Two-dimensional red phosphorus nanosheets, preparation thereof, and third-order nonlinear optical modulator comprising the same
High-purity, thin-layer two-dimensional red phosphorus nanosheets were successfully prepared at low temperature using a pyrolysis reaction method assisted by levorotatory ascorbic acid template. This solved the problems of low yield and thick thickness in the existing technology, and enabled the application of two-dimensional red phosphorus nanosheets in nonlinear optical modulators.
Patent Information
- Application Number
- CN202311735335.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-15
- Publication Date
- 2025-11-25
- Estimated Expiration
- 2043-12-15
AI Technical Summary
Existing methods for preparing two-dimensional red phosphorus suffer from problems such as low yield, high energy consumption, or excessive thickness, making it difficult to prepare high-quality two-dimensional red phosphorus nanosheets in large quantities at low temperatures.
Using levoglucosic acid as a solid template, high-purity two-dimensional red phosphorus nanosheets were prepared by dissolving phosphorus halides in a low-boiling-point solvent and removing them under vacuum, followed by a pyrolysis reaction at the interface, combined with appropriate heating conditions and post-processing steps.
Two-dimensional red phosphorus nanosheets with relatively thin thicknesses, ranging from 1.2 to 100 nm, were successfully fabricated at lower temperatures. These nanosheets are suitable for the fabrication of third-order nonlinear optical modulators and exhibit a significant solvent-dependent effect.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of material science and nonlinear optics. More particularly, it relates to a two-dimensional red phosphorus nanosheet, its preparation and a third-order nonlinear optical modulator comprising the same. BACKGROUND
[0002] Since the discovery of graphene in 2004, two-dimensional materials have become a hot research topic. Since then, thousands of two-dimensional materials have been discovered, such as hexagonal boron nitride, graphene, siliconene and boronene, etc. Among them, red phosphorus has attracted more and more attention in many fields due to its excellent optical and chemical properties. Compared with allotrope black phosphorus, commercial amorphous red phosphorus is low in cost and non-toxic, which helps its wide application in large-scale production and practical application, such as flame retardant, semiconductor dopant and biological therapy. More importantly, red phosphorus has strong visible light response and adjustable bandwidth (1.5-2.4 eV), which makes it very suitable for optical modulation. Red phosphorus can be divided into two types: crystalline and amorphous. Amorphous red phosphorus is a chain-like linear polymer, which is arranged disorderly in space through intermolecular forces. When the growth in one direction is limited, it is easy to form a two-dimensional non-laminated material. At present, the preparation methods of red phosphorus reported include soft template method, solvothermal method, pyrolysis method and ultrasonic method, etc. However, the existing public technologies have their own defects, such as low yield of soft template method, high energy consumption of pyrolysis method, and thick thickness of two-dimensional red phosphorus of ultrasonic method, so it is urgent to develop a new synthesis method with high synthesis yield, low reaction temperature and high quality to prepare two-dimensional red phosphorus. SUMMARY
[0003] To solve the above problems, the first object of the present application is to provide a preparation method of two-dimensional red phosphorus nanosheet. The preparation method is simple in operation, short in synthesis period, and can prepare two-dimensional red phosphorus nanosheet with thin sheet thickness in large quantities at low temperature.
[0004] The second object of the present application is to use the two-dimensional red phosphorus nanosheet prepared by the preparation method as described above.
[0005] The third object of the present application is to provide a third-order nonlinear optical modulator.
[0006] In the present application, the interface refers to the position where the coated phosphorus triiodide layer directly contacts with the levorotatory ascorbic acid.
[0007] To achieve the above first object, the present application adopts the following technical scheme:
[0008] The present application discloses a preparation method of two-dimensional red phosphorus nanosheet, comprising the following steps:
[0009] The halogenated phosphorus is dissolved in a low-boiling-point solvent, L-ascorbic acid is added, and after being uniformly mixed, the low-boiling-point solvent is removed by vacuum at 20-50 DEG C to obtain a precursor;
[0010] The precursor is heated under an inert atmosphere to cause a pyrolysis reaction of the precursor at the interface, and after cooling, washing and freeze-drying, a two-dimensional red phosphorus powder is obtained.
[0011] In the present application, L-ascorbic acid is used as a solid template, and first, halogenated phosphorus dissolved in a low-boiling-point solvent is dispersed around the L-ascorbic acid, and after the low-boiling-point solvent is removed by vacuum, the halogenated phosphorus is uniformly coated on the surface of the L-ascorbic acid to obtain a precursor. Then, by taking advantage of the poor thermal stability of the halogenated phosphorus, the precursor is caused to undergo a pyrolysis reaction at the interface by controlling the heating temperature, thereby removing the halogen. The L-ascorbic acid and unreacted halogenated phosphorus or intermediate state are removed by post-treatment, and finally, a two-dimensional red phosphorus nanosheet with high purity is obtained.
[0012] Further, the halogenated phosphorus is selected from phosphorus tribromide and / or phosphorus triiodide, preferably phosphorus triiodide, and other halogenated phosphorus cannot complete pyrolysis below 100 DEG C to achieve the purpose of removing halogen;
[0013] The halogenated phosphorus is added in an amount of 0.1-1 g, and the L-ascorbic acid is added in an amount of 1-20 g.
[0014] Further, the mass ratio of the halogenated phosphorus to the L-ascorbic acid is 1:20-80. For example, the mass ratio of the halogenated phosphorus to the L-ascorbic acid can be 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, etc.
[0015] In the present application, there are two limiting requirements when selecting a suitable low-boiling-point solvent: one is that the boiling point should not be too high, generally below 100 DEG C, and a too high boiling point is not easy to remove by vacuum, thereby being not conducive to obtaining high-purity two-dimensional red phosphorus; the other is that it cannot react with halogenated phosphorus, especially active halogenated phosphorus such as phosphorus triiodide, which can react with ethanol and water. In a specific embodiment, the low-boiling-point solvent is selected from one or more of cyclohexane (boiling point 81 DEG C), n-hexane (boiling point 69 DEG C), n-heptane (boiling point 98.4 DEG C) and petroleum ether (boiling point 40-80 DEG C).
[0016] When the low-boiling-point solvent is removed by vacuum, the removal method can be adjusted by the technician according to the difficulty of removing the low-boiling-point solvent, for example, a period of vacuum can be used, then nitrogen is added, and vacuum is applied again. By this kind of repeated alternating operation, the low-boiling-point solvent vapor can be carried away by nitrogen. The present application does not further limit the specific operation, as long as the low-boiling-point solvent is removed as much as possible.
[0017] Further, the control of the heating condition is also very crucial when heating the precursor, which directly affects the thickness of the final product, if the heating temperature is too high or the heating time is too long, so that the pyrolysis process not only occurs at the interface, but also diffuses to the outer layer of the halogenated phosphorus, which will make the obtained two-dimensional red phosphorus too thick, if the heating temperature is too low or the heating time is too short, so that the pyrolysis at the interface is not completed, which may not be able to obtain qualified two-dimensional red phosphorus. In a specific embodiment, the heating condition is that the heating temperature is 50-90 DEG C, and the heating time is 10-60 min.
[0018] Further, ethanol and deionized water can be used for washing to remove unreacted L-ascorbic acid, unreacted halogenated phosphorus or intermediates, so as to purify the sample.
[0019] To achieve the above-mentioned second object, the application adopts the following technical scheme:
[0020] The application discloses a two-dimensional red phosphorus nanosheet prepared by the preparation method.
[0021] Further, the average thickness of the two-dimensional red phosphorus nanosheet is 1.2-100 nm, and the average size is 50-400 nm.
[0022] To achieve the above-mentioned third object, the application adopts the following technical scheme:
[0023] The application discloses a third-order nonlinear optical modulator, which comprises a dispersion liquid prepared from the two-dimensional red phosphorus nanosheet.
[0024] Further, the third-order nonlinear optical modulator is prepared by the following steps:
[0025] The two-dimensional red phosphorus nanosheet is dispersed in a solvent to obtain a dispersion liquid, and then the dispersion liquid is placed in a cuvette, and the cuvette is placed in a Z scanning light path, so that the nonlinear optical response is exhibited.
[0026] The concentration of the dispersion liquid is 0.001-0.1 mg / ml; for example, the concentration of the dispersion liquid can be 0.001 mg / ml, 0.002 mg / ml, 0.003 mg / ml, 0.004 mg / ml, 0.005 mg / ml, 0.006 mg / ml, 0.007 mg / ml, 0.008 mg / ml, 0.009 mg / ml, 0.01 mg / ml, 0.02 mg / ml, 0.03 mg / ml, 0.04 mg / ml, 0.05 mg / ml, 0.06 mg / ml, 0.07 mg / ml, 0.08 mg / ml, 0.09 mg / ml, 0.1 mg / ml, etc.
[0027] Further, the solvent is selected from one or more of methanol, ethanol, ethylene glycol, 1,2-propanediol, 1,2,3-propanetriol, 1,2,4-butanetriol, dimethyl sulfoxide, acetone, water.
[0028] Further, the cuvette is made of quartz and has a thickness of 1-5mm.
[0029] Further, the beam waist power density of the Z-scan optical path is 0.1-3GW / cm 2 .
[0030] The beneficial effects of the present application are as follows:
[0031] The application discloses a preparation method of two-dimensional red phosphorus nanosheets.
[0032] The application further discloses a third-order nonlinear optical modulator prepared from the obtained two-dimensional red phosphorus nanosheets. BRIEF DESCRIPTION OF DRAWINGS
[0033] The specific embodiments of the application will be further described in detail below with reference to the accompanying drawings.
[0034] Figure 1 A scanning electron microscope image of the two-dimensional red phosphorus in Example 1 is shown.
[0035] Figure 2 A transmission electron microscope image of the two-dimensional red phosphorus in Example 1 is shown.
[0036] Figure 3 An atomic force microscope image of the two-dimensional red phosphorus in Example 1 is shown.
[0037] Figure 4 Open aperture Z-scan curves of the two-dimensional red phosphorus in Example 1 in different dispersion solvents (laser wavelength is 532nm, beam waist power density is 1.132GW / cm 2 ).
[0038] Figure 5 Open aperture Z-scan curves of the two-dimensional red phosphorus prepared in Example 2 in ethanol (laser wavelength is 532nm, beam waist power density is 1.132GW / cm 2 ).
[0039] Figure 6Open aperture Z-scan curve of the two-dimensional red phosphorus prepared in Example 3 in 1,2,3-propanetriol (laser wavelength of 532 nm, beam waist power density of 2.264 GW / cm 2 ) is shown.
[0040] Figure 7 A transmission electron microscope image of the two-dimensional red phosphorus prepared in Comparative Example 1 is shown.
[0041] Figure 8 Open aperture Z-scan curve of the two-dimensional red phosphorus prepared in Comparative Example 2 in ethanol (laser wavelength of 532 nm, beam waist power density of 1.132 GW / cm 2 ) is shown.
[0042] Figure 9 Open aperture Z-scan curve of the commercial two-dimensional black phosphorus described in Comparative Example 3 in 1,2-propanediol (laser wavelength of 532 nm, beam waist power density of 1.132 GW / cm 2 ) is shown. DETAILED DESCRIPTION
[0043] In order to more clearly illustrate the present application, the present application will be further described with reference to the preferred embodiments and accompanying drawings. Like reference numerals in the drawings indicate like elements. It will be understood by those skilled in the art that the specific description given below is merely illustrative and not restrictive, and should not be construed as limiting the scope of the present application.
[0044] Example 1
[0045] Step one, 0.5 g of phosphorus triiodide was fully dissolved in cyclohexane, ready for use.
[0046] Step two, 15 g of L-ascorbic acid and the cyclohexane solution containing phosphorus triiodide obtained in step one were sequentially added to a three-necked flask, and magnetically stirred until mixed evenly.
[0047] Step three, the three-necked flask was evacuated to negative pressure at 25°C, and maintained for a period of negative pressure, then nitrogen was added, and then vacuumed to negative pressure, and the above operation was alternately cycled for 120 min, and cyclohexane was completely removed to obtain a precursor, and then nitrogen was added to restore the three-necked flask to normal pressure.
[0048] Step four, the three-necked flask was heated to 70°C under a nitrogen atmosphere and maintained for 20 min, so that the precursor was pyrolyzed at the interface.
[0049] Step five, after the pyrolysis reaction was completed, it was naturally cooled to room temperature, and the sample was washed and purified by centrifugation using ethanol and deionized water.
[0050] Step six, the target product two-dimensional red phosphorus powder was obtained by freeze-drying.
[0051] Step 7: Take a total of 5 portions of the two-dimensional red phosphorus powder prepared above, each portion containing 0.05 mg. Using an ultrasonic cleaner, disperse the two-dimensional red phosphorus powder in the solution using 3 ml of 1,2-propanediol, 3 ml of 1,2,3-propanetriol, 3 ml of 1,2-propanediol + 3 ml of 1,2,3-propanetriol, 9 ml of 1,2-propanediol + 3 ml of 1,2,3-propanetriol, and 3 ml of 1,2-propanediol + 9 ml of 1,2,3-propanetriol as dispersion solvents to obtain 5 dispersions.
[0052] Step 8: Take a small amount of each of the above 5 dispersions and place them in different cuvettes. Under the ultraviolet-visible-near-infrared absorption spectrometer, adjust their transmittance to 60% at a laser wavelength of 532nm by adding the same dispersion solvent in turn.
[0053] Step 9: Place the cuvettes with the transmittance adjusted in Step 8 onto the translation stage of the Z-scan optical path, and adjust the beam waist power density of the Z-scan optical path to 1.132 GW / cm². 2 That is, its nonlinear optical response is obtained, and the effect is as follows: Figure 4 As shown.
[0054] Figure 1 The scanning electron microscope image of the two-dimensional red phosphorus powder prepared in Example 1 is shown, and it can be found that the sample has a uniform morphology and size.
[0055] Figure 2 The image shown is a transmission electron microscope image of the two-dimensional red phosphorus powder prepared in Example 1. Figure 2 It can be seen that the material has obvious two-dimensional material characteristics.
[0056] Figure 3 An atomic force microscope image of the two-dimensional red phosphorus powder prepared in Example 1 is shown. Figure 3 It can be seen that the material has an average thickness of 1.62 nm and an average size of 112 nm.
[0057] Figure 4 The Z-scan curve of the two-dimensional red phosphorus prepared in Example 1 in the dispersion solvent is shown (laser wavelength 532 nm, beam waist power density 1.132 GW / cm). 2 As can be seen from the figure, by controlling the ratio of 1,2-propanediol and 1,2,3-propanetriol in the dispersion solvent, its switching between saturated and desaturated absorption can be modulated.
[0058] Example 2
[0059] Step 1: Dissolve 0.5g of phosphorus triiodide completely in cyclohexane and set aside.
[0060] Step two, 15g of L-ascorbic acid and the cyclohexane solution containing phosphorus triiodide obtained in step one were added into the three-necked flask in turn, and magnetically stirred until mixed evenly.
[0061] Step three, the three-necked flask was vacuumed to negative pressure at 25°C, and kept for a period of time, then nitrogen was filled in, and vacuumed to negative pressure again, and the above operation was alternately cycled for 120 min, and cyclohexane was completely removed to obtain the precursor, and then nitrogen was filled in to restore the three-necked flask to normal pressure.
[0062] Step four, the three-necked flask was heated to 70°C in a nitrogen atmosphere and kept for 20 min, so that the precursor was pyrolyzed at the interface.
[0063] Step five, after the pyrolysis reaction was completed, it was naturally cooled to room temperature, and the sample was washed and purified by centrifugation with ethanol and deionized water.
[0064] Step six, the target product two-dimensional red phosphorus powder was obtained by freeze-drying.
[0065] Step seven, 0.05mg of the two-dimensional red phosphorus powder prepared above was taken, and an ultrasonic cleaner was used, and 3ml of ethanol was used as a dispersion solvent to disperse the two-dimensional red phosphorus powder therein, to obtain a dispersion liquid.
[0066] Step eight, a small amount of the above dispersion liquid was placed in a cuvette, and the transmittance at a laser wavelength of 532nm was adjusted to 60% under the ultraviolet-visible-near infrared absorption spectrometer by adding ethanol.
[0067] Step nine, the cuvette with adjusted transmittance in step eight was placed on the translation stage of the Z-scan optical path, and the beam waist power density of the Z-scan optical path was adjusted to 1.132GW / cm 2 , and the nonlinear optical response was obtained, and the effect was shown as Figure 5 .
[0068] Figure 5 The open aperture Z-scan curve of the two-dimensional red phosphorus prepared in Example 2 in ethanol (laser wavelength 532nm, beam waist power density 1.132GW / cm 2 ) is shown. It can be found from the figure that the two-dimensional red phosphorus in ethanol shows the characteristics of saturated absorption.
[0069] Example 3
[0070] Step one, 0.5g of phosphorus triiodide was dissolved in cyclohexane.
[0071] Step two, 15g of L-ascorbic acid and the cyclohexane solution containing phosphorus triiodide obtained in step one were added into the three-necked flask in turn, and magnetically stirred until mixed evenly.
[0072] Step three, vacuumize the three-necked flask to negative pressure at 25℃, keep the negative pressure for a period of time, then fill in nitrogen, vacuumize again to negative pressure, and alternate the above operation for 120 minutes, which can completely remove the cyclohexane to obtain the precursor, then fill in nitrogen to restore the three-necked flask to normal pressure.
[0073] Step four, heat the three-necked flask to 70℃ under nitrogen atmosphere and keep for 20 minutes to make the precursor pyrolyze at the interface.
[0074] Step five, after the pyrolysis reaction is completed, cool it to room temperature naturally, and use ethanol and deionized water to centrifugal wash and purify the sample.
[0075] Step six, obtain the target product two-dimensional red phosphorus powder by freeze-drying.
[0076] Step seven, take 0.05mg of the two-dimensional red phosphorus powder prepared above, use an ultrasonic cleaner, and use 3ml of 1,2,3-propanetriol as a dispersion solvent to disperse the two-dimensional red phosphorus powder therein to obtain a dispersion liquid.
[0077] Step eight, take a small amount of the above dispersion liquid and place it in different cuvettes, and use 1,2,3-propanetriol to adjust the transmittance to 60% at a laser wavelength of 532nm under an ultraviolet-visible-near infrared absorption spectrometer.
[0078] Step nine, place the cuvettes with adjusted transmittance in step eight on the translation stage of the Z-scan optical path, and adjust the beam waist power density of the Z-scan optical path to 2.264GW / cm 2 , and obtain its nonlinear optical response, as shown in Figure 6 .
[0079] Figure 6 The open aperture Z-scan curve of the two-dimensional red phosphorus prepared in Example 3 in 1,2,3-propanetriol (laser wavelength 532nm, beam waist power density 2.264GW / cm 2 ) is shown. It can be found from the figure that the two-dimensional red phosphorus in 1,2,3-propanetriol is a reverse saturable absorber, and the modulation depth of the two-dimensional red phosphorus increases when the beam waist power density increases.
[0080] Comparative Example 1
[0081] Step one, dissolve 0.5g of phosphorus triiodide in cyclohexane.
[0082] Step two, add 15g of L-ascorbic acid and the cyclohexane solution containing phosphorus triiodide obtained in step one into the three-necked flask in turn, and stir magnetically until they are uniformly mixed.
[0083] Step three, at 70°C, the three-necked flask is vacuumed to negative pressure, and the negative pressure is maintained for a period of time, then nitrogen is filled, and the above operation is alternately circulated for 120 min, and the cyclohexane can be completely removed to obtain a precursor, then nitrogen is filled to restore the three-necked flask to normal pressure.
[0084] Step four, under the atmosphere of nitrogen, the three-necked flask is heated to 70°C and maintained for 20 min, so that the precursor is pyrolyzed at the interface.
[0085] Step five, after the pyrolysis reaction is completed, it is naturally cooled to room temperature, and the sample is centrifuged, washed and purified with ethanol and deionized water.
[0086] Step six, the target product two-dimensional red phosphorus powder is obtained by freeze-drying.
[0087] Figure 7 The transmission electron microscope image of the two-dimensional red phosphorus prepared in Comparative Example 1 is shown, and from the figure it can be found that due to the too high temperature during the removal of cyclohexane, the reaction occurs in the liquid phase, so that the thickness of the obtained two-dimensional red phosphorus sheet layer is increased.
[0088] Comparative Example 2
[0089] Step one, 0.5g of phosphorus triiodide is fully dissolved in cyclohexane for standby.
[0090] Step two, 15g of L-ascorbic acid and the cyclohexane solution containing phosphorus triiodide obtained in step one are sequentially added to the three-necked flask, and magnetically stirred until mixed evenly.
[0091] Step three, at 25°C, the three-necked flask is vacuumed to negative pressure, and the negative pressure is maintained for a period of time, then nitrogen is filled, and the above operation is alternately circulated for 120 min, and the cyclohexane can be completely removed to obtain a precursor, then nitrogen is filled to restore the three-necked flask to normal pressure.
[0092] Step four, under the atmosphere of nitrogen, the three-necked flask is heated to 70°C and maintained for 20 min, so that the precursor is pyrolyzed at the interface.
[0093] Step five, after the pyrolysis reaction is completed, it is naturally cooled to room temperature, and the sample is centrifuged, washed and purified with ethanol and deionized water.
[0094] Step six, the target product two-dimensional red phosphorus powder is obtained by freeze-drying.
[0095] Step seven, 0.05mg of the two-dimensional red phosphorus powder prepared above is taken, and an ultrasonic cleaner is used, and 3ml of ethanol is used as a dispersion solvent to disperse the two-dimensional red phosphorus powder therein to obtain a dispersion liquid.
[0096] Step eight, take a small amount of the above dispersion liquid in a cuvette, under the ultraviolet visible near infrared absorption spectrometer, using the way of adding ethanol to adjust its transmittance at 532 nm laser wavelength is 100%.
[0097] Step nine, the cuvette adjusted transmittance in step eight is placed on the translation table of Z scan optical path respectively, adjust the beam waist power density of Z scan optical path to 1.132 GW / cm 2 , the nonlinear optical response is obtained, the effect is shown in Figure 8 .
[0098] Figure 8 The open aperture Z scan curve of the two-dimensional red phosphorus prepared in Comparative Example 2 in ethanol (laser wavelength is 532 nm, beam waist power density is 1.132 GW / cm 2 ) is shown, when the transmittance is 100%, the solvent has no nonlinear optical effect under nanosecond laser.
[0099] Comparative Example 3
[0100] Step one: take 0.05 mg of commercial two-dimensional black phosphorus, use an ultrasonic cleaner, use 3 ml of 1,2-propanediol as a dispersion solvent to disperse the two-dimensional black phosphorus therein, and obtain a dispersion liquid.
[0101] Step two: take a small amount of the above dispersion liquid in a cuvette, under the ultraviolet visible near infrared absorption spectrometer, using the way of adding 1,2-propanediol to adjust its transmittance at 532 nm laser wavelength to 60%.
[0102] Step three: the cuvette adjusted transmittance in step two is placed on the translation table of Z scan optical path respectively, adjust the beam waist power density of Z scan optical path to 1.132 GW / cm 2 , the nonlinear optical response is obtained, the effect is shown in Figure 9 .
[0103] Figure 9 The open aperture Z scan curve of the commercial two-dimensional black phosphorus in 1,2-propanediol described in Comparative Example 3 (laser wavelength is 532 nm, beam waist power density is 1.132 GW / cm 2 ) is shown. It can be found that the commercial two-dimensional black phosphorus is not as good as the two-dimensional red phosphorus prepared in the application in terms of modulation depth and initial nonlinear threshold.
[0104] Comparative Example 4
[0105] Step one, dissolve 0.5 g of phosphorus triiodide in cyclohexane.
[0106] Step two, add 1 g of L-ascorbic acid and the cyclohexane solution containing phosphorus triiodide obtained in step one into a three-necked flask in turn, and magnetically stir until mixed uniformly.
[0107] Step three, the three-necked flask is vacuumed to negative pressure at 25°C, and the negative pressure is kept for a period of time, then nitrogen is filled, and the above operation is alternately circulated for 120 min, so that the cyclohexane can be completely removed to obtain a precursor, and then nitrogen is filled to restore the three-necked flask to normal pressure.
[0108] Step four, the three-necked flask is heated to 70°C under a nitrogen atmosphere and kept for 20 min, so that the precursor can be pyrolyzed at the interface.
[0109] Step five, after the pyrolysis reaction is completed, the sample is naturally cooled to room temperature, and centrifugal washing and purification are performed using ethanol and deionized water.
[0110] Step six, the target product two-dimensional red phosphorus powder is obtained by freeze-drying.
[0111] Since the amount of L-ascorbic acid is small, most of the phosphorus triiodide is not at the interface, and the thickness of the prepared two-dimensional red phosphorus sheet layer is relatively thick, which is not suitable for application in the preparation of nonlinear optical modulators.
[0112] Comparative Example 5
[0113] Step one, 0.5 g of phosphorus triiodide is fully dissolved in cyclohexane for standby.
[0114] Step two, 15 g of L-ascorbic acid and the cyclohexane solution containing phosphorus triiodide obtained in step one are sequentially added to the three-necked flask, and magnetic stirring is performed until the mixture is uniform.
[0115] Step three, the three-necked flask is vacuumed to negative pressure at 25°C, and the negative pressure is kept for a period of time, then nitrogen is filled, and the above operation is alternately circulated for 120 min, so that the cyclohexane can be completely removed to obtain a precursor, and then nitrogen is filled to restore the three-necked flask to normal pressure.
[0116] Step four, the three-necked flask is heated to 120°C under a nitrogen atmosphere and kept for 20 min, so that the precursor can be pyrolyzed at the interface.
[0117] Step five, after the pyrolysis reaction is completed, the sample is naturally cooled to room temperature, and centrifugal washing and purification are performed using ethanol and deionized water.
[0118] Step six, the target product two-dimensional red phosphorus powder is obtained by freeze-drying.
[0119] Since the pyrolysis temperature is too high, the phosphorus triiodide at the non-interface position is decomposed, and the thickness of the prepared two-dimensional red phosphorus sheet layer is relatively thick, which is not suitable for application in the preparation of nonlinear optical modulators.
[0120] Obviously, the above embodiments of the present application are merely exemplary for clearly illustrating the present application, and are not intended to limit the implementation modes of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art, and here, all the implementation modes cannot be exhausted, and any obvious changes or variations derived from the technical solutions of the present application are still within the protection scope of the present application.
Claims
1. A method for preparing two-dimensional red phosphorus nanosheets, characterized in that, Includes the following steps: Phosphorus halide is dissolved in a low-boiling-point solvent, levoglucosic acid is added, and after mixing evenly, the low-boiling-point solvent is removed under vacuum at 20-50 °C to obtain the precursor. The precursor was heated under an inert atmosphere to cause a pyrolysis reaction at the interface. After cooling, washing and freeze-drying, two-dimensional red phosphorus powder was obtained. The low-boiling-point solvent is selected from one or more of cyclohexane, n-hexane, n-heptane, and petroleum ether; The mass ratio of the phosphorus halide to L-ascorbic acid is 1:20-80; The heating conditions are a heating temperature of 50-90 ℃ and a heating time of 10-60 min.
2. The preparation method according to claim 1, characterized in that, The phosphorus halide is selected from phosphorus tribromide and / or phosphorus triiodide; The amount of phosphorus halide added is 0.1-1 g; the amount of L-ascorbic acid added is 1-20 g.
3. A two-dimensional red phosphorus nanosheet, characterized in that, It is prepared by the preparation method described in any one of claims 1-2.
4. The two-dimensional red phosphorus nanosheets according to claim 3, characterized in that, The two-dimensional red phosphorus nanosheets have an average thickness of 1.2-100 nm and an average size of 50-400 nm.
5. A third-order nonlinear optical modulator, characterized in that, This includes dispersions prepared using the two-dimensional red phosphorus nanosheets as described in claim 3 or 4.
6. The third-order nonlinear optical modulator according to claim 5, characterized in that, The third-order nonlinear optical modulator is prepared according to the following steps: Two-dimensional red phosphorus nanosheets are dispersed in a solvent to obtain a dispersion, and then the dispersion is placed in a cuvette to obtain the final product. The concentration of the dispersion is 0.001-0.1 mg / ml.
7. The third-order nonlinear optical modulator according to claim 6, characterized in that, The solvent is selected from one or more of methanol, ethanol, ethylene glycol, 1,2-propanediol, 1,2,3-propanetriol, 1,2,4-butanetriol, dimethyl sulfoxide, acetone, and water.