Defective multifunctional cerium oxide anchored single-atom nanozymes, their preparation methods and applications

Abstract

This invention provides a defective multifunctional cerium oxide-anchored single-atom nanozyme, its preparation method, and its application. It relates to the field of nanozyme preparation. The defective multifunctional cerium oxide-anchored single-atom nanozyme prepared by this invention is small in size and possesses extremely high enzyme-like activity. The defective cerium oxide is rich in oxygen vacancy defects and highly dispersed metal sites, and also exhibits extremely high multiple enzyme-like activity. It combines the downconversion properties of carbon quantum dots, the multiple enzyme-like activity of single-atom carbon dots, and the multiple enzyme-like activity of defective cerium oxide. It can be used to promote plant growth under various stress environments (high and low temperatures, heavy metals, acidified soil, salt stress, drought, etc.), and has significant practical application value.

Description

Technical Field

[0001] This invention relates to the field of nanozyme preparation, and particularly to defective multifunctional cerium oxide-anchored single-atom nanozymes, their preparation methods, and applications. Background Technology

[0002] Abiotic stresses, such as extreme temperatures (high and low temperatures), heavy metal pollution, soil acidification, salt stress, and drought, are major environmental factors that limit crop growth and yield. These stresses disrupt the balance of reactive oxygen species (ROS) metabolism in plants, leading to oxidative stress, which damages cell membranes, proteins, and nucleic acids, ultimately inhibiting plant growth and even causing death.

[0003] Currently, methods to alleviate abiotic stress in crops mainly include the application of chemical amendments, organic fertilizers, or the cultivation of stress-resistant varieties. However, these methods have limitations: chemical amendments may cause secondary pollution and soil compaction; organic fertilizers are slow to take effect and their effects are unstable; and the cultivation of stress-resistant varieties has a long cycle, high cost, and difficulty in coping with complex stresses.

[0004] Nanozymes are a class of nanomaterials with catalytic activity similar to natural enzymes, offering a new approach to solving the aforementioned problems. Among them, cerium oxide nanozymes, due to the presence of Ce... 3+ / Ce 4+ Cerium oxide nanozymes exhibit intrinsic peroxidase-like activity through variable valence cycling, making them suitable for ROS scavenging. However, single cerium oxide nanozymes suffer from limited catalytic active sites, low catalytic efficiency, insufficient stability, and susceptibility to inactivation in complex soil environments. While introducing oxygen vacancy defects can enhance their intrinsic activity, single defect engineering strategies still struggle to achieve efficient synergistic effects of multiple enzyme-like activities, such as superoxide dismutase, peroxidase, and catalase. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing materials and technologies, and to provide a multifunctional cerium oxide-anchored single-atom nanozyme with high catalytic efficiency, good stability, and the ability to simultaneously simulate the activities of multiple natural enzymes, as well as its preparation method and application.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing defective multifunctional cerium oxide-anchored single-atom nanozymes, comprising the following steps:

[0008] 1) Dissolve cerium salt and ethylenediaminetetraacetic acid metal salt in deionized water and stir until completely dissolved. Then add alkaline solution to adjust the pH of the mixed solution to 8.0~11.0 to obtain the precursor solution.

[0009] 2) Transfer the precursor solution obtained in step 1) to a reaction vessel and carry out a hydrothermal reaction at 100~170℃ for 4~24 hours; after the reaction is completed, cool naturally to room temperature, filter, wash and dry the product to obtain a solid powder of cerium oxide adsorbed with ethylenediaminetetraacetic acid metal salt.

[0010] 3) The solid powder obtained in step 2) is placed in a tube furnace and heated to 250-320°C at a heating rate of 2-5°C / min under a reducing atmosphere, and then kept at that temperature for 1-6 hours; then it is naturally cooled to room temperature to obtain an intermediate composite material containing cerium oxide anchored single-atom carbon dot nanozymes with vacancy defects.

[0011] 4) Disperse the intermediate composite material obtained in step 3) in deionized water, then add a low concentration of metal salt solution and stir at room temperature for 2 to 12 hours; then filter, wash and dry to finally obtain the defect-multifunctional cerium oxide-anchored single-atom nanozyme.

[0012] Preferably, in step 1), the cerium salt is selected from cerium chloride, cerium nitrate, and cerium sulfate; the metal in the ethylenediaminetetraacetic acid metal salt is one of Fe, Zn, or Mn; and the mass ratio of the ethylenediaminetetraacetic acid metal salt, cerium salt, and water is 0.05~0.1:1:25.

[0013] Preferably, in step 1), the alkali in the alkaline solution is selected from sodium hydroxide, potassium hydroxide, and calcium hydroxide.

[0014] Preferably, in step 3), the reducing atmosphere is a mixture of hydrogen and an inert gas, wherein the volume fraction of hydrogen is 0.05% to 5.05%.

[0015] Preferably, in step 4), the concentration of the low-concentration metal salt solution is 0.01~0.1 M, and the metal element in the metal salt is at least one of Fe, Zn, and Mn, and the metal element may be the same as or different from that in the ethylenediaminetetraacetic acid metal salt in step 1).

[0016] Secondly, this invention provides a defective multifunctional cerium oxide-anchored single-atom nanozyme, prepared by the above-described method. This nanozyme uses oxygen-vacancy-rich defective cerium oxide as a carrier, on which single-atom carbon dots derived from ethylenediaminetetraacetic acid metal salt through calcination, as well as subsequently introduced metal single atoms, are simultaneously anchored.

[0017] Thirdly, the present invention provides the application of the aforementioned defective multifunctional cerium oxide-anchored single-atom nanozyme in plant growth.

[0018] Preferably, the application includes enhancing the plant's resistance to abiotic stresses, including high temperature, low temperature, heavy metal stress, soil acidification, salt stress, or drought stress.

[0019] Preferably, the size of the defective multifunctional cerium oxide-anchored single-atom nanozyme is 20-100 nm, allowing it to enter plant cells.

[0020] Preferably, the defect-specific multifunctional cerium oxide-anchored single-atom nanoenzyme is used by seed soaking, foliar spraying, or a mixture of both, at a concentration of 50-600 mg / L, and in water as the solvent.

[0021] The beneficial effects of this invention are as follows:

[0022] 1) Synergistic catalysis with superior activity: This invention creatively integrates single-atom carbon dots, metal single atoms, oxygen vacancies, and defective cerium oxide into one unit. Single-atom carbon dots and metal single atoms provide catalytic sites with high intrinsic activity, while the oxygen vacancies of defective cerium oxide can not only serve as active sites but also regulate the electronic structure of the carrier. The synergistic effect of these three elements achieves highly efficient integration of multiple enzyme activities, including superoxide dismutase, peroxidase, and catalase, enabling faster and more comprehensive removal of various reactive oxygen species from plants.

[0023] 2) Stable structure and long-lasting effectiveness: Through a multi-step preparation method of "hydrothermal-calcination-liquid phase anchoring", metal single atoms are stably immobilized on defective cerium oxide support, which effectively prevents the migration and aggregation of single atoms during use and ensures the long-term catalytic stability of the material in complex environments.

[0024] 3) Multi-purpose material with broad application prospects: This composite material shows good mitigation effects against various stresses such as high temperature, low temperature, heavy metals, acidification, salinity and drought. It has broad-spectrum stress resistance characteristics of "multi-purpose material" and has great application potential and market value in the development of new agricultural nanoenzymes. Attached Figure Description

[0025] Figure 1 This is a flowchart illustrating the preparation method of the defective multifunctional cerium oxide-anchored single-atom nanoenzyme composite material of the present invention.

[0026] Figure 2 An optical photograph of the defective multifunctional cerium oxide-anchored single-atom nanoenzyme composite material prepared in Example 1 of this invention.

[0027] Figure 3 Transmission electron microscopy (TEM) image of the defective multifunctional cerium oxide-anchored single-atom nanoenzyme composite material prepared in Example 1 of this invention.

[0028] Figure 4The growth of rice treated with and untreated with the nanozyme of this invention under high temperature stress is shown. Detailed Implementation

[0029] To more clearly illustrate the present invention, the invention will be further described in detail below with reference to embodiments and accompanying drawings. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0030] The flowchart of the preparation method of the multifunctional cerium oxide anchored single-atom nanoenzyme composite material of this invention is as follows: Figure 1 As shown.

[0031] Example 1

[0032] (1) Dissolve 2.0 g of cerium sulfate and 0.2 g of ferric ethylenediaminetetraacetate in 50 mL of deionized water and stir until completely dissolved. Then add sodium hydroxide to adjust the pH of the mixed solution to 10 to obtain the precursor solution.

[0033] (2) The precursor solution obtained in step 1) was transferred to a reaction vessel and subjected to a hydrothermal reaction at 170°C for 6 hours. After the reaction was completed, the product was naturally cooled to room temperature, filtered, washed and dried to obtain a solid powder of cerium oxide adsorbed with ferric ethylenediaminetetraacetate.

[0034] (3) The solid powder obtained in step 2) was placed in a tube furnace, and 5.05% (v / v, volume fraction) H2 / N2 was heated to 250°C at a heating rate of 5°C / min and kept at the temperature for 4 hours; then it was naturally cooled to room temperature to obtain an intermediate composite material containing cerium oxide anchored single-atom carbon dot nanozymes with vacancy defects.

[0035] (4) The intermediate composite material obtained in step 3) was dispersed in deionized water, and then 20 mL of a 20 mmol / L low-concentration ferric chloride solution was added. The mixture was stirred at room temperature for 6 hours. Afterwards, it was filtered, washed, and dried to finally obtain the composite material of the defect-containing multifunctional cerium oxide-anchored single-atom nanozyme. Its solid powder is brownish-red, and optical photographs are shown below. Figure 2 As shown, the transmission electron microscope image is as follows: Figure 3 As shown, the nanozymes prepared in the following examples have the same morphological characterization as those in this example.

[0036] Example 2

[0037] (1) Dissolve 2.0 g of cerium nitrate and 0.2 g of zinc ethylenediaminetetraacetate in 50 mL of deionized water and stir until completely dissolved. Then add sodium hydroxide to adjust the pH of the mixed solution to 10 to obtain the precursor solution.

[0038] (2) The precursor solution obtained in step 1) was transferred to a reaction vessel and subjected to a hydrothermal reaction at 100°C for 24 hours. After the reaction was completed, the product was naturally cooled to room temperature, filtered, washed and dried to obtain a solid powder of cerium oxide adsorbing zinc ethylenediaminetetraacetate.

[0039] (3) The solid powder obtained in step 2) was placed in a tube furnace, and 5.05% (v / v, volume fraction) H2 / N2 was heated to 320°C at a heating rate of 5°C / min and kept at that temperature for 1 hour; then it was naturally cooled to room temperature to obtain an intermediate composite material containing cerium oxide anchored single-atom carbon dot nanozymes with vacancy defects.

[0040] (4) The intermediate composite material obtained in step 3) is dispersed in deionized water, and then 20 mL of 10 mmol / L low-concentration zinc chloride solution is added and stirred at room temperature for 2 hours; then filtered, washed and dried to finally obtain the composite material of the defective multifunctional cerium oxide anchored single-atom nanozyme.

[0041] Example 3

[0042] (1) Dissolve 2.0 g of cerium chloride and 0.2 g of manganese ethylenediaminetetraacetate in 50 mL of deionized water and stir until completely dissolved. Then add sodium hydroxide and adjust the pH of the mixed solution to 10 to obtain the precursor solution.

[0043] (2) The precursor solution obtained in step 1) was transferred to a reaction vessel and subjected to a hydrothermal reaction at 150°C for 12 hours. After the reaction was completed, the product was naturally cooled to room temperature, filtered, washed and dried to obtain a solid powder of cerium oxide adsorbing manganese ethylenediaminetetraacetate.

[0044] (3) The solid powder obtained in step 2) was placed in a tube furnace, and 5.05% (v / v, volume fraction) H2 / N2 was heated to 300°C at a heating rate of 4°C / min and kept at that temperature for 3 hours; then it was naturally cooled to room temperature to obtain an intermediate composite material containing cerium oxide anchored single-atom carbon dot nanozymes with vacancy defects.

[0045] (4) The intermediate composite material obtained in step 3) is dispersed in deionized water, and then 20 mL of 50 mmol / L low concentration manganese chloride solution is added. The mixture is stirred at room temperature for 10 hours. After that, it is filtered, washed and dried to finally obtain the composite material of the defective multifunctional cerium oxide anchored single atom nanozyme.

[0046] Example 4

[0047] (1) Dissolve 2.0 g cerium sulfate and 0.2 g ferric ethylenediaminetetraacetate in 50 mL deionized water and stir until completely dissolved. Then add sodium hydroxide to adjust the pH of the mixed solution to 11 to obtain the precursor solution.

[0048] (2) The precursor solution obtained in step 1) was transferred to a reaction vessel and subjected to a hydrothermal reaction at 170°C for 4 hours. After the reaction was completed, the product was naturally cooled to room temperature, filtered, washed and dried to obtain a solid powder of cerium oxide adsorbed with ferric ethylenediaminetetraacetate.

[0049] (3) The solid powder obtained in step 2) was placed in a tube furnace, and 0.05% (v / v, volume fraction) H2 / N2 was heated to 280°C at a heating rate of 3°C / min and kept at the temperature for 4 hours; then it was naturally cooled to room temperature to obtain an intermediate composite material containing cerium oxide anchored single-atom carbon dot nanozymes with vacancy defects.

[0050] (4) The intermediate composite material obtained in step 3) is dispersed in deionized water, and then 20 mL of 20 mmol / L low-concentration zinc chloride solution is added and stirred at room temperature for 6 hours; then filtered, washed and dried to finally obtain the composite material of the defective multifunctional cerium oxide anchored single-atom nanozyme.

[0051] Example 5

[0052] (1) Dissolve 2.0 g of cerium sulfate and 0.2 g of ferric ethylenediaminetetraacetate in 50 mL of deionized water and stir until completely dissolved. Then add sodium hydroxide to adjust the pH of the mixed solution to 10 to obtain the precursor solution.

[0053] (2) The precursor solution obtained in step 1) was transferred to a reaction vessel and subjected to a hydrothermal reaction at 170°C for 6 hours. After the reaction was completed, the product was naturally cooled to room temperature, filtered, washed and dried to obtain a solid powder of cerium oxide adsorbed with ferric ethylenediaminetetraacetate.

[0054] (3) The solid powder obtained in step 2) was placed in a tube furnace, and 5.05% (v / v, volume fraction) H2 / N2 was heated to 250°C at a heating rate of 5°C / min and kept at that temperature for 4 hours; then it was naturally cooled to room temperature to obtain an intermediate composite material containing cerium oxide anchored single-atom carbon dot nanozymes with vacancy defects.

[0055] (4) The intermediate composite material obtained in step 3) is dispersed in deionized water, and then 20 mL of 100 mmol / L low concentration manganese chloride solution is added and stirred at room temperature for 12 hours; then filtered, washed and dried to finally obtain the composite material of the defective multifunctional cerium oxide anchored single atom nanozyme.

[0056] Example 6

[0057] (1) Dissolve 2.0 g of cerium nitrate and 0.2 g of manganese ethylenediaminetetraacetate in 50 mL of deionized water and stir until completely dissolved. Then add sodium hydroxide to adjust the pH of the mixed solution to 10 to obtain the precursor solution.

[0058] (2) The precursor solution obtained in step 1) was transferred to a reaction vessel and subjected to a hydrothermal reaction at 170°C for 6 hours. After the reaction was completed, the product was naturally cooled to room temperature, filtered, washed and dried to obtain a solid powder of cerium oxide adsorbing manganese ethylenediaminetetraacetate.

[0059] (3) The solid powder obtained in step 2) was placed in a tube furnace, and 3% (v / v, volume fraction) H2 / N2 was heated to 250°C at a heating rate of 5°C / min and kept at the temperature for 4 hours; then it was naturally cooled to room temperature to obtain an intermediate composite material containing cerium oxide anchored single-atom carbon dot nanozymes with vacancy defects.

[0060] (4) The intermediate composite material obtained in step 3) is dispersed in deionized water, and then 20 mL of 20 mmol / L low-concentration ferric chloride solution is added and stirred at room temperature for 6 hours; then filtered, washed and dried to finally obtain the composite material of the defective multifunctional cerium oxide anchored single-atom nanozyme.

[0061] The nanozyme prepared in Example 1 is used as an example to conduct tests to verify the performance of the nanozyme prepared in this invention.

[0062] Test Example: Rice High Temperature Resistance Experiment

[0063] To systematically evaluate the effect of nanozyme treatment on improving the high-temperature resistance of rice, we designed the following experimental procedure: First, plump and uniform rice seeds (Oryza sativa L. cv. 'Nipponbare') were selected and soaked in deionized water (control group) and nanozyme solution (treatment group) at 25℃ for 12 hours, respectively, followed by germination in a constant temperature incubator at 28℃ for 48 hours; after the seeds showed signs of sprouting, they were sown in nutrient soil and placed in an artificial climate chamber (photoperiod 12h / 12h, light intensity 600 μmol / m²). -2 s -1 Within a 70% humidity range, rice was cultivated at normal growing temperatures (28℃ / 25℃ day / night) until the late booting stage. Subsequently, the high-temperature stress group (HT) and the treatment group (T) were subjected to 7 days of periodic high-temperature stress (38℃ / 28℃ day / night), while the normal temperature control group (CK) was maintained at 28℃ / 25℃ throughout. The differences between the groups were compared using analysis of variance to reveal the physiological mechanism and actual yield-increasing effect of nanozyme treatment on alleviating high-temperature stress in rice. Four parallel control groups were set up for each treatment.

[0064] like Figure 4 As shown in Table 1, compared with the untreated sample, rice treated with nanozyme solution showed significantly improved growth under high temperatures, exhibiting visibly greater plant height and leaf area, as well as significant improvements in other agronomic indicators such as thousand-grain weight. Therefore, treatment with 300 mg / L nanozyme solution can significantly promote rice growth under extreme high temperatures.

[0065] Table 1. Agronomic data of rice treated with and untreated with nanozymes

[0066]

[0067] The test example uses the nanozyme prepared in Example 1 to demonstrate its effect. The test results of the other examples are basically the same as those of Example 1.

[0068] Obviously, the above embodiments of the present invention are merely examples to illustrate the present invention more clearly, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all implementation methods here. Any obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for preparing a defective multifunctional ceria-anchored single-atom nanoszyme, characterized in that, The method comprises the following steps: 1) Dissolve cerium salt and metal ethylenediaminetetraacetic acid salt in deionized water, stir until completely dissolved, then add a basic solution, adjust the pH value of the mixed solution to 8.0-11.0, and obtain a precursor solution; 2) Transfer the precursor solution obtained in step 1) to a reaction kettle, and perform hydrothermal reaction at a temperature of 100-170℃ for 4-24 hours; after the reaction is completed, naturally cool to room temperature, and filter, wash and dry the product to obtain a solid powder of cerium oxide adsorbed with metal ethylenediaminetetraacetic acid salt; 3) Place the solid powder obtained in step 2) in a tube furnace, and under a reducing atmosphere, increase the temperature to 250-320℃ at a heating rate of 2-5℃ / min, and maintain the temperature for 1-6 hours; then naturally cool to room temperature to obtain an intermediate composite material of cerium oxide anchored single-atom carbon dot nanoscale enzyme containing vacancy defects; 4) Disperse the intermediate composite material obtained in step 3) in deionized water, then add a low-concentration metal salt solution, stir at room temperature for 2-12 hours; then filter, wash and dry to finally obtain the defective multifunctional cerium oxide anchored single-atom nanoscale enzyme.

2. The production method according to claim 1, characterized by, In step 1), the cerium salt is selected from one of cerium chloride, cerium nitrate and cerium sulfate; the metal in the metal ethylenediaminetetraacetic acid salt is one of Fe, Zn or Mn; and the mass ratio of the metal ethylenediaminetetraacetic acid salt, the cerium salt and water is 0.05-0.1:1:

25.

3. The production method according to claim 2, characterized by, In step 1), the base in the basic solution is selected from one of sodium hydroxide, potassium hydroxide and calcium hydroxide.

4. The method of claim 1, wherein, In step 3), the reducing atmosphere is a mixture of hydrogen and inert gas, wherein the volume fraction of hydrogen is 0.05%-5.05%.

5. The preparation method according to claim 1, characterized in that, In step 4), the concentration of the low-concentration metal salt solution is 0.01-0.1 M, and the metal element in the metal salt is at least one of Fe, Zn and Mn, and can be the same as or different from the metal element in the metal ethylenediaminetetraacetic acid salt in step 1).

6. A defective multifunctional ceria anchored single atom nanoszyme characterized in that, Prepared by the preparation method of any one of claims 1-5.

7. The application of the defective multifunctional cerium oxide anchored single-atom nanoscale enzyme of claim 6 in plant growth.

8. Use according to claim 7, characterized in that, The application includes enhancing the resistance of plants to abiotic stress, including high temperature, low temperature, heavy metal stress, soil acidification, salt stress or drought stress.

9. Use according to claim 7, characterized in that, The size of the defective multifunctional cerium oxide anchored single-atom nanoscale enzyme is 20-100 nm.

10. Use according to claim 7, characterized in that, The use method of the defective multifunctional cerium oxide anchored single-atom nanoscale enzyme is seed soaking or foliar spraying or a mixture of both, and the use concentration is 50-600 mg / L, and the use solvent is water.

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