Preparation method of asymmetric wettability nano-carrier and pesticide delivery application of asymmetric wettability nano-carrier

Abstract

The invention belongs to the technical field of pesticides, and particularly relates to a preparation method of an asymmetric wettability nano-carrier and pesticide delivery application of the asymmetric wettability nano-carrier. In order to improve the deposition efficiency of the mesoporous silicon nano-carrier on the leaf surface of a plant, the invention constructs a Janus mesoporous silicon dioxide nano-carrier (AWJ-MSN) which is obtained by modifying a hydrophilic monomer and a hydrophobic monomer and has asymmetric wettability, and the Janus mesoporous silicon dioxide nano-carrier (AWJ-MSN) is used for loading a hydrophobic pesticide; the obtained AWJ-MSN can obtain improved wettability and leaf surface deposition capability on plant leaves with different wettability; compared with a free hydrophobic pesticide, a delivery system formed after the asymmetric wettability nano-carrier is loaded with the pesticide can enhance leaf surface deposition and provide continuous release of active ingredients, so that the utilization rate of the pesticide is increased, and the environmental risk is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of pesticides, and in particular to a preparation method of an asymmetric wettability nanocarrier and its pesticide delivery application. Background Art

[0002] Pesticides are widely used to control pests, weeds and plant diseases, and play an irreplaceable role in biological disaster control and food production improvement. However, due to the non-wetting characteristics of most plant leaves, pesticide droplets are prone to off-target behaviors such as bouncing, splashing, dripping, and drifting during leaf application, resulting in low final utilization of pesticides. According to statistics, the pesticide utilization rate of China's three major grain crops (rice, corn and wheat) is only 41%, and only 0.1% of the effective ingredients finally reach the biological target site, causing most pesticides to enter the soil and streams, causing serious ecological pollution and human health hazards. At the same time, most pesticide molecules are hydrophobic, and a large amount of organic reagents need to be introduced for dissolution during use, which will inevitably further aggravate the degree of environmental pollution and the health risks to humans. Therefore, how to use environmentally friendly strategies to improve the leaf deposition ability of pesticides has become a very urgent task in the agricultural field.

[0003] Current research mainly uses two strategies to improve the leaf surface deposition ability of pesticide droplets: the first strategy is to add surfactants to the pesticide droplets, relying on them to form intramolecular or intermolecular self-assembled aggregates in the solution, and then regulate the solid-liquid interface interaction. The rapid reduction of surface tension promotes the wetting and spreading of the droplets, and also suppresses splashing and rebounding. Another strategy is to add flexible polymers with good rheological properties to the pesticide droplets, effectively dissipate the system energy through the stretching of the polymer chain, so as to delay the retraction behavior of the droplets after hitting the leaf surface, and then suppress the splashing and rebound of the droplets. The above methods all achieve the deposition of droplets by directly adding some additives to the droplets, which is a simple and effective strategy to improve the deposition of pesticide droplets on the crop surface. Although polymers can enhance the leaf surface deposition ability of pesticides by regulating the viscosity characteristics of pesticides, non-amphiphilic macromolecular polymers have a weak regulatory effect on the air-liquid interface tension, and therefore cannot completely suppress the bouncing behavior of pesticide droplets. Summary of the invention

[0004] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a method for preparing an asymmetric wettability nanocarrier and its pesticide delivery application. The asymmetric wettability nanocarrier can improve the wetting performance of leaf surfaces. It is used to load pesticides and can effectively deliver pesticide molecules, thereby achieving good leaf wetting performance and drug sustained-release performance, thereby improving the utilization rate of pesticides and promoting the environmental protection of the agricultural formulation industry.

[0005] In order to solve one of the above technical problems, one of the purposes of the present invention is to provide a method for preparing an asymmetric wettability nanocarrier, the method comprising the following steps:

[0006] S1, synthesis of mesoporous silica nanoparticles;

[0007] S2, dispersing mesoporous silica particles in water containing a surfactant, using paraffin as the oil phase, and preparing a paraffin-in-water Pickering emulsion by homogenization to obtain a mesoporous silica-solid wax droplet half of which is wrapped by the paraffin;

[0008] S3, dispersing the solid wax droplets in methanol, adding a silane coupling agent, reacting and dissolving the paraffin, and obtaining mesoporous silica nanoparticles half of which are connected with amino groups;

[0009] S4. Dispersing half of the mesoporous silica nanoparticles connected with amino groups in toluene, adding n-octyltrichlorosilane, and obtaining asymmetric wettability Janus mesoporous silica nanoparticles. The asymmetric wettability Janus mesoporous silica nanoparticles are asymmetric wettability nanocarriers.

[0010] The technical principles of the above technical solution are as follows:

[0011] The asymmetric wettability nanocarrier of the present invention can be used as a carrier to load drug molecules such as pesticides. As a delivery system for pesticides, the nanocarrier can significantly expand the target contact area by virtue of its small size, high specific surface area and other characteristics. At the same time, after surface chemical modification, it can further improve the leaf surface adhesion, thereby enhancing its deposition ability on the target leaf surface. At the same time, the nano-formulation of the preparation can also reduce the dependence on organic solvents by virtue of good dispersibility, which is an effective strategy to improve the biocompatibility and environmental friendliness of pesticides. Compared with the molecular-scale pesticide active ingredients, the interfacial interaction between the nano-scale carrier material and the target leaf surface is easier to regulate, so it can be used to improve the target retention ability of the pesticide active ingredients. Amphiphilic Janus nanoparticles are a type of nanomaterial with opposite wetting properties in space. They are generally anisotropic structural materials with nanometer or micrometer sizes. They are mainly formed by chemical modification or other interactions and orderly assembly. Its special structure makes it amphiphilic and interfacial solubilizing. Compared with traditional homogeneous nanoparticles, Janus nanoparticles are more flexible in functional regulation and have some special properties, such as special self-assembly behavior, adsorption at the interface, and the ability to simultaneously deliver drug molecules with different hydrophilicity.

[0012] Preferably, S1 is: dissolving the template in an ethanol aqueous solution at a stirring speed of 150-200 rpm, heating to 70-90°C, then adding 3.20-3.50 mL of ammonia water, the concentration of which is 25%, adding tetraethyl silicate dropwise after the solution is clarified, adjusting the speed to 200-250 rpm to react for 22-24 hours, collecting the product by centrifugation and washing the precipitate with deionized water and ethanol to remove residual reactants, drying the centrifuged product and calcining it in a muffle furnace at 550°C for 6-8 hours to remove the template, and obtaining mesoporous silica nanoparticles; the concentration of the ethanol aqueous solution of the template is 2.2-2.5 mg / mL; the volume ratio of tetraethyl silicate to the ethanol aqueous solution is (6.7-8):1000;

[0013] The S2 is as follows: adding mesoporous silica nanoparticles to an aqueous solution containing a cationic surfactant, and then heating it to 70-80°C; then adding paraffin wax to the mixed solution, keeping it at 70-80°C for 0.5-1h, and stirring it with a low-speed magnetic force; vigorously stirring the obtained mixture in a homogenizer for 120-180s, and then quickly cooling it to room temperature with ice water to produce solid wax droplets containing mesoporous silica nanoparticles; then filtering the solid wax droplets, washing them with deionized water to remove mesoporous silica nanoparticles (MSN for short) with weak adhesion, and then drying the solid wax droplets in a vacuum drying oven at 25-40°C;

[0014] The step S3 comprises: adding a dried solid wax droplet to a methanol solution containing a hydrophilic monomer and maintaining the solution at room temperature for 12 to 14 hours, so that the side of the solid wax droplet that is not coated by the paraffin wax is connected with an amino group, and then dissolving the paraffin wax in the solid wax droplet with xylene or chloroform to obtain mesoporous silica nanoparticles with one side modified by an amino group, collecting the obtained nanoparticles by centrifugation, washing the precipitate with xylene or chloroform, and then washing with anhydrous ethanol, and then collecting the product by centrifugation;

[0015] The S4 is: dispersing mesoporous silica nanoparticles modified by a hydrophilic monomer in an organic solution of a hydrophobic monomer, incubating at room temperature and 120-180 rpm for 2-3 hours to form asymmetric wettability Janus mesoporous silica nanoparticles (abbreviated as AWJ-MSN), and finally collecting the product by centrifugation and washing the precipitate with ethanol.

[0016] Preferably, in S1, the template agent is hexadecyltrimethylammonium bromide or octadecyltrimethylammonium bromide, and the template agent solvent is 16.0-18.0 vt% ethanol aqueous solution.

[0017] Preferably, in S2, the cationic surfactant is dodecyltrimethylammonium bromide or hexadecyltrimethylammonium bromide; in S2, the stirring speed of the homogenizer is 15,000-18,000 rpm; the mass ratio of the mesoporous silica nanoparticles to the paraffin is 1:(5-7). The stirring speed of the homogenizer is 15,000-18,000 rpm, so that the mesoporous silica is evenly distributed in the system to form a relatively stable emulsion. The mass ratio of the mesoporous silica nanoparticles to the paraffin is 1:(5-7) to ensure the formation of a relatively uniform emulsion so that the paraffin fully wraps the mesoporous silica nanoparticles.

[0018] Preferably, in S3, the hydrophilic monomer is a silane coupling agent N-aminoethyl-γ-aminopropyltrimethoxysilane (abbreviated as KH-792) or 3-aminopropyltriethoxysilane (abbreviated as APTES); the temperature for dissolving the solid wax droplets is 32-40°C; the volume ratio of the silane coupling agent to methanol is (0.13-0.14):1, and the reaction is stirred for 12-14 hours. The silane coupling agent is KH-792, which grafts amino groups on the surface of mesoporous silica nanoparticles not wrapped by paraffin. The silane coupling agent and methanol are in the range of a volume ratio of (0.13-0.14):1, which can effectively control the degree of hydroxylation in the reaction.

[0019] Preferably, in S4, the hydrophobic monomer is n-octyltrichlorosilane or octadecyltrichlorosilane.

[0020] In order to solve one of the above technical problems, the second purpose of the present invention is to provide an application of an asymmetric wettability nanocarrier for pesticide delivery. After preparing asymmetric Janus mesoporous silica nanoparticles according to the above steps S1-S4, the asymmetric wettability Janus mesoporous silica nanoparticles are used as carriers to load the pesticide raw material to obtain a nanopesticide with an asymmetric wettability nanocarrier delivery system.

[0021] The present invention modifies hydrophilic groups and hydrophobic groups onto mesoporous silica nanoparticles to construct a mesoporous silica nanocarrier with asymmetric wetting properties (abbreviated as AWJ-MSN), and then the pesticide can be loaded by a solvent method to construct an asymmetric wettability Janus mesoporous silica nanopesticide (abbreviated as Thi@AWJ-MSN) with sustained release and wetting properties. The Janus mesoporous silica nanoparticles with an asymmetric wettability structure developed by the present invention can achieve good leaf wetting properties and drug sustained release properties, reduce bouncing and splashing on the plant leaf surface, so as to increase the deposition of pesticide droplets on the plant leaf surface, thereby improving the utilization rate of pesticides. Promote the environmental protection of the agricultural formulation industry. The present invention constructs an asymmetric wettability Janus mesoporous silica nanopesticide system modified by silane coupling agent KH-792 and n-octyltrichlorosilane, which provides a basis for developing a method for improving the leaf wetting properties of nanopesticides.

[0022] Preferably, the method of using asymmetric wettability Janus mesoporous silica nanoparticles as carriers to load the pesticide technical refers to: dispersing asymmetric wettability Janus mesoporous silica in an organic solvent containing the pesticide technical, stirring, separating and drying to obtain asymmetric wettability Janus mesoporous silica nanopesticide.

[0023] Preferably, the pesticide molecule is thiofuran or fluopyram or emamectin benzoate or avermectin; the drug loading of the asymmetric wettability Janus mesoporous silica nanopesticide is 33-45%; the organic solvent is anhydrous ethanol; the stirring is shaking in a 25°C water bath for 24 hours; and the separation is centrifugal separation at 12000rpm for 20 minutes.

[0024] Preferably, the asymmetric wettability Janus mesoporous silica nanopesticide is made into a powder, a suspension, an emulsifiable concentrate, an aqueous emulsion, a granule, a microcapsule, a sustained-release agent or a nanoparticle preparation for pest control.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention provides a method for preparing an asymmetric wettability nanocarrier and its pesticide delivery application. The asymmetric nanocarrier of the present invention is an asymmetric wettability Janus mesoporous silica nanoparticle, which can be used as a carrier to load drug molecules such as pesticides. As a pesticide delivery system, the nanocarrier can significantly expand the target contact area by virtue of its small size, high specific surface area and other characteristics, and can further improve the leaf surface adhesion after surface chemical modification, thereby enhancing its deposition ability on the target leaf surface. At the same time, the nano-size of the preparation can also reduce the dependence on organic solvents by virtue of good dispersibility, which is an effective strategy to improve the biocompatibility and environmental friendliness of pesticides. Compared with the molecular-scale pesticide active ingredients, the interface between the nano-scale carrier material and the target leaf surface is easier to control, so it can be used to improve the target retention ability of the pesticide active ingredients. Amphiphilic Janus nanoparticles are a type of nanomaterial with opposite wetting properties in space. They are generally anisotropic structural materials with nanometer or micrometer sizes. They are mainly formed by orderly assembly through chemical modification or other interactions. This special structure makes them amphiphilic and interfacially solubilizing. Compared with traditional homogeneous nanoparticles, Janus nanoparticles are more flexible in functional regulation and have some special properties, such as special self-assembly behavior, adsorption on the interface, and the ability to simultaneously deliver drug molecules with different hydrophilicity and hydrophobicity.

[0027] The present invention modifies hydrophilic groups and hydrophobic groups onto mesoporous silica nanoparticles to construct a mesoporous silica nanocarrier (AWJ-MSN) with asymmetric wetting properties, and then the pesticide can be loaded by a solvent method to construct an asymmetric wettability Janus mesoporous silica nanopesticide (Thi@AWJ-MSN) with sustained release and wetting properties. The Janus mesoporous silica nanoparticles (AWJ-MSN) with an asymmetric wettability structure developed by the present invention can achieve good leaf wetting properties and drug sustained release properties, can reduce bouncing and splashing on the plant leaf surface, so as to increase the deposition of pesticide droplets on the plant leaf surface, thereby improving the utilization rate of pesticides. Promote the environmental protection of the agricultural formulation industry. The present invention constructs an asymmetric wettability Janus mesoporous silica nanopesticide system modified by silane coupling agent KH-792 and n-octyltrichlorosilane, which provides a basis for developing a method for improving the leaf wetting properties of nanopesticides.

[0028] The present invention can prepare a Janus mesoporous silica nanocarrier (AWJ-MSN) with asymmetric wettability by adjusting the ratio of hydrophilic and hydrophobic monomers, and further encapsulate pesticide molecules therein to form nanopesticides with good wettability and sustained release properties. The modified asymmetric wettability nanocarrier (AWJ-MSN) prepared by the present invention can also be used in the field of non-pesticide technology to increase the page wettability of non-pesticide preparations. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the preparation of the asymmetric wettability Janus mesoporous silica nanopesticide (Thi@AWJ-MSN) of the present invention.

[0030] Figure 2 SEM images of asymmetric wettability Janus mesoporous silica nanocarrier (a) and asymmetric wettability Janus mesoporous silica nanopesticide (b).

[0031] Figure 3 TEM images of asymmetric wettability Janus mesoporous silica nanocarrier (a) and asymmetric wettability Janus mesoporous silica nanopesticide (b).

[0032] Figure 4 Particle size (a) and potential (b) diagram of asymmetric wettability Janus mesoporous silica nanocarriers.

[0033] Figure 5 Infrared spectra of asymmetric wettability Janus mesoporous silica nanocarrier (a) and asymmetric wettability Janus mesoporous silica nanopesticide (b); TG (e) and DTG (f) graphs of asymmetric wettability Janus mesoporous silica nanocarrier and asymmetric wettability Janus mesoporous silica nanopesticide.

[0034] Figure 6 BET (a) diagram and pore size distribution (b) and (c) diagrams of asymmetric wettability Janus mesoporous silica.

[0035] Figure 7 (a) The contact angles of asymmetric wettability Janus mesoporous silica nanocarriers at different concentrations on cucumber leaves; (b) The retention amount of 1.0 mg / mL asymmetric wettability Janus mesoporous silica nanocarriers on cucumber leaves; (c) The contact angles of 1.0 mg / mL asymmetric wettability Janus mesoporous silica nanocarriers on Shanghai green, cucumber and peanut leaves; (d) The contact angle of 1.0 mg / mL asymmetric wettability Janus mesoporous silica nanopesticide on cucumber leaves.

[0036] Figure 8 The dynamic contact angles of 1.0 mg / mL asymmetric wettability Janus mesoporous silica nanocarrier on cucumber leaf surface (a) and PTFE membrane (b); the dynamic contact angle of 1.0 mg / mL asymmetric wettability Janus mesoporous silica nanopesticide on PTFE membrane.

[0037] Fig. 9(a) Schematic diagram of the parameters for normalizing Ht / D0 and Dt / D0 values; (b) Ht / D0 of a 1.0 mg / mL nanocarrier droplet bouncing when it hits the PTFE membrane surface. t / D0 height value normalization processing parameter diagram and (c)D t / D0 diameter value time relationship normalized processing parameter diagram.

[0038] Fig.10 The images capture the dynamics of water and 1.0 mg / mL MSN, Am-MSN, and AWJ-MSN aqueous suspensions bouncing on the surface of cucumber leaves; the scale bar represents 3 μm.

[0039] Fig.11 (a) The cumulative sustained-release curves of Thi@MSN, Thi@Am-MSN, and Thi@AWJ-MSN, as well as the fitting results under (b) zero-order, (c) first-order, (d) Korsmeyer-Peppas, (e) Higuchi, and (f) Hixson-Crowell models.

[0040] Among them (repeated ones are not repeated):

[0041] Figure 1 In the figure, Paraffin is paraffin; MSN is mesoporous silica nanoparticles; Thi is the hydrophobic pesticide thiothiocarb.

[0042] Figure 2 In the figure, AWJ-MSN is an asymmetric wettability Janus mesoporous silica nanocarrier; Am-MSN is an amino-functionalized mesoporous silica nanoparticle; AWJ-MSN1, AWJ-MSN2, and AWJ-MSN3 are asymmetric wettability Janus mesoporous silica nanocarriers formed by dispersing unilaterally aminated MSN in 0.05vt%, 0.10vt%, and 0.20vt% toluene solutions of the hydrophobic monomer n-octyltrichlorosilane, respectively.

[0043] Figure 3 In the figure, Thi@Am-MSN refers to amino-functionalized mesoporous silica nanoparticles loaded with pesticides; Thi@MSN refers to mesoporous silica nanoparticles loaded with pesticides; Thi@AWJ-MSN is the asymmetric wettability Janus mesoporous silica nanopesticide of the present invention; Thi@AWJ-MSN1, Thi@AWJ-MSN2, and Thi@AWJ-MSN3 refer to nanopesticides obtained by loading pesticides with AWJ-MSN1, AWJ-MSN2, and AWJ-MSN3 as carriers, respectively.

[0044] Figure 4In the figure, Partical Size (nm) is the particle size; PDI value is the aggregation index; Zeta Potential (mv) is the surface zeta potential; Without Thi means no pesticide is loaded; With Thi means pesticide is loaded.

[0045] Figure 5 Medium, Wavenumber(cm -1 ) is Raman shift, unit is wave number; Temperature (℃) is temperature, unit is Celsius; Weiht (%) is weight percentage; Derivative weight (% / ℃) is derivative weight.

[0046] Figure 6 In the table, Relative Pressure (P / P0) is the relative pressure; absorbed volume (cm 3 g -1 STP) is the absorption volume; Pore diameter (nm) is the pore diameter; Diffierential volume (cm 3 g -1 ) is the difference volume.

[0047] Figure 7 In the figure, Brassica chinensis L. is the leaf surface of Shanghai green; Cucumis sativus L. is the leaf surface of cucumber; Arachis hypogaea L. is the leaf surface of peanut; water is water; Contact Angle (°) is the contact angle.

[0048] Figure 8 In the above table, Time is the time.

[0049] Fig. 9 Medium, Normalized spreading height:H t / D0 is the normalized spreading height; Normalized spreading diameter: D t / D0 is the normalized spreading diameter.

[0050] Fig.11In the table, Cumulative release is the cumulative release rate; Zero-order model is the zero-order model; First-order model is the first-order model; Korsmeyer-peppas model is the Korsmeyer-peppas model; Higuchi model is the Higuchi model; Hison-Crowell model is the Hison-Crowell model. DETAILED DESCRIPTION

[0051] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0052] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0053] Preparation method of an asymmetric wettability nanocarrier and its application in pesticide delivery

[0054] 1. Materials and methods

[0055] 1.1 Test Materials

[0056] Tetraethyl silicate (TEOS, 98%), hexadecyltrimethylammonium bromide (CTAB, 99%), N-aminoethyl-γ-aminopropyltrimethoxysilane (KH-792, 95%), and dodecyltrimethylammonium bromide (99%) were from Aladdin Biochemical Technology Co., Ltd., N-octyltrichlorosilane (97%) and paraffin sections were from MacLean Biochemical Technology Co., Ltd., and xylene, anhydrous ethanol, and ammonia (25%) were from Tianjin Damao Chemical Reagent Factory. Methanol was obtained from Tianjin Best Chemical Co., Ltd. Thiofuramide (Thi, 97%) was purchased from Shenzhen Nopoxin Pesticide Co., Ltd. Toluene was obtained from Guangzhou Chemical Reagent Factory. Deionized water was prepared in the laboratory using a reverse osmosis system.

[0057] 1.2 Test methods

[0058] 1.2.1 Preparation of asymmetric wettability Janus mesoporous silica nanocarriers (AWJ-MSNs)

[0059] Combination Figure 1As shown, at 70°C, hexadecyltrimethylammonium bromide (CTAB, 0.45 g) was dissolved in 180 mL of ethanol aqueous solution (16.7 vt%). Subsequently, 3.40 mL of ammonia and 1.50 mL of tetraethyl silicate (TEOS) were added, and the mixture was stirred continuously for 24 h. The reaction product was collected by centrifugation, and the precipitate was washed 3 times with deionized water to remove any residual reactants. In order to remove the template, the dried centrifuged product was calcined in a muffle furnace at 550°C for 6 h.

[0060] 2.0 g of MSN was dispersed in 80 mL of an aqueous solution containing dodecyltrimethylammonium bromide (60 mg / L) and heated to 75 °C. Subsequently, 10 g of paraffin was added to the mixture and stirred at a low speed for 30 min using a magnetic stirrer. The solution was then homogenized at high speed for 120 s to form a Pickering emulsion. After cooling to room temperature, solid wax droplets containing MSN nanoparticles were formed. The solid wax droplets were collected by filtration, washed with deionized water, and dried in a vacuum chamber at 25 °C.

[0061] To obtain unilaterally hydrophilic modified MSNs, 2.0 g of dried solid wax was added to a 20 mL methanol solution containing 12 vt% of the hydrophilic monomer N-[3-(trimethoxysilyl)propyl]ethylenediamine (KH-792). The mixture was stirred at a low speed for 12 h using magnetic stirring. Then, the paraffin in the solid wax droplets was dissolved in xylene at 32 ° C to obtain unilaterally aminated MSNs. The resulting nanoparticles were collected by centrifugation (5000 rpm, 20 min), washed three times with xylene, and washed twice with anhydrous ethanol. Finally, the unilaterally aminated MSNs were vacuum dried for subsequent experiments.

[0062] For the hydrophobic modification of the other side of the unilaterally aminated MSN, 0.3 g of the unilaterally aminated MSN was dispersed in 80 mL of a toluene solution containing 0.05 vt%, 0.10 vt% or 0.20 vt% of the hydrophobic monomer n-octyltrichlorosilane and incubated at a low speed for 2 h to form asymmetric wettability Janus nanocarriers (AWJ-MSN for short). These nanocarriers were named AWJ-MSN1, AWJ-MSN2 and AWJ-MSN3.

[0063] For comparison, 2.0 g of MSN was added to 20 mL of methanol solution containing 24 vt% KH-792 and stirred for 12 h. The resulting nanoparticles were collected by centrifugation (5000 rpm, 20 min), washed twice with anhydrous ethanol, and then vacuum dried for subsequent experiments. The final product was amino-functionalized MSN (Am-MSN).

[0064] 1.2.2. Preparation of asymmetric wetting Janus mesoporous silica nanopesticide (Thi@AWJ-MSN).

[0065] Combination Figure 1 As shown in the figure, 0.5 g of thiofuran (Thi) was dissolved in 50 mL of anhydrous ethanol to prepare a 10 mg / mL pesticide stock solution. Then, 0.2 g of the nanocarrier AWJ-MSN was added to the solution, and after shaking at 25 °C for 24 h, the mixture was centrifuged (12 000 rpm, 20 min) and vacuum dried to obtain Thi@AWJ-MSN.

[0066] For the control groups CK1 and CK2, MSN and Am-MSN were used as nanocarriers instead of AWJ-MSN, while maintaining the same preparation procedure to construct the other two nanopesticides (Thi@MSN and Thi@Am-MSN). Table 1 provides the detailed preparation parameters of all nanopesticides.

[0067] Table 1 Preparation parameters of nanopesticide sustained-release system

[0068]

[0069] 1.3. Drug loading rate and encapsulation efficiency test

[0070] The absorbance of the diluted supernatant was measured at 230 nm using an ultraviolet spectrophotometer. According to the standard curve equation of absorbance (A) and concentration (C) of Thi, A = 0.0295C + 0.0805 (R 2 =0.999), and the concentration of Thi in the supernatant was calculated. Then, the encapsulation efficiency (EE) and loading capacity (LC) of Thi were determined using formulas (1) and (2).

[0071]

[0072] Where m totalThi is the total mass of Thi (mg) in the system, m freeThi is the mass of free Thi (mg) in the system, m Thi@carrier is the mass of the nanopesticide delivery system (mg).

[0073] 1.4 Characterization

[0074] The microstructure of the samples was observed using a scanning electron microscope (SEM) (Hitachi S4800, Japan) and a transmission electron microscope (TEM) (JEOL JEM-F200, Japan). Chemical element analysis was performed on the TEM using an energy dispersive spectrometer (EDS). Thermogravimetric analysis (TGA) and derivative thermogravimetric (DTG) analysis were performed using a TGA2 thermogravimetric analyzer (Mettler-Toledo, Switzerland). The Fourier transform infrared (FTIR) spectrum of the samples was measured using a Spectrum 100 (USA) analyzer at 4000-400 cm -1Each sample was scanned 32 times within the range of 100 μm. The average particle size distribution and zeta potential of the samples were measured using dynamic light scattering (DLS) and 90Plus PALS particle size and zeta potential analyzers (Bruker Corporation, USA). The nitrogen adsorption-desorption isotherms and pore size distribution curves of the samples were determined using an automatic specific surface area and porosity analyzer. The Brunauer-Emmett-Teller (BET) method was used to calculate the pore structure parameters such as specific surface area, pore volume, and pore size distribution in the relative pressure range of P / P0=0 to 1.

[0075] 1.5. Wettability and leaf deposition behavior

[0076] To test the wettability of nanocarriers and nanopesticide sustained-release systems, samples were dispersed in deionized water to prepare aqueous solutions of specific concentrations. A 5 μL sample droplet was placed on a cucumber leaf using a microsampler, and the wettability of the droplet on the leaf surface and PTFE membrane surface was analyzed by measuring the static / dynamic contact angle using a Theta instrument.

[0077] To evaluate the liquid holding capacity (LHC) of the samples on cucumber leaves, indoor-grown cucumber leaves were cut into 2 × 2 cm slices. The cut leaves were weighed and immersed in the prepared water suspensions of MSN, Am-MSN, AWJ-MSN1, AWJ-MSN2, AWJ-MSN3, Thi@MSN, Thi@Am-MSN, Thi@AWJ-MSN1, Thi@AWJ-MSN2, and Thi@AWJ-MSN3 for 5 s, then lifted vertically with tweezers and weighed after dripping off the excess liquid. Each sample was tested three times, and the LHC per unit area (mg / cm 2 ).

[0078]

[0079] Where m before and m after represents the weight of the leaves before and after soaking (mg), S represents the surface area of ​​the leaves (cm 2 ).

[0080] 1.6 Leaf impact test

[0081] The microinjector was mounted on a custom-made fixed-height stand, and a polytetrafluoroethylene (PTFE) membrane or cucumber leaf was attached to a glass slide. The volume of the pesticide droplet was about 10 μL, and the initial diameter was about 2.6 mm. A high-speed camera (Photron, VEO-410L) was used to record the entire process of the droplet impacting the leaf surface at a speed of 5200 frames per second. The droplet velocity before impact was about 2.42 m / s. The detailed parameters of the droplet impact were analyzed using Image J software.

[0082] 1.7. Sustained release test

[0083] Prepare sample solutions of Thi@MSN, Thi@Am-MSN, Thi@AWJ-MSN1, Thi@AWJ-MSN2 and Thi@AWJ-MSN3, each containing 10 mg / mL of Thi. Take 5 mL of sample solution and put it into a dialysis bag (MWCO = 5000 Da). Then put the dialysis bag into a brown conical flask containing 45 mL of release medium (40% ethanol solution) and incubate it in a shaker at 25°C. At specific time intervals, take 1 mL of sample from the release medium for analysis using HPLC.

[0084] The Thi concentration and cumulative release rate (R) at each time point were calculated using formulas (4) and (5). i ).

[0085]

[0086] where c i It represents the concentration of Thi in the release medium at a specific time (mg / L), m Thi Represents the total mass (mg) of Thi added to the dialysis bag.

[0087] 2. Results and Analysis

[0088] 2.1 Preparation and characterization

[0089] Figure 1 The preparation process of asymmetric wettability Janus mesoporous silica nanodrugs (Thi@AWJ-MSN). First, porous spherical mesoporous silica nanoparticles (MSNs) were synthesized by a soft template method. Subsequently, the MSN nanoparticles were interface modified, with half of them blocked with paraffin wax and the other half aminated with KH-792 to obtain half-amino-functionalized MSNs. Finally, the paraffin wax was dissolved and an alkyl chain was attached to the other half of the MSNs to obtain asymmetric wettability Janus mesoporous silica nanoparticles (AWJ-MSNs) with hydrophilic and hydrophobic properties. Subsequently, the hydrophobic pesticide Thi was encapsulated into the AWJ-MSNs through hydrophobic interactions to form Thi@AWJ-MSNs.

[0090] Figure 2(a) shows the nanoscale structures of MSNs, Am-MSNs, AWJ-MSN1, AWJ-MSN2, and AWJ-MSN3 observed by SEM. The images show that all samples have clear boundaries, good dispersion, and no obvious aggregation. MSNs show a uniform spherical structure, a smooth surface, and consistent particle size. In contrast, the surface of Am-MSNs is rougher, which is due to the introduction of amino chains, which increases the surface roughness. It is worth noting that the surface roughness of the particles is further enhanced when alkyl chains are introduced. Therefore, the surfaces of AWJ-MSN1, AWJ-MSN2, and AWJ-MSN3 are also significantly rough. In addition, the roughness increases accordingly with the increase in the content of hydrophobic monomers. This enhanced surface roughness significantly improves the interaction between nanoparticles and the micro / nanostructures of plant leaves, which is crucial for enhancing the leaf surface deposition of nanopesticide delivery systems. Figure 2 (b) SEM images of the nanoscale structures of various nanopesticide delivery systems after encapsulation of Thi onto nanocarriers are presented. No significant changes were observed compared to the corresponding carriers, indicating that the pesticide molecules mainly entered the internal structure of the nanocarriers, which is crucial for the protection of the pesticides. To further verify this, TEM images of Thi@MSN, Thi@Am-MSN, Thi@AWJ-MSN1, Thi@AWJ-MSN2, and Thi@AWJ-MSN3 were collected, as shown in Figure 2. Figure 3 As shown in Figure 2, the nanopesticide sustained-release system exhibits a uniform spherical structure with distinct boundaries and clear particles.

[0091] Figure 4 (a) Shown are the average particle size and PDI of MSN, Am-MSN, AWJ-MSN1, AWJ-MSN2 and AWJ-MSN3. The data show that the particle size of Am-MSN is larger than that of MSN due to the grafting of amino groups. In addition, the particle size of AWJ-MSN increases with the amount of hydrophobic monomer because the addition of hydrophobic alkyl chains increases the volume of the nanocarrier. The PDI equation for measuring the size distribution of nanoparticles reflects greater stability and uniformity with smaller values. The PDI values ​​of AWJ-MSN are all lower than 0.25, and the PDI value of AWJ-MSN2 is the smallest, which is 0.14±0.03, indicating that the dispersion in water is the most stable. At the same time, surface potential is also an important factor in the dispersion of nanoparticles. The Zeta potential of nanocarriers and nanopesticide sustained-release systems is shown in Figure 2. Figure 4 (b) As shown. Due to the presence of silanol groups, MSNs show negative charges, while Am-MSNs show positive charges after amination. The absolute value of the Zeta potential of AWJ-MSNs exceeds 40 mV, indicating that the strong positive charge enhances the repulsive force between nanoparticles in aqueous solution, thereby promoting stable dispersion.

[0092] The structures of MSNs, Am-MSNs and AWJ-MSNs were characterized by FTIR, TG and BET analysis. Figure 5 (a) shows the FTIR spectra of MSN, Am-MSN, AWJ-MSN1, AWJ-MSN2, and AWJ-MSN3. -1 The broad absorption band near 1078 cm -1 The broad absorption band at 800 cm -1 The absorption peak at 800 cm-1 corresponds to the stretching vibration of Si-O-Si. -1 The absorption peak at 1640 cm is stronger than that of MSN and Am-MSN, which is attributed to the presence of C-Cl bonds in AWJ-MSN. -1 The absorption peak at 1650 cm-1 corresponds to the OH bending vibration. -1 The absorption peak at 2930 cm in AWJ-MSN corresponds to the deformation of -NH2. The absorption peak intensity decreases from Am-MSN to AWJ-MSN1, AWJ-MSN2 and AWJ-MSN3, indicating that the -NH2 content in these samples decreases. -1 The absorption peak at is attributed to the antisymmetric contraction of -CH2. These results confirm that MSN, Am-MSN, AWJ-MSN1, AWJ-MSN2 and AWJ-MSN3 were successfully prepared. Figure 5 (b) shows the FTIR spectra of Thi@MSN, Thi@Am-MSN, Thi@AWJ-MSN1, Thi@AWJ-MSN2, and Thi@AWJ-MSN3, which clearly show the 560 cm -1 、1456cm -1 and 1664cm -1 The additional absorption peaks at 3 and 4 correspond to the stretching of C-Br bond, C=C in aromatic ring and conventional C=C bond, respectively. These chemical bonds are the characteristics of Thi, indicating that Thi has been successfully loaded onto the nanocarrier.

[0093] Figure 5 (c) to (f) show the TG and DTG graphs of MSN, Am-MSN, AWJ-MSN1, AWJ-MSN2, AWJ-MSN3, Thi@MSN, Thi@Am-MSN, Thi@AWJ-MSN1, Thi@AWJ-MSN2, and Thi@AWJ-MSN3 in the temperature range of 40 to 700 °C. Figure 5(c) and 5(d), all samples showed a weight loss peak between 40 and 100 °C, which can be attributed to the decomposition of a small amount of absorbed bound water. The weight loss in AWJ-MSN, AWJ-MSN1, AWJ-MSN2 and AWJ-MSN3 was also affected by the modified monomer KH-792. With the increase of the hydrophobic group content in AWJ-MSN, the weight loss rate in the range of 40 to 100 °C decreased, indicating that the proportion of hydrophilic groups in the samples decreased. The TG curve of Am-MSN showed an obvious weight loss peak near 406 °C, which was attributed to the thermal decomposition of KH-792 and MSN. AWJ-MSN1, AWJ-MSN2 and AWJ-MSN3 showed obvious weight loss peaks at 318 °C and 521 °C, which corresponded to the grafting of hydrophilic and hydrophobic groups. In the temperature range of 372 to 616 °C, the weight loss rates of AWJ-MSN1, AWJ-MSN2 and AWJ-MSN3 were similar. However, in the temperature range of 126-367°C, the weight loss rates of AWJ-MSN1, AWJ-MSN2, and AWJ-MSN3 were 13.9%, 10.5%, and 8.8%, respectively. As the number of hydrophobic groups increased, the weight loss rate in the range of 126-367°C decreased, indicating that the proportion of hydrophobic groups was high. These results confirm the successful preparation of MSN, Am-MSN, AWJ-MSN1, AWJ-MSN2, and AWJ-MSN3. Figure 5 Compared with the TG curve in (d), Figure 5 The TG curve in (f) exhibits an additional weight loss step, among which Thi@MSN exhibits a significant weight loss step around 293 °C, which is attributed to the loading of Thi. Since the decomposition temperatures of the hydrophobic group and Thi are similar, the decomposition peaks of the hydrophilic and hydrophobic groups in Thi@AWJ-MSN are shifted.

[0094] The specific surface area (SSA) and pore volume of MSN, Am-MSN, AWJ-MSN1, AWJ-MSN2 and AWJ-MSN3 were determined by the multipoint Brunauer-Emmett-Teller (BET) method, and the pore size distribution was evaluated by the density functional theory (DFT) method. The corresponding pore structure parameters are summarized in Tables 2 and Figure 6 .like Figure 6 As shown in (a), all samples show type IV isotherms with H1 hysteresis loops, indicating the presence of slit-like pores in the structure. From the data in the table, it can be seen that the specific surface area and pore volume of MSN, Am-MSN, AWJ-MSN1, AWJ-MSN2, and AWJ-MSN3 are all reduced, which can be attributed to the grafting of chemical groups. In addition, the specific surface area of ​​AWJ-MSN decreases with the increase of the number of hydrophobic segments. Figure 6(b) shows the pore size distribution of MSN and Am-MSN. Obviously, their pore size distribution is similar, and the pore size is less than 5nm, which belongs to the mesoporous structure. Compared with MSN, Figure 6 As shown in (c), AWJ-MSN1, AWJ-MSN2, and AWJ-MSN3 have larger pore sizes but still have a mesoporous structure. These results indicate that the SSA decreases with the increase of hydrophobic groups. However, despite the decrease in SSA due to the grafting of hydrophilic and hydrophobic groups, the mesoporous structure is still maintained. In addition, the LC and EE of the samples also increase with the increase in the number of hydrophobic groups (Table 2). This indicates that Thi is loaded inside and outside the carrier, and the pesticide loading capacity is affected by SSA, pore size, and surface roughness.

[0095] Table 2 Specific surface area, pore volume and pore size of nanocarriers

[0096]

[0097] 2.2 Analysis of wetting behavior and leaf deposition behavior

[0098] The wettability of nanopesticide delivery systems is crucial for effective leaf deposition during application, as good wettability facilitates efficient spreading on the target leaf surface, thereby minimizing pesticide loss during interfacial transfer. The contact angle of nanoparticles on the solid surface directly reflects their wetting and spreading ability at the target site, which is crucial to the effectiveness of the delivery system of nanopesticides in aqueous suspensions. To evaluate this, the static and dynamic contact angles of water suspension droplets of different concentrations were tested on the cucumber leaf surface. Figure 7 (a) shows the static contact angles of MSN, Am-MSN, AWJ-MSN1, AWJ-MSN2 and AWJ-MSN3 nanoparticle suspensions at different concentrations dropped on cucumber leaves. For AWJ-MSN1 and AWJ-MSN2, the contact angles first decrease and then increase in the concentration range of 0.1 to 2.0 mg / mL. Figure 7 (a) shows that the AWJ-MSN1 droplet has the smallest contact angle at a concentration of 0.5 mg / mL, while the AWJ-MSN2 droplet has the smallest contact angle at a concentration of 1.0 mg / mL. Figure 7 (b) shows the liquid holding capacity (LHC) of 1.0 mg / mL nanocarrier droplets on cucumber leaves. It is noteworthy that the LHC effect of AWJ-MSN2 aqueous suspension on cucumber was improved by nearly 85.59% compared with MSN.

[0099] It is worth noting that the wetting properties of leaves of different crops vary from hydrophilic to weakly hydrophobic and strongly hydrophobic. In addition to the hydrophobic cucumber leaves, the hydrophilic Shanghai green leaves and the strongly hydrophobic peanut leaves were also selected as test objects. The static contact angle of the nanoparticle suspension with a concentration of 1.0 mg / mL was measured on the leaf surfaces of Shanghai green, cucumber and peanut. Figure 7 (c). In all three types of leaves, AWJ-MSN2 droplets exhibited the best wettability. This indicates that nanocarriers with unique asymmetric wetting properties are able to enhance deposition on plant leaves with different wetting properties, indicating that improving leaf deposition capacity has a certain universality. The leaf surfaces of the three plants are characterized by many grooves and hairs due to their unique structures, which usually prevent droplets from adhering to the surface. Despite these challenges, AWJ-MSN2 still exhibited satisfactory leaf surface wettability. This finding suggests that the amphiphilic modification of the nanocarrier significantly enhances the wettability of MSN on the leaf surface, making it more effective on different types of plant leaves. Figure 7 (d) Static contact angle of droplets of nanopesticide delivery system on cucumber leaves. Thi@AWJ-MSN2 droplets show good wettability, indicating that Thi@AWJ-MSN2 has superior static wetting and spreading ability.

[0100] After the pesticide droplets come into contact with the plant leaves through spraying, they will enter a non-equilibrium state instead of reaching equilibrium instantly. Therefore, the temporal changes in the contact angle on the plant leaf surface should not be ignored. The dynamic contact angles of different concentrations of MSN, Am-MSN, AWJ-MSN1, AWJ-MSN2 and AWJ-MSN3 on the cucumber leaf surface were tested. Figure 8 (a) to (c). The data show that the contact angle of the water droplet is affected by the content of nanoparticles in the water suspension. The results show that at a concentration of 1.0 mg / mL, MSN, Am-MSN, AWJ-MSN1 and AWJ-MSN2 reach the minimum contact angle. We compared the dynamic contact angles of various nanocarriers with water on cucumber leaves within 360 s at a concentration of 1.0 mg / mL, as shown in Figure 2. Figure 8(a). Among them, AWJ-MSN2 has the smallest dynamic contact angle, which decreases from 74.2° to 62.2° within 360s, while at 360s, the contact angles of MSN and Am-MSN are 76.1° and 78.3°, respectively, indicating that the dynamic wettability of MSN nanocarriers can be significantly improved by modifying them with appropriate ratios of hydrophilic and hydrophobic monomers. Since most plant leaves in nature are non-wetting and hydrophobic, they easily cause pesticide droplets to deviate from the target, making pesticide spraying more challenging. In order to simulate various non-wetting hydrophobic leaves, an artificial PTFE membrane with a water contact angle of approximately 125° was used, which is instructive for analyzing the wetting and spreading behavior of similar surfaces. Therefore, the dynamic contact angles of 1.0 mg / mL MSN, Am-MSN, AWJ-MSN1, AWJ-MSN2, and AWJ-MSN3, as well as Thi@MSN, Thi@Am-MSN, Thi@AWJ-MSN1, Thi@AWJ-MSN2, and Thi@AWJ-MSN3 were measured on PTFE membranes, as shown in Figure 2 . Figure 8 (b) and (c) show that AWJ-MSN2 and Thi@AWJ-MSN2 exhibit the smallest dynamic contact angles, indicating that they have enhanced wettability on the hydrophobic PTFE membrane.

[0101] 2.3 Leaf impact analysis

[0102] In pesticide spraying, the effective deposition of droplets on the target leaf surface is achieved through a dynamic impact process. This process is affected by the microstructure and composition characteristics of the target leaf. Therefore, the contact angle of the nanopesticide delivery system alone cannot fully reflect its final effective utilization efficiency. It must be analyzed in conjunction with detailed dynamic impact behavior. The droplet impact dynamics of nanocarriers on cucumber and artificial PTFE membranes were further studied using the widely adopted quantitative analysis normalization method. The analysis includes the standardized spreading height (H t / D0) and the standardized spreading diameter (D t / D0), where H t Represents the rebound height, D t represents the contact spreading diameter, and D0 represents the initial droplet radius, such as Fig. 9 (a). The smaller H t / D0 value indicates that the ratio of droplet rebound height to initial droplet radius is low, which makes the droplet less likely to detach from the target surface. t The / D0 value indicates that the ratio of the droplet contact spreading diameter to the initial droplet radius is high, so it is easier to wet and spread.

[0103] Fig. 9 (b) shows the H when a 1.0 mg / mL nanocarrier droplet hits the PTFE membrane t / D0 time variation. AWJ-MSN shows consistent low H throughout the impact process t / D0, indicating that the droplet tends to spread along the liquid-solid interface after contacting the PTFE membrane instead of rebounding to the air-liquid interface, and AWJ-MSN2 exhibits the lowest H t / D0. Compared with water droplets, the maximum rebound height of AWJ-MSN2 droplets decreased by about 55.06%, while the droplet height decreased by about 44.93%. On the other hand, the MSN droplets failed to stabilize within 70ms because their silanol groups could not maintain the energy stability of the liquid-solid and gas-liquid interfaces in a short period of time. This instability often leads to splashing, hindering effective deposition on the blade surface in practical applications. Compared with hydrophilic MSN and Am-MSN droplets, AWJ-MSN1, AWJ-MSN2 and AWJ-MSN3 droplets have larger spreading diameters on the PTFE membrane, among which AWJ-MSN2 has the highest diameter normalization coefficient. This indicates that AWJ-MSN2 has superior leaf surface diffusion ability. Fig. 9 As shown in (c), at 3.99ms, D t AWJ-MSN1 and AWJ-MSN2, both of which have a D0 of about 4.30, reach their maximum diffusion area. t / D0 is approximately 72.73% higher than that of water and 33.33% higher than that of MSN, further demonstrating the effectiveness of AWJ-MSN2 in reducing rebound and enhancing diffusion.

[0104] The jumping behavior of MSN, Am-MSN, AWJ-MSN1, AWJ-MSN2, and AWJ-MSN3 droplets on cucumber leaves was recorded using a high-speed camera, as shown in Figure (10). Although the droplets will break to a certain extent after being released from a certain height and hitting the cucumber leaves, the AWJ-MSN2 droplets are able to coalesce into larger droplets within 20ms. This coalescence reduces the evaporation of smaller droplets, thereby increasing the possibility of droplet deposition on the leaves.

[0105] 2.4. Analysis of sustained-release behavior

[0106] Another strategy to improve the efficiency of pesticide use is to extend its shelf life. Encapsulating pesticides in mesoporous nanocarriers allows controlled release through limited mesoporous channels, thus preventing rapid release. The slow release of pesticide molecules extends the shelf life, ultimately improving the overall utilization efficiency of pesticides. Fig.11The cumulative release rates of Thi@MSN, Thi@Am-MSN, Thi@AWJ-MSN1, Thi@AWJ-MSN2, and Thi@AWJ-MSN3 during 196 h are shown. It is obvious that all nanopesticide release systems exhibited sustained release behavior, fully demonstrating that the nanocarriers designed in this study have the ability to extend the effective period of pesticides. It is worth noting that Thi@Am-MSN showed a rapid release trend in the first 48 h, which may be due to the fact that a small amount of Thi did not enter the mesoporous channels of the nanocarriers but was adsorbed on the outer surface. In contrast, the release of Thi@AWJ-MSN1, Thi@AWJ-MSN2, and Thi@AWJ-MSN3 was relatively slow in the first 48 h, which was due to the high encapsulation and loading efficiency of Thi in the nanocarriers, as shown in the data in Table 3. Satisfactorily, Thi@AWJ-MSN1, Thi@AWJ-MSN2, and Thi@AWJ-MSN3 maintained relatively stable sustained release behavior even after 48 h.

[0107] In order to further explore the release behavior of different samples in sustained-release media, five kinetic models (zero-order model, first-order model, Korsmeyer-Peppas model, Higuchi model and Hixson-Crowell model) were applied. The fitting results are shown in Fig.11 (b) to (f) and Table 3. The results show that the release behavior of Thi from nanoparticles has a high correlation coefficient (R 2 ). The first-order kinetic model explains the relationship between pesticide release and concentration over time, indicating that the release of Thi is proportional to its concentration in the nanocarrier. This relationship leads to a slower release rate in the later stages as the concentration of Thi decreases. In this model, k1 and k2 represent the maximum release amount and release rate of the pesticide, respectively. The results show that nanocarriers with a higher content of hydrophobic monomers are able to slow down the release rate of pesticide molecules. The Korsmeyer-Peppas and Higuchi models are considered to be the most appropriate kinetic models for evaluating the stability of pesticide loading systems because they not only describe the in vitro release of pesticides from the matrix system, but also explain the stability behavior. According to the Korsmeyer-Peppas model, when the k2 value is less than 0.5, the pesticide release behavior in the system conforms to quasi-Fickian diffusion, indicating that the pesticide diffusion occurs through non-swelling matrix diffusion.

[0108] Table 3 Fitting results of sustained release curves of Thi@MSN, Thi@Am-MSN, Thi@AWJ-MSN1, Thi@AWJ-MSN2 and Thi@AWJ-MSN3 within 196 h

[0109]

[0110] In summary, this work successfully prepared asymmetric wettability Janus mesoporous silica nanocarriers (AWJ-MSN) and asymmetric wettability Janus mesoporous silica nanopesticides (Thi@AWJ-MSN). During the modification process, the dispersion state of the nanocarrier can be adjusted by adjusting the volume ratio of hydrophilic monomers and hydrophobic monomers. The experimental results show that the encapsulation efficiency and loading capacity of AWJ-MSN are significantly improved compared with traditional mesoporous silica nanoparticles (MSN). The wettability of AWJ-MSN on plant leaves is also enhanced, and AWJ-MSN2 performs best. Specifically, AWJ-MSN2 has the lowest static contact angle on PTFE membranes and various leaf surfaces, and its dynamic contact angle on cucumber leaves decreases from 74.2° to 62.2° within 360s, indicating that it has excellent wetting and spreading ability. In addition, the droplet impact test shows that the H of AWJ-MSN2 on PTFE membranes is t / D0 is the lowest, D t / D0 was the highest, indicating that the diffusion capacity was improved and the rebound height was reduced, thereby improving the deposition efficiency of the pesticide on the leaf surface. The sustained-release test showed that Thi@AWJ-MSN exhibited controlled-release behavior within 196 h, effectively extending the active duration of the pesticide. This study proposed a new strategy to improve the utilization rate of pesticides and reduce environmental risks, which is helpful for the development of green pesticide formulations and the promotion of sustainable agricultural practices.

[0111] The present invention provides a method for preparing an asymmetric wettability nanocarrier and its pesticide delivery application. The method prepares a Janus mesoporous silica nanocarrier (AWJ-MSN) with asymmetric wettability by adjusting the ratio of hydrophilic and hydrophobic monomers, and further encapsulates pesticide molecules therein to form a nanopesticide with good wettability and sustained release properties. The modified asymmetric wettability Janus mesoporous silica nanoparticles prepared by the present invention can also be used in the field of non-pesticide technology to increase the page wettability of non-pesticide preparations.

[0112] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the protection scope of the present invention.

Claims

1. A method for preparing an asymmetric wettability nanocarrier, characterized in that: The following steps are involved: S1, synthesis of mesoporous silica nanoparticles; S2, dispersing mesoporous silica particles in water containing a surfactant, using paraffin as the oil phase, and preparing a paraffin-in-water Pickering emulsion by homogenization to obtain a mesoporous silica-solid wax droplet half of which is wrapped by the paraffin; S3, dispersing the solid wax droplets in methanol, adding a silane coupling agent, reacting and dissolving the paraffin, and obtaining mesoporous silica nanoparticles half of which are connected with amino groups; S4. Dispersing half of the mesoporous silica nanoparticles connected with amino groups in toluene, adding n-octyltrichlorosilane, and obtaining asymmetric wettability Janus mesoporous silica nanoparticles. The asymmetric wettability Janus mesoporous silica nanoparticles are asymmetric wettability nanocarriers.

2. The method for preparing an asymmetric wettability nanocarrier according to claim 1, characterized in that: The following steps are involved: The S1 is: at a stirring speed of 150-200 rpm, dissolving the template in an ethanol aqueous solution, heating to 70-90° C., then adding 3.20-3.50 mL of ammonia water, the concentration of which is 25%, adding tetraethyl silicate dropwise after the solution is clarified, adjusting the speed to 200-250 rpm to react for 22-24 hours, collecting the product by centrifugation and washing the precipitate with deionized water and ethanol to remove the residual reactants, drying the centrifuged product and calcining it in a muffle furnace at 550° C. for 6-8 hours to remove the template, thereby obtaining mesoporous silica nanoparticles; the concentration of the ethanol aqueous solution of the template is 2.2-2.5 mg / mL; the volume ratio of the tetraethyl silicate to the ethanol aqueous solution is (6.7-8):1000; The S2 is: adding mesoporous silica nanoparticles to an aqueous solution containing a cationic surfactant, and then heating it to 70-80°C; then adding paraffin wax to the mixed solution, keeping it at 70-80°C for 0.5-1h, and stirring it with a low-speed magnetic force; vigorously stirring the obtained mixture in a homogenizer for 120-180s, and then quickly cooling it to room temperature with ice water to produce solid wax droplets containing mesoporous silica nanoparticles; then filtering the solid wax droplets, washing them with deionized water to remove mesoporous silica nanoparticles with weak adhesion, and then drying the solid wax droplets in a vacuum drying oven at 25-40°C; The step S3 comprises: adding a dried solid wax droplet to a methanol solution containing a hydrophilic monomer and maintaining the solution at room temperature for 12 to 14 hours, so that the side of the solid wax droplet that is not coated by the paraffin wax is connected with an amino group, and then dissolving the paraffin wax in the solid wax droplet with xylene or chloroform to obtain mesoporous silica nanoparticles with one side modified by an amino group, collecting the obtained nanoparticles by centrifugation, washing the precipitate with xylene or chloroform, and then washing with anhydrous ethanol, and then collecting the product by centrifugation; The S4 is: dispersing mesoporous silica nanoparticles modified by a hydrophilic monomer in an organic solution of a hydrophobic monomer, incubating at room temperature and 120-180 rpm for 2-3 hours to form asymmetric wettability Janus mesoporous silica nanoparticles, and finally collecting the product by centrifugation and washing the precipitate with ethanol.

3. The method for preparing an asymmetric wettability nanocarrier according to claim 2, characterized in that: In S1, the template agent is hexadecyltrimethylammonium bromide or octadecyltrimethylammonium bromide, and the template agent solvent is 16.0-18.0 vt% ethanol aqueous solution.

4. The method for preparing an asymmetric wettability nanocarrier according to claim 2, characterized in that: In S2, the cationic surfactant is dodecyltrimethylammonium bromide or hexadecyltrimethylammonium bromide; in S2, the stirring speed of the homogenizer is 15,000-18,000 rpm; and the mass ratio of the mesoporous silica nanoparticles to the paraffin is 1:(5-7).

5. The method for preparing an asymmetric wettability nanocarrier according to claim 2, characterized in that: In S3, the hydrophilic monomer is a silane coupling agent N-aminoethyl-γ-aminopropyltrimethoxysilane or 3-aminopropyltriethoxysilane; the temperature for dissolving the solid wax droplets is 32-40°C; the volume ratio of the silane coupling agent to methanol is (0.13-0.14):1, and the reaction is stirred for 12-14 hours; the volume ratio of n-octyltrichlorosilane to toluene is 0.002:1, and the reaction is stirred for 2-3 hours.

6. The method for preparing an asymmetric wettability nanocarrier according to claim 2, characterized in that: In S4, the hydrophobic monomer is n-octyltrichlorosilane or octadecyltrichlorosilane.

7. An application of an asymmetric wettability nanocarrier for pesticide delivery, characterized in that: After the asymmetric Janus mesoporous silica nanoparticles are prepared according to steps S1-S4 of any one of claims 1-6, the asymmetric wettability Janus mesoporous silica nanoparticles are used as carriers to load the pesticide technical to obtain an asymmetric wettability Janus mesoporous silica nanopesticide.

8. The use of an asymmetric wettability nanocarrier for pesticide delivery according to claim 7, characterized in that: The method of using asymmetric wettability Janus mesoporous silica nanoparticles as carriers to load the pesticide technical refers to: dispersing asymmetric wettability Janus mesoporous silica in an organic solvent containing the pesticide technical, stirring, separating and drying to obtain asymmetric wettability Janus mesoporous silica nanopesticide.

9. The use of an asymmetric wettability nanocarrier for pesticide delivery according to claim 8, characterized in that: The pesticide molecule is thiofuran or fluopyram or emamectin or avermectin; the drug loading of the asymmetric wettability Janus mesoporous silica nanopesticide is 33-45%; the organic solvent is anhydrous ethanol; the stirring is shaking for 24 hours under 25°C water bath conditions; and the separation is centrifugal separation at 12000rpm for 20 minutes.

10. The use of an asymmetric wettability nanocarrier for pesticide delivery according to claim 7, characterized in that: The asymmetric wettability Janus mesoporous silica nanopesticide is made into powder, suspension, emulsifiable concentrate, water emulsion, granule, microcapsule, slow-release agent or nanoparticle preparation for pest control.

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