Method for stripping multi-layer MXene material based on thermal expansion and cold contraction effects of low-freezing-point intercalator
Through the thermal expansion and contraction effect and temperature cycle of the low freezing point intercalator, the multi-layer MXene was successfully peeled off into a large-size, defect-free, and single layer, solving the problems of low yield and small size in the prior art, and achieving efficient and scaleable two-dimensional material peeling.
Patent Information
- Application Number
- CN202510689705.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-27
- Publication Date
- 2025-08-15
AI Technical Summary
The prior art has problems such as low yield, small size, easy introduction of impurities and defects when peeling off two-dimensional materials, and difficult to produce on a large scale, especially for multi-layer MXene materials.
A mixed solution of low freezing organic solvent and water is used as the intercalator, and the layer is intercalated at low temperature, and then the multi-layer MXene is peeled off by the thermal expansion and contraction effect of temperature cycles. Combined with centrifugation, the temperature cycle is repeated 4-5 times to achieve the peel.
Efficient peeling of large size (0-10μm), defect-free small layer and single layer MXene is achieved, with a yield of more than 61 wt%. By adjusting the solvent ratio and temperature cycle, the gentleness and scaleability of the peeling process are ensured.
Smart Images
Figure CN120483159A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of two-dimensional material exfoliation, and specifically relates to a method for exfoliating multilayer MXene materials based on the thermal expansion and contraction effect of a low-freezing-point intercalant. Background Art
[0002] As an emerging nanomaterial, two-dimensional materials are only a few atomic layers thick and exhibit unique electronic, optical and mechanical properties. Therefore, they show great application potential in electronics, optoelectronics, energy storage and sensor technology.
[0003] With the deepening understanding of the properties and application potential of two-dimensional materials, a variety of preparation techniques have been developed, each with its own unique advantages and limitations. Mechanical exfoliation is one of the earliest methods used to prepare graphene. Its principle is to remove single or multiple layers of two-dimensional materials from the bulk material through mechanical exfoliation or exfoliation. The advantages of this method include simplicity, the lack of complex equipment, and the ability to obtain high-quality materials. However, the uncontrollable process of mechanical exfoliation leads to low yields and is prone to the introduction of impurities or defects, which limits its application in large-scale production.
[0004] Furthermore, traditional exfoliation methods, such as ultrasonic exfoliation, result in small exfoliated two-dimensional graphene or MXene sheets, typically less than 1 μm, and often contain holes. Freeze-thaw methods also suffer from drawbacks such as small exfoliated sheets, low yields, and uncontrollable wettability with the two-dimensional material surface. Summary of the Invention
[0005] In response to the problems existing in the prior art, the present invention aims to provide a technical solution for a method for exfoliating multilayer MXene materials based on the thermal expansion and contraction effect of a low-freezing-point intercalant, which is specifically achieved through the following technical solutions:
[0006] A method for exfoliating multilayer MXene materials based on the thermal expansion and contraction effect of a low-freezing-point intercalant comprises the following steps:
[0007] 1) Using a mixed solution of a low-freezing-point organic solvent and water as an intercalant, the multilayer MXene material is intercalated under low-temperature conditions to obtain an intercalated multilayer MXene material;
[0008] 2) exfoliating the intercalated multilayer MXene material obtained in step 1) by heating and expanding the material;
[0009] 3) Repeat the temperature cycle of step 1) low temperature and step 2) elevated temperature 4-5 times, centrifuge after the temperature cycle is completed, and collect the upper dispersion.
[0010] Furthermore, the low freezing point organic solvent in step 1) is methanol or ethanol, and the intercalating agent is a 50 vol% ethanol solution or a 58 vol% methanol solution. The intercalating agent has good wettability, a low freezing point, and a high volume change rate.
[0011] Furthermore, the low-temperature intercalation in step 1) is specifically as follows: the multilayer MXene dispersion dispersed in the low-freezing point mixed liquid is refrigerated at 4°C for 24 hours, and then placed in a refrigerator at -20°C for 24 hours to allow a large number of water molecules and organic solvent molecules to shrink and penetrate into the material layers.
[0012] Furthermore, the specific method of temperature expansion in step 2) is: at room temperature of 25-40° C., the MXene dispersion is allowed to stand for 4 hours to allow the water molecules and organic solvent molecules that have penetrated between the layers to expand.
[0013] The above-mentioned process of low-temperature intercalation and temperature expansion is cycled to expand the interlayer spacing to a critical value until the multilayer MXene is successfully exfoliated into a few layers and a single layer of MXene.
[0014] Experiments have shown that the MXene interlayer spacing reaches The uniform peeling force generated by the expansion of the liquid mixture of water and organic solvent molecules prevents localized stress damage, resulting in large (0-10 μm) defect-free sheets. After five temperature cycles, the yield reached 61% by weight. With simple ultrasonic treatment, the yield can reach over 80% by weight.
[0015] The peeling mechanism of the present invention first determines the interlayer spacing through molecular simulation The interlayer forces are significantly weakened, which is the critical condition for exfoliation. The multilayer MXene is then exfoliated using the process of low-temperature contraction and warming expansion.
[0016] Furthermore, in step 3), the ultrasonic time is 5 min, the centrifugal speed is 500 rpm, and the centrifugation is 50-60 min.
[0017] The present invention selects an intercalant with good wettability to the target exfoliation product by adjusting the ratio of the organic-water mixed system, and maintains a liquid state at low temperatures. The mixed solvent system has significant thermal expansion and contraction properties, thereby achieving gentle, efficient and scalable two-dimensional material exfoliation. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 This is the scanning electron microscope image of Ti3AlC2 raw material;
[0019] Figure 2 The product after Ti3AlC2 etching (multilayer Ti3C2T x ) scanning electron micrograph;
[0020] Figure 3 The few layers and single layer Ti3C2T after peeling in Example 1 x (fl / sl-Ti3C2T x ) TEM image;
[0021] Figure 4 The few layers and single layer Ti3C2T after peeling in Example 1 x (fl / sl-Ti3C2T x ) size distribution statistics;
[0022] Figure 5 The single-layer MXene dispersion prepared in Example 1;
[0023] Figure 6 This is a Tyndall effect diagram of the single-layer MXene dispersion prepared in Example 1;
[0024] Figure 7 TEM image of the single-layer MXene after peeling in Example 2;
[0025] Figure 8 This is the TEM image of the comparative example intercalation agent exfoliating MXene. DETAILED DESCRIPTION
[0026] The present invention is further described below in conjunction with specific embodiments to facilitate a better understanding of the present technical solution.
[0027] Material preparation
[0028] Raw material: Ti3AlC2 (MAX phase, purity ≥98%), raw material scanning electron microscope image as shown Figure 1 shown.
[0029] Etchant: HCl+LiF
[0030] Experimental steps:
[0031] Multilayer Ti3C2T x (ml-Ti3C2T x )
[0032] 1) Etching process: Add 40 mL of 9 M HCl solution to a Teflon reactor, followed by 3.2 g of LiF powder and stir for 10 minutes. Place the reactor in an ice-water bath and slowly add 2 g of Ti3AlC2 (complete within 10 minutes), maintaining a small hole in the reactor to allow for gas release. Stir the reaction at 300 rpm in a 40°C oil bath for 36-48 hours.
[0033] 2) Washing process: After the reaction is complete, the mixture is divided equally into two 50 mL centrifuge tubes and the supernatant is discarded. The precipitate is washed twice with 30 mL of 1 M HCl (5000 rpm, 5 min / time) to remove residual LiF. The precipitate is then washed with 30 mL of deionized water until the pH is > 6 and the solution turns dark green. Manual shaking is required after each wash to ensure that the precipitate is fully dispersed. The final product is ml-Ti3C2T x The dispersion was freeze-dried (-20°C, 48h) and used in the subsequent examples. The scanning electron microscopy image of the product is shown in FIG. Figure 2 shown.
[0034] Example 1: Using ethanol aqueous solution as an intercalation agent to peel off the above-prepared material
[0035] The solvents used in this example are: ethanol, purity ≥99%, and deionized water.
[0036] Take 5mLml-Ti3C2T x The dispersion was mixed with 5 mL of anhydrous ethanol (total volume 10 mL, ethanol concentration 50 vol%), shaken for 10 min, and the mixture was placed in a 4 ° C refrigerator for 24 h to allow the solvent molecules to initially insert into the interlayer. It was transferred to a -20 ° C freezer for 24 h to further expand the interlayer spacing by solvent shrinkage (simulation shows The interlayer force is significantly weakened when the sample is removed and allowed to stand at room temperature (25°C) for 4 hours to allow the solvent to expand and produce uniform peeling force. The above temperature cycle (4°C → -20°C → 25°C) is repeated 5 times to optimize the peeling efficiency. After the temperature cycle is completed, the final dispersion is centrifuged at 3500 rpm for 60 minutes. The supernatant is the few-layer / single-layer Ti3C2T x (fl / sl-Ti3C2T x ) dispersion.
[0037] The few-layer and single-layer Ti3C2T x (fl / sl-Ti3C2T x ) is shown in the TEM image of Figure 3 As shown in the diagram, the size distribution statistics are as follows Figure 4 As shown, the monolayer MXene dispersion is Figure 5 As shown, the Tyndall effect is as follows Figure 6 shown.
[0038] Figure 3 It shows that our method successfully exfoliates multilayer MXene into few-layer and single-layer MXene, and there are no obvious defects on the surface of the MXene sheet.
[0039] Figure 4 It shows that multilayer MXene and few-layer and single-layer Ti3C2T before and after exfoliation x (fl / sl-Ti3C2Tx ) flakes are of uniform size, demonstrating that our method is a uniform and gentle exfoliation method that does not damage the MXene flakes. Furthermore, the size of the exfoliated MXene flakes is statistically greater than 10 μm.
[0040] Figure 5 The side view of the single-layer MXene dispersion proves that the multilayer MXene has been successfully exfoliated into few-layer and single-layer MXene.
[0041] Example 2
[0042] The solvents used in this example are: methanol, purity ≥99%, and deionized water.
[0043] Take 4.2mL ml-Ti3C2T x The dispersion was mixed with 5.8 mL of methanol (total volume 10 mL, methanol concentration vol%) and shaken for 10 min. The mixture was placed in a 4°C refrigerator for 24 h to allow the solvent molecules to initially insert into the interlayers. It was then transferred to a -20°C freezer for 24 h to further expand the interlayer spacing by solvent contraction (simulation shows The interlayer force is significantly weakened at this time. Remove the sample and let it rest at room temperature (25°C) for 4 hours to allow the solvent to expand and produce a uniform peel force. Repeat the above temperature cycle (4°C → -20°C → 25°C) for a total of 5 times to optimize the peeling efficiency.
[0044] Centrifugal collection: The final dispersion was centrifuged at 3500 rpm for 60 min, and the supernatant was the few-layer / single-layer Ti3C2T x (fl / sl-Ti3C2T x ) dispersion.
[0045] The TEM image of the single-layer MXene after peeling in Example 2 is as follows: Figure 7 shown. Figure 7 It shows that through TEM testing, it can be intuitively seen that our method successfully peels off multi-layer MXene into few-layer and single-layer MXene, and there are no obvious defects on the surface of the MXene sheet.
[0046] Comparative Example
[0047] In this comparative example, different intercalating agents were used to peel off the prepared materials using the method of the present invention. The TEM images of MXene peeled off by each intercalating agent are shown in FIG. Figure 8 As shown, wherein, ac) 34 vol% dimethyl sulfoxide (DMSO); df) 43 vol% isopropyl alcohol (IPA); gi) 69 vol% ethylene glycol (EG); jl) 83 vol% glycerol (Gly); mo) 42 vol% butanol (Butanol); pr) 33 vol% acetone (Acetone); su) 20 vol% ethanol (EtOH). Figure 8 As can be seen, other intercalating agents failed to achieve satisfactory exfoliation of multilayer MXene. This is because the intercalating agent used in this comparative example failed to simultaneously meet the three key requirements of good wettability, sufficient volume expansion, and a low freezing point. Therefore, none of them could effectively exfoliate the MXene. Only a 58 vol% methanol mixture and a 50 vol% ethanol solution were able to effectively exfoliate the MXene, with the 50 vol% ethanol solution achieving the best results.
Claims
1. A method for exfoliating multilayer MXene materials based on the thermal expansion and contraction effect of a low-freezing-point intercalant, characterized in that: The method comprises the following steps: 1) Using a mixed solution of a low-freezing-point organic solvent and water as an intercalant, the multilayer MXene material is intercalated under low-temperature conditions to obtain the intercalated multilayer MXene material; 2) exfoliating the intercalated multilayer MXene material obtained in step 1) by heating and expanding the material; 3) Repeat the temperature cycle of step 1) low temperature and step 2) high temperature 4-5 times. After the temperature cycle is completed, centrifuge the dispersion and collect the upper layer of the dispersion.
2. The method for exfoliating multilayer MXene materials based on the thermal expansion and contraction effect of a low-freezing-point intercalant according to claim 1, wherein: The low freezing point organic solvent in step 1) is methanol or ethanol, and the intercalant is selected from 30-60 vol% ethanol solution or 30-60 vol% methanol solution; preferably 50 vol% ethanol aqueous solution or 58 vol% methanol aqueous solution.
3. The method for exfoliating multilayer MXene materials based on the thermal expansion and contraction effect of a low-freezing-point intercalant according to claim 1, characterized in that: The low-temperature intercalation in step 1) is specifically as follows: the multilayer MXene dispersion dispersed in a low-freezing-point mixed liquid is refrigerated at 4°C for 24 hours, and then placed in a -20°C refrigerator for 24 hours to allow a large number of water molecules and organic solvent molecules to shrink and penetrate between the material layers.
4. The method for exfoliating multilayer MXene materials based on the thermal expansion and contraction effect of a low-freezing-point intercalant according to claim 1, wherein: The specific method of temperature expansion in step 2) is: at room temperature of 25-40 ° C, the MXene dispersion is allowed to stand for 4 hours to allow the water molecules and organic solvent molecules that have penetrated between the layers to expand, expand the interlayer spacing to a critical value, and until the multilayer MXene is successfully stripped into few layers and single layer MXene.
5. The method for exfoliating multilayer MXene materials based on the thermal expansion and contraction effect of a low-freezing-point intercalant according to claim 1, wherein: In step 3), the centrifugation time is 5 minutes, the centrifugal speed is 500 rpm, and the centrifugation time is 30-60 minutes.