Preparation and application of bimetallic-based nano material Ag-coated AIF-8

Abstract

The invention discloses preparation and application of a bimetallic-based nano material Ag-coated AIF-8, and belongs to the field of metal organic framework materials. The preparation method of the bimetallic-based nano material Ag-coated AIF-8 comprises the following steps: mixing a zinc salt and 2-methylimidazole in a solvent to obtain a precursor solution; and mixing the precursor solution with silver salt, reacting in a dark place, and then reacting under an illumination condition to obtain the bimetallic-based nano material Ag (at) AIF-8. The invention provides a high-efficiency, environment-friendly and multifunctional plant disease prevention and control composite material which is used for solving the problems of disease prevention and control and pesticide residues in the current agricultural field and providing powerful support for agricultural sustainable development. The bimetallic-based nano material Ag-coated AIF-8 disclosed by the invention has broad-spectrum antibacterial activity, and can play a synergistic effect after being used as a pesticide carrier for loading berberine.

Description

Technical Field

[0001] The present invention relates to the field of metal organic framework materials, and in particular to the preparation and application of a bimetallic-based nanomaterial Ag@AIF-8. Background Art

[0002] Effective prevention and control of plant diseases is a key link to ensure healthy plant growth and improve agricultural production efficiency. Although the use of traditional chemical pesticides has controlled the spread of diseases to a certain extent, its long-term and excessive use not only leads to the enhancement of pathogen resistance, but also poses a potential threat to the ecological environment and human health. Therefore, it is particularly important to develop an efficient, environmentally friendly and sustainable method for plant disease prevention and control.

[0003] In recent years, the application of nanotechnology in the agricultural field has become increasingly widespread. Among them, nanosilver, as a new type of antibacterial material, has the advantages of high efficiency, broad spectrum, and no drug resistance, and has broad application prospects in the agricultural field. Nanosilver can effectively inhibit or kill a variety of plant pathogens, thereby significantly reducing the incidence of diseases. However, although the single use of nanosilver has a good bactericidal effect, its stability and durability in the soil still need to be improved, and it lacks the satisfaction of other agricultural needs, such as soil improvement and plant nutrition supplementation.

[0004] Zeolitic imidazolate framework material ZIF-8, as a new type of porous metal-organic framework material, has attracted much attention due to its high specific surface area, good chemical stability and unique catalytic properties. ZIF-8 can not only serve as an excellent carrier for loading and slow-release of active substances such as pesticides or fertilizers, but also provide trace zinc elements required for plant growth to promote plant growth. However, although the existing ZIF-8 has shown certain performance advantages, it still faces problems such as cumbersome preparation steps, high cost, and poor product performance in practical applications, and still needs further improvement. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation and application of a bimetallic nanomaterial Ag@AIF-8 to solve the above-mentioned problems in the background technology. The present invention provides an efficient, environmentally friendly, and multifunctional composite material for plant disease control, which is used to solve the current disease control problems and pesticide residue problems faced by the agricultural field, and provide strong support for the sustainable development of agriculture. The bimetallic nanomaterial Ag@AIF-8 of the present invention has a broad spectrum of antibacterial activity, and after being loaded with berberine as a pesticide carrier, it can play a synergistic role.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention is to provide a method for preparing a bimetallic nanomaterial Ag@AIF-8, comprising the following steps:

[0008] mixing zinc salt and 2-methylimidazole in a solvent to obtain a precursor solution;

[0009] The precursor solution is mixed with silver salt, reacted in the dark, and then reacted under light conditions to obtain the bimetallic-based nanomaterial Ag@AIF-8.

[0010] Preferably, the precursor solution also contains berberine; the mass ratio of the zinc salt to berberine is 1:1-3.

[0011] Preferably, the zinc salt is zinc nitrate and / or zinc chloride; the mass ratio of the zinc salt to 2-methylimidazole is 680:3285.

[0012] Preferably, the solvent is methanol.

[0013] Preferably, the silver salt is AgNO 3 ; The mass ratio of the silver salt to the zinc salt is 850:680.

[0014] Preferably, the light-proof reaction time is 3-12 hours.

[0015] Preferably, the reaction time under the illumination condition is 30 min.

[0016] The second technical solution of the present invention is to provide a bimetallic nanomaterial Ag@AIF-8 obtained according to the above preparation method.

[0017] The third technical solution of the present invention is to provide an application of the above-mentioned bimetallic nanomaterial Ag@AIF-8 in plant disease prevention and control.

[0018] Technical solution 4 of the present invention: provides an application of the above-mentioned bimetallic-based nanomaterial Ag@AIF-8 in photocatalytic degradation of chemical pesticides.

[0019] The present invention proposes a plant disease prevention and control method based on a nano-silver and ZIF-8 composite material, which combines the bactericidal performance and photodegradation ability of nano-silver with the function of loading pesticides to form a multifunctional composite nano-material. The composite nano-material can not only effectively kill plant pathogens to prevent and control diseases, but also degrade chemical pesticide residues through the photolysis of the composite material to reduce the pollution of pesticides to the environment.

[0020] The beneficial technical effects of the present invention are as follows:

[0021] The present invention provides an efficient, environmentally friendly, and multifunctional composite material for plant disease prevention and control, which is used to solve the current disease prevention and control problems and pesticide residue problems faced by the agricultural field, and provide strong support for the sustainable development of agriculture. The Ag@ZIF-8 nanocomposite material obtained by the preparation process of the present invention has Ag elements uniformly dispersed on the surface of nanoparticles. After the sample is irradiated with visible light, a small amount of AgCl is reduced to single substance Ag, thereby enhancing the bactericidal effect of the product.

[0022] The bimetallic nanomaterial Ag@AIF-8 of the present invention has a broad spectrum of antibacterial activity, and can play a synergistic role after being loaded with berberine as a pesticide carrier. When crops are infected with pathogens, the nanomaterial of the present invention can rapidly increase the antioxidant enzyme activity of plants and induce plants to develop disease resistance. The product system has a significant preventive effect on diseases such as tobacco bacterial wilt, and can achieve a significant antibacterial effect at a very small addition amount. The active inhibitory effect on bacterial wilt bacteria is much higher than that of berberine, and has a good application value.

[0023] Furthermore, the product of the present invention can significantly increase the degradation rate of pesticides, has strong photocatalytic activity, and helps to promote the degradation of pesticides. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 Scanning electron microscope image of Ag@ZIF-8.

[0026] Figure 2 The mapping diagram and element ratio diagram of Ag@ZIF-8. Among them, (a) is the microscopic morphology diagram, (b) is the mapping diagram of the C element, (c) is the mapping diagram of the N element, (d) is the mapping diagram of the O element, (e) is the mapping diagram of the Ag element, (f) is the mapping diagram of the Zn element, (g) is the mapping diagram of the Cl element, (h) is the element mapping diagram, and (i) is the element ratio diagram.

[0027] Figure 3 The XPS analysis diagram of Ag@ZIF-8 and the fitting curves of Zn and Ag elements and the Cl2p narrow scan spectrum. Among them, (a) is the XPS analysis diagram, (b) and (c) are the fitting curves of Zn element, (d) and (e) are the fitting curves of Ag element, and (f) is the Cl2p narrow scan spectrum.

[0028] Figure 4 This is the growth curve of R. solanacearum after being treated with different concentrations of Ber, Ag@ZIF-8 and Ag@Ber@ZIF-8.

[0029] Figure 5 SEM images of the morphological changes of R. solanacearum after treatment with Ber, Ag@ZIF-8 and Ag@Ber@ZIF-8.

[0030] Figure 6 The control effect of Ag@ZIF-8 on different pathogens.

[0031] Figure 7 The effect of Ag@ZIF-8 on the mycelial growth of different pathogens.

[0032] Figure 8 The effects of Ber, Ag@ZIF-8 and Ag@Ber@ZIF-8 on tobacco antioxidant enzymes. (a) is SOD enzyme activity, (b) is PPO enzyme activity, (c) is CAT enzyme activity, and (d) is POD enzyme activity.

[0033] Fig. 9 The degradation of chemical pesticide tebuconazole after Ag@ZIF-8 treatment. DETAILED DESCRIPTION

[0034] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0035] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0036] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the invention pertains. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention.

[0037] The words “include,” “including,” “have,” “contain,” etc. used in the present invention are open-ended terms, meaning including but not limited to.

[0038] Unless otherwise specified, "overnight" in the present invention is calculated as 10-12 hours.

[0039] All raw materials used in the following examples and comparative examples of the present invention are commercially available products.

[0040] Example 1

[0041] A preparation method of a bimetallic nanomaterial Ag@AIF-8, the specific steps are as follows:

[0042] 680 mg ZnCl 2 and 3285 mg 2-methylimidazole were placed in 50 mL methanol solution, and then 1000 mg berberine (Ber) was added to the 2-methylimidazole solution. 2 The solution was added dropwise to the solution system and stirred for 30 minutes to obtain a precursor solution;

[0043] 850mgAgNO 3 Dispersed in 50 mL of ethanol, then poured into the precursor solution, reacted in the dark for 6 hours and then reacted under natural light for 30 minutes, then the precipitate was collected by centrifugation, washed thoroughly with ethanol, and dried thoroughly at 60°C to obtain the final product (denoted as Ag@Ber@ZIF-8).

[0044] Example 2

[0045] The only difference from Example 1 is that the addition of berberine in the precursor solution is omitted; the prepared product is recorded as Ag@ZIF-8.

[0046] Effect verification

[0047] 1. Product Characterization

[0048] Figure 1 Scanning electron microscope image of Ag@ZIF-8.

[0049] Depend on Figure 1 It can be seen that the product has an octahedral structure.

[0050] Figure 2The mapping diagram and element ratio diagram of Ag@ZIF-8. Among them, (a) is the microscopic morphology diagram, (b) is the mapping diagram of the C element, (c) is the mapping diagram of the N element, (d) is the mapping diagram of the O element, (e) is the mapping diagram of the Ag element, (f) is the mapping diagram of the Zn element, (g) is the mapping diagram of the Cl element, (h) is the element mapping diagram, and (i) is the element ratio diagram.

[0051] Figure 2 It shows that the Ag element is evenly dispersed on the surface of the nanoparticles.

[0052] Figure 3 The XPS analysis diagram of Ag@ZIF-8 and the fitting curves of Zn and Ag elements and the Cl2p narrow scan spectrum. Among them, (a) is the XPS analysis diagram, (b) and (c) are the fitting curves of Zn element, (d) and (e) are the fitting curves of Ag element, and (f) is the Cl2p narrow scan spectrum.

[0053] Figure 3 In the characterization analysis of Ag@ZIF-8, three elements, Cl, Ag and Zn, were detected by high-resolution XPS. The characteristic peaks at the binding energies of 1044eV and 1022eV were attributed to Zn in ZnO. 2+ 2p 1 / 2 and Zn 2p 3 / 2 The peaks of the Ag 3d spectrum at 372.7 eV and 366.7 eV correspond to the Ag in AgCl. + , and the two small peaks at 373.7eV and 367.7eV correspond to metallic Ag. This result shows that after the sample is irradiated with visible light, a small amount of AgCl is reduced to elemental Ag; the Cl2p narrow scan spectrum shows that chlorine element exists in the nanoparticles.

[0054] 2. Ag@ZIF-8 and drug delivery system for the prevention and control of tobacco bacterial wilt

[0055] The growth curve method was used to further evaluate the antibacterial activity of nanomaterials Ag@ZIF-8, Ag@Ber@ZIF-8 and berberine (Ber) against R. solanacearum. The specific test method was as follows: First, 5 μL of different test samples were added to a 96-well polystyrene plate, and then 90 μL of NB liquid culture medium was added for dilution; then, 5 μL of fresh R. solanacearum bacterial culture cultured overnight was added to each treatment group so that the final concentration of the test sample was 0.625-20 mg / L. All treatment groups were cultured at 30°C, and the absorbance at 600 nm was detected using an enzyme reader at 0, 2, 4, 6, 8, 10 and 12 hours. Each group of experiments was repeated 4 times, and the results are as follows: Figure 4 shown.

[0056] Figure 4 This is the growth curve of R. solanacearum after being treated with different concentrations of Ber, Ag@ZIF-8 and Ag@Ber@ZIF-8.

[0057] Depend on Figure 4 It can be seen that after treatment with berberine solution alone, the inhibitory effect was not significant at a concentration of 40 mg / L, but it showed an antibacterial effect when the concentration was higher than this, and the growth of bacterial wilt was significantly inhibited when the concentration reached 160 mg / L. At the same concentration, the nanomaterials Ag@ZIF-8 and Ag@Ber@ZIF-8 had significant differences in their effects on the activity of R. solanacearum compared with the Ber group. When the concentration was higher than 1.25 mg / L, the inhibitory effect was equivalent to the activity of berberine at a high concentration of 160 mg / L.

[0058] 3. Study on the control mechanism of tobacco bacterial wilt by Ag@ZIF-8 and drug delivery system

[0059] Scanning electron microscopy was used to analyze the cell morphological changes of Ralstonia solanacearum. The specific test method was as follows: Ber, Ag@ZIF-8, and Ag@Ber@ZIF-8 were added to the fresh R. solanacearum culture solution overnight to a final concentration of 200 μg·mL -1 The cells were cultured at 28°C for 24 hours, and the precipitate was collected after centrifugation and washing. The cells were fixed with 2.5% glutaraldehyde and then dehydrated with 30%, 50%, 70%, 90% and 100% ethanol in a gradient manner. Finally, the cells were treated with gold spraying and the morphology of the cells was observed under a scanning electron microscope. Figure 5 shown.

[0060] Figure 5 SEM images of the morphological changes of R. solanacearum after treatment with Ber, Ag@ZIF-8 and Ag@Ber@ZIF-8.

[0061] Depend on Figure 5 It can be seen that the surface of the bacterial wilt pathogen treated with the blank group (CK) was intact, and the bacterial length was about 1 μm; the bacterial growth was inhibited after Ber treatment, but there was no obvious effect on the bacterial surface structure; on the contrary, 200 μg·mL -1 After treatment with Ag@ZIF-8 and Ag@Ber@ZIF-8, the bacterial morphology was severely damaged. Most of the bacterial cells in the field of view were deformed, with a length far less than 0.5 μm, wrinkled, and even ruptured.

[0062] 4. Evaluation of the control effect of Ag@ZIF-8 and drug delivery system on other pathogens

[0063] Add Ag@ZIF-8 to the melted PDA medium and mix well to make the final content in the medium 0.1-500 mg / L. After the medium solidifies, use a sterile punch to take the pathogen cakes of tobacco black shank, wheat stem base rot, tobacco brown spot, grape gray mold and rice sheath blight of the same growth conditions, place them in the center of the PDA medium, and culture at 25°C to observe the growth of the pathogens. PDA without adding nanomaterials was used as the control, and each group was repeated three times. The test results are as follows Figure 6 shown.

[0064] Figure 6 The control effect of Ag@ZIF-8 on different pathogens.

[0065] Figure 6 The results showed that the nanomaterial Ag@ZIF-8 had no obvious antibacterial activity against tobacco black shank, but showed excellent protective effects against the other five pathogens, indicating that Ag@ZIF-8 has a broad-spectrum antibacterial activity and can play a synergistic role in the process of being used as a pesticide carrier.

[0066] 5. Antibacterial effect of Ag@ZIF-8 on other pathogens

[0067] Grape gray mold, tobacco target spot and wheat stem rot were selected as research objects to explore the effect of nanomaterials on the growth of pathogenic mycelium. The specific test method is: Ag@ZIF-8 is configured into 50mg / L PDA culture medium. After the culture medium solidifies, sterilized cellophane is spread on the surface of the culture medium. After there are no obvious water marks on the surface of the cellophane, the pathogen is inoculated and compared with the PDA culture medium treatment group without Ag@ZIF-8; the culture is cultured at a constant temperature of 25℃, and the difference in mycelial morphology is observed after 48h. The results are as follows Figure 7 shown.

[0068] Figure 7 The effect of Ag@ZIF-8 on the mycelial growth of different pathogens.

[0069] Figure 7 The results showed that the hyphae of the pathogen of grape gray mold were bent and deformed after being treated with Ag@ZIF-8; the hyphae of the pathogen of tobacco target spot were not significantly affected, but the diameter was reduced; the hyphae of the pathogen of wheat stem rot grew in a disorderly manner and the distance between branches became larger, which was significantly affected.

[0070] 6. Effects of Ag@ZIF-8 and drug delivery system on enzymes related to tobacco growth and metabolism

[0071] The concentration was 100 μg mL -1Tobacco seeds were treated with three samples of Ber, Ag@Ber@ZIF-8 and Ag@ZIF-8, and then transplanted into pots and cultured for 7 days. The tobacco plants were inoculated with R. solanacearum cell suspension (OD600=0.1); 24 hours later, the corresponding plants were watered with 10 mL of the suspension by root exposure method, and the enzyme activities of superoxide dismutase (SOD), polyphenol oxidase (PPO), catalase (CAT) and peroxidase (POD) in tobacco were measured 24, 72 and 144 hours after inoculation, respectively. Untreated plants (CK- (healthy; negative control)) and plants that were not treated after inoculation (CK+ (infected; positive control)) were used as controls. Samples were taken and the leaves were weighed at the set time points, then ground with liquid nitrogen in a pre-cooled mortar and stored on ice for further enzyme activity determination. The results are shown in Figure 2. Figure 8 shown.

[0072] Figure 8 The effects of Ber, Ag@ZIF-8 and Ag@Ber@ZIF-8 on tobacco antioxidant enzymes. (a) is SOD enzyme activity, (b) is PPO enzyme activity, (c) is CAT enzyme activity, and (d) is POD enzyme activity.

[0073] Figure 8 The results showed that after different treatment times, the activities of SOD, PPO, CAT, and POD of healthy plants remained relatively stable, but tobacco treated with bacterial wilt bacteria showed significant differences after different treatments. The SOD enzyme activity of tobacco plants that had not been treated showed a significant increase trend from 24h to 144h after inoculation, and CAT reached the highest value 24h after inoculation, but PPO and POD did not change significantly. Compared with berberine, the activities of SOD and CAT in tobacco plants treated with Ag@ZIF-8 nanocomposites and Ag@Ber@ZIF-8 gradually increased, while the activities of PPO and POD remained relatively stable, showing a trend of first increasing and then decreasing, indicating that nanomaterials can quickly increase the antioxidant enzyme activity of plants after infection with pathogens and induce plants to develop disease resistance. In addition, Ag@ZIF-8 nanocomposites can significantly increase the activities of PPO and POD in tobacco 24h after infection, which may be related to cell damage and stress response caused by infection.

[0074] 7. Photocatalytic activity

[0075] Under ultraviolet light irradiation, a tebuconazole sample was added to an aqueous solution, and then the nanocomposite material was added. The solution without the composite material was used as a control (TC) to explore the photocatalytic degradation of tebuconazole by the composite material to explore its photocatalytic activity. The specific test method is: take 50mL of the reaction solution in a stoppered quartz test tube (200mm long, 25mm inner diameter) and place it in a photolysis reaction box. The light source is a 500W xenon lamp, and the quartz tube is 10cm away from the light source; prepare a tebuconazole aqueous solution with a concentration of 10mg / L, and then add 100mg of the synthesized sample to 20mL of the tebuconazole aqueous solution; take out the solution at a certain time interval, and centrifuge it through the membrane for detection. The temperature in the photochemical reactor is (25±1)℃. Each treatment is repeated 3 times.

[0076] Comparison of photolysis efficiency using the first-order kinetic model:

[0077] In(C 0 / C t )=-kt 1 / 2

[0078] Where k is the rate constant; C 0 is the initial mass concentration of tebuconazole (mg / L); C t is the mass concentration of tebuconazole at time t (mg / L); k is the photolysis rate constant of tebuconazole (h-1); t 1 / 2 is the photolysis half-life (h).

[0079] Fig. 9 The degradation of chemical pesticide tebuconazole after Ag@ZIF-8 treatment.

[0080] Fig. 9 The photocatalytic activity of the synthesized samples for the removal of tebuconazole in water under UV irradiation was shown. In the 6-hour photolysis experiment, in the absence of a catalyst (TC), the tebuconazole technical was only slightly degraded under visible light irradiation, indicating that the photolysis effect was negligible. In the presence of the Ag@ZIF-8 nanocomposite, the degradation rate of tebuconazole increased significantly, and the residual amount of active ingredients was less than 40% after only 0.5 h of illumination, indicating that the Ag@ZIF-8 nanocomposite has a strong photocatalytic activity and helps promote the degradation of pesticides.

[0081] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a bimetallic nanomaterial Ag@AIF-8, characterized in that: The following steps are involved: mixing zinc salt and 2-methylimidazole in a solvent to obtain a precursor solution; The precursor solution is mixed with silver salt, reacted in the dark, and then reacted under light conditions to obtain the bimetallic-based nanomaterial Ag@AIF-8.

2. The preparation method according to claim 1, characterized in that: The precursor solution also contains berberine; the mass ratio of the zinc salt to berberine is 1:1-3.

3. The preparation method according to claim 1, characterized in that: The zinc salt is zinc nitrate and / or zinc chloride; the mass ratio of the zinc salt to 2-methylimidazole is 680:3285.

4. The preparation method according to claim 1, characterized in that: The solvent is methanol.

5. The preparation method according to claim 1, characterized in that: The silver salt is AgNO3; the mass ratio of the silver salt to the zinc salt is 850:

680.

6. The preparation method according to claim 1, characterized in that: The light-proof reaction time is 3-12 hours.

7. The preparation method according to claim 1, characterized in that: The reaction time under the illumination conditions is 30 min.

8. A bimetallic nanomaterial Ag@AIF-8 obtained according to the preparation method according to any one of claims 1 to 7.

9. Use of the bimetallic nanomaterial Ag@AIF-8 according to claim 8 in plant disease prevention and control.

10. Use of the bimetallic nanomaterial Ag@AIF-8 according to claim 8 in photocatalytic degradation of chemical pesticides.

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