Preparation method of hierarchically structured ZnO regulated by chiral molecules
The synthesis of ZnO with a hierarchical structure through bichial molecular regulation and hydrothermal method solves the problem of the thermodynamic limit of the microscopic self-assembly behavior of nanomaterials, and achieves the effect of improving nanocatalytic efficiency and catalytic performance.
Patent Information
- Application Number
- CN202410510761.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-26
- Publication Date
- 2025-06-17
- Estimated Expiration
- 2044-04-26
AI Technical Summary
The microscopic self-assembly behavior of existing nanomaterials is limited by the equilibrium driven by Gibbs free energy, resulting in thermodynamic limits in the active catalytic points, making it difficult to improve nanocatalytic efficiency.
Through bichronous molecular regulation, ZnO with a hierarchical structure was synthesized by hydrothermal method, and the crystal surface growth and curling of the crystals were induced by bichronous molecules to prepare a curled spiral nanoflower structure.
It improves the catalytic performance of ZnO and produces more active catalytic center points, which is simple and efficient, has high energy utilization, and has good repeatability and controllability.
Smart Images
Figure CN118221153B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of nanomaterial synthesis, and particularly relates to a method for preparing ZnO with a hierarchical structure by regulating with chiral molecules. Background Art
[0002] Due to their small size, a large percentage of the surface volume, different surface bond states and electronic states from the interior, and incomplete surface atom coordination, etc., the active sites on the surface of nanocatalysts increase, which makes nanocatalysts exhibit many new characteristics. In a reaction, the size, morphology, surface properties, etc. of a nanocatalyst have an important influence on its activity and selectivity.
[0003] In recent years, it has been found that nanozinc oxide exhibits many special functions in catalysis, optics, magnetism, mechanics, etc., and has important application values in many fields such as ceramics, chemical engineering, electronics, optics, biology, and medicine, and has special properties and uses that cannot be compared with ordinary zinc oxide. Nanozinc oxide can be used as an ultraviolet light shielding material, antibacterial agent, fluorescent material, photocatalytic material, etc. in the fields of textiles, coatings, etc.
[0004] Nanozinc oxide (ZnO), white hexagonal crystal system crystals or spherical particles, with a particle size less than 100 nm, an average particle size of 50 nm, a specific surface area greater than 4 m 2 / g, good fluidity, extremely high chemical activity, excellent catalytic and photocatalytic activities, and having functions of resisting infrared and ultraviolet radiation and sterilization. The refinement of nanozinc oxide grains causes changes in its surface electronic structure and crystal structure, resulting in surface effects, volume effects, quantum size effects, macroscopic tunneling effects, as well as characteristics such as high transparency and high dispersibility that macroscopic objects do not have. Nanozinc oxide can also catalyze the photolysis of organic molecule. ZnO with a size of 10 - 25 nm can be used for the catalytic photolysis of phenol and can also be used as a catalyst for the direct synthesis of methanol by CO hydrogenation. Compared with ordinary ZnO, it can significantly improve the CO conversion rate and methanol recovery rate.
[0005] However, at present, the microscopic self-assembly behavior of nanomaterials is still limited by the equilibrium driven by the Gibbs free energy, and there is a thermodynamic limit for the active catalytic sites in nanomaterials.
[0006] Therefore, how to regulate the equilibrium points in the microscopic self-assembly behavior of nanomaterials to generate more active catalytic centers is the difficulty in improving the current nano-catalytic efficiency and also the key to enhancing the catalytic efficiency of nanomaterials. Summary of the Invention
[0007] In view of this, some embodiments disclose a method for preparing ZnO with a hierarchical structure by regulating with chiral molecules, including:
[0008] S1. Prepare a chiral molecule solution;
[0009] S2. Add zinc acetate dihydrate to the chiral molecule solution and stir evenly to obtain a mixed solution.
[0010] S3. Add ammonium carbonate to the mixed solution and stir for a certain period of time.
[0011] S4. Place the mixed solution obtained in step S3 in a hydrothermal autoclave with a polytetrafluoroethylene liner for hydrothermal reaction.
[0012] S5. Centrifuge the reaction product obtained in step S4, and then calcine it to obtain ZnO with a hierarchical structure.
[0013] For the preparation method of ZnO with a hierarchical structure regulated by chiral molecules disclosed in some embodiments, step S1 specifically includes:
[0014] Add the chiral molecule to ultrapure water, a mixed solution of DMF and ultrapure water, a mixed solution of ethanol and ultrapure water, or a mixed solution of ethylene glycol and ultrapure water, and stir until dissolved to obtain a chiral molecule solution.
[0015] For the preparation method of ZnO with a hierarchical structure regulated by chiral molecules disclosed in some embodiments, the chiral molecule includes methionine and cysteine.
[0016] For the preparation method of ZnO with a hierarchical structure regulated by chiral molecules disclosed in some embodiments, the methionine is L-methionine and the cysteine is L-cysteine.
[0017] For the preparation method of ZnO with a hierarchical structure regulated by chiral molecules disclosed in some embodiments, the volume ratio of ultrapure water to DMF is 1:1.
[0018] For the preparation method of ZnO with a hierarchical structure regulated by chiral molecules disclosed in some embodiments, the volume ratio of ultrapure water to ethanol is 1:1.
[0019] For the preparation method of ZnO with a hierarchical structure regulated by chiral molecules disclosed in some embodiments, the volume ratio of ultrapure water to ethylene glycol is 1:1.
[0020] For the preparation method of ZnO with a hierarchical structure regulated by chiral molecules disclosed in some embodiments, in step S3, the stirring reaction time is 30 min.
[0021] For the preparation method of ZnO with a hierarchical structure regulated by chiral molecules disclosed in some embodiments, the reaction temperature of the hydrothermal reaction is 120 °C and the reaction time is 2 h.
[0022] The preparation method of hierarchically structured ZnO regulated by chiral molecules disclosed in some embodiments has a calcination temperature of 550 °C and a time of 6 h.
[0023] The preparation method of hierarchically structured ZnO regulated by chiral molecules disclosed in the embodiments of the present invention involves adding zinc acetate dihydrate and ammonium carbonate to a chiral molecule solution to undergo a precipitation reaction, then synthesizing the precipitate in the chiral molecule solution into crystals through a hydrothermal method, and finally subjecting the crystals to a calcination treatment to obtain hierarchically structured ZnO. By inducing the crystal planes of the crystals to grow along a certain direction through chiral molecules, a flaky nanostructure is obtained; the induction of chiral molecules forces the obtained flaky nanostructure to curl along a certain axis, generating a fine deformation axis and obtaining a coiled helical nanoflower structure; by changing the polarity of the solvent, the degree of deprotonation of chiral molecules is changed, indirectly improving the interaction between chiral molecules and Zn 2+ or the interaction between crystal planes, and preparing coiled helical nanoflower structures with different shapes; ZnO with this helical nanoflower structure has a complex hierarchical structure and a large specific surface area, capable of generating more active catalytic center sites, thereby improving the catalytic performance of ZnO.
[0024] The preparation method of hierarchically structured ZnO regulated by chiral molecules disclosed in the embodiments of the present invention is simple, efficient, has high energy utilization rate, good repeatability, and high controllability. Description of the Drawings
[0025] Figure 1 SEM and TEM images of hierarchically structured ZnO in Example 1;
[0026] Figure 2 SEM and EDS sectional images of hierarchically structured ZnO in Example 2;
[0027] Figure 3 SEM and TEM images of hierarchically structured ZnO in Example 3;
[0028] Figure 4 SEM and TEM images of hierarchically structured ZnO in Example 4;
[0029] Figure 5 SEM image of hierarchically structured ZnO in Example 5;
[0030] Figure 6 SEM image of hierarchically structured ZnO in Example 6;
[0031] Figure 7 SEM image of hierarchically structured ZnO in Comparative Example 1;
[0032] Figure 8 SEM image of hierarchically structured ZnO in Comparative Example 2. Detailed implementation manners
[0033] As used herein, the term "embodiment" for any embodiment described as "exemplary" does not have to be construed as being superior to or better than other embodiments. For performance index tests in the embodiments of the present application, unless otherwise specified, conventional test methods in the art are adopted. It should be understood that the terms described in the present application are only used to describe specific embodiments and are not used to limit the content disclosed in the present application.
[0034] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by those of ordinary skill in the technical field to which this application belongs; other test methods and technical means not specifically noted in this application refer to the experimental methods and technical means commonly adopted by those of ordinary skill in the art.
[0035] The terms "substantially" and "about" used herein are used to describe minor fluctuations. For example, they can refer to less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Numerical data presented or represented in a range format herein is used only for convenience and brevity and should therefore be interpreted flexibly as including not only the values explicitly listed as the bounds of the range but also all individual values or sub-ranges included within the range. For example, the numerical range of "1 to 5%" should be interpreted as including not only the explicitly listed values from 1% to 5% but also the individual values and sub-ranges within the indicated range. Thus, within this numerical range, individual values such as 2%, 3.5%, and 4% are included, and sub-ranges such as 1% to 3%, 2% to 4%, and 3% to 5% are included, etc. This principle also applies to ranges that list only one numerical value. In addition, such an interpretation applies regardless of the width of the range or the characteristics described.
[0036] In this application, including in the claims, conjunctions such as "comprising", "including", "carrying", "having", "containing", "involving", "accommodating", etc. are understood to be open-ended, that is, meaning "including but not limited to". Only the conjunctions "consisting of" and "composed of" are closed conjunctions.
[0037] To better illustrate the content of this application, numerous specific details are given in the following specific embodiments. Those skilled in the art should understand that this application can be implemented without some specific details. In the embodiments, some methods, means, instruments, devices, etc. well-known to those skilled in the art are not described in detail in order to highlight the gist of this application.
[0038] On the premise of no conflict, the technical features disclosed in the embodiments of the present application can be arbitrarily combined, and the obtained technical solutions belong to the content disclosed in the embodiments of the present application. It should be noted that the terms "center", "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. mentioned in the present application indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing technical features and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation to the present invention, unless it conflicts with the context. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance, unless it conflicts with the context.
[0039] In some embodiments, the preparation method of ZnO with a hierarchical structure regulated by chiral molecules includes:
[0040] S1. Prepare a chiral molecule solution;
[0041] S2. Add zinc acetate dihydrate to the chiral molecule solution and stir evenly to obtain a uniform and clear mixed solution; Generally, add zinc acetate dihydrate to the chiral molecule solution at 0 °C to prevent the hydrolysis and oxidation of zinc acetate dihydrate;
[0042] S3. Add ammonium carbonate to the mixed solution and stir for a certain time. Ammonium carbonate hydrolyzes in the mixed solution to produce a large amount of OH - , making the mixed solution weakly alkaline. Zn in the mixed solution 2+ precipitates rapidly in the alkaline environment to form basic zinc carbonate;
[0043] S4. Place the mixed solution obtained in step S3 in a polytetrafluoroethylene-lined autoclave for hydrothermal reaction and recrystallization; Chiral molecules can act on the coordination bonds of Zn 2+ . During the crystal growth process, chiral molecules, on the one hand, act as surfactants, and on the other hand, play a role in synergistically tuning the corresponding selectivity at the molecular-crystal plane interface. They can induce the crystal plane to grow along a certain direction to obtain a flaky nanostructure, and can also force the obtained flaky nanostructure to curl along a certain axis to generate a fine deformation axis, obtaining a curly spiral-like nanoflower structure;
[0044] S5. Centrifuge and separate the reaction product obtained in step S4, and then calcine to obtain ZnO with a hierarchical structure.
[0045] In some embodiments, step S1 specifically includes:
[0046] Using ultrapure water, a mixed solution of DMF and ultrapure water, a mixed solution of ethanol and ultrapure water, or a mixed solution of ethylene glycol and ultrapure water as the solvent;
[0047] Adding the chiral molecules into ultrapure water, a mixed solution of DMF and ultrapure water, a mixed solution of ethanol and ultrapure water, or a mixed solution of ethylene glycol and ultrapure water, and stirring until dissolved to obtain a chiral molecule solution.
[0048] In some embodiments, the volume of the chiral molecule solution is 15 mL.
[0049] In some embodiments, the chiral molecules include methionine and cysteine.
[0050] In some embodiments, methionine includes L-methionine and D-methionine.
[0051] In some embodiments, cysteine includes L-cysteine and D-cysteine.
[0052] In some embodiments, the preferred chiral molecules are L-methionine and L-cysteine.
[0053] In some embodiments, the addition amount of cysteine is 100 - 500 μL, and the concentration of cysteine is 0.02 - 2 mmol / L.
[0054] Preferably, the addition amount of methionine is 1 mmol, the addition amount of cysteine is 100 μL, the concentration of cysteine is 0.02 mmol / L, the addition amount of zinc acetate dihydrate is 0.75 - 3.0 mmol, and the addition amount of ammonium carbonate is 0.5 mmol.
[0055] In some embodiments, in the chiral molecule solution in step S1, the concentration of methionine is 0.067 mol / L.
[0056] In some embodiments, in the mixed solution in step S2, the concentration of zinc acetate dihydrate is 0.05 - 0.2 mol / L.
[0057] In some embodiments, in the mixed solution in step S3, the concentration of ammonium carbonate is 0.033 mol / L.
[0058] In some embodiments, the volume ratio of ultrapure water to DMF is 1:1. Changing the polarity of the solvent can change the degree of deprotonation of the chiral molecules, and can indirectly improve the interaction between the chiral molecules and Zn 2+ or the crystal crystal plane, and prepare nanorose structures with different coiled-coil shapes.
[0059] In some embodiments, the volume ratio of ultrapure water to ethanol is 1:1.
[0060] In some embodiments, the volume ratio of ultrapure water to ethylene glycol is 1:1.
[0061] In some embodiments, in step S3, the stirring reaction time is 30 min.
[0062] In some embodiments, the reaction temperature of the hydrothermal reaction is 120 °C and the reaction time is 2 h.
[0063] In some embodiments, the rotation speed of the centrifugal separation is 4500 - 5500 rpm.
[0064] In some embodiments, the calcination temperature is 550 °C and the time is 6 h.
[0065] The following further exemplarily illustrates the technical details in conjunction with embodiments.
[0066] Example 1
[0067] Figure 1 SEM and TEM images of ZnO with a hierarchical structure disclosed in Example 1.
[0068] This Example 1 discloses a preparation method of ZnO with a hierarchical structure regulated by chiral molecules, including:
[0069] Dissolve 100 μL of L-cysteine with a concentration of 0.02 mmol / L and 1 mmol of L-methionine in 15 mL of ultrapure water by stirring to prepare a chiral molecule solution;
[0070] Add 1.5 mmol of zinc acetate dihydrate to the chiral molecule solution at 0 °C and stir evenly to obtain a homogeneous and clear mixed solution;
[0071] Add 0.5 mmol of ammonium carbonate to the mixed solution and stir for 30 min;
[0072] Place the mixed solution into a high-pressure autoclave with a 50 mL polytetrafluoroethylene liner for hydrothermal reaction, with a reaction temperature of 120 °C and a reaction time of 2 h;
[0073] Centrifuge the reaction product obtained from the hydrothermal reaction twice at a rotation speed of 5000 rpm for 10 min each time, and then calcine to obtain ZnO with a hierarchical structure. Figure 1 Regions (a) and (b) are SEM images of ZnO, and regions (c) and (d) are TEM images of ZnO in the figure. As Figure 1 shown, the ZnO prepared in this example has an obvious flower-like spherical structure, with a relatively large diameter of the flower shape and a fragmented structure.
[0074] Example 2
[0075] Figure 2SEM and EDS layered images of ZnO with a hierarchical structure disclosed in Example 2.
[0076] Example 2 discloses a method for preparing ZnO with a hierarchical structure regulated by chiral molecules, including:
[0077] Add 100 μL of L-cysteine with a concentration of 0.02 mmol / L and 1 mmol of L-methionine to 15 mL of ultrapure water and stir to dissolve to prepare a chiral molecule solution;
[0078] Add 0.75 mmol of zinc acetate dihydrate to the chiral molecule solution at 0 °C and stir evenly to obtain a homogeneous and clear mixed solution;
[0079] Add 0.5 mmol of ammonium carbonate to the mixed solution and stir for reaction for 30 min;
[0080] Place the mixed solution into a polytetrafluoroethylene-lined autoclave with a volume of 50 mL for hydrothermal reaction. The reaction temperature is 120 °C and the reaction time is 2 h;
[0081] Centrifuge the reaction product obtained from the hydrothermal reaction twice at a speed of 5000 rpm for 10 min each time, and then calcine to obtain ZnO with a hierarchical structure. Figure 2 In region (a) and (b) are SEM images of ZnO. In the figure, regions (c) and (d) are EDS distribution maps of Zn element and O element respectively. As Figure 2 shown, the ZnO prepared in this example has an obvious flower-ball structure, with a relatively large diameter of the flower shape and an obvious sheet-like structure.
[0082] Example 3
[0083] Figure 3 SEM and TEM images of ZnO with a hierarchical structure disclosed in Example 3.
[0084] Example 3 discloses a method for preparing ZnO with a hierarchical structure regulated by chiral molecules, including:
[0085] Add 100 μL of L-cysteine with a concentration of 0.02 mmol / L and 1 mmol of L-methionine to a mixed solution of 15 mL of ultrapure water and DMF and stir to dissolve to prepare a chiral molecule solution; wherein, the volume ratio of ultrapure water to DMF is 1:1;
[0086] Add 1.5 mmol of zinc acetate dihydrate to the chiral molecule solution at 0 °C and stir evenly to obtain a homogeneous and clear mixed solution;
[0087] Add 0.5 mmol of ammonium carbonate to the mixed solution and stir for reaction for 30 min;
[0088] The mixed solution was placed in a 50 mL Teflon-lined autoclave for hydrothermal reaction at a reaction temperature of 120 °C for 2 h;
[0089] The reaction product obtained from the hydrothermal reaction was centrifuged twice at 5000 rpm for 10 min each time, and then calcined to obtain ZnO with a hierarchical structure. Figure 3 Regions (a) and (b) in the figure are SEM images of ZnO, and regions (c) and (d) in the figure are TEM images of ZnO. As Figure 3 shown, the ZnO prepared in this example has an obvious flower cluster structure, with a small diameter of the flower shape, clustered together, and the structure is petal-shaped.
[0090] Example 4
[0091] Figure 4 SEM and TEM images of ZnO with a hierarchical structure disclosed in Example 4.
[0092] Example 4 discloses a preparation method of ZnO with a hierarchical structure regulated by chiral molecules, including:
[0093] 100 μL of L-cysteine with a concentration of 0.02 mmol / L and 1 mmol of L-methionine were added to a mixed solution of 15 mL of ultrapure water and ethanol and stirred to dissolve to prepare a chiral molecule solution; the volume ratio of ultrapure water to ethanol was 1:1;
[0094] 1.5 mmol of zinc acetate dihydrate was added to the chiral molecule solution at 0 °C and stirred evenly to obtain a homogeneous and clear mixed solution;
[0095] 0.5 mmol of ammonium carbonate was added to the mixed solution and stirred for reaction for 30 min;
[0096] The mixed solution was placed in a 50 mL Teflon-lined autoclave for hydrothermal reaction at a reaction temperature of 120 °C for 2 h;
[0097] The reaction product obtained from the hydrothermal reaction was centrifuged twice at 5000 rpm for 10 min each time, and then calcined to obtain ZnO with a hierarchical structure. Figure 4 Regions (a) and (b) in the figure are SEM images of ZnO, and regions (c) and (d) in the figure are TEM images of ZnO. As Figure 4 shown, the ZnO prepared in this example has an obvious flower cluster structure, with a small diameter of the flower shape, clustered together, and the structure is petal-shaped.
[0098] As can be seen from Comprehensive Examples 1 to 4, compared with ZnO prepared from a single solvent, ZnO prepared from a mixed solvent has a smaller diameter and a more compact distribution.
[0099] Example 5
[0100] Figure 5 SEM image of ZnO with a hierarchical structure disclosed in Example 5.
[0101] This Example 5 discloses a preparation method of ZnO with a hierarchical structure regulated by a chiral molecule, including:
[0102] Add 100 μL of L-cysteine with a concentration of 0.02 mmol / L and 1 mmol of L-methionine into a mixed solution of 15 mL of ultrapure water and ethanol, and stir to dissolve to prepare a chiral molecule solution; the volume ratio of ultrapure water to ethanol is 1:1;
[0103] Add 3.0 mmol of zinc acetate dihydrate to the chiral molecule solution at 0 °C and stir evenly to obtain a uniform and clear mixed solution;
[0104] Add 0.5 mmol of ammonium carbonate to the mixed solution and stir for reaction for 30 min;
[0105] Place the mixed solution into a polytetrafluoroethylene-lined autoclave with a volume of 50 mL for hydrothermal reaction, the reaction temperature is 120 °C, and the reaction time is 2 h;
[0106] Centrifuge the reaction product obtained from the hydrothermal reaction twice at a speed of 5000 rpm for 10 min each time, and then calcine to obtain ZnO with a hierarchical structure. As Figure 5 shown, the ZnO prepared in this example has an obvious flaky structure, with a larger flake shape and clustered together.
[0107] As can be seen from Comprehensive Examples 1 to 5, compared with Examples 1 to 4, the amount of zinc acetate dihydrate used in this example is larger, and the ZnO flakes obtained are larger and show a stacked shape.
[0108] Example 6
[0109] Figure 6 SEM image of ZnO with a hierarchical structure disclosed in Example 6.
[0110] This Example 6 discloses a preparation method of ZnO with a hierarchical structure regulated by a chiral molecule, including:
[0111] 100 μL of L-cysteine with a concentration of 0.02 mmol / L and 1 mmol of L-methionine were added to a mixed solution of 15 mL of ultrapure water and ethylene glycol and stirred to dissolve to prepare a chiral molecular solution; the volume ratio of ultrapure water to ethylene glycol was 1:1;
[0112] At 0 °C, 1.5 mmol of zinc acetate dihydrate was added to the chiral molecular solution and stirred evenly to obtain a uniformly clear mixed solution;
[0113] 0.5 mmol of ammonium carbonate was added to the mixed solution and stirred for reaction for 30 min;
[0114] The mixed solution was placed in a 50 mL polytetrafluoroethylene-lined autoclave for hydrothermal reaction, the reaction temperature was 120 °C, and the reaction time was 2 h;
[0115] The reaction product obtained from the hydrothermal reaction was centrifuged twice at a speed of 5000 rpm for 10 min each time, and then calcined to obtain ZnO with a hierarchical structure. As Figure 6 shown, the ZnO prepared in this example has an obvious flower-like spherical structure, with smaller sheet types and clustered together.
[0116] Based on Examples 4 to 6, compared with the ZnO prepared using a mixed solution of water and ethanol as the solvent in Examples 4 and 5, the ZnO prepared in this example has smaller sheet types and presents a flower-like spherical shape.
[0117] Comparative Example 1
[0118] Figure 7 It is the SEM image of ZnO with a hierarchical structure disclosed in Comparative Example 1.
[0119] This Comparative Example 1 discloses a preparation method of ZnO with a hierarchical structure regulated by chiral molecules, including:
[0120] 100 μL of L-cysteine with a concentration of 0.02 mmol / L and 1 mmol of L-methionine were added to a mixed solution of 15 mL of ultrapure water and ethanol and stirred to dissolve to prepare a chiral molecular solution; the volume ratio of ultrapure water to ethanol was 2:1;
[0121] At 0 °C, 1.5 mmol of zinc acetate dihydrate was added to the chiral molecular solution and stirred evenly to obtain a uniformly clear mixed solution;
[0122] 0.5 mmol of ammonium carbonate was added to the mixed solution and stirred for reaction for 30 min;
[0123] The mixed solution was placed in a 50 mL polytetrafluoroethylene-lined autoclave for hydrothermal reaction, the reaction temperature was 120 °C, and the reaction time was 2 h;
[0124] The reaction product obtained from the hydrothermal reaction was centrifuged twice at a speed of 5000 rpm for 10 minutes each time, and then calcined to obtain ZnO with a hierarchical structure. As Figure 7 shown, the ZnO stacked structure prepared in Comparative Example 1 is disordered and unevenly distributed.
[0125] Comparative Example 2
[0126] Figure 8 is the SEM image of ZnO with a hierarchical structure disclosed in Comparative Example 2.
[0127] This Comparative Example 2 discloses a preparation method of ZnO with a hierarchical structure regulated by chiral molecules, including:
[0128] 100 μL of L-cysteine with a concentration of 0.02 mmol / L and 1 mmol of L-methionine were added to a mixed solution of 15 mL of ultrapure water and ethanol and stirred to dissolve to prepare a chiral molecule solution; the volume ratio of ultrapure water to ethanol was 1:2;
[0129] 1.5 mmol of zinc acetate dihydrate was added to the chiral molecule solution at 0 °C and stirred evenly to obtain a uniformly clear mixed solution;
[0130] 0.5 mmol of ammonium carbonate was added to the mixed solution and stirred for reaction for 30 minutes;
[0131] The mixed solution was placed in a high-pressure autoclave with a polytetrafluoroethylene liner with a volume of 50 mL for hydrothermal reaction, the reaction temperature was 120 °C, and the reaction time was 2 h;
[0132] The reaction product obtained from the hydrothermal reaction was centrifuged twice at a speed of 5000 rpm for 10 minutes each time, and then calcined to obtain ZnO with a hierarchical structure. As Figure 8 shown, the ZnO clusters prepared in Comparative Example 2 are in a group, the structure is disordered and irregular, and the sheet type is not obvious.
[0133] The preparation method of ZnO with a hierarchical structure regulated by chiral molecules disclosed in the embodiment of the present invention adds zinc acetate dihydrate and ammonium carbonate to the chiral molecule solution to undergo a precipitation reaction, and then synthesizes and crystallizes the precipitate in the chiral molecule solution by hydrothermal method. Finally, the crystal is calcined to obtain ZnO with a hierarchical structure. The chiral molecule induces the crystal plane to grow along a certain direction to obtain a flaky nanostructure; the induction of the chiral molecule forces the obtained flaky nanostructure to curl along a certain axis to generate a fine deformation axis and obtain a curled helical nanoflower structure; by changing the polarity of the solvent, the degree of deprotonation of the chiral molecule is changed, and indirectly, the interaction between the chiral molecule and Zn 2+Or through the interaction of crystal crystal planes, nanoflower structures with different coiled-coil shapes are prepared; ZnO with such a helical nanoflower structure has a complex hierarchical structure and a large specific surface area, which can generate more active catalytic center sites, thereby improving the catalytic performance of ZnO.
[0134] The preparation method of ZnO with a hierarchical structure regulated by chiral molecules disclosed in the embodiments of the present invention is simple, efficient, has high energy utilization rate, good repeatability and high controllability.
[0135] The technical solutions disclosed in the present invention and the technical details disclosed in the embodiments are only exemplary illustrations of the inventive concept of the present invention, and do not constitute a limitation on the technical solutions of the present invention. Any conventional changes, substitutions or combinations made to the technical details disclosed in the embodiments of the present invention have the same inventive concept as the present invention and are within the protection scope of the claims of the present invention.
Claims
1. A method for preparing ZnO having a hierarchical structure by regulating a chiral molecule, characterized in that: include: S1. Prepare a chiral molecular solution; The two-handed molecules are methionine and cysteine, the methionine is L-methionine or D-methionine, and the cysteine is L-cysteine or D-cysteine; the two-handed molecules are added to ultrapure water, a mixed solution of DMF and ultrapure water in a volume ratio of 1:1, a mixed solution of ethanol and ultrapure water in a volume ratio of 1:1, or a mixed solution of ethylene glycol and ultrapure water in a volume ratio of 1:1, and stirred until dissolved to obtain a two-handed molecule solution; the volume of the two-handed molecule solution is 15 mL, the amount of cysteine added is 100-500 μL, the concentration of cysteine is 0.02-2 mmol / L, the amount of methionine added is 1 mmol, the amount of zinc acetate dihydrate added is 0.75-3.0 mmol, and the amount of ammonium carbonate added is 0.5 mmol; S2, adding zinc acetate dihydrate to the two-handed molecular solution and stirring evenly to obtain a mixed solution; S3, adding ammonium carbonate to the mixed solution and stirring for a certain period of time; S4, placing the mixed solution obtained in step S3 in a polytetrafluoroethylene-lined autoclave for hydrothermal reaction; S5. Centrifugally separate the reaction product obtained in step S4, and then calcine it to obtain ZnO with a hierarchical structure.
2. The method for preparing ZnO with a hierarchical structure by controlling the chiral molecules according to claim 1, characterized in that: The amount of cysteine added was 100 μL, and the concentration of cysteine was 0.02 mmol / L.
3. The method for preparing ZnO with a hierarchical structure by controlling the chiral molecules according to claim 1, characterized in that: The methionine is L-methionine, and the cysteine is L-cysteine.
4. The method for preparing ZnO with a hierarchical structure by controlling the chiral molecules according to claim 1, characterized in that: In step S5, the rotation speed of the centrifugal separation is 4500-5500 rpm.
5. The method for preparing ZnO with a hierarchical structure by controlling the chiral molecules according to claim 1, characterized in that: In step S3, the stirring reaction time is 30 minutes.
6. The method for preparing ZnO with a hierarchical structure by controlling the chiral molecules according to claim 1, characterized in that: The reaction temperature of the hydrothermal reaction is 120° C. and the reaction time is 2 h.
7. The method for preparing ZnO with a hierarchical structure by controlling the chiral molecules according to claim 1, characterized in that: The calcination temperature is 550° C. and the calcination time is 6 hours.