Herbicide and preparation method thereof

Abstract

The invention discloses a herbicide and a preparation method thereof, and belongs to the technical field of herbicides. The herbicide is mainly prepared in the mode that graphene oxide adsorbs diquat molecules and is loaded on ZIF-8, and the ZIF-8 is spontaneously formed on the outer layer. The herbicide has visible light and pH responsiveness, graphene oxide can be rapidly combined with diquat molecules, meanwhile, the good photo-thermal conversion effect is achieved, disintegration of materials is accelerated through heat absorption under irradiation of visible light, the release rate of the herbicide is increased, the problem that the release rate of ZIF-8 wrapped herbicides in practical application is not consistent with the requirement is solved, and the herbicide has good application prospects. The ZIF-8 can improve the adhesion on the leaves, increase the retention volume of diquat on the leaf surfaces of weeds, increase the utilization rate of diquat, enable the diquat to have longer effect time, and have good application prospects in practical application.

Description

Technical Field

[0001] The invention belongs to the technical field of herbicides, and particularly relates to a herbicide and a preparation method thereof. Background Art

[0002] Diquat is a pyridine herbicide that can be quickly absorbed by the green tissue of plants, causing them to wither. This agent has a broad spectrum of weed control, fast action, is easy to use, does not kill roots, can preserve water and soil, and is environmentally friendly. However, diquat has a relatively short duration of effect. Excessive use will affect the quality and safety of agricultural products and the safety of the ecological environment, and also increase the input of agricultural production and the cost of manual application. Therefore, how to improve the utilization efficiency or increase the effect time has become an urgent problem to be solved.

[0003] MOFs have the advantages of large surface area, adjustable pore size, diverse structure, high loading capacity and good biocompatibility, and are currently widely used in pesticide loading research. Using ZIF-8 materials to load and coat pesticide compounds, through the construction of the drug loading system, targeted design, and optimization of the dispersed morphology of pesticide particles, the pesticide can be given the performance of controlled release, improve the biological activity of the active ingredients of the pesticide, and thus improve the effective utilization rate of the pesticide. In addition, Zn is also a trace element necessary for plant growth, and the imidazole group is an important component of histidine, so ZIF-8 is an ideal pesticide carrier material. The patent application with publication number CN 117958256 A discloses a high-adhesion and responsive release nanopesticide system based on β-CD / ZIF-8@ST and its preparation method, which is obtained by encapsulating a torsion block-like topological structure formed by β-cyclodextrin, ZIF-8 and mesoporous silica nanoparticles with tannic acid, which greatly improves the wettability and leaf adhesion performance of the nanopesticide system.

[0004] However, in the actual application of agricultural pest control, the release behavior of ZIF-8 drug delivery does not match the pest control needs, and other pesticides are usually required to achieve a more ideal pest control effect. Therefore, how to design the ZIF-8 drug delivery system, control its release behavior through modification or improvement of the preparation method, and make the release dose of the pesticide active ingredient consistent with the actual needs is also a future research focus. Summary of the invention

[0005] The object of the present invention is to provide a herbicide and a preparation method thereof, so as to solve the problem of low utilization rate of the herbicide.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A herbicide is composed of diquat / graphene oxide and ZIF-8, and comprises 2 to 5 parts of graphene oxide and 12 to 15 parts of diquat by weight, wherein the ZIF-8 is spontaneously formed outside the diquat / graphene oxide.

[0008] Furthermore, the diquat / graphene oxide is prepared by the following steps:

[0009] The graphene oxide is dispersed in a diquat-containing aqueous solution according to a certain proportion, stirred at room temperature for 23 to 24 hours, washed with deionized water, centrifuged, and freeze-dried to obtain diquat / graphene oxide.

[0010] Furthermore, the aqueous solution containing diquat is a mixture of water and diquat, and each 50 mL of the aqueous solution containing diquat contains 1.2 to 1.5 g of diquat.

[0011] Furthermore, the mass ratio of the graphene oxide to the diquat aqueous solution is 0.2-0.5:50-55.

[0012] A method for preparing a herbicide comprises the following steps:

[0013] The diquat / graphene oxide dispersion was added to the 2-methylimidazole aqueous solution and stirred for 5 to 6 minutes. The mixed solution was then added dropwise to the zinc nitrate hexahydrate aqueous solution and stirred at room temperature for 2 to 3 hours to obtain a white suspension. The suspension was washed by centrifugation and dried for 22 to 24 hours to obtain diquat / graphene oxide @ ZIF-8.

[0014] Furthermore, the concentration of the diquat / graphene oxide dispersion is 60-65 mg / mL.

[0015] Furthermore, the mass ratio of the zinc nitrate hexahydrate to 2-methylimidazole is 1-2:9.5-10.

[0016] Furthermore, the concentration of the 2-methylimidazole aqueous solution is 0.24-0.27 g / mL, and the concentration of the zinc nitrate hexahydrate aqueous solution is 0.24-0.27 g / mL.

[0017] Furthermore, the volume ratio of the diquat / graphene oxide dispersion to the 2-methylimidazole aqueous solution is 10-11:38-40.

[0018] Beneficial effects of the present invention:

[0019] (1) The ZIF-8 nanoshell used in the present invention has the biological characteristics of easy preparation, high porosity and pH responsiveness. The pH responsiveness of ZIF-8 is manifested as a slow release of herbicide molecules, which increases the effect time. The surface of weed leaves is usually negatively charged, while diquat / graphene oxide @ ZIF-8 is positively charged, so the polar groups on the surface of the leaves are more likely to form electrostatic or hydrogen bonds with the ZIF-8 nanoparticles, thereby forming high adhesion and improving the utilization rate of the herbicide. In addition, the system can provide the trace element zinc required by plants, and the imidazole group is an important component of histidine.

[0020] (2) The graphene oxide used in the present invention is negatively charged in aqueous solution and can better combine with diquat molecules; at the same time, graphene oxide has a good photothermal conversion effect, absorbs heat under light irradiation to accelerate the disintegration of nanoparticles, and increases the release rate of the herbicide, solving the problem that the release rate of the ZIF-8-encapsulated herbicide does not match the demand in practical applications; in addition, the oxidative stress response generated by graphene oxide is manifested as a concentration-dependent increase in active oxygen, which can inhibit plant growth. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0022] Example 1

[0023] This embodiment provides a herbicide, which is prepared by the following steps:

[0024] In the first step, 0.5 g of graphene oxide is dispersed in 50 mL of an aqueous solution containing 1.5 g of diquat, stirred at room temperature for 24 h, then washed with water and centrifuged, and freeze-dried to obtain diquat / graphene oxide.

[0025] In the second step, prepare a diquat / graphene oxide dispersion (60 mg / mL). Then take 10g of 2-methylimidazole and dissolve it in 40mL of deionized water, weigh 1g of zinc nitrate hexahydrate and dissolve it in 4mL of deionized water, and stir at room temperature for 5 minutes to fully dissolve it. Take 10mL of diquat / graphene oxide dispersion and add it to the 2-methylimidazole solution, stir and mix for 5 minutes, then add the mixed solution dropwise to the zinc nitrate hexahydrate aqueous solution, stir at 1200r / min for 2h at room temperature to obtain a white suspension, centrifuge at 12000r / min for 10min to obtain a white precipitate, wash it 3 times with water to remove excess reactants, and dry it at 65℃ for 24h to obtain diquat / graphene oxide @ ZIF-8.

[0026] Example 2

[0027] The present embodiment is different from the embodiment 1 in that “0.5 g of graphene oxide” is changed to “0.2 g of graphene oxide”.

[0028] The remaining raw materials and preparation process remain the same as in Example 1.

[0029] Example 3

[0030] The present embodiment is different from the embodiment 1 in that “1 g zinc nitrate hexahydrate” is replaced with “2 g zinc nitrate hexahydrate”.

[0031] The remaining raw materials and preparation process remain the same as in Example 1.

[0032] Comparative Example 1

[0033] The difference between this comparative example and Example 1 is that graphene oxide is not added.

[0034] The remaining raw materials and preparation process remain the same as in Example 1.

[0035] Comparative Example 2

[0036] The difference between this comparative example and Example 1 is that "zinc nitrate hexahydrate" is replaced by "cobalt nitrate hexahydrate".

[0037] The remaining raw materials and preparation process remain the same as in Example 1.

[0038] Comparative Example 3

[0039] The present embodiment is different from the embodiment 1 in that the graphene oxide, the diquat aqueous solution and the 2-methylimidazole are directly mixed.

[0040] The specific implementation steps are as follows: 0.5g of graphene oxide, 50mL of an aqueous solution containing 1.2g of diquat and 10g of 2-methylimidazole are dissolved in 20mL of deionized water, 1g of zinc nitrate hexahydrate is weighed and dissolved in 4mL of deionized water, and stirred at room temperature for 5min to fully dissolve. 10mL of diquat / graphene oxide dispersion is added to the 2-methylimidazole solution, stirred and mixed for 5min, and then the mixed solution is added dropwise to the zinc nitrate hexahydrate aqueous solution, stirred at 1200r / min for 2h at room temperature to obtain a white suspension, centrifuged at 12000r / min for 10min to obtain a white precipitate, washed with water 3 times to remove excess reactants, and dried at 65℃ for 24h to obtain diquat / graphene oxide @ ZIF-8.

[0041] The remaining raw materials and preparation process remain the same as in Example 1.

[0042] Comparative Example 4

[0043] The difference between this comparative example and Example 1 is that the second step is removed.

[0044] The specific implementation steps are as follows: 0.5 g of graphene oxide is dispersed in 50 mL of an aqueous solution containing 1.2 g of diquat, stirred at room temperature for 24 h, then washed with water and centrifuged, and freeze-dried to obtain diquat / graphene oxide.

[0045] The remaining raw materials and preparation process remain the same as in Example 1.

[0046] Comparative Example 5

[0047] The difference between this comparative example and Example 1 is that no treatment is done on diquat.

[0048] The remaining raw materials and preparation process remain the same as in Example 1.

[0049] The performance tests were performed on Examples 1 to 3 and Comparative Examples 1 to 5.

[0050] The cumulative release of diquat / graphene oxide @ ZIF-8 under different pH conditions was determined by room temperature static release method. 10.0 mg of diquat / graphene oxide @ ZIF-8 sample weighed accurately was added to 10 mL of PBS buffer with different pH values. After 8 h, 0.2 mL of the suspension was taken out from the system, and then 0.2 mL of PBS buffer with the same pH value was added. After filtering with a 0.22 μm filter membrane, the absorbance value was measured by UV-Vis, and the concentration of diquat in the filtrate was calculated.

[0051] Calculate the release ratio of diquat / graphene oxide @ ZIF-8. Prepare 5 mL of diquat / graphene oxide @ ZIF-8 aqueous solution with a concentration of 1 mg / mL, and place it under dark and visible light irradiation conditions. The solution was preheated for 15 minutes before visible light irradiation. In a small 25 mL glass beaker, it was continuously irradiated on a rotating platform 20 cm away from the light source for 12 hours, and the absorbance value was measured by UV-vis to calculate the release of diquat; prepare a diquat / graphene oxide @ ZIF-8 aqueous solution with a concentration of 1 mg / mL, place it under dark and visible light irradiation conditions, and measure the release of diquat after continuous treatment for 12 hours. Use UV-vis to measure the ultraviolet absorption spectrum of diquat / graphene oxide @ ZIF-8 under different conditions.

[0052] Leaf retention rate: 5 mL of diquat and diquat / graphene oxide @ ZIF-8 aqueous solution of appropriate concentration were evenly sprayed on barnyard grass leaves, and the weeds were placed on a glass culture dish at an angle of 30°. Then, 5 mL of PBS (pH 5.6) was evenly sprayed to simulate rain erosion. After the leaf droplets dried naturally, the leaves were immersed in 5 mL of PBS and shaken at 150 r / min for 10 minutes to extract the remaining diquat from the leaf surface into the solution. Finally, the concentration of diquat in the solution was measured by UV-Vis, and the retention rate on the leaves was calculated.

[0053] Contact angle measurement: Select fresh barnyard grass leaves of the same size, wash them carefully several times with distilled water to remove dust on the leaf surface and ensure that the leaf surface is not damaged. After air-drying the moisture on the leaf surface at room temperature, cut the leaf into 5 cm × 2 cm size and place it flat on the contact angle measurement platform. The samples prepared in Examples 1-3 and Comparative Examples 1-5 are respectively dripped on the leaf, and the contact angle with the barnyard grass leaf is measured.

[0054] The results are shown in Table 1:

[0055] Table 1

[0056]

[0057]

[0058] As can be seen from Table 1, the release amount in Example 1 at pH = 5.6 reached 80.2%, the release amount under light conditions was 16.7%, and the release amount under the conditions of light + (pH = 5.6) simulating the actual application environment reached 98.4%, the leaf retention rate also reached 80.6%, and the contact angle with the leaf was 91.53 ± 1.39°. Compared with Example 1, Example 3 showed a decrease in the release amount, because the increase in the concentration of zinc nitrate hexahydrate during the synthesis process led to the irregular structure of the ZIF shell, which affected the reduction of the loading rate and caused the release amount to decrease accordingly.

[0059] Compared with Examples 1-2, the retention amount including the release amount and the contact angle performance of Comparative Example 1 decreased, indicating that graphene oxide can better adsorb herbicide molecules on the one hand, loaded on ZIF-8, and can absorb light and heat on the other hand, promote the release of herbicide molecules, and improve absorption efficiency. In addition, the active oxygen generated by the oxidative stress reaction of graphene oxide inhibits the growth of plants. The nanoshell synthesized in Comparative Example 2 is ZIF-67, and ZIF-8 has a better encapsulation rate than ZIF-8-67 in the embodiment; Comparative Example 3 is mainly manifested in the change of retention amount and contact angle compared with Example 1, indicating the adsorption of graphene oxide on diquat molecules during the synthesis process; Comparative Example 4 is compared with Example 1, without the encapsulation of ZIF-8, the retention rate on the leaves is significantly reduced, and the contact angle with the leaves is also increased, indicating that ZIF-8 has a better affinity with the leaf surface, improves the retention of diquat on the weed leaf surface, improves the utilization rate of diquat, and lasts longer.

[0060] In summary, the herbicide and preparation method thereof provided by the present invention reduce the contact angle between the herbicide and the leaves, make the herbicide more adherent to the leaves, make the herbicide molecules have a sustained release effect and be more adaptable to actual application conditions, improve the utilization rate of diquat, and have good application prospects.

[0061] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0062] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A herbicide, characterized in that: The herbicide consists of diquat / graphene oxide and ZIF-8, and includes 2 to 5 parts of graphene oxide and 12 to 15 parts of diquat by weight. The ZIF-8 is spontaneously formed outside the diquat / graphene oxide.

2. A herbicide according to claim 1, characterized in that: The diquat / graphene oxide is prepared by the following steps: The graphene oxide is dispersed in a diquat-containing aqueous solution according to a certain proportion, stirred at room temperature for 23 to 24 hours, washed with deionized water and centrifuged, and freeze-dried to obtain diquat / graphene oxide.

3. A herbicide according to claim 2, characterized in that: The aqueous solution containing diquat is a mixture of water and diquat, and each 50 mL of the aqueous solution containing diquat contains 1.2 to 1.5 g of diquat; The mass ratio of the graphene oxide to the diquat aqueous solution is 0.2-0.5:50-55.

4. A method for preparing the herbicide according to any one of claims 1 to 3, characterized in that: The following steps are involved: The diquat / graphene oxide dispersion was added to the 2-methylimidazole aqueous solution and stirred for 5 to 6 minutes. The mixed solution was then added dropwise to the zinc nitrate hexahydrate aqueous solution and stirred at room temperature for 2 to 3 hours to obtain a white suspension. The suspension was washed by centrifugation and dried for 22 to 24 hours to obtain diquat / graphene oxide @ ZIF-8.

5. The method for preparing a herbicide according to claim 4, characterized in that: The concentration of the diquat / graphene oxide dispersion is 60-65 mg / mL.

6. The method for preparing a herbicide according to claim 4, characterized in that: The mass ratio of zinc nitrate hexahydrate to 2-methylimidazole is 1-2:9.5-10; The concentration of the 2-methylimidazole aqueous solution is 0.24-0.27 g / mL, the concentration of the zinc nitrate hexahydrate aqueous solution is 0.24-0.27 g / mL, and the volume ratio of the diquat / graphene oxide dispersion to the 2-methylimidazole aqueous solution is 10-11:38-40.

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