Preparation method for synthesizing ultrathin magnetic nanosheet at room temperature through ligand induction

Abstract

The invention relates to a ligand-induced room-temperature ultrathin magnetic nanosheet synthesis preparation method, which comprises: mixing a metal-ligand solution and an anion-ligand solution, and carrying out a heating reaction to obtain a ligand-induced room-temperature ultrathin magnetic nanosheet, wherein the metal-ligand solution comprises a Cu source, a Cr source and a first ligand; the anion-ligand solution comprises an anion X source and a second ligand; x is Se or Te; the first ligand is selected from one or two of oleylamine or oleyl alcohol; the second ligand is selected from one of oleylamine or tri-n-octylphosphine. Compared with the prior art, the method has the advantages that specific crystallographic orientation is stabilized by adjusting the adsorption capacity of ligands and surface ions in an organic liquid phase synthesis mode, anisotropic growth is guided, and the problems that in the prior art, room-temperature ultrathin nanosheet preparation excessively depends on substrate growth, and the steps are tedious are solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of two-dimensional magnetic nanomaterials, and relates to a preparation method of ligand-induced synthesis of a room-temperature ultrathin magnetic nanosheet. BACKGROUND

[0002] The discovery of the intrinsic ferromagnetism of atom-thick materials (such as CrI3, CrGeTe3) has become a research hotspot in the field of low-dimensional spintronics. These materials can be precisely controlled in magnetic state using external triggers (such as electric field, strain or light), providing a way for the next generation of memory and logic devices. However, the Curie temperature (T C ) of most two-dimensional magnets is low, usually below 100K, far below the operating requirements of electronic devices.

[0003] CuCr2X4 (X = Se, Te) has become a promising candidate material due to its room-temperature ferromagnetism (T C ≈ 300-360K), metallic conductivity and strong perpendicular magnetic anisotropy. Unlike van der Waals (vdW) magnets that rely on weak interlayer interactions, CuCr2X4 adopts a cubic close-packed structure with covalent bonds, avoiding the Mermin-Wagner restriction of long-range magnetic order in two-dimensional systems. Despite these advantages, it is fundamentally challenging to synthesize ultrathin, phase-pure CuCr2X4 from three-dimensional non-vdW bulk lattices because of its stronger lattice energy isotropy, which lacks the intrinsic anisotropic growth that drives vdW materials to naturally adopt a layered two-dimensional morphology.

[0004] In the existing technology, the preparation of ultrathin, phase-pure CuCr2X4 nanosheets is mainly chemical vapor deposition (CVD), using Cu source, Cr source, elemental Te or Se as raw materials, and heating to 760℃ in a single-temperature zone tube furnace for 1h to synthesize CuCr2X4 nanosheets. This method relies heavily on the substrate to stabilize the growth, limiting scalability, and the cumbersome operation steps and extremely high temperature in the existing technology bring inconvenience to the operator.

[0005] The prior art CN113697777A discloses a rhombohedral CuCrSe2 nanomaterial and a preparation method and application thereof. The crystal form of the CuCrSe2 nanomaterial is rhombohedral, and the micro-morphology thereof is a nanoscale disc-shaped and / or polygonal flake structure. The preparation method comprises the following steps: (1) performing a solvothermal reaction on a high-boiling-point reaction medium containing a soluble copper source, a chromium source and a selenium source; and (2) separating the solid product in the solvothermal reaction and removing the residual solvent on the surface of the solid product. The rhombohedral CuCrSe2 nanomaterial synthesized by the method has high crystallinity, high monodispersity and uniform size and morphology, and has a disc-shaped or polygonal flake structure. The method has mild reaction conditions and a simple process, and realizes controllable preparation of the rhombohedral CuCrSe2 nanomaterial with controllable size, uniform morphology, high crystallinity and monodispersity. The nanomaterial has a wide application prospect in the field of optoelectronic devices. However, the nanomaterial prepared by the technical solution has a small particle size (10-30 nm), is prone to spontaneous agglomeration, affects the processing performance and storage stability of the material, and causes difficulty in separating and removing impurities / small molecule clusters, thereby greatly increasing the cost of mass production. SUMMARY

[0006] The purpose of the present application is to provide a preparation method for synthesizing ligand-induced room-temperature ultrathin magnetic nanosheets, which uses an organic liquid-phase synthesis method to stabilize specific crystallographic orientations by adjusting the adsorption ability of ligands and surface ions, guide anisotropic growth, and realize the phase-selective growth of target materials with different stoichiometric ratios, thereby solving the problem of excessive dependence on substrate growth and small material size in the prior art.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] A preparation method for ligand-induced room-temperature ultrathin magnetic nanosheets, comprising: mixing a metal-ligand solution and an anion-ligand solution and heating to react, to obtain a product.

[0009] The metal-ligand solution comprises a Cu source, a Cr source and a first ligand.

[0010] The anion-ligand solution comprises an anion X source and a second ligand; X is Se or Te.

[0011] The first ligand is selected to be one or both of oleylamine and oleyl alcohol; and the second ligand is selected to be one of oleylamine and tri-n-octylphosphine.

[0012] Tri-n-octylphosphine can better stabilize the intermediate state of Cu2Se, and oleylamine can better stabilize the intermediate state of CuSe. The chemical stoichiometric ratio of the product corresponding to different intermediate states is not consistent, and the phase-selective growth of the target material is realized by ligand induction.

[0013] The present application utilizes its adsorption ability with surface ions to stabilize specific crystallographic orientation, realizes the preparation of ultrathin nanosheets through the cation exchange route, and solves the problem of substrate growth in the prior art.

[0014] In some specific embodiments, the reaction temperature in the heating reaction is 280-350℃, the reaction time is 0.5-4h, and the reaction atmosphere is nitrogen or inert gas.

[0015] In some specific embodiments, the Cu source is selected from one of CuCl, CuCl2 or Cu(acac)2; the Cr source is selected from one of Cr(acac)3, Cr(CO)6 or CrCl3; and the anion X source is selenium powder or tellurium powder.

[0016] In some specific embodiments, the molar ratio of the Cu source, the Cr source and the anion X source is 1:(2-8):(4-16).

[0017] In some specific embodiments, the first ligand is oleyl alcohol.

[0018] In some specific embodiments, the feeding ratio of the Cu source and the first ligand is 0.1-0.2mmol:6-8mL.

[0019] The feeding ratio of the anion X source and the second ligand is 0.4-1.6mmol:0.8-5mL. Preferably, the concentration of the anion-ligand solution is 0.5-1mmol / mL.

[0020] In some specific embodiments, the preparation method of the metal-ligand solution comprises: mixing the Cu source, the Cr source and the first ligand and performing heating treatment to obtain.

[0021] In some specific embodiments, in the heating treatment, the heating temperature is 100-180℃, the heating time is 0.5-1h, and the heating atmosphere is nitrogen or inert gas.

[0022] In some specific embodiments, the preparation method of the anion-ligand solution comprises: mixing the anion X source and the second ligand and performing heating treatment to obtain.

[0023] In some specific embodiments, in the heating treatment, the heating temperature is 150-330℃, the heating time is 0.5-1h, and the heating atmosphere is nitrogen or inert gas.

[0024] In some specific embodiments, after the reaction product mixture of the heating reaction is cooled and washed, the ultrathin magnetic nanosheets are obtained and sealed.

[0025] The washing includes washing with a mixture of n-hexane and anhydrous ethanol.

[0026] In the storage, the storage solvent is n-hexane; and the storage atmosphere is nitrogen or inert gas.

[0027] The present application solves the problems of poor selectivity (generation of binary mixed phases), thermodynamic disadvantage, slow kinetics, functional group interference and the like which cannot be avoided or overcome in one-step direct reaction by means of two-step method. Although the operation times and time cost are increased, higher target product yield, better purity, stronger controllability, milder reaction conditions and the possibility of realizing complex molecule synthesis are obtained.

[0028] Compared with the prior art, the present application has the following characteristics:

[0029] 1) When a ternary or quaternary material is synthesized by a traditional chemical method, the formation of a binary phase may be caused by different reactivity of precursors, and pure-phase CuCr2X4 (X=Se, Te) nanosheets cannot be obtained, and the material itself does not meet the two-dimensional category. The present application uses a ligand-induced room-temperature ultrathin magnetic nanosheet synthesis method to realize anisotropic growth of ultrathin nanosheet CuCr2X4 (X=Se, Te) nanosheets under low-temperature and short-time conditions. The reaction temperature is lower than 350 DEG C, the reaction temperature is low, the period is short, and the energy consumption is greatly reduced.

[0030] 2) The CuCr2X4 (X=Se, Te) nanosheet provided by the present application has a cubic crystal structure, uniform morphology and controllable size. The nanosheet in the present application has a larger size and a thinner thickness compared with the nanosheet prepared by the prior art. The diameter of the nanosheet is 0.1-4 mu m, and the thickness is 3-20 nm. The nanosheet structure of this size can provide a continuous electron transmission channel, and does not need to be prepared into a film by spin coating or the like, avoiding the problems of uneven thickness or discontinuous stacking, and being conducive to expanding the application of the material to the fields of high-frequency radio frequency transistors and ultra-low power logic chips. At the same time, the thickness of the nanosheet also endows it with super-high bending toughness, and can be applied to the field of implantable biosensors.

[0031] 3) The technology provided by the present application can realize anisotropic growth of ultrathin nanosheet CuCr2X4 (X=Se, Te) nanosheets by adjusting the use of ligands, and obtain pure-phase CuCrX2 (X=Se, Te) nanosheets with different stoichiometric ratios, establishing a diversified two-dimensional material platform with controllable composition.

[0032] 4) The existing preparation technology needs more oriented substrate support, ultra-high reaction temperature and ultra-long reaction time, the application uses the adsorption capacity and stability of ligand and surface ions to stabilize specific crystallographic orientation, realizes the preparation of ultrathin nanosheets through the cation exchange method, solves the problem that the preparation of ultrathin nanosheets in the prior art depends on substrate growth, establishes an expandable route for preparing self-supporting two-dimensional magnets, and promotes the design of spin electronic materials with adjustable anisotropy and thickness-dependent function. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is the X-ray diffraction pattern of CuCr2Te4 nanosheets obtained in Examples 1-6 of the application;

[0034] Figure 2 is the X-ray diffraction pattern of CuCr2Se4 nanosheets obtained in Examples 7-8 of the application;

[0035] Figure 3 is the X-ray diffraction pattern of CuCrSe2 nanosheets obtained in Examples 9-10 of the application;

[0036] Figure 4 is the TEM image of CuCr2Te4 nanosheets obtained in Examples 1-6 of the application;

[0037] Figure 5 is the TEM image of CuCr2Se4 nanosheets obtained in Examples 7-8 of the application;

[0038] Figure 6 is the TEM image of CuCrSe2 nanosheets obtained in Examples 9-10 of the application;

[0039] Figure 7 is the M-H graph of CuCr2Te4 nanosheets obtained in Example 1 of the application;

[0040] Figure 8 is the M-H graph of CuCr2Se4 nanosheets obtained in Example 7 of the application;

[0041] Figure 9 is the thickness distribution graph of CuCr2Te4 nanosheets obtained in Example 1 of the application;

[0042] Figure 10 is the X-ray diffraction pattern of nanosheets obtained in Comparative Example 1 of the application;

[0043] Figure 11 is the X-ray diffraction pattern of nanosheets obtained in Comparative Example 2 of the application;

[0044] Figure 12 is the X-ray diffraction pattern of nanosheets obtained in Comparative Example 3 of the application;

[0045] Figure 13 is the low-temperature M-H graph of the nanosheet obtained in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0046] The present application will be described in detail below with reference to the drawings and specific examples. The present embodiment is implemented on the premise of the technical scheme of the present application, and detailed implementation and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0047] The following are more detailed implementation cases, which further illustrate the technical scheme of the present application and the technical effects that can be obtained.

[0048] In the following examples, unless otherwise specified, the raw reagents or processing techniques are all conventional commercially available products or conventional processing techniques in the art. In the following examples, the nitrogen or inert gas atmosphere is carried out under a Schlenk device.

[0049] In the synthesis of CuCr2X4(X=Se, Te), the use of the first ligand (oleylamine or oleyl alcohol) can induce the anisotropic growth of the product morphology, realizing the synthesis of room-temperature ultrathin magnetic nanosheets. Specifically, when the first ligand is oleyl alcohol, the terminal functional group (-OH) can induce the anisotropic growth of CuCr2X4(X=Se, Te);

[0050] When X is Se, the use of the second ligand (oleylamine or tri-n-octylphosphine) can induce the change of its composition structure, realizing the synthesis of different stoichiometric ratio CuCrSe2nanosheets. Specifically, when the second ligand is oleylamine, CuCr2Se4is obtained, and when the second ligand is tri-n-octylphosphine, CuCrSe2nanosheets are obtained.

[0051] Example 1

[0052] The present embodiment provides a preparation method for ligand-induced room-temperature ultrathin magnetic nanosheet synthesis, which is obtained by the following preparation steps:

[0053] (1) 0.125 mmol of CuCl2, 1 mmol of Cr(CO)6 and 6 mL of oleyl alcohol were added to a three-necked flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 100℃, and kept at 100℃ for 30 min under N2 protection to obtain a uniformly dispersed metal precursor solution;

[0054] (2) 1.6 mmol of Te powder and 1.6 mL of tri-n-octylphosphine were added to a three-necked flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 150℃, and kept at 150℃ for 30 min under N2 protection to obtain a uniformly dispersed Te precursor solution;

[0055] (3) the suspension containing the Te source is rapidly injected into the metal precursor solution;

[0056] (4) gradually heated to 300°C under N2protection, and kept for 1 h to obtain the nanosheet material, with a stirring rate of 500 rpm;

[0057] (5) cooled to room temperature, and the product is washed by centrifugation with anhydrous ethanol and n-hexane for 3-4 times, and then naturally dried to obtain the nanosheet with a structure of CuCr2Te4.

[0058] Example 2

[0059] The preparation method of the ligand-induced room-temperature ultrathin magnetic nanosheet synthesis provided in this example is different from that of Example 1 only in that:

[0060] In step (1), 6 mL of oleyl alcohol is replaced by 6 mL of oleylamine.

[0061] The rest is the same as in Example 1.

[0062] The specific process is as follows:

[0063] (1) 0.125 mmol of CuCl2, 1 mmol of Cr(CO)6 and 6 mL of oleylamine are added to a three-necked flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 100°C, and kept for 30 min under N2protection to obtain a uniformly dispersed metal precursor solution;

[0064] (2) 1.6 mmol of Te powder and 1.6 mL of tri-n-octylphosphine are added to a three-necked flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 150°C, and kept for 30 min under N2protection to obtain a uniformly dispersed Te precursor solution;

[0065] (3) the suspension containing the Te source is rapidly injected into the metal precursor solution;

[0066] (4) gradually heated to 300°C under N2protection, and kept for 1 h to obtain the nanosheet material, with a stirring rate of 500 rpm;

[0067] (5) cooled to room temperature, and the product is washed by centrifugation with anhydrous ethanol and n-hexane for 3-4 times, and then naturally dried to obtain the nanosheet with a structure of CuCr2Te4.

[0068] Example 3

[0069] The preparation method of the ligand-induced room-temperature ultrathin magnetic nanosheet synthesis provided in this example is different from that of Example 1 only in that:

[0070] In step (1), 6 mL of organic solvent is replaced by 6 mL of mixed reagent of oleylamine and oleyl alcohol mixed at a volume ratio of 2:1;

[0071] The rest is the same as in Example 1.

[0072] The specific process is as follows:

[0073] (1) 0.125 mmol of CuCl2, 1 mmol of Cr(CO)6 and 6 mL of organic solvent (mixed at a volume ratio of 2:1 of oleylamine and oleyl alcohol) are added to a three-necked flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 100°C, and kept at 100°C for 30 min under N2 protection to obtain a uniformly dispersed metal precursor solution;

[0074] (2) 1.6 mmol of Te powder and 1.6 mL of tri-n-octylphosphine are added to a three-necked flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 150°C, and kept at 150°C for 30 min under N2 protection to obtain a uniformly dispersed Te precursor solution;

[0075] (3) The suspension containing the Te source is rapidly injected into the metal precursor solution;

[0076] (4) Under N2 protection, gradually heat to 300°C and keep for 1 h to obtain nanosheet materials, and the stirring rate is 500 revolutions per minute;

[0077] (5) Cool to room temperature, and the product is washed by centrifugation with anhydrous ethanol and n-hexane for 3-4 times, and then naturally dried to obtain nanosheets with a structure of CuCr2Te4.

[0078] Example 4

[0079] The present example provides a preparation method for ligand-induced room-temperature ultrathin magnetic nanosheet synthesis, which is different from Example 1 only in that:

[0080] In step (1), 6 mL of organic solvent is replaced by 6 mL of mixed reagent of oleylamine and oleyl alcohol mixed at a volume ratio of 1:2;

[0081] The rest is the same as in Example 1.

[0082] The specific process is as follows:

[0083] (1) 0.125 mmol of CuCl2, 1 mmol of Cr(CO)6 and 6 mL of organic solvent (mixed at a volume ratio of 1:2 of oleylamine and oleyl alcohol) are added to a three-necked flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 100°C, and kept at 100°C for 30 min under N2 protection to obtain a uniformly dispersed metal precursor solution;

[0084] (2) 1.6 mmol of Te powder and 1.6 mL of tri-n-octylphosphine were added into a three-neck flask equipped with a temperature probe and a magnetic stirrer, and gradually heated to 150°C under N2 protection for 30 min to obtain a uniformly dispersed Te precursor solution;

[0085] (3) The suspension containing the Te source was rapidly injected into the metal precursor solution;

[0086] (4) The temperature was gradually increased to 300°C under N2 protection, and the reaction was kept for 1 h to obtain nanosheet materials, with a stirring rate of 500 rpm;

[0087] (5) After cooling to room temperature, the product was washed by centrifugation with anhydrous ethanol and n-hexane for 3-4 times, and then naturally dried to obtain nanosheets with a structure of CuCr2Te4.

[0088] Example 5

[0089] The embodiment provides a preparation method for ligand-induced room-temperature ultrathin magnetic nanosheet synthesis, which is different from the preparation method of Example 1 only in that:

[0090] In step (1), the Cu source is replaced by CuCl;

[0091] The amount of CuCl used is 0.2 mmol, the amount of Te source used is 1 mmol, and the amount of tri-n-octylphosphine used is 1 mL;

[0092] The rest is the same as in Example 1.

[0093] The specific process is as follows:

[0094] (1) 0.2 mmol of CuCl, 1 mmol of Cr(CO)6 and 6 mL of oleyl alcohol were added into a three-neck flask equipped with a temperature probe and a magnetic stirrer, and gradually heated to 100°C under N2 protection for 30 min to obtain a uniformly dispersed metal precursor solution;

[0095] (2) 1 mmol of Te powder and 1 mL of tri-n-octylphosphine were added into a three-neck flask equipped with a temperature probe and a magnetic stirrer, and gradually heated to 150°C under N2 protection for 30 min to obtain a uniformly dispersed Te precursor solution;

[0096] (3) The suspension containing the Te source was rapidly injected into the metal precursor solution;

[0097] (4) The temperature was gradually increased to 300°C under N2 protection, and the reaction was kept for 1 h to obtain nanosheet materials, with a stirring rate of 500 rpm;

[0098] (5) cooling to room temperature, the product is washed by centrifugation with anhydrous ethanol and n-hexane for 3-4 times, and then naturally dried to obtain nanosheets with a structure of CuCr2Te4.

[0099] Example 6

[0100] The embodiment provides a preparation method of ligand-induced room-temperature ultrathin magnetic nanosheet synthesis, which is different from the preparation method of the embodiment 1 only in that:

[0101] In step (1), the Cu source is replaced by Cu(acac)2.

[0102] The use amount of Cu(acac)2 is 0.1 mmol, the use amount of the Te source is 1.2 mmol, and the use amount of tri-n-octylphosphine is 2 mL.

[0103] The rest is the same as the embodiment 1.

[0104] The specific process is as follows:

[0105] (1) 0.1 mmol of Cu(acac)2, 1 mmol of Cr(CO)6 and 6 mL of oleyl alcohol are added into a three-necked flask provided with a temperature detector and a magnetic stirrer, gradually heated to 100 DEG C, and kept at 100 DEG C for 30 min under N2 protection to obtain a uniformly dispersed metal precursor solution;

[0106] (2) 1.2 mmol of Te powder and 2 mL of tri-n-octylphosphine are added into a three-necked flask provided with a temperature detector and a magnetic stirrer, gradually heated to 150 DEG C, and kept at 150 DEG C for 30 min under N2 protection to obtain a uniformly dispersed Te precursor solution;

[0107] (3) The suspension containing the Te source is rapidly injected into the metal precursor solution;

[0108] (4) Under N2 protection, gradually heated to 300 DEG C, and kept at 300 DEG C for 1 h to obtain nanosheet materials, and the stirring rate is 500 revolutions per minute;

[0109] (5) cooling to room temperature, the product is washed by centrifugation with anhydrous ethanol and n-hexane for 3-4 times, and then naturally dried to obtain nanosheets with a structure of CuCr2Te4.

[0110] Example 7

[0111] The embodiment provides a preparation method of ligand-induced room-temperature ultrathin magnetic nanosheet synthesis, which is different from the preparation method of the embodiment 1 only in that:

[0112] (1) 0.1 mmol CuCl, 0.22 mmol CrCl3·6H2O, 8 mL oleyl alcohol were added into a three-neck flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 100°C, and kept for 30 min, heated to 150°C under N2protection, and kept for 30 min to obtain a uniformly dispersed metal precursor solution;

[0113] (2) 1 mmol Se powder and 3 mL oleylamine were added into a three-neck flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 100°C, and kept for 30 min, heated to 330°C under N2protection, and kept for 30 min to obtain a uniformly dispersed Se precursor solution;

[0114] (3) The metal precursor solution was rapidly injected into the suspension containing the Se source;

[0115] (4) Under N2protection, gradually heated to 340°C, and kept for 2 h of reaction at a stirring rate of 300 revolutions per minute;

[0116] (5) Cooled to room temperature, and the product was washed by centrifugation with anhydrous ethanol and n-hexane for 3-4 times, and then naturally dried to obtain nanosheets with a structure of CuCr2Se4.

[0117] Example 8

[0118] The present example provides a preparation method for ligand-induced room-temperature ultrathin magnetic nanosheet synthesis, which is different from that of Example 7 only in that:

[0119] In step (1), 8 mL of oleyl alcohol was replaced by oleylamine;

[0120] The rest is the same as Example 7.

[0121] (1) 0.1 mmol CuCl, 0.22 mmol CrCl3·6H2O, 8 mL oleylamine were added into a three-neck flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 100°C, and kept for 30 min, heated to 150°C under N2protection, and kept for 30 min to obtain a uniformly dispersed metal precursor solution;

[0122] (2) 1 mmol Se powder and 3 mL oleylamine were added into a three-neck flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 100°C, and kept for 30 min, heated to 330°C under N2protection, and kept for 30 min to obtain a uniformly dispersed Se precursor solution;

[0123] (3) The metal precursor solution was rapidly injected into the suspension containing the Se source;

[0124] (4) gradually increase the temperature to 340°C under N2 protection, keep the reaction for 2h, and the stirring rate is 300 rpm;

[0125] (5) cool to room temperature, and the product is washed by centrifugation with anhydrous ethanol and n-hexane for 3-4 times, and then naturally dried to obtain nanosheets with a structure of CuCr2Se4.

[0126] Example 9

[0127] The embodiment provides a preparation method of ligand-induced room-temperature ultrathin magnetic nanosheet synthesis, and the difference between the preparation method and that of Example 7 is only that:

[0128] The Se source in step (2) is treated with tri-n-octylphosphine;

[0129] The amount of tri-n-octylphosphine used is 1 mL, and the amount of Se source used is 1 mmol;

[0130] The rest is the same as in Example 7.

[0131] The specific process is as follows:

[0132] (1) 0.1 mmol of CuCl, 0.22 mmol of CrCl3·6H2O and 8 mL of oleyl alcohol are added into a three-necked flask provided with a temperature detector and a magnetic stirrer, gradually heated to 100°C, kept for 30 min, and heated to 150°C under N2 protection, kept for 30 min, to obtain a uniformly dispersed metal precursor solution;

[0133] (2) 1 mmol of Se powder and 1 mL of tri-n-octylphosphine are added into a three-necked flask provided with a temperature detector and a magnetic stirrer, gradually heated to 100°C, kept for 30 min, and heated to 330°C under N2 protection, kept for 30 min, to obtain a uniformly dispersed Se precursor solution;

[0134] (3) the metal precursor solution is rapidly injected into the suspension containing the Se source;

[0135] (4) gradually increase the temperature to 340°C under N2 protection, keep the reaction for 2h, and the stirring rate is 300 rpm;

[0136] (5) cool to room temperature, and the product is washed by centrifugation with anhydrous ethanol and n-hexane for 3-4 times, and then naturally dried to obtain nanosheets with a structure of CuCrSe2.

[0137] Example 10

[0138] The embodiment provides a preparation method of ligand-induced room-temperature ultrathin magnetic nanosheet synthesis, and the difference between the preparation method and that of Example 9 is only that:

[0139] The Cu source is replaced by Cu(acac)2, and the Cr source is replaced by Cr(acac)3.

[0140] The amount of Cu(acac)2 used is 0.2 mmol, and the amount of Cr(acac)3 used is 0.8 mmol.

[0141] The rest is the same as Example 9.

[0142] The specific process is as follows:

[0143] (1) 0.2 mmol of Cu(acac)2, 0.8 mmol of Cr(acac)3, and 8 mL of oleyl alcohol were added to a three-necked flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 100°C, and kept for 30 min, then heated to 150°C under N2 protection, and kept for 30 min to obtain a uniformly dispersed metal precursor solution;

[0144] (2) 1 mmol of Se powder and 1 mL of tri-n-octylphosphine were added to a three-necked flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 100°C, and kept for 30 min, then heated to 330°C under N2 protection, and kept for 30 min to obtain a uniformly dispersed Se precursor solution;

[0145] (3) The metal precursor solution was rapidly injected into the suspension containing the Se source;

[0146] (4) Under N2 protection, gradually heated to 340°C, and kept for 2 h of reaction, with a stirring rate of 300 revolutions per minute;

[0147] (5) Cooled to room temperature, the product was washed with anhydrous ethanol and n-hexane by centrifugation for 3-4 times, and then naturally dried to obtain nanosheets with a structure of CuCrSe2.

[0148] Comparative Example 1:

[0149] This comparative example provides a preparation method for synthesizing ultrathin magnetic nanosheets, which is different from Example 1 only in that:

[0150] The Cu source, Cr source, Te source, tri-n-octylphosphine, and oleyl alcohol were mixed and then added to a three-necked flask;

[0151] The rest is the same as Example 1.

[0152] The specific steps are as follows:

[0153] (1) 0.125 mmol CuCl2, 1 mmol Cr(CO)6, 1.6 mmol Te powder, 1.6 mL tri-n-octylphosphine and 6 mL oleyl alcohol were added into a three-neck flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 100°C, and kept for 30 min, gradually heated to 300°C under N2 protection, and kept for 1 h with a stirring rate of 500 rpm;

[0154] (2) After cooling to room temperature, the product was washed by centrifugation with anhydrous ethanol and n-hexane for 3-4 times, and then naturally dried to obtain the target material.

[0155] Comparative Example 2:

[0156] This comparative example provides a preparation method for synthesizing ultrathin magnetic nanosheets, which is different from Example 7 only in that:

[0157] The Cu source, Cr source, Se source, oleylamine and oleyl alcohol were mixed and then added into a three-neck flask;

[0158] The rest was the same as Example 7.

[0159] The specific steps are as follows:

[0160] (1) 0.1 mmol CuCl, 0.22 mmol CrCl3·6H2O, 1 mmol Se powder, 3 mL oleylamine and 8 mL oleyl alcohol were added into a three-neck flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 100°C, and kept for 30 min, gradually heated to 340°C under N2 protection, and kept for 2 h with a stirring rate of 300 rpm;

[0161] (2) After cooling to room temperature, the product was washed by centrifugation with anhydrous ethanol and n-hexane for 3-4 times, and then naturally dried to obtain the target material.

[0162] Comparative Example 3:

[0163] This comparative example provides a preparation method for synthesizing ultrathin magnetic nanosheets, which is different from Example 9 only in that:

[0164] The Cu source, Cr source, Se source, tri-n-octylphosphine and oleyl alcohol were mixed and then added into a three-neck flask;

[0165] The rest was the same as Example 9.

[0166] The specific steps are as follows:

[0167] (1) 0.1 mmol CuCl, 0.22 mmol CrCl3·6H2O, 1 mmol Se powder, 1 mL tri-n-octylphosphine and 8 mL oleyl alcohol were added into a three-necked flask equipped with a temperature probe and a magnetic stirrer, gradually heated to 100°C, and kept for 30 min, gradually heated to 340°C under N2 protection, and kept for 2 h with a stirring rate of 300 rpm;

[0168] (2) After cooling to room temperature, the product was washed by centrifugation with anhydrous ethanol and n-hexane for 3-4 times, and then dried naturally to obtain the target material.

[0169] Application Examples

[0170] This example is used to characterize the nanosheets prepared in Examples 1-10, including:

[0171] Figures 1-3 The X-ray diffraction patterns of the target products obtained in Examples 1-6, Examples 7-8 and Examples 9-10, respectively. As can be seen from the comparison of the characterization patterns, all the diffraction peaks well correspond to the corresponding crystal faces of the target materials CuCr2Te4 (JCPDS Card No. 04-004-0093), CuCr2Se4 (JCPDS Card No. 01-089-2394) and CuCrSe2 (JCPDS Card No. 01-082-2589), and no other impurity peaks appear, indicating that the target products prepared by the method of this example are pure phase materials.

[0172] Figure 4 The transmission electron microscope (TEM) images of the target products obtained in Examples 1-6, respectively. It is shown that the CuCr2Te4 prepared by the method is a two-dimensional nanomaterial in the form of ultra-thin sheets, with a diameter of about 0.1-4 μm and a thickness of 3-20 nm; the comparison of Examples 1-4 shows that when the terminal functional groups of the ligand are mainly hydroxyl groups (-OH), the ligand plays a role in inducing the anisotropic growth of the material to an ultra-thin nanosheet, on the contrary, if the terminal functional groups of the ligand are mainly (-NH2), the material exists more in the form of nanocrystals or nanoparticles. Similarly, Figure 5 The results of Examples 7-8 show similar results to Figure 4 .

[0173] Figure 6 The transmission electron microscope (TEM) images of the target products obtained in Examples 9-10, respectively, show that the CuCrSe2 prepared by the method is a two-dimensional nanomaterial in the form of sheets, with a diameter of about 100 nm and a thickness of about 15 nm.

[0174] Figure 7The low-temperature and room-temperature magnetic characterization images of the target product obtained in Example 1 show that the coercivity is 1140 Oe at low temperature and 20 Oe at high temperature, indicating that the target material has strong room-temperature magnetism and can be tried in the field of high-temperature magnetic storage devices. Similarly, Figure 8 The results also show that the results prepared in Example 7 are similar to Figure 7 The results prepared in Example 7.

[0175] Figure 9 The thickness distribution diagram of the CuCr2Te4 nanosheet obtained in Example 1. The thickness is distributed between 3-10 nm, mainly concentrated at 6 nm, indicating that the CuCr2Te4 prepared by the method is a two-dimensional nanomaterial in the form of ultra-thin sheet.

[0176] Figure 10 The X-ray diffraction diagram of the target product obtained in Example 1 and Comparative Example 1. From the comparison of the characterization diagrams, it can be seen that when prepared by one-step method, the problems of poor selectivity, thermodynamic disadvantage, slow kinetics, functional group interference, etc. in the reaction process cannot be avoided, resulting in the existence of part of impurity peaks in the target material. Similarly, Figure 11 and Figure 12 The results show that the results prepared in Comparative Example 2 and Comparative Example 3 are similar to Figure 10 The results prepared in Example 7.

[0177] Figure 13 The low-temperature hysteresis loop comparison diagram of the target product obtained in Example 1 and Comparative Example 1. From the comparison of the characterization, it can be seen that the coercivity of the material in Comparative Example 1 is much smaller than that of Example 1 at low temperature due to the existence of impurities, indicating that the magnetic performance of the material prepared in the comparative example is slightly worse than that of Example 1.

[0178] The above description of the embodiments is for the convenience of the ordinary skilled person in the art to understand and use the invention. Those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described herein to other embodiments without having to go through creative labor. Therefore, the present application is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present application should be within the scope of protection of the present application.

Claims

1. A method for the preparation of ligand-induced room temperature ultrathin magnetic nanosheets, characterized by, The application relates to a preparation method of a Cu-Cr-Se or Cu-Cr-Te alloy, and belongs to the technical field of alloy preparation. Mixing and heating a metal-ligand solution and an anion-ligand solution to obtain a reaction product; The metal-ligand solution comprises a Cu source, a Cr source and a first ligand; The anion-ligand solution comprises an anion X source and a second ligand; X is Se or Te; The first ligand is selected from one or both of oleylamine and oleyl alcohol; and the second ligand is selected from one of oleylamine and tri-n-octylphosphine.

2. The method for preparing ligand-induced room temperature ultrathin magnetic nanosheets according to claim 1, characterized in that, In the heating reaction, the reaction temperature is 280-350 DEG C, the reaction time is 0.5-4 h, and the reaction atmosphere is nitrogen or inert gas.

3. The method for preparing ligand-induced room temperature ultrathin magnetic nanosheets according to claim 1, characterized in that, The Cu source is selected from one of CuCl, CuCl2 or Cu(acac)2; the Cr source is selected from one of Cr(acac)3, Cr(CO)6 or CrCl3; and the anion X source is selenium powder or tellurium powder.

4. The method for preparing ligand-induced room-temperature ultrathin magnetic nanosheets according to claim 3, characterized in that, The molar ratio of the Cu source, the Cr source and the anion X source is 1:(2-8):(4-16).

5. The method for preparing ligand-induced room temperature ultrathin magnetic nanosheets according to claim 1, characterized in that, The first ligand is oleyl alcohol.

6. The method of claim 5, wherein the ligand is selected from the group consisting of cysteine, cysteine derivatives, glutathione, glutathione derivatives, and combinations thereof. The feeding ratio of the Cu source and the first ligand is 0.1-0.2 mmol:6-8 mL; The feeding ratio of the anion X source and the second ligand is 0.4-1.6 mmol:0.8-5 mL.

7. The method for preparing ligand-induced room-temperature ultrathin magnetic nanosheets according to claim 1, wherein, The preparation method of the metal-ligand solution comprises the following steps: mixing a Cu source, a Cr source and a first ligand and performing heating treatment to obtain.

8. The method for preparing ligand-induced room-temperature ultrathin magnetic nanosheets according to claim 7, characterized in that, In the heating treatment, the heating temperature is 100-180 DEG C, the heating time is 0.5-1 h, and the heating atmosphere is nitrogen or inert gas.

9. The method for preparing ligand-induced room temperature ultrathin magnetic nanosheets according to claim 1, wherein, The preparation method of the anion-ligand solution comprises the following steps: mixing an anion X source and a second ligand and performing heating treatment to obtain.

10. The method for preparing ligand-induced room-temperature ultrathin magnetic nanosheets according to claim 9, characterized in that, In the heating treatment, the heating temperature is 150-330 DEG C, the heating time is 0.5-1 h, and the heating atmosphere is nitrogen or inert gas.

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