Method for preparing ultrathin SnSe nanosheet with few atomic layers based on intercalation compound precursor

Abstract

The invention belongs to the technical field of nano material preparation, and particularly relates to a method for preparing a few-atomic-layer ultrathin SnSe nanosheet based on an intercalation compound precursor. The invention discloses a method for preparing a low-atomic-layer ultra-thin (lt; lt) material by taking ethanolamine as an intercalator based on an intercalation-de-intercalation strategy. According to the method, ethanol amine is used as an intercalator through a hydrothermal method, an ethanol amine intercalated SnSe hybrid precursor is firstly synthesized, then the ultrathin SnSe nanosheet is obtained through deintercalation treatment, the thickness of the prepared nanosheet can reach the atomic level (about 2-3 atomic layers), and the method is simple in process, low in cost, high in product quality and suitable for industrial production. The problems that an existing process is complex, and product size and thickness are difficult to control are solved. In addition, the ultrathin SnSe nanosheet prepared by the method shows excellent application prospects in the fields of piezoelectric devices, photoelectric detection, flexible electronics, energy conversion and the like.

Description

Technical Field

[0001] This invention belongs to the field of nanomaterial preparation technology, specifically relating to a method for preparing low-atom-layer ultrathin SnSe nanosheets based on intercalation compound precursors. Background Technology

[0002] Two-dimensional layered semiconductor materials have broad application prospects in optoelectronic devices, flexible electronics, and other fields. Among them, tin selenide (SnSe), a group IV-VI compound, has attracted much attention due to its unique layered crystal structure and excellent physical properties. Studies have shown that when SnSe is thinned to the two-dimensional limit, it not only exhibits a layer-dependent tunable bandgap but also displays in-plane ferroelectricity and giant piezoelectricity at room temperature. Therefore, it has great application potential in cutting-edge fields such as non-volatile memories and piezoelectric nanogenerators. Thus, achieving the controllable preparation of high-quality, ultrathin SnSe nanosheets is key to unlocking its novel properties and promoting its applications.

[0003] Currently, methods for preparing two-dimensional SnSe nanosheets are mainly divided into two categories: top-down and bottom-up. Although the top-down mechanical exfoliation method can obtain high-quality single crystals, the strong interlayer van der Waals forces make it difficult to obtain ultrathin samples, with a typical thickness of about 190 nm. Moreover, the yield is extremely low and cannot be scaled up (P. Li, Z. Zhang, W. Shen, C. Hu, W. Shen, D. Zhang, A self-powered 2D-material sensor unit driven by a SnSe piezoelectricnanogenerator, Journal of Materials Chemistry A, 9 (2021) 4716-4723.). Liquid-phase exfoliation is simple to operate and scalable. With ultrasonic assistance, the thinnest bilayer (about 1 nm) SnSe nanosheets can be obtained. However, it requires up to 20 hours of ultrasonic treatment, the product has a small lateral size (50-500 nm), and fractional centrifugation is required to obtain a narrow thickness distribution (Y. Huang, L. Li, Y.-H. Lin, C.-W. Nan, Liquid Exfoliation Few-Layer SnSeNanosheets with Tunable Band Gap, Journal of Physical Chemistry C, 121 (2017)17530-17537.). In terms of bottom-up vapor deposition, chemical vapor deposition can grow large-area (>20 μm) single-crystal SnSe flakes on mica and SiO2 / Si substrates, but the product thickness is relatively thick (>20 nm), the equipment is complex and the cost is high, and the yield is limited (ZG Wang, F. Pang, A facile way to control phase of tin selenide flakes by chemical vapor deposition, Chemical Physics Letters, 702 (2018) 90-95.).Physical vapor deposition (PVD) can grow vertically aligned SnSe nanosheets (approximately 20-30 nm thick) on various substrates without the need for a catalyst. However, the reaction temperature is as high as 660°C, which still does not meet the ultrathin standard (X.-H. Ma, K.-H. Cho, Y.-M. Sung, Growth mechanism of vertically aligned SnSe nanosheets via physical vapor deposition, Crystengcomm, 16 (2014) 5080-5086.). Molecular beam epitaxy can precisely control the thickness down to a single layer (approximately 0.6 nm) and has been found to possess self-limiting stoichiometry properties in SnSe. However, the equipment is extremely expensive and complex, the growth rate is slow, and the yield is extremely low, making it unsuitable for large-scale production (JR Chin, MB Frye, DS-H. Liu, M. Hilse, IC Graham, J. Shallenberger, K. Wang, R. Engel-Herbert, M. Wang, YK Shin, N. Nayir, ACT van Duin, LM Garten, Self-limiting stoichiometry in SnSehin films, Nanoscale, 15 (2023) 9973-9984.). Liquid-phase synthesis has successfully prepared single-layer (approximately 1.0 nm, four atomic layers thick) single-crystal SnSe nanosheets in a one-pot process at 260 °C. However, it requires the use of 1,10-phenanthroline as a specific morphology control agent, resulting in a small lateral size (approximately 300 nm) that limits its further applications (L. Li, Z. Chen, Y. Hu, XW Wang, T. Zhang, W. Chen, QB Wang, Single-Layer Single-Crystalline SnSe Nanosheets, Journal of the American Chemical Society, 135(2013) 1213-1216.). In summary, while existing methods each have their own advantages, they still suffer from problems such as complex processes, high equipment requirements, difficulty in controlling product thickness, or small lateral sizes, making it difficult to simultaneously meet the comprehensive requirements of high quality, ultrathinness, large size, and scalable preparation. In particular, controllable preparation methods that can achieve atomic-level thickness (few atomic layers) SnSe nanosheets are still rarely reported.

[0004] Intercalation-assisted exfoliation, as an emerging strategy, weakens van der Waals forces by introducing molecules or ions into the interlayer of layered materials. This not only enables efficient exfoliation but also serves as a crystal engineering tool to control the microstructure of materials and even induce novel properties. For example, previous studies have successfully induced room-temperature ferroelectricity in few-layer SnS2 using a molecular intercalation strategy (P. Wang, S. Sun, W. Zhao, J. Wang, S. Jin, X. Lai, J. Jian, Out-of-planeferroelectricity and piezoelectricity in few-layer tin disulfide nanobeltsexfoliated from an inorganic-organic hybrid, Chemical Engineering Journal, 504 (2025).). However, there are currently no reports on the preparation of few-layer SnSe nanosheets using this method.

[0005] To address the shortcomings of the existing technologies, it is necessary to develop a method for preparing ultrathin SnSe nanosheets based on an intercalation-deintercalation strategy, in order to overcome the problems of complex processes and difficulty in controlling product size and thickness. Summary of the Invention

[0006] To overcome the shortcomings of existing technologies in preparing high-quality, atomically thin (few atomic layers) ultrathin tin selenide (SnSe) nanosheets simply and efficiently, this invention provides a method for preparing few atomic layer ultrathin SnSe nanosheets based on an intercalation-deintercalation strategy. This method uses ethanolamine as an intercalating agent via a hydrothermal process to first synthesize an ethanolamine-intercalated SnSe hybrid precursor, and then obtains ultrathin SnSe nanosheets through a deintercalation treatment. This solves the problems of low yield in existing mechanical exfoliation methods, numerous product defects in liquid phase exfoliation methods, and complex and costly equipment in chemical vapor deposition methods, achieving the goal of simple process, low cost, and high-quality product preparation.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a method for preparing few-atom-layer ultrathin SnSe nanosheets based on intercalation compound precursors, the method comprising the following steps: S1. Preparation of ethanolamine-intercalated SnSe precursor: Selenium source, tin source and ethanolamine are mixed, and after solvothermal reaction, unreacted ethanolamine is removed by centrifugation, residual amine is removed by washing, and finally dried to obtain ethanolamine-intercalated SnSe precursor. S2. Preparation of ultrathin SnSe nanosheets: The SnSe precursor obtained in step S1 is dispersed in water, subjected to ultrasonic-assisted deintercalation treatment, and the unexfoliated sample is removed by centrifugation. After drying, ultrathin SnSe nanosheets are obtained.

[0008] Using the above method, SnSe nanosheets with atomic-level thickness can be obtained, with a thickness as low as about 2-3 atomic layers (about 2.61 nm). Preferably, in step S1, the selenium source is selenium powder (Se) with a purity of 99.999%; the tin source is stannous chloride dihydrate (SnCl2·2H2O) with a purity of 99.99%.

[0009] Preferably, in step S1, the molar ratio of the selenium source to the tin source is 1:1.

[0010] Preferably, in step S1, the ethanolamine is used as both a reaction solvent and an intercalating agent, and the amount used is 20-40 mL of ethanolamine per 1 mmol of tin source, preferably 30 mL.

[0011] Preferably, in step S1, the mixing is performed by first adding selenium powder to ethanolamine and stirring to disperse it, then adding tin source and continuing to stir to ensure that the raw materials are fully mixed.

[0012] Preferably, in step S1, the solvothermal reaction is carried out under closed conditions at a temperature of 80-140 °C for a reaction time of 12-48 h.

[0013] More preferably, the solvothermal reaction is carried out under closed conditions at a temperature of 120 °C for 24 h. Under these conditions, the intercalation characteristic peak of the precursor is strongest, and the intercalation effect is best.

[0014] Preferably, in step S1, the centrifugation speed is 10000-15000 rpm and the time is 1-5 min; the washing is performed by washing with ethanol more than 3 times.

[0015] Preferably, in step S1, the drying is vacuum drying at a temperature of 50-70 ℃ for 6-12 hours.

[0016] Preferably, in step S2, the SnSe precursor is dispersed at a concentration of 1-2 mg / mL in water, more preferably 1.25 mg / mL (i.e., 50 mg of precursor dispersed in 40 mL of deionized water).

[0017] Preferably, in step S2, the ultrasound-assisted deintercalation process uses low-power ultrasound, with an ultrasound time of 15-120 min, an ultrasound frequency of 30-50 W, and the temperature is maintained at room temperature to 35°C during the ultrasound process.

[0018] More preferably, the ultrasonic-assisted deintercalation process uses low-power ultrasound for 15 minutes. At this time, the yield and thickness uniformity of the resulting nanosheets are optimal.

[0019] Preferably, in step S2, the centrifugation separation is performed as follows: first, centrifuge at a low speed of 3000-5000 rpm for 5-15 min to remove unpeeled samples; then, take the supernatant and centrifuge at a high speed of 10000-15000 rpm for 20-40 min to collect the lower layer of nanosheets.

[0020] Preferably, in step S2, the drying is vacuum drying at a temperature of 50-70 ℃ for 6-12 hours.

[0021] The second aspect of the present invention also provides a few-atom-layer ultrathin SnSe nanosheet prepared by the method described in the first aspect.

[0022] The ultrathin SnSe nanosheets obtained by the method of the present invention have a thickness of about 2.61 nm, an average thickness of about 8.28 nm, and a lateral dimension of 2-9 µm.

[0023] Compared with the prior art, the beneficial effects of the present invention are: This invention discloses a method for preparing ultrathin (<10 nm) SnSe nanosheets with few atomic layers using an intercalation-deintercalation strategy and ethanolamine as an intercalating agent. The prepared nanosheets can reach atomic-level thickness (approximately 2-3 atomic layers), and the process is simple, low-cost, and produces high-quality products, overcoming the problems of complex processes and difficulty in controlling product size and thickness in existing methods. Specifically, this invention has the following advantages: 1. First-ever successful preparation of ultrathin SnSe nanosheets using an ethanolamine intercalation-deintercalation strategy: This invention is the first to utilize ethanolamine as an intercalating agent, successfully synthesizing an ethanolamine-intercalated SnSe inorganic-organic hybrid precursor via a solvothermal method, and then achieving controllable preparation of ultrathin SnSe nanosheets using ultrasonic-assisted deintercalation. This method differs from traditional mechanical exfoliation, liquid-phase exfoliation, and chemical vapor deposition methods, providing a novel technical route for the preparation of two-dimensional SnSe nanomaterials.

[0024] 2. Controllable preparation of SnSe nanosheets with atomic-level thickness and few atomic layers: The SnSe nanosheets prepared using the method of this invention have controllable thickness, with a minimum thickness of 2.61 nm, corresponding to a thickness of approximately 2-3 atomic layers. This truly achieves the ultrathin preparation of SnSe nanosheets with atomic-level thickness and few atomic layers. Simultaneously, the product exhibits good crystallinity and high purity, laying a material foundation for the study and application of its intrinsic properties. Compared with existing technologies, this invention successfully reduces the thickness to at least the atomic layer scale while maintaining a large lateral dimension (2-9 µm), solving the technical challenge of simultaneously achieving ultrathinness and large size.

[0025] 3. Simple process, mild conditions, and low cost: The method of this invention for preparing ultrathin SnSe nanosheets does not require complex and expensive equipment (such as the high vacuum system required for CVD and PVD), nor does it require toxic or harmful transport agents or surfactants. Furthermore, the reaction temperature is low (80–140℃), the operation is simple, ethanolamine serves as both a solvent and an intercalating agent, the raw materials are readily available and environmentally friendly, making it suitable for large-scale production.

[0026] 4. Significant intercalation effect and controllable deintercalation: The ultrathin SnSe nanosheets prepared using the method of this invention exhibit strong precursor intercalation characteristic peaks, indicating that ethanolamine successfully intercalates into the SnSe interlayer, effectively increasing the interlayer spacing and weakening van der Waals forces. Furthermore, the degree of deintercalation can be flexibly adjusted by controlling the ultrasonic treatment time, thereby achieving effective control over the nanosheet thickness.

[0027] 5. Provide support for the research and application of SnSe-based functional materials: The ultrathin SnSe nanosheets prepared by the method of this invention are expected to show excellent application prospects in the following fields due to their thinness, large specific surface area and good crystallinity: (1) Piezoelectric devices: Ultrathin SnSe has an intrinsic non-centrosymmetric structure and is expected to show significant piezoelectric response; (2) Photoelectric detection: The layer-dependent tunable band gap makes it have important application potential in broadband detection; (3) Flexible electronics: The nanosheets have controllable size and good flexibility and can be compatible with flexible substrates; (4) Energy conversion: As a thermoelectric material or catalyst carrier, it can give full play to its high specific surface area advantage. Attached Figure Description

[0028] Figure 1 XRD patterns of the ethanolamine-intercalated SnSe precursor and the exfoliated SnSe nanosheets in Example 1 (a) and XRD patterns of the ethanolamine-intercalated SnSe precursor at different temperatures in Examples 1-3 (b); Figure 2 These are SEM images of the ethanolamine-intercalated SnSe precursor at different magnifications in Example 1; Figure 3 These are high-magnification SEM images of the ultrathin SnSe nanosheets obtained by peeling off different regions in Example 1; Figure 4 Figure (a), (b), and (c) are AFM characterization diagrams of the few-layer SnSe nanosheets prepared in Example 1, along with a thickness distribution histogram and (d) a lateral size distribution histogram. The inset in Figure (b) is a height profile corresponding to the thinnest part of the nanosheet.

[0029] Figure 5 Optical microscope images at different ultrasound times: (a) 15 min; (b) 60 min; (c) 120 min. Detailed Implementation

[0030] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0032] Example 1: A method for preparing ultrathin (<10 nm) SnSe nanosheets with few atomic layers based on intercalation compound precursors 1. Preparation of ethanolamine intercalated SnSe precursor Add 1 mmol of selenium powder (Se, purity 99.999%) to 30 mL of ethanolamine and stir magnetically for 30 min to fully disperse the selenium powder; then add 1 mmol of stannous chloride dihydrate (SnCl2·2H2O, purity 99.99%) and continue stirring magnetically for 30 min to obtain a mixture.

[0033] The mixture was transferred to a 50 mL stainless steel reactor lined with polytetrafluoroethylene, sealed, and heated at 120°C for 24 h. After the reaction was complete, it was allowed to cool naturally to room temperature.

[0034] The reaction product was centrifuged at 14,000 rpm for 1 min to remove unreacted ethanolamine; then the sample was washed with anhydrous ethanol more than three times to remove residual amine; finally, the washed sample was dried in a vacuum drying oven at 60℃ for 12 h to obtain the ethanolamine intercalated SnSe precursor.

[0035] 2. Preparation of ultrathin SnSe nanosheets Take 50 mg of the ethanolamine-intercalated SnSe precursor prepared in the above steps, disperse it in 40 mL of deionized water, and sonicate it for 15 min using an ultrasonic cleaner at low power (30-50W). Since prolonged ultrasonic operation can cause the water temperature to rise, excessively high temperatures (e.g., exceeding 35℃) may accelerate the degradation of the nanosheets. Therefore, to ensure consistent exfoliation results, the ultrasonic temperature is controlled below 35℃. Specifically, add an appropriate amount of cold water to the ultrasonic cleaner, and replace the cold water when the water temperature approaches 35℃, maintaining the temperature within the range of room temperature to 35℃. This method is simple and easy to implement, requires no additional temperature control equipment, and is suitable for routine laboratory operations.

[0036] After sonication, the resulting dispersion was centrifuged at 4000 rpm for 10 min to remove unpeeled samples; then the supernatant was centrifuged at 14000 rpm for 30 min to collect the lower nanosheets.

[0037] The obtained nanosheets were dried in a vacuum drying oven at 60°C for 12 hours to obtain ultrathin SnSe nanosheets.

[0038] Example 2: 1. Preparation of ethanolamine intercalated SnSe precursor The preparation method is basically the same as in Example 1, except that the temperature of the solvothermal reaction is 80°C.

[0039] 2. Preparation of ultrathin SnSe nanosheets The preparation method is the same as in Example 1.

[0040] Example 3: 1. Preparation of ethanolamine intercalated SnSe precursor The preparation method is basically the same as in Example 1, except that the temperature of the solvothermal reaction is 140°C.

[0041] 2. Preparation of ultrathin SnSe nanosheets The preparation method is the same as in Example 1.

[0042] Example 4: 1. Preparation of ethanolamine intercalated SnSe precursor The preparation method is the same as in Example 1.

[0043] 2. Preparation of ultrathin SnSe nanosheets The preparation method is basically the same as in Example 1, except that the ultrasonic treatment time is 30 min.

[0044] Comparative Example 1: 1. Preparation of ethanolamine intercalated SnSe precursor The preparation method is basically the same as in Example 1, except that the temperature of the solvothermal reaction is 60°C.

[0045] 2. Preparation of ultrathin SnSe nanosheets The preparation method is the same as in Example 1.

[0046] Comparative Example 2: 1. Preparation of ethanolamine intercalated SnSe precursor The preparation method is the same as in Example 1.

[0047] 2. Preparation of ultrathin SnSe nanosheets The preparation method is basically the same as in Example 1, except that: no ultrasonic treatment was performed, the precursor dispersion was directly centrifuged at 4000 rpm for 10 min, and then the supernatant was centrifuged at 14000 rpm for 30 min, and the lower layer product was collected.

[0048] Experimental Example: Performance Characterization of SnSe Nanosheets 1. XRD characterization The ethanolamine-intercalated SnSe precursor and ultrathin SnSe nanosheets prepared in Example 1 were characterized by X-ray diffraction (XRD) using Cu Kα rays (λ = 1.5406 Å) with a scanning range of 5–60°. The XRD characterization results of the ethanolamine-intercalated SnSe precursor are as follows: Figure 1 The curve below shows the XRD characterization results of the ultrathin SnSe nanosheets. Figure 1 As shown by the curve above a. From Figure 1 As can be seen in curve a, a new diffraction peak appears in the low-angle region (approximately 2θ = 10°) of the intercalation precursor (lower curve), indicating that ethanolamine was successfully inserted into the SnSe interlayer, and the interlayer spacing was expanded. After exfoliation, this peak disappeared in the product (upper curve), and the diffraction peak was consistent with the standard SnSe card (PDF#48-1224), indicating that ethanolamine was removed, the layered structure of SnSe was restored, and the product had good crystallinity and high purity.

[0049] 2. SEM characterization The ethanolamine-intercalated SnSe precursor and ultrathin SnSe nanosheets prepared in Example 1 were characterized by scanning electron microscopy (SEM). The SEM characterization results of the ethanolamine-intercalated SnSe precursor are as follows: Figure 2 As shown, the SEM characterization results of the ultrathin SnSe nanosheets are as follows: Figure 3 As shown. Figure 2 The intercalation precursor exhibits a nanosheet morphology with a smooth surface. Figure 3 The results showed that the product retained a sheet-like morphology after peeling, with a lateral dimension of about 4 µm.

[0050] 3. AFM characterization The ethanolamine-intercalated SnSe precursor and ultrathin SnSe nanosheets prepared in Example 1 were characterized by atomic force microscopy (AFM). The results are as follows: Figure 4 As shown. Figure 4 Figure a shows the AFM morphology of multiple nanosheets. As can be observed from the figure, the prepared SnSe nanosheets exhibit a regular sheet-like morphology with a smooth surface, consistent with SEM observations. Figure 4b shows the AFM morphology of the thinnest nanosheet (based on 100 nanosheets, all prepared using the method of Example 1), with the inset showing the corresponding height profile. Measurements show that the thickness of this nanosheet is approximately 2.61 nm. Based on the calculation standard that the thickness of a single SnSe atomic layer is approximately 0.6 nm (step height) or a four-atom-layer complete structural unit is approximately 1.0 nm, this thickness corresponds to approximately 2-3 complete structural units or approximately 4-5 atomic layers, confirming that the method of this invention can prepare ultrathin SnSe nanosheets with atomic-level thickness and few atomic layers. Figure 4 c is a histogram of thickness distribution based on 100 nanosheets (all prepared using the method in Example 1). Figure 4 Figure d shows the histogram of lateral size distribution based on the same batch of nanosheets. Statistical results show that the nanosheet thickness is mainly concentrated in the range of 2-10 nm, with an average thickness of approximately 8.28 nm; the lateral size is mainly distributed in the range of 2-9 µm, with an average lateral size of approximately 5.85 µm. This indicates that the SnSe nanosheets prepared by the method of this invention have the characteristics of thinness and good uniformity, while achieving a low atomic layer thickness while maintaining micron-level lateral dimensions.

[0051] 4. Effect of reaction temperature on intercalation effect The effect of different reaction temperatures on the intercalation effect was investigated. Intercalation precursors were prepared at 80℃, 120℃, and 140℃ according to the methods of Examples 2, 1, and 3, respectively, and characterized by XRD.

[0052] Figure 1 b presents the XRD patterns of the ethanolamine-intercalated SnSe precursor at different temperatures. The results show that at a reaction temperature of 80℃, the intercalation precursor exhibits a weak intercalation characteristic peak; at a reaction temperature of 120℃, the intercalation characteristic peak is the strongest, indicating the best intercalation effect; at a reaction temperature of 140℃, the intensity of the intercalation characteristic peak slightly decreases. This indicates that 120℃ is the preferred reaction temperature. When the reaction temperature is too low (e.g., below 80℃), the intercalation reaction is difficult to proceed effectively, and a product with obvious intercalation characteristics cannot be formed.

[0053] 5. The effect of ultrasonic time on the peeling effect The effect of different ultrasonic times on the ablation effect was investigated. Based on Examples 1 (15 min of ultrasonication) and 4 (30 min of ultrasonication), control cases with ultrasonic times of 60 min and 120 min were also set up to examine the effect of ultrasonic time on the ablation effect. Figure 5 As shown.

[0054] The results showed that the yield and thickness uniformity of the obtained nanosheets were optimal when the ultrasonic time was 15 min. As the ultrasonic time was extended to 60 min and 120 min, the nanosheet size tended to decrease, the uniformity decreased, and degradation may even occur. This indicates that 15 min is the preferred ultrasonic time. Too short an ultrasonic time (e.g., less than 15 min) may lead to insufficient exfoliation, resulting in an inability to obtain a large number of ultrathin nanosheets.

[0055] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for preparing few-atom-layer ultrathin SnSe nanosheets based on intercalation compound precursors, characterized in that, The method includes the following steps: S1. Preparation of ethanolamine-intercalated SnSe precursor: Selenium source, tin source and ethanolamine are mixed, and after solvothermal reaction, unreacted ethanolamine is removed by centrifugation, residual amine is removed by washing, and finally dried to obtain ethanolamine-intercalated SnSe precursor. S2. Preparation of ultrathin SnSe nanosheets: The SnSe precursor obtained in step S1 is dispersed in water, subjected to ultrasonic-assisted deintercalation treatment, and the unexfoliated sample is removed by centrifugation. After drying, ultrathin SnSe nanosheets are obtained.

2. The method for preparing few-atom-layer ultrathin SnSe nanosheets based on intercalation compound precursors according to claim 1, characterized in that, In step S1, the selenium source is selenium powder with a purity of 99.999%; the tin source is stannous chloride dihydrate with a purity of 99.99%.

3. The method for preparing few-atom-layer ultrathin SnSe nanosheets based on intercalation compound precursors according to claim 1, characterized in that, In step S1, the molar ratio of the selenium source to the tin source is 1:

1.

4. The method for preparing few-atom-layer ultrathin SnSe nanosheets based on intercalation compound precursors according to claim 1, characterized in that, In step S1, the amount of ethanolamine used is 20-40 mL of ethanolamine per 1 mmol of tin source.

5. The method for preparing few-atom-layer ultrathin SnSe nanosheets based on intercalation compound precursors according to claim 1, characterized in that, In step S1, the solvothermal reaction is carried out under closed conditions at a temperature of 80-140 °C for a reaction time of 12-48 h.

6. The method for preparing few-atom-layer ultrathin SnSe nanosheets based on intercalation compound precursors according to claim 1, characterized in that, In step S1, the centrifugation speed is 10000-15000 rpm and the time is 1-5 min; the washing is performed by washing with ethanol more than 3 times.

7. The method for preparing few-atom-layer ultrathin SnSe nanosheets based on intercalation compound precursors according to claim 1, characterized in that, In step S2, the SnSe precursor is dispersed at a concentration of 1-2 mg / mL in water.

8. The method for preparing few-atom-layer ultrathin SnSe nanosheets based on intercalation compound precursors according to claim 1, characterized in that, In step S2, the ultrasound-assisted deintercalation process uses low-power ultrasound, with an ultrasound time of 15-120 min and an ultrasound frequency of 30-50 W. During the ultrasound process, the temperature is maintained between room temperature and 35°C.

9. The method for preparing few-atom-layer ultrathin SnSe nanosheets based on intercalation compound precursors according to claim 1, characterized in that, In step S2, the centrifugation separation is as follows: first, centrifuge at a low speed of 3000-5000 rpm for 5-15 min to remove the unpeeled sample; take the supernatant and centrifuge at a high speed of 10000-15000 rpm for 20-40 min to collect the lower layer of nanosheets.

10. The few-atom-layer ultrathin SnSe nanosheets prepared by the method according to any one of claims 1-9.

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