Single-atom nanozyme with vacancy defect and selective light emission function, and preparation method and application thereof

Abstract

The present application relates to a single-atom nanoenzyme with a vacancy defect and a selective light emission function, a preparation method and application thereof, and relates to the technical field of nanoenzyme preparation.The chemical general formula of the single-atom nanoenzyme is M-RE / Ov-CeO2, wherein: M represents an atomically dispersed transition metal single atom, and is selected from one of Fe, Zn and Mn; RE represents an atomically dispersed rare earth metal single atom, and is selected from one of Eu, Tb, Sm and Y; Ov represents an oxygen vacancy in a cerium oxide base; and the transition metal single atom M and the rare earth metal single atom RE are jointly anchored in an oxygen vacancy-rich cerium oxide CeO2 nanocrystal lattice through M-O-Ce and RE-O-Ce coordination bonds.The single-atom nanoenzyme of the present application has dual functions of light quality conversion and active oxygen scavenging, and has the characteristics of environmental friendliness and high biological safety while realizing plant stress resistance and yield increase.

Description

Technical Field

[0001] This invention relates to the field of nanozyme preparation technology, and in particular to single-atom nanozymes with vacancy defects and selective light emission functions, their preparation methods, and applications. Background Technology

[0002] Global climate change is causing increasingly severe abiotic stresses such as high temperatures, drought, and salinity, posing a significant threat to agricultural production. These stresses induce excessive production of reactive oxygen species in plants, leading to oxidative damage, ultimately inhibiting growth and causing yield reduction. Traditional solutions, such as breeding stress-resistant varieties, are time-consuming, and the application of chemical stress-resistance agents has limited effectiveness and may cause environmental pollution.

[0003] Nanozyme technology offers a new approach to solving this problem. For example, cerium oxide nanozymes, due to their variable Ce content... 3+ / Ce 4+ In terms of valence state, it can mimic the activity of antioxidant enzymes and scavenge reactive oxygen species. However, the catalytic efficiency, stability, and biosafety of ordinary cerium oxide nanozymes in complex soil environments still need improvement. More importantly, its function is singular; it can only passively scavenge reactive oxygen species and cannot actively regulate light energy, a key factor affecting plant growth. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide single-atom nanozymes with vacancy defects and selective light emission functions, as well as their preparation methods and applications. By constructing a ternary synergistic system of "single-atom catalytic center-oxygen vacancy-rare earth luminescent center", plants are endowed with dual capabilities of "light regulation" and "oxidative protection", thereby significantly enhancing the survival and growth ability of plants under various adverse conditions.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] In a first aspect, the present invention provides a single-atom nanozyme with vacancy defects and selective light emission functions, having the general chemical formula M-RE / Ov-CeO2, wherein:

[0007] M represents atomically dispersed transition metal single atoms, selected from one of Fe, Zn, and Mn;

[0008] RE represents atomically dispersed rare earth metal single atoms, selected from one of Eu (Eu), Tb (Terbium), Sm (Samarium), and Y (Yttrium);

[0009] Ov represents oxygen vacancies in the cerium oxide substrate;

[0010] The transition metal single atom M and the rare earth metal single atom RE are anchored together in the oxygen-vacant CeO2 nanolattice through MO-Ce and RE-O-Ce coordination bonds, respectively.

[0011] Preferably, the molar ratio of the transition metal single atom M to the rare earth metal single atom RE is 1:10 to 10:1.

[0012] This single-atom nanozyme can mimic the catalytic activity of superoxide dismutase and catalase. The rare-earth metal single atom RE produces a characteristic emission spectrum of 400-700 nm under ultraviolet light excitation, wherein when RE is Eu, its characteristic emission peak is located at 610-620 nm.

[0013] Secondly, the present invention provides a method for preparing the above-mentioned single-atom nanozyme, comprising the following steps:

[0014] 1) Dissolve cerium salt, transition metal salt and rare earth metal salt in deionized water, add organic ligand, then add alkaline solution, adjust the pH of the mixed solution to 8.0~11.0, and stir at 60~80℃ until homogeneous;

[0015] 2) Transfer the solution from step 1) to a reaction vessel and hydrothermally react at 140~180℃ for 8~16 hours. After the reaction is completed, centrifuge, wash and dry to obtain precursor powder. This process uses a ligand to regulate crystal growth, simultaneously form initial oxygen vacancies, and obtain a uniform nano precursor.

[0016] 3) The precursor powder obtained in step 2) is heated to 350-500℃ at a heating rate of 2-5℃ / min under a reducing atmosphere and held at that temperature for 1-2 hours. This step further increases the oxygen vacancy density and firmly anchors M and RE in the CeO2 lattice in the form of single atoms, finally obtaining the product M-RE / Ov-CeO2.

[0017] Preferably, in step 1):

[0018] The cerium salt is one of cerium nitrate, cerium chloride, or cerium acetate;

[0019] The transition metal salt is one of the corresponding nitrate, chloride, or acetate of the transition metal;

[0020] The rare earth metal salt is one of the corresponding nitrates or chlorides of rare earth metals;

[0021] The organic ligand is citric acid or disodium ethylenediaminetetraacetate, and its molar ratio with the total metal ions in the aqueous solution is 1:1 to 3:1.

[0022] The alkali in the alkaline solution is selected from sodium hydroxide, potassium hydroxide, or calcium hydroxide.

[0023] Preferably, the reducing atmosphere in step 3) is a mixture of hydrogen and an inert gas, wherein the volume fraction of hydrogen is 3% to 8%.

[0024] Thirdly, the present invention provides the application of the above-mentioned single-atom nanozymes in plant stress resistance and yield increase.

[0025] Preferably, the stress resistance includes resistance to abiotic stresses, which include at least one of drought, salinity, high temperature, and low temperature.

[0026] Preferably, the application includes promoting plant growth under extreme stress conditions, including treating plants with the single-atom nanozyme, utilizing its light conversion properties to convert ultraviolet light into specific light, and utilizing its enzymatic catalytic activity to remove reactive oxygen species in the plant.

[0027] More preferably, the method of using the single-atom nanozyme includes foliar spraying or seed soaking; wherein the concentration of the single-atom nanozyme is 10~500 mg / L.

[0028] More preferably, the single-atom nanozyme has a size of 20-80 nm, allowing it to enter plant cells.

[0029] The beneficial effects of this invention are as follows:

[0030] 1) Combining Active Defense and Passive Protection: This invention is the first to integrate the two major functions of "photoregulation" and "oxidative protection" into a single material. Rare earth single atoms actively enhance the photosynthetic efficiency and energy state of plants through light conversion, strengthening their basic stress resistance; while single-atom nanoenzymes passively protect plants from oxidative damage by scavenging reactive oxygen species. The two work synergistically to fundamentally improve the plant's stress resistance. Specifically:

[0031] Optical-to-material conversion: Rare earth single atoms in materials (such as Eu) 3+ It can effectively convert ultraviolet light in sunlight into orange-red light (~615 nm). This wavelength can be efficiently absorbed by the plant photoreceptor phytochrome B, thereby promoting photosynthesis, delaying aging, and enhancing photomorphogenesis.

[0032] Reactive oxygen species scavenging: Transition metal single atoms (such as Fe) in the material work in concert with oxygen vacancies to efficiently mimic the cascade reaction of superoxide dismutase and catalase, promptly removing superoxide anions and hydrogen peroxide accumulated under stress conditions and maintaining cellular redox homeostasis.

[0033] 2) Green and efficient, multi-functional: This material utilizes "waste light" (ultraviolet light) from sunlight, converting it into "useful light," while simultaneously and efficiently decomposing "toxins" (reactive oxygen species) within plants, achieving dual high-efficiency utilization of energy and matter. It is effective against various stresses such as high temperature, drought, and salinity, exhibiting broad-spectrum efficacy.

[0034] 3) Environmentally friendly and highly biosafe: The material is based on CeO2 with good biocompatibility. The single-atom level metal loading greatly reduces the potential risks of heavy metals, and the preparation process is green and controllable. Attached Figure Description

[0035] Figure 1 This is a flowchart of the preparation method of the single-atom nanozyme with vacancy defects and selective light emission function of the present invention.

[0036] Figure 2 An optical photograph of the single-atom nanozyme prepared in Example 1 of this invention.

[0037] Figure 3 Transmission electron microscopy (TEM) image of the single-atom nanozyme prepared in Example 1 of this invention.

[0038] Figure 4 The growth of wheat treated with and untreated by the nanozyme of this invention under drought stress is shown. Detailed Implementation

[0039] 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.

[0040] The flowchart of the preparation method of this invention is as follows: Figure 1 As shown.

[0041] Example 1: Fe-Eu / Ov-CeO2 (hydrothermal at 160°C, calcined at 450°C)

[0042] 1) Precursor solution: Dissolve 4.34 g Ce(NO3)3·6H2O (0.01 mol), 0.202 g Fe(NO3)3·9H2O (0.5 mmol), and 0.446 g Eu(NO3)3·6H2O (1.0 mmol) in 80 mL of deionized water. Add 4.20 g citric acid, then add sodium hydroxide to adjust the pH of the mixture to 8. Stir at 70°C until homogeneous.

[0043] 2) Hydrothermal crystallization: The solution was transferred to a 100 mL reactor and reacted at 160°C for 12 hours. After centrifugation, washing, and drying at 60°C, the precursor powder was obtained.

[0044] 3) Controlled calcination: Under a 5% H2 / Ar atmosphere, the temperature was increased to 450℃ at a rate of 3℃ / min, held at that temperature for 2 hours, and then cooled to obtain Fe-Eu / Ov-CeO2. Optical photographs are shown below. Figure 2 As shown, the transmission electron microscope image is as follows: Figure 3 As shown in the figure. The results show that the obtained material is brownish-yellow and its microscale size is less than 100 nm.

[0045] Example 2: Zn-Tb / Ov-CeO2 (hydrothermal at 140°C, calcined at 400°C)

[0046] 1) Precursor solution: Dissolve 4.34 g Ce(NO3)3·6H2O (0.01 mol), 0.121 g Zn(NO3)2·3H2O (0.5 mmol), and 0.452 g Tb(NO3)3·6H2O (1.0 mmol) in 80 mL of deionized water. Add 3.72 g disodium EDTA, then add sodium hydroxide to adjust the pH of the mixture to 9. Stir at 70°C until homogeneous.

[0047] 2) Hydrothermal crystallization: The solution was reacted at 140°C for 10 hours. Subsequent treatment was the same as in Example 1.

[0048] 3) Controllable calcination: Under a 5% H2 / Ar atmosphere, the temperature is increased to 400℃ at 3℃ / min and calcined for 2 hours to obtain Zn-Tb / Ov-CeO2.

[0049] Example 3: Mn-Sm / Ov-CeO2 (hydrothermal at 180°C, calcined at 500°C)

[0050] 1) Precursor solution: Dissolve 4.34 g Ce(NO3)3·6H2O (0.01 mol), 0.169 g MnSO4·H2O (1.0 mmol), and 0.387 g Sm(NO3)3·6H2O (0.85 mmol) in 80 mL of deionized water. Add 4.20 g citric acid, then add sodium hydroxide to adjust the pH of the mixture to 10, and stir at 70°C until homogeneous.

[0051] 2) Hydrothermal crystallization: The solution was reacted at 180°C for 8 hours. Subsequent treatment was the same as in Example 1.

[0052] 3) Controllable calcination: Under a 5% H2 / Ar atmosphere, the temperature is increased to 500℃ at 3℃ / min and calcined for 1.5 hours to obtain Mn-Sm / Ov-CeO2.

[0053] Example 4: Fe-Y / Ov-CeO2 (hydrothermal at 150°C, calcined at 380°C)

[0054] 1) Precursor solution: Dissolve 4.34 g Ce(NO3)3·6H2O (0.01 mol), 0.202 g Fe(NO3)3·9H2O (0.5 mmol), and 0.383 g Y(NO3)3·6H2O (1.0 mmol) in 80 mL of deionized water. Add 4.20 g citric acid, then add sodium hydroxide to adjust the pH of the mixture to 11. Stir at 70°C until homogeneous.

[0055] 2) Hydrothermal crystallization: The solution was reacted at 150°C for 14 hours. Subsequent treatment was the same as in Example 1.

[0056] 3) Controllable calcination: Under a 5% H2 / Ar atmosphere, the temperature is increased to 380℃ at 2℃ / min and calcined for 3 hours to obtain Fe-Y / Ov-CeO2.

[0057] Example 5: Zn-Eu / Ov-CeO2 (hydrothermal at 170°C, calcined at 420°C)

[0058] 1) Precursor solution: Dissolve 4.34 g Ce(NO3)3·6H2O (0.01 mol), 0.121 g Zn(NO3)2·3H2O (0.5 mmol), and 0.446 g Eu(NO3)3·6H2O (1.0 mmol) in 80 mL of deionized water. Add 4.20 g citric acid, then add sodium hydroxide to adjust the pH of the mixture to 8. Stir at 70°C until homogeneous.

[0059] 2) Hydrothermal crystallization: The solution was reacted at 170°C for 11 hours. Subsequent treatment was the same as in Example 1.

[0060] 3) Controllable calcination: Under a 5% H2 / Ar atmosphere, the temperature is increased to 420℃ at 4℃ / min and calcined for 2 hours to obtain Zn-Eu / Ov-CeO2.

[0061] Example 6: Fe-Tb / Ov-CeO2 (hydrothermal at 160°C, calcined at 480°C)

[0062] 1) Precursor solution: Dissolve 4.34 g Ce(NO3)3·6H2O (0.01 mol), 0.202 g Fe(NO3)3·9H2O (0.5 mmol), and 0.452 g Tb(NO3)3·6H2O (1.0 mmol) in 80 mL of deionized water. Add 4.20 g citric acid, then add sodium hydroxide to adjust the pH of the mixture to 9. Stir at 70°C until homogeneous.

[0063] 2) Hydrothermal crystallization: The solution was reacted at 160°C for 12 hours. Subsequent treatment was the same as in Example 1.

[0064] 3) Controllable calcination: Under a 5% H2 / Ar atmosphere, the temperature is increased to 480℃ at 3℃ / min and calcined for 1 hour to obtain Fe-Tb / Ov-CeO2.

[0065] 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.

[0066] Test Example: Wheat Drought Resistance Experiment

[0067] To systematically evaluate the effect of nanozyme treatment on improving drought resistance in wheat, we designed the following experimental procedure: First, plump and uniform wheat seeds (Triticum aestivum L. cv. 'Zhengmai 136') were selected and soaked for 12 hours at 25℃ in deionized water (control group) and a 200 mg / L Fe-Eu / Ov-CeO2 nanozyme solution (treatment group), respectively. Then, they were sown in nutrient soil at room temperature and placed in an artificial climate chamber (photoperiod 14h / 10h, light intensity 500 μmol / m²). -2 s -1 Within a humidity range of 65%, wheat was cultivated to the three-leaf-one-heart stage under normal growing temperatures (day / night 22℃ / 18℃). Subsequently, water supply was stopped for the drought stress group (DS) and the nanozyme treatment group (DS+NMs), maintaining the soil volumetric water content at a drought stress level of approximately 40% for 15 days, while the normal control group (CK) maintained a soil water content of 70%–75%. Analysis of variance was used to compare the differences between groups to reveal the physiological mechanism and actual growth-promoting effect of nanozyme treatment in alleviating wheat drought stress. Four biological replicates were set up for each treatment.

[0068] like Figure 4As shown in Table 1, compared with the untreated sample (left), wheat treated with nanozyme solution (right) showed that nanozymes significantly improved wheat growth under drought stress, exhibiting visibly higher plant height, greener leaves, and more vigorous biomass. Other agronomic indicators, such as thousand-grain weight, were also significantly improved. Therefore, treatment with 200 μg / mL Fe-Eu / Ov-CeO2 nanozyme solution can significantly promote wheat growth and survival under drought stress.

[0069] Table 1. Agronomic data of wheat seedlings treated with and untreated with nanozymes

[0070]

[0071] 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.

[0072] 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 single-atom nanozyme with vacancy defects and selective light emission functions, characterized in that, The general chemical formula is M-RE / Ov-CeO2, where: M represents atomically dispersed transition metal single atoms, selected from one of Fe, Zn, and Mn; RE represents atomically dispersed rare earth metal single atoms, selected from one of Eu, Tb, Sm, and Y; Ov represents oxygen vacancies in the cerium oxide substrate; The transition metal single atom M and the rare earth metal single atom RE are anchored together in the cerium oxide CeO2 nanolattice rich in oxygen vacancies through MO-Ce and RE-O-Ce coordination bonds, respectively. The preparation method of the single-atom nanozyme includes the following steps: 1) Dissolve cerium salt, transition metal salt and rare earth metal salt in deionized water, add organic ligand, then add alkaline solution, adjust the pH of the mixed solution to 8.0~11.0, and stir at 60~80℃ until homogeneous; 2) Transfer the solution from step 1) to a reaction vessel and hydrothermally react at 140~180℃ for 8~16 hours. After the reaction is completed, centrifuge, wash and dry to obtain precursor powder. 3) The precursor powder obtained in step 2) is heated to 350-500℃ at a heating rate of 2-5℃ / min under a reducing atmosphere and kept at that temperature for 1-2 hours to finally obtain the product M-RE / Ov-CeO2.

2. The single-atom nanozyme according to claim 1, characterized in that, The molar ratio of the transition metal single atom M to the rare earth metal single atom RE is 1:10 to 10:

1.

3. The method for preparing the single-atom nanozyme according to claim 1 or 2, characterized in that, Includes the following steps: 1) Dissolve cerium salt, transition metal salt and rare earth metal salt in deionized water, add organic ligand, then add alkaline solution, adjust the pH of the mixed solution to 8.0~11.0, and stir at 60~80℃ until homogeneous; 2) Transfer the solution from step 1) to a reaction vessel and hydrothermally react at 140~180℃ for 8~16 hours. After the reaction is completed, centrifuge, wash and dry to obtain precursor powder. 3) The precursor powder obtained in step 2) is heated to 350-500℃ at a heating rate of 2-5℃ / min under a reducing atmosphere and kept at that temperature for 1-2 hours to finally obtain the product M-RE / Ov-CeO2.

4. The preparation method according to claim 3, characterized in that, In step 1): The cerium salt is one of cerium nitrate, cerium chloride, or cerium acetate; The transition metal salt is one of the corresponding nitrate, chloride, or acetate of the transition metal; The rare earth metal salt is one of the corresponding nitrates or chlorides of rare earth metals; The organic ligand is citric acid or disodium ethylenediaminetetraacetate, and its molar ratio with the total metal ions in the aqueous solution is 1:1 to 3:

1. The alkali in the alkaline solution is selected from sodium hydroxide, potassium hydroxide, or calcium hydroxide.

5. The preparation method according to claim 3, characterized in that, The reducing atmosphere mentioned in step 3) is a mixture of hydrogen and an inert gas, wherein the volume fraction of hydrogen is 3% to 8%.

6. The application of the single-atom nanozyme according to claim 1 or 2 in plant stress resistance and yield increase.

7. The application according to claim 6, characterized in that, The stress resistance includes resistance to abiotic stresses, which include at least one of drought, salinity, high temperature, and low temperature.

8. The application according to claim 6, characterized in that, The applications include promoting plant growth under extreme stress conditions, including treating plants with the single-atom nanozymes, utilizing their light conversion properties to convert ultraviolet light into specific light, and utilizing their enzymatic catalytic activity to remove reactive oxygen species in the plant.

9. The application according to claim 8, characterized in that, The method of using the single-atom nanozyme includes foliar spraying or seed soaking; wherein the concentration of the single-atom nanozyme is 10~500 mg / L.

10. The application according to claim 6, characterized in that, The size of the single-atom nanozyme is 20~80 nm.

Images