solid, cannot be directly dispersed in an aqueous system. However, organic solvents can achieve efficient dissolution by forming van der Waals forces between hydrophobic groups (ester groups) and the alkyl and aromatic rings of pesticide molecules, dispersing the technical material into molecular-level units and preventing its aggregation into large particles. The organic solvents are polar, capable of both stably dissolving the pesticide and forming a compatible interface with the aqueous phase. Under the surface activity of the template agent, oil-in-water emulsion droplets are formed. These droplets act as micro-containers for the pesticide, fixing the pendimethalin technical material within the oil phase. The subsequent directional coating of the silicon source provides a clear loading target. After the silicon source is dropped into the system, it hydrolyzes to generate silicic acid molecules. Because the interfacial tension between the oil phase and the aqueous phase is lower than that inside the aqueous phase, these molecules preferentially aggregate and condense on the surface of the droplets, gradually forming a silica shell. At this time, the organic solvent directly affects the uniformity of the silicon source coating by adjusting the stability and particle size of the oil phase droplets. The organic solvent solves the problem of pesticide dissolution and dispersion. The silicon source uses these dispersed pesticide micro-units to construct a loading carrier. The three work together to achieve efficient loading, controlled release and environmental stability of pesticides, ultimately improving the weeding effect.

[0012] Optionally, the mass ratio of the silicon source, template agent, and catalyst is 1:0.3-0.4:1.5-1.8.

[0013] By adopting the above technical solution, the pore size, specific surface area, and pore volume of mesoporous silica are key factors affecting the loading efficiency of pendimethalin technical. The combined use of silicon source, template agent, and catalyst can precisely control the mesoporous structure. The template agent self-assembles into micelles in the aqueous phase, and its size determines the mesoporous pore size. The silicon source forms a silica shell on the surface of the micelles through hydrolysis and condensation, and the shell thickness further affects the final pore size. The uniform dispersion of the template agent micelles promotes the directional deposition of the silicon source around the micelles during the hydrolysis and condensation process, forming a mesoporous structure with uniform pore size distribution and ordered channels, avoiding the problems of disordered channels and pore size fluctuations caused by the lack of a template. This combination of template-determined structure and silicon source-built framework significantly increases the specific surface area of ​​the mesoporous silica carrier, increases the drug loading sites, and improves the loading capacity of pendimethalin technical.

[0014] The alkoxy groups in silicon source molecules exhibit strong chemical stability, resulting in slow and incomplete hydrolysis in a room-temperature pure water system, which is insufficient to meet the efficiency requirements for mesoporous structure construction. The addition of a catalyst can activate the silicon source activity through two pathways. Firstly, the alkaline catalyst releases hydroxide ions in the aqueous phase. These hydroxyl ions act as nucleophiles, attacking Si atoms in the silicon source molecule, weakening the Si-OC bond energy, and lowering the activation energy of the hydrolysis reaction, thus significantly increasing the hydrolysis rate of the silicon source. Secondly, the catalyst adjusts the pH of the system, altering the electron cloud distribution of the silicon source molecule, enhancing the electrophilicity of Si atoms, and further promoting the substitution reaction between water molecules and alkoxy groups. This ensures that the silicon source can be efficiently converted into a reactive siloxane intermediate, laying the material foundation for subsequent condensation reactions.

[0015] Optionally, the silicon source is selected from one or both of tetraethyl orthosilicate and tetramethyl orthosilicate; the template agent is selected from one or more of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, and dodecyltrimethylammonium bromide.

[0016] Optionally, the catalyst is selected from one or more of concentrated ammonia, sodium hydroxide, and triethylamine.

[0017] By adopting the above technical solution, the silicon source needs to be hydrolyzed to generate silicic acid, and then condensed to form a silica framework. This process is extremely slow at room temperature. The catalyst significantly accelerates the reaction by providing hydroxide ions. At the same time, the hydroxide ions provided by the catalyst can reduce the activation energy of the condensation reaction, promote the rapid cross-linking of silicic acid molecules, and form a stable silica coating layer, which is wrapped on the surface of the oil phase droplets (containing dimethyl pendimethalin) of the oil-in-water emulsion, laying the framework foundation for the subsequent formation of mesoporous structures.

[0018] Optionally, the organic solvent is selected from one or more of methanol, acetone and ethyl acetate.

[0019] By adopting the above technical solution, the oil phase solvent has strong hydrophobic groups, which can combine with the hydrophobic structure in the dimethyl pendimethalin molecule through van der Waals forces to achieve efficient dissolution; it can meet the needs of high-concentration pesticide oil phase preparation, avoid the formation of precipitation due to insufficient dissolution of the active ingredient, and avoid affecting the uniformity of subsequent loading; at the same time, the oil phase solvent ensures the stable existence of the emulsion by adjusting its compatibility and surface tension with the aqueous phase, and provides a uniform reaction environment for the hydrolysis and condensation of silicon source.

[0020] In summary, this application has the following beneficial effects: 1. The mesoporous silica (MSNs) prepared by the template method in this application have a regular and ordered pore structure and a large specific surface area, which can efficiently load pendimethalin technical. By grafting acetal bonds on the surface of MSNs, they have excellent acid pH-responsive release characteristics. In a neutral water environment, they can effectively inhibit drug leakage, while in the rhizosphere of weeds and the slightly acidic environment of soil, the acetal bonds undergo specific hydrolytic breakage, realizing precise drug release. In the coating solution sprayed on the outer layer, cellulose can be specifically degraded by cellulase in weed roots and soil. The pH response of the acetal bonds will achieve dual controlled release, improve the targeting of weed control and reduce the impact on crops and the environment. At the same time, PVA in the coating solution forms a hydrophobic protective film with a certain strength with AKD, which can effectively reduce rainwater leaching loss and improve the stability of nanoparticles in water and soil.

[0021] 2. In this application, cellulose is used as the film-forming substrate, combined with PVA to improve the dispersibility and film adhesion strength of the system, and AKD is introduced to impart hydrophobic properties to the film layer. The three components can form a uniform and stable coating system after compounding. After spraying, a continuous and dense protective film can be formed on the surface of drug-loaded mesoporous silica. On the one hand, the characteristic of cellulose being degraded by cellulase in the rhizosphere of weeds can be used to achieve enzyme-triggered drug release. On the other hand, the hydrophobic effect of AKD can reduce the risk of rapid dissolution and leakage of the formulation when it comes into contact with water. At the same time, PVA enhances the adhesion and structural integrity of the film layer, effectively improving the rain erosion resistance and storage stability of the nano herbicide, and achieving the synergistic effect of enzyme-responsive controlled release and physical protection.

[0022] 3. In this application, the combined use of silicon source, template agent and catalyst, the structure guidance of template agent and the framework construction of silicon source form a synergistic effect to achieve precise control of mesoporous structure, ensuring that pesticide molecules can smoothly enter and be loaded into the pores to achieve high loading. At the same time, the appropriate pore size can produce a diffusion control effect on pesticide release, thereby achieving a slow release effect. The hydroxide ions provided by the catalyst can reduce the activation energy of condensation reaction, promote the rapid cross-linking of silicic acid molecules, and lay the framework foundation for the subsequent formation of mesoporous structure. Detailed Implementation

[0023] The following embodiments provide a further detailed description of this application. Preparation example of coating solution

[0024] The raw materials are sourced as follows: cellulose is selected from Renqiu Litian Chemical Co., Ltd., model number LT-011; polyvinyl alcohol is selected from Shandong Jinyu New Material Co., Ltd., product number 516; AKD is selected from Hubei Watson Chemical Technology Co., Ltd., grade industrial; sodium acetate is prepared from acetic acid, sodium acetate and deionized water.

[0025] Preparation Example 1-1: 1g of cellulose was added to 60g of sodium acetate buffer solution and sonicated at 300W for 30min to obtain a cellulose solution. 0.5g of PVA was added to 10g of deionized water, heated to 80℃, and stirred at 500r / min to obtain a PVA solution. The PVA solution and 0.3g of AKD were added to the cellulose solution to obtain a coating solution.

[0026] Preparation Example 1-2: 1g of cellulose was added to 50g of sodium acetate buffer solution and sonicated at 300W for 30min to obtain a cellulose solution. 0.4g of PVA was added to 10g of deionized water, heated to 75℃, and stirred at 500r / min to obtain a PVA solution. The PVA solution and 0.25g of AKD were added to the cellulose solution to obtain a coating solution.

[0027] Preparation Examples 1-3: 1g of cellulose was added to 40g of sodium acetate buffer solution and sonicated at 300W for 30min to obtain a cellulose solution. 0.3g of PVA was added to 10g of deionized water, heated to 70℃, and stirred at 500r / min to obtain a PVA solution. The PVA solution and 0.2g of AKD were added to the cellulose solution to obtain a coating solution.

[0028] Preparation Example 1-4: The difference from Preparation Example 1-1 is that AKD was not added. 1g of cellulose was added to 60g of sodium acetate buffer solution, and the solution was sonicated at 300W for 30min to obtain a cellulose solution. 0.5g of PVA was added to 10g of deionized water, heated to 80℃, and stirred at 500r / min to obtain a PVA solution. The PVA solution was then added to the cellulose solution to obtain a coating solution. Example

[0029] Example 1: A method for preparing a nano-herbicide using mesoporous silica as a carrier, comprising the following steps: 0.4g of template agent was dissolved in 120g of deionized water and ultrasonically dispersed at 250W for 10min until completely dissolved. After standing for 5 minutes until no bubbles appeared on the surface, 1g of silicon source was added dropwise to the deionized water at a rate of 2mL / min. Finally, 1.8g of catalyst was added dropwise to the solution at a rate of 3mL / min. After stirring, a suspension was obtained. The suspension was centrifuged at 8000r / min, washed twice with ethanol, and once with deionized water. The template agent was removed by extraction to obtain MSNs. The template agent was hexadecyltrimethylammonium bromide, the silicon source was tetraethyl orthosilicate, and the catalyst was concentrated ammonia. 1.2 g MSNs were dispersed in 50 g toluene, 0.3 g APTES was added, and the mixture was refluxed at 80 °C for 24 h under nitrogen protection. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-NH2. MSNs-NH2 was dispersed in 50 g ethanol, 0.5 g glutaraldehyde was added, and the mixture was stirred at 27 °C for 6 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-CHO. MSNs-CHO was dispersed in 50 g ethanol, 0.3 g ethylene glycol and 0.02 g p-toluenesulfonic acid were added, and the mixture was stirred at 40 °C for 24 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain acetal-grafted MSNs. The acetal-grafted MSNs were dispersed in 8g of organic solvent, and 0.3g of pendimethalin technical was added. The mixture was stirred at 500r / min for 6h, filtered, washed three times with deionized water, coated with a coating solution, and vacuum dried to obtain a nano-herbicide with mesoporous silica as the carrier. The organic solvent was acetone, and the coating solution was prepared in Preparation Example 1-1.

[0030] Example 2: A method for preparing a nano-herbicide using mesoporous silica as a carrier, comprising the following steps: 0.3g of template agent was dissolved in 120g of deionized water and ultrasonically dispersed at 250W for 10min until completely dissolved. After standing for 5 minutes until no bubbles appeared on the surface, 1g of silicon source was added dropwise to the deionized water at a rate of 2mL / min. Finally, 1.5g of catalyst was added dropwise to the solution at a rate of 3mL / min. After stirring, a suspension was obtained. The suspension was centrifuged at 8000r / min, washed twice with ethanol, and washed once with deionized water. The template agent was removed by extraction to obtain MSNs. The template agent was hexadecyltrimethylammonium bromide, the silicon source was tetraethyl orthosilicate, and the catalyst was concentrated ammonia. 1.15 g MSNs were dispersed in 50 g toluene, 0.28 g APTES were added, and the mixture was refluxed at 80 °C for 24 h under nitrogen protection. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-NH2. MSNs-NH2 was dispersed in 50 g ethanol, 0.5 g glutaraldehyde was added, and the mixture was stirred at 27 °C for 6 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-CHO. MSNs-CHO was dispersed in 50 g ethanol, 0.3 g ethylene glycol and 0.018 g p-toluenesulfonic acid were added, and the mixture was stirred at 40 °C for 24 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain acetal-grafted MSNs. The acetal-grafted MSNs were dispersed in 5g of organic solvent, and 0.1g of pendimethalin technical was added. The mixture was stirred at 500r / min for 6h, filtered, washed three times with deionized water, coated with a coating solution, and vacuum dried to obtain a nano-herbicide with mesoporous silica as the carrier. The organic solvent was acetone, and the coating solution was prepared from Preparation Examples 1-2.

[0031] Example 3: A method for preparing a nano-herbicide using mesoporous silica as a carrier, comprising the following steps: 0.5g of template agent was dissolved in 120g of deionized water and ultrasonically dispersed at 250W for 10min until completely dissolved. After standing for 5 minutes until no bubbles appeared on the surface, 3g of silicon source was added dropwise to the deionized water at a rate of 2mL / min. Finally, 1.8g of catalyst was added dropwise to the solution at a rate of 3mL / min. After stirring, a suspension was obtained. The suspension was centrifuged at 8000r / min, washed twice with ethanol, and washed once with deionized water. The template agent was removed by extraction to obtain MSNs. The template agent was hexadecyltrimethylammonium bromide, the silicon source was tetraethyl orthosilicate, and the catalyst was concentrated ammonia. 1.1 g MSNs were dispersed in 50 g toluene, 0.25 g APTES were added, and the mixture was refluxed at 80 °C for 24 h under nitrogen protection. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-NH2. MSNs-NH2 was dispersed in 50 g ethanol, 0.5 g glutaraldehyde was added, and the mixture was stirred at 27 °C for 6 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-CHO. MSNs-CHO was dispersed in 50 g ethanol, 0.3 g ethylene glycol and 0.015 g p-toluenesulfonic acid were added, and the mixture was stirred at 40 °C for 24 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain acetal-grafted MSNs. The acetal-grafted MSNs were dispersed in 10g of organic solvent, and 0.4g of pendimethalin technical was added. The mixture was stirred at 500r / min for 6h, filtered, washed three times with deionized water, coated with a coating solution, and vacuum dried to obtain a nano-herbicide with mesoporous silica as the carrier. The organic solvent was acetone, and the coating solution was prepared from Preparation Examples 1-3.

[0032] Example 4: A method for preparing a nano-herbicide using mesoporous silica as a carrier, comprising the following steps: 0.2g of template agent was dissolved in 100g of deionized water and ultrasonically dispersed at 250W for 10min until completely dissolved. After standing for 5 minutes until no bubbles appeared on the surface, 1g of silicon source was added dropwise to the deionized water at a rate of 2mL / min. Finally, 1.4g of catalyst was added dropwise to the solution at a rate of 3mL / min. After stirring, a suspension was obtained. The suspension was centrifuged at 8000r / min, washed twice with ethanol, and washed once with deionized water. The template agent was removed by extraction to obtain MSNs. The template agent was hexadecyltrimethylammonium bromide, the silicon source was tetraethyl orthosilicate, and the catalyst was concentrated ammonia. 1 g of MSNs was dispersed in 50 g of toluene, 0.2 g of APTES was added, and the mixture was refluxed at 80 °C for 24 h under nitrogen protection. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-NH2. MSNs-NH2 was dispersed in 50 g of ethanol, 0.5 g of glutaraldehyde was added, and the mixture was stirred at 27 °C for 6 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-CHO. MSNs-CHO was dispersed in 50 g of ethanol, 0.3 g of ethylene glycol and 0.01 g of p-toluenesulfonic acid were added, and the mixture was stirred at 40 °C for 24 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain acetal-grafted MSNs. The acetal-grafted MSNs were dispersed in 5g of organic solvent, and 0.1g of pendimethalin technical grade was added. The mixture was stirred at 500r / min for 6h, filtered, washed three times with deionized water, sprayed with a coating solution, and vacuum dried to obtain a nano-herbicide with mesoporous silica as the carrier. The organic solvent was acetone.

[0033] Example 5: A method for preparing a nano-herbicide using mesoporous silica as a carrier, comprising the following steps: 0.4g of template agent was dissolved in 120g of deionized water and ultrasonically dispersed at 250W for 10min until completely dissolved. After standing for 5 minutes until no bubbles appeared on the surface, 1g of silicon source was added dropwise to the deionized water at a rate of 2mL / min. Finally, 1.8g of catalyst was added dropwise to the solution at a rate of 3mL / min. After stirring, a suspension was obtained. The suspension was centrifuged at 8000r / min, washed twice with ethanol, and once with deionized water. The template agent was removed by extraction to obtain MSNs. The template agent was hexadecyltrimethylammonium bromide, the silicon source was tetraethyl orthosilicate, and the catalyst was concentrated ammonia. 1.2 g MSNs were dispersed in 50 g toluene, 0.3 g APTES was added, and the mixture was refluxed at 80 °C for 24 h under nitrogen protection. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-NH2. MSNs-NH2 was dispersed in 50 g ethanol, 0.5 g glutaraldehyde was added, and the mixture was stirred at 27 °C for 6 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-CHO. MSNs-CHO was dispersed in 50 g ethanol, 0.3 g ethylene glycol and 0.02 g p-toluenesulfonic acid were added, and the mixture was stirred at 40 °C for 24 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain acetal-grafted MSNs. The acetal-grafted MSNs were dispersed in 9g of organic solvent, and 0.4g of pendimethalin technical grade was added. The mixture was stirred at 500r / min for 6h, filtered, washed three times with deionized water, coated with a coating solution, and vacuum dried to obtain a nano-herbicide with mesoporous silica as the carrier. The organic solvent was acetone.

[0034] Example 6: A method for preparing a nano-herbicide using mesoporous silica as a carrier, comprising the following steps: 0.2g of template agent was dissolved in 120g of deionized water and ultrasonically dispersed at 250W for 10min until completely dissolved. After standing for 5 minutes until no bubbles appeared on the surface, 1g of silicon source was added dropwise to the deionized water at a rate of 2mL / min. Finally, 1.4g of catalyst was added dropwise to the solution at a rate of 3mL / min. After stirring, a suspension was obtained. The suspension was centrifuged at 8000r / min, washed twice with ethanol, and washed once with deionized water. The template agent was removed by extraction to obtain MSNs. The template agent was hexadecyltrimethylammonium bromide, the silicon source was tetraethyl orthosilicate, and the catalyst was concentrated ammonia. 1.2 g MSNs were dispersed in 50 g toluene, 0.3 g APTES was added, and the mixture was refluxed at 80 °C for 24 h under nitrogen protection. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-NH2. MSNs-NH2 was dispersed in 50 g ethanol, 0.5 g glutaraldehyde was added, and the mixture was stirred at 27 °C for 6 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-CHO. MSNs-CHO was dispersed in 50 g ethanol, 0.3 g ethylene glycol and 0.02 g p-toluenesulfonic acid were added, and the mixture was stirred at 40 °C for 24 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain acetal-grafted MSNs. The acetal-grafted MSNs were dispersed in 8g of organic solvent, and 0.3g of pendimethalin technical grade was added. The mixture was stirred at 500r / min for 6h, filtered, washed three times with deionized water, coated with a coating solution, and vacuum dried to obtain a nano-herbicide with mesoporous silica as the carrier. The organic solvent was acetone.

[0035] Example 7: A method for preparing a nano-herbicide using mesoporous silica as a carrier, the difference from Example 1 is that the catalyst is hydrochloric acid.

[0036] Example 8: A method for preparing a nano-herbicide using mesoporous silica as a carrier, differing from Example 1 in that the MSNs are not amino-modified, and includes the following steps: 0.4g of template agent was dissolved in 120g of deionized water and ultrasonically dispersed at 250W for 10min until completely dissolved. After standing for 5 minutes until no bubbles appeared on the surface, 1g of silicon source was added dropwise to the deionized water at a rate of 2mL / min. Finally, 1.8g of catalyst was added dropwise to the solution at a rate of 3mL / min. After stirring, a suspension was obtained. The suspension was centrifuged at 8000r / min, washed twice with ethanol, and once with deionized water. The template agent was removed by extraction to obtain MSNs. The template agent was hexadecyltrimethylammonium bromide, the silicon source was tetraethyl orthosilicate, and the catalyst was concentrated ammonia. 1.2 g MSNs were dispersed in 50 g ethanol, 0.5 g glutaraldehyde was added, and the mixture was stirred at 27 °C for 6 h. After centrifugation at 8000 r / min, the MSNs were washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-CHO. MSNs-CHO was dispersed in 50 g ethanol, 0.3 g ethylene glycol and 0.02 g p-toluenesulfonic acid were added, and the mixture was stirred at 40 °C for 24 h. After centrifugation at 8000 r / min, the MSNs were washed twice with ethanol, once with deionized water, and dried under vacuum to obtain acetal-grafted MSNs. The acetal-grafted MSNs were dispersed in 8g of organic solvent, and 0.3g of pendimethalin technical grade was added. The mixture was stirred at 500r / min for 6h, filtered, washed three times with deionized water, coated with a coating solution, and vacuum dried to obtain a nano-herbicide with mesoporous silica as the carrier. The organic solvent was acetone.

[0037] Example 9: A method for preparing a nano-herbicide using mesoporous silica as a carrier, differing from Example 1 in that it does not undergo aldehyde modification, and includes the following steps: 0.4g of template agent was dissolved in 120g of deionized water and ultrasonically dispersed at 250W for 10min until completely dissolved. After standing for 5 minutes until no bubbles appeared on the surface, 1g of silicon source was added dropwise to the deionized water at a rate of 2mL / min. Finally, 1.8g of catalyst was added dropwise to the solution at a rate of 3mL / min. After stirring, a suspension was obtained. The suspension was centrifuged at 8000r / min, washed twice with ethanol, and once with deionized water. The template agent was removed by extraction to obtain MSNs. The template agent was hexadecyltrimethylammonium bromide, the silicon source was tetraethyl orthosilicate, and the catalyst was concentrated ammonia. 1.2 g MSNs were dispersed in 50 g toluene, 0.3 g APTES was added, and the mixture was refluxed at 80 °C for 24 h under nitrogen protection. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain MSNs-NH2. MSNs-NH2 was dispersed in 50 g ethanol, 0.3 g ethylene glycol and 0.02 g p-toluenesulfonic acid were added, and the mixture was stirred at 40 °C for 24 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and dried under vacuum to obtain acetal-grafted MSNs. The acetal-grafted MSNs were dispersed in 8g of organic solvent, and 0.3g of pendimethalin technical grade was added. The mixture was stirred at 500r / min for 6h, filtered, washed three times with deionized water, coated with a coating solution, and vacuum dried to obtain a nano-herbicide with mesoporous silica as the carrier. The organic solvent was acetone.

[0038] Example 10: A method for preparing a nano-herbicide using mesoporous silica as a carrier, differing from Example 1 in that it does not undergo acetalization modification, and includes the following steps: 0.4g of template agent was dissolved in 120g of deionized water and ultrasonically dispersed at 250W for 10min until completely dissolved. After standing for 5 minutes until no bubbles appeared on the surface, 1g of silicon source was added dropwise to the deionized water at a rate of 2mL / min. Finally, 1.8g of catalyst was added dropwise to the solution at a rate of 3mL / min. After stirring, a suspension was obtained. The suspension was centrifuged at 8000r / min, washed twice with ethanol, and once with deionized water. The template agent was removed by extraction to obtain MSNs. The template agent was hexadecyltrimethylammonium bromide, the silicon source was tetraethyl orthosilicate, and the catalyst was concentrated ammonia. 1.2 g MSNs were dispersed in 50 g toluene, 0.3 g APTES was added, and the mixture was refluxed at 80 °C for 24 h under nitrogen protection. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and vacuum dried to obtain MSNs-NH2. MSNs-NH2 was then dispersed in 50 g ethanol, 0.5 g glutaraldehyde was added, and the mixture was stirred at 27 °C for 6 h. After centrifugation at 8000 r / min, the mixture was washed twice with ethanol, once with deionized water, and vacuum dried to obtain MSNs-CHO. The MSNs-CHO was dispersed in 8g of organic solvent, and 0.3g of pendimethalin technical grade was added. The mixture was stirred at 500r / min for 6h, filtered, washed three times with deionized water, coated with a coating solution, and vacuum dried to obtain a nano herbicide with mesoporous silica as the carrier. The organic solvent was acetone.

[0039] Example 11: The difference from Example 10 is that the coating solution was prepared by Preparation Examples 1-4. Comparative Example

[0040] Comparative Example 1: A method for preparing a nano-herbicide using mesoporous silica as a carrier, which differs from Example 1 in that no coating solution is sprayed.

[0041] Comparative Example 2: Shandong Yueming Biotechnology Co., Ltd., 330 g / L pendimethalin EC, without carrier loading. Performance testing

[0042] Nanoparticle herbicides using mesoporous silica as a carrier were prepared according to the methods in the examples and comparative examples, and their performance was tested according to the following methods. The test results are recorded in Table 1.

[0043] 1. Weed control effect 1.1 Geographical location of the experiment The experiment was conducted at the Jiangxi Provincial Seed Breeding Farm, Yinsanjiao Management Committee, Nanchang County, Jiangxi Province, a traditional rice-growing area located in a contiguous plain. All experimental plots had uniform water and fertilizer conditions and relatively flat terrain.

[0044] 1.2 Test target conditions The weeds in the experimental field were: Eclipta prostrata, barnyard grass, crabgrass, and sedge; the weed density was high and the distribution was relatively uniform.

[0045] 1.3 Experimental Crops, Varieties, and Growth Status The experimental crop was rice grown in dry-seedling beds, with the variety being Huanghuazhan. The rice in the dry-seedling beds grew normally.

[0046] 1.4 Soil Types at the Experimental Site The soil is clay loam, with good soil quality, high fertility, high organic matter content, and a pH of around 6.2. The previous crop was rice, and herbicides were used on the previous rice crop, but there was no herbicide damage to the current dry-seedling rice.

[0047] 1.5 Meteorological Data On May 21st, the day before pesticide application, there was light rain and temperatures ranging from 21.6 to 23.8℃. On May 22nd, the day of application, it was cloudy with temperatures ranging from 22 to 28.2℃. On May 23rd, it was partly cloudy with temperatures ranging from 23.1 to 30.4℃. On May 24th, it was partly cloudy with temperatures ranging from 24.1 to 33.6℃. On May 25th, it was cloudy with temperatures ranging from 24.9 to 33.8℃. On May 26th, it was cloudy with temperatures ranging from 25.1 to 34.5℃. On May 27th, there was moderate to heavy rain with temperatures ranging from 21.9 to 30.9℃. On May 28th, it was partly cloudy with temperatures ranging from 19 to 27.7℃. On May 29th, it was partly cloudy with temperatures ranging from 20.5 to 30.1℃. During the experiment, no adverse weather conditions occurred that would affect the results.

[0048] 1.6 Data Detection The nano-herbicides prepared in Examples 1-11 and Comparative Example 1 (active ingredient dosage 792 g / ha) and the control herbicide of Comparative Example 2 (active ingredient dosage 792 g / ha) were divided into 14 groups to treat the paddy field. Each treatment was repeated 4 times, for a total of 14 treatments. Each plot area was 20 m². 2 A total of 56 plots were randomly arranged in blocks. The application method was to apply the pesticide evenly to the target area, once after sowing and before the emergence of rice seedlings in dry-seedling fields.

[0049] Survey method: Four points were randomly selected in each community, and the survey was conducted at each point for 0.25m. 2 A total of 1m was surveyed. 2 The number of surviving weeds was investigated at 15, 30, 45, 60, 90, and 120 days after application, and the control efficacy per plant was calculated.

[0050] Methods for calculating drug efficacy: Control efficacy per plant = (number of weeds in blank control - number of weeds in treatment) / number of weeds in blank control × 100%.

[0051] Table 1. Test data on the weed control efficacy of the nano-herbicides prepared in the examples and comparative examples.

[0052] As can be seen from Examples 1-4 and Table 1, the nano-herbicide prepared in this application using mesoporous silica as a carrier has excellent slow-release and control effects, and the control efficacy is still above 81% 120 days after administration.

[0053] Combining Examples 1 and 5 with Table 1, it can be seen that the slow-release effect of the nano herbicide prepared in Example 5 is reduced compared to Example 1. This indicates that when silicon source, pendimethalin technical and organic solvent are used in combination within a certain ratio range, the slow-release effect of the nano herbicide with mesoporous silica as carrier is better.

[0054] Combining Examples 1 and 6 with Table 1, it can be seen that the slow-release effect of the nano-herbicide prepared in Example 6 is reduced compared to Example 1. This indicates that when silicon source, template agent and catalyst are used in combination within a certain range, the slow-release effect of nano-herbicide with mesoporous silica as carrier is better.

[0055] Combining Examples 1 and 7 with Table 1, it can be seen that the slow-release effect of the nano herbicide prepared in Example 8 is reduced compared to Example 1. This indicates that the alkaline catalyst activates the activity of the silicon source, reduces the activation energy of the hydrolysis reaction, and significantly increases the hydrolysis rate of the silicon source, thereby improving the slow-release effect of mesoporous silica.

[0056] Combining Examples 1 and 8-10 with Table 1, it can be seen that the sustained-release effect of the nano herbicides prepared in Examples 8-10 is reduced compared to Example 1. This indicates that by sequentially modifying the surface of MSNs with amination, aldehyde formation, and acetalization, pH-responsive acetal bonds are constructed, resulting in MSNs with surface-modified acetal bonds. In the rhizosphere of weeds and the slightly acidic environment of the soil, the acetal bonds undergo specific hydrolytic cleavage, achieving precise drug release and thus improving the sustained-release effect.

[0057] Combining Examples 1 and 11 with Table 1, it can be seen that the slow-release effect of the nano herbicide prepared in Example 11 is reduced compared to Example 1. This indicates that AKD imparts hydrophobic properties to the membrane layer, enhances its resistance to rainwater erosion, and thus improves the slow-release effect.

[0058] Combining Example 1 and Comparative Example 1 with Table 1, it can be seen that the slow-release effect of the nano herbicide prepared in Comparative Example 1 is reduced compared to Example 1. This indicates that cellulose, as a film-forming substrate, combined with PVA to improve the dispersibility and film adhesion strength of the system, and the introduction of AKD to impart hydrophobic properties to the film layer, can form a uniform and stable coating system after compounding. After spraying, a continuous and dense protective film can be formed on the surface of the drug-loaded mesoporous silica, reducing the risk of rapid dissolution and leakage of the formulation when exposed to water. At the same time, relying on PVA to enhance the adhesion and structural integrity of the film layer, the nano herbicide's resistance to rain erosion and storage stability are effectively improved.

[0059] As can be seen from Example 1 and Comparative Example 2, and Table 1, compared with Example 1, the non-slow-release pesticide in Comparative Example 2 showed a plant control efficacy of only 34.57% after 120 days of administration, indicating that the nano-herbicide prepared in this application has excellent slow-release effect and good prospects for promotion and application.

[0060] 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 nano-herbicide using mesoporous silica as a carrier, characterized in that, Includes the following steps: The template agent is dissolved in water, and a silicon source and catalyst are added dropwise. After stirring, a suspension is obtained. The suspension is centrifuged, washed, and the template agent is removed to obtain MSNs. MSNs were dispersed in toluene, APTES was added, and the mixture was refluxed at 60-80℃ for 12-24 h under nitrogen protection. After centrifugation, washing, and drying, MSNs-NH2 was obtained. MSNs-NH2 was dispersed in ethanol, glutaraldehyde was added, and the mixture was stirred at 23-27℃ for 4-6 h. After centrifugation, washing, and drying, MSNs-CHO was obtained. MSNs-CHO was dispersed in ethanol, ethylene glycol and p-toluenesulfonic acid were added, and the mixture was stirred at 35-40℃ for 12-24 h. After centrifugation, washing, and drying, acetal-grafted MSNs were obtained. The mass ratio of MSNs, APTES, glutaraldehyde, ethylene glycol, and p-toluenesulfonic acid was 1-1.2:0.2-0.3:0.5:0.3:0.01-0.

02. The acetal-grafted MSNs were dispersed in an organic solvent, and pendimethalin technical was added. The mixture was stirred for 4-6 hours, filtered, washed, coated with a coating solution, and vacuum dried to obtain a nano-herbicide with mesoporous silica as the carrier. The preparation method of the coating solution includes the following steps: Cellulose is added to a buffer solution and sonicated to obtain a cellulose solution. PVA is added to water and heated to 70-80℃ and stirred to obtain a PVA solution. The PVA solution and AKD are added to the cellulose solution to obtain a coating solution. The mass ratio of cellulose, buffer solution, PVA and AKD is 1:40-60:0.3-0.5:0.2-0.

3.

2. The method for preparing a nano-herbicide using mesoporous silica as a carrier according to claim 1, characterized in that, The raw materials used in the nano herbicide with mesoporous silica as a carrier are as follows by weight: 1-3 parts silicon source, 0.2-0.5 parts template agent, 0.1-0.4 parts pendimethalin technical grade, 100-120 parts deionized water, 5-10 parts organic solvent, and 1.4-1.8 parts catalyst.

3. The method for preparing a nano-herbicide using mesoporous silica as a carrier according to claim 1, characterized in that, The mass ratio of the silicon source, pendimethalin technical material, and organic solvent is 1:0.1-0.3:5-8.

4. The method for preparing a nano-herbicide using mesoporous silica as a carrier according to claim 1, characterized in that, The mass ratio of the silicon source, template agent, and catalyst is 1:0.3-0.4:1.5-1.

8.

5. The method for preparing a nano-herbicide using mesoporous silica as a carrier according to claim 1, characterized in that, The silicon source is selected from one or both of tetraethyl orthosilicate and tetramethyl orthosilicate; the template agent is selected from one or more of hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride and dodecyltrimethylammonium bromide.

6. The method for preparing a nano-herbicide using mesoporous silica as a carrier according to claim 1, characterized in that, The catalyst is selected from one or more of concentrated ammonia, sodium hydroxide, and triethylamine.

7. The method for preparing a nano-herbicide using mesoporous silica as a carrier according to claim 1, characterized in that, The organic solvent is selected from one or more of methanol, acetone and ethyl acetate.

8. A nano-herbicide using mesoporous silica as a carrier, characterized in that, It is prepared by any one of the preparation methods described in claims 1-7.

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