Room-temperature ferromagnetic MXene heterojunction composite material, and preparation method and application thereof

Abstract

This invention belongs to the field of advanced functional materials and spintronics technology, and discloses a room-temperature ferromagnetic MXene heterojunction composite material, its preparation method, and its applications. The composite material is amorphous molybdenum oxide nanosheets (MoO₂). 3‑x The heterojunction formed with MXene. Preparation method: (1) Preparation of amorphous molybdenum oxide nanosheets MoO 3‑x (2) After ultrasonically dispersing MXene powder in an ice bath in water, centrifuge to obtain MXene nanosheets; (3) MoO 3‑x After ultrasonic dispersion of MXene nanosheets in ethanol (1#), the mixture was stirred and reacted under supercritical conditions, then cooled, depressurized, and dried to obtain the target product. This invention relates to the application of the room-temperature ferromagnetic MXene heterojunction composite material in spintronic devices. The MXene heterojunction composite material prepared in this invention possesses both high saturation magnetization and long-range ferromagnetism with a Curie temperature above room temperature.

Description

Technical Field

[0001] This invention belongs to the field of advanced functional materials and spintronics technology, specifically relating to a room-temperature ferromagnetic MXene heterojunction composite material, its preparation method, and its application. Background Technology

[0002] As electronic technology advances towards miniaturization and low power consumption, two-dimensional ferromagnetic materials with highly tunable spin properties have become crucial for developing next-generation spintronic devices. However, achieving long-range magnetic order in two-dimensional systems is extremely difficult due to the thermal fluctuation effect in Mermin-Wagner theory. Although some crystals exhibit intrinsic two-dimensional magnetism, they generally suffer from drawbacks such as low Curie temperature and sensitivity to external fields. Therefore, the search for novel two-dimensional materials that combine metallic properties, high Curie temperature, and strong interface control potential has become an urgent need.

[0003] Transition metal carbides / nitrides (MXenes) are ideal two-dimensional spintronics platforms due to their abundant compositional space, excellent conductivity, and tunable surface properties. However, their intrinsic properties are mostly paramagnetic or diamagnetic. Existing single strategies for exciting magnetism (such as element doping, surface functional group engineering, precursor engineering, and defect engineering) have significant limitations: extremely low saturation magnetization (<0.01 emu / g), Curie temperature far below room temperature, or a contradiction between maintaining the integrity of the two-dimensional structure and improving magnetism, making it difficult to meet the requirements of practical devices (Mater. Today Chem., 2020, 16, 100271; Appl. Surf. Sci., 2019, 479, 216-224; Ceram. Int., 2020, 46, 27419-27425; Carbon 2020, 157, 90-96). To overcome the bottleneck of magnetic modulation of single MXene materials, constructing magnetic composite systems through heterogeneous interface engineering has proven to be a universal and efficient strategy applicable to the MXene family. However, traditional MXene heterostructure construction processes (wet chemical methods and high-temperature heat treatment) face multiple technical bottlenecks: the capillary action of liquid-phase drying easily leads to severe stacking and aggregation of nanosheets; high temperatures easily induce deep oxidation of MXene, destroying the conductive framework; and traditional processes can only form weak physical contacts, resulting in extremely low interfacial electronic coupling efficiency, which severely hinders spin exchange dynamics.

[0004] In summary, there is an urgent need to develop a novel preparation method that is universally applicable to the MXene family. This method should overcome the defects of traditional processes, such as agglomeration, easy oxidation, and weak interfacial contact, while maintaining the integrity of the two-dimensional structure of MXene. Furthermore, the prepared material should possess both high saturation magnetization and long-range ferromagnetism at room temperature. Summary of the Invention

[0005] To address the problems of two-dimensional nanosheet aggregation, easy oxidation of MXene, and weak interfacial coupling caused by traditional MXene heterostructure construction processes, the present invention aims to provide a room-temperature ferromagnetic MXene heterostructure composite material, its preparation method, and its application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A room-temperature ferromagnetic MXene heterojunction composite material, wherein the composite material is amorphous molybdenum oxide nanosheets (MoO). 3-x The heterostructure formed with MXene; in the composite material, MoO, by mass ratio 3-x :MXene=1:(1~6). MoO 3-x This indicates the presence of oxygen vacancies in molybdenum oxide (MoO3).

[0007] The preparation method of the room temperature ferromagnetic MXene heterojunction composite material includes the following steps: (1) Preparation of amorphous molybdenum oxide nanosheets (MoO) 3-x ; (2) After ultrasonically dispersing MXene powder in an ice bath in water, centrifuge to obtain MXene nanosheet dispersion; (3) Weigh 2-15 parts by weight of the amorphous molybdenum oxide nanosheets (MoO) prepared in step (1). 3-x Simultaneously, weigh the MXene nanosheet dispersion prepared in step (2) to ensure that the MXene nanosheets it provides meet the MoO2 requirement. 3-x The mass ratio of MXene to Mxene is 1:(1~6). After mixing, water and anhydrous ethanol are added according to the volume of water contained in the weighed MXene nanosheet dispersion, so that the total volume of the final mixed solvent in the system reaches 5~20 parts by volume and the final mixed solvent is 1# ethanol. The mixture is ultrasonically dispersed and transferred to a supercritical device. Carbon dioxide is injected into the supercritical device, and the reaction is stirred for 2~6 hours under supercritical conditions of 35~80℃ and 8~20Mpa. After the reaction is completed, the mixture is naturally cooled to room temperature, depressurized, and dried to obtain a room temperature ferromagnetic MXene heterojunction composite material. The mass parts are expressed in mg, the volume parts are expressed in mL, and the 1# ethanol is 30~80v% ethanol.

[0008] Preferably, in step (2), the MXene is titanium-based MXene.

[0009] Furthermore, in step (2), the MXene is Ti3C2T. x or Ti3CNT x .

[0010] Preferably, in step (2), the ratio of raw material usage is MXene powder: water = (5~20) mg: 1 mL.

[0011] Preferably, in step (2): the ultrasonic dispersion time is 1~3h; the centrifugation speed is 2000~6000rpm and the time is 20~50min.

[0012] Ideally, in step (3), the ultrasonic dispersion time is 5~30 min.

[0013] In this invention, amorphous molybdenum oxide nanosheets (MoO) 3-x The molybdenum trioxide (MoO3) nanosheets can be prepared by referring to existing technologies. The preferred preparation process of step (1) is as follows: molybdenum trioxide powder (crystalline, phase: α-MoO3 phase) is ultrasonically dispersed in 2# ethanol, then transferred to a supercritical device and stirred for 2~6 hours under supercritical conditions of 35~80℃ and 8~20Mpa. After the reaction is completed, the mixture is naturally cooled to room temperature, depressurized, centrifuged, and the supernatant is dried to obtain amorphous molybdenum trioxide nanosheets (MoO3). 3-x The 2# ethanol is 30~80 v% ethanol, and the raw material ratio is molybdenum trioxide powder : 2# ethanol = 100 mg : (5~20) mL.

[0014] Preferably, in step (1): the ultrasonic dispersion time is 1~3h; the centrifugation speed is 2000~6000rpm and the time is 10~30min; the drying temperature is 40~70℃.

[0015] Application of the room-temperature ferromagnetic MXene heterojunction composite material in spintronic devices.

[0016] Beneficial effects: (1) This invention utilizes the zero surface tension and high diffusion characteristics of supercritical carbon dioxide fluid to solve the problem of severe stacking and aggregation of two-dimensional MXene nanosheets caused by capillary action in traditional liquid-phase drying and wet chemical methods; at the same time, the mild supercritical reaction environment (35~80℃) effectively avoids the deep oxidation of the MXene framework under traditional high-temperature treatment, and greatly preserves its excellent conductive framework and two-dimensional structural integrity. (2) Breaking through the limitation that materials in traditional heterogeneous interface engineering can only form weak physical contact, this invention utilizes the interfacial wetting and high mass transfer efficiency of supercritical carbon dioxide in amorphous MoO2. 3-x Nanosheets and Ti3C2T x or Ti3CNT x Strong interfacial chemical bonds were successfully constructed between MXenes, which improved the interfacial electronic coupling efficiency and promoted the spin exchange dynamics of the heterostructure. (3) Successfully broke through the bottleneck of magnetic control of single MXene materials. Through the synergistic effect of interface engineering and supercritical fluid, the prepared MXene heterojunction composite material has both high saturation magnetization and long-range ferromagnetism with Curie temperature higher than room temperature, solving the problems of traditional two-dimensional materials being sensitive to thermal fluctuations and having low Curie temperature. (4) The preparation method of the present invention is green and environmentally friendly, with simple process flow and mild conditions. It has broad applicability to the MXene family and is easy to scale up. It provides key material basis and technical support for the development of the next generation of new spintronic devices with both metallicity and high Curie temperature. Attached Figure Description

[0017] Figure 1 SC-MoO prepared in Example 1 of this invention 3-x / Ti3C2T x Figure 1 shows the TEM image (a) and HRTEM images (b-c); Figure 2c is a magnified image of the area within the box in Figure 2b.

[0018] Figure 2 Ti3C2T prepared in Example 1 of this invention x MoO 3-x and SC-MoO 3-x / Ti3C2T x The XRD pattern (the bottom vertical line corresponds to the standard card PDF No. 05-0508 for α-MoO3).

[0019] Figure 3 Ti3C2T prepared in Example 1 of this invention x MoO 3-x and SC-MoO 3-x / Ti3C2T x XPS fine spectrum: (a) Ti3C2T x With SC-MoO 3-x / Ti3C2T x (a) C 1s fine spectrum; (b) Ti3C2T x MoO 3-x With SC-MoO 3-x / Ti3C2T x O1s fine spectrum; (c) Ti3C2T x With SC-MoO 3-x / Ti3C2T x (d) Fine spectrum of Ti 2p; MoO 3-x With SC-MoO 3-x / Ti3C2T x Fine 3d spectra of Mo.

[0020] Figure 4 Ti3C2T prepared in Example 1 of this invention x MoO 3-x and SC-MoO 3-x / Ti3C2T x Magnetic characterization results: (a) MH curve at 300 K; (b) magnified MH curve near H=0 in Figure (a); (c) SC-MoO 3-x / Ti3C2T x (d) shows the ZFC and FC magnetization curves under an external field of 500 Oe; (c) is a magnified view of the part of Figure (c) in the range of 290 K to 360 K.

[0021] Figure 5 SC-MoO prepared in Example 2 of this invention 3-x / Ti3CNT x Figure 1 shows the TEM image (a) and HRTEM images (b-c); Figure 2c is a magnified image of the area within the box in Figure 2b.

[0022] Figure 6 Ti3CNTs prepared in Example 2 of this invention x MoO 3-x and SC-MoO 3-x / Ti3CNT x The XRD pattern (the bottom vertical line corresponds to the standard card PDF No. 05-0508 for α-MoO3).

[0023] Figure 7 Ti3CNTs prepared in Example 2 of this invention x MoO 3-x and SC-MoO 3-x / Ti3CNT x XPS fine spectrum: (a) Ti3CNT x With SC-MoO 3-x / Ti3CNT x (a) C 1s fine spectrum; (b) Ti3CNT x With SC-MoO 3-x / Ti3CNT x (c) Fine N 1s spectrum; Ti3CNT x With SC-MoO 3-x / Ti3CNT x (d) Fine spectrum of Ti 2p; MoO 3-x With SC-MoO 3-x / Ti3CNT x Fine 3d spectra of Mo.

[0024] Figure 8Ti3CNTs prepared in Example 2 of this invention x MoO 3-x and SC-MoO 3-x / Ti3CNT x Magnetic characterization results: (a) MH curve at 300 K; (b) magnified MH curve near H=0 in Figure (a); (c) SC-MoO 3-x / Ti3CNT x (d) shows the ZFC and FC magnetization curves under an external field of 500 Oe; (c) is a magnified view of the part of Figure (c) in the range of 290 K to 360 K.

[0025] Figure 9 SC-MoO prepared as Comparative Example 1 of the present invention 3-x MH curve at 300K.

[0026] Figure 10 SC-Ti3C2T prepared as Comparative Example 2 of this invention x MH curve at 300K.

[0027] Figure 11 SC-Ti3CNT prepared as Comparative Example 3 of the present invention x MH curve at 300K. Detailed Implementation

[0028] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the described embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0029] Example 1

[0030] A method for preparing a room-temperature ferromagnetic MXene heterojunction composite material, comprising the following steps: (1) Two-dimensional amorphous molybdenum oxide nanosheets (MoO) 3-x Preparation: 100 mg of commercially available molybdenum trioxide powder (crystalline, phase: α-MoO3) was added to 10 mL of 45 v% ethanol and sonicated for 120 min to achieve thorough dispersion. The dispersion was then transferred to a supercritical reactor (high-pressure reactor), heated to 80 °C, and carbon dioxide gas was introduced until the pressure reached 12 MPa. The mixture was stirred and reacted under supercritical conditions for 3 h. After the reaction was complete, the mixture was allowed to cool naturally to room temperature, and the pressure was uniformly released to dissipate carbon dioxide gas. The product was collected and centrifuged at 3000 rpm for 15 min to remove aggregates, and the supernatant was collected. Finally, the supernatant was dried in a 60 °C forced-air drying oven to obtain MoO3. 3-x Nanoparticle powder; (2) Two-dimensional Ti3C2T x Preparation of nanosheet dispersion: Weigh 250mg of multilayer clay-like Ti3C2T x The powder was added to 25 mL of deionized water and ultrasonically exfoliated for 60 min under sealed conditions and an ice-water bath. The resulting dispersion was then transferred to a centrifuge tube and centrifuged at 3000 rpm for 30 min, allowing incompletely exfoliated thick particles and multilayered residues to settle to the bottom. The clear, dark liquid phase at the top was the highly exfoliated two-dimensional Ti3C2T. x The nanosheet dispersion was prepared, and 2 mL of the clear, dark liquid phase at the top was taken, dried, and weighed to determine the obtained Ti3C2T. x Concentration of the nanosheet dispersion; (3) Two-dimensional amorphous molybdenum oxide (MoO) 3-x / Ti3C2T x Preparation of heterojunctions: Weigh 6 mg of the MoO prepared in step (1) 3-x Nanosheets, and Ti3C2T prepared according to step (2) x The concentration of the nanosheet dispersion is determined by weighing an appropriate volume of Ti3C2T. x Nanosheet dispersion to ensure the supply of Ti3C2T x The nanosheets are 6 mg; weigh out the MoO2. 3-x Nanosheets and Ti3C2T x After mixing the nanosheet dispersion, according to the weighed Ti3C2T xThe volume of water in the nanosheet dispersion was adjusted by adding appropriate amounts of deionized water and anhydrous ethanol to bring the total volume of the final mixed solvent to 10 mL. The final mixed solvent was 50 v% ethanol (i.e., the proportion of anhydrous ethanol in the mixed solvent was 50 v%). The mixture was ultrasonically dispersed for 10 min to obtain a dispersion. This dispersion was then rapidly transferred to a supercritical reactor, heated to 60 °C, and carbon dioxide gas was introduced until the pressure reached 20 MPa. The reaction was carried out under supercritical conditions for 3 h. After the reaction was complete, the mixture was allowed to cool naturally to room temperature, and the pressure was uniformly released to release carbon dioxide gas. The product was collected and freeze-dried to obtain the target product, labeled SC-MoO. 3-x / Ti3C2T x .

[0031] Figure 1 SC-MoO prepared in Example 1 of this invention 3-x / Ti3C2T x Figure 1 shows the TEM image (a) and HRTEM images (b-c); Figure 2c is a magnified image of the area within the box in Figure 2b. Figure 1 a shows a sheet-like structure; Figure 1 c shows the presence of two different lattice fringes, in which Ti3C2T x The interplanar spacing is 0.160 nm, corresponding to the (110) crystal plane, while the circled area shows a clearly distinguishable amorphous structure of molybdenum oxide, indicating crystalline Ti3C2T. x With amorphous MoO 3-x A closely contacted heterogeneous interface was formed at the nanoscale.

[0032] Figure 2 Ti3C2T prepared in Example 1 of this invention x MoO 3-x and SC-MoO 3-x / Ti3C2T x The XRD pattern (the bottom vertical line corresponds to the standard card PDF No. 05-0508 for α-MoO3). Figure 2 Display: Ti3C2T x The disappearance of the strongest peak of the MAX phase at 39° in the XRD pattern confirms that the Al atomic layer of MAX has been successfully removed. Its (002) characteristic peak shifted to a lower angle of 6.2°, indicating that the Al layer peeling and the introduction of surface functional groups significantly increased the interlayer spacing. The retention of multiple higher-order crystal plane diffraction peaks further confirms that it has a highly ordered layered structure. 3-x The XRD pattern shows obvious broadened and diffuse peaks located in the range of 2θ = 15° to 35°, lacking the typical sharp diffraction peaks of α-MoO3 (PDF No. 05-0508), indicating the presence of numerous internal defects; SC-MoO3-x / Ti3C2T x XRD patterns show that Ti3C2T x The (002) peak shifted to a smaller angle to 2θ = 5.9°, and the (110) peak disappeared, indicating that supercritical fluid treatment weakened the Ti3C2T x The interlayer van der Waals forces lead to an increase in interlayer spacing. This severe structural exfoliation and lattice distortion are often accompanied by the generation of abundant surface defects or lattice vacancies. These defect sites not only provide crystalline sites for MoO 3-x The load provides an anchoring point and may also be a key factor in inducing room temperature ferromagnetism in composite materials.

[0033] Figure 3 Ti3C2T prepared in Example 1 of this invention x MoO 3-x and SC-MoO 3-x / Ti3C2T x XPS fine spectrum: (a) Ti3C2T x With SC-MoO 3-x / Ti3C2T x (a) C 1s fine spectrum; (b) Ti3C2T x MoO 3-x With SC-MoO 3-x / Ti3C2T x O1s fine spectrum; (c) Ti3C2T x With SC-MoO 3-x / Ti3C2T x (d) Fine spectrum of Ti 2p; MoO 3-x With SC-MoO 3-x / Ti3C2T x Fine 3d spectra of Mo. In C 1s ( Figure 3 a) and Ti 2p spectrum ( Figure 3 In c), the C-Ti bond strength significantly decreased after recombination (Ti-C content decreased from 29% to 20%), confirming the introduction of carbon vacancies. Simultaneously, the low-valence Ti... 2+ The proportion decreased, and the price of Ti decreased. 3+ Ti 4+ The increase in oxygen-containing carbon species indicates that low-valent titanium participated in the reaction as a reducing agent, and that the system underwent slight oxidation in the SC CO2 environment. O 1s spectrum ( Figure 3 b) Confirmation: SC-MoO 3-x / Ti3C2T x Strong Ti-O-Mo interfacial bonds were successfully formed at 530.0 eV. Mo 3d spectrum ( Figure 3d) indicates that after supercritical recombination, the Mo 3d binding energy shifts to lower energies, and Mo... 5+ The proportion of species jumped significantly to 47.7%, indicating that the recombination process successfully induced a large number of Mo atoms with unpaired electrons. 5+ The spin center lays the material basis for enhancing the ferromagnetic response of the material.

[0034] Figure 4 Ti3C2T prepared in Example 1 of this invention x MoO 3-x and SC-MoO 3-x / Ti3C2T x Magnetic characterization results: (a) MH curve at 300 K; (b) magnified MH curve near H=0 in Figure (a); (c) SC-MoO 3-x / Ti3C2T x (d) shows the ZFC and FC magnetization curves under an external field of 500 Oe; (c) is a magnified view of the part of Figure (c) in the range of 290 K to 360 K. Figure 4 a indicates that pure Ti3C2T x It exhibits diamagnetism and is amorphous MoO. 3-x Even under high fields, it is dominated by diamagnetism, and none of the individual materials exhibit long-range ferromagnetic order at room temperature; in contrast, SC-MoO 3-x / Ti3C2T x It exhibits a typical S-shaped hysteresis loop, with a saturation magnetization of 0.072 emu / g, and significant room-temperature ferromagnetism; Figure 4 As shown in b, SC-MoO 3-x / Ti3C2T x The extremely low coercivity (34 Oe) and remanent magnetization (0.0011 emu / g) demonstrate that this composite system is a typical soft magnetic material, exhibiting extremely low energy loss during magnetic field reversal, which highly meets the requirements of low-power two-dimensional spintronic devices. Furthermore, as... Figure 4 As shown in c, the ZFC-FC curves show significant separation across the entire test temperature range, confirming the stable long-range magnetic interaction within the system; from Figure 4 The magnified details of d show that the two curves do not overlap until 340K, indicating that the spin exchange coupling energy induced by strong interface coupling and defects is sufficient to resist thermal fluctuations above room temperature, and the Curie temperature of the system is higher than 340K.

[0035] Example 2

[0036] A method for preparing a room-temperature ferromagnetic MXene heterojunction composite material, comprising the following steps: (1) Two-dimensional amorphous molybdenum oxide nanosheets (MoO) 3-x Preparation: The preparation method is the same as step (1) in Example 1; (2) Two-dimensional Ti3CNT x Preparation of nanosheet dispersion: Weigh 250mg of multilayer clay-like Ti3CNT x The powder was added to 25 mL of deionized water and ultrasonically exfoliated for 60 min under sealed conditions and an ice-water bath. The resulting dispersion was then transferred to a centrifuge tube and centrifuged at 3000 rpm for 30 min, allowing incompletely exfoliated thick particles and multilayer residues to settle to the bottom. The clear, dark liquid phase at the top was the highly exfoliated two-dimensional Ti3CNT. x The nanosheet dispersion was prepared, and 2 mL of the clear, dark liquid phase at the top was taken, dried, and weighed to determine the obtained Ti3CNT. x Concentration of the nanosheet dispersion; (3) Two-dimensional amorphous molybdenum oxide (MoO) 3-x / Ti3CNT x Preparation of heterojunctions: Weigh 5 mg of the MoO2 obtained in step (1) 3-x Nanosheets, and Ti3CNTs prepared according to step (2). x The concentration of the nanosheet dispersion is determined by weighing an appropriate volume of Ti3CNT. x Nanosheet dispersion to ensure the supply of Ti3CNT x The nanosheets are 15 mg; weigh out the MoO2. 3-x Nanosheets and Ti3CNT x After mixing the nanosheet dispersion, according to the weighed Ti3CNT... x The volume of water in the nanosheet dispersion was adjusted by adding appropriate amounts of deionized water and anhydrous ethanol to bring the total volume of the final mixed solvent to 10 mL. The final mixed solvent was 50 v% ethanol. The mixture was ultrasonically dispersed for 10 min to obtain a dispersion. This dispersion was then rapidly transferred to a supercritical reactor, heated to 45 °C, and carbon dioxide gas was introduced until the pressure reached 12 MPa. The reaction was stirred for 3 h under supercritical conditions. After the reaction was complete, the mixture was allowed to cool naturally to room temperature, and the pressure was uniformly released to release the carbon dioxide gas. The product was collected and freeze-dried to obtain the target product, labeled SC-MoO. 3-x / Ti3CNT x .

[0037] Figure 5 SC-MoO prepared in Example 2 of this invention 3-x / Ti3CNT x TEM image (a) and HRTEM images (b-c); Figure c is a magnified image of the area within the box in Figure b. Figure 5As shown in a, the composite sample still maintains a two-dimensional ultrathin lamellar morphology; HRTEM image ( Figure 5 b) and c) show that the sample contains both clear lattice fringes and disordered regions, with a lattice spacing of approximately 0.220 nm, corresponding to Ti3CNT. x The (103) crystal plane; while the circular regions with no obvious lattice fringes correspond to amorphous MoO. 3-x This indicates that crystalline Ti3CNT x With amorphous MoO 3-x A closely contacted heterogeneous interface was formed at the nanoscale.

[0038] Figure 6 Ti3CNTs prepared in Example 2 of this invention x MoO 3-x and SC-MoO 3-x / Ti3CNT x The XRD pattern (the bottom vertical line corresponds to the standard card PDF No. 05-0508 for α-MoO3). For example... Figure 6 As shown, Ti3CNT x The characteristic peak of the MAX phase disappears at 2θ=39° and a sharp (002) peak appears at 7.5°, confirming that the precursor MAX has been completely etched and stripped into a highly ordered two-dimensional structure; the high-angle (00l) peak and the (110) peak at 60.8° prove that its c-axis long-range order and in-plane crystal framework are intact; at the same time, MoO 3-x The sample exhibited diffuse diffraction characteristics and lacked sharp crystalline peaks, indicating that supercritical CO2 treatment successfully prepared amorphous two-dimensional nanosheets; for SC-MoO 3-x / Ti3CNT x The (002) stacking peaks characteristic of its MXene form sharply weaken or even disappear, indicating that the loaded amorphous MoO 3-x The steric hindrance effectively inhibits the re-stacking of nanosheets, SC-MoO 3-x / Ti3CNT x Maintaining the amorphous dispersion characteristics and retaining the weak (110) peak demonstrates that the mild process of this invention successfully constructs a heterogeneous interface while perfectly preserving MoO. 3-x Amorphous network and Ti3CNT x The in-plane framework avoids unintended crystallization.

[0039] Figure 7 Ti3CNTs prepared in Example 2 of this invention x MoO 3-x and SC-MoO 3-x / Ti3CNT x XPS fine spectrum: (a) Ti3CNT x With SC-MoO3-x / Ti3CNT x (a) C 1s fine spectrum; (b) Ti3CNT x With SC-MoO 3-x / Ti3CNT x (c) Fine N 1s spectrum; Ti3CNT x With SC-MoO 3-x / Ti3CNT x (d) Fine spectrum of Ti 2p; MoO 3-x With SC-MoO 3-x / Ti3CNT x Fine 3d spectra of Mo. In C 1s ( Figure 7 a) and N 1s ( Figure 7 b) In the fine spectrum: after recombination, the signal intensities of C-Ti and N-Ti bonds decreased rapidly and synchronously (the N-Ti area ratio decreased from 27.3% to 3.0%), the surface oxygen-containing species increased, and the N 1s and Mo 3p orbital features highly overlapped. This directly confirms the tight recombination of the heterogeneous components, and the breaking of MXene framework bonds induced a large number of carbon and nitrogen dual defects. Ti 2p spectrum ( Figure 7 c) Indications: Ti-C / N bond weakening, high-valence Ti 4+ The significant increase in the proportion and the shift of the spectral peak towards higher binding energies indicate that Ti atoms, acting as electron donors, have lost electrons. Correspondingly, the Mo 3d spectrum ( Figure 7 In d), the characteristic peaks shift overall to lower energies, indicating the presence of low-valence Mo. 5+ The proportion increased from 10.7% to 20.0%, proving that amorphous MoO 3-x It acts as an electron acceptor, receiving electrons. In summary, this confirms that Ti3CNT... x To MoO 3-x The directional charge transfer process alters the electronic state of Mo and leads to the loss of electrons and framework instability of Ti.

[0040] Figure 8 Ti3CNTs prepared in Example 2 of this invention x MoO 3-x and SC-MoO 3-x / Ti3CNT x Magnetic characterization results: (a) MH curve at 300 K; (b) magnified MH curve near H=0 in Figure (a); (c) SC-MoO 3-x / Ti3CNT x (d) shows the ZFC and FC magnetization curves under an external field of 500 Oe; (c) is a magnified view of Figure (c) in the range of 290 K to 360 K. Figure 8 As shown in a, Ti3CNT x with MoO 3-xIt exhibits an extremely weak ferromagnetic signal in the low magnetic field region, but when the applied magnetic field exceeds 1200 Oe, its response is rapidly dominated by diamagnetism. In contrast, SC-MoO 3-x / Ti3CNT x A distinct S-shaped hysteresis loop was observed, with a saturation magnetization of approximately 0.023 emu / g, indicating that the system exhibited a ferromagnetic response at room temperature; further amplification of the low magnetic field region ( Figure 8 b) It can be seen that: SC-MoO 3-x / Ti3CNT x It exhibits relatively low coercivity and remanent magnetization, at 55 Oe and 0.0015 emu / g respectively, displaying typical soft magnetic characteristics; such as Figure 8 As shown in c, the ZFC and FC curves exhibit a continuous separation across the entire test temperature range of 2K to 350K, indicating the establishment of a robust spin-exchange coupling network within the system; further observation... Figure 8 Detailed magnification of the high-temperature region in section d reveals that, although the ZFC and FC curves show a slow convergence trend as the temperature rises, they do not overlap or cross until the upper limit of the test temperature of 350K. This indicates that the Curie temperature of this system is greater than 350 K, and its magnetic order thermal stability is better than that of SC-MoO in Example 1. 3-x / Ti3C2T x The system has been enhanced, demonstrating its potential to maintain stable long-range ferromagnetism under both room temperature and heating conditions in practical devices.

[0041] Compare with Example 1 The difference between this comparative example 1 and example 1 is that step (2) was not performed, and the MoO obtained in step (1) was directly applied. 3-x SC-MoO was obtained by supercritical treatment following the procedure in step (3). 3-x The specific process is as follows: (1) Two-dimensional amorphous molybdenum oxide nanosheets (MoO) 3-x Preparation: Same as step (1) in Example 1; (2) SC-MoO 3-x Preparation of; Weigh 6 mg of the MoO2 obtained in step (1) 3-x Nanosheets were placed in 10 mL of 50 v% ethanol and ultrasonically dispersed for 10 min to obtain a dispersion. This dispersion was then rapidly transferred to a supercritical reactor, heated to 60 °C, and carbon dioxide gas was introduced until the pressure reached 20 MPa. The reaction was carried out under supercritical conditions for 3 h. After the reaction was complete, the mixture was allowed to cool naturally to room temperature, and the pressure was uniformly released to dissipate the carbon dioxide gas. The product was collected and freeze-dried to obtain control product 1, labeled SC-MoO. 3-x .

[0042] Figure 9 SC-MoO prepared according to Example 1 of this invention 3-x MH curve at 300K. Figure 9 Display: SC-MoO 3-x Its saturation magnetization is only 0.010 emu / g, exhibiting weak ferromagnetism.

[0043] Compare with Example 2 The difference between Comparative Example 2 and Example 1 is that step (1) was not performed, and the Ti3C2T obtained in step (2) was directly applied. x The nanosheet dispersion was subjected to supercritical treatment according to the process in step (3) to obtain SC-Ti3C2T. x The specific process is as follows: (1) Two-dimensional Ti3C2T x Preparation of nanosheet dispersion: Same as step (2) in Example 1; (2) SC-Ti3C2T x Preparation: Weigh out a sample containing 6mg Ti3C2T x Step (2) to obtain Ti3C2T x Nanosheet dispersion, based on the weighed Ti3C2T x The volume of water in the nanosheet dispersion was adjusted by adding appropriate amounts of deionized water and anhydrous ethanol to bring the total volume of the final mixed solvent to 10 mL. The final mixed solvent was 50 v% ethanol. The dispersion was ultrasonically dispersed for 10 min. This dispersion was then rapidly transferred to a supercritical reactor, heated to 60 °C, and carbon dioxide gas was introduced until the pressure reached 20 MPa. The reaction was carried out under supercritical conditions for 3 h. After the reaction was complete, the mixture was allowed to cool naturally to room temperature, and the pressure was uniformly released to release the carbon dioxide gas. The product was collected and freeze-dried to obtain control product 2, labeled SC-Ti3C2T. x .

[0044] Figure 10 SC-Ti3C2T prepared as Comparative Example 2 of this invention x MH curve at 300K. Figure 10 Display: SC-Ti3C2T x Its saturation magnetization is only 0.0051 emu / g, exhibiting weak ferromagnetism.

[0045] Compare with Example 3 The difference between this comparative example 3 and example 2 is that step (1) was not performed, and the Ti3CNT obtained in step (2) was directly applied. xThe nanosheet dispersion was subjected to supercritical treatment according to the process in step (3) to obtain SC-Ti3CNT. x The specific process is as follows: (1) Two-dimensional Ti3CNT x Preparation of nanosheet dispersion: Same as step (2) in Example 2; (2) SC-Ti3CNT x Preparation: Weigh out a sample containing 15mg Ti3CNT x Step (2) to prepare two-dimensional Ti3CNTs x Nanosheet dispersion, based on the weighed Ti3CNT x The volume of water in the nanosheet dispersion was adjusted by adding appropriate amounts of deionized water and anhydrous ethanol to bring the total volume of the final mixed solvent to 10 mL. The final mixed solvent was 50 v% ethanol. The dispersion was ultrasonically dispersed for 10 min. This dispersion was then rapidly transferred to a supercritical reactor, heated to 45 °C, and carbon dioxide gas was introduced until the pressure reached 12 MPa. The reactor was stirred and reacted under supercritical conditions for 3 h. After the reaction was complete, the mixture was allowed to cool naturally to room temperature, and the pressure was uniformly released to dissipate the carbon dioxide gas. The product was collected and freeze-dried to obtain control product 3, labeled SC-Ti3CNT. x .

[0046] Figure 11 SC-Ti3CNT prepared as Comparative Example 3 of the present invention x MH curve at 300K. Figure 11 Display: SC-Ti3CNT x Its saturation magnetization is only 0.00066 emu / g, exhibiting extremely weak ferromagnetism.

[0047] contrast Figure 4 , Figure 8 and Figures 9-11 The results show that the heterojunction SC-MoO prepared in Example 1... 3-x / Ti3C2T x Or the heterojunction SC-MoO prepared in Example 2 3-x / Ti3CNT x The magnetic properties are far superior to those of SC-MoO prepared in Examples 1-3. 3-x SC-Ti3C2T x SC-Ti3CNT x These non-heterojunction materials fully demonstrate that, in the heterojunction of this invention, MoO 3-x With Ti3C2T x / Ti3CNT xIt played a synergistic role, achieving a technical effect of 1+1>2.

Claims

1. A room-temperature ferromagnetic MXene heterojunction composite material, characterized in that: The composite material is amorphous molybdenum oxide nanosheets (MoO). 3-x The heterostructure formed with MXene; in the composite material, MoO, by mass ratio 3-x :MXene=1:(1~6) 2. A method for preparing the room-temperature ferromagnetic MXene heterojunction composite material as described in claim 1, characterized in that, The steps are as follows: (1) Preparation of amorphous molybdenum oxide nanosheets (MoO) 3-x ; (2) After ultrasonically dispersing MXene powder in an ice bath in water, centrifuge to obtain MXene nanosheet dispersion; (3) Weigh 2-15 parts by weight of the amorphous molybdenum oxide nanosheets (MoO) prepared in step (1). 3-x Simultaneously, weigh the MXene nanosheet dispersion prepared in step (2) to ensure that the MXene nanosheets it provides meet the MoO2 requirement. 3-x The mass ratio of MXene to Mxene is 1:(1~6). After mixing, water and anhydrous ethanol are added according to the volume of water contained in the weighed MXene nanosheet dispersion, so that the total volume of the final mixed solvent in the system reaches 5~20 parts by volume and the final mixed solvent is 1# ethanol. The mixture is ultrasonically dispersed and transferred to a supercritical device. Carbon dioxide is injected into the supercritical device, and the reaction is stirred for 2~6 hours under supercritical conditions of 35~80℃ and 8~20Mpa. After the reaction is completed, the mixture is naturally cooled to room temperature, depressurized, and dried to obtain a room temperature ferromagnetic MXene heterojunction composite material. The mass parts are expressed in mg, the volume parts are expressed in mL, and the 1# ethanol is 30~80v% ethanol.

3. The method for preparing the room-temperature ferromagnetic MXene heterojunction composite material as described in claim 2, characterized in that: In step (2), the MXene is titanium-based MXene.

4. The method for preparing the room-temperature ferromagnetic MXene heterojunction composite material as described in claim 3, characterized in that: In step (2), the MXene is Ti3C2T x or Ti3CNT x .

5. The method for preparing the room-temperature ferromagnetic MXene heterojunction composite material as described in claim 2, characterized in that: In step (2), the ratio of raw material usage is MXene powder: water = (5~20) mg: 1 mL.

6. The method for preparing the room-temperature ferromagnetic MXene heterojunction composite material as described in claim 2, characterized in that, In step (2): the ultrasonic dispersion time is 1~3h; the centrifugation speed is 2000~6000rpm and the time is 20~50min.

7. The method for preparing the room-temperature ferromagnetic MXene heterojunction composite material as described in claim 2, characterized in that: In step (3), the ultrasonic dispersion time is 5~30 min.

8. The method for preparing the room-temperature ferromagnetic MXene heterojunction composite material according to any one of claims 1 to 7, characterized in that, The preparation process of step (1) is as follows: molybdenum trioxide powder is ultrasonically dispersed in ethanol (2#), then transferred to a supercritical device and stirred for 2-6 hours under supercritical conditions of 35-80℃ and 8-20 MPa. After the reaction is completed, the mixture is naturally cooled to room temperature, depressurized, centrifuged, and the supernatant is dried to obtain amorphous molybdenum oxide nanosheets (MoO). 3-x The 2# ethanol is 30~80 v% ethanol, and the raw material ratio is molybdenum trioxide powder : 2# ethanol = 100 mg : (5~20) mL.

9. The method for preparing the room-temperature ferromagnetic MXene heterojunction composite material as described in claim 8, characterized in that, In step (1): the ultrasonic dispersion time is 1~3h; the centrifugation speed is 2000~6000rpm and the time is 10~30min; the drying temperature is 40~70℃.

10. The application of the room-temperature ferromagnetic MXene heterojunction composite material as described in claim 1 in spintronic devices.

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