A preparation method of few-layer molybdenum disulfide nanosheets

Abstract

The present invention discloses a method for preparing few-layer molybdenum disulfide nanosheets, belonging to the technical field of manufacturing or processing of nanostructures. In the method of the present invention, molybdenum disulfide particles are first placed in a container made of metal, and continuous multiple accumulative rolling is carried out on it under the condition of no lubrication at room temperature; under the action of the rolling force, the container undergoes plastic deformation, so that the shear stress parallel to the rolling direction is applied between the layers inside the molybdenum disulfide, and deformation occurs accordingly. Due to the deformation, stress concentration is generated, causing the sulfur-molybdenum bonds to break. At the same time, the shear stress is greater than the van der Waals force between the layers inside the molybdenum disulfide, resulting in the molybdenum disulfide being peeled off along the direction parallel to the rolling direction. As the total number of rolling passes increases, the molybdenum disulfide is gradually peeled off to form layered molybdenum disulfide nanosheets, and the number of layers gradually decreases. The raw material used in this method is molybdenum disulfide, and the required equipment is industrial production equipment. The operation is simple, the cost is low, and there is no chemical pollution.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing or processing nanostructures, and particularly relates to a method for preparing few-layer molybdenum disulfide nanosheets. Background Art

[0002] Layered molybdenum disulfide nanosheets are a graphene-like two-dimensional nanomaterial. In recent years, they have become an emerging research focus in the field of materials science due to their unique physical and chemical properties. Graphene-like MoS2 composed of single-layer or few-layer molybdenum disulfide is a new type of two-dimensional layered compound with a structure and properties similar to those of graphene. This two-dimensional nanomaterial is composed of single-layer or multi-layer molybdenum disulfide in a hexagonal crystal system. The single-layer molybdenum disulfide consists of an "A-B-A" type "sandwich" layered structure, with sulfur atom layers on both the upper and lower layers and a molybdenum atom layer in the middle, and the layer spacing is about 0.65 nm. Due to the special nature of its structure, when the molybdenum disulfide material is exfoliated into few-layers or single-layer, its semiconductor gap changes from an indirect bandgap structure to a direct bandgap structure, resulting in a significant increase in the photon absorption cross-section and fluorescence quantum efficiency of the material, which can be used to manufacture more energy-efficient electronic chips and optoelectronic devices; in addition, the layered molybdenum disulfide has low thermal conductivity, and there is a slip effect between layers, making the material have good flame retardant and lubrication effects. A large number of studies have shown that adding only a small amount of layered molybdenum disulfide nanosheets can significantly improve the performance of composite materials, and it has a wide application background in the fields of optoelectronics, energy storage, lubrication, composite materials, etc. Therefore, the preparation of few-layer molybdenum disulfide nanosheets has great application background and practical significance.

[0003] Currently, the preparation methods of layered molybdenum disulfide nanosheets are mainly divided into two types: bottom-up synthesis methods and top-down exfoliation methods. The bottom-up synthesis methods mainly use chemical deposition methods. For example, the Chinese patent with the patent number CN202110746384.1 discloses a method for preparing single-layer molybdenum disulfide materials through a two-temperature zone chemical vapor deposition system in high and low temperature zones. After pretreating a mixed solution of an organic solvent and ammonium molybdate, single-layer molybdenum disulfide nanosheets are prepared on the substrate surface by chemical vapor deposition process. However, chemical vapor deposition requires a high reaction temperature (600 - 850 °C), the reaction process needs to be protected by inert gas, and there are problems with waste treatment of reaction products. Therefore, this preparation method has complex processes, high costs, and is prone to generating harmful gases, which is not conducive to large-scale and high-efficiency preparation.

[0004] The bottom-up exfoliation methods mainly include ion intercalation method, liquid-phase exfoliation method, mechanical exfoliation method, etc. The ion intercalation method is a method with relatively high production efficiency at present. However, the ion intercalation method requires specific ions as stabilizers and an oxygen-free and water-free working environment during the intercalation process, which has strict requirements for the industrial production environment. The liquid-phase exfoliation method is a method for preparing molybdenum disulfide nanosheets by ultrasonic oscillation. Although this method is simple to operate and the preparation conditions are relatively loose, its exfoliation degree and efficiency are lower than other means. For example, the Chinese patent with the patent number CN201410081869.3 discloses a preparation method of magnetic layered molybdenum disulfide, in which the ultrasonic dispersion time in the first step is as long as 8 hours, and the preparation efficiency is low. The traditional mechanical exfoliation method is a relatively mature preparation method, and few-layer molybdenum disulfide can be exfoliated by means such as special tapes or ball mills. However, it is difficult to ensure that the size of the exfoliated molybdenum disulfide is at the nanoscale, and the production efficiency is low. Therefore, the application of this method is still limited by the disadvantages of small preparation scale and poor repeatability. Summary of the Invention

[0005] In view of the above defects of the prior art, in the first aspect of the present invention, there is provided a method for preparing few-layer molybdenum disulfide nanosheets with simple process, low yield of harmful waste and high production efficiency, including the following steps:

[0006] (1) A metal container with an accommodation space and an open end is annealed and surface-dedusted to obtain a purified container for standby;

[0007] (2) Molybdenum disulfide is added to the accommodation space of the purified container, and after the addition is completed, the open end is sealed to obtain a sealed container for standby;

[0008] (3) The sealed container is pressed into a flat shape, and then placed in a mold to obtain a pre-rolled metal part for standby;

[0009] (4) The pre-rolled metal part is rolled. After each rolling, the rolled metal part is folded to achieve deformation in the thickness direction, and the rolling process is repeated to obtain a rolled metal part for standby;

[0010] (5) The rolled metal part is transferred to a dispersion liquid, and after ultrasonic treatment, the upper-layer dispersion liquid is collected; the upper-layer dispersion liquid is dried to obtain few-layer molybdenum disulfide nanosheets.

[0011] Preferably, in the step (1), the metal container is made of a metal or metal alloy that is easy to process and has good ductility.

[0012] More preferably, the metal container is a cylindrical metal tube made of copper or aluminum.

[0013] Preferably, in the step (1), the annealing treatment is carried out as follows: the metal container is placed in an environment filled with inert protective gas and annealed at 600 - 700 °C for 2 - 8 h.

[0014] Preferably, in the step (2), by mass percentage, the addition amount of molybdenum disulfide is 1% - 5% of the mass of the purified container.

[0015] Preferably, in the step (4), the rolling is carried out at 10 - 25 °C and under non-lubricated conditions.

[0016] Preferably, in the step (4), the rolling speed of the rolling is 100 - 300 mm / min.

[0017] Preferably, in the step (4), one pass is defined as one rolling, and the deformation amount of each pass of rolling in the deformation in the thickness direction is denoted as X. In percentage, X ≤ 80%.

[0018] Further preferably, one pass is defined as one rolling, and the total number of passes of rolling is denoted as N. The relationship between the total number of passes of rolling N and the deformation amount X of the deformation in the thickness direction satisfies the following formula: N ≥ log (1-X) 8.88e -16 .

[0019] Preferably, in the step (5), the dispersion liquid is a liquid that does not react with the metal container and molybdenum disulfide and has strong volatility.

[0020] Further preferably, the dispersion liquid is at least one of acetone, absolute ethanol, and absolute methanol.

[0021] After annealing, the hardness of the metal tube is reduced, its machinability is improved, residual stress is eliminated, dimensions are stabilized, and the tendency of deformation and crack is reduced; at the same time, it also plays a role in refining grains, adjusting the structure and eliminating structural defects; for the completely annealed metal tube, impurity removal treatments such as removing the oxide film and degreasing are carried out to prevent impurity contamination of the sample.

[0022] After molybdenum disulfide is added to the metal tube, it is continuously and repeatedly accumulated and rolled under non-lubricated conditions at 10 - 25 °C, and few-layer molybdenum disulfide nanosheets are prepared by ultrasonic separation. During the rolling process, the sample is folded after each rolling, and a certain deformation amount in the thickness direction is obtained. As the total number of rolling passes increases, the molybdenum disulfide particles are gradually thinned to form layered molybdenum disulfide nanosheets. Taking the metal tube made of copper as an example, after rolling and thinning, the few-layer molybdenum disulfide nanosheets are uniformly dispersed in the copper medium to obtain a molybdenum disulfide - copper composite.

[0023] The obtained molybdenum disulfide - copper composite after rolling is placed in the dispersion liquid. Since the density of molybdenum disulfide (4.8 g / cm-3 ) much smaller than copper (8.96 g / cm -3 ), and this composite is prepared by a mechanical method under the condition of 10 - 25 °C. Therefore, the mechanical bonding force between molybdenum disulfide and copper medium is limited. Under the action of ultrasonic vibration, few-layer molybdenum disulfide nanosheets will be peeled off from the copper medium and temporarily float in the upper dispersion liquid. The upper dispersion liquid is collected and few-layer molybdenum disulfide nanosheets can be obtained after drying.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] The preparation method of the present invention has a simple process. The rolling process is applicable to industrial rolling mills, with low cost and no harmful gases and wastes generated during the preparation process, which is conducive to large-scale and high-efficiency production of few-layer molybdenum disulfide nanosheets. The process of the present invention is flexible and controllable. The deformation amount X and the total number of rolling passes N of the rolling process can be flexibly controlled according to actual needs, satisfying N ≥ log (1-X) 8.88e -16 to achieve appropriate regulation. By using the preparation method of the present invention, few-layer molybdenum disulfide nanosheets can be prepared with high product quality, fully demonstrating the performance of molybdenum disulfide. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the cross-sectional optical microscope (OM) picture of the molybdenum disulfide - copper composite obtained by 50 passes of rolling in Example 1 of the present invention;

[0027] Figure 2 is the transmission electron microscope (TEM) picture of the few-layer molybdenum disulfide nanosheets prepared in Example 1 of the present invention. In the figure, d represents the layer spacing;

[0028] Figure 3 is the cross-sectional optical microscope (OM) picture of the molybdenum disulfide - copper composite obtained by 100 passes of rolling in Example 2 of the present invention;

[0029] Figure 4 is the transmission electron microscope (TEM) picture of the few-layer molybdenum disulfide nanosheets prepared in Example 2 of the present invention. In the figure, d represents the layer spacing, and the 2L and 3L marks respectively represent that the number of layers of the few-layer molybdenum disulfide nanosheets is 2 layers and 3 layers, and there is no such mark for a single layer;

[0030] Figure 5 is the diffraction spot ring picture of the few-layer molybdenum disulfide nanosheets prepared in Example 2 of the present invention. In the figure, (00 6), (0 0 9), and (1 0 11) correspond to the crystal plane indices of molybdenum disulfide. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present invention will be further described below by way of examples, but the present invention is not limited to the scope of the described examples. For the experimental methods without specific conditions in the following examples, they are carried out according to conventional methods and conditions, or selected according to the product specifications.

[0032] In the following examples:

[0033] Molybdenum disulfide, average particle size 45 μm.

[0034] Example 1

[0035] A preparation method of few-layer molybdenum disulfide nanosheets:

[0036] (1) Take a pure copper tube with dimensions of 15×100×1 mm (diameter×length×wall thickness), place it in a 600 °C tubular furnace with argon protective gas for annealing for 2 h; perform surface impurity removal on the completely annealed pure copper tube to remove the oxide film and degrease it to obtain a purified copper tube for standby;

[0037] (2) Compact and seal one end of the purified copper tube, then weigh 5% of the mass of the purified copper tube of molybdenum disulfide, pour it into the purified copper tube with one end compacted and sealed, and then compact and seal the other end of the purified copper tube to obtain a sealed copper tube for standby;

[0038] (3) Press the whole sealed copper tube into a flat shape, and then place it in a mold with a pit to obtain a pre-rolled copper workpiece for standby;

[0039] (4) Under the condition of no lubrication at 25 °C, use an industrial rolling mill to perform multi-pass cumulative rolling on the pre-rolled copper workpiece. The rolling speed is 187 mm / min. After each rolling, fold the rolled copper workpiece to achieve its deformation in the thickness direction. The deformation amount X of each pass of rolling is 50%. Repeat the rolling process. The total number of rolling passes N is 50 passes (generally speaking, the deformation amount X of each pass of rolling ≤ 80%, and the corresponding total number of rolling passes N ≥ log (1-X) 8.88e -16 , in this example, the deformation amount X of each pass of rolling is preferably 50%, and the total number of rolling passes N is preferably 50 passes), to obtain a molybdenum disulfide-copper composite for standby;

[0040] (5) Immerse the molybdenum disulfide-copper composite completely in 30 mL of absolute ethanol, and perform ultrasonic treatment for 0.5 h with an ultrasonic cleaner to peel the few-layer molybdenum disulfide nanosheets from the copper medium and float them on the upper layer of absolute ethanol. Use a dropper to take the upper layer of absolute ethanol, and obtain few-layer molybdenum disulfide nanosheets after drying.

[0041] Observe the cross-section of the molybdenum disulfide-copper composite obtained in this example through an optical microscope. From Figure 1It can be seen that the black molybdenum disulfide is in the shape of slender strips and is relatively evenly distributed in the copper medium. By observing the few-layer molybdenum disulfide nanosheets obtained in this example through a transmission electron microscope, from Figure 2 it can be seen that the molybdenum disulfide particles have obtained a layered structure after 50 passes of cumulative rolling. The number of layers is 17, and the layer spacing is 0.638 nm. The results show that with the process of cumulative rolling, the micron-sized molybdenum disulfide particles (45 μm) are gradually unfolded and peeled into a nano-sized layered structure.

[0042] Example 2

[0043] A preparation method of few-layer molybdenum disulfide nanosheets:

[0044] (1) Take a pure copper tube with dimensions of 15×100×1 mm (diameter×length×wall thickness), place it in a 600 °C tube furnace with argon protective gas for 2 h for annealing treatment; perform surface impurity removal on the completely annealed pure copper tube, remove the oxide film and degrease it to obtain a purified copper tube for standby;

[0045] (2) Compact and seal one end of the purified copper tube, then weigh 5% of the mass of the purified copper tube of molybdenum disulfide, pour it into the purified copper tube with one end compacted and sealed, and then compact and seal the other end of the purified copper tube to obtain a sealed copper tube for standby;

[0046] (3) Press the whole sealed copper tube into a flat shape, and then place it in a mold with a pit to obtain a pre-rolled copper workpiece for standby;

[0047] (4) Under the condition of no lubrication at 25 °C, use an industrial rolling mill to perform multi-pass cumulative rolling on the pre-rolled copper workpiece. The rolling speed is 187 mm / min. After each rolling, fold the rolled copper workpiece to achieve its deformation in the thickness direction. The deformation amount X of each pass of rolling is 50%. Repeat the rolling process. The total number of rolling passes N is 100 passes (generally speaking, the deformation amount X of each pass of rolling ≤ 80%, and the corresponding total number of rolling passes N ≥ log (1-X) 8.88e -16 , in this example, the deformation amount X of each pass of rolling is preferably 50%, and the total number of rolling passes N is preferably 100 passes), to obtain a molybdenum disulfide-copper composite for standby;

[0048] (5) Immerse the molybdenum disulfide-copper composite completely in 30 mL of absolute ethanol, and perform ultrasonic treatment for 0.5 h with an ultrasonic cleaner to peel the few-layer molybdenum disulfide nanosheets from the copper medium and float them on the upper layer of absolute ethanol. Use a dropper to take the upper layer of absolute ethanol, and obtain few-layer molybdenum disulfide nanosheets after drying.

[0049] By observing the cross-section of the molybdenum disulfide-copper composite obtained in this example through an optical microscope, from Figure 3It can be seen that molybdenum disulfide with a slender black strip shape is evenly distributed in the copper medium. By observing the few-layer molybdenum disulfide nanosheets obtained in this example through a transmission electron microscope, from Figure 4 it can be seen that after 100 times of cumulative rolling, molybdenum disulfide particles have obtained few-layer molybdenum disulfide nanosheets. Most of the layers are 2 - 3 layers, and a small amount are single layers. The layer spacing basically conforms to the standard layer spacing of molybdenum disulfide (0.65 nm). Figure 5 This is the diffraction spot of the few-layer molybdenum disulfide nanosheets of this example. In the figure, (0 0 6), (0 0 9), and (1011) correspond to the crystal plane indices of molybdenum disulfide, and the calibration result conforms to the molybdenum disulfide standard card.

[0050] Example 3

[0051] A preparation method of few-layer molybdenum disulfide nanosheets:

[0052] (1) Take a pure copper tube with dimensions of 15×100×1 mm (diameter × length × wall thickness), place it in a 700 °C tube furnace with argon protective gas for 8 h for annealing treatment; perform surface impurity removal on the completely annealed pure copper tube, remove the oxide film and degrease it to obtain a purified copper tube for standby;

[0053] (2) Compact and seal one end of the purified copper tube, then weigh molybdenum disulfide with a mass percentage of 1% of the mass of the purified copper tube, pour it into the purified copper tube with one end compacted and sealed, and then compact and seal the other end of the purified copper tube to obtain a sealed copper tube for standby;

[0054] (3) Press the entire sealed copper tube into a flat shape, and then place it in a mold with a pit to obtain a pre-rolled copper workpiece for standby;

[0055] (4) Under the condition of no lubrication at 10 °C, use an industrial rolling mill to perform multi-pass cumulative rolling on the pre-rolled copper workpiece. The rolling speed is 100 mm / min. After each rolling, fold the rolled copper workpiece to achieve its deformation in the thickness direction. The deformation amount X for each pass of rolling is 50%. Repeat the rolling process. The total number of rolling passes N is 50 passes (generally, the deformation amount X for each pass of rolling ≤ 80%, and the corresponding total number of rolling passes N ≥ log (1-X) 8.88e -16 , in this example, the deformation amount X for each pass of rolling is preferably 50%, and the total number of rolling passes N is preferably 50 passes), to obtain a molybdenum disulfide - copper composite workpiece for standby;

[0056] (5) Immerse the molybdenum disulfide - copper composite workpiece completely in 30 mL of acetone, and perform ultrasonic treatment for 0.5 h with an ultrasonic cleaner to strip the few-layer molybdenum disulfide nanosheets from the copper medium and float them on the upper layer of acetone. Use a dropper to take the upper layer of acetone, and obtain few-layer molybdenum disulfide nanosheets after drying.

[0057] Example 4

[0058] A preparation method of few-layer molybdenum disulfide nanosheets:

[0059] (1) Take a pure aluminum tube with dimensions of 15×100×1 mm (diameter×length×wall thickness), put it into a 600 °C tube furnace with argon protective gas for calcination for 2 h for annealing treatment; perform surface impurity removal on the completely annealed pure aluminum tube, remove the oxide film and degrease it to obtain a purified aluminum tube for standby;

[0060] (2) Compact and seal one end of the purified aluminum tube, then weigh molybdenum disulfide with a mass percentage of 5% of the mass of the purified aluminum tube, pour it into the purified aluminum tube with one end compacted and sealed, and then compact and seal the other end of the purified aluminum tube to obtain a sealed aluminum tube for standby;

[0061] (3) Press the whole sealed aluminum tube into a flat shape, and then put it into a mold with a pit to obtain a pre-rolled aluminum workpiece for standby;

[0062] (4) Under the condition of no lubrication at 25 °C, use an industrial rolling mill to perform multi-pass cumulative rolling on the pre-rolled aluminum workpiece. The rolling speed is 300 mm / min. After each rolling, fold the rolled aluminum workpiece to achieve its deformation in the thickness direction. The deformation amount X of each pass of rolling is 50%. Repeat the rolling process. The total number of rolling passes N is 50 passes (generally, the deformation amount X of each pass of rolling ≤ 80%, and the corresponding total number of rolling passes N ≥ log (1-X) 8.88e -16 , in this example, the deformation amount X of each pass of rolling is preferably 50%, and the total number of rolling passes N is preferably 50 passes), to obtain a molybdenum disulfide-aluminum composite for standby;

[0063] (5) Immerse the molybdenum disulfide-aluminum composite completely in 30 mL of anhydrous methanol, and perform ultrasonic treatment for 0.5 h with an ultrasonic cleaner to peel off the few-layer molybdenum disulfide nanosheets from the aluminum medium and float them on the upper layer of anhydrous methanol. Use a dropper to take the upper layer of anhydrous methanol, and obtain few-layer molybdenum disulfide nanosheets after drying.

[0064] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A preparation method of few-layer molybdenum disulfide nanosheets, characterized in that, It includes the following steps: (1) A metal accommodating member having an accommodating space and an open end is annealed and surface-dedusted to obtain a purified accommodating member for standby; The metal accommodating member is a cylindrical metal tube made of copper; (2) Molybdenum disulfide is added to the accommodating space of the purified accommodating member, and after the addition is completed, the open end is sealed to obtain a sealed accommodating member for standby; (3) The sealed accommodating member is pressed into a flat shape and then placed in a mold to obtain a pre-rolled metal member for standby; (4) The pre-rolled metal member is rolled. After each rolling, the rolled metal member is folded to achieve deformation in the thickness direction, and the rolling process is repeated to obtain a rolled metal member for standby; The rolling is carried out at 10~25°C and under non-lubricated conditions; the rolling speed of the rolling is 100~300 mm / min; Denote one pass as one rolling, and denote the deformation amount of each pass of rolling in the thickness direction as X, in percentage, X≤80%; Let the total number of rolling passes be denoted as N, and the relationship between the total number of rolling passes N and the deformation amount X of the deformation in the thickness direction satisfies the following formula: ; (5) The rolled metal member is transferred to a dispersion liquid, ultrasonically treated, and the upper-layer dispersion liquid is collected; The upper-layer dispersion liquid is dried to obtain few-layer molybdenum disulfide nanosheets; The dispersion liquid is a liquid that does not react with the metal accommodating member and molybdenum disulfide and has strong volatility.

2. The preparation method according to claim 1, characterized in that: In the step (1), the annealing treatment method is as follows: The metal accommodating member is placed in an environment filled with an inert protective gas and annealed at 600~700°C for 2~8 h.

3. The preparation method according to claim 1, characterized in that: In the step (2), by mass percentage, the addition amount of the molybdenum disulfide is 1%~5% of the mass of the purified accommodating member.

4. The preparation method according to claim 1, wherein: The dispersion liquid is at least one of acetone, absolute ethanol, and absolute methanol.

Images