Two-dimensional magnetic MnO nanosheet as well as preparation method and application thereof

Abstract

The invention provides a two-dimensional magnetic MnO nanosheet as well as a preparation method and application thereof. The morphology of the two-dimensional magnetic MnO nanosheet comprises a triangular morphology and / or a quadrilateral morphology. According to the preparation method disclosed by the invention, double precursors (elemental manganese and a manganese compound) are provided as reaction precursors of Mn, and the two-dimensional magnetic MnO nanosheet with the special morphology is controllably prepared through chemical vapor deposition in an oxygen-containing atmosphere. The nanosheet has a proper band gap and excellent performance, and can be widely applied to various fields of electronic, photoelectron or spinning devices and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of two-dimensional magnetic materials and relates to a two-dimensional magnetic MnO nanosheet and a preparation method and application thereof. Background Art

[0002] The rise of two-dimensional materials stems from the successful exfoliation of graphene from graphite sheets. Their exceptional properties, including ultrahigh carrier mobility, quantum Hall effect, large specific surface area, and Young's modulus, provide a promising platform for exploring low-dimensional quantum physics phenomena. Two-dimensional magnetic materials, a key branch of these materials, are not only a crucial platform for studying and understanding the fundamental physical properties of low-dimensional materials but also possess a wide range of applications in spintronics, magnetic memory devices, logic circuits, and sensors.

[0003] Metal oxides have attracted considerable interest in a variety of applications, including piezoelectrics, electronics, optoelectronics, and dielectric materials. In particular, magnetic metal oxides have occupied an important position due to their potential applications in magnetic sensing and high-density data storage devices. They typically have a tightly packed structure, and these non-van der Waals structures with isotropic covalent bonds generally make them easy to stack into three-dimensional bulk materials. In recent years, the study of their ultrathin two-dimensional nanostructures has attracted great interest because they exhibit many fascinating properties arising from the strong confinement of phonons, photons, and electrons. Two-dimensional magnetic metal oxides offer exciting technological opportunities for exploring magnetism at atomically thin layers.

[0004] Two-dimensional magnetic semiconductor manganese oxide (MnO) has a high Neel temperature (T n =118K), a tunable band gap, and high surface activity demonstrate significant potential for applications in catalysis, electrochemistry, energy, electronics, optoelectronics, and spintronic devices. Existing MnO materials are primarily prepared via sol-gel, hydrothermal, electrodeposition, and thermal decomposition methods. The resulting nanoparticles exhibit a variety of oxidation states (+2, +3, and +4) and can form mixed-phase nanostructures of MnO, MnO2, Mn2O3, and Mn3O4. The sol-gel method requires expensive and toxic raw materials, and its reaction cycle is long, typically taking several days to several weeks. The hydrothermal method offers numerous advantages for preparing nanomaterials, but it is prone to environmental pollution during the preparation of MnO materials and requires high reactor precision, increasing equipment costs and operational complexity. While the electrodeposition method is simple and easy to operate, it faces numerous challenges, including high equipment costs and energy consumption. The thermal decomposition method requires a high temperature environment, resulting in high energy consumption. Furthermore, the method has stringent requirements for process parameters, making the reaction difficult to control. In addition, the synthesis of two-dimensional MnO nanosheets is difficult, and there is currently a lack of controllable, efficient and stable methods to prepare MnO nanosheets with different shapes.

[0005] Therefore, how to obtain two-dimensional magnetic MnO materials with excellent performance and stable structure is a technical problem that needs to be solved urgently. Summary of the Invention

[0006] To address the shortcomings of the prior art, the present invention provides two-dimensional magnetic MnO nanosheets, their preparation method, and uses. The two-dimensional magnetic MnO nanosheets provided by the present invention exhibit unique triangular and / or quadrilateral morphologies, possess a suitable band gap, and exhibit excellent performance, enabling widespread application in a variety of fields, including electronics, optoelectronics, and spintronic devices.

[0007] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a two-dimensional magnetic MnO nanosheet, wherein the morphology of the two-dimensional magnetic MnO nanosheet includes a triangular morphology and / or a quadrilateral morphology.

[0009] The two-dimensional magnetic MnO nanosheets provided by the present invention have special triangular and / or quadrilateral morphologies, good material stability, high crystallinity, high density, and a suitable band gap, and can be widely used in various fields such as electronics, optoelectronics or spin devices.

[0010] Compared with conventional two-dimensional magnetic materials that require mechanical exfoliation before normal use, the single-crystal MnO two-dimensional magnetic material provided by the present invention has the advantages of low cost, large size (the longest side is ≥10μm), uniform thickness and clean interface.

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0012] Preferably, in the two-dimensional magnetic MnO nanosheets with triangular morphology, the thickness of the nanosheets is 100 to 500 nm, for example, 100 nm, 125 nm, 150 nm, 175 nm, 200 nm, 225 nm, 250 nm, 275 nm, 300 nm, 325 nm, 350 nm, 375 nm, 400 nm, 425 nm, 450 nm, 475 nm or 500 nm, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0013] Preferably, in the two-dimensional magnetic MnO nanosheets with a triangular morphology, the length of each side of the nanosheet is independently 1 to 10 μm, for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm, etc., but are not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0014] In the present invention, in the triangular morphology of the two-dimensional magnetic MnO nanosheets, the thickness of the nanosheets is regulated to be 100-500 nm and / or the length of each side of the nanosheets is independently 1-10 μm, which is more conducive to promoting the process of preparing electronic devices using two-dimensional MnO nanosheets and also provides a material basis for preparing complex heterostructures.

[0015] Preferably, in the two-dimensional magnetic MnO nanosheets with a quadrilateral morphology, the thickness of the nanosheets is 10 to 150 nm, for example, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm or 150 nm, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0016] Preferably, in the two-dimensional magnetic MnO nanosheets with a quadrilateral morphology, the length of each side of the nanosheet is independently 1 to 4 μm, for example, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm or 4 μm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0017] In the present invention, in the quadrilateral morphology of the two-dimensional magnetic MnO nanosheets, the thickness of the nanosheets is regulated to be 10 to 150 nm and / or the lengths of the respective sides of the nanosheets are independently regulated to be 1 to 4 μm, which is more conducive to promoting the process of preparing electronic devices from two-dimensional MnO nanosheets and also provides a material basis for preparing complex heterostructures.

[0018] In a second aspect, the present invention provides a method for preparing the two-dimensional magnetic MnO nanosheets as described in the first aspect, the preparation method comprising the following steps:

[0019] Passing an oxygen-containing gas into the first raw material to react by chemical vapor deposition to obtain the two-dimensional magnetic MnO nanosheets;

[0020] The first raw material includes elemental manganese and manganese compounds; the morphology of the two-dimensional magnetic MnO nanosheets includes triangular morphology and / or quadrilateral morphology.

[0021] It should be noted that the oxygen-containing gas in the present invention is a gas containing at least oxygen, for example, pure oxygen, or a mixture of oxygen and other gases, such as a mixture of oxygen and a protective gas (nitrogen or argon), or air. Those skilled in the art can adaptably select and adjust the specific type of oxygen-containing gas and the volume proportion of oxygen according to actual needs.

[0022] Furthermore, it is understood that the valence state of manganese in the manganese compound of the present invention is +2.

[0023] The preparation method provided by the present invention prepares two-dimensional magnetic MnO nanosheets with special triangular and / or quadrilateral morphologies by synergistically combining two different manganese sources with an oxygen-containing gas under the action of a chemical vapor deposition method. This overcomes the problem that existing growth technologies are difficult to controllably grow MnO nanosheets, fills a gap in the prior art, and provides a material basis for the study of the physical properties of two-dimensional magnetic material MnO nanosheets. The method is simple to operate, efficient and time-saving, low-cost, and pollution-free. The preparation process has strong controllability, and the obtained nanosheets have high density and regular shape.

[0024] In the present invention, the two essential conditions for chemical vapor deposition (CVD)—a manganese source precursor and an oxygen-containing gas—must work together to produce the desired two-dimensional magnetic MnO nanosheets. However, if chemical vapor deposition is not used, and a reaction process such as hydrothermal reaction is used instead, MnO nanoparticles may be obtained instead of high-quality two-dimensional MnO nanosheets. Using only a single manganese source makes it impossible to precisely control the morphology and thickness of the two-dimensional MnO nanosheets, while using an oxygen-free gas (such as nitrogen) will prevent the synthesis of two-dimensional MnO nanosheets.

[0025] Preferably, the manganese compound comprises a manganese halide.

[0026] In the present invention, manganese halides are selected to better exert a synergistic effect with elemental manganese. Compared with other manganese compounds, such as manganese sulfate, they have the advantages of low cost, low toxicity and low melting point. The present invention does not specifically limit the manganese halides. The present invention is applicable to any type of substance that can be known to those skilled in the art within a reasonable range, for example, it can be at least one of manganese chloride (MnCl2), manganese fluoride (MnF2) or manganese iodide (MnI2).

[0027] Preferably, the first raw material further includes molten salt.

[0028] In the process of preparing MnO, the present invention adds molten salt as a raw material, which plays a role in lowering the melting point of elemental manganese and manganese compounds.

[0029] In addition, the molten salt in the present invention is selected from conventional technologies, for example, the molten salt includes but is not limited to NaCl, NaBr, KCl, KBr, CaCl2, etc.

[0030] Preferably, based on the total mass of the first raw material being 120 mg, the amount of the molten salt added is 3 to 8 mg, for example, 3 mg, 4 mg, 5 mg, 6 mg, 7 mg or 8 mg, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0031] Preferably, the reaction system for chemical vapor deposition reaction also includes a substrate, and the shortest linear distance between the substrate and the first raw material is 0.1 to 0.2 mm, for example, 0.1 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.17 mm, 0.18 mm, 0.19 mm or 0.2 mm, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0032] In the chemical vapor deposition reaction process of the present invention, when the reaction system includes a substrate, a gap is left between the substrate and the raw material, which is more conducive to the epitaxial growth of MnO nanosheets. The shortest linear distance between the substrate and the first raw material is regulated to be 0.1 to 0.2 mm, further increasing the vapor pressure concentration on the surface of the reaction substrate, which is more conducive to the growth of two-dimensional MnO nanosheets.

[0033] It should also be noted that the present invention does not specifically limit the specific material type of the substrate. The present invention is applicable to conventional substrate materials that can be known to technical personnel in this field within a reasonable range. For example, the substrate includes but is not limited to sapphire substrate, mica, magnesium oxide substrate, etc.

[0034] Preferably, in the first raw material, the mass of elemental manganese is 100-200 mg, for example, 100 mg, 110 mg, 120 mg, 130 mg, 140 mg, 150 mg, 160 mg, 170 mg, 180 mg, 190 mg or 200 mg, and the mass of the manganese compound is 9-13 mg, for example, 9 mg, 9.5 mg, 10 mg, 10.5 mg, 11 mg, 11.5 mg, 12 mg, 12.5 mg or 13 mg, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0035] The present invention adjusts the mass of elemental manganese in the first raw material to 100-200 mg and the mass of the coordinated manganese compound to 9-13 mg, thereby reducing the vapor pressure concentration of the manganese source precursor and being more conducive to the formation of metastable triangular-shaped MnO nanosheets.

[0036] Preferably, in the first raw material, the mass of elemental manganese is 200-300 mg (excluding 200 mg), for example, 210 mg, 220 mg, 230 mg, 240 mg, 250 mg, 260 mg, 270 mg, 280 mg, 290 mg or 300 mg, and the mass of the manganese compound is 9-13 mg, for example, 9 mg, 9.5 mg, 10 mg, 10.5 mg, 11 mg, 11.5 mg, 12 mg, 12.5 mg or 13 mg, but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0037] The present invention regulates the mass of elemental manganese in the first raw material to be 200-300 mg, and the mass of the compound excluding 200 mg of synergistic manganese is 9-13 mg. The high content of elemental manganese powder increases the vapor pressure concentration of the manganese source precursor, which is more conducive to the formation of MnO nanosheets with a quadrilateral morphology when combined with oxygen.

[0038] Preferably, the oxygen in the oxygen-containing gas has an inlet flow rate of 10 to 20 sccm, for example, 10 sccm, 11 sccm, 12 sccm, 13 sccm, 14 sccm, 15 sccm, 16 sccm, 17 sccm, 18 sccm, 19 sccm or 20 sccm, etc., but is not limited to the listed values, and other values not listed within the numerical range are also applicable.

[0039] It should be noted that the present invention only limits the flow rate of oxygen in the oxygen-containing gas. Those skilled in the art can adjust the flow rate of the entire oxygen-containing gas according to the volume ratio of oxygen in the oxygen-containing gas.

[0040] Preferably, the reaction temperature of the reaction is 750-850°C, for example, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C or 850°C, etc., but is not limited to the listed values, and other unlisted values within this numerical range are also applicable.

[0041] When preparing MnO nanosheets, the flow rate of oxygen in the oxygen-containing gas is regulated to be 10-20 sccm and / or the reaction temperature is regulated to be 750-850° C., which is more conducive to obtaining two-dimensional magnetic MnO nanosheets with regular and complete morphology, stable structure and better performance.

[0042] Preferably, the reaction time is 20 to 30 min, for example, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min or 30 min, etc., but is not limited to the listed values, and other unlisted values within the numerical range are also applicable.

[0043] In a third aspect, the present invention further provides a use of a two-dimensional magnetic MnO nanosheet, which comprises using the two-dimensional magnetic MnO nanosheet as described in the first aspect or the two-dimensional magnetic MnO nanosheet prepared by the preparation method described in the second aspect in an electronic device, an optoelectronic device or a spintronic device.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] (1) The two-dimensional magnetic MnO nanosheets provided by the present invention have a special triangular morphology and / or quadrilateral morphology, good material stability, high crystallinity, high density, and a suitable band gap, and can be widely used in various fields such as electronics, optoelectronics or spin devices.

[0046] (2) The preparation method provided by the present invention uses a chemical vapor deposition method to prepare two-dimensional magnetic MnO nanosheets with special triangular and / or quadrilateral morphologies through the coordinated cooperation of two different manganese sources and the action of oxygen-containing gas. This overcomes the problem that existing growth technologies are difficult to grow MnO nanosheets, fills the gap in the existing technology, and provides a material basis for the study of the physical properties of two-dimensional magnetic material MnO nanosheets. At the same time, the operation is simple, efficient, time-saving, low-cost and pollution-free. At the same time, the preparation process has strong controllability, and the obtained nanosheets have high density and regular shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Schematic diagram of the preparation process provided in Example 1.

[0048] Figures 2 to 4 All are optical photographs of MnO nanosheets prepared in Example 1.

[0049] Figure 5 This is an atomic force microscope photograph of the MnO nanosheets prepared in Example 1.

[0050] Figure 6 This is the XRD pattern of the MnO nanosheets prepared in Example 1.

[0051] Figure 7 This is the Raman spectrum of the MnO nanosheets prepared in Example 1.

[0052] Figure 8 This is the X-ray photoelectron spectrum of the MnO nanosheets prepared in Example 1.

[0053] Figure 9 Schematic diagram of the crystal results of MnO nanosheets prepared in Example 1.

[0054] Figure 10 This is the MnO atomic image of the MnO nanosheet prepared in Example 1 along the [0-10] zone axis.

[0055] Figure 11 for Figure 10 The corresponding selected area electron diffraction pattern.

[0056] Figure 12 This is an optical photograph of the MnO nanosheets prepared in Example 7.

[0057] Figure 13 This is an optical photograph of the MnO nanosheets prepared in Example 8.

[0058] Figure 14 This is an optical photograph of the MnO nanosheets prepared in Example 13.

[0059] Figure 15 This is an optical photograph of the MnO nanosheets prepared in Example 14.

[0060] Figure 16 This is an optical photograph of the MnO nanosheets prepared in Example 15.

[0061] Figure 17 This is an optical photograph of the MnO nanosheets prepared in Comparative Example 3.

[0062] Figure 18 This is an optical photograph of the MnO nanosheets prepared in Example 16.

[0063] Figure 19 This is an atomic force microscope photograph of the MnO nanosheets prepared in Example 16.

[0064] Figure 20 This is an optical photograph of the MnO nanosheets prepared in Example 21.

[0065] Figure 21 This is an optical photograph of the MnO nanosheets prepared in Comparative Example 5. DETAILED DESCRIPTION

[0066] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0067] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.

[0068] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0069] Example 1

[0070] This embodiment provides a two-dimensional magnetic MnO nanosheet having a triangular morphology. The thickness and the length of the longest side of the nanosheet are shown in Table 1.

[0071] like Figure 1 As shown, the preparation method of the two-dimensional magnetic MnO nanosheets is as follows:

[0072] (1) Cleaning the substrate:

[0073] Place the cut sapphire substrate in acetone and alcohol solutions in turn, and use an ultrasonic cleaner to clean each for 20 minutes. After cleaning, blow dry the substrate surface with nitrogen to remove impurities such as organic matter and dust particles on the surface.

[0074] (2) Weighing:

[0075] 100 mg of Mn powder, 10 mg of MnCl2 powder, and 5 mg of NaCl powder were weighed as reaction precursors (first raw materials), the three powders were fully mixed, and placed in a quartz boat. The sapphire substrate cleaned in step (1) was placed behind the mixed powders, leaving only a small space in between to ensure that the shortest linear distance between the substrate and the first raw material was 0.15 mm, which was conducive to the epitaxial growth of the sample.

[0076] (3) Place the quartz boat containing the first raw material and the substrate in the center of the heating zone of the tube furnace, with the end containing the mixed chemical close to the tuyere to ensure a continuous supply of Mn source so that it can be deposited on the substrate;

[0077] (4) Gas washing:

[0078] Use a mechanical pump to remove as much air as possible from the quartz tube and purge it with argon (flow rate of 200 sccm) for 40 min;

[0079] (5) Set the temperature and air flow:

[0080] During the reaction, a mixed gas of Ar and O2 was used as the carrier gas, with a flow rate ratio of Ar:O2=10:1 (Ar was 200 sccm, O2 was 20 sccm), and the temperature was raised to 800°C at a heating rate of 30°C / min. Then, the temperature was kept at 800°C for 20 minutes. After the reaction was completed, when the temperature in the warm zone was about to drop below 700°C, the O2 supply was stopped, and the temperature was naturally cooled to room temperature to obtain the two-dimensional magnetic MnO nanosheets.

[0081] Example 2

[0082] This embodiment provides a two-dimensional magnetic MnO nanosheet having a triangular morphology. The thickness and the length of the longest side of the nanosheet are shown in Table 1.

[0083] The preparation method of the two-dimensional magnetic MnO nanosheets is as follows:

[0084] (1) Cleaning the substrate:

[0085] Place the cut sapphire substrate in acetone and alcohol solutions in turn, and use an ultrasonic cleaner to clean each for 20 minutes. After cleaning, blow dry the substrate surface with nitrogen to remove impurities such as organic matter and dust particles on the surface.

[0086] (2) Weighing:

[0087] 150 mg of Mn powder, 9 mg of MnCl2 powder, and 5 mg of NaCl powder were weighed as reaction precursors (first raw materials), the three powders were fully mixed, and placed in a quartz boat. The sapphire substrate cleaned in step (1) was placed behind the mixed powders, leaving only a small space in between to ensure that the shortest linear distance between the substrate and the first raw material was 0.2 mm, which was conducive to the epitaxial growth of the sample.

[0088] (3) Place the quartz boat containing the first raw material and the substrate in the center of the heating zone of the tube furnace, with the end containing the mixed chemical close to the tuyere to ensure a continuous supply of Mn source so that it can be deposited on the substrate;

[0089] (4) Gas washing:

[0090] Use a mechanical pump to remove as much air as possible from the quartz tube and purge it with argon (flow rate of 200 sccm) for 40 min;

[0091] (5) Set the temperature and air flow:

[0092] During the reaction, a mixed gas of Ar and O2 was used as the carrier gas, with the flow rate ratio of Ar:O2=10:1 (Ar was 200 sccm, O2 was 15 sccm), and the temperature was raised to 850°C at a heating rate of 30°C / min. Then, the temperature was kept at 850°C for 20 minutes. After the reaction was completed, when the temperature in the warm zone was about to drop below 700°C, the O2 supply was stopped, and the temperature was naturally cooled to room temperature to obtain the two-dimensional magnetic MnO nanosheets.

[0093] Example 3

[0094] This embodiment provides a two-dimensional magnetic MnO nanosheet having a triangular morphology. The thickness and the length of the longest side of the nanosheet are shown in Table 1.

[0095] The preparation method of the two-dimensional magnetic MnO nanosheets is as follows:

[0096] (1) Cleaning the substrate:

[0097] Place the cut sapphire substrate in acetone and alcohol solutions in turn, and use an ultrasonic cleaner to clean each for 20 minutes. After cleaning, blow dry the substrate surface with nitrogen to remove impurities such as organic matter and dust particles on the surface.

[0098] (2) Weighing:

[0099] 200 mg of Mn powder, 13 mg of MnCl2 powder, and 5 mg of NaCl powder were weighed separately as reaction precursors (first raw materials). The three powders were fully mixed and placed in a quartz boat. The sapphire substrate cleaned in step (1) was placed behind the mixed powders, leaving only a small space in between to ensure that the shortest linear distance between the substrate and the first raw material was 0.1 mm, which was conducive to the epitaxial growth of the sample.

[0100] (3) Place the quartz boat containing the first raw material and the substrate in the center of the heating zone of the tube furnace, with the end containing the mixed chemical close to the tuyere to ensure a continuous supply of Mn source so that it can be deposited on the substrate;

[0101] (4) Gas washing:

[0102] Use a mechanical pump to remove as much air as possible from the quartz tube and purge it with argon (flow rate of 200 sccm) for 40 min;

[0103] (5) Set the temperature and air flow:

[0104] During the reaction, a mixed gas of Ar and O2 was used as the carrier gas, with the flow rate ratio of Ar:O2=10:1 (Ar was 200 sccm, O2 was 15 sccm), and the temperature was raised to 750°C at a heating rate of 30°C / min. Then, the temperature was kept at 750°C for 20 minutes. After the reaction was completed, when the temperature in the warm zone was about to drop below 700°C, the O2 supply was stopped, and the temperature was naturally cooled to room temperature to obtain the two-dimensional magnetic MnO nanosheets.

[0105] Example 4

[0106] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, molten salt NaCl is not added; the rest of the preparation methods and parameters are consistent with those of embodiment 1.

[0107] Example 5

[0108] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the shortest linear distance between the substrate and the first raw material is adjusted to 0 mm; the rest of the preparation methods and parameters are consistent with those of embodiment 1.

[0109] Example 6

[0110] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the shortest linear distance between the substrate and the first raw material is adjusted to 0.3 mm; the rest of the preparation methods and parameters are consistent with those of embodiment 1.

[0111] Example 7

[0112] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, 80 mg of Mn powder is weighed; the rest of the preparation methods and parameters are consistent with those of embodiment 1.

[0113] Example 8

[0114] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, 210 mg of Mn powder is weighed; the rest of the preparation methods and parameters are consistent with those of embodiment 1.

[0115] Example 9

[0116] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, 5 mg of MnCl2 powder is weighed; the rest of the preparation methods and parameters are consistent with those of embodiment 1.

[0117] Example 10

[0118] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, 15 mg of MnCl2 powder is weighed; the rest of the preparation method and parameters are consistent with those of embodiment 1.

[0119] Example 11

[0120] The difference between this embodiment and embodiment 1 is that in step (2), MnSO4 is selected as the manganese compound to replace MnCl2; the rest of the preparation method and parameters are consistent with those of embodiment 1.

[0121] Example 12

[0122] The difference between this embodiment and embodiment 1 is that in step (5) of this embodiment, the flow rate of O2 is 5 sccm; the rest of the preparation method and parameters are consistent with those of embodiment 1.

[0123] Example 13

[0124] The difference between this embodiment and embodiment 1 is that in step (5) of this embodiment, the flow rate of O2 is 40 sccm; the rest of the preparation method and parameters are consistent with those of embodiment 1.

[0125] Example 14

[0126] The difference between this embodiment and embodiment 1 is that in step (5) of this embodiment, the temperature of chemical vapor deposition is 700° C.; the rest of the preparation methods and parameters are consistent with those of embodiment 1.

[0127] Example 15

[0128] The difference between this embodiment and embodiment 1 is that in step (5) of this embodiment, the temperature of chemical vapor deposition is 900° C.; the rest of the preparation methods and parameters are consistent with those of embodiment 1.

[0129] Comparative Example 1

[0130] The difference between this comparative example and Example 1 is that the manganese source in step (2) of this comparative example is only Mn powder, weighing 110 mg, and does not contain MnCl2 powder; the rest of the preparation method and parameters are consistent with Example 1.

[0131] Comparative Example 2

[0132] The difference between this comparative example and Example 1 is that the manganese source in step (2) of this comparative example is only MnCl2 powder, weighing 110 mg, and does not contain Mn powder; the rest of the preparation method and parameters are consistent with Example 1.

[0133] Comparative Example 3

[0134] The difference between this comparative example and Example 1 is that in step (5) of this comparative example, the flow rate of O2 in the introduced gas is 0 sccm; the rest of the preparation methods and parameters are consistent with those in Example 1.

[0135] Comparative Example 4

[0136] This embodiment provides a method for preparing MnO, comprising the following steps:

[0137] 2 mmol of Mn(NO3)2 and 1.3 g of dimethylimidazole were added to 40 mL of distilled water and stirred at room temperature until dissolved. The Mn(NO3)2 solution was then poured into the dimethylimidazole solution, causing the solution to rapidly change color. Stirring was continued at room temperature for 4 hours. The resulting suspension was centrifuged, washed, and then dried in an oven at 60°C to obtain the precursor material. Sintering at 550°C in an Ar / H2 mixed atmosphere yielded uniform manganese monoxide nanoparticles.

[0138] Figure 1 This is a schematic diagram of the specific preparation process for growing two-dimensional magnetic MnO nanosheets using the chemical vapor deposition method used in Example 1 of the present invention. As can be seen from the figure, using Mn powder and MnCl2 as the Mn source, an appropriate amount of Ar / O2 carrier gas is introduced into a quartz tube, the temperature is raised to 800°C at 30°C / min, and after holding for 20 minutes, the temperature is naturally cooled to room temperature to obtain high-quality MnO nanosheets. The two-dimensional MnO preparation method proposed in the present invention is simple to operate, efficient, time-saving, low-cost, and has strong controllability during the process. It can efficiently and quickly prepare high-quality two-dimensional MnO nanosheets of varying thicknesses.

[0139] Figures 2 to 4 All show optical photographs of the MnO nanosheets prepared in Example 1.

[0140] Figure 5 Atomic force images and corresponding height profiles of the triangular MnO nanosheets prepared in Example 1. The AFM image shows that the grown MnO samples are regularly shaped like triangles. The height profiles reveal that the resulting MnO nanosheets have thicknesses of 113 nm, 125 nm, and 249 nm, respectively.

[0141] Figure 6 This is the XRD pattern of the MnO nanosheets prepared in Example 1, along with the X-ray diffraction spectrum of the substrate (Al2O3) and the corresponding standard card. In the MnO system, a single diffraction peak at 34.9° corresponds to the (111) crystal plane of MnO, indicating that MnO grows preferentially along the

[111] band axis on the alumina substrate. Furthermore, the X-ray diffraction spectrum contains only pure substrate and sample peaks, with no other impurities present, confirming the synthesis of high-quality MnO crystals.

[0142] Figure 7 This is the Raman spectrum of the MnO nanosheets prepared in Example 1. Figure 7 It can be seen that the Raman spectra of MnO and sapphire substrate are common. In addition to the sapphire substrate peak, there is also a characteristic peak at 646cm-1 , this characteristic peak belongs to the vibration mode of the Mn-O bond in MnO.

[0143] Figure 8 This is the X-ray photoelectron spectrum of the MnO nanosheets prepared in Example 1. Figure 8 It can be seen that the XPS spectrum of MnO shows peaks at 641.5 eV and 653.5 eV, which correspond to the binding energies of Mn 2p3 / 2 and Mn 2p1 / 2 ( Figure 8 a), which means that the valence state of the Mn element in the sample is divalent; and the peak at 530.6eV belongs to the O1s binding energy in MnO ( Figure 8 b) The rest are located in XX and are satellite peaks.

[0144] Figures 9 to 11 This is the crystal structure model of the MnO crystal in Example 1 along the

[001] zone axis. Figure 9 The crystal structure diagram of the MnO nanosheet of Example 1 is shown in FIG. MnO crystal belongs to the cubic system and has a space group of Figure 10 This is an atomic image of the Mn nanosheet along the [0-10] axis in Example 1. A cross-sectional MnO sample was prepared using confocal ion beam electron microscopy (FIB). Along the [0-10] axis, the interplanar spacing d is 0.26 nm, corresponding to the (111) plane of MnO. Figure 11 for Figure 10 The corresponding selected area electron diffraction pattern. The selected area electron diffraction pattern shows distorted hexagonal diffraction spots, which correspond to the (111), (200) and (1īī) crystal planes of MnO.

[0145] Figure 12 This is an optical photograph of the MnO nanosheets prepared in Example 7. When the reaction source content ratio (Mn:MnCl2) is less than 10, the obtained MnO nanosheets are smaller in size and square in shape.

[0146] Figure 13 This is an optical photograph of the MnO nanosheets prepared in Example 8. When the reaction source content ratio (Mn:MnCl2) is greater than 10, thicker triangular MnO nanosheets are obtained.

[0147] Figure 14 This is an optical photograph of the MnO nanosheets prepared in Example 13. When 40 sccm of O2 was introduced, thicker triangular MnO nanosheets were obtained.

[0148] Figure 15 This is an optical photograph of the MnO nanosheets prepared in Example 14. When the growth temperature is 700°C, smaller triangular MnO nanosheets are obtained.

[0149] Figure 16 This is an optical photograph of the MnO nanosheets prepared in Example 15. When the growth temperature is 900°C, thicker triangular-shaped MnO nanosheets are grown.

[0150] Figure 17 This is an optical photograph of the MnO nanosheets prepared in Comparative Example 3. When the O2 flow into the tube furnace is 0 sccm, no MnO nanosheets can be epitaxially grown on the substrate.

[0151] Figure 18 This is an optical photograph of the MnO nanosheets prepared in Example 16.

[0152] Figure 19 Atomic force images and corresponding height profiles of the square-shaped MnO nanosheets prepared in Example 16. The AFM image shows that the grown MnO sample is quadrilateral. The height profiles show that the resulting MnO nanosheets have thicknesses of 40 nm, 59 nm, and 103 nm, respectively.

[0153] Figure 20 This is an optical photograph of the MnO nanosheets prepared in Example 21. When 40 sccm of O2 was introduced, thicker quadrilateral MnO nanosheets were obtained.

[0154] Figure 21 This is an optical photograph of the MnO nanosheets produced in Comparative Example 5. When the O₂ flow rate in the tube furnace was 0 sccm, no MnO nanosheets could be grown epitaxially on the substrate. The MnO products provided in Examples 1-15 and Comparative Examples 1-4 were characterized for morphology, side length, and thickness using optical microscopy, atomic force microscopy, X-ray diffractometer, Raman spectrometer, X-ray photoelectron spectroscopy, and transmission electron microscopy. The results are shown in Table 1.

[0155] Table 1

[0156]

[0157]

[0158] Example 16

[0159] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, 250 mg of Mn powder, 10 mg of MnCl2 powder and 5 mg of NaCl powder are weighed as reaction precursors (first raw materials); the rest of the preparation methods and parameters are consistent with those of embodiment 1.

[0160] Example 17

[0161] The difference between this embodiment and embodiment 16 is that in step (2) of this embodiment, 201 mg of Mn powder is weighed; the rest of the preparation methods and parameters are consistent with those of embodiment 16.

[0162] Example 18

[0163] The difference between this embodiment and embodiment 16 is that in step (2) of this embodiment, 300 mg of Mn powder is weighed; the rest of the preparation methods and parameters are consistent with those of embodiment 16.

[0164] Example 19

[0165] The difference between this embodiment and embodiment 16 is that in step (2) of this embodiment, 5 mg of MnCl2 powder is weighed; the rest of the preparation methods and parameters are consistent with embodiment 16.

[0166] Example 20

[0167] The difference between this embodiment and embodiment 16 is that in step (5) of this embodiment, the flow rate of O2 is 10 sccm; the rest of the preparation methods and parameters are consistent with embodiment 16.

[0168] Example 21

[0169] The difference between this embodiment and embodiment 16 is that in step (5) of this embodiment, the flow rate of O2 is 40 sccm; the rest of the preparation methods and parameters are consistent with embodiment 16.

[0170] Comparative Example 5

[0171] The difference between this comparative example and Example 16 is that in step (5) of this comparative example, the flow rate of O2 in the gas introduced is 0 sccm; the rest of the preparation methods and parameters are consistent with Example 16.

[0172] The morphology, side length, and thickness of the MnO products provided in Examples 16-21 and Comparative Example 5 were characterized using optical microscopy, atomic force microscopy, X-ray diffractometer, Raman spectrometer, X-ray photoelectron spectroscopy, and transmission electron microscopy. The characterization results are shown in Table 2.

[0173] Table 2

[0174] Morphology Thickness (nm) Longest side length (μm) Example 16 quadrilateral 12 4 Example 17 quadrilateral 16 2 Example 18 quadrilateral 40 4 Example 19 quadrilateral 59 2 Example 20 quadrilateral 89 1.5 Example 21 quadrilateral 138 2 Comparative Example 5 none none none

[0175] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A two-dimensional magnetic MnO nanosheet, characterized in that: The morphology of the two-dimensional magnetic MnO nanosheets includes a triangular morphology and / or a quadrilateral morphology.

2. The two-dimensional magnetic MnO nanosheet according to claim 1, characterized in that In the triangular-shaped two-dimensional magnetic MnO nanosheet, the thickness of the nanosheet is 100-500 nm, and the length of each side of the nanosheet is independently 1-10 μm.

3. The two-dimensional magnetic MnO nanosheet according to claim 1, characterized in that In the quadrilateral morphology of the two-dimensional magnetic MnO nanosheet, the thickness of the nanosheet is 10 to 150 nm, and the length of each side of the nanosheet is independently 1 to 4 μm.

4. A method for preparing the two-dimensional magnetic MnO nanosheets according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: Passing an oxygen-containing gas into the first raw material to react by chemical vapor deposition to obtain the two-dimensional magnetic MnO nanosheets; The first raw material includes elemental manganese and manganese compounds; the morphology of the two-dimensional magnetic MnO nanosheets includes triangular morphology and / or quadrilateral morphology.

5. The preparation method according to claim 4, characterized in that The manganese compound includes manganese halide; Preferably, the first raw material further comprises molten salt; Preferably, based on the total mass of the first raw material being 120 mg, the amount of the molten salt added is 3 to 8 mg.

6. The preparation method according to claim 4, characterized in that The reaction system for performing the reaction by chemical vapor deposition further includes a substrate, and the shortest linear distance between the substrate and the first raw material is 0.1 to 0.2 mm.

7. The preparation method according to claim 4, characterized in that In the first raw material, the mass of elemental manganese is 100-200 mg, and the mass of the manganese compound is 9-13 mg.

8. The preparation method according to claim 4, characterized in that In the first raw material, the mass of elemental manganese is 200 to 300 mg (excluding 200 mg), and the mass of the manganese compound is 9 to 13 mg.

9. The preparation method according to claim 4, characterized in that The oxygen in the oxygen-containing gas has an inlet flow rate of 10 to 20 sccm; Preferably, the reaction temperature is 750-850° C., and the reaction time is 20-30 min.

10. Use of a two-dimensional magnetic MnO nanosheet, characterized in that: The use includes using the two-dimensional magnetic MnO nanosheets according to any one of claims 1 to 3 or the two-dimensional magnetic MnO nanosheets prepared by the preparation method according to any one of claims 4 to 9 in electronic devices, optoelectronic devices or spintronic devices.

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