A Pickering emulsion with bidirectional systemic conduction function and its preparation method

Abstract

This invention discloses a bifenthrin Pickering emulsion with bidirectional systemic translocation function and its preparation method, belonging to the fields of pesticide formulation processing and nano-agricultural technology. This invention uses sodium lignosulfonate and nano-titanium dioxide as composite stabilizers, loading bifenthrin into a water-in-oil Pickering emulsion. The Pickering emulsion prepared by this invention exhibits excellent resistance to photodegradation and rain erosion. More importantly, it achieves bidirectional systemic translocation of bifenthrin within plants, demonstrating significantly better control efficacy against piercing-sucking pests such as wheat aphids than commercially available water-in-oil emulsions. Furthermore, it is environmentally friendly, aligning with the development direction of green nano-pesticides.

Description

Technical Field

[0001] This invention belongs to the field of pesticide formulation processing and nano-agricultural technology, specifically relating to a bifenthrin Pickering emulsion with bidirectional systemic conduction function and its preparation method. Background Technology

[0002] Wheat (Triticum aestivum L.) is one of the world's most important food crops, providing a primary source of food for approximately 40% of the world's population. Its high and stable yields are of paramount strategic importance for ensuring national food security. However, wheat is frequently subjected to various biological stresses during its cultivation and growth, among which insect pests are a major factor leading to reduced yields and lower quality. Wheat aphids, in particular, are characterized by their rapid reproduction rate and strong adaptability. They often congregate on leaves, stems, and ears, sucking sap and not only directly depriving the plant of nutrients but also acting as vectors for diseases such as barley yellow dwarf virus, seriously threatening wheat production.

[0003] Currently, chemical control remains the dominant method for controlling wheat pest outbreaks in agricultural production due to its advantages such as rapid effectiveness, low cost, and ease of use. Among the many chemical insecticides, pyrethroid pesticides are widely used for the control of various crop pests because of their high efficiency, broad spectrum, and relatively low toxicity to mammals.

[0004] Bifenthrin (BF) is a highly effective pyrethroid insecticide widely used to control agricultural pests such as wheat aphids. However, BF itself has extremely poor water solubility and is sensitive to light, easily undergoing photodegradation. Currently, most commercially available BF formulations are emulsifiable concentrates (EC) and emulsions (EW), which contain large amounts of benzene-based organic solvents and synthetic surfactants.

[0005] Furthermore, wheat leaves have a rich hydrophobic waxy layer and steep leaf angles. Traditional pesticide droplets, upon contact with the leaf surface, are prone to bouncing and rolling off, resulting in low pesticide deposition on the target crop, leading to pesticide waste and environmental non-point source pollution. More importantly, traditional pyrethroid pesticides typically lack systemic conductivity, making them difficult to transport within the plant and ineffective against pests in hidden parts or roots.

[0006] The existing commercial formulations of bifenthrin and conventional emulsion technology have the following technical defects: (1) lack of systemic conductivity, limited insecticidal range, and poor control effect on borers or root pests; (2) poor interfacial adhesion performance, serious loss of pesticide solution, and low utilization rate; (3) poor photostability and short duration of effect; (4) weak resistance to rain washout, requiring repeated application; (5) environmental and biosafety risks, traditional emulsifiable concentrates rely on a large amount of organic solvents and synthetic surfactants, which are prone to phytotoxicity and have high toxicity to non-target organisms.

[0007] Therefore, it is of great significance to develop a novel delivery system that is environmentally friendly, resistant to photodegradation and rain erosion, and capable of bidirectional transport within plants. Summary of the Invention

[0008] In view of this, the purpose of this invention is to provide a bifenthrin Pickering emulsion with bidirectional systemic conduction function and its preparation method, so as to solve the problems of lack of systemic conduction, poor interfacial adhesion, poor photostability and environmental unfriendliness of bifenthrin formulations in the prior art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a bifenthrin Pickering emulsion with bidirectional systemic conduction function, prepared from the following components in parts by weight: Bifenthrin 25-40 parts; Solvent: 100-200 parts; 200-400 parts water; 10-30 parts of lignin sulfonate; 60-100 parts of nano titanium dioxide.

[0010] Preferably, the solvent is rosin-based vegetable oil, fatty acid methyl ester, or biodiesel.

[0011] The present invention also provides a method for preparing the above-mentioned bifenthrin Pickering emulsion, comprising the following steps: S1. Weigh the raw materials according to the parts by weight; S2. Mix water, lignin sulfonate, and nano-titanium dioxide evenly, and adjust the pH to 4; then grind to form a composite nanoparticle mixture; S3. Dissolve the bifenthrin technical material in a solvent to obtain a bifenthrin solution; S4. Using bifenthrin solution as the oil phase and composite nanoparticle mixture as the aqueous phase; the oil phase and aqueous phase are mixed and then subjected to high-speed shearing to obtain Pickering emulsion.

[0012] Preferably, the grinding parameters in S2 are: 2000-4000 rpm, 0.5-1.5h.

[0013] Preferably, the volume ratio of the oil phase to the water phase in S4 is (2-5):(5-8).

[0014] Preferably, the high-speed shearing parameters in S4 are: 8000-12000 rpm, 5-15 min.

[0015] It contains at least the following beneficial technical effects: The Pickering emulsion prepared in this invention imparts significant interfacial transfer efficiency and bidirectional transport capabilities to bifenthrin, broadening its insecticidal spectrum. It not only controls foliar pests but also effectively controls pests in roots and hidden areas. The rough interfacial structure constructed using lignin sulfonate and nano-titanium dioxide significantly improves the wettability and adhesion of droplets on the hydrophobic surface of wheat leaves, greatly reducing droplet bouncing and rolling, and increasing pesticide deposition rate. Nano-titanium dioxide provides UV shielding, while sodium lignin sulfonate provides antioxidant properties; the two synergistically protect bifenthrin, prolonging its effective duration. Simultaneously, the emulsion forms a dense film structure on the leaf surface, resisting rain washout. The Pickering emulsion exhibits significant slow-release characteristics, demonstrating significantly better control of wheat aphids than commercially available emulsifiable concentrates. It eliminates traditional synthetic surfactants and harmful organic solvents, exhibiting low toxicity and no negative impact on normal wheat growth. Attached Figure Description

[0016] Figure 1 The following are the multiple light scattering stability diagrams of the Pickering emulsion of the present invention with different oil-water ratios: (A) 2:8; (B) 3:7; (C) 4:6; (D) 5:5; (E) BF EW; (F) TSI value.

[0017] Figure 2 The particle size distribution of the Pickering emulsion of the present invention is shown in (A) TEM image; (B) particle size distribution diagram; and (C) photograph of the emulsion appearance.

[0018] Figure 3 The following diagrams illustrate the downward transport of the Pickering emulsion of this invention: (A) BF PEs fluorescence image; (B) BF EW fluorescence image; (C) fluorescence intensity; (D) root transport factor; (E) stem transport factor.

[0019] Figure 4 The images show the upward transport of the Pickering emulsion of this invention: (A) BF PEs fluorescence image; (B) BF EW fluorescence image; (C) fluorescence intensity; (D) leaf transport factor; (E) stem transport factor.

[0020] Figure 5 The figures (A) and (B) show the release of the Pickering emulsion of the present invention at different pH values.

[0021] Figure 6 This describes the bouncing behavior of Pickering emulsion droplets.

[0022] Figure 7 The inhibition rate of Pickering emulsion against wheat aphids. Detailed Implementation

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0026] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0027] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0028] Unless otherwise specified, "room temperature" and "normal temperature" in this invention refer to 25±2℃.

[0029] Unless otherwise specified, all raw materials or instruments used in the following embodiments of the present invention are commercially available.

[0030] Example 1 Preparation of Bifenthrin Pickering Emulsion Preparation of composite nanoparticle slurry: Add 20g of sodium lignosulfonate to 300g of water, stir until homogeneous, then add 80g of nano-titanium dioxide (TiO2, particle size approximately 20-50nm, purity 99.8%), mix thoroughly using a high-speed shear mill, and adjust the pH of the dispersion to 4.0 with dilute hydrochloric acid. Pour the mixture into a sand mill loaded with zirconia grinding beads (diameter 0.8-1.0mm), and grind at 3000 rpm for 1 hour to obtain composite nanoparticle slurry (aqueous phase).

[0031] Preparation of the oil phase: 98.5% bifenthrin technical grade was dissolved in pine resin-based vegetable oil solvent ND-45 to prepare an oil phase with a concentration of 2.5% w / w.

[0032] Emulsification: The oil phase and aqueous phase were mixed at oil-water volume ratios of 2:8, 3:7, 4:6, and 5:5, respectively, and then sheared at 10,000 rpm for 10 min using a high-homogeneity shear press to obtain a stable Pickering emulsion. After standing for 24 h, the emulsion showed no obvious stratification, water separation, or demulsification, and appeared as a milky white, homogeneous liquid.

[0033] Experimental Example 1: Stability Determination The multi-scattering stability of the samples was determined using a TurBiscan LabExpert multiple light scattering instrument. Approximately 20 mL of undiluted Pickering emulsion sample was poured into a cylindrical glass cell. The length of the sample (approximately 40 mm) was scanned using a measuring probe, with measurements taken every 40 μm from the bottom to the top of the cell to obtain the transmittance values. All samples were scanned every 1 hour at 25°C for a total of 24 hours to obtain stability characteristic maps. The TurBiscan Stability Index (TSI) was calculated using TurBiscan Easysoft software.

[0034] See results Figure 1 .

[0035] Figure 1 (AF) shows the multiple light scattering stability and appearance of bifenthrin Pickering emulsions (BF PEs) prepared with different oil-water ratios. During 24 h of storage, the emulsions at oil-water ratios of 2:8, 3:7, and 5:5 exhibited particle aggregation and bottom stratification, indicating poor stability. However, at an oil-water ratio of 4:6, the backscattered light intensity of the emulsion remained unchanged, and the TSI value was less than 0.1, demonstrating good dispersion stability. Therefore, the BF PE emulsion with an oil-water ratio of 4:6 was selected for further research.

[0036] Experimental Example 2: Particle Size and Morphology Characterization TEM results showed the diameter and particle distribution of the emulsion, as shown in Figure 2A. The BF PEs droplets were uniformly distributed and did not aggregate, further demonstrating the good dispersibility of the emulsion. As shown in Figure 2B (BC), the particle size, PDI, and Zeta potential of the BF PEs measured by DLS were 95.09 nm, 0.033 mV, and -41.56 mV, respectively. Observation of the appearance of emulsions with different oil-water ratios revealed that using TSL composite particles as the aqueous phase, after shear emulsification with the oil phase, formed a stable Pickering emulsion with a robust interfacial film, preventing droplet aggregation through its spatial structure.

[0037] Test Example 3: Bidirectional Inhalation and Conduction Test Downward translocation behavior: As shown in Figures 3A and 3B, Nile red (NR, a lipophilic molecule) and the active ingredient were loaded together into the BF PEs system. After treatment for 1, 2, and 4 h, red fluorescence signals were detected in the roots using confocal laser scanning microscopy (CLSM), indicating that the BF PEs had been translocated from the leaves to the roots. As shown in Figure 3C, the fluorescence intensity in the roots increased over time, with NR-BF PEs exhibiting the highest fluorescence intensity. TF... r / l and TF s / l The TF value characterizes the downward transport capacity of BFPEs (Figure 3D, E). Within 4–24 h, the TF value of the BFPE solution... r / l Value greater than TF s / l Values, where the TF of BFPEs r / l Value and TF s / l The increases of 1.97 and 1.67 times respectively indicate that BF PEs can achieve long-distance transport within plants, significantly improving the translocation capacity of non-systemic pesticides.

[0038] Upward translocation behavior: NR-labeled (NR-BF PEs) and (NR-BF EW) were diluted to the same concentration (50 mg / L), and wheat seedlings were cultured in the solution. Leaf samples were then collected at 1, 2, and 3 h to observe upward translocation. As shown in Figure 4A, within 4 h, the upward translocation capacity of NR-BF PEs was significantly higher than that of NR-BF EW at the same time point. In contrast, upward translocation of NR-BF EW was very difficult (Figure 4B). Quantitative analysis of fluorescence intensity showed that the concentration of NR in the leaves increased with time (Figure 4C), and NR-BF PEs exhibited the highest intensity density during upward translocation.

[0039] Use TF l / r Value and TF s / rThe TF value characterizes the upward transport capacity of BFPEs (Figure 34D, E). Within 4–24 h, the TF value of the BFPEs solution... r / l Value greater than TF s / l Values, where the TF of BF PEs l / r Value and TF s / r The increases were 1.16 and 1.61 times respectively, with relatively small changes. This indicates that BF PEs achieve absorption of pesticide solution from the roots and then transport to the stems and leaves, giving non-systemic pesticides the ability to be transported upwards.

[0040] Test Example 4: Resistance to Photolysis Test As shown in Figure 5A, the sustained-release behavior of the Pickering emulsion differed significantly at different pH values, exhibiting a strong pH-responsive characteristic. The emulsion released rapidly within the first 24 hours, with cumulative release rates reaching 37.65%, 46.83%, and 72.01% at pH 4, 7, and 9, respectively. After 60 hours, the release rate slowed down, as the BF PEs gradually diffused into the surrounding medium. The final cumulative release of BF PEs after 180 hours was 62.33% at pH 4, 76.02% at pH 7, and 90.81% at pH 9. This phenomenon is attributed to the positive charge of nano-TiO2 under acidic conditions, which further weakens the electrostatic repulsion with SL, enhances adsorption, and leads to a slower release rate. This is consistent with the results of forming stable TSL composite particles under acidic conditions.

[0041] Test Example 5: Droplet Bouncing Test The bouncing behavior of BF PEs and BF EW on wheat leaves was studied using visualization techniques with a high-speed camera system. As shown in Figure 6A, after the droplets impacted the leaf, the BF EW droplets retracted and broke up, making it difficult for them to deposit on the leaf. In contrast, the BF PEs droplets did not break up or bounce, and their retraction speed was significantly reduced, eventually adhering to the leaf in a spherical state. The bouncing behavior of droplets on wheat leaves at an angle is shown in Figure 6B. After impact, the BF EW droplets quickly rolled off the leaf completely due to their poor adhesion. In contrast, the BF PEs droplets had better adhesion to the wheat leaf, allowing them to remain on the leaf.

[0042] Experiment Example 6: Indoor toxicity determination against wheat aphids As shown in Figure 7, in all treatment groups, with increasing BF concentration, both BF PEs and BF EW showed inhibitory effects on aphids, with BF PEs exhibiting higher inhibitory activity than BF EW. This was confirmed by LC-MS. 50 The values ​​represent the insecticidal activity of different pesticide solutions. As shown in Table 1, the LC50 values ​​of BF PEs and BF EW were calculated 24 h after infection. 50The values ​​were 2.544 mg / L (2.091–3.079, 95% confidence interval) and 4.429 mg / L (3.649–5.481, 95% confidence interval), respectively. After 48 h of infection, the LC50 values ​​for BF PEs and BF EW were... 50 The values ​​were 1.18 mg / L (2.091–3.079, 95% confidence interval) and 2.161 mg / L (3.649–5.481, 95% confidence interval), respectively, indicating that BFPEs exhibited high insecticidal activity.

[0043] Table 1. Toxicity of Pickering against Wheat Aphids

[0044] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A bifenthrin Pickering emulsion with bidirectional systemic conduction function, characterized in that, It is prepared from the following components in parts by weight: Bifenthrin 25-40 parts; Solvent: 100-200 parts; 200-400 parts water; 10-30 parts of lignin sulfonate; 60-100 parts of nano titanium dioxide.

2. The bifenthrin Pickering emulsion according to claim 1, characterized in that, The solvent is rosin-based vegetable oil, fatty acid methyl ester, or biodiesel.

3. The method for preparing the bifenthrin Pickering emulsion according to claim 2, characterized in that, Includes the following steps: S1. Weigh the raw materials according to the parts by weight; S2. Mix water, lignin sulfonate, and nano-titanium dioxide evenly, and adjust the pH to 4; then grind to form a composite nanoparticle mixture; S3. Dissolve the bifenthrin technical material in a solvent to obtain a bifenthrin solution; S4. Using bifenthrin solution as the oil phase and composite nanoparticle mixture as the aqueous phase; the oil phase and aqueous phase are mixed and then subjected to high-speed shearing to obtain Pickering emulsion.

4. The method according to claim 3, characterized in that, The grinding parameters in S2 are: 2000-4000 rpm, 0.5-1.5h.

5. The method according to claim 3, characterized in that, The volume ratio of the oil phase to the water phase in S4 is (2-5):(5-8).

6. The method according to claim 3, characterized in that, The high-speed shearing parameters in S4 are: 8000-12000 rpm, 5-15 min.

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