Iron-based / sodium alginate gel nanocomposite and application thereof

Abstract

This invention discloses an iron-based / sodium alginate gel nanocomposite material and its applications, relating to the field of nanobiotechnology. The invention first adds MIL-101 nanoparticles to a magnesium sulfate solution and / or a calcium formate solution, stirring to obtain MIL-101 loaded with ionic compounds; then, sodium alginate solution is added and mixed thoroughly, followed by the addition of a calcium ion crosslinking agent for crosslinking, resulting in the iron-based / sodium alginate gel nanocomposite material. This composite material can be absorbed by plants, enabling the absorption and transport of calcium and magnesium ions within the plant, fundamentally improving the transport performance of these two elements within the plant. This can solve plant nutrient deficiency symptoms caused by calcium / magnesium deficiency, thereby improving plant yield and quality indicators. Furthermore, this invention utilizes the iron-based / sodium alginate gel nanocomposite material mixed with a surfactant to prepare an iron-based nano-fertilizer. This nano-fertilizer exhibits good permeability, spreading properties, and erosion resistance in plant leaves.

Description

Technical Field

[0001] This invention relates to the field of nanobiotechnology, and in particular to an iron-based / sodium alginate gel nanocomposite material and its applications. Background Technology

[0002] Calcium and magnesium are essential medium-level nutrients for plant growth and development. Their deficiency leads to typical physiological deficiency symptoms, severely impacting crop yield and quality. Calcium, being a non-mobile element, is transported almost exclusively through the xylem within plants, relying on transpiration pull for upward transport, resulting in a slow rate of transport. Furthermore, calcium readily forms insoluble calcium salts within plants, precipitating out and becoming fixed, thus causing calcium deficiency. While magnesium has moderate mobility within plants, its availability faces several constraints. For example, magnesium ions in the soil are easily chemically fixed or strongly antagonized by cations such as potassium and ammonium, reducing absorption efficiency. After entering the plant, some magnesium remains in vacuoles of older leaves or is stored as phytates, limiting the flux and rate of its transport to new tissues.

[0003] Nanomaterials are mainly used in agriculture for applications such as nano-fertilizers, nano-preservatives, nano-pesticides, and nano-environmental improvement. Active substances may be lost during application due to drift, runoff, evaporation, photolysis, hydrolysis, and microbial degradation. Nanomaterials with high surface area and appropriate adsorption properties can reduce runoff and lower release kinetics, thereby minimizing losses.

[0004] Metal-organic frameworks (MOFs), as emerging porous nanomaterials, represent an important branch of the nanomaterials field. Composed of organic ligands and metal ions, these ordered porous nanomaterials possess advantages such as high porosity, large specific surface area, and tunable structure, making them a highly promising nutrient delivery platform. However, most MOFs exhibit poor dispersibility in aqueous solutions, readily agglomerating and settling, making it difficult to form stable and uniform suspensions in plant irrigation and fertilization systems or foliar sprays. This property severely limits their application in agricultural fertilizers and pesticides.

[0005] Therefore, there is an urgent need to develop a composite material that can load calcium or magnesium ions and has good dispersibility using metal-organic frameworks as raw materials, so as to significantly improve the transport performance of calcium and magnesium ions in plants and thus more effectively prevent and control nutrient deficiency in plants. Summary of the Invention

[0006] To address the aforementioned limitations of existing technologies, the present invention aims to provide an iron-based / sodium alginate gel nanocomposite material and its applications. The invention first adds MIL-101 nanoparticles to a magnesium sulfate solution and / or a calcium formate solution, stirring to obtain MIL-101 loaded with ionic compounds; then, sodium alginate solution is added and mixed thoroughly, followed by the addition of a calcium ion crosslinking agent for crosslinking, resulting in the iron-based / sodium alginate gel nanocomposite material. This composite material can be absorbed by plants, enabling the absorption and transport of calcium and magnesium ions within the plant, fundamentally improving the transport performance of these two elements within the plant. This can solve plant nutrient deficiency symptoms caused by calcium / magnesium deficiency, thereby improving plant yield and quality indicators. Furthermore, the present invention utilizes the iron-based / sodium alginate gel nanocomposite material mixed with a surfactant to prepare an iron-based nano-fertilizer. This nano-fertilizer exhibits excellent permeability, spreading properties, and erosion resistance in plant leaves.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an iron-based / sodium alginate gel nanocomposite material, which is prepared by the following method: (1) Add MIL-101 nanoparticles to an ionic compound solution, stir and centrifuge, collect the precipitate after centrifugation, dry it, and obtain MIL-101 loaded with ionic compound. (2) Add sodium alginate solution to MIL-101 loaded with ionic compound, mix well, add crosslinking agent, react, and obtain iron-based / sodium alginate gel nanocomposite material. The ionic compound solution is a magnesium sulfate solution and / or a calcium formate solution.

[0008] Preferably, in step (1), the MIL-101 nanoparticles are prepared by the following method: FeCl3·6H2O solution and 2-aminoterephthalic acid solution are mixed and stirred to obtain a mixture; the mixture is placed at 100-120℃ for 15-25h, and after the reaction is completed, it is centrifuged and dried to obtain MIL-101 nanoparticles.

[0009] Furthermore, the FeCl3·6H2O solution is prepared by mixing FeCl3·6H2O and N,N-dimethylformamide, with a concentration of 0.01-1 mol / L; the 2-aminoterephthalic acid solution is prepared by mixing 2-aminoterephthalic acid and N,N-dimethylformamide, with a concentration of 0.1-1 mol / L.

[0010] Furthermore, the volume ratio of FeCl3·6H2O solution to 2-aminoterephthalic acid solution is 1:(0.5-1.5).

[0011] Furthermore, the stirring time is 20-40 minutes.

[0012] Preferably, in step (1), the size of the MIL-101 nanoparticles is 450-600 nm.

[0013] Preferably, in step (1), the concentration of the ionic compound solution is 160-245 g / L.

[0014] Preferably, in step (1), the ratio of the amount of MIL-101 nanoparticles to the ionic compound solution added is 50 g: (1-2) L.

[0015] Preferably, in step (1), the stirring speed is 300-400 rpm and the stirring time is 36-60 h.

[0016] Preferably, in step (2), the concentration of sodium alginate solution is 0.1%-2.0% (w / v).

[0017] Preferably, in step (2), the ratio of the amount of the loaded ionic compound MIL-101, the sodium alginate solution and the crosslinking agent added is (0.05-0.15) g: (15-25) mL: 0.1 mL.

[0018] Preferably, in step (2), the crosslinking agent is a calcium salt solution with a concentration of 0.05-0.15 mol / L.

[0019] Furthermore, the calcium salt is calcium chloride.

[0020] Preferably, in step (2), the reaction time is 0.5-6h.

[0021] In a second aspect, the present invention provides the application of the above-mentioned iron-based / sodium alginate gel nanocomposite material in the preparation of iron-based nanofertilizers.

[0022] In a third aspect, the present invention provides an iron-based nano-fertilizer, the iron-based nano-fertilizer comprising the above-mentioned iron-based / sodium alginate gel nanocomposite material and a surfactant additive.

[0023] Preferably, the surfactant is a polyether-modified trisiloxane.

[0024] Preferably, the mass ratio of the iron-based / sodium alginate gel nanocomposite material to the surfactant is (90-110):1.

[0025] In a fourth aspect, the present invention provides the application of the above-mentioned iron-based nano-fertilizer in any one of the following (1)-(4): (1) Improve the transport performance of calcium or magnesium elements in plants; (2) Prepare products that improve the transport performance of calcium or magnesium elements in plants; (3) Prevention and treatment of plant nutrient deficiency; (4) Prepare products for the prevention and treatment of plant nutrient deficiency.

[0026] The beneficial effects of this invention are: 1. In this invention, MIL-101 nanoparticles are first added to magnesium sulfate solution and / or calcium formate solution and stirred to obtain MIL-101 loaded with ionic compounds; then sodium alginate solution is added and mixed well, and calcium ion crosslinking agent is added to crosslink to obtain iron-based / sodium alginate gel nanocomposite material.

[0027] The iron-based / sodium alginate gel nanocomposite material prepared in this invention can promote the absorption and transport of calcium and magnesium ions in plants, fundamentally improving the transport performance of these two elements and solving plant nutrient deficiency symptoms caused by calcium and magnesium deficiencies. The pH-controlled release system enables the slow release of calcium and magnesium. These two aspects work synergistically to ultimately improve the yield and quality indicators of plants. 2. This invention utilizes a calcium ion crosslinking agent to crosslink sodium alginate on the surface of an iron-based MOF, forming a stable hydrogel layer. This hydrogel layer can improve the water solubility and dispersion stability of MIL-101 nanoparticles in water, effectively avoiding the problem of easy aggregation and sedimentation of MIL-101 nanoparticles in aqueous solutions, thus ensuring its applicability.

[0028] 3. This invention also utilizes an iron-based / sodium alginate gel nanocomposite material mixed with a surfactant to prepare an iron-based compound fertilizer with excellent permeability. The addition of the surfactant reduces the surface tension of the nano-fertilizer liquid on the leaves, allowing it to spread and wet quickly on the plant leaves and enhancing penetration, thus promoting the efficient absorption of calcium and magnesium elements by the leaves. Furthermore, it has chelating and complexing effects on the trace element iron and the medium elements calcium and magnesium, further promoting the efficient absorption of the nano-fertilizer by vegetables. Attached Figure Description

[0029] Figure 1 : A physical image of the MIL-101 nanoparticles prepared in Example 1; Figure 2 Scanning electron microscope image of MIL-101 nanoparticles prepared in Example 1; Figure 3 Transmission electron microscopy image of MIL-101 nanoparticles prepared in Example 1; Figure 4 Nitrogen adsorption curve of MIL-101 nanoparticles prepared in Example 1; Figure 5 TEM image of the iron-based / sodium alginate gel nanocomposite material prepared in Example 1; Figure 6 Figure 1 shows the average number of leaves of Swiss chard after treatment with different concentrations of iron-based / sodium alginate gel nanocomposite materials. Figure 7 Figure 1 shows the average plant height of Swiss chard after treatment with different concentrations of iron-based / sodium alginate gel nanocomposite materials. Figure 8 In Experiment Example 2, the fluorescence distribution of DOX@iron-based sodium alginate solution on the leaves of Swiss chard; Figure 9 In Experiment 3, the penetration effect of iron-based nano-fertilizer solution containing polyether-modified trisiloxane and iron-based nano-fertilizer solution without polyether-modified trisiloxane on Swiss chard leaves is shown in the figure. Figure 10 Example 3 shows the spreading effect of iron-based nano-fertilizer solution containing polyether-modified trisiloxane and iron-based nano-fertilizer solution without polyether-modified trisiloxane on Swiss chard leaves. Figure 11 Example 4: The penetration effect of the doxorubicin-labeled iron-based nano-fertilizer solution on the leaves of Swiss chard after rinsing; Figure 12 : In Experiment 5, the spinach quality indexes corresponding to different treatment groups are shown in the graph; Figure 13 : In Experiment 5, the quality index of Swiss chard corresponding to different treatment groups is shown in the figure. Detailed Implementation

[0030] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0031] As described in the background section, calcium has poor mobility within plants, while magnesium is easily chemically fixed, antagonized, or aged. These characteristics result in insufficient effective transport of calcium and magnesium within plants, leading to nutrient deficiencies. Furthermore, although MOFs possess advantages such as high porosity, large specific surface area, and tunable structure, they exhibit poor dispersibility in aqueous solutions, easily agglomerating and settling, making it difficult to form stable and uniform suspensions in plant irrigation and fertilization systems or foliar sprays.

[0032] Based on this, the present invention provides an iron-based / sodium alginate gel nanocomposite material and an iron-based nano-fertilizer prepared using the composite material. The iron-based / sodium alginate gel nanocomposite material is prepared by the following method: MIL-101 nanoparticles are added to a calcium formate / magnesium sulfate solution, stirred, and centrifuged to obtain MIL-101 loaded with ionic compounds; then, sodium alginate solution is added to the loaded MIL-101, mixed, and a calcium ion crosslinking agent is added. After a crosslinking reaction, the iron-based / sodium alginate gel nanocomposite material is obtained.

[0033] First, this invention utilizes MIL-101 nanoparticles to load calcium formate / magnesium sulfate. While MOF materials primarily rely on physical adsorption or encapsulation for molecule loading, ion loading relies mainly on electrostatic interactions and framework bonding. The ability of a MOF material to load ions, and the loading effect, is primarily determined by charge matching, functional sites, and size sieving effects. Specifically, for an MOF material to load ions, it must carry an opposite charge to the target ion to achieve electrostatic adsorption. The metal sites of the MOF material can act as Lewis acid sites, binding with anions or electron-rich groups. The ion size must be large enough to pass through the MOF's pores; otherwise, even with electrostatic attraction, it cannot enter the MOF's pores. Furthermore, the hydration energy, dehydration effect, hydrated ion size, and specific interactions with the framework also affect the loading difficulty. Thus, MOF molecule loading is a relatively non-specific physical process, while ion loading is a more selective process dominated by electrostatics, coordination, and steric effects. Designing MOFs for ion loading requires comprehensive consideration of the framework's charge state, pore size, functional sites, and the target ion's hydration energy, hydration radius, and chemical properties. Therefore, not all MOF materials can be loaded with calcium / magnesium ions. Based on charge matching, functional sites, pore size and the properties of the target ions, the inventors screened MIL-101 as a carrier to achieve efficient loading of calcium and magnesium ions.

[0034] The iron-based / sodium alginate gel nanocomposite material prepared by this invention can promote the transport of calcium / magnesium ions and also has sustained-release properties. Specifically: This composite material improves transport performance through a biomimetic mechanism and continuous supply. Alginate protects calcium / magnesium ions through chelation, preventing them from precipitating and becoming immobilized; the gel structure of the composite material, similar to plant cell wall components, facilitates ion exchange.

[0035] This composite material has a three-layer functional structure. Its core is an ion-loaded MIL-101 layer, the middle layer is a sodium alginate layer, and the outermost layer is a calcium alginate hydrogel network formed by calcium ion crosslinking. The sustained-release mechanism of this structure is mainly based on a two-layer regulation of spatial confinement, physical structural barriers, diffusion pathways, and chemical interactions. Specifically, spatial confinement: the nanopores of MIL-101 spatially confine calcium / magnesium ions, requiring the ions to overcome the physical resistance of the pores to diffuse. Structural barriers: sodium alginate reacts with calcium... 2+A characteristic "egg-box" structure is formed, constituting a dense physical hydrogel network. This network acts as the first controlled-release barrier: after ions are released from the MOF, they must pass through this viscous gel layer to enter the external environment, significantly slowing down the water permeation rate and the outward diffusion of ions. The diffusion path and chemical interactions are both regulated: the micropores of the MOF and the mesopores / macropores of the gel form a hierarchical pore structure. Ca / Mg elements must traverse a complex path from MOF pores to the MOF surface, then to the gel network, and finally to the external environment, significantly increasing the tortuosity of diffusion. Sodium alginate contains a large number of carboxyl groups, which can undergo ion exchange or complexation with trace elements (metal ions). 2+ After cross-linking, other external cations (such as K) + Na + (Or other ions in the soil) may gradually displace the Ca in the calcium alginate gel through ion exchange mechanisms. 2+ Simultaneously, the gel network gradually loosens and internal trace elements are slowly released.

[0036] This invention also utilizes an iron-based / sodium alginate gel nanocomposite material mixed with a surfactant to prepare an iron-based compound fertilizer with excellent permeability. The addition of the surfactant reduces the surface tension of the nano-fertilizer liquid on the leaves, allowing it to spread and wet quickly on the plant leaves and enhance penetration, thus promoting the efficient absorption of calcium and magnesium elements by the leaves.

[0037] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0038] The experimental materials used in the embodiments of this invention are all conventional experimental materials in the art and can be purchased through commercial channels.

[0039] Example 1: Preparation of iron-based / sodium alginate gel nanocomposite material (1) Dissolve 4.0218g FeCl3·6H2O in 60mL N,N-dimethylformamide and sonicate until fully dissolved to obtain FeCl3·6H2O solution; dissolve 1.3476g 2-aminoterephthalic acid in 60mL N,N-dimethylformamide and sonicate until fully dissolved to obtain 2-aminoterephthalic acid solution; FeCl3·6H2O solution and 2-aminoterephthalic acid solution were mixed at a volume ratio of 1:1 and stirred at 350 rpm for 30 min to obtain a mixture. The mixture was transferred to a high-pressure reactor and reacted at 110 °C for 20 h. After the reaction, the product was taken out and washed with N,N-dimethylformamide and ethanol in sequence, centrifuged at 9000 r / min for 5 min, and then freeze-dried under vacuum to obtain MIL-101 nanoparticles. (2) Add 50g of MIL-101 nanoparticles to 1.8L of calcium formate solution with a concentration of 161g / L, sonicate for 5min to fully disperse the MIL-101 nanoparticles, stir at 350rpm for 48h at room temperature, centrifuge at 4℃ and 9000r / min for 5min after stirring, collect the precipitate after centrifugation, freeze dry under vacuum at -50℃ for 48h to obtain MIL-101 loaded with ionic compound, denoted as Ca@MIL-101; (3) Take 0.1g Ca@MIL-101, add 20 mL of sodium alginate solution with a concentration of 0.1% (w / v), mix well, add 0.1 mL of calcium chloride solution with a concentration of 0.1 mol / L (crosslinking agent), and react at room temperature for 2 h. After the reaction, iron-based / sodium alginate gel nanocomposite material is obtained.

[0040] The structure of the MIL-101 nanoparticles obtained in step (1) was characterized, such as... Figures 1-5 As shown. Figure 1 Here is a physical image of MIL-101 nanoparticles, obtained through... Figure 1 It can be seen that the prepared MIL-101 nanoparticles are brown. Figure 2 and Figure 3 Here is an electron microscope image of MIL-101, obtained through... Figure 2-3 It can be seen that MIL-101 consists of octahedral particles with an average particle size of 500 nm. Furthermore, the adsorption performance of MIL-101 was tested, and the results are as follows: Figure 4 As shown. By Figure 4 It can be seen that MIL-101 is a microporous material with a relatively uniform pore size distribution. (From...) Figure 5 It can be seen that the structure of the iron-based / sodium alginate gel nanocomposite is similar to that of the MIL-101 nanoparticles, with a cross-linked layer formed on its exterior.

[0041] In addition, the calcium loading rate of Ca@MIL-101 was calculated, and the calcium loading rate of the prepared Ca@MIL-101 was 61.73%.

[0042] The formula for calculating the calcium loading rate is: Calcium loading rate (%) = [(C0V0-C1V1) / C0V0] × 100%; In the formula, C0 is the initial calcium ion concentration; V0 is the initial solution volume; C1 is the residual calcium ion concentration in the supernatant after adsorption; and V1 is the supernatant volume.

[0043] Example 2: Preparation of iron-based / sodium alginate gel nanocomposite materials (1) MIL-101 nanoparticles were prepared according to the method of Example 1. 1.8 L of magnesium sulfate solution with a concentration of 242 g / L was taken, 50 g of MIL-101 nanoparticles were added, and the mixture was sonicated for 5 min to fully disperse the MIL-101 nanoparticles. The mixture was stirred at 350 rpm for 48 h at room temperature. After stirring, the mixture was centrifuged at 4 °C and 9000 r / min for 5 min. The precipitate after centrifugation was collected and freeze-dried under vacuum at -50 °C for 48 h to obtain MIL-101 loaded with ionic compounds, denoted as Mg@MIL-101. (2) Take 0.1g Mg@MIL-101, add 20 mL of sodium alginate solution with a concentration of 0.1%, mix well, add 0.1 mL of calcium chloride solution with a concentration of 0.1 mol / L (crosslinking agent), and react at room temperature for 2 h. After the reaction, iron-based / sodium alginate gel nanocomposite material is obtained.

[0044] The calcium loading rate of Mg@MIL-101 was calculated. The calculated magnesium loading rate in the prepared Mg@MIL-101 was 45.31%.

[0045] The formula for calculating the magnesium loading rate is: Magnesium loading rate (%) = [(C0V0-C1V1) / C0V0] × 100%; In the formula, C0 is the initial magnesium ion concentration; V0 is the initial solution volume; C1 is the residual magnesium ion concentration in the supernatant after adsorption; and V1 is the supernatant volume.

[0046] Example 3: Iron-based compound fertilizer was prepared by mixing the iron-based / sodium alginate gel nanocomposite material from Example 1 and polyether-modified trisiloxane at a mass ratio of 100:1.

[0047] Experimental Example 1: Growth Promotion Experiment This experiment used Swiss chard as the experimental plant. Details are as follows: (1) The iron-based / sodium alginate gel nanocomposites prepared in Example 1 and Example 2 were mixed with deionized water to prepare iron-based / sodium alginate gel nanocomposite solutions with concentrations of 50 mg / L, 100 mg / L and 200 mg / L. Water was set up as a control group.

[0048] (2) When the Swiss chard has grown to three leaves, the iron-based / sodium alginate gel nanocomposite solution corresponding to Example 1 was sprayed using an ultra-low volume sprayer. The average number of leaves at different time points was measured, and the results are as follows: Figure 6 As shown.

[0049] The term "leaf count" refers to the total number of fully unfolded green leaves (excluding cotyledons, withered leaves, and yellowed leaves) on the plant, with fixed-point and fixed-plant observations. Ten representative plants were selected from each group, and the leaves were counted manually one by one, with the average value taken. At least three replicates were set up, and the statistics were collected at fixed time points (e.g., 9-10 am).

[0050] (3) Take another Swiss chard and cultivate it until it has three leaves. Spray it with the iron-based / sodium alginate gel nanocomposite solution corresponding to Example 2. Measure the plant height at different time points and take the average value. The results are as follows: Figure 7 As shown.

[0051] Depend on Figure 6 and Figure 7 It can be seen that the average plant height of the 50 mg / L and 100 mg / L treatment groups was higher and the number of leaves increased faster than that of the water control group. The 100 mg / L treatment group grew better than the 50 mg / L treatment group, while the growth of the 200 mg / L treatment group was not much different from that of the water control group. Therefore, 100 mg / L is the appropriate concentration.

[0052] Experimental Example 2: Transmission Performance (1) Weigh 8 mg of doxorubicin hydrochloride (DOX) into 80 mL of purified water, dissolve it evenly to obtain DOX solution; prepare MIL-101 nanoparticles according to the method of Example 1, add 50 mg of MIL-101 nanoparticles to DOX solution, stir magnetically for 24 h in the dark, collect the precipitate after centrifugation, and obtain DOX@MIL-10. Then take 0.1g of DOX@MIL-10, add 20mL of 0.1% (w / v) sodium alginate solution, mix well, then add 0.1mL of 0.1mol / L calcium chloride solution, react at room temperature for 2h to obtain DOX@iron-based sodium alginate gel; add 20mL of purified water and mix well to obtain DOX@iron-based sodium alginate solution, for later use; (2) DOX@iron-based sodium alginate solution was added dropwise to the middle of the main vein and petiole of *Salvia splendens* leaves, respectively. After standing for 1 h, the leaves were cut and placed in plant tissue fixative. After safranin-fast green staining, the sections were processed using paraffin embedding technology. Fluorescence and white light photography were performed under a fluorescence microscope. By analyzing the fluorescence range and area of ​​the sections, the biodistribution of the nanocarrier in the plant tissue was obtained. The results are as follows: Figure 8 As shown.

[0053] Depend on Figure 8 It can be seen that the red fluorescence in the leaf tissue is mainly distributed between the mesophyll cells, and is most densely distributed and has the strongest fluorescence intensity in the vascular bundle tissue cells. Clear fluorescence distribution can also be observed in the petiole, indicating that the iron-based sodium alginate carrier can be absorbed by the plant leaves and transported through the vascular bundle.

[0054] Experimental Example 3: Penetration and Spreading Performance 1. Permeability: (1) The iron-based nano-fertilizer prepared in Example 3 was mixed with deionized water to prepare an iron-based nano-fertilizer solution with a concentration of 200 mg / L; Doxorubicin hydrochloride and deionized water were mixed to prepare a doxorubicin solution with a concentration of 2 g / L; 5 mL of iron-based nano-fertilizer solution was added to the doxorubicin solution and stirred to perform adsorption labeling to obtain a doxorubicin-labeled iron-based nano-fertilizer solution. Another control group was set up without the addition of polyether-modified trisiloxane. Specifically, the iron-based / sodium alginate gel nanocomposite material prepared in Example 1 was mixed with deionized water to prepare an iron-based nano-fertilizer solution with a concentration of 200 mg / L. The iron-based nano-fertilizer solution was added to the doxorubicin solution and stirred to perform adsorption labeling to obtain a doxorubicin-labeled iron-based nano-fertilizer solution. (2) Take fresh Swiss chard leaves and add 10 μL, 100 μL, and 200 μL of doxorubicin-labeled iron-based nano-fertilizer solution and 10 μL of control solution to the leaves respectively. After the leaves are naturally dried, observe them under a super depth-of-field microscope to check whether nano-fertilizer accumulation can be observed on the leaves, and take pictures to record the results. Figure 9 As shown; Depend on Figure 9 It can be seen that when 10 μL of iron-based nano-fertilizer solution without polyether-modified trisiloxane is added to Swiss chard leaves, the droplets do not spread easily, and under a super depth-of-field microscope, there is obvious accumulation with clear droplet boundaries. When 10 μL, 100 μL, and 200 μL of iron-based nano-fertilizer solution containing polyether-modified trisiloxane are added to Swiss chard leaves, the droplets spread rapidly and dry quickly. Under a super depth-of-field microscope, no obvious accumulation or droplet boundaries are observed; a small amount of accumulation was found on the vegetable leaves in the 100 μL treatment group, while a large amount of accumulation was found in the 200 μL treatment group. Therefore, the addition of the surfactant polyether-modified trisiloxane improves the penetration effect of the iron-based / sodium alginate gel nanocomposite material.

[0055] 2. Spreading performance: Leaves of spinach and Swiss chard were taken separately, and one drop each of doxorubicin-labeled iron-based nano-fertilizer solution containing polyether-modified trisiloxane and doxorubicin-labeled iron-based nano-fertilizer solution without polyether-modified trisiloxane was added to each. The distribution of fluorescent nano-fertilizer on the leaf surface was observed using a small animal imaging system. The results are as follows: Figure 10 As shown.

[0056] Depend on Figure 10It can be seen that on the right leaf, the nano-fertilizer droplets without polyether-modified trisiloxane aggregated but did not disperse, showing no obvious spreading phenomenon. In contrast, on the left leaf, the nano-fertilizer droplets with polyether-modified trisiloxane spread rapidly over most of the leaf. This indicates that the addition of the surfactant polyether-modified trisiloxane improved the spreading effect of the nano-fertilizer.

[0057] Test Example 4: Erosion Resistance In Experiment 3, scallop leaves with 100 μL and 200 μL of doxorubicin-labeled iron-based nano-fertilizer solution were selected for rinsing tests.

[0058] Artificial natural rainfall was used to wash the leaves of Swiss chard. The water volume and washing time were consistent across all groups. The wash liquid from each group was collected and centrifuged. The washed leaves were then observed under a super-depth-of-field microscope to check for the presence of nano-fertilizer accumulation. The results were photographed and recorded. Figure 11 As shown.

[0059] Depend on Figure 11 It can be seen that the original accumulation was washed away by the water flow, but it still adhered to the surface. No obvious brown solid nano-fertilizer was observed in the collected flushing liquid. The precipitate mass after centrifugation was extremely small, indicating that the foliar fertilizer has good resistance to rainwater erosion and has a high retention rate.

[0060] Experimental Example 5: Growth-promoting performance This experiment used spinach and Swiss chard as experimental subjects and cultivated them in a greenhouse.

[0061] This experiment consisted of 5 treatment groups, as follows: T1: Iron-based / sodium alginate gel nanocomposite material prepared in Example 1; T2: Iron-based / sodium alginate gel nanocomposite material prepared in Example 2; T3: MIL-101 / sodium alginate gel composite material, which is prepared by the following method: Take 0.1g of MIL-101 nanoparticles, add 20 mL of 0.1% sodium alginate solution, mix well, add 0.1 mL of 0.1mol / L calcium chloride solution (crosslinking agent), react at room temperature for 2 h, and after the reaction, the MIL-101 / sodium alginate gel composite material is obtained; T4: Calcium formate; T5: Magnesium sulfate.

[0062] Spinach and Swiss chard germinated 3-4 days after sowing. When the vegetables reached the stage of four leaves and one bud, they were sprayed with a 100 mg / L nano-fertilizer solution. The nano-fertilizer was made by mixing materials from different treatment groups and polyether-modified trisiloxane (surfactant) at a mass ratio of 100:1. An equal volume of water was sprayed as a control group (CK).

[0063] Once the vegetables reached maturity, the yield indicators (plant height, number of leaves, fresh weight, dry weight) and quality indicators (soluble protein content, nitrate content, chlorophyll content, soluble sugar content, vitamin C content) of Swiss chard and spinach were tested. The results are shown in Tables 1-2 and 1-3. Figure 12-13 As shown. Among them, Yield indicators: Plant height was obtained by in-situ field measurement; fresh weight of vegetables was measured, and three plants were taken from each treatment and each replicate to measure the fresh weight and take the average value; a portion of fresh sample was divided into quarters and blanched in an oven at 105℃ for 30 min, and then transferred to an oven at 75℃ to dry to constant weight and weighed.

[0064] Quality indicators: Protein content of vegetables was determined by Coomassie brilliant blue method, nitrate content was measured by ultraviolet spectrophotometry, chlorophyll content was determined by high performance liquid chromatography, soluble sugar content was determined by anthrone method, and vitamin C content was determined by 2,6-dichlorophenolindophenol titration method.

[0065] Table 1. Quality Indicators of Spinach Note: After the data in the same column, different letters indicate significant differences between treatments. P <0.05), the same applies below.

[0066] Table 2. Quality index data of Swiss chard As shown in Tables 1 and 2, regarding yield indicators, after applying the iron-based / sodium alginate gel nanocomposites prepared in Examples 1 and 2 of this invention (T1 and T2), the plant height, number of leaves, fresh weight, and dry weight of Swiss chard and spinach were significantly higher than those obtained using only the MIL-101 / sodium alginate gel nanocomposites, calcium formate, and magnesium sulfate (T3-T5). Therefore, the iron-based / sodium alginate gel nanocomposites of this invention have a significant effect on improving the plant height, fresh weight, and dry weight of vegetables.

[0067] Depend on Figures 12-13It can be seen that, in terms of quality indicators, compared with the CK control group, groups T1 and T2 significantly promoted chlorophyll, vitamin C, soluble protein, and soluble sugar in vegetables (P < 0.05), and significantly reduced nitrate content in vegetables (P < 0.05), proving that nanocarriers can load mineral elements into vegetables and be effectively utilized by them, thereby improving the nutritional structure of vegetables. Compared with the calcium formate treatment group T4, T1 significantly increased chlorophyll and vitamin C, and significantly reduced nitrate. For Swiss chard, T1 significantly increased soluble sugar and soluble protein compared with T4. Compared with the magnesium sulfate treatment group T5, T2 significantly increased chlorophyll, soluble sugar, and vitamin C, and significantly reduced nitrate, proving that nano-fertilizer can further enhance fertilizer efficiency. Compared with direct spraying, nano-loading has a better effect.

[0068] Test Example 6: Sustained-release performance To simulate the nutrient requirements of plants at different growth stages and under different soil conditions, buffer solutions with different pH values ​​(4.0, 7.4, and 10.0) were prepared. The buffer solution with pH 4.0 was a citrate-sodium citrate buffer solution; the buffer solution with pH 7.4 was a phosphate buffer solution (PBS); and the buffer solution with pH 10.0 was a sodium carbonate-sodium bicarbonate buffer solution.

[0069] The iron-based / sodium alginate gel nanocomposite material prepared in Example 1 was placed in a dialysis bag and immersed in 40 mL of buffer solutions with different pH values. The mixture was then magnetically stirred to ensure uniform dispersion. The dialysis bag was placed in a constant-temperature shaking incubator at a temperature of 25 ± 1 °C and a shaking rate of 110 rpm to simulate a natural environment. At different time points (0 h, 2 h, 4 h, 8 h, 12 h, 24 h, 48 h, 72 h, 7 d, 14 d, 21 d, and 40 d), 3 mL of supernatant was taken from each system, and an equal volume of buffer solution of the same pH was simultaneously added to maintain a constant external liquid volume. The concentration of calcium ions in the supernatant was determined by inductively coupled plasma atomic emission spectrometry, and the cumulative release rate (%) at each time point was calculated. The results are shown in Table 3.

[0070] The formula for calculating the cumulative release rate (%) is: ; In the formula, V0 is the volume of the buffer solution, mL; Cn is the calcium ion concentration measured at the nth sampling, mg / mL; i is the number of samplings, i≤n, Ci is the calcium ion concentration measured at the ith sampling, mg / mL; M is the mass of calcium ions in the iron-based / sodium alginate gel nanocomposite material, mg.

[0071] Table 3. Cumulative release rate at different time points under different pH values. As shown in Table 3, the release of calcium ions from the iron-based / sodium alginate gel nanocomposite exhibits a slow-release characteristic that gradually increases over time at different pH values ​​(4.0, 7.4, and 10.0). This demonstrates that the iron-based / sodium alginate gel nanocomposite can achieve slow-release of calcium ions to meet the nutritional needs of plants throughout their entire growth cycle.

[0072] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An iron-based / sodium alginate gel nanocomposite material, characterized in that, The iron-based / sodium alginate gel nanocomposite material was prepared by the following method: (1) Add MIL-101 nanoparticles to an ionic compound solution, stir and centrifuge, collect the precipitate after centrifugation, dry it, and obtain MIL-101 loaded with ionic compound. (2) Add sodium alginate solution to MIL-101 loaded with ionic compound, mix well, add crosslinking agent, react, and obtain iron-based / sodium alginate gel nanocomposite material. The ionic compound solution is a magnesium sulfate solution and / or a calcium formate solution.

2. The iron-based / sodium alginate gel nanocomposite material as described in claim 1, characterized in that, In step (1), the MIL-101 nanoparticles are prepared by the following method: FeCl3·6H2O solution and 2-aminoterephthalic acid solution were mixed and stirred to obtain a mixed solution. The mixed solution was placed at 100-120℃ and reacted for 15-25 h. After the reaction was completed, MIL-101 nanoparticles were obtained by centrifugation and drying.

3. The iron-based / sodium alginate gel nanocomposite material as described in claim 2, characterized in that, The concentration of FeCl3·6H2O solution is 0.01-1 mol / L; the concentration of 2-aminoterephthalic acid solution is 0.1-1 mol / L; the volume ratio of FeCl3·6H2O solution to 2-aminoterephthalic acid solution is 1:(0.5-1.5).

4. The iron-based / sodium alginate gel nanocomposite material as described in claim 1, characterized in that, In step (1), the concentration of the ionic compound solution is 160-245 g / L, the ratio of MIL-101 nanoparticles to ionic compound solution is 50 g: (1-2) L, the stirring speed is 300-400 rpm, and the stirring time is 36-60 h.

5. The iron-based / sodium alginate gel nanocomposite material as described in claim 1, characterized in that, In step (2), the concentration of sodium alginate solution is 0.1%-2.0%; the crosslinking agent is a calcium salt solution with a concentration of 0.05-0.15 mol / L; The ratio of the amount of MIL-101 loaded with ionic compounds, sodium alginate solution and crosslinking agent added is (0.05-0.15) g : (15-25) mL : 0.1 mL.

6. The iron-based / sodium alginate gel nanocomposite material as described in claim 1, characterized in that, In step (2), the reaction time is 0.5-6 h.

7. The application of the iron-based / sodium alginate gel nanocomposite material according to any one of claims 1-6 in the preparation of iron-based nano-fertilizer.

8. An iron-based nano-fertilizer, characterized in that, The iron-based nano-fertilizer includes the iron-based / sodium alginate gel nanocomposite material and the surfactant as described in any one of claims 1-6.

9. The iron-based nano-fertilizer as described in claim 8, characterized in that, The surfactant is a polyether-modified trisiloxane, and the mass ratio of the iron-based / sodium alginate gel nanocomposite material to the surfactant is (90-110):

1.

10. The use of the iron-based nano-fertilizer according to claim 8 or 9 in any one of the following (1)-(4): (1) Improve the transport performance of calcium or magnesium elements in plants; (2) To prepare products that improve the transport performance of calcium or magnesium elements in plants; (3) Prevention and treatment of plant nutrient deficiency; (4) Prepare products for the prevention and treatment of plant nutrient deficiency.

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