Preparation method, analysis method and measurement method of single-layer two-dimensional material

Abstract

A method for preparing a single-layer two-dimensional material comprises the following steps: providing a dihydrated acetate having the general formula M(CH3COO)2·2H2O, wherein M may be a metal ion such as cadmium or zinc. Dissolving the dihydrated acetate in ethylenediamine and heating to 60°C for two hours to form a metal cation precursor solution. Providing a chalcogen powder, wherein the chalcogen powder is selected from sulfur, selenium, or tellurium. Dissolving the chalcogen powder and sodium borohydride in ethylenediamine and allowing to stand at room temperature for 24 hours to form a chalcogen precursor solution. Mixing the metal cation precursor solution with the chalcogen precursor solution to form a mixed solution. Placing the mixed solution in a high-temperature and high-pressure reactor to react and form a single-layer two-dimensional material. The present invention also provides a method for analyzing the spin properties and spintronics measurements of single-layer two-dimensional materials, as well as a method for measuring directional single-layer two-dimensional materials using an electron paramagnetic resonance spectrometer.

Description

Technical Field

[0001] The present invention relates to a material used in the field of quantum optics, and in particular to a method for preparing a quantum semiconductor material and a method for analyzing the spin properties of the material and measuring spin electronics. Background Art

[0002] Two-dimensional (2D) materials with flat shapes and uniform thickness, such as nanosheets, quantum wells, and quantum ribbons, have attracted widespread attention due to their optical properties at room temperature and strong quantum confinement in the vertical direction. Current methods for growing 2D nanosheets primarily rely on chemical vapor deposition (CVD) in the gas phase and solution methods, while large-scale synthesis remains under investigation.

[0003] Cadmium selenide (CdSe) is one of the most recognized semiconductors for optical and catalytic applications. It has been synthesized into a variety of desired morphologies, including molecular nanoclusters, 0D nanoparticles, 1D nanowires, and 2D nanosheets. Therefore, colloidal 2D nanosheets are of particular interest due to their tunable thickness, low defect count, enhanced quantum yield, giant oscillator strength transition (GOST), and emission properties for nanolasers and displays. The advantages of single-layer 2D materials are that the oscillator strength effectively triggers light-matter interactions, leading to enhanced quantum optical effects and spintronic resonance effects.

[0004] However, existing two-dimensional nanosheets require extremely low temperatures to exhibit spintronic properties suitable for quantum optics applications. When used as quantum materials, they require significant energy and cost to maintain at ambient temperature.

[0005] This "Background" section is intended only to facilitate understanding of the present invention. Therefore, the information disclosed in this section may contain information that is not known to a person skilled in the art. Furthermore, the information disclosed in this section does not represent the problems to be solved by the present invention or one or more embodiments, nor does it represent that the information was known or understood by a person skilled in the art before the filing of this application. Summary of the Invention

[0006] This invention provides a method for preparing a single-layer two-dimensional material using a one-step chemical solvothermal synthesis method. The synthesis process does not require the use of special selenium precursors or toxic carbon monoxide gas. The resulting single-layer two-dimensional material exhibits high crystallinity and a tunable manganese doping concentration. It exhibits quantum properties of light and matter, such as spin and spintronics, at room temperature and in low magnetic fields.

[0007] The present invention provides a method for analyzing single-layer two-dimensional materials. A sample with directional alignment is prepared by spin coating. Electron paramagnetic resonance spectra are measured under perpendicular and parallel magnetic fields using an electron paramagnetic resonance spectrometer. By measuring the spin resonance magnetic field spectra, the energy differences between different spin states of electrons in zero magnetic field are analyzed. A magnetic circular anisotropy spectrometer is used to obtain the electron transition spin spectra of the material at room temperature and in a low magnetic field (-0.8T to +0.8T). The half-maximum width of the magneto-optically active transition absorption and the difference in absorption between left- and right-handed light are fitted with a Gaussian function, and the Zeeman splitting energy under the magnetic field is calculated. This proportional relationship between energy and magnetic field is called the effective Lande factor, and its magnitude indicates the ability of the magnetic field to modulate the spin flip associated with the electron transition and its relative polarization.

[0008] Other purposes and advantages of the present invention can be further understood from the technical features disclosed in the present invention.

[0009] To achieve one or part or all of the above-mentioned purposes or other purposes, a method for preparing a single-layer two-dimensional material provided in one embodiment of the present invention includes the following steps: providing a dihydrated acetate having the general formula M(CH3COO)2·2H2O, wherein M is a metal ion cadmium or zinc. Dissolving the dihydrated acetate in ethylenediamine and heating to 60°C for two hours to form a metal cation precursor solution. Providing a chalcogen powder, wherein the chalcogen powder is selected from sulfur, selenium or tellurium. Dissolving the chalcogen powder and sodium borohydride in ethylenediamine and standing at room temperature for 24 hours to form a chalcogen precursor solution. Mixing the metal cation precursor solution and the chalcogen precursor solution to form a mixed solution. Placing the mixed solution in a high-pressure closed reactor to react to form a single-layer two-dimensional material.

[0010] In one embodiment of the present invention, the method for forming the metal cation precursor solution includes dissolving manganese acetate tetrahydrate and acetate dihydrate in ethylenediamine at 60°C.

[0011] In one embodiment of the present invention, the molar concentration of manganese doping in the metal cation precursor solution is between 0-15%.

[0012] In one embodiment of the present invention, the method for preparing the single-layer two-dimensional material further includes mixing the single-layer two-dimensional material with trioctylphosphine in an oxygen-free environment for purification.

[0013] In one embodiment of the present invention, the purification method includes mixing the monolayer two-dimensional material with trioctylphosphine, adding dimethylformamide, and repeating the centrifugation treatment 3-4 times.

[0014] In one embodiment of the present invention, the purification method further comprises repeating the centrifugation treatment 3-4 times, adding ethanol, repeating the centrifugation treatment 3-4 times, and then drying by vacuum.

[0015] In one embodiment of the present invention, the method of placing the mixed solution into a high-pressure sealed reactor to react comprises conducting the reaction at 120° C.-250° C.

[0016] To achieve one, some, or all of the above-mentioned objectives, or other objectives, one embodiment of the present invention provides a method for measuring anisotropic single-layer two-dimensional materials using an electron paramagnetic resonance spectrometer, comprising the following steps: providing a single-layer two-dimensional material prepared by the above-mentioned preparation method; uniformly dispersing the single-layer two-dimensional material in ethanol to form a measurement sample; spin-coating or drop-coating the measurement sample onto a glass slide and placing it into a measurement tube of an electron paramagnetic resonance spectrometer; adjusting the measurement tube so that the measurement sample on the glass slide is perpendicular or parallel to the magnetic field; and measuring the sample using an electron paramagnetic resonance spectrometer.

[0017] In one embodiment of the present invention, the method of placing the measurement sample on the glass slide includes directly dropping 3-10 drops of the measurement sample on the glass slide, or repeating the spin coating method 10-100 times to prepare for placement on the glass slide.

[0018] To achieve one, some, or all of the above-mentioned objectives, or other objectives, a method for analyzing a single-layer two-dimensional material provided in one embodiment of the present invention includes the following steps: providing a single-layer two-dimensional material prepared by the above-mentioned preparation method; uniformly dispersing the single-layer two-dimensional material in ethanol to form a measurement sample; applying the measurement sample by spin coating at a rotation speed of 3000-5000 RPM, and dripping 10-100 drops of the measurement sample onto a glass slide to complete the configuration of a directionally aligned sample on the glass slide; placing the glass slide in a magnetic circular anisotropy spectrometer to measure the absorbance of the sample for left-handed and right-handed polarized light in a magnetic field ranging from -0.8T to +0.8T; analyzing the absorbance at different wavelengths using a Gaussian function using the electron transition superposition method to obtain the intensity and half-width of the magneto-optical transition absorption peak; deriving the Zeeman splitting energy under the magnetic field from the intensity and half-width of the magneto-optical transition absorption peak; plotting this energy against the magnetic field to obtain a linear relationship; the slope of this relationship is the effective Lande factor for the magneto-optical transition.

[0019] In the method for preparing a single-layer two-dimensional material according to an embodiment of the present invention, a high-temperature solvent method is used to synthesize a highly crystalline organic-inorganic composite single-layer two-dimensional material using ethylenediamine and a metal precursor. Tetracoordinated manganese ions are effectively doped as magneto-optically active spin centers, and a coating method is used to form a sample with a directional arrangement of the two-dimensional material. Electron paramagnetic resonance spectroscopy measures the directional arrangement of the sample in a perpendicular or parallel magnetic field, and the spin center exhibits a high zero-field splitting energy and an anisotropic resonance absorption spectrum. Measurement of magnetic circular dichroism spectra can be used to infer the resonance energy that varies with the magnetic field. The tetracoordinated manganese ions exhibit a strong Zeeman effect in the single-layer two-dimensional material, indicating magneto-optical properties that effectively flip spin electrons at room temperature and low magnetic fields.

[0020] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, which can be implemented in accordance with the contents of the specification, and to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the following specifically cites preferred embodiments and describes them in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the direction-dependent electron paramagnetic resonance spectrum of a single-layer two-dimensional material doped with manganese ions.

[0022] Figure 2 Schematic diagram of the spectral simulation of a sample of manganese ion-doped single-layer two-dimensional material in the S=5 / 2 spin system.

[0023] Figure 3 3D display of Kramer's Twin Peaks 5 Schematic diagram of the energy levels of a spin system.

[0024] Figure 4 Schematic diagram of the absorption spectrum of manganese ion-doped single-layer two-dimensional materials, its first differential, and the related magnetic circular dichroism spectrum under a magnetic field.

[0025] Figure 5 Schematic diagram of the results of extracting the effective Lande factor from the slope of the Zeeman splitting energy versus magnetic field for a single-layer two-dimensional material. DETAILED DESCRIPTION

[0026] The present invention is further illustrated by way of examples below, but the present invention is not limited to the scope of the examples. Experimental methods in the following examples where specific conditions are not specified were performed according to conventional methods and conditions, or selected according to the product specifications.

[0027] To make the efficacy of the present invention easier to understand, specific examples, as well as detection methods and results for the examples are provided below, but are not intended to limit the present invention.

[0028] Example 1

[0029] Preparation method of single-layer two-dimensional material of the present invention

[0030] The single-layer two-dimensional material of the present invention is essentially prepared in a nitrogen-filled, sealed container in a glove box with a low water and oxygen content (<10 ppm). The starting material in this embodiment is a dihydrated acetate salt having the general formula M(CH3COO)2·2H2O, where M is a metal cation. More specifically, M is, for example, cadmium or zinc, but is not limited thereto. In one embodiment, cadmium acetate dihydrate (Cd(OAc)2·2H2O) or zinc acetate dihydrate (Zn(OAc)2·2H2O) (3.00 mmol) is weighed into a sample bottle, and a magnet is added to help stir it evenly. It is then dissolved in ethylenediamine (0.52 mol) and heated to 60°C for two hours. This heating step helps the cadmium acetate dihydrate or zinc acetate dihydrate dissolve in the ethylenediamine. After two hours of reaction, the solution is cooled back to room temperature, resulting in a white turbid solution, which is the metal cation precursor solution.

[0031] On the other hand, chalcogen powder (5.40 mmol) and sodium borohydride (5.40 mmol) are dissolved in ethylenediamine (0.022 mol). The chalcogen powder described in the present invention refers to the powder of sulfur, selenium or tellurium in the chalcogen. Sodium borohydride is used as a reducing agent to activate the chalcogen. Ethylenediamine serves as a dissolving solvent on the one hand and a ligand of the material on the other hand. After standing at room temperature for 24 hours, in this embodiment, when selenium powder is used, for example, the color of the solution will slowly change from the original black solution to a dark green solution and finally to a transparent colorless solution. It should be understood that when different chalcogens are used, the change in the color of the solution may also be different. The above-mentioned solution color change can provide a preliminary understanding of the oxidation state of sulfur, selenium or tellurium because the addition of sodium borohydride reduces it from (0) to (-2). The transparent solution synthesized here is called a chalcogen precursor solution.

[0032] In this embodiment, the metal cation in the metal cation precursor solution is cadmium, and the chalcogen in the chalcogen precursor solution is selenium. However, the above embodiment is not intended to limit the scope of the present invention. The prepared chalcogen precursor solution is added to the metal cation precursor solution to form a mixed solution. The mixed solution is yellow-green in color. After being stirred at room temperature for 24 hours, the mixed solution turns white. The components contained in the solution are organic-inorganic CdSe(en) 0.5, where en is the abbreviation of ethylenediamine, representing that the inorganic cadmium selenide is dispersed in the ethylenediamine solvent. The mixed solution is then placed in a sample bottle and sealed in an autoclave. After being sent out of the glove box, the reaction is carried out at 120°C-250°C in a temperature-controlled reactor, which is the solvothermal method well known in the prior art. The solvothermal method refers to a synthetic method in which the original mixture reacts in a closed system, such as a high-pressure reactor, using an organic or non-aqueous solvent as a solvent at a certain temperature and the autogenous pressure of the solution. It differs from the hydrothermal reaction in that the solvent used is organic instead of water. In this embodiment, the solvent used is ethylenediamine. After 24 hours of reaction, a structurally stable single-layer two-dimensional material is formed, and the chemical formula is ME(en) 0.5 , wherein M is cadmium or zinc, and E is sulfur, selenium or tellurium. In this embodiment, CdSe(en) 0.5 For example, this single-layer two-dimensional material is the final product of the present invention.

[0033] After the high-temperature reaction, the monolayer two-dimensional material is returned to the glove box and mixed with trioctylphosphine in a nitrogen (oxygen-free) environment. Since the synthesis ratio used in the present invention is to react an excess of the chalcogen element precursor solution (selenium) with the metal cation precursor solution (cadmium), in order to avoid obtaining a monolayer two-dimensional material product CdSe(en) in the final product, the monolayer two-dimensional material product is mixed with trioctylphosphine. 0.5 Tri-n-octylphosphine (TOP), which has strong Lewis base properties, is added to the mixture with selenium powder to form a soluble compound with elemental selenium, so that unreacted selenium powder can be removed in the subsequent purification process.

[0034] The purification method uses dimethylformamide (N,N-dimethylformide, DMF), an aprotic solvent, and an appropriate amount of product in a centrifuge tube. The soluble by-product selenium-trioctylphosphine is soluble in the aprotic solvent. The product is separated from the solvent by centrifugation (6500rpm, 10min) to remove the by-products of the reaction. This centrifugation process is repeated 3-4 times to effectively remove the reaction by-products and unreacted precursors. Finally, ethanol is added for washing and the remaining dimethylformamide is removed by centrifugation for about 3-4 times. Finally, vacuum drying is used to obtain a purified single-layer two-dimensional material as a powder solid.

[0035] Example 2

[0036] Preparation method of manganese ion-doped single-layer two-dimensional material

[0037] The single-layer two-dimensional material of this embodiment also includes manganese ion doping. During the preparation process, it is basically necessary to prepare it in a closed container filled with nitrogen and a glove box equipment with very low water and oxygen content. The starting materials of this embodiment are manganese acetate tetrahydrate (Mn(OAc)2·4H2O) and dihydrate acetates, which have the general formula M(CH3COO)2·2H2O, where M is a metal cation. More specifically, M is, for example, cadmium or zinc, but is not limited to this. The molar concentration percentage of manganese ion doping is, for example, 0-15%. Specifically, three different concentrations of 0.5% (0.015 mmol), 4.0% (0.120 mmol) and 7.7% (0.231 mmol) are added according to the manganese / cadmium or manganese / zinc ratio. In one embodiment, manganese acetate tetrahydrate (Mn(OAc)2·4H2O) and cadmium acetate dihydrate (Cd(OAc)2·2H2O) or zinc acetate dihydrate (Zn(OAc)2·2H2O) (3.00mmol) are weighed in a sample bottle, and a magnet is added to help stir evenly. Then, ethylenediamine (0.52mol) is used to dissolve them and the mixture is heated to 60°C for two hours. This heating step can help manganese acetate tetrahydrate and cadmium acetate dihydrate or zinc acetate dihydrate dissolve in ethylenediamine. After two hours of reaction, the mixture is cooled back to room temperature, and a white turbid solution is formed. This solution is the manganese ion-doped metal cation precursor solution. Depending on the material used, it can be a general formula of Mn x Cd 1-x Se(en) 0.5 Manganese / cadmium precursor or a general formula of Mn x Zn 1-x Se(en) 0.5 A manganese / zinc precursor wherein x is 0-15%.

[0038] On the other hand, chalcogen powder (5.40 mmol) and sodium borohydride (5.40 mmol) are dissolved in ethylenediamine (0.022 mol). The chalcogen powder described in the present invention refers to the powder of sulfur, selenium or tellurium in the chalcogen. Sodium borohydride is used as a reducing agent to activate the chalcogen. Ethylenediamine serves as a dissolving solvent on the one hand and a ligand of the material on the other hand. After standing at room temperature for 24 hours, in this embodiment, when selenium powder is used, for example, the color of the solution will slowly change from the original black solution to a dark green solution and finally to a transparent colorless solution. It should be understood that when different chalcogens are used, the change in the color of the solution may also be different. The above-mentioned solution color change can provide a preliminary understanding of the oxidation state of sulfur, selenium or tellurium because the addition of sodium borohydride reduces it from (0) to (-2). The transparent solution synthesized here is called a chalcogen precursor solution.

[0039] In this embodiment, the metal cation in the manganese ion-doped metal cation precursor solution is cadmium, and the chalcogen in the chalcogen precursor solution is selenium. However, the above embodiment is not intended to limit the scope of the present invention. The prepared chalcogen precursor solution is added to the manganese ion-doped metal cation precursor solution to form a mixed solution. The color of the mixed solution is yellow-green. After being fully stirred at room temperature for 24 hours, the mixed solution turns white. The components contained in the solution are organic-inorganic Mn x Cd 1-x Se(en) 0.5 , where en is the abbreviation of ethylenediamine, representing inorganic manganese ions doped with cadmium selenide dispersed in ethylenediamine solvent. The mixed solution is then placed in a sample bottle and sealed in an autoclave. After being sent out of the glove box, the reaction is carried out at 120°C-250°C in a temperature-controlled reactor, which is the solvothermal method well known in the prior art. Solvothermal refers to a synthetic method in which the original mixture reacts in a closed system, such as an autoclave, with an organic or non-aqueous solvent as a solvent at a certain temperature and the autogenous pressure of the solution. It differs from the hydrothermal reaction in that the solvent used is organic instead of water. In this embodiment, the solvent used is ethylenediamine. After 24 hours of reaction, a structurally stable single-layer two-dimensional material is formed, and the chemical formula is Mn x M 1-x E(en) 0.5 , wherein M is cadmium or zinc, and E is sulfur, selenium or tellurium. In this embodiment, Mn x Cd 1-x Se(en) 0.5 For example, the manganese ion-doped single-layer two-dimensional material is the final product of the present invention.

[0040] After the high-temperature reaction, the manganese ion-doped single-layer two-dimensional material is returned to the glove box and mixed with trioctylphosphine in a nitrogen (oxygen-free) environment. Since the synthesis ratio used in the present invention is to react an excess of the chalcogen element precursor solution (selenium) with the manganese ion-doped metal cation precursor solution (cadmium), in order to avoid obtaining the manganese ion-doped single-layer two-dimensional material product Mn in the final product, the product is mixed with trioctylphosphine. x Cd 1-x Se(en) 0.5 Tri-n-octylphosphine (TOP), which has strong Lewis base properties, is added to the mixture with unreacted selenium powder to form a soluble compound with elemental selenium, so as to remove the unreacted selenium powder in the subsequent purification process.

[0041] The purification method uses dimethylformamide (N,N-dimethylformide, DMF), an aprotic solvent, and an appropriate amount of the product in a centrifuge tube. The soluble byproduct selenium-trioctylphosphine is soluble in the aprotic solvent. The product is separated from the solvent by centrifugation (6500rpm, 10min) to remove the byproducts of the reaction. This centrifugation process is repeated 3-4 times to effectively remove the reaction byproducts and unreacted precursors. Finally, ethanol is added for washing and the remaining dimethylformamide is removed by centrifugation for about 3-4 times. Finally, vacuum drying is used to obtain the purified manganese ion-doped single-layer two-dimensional material as a powder solid.

[0042] Example 3

[0043] Measuring directional monolayer two-dimensional materials using electron paramagnetic resonance spectroscopy

[0044] Electron paramagnetic resonance (EPR), also known as electron spin resonance spectroscopy, uses microwave radiation to detect materials with unpaired electrons. Due to the characteristic of electron spins being +1 / 2 and -1 / 2, an external magnetic field generates a difference between two energy states. As the strength of the applied magnetic field increases, the energy difference between the energy levels widens until it matches the microwave radiation, leading to photon absorption. Electron paramagnetic resonance spectroscopy typically varies the magnetic field while maintaining the microwave frequency, measuring the magnetic resonance phenomenon produced by unpaired electrons in the presence of a magnetic field.

[0045] The material used for measurement in this embodiment is the product of Example 2, a single-layer two-dimensional material doped with manganese ions, with the general formula Mn x Cd 1-x Se(en) 0.5 For example, the material is a two-dimensional quantum structure, doped with divalent manganese ions with unpaired electrons. Since the spin electrons are confined to the X, Y, and Z bond spaces, they are not only directional, but also the effective Lande factor g of the spin state (ΔE = gβ) is measured under different magnetic field directions. e B, ΔE is the microwave radiation energy, β e The relationship between the electron Bohr magnetic element, B, and g, which represents the resonant energy required for electron spin flipping under a magnetic field, is also different (different energy level splitting under a magnetic field), indicating that the electron spin is affected by the forces coupled to orbitals and other electrons. Therefore, measuring the electron paramagnetic resonance spectrum of directional samples can confirm that two-dimensional materials possess bonding anisotropy.

[0046] In general sample measurement, a suitable amount of a powdered solid manganese ion-doped single-layer two-dimensional material is taken as a sample and placed into a measuring tube of an electron paramagnetic resonance spectrometer, which is, for example, but not limited to, a quartz tube.

[0047] On the other hand, in directional sample measurements, a rectangular glass slide is first cut into elongated shapes. A powdered solid manganese ion-doped monolayer 2D material is then evenly dispersed in ethanol and diluted to an appropriate concentration to form a measurement sample. Approximately 3-10 drops of the measurement sample are then dripped onto the elongated glass slide, or the sample is spin-coated and allowed to air-dry until a layer of white sample forms on the slide. The slide containing the measurement sample is then placed into the measurement tube of an electron paramagnetic resonance spectrometer, the aforementioned quartz tube. The rotating measurement tube is adjusted so that the measurement sample on the slide is perpendicular or parallel to the magnetic field. The sample is then measured using the electron paramagnetic resonance spectrometer, completing the directional sample measurement experiment.

[0048] The experimental results are as follows Figure 1 As shown, Figure 1 represents the manganese doping concentration x = 0.5% Mn x Cd 1-x Se(en) 0.5 Direction-dependent electron paramagnetic resonance spectrum of a manganese ion-doped monolayer two-dimensional material at 4K (temperature), where ※ represents measurement of a non-directional powder sample, / / represents measurement of a directional sample parallel to the magnetic field, and ⊥ represents measurement of a directional sample perpendicular to the magnetic field. Figure 1 The X-axis is the magnitude of the magnetic field, and the Y-axis is the intensity. Figure 1 Directional electron paramagnetic resonance spectra in different directions can confirm that two-dimensional materials have bonding anisotropy. Figure 2 Spectral and simulation results (gray) of a sample of a monolayer two-dimensional material doped with manganese ions at 4K in the S=5 / 2 spin system. Figure 2 The X-axis is the magnitude of the magnetic field, and the Y-axis is the intensity. Figure 2 The spectral simulation results in can obtain the zero-field-splitting parameter (D value) given in the spin Hamiltonian, which is 3850MHz. Figure 3 The X-axis is the magnitude of the external magnetic field, and the Y-axis is the energy of different spin states. Figure 3 3D display of Kramer's Twin Peaks 5 Schematic diagram of the energy levels of the spin system, the relationship between the energy difference between different spin states (±1 / 2, ±3 / 2, ±5 / 2) and the magnetic field, and the use of Figure 2 The energy differences (2D and 4D values) of ±1 / 2→±3 / 2 and ±3 / 2→±5 / 2 under zero magnetic field were calculated from the D value results of the spectral simulation.

[0049] Example 4

[0050] Analytical methods for spintronics in single-layer two-dimensional materials

[0051] Magnetic circular dichroism (MCD) spectroscopy uses circularly polarized light to study transitions between electronic states. MCD spectroscopy reveals differences in absorption intensity between left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) visible and ultraviolet light of varying energies in a directional magnetic field. This difference can be used to estimate the magnitude of the Zeeman splitting produced by the magnetic field. Sample preparation for MCD is limited by its absorption spectroscopy method. Therefore, powder samples must be prepared in the form of thin films. These films should be neither too thick to prevent light from penetrating nor too thin to minimize sample volume and generate a weak signal.

[0052] In this embodiment, the material used for measurement is the product of Example 2, the manganese ion-doped single-layer two-dimensional material, with the general formula Mn x Cd 1-x Se(en) 0.5 For example, the material is a two-dimensional quantum structure, doped with divalent manganese ions with unpaired electrons and bonded to a two-dimensional monolayer plane. The powdered solid manganese ion-doped monolayer two-dimensional material is uniformly dispersed in ethanol to form a measurement sample. On the other hand, a square quartz cover glass is provided, which is cleaned with ethanol and isopropanol three times each and dried to ensure that the square quartz cover glass is not contaminated. The cleaned square quartz cover glass is placed on a spin coater and coated at a speed of 3000RPM-5000RPM. Then, a small amount of the measurement sample is taken and about 10-100 drops are dripped onto the surface of the square quartz cover glass. It is dried by rotation to complete the preparation of the measurement sample.

[0053] Next, the square quartz cover glass was placed in a magnetic circular anisotropy spectrometer to measure the difference in absorbance of left-handed polarized light to right-handed polarized light of the sample under different magnetic fields. The magnetic field used in this embodiment ranged from -0.8T to +0.8T.

[0054] After the measurement, the absorption spectrum at different wavelengths is analyzed using the Gaussian function using the electron transition overlap method. Quantum materials have complex energy level systems, and the absorption spectrum reveals the absorption energy and intensity of their electron transitions. Therefore, the overlap method can be used to fit the characteristic peaks of different electron transitions. The Gaussian function can represent the intensity and half-maximum width of the electron transition absorption peak.

[0055] Figure 4Schematic diagram of the absorption spectrum and its first derivative of a manganese-ion-doped monolayer two-dimensional material at 300K, along with the associated magnetic circular anisotropy spectrum (-0.8T to +0.8T) under a magnetic field. The top figure shows the optical absorption (dashed line) and its first derivative (dotted line), while the bottom figure shows the corresponding magnetic circular anisotropy spectrum. The top figure shows the absorption spectrum in the absence of a magnetic field, while the bottom figure shows the difference between the absorption spectra of left-handed and right-handed light under a magnetic field.

[0056] The Zeeman splitting energy in a magnetic field is derived using the intensity and half-width of the magneto-optical transition absorption peak. Energy level theory explains the orbital motion of electrons outside the nucleus. Electrons can only move in specific, discrete orbits. Electrons in each orbit have distinct atomic energy levels, and energy transitions between these energy levels are unaffected by magnetic fields. In the presence of a magnetic field, atomic energy levels split into more energy levels due to differences in spin. This energy asymmetry creates a difference in energy levels called Zeeman splitting.

[0057] Next, the linear relationship between energy and magnetic field was calculated. The slope of this linear relationship is the effective Landé factor (g) for magneto-optical transitions. The Landé factor g combines the orbital angular momentum, spin angular momentum, and total electronic angular momentum (L+S) of the atomic energy state, all of which contribute to the coupling of the electron spin magnetic moment under a magnetic field. Therefore, the ratio of the difference in the Zeeman splitting energy levels produced by a magnetic field to the magnetic field can be used to determine the Landé factor g. A larger value indicates a relatively larger Zeeman effect under a smaller magnetic field. The effective Landé factor is also an important indicator for the application of dilute magnetic semiconductors in spintronic devices. Monolayer semiconductors exhibit quantum confinement effects at the atomic level (<0.3nm). The spectra described above indicate that electrons exhibit strong Zeeman and zero-field splitting energies, exhibiting effective Landé factors at room temperature on the same order of magnitude as those observed at liquid helium temperatures. The long lifetime, spin coupling, and superparamagnetic properties of room-temperature magnetic semiconductors have great research potential and application value, potentially enabling future applications in spin memory, quantum bits, polariton lasers, and magnetic resonance imaging.

[0058] Figure 5 Schematic diagram of the method for extracting the effective Lande factor from the slope of the Zeeman splitting energy versus magnetic field for a single-layer two-dimensional material. Figure 5The upper figure uses a single-layer two-dimensional material without manganese ions prepared in Example 1, while the lower figure uses a single-layer two-dimensional material doped with manganese ions prepared in Example 2. The slope relationship between magnetic field and energy is the Landé g factor. The different Landé g factors extracted from the two batches of samples by transition overlap analysis are listed in brackets in the figure. The material without manganese doping in the upper figure shows a correlation graph with a smaller slope, and the Zeeman splitting energy is inversely proportional to the direction of the magnetic field. The material doped with manganese in the lower figure shows a correlation graph with a slope increased by at least one order of magnitude. At this time, the manganese ions are subject to strong quantum effects, and their Zeeman splitting energy shows a huge Landé g factor, and shows a positive relationship with the magnetic field, indicating that the resonance energy required to flip the electron spin under the magnetic field is low.

[0059] In summary, in the preparation method of the single-layer two-dimensional material of the embodiment of the present invention, a high-temperature solvent method is used to synthesize a highly crystalline organic-inorganic composite single-layer two-dimensional material using ethylenediamine and a metal precursor. Tetracoordinated manganese ions are effectively doped as magneto-optically active spin centers, and a coating method is used to form a sample with a directional arrangement of the two-dimensional material. Electron paramagnetic resonance spectroscopy measures the above-mentioned directional arrangement sample in a perpendicular or parallel magnetic field. The spin center exhibits a high zero-field splitting energy and an anisotropic resonance absorption energy spectrum. The measurement of magnetic circular dichroism spectrum can be used to infer the resonance energy that changes with the magnetic field. The tetracoordinated manganese ions have a strong Zeeman effect in the single-layer two-dimensional material, indicating magneto-optical properties that effectively flip the spin electrons at room temperature and low magnetic fields.

[0060] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment, it is not intended to limit the present invention. Any technician familiar with the present profession can make slight changes or modifications to equivalent embodiments of equivalent changes using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a single-layer two-dimensional material, characterized in that: The following steps are involved: Providing dihydrated acetates having the general formula M(CH3COO)2·2H2O, wherein M is a metal ion of cadmium or zinc; Dissolving the dihydrated acetate in ethylenediamine and heating to 60° C. for two hours to form a metal cation precursor solution; Providing a chalcogen element powder, wherein the chalcogen element powder is selected from sulfur, selenium or tellurium; Dissolving the chalcogen element powder and sodium borohydride in ethylenediamine, and allowing the mixture to stand at room temperature for 24 hours to form a chalcogen element precursor solution; mixing the metal cation precursor solution and the chalcogen element precursor solution to form a mixed solution; and The mixed solution is placed in a high-pressure reactor to react and form a single-layer two-dimensional material.

2. The method for preparing a single-layer two-dimensional material according to claim 1, wherein: The method for forming the metal cation precursor solution includes dissolving manganese acetate tetrahydrate and the acetate dihydrate in ethylenediamine at 60°C.

3. The method for preparing a single-layer two-dimensional material according to claim 2, wherein: The molar concentration of manganese ions in the metal cation precursor solution is between 0-15%.

4. The method for preparing a single-layer two-dimensional material according to claim 1, wherein: The preparation method of the single-layer two-dimensional material further includes mixing the single-layer two-dimensional material with trioctylphosphine in an oxygen-free environment for purification.

5. The method for preparing a single-layer two-dimensional material according to claim 4, wherein: The purification method includes mixing the single-layer two-dimensional material with trioctylphosphine, adding dimethylformamide, and repeating centrifugation 3-4 times.

6. The method for preparing a single-layer two-dimensional material according to claim 5, wherein: The purification method further includes repeating centrifugation 3-4 times, adding ethanol, repeating centrifugation 3-4 times, and then drying by vacuum.

7. The method for preparing a single-layer two-dimensional material according to claim 1, wherein: The method of placing the mixed solution into the high-pressure reactor to carry out the reaction includes carrying out the reaction at 120° C.-250° C.

8. A method for measuring a directional single-layer two-dimensional material using an electron paramagnetic resonance spectrometer, characterized in that: The following steps are involved: Providing a single-layer two-dimensional material prepared by the preparation method according to any one of claims 1 to 7; The single-layer two-dimensional material is uniformly dispersed in ethanol to form a measurement sample; The measurement sample is arranged on a glass slide and placed in a measurement tube of an electron paramagnetic resonance spectrometer; adjusting the measuring tube so that the measuring sample on the glass slide is perpendicular to or parallel to the magnetic field; and The measurement sample was measured using an electron paramagnetic resonance spectrometer.

9. The method for measuring a directional single-layer two-dimensional material using an electron paramagnetic resonance spectrometer according to claim 8, wherein: The method of disposing the measurement sample on the glass slide includes dropping 3-10 drops of the measurement sample on the glass slide by a dropping method, or disposing the measurement sample on the glass slide by a spin coating method.

10. A method for analyzing a single-layer two-dimensional material, characterized in that: The following steps are involved: A single-layer two-dimensional material prepared by the preparation method of any one of claims 1 to 7 is provided; the single-layer two-dimensional material is uniformly dispersed in ethanol to form a measurement sample; the measurement sample is disposed on a glass slide by a spin coating method, wherein the coating is performed at a rotation speed of 3000RPM-5000RPM, and 10-100 drops of the measurement sample are dripped onto the glass slide; the glass slide is placed in a magnetic circular anisotropy spectrometer, and the absorbance of left-handed polarized light and right-handed polarized light of the measurement sample in a magnetic field of -0.8T to +0.8T is measured; the absorbance of different wavelengths is analyzed by the electron transition superposition method using a Gaussian function to obtain the intensity and half-maximum width of the magneto-optical transition absorption peak; the Zeeman splitting energy under the magnetic field is derived based on the intensity and half-maximum width of the magneto-optical transition absorption peak; The effective Lande factor under magneto-optical transition is obtained from the linear relationship between the energy and the magnetic field and the slope of the linear relationship.

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