An organic phosphonic acid modified black phosphorus nanosheet and a preparation method and application thereof

Abstract

The application discloses an organic phosphonic acid modified black phosphorus nanosheet and a preparation method and application thereof. The preparation method of the organic phosphonic acid modified black phosphorus nanosheet comprises the following steps: dispersing black phosphorus powder in a first solvent to obtain a black phosphorus dispersion liquid; then performing ultrasonic exfoliation on the black phosphorus dispersion liquid to obtain black phosphorus nanosheets; dispersing the black phosphorus nanosheets and organic phosphonic acid in a second solvent to obtain a black phosphorus nanosheet dispersion liquid; and performing a solvothermal reaction on the black phosphorus nanosheet dispersion liquid to obtain the organic phosphonic acid modified black phosphorus nanosheet. The solvothermal synthesis process is adopted to make the organic phosphonic acid molecules form firm covalent bonding with the phosphorus atoms on the surface of the black phosphorus through P-O bonds, and meanwhile, the dispersion requirements of different solvent systems can be accurately adapted through the regulation of the structure of the organic phosphonic acid molecules, so that the dispersion stability, environmental stability and oil solubility / water solubility of the black phosphorus nanosheet are significantly improved, and the application of the black phosphorus nanosheet in multiple fields such as lubrication, photoelectricity, energy storage and the like is expanded.

Description

Technical Field

[0001] This invention relates to the field of black phosphorus, and more specifically, to an organophosphonic acid-modified black phosphorus nanosheet, its preparation method, and its application. Background Technology

[0002] Black phosphorus (BP) is a novel two-dimensional layered material with an adjustable band gap (0.3-2.0 eV), high carrier mobility, and excellent optoelectronic properties. Compared with the shortcomings of graphene (zero band gap) and molybdenum disulfide (MoD) (low carrier mobility), black phosphorus combines the advantages of adjustable band gap and high carrier transport capacity, demonstrating irreplaceable application advantages in many industrial and scientific research fields.

[0003] Black phosphorus nanosheets have broad application prospects in fields such as lubricant additives, optoelectronic materials, and energy storage devices due to their unique layered structure. In particular, when used as a lubricant additive, their layered structure can achieve excellent anti-wear and friction reduction effects through interlayer slippage, making them a promising new functional material in the field of high-end equipment lubrication.

[0004] However, currently, black phosphorus nanosheets in related technologies still have the following drawbacks: (1) Poor oil solubility: The intrinsic surface of black phosphorus nanosheets is hydrophilic, which makes it extremely incompatible with non-polar oil-based media such as lubricating oil and liquid paraffin. It is difficult to achieve stable and uniform dispersion in oil-based systems and it is very easy to agglomerate and settle, which directly limits its large-scale industrial application as an oil-based lubricating additive.

[0005] (2) Insufficient dispersion stability: Unmodified black phosphorus nanosheets have extremely high surface energy. In conventional solvents such as water and ethanol, they are prone to agglomeration and precipitation due to van der Waals forces, making it impossible to achieve long-term stable dispersion. At the same time, the agglomerated black phosphorus nanosheets will lose the unique performance advantages of two-dimensional materials, greatly reducing their effectiveness.

[0006] (3) Limited effect of physical adsorption modification: In related technologies, the surface modification of black phosphorus is mostly achieved by physical adsorption. The modifier and the black phosphorus surface are only bonded by weak van der Waals forces and hydrogen bonds. The bonding force is extremely weak. Under actual application conditions such as solvent dilution, high temperature, and high shear, the modifier is very easy to desorb from the black phosphorus surface, resulting in the failure of the modification effect and failing to meet the requirements of long-term service.

[0007] (4) Limited selection of modifiers: Traditional modifiers used for black phosphorus modification, such as citric acid and tartaric acid, are small molecule organic acids. Their binding force with the surface of black phosphorus is mainly physical adsorption or weak coordination. They are difficult to form stable covalent bonds with phosphorus atoms on the surface of black phosphorus. They cannot fundamentally solve the core problems of black phosphorus's easy agglomeration, easy oxidation, and poor interfacial compatibility. At the same time, the modifiers have poor structural tunability and cannot adapt to the personalized needs of different solvent systems and different application scenarios. Summary of the Invention

[0008] This invention is based on the inventor's discovery and understanding of the following facts and problems: current black phosphorus nanosheets have defects such as poor oil solubility, insufficient dispersion stability, and limited physical adsorption modification effect.

[0009] This invention aims to at least partially solve one of the technical problems in related technologies. To this end, embodiments of this invention propose an organophosphonic acid-modified black phosphorus nanosheet, its preparation method, and its applications. A solvothermal synthesis process is used to enable organophosphonic acid molecules to form a strong covalent bond with phosphorus atoms on the surface of black phosphorus through PO bonds. Simultaneously, by regulating the molecular structure of the organophosphonic acid, it can precisely adapt to the dispersion requirements of different solvent systems, significantly improving the dispersion stability, environmental stability, and oil / water solubility of the black phosphorus nanosheets, thus expanding its applications in multiple fields such as lubrication, optoelectronics, and energy storage.

[0010] This invention provides a method for preparing organophosphonic acid-modified black phosphorus nanosheets, comprising the following steps: (1) Disperse black phosphorus powder in a first solvent to obtain a black phosphorus dispersion; then perform ultrasonic exfoliation on the black phosphorus dispersion to obtain black phosphorus nanosheets; (2) The black phosphorus nanosheets and organophosphonic acid are dispersed in a second solvent to obtain a black phosphorus nanosheet dispersion; the black phosphorus nanosheet dispersion is subjected to a solvothermal reaction to obtain organophosphonic acid modified black phosphorus nanosheets.

[0011] In some embodiments, in step (1), the particle size of the black phosphorus powder is less than 100 μm; And / or, the concentration of the black phosphorus dispersion is 1-5 mg / mL.

[0012] In some embodiments, in step (1), the power of the ultrasonic ablation is 200-500 W; And / or, the ultrasonic ablation time is 1-4 h; And / or, the temperature of the ultrasonic ablation is 0-5°C.

[0013] In some embodiments, in step (2), the organophosphonic acid includes at least one of phenylphosphonic acid, phytic acid, methylphosphonic acid, propylphosphonic acid, n-dodecylphosphonic acid, and n-octadecylphosphonic acid.

[0014] In some embodiments, in step (2), the mass ratio of the black phosphorus nanosheets to the organophosphonic acid is 1:0.5-5; And / or, the second solvent includes at least one of n-hexane, ethanol, and water; And / or, the concentration of the black phosphorus nanosheet dispersion is 1-10 mg / mL.

[0015] In some embodiments, in step (2), the temperature of the solvothermal reaction is 120-200°C; And / or, the solvothermal reaction time is 6-24 h.

[0016] In some embodiments, in step (1), the blocky black phosphorus crystals are ground and sieved to obtain black phosphorus powder.

[0017] This invention provides an organophosphonic acid-modified black phosphorus nanosheet, which is prepared using the method described in this invention.

[0018] In some embodiments, the thickness of the organophosphonic acid modified black phosphorus nanosheets is 5-50 nm; And / or, the lateral dimensions of the organophosphonic acid modified black phosphorus nanosheets are 300-1500 nm; And / or, the PO bond grafting rate of the organophosphonic acid modified black phosphorus nanosheets is 5-20%.

[0019] This invention provides an application of organophosphonic acid-modified black phosphorus nanosheets for use as lubricating additives, optoelectronic materials, and energy storage electrode materials.

[0020] The organophosphonic acid-modified black phosphorus nanosheets and their preparation method provided by this invention employ a solvothermal synthesis process to enable organophosphonic acid molecules to form a strong covalent bond with phosphorus atoms on the surface of black phosphorus through PO bonds. This constructs a stable covalently modified structure on the surface of the black phosphorus nanosheets, fundamentally solving the problems of easy aggregation, easy oxidation, and poor interfacial compatibility of black phosphorus nanosheets. Furthermore, by regulating the molecular structure of organophosphonic acid, it is possible to precisely adapt to the dispersion requirements of different solvent systems, significantly improving the dispersion stability, environmental stability, and oil / water solubility of black phosphorus nanosheets, thus expanding their application boundaries in multiple fields such as lubrication, optoelectronics, and energy storage. Specifically: (1) Constructing a stable PO covalent bond structure: Through solvothermal reaction, the phosphate group (-PO3H2) in the organophosphonic acid molecule undergoes a dehydration condensation reaction with the phosphorus atoms on the surface of black phosphorus to form a stable POP covalent bond. The bond energy of the POP covalent bond is as high as about 360 kJ / mol, and the covalent bond binding force is stronger than that of traditional physical adsorption, weak coordination modification, and hydrogen bonding. The modified layer is firmly bonded to the black phosphorus substrate. Under complex working conditions such as high temperature, high shear, and solvent dilution, the modifier is not easy to desorb, and the modification effect is stable for a long time, which fundamentally solves the problem of easy desorption of the modifier. At the same time, the dense covalent modification layer can effectively isolate external oxygen and moisture, fundamentally inhibiting the oxidative degradation of black phosphorus.

[0021] (2) The molecular structure of organophosphonic acid is adjustable, enabling precise control of interfacial properties and wide adaptability: The alkyl chain length of organophosphonic acid can be flexibly selected from C1 (methylphosphonic acid) to C18 (n-octadecylphosphonic acid). By selecting organophosphonic acid with different chain lengths (C1-C18), the lipophilic / hydrophilic balance of organophosphonic acid modified black phosphorus nanosheets can be directionally controlled. Short-chain organophosphonic acid modification can achieve excellent water solubility, while long-chain organophosphonic acid (e.g., n-dodecylphosphonic acid, n-octadecylphosphonic acid) modification can achieve excellent oil solubility. According to the solvent characteristics of the application scenario, the lipophilicity and hydrophilicity of modified black phosphorus nanosheets can be precisely controlled, which can flexibly adapt to the application requirements of different solvent systems such as water-based and oil-based. For example, it can be adapted to polar systems such as water-based lubrication and aqueous synthesis, as well as non-polar oil-based systems such as high-end lubricating oil and oil-based optoelectronic processing. The application adaptability is extremely strong, breaking through the limitation of single adaptability of traditional modification methods.

[0022] (3) Ice bath ultrasonic exfoliation can counteract the heat generated by ultrasound in a low-temperature environment, inhibit the thermal oxidation of black phosphorus and the generation of by-products, and obtain few-layer black phosphorus nanosheets with complete structure and sufficient intrinsic phosphorus atom active sites on the surface. This pre-process not only provides sufficient active sites for subsequent organophosphonic acid solvothermal modification, ensuring the grafting rate of PO bonds and the uniform modification effect of the entire surface, but also reduces the competition of oxidative impurities for reaction sites and improves the efficiency of modification reaction. The two form a process synergy of "front-end activity preservation and loss control - back-end covalent sealing", which together ensures the excellent dispersion stability and environmental stability of modified black phosphorus nanosheets.

[0023] (4) Using solvothermal method to achieve efficient covalent modification: The surface of black phosphorus is modified by solvothermal synthesis process. The high temperature and high pressure environment under solvothermal conditions can provide sufficient reaction activation energy, which greatly promotes the chemical reaction between organophosphonic acid and black phosphorus surface, improves grafting efficiency and grafting uniformity. At the same time, the process is simple to operate, the reaction conditions are mild and controllable, and the batch stability is good, which is suitable for large-scale industrial production.

[0024] (5) Achieving synergistic multi-point anchoring of polyphosphate groups: This invention can use organic phosphonic acids containing multiple phosphate groups, such as phytic acid, as modifiers. A single molecule can form covalent bonds with multiple phosphorus atoms on the surface of black phosphorus through multiple phosphate groups, thereby achieving multi-point anchoring modification, further improving the bonding stability and structural compactness of the modified layer. At the same time, multi-point anchoring can form a more complete protective layer, which greatly improves the antioxidant performance and environmental stability of black phosphorus.

[0025] (6) The process is simple and controllable, suitable for large-scale production: The ultrasonic and solvothermal modification processes are easy to operate, the reaction conditions are mild and controllable, no complex equipment or harsh reaction environment is required, the batch stability is good, the raw materials are readily available, the production cost is controllable, and it has the conditions for large-scale industrial production.

[0026] (7) Multifunctional application scenarios: Depending on the type of organophosphonic acid, the modified black phosphorus nanosheets can be adapted to multiple fields such as oil-based lubrication, water-based lubrication, metal corrosion inhibition, heavy oil viscosity reduction, and optoelectronic materials. They can be used as functional additives to improve performance, or as core functional materials to prepare optoelectronic devices, and have extremely strong industrial application value. Attached Figure Description

[0027] Figure 1 This is a transmission electron microscope (TEM) image of the octadecylphosphonic acid-modified black phosphorus nanosheets from Example 1. Detailed Implementation

[0028] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0029] An embodiment of the present invention provides a method for preparing organophosphonic acid-modified black phosphorus nanosheets, comprising the following steps: (1) Disperse black phosphorus powder in a first solvent to obtain a black phosphorus dispersion; then perform ultrasonic exfoliation on the black phosphorus dispersion to obtain black phosphorus nanosheets; (2) The black phosphorus nanosheets and organophosphonic acid are dispersed in a second solvent to obtain a black phosphorus nanosheet dispersion; the black phosphorus nanosheet dispersion is subjected to a solvothermal reaction to obtain organophosphonic acid modified black phosphorus nanosheets.

[0030] Preparation method of organophosphonic acid modified black phosphorus nanosheets according to embodiments of the present invention: (1) PO covalent bond formation mechanism: Under solvothermal high temperature and high pressure reaction conditions, the phosphate group (-PO3H2) in the organophosphonic acid molecule undergoes a dehydration condensation reaction with the phosphorus atoms on the surface of black phosphorus. The phosphorus atoms on the surface of black phosphorus have lone pairs of electrons, which can nucleophilically attack the P=O bond in the phosphate group, remove one molecule of water, and form a stable POP covalent bond, thus achieving a firm anchoring of the organophosphonic acid molecule on the surface of black phosphorus.

[0031] (2) Solvothermal reaction-promoting mechanism: The high temperature and closed high pressure environment under solvothermal conditions can provide sufficient activation energy for the reaction system, effectively breaking the energy barrier between phosphate groups and black phosphorus atoms, greatly promoting the dehydration condensation chemical reaction between the two, and improving the reaction efficiency and grafting rate. At the same time, the solvothermal environment can enable organophosphonic acid molecules to achieve uniform molecular-level dispersion in the solvent, which is conducive to their uniform adsorption and reaction on the surface of black phosphorus nanosheets, achieving uniform modification of the entire surface, and avoiding the problems of uneven grafting, low grafting rate and poor performance in room temperature reaction.

[0032] (3) Alkyl chain orientation mechanism: After the organophosphonic acid molecule is anchored to the surface of black phosphorus through the phosphate group at the head, the alkyl chain (R-) at the tail is oriented outward. Long-chain alkyl (C12-C18) has strong compatibility with non-polar oil-based media, which can give black phosphorus excellent oil solubility; short-chain alkyl (C1-C3) is more polar, which can make the modified black phosphorus maintain good hydrophilicity, thus achieving a precise interface modification effect of "head anchoring and tail regulation".

[0033] (4) Dispersion stability improvement mechanism: Steric hindrance effect: The organophosphonic acid molecules grafted onto the surface of black phosphorus can form a dense organic protective layer on the surface of the nanosheets, generating a strong steric hindrance effect, which effectively prevents the aggregation and stacking of black phosphorus nanosheets due to van der Waals forces, thus ensuring the dispersion stability of the nanomaterials from a structural perspective. Solvent compatibility effect: The outward-arranged alkyl chains can form good solvation with the corresponding solvent, which greatly improves the interfacial compatibility between black phosphorus nanosheets and solvents, reduces interfacial energy, further inhibits the aggregation and sedimentation of nanosheets, and achieves long-term stable dispersion. Chemical stability enhancement effect: The dense modification layer formed by POP covalent bonds can effectively isolate oxygen and moisture in the external environment from contact with the intrinsic structure of black phosphorus, inhibit the oxidative degradation reaction of black phosphorus, greatly improve the environmental stability of black phosphorus, and avoid the problems of nanosheet structure damage, performance degradation and agglomeration caused by oxidation.

[0034] In some embodiments, in step (1), the blocky black phosphorus crystals are ground and sieved to obtain black phosphorus powder; Optionally, the grinding is carried out under an inert atmosphere; the inert atmosphere includes at least one of argon or nitrogen; the grinding is carried out in an inert atmosphere glove box; the grinding is carried out in a mortar, optionally an agate mortar; the grinding time is 15-30 min, specifically, for example, 15 min, 20 min, 25 min, 30 min; the blocky black phosphorus crystals are ground to obtain coarse black phosphorus powder; Optionally, the black phosphorus coarse powder obtained by grinding is sieved through a standard sieve to collect black phosphorus powder with a particle size of less than 100 μm. Optionally, after sieving, the sample is sealed and stored in an inert atmosphere to prevent oxidation and failure; the inert atmosphere includes at least one of argon or nitrogen.

[0035] In some embodiments, in step (1), the particle size of the black phosphorus powder is less than 100 μm.

[0036] In some embodiments, in step (1), the first solvent comprises N-methylpyrrolidone (NMP).

[0037] In some embodiments, in step (1), the dispersion process involves shaking and oscillating.

[0038] In some embodiments, in step (1), the concentration of the black phosphorus dispersion is 1-5 mg / mL, specifically, for example, 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL. This embodiment of the invention further facilitates the ultrasonic exfoliation and organophosphonic acid modification of black phosphorus.

[0039] In some embodiments, in step (1), the black phosphorus dispersion is ultrasonically exfoliated to obtain black phosphorus nanosheets; Optionally, the ultrasound is performed using an ultrasonic cell disruptor; Optionally, the power of the ultrasonic ablation is 200-500 W, specifically, for example, 200 W, 300 W, 400 W, 500 W, preferably 300-400 W; Optionally, the ultrasonic stripping time is 1-4 hours, specifically, for example, 1 hour, 2 hours, 3 hours, and 4 hours; the ultrasonic process is started and stopped intermittently to avoid the oxidation of black phosphorus caused by the increase in system temperature; Optionally, the ultrasonic ablation is performed under constant temperature conditions in an ice-water bath; the temperature of the ultrasonic ablation is 0-5℃, specifically, for example, 0℃, 1℃, 2℃, 3℃, 4℃, 5℃; Optionally, the ultrasonic ablation is performed under inert gas protection conditions; the inert atmosphere includes at least one of argon or nitrogen.

[0040] In this invention, ultrasonic exfoliation utilizes cavitation to break the van der Waals forces between black phosphorus layers, efficiently preparing few-layer black phosphorus nanosheets with intact structures and sufficient specific surface area. This provides ample surface reaction sites for subsequent covalent modification with organophosphonic acids. Furthermore, this wet process is easily integrated with subsequent solvothermal modification steps, adapting to the needs of large-scale production. However, excessively high system temperatures accelerate the oxidation and deactivation of black phosphorus, damage the layer structure, and induce solvent decomposition, introducing impurities and directly reducing the PO bond grafting rate and modification effect in subsequent modifications. Conversely, insufficient ultrasonic power or duration leads to inadequate exfoliation and insufficient yield of few-layer nanosheets; excessively high power or excessively long duration causes excessive layer breakage, a surge in defects, and exacerbates the risk of heat generation and oxidation, while also increasing energy consumption and production costs.

[0041] In some embodiments, after ultrasonic exfoliation, centrifugation, washing, and drying are performed to obtain black phosphorus nanosheets; Optionally, the centrifugation includes first centrifuging at low speed to remove large particles of precipitate, and then centrifuging at high speed to collect the precipitate; specifically, the dispersion after ultrasonic stripping is centrifuged at low speed of 3000-5000 rpm for 5-10 min to remove large particles of black phosphorus precipitate that are not completely stripped, and the upper dispersion is retained; the upper dispersion (supernatant) obtained by the above centrifugation is centrifuged at high speed of 10000-15000 rpm for 10-20 min, and after centrifugation, the supernatant is removed and the bottom precipitate is collected; Optionally, the precipitate is washed three times with anhydrous ethanol; specifically, for example, the collected precipitate is washed and centrifuged with anhydrous ethanol, and the washing is repeated three times to remove residual NMP solvent. Optionally, the washed product is placed in a vacuum drying oven for thorough drying to obtain few-layer black phosphorus nanosheet powder; Optionally, the entire process of centrifugation, washing, and drying is carried out under an inert atmosphere to prevent oxidation.

[0042] In some embodiments, in step (2), the organophosphonic acid includes at least one of phenylphosphonic acid, phytic acid, methylphosphonic acid, propylphosphonic acid, n-dodecylphosphonic acid, and n-octadecylphosphonic acid; wherein the organophosphonic acid includes at least one of water-soluble modified phosphonic acid and oil-soluble modified phosphonic acid; the water-soluble modified phosphonic acid includes at least one of phytic acid, methylphosphonic acid, and propylphosphonic acid; and the oil-soluble modified phosphonic acid includes at least one of phenylphosphonic acid, n-dodecylphosphonic acid, and n-octadecylphosphonic acid.

[0043] In this invention, organophosphonic acids are a class of organic compounds containing P(O)(OH)2 or RP(O)(OH)2 structures, commonly including phenylphosphonic acid, phytic acid, methylphosphonic acid, propylphosphonic acid, n-dodecylphosphonic acid, and n-octadecylphosphonic acid. The phosphate groups in organophosphonic acid molecules possess extremely strong coordination ability, forming stable chemical bonds with various metal and non-metal surfaces. They have a mature application foundation in material surface modification, metal corrosion inhibition, and interface modification. Their molecular structures are highly designable; by adjusting the alkyl chain length and the number of functional groups, the interfacial properties of the modified material can be precisely controlled. Specifically, this invention uses phytic acid-modified black phosphorus nanosheets, which simultaneously possess excellent hydrophilicity, aqueous dispersion stability, and strong metal coordination ability. They can be used as a water-based lubricant additive or as a metal corrosion inhibitor to achieve long-term protection, realizing multifunctional applications of a single material and expanding the application boundaries of black phosphorus nanosheets. Using n-dodecylphosphonic acid and n-octadecylphosphonic acid to modify black phosphorus nanosheets provides excellent oil solubility. The present invention allows for the selection of suitable organophosphonic acids based on application requirements, such as the polarity of the target solvent system and the needs of the application scenario.

[0044] In some embodiments, in step (2), the mass ratio of the black phosphorus nanosheets to the organophosphonic acid is 1:0.5-5, specifically, for example, 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, preferably 1:1-3.

[0045] In this embodiment of the invention, the mass ratio of black phosphorus nanosheets to organophosphonic acid is 1:0.5-5, which is beneficial to further improve the dispersibility and stability of organophosphonic acid modified black phosphorus nanosheets.

[0046] In some embodiments, in step (2), the second solvent includes at least one of n-hexane, ethanol, and water; optionally, the second solvent includes a hexane / ethanol mixed solvent, for example, a hexane to ethanol volume ratio of 1:10; the second solvent includes an ethanol / water mixed solvent, for example, an ethanol to water volume ratio of 1:5; in specific embodiments, the second solvent used in the preparation of octadecylphosphonic acid modified black phosphorus nanosheets and dodecylphosphonic acid modified black phosphorus is a hexane / ethanol mixed solvent (volume ratio 1:10); the second solvent used in the preparation of phytic acid modified black phosphorus nanosheets is an ethanol / water mixed solvent (volume ratio 1:5).

[0047] In this embodiment of the invention, the second solvent combination is flexible and can be adapted to organophosphonic acids of different polarities, ensuring that the modifier is fully dissolved and dispersed; it enables black phosphorus nanosheets to be uniformly dispersed at a suitable concentration, improving grafting uniformity and grafting rate; the solvent properties are stable, adaptable to solvothermal reaction conditions and do not cause side reactions, while being easy to remove and leaving no residue, with controllable cost, and suitable for large-scale production.

[0048] In some embodiments, in step (2), the black phosphorus nanosheets and organophosphonic acid are dispersed in a second solvent to obtain a black phosphorus nanosheet dispersion; optionally, the concentration of the black phosphorus nanosheet dispersion is 1-10 mg / mL, specifically, for example, 1 mg / mL, 3 mg / mL, 5 mg / mL, 8 mg / mL, 10 mg / mL, preferably 3-5 mg / mL.

[0049] In some embodiments, in step (2), the dispersion process involves stirring and ultrasonic dispersion to achieve uniformity.

[0050] In some embodiments, in step (2), the black phosphorus nanosheet dispersion is subjected to a solvothermal reaction to obtain organophosphonic acid modified black phosphorus nanosheets; Optionally, the temperature of the solvothermal reaction is 120-200°C, specifically, for example, 120°C, 150°C, 180°C, 200°C, preferably 150-180°C; Optionally, the solvothermal reaction time is 6-24 h, specifically, for example, 6 h, 10 h, 12 h, 16 h, 18 h, 20 h, 24 h, preferably 10-16 h; Optionally, the solvothermal reaction is carried out under an inert gas atmosphere; the inert atmosphere includes at least one of argon or nitrogen. Optionally, the solvothermal reaction is carried out in a solvothermal reactor, specifically a stainless steel solvothermal reactor; specifically, the uniformly dispersed black phosphorus nanosheet dispersion is transferred to a stainless steel solvothermal reactor lined with polytetrafluoroethylene, sealed tightly to ensure no leakage during the reaction process, and then the sealed reactor is placed in a constant temperature forced-air oven to carry out the solvothermal reaction. Optionally, the solvothermal reaction is allowed to cool naturally to room temperature. Specifically, after the solvothermal reaction is completed, the oven is closed, and the reactor is allowed to cool naturally to room temperature inside the oven to avoid damage to the reactor lining caused by sudden cooling. Then, the product mixture inside the reactor is removed.

[0051] In some embodiments, in step (2), the product after the solvothermal reaction is centrifuged, washed and dried to obtain organophosphonic acid modified black phosphorus nanosheets. Optionally, the product mixture after the solvothermal reaction is centrifuged at a speed of 8000-12000 rpm to remove the supernatant and collect the bottom modified product precipitate; Optionally, the product precipitate is washed and centrifuged alternately with n-hexane and anhydrous ethanol, with each solvent being used to wash three times to fully remove unreacted free organophosphonic acid, residual solvent and other impurities. Optionally, the washed and purified product is placed in a vacuum drying oven at 50-70℃ and dried for 8-12 h to fully remove residual solvent, and finally, highly dispersed and stable black phosphorus nanomaterials with organophosphonic acid covalent modification are obtained. Optionally, the product can be sealed and stored in an inert atmosphere away from light.

[0052] An organophosphonic acid-modified black phosphorus nanosheet of this invention is prepared using the preparation method described in this invention.

[0053] In some embodiments, the thickness of the organophosphonic acid-modified black phosphorus nanosheets is 5-50 nm, specifically, for example, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, preferably 10-30 nm; the lateral dimension of the organophosphonic acid-modified black phosphorus nanosheets is 300-1500 nm, specifically, for example, 300 nm, 500 nm, 800 nm, 1000 nm, 1200 nm, 1500 nm; the lateral dimension refers to the scale perpendicular to the thickness direction. In these embodiments of the invention, it is beneficial to further improve the dispersibility and stability of the organophosphonic acid-modified black phosphorus nanosheets.

[0054] In some embodiments, the PO bond grafting rate of the organophosphonic acid modified black phosphorus nanosheets is 5-20%, specifically 5%, 8%, 10%, 12%, 15%, 20%, for example, preferably 10-15%. The PO bond grafting rate of this invention refers to the molar percentage of the number of phosphorus atoms on the surface of the organophosphonic acid modified black phosphorus nanosheets that participate in the formation of PO covalent bonds (specifically, in this invention, it specifically refers to the POP bridging covalent bonds formed by the dehydration condensation of phosphorus atoms on the black phosphorus surface and organophosphonic acid molecules), relative to the total number of phosphorus atoms on the black phosphorus surface. It is used to quantitatively characterize the degree of covalent modification of phosphorus atoms on the surface of the organophosphonic acid modified black phosphorus nanosheets by organophosphonic acid.

[0055] In this embodiment of the invention, the PO bond grafting rate is 5-20%, which is beneficial for further improving the dispersibility and stability of organophosphonic acid modified black phosphorus nanosheets. Grafting at room temperature results in uneven grafting, low grafting rate, and poor performance. A low grafting rate makes it difficult to form a dense covalent modification layer, and the steric hindrance and oxygen / water isolation effects are insufficient, limiting improvements in dispersion stability, antioxidant properties, and solvent compatibility. Uneven grafting causes localized exposure of the sheets, making them prone to premature agglomeration and oxidation, leading to large batch-to-batch performance fluctuations. Under complex operating conditions, the modification effect is prone to rapid failure, resulting in poor service life.

[0056] An application of organophosphonic acid-modified black phosphorus nanosheets according to an embodiment of the present invention is used in lubricating additives, optoelectronic materials, and energy storage electrode materials.

[0057] In some embodiments, it is used for oil-based lubrication, water-based lubrication, and optoelectronic materials.

[0058] In some embodiments, it is used for lubricating oil.

[0059] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0060] Example 1: A method for preparing octadecylphosphonic acid-modified black phosphorus nanosheets (oil-soluble optimized) includes the following steps: (1) Preparation of black phosphorus nanosheets: 1 g of black phosphorus powder with a particle size of less than 100 μm obtained by grinding and sieving was dispersed in 200 mL of N-methylpyrrolidone (NMP) to prepare a dispersion of 5 mg / mL. The dispersion was ultrasonically exfoliated under ice-water bath conditions. The ultrasonic power was set to 300 W and the ultrasonic time was 2 h. The temperature of the system was controlled by intermittent start and stop during the ultrasonic process. After sonication, the dispersion was centrifuged at 4000 rpm for 5 min, the supernatant was collected, and then the supernatant was centrifuged at 12000 rpm for 15 min. The bottom precipitate was collected, washed three times with anhydrous ethanol, and vacuum dried to obtain few-layer black phosphorus nanosheets. The entire process was protected by an inert atmosphere.

[0061] (2) Solvent thermal modification: Weigh 100 mg of the prepared black phosphorus nanosheets and disperse them together with 200 mg of n-octadecylphosphonic acid in 30 mL of n-hexane / ethanol mixed solvent (volume ratio 1:10). The mixture is fully ultrasonically dispersed to obtain a black phosphorus nanosheet dispersion. The black phosphorus nanosheet dispersion is then transferred to a 50 mL stainless steel solvothermal reactor lined with polytetrafluoroethylene. After sealing, the reactor is placed in a constant temperature oven and the solvothermal reaction temperature is set at 160℃. The reaction is maintained at this temperature for 12 h.

[0062] After the solvothermal reaction was completed, the mixture was naturally cooled to room temperature. The product mixture was then removed and centrifuged at 10,000 rpm for 10 min to collect the precipitate. The precipitate was washed three times each with hexane and anhydrous ethanol to thoroughly remove unreacted free organophosphonic acid and impurities. The washed product was then placed in a vacuum drying oven at 60 °C and dried for 10 h to finally obtain highly oil-soluble n-octadecylphosphonic acid modified black phosphorus nanosheets.

[0063] Characterization results of octadecylphosphonic acid modified black phosphorus nanosheets: like Figure 1 As shown, transmission electron microscopy (TEM) characterization revealed that the octadecylphosphonic acid-modified black phosphorus nanosheets retained a complete two-dimensional layered structure without significant structural damage.

[0064] Fourier transform infrared (FTIR) spectroscopy measurements showed that the spectrum was at 1080 cm⁻¹. -1 A distinct POP characteristic peak appears at 2850 cm⁻¹. -1 and 2920 cm -1 The presence of the -CH2- characteristic peak of n-octadecyl group indicates successful grafting of n-octadecylphosphonic acid molecules.

[0065] The X-ray photoelectron spectroscopy (XPS) P 2p spectrum showed a distinct POP bond characteristic peak at 133.1 eV, directly proving the successful formation of covalent bonds.

[0066] Dispersion tests showed that the octadecylphosphonic acid modified black phosphorus nanosheets exhibited dispersion stability in hexane for over 30 days, with no significant precipitation or agglomeration.

[0067] Example 2: Dodecylphosphonic acid modified black phosphorus nanosheets (oil solubility optimized) The preparation method is the same as that in Example 1, except that in step (2), an equal mass of n-dodecylphosphonic acid is used instead of n-octadecylphosphonic acid.

[0068] Performance test results: The prepared dodecylphosphonic acid modified black phosphorus nanosheets exhibited dispersion stability in liquid paraffin for more than 20 days with no obvious agglomeration and sedimentation, and demonstrated excellent dispersion stability and compatibility in general industrial lubricant systems.

[0069] Example 3: Phytic acid-modified black phosphorus nanosheets (water solubility optimized) The preparation method is the same as in Example 1, except that in step (2), phytic acid of equal mass is used to replace octadecylphosphonic acid, and the second solvent, hexane / ethanol mixed solvent, is replaced with an equal volume of ethanol / water mixed solvent (volume ratio 1:5).

[0070] Performance test results: The prepared phytic acid modified black phosphorus nanosheets showed dispersion stability in water for more than 30 days with no obvious agglomeration, and could be stably stored in air for more than 9 days with no obvious oxidative degradation. They also exhibited excellent metal coordination ability and corrosion inhibition performance.

[0071] Table 1 below shows a comparison of the effects of black phosphorus before and after modification in the embodiments of the present invention. The unmodified black phosphorus powder before modification is the black phosphorus powder before ultrasonic exfoliation.

[0072] Table 1 Performance indicators Before improvement (unmodified black phosphorus nanosheets) Improved (organophosphonic acid modified black phosphorus nanosheets) Improvement effect Dispersion stability in n-hexane Precipitation within 12 hours Maintain stable dispersion for more than 30 days Dispersion stability improved by more than 60 times Dispersion stability in liquid paraffin Precipitation within 24 hours Maintain stable dispersion for more than 20 days Dispersion stability improved by more than 20 times Dispersion stability in anhydrous ethanol Precipitation occurred within 48 hours Maintain stable dispersion for more than 30 days Dispersion stability improved by more than 15 times oil-soluble Poor, easy to reunite Excellent (phenylphosphonic acid, C12-C18 phosphonic acid modification) Significantly improved oil solubility Water-soluble Difference Excellent (modified with short-chain phosphonic acid and phytic acid) Significantly improved water solubility air stability Significant oxidation within 24 hours Stable for more than 7 days Stability improved by more than 7 times PO bond grafting rate 0 5-20% Covalent modification successful In this embodiment of the invention, a solvothermal synthesis process is used to enable organophosphonic acid molecules to form a strong covalent bond with phosphorus atoms on the surface of black phosphorus through PO bonds. At the same time, by regulating the molecular structure of organophosphonic acid, it is possible to precisely adapt to the dispersion requirements of different solvent systems, significantly improve the dispersion stability, environmental stability, and oil / water solubility of black phosphorus nanosheets, and expand their applications in multiple fields such as lubrication, optoelectronics, and energy storage.

[0073] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0074] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A method for preparing organophosphonic acid-modified black phosphorus nanosheets, characterized in that, Includes the following steps: (1) Disperse black phosphorus powder in a first solvent to obtain a black phosphorus dispersion; then perform ultrasonic exfoliation on the black phosphorus dispersion to obtain black phosphorus nanosheets; (2) The black phosphorus nanosheets and organophosphonic acid are dispersed in a second solvent to obtain a black phosphorus nanosheet dispersion; the black phosphorus nanosheet dispersion is subjected to a solvothermal reaction to obtain organophosphonic acid modified black phosphorus nanosheets.

2. The method for preparing organophosphonic acid modified black phosphorus nanosheets according to claim 1, characterized in that, In step (1), the particle size of the black phosphorus powder is less than 100 μm; And / or, the concentration of the black phosphorus dispersion is 1-5 mg / mL.

3. The method for preparing organophosphonic acid modified black phosphorus nanosheets according to claim 1, characterized in that, In step (1), the power of the ultrasonic ablation is 200-500 W; And / or, the ultrasonic ablation time is 1-4 h; And / or, the temperature of the ultrasonic ablation is 0-5°C.

4. The method for preparing organophosphonic acid modified black phosphorus nanosheets according to claim 1, characterized in that, In step (2), the organophosphonic acid includes at least one of phenylphosphonic acid, phytic acid, methylphosphonic acid, propylphosphonic acid, n-dodecylphosphonic acid, and n-octadecylphosphonic acid.

5. The method for preparing organophosphonic acid modified black phosphorus nanosheets according to claim 1, characterized in that, In step (2), the mass ratio of black phosphorus nanosheets to organophosphonic acid is 1:0.5-5; And / or, the second solvent includes at least one of n-hexane, ethanol, and water; And / or, the concentration of the black phosphorus nanosheet dispersion is 1-10 mg / mL.

6. The method for preparing organophosphonic acid modified black phosphorus nanosheets according to claim 1, characterized in that, In step (2), the temperature of the solvothermal reaction is 120-200 °C; And / or, the solvothermal reaction time is 6-24 h.

7. The method for preparing organophosphonic acid modified black phosphorus nanosheets according to claim 1, characterized in that, In step (1), the blocky black phosphorus crystals are ground and sieved to obtain black phosphorus powder.

8. An organophosphonic acid-modified black phosphorus nanosheet, characterized in that, It is prepared by any one of claims 1-7.

9. The organophosphonic acid-modified black phosphorus nanosheets according to claim 8, characterized in that, The thickness of the organophosphonic acid modified black phosphorus nanosheets is 5-50 nm; And / or, the lateral dimensions of the organophosphonic acid modified black phosphorus nanosheets are 300-1500 nm; And / or, the PO bond grafting rate of the organophosphonic acid modified black phosphorus nanosheets is 5-20%.

10. An application of the organophosphonic acid-modified black phosphorus nanosheets according to claim 8 or 9, characterized in that, Used in lubricating additives, optoelectronic materials, and energy storage electrode materials.

Images