Boron nanoparticles as well as preparation method and application thereof

Abstract

The invention discloses boron nanoparticles as well as a preparation method and application thereof, and belongs to the technical field of nano fertilizers. The preparation method of the boron nanoparticles comprises the following steps: S1, adding soluble calcium salt into a PVP (Polyvinyl Pyrrolidone) solution to obtain a soluble calcium salt solution; and S2, adding the soluble calcium salt solution into the borax solution, stirring to obtain a precipitate, and calcining the precipitate at 400-500 DEG C to obtain the boron nanoparticles. In addition, the invention also provides the boron nano-particles prepared by the preparation method or application of the boron nano-particles in improving the salt tolerance of rape. According to the boron nanoparticles prepared by the method, the salt tolerance of the rape is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of nano-fertilizers, and particularly relates to a boron nanoparticle, a preparation method thereof, and an application thereof. Background Art

[0002] Salt stress is one of the important abiotic stresses restricting global agricultural production. Especially in arid and semi-arid regions, soil salinization leads to the growth inhibition of crops and a sharp reduction in yield. According to the statistics of the Food and Agriculture Organization of the United Nations, about 20% of the irrigated farmland and more than 6% of the cultivated land in the world are affected by salinization. Among them, there are 1.5 billion mu of saline-alkali land in China, and about 500 million mu has the potential for development and utilization, which is the strategic reserve resource of cultivated land in China. Salt stress destroys the physiological functions of plants through three mechanisms: ion toxicity, osmotic stress, and oxidative damage. Among them, the root system, as the organ directly contacting soil salts, the decline of its structure and function is the key link for the loss of plant salt tolerance.

[0003] Rapeseed (Brassica napus L.) is an important oil crop, which is widely used in the production of edible oil, biodiesel, and feed. However, rapeseed is relatively sensitive to salt stress, and its yield is affected by salt stress. In arid and semi-arid regions, the area of saline soil is expanding year by year, seriously threatening the yield stability of rapeseed cultivation. Therefore, analyzing the salt tolerance mechanism of rapeseed and developing efficient stress resistance strategies are of great significance for ensuring global grain and oil security.

[0004] How to improve the salt tolerance of rapeseed is a technical problem that needs to be solved by the existing technology. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above technical deficiencies, and provide a boron nanoparticle, a preparation method thereof, and an application thereof, so as to solve the technical problem of how to improve the salt tolerance of rapeseed in the existing technology.

[0006] To achieve the above technical purpose, the technical solution of the present invention provides a preparation method of a boron nanoparticle, including the following steps:

[0007] S1. Adding a soluble calcium salt to a PVP (i.e., polyvinylpyrrolidone) solution to obtain a soluble calcium salt solution;

[0008] S2. Adding the soluble calcium salt solution to a borax solution and stirring to obtain a precipitate, and calcining the precipitate at 400 - 500 °C to obtain the boron nanoparticle.

[0009] In any embodiment, in step S1, the PVP solution is prepared by dissolving polyvinylpyrrolidone in water.

[0010] In any embodiment, in step S2, the soluble calcium salt solution is added to the borax solution at 45 - 50 °C.

[0011] In any embodiment, in step S2, the calcination time is 3 - 4 h.

[0012] In any embodiment, in step S1, the soluble calcium salt is calcium chloride.

[0013] In addition, the present invention also provides a boron nanoparticle prepared by the above preparation method.

[0014] In any embodiment, the morphology of the boron nanoparticle is an irregular circular structure; and / or, the particle size of the boron nanoparticle is 40 - 80 nm; and / or, the chemical formula of the boron nanoparticle is CaO·2B2O3·10H2O.

[0015] In addition, the present invention also provides an application of the boron nanoparticle prepared by the above preparation method or the above boron nanoparticle in improving the salt tolerance of rapeseed.

[0016] In any embodiment, when the rapeseed grows to the four - leaf stage, nutrient solution is applied, and the nutrient solution is replaced every 5 - 6 days. The concentration of boron nanoparticles in the used nutrient solution is 45 - 55 μM.

[0017] In any embodiment, the rapeseed is Brassica napus.

[0018] Compared with the prior art, the beneficial effects of the present invention include: The preparation method of the boron nanoparticle proposed by the present invention includes adding a soluble calcium salt to a PVP solution to obtain a soluble calcium salt solution; adding the soluble calcium salt solution to a borax solution and stirring to obtain a precipitate, and calcining the precipitate at 400 - 500 °C to obtain the boron nanoparticle. The present invention uses a soluble calcium salt and borax as synthesis raw materials and polyvinylpyrrolidone as a capping agent to prepare a nano - boron fertilizer. The synthesis method is simple and the cost is low, and it has the effect of significantly improving the utilization rate of boron fertilizer in saline - alkali land and significantly improving the salt tolerance of rapeseed. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 shows the morphology and particle size distribution of the boron nanoparticle prepared in Example 1 of the present invention; Figure 1 A: SEM image of the boron nanoparticle; Figure 1 B: TEM image of the boron nanoparticle; Figure 1 C: SEM image of the boron nanoparticle dissolved in ultrapure water; Figure 1 D: Particle size distribution diagram of the boron nanoparticle.

[0020] Figure 2 shows the biomass of rapeseed after the application of boron nanoparticles under salt stress in Example 2 of the present invention.

[0021] Figure 3It is the root morphology of rapeseed after the application of boron nanoparticles under salt stress in Example 2 of the present invention.

[0022] Figure 4 It is the cell wall composition of rapeseed after the application of boron nanoparticles under salt stress in Example 2 of the present invention. Detailed implementation manners

[0023] The "ranges" disclosed in this application are defined in the form of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "a-b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been fully listed herein, and "0-5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0024] If there is no special instruction, the "including" and "comprising" mentioned in this application mean open-ended, and can also be closed-ended. For example, the "including" and "comprising" can mean that other components not listed can also be included or comprised, or can only include or comprise the listed components.

[0025] If there is no special instruction, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) while B is true (or exists); or both A and B are true (or exist).

[0026] This detailed implementation manner provides a preparation method of boron nanoparticles, including the following steps:

[0027] S1. Add a soluble calcium salt to the PVP solution to obtain a soluble calcium salt solution; the PVP solution is prepared by dissolving polyvinylpyrrolidone in water; in some embodiments, the soluble calcium salt is calcium chloride;

[0028] S2. Add the soluble calcium salt solution to the borax solution at 45 - 50 °C and stir for 1 - 2 h to obtain a precipitate. Calcinate the precipitate at 400 - 500 °C for 3 - 4 h to obtain the boron nanoparticles. The soluble calcium salt is calcium chloride, and the soluble calcium salt solution is added to the borax solution according to the mass ratio of calcium chloride to borax of 1:3.5.

[0029] This specific embodiment also proposes a kind of boron nanoparticles prepared by the above - mentioned preparation method. The morphology of the boron nanoparticles is an irregular circular structure, the particle size of the boron nanoparticles is 40 - 80 nm, and the chemical formula of the boron nanoparticles is CaO·2B2O3·10H2O.

[0030] This specific embodiment also proposes the application of the boron nanoparticles prepared by the above - mentioned preparation method or the above - mentioned boron nanoparticles in improving the salt tolerance of rapeseed. When the rapeseed grows to the four - leaf stage, nutrient solution is applied, and the nutrient solution is replaced every 5 - 6 days. The concentration of boron nanoparticles in the used nutrient solution is 45 - 55 μM.

[0031] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0032] In the present invention, terms such as "some embodiments", "this embodiment" and examples, etc. are involved, which describe subsets of all possible embodiments. However, it can be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict.

[0033] If similar descriptions such as "first / second" appear in the application documents, the following description will be added. In the following description, the terms "first\second\third" only distinguish similar objects and do not represent a specific order for the objects. It can be understood that "first\second\third" can be interchanged with a specific order or sequence when allowed, so that the embodiments described here can be implemented in an order other than that illustrated or described here.

[0034] In this embodiment, the term "and / or" only describes the association relationship of associated objects, indicating that there can be three relationships. For example, object A and / or object B can represent: object A exists alone, object A and object B exist simultaneously, and object B exists alone.

[0035] The embodiments of the present application will be described below. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application. For those techniques or conditions not specified in the embodiments, they shall be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. For the reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0036] Example 1

[0037] This example presents a kind of boron nanoparticles, which are prepared by the following steps:

[0038] Dissolve 1 g of polyvinylpyrrolidone (PVP) in 100 mL of deionized water; add calcium chloride to the prepared 100 mL of PVP solution according to a concentration of 0.2 mol / L of calcium chloride to obtain a uniform calcium chloride solution; dissolve borax in 100 mL of deionized water according to a concentration of 0.2 mol / L of borax to obtain a borax solution. Heat the calcium chloride solution and the borax solution to 48 °C and stir for 1 h. Subsequently, slowly add the calcium chloride solution drop by drop to the borax solution and stir for 1 h to obtain a more uniform precipitate. Centrifuge and wash the precipitate, and after drying, calcine it in an electric resistance furnace at 500 °C for 3 h to obtain boron nanoparticles, namely B-NPs.

[0039] Characterization of the boron nanoparticles prepared in this example:

[0040] Take 10 mg of boron nanoparticles, dissolve them in 50 mL of deionized water, perform ultrasonic treatment for 30 min, dip a special copper mesh for electron microscopy into the suspension and let it dry naturally, and send it to the electron microscopy platform of Wuhan Navi Innovation Co., Ltd. to observe its morphology and distribution. The results are shown in Figure 1 .

[0041] The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show that the solid morphology of nano-boron presents an irregular circular structural form with a certain degree of aggregation in the distribution. According to the particles in the figure, the solid particle size distribution of nano-boron is in the range of 100 - 120 nm ( Figure 1 A and B). After dissolving in deionized water, nano-boron presents a regular circular structure with a relatively dispersed distribution. By calculating the particle size distribution of nano-boron, it is in the range of 40 - 80 nm, and the average particle size is 67.83 nm ( Figure 1 C and D).

[0042] Example 2

[0043] This example provides an application of the boron nanoparticles prepared in Example 1 in improving the salt tolerance of rapeseed. The specific steps are as follows:

[0044] Seed germination: The rapeseed variety used for testing was "Huayouza 62." Select plump, uniform seeds, soak them in tap water for 2 hours, and evenly place them in a Petri dish lined with filter paper. Add approximately 1 / 3 of the volume of ultrapure water and vernalize them in a dark refrigerator at 4°C for 4 hours. Then, transfer them to a 30°C incubator and incubate them in the dark for 24 hours.

[0045] Seedling transplanting and experimental conditions: After the seeds germinate, they are evenly transplanted on gauze and cultured with pure water. The temperature of the light culture room is set at 22°C, the photoperiod is set at 14h (light) / 10h (dark), and the light intensity is set at 300-320μmol / m 2 When the roots grow to 4-5 cm, transplant the evenly growing seedlings into 4L black plastic pots for cultivation.

[0046] Experimental treatment and application: A total of 5 treatments were set up in the experiment: -B (no boron fertilizer), CK (50 μM H3BO3), B-NPs (50 μM B-NPs), S (150 mM NaCl), S + B-NPs (150 mM NaCl + 50 μM B-NPs). Three pots were set up for each treatment, with 12 seedlings in each pot. The nutrient solution was replaced every 5 days and the plants were harvested after obvious differences appeared. It should be noted that the nutrient solution was prepared by dissolving the components in each group in water. The nutrient solution of the -B group was a boron-free Hoagland and Arnon nutrient solution. For example, the nutrient solution of the S group was prepared by dissolving NaCl in water, the nutrient solution of the B-NPs group was prepared by dissolving the boron nanoparticles of Example 1 in water, and the nutrient solution of the S + B-NPs group was prepared by dissolving the boron nanoparticles of Example 1 in water and NaCl in water; the nutrient solution of the CK group was prepared by dissolving H3BO3 in water, and the amount of nutrient solution used in each group was 4 L.

[0047] Measurement items and methods:

[0048] Biomass determination: At harvest, wash the plants, measure plant height and root length, record the fresh weight of aboveground and underground parts, fix at 105°C, dry at 70°C to constant weight, and record the dry weight;

[0049] Root morphology and characteristics: Root-related morphological characteristics were measured using a root scanner. The data were analyzed using WinRHIZO software to determine total root length, total number of roots, average root diameter, total root volume, number of root tips, and total root projected area.

[0050] Determination of cell wall component content: Fresh samples were treated with deionized water, ethanol, methanol-chloroform and acetone, respectively, to obtain crude cell walls. Chelated pectin was extracted with imidazole, and alkali-soluble pectin was extracted with sodium carbonate. The uronic acid content in pectin was determined by the hydrochloric acid colorimetric method. Hemicellulose 1 and hemicellulose 2 were extracted with potassium hydroxide, respectively, and the hemicellulose content was determined by the phenol colorimetric method.

[0051] The growth of rapeseed plants was evaluated based on plant height, root length, and fresh and dry weights of the plants. As Figure 2 shown, both salt stress and boron deficiency significantly inhibited the growth of rapeseed. Compared with CK, the -B treatment and S treatment reduced plant height by 27.55% and 35.47%, root length by 57.02% and 30.73%, respectively. There was no significant difference between the application of boron nanoparticles under non-salt treatment and the CK treatment. Meanwhile, under salt treatment, the application of boron nanoparticles alleviated the damage caused by salt stress, promoted the recovery of plants, and increased plant height by 37.43%, root length by 23.47%, leaf fresh weight by 71.49%, leaf dry weight by 50.24%, root fresh weight by 53.87% and root dry weight by 44%. This indicates that boron nanoparticles can mitigate the growth inhibition caused by salt stress.

[0052] Through the study of root morphology, it was found that -B significantly inhibited the growth of plants. The elongation of the main root of the root system was hindered, the number of lateral roots decreased, the overall root system became thicker, and the root tip swelled. This was manifested in a severe decrease in total root length, total root number, total root volume, root tip number, and total root projected area, which decreased by 85.28%, 54.90%, 76.05%, 60.09%, and 79.82% respectively compared with the CK treatment, and the average root diameter increased by 42.15% ( Figure 3 ; Table 1). Compared with salt stress, the application of boron nanoparticles promoted the development of the root system, and the number of lateral roots increased. Compared with the S treatment, it significantly increased total root length, total root number, average root diameter, total root volume, root tip number, and total root projected area by 80.71%, 129.68%, 16.88%, 54.2%, 87.32%, and 70.44% respectively. This indicates that boron nanoparticles significantly promote root development and alleviate the damage of salt stress to the root system. Under non-salt stress, the application of boron nanoparticles also significantly promoted total root length and total root projected area compared with the CK group. In summary, boron nanoparticles can promote root growth to mitigate rapeseed salt stress damage.

[0053] Table 1 Effects of boron nanoparticles on the morphological characteristics of rapeseed roots under salt stress

[0054]

[0055]

[0056] According to Figure 4Analysis of the contents of different components of the cell wall (pectin and hemicellulose) found that under non-salt treatment, the application of boron nanoparticles only significantly increased the content of root hemicellulose 2, while under salt stress, the application of boron nanoparticles significantly increased the content of chelated pectin in rape leaves and roots, by 27.67% and 57.32% respectively, promoted the content of root alkali-soluble pectin, and increased by 35.64%. The application of boron nanoparticles under salt stress promoted the content of root cellulose 1, significantly increasing by 24.39%, while the content of cellulose 1 in leaves did not increase. Through the analysis of cellulose 2, it was found that the application of boron nanoparticles promoted the content of leaf cellulose 2, but did not significantly promote the content of root cellulose 2. This indicates that the application of boron nanoparticles promotes the recovery of the rape cell wall under salt stress and has a positive promoting effect on improving salt tolerance.

[0057] Through the analysis of rape biomass, root morphological characteristics and cell wall components, it was found that boron deficiency led to the inhibition of cell division in the root tip meristem of rape. Under salt stress, the application of nano-boron supplemented boron elements, restored pectin cross-linking, increased the content of chelated pectin, promoted the accumulation of hemicellulose at the same time, stabilized the cell wall structure, reduced salt-induced cell wall degradation, enhanced the rigidity of the cell wall, thus supporting the activity of the root tip meristem, promoting the elongation of the main root and the branching of lateral roots, and further improving the salt tolerance of rape.

[0058] Example 3

[0059] This example presents a kind of boron nanoparticles, which are prepared by the following steps:

[0060] Dissolve 1 g of polyvinylpyrrolidone (PVP) in 100 mL of deionized water; add calcium chloride to the prepared 100 mL PVP solution according to the concentration of 0.2 mol / L of calcium chloride to obtain a uniform calcium chloride solution;

[0061] Dissolve borax in 100 mL of deionized water according to the concentration of 0.2 mol / L of borax to obtain a borax solution. Heat the calcium chloride solution and the borax solution to 45 °C and stir for 2 h. Subsequently, slowly add the calcium chloride solution drop by drop to the borax solution, stir for 1 h to obtain a more uniform precipitate. Centrifuge and wash the precipitate, and calcine it in an electric resistance furnace at 450 °C for 4 h to obtain boron nanoparticles.

[0062] Example 4

[0063] This example presents a kind of boron nanoparticles, which are prepared by the following steps:

[0064] Dissolve 1 g of polyvinylpyrrolidone (PVP) in 100 mL of deionized water; add calcium chloride to the prepared 100 mL PVP solution according to the concentration of 0.2 mol / L of calcium chloride to obtain a uniform calcium chloride solution;

[0065] Dissolve borax in 100 mL of deionized water according to a concentration of 0.2 mol / L of borax to obtain a borax solution. Heat the calcium chloride solution and the borax solution to 50 °C respectively and stir for 1.5 h. Subsequently, slowly add the calcium chloride solution drop by drop to the borax solution and stir for 2 h to obtain a more uniform precipitate. Centrifuge and wash the precipitate, and calcine it in an electric resistance furnace at 400 °C for 3.5 h to obtain boron nanoparticles.

[0066] It should be noted that the boron nanoparticles prepared in Examples 3 and 4 have performance equivalent to that of the boron nanoparticles prepared in Example 1 in terms of improving the salt tolerance of rapeseed.

[0067] In summary, boron nanoparticles slow down the damage of salt stress to rapeseed by significantly promoting root development, increasing the contents of leaf chelated pectin and cellulose 1, and root chelated pectin, alkali-soluble pectin and hemicellulose 2, enhancing the salt tolerance of rapeseed, and providing strong technical support for the high yield of rapeseed in saline-alkali land.

[0068] Boron is an essential micronutrient for plants. It maintains cell wall integrity by stabilizing the rhamnogalacturonan-II dimer of pectin and regulates meristem activity. Under boron-deficient conditions, plant roots show enlarged root tips, reduced lateral roots and loose cell walls, and the stress resistance ability is greatly reduced. However, the application of traditional boron fertilizers in saline soils faces severe challenges. The increase in soil pH induced by salts promotes the fixation of boron in the form of insoluble borates, resulting in a decrease in the available boron content. At the same time, high-concentration sodium ions compete with boron for plant absorption sites, exacerbating the boron deficiency symptoms of crops. The boron nanoparticles proposed in the present invention have a smaller particle size, enabling them to effectively penetrate the cell membrane of plants or directly enter the plant body through the roots, avoiding soil fixation, improving fertilizer efficiency, regulating the physiological mechanisms, nutrient metabolism and cell wall growth of plants, improving the stress resistance of crops, and the boron nanoparticles act on the roots and cell walls, as well as the dynamic regulation of cell wall components and root architecture remodeling under salt stress.

[0069] This study developed a new type of nano-boron fertilizer, explored its application potential for rapeseed in saline soils, analyzed the regulation mechanism of nano-boron on the dynamic balance of multiple components of rapeseed cell walls under salt stress, revealed the functional relationship between root remodeling and cell wall structure strengthening, promoted the nutrient absorption efficiency of crops, improved the yield and quality of agricultural crops, and provided a new technical approach for the sustainable development of agricultural production.

[0070] Other beneficial technical effects of the present invention include:

[0071] (1) The present invention uses calcium chloride and borax as synthetic raw materials and polyvinylpyrrolidone as a capping agent to prepare boron nanoparticles. The synthesis method is simple and the cost is low, and it has the effect of significantly improving the utilization rate of boron fertilizer in saline-alkali land.

[0072] (2) The boron nanoparticles used in the present invention not only provide essential boron elements for rapeseed, but also reduce the damage of rapeseed under salt stress and promote the development of roots.

[0073] (3) The boron nanoparticles used in the present invention promote the recovery of the cell wall of rapeseed under salt stress, increase the contents of pectin and hemicellulose, and further improve the salt tolerance of rapeseed.

[0074] The specific embodiments of the present invention described above do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and deformations made according to the technical concept of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing boron nanoparticles, characterized in that, It includes the following steps: S1. Add soluble calcium salt to the PVP solution to obtain a soluble calcium salt solution; S2. Add the soluble calcium salt solution to the borax solution and stir to obtain a precipitate, and calcine the precipitate at 400 - 500 °C to obtain the boron nanoparticles.

2. The preparation method of the boron nanoparticles according to claim 1, wherein, In step S1, the PVP solution is prepared by dissolving polyvinylpyrrolidone in water.

3. The preparation method of boron nanoparticles according to claim 1, characterized in that, In step S2, add the soluble calcium salt solution to the borax solution at 45 - 50 °C.

4. The preparation method of the boron nanoparticles according to claim 1, wherein, In step S2, the calcination time is 3 - 4 h.

5. The preparation method of boron nanoparticles according to claim 1, characterized in that, In step S1, the soluble calcium salt is calcium chloride.

6. A boron nanoparticle, characterized in that, Prepared by the preparation method according to any one of claims 1 - 5.

7. The boron nanoparticles according to claim 6, characterized in that, The morphology of the boron nanoparticles is an irregular circular structure; and / or, the particle size of the boron nanoparticles is 40 - 80 nm; and / or, the chemical formula of the boron nanoparticles is CaO·2B2O3·10H2O.

8. Application of the boron nanoparticles prepared by the preparation method according to any one of claims 1 - 5 or the boron nanoparticles according to any one of claims 6 - 7 in improving the salt tolerance of rapeseed.

9. The application according to claim 8, characterized in that, When the rapeseed grows to the four - leaf stage, apply nutrient solution and change the nutrient solution every 5 - 6 days. The concentration of boron nanoparticles in the used nutrient solution is 45 - 55 μM.

10. The application according to claim 8, wherein, The rapeseed is Brassica napus.

Images