Microwave crystallization preparation method and application of transition metal nitride ultrathin nanosheet
The preparation of ultrathin transition metal nitride nanosheets by microwave crystallization solves the problem of traditional high-temperature and high-pressure sintering, realizes high-sensitivity and background-free surface-enhanced Raman scattering detection, and provides low-cost and high-performance nanosheet applications.
Patent Information
- Application Number
- CN202511788119.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-01
- Publication Date
- 2026-02-10
AI Technical Summary
Existing technologies make it difficult to prepare ultrathin nanosheets of transition metal nitrides under high temperature and high pressure conditions, which leads to grain sintering and aggregation. Furthermore, existing SERS substrates have low enhancement factors and are subject to intrinsic Raman signal interference, while noble metal substrates are costly and have poor stability.
Ultrathin nanosheets of transition metal nitrides were prepared by microwave crystallization. The transition metal salt, Li3N and ethylenediamine were dissolved in o-xylene, heated, centrifuged, washed and vacuum dried, and then rapidly microwave-heated in a nitrogen atmosphere to obtain crystalline nanosheets with a thickness of 1-2 nm, avoiding sintering. These nanosheets were then used for surface-enhanced Raman spectroscopy detection.
The prepared nanosheets have uniform thickness, outstanding surface-enhanced Raman spectroscopy effect, no background interference, detection limit as low as 10⁻¹³ M, enhancement factor as high as 8.6×10⁷, and excellent stability, making them suitable for trace detection.
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Figure CN121493884A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of nanomaterial preparation and optical sensing, and particularly relates to a microwave crystallization preparation method of transition metal nitride ultrathin nanosheets and application thereof in surface enhanced Raman scattering. BACKGROUND
[0002] Transition metal nitrides (such as titanium nitride, molybdenum nitride and tungsten nitride) have great potential in the fields of catalysis, energy and sensing due to their gold-like properties (high conductivity, localized surface plasmon resonance effect). The ultrathin two-dimensional structure can significantly improve the performance of the material, but TMN is mostly non-laminated structure, and it is difficult to prepare ultrathin nanosheets by chemical exfoliation method. Traditional synthesis methods require high temperature (>700°C) and high pressure conditions, which cause serious sintering and aggregation of crystal grains, and cannot maintain the ultrathin morphology. The existing semiconductor SERS substrates (such as TiO2 and WO3) have problems such as low enhancement factor and interference of intrinsic Raman signal; the noble metal substrate has high cost and poor stability. Therefore, there is an urgent need to develop a mild and efficient synthesis method of TMN ultrathin nanosheets and realize its SERS application without background interference. SUMMARY
[0003] To solve the above technical problems, the application provides a rapid and non-destructive crystallization method of TMN ultrathin nanosheets, which solves the problem of structure sintering caused by traditional high-position synthesis and develops its application as a high-sensitivity and background-free SERS substrate.
[0004] Specifically, the application provides the following technical solutions:
[0005] In a first aspect, the application provides a microwave crystallization preparation method of transition metal nitride ultrathin nanosheets, comprising the following steps:
[0006] (1) Dissolve transition metal salt and Li3N in o-xylene solution, then add ethylenediamine solution, stir thoroughly, heat the solution, collect by centrifugation, wash and vacuum dry to obtain amorphous transition metal nitride nanosheets; the transition metal salt is WCl6, VCl3 or MoCl5;
[0007] (2) Under a nitrogen atmosphere, the amorphous transition metal nitride nanosheets are rapidly microwave-heated to obtain highly crystalline transition metal nitride nanosheets.
[0008] In the present application, by stirring WCl6 (VCl3, MoCl5), Li3N, ethylenediamine and o-xylene to complete dissolution, then by heating, through centrifugal filtration washing and vacuum drying to obtain amorphous TMN nanosheet, after rapid microwave heating treatment to obtain crystalline TMN nanosheet, the nanosheet has a thickness of about 1-2 nm, no sintering phenomenon is found, and has an excellent surface enhanced Raman spectroscopy effect.
[0009] The microwave crystallization preparation method of the transition metal nitride ultrathin nanosheet according to the present application, in step (1):
[0010] When the transition metal salt is WCl6, the mass ratio of WCl6, Li3N, ethylenediamine, o-xylene is 11:1:129:1005.
[0011] When the transition metal salt is VCl3, the mass ratio of VCl3, Li3N, ethylenediamine, o-xylene is 5:1:129:1006.
[0012] When the transition metal salt is MoCl5, the mass ratio of MoCl5, Li3N, ethylenediamine, o-xylene is 8:1:129:1006.
[0013] The microwave crystallization preparation method of the transition metal nitride ultrathin nanosheet according to the present application, in step (1), the sufficient stirring process is: magnetic stirring at a speed of 350-400 r / min for 2 h at 24-28℃.
[0014] The microwave crystallization preparation method of the transition metal nitride ultrathin nanosheet according to the present application, in step (1), the heating temperature is 180-200℃, and the time is 5-6 h.
[0015] The microwave crystallization preparation method of the transition metal nitride ultrathin nanosheet according to the present application, in step (1), the centrifugal collection and washing process includes the following steps: first, centrifugal washing with deionized water for 2-3 times, and then repeated centrifugal washing with anhydrous ethanol for 2-3 times; the vacuum drying temperature is 40-60℃, and the drying time is 2-3 h.
[0016] The microwave crystallization preparation method of the transition metal nitride ultrathin nanosheet according to the present application, in step (2), the microwave heating power is 1000 W, and the heating time is 10-25 s.
[0017] In the present application, by using the above preferred raw materials and proportions and processing methods and reaction conditions, the prepared TMN nanosheet has a thickness of about 1-2 nm, and the performance is further improved, and has a more excellent surface enhanced Raman spectroscopy effect.
[0018] In a second aspect, the application provides the TMN nanosheet with surface-enhanced Raman effect prepared by the microwave crystallization method.
[0019] In a third aspect, the application provides application of the TMN nanosheet with surface-enhanced Raman effect in preparation of a surface-enhanced Raman spectrum detection substrate.
[0020] The method for preparing the surface-enhanced Raman spectrum detection substrate comprises the following steps: dispersing 20 mg of the TMN nanosheet with surface-enhanced Raman effect in 10 mL of deionized water, placing the mixture in a vacuum freeze dryer after filtration, reducing the temperature to-40℃ at a rate of 0.3℃ / min, and then keeping the temperature at-40℃ for 24 h to obtain a flexible substrate.
[0021] The microwave crystallization method for preparing the transition metal nitride ultrathin nanosheet and the application thereof are different from the prior art (beneficial effects) in that:
[0022] The preparation process of the surface-enhanced Raman effect TMN nanosheet provided by the application has strong controllability, the prepared nanosheet has a thickness of about 1-2 nm, has no sintering or aggregation phenomenon, has excellent surface-enhanced Raman spectrum effect, has no Raman signal interference of the substrate itself, has high spectrum resolution, has strong stability, can be stored for a long time in air at room temperature, and has important significance for detection of toxic and harmful substances in consumer products.
[0023] The microwave crystallization method for preparing the transition metal nitride ultrathin nanosheet and the application thereof will be further described below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS
[0024] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.
[0025] Figure 1 XRD spectrum of the amorphous WN nanosheet prepared in the embodiment 1 of the application;
[0026] Figure 2 SEM photo of the amorphous WN nanosheet prepared in the embodiment 1 of the application;
[0027] Figure 3 EDS spectrum of the amorphous WN nanosheet prepared in the embodiment 1 of the application;
[0028] Figure 4The XRD pattern of the crystalline WN nanosheets prepared in Example 1 of this invention;
[0029] Figure 5 This is a SEM image of the crystalline WN nanosheets prepared in Example 1 of the present invention;
[0030] Figure 6 This is an HRTEM image of the crystalline WN nanosheets prepared in Example 1 of this invention;
[0031] Figure 7 The attached spectra are of nitrogen adsorption and desorption of the crystalline WN nanosheets prepared in Example 1 of this invention.
[0032] Figure 8 The crystalline WN nanosheets prepared in Example 1 of this invention have a concentration of 10 -13 The surface-enhanced Raman spectrum of M's R6G; where the horizontal axis represents the Raman shift, in cm. -1 The vertical axis represents the Raman light intensity (Counts);
[0033] Figure 9 The crystalline WN nanosheets prepared in Example 1 of this invention have a concentration of 10 -7 -10 -11 The surface-enhanced Raman spectrum of M's R6G; where the horizontal axis represents the Raman shift, in cm. -1 The vertical axis represents the Raman light intensity (Counts);
[0034] Figure 10 The XRD pattern of the amorphous MoN nanosheets prepared in Example 3 of this invention;
[0035] Figure 11 This is a SEM image of the amorphous MoN nanosheets prepared in Example 3 of the present invention;
[0036] Figure 12 The EDS spectrum of the amorphous MoN nanosheets prepared in Example 3 of this invention;
[0037] Figure 13 This is an HRTEM image of the amorphous MoN nanosheets prepared in Example 3 of the present invention;
[0038] Figure 14 The XRD pattern of the crystalline MoN nanosheets prepared in Example 3 of this invention;
[0039] Figure 15 This is a SEM image of the crystalline MoN nanosheets prepared in Example 3 of the present invention;
[0040] Figure 16This is an HRTEM image of the crystalline MoN nanosheets prepared in Example 3 of the present invention;
[0041] Figure 17 The XRD pattern of the crystalline VN nanosheets prepared in Example 4 of this invention;
[0042] Figure 18 This is a SEM image of the crystalline VN nanosheets prepared in Example 4 of the present invention;
[0043] Figure 19 This is an HRTEM image of the crystalline VN nanosheets prepared in Example 4 of the present invention;
[0044] Figure 20 XPS spectrum of the crystalline VN nanosheets prepared in Example 4 of this invention;
[0045] Figure 21 TEM image of the crystalline WN sample prepared in Comparative Example 1;
[0046] Figure 22 The attached spectra show the nitrogen adsorption and desorption of the crystalline WN sample prepared in Comparative Example 1.
[0047] Figure 23 TEM image of the WN sample prepared for Comparative Example 2. Detailed Implementation
[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0049] Unless otherwise specified, specific techniques or conditions in the embodiments of this invention shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Devices, instruments, reagents, etc., whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels. All raw materials used in this invention are readily available in the domestic market.
[0050] Example 1
[0051] This embodiment provides a method for preparing crystalline WN nanosheets:
[0052] 1) WCl6 (1 mmol), Li3N (1 mmol), ethylenediamine (5 mL), and o-xylene (40 mL) were mixed and magnetically stirred at 380 r / min for 2 h at 26 °C. The solution was then transferred to a Teflon-lined stainless steel autoclave and heated to 180 °C at a heating rate of 2 °C / min, and then maintained at 180 °C for 5 h. The black product was collected by centrifugation, washed three times with deionized water and three times with anhydrous ethanol, and then dried in a vacuum drying oven at 40 °C for 3 h to obtain amorphous WN nanosheets.
[0053] 2) Place 0.3 g of amorphous WN nanosheets in a quartz boat, put it in a microwave oven in a glove box, and heat it at 1000 W for 20 s. After natural cooling, crystalline WN nanosheets are obtained. The glove box is filled with nitrogen gas.
[0054] The sample obtained in step 1) was subjected to XRD ( Figure 1 SEM ( Figure 2 ), EDS ( Figure 3 Characterization revealed that the product was amorphous WN nanosheets.
[0055] The obtained sample in step 2) was subjected to XRD ( Figure 4 SEM ( Figure 5 ), HRTEM Figure 6 Characterization revealed that the product was crystalline WN nanosheets, and nitrogen adsorption and desorption tests showed a specific surface area of 109.3 m². 2 g -1 ( Figure 7 ).
[0056] Example 2
[0057] This embodiment provides SERS performance testing of crystalline WN nanosheets:
[0058] 1) 20 mg of crystalline WN nanosheets were dispersed in 10 mL of deionized water, filtered, and then placed in a vacuum freeze dryer to cool to -40 °C at a rate of 0.3 °C / min. The solution was then kept at -40 °C for 24 h to obtain a flexible substrate.
[0059] 2) Take the above flexible SERS substrate and drop small amounts (20 µL) of R6G aqueous solutions of different concentrations (10 µL) onto it. -7 -10 -13 (M), air-dried for 10 minutes, followed by SERS testing.
[0060] SERS testing showed that, as a flexible SERS substrate, crystalline WN nanosheets achieved a detection concentration of 10 for R6G. -13 M ( Figure 8 ), in 10-7 -10 -11 It exhibits excellent detection performance within the M range. Figure 9 ).
[0061] Example 3
[0062] This embodiment provides a method for preparing crystalline MoN nanosheets:
[0063] 1) MoCl5 (1 mmol), Li3N (1 mmol), ethylenediamine (5 mL), and o-xylene (40 mL) were mixed and magnetically stirred at 380 r / min for 2 h at 26 °C. The solution was then transferred to a Teflon-lined stainless steel autoclave and heated to 180 °C at a heating rate of 2 °C / min, and then maintained at 180 °C for 5 h. The black product was collected by centrifugation, washed three times with deionized water and three times with anhydrous ethanol, and then dried in a vacuum drying oven at 40 °C for 3 h to obtain amorphous MoN nanosheets.
[0064] 2) Place 0.3 g of amorphous MoN nanosheets in a quartz boat, put it in a microwave oven in a glove box, and heat it at 1000 W for 20 s. After natural cooling, crystalline MoN nanosheets are obtained. The glove box is filled with nitrogen gas.
[0065] The sample obtained in step 1) was subjected to XRD ( Figure 10 SEM ( Figure 11 ), EDS ( Figure 12 ), HRTEM Figure 13 Characterization revealed that the product is amorphous MoN nanosheets.
[0066] The obtained sample in step 2) was subjected to XRD ( Figure 14 SEM ( Figure 15 ), HRTEM Figure 16 Characterization revealed that the product is crystalline MoN nanosheets.
[0067] Example 4
[0068] This embodiment provides a method for preparing crystalline VN nanosheets:
[0069] 1) VCl3 (1 mmol), Li3N (1 mmol), ethylenediamine (5 mL), and o-xylene (40 mL) were mixed and magnetically stirred at 380 r / min for 2 h at 26 °C. The solution was then transferred to a Teflon-lined stainless steel autoclave and heated to 180 °C at a heating rate of 2 °C / min, and then maintained at 180 °C for 5 h. The black product was collected by centrifugation, washed three times with deionized water and three times with anhydrous ethanol, and then dried in a vacuum drying oven at 40 °C for 3 h to obtain amorphous MoN nanosheets.
[0070] 2) Place 0.3 g of amorphous VN nanosheets in a quartz boat, put it in a microwave oven in a glove box, and heat it at 1000 W for 20 s. After natural cooling, crystalline MoN nanosheets are obtained. The glove box is filled with nitrogen gas.
[0071] The final sample obtained was subjected to XRD ( Figure 17 SEM ( Figure 18 ), HRTEM Figure 19 XPS Figure 20 Characterization revealed that the final product was crystalline VN nanosheets.
[0072] Example 5
[0073] The difference from Example 1 is as follows:
[0074] In step 1), the parameters of the Teflon-lined stainless steel autoclave were set to react at 200℃ for 6 h; the autoclave was washed twice with deionized water and twice with anhydrous ethanol; and the parameters of the vacuum drying oven were set to dry at 60℃ for 2 h.
[0075] In step 2), the heating time is 10 s or 25 s.
[0076] The rest of the content is the same as in Example 1, and the final sample obtained has similar characterization results and detection effects as in Example 1.
[0077] Comparative Example 1
[0078] The difference between this comparative example and Example 1 is that the amorphous WN nanosheets obtained in step 1) were placed in a tube furnace and heated to 600°C at a rate of 1°C / min, and held for 30 min. Under otherwise unchanged experimental conditions, although crystallization also occurred, TEM characterization results showed obvious sintering phenomena in the samples. Figure 21 The nitrogen adsorption and desorption tests showed a specific surface area of 9.2 m². 2 g -1 ( Figure 22 ).
[0079] Comparative Example 2
[0080] The difference between this comparative example and Example 1 is that the amorphous WN nanosheets obtained in step 1) were placed in a tube furnace and heated to 600°C at a rate of 1°C / min, and held for 10 min. TEM characterization of the sample showed ( Figure 23 The morphology of the nanosheets was completely destroyed.
[0081] This invention discloses a method for rapidly and non-destructively converting amorphous transition metal nitride (TMN) ultrathin nanosheets into crystalline nanosheets via microwave crystallization, and its application as a high-performance surface-enhanced Raman scattering (SERS) substrate. Based on the semi-metallic properties of TMN, this method utilizes microwave heating to induce the crystallization of amorphous nanosheets within 10-20 seconds, avoiding the problems associated with traditional high-temperature sintering. The resulting crystalline TMN nanosheets (such as WN, MoN, and VN) have a thickness of only 1-2 nm, a specific surface area as high as 109.3 m² / g, and exhibit no intrinsic Raman signal. As a SERS substrate, it achieves a detection limit for R6G as low as 10⁻¹³ M and an enhancement factor of 8.6 × 10⁻¹³ M. 7 The signal exhibits excellent uniformity (RSD=5.4%) and stability (no attenuation after 180 days). This invention solves the challenge of synthesizing ultrathin TMN structures, providing a low-cost, high-sensitivity non-metallic SERS platform for trace detection.
[0082] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A microwave crystallization method for preparing ultrathin transition metal nitride nanosheets, characterized in that: Includes the following steps: (1) Dissolve the transition metal salt and Li3N in o-xylene solution, then add ethylenediamine solution, stir thoroughly, heat the solution, collect by centrifugation, wash and vacuum dry to obtain amorphous transition metal nitride nanosheets; the transition metal salt is WCl6, VCl3 or MoCl5; (2) In a nitrogen atmosphere, the amorphous transition metal nitride nanosheets are rapidly microwave heated to obtain highly crystalline transition metal nitride nanosheets.
2. The microwave crystallization preparation method of transition metal nitride ultrathin nanosheets according to claim 1, characterized in that: In step (1): When the transition metal salt is WCl6, the mass ratio of WCl6, Li3N, ethylenediamine, and o-xylene is 11:1:129:1005. When the transition metal salt is VCl3, the mass ratio of VCl3, Li3N, ethylenediamine, and o-xylene is 5:1:129:1006. When the transition metal salt is MoCl5, the mass ratio of MoCl5, Li3N, ethylenediamine, and o-xylene is 8:1:129:1006.
3. The microwave crystallization preparation method of transition metal nitride ultrathin nanosheets according to claim 1, characterized in that: In step (1), the thorough stirring process is as follows: magnetic stirring at a speed of 350-400 r / min for 2 hours under conditions of 24-28℃.
4. The microwave crystallization preparation method of transition metal nitride ultrathin nanosheets according to claim 1, characterized in that: In step (1), during the heating process, the temperature is increased to 180-200℃ at a heating rate of 2℃ / min, and the holding time after heating is 5-6 h.
5. The microwave crystallization preparation method of transition metal nitride ultrathin nanosheets according to claim 1, characterized in that: In step (1), the centrifugation collection and washing process includes the following steps: first, centrifuge and wash with deionized water 2-3 times, and then repeat centrifugation and wash with anhydrous ethanol 2-3 times; the vacuum drying temperature is 40-60℃, and the drying time is 2-3 h.
6. The microwave crystallization preparation method of transition metal nitride ultrathin nanosheets according to claim 1, characterized in that: In step (2), the power of microwave heating is 1000 W and the heating time is 10-25 s.
7. TMN nanosheets with surface-enhanced Raman effect prepared by the microwave crystallization method of transition metal nitride ultrathin nanosheets according to any one of claims 1 to 6.
8. The application of the TMN nanosheets with surface-enhanced Raman effect as described in claim 7 in the preparation of a surface-enhanced Raman spectroscopy detection substrate.
9. The application according to claim 8, characterized in that: The method for preparing the surface-enhanced Raman spectroscopy detection substrate includes the following steps: 20 mg of TMN nanosheets with surface-enhanced Raman effect are dispersed in 10 mL of deionized water, filtered, and then placed in a vacuum freeze dryer to cool to -40 °C at a rate of 0.3 °C / min, and then dried at -40 °C for 24 h to obtain a flexible substrate.