High-stability organic phosphorus functionalized black phosphorus nanosheet dispersion liquid and preparation method thereof

Abstract

The application relates to a high-stability organic phosphorus functionalized black phosphorus nanosheet dispersion liquid and a preparation method thereof, the organic phosphorus functionalized black phosphorus nanosheet dispersion liquid comprises organic phosphorus functionalized black phosphorus nanosheets and a low-boiling-point organic solvent, the solid content of the organic phosphorus functionalized black phosphorus nanosheets in the low-boiling-point organic solvent is 0.20-0.50 mg / mL, the organic phosphorus functionalized black phosphorus nanosheets are in a sheet layer structure, the average thickness is 1.56-2.21 nm, the average layer number is 3-5 layers, and the organic phosphorus functionalized black phosphorus nanosheets are black phosphorus nanosheets which are surface-modified with organic phosphonic acid and ammonium salt thereof. The organic phosphorus functionalized black phosphorus nanosheet dispersion liquid is prepared by adopting a mechanical ball milling-liquid phase ultrasonic coupling method, the obtained high-stability organic phosphorus functionalized black phosphorus nanosheet dispersion liquid has good storage stability under high solid content in a low-boiling-point solvent, can be stably stored in air for more than 16 days, and can be stored in a nitrogen atmosphere for more than 27 days.

Description

Technical Field

[0001] This invention relates to the field of two-dimensional nanomaterial preparation, specifically to a highly stable organophosphorus functionalized black phosphorus nanosheet dispersion and its preparation method. Background Technology

[0002] Black phosphorus (BP) nanosheets, as an emerging two-dimensional nanomaterial, have broad prospects in energy storage devices, catalysts, sensors, and biomedical devices. Black phosphorus nanosheet dispersions offer advantages such as ease of application and large-scale preparation, but the dispersion medium significantly impacts their storage stability. Currently, most black phosphorus nanosheet dispersions use organic solvents with boiling points above 150℃, such as N,N-dimethylformamide (DMF, 153℃), dimethyl sulfoxide (DMSO, 189℃), and N-methylpyrrolidone (NMP, 203℃), as dispersion media. The Hansen solubility parameters (indicators used to assess the compatibility between nanomaterials and organic solvents) of these high-boiling-point organic solvents are quite close to those of black phosphorus nanosheets. Chinese invention patent CN201910862043.3 discloses a method for exfoliating high-quality, low-layer black phosphorus nanosheets in N,N-dimethylformamide via liquid-phase ultrasonication. However, solvent removal is necessary in applications. High-boiling-point solvents are difficult to remove, while low-boiling-point solvents (such as anhydrous ethanol, acetone, and butanone, with anhydrous ethanol having the highest boiling point at 78.5℃) have advantages such as easy removal and less residue. Dispersing black phosphorus nanosheets in low-boiling-point solvents to form a stable dispersion is of greater significance, especially for applications where the operating temperature should not be too high, such as photothermal therapy, batteries, and electronic devices. However, the Hansen solubility parameters of black phosphorus nanosheets and low-boiling-point solvents do not match, making it difficult to form a stable black phosphorus nanosheet dispersion. Chinese invention patent CN201610680032.X discloses a black phosphorus nanosheet, its preparation method, and its application. The preparation method involves placing black phosphorus powder in oxygen-free water, controlling the solution to be alkaline, and then subjecting it to ultrasonic treatment in an inert environment. The resulting mixed solution is centrifuged to collect the supernatant, yielding a black phosphorus nanosheet dispersion with a solid content of 0.15 mg / mL. The average thickness of the black phosphorus nanosheets is 10 nm (approximately 20 layers), and the lateral dimension is 250 nm. This dispersion can be stored for 3 days in an air atmosphere and is stable for 7 days in a nitrogen atmosphere. This method avoids the use of organic solvents, but the storage time is still relatively short when the solid content is low.

[0003] The aforementioned patented methods all employ ultrasonication to prepare black phosphorus nanosheets. Ultrasonication achieves exfoliation by weakening the interlayer interactions of the nanosheets through ultrasonic cavitation in a liquid system. However, due to uneven ultrasonic wave distribution causing variations in the intensity of the cavitation zones, the resulting black phosphorus nanosheets are uneven in size and have a large thickness, leading to low solid content and poor stability in the dispersion. Currently, there is still a lack of effective methods to obtain black phosphorus nanosheet dispersions with high solid content and high stability in low-boiling-point solvents. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a highly stable organophosphorus functionalized black phosphorus nanosheet dispersion. This dispersion maintains a high solids content in low-boiling-point solvents and exhibits good storage stability. Furthermore, the dispersion demonstrates good storage stability under both nitrogen and air atmospheres.

[0005] In another aspect, the present invention provides a method for preparing an organophosphorus functionalized black phosphorus nanosheet dispersion, wherein the preparation method is a mechanical ball milling-liquid phase ultrasonic coupling method, which can realize the large-scale and efficient preparation of black phosphorus nanosheets with high solid content dispersion in low boiling point solvents.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] In a first aspect, a highly stable organophosphorus functionalized black phosphorus nanosheet dispersion is provided. The organophosphorus functionalized black phosphorus nanosheet dispersion comprises organophosphorus functionalized black phosphorus nanosheets and a low-boiling-point organic solvent. The solid content of the organophosphorus functionalized black phosphorus nanosheets in the low-boiling-point organic solvent is 0.20–0.50 mg / mL. The organophosphorus functionalized black phosphorus nanosheets have a layered structure with an average thickness of 1.56 nm to 2.21 nm and an average number of layers of 3–5. The organophosphorus functionalized black phosphorus nanosheets are black phosphorus nanosheets with surface modification of organophosphonic acid and organophosphonic acid ammonium salt.

[0008] The organophosphorus functionalized black phosphorus nanosheet dispersion has a stable shelf life of ≥9 days in air and ≥16 days under a nitrogen atmosphere.

[0009] The organophosphorus functionalized black phosphorus nanosheet dispersion is obtained by modifying aminated black phosphorus nanosheets with organophosphonic acid in a low-boiling-point organic solvent;

[0010] The aminated black phosphorus nanosheets are obtained by mechanically ball-milling ground black phosphorus crystals with nitrogen-containing additives and ball milling beads in an inert atmosphere.

[0011] The organophosphonic acid is selected from one or more of phenylphosphonic acid, phytic acid, methylphosphonic acid, and propylphosphonic acid;

[0012] The low-boiling-point organic solvent is an organic solvent with a boiling point below 100°C; further, the low-boiling-point organic solvent is selected from one or more of anhydrous ethanol, methanol, acetone, and butanone.

[0013] The nitrogen-containing additive is selected from one or more of hexamethylenediamine, diisopropanolamine, hexamethylenediamine adipate, and tetraethylammonium sulfate;

[0014] The grinding balls are stainless steel balls;

[0015] The mass ratio of the aminated black phosphorus nanosheets to the organophosphonic acid is 1:0.5-2.5; the amount of organophosphonic acid used is 0.05-0.25g per 100mL of low-boiling-point organic solvent.

[0016] The mass ratio of the black phosphorus crystals, nitrogen-containing additives, and grinding beads is 1:(4-6):(50-80).

[0017] Secondly, a method for preparing a highly stable organophosphorus functionalized black phosphorus nanosheet dispersion is provided, comprising the following steps:

[0018] (1) Preparation of aminated black phosphorus nanosheets: The ground black phosphorus crystals, nitrogen-containing additives and ball milling beads were mechanically ball milled in an inert atmosphere, cooled to room temperature and then sieved, washed and dried to obtain aminated black phosphorus nanosheets.

[0019] (2) Preparation of organophosphorus functionalized black phosphorus nanosheet dispersion: Dissolve organophosphonic acid in a low-boiling-point organic solvent, add aminated black phosphorus nanosheets and then ultrasonically disperse; after ultrasonic dispersion, centrifuge the obtained suspension to remove solid substances, and the resulting supernatant is organophosphorus functionalized black phosphorus nanosheet dispersion.

[0020] The nitrogen-containing additive in step (1) is selected from one or more of diisopropanolamine, hexamethylenediamine, hexamethylenediamine adipate, and tetraethylammonium sulfate;

[0021] The organophosphonic acid in step (2) is selected from one or more of phenylphosphonic acid, phytic acid, methylphosphonic acid, and propylphosphonic acid;

[0022] The grinding in step (1) is carried out in a glove box under an inert atmosphere, where black phosphorus crystals are placed in a mortar and ground for 20 to 40 minutes.

[0023] In step (1), the mass ratio of black phosphorus crystals, nitrogen-containing additives, and grinding beads is 1:(4-6):(50-80);

[0024] The inert atmosphere in step (1) is helium, nitrogen or argon;

[0025] The grinding balls used in step (1) are stainless steel balls;

[0026] In step (1), the mechanical ball milling is carried out after the ball milling jar is sealed in a glove box containing an inert atmosphere; the mechanical ball milling program is set to ball milling at a speed of 500-800 r / min at room temperature, with a cycle of 30±3 min of unidirectional ball milling and 6±3 min of stopping, for a total of 41-45 cycles, with a total duration of 22-28 h.

[0027] The washing method in step (1) is centrifugal washing; centrifugal washing involves rinsing the product with deionized water, separating it by centrifugation, and then taking the precipitated product. This process is repeated 3 to 6 times. The centrifugation conditions are a rotation speed of 9000 to 12000 r / min and a single centrifugation time of 6 to 10 min.

[0028] In step (1), the drying is vacuum drying. The product is placed in a vacuum oven with a set temperature of 50-75°C and dried for 8-12 hours. After drying, a gray-black powder is obtained, which is amino-modified black phosphorus nanosheets.

[0029] In step (2), the mass ratio of aminated black phosphorus nanosheets to organophosphonic acid is 1:0.5-2.5; the amount of organophosphonic acid used is 0.05-0.25g per 100mL of low-boiling-point organic solvent.

[0030] In step (2), the low-boiling-point organic solvent is an organic solvent with a boiling point below 100°C; further, the low-boiling-point organic solvent is selected from one or more of anhydrous ethanol, methanol, acetone, and butanone.

[0031] In step (2), the ultrasonic dispersion is performed under the protection of light and inert gas at a temperature of 10-35°C, with an ultrasonic power of 400-600W and an ultrasonic time of 4-6h.

[0032] Furthermore, the light-shielding method involves wrapping a blue-capped bottle containing a dispersion of aminated black phosphorus nanosheets and organophosphonic acid in tin foil and then covering it with the top cap of an ultrasonic instrument; the inert gas is helium, nitrogen, or argon.

[0033] In step (2), the suspension is centrifuged at a speed of 2000-4000 r / min for 5-12 min.

[0034] Furthermore, the organophosphorus functionalized black phosphorus nanosheet dispersion in step (2) is prepared by taking out the supernatant after centrifugation, placing it in a blue-capped bottle, and filling it with an inert gas for preservation; the inert gas is helium, nitrogen, or argon.

[0035] The beneficial effects of this invention are as follows:

[0036] (1) The organophosphorus functionalized black phosphorus nanosheets obtained in this invention have a lateral dimension of 100-140 nm, an average thickness of 1.56 nm to 2.21 nm, an average number of layers of 3-5, and good dimensional stability.

[0037] (2) In this invention, black phosphorus crystals and nitrogen-containing additives are first mechanically ball-milled to obtain aminated black phosphorus nanosheets. Then, an ultrasonic method is used to promote the formation of covalent bonds between the aminated black phosphorus nanosheets and organophosphonic acid. The mechanical ball-milling-liquid-ultrasonic coupling method is used to achieve highly stable dispersion of organophosphorus functionalized black phosphorus nanosheets in low-boiling-point solvents. This preparation process is simple and reproducible.

[0038] (3) The highly stable organophosphorus functionalized black phosphorus nanosheet dispersion obtained by the present invention can be stably stored in air for more than 9 days, and can be stably stored for up to 40 days. Under nitrogen atmosphere, it can be stored for more than 16 days, and can be stably stored for up to 56 days. Attached Figure Description

[0039] Figure 1 This is a schematic diagram illustrating the experimental preparation of the organophosphorus functionalized black phosphorus nanosheet dispersion in an embodiment of the present invention;

[0040] Figure 2 Transmission electron microscopy image of BPN-3@PA prepared in Example 3;

[0041] Figure 3 Raman spectra of BPN-3@PA and BPN-3 prepared in Example 3;

[0042] Figure 4 High-resolution P 2p X-ray photoelectron spectrum of BPN-3@PA prepared in Example 3;

[0043] Figure 5 The infrared spectrum of BPN-3@PA prepared in Example 3;

[0044] Figure 6 The UV absorption curve of the BPN-3@PA dispersion prepared in Example 3 after standing for 27 days under a nitrogen atmosphere;

[0045] Figure 7 The UV absorption curve of the BPN-3@PA dispersion prepared in Example 3 after standing in air for 16 days;

[0046] Figure 8 The particle size distribution of the BPN-3@PA dispersion prepared in Example 3 before and after standing in air for 16 days is shown. Detailed Implementation

[0047] To better understand the present invention, the following description, in conjunction with the accompanying drawings and embodiments, will further illustrate the present invention. However, the embodiments of the present invention are not limited thereto. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the scope of protection of the invention.

[0048] The black phosphorus crystals used in the various embodiments and comparative examples of this invention were provided by Kunming Black Phosphorus Technology Co., Ltd. (China); the ultrasonic cleaner was a product of Kunshan Ultrasonic Instrument Co., Ltd. (model KQ-400KD); and the ball mill was a product of Nanjing Nanda Instrument Co., Ltd. (model QM-DK2).

[0049] Figure 1 This is a schematic diagram illustrating the experimental preparation of organophosphorus functionalized black phosphorus nanosheet dispersions in the following examples.

[0050] Example 1

[0051] (1) Grind 2g of black phosphorus crystals in a glove box under nitrogen atmosphere for 20min. Then, grind them together with 8g of hexamethylenediamine (Beijing Inokai Technology Co., Ltd.) and 100g of stainless steel balls in a glove box under nitrogen atmosphere in a 200mL ball mill jar. Then, place it in a ball mill for mechanical ball milling. The mechanical ball milling program is as follows: ball milling at 500r / min for 27min in one direction and stopping for 3min, for a total of 44 cycles, with a total duration of 22h. After ball milling, cool to room temperature, open the jar, and sieve to remove the ball balls. Transfer the resulting mixture to a 500mL beaker, add 150mL of deionized water for washing, centrifuge at 9000r / min for 10min, and discard the supernatant. Continue to wash the precipitate with deionized water and centrifuge again, repeating the operation 3 times. Dry the resulting precipitate in a vacuum oven at 50℃ for 12h to obtain 1.4g of gray-black solid, which is aminated black phosphorus nanosheets, named BPN-1.

[0052] (2) Add 0.15g of methylphosphonic acid (M-6-P) to a blue-capped bottle containing 100mL of anhydrous ethanol and stir evenly at room temperature. Then, add 0.1g of BPN-1 to the blue-capped bottle in a glove box under nitrogen atmosphere. Seal the blue-capped bottle with a film and wrap it with tin foil. Take out the blue-capped bottle and put it into an ultrasonic instrument with a top cover. Use an external cooling water system to control the water temperature at 10℃ and sonicate at 400W power for 5h. Then, centrifuge the obtained suspension at 2000r / min for 12min to remove unstable BPN-1 powder. Collect the supernatant and put it into a blue-capped bottle and fill it with nitrogen for protection to obtain a dispersion of methylphosphonic acid functionalized black phosphorus nanosheets, named BPN-1@M-6-P dispersion, with a solid content of 0.20mg / mL.

[0053] Example 2

[0054] (1) Grind 2g of black phosphorus crystals in a glove box under helium atmosphere for 25min. Then, grind them together with 11g of diisopropanolamine (Beijing Inokai Technology Co., Ltd.) and 120g of stainless steel balls in a glove box under helium atmosphere in a 200mL ball milling jar. Then, place it in a ball mill for mechanical ball milling. The mechanical ball milling program is as follows: ball milling at 600r / min for 29min in one direction and stopping for 5min, for a total of 45 cycles, with a total duration of 25.5h. After ball milling, cool to room temperature, open the jar, and sieve to remove the ball balls. Transfer the resulting mixture to a 500mL beaker, add 200mL of deionized water for washing, centrifuge at 10000r / min for 9min, discard the supernatant, wash the precipitate with deionized water again, centrifuge again, and repeat the operation 4 times. Dry the resulting precipitate in a vacuum oven at 60℃ for 11h to obtain 1.5g of gray-black solid, which is aminated black phosphorus nanosheets, named BPN-2.

[0055] (2) Add 0.05g of phenylphosphonic acid (PPA) to a blue-capped bottle containing 100mL of methanol and stir evenly at room temperature. Then, add 0.1g of BPN-2 to the bottle in a glove box under helium atmosphere. Seal the blue-capped bottle with a film and wrap it with tin foil. Take out the blue-capped bottle and put it into an ultrasonic instrument with a top cap. Use an external cooling water system to control the water temperature at 20℃ and sonicate at 450W power for 5.5h. Then, centrifuge the obtained suspension at 2500r / min for 10min to remove unstable BPN-2 powder. Collect the supernatant and put it into a blue-capped bottle and fill it with helium for protection to obtain a phenylphosphonic acid functionalized black phosphorus nanosheet dispersion, named BPN-2@PPA dispersion, with a solid content of 0.27mg / mL.

[0056] Example 3

[0057] (1) Grind 2g of black phosphorus crystals in an argon-atmosphere glove box for 30 min, then seal them with 10g of tetraethylammonium sulfate (Beijing Inokai Technology Co., Ltd.) and 140g of stainless steel balls in an argon-atmosphere glove box in a 200mL ball mill jar, and then place them in a ball mill for mechanical ball milling. The mechanical ball milling program is as follows: ball milling at 700r / min for 30 min in one direction and stopping for 6 min, for a total of 43 cycles, with a total duration of 25.8h. After ball milling, cool to room temperature, open the jar, and sieve to remove the ball milling beads. Transfer the resulting mixture to a 500mL beaker, add 300mL of deionized water for washing, centrifuge at 11000r / min for 8 min, discard the supernatant, wash the precipitate with deionized water again, centrifuge again, and repeat the operation 5 times. Dry the resulting precipitate in a vacuum oven at 65℃ for 10h to obtain 1.6g of gray-black solid, which is aminated black phosphorus nanosheets, named BPN-3.

[0058] (2) Add 0.1g of phytic acid (PA) to a blue-capped bottle containing 100mL of acetone and stir at room temperature. Then, add 0.1g of BPN-3 to the bottle in an argon-atmosphere glove box, seal the blue-capped bottle with a film, wrap the blue-capped bottle with tin foil, remove the blue-capped bottle and place it in an ultrasonic instrument with a top cap; use an external cooling water system to control the water temperature at 25℃, sonicate at 500W power for 6h, and then centrifuge the resulting suspension at 3000r / min for 8min to remove unstable BPN-3 powder. Collect the supernatant and put it into a blue-capped bottle, and fill it with argon gas for protection to obtain a phytic acid-functionalized black phosphorus nanosheet dispersion, named BPN-3@PA dispersion, with a solid content of 0.50mg / mL;

[0059] Appendix Figure 2 The image shows a transmission electron microscope (TEM) image of BPN-3@PA. Figure 2 As can be seen from (a), the nanosheets have a smooth and flat surface, and their lateral dimensions range from 100 to 140 nm, exhibiting good dimensional uniformity; furthermore, high-resolution TEM images (attached) show that... Figure 2 (b) It can be seen that the thickness of the phytic acid-functionalized black phosphorus nanosheets is about 1.56 nm. Based on the thickness of a single BP nanosheet being 0.52 nm, it is equivalent to 3 layers thick.

[0060] Appendix Figure 3 Raman spectra of BPN-3 and BPN-3@PA were compared, and three characteristic vibrational peaks were found in both BPN-3 and BPN-3@PA: 361 cm⁻¹ -1 out-of-plane vibration (A) g 1 ), 438cm -1 In-plane vibration (B) 2g ) and 465cm-1 In-plane vibration A g 2 This indicates that liquid-phase ultrasound did not significantly damage the structure of black phosphorus nanosheets;

[0061] X-ray photoelectron spectroscopy (XPS) analysis was performed on BPN-3@PA, and the high-resolution P 2p XPS spectrum is attached. Figure 4 As shown, five peaks appeared at 130.1 eV, 131.1 eV, 133.9 eV, 133.6 eV, and 134.8 eV, corresponding to PP bonds (P2p bonds), respectively. 3 / 2 and P 2p 1 / 2 ), PN bond, H3PO4 - And PO bond; Fourier transform infrared (FT-IR) spectra of BPN-3 and BPN-3@PA are attached. Figure 5 3600cm -1 The peak at 2760-2930cm -1 The broad peaks at 1533 cm⁻¹ correspond to the stretching vibrations of the OH and P-OH bonds in phytic acid, respectively. -1 An NH3-like substance appeared at that location. + The above results fully demonstrate the successful functionalization and modification of aminated black phosphorus nanosheets with phytic acid.

[0062] Appendix Figure 6 and 7 The UV absorption curves of BPN-3@PA dispersions after different standing times are shown in the attached figures. Figure 6 It was found that the absorbance of the BPN-3@PA dispersion in nitrogen did not change significantly over 27 days, indicating that the dispersion can be stored for at least 27 days without significant aggregation; (See attached image) Figure 7 The absorbance change of the BPN-3@PA dispersion in air indicates that the BPN-3@PA dispersion can be stably stored for more than 16 days without significant oxidation; (See attached image) Figure 8 In the study, the particle size of the BPN-3@PA dispersion remained between 100 and 140 nm after 16 days of storage, indicating that the dispersion maintained good dispersion in the solvent after 16 days of sedimentation treatment. These results demonstrate that the BPN-3@PA dispersion has good storage stability.

[0063] Example 4

[0064] (1) Grind 2g of black phosphorus crystals in a glove box under helium atmosphere for 40min. Then, grind them together with 12g of hexamethylenediamine adipic acid salt (Beijing Inokai Technology Co., Ltd.) and 160g of stainless steel balls in a glove box under helium atmosphere in a 200mL ball milling jar. Then, place it in a ball mill for mechanical ball milling. The mechanical ball milling program is as follows: ball milling at 800r / min for 33min in one direction and stopping for 8min, for a total of 41 cycles, with a total duration of 28h. After ball milling, cool to room temperature, open the jar, and sieve to remove the grinding balls. Transfer the resulting mixture to a 500mL beaker, add 450mL of deionized water for washing, centrifuge at 12000r / min for 6min, discard the supernatant, wash the precipitate with deionized water again, centrifuge again, and repeat the operation 6 times. Dry the resulting precipitate in a vacuum oven at 75℃ for 8h to obtain 1.7g of gray-black solid, which is aminated black phosphorus nanosheets, named BPN-5.

[0065] (2) Add 0.25g of propylphosphonic acid (PPAC) to a blue-capped bottle containing 100mL of butanone and stir evenly at room temperature. Then, add 0.1g of BPN-4 to the blue-capped bottle in a glove box under helium atmosphere. Seal the blue-capped bottle with a film and wrap it with tin foil. Take out the blue-capped bottle and put it into an ultrasonic instrument with a top cover. Control the water temperature at 35℃ and sonicate at 600W power for 4h. Then centrifuge the resulting suspension at 4000r / min for 5min to remove unstable BPN-4 powder. Collect the supernatant and put it into a blue-capped bottle and fill it with helium for protection to obtain a propylphosphonic acid functionalized black phosphorus nanosheet dispersion, named BPN-4@PPAC dispersion, with a solid content of 0.30mg / mL.

[0066] Example 5

[0067] In an argon-atmospheric glove box, 80 mL of the 0.5 mg / mL phytic acid-functionalized black phosphorus nanosheet dispersion prepared in Example 3 and 20 mL of acetone were added to a blue-capped bottle. The blue-capped bottle was sealed with a film and wrapped with tin foil. The bottle was then placed in an ultrasonic instrument with a top cap. The water temperature was controlled at 25°C using an external cooling water system, and the mixture was ultrasonicated at 600W power for 5 minutes to obtain the phytic acid-functionalized black phosphorus nanosheet dispersion, named BPN-3@PA-0.4 dispersion, with a solid content of 0.4 mg / mL.

[0068] Example 6

[0069] In an argon-atmospheric glove box, 60 mL of the 0.5 mg / mL phytic acid-functionalized black phosphorus nanosheet dispersion prepared in Example 3 and 40 mL of acetone were added to a blue-capped bottle. The blue-capped bottle was sealed with a film and wrapped with tin foil. The bottle was then placed in an ultrasonic instrument with a top cap. The water temperature was controlled at 25°C using an external cooling water system, and the mixture was ultrasonicated at 600W power for 10 min to obtain the phytic acid-functionalized black phosphorus nanosheet dispersion, named BPN-3@PA-0.3 dispersion, with a solid content of 0.3 mg / mL.

[0070] Comparative Example 1

[0071] The aminated black phosphorus nanosheets (BPN-3) prepared in step (1) of Example 3 were directly taken and ultrasonically treated in the same way as in step (2) of Example 3 without adding phytic acid. The supernatant was collected and placed in a blue-capped bottle and filled with argon gas for protection to obtain an aminated black phosphorus nanosheet dispersion without organophosphorus functionalization, which was named BPN-3 dispersion.

[0072] Comparative Example 2

[0073] In step (1) of Example 3, only 2g of black phosphorus crystals were added for mechanical ball milling to obtain unaminated black phosphorus nanosheets, which were named BP nanosheets. Then, phytic acid was added and ultrasonically treated in the same way as in step (2) of Example 3. The collected supernatant was placed in a blue-capped bottle and filled with argon gas for protection. This was a dispersion of black phosphorus nanosheets modified only with organophosphonic acid, which was named BP@PA dispersion.

[0074] Comparative Example 3

[0075] The ultrasonic treatment in step (2) of Example 3 was replaced with stirring; the stirring time was 24h; the organophosphorus functionalized black phosphorus nanosheet dispersion prepared by mechanical ball milling-stirring was obtained and named BPN-3@PA(M-Stir) dispersion.

[0076] Comparative Example 4

[0077] 0.1g of black phosphorus crystals were ground in a glove box under an argon atmosphere for 30 minutes. Then, they were added together with 0.5g of tetraethylammonium sulfate and 0.1g of phytic acid into a vial containing 100mL of acetone and sonicated. The conditions before and after sonication were the same as in step (2) of Example 3. The resulting organic phosphorus functionalized black phosphorus nanosheet dispersion prepared by liquid-phase sonication was named BPN@PA(S) dispersion.

[0078] Comparative Example 5

[0079] BP-DMF dispersions were prepared using the method described in the literature Polymer Ionic Liquid Stabilized Black Phosphorus for Environmental Robust Flexible Optoelectronics (Advanced Functional Materials, 28(2018)1805311).

[0080] Transmission electron microscopy (TEM) images were observed using a JEM-2100F TEM from NEC Corporation; Raman spectra were recorded using a Lab RAM Aramis Raman spectrometer from Horiba Jobin Yvon (France), with a helium laser line at 632.8 nm as the light source; XPS spectra were measured using an Axis Ultra-DLD X-ray photoelectron spectroscopy system from Kratos (UK); infrared spectra were measured using a Vertex 70 Fourier transform infrared spectrometer from Bruker (Germany); and UV-Vis absorption spectra were measured using a HITACHI U-3900H (Japan). The testing conditions were room temperature, using a 1 cm path length cuvette, 4 mL of different dispersions, scanning the range from 300 to 800 nm, and recording the absorbance at 465 nm. The particle size and distribution of the dispersion before and after standing were measured using a dynamic light scattering particle size analyzer with a HORIBA SZ-100Z instrument from Japan. The thickness and number of nanosheets were recorded using an atomic force microscope with a Hitachi AFM5100N instrument from NEC Corporation.

[0081] The solid content of the black phosphorus nanosheet dispersions in Examples 1-6 and Comparative Examples 1-5 is shown in Table 1, and the groups modified in Examples 1-6 and Comparative Examples 1-5 are shown in Table 2. The black phosphorus nanosheets in the above examples and comparative examples were characterized by AFM, and the thickness and number of layers of the black phosphorus nanosheets were measured (average value) as shown in Table 3.

[0082] Examples 1-6 and Comparative Examples 1-5 used the relationship between the absorbance of the characteristic peak at 465 nm of the ultraviolet absorption curve of black phosphorus nanosheets and the deposition time to determine the stable storage time of each dispersion in air and nitrogen. The results are shown in Tables 4 and 5.

[0083] Table 1 Solid content of Examples 1-6

[0084] Black phosphorus nanosheet dispersion Solid content / mg / mL Black phosphorus nanosheet dispersion Solid content / mg / mL Example 1 0.20 Comparative Example 1 0.12 Example 2 0.27 Comparative Example 2 0.05 Example 3 0.50 Comparative Example 3 0.08 Example 4 0.30 Comparative Example 4 0.06 Example 5 0.40 Comparative Example 5 0.15 Example 6 0.30

[0085] Table 2 Modification groups of Examples 1-6 and Comparative Examples 1-5

[0086]

[0087] Table 3 Average thickness and average number of layers in Examples 1-6 and Comparative Examples 1-5

[0088]

[0089]

[0090] Table 4. Stability in air for Examples 1-6 and Comparative Examples 1-5

[0091] Black phosphorus nanosheet dispersion Storage days Black phosphorus nanosheet dispersion Storage days Example 1 9 Comparative Example 1 8 Example 2 9 Comparative Example 2 3 Example 3 16 Comparative Example 3 6 Example 4 12 Comparative Example 4 4 Example 5 26 Comparative Example 5 4 Example 6 40

[0092] Table 5. Stability of Examples 1-6 and Comparative Examples 1-5 in nitrogen atmosphere

[0093] Black phosphorus nanosheet dispersion Storage days Black phosphorus nanosheet dispersion Storage days Example 1 19 Comparative Example 1 13 Example 2 22 Comparative Example 2 9 Example 3 27 Comparative Example 3 10 Example 4 16 Comparative Example 4 12 Example 5 42 Comparative Example 5 10 Example 6 56

[0094] As shown in Table 1, the solid content of the high-stability organophosphorus functionalized black phosphorus nanosheet dispersion of the present invention is higher than 0.20 mg / mL. As shown in Table 2, the black phosphorus nanosheets of Examples 1 to 6 are all modified with organophosphonic acid and organophosphonate ammonium salt. Comparative Examples 1 and 2 are treated with a single nitrogen-containing adjuvant or organophosphonic acid. The former is only aminated surface modification, and the latter is only organophosphonic acid modification. Comparative Examples 3 and 4 are prepared by different methods from the examples, but are still modified with organophosphonic acid and organophosphonate ammonium salt. Comparative Example 5 is modified with hexafluorophosphonate. As shown in Table 3, the average thickness of the organophosphorus functionalized black phosphorus nanosheets prepared in Examples 1 to 6 is less than 3 nm and the average number of layers is less than 5 (generally, a number of layers less than 5 is considered as a few-layer black phosphorus nanosheet). The average thickness of the black phosphorus nanosheets applied in Comparative Examples 1 to 5 is greater than 3 nm, and they are all multilayer black phosphorus nanosheets.

[0095] As shown in Tables 4 and 5, the highly stable organophosphorus functionalized black phosphorus nanosheet dispersion of the present invention exhibits excellent antioxidant capacity and can be stored in air for a long period of time, exceeding 9 days, with a maximum storage time of over 16 days (Example 3). It can also be stably stored under a nitrogen atmosphere for 27 days without significant agglomeration. The organophosphorus functionalized black phosphorus nanosheets have a lateral dimension of 100–140 nm, an average thickness of 1.56 nm to 2.21 nm, and an average number of 3–5 layers, exhibiting good dimensional stability and uniformity. Examples 5 and 6 are phytic acid functionalized black phosphorus nanosheet dispersions diluted in Example 3. With decreasing solid content of the black phosphorus nanosheets, the antioxidant capacity and anti-agglomeration ability significantly improve. Specifically, the phytic acid functionalized black phosphorus nanosheet dispersion with a solid content of 0.30 mg / mL can be stably stored in air for over 40 days and under a nitrogen atmosphere for over 56 days, demonstrating the excellent stability of the organophosphorus functionalized black phosphorus nanosheet dispersion prepared by the present invention.

[0096] Comparative Example 1, consisting of ammoniated black phosphorus nanosheets without organophosphonic acid modification, could be stored in air for 8 days and under a nitrogen atmosphere for 13 days. This indicates that the introduction of nitrogen-containing additives not only facilitated the exfoliation of black phosphorus but also introduced amino functional groups at the edges of the black phosphorus nanosheets. This helps prevent agglomeration and oxidation of the black phosphorus nanosheet edges during short-term storage. However, since the amino groups did not completely cover the surface of the black phosphorus nanosheets, oxidation and agglomeration still occurred over time, resulting in less than ideal storage stability. Comparative Example 2, consisting of black phosphorus nanosheets modified only with organophosphonic acid without aminated surface modification, not only readily transformed into red phosphorus but also exhibited highly reactive edges that were more susceptible to oxidation upon contact with air. Furthermore, the black phosphorus nanosheets agglomerated due to van der Waals forces. Therefore, the unaminated black phosphorus nanosheet dispersion showed poor stability under both air and nitrogen atmospheres.

[0097] Comparative Example 3, an organophosphorus functionalized black phosphorus nanosheet dispersion prepared by mechanical ball milling and stirring, showed stable storage time of 6 days in air and 10 days in a nitrogen atmosphere. This indicates that stirring cannot promote good adhesion between organophosphonic acid and black phosphorus nanosheets, resulting in insufficient protection of the black phosphorus nanosheet surface. Comparative Example 4, an organophosphorus functionalized black phosphorus nanosheet dispersion prepared solely by liquid-phase ultrasonication, exhibited poor stability in both air and nitrogen atmospheres. This is because the black phosphorus nanosheets prepared by liquid-phase ultrasonication are thicker, making the dispersion more prone to aggregation. Comparative Example 5, a black phosphorus nanosheet dispersion prepared using DMF with a boiling point of 153℃ as a solvent, showed relatively poor air stability compared to the present invention, only able to be stably stored in air for 4 days and in a nitrogen atmosphere for 10 days. Furthermore, the high-boiling-point solvent is difficult to remove during application, and the high processing temperature can also damage the surface of the black phosphorus nanosheets, affecting their performance.

[0098] This invention prepares a highly stable organophosphorus functionalized black phosphorus nanosheet dispersion using a mechanical ball milling-liquid-phase ultrasonic coupling method under an inert atmosphere. The good dispersion stability and antioxidant properties are mainly due to the following reasons: (1) In the mechanical ball milling stage, under the action of nitrogen-containing additives, the black phosphorus nanosheets are peeled off by collision or vertical impact during the rolling process of the milling beads, and amino groups are introduced at the edges of the black phosphorus nanosheets. The amino functional groups then react with organophosphonic acids to form organophosphonic acid ammonium salts, thereby increasing the interaction between organophosphonic acids and the surface of black phosphorus nanosheets, which helps to prevent oxidation at the edges of the modified black phosphorus nanosheets; (2) In the liquid-phase ultrasonic stage, the ultrasonic cavitation further achieves the peeling of nanosheets and promotes the good adhesion of organophosphonic acids with antioxidant properties to the surface of black phosphorus nanosheets, making the functionalized black phosphorus nanosheets less prone to oxidation. Furthermore, organophosphonic acids can act as an isolation layer to prevent the agglomeration between the layers and ensure stable dispersion in the solvent. In addition, the preparation process of the highly stable organophosphorus functionalized black phosphorus nanosheet dispersion of this invention has good repeatability, low cost, and long stable storage time.

Claims

1. A highly stable organophosphorus functionalized black phosphorus nanosheet dispersion, characterized in that, The organophosphorus functionalized black phosphorus nanosheet dispersion comprises organophosphorus functionalized black phosphorus nanosheets and a low-boiling-point organic solvent. The solid content of the organophosphorus functionalized black phosphorus nanosheets in the low-boiling-point organic solvent is 0.20–0.50 mg / mL. The organophosphorus functionalized black phosphorus nanosheets have a layered structure with an average thickness of 1.56 nm to 2.21 nm and an average number of 3–5 layers. The organophosphorus functionalized black phosphorus nanosheets are black phosphorus nanosheets with surface modification of organophosphonic acid and its ammonium salt. The organophosphorus functionalized black phosphorus nanosheet dispersion is obtained by dissolving organophosphonic acid in a low-boiling-point organic solvent, adding aminated black phosphorus nanosheets, and then ultrasonically dispersing the dispersion. After ultrasonic dispersion, the resulting suspension is centrifuged to remove solid substances. The aminated black phosphorus nanosheets are obtained by mechanically ball milling ground black phosphorus crystals with nitrogen-containing additives and ball milling beads in an inert atmosphere; The organophosphonic acid is selected from one or more of phenylphosphonic acid, phytic acid, methylphosphonic acid, and propylphosphonic acid; The low-boiling-point organic solvent is an organic solvent with a boiling point below 100°C; The nitrogen-containing additive is selected from one or more of diisopropanolamine, hexamethylenediamine, hexamethylenediamine adipic acid salt, and tetraethylammonium sulfate; The mass ratio of the aminated black phosphorus nanosheets to the organophosphonic acid is 1:0.5-2.5; the amount of organophosphonic acid used is 0.05-0.25g per 100mL of low-boiling-point organic solvent. The mass ratio of the black phosphorus crystals, nitrogen-containing additives, and grinding beads is 1:(4-6):(50-80).

2. The highly stable organophosphorus functionalized black phosphorus nanosheet dispersion according to claim 1, characterized in that, The organophosphorus functionalized black phosphorus nanosheet dispersion has a stable shelf life of ≥9 days in air and ≥16 days under a nitrogen atmosphere.

3. The highly stable organophosphorus functionalized black phosphorus nanosheet dispersion according to claim 1, characterized in that, The grinding balls are stainless steel balls; the low-boiling-point organic solvent is selected from one or more of anhydrous ethanol, methanol, acetone, and butanone.

4. A method for preparing a highly stable organophosphorus functionalized black phosphorus nanosheet dispersion according to any one of claims 1-3, characterized in that, Includes the following steps: (1) Preparation of aminated black phosphorus nanosheets: The ground black phosphorus crystals, nitrogen-containing additives and ball milling beads were mechanically ball milled in an inert atmosphere, cooled to room temperature and then sieved, washed and dried to obtain aminated black phosphorus nanosheets. (2) Preparation of organophosphorus functionalized black phosphorus nanosheet dispersion: Dissolve organophosphonic acid in a low-boiling-point organic solvent, add aminated black phosphorus nanosheets and then ultrasonically disperse; after ultrasonic dispersion, centrifuge the obtained suspension to remove solid substances, and the resulting supernatant is organophosphorus functionalized black phosphorus nanosheet dispersion.

5. The method for preparing the highly stable organophosphorus functionalized black phosphorus nanosheet dispersion according to claim 4, characterized in that, The grinding in step (1) is carried out in a glove box under an inert atmosphere, where black phosphorus crystals are placed in a mortar and ground for 20 to 40 minutes. The inert atmosphere in step (1) is helium, nitrogen or argon; In step (1), the mechanical ball milling is performed in a glove box containing an inert atmosphere after the ball mill jar is sealed. The mechanical ball milling program is set to perform ball milling at a speed of 500-800 r / min at room temperature, with one cycle consisting of 30±3 min of unidirectional ball milling followed by a 6±3 min pause, for a total of 41-45 cycles, with a total duration of 22-28 h. In step (1), the washing method is centrifugal washing. Centrifugal washing involves rinsing the product with deionized water, followed by centrifugal separation. Collect the sedimentation product; this process is repeated 3 to 6 times. The centrifugation conditions are a rotation speed of 9000 to 12000 r / min and a single centrifugation time of 6 to 10 min. In step (1), the drying is vacuum drying. The product is placed in a vacuum oven with a set temperature of 50-75°C and dried for 8-12 hours. After drying, a gray-black powder is obtained, which is amino-modified black phosphorus nanosheets.

6. The method for preparing the highly stable organophosphorus functionalized black phosphorus nanosheet dispersion according to claim 4, characterized in that, In step (2), the ultrasonic dispersion is carried out under the protection of light and inert gas at a temperature of 10-35°C, with an ultrasonic power of 400-600W and an ultrasonic time of 4-6h. In step (2), the suspension is centrifuged at a speed of 2000-4000 r / min for 5-12 min.

7. The method for preparing the highly stable organophosphorus functionalized black phosphorus nanosheet dispersion according to claim 6, characterized in that, The light-shielding method is: wrapping a blue-capped bottle containing a dispersion of aminated black phosphorus nanosheets and organophosphonic acid in tin foil, and then covering it with the top cap of an ultrasonic instrument; the inert gas is: helium, nitrogen, or argon.

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