A porous silica-based alginate nanocomposite, a preparation method and applications thereof

Abstract

The application discloses a kind of porous silica alginate nanocomposites (Alg-P-NSA), preparation method and application, the porous silica alginate nanocomposite method includes the following weight percentage range components: alginate (Alg): 0.5-40%;Porous nanosilica (P-NSA): 31-98%;Metal element: 0.5-24%, moisture (H2O): 1-5%.Alg-P-NSA of the application can enter plant leaf stomata, be absorbed and utilized by plant, and can also be slowly and stably released, and the application effect on leaf mustard is good, solves the problem that calcium alginate cannot be absorbed by plant, and plays a slow-release role.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of nanotechnology and seaweed applications, in particular to a porous silica based calcium alginate nanocomposite (Alg-P-NSA), a preparation method and applications thereof. BACKGROUND

[0002] Nanofertilizers, as a nutrient carrier, provide nutrients to the plant system for a long time without causing harm to the environment through targeted fertilization or slow / controlled release mechanisms, which can not only improve nutrient and utilization efficiency, but also reduce the frequency of chemical fertilizer use, thereby maximizing the potential negative effects associated with soil pollution caused by excessive use of chemical fertilizers. Nanotechnology has the potential to precisely deliver agricultural chemicals to improve disease resistance, plant growth, and nutrient utilization. Nanotechnology is a promising technology that can inhibit the release of chemicals under controlled conditions, reduce current application rates, and improve the efficiency of fertilizers or pesticides. In addition, there are many nanomaterials, including polymer nanoparticles, zinc oxide nanoparticles, iron oxide nanoparticles, gold nanoparticles, and silver nanoparticles, which can be easily synthesized and used as fertilizers or pesticides. Therefore, nanotechnology has great potential for the development of sustainable agriculture.

[0003] Nanosilica is an inorganic chemical material commonly known as white carbon black. Due to its ultra-fine nanoscale size ranging from 1 to 100 nm, it has many unique properties, such as optical properties against ultraviolet light, which can improve the anti-aging, strength, and chemical resistance of other materials. It has a very wide range of applications. Nanoscale silica is an amorphous white powder that is non-toxic, odorless, and non-polluting, with a spherical microstructure in a flocculent and reticular quasi-particle structure, a molecular formula of SiO2, and insoluble in water.

[0004] The calcium content in plants is 0.1-0.5%, most of which exists in the cell wall. Calcium plays a very important role in plants: stabilizing cell membranes, calcium can bridge the phosphate, phosphate ester on the surface of biological membranes with the carboxyl group of proteins, thereby stabilizing the structure of biological membranes and maintaining the function of selective absorption of cell membranes. If calcium is deficient, or Ca 2+ is replaced by heavy metal ions or protons, cytoplasmic extravasation and decreased selective absorption capacity can occur. In severe cases of calcium deficiency, the structure of the protoplast membrane is completely disintegrated. Stabilizing cell walls, there is a rich Ca 2+At the calcium binding site, the vast majority of calcium binds to pectin in the cell wall, maintaining cell wall structure and regulating membrane permeability and related physiological and biochemical processes. In the storage tissues of apple fruits, up to 90% of the total calcium is bound to the cell wall. Calcium deficiency hinders cell wall synthesis, suppressing cell division in meristematic tissues such as shoot and root tips. Simultaneously, calcium deficiency causes cell wall disintegration, making cells more susceptible to pathogen infection. Calcium also participates in information transmission; when a signal reaches the cell, the plasma membrane binds to calcium. 2+ Permeability increases instantaneously. When Ca in the cytoplasm... 2+ When its concentration increases to a certain threshold, it binds to a calmodulin (CAM) to form a Ca-CAM complex, activating CAM. This activated CAM can further activate various key enzymes in the plant, such as phospholipases, NAD kinases, and Ca2+. 2+ ATPases and other enzymes induce physiological responses in cells corresponding to the signals, such as cell division and substance synthesis. This affects crop quality; a higher calcium content in mature fruits can effectively prevent rotting during post-harvest storage, extend the storage period, and improve the preservation quality of the fruit.

[0005] Alginic acid (ALA) is a long-chain polymer composed of (1→4)-β-crosslinked D-mannuronic acid and (1→4)-α-crosslinked guluronic acid, and is a natural polysaccharide. In its natural state, ALA exists in the cytoplasm, where it strengthens the cell wall. The main function of alginate in plants is to stimulate the activity of defense enzyme systems, enhancing their resistance to drought, cold, and salinity. Appropriate use of alginate can regulate plant growth, promote flower bud differentiation, increase fruit set, and reduce fruit drop and cracking. Furthermore, alginate can promote root development and improve the absorption and utilization of soil nutrients and water. Appropriate application of alginate to plants can increase chlorophyll content, improve photosynthetic efficiency, significantly increase yield, and improve quality.

[0006] Calcium alginate is a powder, white to light yellow in color, odorless and tasteless, insoluble in water and organic solvents, and sparingly soluble in ethanol. Therefore, calcium alginate cannot be directly absorbed and utilized by plants.

[0007] Currently, there are no reports on how to comprehensively utilize nanotechnology, alginate, and calcium ions. The purpose of this invention is to develop porous silica-based alginate nanocomposite materials containing trace elements, in order to combine the advantages of each material and thus improve the growth and development of crops. Summary of the Invention

[0008] In view of the above, the present application provides a porous silica-based calcium alginate nanocomposite, a preparation method and application thereof. The nanocomposite can enter the stomata of plant leaves, be absorbed by plants, and be slowly and stably released. The application effect is good on cauliflowers and leaf mustards, and the problem that calcium alginate cannot be absorbed by plants is solved, and a slow-release effect is also achieved.

[0009] More specifically, according to an aspect of the present application, there is provided a porous silica-based alginate nanocomposite, comprising the following components in the following weight percentage ranges:

[0010] alginate (Alg): 0.5-40%; porous nanosilica (P-NSA): 31-98%; metal element: 0.5-24%; and water (H2O): 1-5%.

[0011] According to an embodiment of the present application, the nanocomposite comprises the following components in the following weight percentage ranges:

[0012] alginate: 10-20%; porous nanosilica: 62-83%; metal element: 6-15%; and water: 1-3%.

[0013] According to an embodiment of the present application, the porous nanosilica is microporous silica spheres or mesoporous silica spheres.

[0014] According to an embodiment of the present application, the metal comprises calcium.

[0015] According to another aspect of the present application, there is provided a preparation method of a porous silica-based alginate nanocomposite, comprising:

[0016] 1) dispersing microporous silica spheres or mesoporous silica spheres in a solution containing sodium alginate;

[0017] 2) slowly adding a salt solution of the metal element, and stirring at room temperature for 10-200 min;

[0018] 3) adding n-hexane, and stirring for 1-3 h;

[0019] 4) filtering the obtained solution, washing with ethanol, and then centrifuging; and

[0020] 5) drying the precipitate obtained by centrifugation at 60-105°C for 4-7 h to obtain Alg-P-NSA.

[0021] According to an embodiment of the present application, the salt solution of the metal element is selected from saturated solutions of chloride salts and nitrate salts, and the metal is preferably calcium.

[0022] According to the embodiment of the present application, wherein in step 1), the concentration of sodium alginate solution is 0.025%-2.5%; the concentration of microporous silica spheres or mesoporous silica spheres in the dispersion is 60-100 g / L.

[0023] According to the embodiment of the present application, wherein in step 2), the amount of the salt solution of the metal element is 10-20% of the amount of the sodium alginate solution.

[0024] According to the embodiment of the present application, wherein in step 2), the amount of the n-hexane is 20-60% of the amount of the salt solution of the metal element.

[0025] According to another aspect of the present application, the porous silica-based sodium alginate nanocomposite is applied in foliar fertilization, for example, as a foliar fertilizer, applied to the leaves of mustard and cauliflower, etc.

[0026] The Alg-P-NSA of the present application can be sprayed on plants, can enter the stomata of leaves, and there is no retention on the surface of leaves. For example, 28 days after spraying, compared with the control, the treated plant leaves are wide, thick, green, the plant grows well, the plant is high and the stem is thick, and has obvious slow-release effect. The essential reason is that the Alg-P-NSA meets the different time requirements of crops for medium and trace elements by controlling the release time and speed of medium and trace elements, thereby improving the health of crops and the quality of agricultural products, and providing technical support for reducing the application amount of chemical pesticides. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The figure is a chart of the influence of different forms of calcium according to the embodiment of the present application on the physiological indicators of mustard leaves (drought stress from the 21st to the 28th day); and

[0028] Figure 2 The figure is a chart of the influence of different forms of calcium according to the embodiment of the present application on the physiological indicators of mustard leaves (drought stress from the 21st to the 28th day); and DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The test materials used in the following embodiments are all obtained from conventional stores unless otherwise specified.

[0031] Example 1

[0032] Sodium alginate was loaded by impregnation method, and the concentration of sodium alginate solution was 0.5%. 5 g of microporous silica spheres were dissolved and dispersed in 50 ml of sodium alginate solution; then 10 ml of saturated calcium chloride solution was added, and the reaction was carried out for 30 min; 2.5 ml of n-hexane was added to the solution after the reaction, and stirred for 2 h; suction filtration was carried out, and 10 ml of anhydrous ethanol was used for washing and filtration twice to remove other soluble substances adsorbed on the surface of the carrier material; transferred into a centrifugal device (3000 r / min), centrifuged for 30 min; the precipitate was taken out, dried at 85°C for 4 h, and a microporous silica-based sodium alginate trace element nanocomposite powder (named: Alg-Ca-NSA-0.5) was obtained.

[0033] Example 2

[0034] Sodium alginate was loaded by impregnation method, and the concentration of sodium alginate solution was 0.5%. 5 g of microporous silica spheres were dissolved and dispersed in 50 ml of sodium alginate solution; then 10 ml of saturated calcium chloride solution was added, and the reaction was carried out for 30 min; 2.5 ml of n-hexane was added to the solution after the reaction, and stirred for 2 h; suction filtration was carried out, and 10 ml of anhydrous ethanol was used for washing and filtration twice to remove other soluble substances adsorbed on the surface of the carrier material; transferred into a centrifugal device (3000 r / min), centrifuged for 30 min; the precipitate was taken out, dried at 85°C for 4 h, and a microporous silica-based sodium alginate trace element nanocomposite powder (named: Alg-Ca-NSA-0.5) was obtained.

[0035] Example 3

[0036] Sodium alginate was loaded by impregnation method, and the concentration of sodium alginate solution was 0.7%. 4 g of mesoporous silica spheres were dissolved and dispersed in 50 ml of sodium alginate solution; then 8 ml of saturated calcium chloride solution was added, and the reaction was carried out for 40 min; 2.5 ml of n-hexane was added to the solution after the reaction, and stirred for 3 h; suction filtration was carried out, and 10 ml of anhydrous ethanol was used for washing and filtration twice to remove other soluble substances adsorbed on the surface of the carrier material; transferred into a centrifugal device (3000 r / min), centrifuged for 40 min; the precipitate was taken out, dried at 85°C for 7 h, and a microporous silica-based sodium alginate trace element nanocomposite powder (named: Alg-Ca-P-BMMs-0.7) was obtained.

[0037] Example 4

[0038] Sodium alginate was loaded by impregnation method with a sodium alginate solution concentration of 0.9%. 3 g of the microporous silica spheres were dissolved in 50 ml of the sodium alginate solution; then 5 ml of a saturated calcium chloride solution was added, and the reaction was allowed to proceed for 50 min; after the reaction, 2.5 ml of n-hexane was added to the solution, and stirring was performed for 1 h; suction filtration was performed, and the material was washed and filtered twice with 10 ml of anhydrous ethanol to remove other soluble substances adsorbed on the surface of the carrier material; the material was transferred to a centrifuge device (3000 r / min), and centrifugation was performed for 40 min; the precipitate was taken, and drying was performed at 90 °C for 6 h to obtain the trace element nanocomposite powder based on porous silica alginate (named: Alg-Ca-P-NSA-0.9).

[0039] Example 5

[0040] Sodium alginate was loaded by impregnation method with a sodium alginate solution concentration of 1.0%. 4 g of the mesoporous silica spheres were dissolved in 50 ml of the sodium alginate solution; then 7 ml of a saturated calcium nitrate solution was added, and the reaction was allowed to proceed for 60 min; after the reaction, 2.5 ml of n-hexane was added to the solution, and stirring was performed for 3 h; suction filtration was performed, and the material was washed and filtered twice with 10 ml of anhydrous ethanol to remove other soluble substances adsorbed on the surface of the carrier material; the material was transferred to a centrifuge device (3000 r / min), and centrifugation was performed for 60 min; the precipitate was taken, and drying was performed at 70 °C for 5 h to obtain the trace element nanocomposite powder based on porous silica alginate (named: Alg-Ca-P-BMMs-1.0).

[0041] Example 6

[0042] Sodium alginate was loaded by impregnation method with a sodium alginate solution concentration of 2.5%. 3 g of the mesoporous silica spheres were dissolved in 50 ml of the sodium alginate solution; then 10 ml of a saturated calcium chloride solution was added, and the reaction was allowed to proceed for 150 min; after the reaction, 2.5 ml of n-hexane was added to the solution, and stirring was performed for 1 h; suction filtration was performed, and the material was washed and filtered twice with 10 ml of anhydrous ethanol to remove other soluble substances adsorbed on the surface of the carrier material; the material was transferred to a centrifuge device (3000 r / min), and centrifugation was performed for 50 min; the precipitate was taken, and drying was performed at 95 °C to obtain the trace element nanocomposite powder based on porous silica alginate (named: Alg-Ca-P-BMMs-2.5).

[0043] Example 7

[0044] Brassica juncea was treated with water, Alg-Ca-NSA-0.5 (Example 1), Alg-Ca-N-NSA-0.5 (Example 2), CaCl2 and EDTA CaK2. The leaves were collected on the 28th day to detect malondialdehyde (MDA), superoxide dismutase (SOD) and peroxidase (POD), respectively, and the 21st to 28th days were set as drought stress without watering. The experimental results are shown in Table 1. Figure 1 and Figure 2 .

[0045] From the growth trend of Brassica juncea after various treatments on the 28th day, when CaCl2 was diluted 500 times, the leaves became narrow, and flowering and striping phenomena appeared, which was not conducive to the growth of the edible part of Brassica juncea. At the same time, compared with other examples, the growth trend of Brassica juncea treated with 500 times diluted Alg-Ca-NSA-0.5 of the application was the best, the split leaves were more, and the contents of superoxide dismutase (SOD) and peroxidase (POD) were the highest, and the content of malondialdehyde (MDA) was the lowest, which indicated that the compound of the application was conducive to the growth of crops and could improve the quality of crops.

[0046] The application of Alg-P-NSA in agriculture is proposed for the first time, which is sprayed on plants and can enter the stomata on the surface of leaves, and there is no retention phenomenon on the leaf area, indicating that it can be absorbed by the leaf surface of plants and has a certain slow-release effect. After 28 days of spraying, compared with the control, the treated plant leaves are wide, thick and green, the plant grows well, the plant height and stem diameter are increased; Alg-P-NSA can control the release time and speed of medium and trace elements, solve the different time needs of crops for medium and trace elements, thereby improve the health of crops and the quality of agricultural products, and provide technical support for reducing the application amount of chemical pesticides.

[0047] Although the preferred embodiments of the application have been described, those skilled in the art can make further changes and modifications to these embodiments once they know the basic inventive concept. Therefore, the appended claims are intended to be interpreted as including all changes and modifications falling within the scope of the application. Obviously, those skilled in the art can make various modifications and variations to the application without departing from the spirit and scope of the application. Thus, if these modifications and variations of the application fall within the scope of the claims of the application and their equivalents, the application also intends to include these modifications and variations.

Claims

1. A porous silica-based alginate nanocomposite (Alg-P-NSA) characterized in that, The nanocomposite comprises the following weight percentage ranges of components: Alginate (Alg): 10-20%; Porous nano-silica (P-NSA): 62-83%; Metal element: 6-15%, Water (H2O): 1-3%; The porous nano-silica is microporous silica spheres; and the metal element is calcium.

2. The method for preparing the porous silica-based alginate nanocomposite according to claim 1, characterized in that, The method comprises: 1) dispersing microporous silica spheres in a solution containing sodium alginate; 2) slowly adding a salt solution of the metal element and stirring at room temperature for 10-200 min; 3) adding n-hexane and stirring for 1-3 h; 4) filtering the resulting solution, washing with ethanol, and then centrifuging; and 5) drying the precipitate obtained by centrifugation at 60-105℃ for 4-7 h to obtain Alg-P-NSA; The metal element is calcium.

3. The method of claim 2, wherein: The salt solution of the metal element is selected from saturated solutions of chloride and nitrate salts.

4. The method of claim 2, wherein: In step 1), the concentration of the sodium alginate solution is 0.025%-2.5%; and the concentration of the microporous silica spheres in the dispersion is 60-100 g / L.

5. The method of claim 2, wherein: In step 2), the amount of the salt solution of the metal element is 10-20% of the amount of the sodium alginate solution.

6. The method of claim 2, wherein: In step 2), the amount of the n-hexane is 20-60% of the amount of the salt solution of the metal element.

7. Use of the porous silica-based alginate nanocomposite according to claim 1 in foliar fertilization.

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