Biological composite nano-selenium nutrient solution as well as preparation method and application thereof

Abstract

The invention discloses a biological composite nano-selenium nutrient solution as well as a preparation method and application thereof. The preparation method comprises the following steps: firstly, carrying out amidation reaction on biodegradable natural high-molecular polymer small-molecular organic acid to prepare a film-forming agent, and then loading nano-selenium on the film-forming agent, thereby obtaining the biological composite nano-selenium nutrient solution. The biological composite selenium nutrient solution not only has basic functions of traditional fertilizers, but also realizes a slow-release supply function of nano-selenium. And in the natural degradation process, nutrients can be continuously and stably released, and continuous support is provided for growth of crops. After the fertilizer is used for a long time, the content of organic matters and selenium in soil can be remarkably increased, the phenomenon that the fertilizer is lost along with water is effectively reduced, the soil structure is gradually improved, the soil is more fertile and breathable, and a more excellent growth environment is created for crops. The sprayed nutrient solution is non-toxic and harmless, so that the crop quality can be further improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of agriculture, and particularly relates to a biological compound nano-selenium nutrient solution and a preparation method and application thereof. BACKGROUND

[0002] Selenium is an essential trace element and nutrient substance for human body, and plays a crucial role in the human body. It can synergize with vitamin E to resist oxidation, enhance human immunity, prevent diabetes, cataract, and cardiovascular and cerebrovascular diseases. It can also promote bone formation, prevent arthritis, osteosclerosis, and osteoporosis, and the like. In terms of plant growth, appropriate amount of selenium entering the plant body can enhance peroxidase activity, and enhance the ability of the plant to resist oxidation, adversity, and aging, so as to ensure normal growth and development of the plant. In selenium-poor areas, application of selenium fertilizer can promote photosynthesis of crops, strengthen root development, improve the utilization rate of nutrients of crops, enhance the resistance of plants to diseases and pests, and improve yield, and can significantly improve the storage and preservation capacity of fruits and vegetables.

[0003] Traditional selenium fertilizers (such as inorganic selenium fertilizers) mostly have the disadvantages of low absorption rate, easy rainwater washing or loss in foliar spraying, and easy toxicity to crops when the concentration of selenite is not controlled. In addition, when inorganic selenium fertilizer is directly applied to soil, selenium element is easily converted into a difficult-to-absorb form or fixed by soil, resulting in an effective utilization rate of only about 30%. Moreover, the morphological transformation of selenium in soil is complex, and the absorption of crops is unstable, resulting in large fluctuations in selenium content and uneven quality of selenium-rich agricultural products.

[0004] CN202411366535.0 discloses a chitosan functionalized nano-selenium fertilizer and application thereof, which is composed of chitosan functionalized nano-selenium, tetrahydropyrimidine, alginic acid, a surface active substance, and deionized water, promotes the absorption of chitosan functionalized nano-selenium by plants, and significantly improves the selenium content in tea leaves. However, this patent has obvious functional limitations, and the single selenium element supplementing function cannot meet the demand of modern agriculture for multifunctional compound fertilizers. The chitosan-alginic acid carrier system used in this technology has pH sensitivity and nano-selenium agglomeration problems, and the slow-release performance is unstable in actual field application, and the anti-rainwater washing design is completely ignored, resulting in insufficient fertilizer efficiency durability. More importantly, this scheme lacks the integration of disease and pest protection function, neither adds antibacterial active ingredients nor establishes an adversity regulation mechanism, and cannot achieve the goal of reducing the use of pesticides, and is difficult to meet the production requirements of "green label" selenium-rich agricultural products.

[0005] From the perspective of my country's agricultural development, many regions suffer from severe selenium deficiency in their soils, making selenium-enriched agricultural products highly sought after in the market. However, selenium has the characteristic of "beneficial in moderation, harmful in excess." Due to the lack of unified application standards, farmers are prone to blindly increasing the dosage, leading to selenium poisoning in crops or insufficient dosage, resulting in crops failing to meet selenium enrichment standards. Therefore, developing a method for preparing a nano-selenium bio-composite nutrient solution that can significantly improve pest and disease resistance by combining it with controlled-release carriers that promote plant growth has significant practical application value and social benefits. These solutions can significantly improve crop selenium absorption, increase crop yield, and enhance crop quality while reducing the incidence of pests and diseases, thereby reducing pesticide use and meeting the requirements for "green label" selenium-enriched agricultural products, thus significantly improving the profitability of agricultural production. Summary of the Invention

[0006] To address the shortcomings and deficiencies of existing technologies, the primary objective of this invention is to provide a method for preparing a bio-composite nano-selenium nutrient solution. This preparation process is simple, easy to implement, and requires low cost.

[0007] This invention first utilizes an amidation reaction between a biodegradable natural polymer and a small-molecule organic acid (a type of substance with plant hormone function) that promotes growth and has antibacterial properties. In the amidation reaction, the amino groups (-NH2) on the natural polymer chain react with the carboxyl groups (-COOH) in the small-molecule organic acid to form amide bonds (-CONH-), thereby attaching the small-molecule organic acid to the natural polymer and preparing a multifunctional polymer hydrogel carrier. This polymer hydrogel not only possesses excellent leaf wettability, adhesion, film-forming properties, and biodegradability, but also exhibits multiple functions such as water absorption and retention, and slow-release fertilizer, improving fertilizer utilization. For example, salicylic acid can enhance plant stress resistance, induce plant disease resistance, regulate plant growth and development, inhibit fruit decay and spoilage, and extend the shelf life of fruits; citric acid has inhibitory effects on certain pathogens and pests; L-malic acid can be used as a plant growth regulator to promote plant growth and development. The introduction of these organic acids endows the hydrogel carrier with not only excellent physicochemical properties, but also significant antibacterial, disease-resistant, and growth-promoting effects.

[0008] In the preparation of nano-selenium, this invention uses the reaction of sodium selenite and vitamin C to prepare nano-sized selenium particles, which not only avoids the toxicity to plants caused by direct use of sodium selenite, but also allows these nanoparticles, due to their unique size effect, to penetrate leaf stomata and cuticle gaps to directly enter plant cells, resulting in significantly higher absorption efficiency than traditional selenium fertilizers. Simultaneously, nano-selenium can be slowly released within the plant, effectively avoiding the toxic risks associated with high concentrations of selenite at once and greatly extending the duration of action. By loading nano-selenium onto a polymer hydrogel carrier, the technical challenges of easy aggregation and oxidation of nanoparticles are successfully solved, significantly improving the stability of the system. This invention further adds the natural antibacterial agent potassium cinnamate. This component not only effectively prevents fungal infections and other diseases in crops, reducing the use of chemical pesticides and improving the safety of agricultural products, but also has plant growth regulation functions. The resulting bio-compound selenium nutrient solution exhibits significant advantages in crop cultivation, effectively increasing the selenium content of crops, achieving a comprehensive upgrade in internal nutrition, and improving the taste and flavor of crops, thus contributing to the cultivation of higher-quality grains and fruits and vegetables.

[0009] Another object of the present invention is to provide a bio-composite nano-selenium nutrient solution prepared by the above method.

[0010] This invention relates to a bio-compound selenium nutrient solution, an innovative agricultural formulation integrating multiple functions. Nano-sized elemental selenium particles, due to their tiny size, can penetrate the leaf barrier and directly enter plant cells, significantly improving absorption efficiency. Simultaneously, the carefully selected organic acid components not only endow the product with antibacterial and disease-resistant properties but also regulate plant growth and development. The added potassium cinnamate further enhances the product's antibacterial function, reducing the use of chemical pesticides. This innovative structural design allows the nutrient solution to continuously and stably release selenium and other nutrients during natural degradation, providing crops with nutrient supply for several weeks. Compared to traditional selenium fertilizers, this system significantly improves nutrient utilization while effectively avoiding the toxic risks associated with high concentrations of selenium. Long-term use can significantly increase the organic matter and selenium content in the soil, effectively reducing fertilizer loss through water, gradually improving soil structure, making the soil more fertile and aerated, and creating a better growing environment for crops. Furthermore, the sprayed nutrient solution is non-toxic and harmless, further improving crop quality.

[0011] Another object of the present invention is to provide the application of the above-mentioned bio-composite nano-selenium nutrient solution in crop cultivation.

[0012] To achieve this objective, the present invention employs the following technical solution:

[0013] In a first aspect, the present invention provides a method for preparing a bio-composite nano-selenium nutrient solution, comprising the following steps:

[0014] (1) Mix natural polymer-acetic acid solution and small molecule organic acid-ethanol solution, adjust the pH of the mixture, heat and reflux the reaction, stop the reaction and cool to room temperature to obtain product mixture;

[0015] (2) Sodium selenite, potassium cinnamate and vitamin C were reacted under solvent dissolution conditions to obtain a product mixture;

[0016] (3) Under stirring conditions, the product mixture of step (2) is added dropwise to the product mixture of step (1). After the addition is complete, the stirring reaction continues to obtain the bio-composite nano selenium nutrient solution.

[0017] Preferably, in the natural polymer-acetic acid solution described in step (1), the mass concentration of the natural polymer is 1-10% (e.g., 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.); the concentration of acetic acid is 1-10% (w / v) (e.g., 1% (w / v), 1.5% (w / v), 2% (w / v), 3% (w / v), 4% (w / v), 5% (w / v), 6% (w / v), 7% (w / v), 8% (w / v), 9% (w / v), 10% (w / v), etc.). Any other specific values ​​within the above range can be selected, and will not be elaborated upon here.

[0018] Preferably, in step (1), the natural polymer includes at least one of silk fibroin, chitosan and gelatin.

[0019] The molecular weight of the chitosan is (1-3)×10. 5 .

[0020] Preferably, in the small molecule organic acid-ethanol solution described in step (1), the concentration of the small molecule organic acid is 0.05–0.5 mol / L (e.g., 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, etc.), and the concentration of ethanol is ≥95% (w / v) (e.g., 95% (w / v), 96% (w / v), 97% (w / v), 98% (w / v), 99% (w / v), etc.). Any other specific values ​​within the above range can be selected, and will not be elaborated further here.

[0021] Preferably, in step (1), the small molecule organic acid includes at least one of salicylic acid, DL-malic acid and citric acid.

[0022] Preferably, in step (1), the mass ratio of the natural polymer to the small organic acid is 2.5:1 to 1:2.5 (e.g., 2.5:1, 2.0:1, 1.5:1, 1:1, 1:1.5, 1:2.0, 1:2.5, etc.). Any other specific value within the above range can be selected, and it is not convenient to elaborate on them here.

[0023] Preferably, the temperature of the heating reflux reaction in step (1) is 40–80°C (e.g., 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 78.5°C, 80°C), and the time is 2–10 h (e.g., 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, etc.). Any other specific point value within the above range can be selected, and it is inconvenient to elaborate on them here.

[0024] Preferably, the stirring speed for the heating reflux reaction in step (1) is 200–1200 r / min (e.g., 200 r / min, 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min, 1000 r / min, 1100 r / min, 1200 r / min, etc.). Any other specific value within the above range can be selected, and it is inconvenient to elaborate on them here.

[0025] Preferably, the pH value in step (1) is 5.0 to 5.5. Any other specific value within the above range can be selected, and it is not convenient to elaborate on them here.

[0026] Preferably, the pH adjuster used in step (1) to adjust the product mixture includes a sodium hydroxide solution; the mass concentration of the adjuster is 0.1–1 mol / L (e.g., 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, etc.). Any other specific value within the above range can be selected, and it is inconvenient to elaborate on them here.

[0027] Preferably, the molar ratio of sodium selenite, potassium cinnamate, and vitamin C in step (2) is 1:(0.3-0.7):(8-12). Within this range, the molar ratio of potassium cinnamate can be 0.3, 0.4, 0.5, 0.6, 0.7, etc., and the molar ratio of vitamin C can be 8, 9, 10, 11, 12, etc.; any other specific values ​​within the above range can be selected, which will not be elaborated here.

[0028] Preferably, step (2) specifically involves mixing sodium selenite solution and potassium cinnamate solution, and then adding vitamin C solution to react; the concentration of the sodium selenite solution is 0.05–0.15 mol / L (e.g., 0.05 mol / L, 0.1 mol / L, 0.15 mol / L, etc.); the concentration of the potassium cinnamate solution is 0.02–0.08 mol / L (e.g., 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, etc.); and the concentration of the vitamin C solution is 0.05–0.2 mol / L (e.g., 0.05 mol / L, 0.07 mol / L, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, etc.). Any other specific values ​​within the above range can be selected, and will not be elaborated upon here.

[0029] Preferably, the solvent in step (2) includes water.

[0030] Preferably, the reaction in step (2) is carried out at room temperature for 0.5 to 3 hours (e.g., 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc.). Any other specific values ​​within the above range can be selected, which will not be elaborated here.

[0031] Preferably, in step (3), the mass ratio of the product mixture from step (2) to the product mixture from step (1) is 1:5 to 1:7 (e.g., 1:5, 1:6, 1:7, etc.). Any other specific point value within the above range can be selected, and it is not convenient to elaborate on them here.

[0032] Preferably, the dripping time in step (3) is 0.5 to 2 hours (e.g., 0.5 hours, 1 hour, 1.5 hours, 2 hours, etc.). Any other specific point value within the above range can be selected, and it is not convenient to elaborate on them here.

[0033] Preferably, the stirring speed in step (3) is 200–1000 r / min (e.g., 200 r / min, 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min, 1000 r / min, etc.). Any other specific value within the above range can be selected, and it is not convenient to elaborate on them here.

[0034] Preferably, the reaction time for continued stirring in step (3) is 2 to 12 hours (e.g., 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, etc.). Any other specific point value within the above range can be selected, and it is inconvenient to elaborate on them here.

[0035] Secondly, the present invention provides a bio-composite nano-selenium nutrient solution prepared by the above preparation method.

[0036] The bio-composite selenium nutrient solution contains nano-selenium particles with a size of 600–800 nm (e.g., 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, etc.). Any other specific value within the above range can be selected, and will not be elaborated further here.

[0037] Thirdly, the present invention provides the application of the above-mentioned bio-composite nano-selenium nutrient solution in crop cultivation.

[0038] Preferably, the application involves uniformly diluting the bio-compound selenium nutrient solution with water at a ratio of 800 to 1000 times (e.g., 800, 820, 850, 870, 900, 920, 950, 970, 1000, etc.) for foliar spraying and / or root irrigation. Any other specific values ​​within the above range can be selected, and will not be elaborated upon here.

[0039] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0040] (1) The product of this invention integrates multiple functions such as efficient absorption of nano-selenium, growth regulation of organic acids, and antibacterial protection of cinnamic acid, forming a synergistic composite system. Moreover, the selection of fully biodegradable materials and production process ensures that the product is harmless to the environment, and long-term use can improve soil quality and increase organic matter content. It can not only meet the market's demand for selenium-rich agricultural products, but also ensure food safety through scientific selenium content control, achieving a perfect balance between nutrition and safety.

[0041] (2) The heating reflux technology used in this invention can effectively suppress the occurrence of side reactions, thereby reducing the generation of by-products and greatly improving the utilization rate of raw materials. It reduces production costs from the source and avoids resource waste. Moreover, the preparation process is simple and easy to operate, and has good prospects for industrial application.

[0042] (3) The bio-composite nano-selenium nutrient solution prepared by the present invention has good adhesion. After spraying, it can adhere tightly to the surface of crops, thereby forming a transparent and protective film, which can reverse the decline in fertilizer efficiency during the rainy season and effectively ensure that the fertilizer can exert its due effectiveness.

[0043] (4) When the present invention is sprayed on the surface of crops, it can achieve long-term precise control and release of selenium, and continuously provide stable selenium supplementation at different stages of crop growth, so that the selenium content of crops is controlled within the safe range of the "Hygienic Standard for Selenium Content in Food" (GB 13105-91), which not only meets people's health needs for selenium-enriched food, but also provides a solid guarantee for food safety. Attached Figure Description

[0044] Figure 1 This is a SEM image of the selenium nanoparticles prepared in Example 3.

[0045] Figure 2 shows the chives before application in Example 2. Figure 2a )back( Figure 2b The selenium content of the leek was tested. (Application process: When the leeks are 15 days old, shake the prepared bio-composite nano-selenium nutrient solution well, dilute it 800 times, and spray it on the leaves. Spray again after 5 days.)

[0046] Figure 3 The yield data for sugarcane after application in Example 10 (experimental group) and Comparative Example 8 (control group) are shown. (Application process: Two months before sugarcane harvest, the prepared bio-composite nano-selenium nutrient solution was shaken well, diluted 800 times, and sprayed on the leaves. If it rains within 4 hours after spraying, re-spraying is required.) Detailed Implementation

[0047] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.

[0048] Unless otherwise specified in the embodiments of this invention, the conditions shall be performed according to conventional conditions or conditions recommended by the manufacturer. All raw materials and reagents used, unless otherwise specified, are commercially available conventional products.

[0049] Example 1

[0050] (1) Take 2.00g of chitosan (molecular weight 2×10⁻⁶) 5 Slowly add the chitosan to 100 mL of 2% (w / v) acetic acid solution and stir for 2 hours until the chitosan is completely dissolved, resulting in a clear and transparent chitosan-acetic acid solution.

[0051] (2) Dissolve 5.00g of DL-malic acid in 100mL of 95% (w / v) ethanol solution and stir for 30min to obtain malic acid-ethanol solution.

[0052] (3) Slowly pour the chitosan-acetic acid solution prepared in step (1) into the malic acid-ethanol solution prepared in step (2), mix well, and adjust the pH value to 5.0-5.5 with 0.1 mol / L sodium hydroxide solution. Then transfer the mixed solution to a three-necked flask equipped with a reflux condenser, and reflux for 3 hours (500 r / min) under oil bath heating conditions (oil bath temperature set at 60℃). After the reaction is completed, cool to room temperature to obtain product A.

[0053] (4) At room temperature, mix 6 mL of 0.1 mol / L sodium selenite solution and 6 mL of 0.05 mol / L potassium cinnamate solution evenly, add 30 mL of 0.2 mol / L vitamin C solution, and shake continuously for 1 hour during the addition process to ensure that the solution is fully mixed and reacted, and finally obtain product B.

[0054] (5) Under stirring conditions, slowly add product B prepared in step (4) to product A prepared in step (3) (m A :m B =5:1), the dropwise addition process lasted for 30 minutes. After the dropwise addition was completed, the reaction was stirred for another 2 hours (stirring at 800 r / min) to ensure that product B was fully loaded onto product A. Finally, a bio-composite nano-selenium nutrient solution was obtained.

[0055] Example 2

[0056] (1) Take 2.00g of chitosan (molecular weight 2×10⁻⁶) 5 Slowly add the chitosan to 100 mL of 2% (w / v) acetic acid solution and stir for 2 hours until the chitosan is completely dissolved, resulting in a clear and transparent chitosan-acetic acid solution.

[0057] (2) Dissolve 4.00g of citric acid in 100mL of 95% (w / v) ethanol solution and stir for 30min to obtain citric acid-ethanol solution.

[0058] (3) Slowly pour the chitosan-acetic acid solution prepared in step (1) into the citric acid-ethanol solution prepared in step (2), mix well, and adjust the pH of the reaction solution to 5.0-5.5 with 0.2 mol / L sodium hydroxide solution. Then transfer the mixed solution to a three-necked flask equipped with a reflux condenser and reflux for 3 hours (500 r / min) under oil bath heating conditions (oil bath temperature set at 60℃). After the reaction is completed, cool to room temperature to obtain product A.

[0059] (4) At room temperature, mix 6 mL of 0.1 mol / L sodium selenite solution and 6 mL of 0.05 mol / L potassium cinnamate solution evenly, add 30 mL of 0.2 mol / L vitamin C solution, and shake continuously for 1 hour during the addition process to ensure that the solution is fully mixed and reacted, and finally obtain product B.

[0060] (5) Under stirring conditions, slowly add product B prepared in step (4) to product A prepared in step (3) (m A :m B =5:1), the dropwise addition process lasted for 30 minutes. After the dropwise addition was completed, the reaction was stirred for another 2 hours (stirring at 800 r / min) to ensure that product B was fully loaded onto product A. Finally, a bio-composite nano-selenium nutrient solution was obtained.

[0061] Example 3

[0062] (1) Take 2.00g of chitosan (molecular weight 2×10⁻⁶) 5 Slowly add the chitosan to 100 mL of 2% (w / v) acetic acid solution and stir for 2 hours until the chitosan is completely dissolved, resulting in a clear and transparent chitosan-acetic acid solution.

[0063] (2) Dissolve 3.00g of salicylic acid in 100mL of 95% (w / v) ethanol solution and stir for 30min to form salicylic acid-ethanol solution.

[0064] (3) Slowly pour the chitosan-acetic acid solution prepared in step (1) into the salicylic acid-ethanol solution prepared in step (2), mix well, and adjust the pH of the reaction solution to 5.0-5.5 with 0.5 mol / L sodium hydroxide solution. Then transfer the mixed solution to a three-necked flask equipped with a reflux condenser and reflux for 3 hours (500 r / min) under oil bath heating conditions (oil bath temperature set at 80℃). After the reaction is completed, cool to room temperature to obtain product A.

[0065] (4) At room temperature, mix 6 mL of 0.1 mol / L sodium selenite solution and 6 mL of 0.05 mol / L potassium cinnamate solution evenly, add 30 mL of 0.2 mol / L vitamin C solution, and shake continuously for 1 hour during the addition process to ensure that the solution is fully mixed and reacted, and finally obtain product B.

[0066] (5) Under stirring conditions, slowly add product B prepared in step (4) to product A prepared in step (3) (m A :m B =5:1), the dropwise addition process lasted for 30 minutes. After the dropwise addition was completed, the reaction was stirred for another 2 hours (stirring at 800 r / min) to ensure that product B was fully loaded onto product A. Finally, a bio-composite nano-selenium nutrient solution was obtained.

[0067] Comparative Example 1

[0068] The difference between this comparative example and Example 3 is that the amount of salicylic acid is increased to 5.00g, while all other raw materials and steps are exactly the same as in Example 3.

[0069] Comparative Example 2

[0070] The difference between this comparative example and Example 3 is that salicylic acid is not added; all other raw materials and steps are exactly the same as in Example 3.

[0071] Example 4

[0072] (1) Slowly add 3.00g of silk fibroin to 100mL of 2% (w / v) acetic acid solution and stir for 2h until the silk fibroin is completely dissolved to obtain a clear and transparent silk fibroin-acetic acid solution.

[0073] (2) Dissolve 3.00g of salicylic acid in 100mL of 95% (w / v) ethanol solution and stir for 30min to form salicylic acid-ethanol solution.

[0074] (3) Slowly pour the silk fibroin-acetic acid solution prepared in step (1) into the salicylic acid-ethanol solution prepared in step (2), mix well, adjust the pH of the reaction solution to 5.0-5.5 with 0.5 mol / L sodium hydroxide solution, and then transfer the mixed solution to a three-necked flask equipped with a reflux condenser. Under oil bath heating conditions (oil bath temperature set at 40℃), reflux for 3 hours (rotation speed of 500 r / min). After the reaction is completed, cool to room temperature to obtain product A.

[0075] (4) At room temperature, mix 6 mL of 0.1 mol / L sodium selenite solution and 6 mL of 0.05 mol / L potassium cinnamate solution evenly, add 30 mL of 0.2 mol / L vitamin C solution, and shake continuously for 1 hour during the addition process to ensure that the solution is fully mixed and reacted, and finally obtain product B.

[0076] (5) Under stirring conditions, slowly add product B prepared in step (4) to product A prepared in step (3) (m A :m B =5:1), the dropwise addition process lasted for 30 minutes. After the dropwise addition was completed, the reaction was stirred for another 2 hours (stirring at 800 r / min) to ensure that product B was fully loaded onto product A. Finally, a bio-composite nano-selenium nutrient solution was obtained.

[0077] Comparative Example 3

[0078] The difference between this comparative example and Example 4 is that the amount of silk fibroin is increased to 8.00g, while all other raw materials and steps are exactly the same as in Example 4.

[0079] Comparative Example 4

[0080] The difference between this comparative example and Example 4 is that no silk fibroin is added; all other raw materials and steps are exactly the same as in Example 4.

[0081] Example 5

[0082] (1) Slowly add 2.00g of gelatin to 100mL of 2% (w / v) acetic acid solution while stirring. Let it stand and soak for 1 hour to allow it to fully absorb water and swell. Heat the swollen gelatin to 60℃ in a hot water bath and continue stirring until the gelatin is completely dissolved to obtain a transparent gel solution.

[0083] (2) Dissolve 3.00g of salicylic acid in 100mL of 95% (w / v) ethanol solution and stir for 30min to form salicylic acid-ethanol solution.

[0084] (3) Slowly pour the transparent adhesive solution prepared in step (1) into the salicylic acid-ethanol solution prepared in step (2), mix well, and adjust the pH of the reaction solution to 5.0-5.5 with 0.5 mol / L sodium hydroxide solution. Then transfer the mixed solution to a three-necked flask equipped with a reflux condenser, and reflux for 3 hours (500 r / min) under oil bath heating conditions (oil bath temperature set at 55℃). After the reaction is completed, cool to room temperature to obtain product A.

[0085] (4) At room temperature, mix 6 mL of 0.1 mol / L sodium selenite solution and 6 mL of 0.05 mol / L potassium cinnamate solution evenly, add 30 mL of 0.2 mol / L vitamin C solution, and shake continuously for 1 hour during the addition process to ensure that the solution is fully mixed and reacted, and finally obtain product B.

[0086] (5) Under stirring conditions, slowly add product B prepared in step (4) to product A prepared in step (3) (m A :m B =5:1), the dropwise addition process lasted for 30 minutes. After the dropwise addition was completed, the reaction was stirred for another 2 hours (stirring at 800 r / min) to ensure that product B was fully loaded onto product A. Finally, a bio-composite nano-selenium nutrient solution was obtained.

[0087] Comparative Example 5

[0088] The difference between this comparative example and Example 5 is that 100 mL of 2% (w / v) acetic acid solution was replaced with ultrapure water; all other raw materials and steps are exactly the same as in Example 5.

[0089] Example 6

[0090] (1) Take 2.00g of chitosan (molecular weight 2×10⁻⁶) 5Slowly add the chitosan to 100 mL of 1.5% (w / v) acetic acid solution and stir for 2 hours until the chitosan is completely dissolved, resulting in a clear and transparent chitosan-acetic acid solution.

[0091] (2) Dissolve 3.00g of salicylic acid in 100mL of 95% (w / v) ethanol solution and stir for 30min to form salicylic acid-ethanol solution.

[0092] (3) Slowly pour the chitosan-acetic acid solution prepared in step (1) into the salicylic acid-ethanol solution prepared in step (2), mix well, and adjust the pH of the reaction solution to 5.0-5.5 with 0.5 mol / L sodium hydroxide solution. Then transfer the mixed solution to a three-necked flask equipped with a reflux condenser and reflux for 3 hours (500 r / min) under oil bath heating conditions (oil bath temperature set at 80℃). After the reaction is completed, cool to room temperature to obtain product A.

[0093] (4) At room temperature, mix 6 mL of 0.05 mol / L sodium selenite solution and 6 mL of 0.05 mol / L potassium cinnamate solution evenly, add 30 mL of 0.2 mol / L vitamin C solution, and shake continuously for 1 hour during the addition process to ensure that the solution is fully mixed and reacted, and finally obtain product B.

[0094] (5) Under stirring conditions, slowly add product B prepared in step (4) to product A prepared in step (3) (m A :m B =5:1), the dropwise addition process lasted for 30 minutes. After the dropwise addition was completed, the reaction was stirred for another 2 hours (stirring at 800 r / min) to ensure that product B was fully loaded onto product A. Finally, a bio-composite nano-selenium nutrient solution was obtained.

[0095] Comparative Example 6

[0096] The difference between this comparative example and Example 6 is that the sodium selenite is changed to 0.2 mol / L, while all other raw materials and steps are exactly the same as in Example 6.

[0097] Comparative Example 7

[0098] The difference between this comparative example and Example 6 is that sodium selenite is not added; all other raw materials and steps are exactly the same as in Example 6.

[0099] Example 7

[0100] (1) Slowly add 2.00g of gelatin to 100mL of 2% (w / v) acetic acid solution while stirring. Let it stand and soak for 1 hour to allow it to fully absorb water and swell. Heat the swollen gelatin to 60℃ in a hot water bath and continue stirring until the gelatin is completely dissolved to obtain a transparent gel solution.

[0101] (2) Dissolve 1.00g of citric acid in 100mL of 95% (w / v) ethanol solution and stir for 30min to form citric acid-ethanol solution.

[0102] (3) Slowly pour the transparent adhesive solution prepared in step (1) into the citric acid-ethanol solution prepared in step (2), mix well, and adjust the pH of the reaction solution to 5.0-5.5 with 0.2 mol / L sodium hydroxide solution. Then transfer the mixed solution to a three-necked flask equipped with a reflux condenser, and reflux for 3 hours (500 r / min) under oil bath heating conditions (oil bath temperature set at 40℃). After the reaction is completed, cool to room temperature to obtain product A.

[0103] (4) At room temperature, mix 6 mL of 0.1 mol / L sodium selenite solution and 6 mL of 0.02 mol / L potassium cinnamate solution evenly, add 30 mL of 0.2 mol / L vitamin C solution, and shake continuously for 1 hour during the addition process to ensure that the solution is fully mixed and reacted, and finally obtain product B.

[0104] (5) Under stirring conditions, slowly add product B prepared in step (4) to product A prepared in step (3) (m A :m B =5:1), the dropwise addition process lasted for 30 minutes. After the dropwise addition was completed, the reaction was stirred for another 2 hours (stirring at 800 r / min) to ensure that product B was fully loaded onto product A. Finally, a bio-composite nano-selenium nutrient solution was obtained.

[0105] Comparative Example 8

[0106] The difference between this comparative example and Example 7 is that the potassium cinnamate is changed to 0.10 mol / L, while all other raw materials and steps are exactly the same as in Example 7.

[0107] Comparative Example 9

[0108] The difference between this comparative example and Example 7 is that potassium cinnamate is not added; all other raw materials and steps are exactly the same as in Example 7.

[0109] Example 8

[0110] (1) Slowly add 2.00g of silk fibroin to 100mL of 2% (w / v) acetic acid solution and stir for 2h until the silk fibroin is completely dissolved to obtain a clear and transparent silk fibroin-acetic acid solution.

[0111] (2) Dissolve 5.00g of DL-malic acid in 100mL of 95% (w / v) ethanol solution and stir for 30min to form malic acid-ethanol solution.

[0112] (3) Slowly pour the silk fibroin-acetic acid solution prepared in step (1) into the malic acid-ethanol solution prepared in step (2), mix well, and adjust the pH of the reaction solution to 5.0-5.5 with 0.1 mol / L sodium hydroxide solution. Then transfer the mixed solution to a three-necked flask equipped with a reflux condenser and reflux for 3 hours (500 r / min) under oil bath heating conditions (oil bath temperature set at 40℃). After the reaction is completed, cool to room temperature, filter, and obtain product A.

[0113] (4) At room temperature, mix 6 mL of 0.1 mol / L sodium selenite solution and 6 mL of 0.05 mol / L potassium cinnamate solution evenly, add 30 mL of 0.2 mol / L vitamin C solution, and shake continuously for 1 hour during the addition process to ensure that the solution is fully mixed and reacted, and finally obtain product B.

[0114] (5) Under stirring conditions, slowly add product B prepared in step (4) to product A prepared in step (3) (m A :m B =5:1), the dropwise addition process lasted for 30 minutes. After the dropwise addition was completed, the reaction was stirred for 2 hours (stirring at 800 r / min) to ensure that product B was fully loaded onto product A. Finally, a bio-composite nano-selenium nutrient solution was obtained.

[0115] Comparative Example 10

[0116] The difference between this comparative example and Example 8 is that vitamin C is replaced with 20 mL of 0.3 mol / L, while all other raw materials and steps are exactly the same as in Example 8.

[0117] Comparative Example 11

[0118] The difference between this comparative example and Example 8 is that vitamin C is not added and the shaking step is omitted; all other ingredients and steps are exactly the same as in Example 8.

[0119] Example 9

[0120] (1) Slowly add 2.00g of silk fibroin to 100mL of 2% (w / v) acetic acid solution and stir for 2h until the silk fibroin is completely dissolved to obtain a clear and transparent silk fibroin-acetic acid solution.

[0121] (2) Dissolve 5.00g of citric acid in 100mL of 95% (w / v) ethanol solution and stir for 30min to form citric acid-ethanol solution.

[0122] (3) Slowly pour the silk fibroin-acetic acid solution prepared in step (1) into the citric acid-ethanol solution prepared in step (2), mix well, adjust the pH of the reaction solution to 5.0-5.5 with 0.2 mol / L sodium hydroxide solution, and then transfer the mixed solution to a three-necked flask equipped with a reflux condenser. Under oil bath heating conditions (oil bath temperature set at 40℃), reflux for 3 hours (rotation speed at 500 r / min). After the reaction is completed, cool to room temperature, filter, and obtain product A.

[0123] (4) At room temperature, mix 6 mL of 0.1 mol / L sodium selenite solution and 6 mL of 0.05 mol / L potassium cinnamate solution evenly, add 30 mL of 0.2 mol / L vitamin C solution, and shake continuously for 1 hour during the addition process to ensure that the solution is fully mixed and reacted, and finally obtain product B.

[0124] (5) Under stirring conditions, slowly add product B prepared in step (4) to product A prepared in step (3) (m A :m B =5:1), the dropwise addition process lasted for 30 minutes. After the dropwise addition was completed, the reaction was stirred for another 2 hours (stirring at 800 r / min) to ensure that product B was fully loaded onto product A. Finally, a bio-composite nano-selenium nutrient solution was obtained.

[0125] Comparative Example 12

[0126] (1) Slowly add 2.00g of silk fibroin to 100mL of 2% (w / v) acetic acid solution and stir for 2h until the silk fibroin is completely dissolved to obtain a clear and transparent silk fibroin-acetic acid solution.

[0127] (2) Dissolve 5.00g of citric acid in 100mL of 95% (w / v) ethanol solution and stir for 30min to form citric acid-ethanol solution.

[0128] (3) Slowly pour the silk fibroin-acetic acid solution prepared in step (1) into the citric acid-ethanol solution prepared in step (2), mix well, then add 6 mL of 0.05 mol / L potassium cinnamate solution, adjust the pH of the reaction solution to 5.0-5.5 with 0.2 mol / L sodium hydroxide solution, and then transfer the mixed solution to a three-necked flask equipped with a reflux condenser. Under oil bath heating conditions (oil bath temperature set at 40℃), reflux for 3 h (rotation speed at 500 r / min). After the reaction is completed, cool to room temperature, filter, and obtain product A.

[0129] (4) At room temperature, add 30 mL of 0.2 mol / L vitamin C solution to 6 mL of 0.1 mol / L sodium selenite solution. Shake continuously for 1 hour during the addition process to ensure that the solution is fully mixed and reacted, and finally obtain product B.

[0130] (5) Under stirring conditions, slowly add product B prepared in step (4) to product A prepared in step (3) (m A :m B =5:1), the dropwise addition process lasted for 30 minutes. After the dropwise addition was completed, the reaction was stirred for another 2 hours (stirring at 800 r / min) to ensure that product B was fully loaded onto product A. Finally, a bio-composite nano-selenium nutrient solution was obtained.

[0131] Example 10

[0132] (1) Slowly add 2.00g of gelatin to 100mL of 2% (w / v) acetic acid solution while stirring. Let it stand and soak for 1 hour to allow it to fully absorb water and swell. Heat the swollen gelatin to 60℃ in a hot water bath and continue stirring until the gelatin is completely dissolved to obtain a transparent gel solution.

[0133] (2) Dissolve 5.00g of DL-malic acid in 100mL of 95% (w / v) ethanol solution and stir for 30min to form malic acid-ethanol solution.

[0134] (3) Slowly pour the transparent adhesive solution prepared in step (1) into the malic acid-ethanol solution prepared in step (2), mix well, and adjust the pH of the reaction solution to 5.0-5.5 with 0.1 mol / L sodium hydroxide solution. Then transfer the mixed solution to a three-necked flask equipped with a reflux condenser, and reflux for 3 hours (500 r / min) under oil bath heating conditions (oil bath temperature set at 78.5℃). After the reaction is completed, cool to room temperature to obtain product A.

[0135] (4) At room temperature, mix 6 mL of 0.1 mol / L sodium selenite solution and 6 mL of 0.05 mol / L potassium cinnamate solution evenly, add 30 mL of 0.2 mol / L vitamin C solution, and shake continuously for 1 hour during the addition process to ensure that the solution is fully mixed and reacted, and finally obtain product B.

[0136] (5) Under stirring conditions, slowly add product B prepared in step (4) to product A prepared in step (3) (m A :m B =5:1), the dropwise addition process lasted for 30 minutes. After the dropwise addition was completed, the reaction was stirred for another 2 hours (stirring at 800 r / min) to ensure that product B was fully loaded onto product A. Finally, a bio-composite nano-selenium nutrient solution was obtained.

[0137] Comparative Example 13

[0138] The difference between this comparative example and Example 10 is that the oil bath heating condition in step (3) is changed to room temperature reaction, while all other raw materials and steps are exactly the same as in Example 10.

[0139] Table 1 shows the cumulative selenium release rate of the bio-composite selenium nutrient solution in soil leachate at 25℃ and pH 6.5 for 7, 14, and 21 days, respectively. As can be seen from Table 1, different amounts of natural high molecular weight polymers, small molecule organic acids, sodium selenite, vitamin C, and potassium cinnamate can affect the slow-release performance of the bio-composite nano selenium nutrient solution.

[0140] Table 1. Statistical data on the sustained-release performance of nano-selenium at different number of days in the examples and comparative examples.

[0141]

[0142] Experimental results show that the bio-composite nano-selenium nutrient solution provided by the present invention has excellent selenium slow-release effect. In the optimal embodiment, the cumulative release rate can reach 82.35% after 21 days. Furthermore, it continuously releases selenium through a slow-release mechanism, meeting the needs of crops at different growth stages, reducing soil erosion, and improving the efficiency of selenium absorption by crops.

[0143] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a biological composite nano-selenium nutrient solution, characterized in that, Includes the following steps: (1) Mix natural polymer-acetic acid solution and small molecule organic acid-ethanol solution, adjust the pH of the mixture, heat and reflux the reaction, stop the reaction and cool to room temperature to obtain product mixture; (2) Sodium selenite, potassium cinnamate and vitamin C were reacted under solvent dissolution conditions to obtain a product mixture; (3) Under stirring conditions, the product mixture of step (2) is added dropwise to the product mixture of step (1). After the addition is complete, the stirring reaction continues to obtain the bio-composite nano selenium nutrient solution.

2. The method for preparing a bio-composite nano-selenium nutrient solution according to claim 1, characterized in that, In step (1), the natural polymer-acetic acid solution has a mass concentration of 1-10% and an acetic acid concentration of 1-10% (w / v). And / or, in the small molecule organic acid-ethanol solution described in step (1), the concentration of the small molecule organic acid is 0.05-0.5 mol / L; the concentration of ethanol is ≥95% (w / v); And / or, in step (1), the mass ratio of the natural high molecular weight polymer to the small molecular weight organic acid is 2.5:1 to 1:2.5; And / or, the pH in step (1) is 5.0 to 5.5; And / or, the pH adjuster used in step (1) to adjust the pH of the product mixture includes sodium hydroxide solution; the mass concentration of the adjuster is 0.1 to 1 mol / L.

3. The method for preparing a bio-composite nano-selenium nutrient solution according to claim 1 or 2, characterized in that, Step (2) specifically involves mixing sodium selenite solution and potassium cinnamate solution, and then adding vitamin C solution to carry out the reaction. And / or, the concentration of the sodium selenite solution is 0.05–0.15 mol / L; And / or, the concentration of the potassium cinnamate solution is 0.02–0.08 mol / L; And / or, the concentration of the vitamin C solution is 0.05–0.2 mol / L; And / or, the solvent in step (2) includes water; And / or, the molar ratio of sodium selenite, potassium cinnamate and vitamin C in step (2) is 1:(0.3-0.7):(8-12).

4. The method for preparing a bio-composite nano-selenium nutrient solution according to claim 1 or 2, characterized in that, In step (3), the mass ratio of the product mixture in step (2) to the product mixture in step (1) is 1:5 to 1:

7.

5. The method for preparing a bio-composite nano-selenium nutrient solution according to claim 1 or 2, characterized in that, In step (1), the natural polymer includes at least one of silk fibroin, chitosan and gelatin; And / or, the molecular weight of the chitosan is (1-3)×10⁻⁶. 5 ; And / or, in step (1), the small molecule organic acid includes at least one of salicylic acid, DL-malic acid and citric acid.

6. The method for preparing a bio-composite nano-selenium nutrient solution according to claim 1 or 2, characterized in that, The temperature of the heating reflux reaction in step (1) is 40-80℃; the time is 2-10h.

7. The method for preparing a bio-composite nano-selenium nutrient solution according to claim 3, characterized in that, The reaction in step (2) is carried out at room temperature for 0.5 to 3 hours.

8. The method for preparing a bio-composite nano-selenium nutrient solution according to claim 4, characterized in that, The stirring reaction in step (3) is continued for 2 to 12 hours; And / or, the dripping time in step (3) is 0.5 to 2 hours.

9. A bio-composite nano-selenium nutrient solution prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the bio-composite nano-selenium nutrient solution according to claim 9 in crop cultivation.

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