阅读说明：本技术 一种黑磷纳米片及其制备方法与应用 (Black phosphorus nanosheet and preparation method and application thereof ) 是由 陈杰 骆艳华 裴晓东 王凡 汤凤林 朱叶峰 申保金 杨修光 张玲 于 2020-05-27 设计创作，主要内容包括：本发明公开了一种黑磷纳米片及其制备方法与应用,属于功能材料生产技术领域。该方法以黑磷薄片作为电解阳极,与惰性电极、碱性水系电解液共同构建电化学反应体系,其中,所述碱性水系电解液包含溶解有环氧树脂的N-N二甲基甲酰胺溶液。在碱性水系电解液中使制备后的黑磷纳米片结构更趋于稳固、不易破坏、氧化度降低,在碱性条件下,利于提高阳极的黑磷材料的插层剥离效果,使得黑磷剥离更加完全。(The invention discloses a black phosphorus nanosheet and a preparation method and application thereof, and belongs to the technical field of functional material production. The method comprises the steps of taking a black phosphorus sheet as an electrolytic anode, and constructing an electrochemical reaction system together with an inert electrode and an alkaline aqueous electrolyte, wherein the alkaline aqueous electrolyte contains an N-N dimethylformamide solution dissolved with epoxy resin. The prepared black phosphorus nanosheet structure tends to be more stable and stable in alkaline aqueous electrolyte, is not easy to damage, and has reduced oxidation degree, so that the intercalation stripping effect of the black phosphorus material of the anode is improved under the alkaline condition, and the black phosphorus is stripped more completely.)

1. The preparation method of the black phosphorus nanosheet is characterized in that a black phosphorus sheet is used as an electrolytic anode, and an electrochemical reaction system is constructed together with an inert electrode and an alkaline aqueous electrolyte, wherein the alkaline aqueous electrolyte comprises an N-N dimethylformamide solution dissolved with epoxy resin.

2. A method of preparing black phosphorus nanoplatelets according to claim 1 comprising the following specific steps:

s101, selecting electrodes:

taking a black phosphorus sheet as an electrolytic anode; selecting an inert electrode as an electrolytic cathode;

step S102, preparing an alkaline aqueous electrolyte:

1) preparing 0.1-2 mol/L sulfate solution A and 0.1-2 mol/L sulfate solution B, adding an alkaline solution into the sulfate solution B, adjusting the pH value of the sulfate solution B to 8-14, and uniformly mixing to obtain alkaline water system electrolyte C;

2) preparing an N-N dimethylformamide solution in which epoxy resin is dissolved;

step S103, reactive stripping:

in a constant temperature environment of 0-10 ℃, a black phosphorus sheet is taken as an anode, an inert electrode is taken as a cathode, a sulfate solution A is taken as an electrolyte, and the surface current density is controlled to be 200-500 mA/dm under the direct current voltage of 2.5-3.5V²Keeping the temperature for 1-3 h stably; then transferring the anode and the cathode into an alkaline water system electrolyte C, simultaneously adding an N-N dimethylformamide solution dissolved with epoxy resin into the alkaline water system electrolyte C, stabilizing the voltage at 5-10V, keeping the distance between the electrodes unchanged, and controlling the surface current density at 600-900 mA/dm²And continuing electrifying for 0.5-1.5 h to obtain black phosphorus nanosheet precipitate at the bottom of the alkaline aqueous electrolyte C.

3. A preparation method of black phosphorus nanosheet according to claim 2, wherein the epoxy resin is E44 or E51, wherein the mass of the epoxy resin is 0.1-2% of the mass of N-N dimethylformamide.

4. A method of producing a black phosphorus nanosheet according to claim 3, wherein the epoxy resin is present in an amount of 0.5 to 1% by mass of N-N dimethylformamide.

5. A method of producing black phosphorus nanoplate according to claim 2, wherein the volume ratio of the epoxy resin dissolved N-N dimethylformamide solution to the alkaline aqueous electrolyte C is 1: 50-1: 200.

6. a method of producing black phosphorus nanoplate according to claim 2, wherein the volume ratio of the epoxy resin dissolved N-N dimethylformamide solution to the alkaline aqueous electrolyte C is 1: 100-1: 120.

7. a method for preparing black phosphorus nanosheets as recited in claim 2, wherein the black phosphorus flakes are formed from a black phosphorus material that is one or more of a black phosphorus single crystal and a black phosphorus powder by pressing with a tablet press.

8. A method of preparing black phosphorus nanoplatelets according to claim 2 wherein the sulfate is selected from one or more of ammonium sulfate, ammonium bisulfate, sodium sulfate, sodium bisulfate, potassium sulfate, potassium bisulfate.

9. A method of making black phosphorus nanoplatelets according to claim 2 wherein the alkaline solution is ammonia, sodium hydroxide solution or potassium hydroxide solution.

10. A method for producing a black phosphorus nanosheet according to claim 9, wherein the alkaline solution is ammonia, ammonia is added to the sulfate solution B, the pH is adjusted to 8 to 10, and the mixed solution is stirred at uniform speed for 15 to 20 minutes; and carrying out ultrasonic treatment for 1-10 minutes at 15-30 ℃ and 30-60W.

11. A method of making black phosphorus nanoplatelets according to claim 2 wherein the inert electrode is a platinum electrode or a gold electrode or a carbon rod.

12. A method of making black phosphorus nanoplatelets according to claim 2 further comprising the steps of:

step S104, cleaning and extracting

Dissolving the precipitate obtained in the step S103 in an organic solvent, and performing ultrasonic treatment for 20-40 minutes at the room temperature under the power of 30-100W to obtain a solution D; centrifuging the solution D at the speed of 2000-4000 rpm for 20-40 minutes; and (4) carrying out suction filtration and cleaning on the centrifuged supernatant for 5-10 times by using deionized water to obtain a separated solid.

13. A method of preparing black phosphorus nanoplatelets according to claim 12 wherein the organic solvent of step S104 is one or more of N-N dimethylformamide, N methylpyrrolidone, dimethylsulfoxide, isopropanol; the amount of the organic solvent is 1-2 ml/mg of the precipitate obtained by the stripping reaction in the step S103.

14. A method of producing black phosphorus nanoplatelets according to claim 12 wherein the centrifuged bottom precipitate is washed and recovered and can be reused for the anode in the production step S101.

15. A method of making black phosphorus nanoplatelets according to claim 12 further comprising the steps of:

step S105, drying

And (5) drying the solid separated in the step (S104) to obtain the black phosphorus nanosheet.

16. A method of producing black phosphorus nanoplatelets according to claim 15 wherein the drying in step S105 is vacuum drying or freeze drying.

17. A black phosphorus nanosheet prepared by the method of claim 16, wherein the proportion of oxygen relative to the total mass of the black phosphorus nanosheet is no more than 15%, the size of the black phosphorus nanosheet is no less than 1 μm, and the number of layers is no more than 10.

18. Use of the black phosphorus nanoplate of claim 17 in semiconductor materials, biomedical carriers.

Technical Field

The invention belongs to the technical field of functional material production, and particularly relates to a black phosphorus nanosheet and a preparation method thereof.

Background

In recent years, black phosphorus nanosheets (also called black phosphorus nanosheets) having a single-layer or few-layer black phosphorus atomic layer structure have high carrier mobility (200-1000 cm)²V^-1s^-1) Adjustable direct bandgap, large on-off ratio characteristics (10)⁴～10⁵) And anisotropy, etc., are becoming the most promising two-dimensional semiconductor materials for high-performance electronic and optoelectronic devices. The atomic layers of the black phosphorus are also stacked on each other by weak interlayer acting force, and the acting force has the characteristics of van der waals force, so that the mechanical stripping (tape tearing method) is reliable laboratory technology to prepare the high-quality black phosphorus nanosheet with extremely small quantity. The preparation of a large amount of two-dimensional materials can be realized by a chemical stripping method, but the method can introduce defects or generate phase transformation, so that the electrical properties of the two-dimensional materials are reduced, and the method is not suitable for the preparation of high-quality black phosphorus nanosheets. Recently, liquid phase ultrasonic stripping is considered as an effective way to prepare high-quality black phosphorus nanosheets, and the method does not produce intermediate chemical reactions, but has the disadvantage that the stripping effect is limited by the energy of the ultrasonic waves used and the lengthy stripping time. The development of a preparation strategy with high intrinsic degree, high yield and environmental friendliness still faces challenges, and the realization of low-cost large-scale preparation of black phosphorus nanosheets through principle innovation and process technology improvement is still an important research topic in the field of black phosphorus nanosheet materials.

There are many documents reporting methods of black phosphorus nanoplates, such as: the publication No. US20180138039A1 adopts ultraviolet radiation to strip black phosphorus, and obtains black phosphorus nanosheets with fewer layers and lower oxidation degree, but the process is more complicated, and certain damage to human bodies is requiredHigh intensity ultraviolet rays, and thus difficult to industrially scale up. The publication No. CN105236366A adopts liquid phase shearing force generated by a high-speed rotating cutter head to strip black phosphorus crystals to obtain black phosphorus nanosheet dispersion liquid, and finally, the clean black phosphorus nanosheets can be obtained through centrifugation, filtration and cleaning. But the stripping effect is limited due to the process being too crude. Publication No. CN104876199A discloses a method for preparing a few-layer black phosphorus sheet by ultrasonically stripping black phosphorus, wherein black phosphorus powder is intercalated by using an intercalating agent, stripped through ultrasonic water bath treatment after air is isolated, and dried in vacuum to obtain a few-layer black phosphorus sheet material. Among them, the electrochemical stripping method is also a common method, but most of the electrochemical stripping methods use an organic electrolyte due to the characteristic that black phosphorus is easily oxidized in an aqueous solution. Publication No. CN109019540A discloses a method for preparing black phosphorus nanosheets by electrolytic stripping in a high-concentration (0.1-15M) onium cation salt solution, but a plurality of organic solvents with high viscosity are involved in the processing process of the process, so that difficulty is brought to subsequent processing. Publication No. CN104779380A discloses a method for electrochemically preparing phosphenes, which comprises assembling an electrolytic cell with an inert electrode as a positive electrode and phosphorus as a negative electrode, applying a DC or AC voltage between two stages of the electrolytic cell to make the cell be stripped into phosphenes under the action of an electric field, but the cations are mainly intercalated at the negative electrode end, and most of the cations in an aqueous electrolyte are Li⁺、Na⁺The intercalation effect of the small ions is very limited, and the exfoliation intrinsic degree is more difficult to control. Publication No. CN110627028A discloses a method for preparing two-dimensional ultrathin black phosphorus by introducing hydroxyl groups from an organic solvent rich in hydroxyl functional groups, wherein the organic solvent is used for introducing the hydroxyl functional groups on the surface of the black phosphorus so that the black phosphorus stably exists in the air.

In addition, Ambrosi (Angew Chem Int Edit,2017,56,10443) and the like electrolyze black phosphorus crystals in sulfuric acid solution to obtain black phosphorus with high oxidation degree, which does not meet the application requirements of high-end products. Yang (Angew Chem IntEdit,2018,57,4677) and the like reduce the oxidation degree of the black phosphorus nanosheets by means of cathode electrolysis of the black phosphorus crystals, but the size and thickness of the black phosphorus nanosheets cannot be controlled, and the process is difficult to scale up due to the need for expensive organic salt solutions.

In summary, the organic electrolyte has a high cost at present, and is difficult to be industrially scaled up, and the aqueous electrolyte is prepared by using an acidic solution or a neutral electrolyte, so that the black phosphorus prepared by the method has a high oxidation degree, and the application of subsequent high-end products is difficult to meet.

Disclosure of Invention

1. Problems to be solved

Aiming at the problem of high black phosphorus oxidation degree caused by the preparation of the black phosphorus nanosheet in the aqueous electrolyte, the invention provides the preparation method of the black phosphorus nanosheet and the obtained black phosphorus nanosheet, wherein the black phosphorus nanosheet is low in oxygen content, few in layer number and excellent in service performance.

The invention also provides an application of the black phosphorus nanosheet in a two-dimensional semiconductor material.

2. Technical scheme

In order to solve the problems, the technical scheme adopted by the invention is as follows:

the preparation method of the black phosphorus nanosheet provided by the invention is characterized in that a black phosphorus sheet is used as an electrolytic anode, and an electrochemical reaction system is constructed together with an inert electrode and an alkaline aqueous electrolyte, wherein the alkaline aqueous electrolyte contains an N-N dimethylformamide solution dissolved with epoxy resin.

Further, the preparation method of the black phosphorus nanosheet comprises the following specific steps:

step S101, selecting electrodes

Taking a black phosphorus sheet as an electrolytic anode; selecting an inert electrode as an electrolytic cathode;

step S102, preparing an alkaline aqueous electrolyte

1) Preparing 0.1-2 mol/L sulfate solution A and 0.1-2 mol/L sulfate solution B, adding an alkaline solution into the sulfate solution B, adjusting the pH value of the sulfate solution B to 8-14, and uniformly mixing to obtain alkaline water system electrolyte C;

2) preparing an N-N dimethylformamide solution in which epoxy resin is dissolved;

step S103, reactive exfoliation

In a constant temperature environment of 0-10 ℃, a black phosphorus sheet is taken as an anode, an inert electrode is taken as a cathode, a sulfate solution A is taken as an electrolyte, and the surface current density is controlled to be 200-500 mA/dm under the direct current voltage of 2.5-3.5V²Keeping the temperature for 1-3 h stably; then transferring the anode and the cathode into an alkaline water system electrolyte C, simultaneously adding an N-N dimethylformamide solution dissolved with epoxy resin into the alkaline water system electrolyte C, stabilizing the voltage at 5-10V, keeping the distance between the electrodes unchanged, and controlling the surface current density at 600-900 mA/dm²And continuing electrifying for 0.5-1.5 h to obtain black phosphorus nanosheet precipitate at the bottom of the alkaline aqueous electrolyte C.

In one possible embodiment of the invention, the epoxy resin is E44 or E51, wherein the mass ratio of the epoxy resin to the N-N dimethylformamide is 0.1 to 2%, preferably 0.5 to 1%.

In one possible embodiment of the present invention, the volume ratio of the N-N dimethylformamide solution in which the epoxy resin is dissolved to the alkaline aqueous electrolyte C is 1: 50-1: 200, preferably in a volume ratio of 1: 100-1: 120.

in one possible embodiment of the invention, the black phosphorus thin slice is formed by pressing black phosphorus material through a tabletting device, and the black phosphorus material is one or more of black phosphorus single crystal and black phosphorus powder.

In one possible embodiment of the present invention, the sulfate is selected from one or more of ammonium sulfate, ammonium bisulfate, sodium sulfate, sodium bisulfate, potassium sulfate, and potassium bisulfate.

In one possible embodiment of the invention, the alkaline solution is ammonia water, a sodium hydroxide solution or a potassium hydroxide solution, preferably the alkaline solution is ammonia water, the ammonia water is added into the sulfate solution B, the pH value is adjusted to 8-10, and the mixed solution is uniformly stirred for 15-20 minutes; and carrying out ultrasonic treatment for 1-10 minutes at 15-30 ℃ and 30-60W.

In one possible embodiment of the present invention, the inert electrode is a platinum electrode or a gold electrode or a carbon rod.

Furthermore, the preparation method of the black phosphorus nanosheet further comprises the following steps:

step S104, cleaning and extracting

Dissolving the precipitate obtained in the step S103 in an organic solvent, and performing ultrasonic treatment for 20-40 minutes at the room temperature under the power of 30-100W to obtain a solution D; centrifuging the solution D at the speed of 2000-4000 rpm for 20-40 minutes; and (4) carrying out suction filtration and cleaning on the centrifuged supernatant for 5-10 times by using deionized water to obtain a separated solid.

In a possible embodiment of the present invention, the organic solvent in step S104 is one or more of N-N dimethylformamide, N methylpyrrolidone, dimethyl sulfoxide, and isopropanol; the amount of the organic solvent is 1-2 ml/mg of the precipitate obtained by the stripping reaction in the step S103.

In one possible embodiment of the present invention, the centrifuged lower layer precipitate is washed and recovered, and can be reused for preparing the anode in step S101.

Furthermore, the electrochemical preparation method of the black phosphorus nanosheet further comprises the following steps:

step S105, drying

And (5) drying the solid separated in the step (S104) to obtain the black phosphorus nanosheet.

In a possible embodiment of the present invention, the drying manner in step S105 is vacuum drying or freeze drying.

The invention also relates to a black phosphorus nanosheet prepared by any one of the methods, the black phosphorus nanosheet is not an oxidized black phosphorus nanosheet but an intrinsic black phosphorus nanosheet with low oxidation degree, the oxygen content of the black phosphorus nanosheet is low, and the proportion of oxygen element relative to the total mass of the black phosphorus nanosheet is not more than 15%; the prepared black phosphorus nanosheet is large in size and not smaller than 1 mu m; the number of layers is less than 10.

3. Advantageous effects

Compared with the prior art, the invention has the beneficial effects that:

(1) according to the preparation method, the black phosphorus sheet is used as an electrolytic anode, the alkaline water system electrolyte contains an N-N dimethylformamide solution dissolved with epoxy resin, the prepared black phosphorus nanosheet structure tends to be more stable and firm, is not easy to damage and has reduced oxidation degree in the alkaline water system electrolyte, and the intercalation stripping effect of the black phosphorus material of the anode is favorably improved under the alkaline condition, so that the black phosphorus is stripped more completely;

(2) according to the preparation method, the pH adjusting solution adopted by the alkaline water-based electrolyte is ammonia water, so that on one hand, an alkaline atmosphere can be provided; on the other hand, subsequent thorough removal is convenient, and if alkaline reagents such as sodium hydroxide, potassium hydroxide and the like are used, certain residue will be left in subsequent cleaning, so that the purity of the obtained black phosphorus nanosheet is influenced; in the heating evaporation process, ammonia gas is discharged from the black phosphorus layer, and the process can help the black phosphorus to be stripped, so that the layer number of the stripped black phosphorus nanosheets is further reduced;

(3) compared with the current situation that the existing mass-production black phosphorus nanosheet is high in oxidation degree, small in size and large in layer number, the black phosphorus nanosheet obtained by the preparation method disclosed by the invention is not more than 20% in maximum oxygen content, more than 2 microns in average size and less than 10 layers in layer number, and the low-cost large-scale preparation of the high-intrinsic-degree black phosphorus nanosheet is favorably realized through improvement.

Drawings

Fig. 1 is a transmission electron micrograph of black phosphorus nanoplates prepared in example 1;

fig. 2 is an atomic force microscope image of black phosphorus nanoplates prepared in example 1;

fig. 3 is a comparison of raman spectra of the black phosphorus nanoplates prepared in example 1 and the black phosphorus nanoplates prepared by a conventional liquid phase stripping process;

FIG. 4 is a comparison graph of infrared spectra of black phosphorus nanoplates prepared in example 1 and black phosphorus nanoplates prepared by a conventional liquid phase exfoliation process;

fig. 5 is a graph comparing the thickness statistics of black phosphorus nanoplates prepared in example 1 with black phosphorus nanoplates prepared by a conventional liquid phase exfoliation process;

fig. 6 is a graph comparing the statistical size of the black phosphorus nanoplates prepared in example 1 with that prepared by a conventional liquid phase stripping process;

fig. 7 is a graph of an atomic force microscope and X-ray photoelectron spectroscopy P2P of black phosphorus nanoplates prepared at different pH;

FIG. 8 is a transmission electron micrograph of black phosphorus nanoplates prepared according to comparative examples 1-2;

FIG. 9 is an atomic force microscope image of black phosphorus nanoplates prepared at different sonication times with other conditions controlled;

fig. 10 is a transmission electron microscopy image of black phosphorus nanoplates prepared under different ultrasound solvents with other conditions controlled unchanged.

Detailed Description

Exemplary embodiments of the present invention are described in detail below. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be realized and that various changes to the invention may be made without departing from the spirit and scope of the present invention. The following more detailed description of the embodiments of the invention is not intended to limit the scope of the invention, as claimed, but is presented for purposes of illustration only and not limitation to describe the features and characteristics of the invention, to set forth the best mode of carrying out the invention, and to sufficiently enable one skilled in the art to practice the invention. Accordingly, the scope of the invention is to be limited only by the following claims.

The preparation method of the black phosphorus nanosheet comprises the steps of taking a black phosphorus sheet as an electrolytic anode, and constructing an electrochemical reaction system together with an inert electrode and an alkaline aqueous electrolyte, wherein the inert electrode can be a platinum electrode or a gold electrode or a carbon rod, and the alkaline aqueous electrolyte comprises an N-N dimethylformamide solution dissolved with epoxy resin.

Wherein the epoxy resin is E44 or E51, and the mass ratio of the epoxy resin to the N-N dimethylformamide is 0.1-2%, preferably 0.5-1%. The volume ratio of the N-N dimethylformamide solution dissolved with the epoxy resin to the alkaline aqueous electrolyte C is 1: 50-1: 200, preferably in a volume ratio of 1: 100-1: 120. the inventor has proved through a lot of experiments that the addition amount of the epoxy resin is preferably 0.1-2%, and the influence is hardly caused in this range, but the conductivity of the electrolyte is influenced when the addition amount exceeds 2%.

It should be noted that: the black phosphorus electrolytic reaction has short time, the problem of synchronous oxidation and decomposition exists in the electrolytic process, most of products finally obtained by electrolysis are phosphorus oxide and cannot be used for high-end products such as semiconductor materials and the like, in addition, the black phosphorus nanosheet has poor stability, the black phosphorus is easily oxidized in water or air, and the oxidation speed is higher when the number of layers is smaller. Through a large number of experiments, the inventor adds the epoxy resin in the electrolytic process, and the epoxy resin contains epoxy groups, so that the black phosphorus surface has excellent bonding strength, good dielectric property, small set shrinkage, good product dimensional stability, high hardness, good flexibility and stability to alkali and most solvents. The addition of the above-mentioned small amount of epoxy resin to the electrolyte slightly reduces the conductivity of the alkaline aqueous electrolyte, but: on one hand, due to the polymer structure, the black phosphorus can interact with phosphorus on the surface of the black phosphorus, the possibility of direct contact between the black phosphorus and oxygen or hydroxyl free radicals in electrolyte is reduced, chemical reaction is generated, the stripping intercalation effect between the black phosphorus layer and the interlayer is not influenced, and the oxidation and decomposition problems of the black phosphorus in the electrolytic process can be effectively prevented; on the other hand, the epoxy resin has larger molecular volume, so that the interaction between the black phosphorus layers can be weakened to a certain degree in the intercalation process, and the subsequent intercalation is easier to carry out.

The black phosphorus thin slice is formed by pressing a black phosphorus material through tabletting equipment, the thickness of the tabletting is 2-5 mm, and the black phosphorus material is one or more of black phosphorus single crystal and black phosphorus powder.

Wherein the sulfate is selected from one or more of ammonium sulfate, ammonium bisulfate, sodium sulfate, sodium bisulfate, potassium sulfate and potassium bisulfate.

In addition, the alkaline solution is ammonia water, a sodium hydroxide solution or a potassium hydroxide solution, the preferred alkaline solution is ammonia water, the ammonia water is added into the sulfate solution B, the pH value is adjusted to be 8-10, and the mixed solution is uniformly stirred for 15-20 minutes; and carrying out ultrasonic treatment for 1-10 minutes at 15-30 ℃ and 30-60W. Compared with alkaline reagents such as sodium hydroxide, potassium hydroxide and the like, the obtained black phosphorus nanosheet is high in purity; during the heating evaporation process, ammonia gas can be discharged from the black phosphorus layer, and the process can help the black phosphorus to be stripped, so that the layer number of the stripped black phosphorus nanosheets is further reduced.

The experimental procedures used in the following examples are conventional unless otherwise specified.

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.