A method for aqueous phase bulk exfoliation of transition metal dichalcogenide monolayers

Abstract

The application discloses a method for preparing transition metal dichalcogenide monolayer by water phase large-scale exfoliation, and belongs to the technical field of new material preparation. The application can exfoliate a wide range of TMDs in water without using any chemical additive in a liquid exfoliation process; a TMD phase with a pre-intercalated layer is exfoliated in water by using a probe ultrasonic cavitation mechanical exfoliation to generate various TMD monolayers. The application uses water as a solvent, is low in cost, does not use any additive, and does not have the problem that the added additive is attached to the surface of a TMD flake and then affects the overall performance of the TMD flake. The application has high TMD monolayer yield, can be prepared on a large scale, and has high concentration and high stability. The two-dimensional TMD prepared by the application can be mixed and combined with a series of functional materials to form a two-dimensional multifunctional heterostructure, and can form a stable colloidal dispersion at a high concentration, thereby providing a multifunctional platform for assembling various multifunctional composite materials.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of new material preparation, and particularly relates to a method for preparing transition metal dichalcogenide monolayer by water phase large-scale exfoliation. BACKGROUND

[0002] Two-dimensional (2D) transition metal dichalcogenides (TMDs) as a class of two-dimensional materials other than graphene have great potential applications in various fields from optics to electronics, optoelectronics, energy storage and catalysis. Compared with graphene, they have tunable bandgaps. For example, as one of the main TMDs, molybdenum disulfide (MoS2) has a bandgap of 1.9 eV for a single monolayer, but the bandgap decreases with the increase of layer thickness due to quantum confinement. Benefiting from its direct bandgap, the monolayer of MoS2 shows excellent electrical properties, such as high in-plane mobility and high current on / off ratio, which makes it an attractive channel material for low-power and high-performance transistors. High-quality and stable TMD monolayer materials are ideal material candidates for hydrogels, biological composites and green electronic products.

[0003] So far, there are several methods for preparing monolayer and multilayer two-dimensional TMD nanosheets, including mechanical exfoliation, CVD growth, chemical / electrochemical lithium intercalation and exfoliation, and liquid phase exfoliation in organic solvents. However, the main problems of the organic lithium intercalation and exfoliation method in organic solvents are low yield and low concentration of TMD monolayer sheets, decomposition into sub-nanoscale sheets, uneven thickness, and formation of metal nanoparticles and Li2S precipitates. These problems limit the development of solution-processed TMDs in applications such as thin film electronics that require clean and large-size sheets. In addition, electrochemical intercalation of lithium or organic molecules (such as tetraheptylammonium cations or hydrazine) can exfoliate high-quality MoS2 and WS2 monolayers in organic solvents, but these methods require expensive large TMD single crystals as cathodes for intercalation reactions. In addition, almost all of the above TMD sheets must be dispersed in toxic organic solvents, such as isopropanol, n-methylpyrrolidone or dimethyl sulfoxide. In the existing reports, two-dimensional MXenes in water can be assembled by LbL with near-monolayer precision at each deposition, but two-dimensional TMD monolayers are difficult to use in such LbL processes unless they are dispersed in water. In addition, the lack of water-based two-dimensional TMDs also limits their combination with large-scale water-dispersible nanomaterials (such as MXenes, graphene and nanocellulose) into two-dimensional multifunctional heterostructures. The above possibilities are currently closed to 2D TMDs unless they can be exfoliated into a high-concentration monolayer solution in water. Therefore, the manufacture of water-dispersible high-concentration two-dimensional TMD monolayers is of great significance for practical applications. SUMMARY

[0004] The present application aims to provide a method for preparing transition metal dichalcogenide monolayer by aqueous large-scale exfoliation, so as to make up for the deficiency of the prior art.

[0005] The present application solves the above-mentioned important problems by developing a multifunctional combination strategy which can be used for large-scale delamination of a wide range of TMDs in water without using any chemical additives in the liquid exfoliation process; the TMD phase of the pre-intercalated layer is delaminated in water by using probe ultrasonic cavitation mechanical exfoliation to produce various TMD monolayers, including MoS2, WS2, MoSe2, WSe2 and ReS2.

[0006] In order to achieve the above-mentioned purpose, the present application is realized by the following technical scheme:

[0007] A method for preparing transition metal dichalcogenide monolayer by aqueous large-scale exfoliation, comprising the following steps:

[0008] Step one: preparing lithium pre-intercalated TMD powder:

[0009] (1) The TMD crystal powder is immersed in a n-butyllithium / hexane solution for pre-intercalation;

[0010] (2) After the pre-intercalation is completed, the solution is filtered and washed, and the lithium intercalated TMD crystal is recovered to obtain a lithium pre-intercalated layered TMD crystal;

[0011] Step two: preparing water-swollen exfoliated TMD clay-like multilayer:

[0012] (3) The lithium pre-intercalated layered TMD crystal is immersed in deoxygenated deionized water and subjected to ultrasonic treatment;

[0013] (4) The deionized water is washed and centrifuged to obtain a TMD clay-like multilayer structure with interlayer water molecules swollen;

[0014] Step three: preparing an aqueous TMD monolayer colloidal dispersion system:

[0015] (5) The TMD clay-like multilayer is dispersed into deoxygenated deionized water, and probe ultrasonic exfoliation is performed under ice bath conditions;

[0016] (6) Finally, centrifugal separation is performed, and only the supernatant volume is taken as the transition metal dichalcogenide monolayer colloidal dispersion liquid after centrifugation.

[0017] Further, the reaction conditions in step (1) are that the water and oxygen content are less than 0.1 ppm, the pre-intercalation reaction time is 3-5 days, and magnetic stirring is continuously performed throughout the process in an inert gas atmosphere.

[0018] Further, the step (2) is carried out in inert gas, and the alkane organic solvent is used for washing.

[0019] Further, the step (3) is carried out under ice bath condition, and the ultrasonic power is 220-260 W, and the time is 30-35 min, and the pre-intercalated lithium ions are washed out.

[0020] Further, in the step (4), the deionized water is used for washing, so that the pre-intercalated lithium ions are sufficiently removed, and the water molecules are further intercalated to peel off the TMD multilayer, and the centrifugal condition is that the rotation speed is 4000-5000 rpm, and the separation time is 2-30 min.

[0021] Further, in the step (5), the probe ultrasonic peeling time is 30-35 min, and the power is 250-300 W.

[0022] Further, in the step (6), the centrifugal condition is that the rotation speed is 3000-4000 rpm, and the centrifugal separation time is 20-25 min, and after centrifugal separation, only 3 / 4 of the supernatant volume is the best.

[0023] The transition metal dichalcogenide monolayer prepared by the above method is applied to electronic products.

[0024] Compared with the prior art, the beneficial effects of the present application are reflected in:

[0025] The present application uses water as a solvent, which is low in cost and does not use any additives, so that the problem that the added additives are attached to the surface of the TMD sheet and affect the overall performance of the TMD sheet does not occur. -1 The TMD monolayer prepared by the present application has high yield, can be prepared on a large scale, and has a concentration higher than 2.5 g / L , has high stability, and the stability exceeds one month.

[0026] The water-dispersed TMD is mainly in the 1T metal phase at the beginning, and can be converted into the 2H semiconductor phase after annealing. The two-dimensional TMD prepared by the present application can be combined with a series of functional materials (including MXene, graphene and nanocellulose) to form a two-dimensional multifunctional heterostructure, and can form a stable colloidal dispersion at a high concentration, which provides a multifunctional platform for assembling various multifunctional composite materials. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 Colloidal dispersions in water at different concentrations, wherein a is MoS2, b is WSe2, c is MoSe2, d is ReS2, and e is WS2.

[0028] Figure 2 Zeta potential of various TMD dispersions as a function of time.

[0029] Figure 3 Atomic force microscope images and thickness distribution maps of well-dispersed MoS2 flakes, wherein A is an atomic force microscope image, B is a thickness distribution map, 1, 2, 3 represent the first position, the second position, the third position, respectively.

[0030] Figure 4 MoS2 films prepared and MoS2 / CNF, MoS2 / Graphene, MoS2 / MXene composite films prepared according to a mass ratio of 1:1.

[0031] Figure 5 Typical stress-strain curves of MoS2 films and MoS2 / CNF, MoS2 / Graphene, MoS2 / MXene composite films prepared according to a mass ratio of 1:1. DETAILED DESCRIPTION

[0032] The technical solutions described in the present application will be further described and explained below by specific embodiments in conjunction with the accompanying drawings.

[0033] Example 1:

[0034] The specific preparation steps of a two-dimensional MoS2 monolayer are as follows:

[0035] Step one: preparation of lithium pre-intercalated MoS2 powder.

[0036] (A) Under the condition that the water and oxygen content are both less than 0.1 ppm, 1 g of MoS2 crystal powder is immersed in 6 ml of 2.5 M n-butyllithium / hexane solution for pre-intercalation. The pre-intercalation reaction time is 3-5 days, and magnetic stirring is continuously carried out at a speed of 350 rpm. The process is carried out in a glove box filled with inert argon gas.

[0037] (B) After the pre-intercalation is completed, the solution is filtered and washed with hexane at least four times to remove excess lithium and organic residues, and the lithium intercalated MoS2 crystal is recovered. The volume of hexane solution used is about 100 ml. The process is carried out in a glove box filled with inert argon gas.

[0038] Step two: preparation of water-swelling exfoliated MoS2 clay-like multilayer.

[0039] (A) The lithium pre-intercalated layered MoS2 crystal prepared in step one is immersed in 100 ml of deionized water containing oxygen gas and ultrasonicated for 30 min in an ice bath to wash out the pre-intercalated lithium ions.

[0040] (B) Wash with deionized water for 3-4 times to remove lithium ions in the pre-intercalated layer, and at the same time, water molecules are further intercalated to exfoliate the MoS2 multilayer, and centrifugal separation is performed at a speed of 4500 rpm for 2-30 min to obtain a MoS2 clay-like multilayer structure expanded by interlayer water molecules. It should be noted that the centrifuge tube should be shaken by hand for at least two minutes before centrifugation to ensure that the precipitate is evenly dispersed.

[0041] Step three: preparation of an aqueous MoS2 monolayer colloidal dispersion.

[0042] (A) The water-swollen exfoliated MoS2 clay-like multilayer prepared in step two is dispersed into deoxygenated deionized water, and probe ultrasonic exfoliation is performed under ice bath conditions. The probe ultrasonic exfoliation time is 30 min, the power is 260 W, and the interval is 4 s on / 2 s off.

[0043] (B) By centrifugal separation at a speed of 3000 rmp for 20 min, only 3 / 4 of the supernatant volume after centrifugation is taken as the final MoS2 monolayer colloidal dispersion.

[0044] As shown in Figure 1 , the concentration of the MoS2 dispersion prepared by the present application is as high as 5.1 g L -1 , and after one month of storage, the Zeta potential changes little and the dispersion does not precipitate or aggregate (as shown in Figure 2 ), showing high stability. Figure 3 The atomic force microscope image and thickness distribution graph of the MoS2 flakes show that the average thickness of the monolayer MoS2 flakes is 1.4 nm. In addition, the MoS2 prepared by the present application can be dispersed in water and can be blended with other materials in water to prepare composite materials, Figure 4 The MoS2 film prepared and the MoS2 / CNF, MoS2 / Graphene, MoS2 / MXene composite films prepared according to a mass ratio of 1:1 show that the prepared composite films have a smooth surface, uniform thickness, and no cracks. Figure 5 The typical stress-strain curve of the MoS2 film and the MoS2 / MXene, MoS2 / CNF, MoS2 / Graphene composite films prepared according to a mass ratio of 1:1 shows that the mechanical strength of the MoS2 / CNF composite film is the highest, reaching 178 MPa.

[0045] Example 2:

[0046] A specific preparation procedure for a two-dimensional WSe2 monolayer is as follows:

[0047] Step one: preparation of lithium pre-intercalated WSe2 powder.

[0048] (A) Under conditions where the water and oxygen contents are both less than 0.1 ppm, 1 g of WSe2 crystal powder was impregnated in 6 ml of 2.5 M n-butyllithium / hexane solution for pre-intercalation. The pre-intercalation reaction time was 3-5 days, and the mixture was continuously magnetically stirred at 350 rpm. This process was carried out in a glove box filled with inert argon gas.

[0049] (B) After pre-intercalation, the solution is filtered and washed with hexane at least four times to remove excess lithium and organic residues, and the lithium-intercalated WSe2 crystals are recovered. The volume of hexane solution used is approximately 100 ml. This process is carried out in a glove box filled with inert argon gas.

[0050] Step 2: Prepare water-swellable exfoliated WSe2 clay-like multilayers.

[0051] (A) The lithium pre-intercalated layered WSe2 crystals obtained in step one were immersed in 100 ml of oxygen-containing deionized water and sonicated for 30 min under ice bath conditions to wash out the pre-intercalated lithium ions.

[0052] (B) Wash with deionized water 3-4 times to thoroughly remove pre-intercalated lithium ions, while allowing water molecules to further intercalate and peel off the WSe2 multilayers. Centrifuge at 4500 rpm for 2-30 min to obtain a WSe2 clay-like multilayer structure with expanded interlayer water molecules. Note that the centrifuge tube should be shaken by hand for at least two minutes before centrifugation to ensure that the precipitate is evenly dispersed.

[0053] Step 3: Prepare an aqueous WSe2 monolayer colloidal dispersion.

[0054] (A) The water-swellable exfoliated WSe2 clay-like multilayer obtained in step two was further dispersed in deoxygenated deionized water and exfoliated using a probe under ice bath conditions. The probe ultrasonic exfoliation time was 30 min, the power was 260 W, and the interval was 4 s on / 2 s off.

[0055] (B) The mixture was centrifuged at 3000 rpm for 20 min, and only 3 / 4 of the supernatant volume was taken as the final WSe2 monolayer colloidal dispersion.

[0056] like Figure 1 As shown in Figure a, the concentration of the WSe2 dispersion prepared by this invention is as high as 2.5 g / L. -1 Furthermore, after one month of storage, its Zeta potential showed almost no change and the dispersion did not exhibit precipitation or aggregation (e.g. Figure 2 As shown in the figure, it exhibits high stability. Furthermore, the WSe2 obtained in this invention is a monolayer and can be dispersed in water, allowing it to be blended with other materials in water to prepare composite materials.

[0057] Example 3:

[0058] The specific preparation steps of a two-dimensional MoSe2 monolayer are as follows:

[0059] Step 1: Prepare lithium pre-intercalated MoSe2 powder.

[0060] (A) Under conditions where the water and oxygen contents are both less than 0.1 ppm, 1 g of MoSe2 crystal powder was impregnated in 6 ml of 2.5 M n-butyllithium / hexane solution for pre-intercalation. The pre-intercalation reaction time was 3-5 days, and the mixture was continuously magnetically stirred at 350 rpm. This process was carried out in a glove box filled with inert argon gas.

[0061] (B) After pre-intercalation, the solution is filtered and washed with hexane at least four times to remove excess lithium and organic residues, and the lithium-intercalated MoSe2 crystals are recovered. The volume of hexane solution used is approximately 100 ml. This process is carried out in a glove box filled with inert argon gas.

[0062] Step 2: Prepare water-swellable exfoliated MoSe2 clay-like multilayers.

[0063] (A) The lithium pre-intercalated layered MoSe2 crystals obtained in step one were immersed in 100 ml of oxygen-containing deionized water and sonicated for 30 min under ice bath conditions to wash out the pre-intercalated lithium ions.

[0064] (B) Wash with deionized water 3-4 times to thoroughly remove pre-intercalated lithium ions, while allowing water molecules to further intercalate and strip the MoSe2 multilayers. Centrifuge at 4500 rpm for 2-30 min to obtain a MoSe2 clay-like multilayer structure with expanded interlayer water molecules. Note that the centrifuge tube should be shaken by hand for at least two minutes before centrifugation to ensure that the precipitate is evenly dispersed.

[0065] Step 3: Prepare an aqueous MoSe2 monolayer colloidal dispersion.

[0066] (A) The water-swellable, exfoliated MoSe2 clay-like multilayer obtained in step two was redispersed in deoxygenated deionized water and exfoliated using a probe under ice bath conditions. The probe ultrasonic exfoliation time was 30 min, the power was 260 W, and the interval was 4 s on / 2 s off.

[0067] (B) The supernatant was centrifuged at 3000 rpm for 20 min and only 3 / 4 of the volume was taken as the final MoSe2 monolayer colloidal dispersion.

[0068] like Figure 1 As shown in a, the concentration of the MoSe2 dispersion prepared by this invention is as high as 3.7 g / L. -1and after one month of standing, its Zeta potential hardly changed and the dispersion did not show any precipitation or agglomeration (as shown in Figure 2 In addition, the MoSe2 prepared by the present application is single-layered and can be dispersed in water, and can be blended with other materials in water to prepare composite materials.

[0069] Example 4:

[0070] The specific preparation steps of a two-dimensional ReS2 single layer are as follows:

[0071] Step one: preparation of lithium pre-intercalated ReS2 powder.

[0072] (A) 1 g of ReS2 crystal powder was immersed in 6 ml of 2.5 M n-butyllithium / hexane solution for pre-intercalation under the condition that the water and oxygen contents were less than 0.1 ppm. The pre-intercalation reaction time was 3-5 days, and magnetic stirring was continuously carried out at a speed of 350 rpm. The process was carried out in a glove box filled with inert argon gas.

[0073] (B) After the pre-intercalation was completed, the solution was filtered and washed with hexane at least four times to remove excess lithium and organic residues, and the lithium-intercalated ReS2 crystal was recovered. The volume of the hexane solution was about 100 ml. The process was carried out in a glove box filled with inert argon gas.

[0074] Step two: preparation of water-swollen exfoliated ReS2 clay-like multilayer.

[0075] (A) The lithium pre-intercalated layered ReS2 crystal prepared in step one was immersed in 100 ml of deionized water containing oxygen and subjected to ultrasonic treatment for 30 min in an ice bath to wash out the pre-intercalated lithium ions.

[0076] (B) The pre-intercalated lithium ions were further removed by washing with deionized water for 3-4 times, and water molecules were further intercalated and exfoliated from the ReS2 multilayer. The water-swollen ReS2 clay-like multilayer structure was prepared by centrifugation at a speed of 4500 rpm for 2-30 min. It should be noted that the centrifuge tube should be shaken by hand for at least two minutes before centrifugation to ensure uniform dispersion of the precipitate.

[0077] Step three: preparation of a ReS2 single-layer colloidal dispersion in water.

[0078] (A) The water-swollen exfoliated ReS2 clay-like multilayer prepared in step two was dispersed in deoxygenated deionized water and exfoliated using a probe sonicator under ice bath conditions. The probe sonication exfoliation time was 30 min, the power was 260 W, and the interval was 4 s on / 2 s off.

[0079] (B) The ReS2 monolayer colloidal dispersion was obtained by centrifugation at 3000 rpm for 20 min, and only 3 / 4 of the supernatant volume was taken as the final dispersion.

[0080] like Figure 1 As shown in Figure a, the ReS2 dispersion prepared by this invention has a concentration as high as 3.5 g / L. -1 Furthermore, after one month of storage, its Zeta potential showed almost no change and the dispersion did not exhibit precipitation or aggregation (e.g. Figure 2 As shown in the figure, it exhibits high stability. Furthermore, the ReS2 prepared in this invention is a monolayer and can be dispersed in water, allowing it to be blended with other materials in water to prepare composite materials.

[0081] Example 5:

[0082] The specific preparation steps of a two-dimensional WS2 monolayer are as follows:

[0083] Step 1: Prepare lithium pre-intercalated WS2 powder.

[0084] (A) Under conditions where the water and oxygen contents are both less than 0.1 ppm, 1 g of WS2 crystal powder was impregnated in 6 ml of 2.5 M n-butyllithium / hexane solution for pre-intercalation. The pre-intercalation reaction time was 3-5 days, and the mixture was continuously magnetically stirred at 350 rpm. This process was carried out in a glove box filled with inert argon gas.

[0085] (B) After pre-intercalation, the solution is filtered and washed with hexane at least four times to remove excess lithium and organic residues, and the lithium-intercalated WS2 crystals are recovered. The volume of hexane solution used is approximately 100 ml. This process is carried out in a glove box filled with inert argon gas.

[0086] Step 2: Prepare water-swellable exfoliated WS2 clay-like multilayers.

[0087] (A) The lithium pre-intercalated layered WS2 crystals obtained in step one were immersed in 100 ml of oxygen-containing deionized water and sonicated for 30 min under ice bath conditions to wash out the pre-intercalated lithium ions.

[0088] (B) Wash with deionized water 3-4 times to thoroughly remove pre-intercalated lithium ions, while allowing water molecules to further intercalate and peel off the WS2 multilayers. Centrifuge at 4500 rpm for 2-30 min to obtain a clay-like multilayer structure of WS2 with expanded interlayer water molecules. Note that the centrifuge tube should be shaken by hand for at least two minutes before centrifugation to ensure that the precipitate is evenly dispersed.

[0089] Step 3: Prepare an aqueous WS2 monolayer colloidal dispersion system.

[0090] (A) The water-swellable exfoliated WS2 clay-like multilayer obtained in step two was further dispersed in deoxygenated deionized water and exfoliated using a probe under ice bath conditions. The probe ultrasonic exfoliation time was 30 min, the power was 260 W, and the interval was 4 s on / 2 s off.

[0091] (B) The WS2 monolayer colloidal dispersion was obtained by centrifugation at 3000 rpm for 20 min, and only 3 / 4 of the supernatant volume was taken as the final WS2 monolayer colloidal dispersion.

[0092] like Figure 1 As shown in Figure a, the concentration of the WS2 dispersion prepared by this invention is as high as 9.5 g / L. -1 Furthermore, after one month of storage, its Zeta potential showed almost no change and the dispersion did not exhibit precipitation or aggregation (e.g. Figure 2 As shown in the figure, it exhibits high stability. Furthermore, the WS2 obtained in this invention is a single layer and can be dispersed in water, allowing it to be blended with other materials in water to prepare composite materials.

[0093] Example 6:

[0094] The specific preparation steps of a MoS2 / CNF composite thin film are as follows:

[0095] The obtained MoS2 dispersion and a 1 wt% CNF aqueous dispersion were mixed at a MoS2:CNF mass ratio of 1:1 to form a uniformly mixed dispersion. After vacuum filtration, the mixture was dried under vacuum at -1 bar and 90°C for 15 min using a vacuum heating dryer and then peeled off from the filter membrane to obtain an independent, self-supporting MoS2 / CNF composite film.

[0096] The self-supporting MoS2 / CNF composite film with a MoS2:CNF mass ratio of 1:1 prepared in Example 6 has a smooth surface, uniform thickness, and is free of cracks (e.g., Figure 4 As shown), the composite film has a thickness of approximately 10 μm and a mechanical strength as high as 178 MPa (as shown). Figure 5 (As shown).

[0097] Example 7:

[0098] The specific preparation steps of a MoS2 / Graphene composite thin film are as follows:

[0099] The obtained MoS2 dispersion and a concentration of 1 g / L were mixed. -1Graphene water dispersion was mixed according to a MoS2: Graphene mass ratio of 1:1. After vacuum filtration, the vacuum drying was performed in a vacuum heating dryer at -1 bar and 90 °C for 15 min, and the self-supporting MoS2 / Graphene composite film was peeled off from the filter membrane.

[0100] The self-supporting MoS2 / Graphene composite film prepared in Example 7 had a smooth surface, uniform thickness, and no cracks (as shown in FIG. 2B), and the thickness of the composite film was about 10 pm, and the mechanical strength was 15 MPa (as shown in FIG. 2C). Figure 4 Figure 5

[0101] Example 8:

[0102] A MoS2 / MXene composite film was prepared according to the following steps:

[0103] The MoS2 dispersion and MXene water dispersion with a concentration of 1 g L -1 -1 were mixed according to a MoS2: MXene mass ratio of 1:1. After vacuum filtration, the vacuum drying was performed in a vacuum heating dryer at -1 bar and 90 °C for 15 min, and the self-supporting MoS2 / MXene composite film was peeled off from the filter membrane.

[0104] The self-supporting MoS2 / MXene composite film prepared in Example 8 had a smooth surface, uniform thickness, and no cracks (as shown in FIG. 4B), and the thickness of the composite film was about 10 pm, and the mechanical strength was as high as 69.71 MPa (as shown in FIG. 4C). Figure 4 Figure 5

[0105] From the above examples, it can be seen that:

[0106] ​​​​The two-dimensional TMD prepared by the application can be mixed with a series of functional materials (including MXene, graphene and nanocellulose), can form stable colloidal dispersions at high concentrations, and can be assembled into various multifunctional independent self-supporting composite film materials in a dry or even wet hydrogel state, which provides a multifunctional platform for assembling various multifunctional composite materials. The independent self-supporting composite film prepared has a thickness of only about 10 mu m, the composite film surface is smooth, the thickness is uniform, and no cracks are present. The mechanical strength of the MoS2 / Graphene composite film is 15 MPa, and the mechanical strength of the MoS2 / MXene composite film is as high as 69.71 MPa. Compared with other composite films, the MoS2 / CNF composite film shows the highest mechanical strength of 178 MPa. This provides multiple possibilities for the application of 2D TMD nanocomposites in the fields of flexible electronics, soft robots and energy storage.

[0107] Finally, although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A method for preparing a single-layer dispersion of transition metal dichalcogenides by large-scale aqueous phase exfoliation, characterized in that, The method includes the following steps: (1) TMD crystal powder was pre-intercalated in a n-butyllithium / hexane solution. The reaction conditions were that the water and oxygen contents were both less than 0.1 ppm, the pre-intercalation reaction time was 3-5 days, and magnetic stirring was performed continuously. The whole process was carried out in an inert gas atmosphere. (2) After the pre-intercalation is completed, the solution is filtered and washed in an inert gas atmosphere. The washing is performed with alkane organic solvents to recover the lithium-intercalated TMD crystals and obtain lithium-pre-intercalated layered TMD crystals. (3) Immerse the lithium pre-intercalated layered TMD crystal in deoxygenated deionized water and perform ultrasonication under ice bath conditions. The ultrasonic power is 220-260W and the time is 30-35min to wash out the pre-intercalated lithium ions. (4) Wash with deionized water and then centrifuge to obtain a TMD clay-like multilayer structure with the expansion of interlayer water molecules; use deionized water to wash thoroughly to remove pre-intercalated lithium ions, while allowing water molecules to further intercalate and peel off the TMD multilayer. The centrifugation conditions are: 4000-5000 rpm speed, separation for 2-30 min. (5) The TMD clay-like multilayer is redispersed in deoxygenated deionized water and ultrasonically peeled off using a probe under ice bath conditions. The ultrasonic peeling time is 30-35 min and the power is 250-300 W. (6) Finally, centrifuge the mixture and take only the volume of the supernatant as the transition metal dichalcogenide monolayer colloidal dispersion. In step (6), the centrifugation conditions are 3000-4000 rpm for 20-25 min, and taking only 3 / 4 of the volume of the supernatant after centrifugation is optimal.

2. The application of the transition metal dichalcogenide monolayer dispersion prepared by the method of claim 1 in electronic products.

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