Nanosheet as well as preparation method and application thereof

Abstract

The invention relates to the technical field of nano materials, and discloses a nanosheet and a preparation method and application thereof, the nanosheet has a core-shell structure, the core structure is indium arsenide, and the shell structure is indium phosphide. The nanosheet obtained by the invention is a wurtzite crystal form nanocrystal with a metastable phase.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and in particular to a nanosheet and a preparation method and application thereof. Background Art

[0002] Nanomaterials refer to materials that have at least one dimension in three-dimensional space at nanometer size or are composed of them as basic units, which is roughly equivalent to the scale of 10-1000 atoms closely packed together.

[0003] Nanomaterials are the bridge between single atoms, molecules and bulk materials, and mainly include zero-dimensional nanomaterials (nanoclusters, nanoparticles), one-dimensional nanomaterials (nanowires, nanorods) and two-dimensional nanomaterials (nanosheets). The microstructure of nanomaterials determines their energy state density, which in turn affects their optical and electrical properties. For example, when the size of semiconductor materials reaches the nanoscale, they have adjustable optical properties.

[0004] Semiconductor nanocrystals have excellent optical and optoelectronic properties and have bright application prospects in the fields of display, lighting, photovoltaics and bioimaging. At present, the most mature semiconductor nanocrystals are Cd-based chalcogenide nanocrystal systems, whose optical properties and crystal structures are highly controllable, but the heavy metal elements they contain limit their actual production applications. III-V nanocrystals are promising luminescent materials that do not contain heavy metal elements (lead / cadmium / mercury). Through the regulation of composition and size, the emission wavelength of III-V nanocrystals can be adjusted from visible light to short-wave infrared. Compared with Cd-based chalcogenide semiconductor nanocrystals, III-V nanocrystals have a smaller dielectric constant and a weaker shielding effect, which is conducive to the effective separation and extraction of charges. In the prior art, III-V nanocrystals directly prepared by molecular precursors are generally stable cubic sphalerite crystal structures, resulting in spherical nanocrystals with no anisotropy in luminescence. Metastable wurtzite III-V nanocrystals have a relatively asymmetric crystal structure and therefore have the potential for anisotropic luminescence. They can also be used as seeds to synthesize anisotropic semiconductor heterostructures. However, the synthesis of metastable wurtzite nanocrystals has been difficult to achieve. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a nanosheet and a preparation method and application thereof. The nanosheet obtained by the present invention is a metastable wurtzite crystal nanocrystal.

[0006] The invention provides a nanosheet. The nanosheet has a core-shell structure, wherein the core structure is indium arsenide (InAs) and the shell structure is indium phosphide (InP).

[0007] Furthermore, the nanosheet has a wurtzite crystal structure.

[0008] The present invention also provides a method for preparing the nanosheet, which comprises: A nanosheet template (Cu3As / Cu3P) with a core-shell structure is prepared, and the nanosheet template is subjected to an ion exchange method to obtain a nanosheet (InAs / InP).

[0009] Furthermore, the method for preparing the nanosheet template having a core-shell structure comprises: Step 1: dissolving cuprous chloride and trioctylphosphine (TOP) in oleylamine (OAm), heating and degassing, heating and reacting under an inert gas, washing, and obtaining an intermediate product, cuprous arsenide (Cu3As) nanocrystals; Step 2: By growing at least one layer of cuprous phosphide shell on the surface of cuprous arsenide nanocrystals, a nanosheet template (Cu3As / Cu3P) with a core-shell structure is obtained.

[0010] Furthermore, in step 1, the molar ratio of cuprous chloride to trioctylphosphine in cuprous chloride is 1:2-1:6, calculated as copper ions.

[0011] Furthermore, in step 1, the molar ratio of cuprous chloride to trioctylphosphine in cuprous chloride is 1:2.5, calculated as copper ions.

[0012] Furthermore, in step 1, the molar concentration of cuprous chloride in oleylamine is 0.6 mmol / 5 mL.

[0013] Furthermore, in step 1, the specific process of heating degassing includes heating to 80° C. and performing vacuum degassing for 1 hour while maintaining the temperature at 80° C.

[0014] Furthermore, in step 1, the specific process of the temperature-raising reaction under the inert gas includes: heating to 150° C. under a nitrogen atmosphere, adding an arsenic precursor solution, maintaining for 2 min-4 min, and cooling to room temperature.

[0015] Furthermore, the preparation method of the arsenic precursor solution includes: adding tri(trimethylsilyl)arsenic to octadecene, wherein the molar concentration of tri(trimethylsilyl)arsenic in octadecene is 0.1 mmol / mL.

[0016] Furthermore, the volume ratio of the arsenic precursor solution to oleylamine is 1:5.

[0017] Furthermore, the room temperature is 16°C-28°C.

[0018] Furthermore, the specific method of washing includes: adding toluene and acetonitrile, and washing by centrifugation three times.

[0019] Furthermore, in step 2, three layers of cuprous phosphide shell are grown on the surface of the cuprous arsenide nanocrystal.

[0020] Furthermore, in step 2, the specific process of growing three layers of cuprous phosphide shell on the surface of cuprous arsenide nanocrystals includes: Step 21: dissolving cuprous chloride and trioctylphosphine in oleylamine and octadecene, heating and degassing, and heating under inert gas; adding a mixed solution of cuprous arsenide nanocrystal solution, octadecene, tri(trimethylsilyl)phosphine, and octylamine to react, mixing evenly, cooling to room temperature, washing three times under inert gas, and dispersing the washed product in n-hexane; Step 22: dissolving cuprous chloride and trioctylphosphine in oleylamine and octadecene, heating and degassing, and heating under inert gas; adding a mixed solution of the product dispersed in n-hexane in step 21, octadecene, tri(trimethylsilyl)phosphine, and octylamine to react, mixing evenly, cooling to room temperature, washing three times under inert gas, and dispersing the washed product in n-hexane; Step 23: dissolving cuprous chloride and trioctylphosphine in oleylamine and octadecene, heating and degassing, and heating under inert gas; adding a mixed solution of the product dispersed in n-hexane in step 22, octadecene, tri(trimethylsilyl)phosphine, and octylamine to react, mixing evenly, cooling to room temperature, washing three times under inert gas, and obtaining a nanosheet template with a core-shell structure after washing.

[0021] Furthermore, in step 21, the molar ratio of cuprous chloride to trioctylphosphine is 1:9.

[0022] Furthermore, in step 21, the volume ratio of oleylamine to octadecene is 4:1.

[0023] Furthermore, in step 21, after cuprous chloride and trioctylphosphine are dissolved in oleylamine and octadecene, the molar concentration of cuprous chloride is 0.3 mmol / 5 mL.

[0024] Furthermore, in step 21, the temperature of heating degassing is 80° C. and the time is 50 min-60 min.

[0025] Furthermore, in step 21, heating under inert gas specifically includes: heating to 180° C. under nitrogen atmosphere.

[0026] Furthermore, in step 21, the molar concentration of the cuprous arsenide nanocrystal solution is 0.04 mmol / mL.

[0027] Furthermore, in step 21, the method for preparing the cuprous arsenide nanocrystal solution includes dispersing the cuprous arsenide nanocrystals in n-hexane.

[0028] Furthermore, in step 21, the volume ratio of the cuprous arsenide nanocrystal solution to octadecene is 7:5.

[0029] Furthermore, in step 21, in the mixed solution, the molar concentration of octylamine is 0.018 mmol / 1.2 mL, and the molar concentration of tris(trimethylsilyl)phosphine is 6 μmol / 1.2 mL.

[0030] Furthermore, the inert atmosphere is nitrogen.

[0031] Furthermore, in step 22, the molar ratio of cuprous chloride to trioctylphosphine is 1:9.

[0032] Furthermore, in step 22, the volume ratio of oleylamine to octadecene is 4:1.

[0033] Furthermore, in step 22, after cuprous chloride and trioctylphosphine are dissolved in oleylamine and octadecene, the molar concentration of cuprous chloride is 0.3 mmol / 5 mL.

[0034] Furthermore, in step 22, the temperature of heating degassing is 80° C. and the time is 50 min-60 min.

[0035] Furthermore, in step 22, heating under inert gas specifically includes: heating to 180° C. under nitrogen atmosphere.

[0036] Furthermore, in step 22, the molar concentration of the product dispersed in n-hexane in step 21 is 0.04 mmol / mL.

[0037] Furthermore, in step 22, the volume ratio of the product dispersed in n-hexane to octadecene is 1:1.

[0038] Furthermore, in step 22, in the mixed solution, the molar concentration of octylamine is 0.026 mmol / mL, and the molar concentration of tris(trimethylsilyl)phosphine is 7.2 μmol / mL.

[0039] Furthermore, in step 23, the molar ratio of cuprous chloride to trioctylphosphine is 1:9.

[0040] Furthermore, in step 23, the volume ratio of oleylamine to octadecene is 4:1.

[0041] Furthermore, in step 23, after cuprous chloride and trioctylphosphine are dissolved in oleylamine and octadecene, the molar concentration of cuprous chloride is 0.3 mmol / 5 mL.

[0042] Furthermore, in step 23, the temperature of heating degassing is 80° C. and the time is 50 min-60 min.

[0043] Furthermore, in step 23, heating under inert gas specifically includes: heating to 180° C. under nitrogen atmosphere.

[0044] Furthermore, in step 23, the molar concentration of the product dispersed in n-hexane in step 22 is 0.028 mmol / mL.

[0045] Furthermore, in step 23, the volume ratio of the product dispersed in n-hexane and octadecene is 1:1.

[0046] Furthermore, in step 23, in the mixed solution, the molar concentration of octylamine is 0.024 mmol / mL, and the molar concentration of tris(trimethylsilyl)phosphine is 8 μmol / mL.

[0047] Furthermore, the step of obtaining the nanosheets by using the ion exchange method on the nanosheet template is as follows: The indium precursor solution is heated under a nitrogen atmosphere, octadecene dispersed with a nanosheet template is added, reacted, cooled to room temperature, and washed.

[0048] Furthermore, the volume ratio of the indium precursor solution to octadecene dispersed with the nanosheet template is 4.75:2.

[0049] Furthermore, the molar concentration of the nanosheet template in octadecene is 0.1 mmol / 2 mL.

[0050] Furthermore, the indium precursor solution was heated to 180° C. under a nitrogen atmosphere.

[0051] Furthermore, the reaction temperature is 180° C., and the reaction time is 40 min-50 min.

[0052] Furthermore, based on the indium element in the indium precursor solution, the molar concentration of the indium precursor solution is 1.2 mmol / 4.75 mL.

[0053] Furthermore, the preparation method of the indium precursor solution includes: mixing indium chloride, trioctylphosphine and octadecene, heating and degassing, continuing to heat in a nitrogen atmosphere for reaction, and cooling to room temperature to obtain an indium precursor solution.

[0054] Furthermore, the volume ratio of trioctylphosphine to octadecene is 11.8:13.2.

[0055] Furthermore, the temperature of the heating degassing is 80°C.

[0056] Furthermore, the nitrogen atmosphere is continuously heated to a reaction temperature of 200° C. and maintained for 2 hours.

[0057] The embodiments of the present invention have the following technical effects: 1. The nanosheets obtained by the method of the present invention have a wurtzite crystal structure. The Cu3As / Cu3P nanocrystals of the nanosheet template are in a relatively asymmetric hexagonal phase, and tend to form copper vacancies inside. These characteristics reduce the kinetic barriers of the exchange reaction and increase the rate of cation exchange. By introducing the In element, the metastable wurtzite InAs / InP core-shell nanocrystals can be successfully synthesized; in addition, in the present invention, since the nanocrystals prepared are wurtzite-structured, the degree of symmetry of the crystal structure is relatively low, and it is easier to form the nanocrystal morphology structure of the present invention. The two-dimensional nanocrystals under this morphology have anisotropic luminescence characteristics, which can not only emit deflected light, but also achieve higher external quantum efficiency.

[0058] 2. In the method of the present invention, by preparing a shell structure grown on the surface of the InAs core structure, the InAs / InP core-shell nanocrystals can achieve an emission wavelength of 1050nm; and by controlling the size of the core structure by the method of the present invention, it can ultimately be determined that the wavelength length of the InAs / InP core-shell nanocrystals emitted is adjustable in the range of 900~1500nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0060] Figure 1 is the test result provided by the embodiment of the present invention, wherein Figure 1 Figure a is a transmission electron microscope characterization image. Figure 1 b in the figure is the energy dispersive X-ray spectroscopy (EDX) element distribution diagram, which are the As element distribution diagram, In element distribution diagram, and P element distribution diagram. Figure 1 c in the figure is the XRD pattern.

[0061] Figure 2 1 is the absorption spectrum and fluorescence spectrum test results of the embodiment of the present invention, wherein the solid line is the absorption spectrum and the dotted line is the fluorescence spectrum. DETAILED DESCRIPTION

[0062] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0063] In a first aspect, some embodiments of the present invention provide a nanosheet having a core-shell structure, wherein the core structure is indium arsenide (InAs) and the shell structure is indium phosphide (InP).

[0064] In some embodiments, the nanosheet has a wurtzite crystal structure.

[0065] In a second aspect, some embodiments of the present invention further provide a method for preparing the nanosheet, the method comprising: A nanosheet template (Cu3As / Cu3P) with a core-shell structure is prepared, and the nanosheet template is subjected to an ion exchange method to obtain a nanosheet (InAs / InP).

[0066] In some embodiments, the method for preparing the nanosheet template having a core-shell structure includes: Step 1: dissolving cuprous chloride and trioctylphosphine (TOP) in oleylamine (OAm), heating and degassing, heating and reacting under an inert gas, washing, and obtaining an intermediate product, cuprous arsenide (Cu3As) nanocrystals; Step 2: By growing at least one layer of cuprous phosphide shell on the surface of cuprous arsenide nanocrystals, a nanosheet template (Cu3As / Cu3P) with a core-shell structure is obtained.

[0067] In the preparation method of the present invention, the wavelength length of the final nanosheet emission can be adjusted by adjusting the size of the core structure. Through the method parameters of the present invention, the final nanosheet emission wavelength can be adjusted within the range of 900nm-1500nm.

[0068] In some embodiments, in step 1, the molar ratio of cuprous chloride to trioctylphosphine is 1:2-1:6, calculated as copper ions in cuprous chloride.

[0069] In some embodiments, in step 1, the molar ratio of cuprous chloride to trioctylphosphine is 1:2.5, calculated as copper ions in cuprous chloride.

[0070] In some embodiments, in step 1, the molar concentration of cuprous chloride in oleylamine is 0.6 mmol / 5 mL.

[0071] In some embodiments, in step 1, the specific process of heating degassing includes heating to 80° C. and performing vacuum degassing for 1 hour while maintaining the temperature at 80° C.

[0072] In some embodiments, in step 1, the specific process of the temperature-raising reaction under the inert gas includes: heating to 150° C. under a nitrogen atmosphere, adding an arsenic precursor solution, maintaining for 2 min-4 min, and cooling to room temperature.

[0073] In some embodiments, the method for preparing the arsenic precursor solution includes: adding tri(trimethylsilyl)arsenic to octadecene, wherein the molar concentration of tri(trimethylsilyl)arsenic in octadecene is 0.1 mmol / mL.

[0074] In some embodiments, the volume ratio of the arsenic precursor solution to oleylamine is 1:5.

[0075] In some embodiments, the room temperature is 16°C-28°C.

[0076] In some embodiments, the specific method of washing includes: adding toluene and acetonitrile, and washing by centrifugation three times.

[0077] In some embodiments, in step 2, three layers of cuprous phosphide shell are grown on the surface of the cuprous arsenide nanocrystal.

[0078] In some embodiments, in step 2, the specific process of growing three layers of cuprous phosphide shell on the surface of cuprous arsenide nanocrystals includes: Step 21: dissolving cuprous chloride and trioctylphosphine in oleylamine and octadecene, heating and degassing, and heating under inert gas; adding a mixed solution of cuprous arsenide nanocrystal solution, octadecene, tri(trimethylsilyl)phosphine, and octylamine to react, mixing evenly, cooling to room temperature, washing three times under inert gas, and dispersing the washed product in n-hexane; Step 22: dissolving cuprous chloride and trioctylphosphine in oleylamine and octadecene, heating and degassing, and heating under inert gas; adding a mixed solution of the product dispersed in n-hexane in step 21, octadecene, tri(trimethylsilyl)phosphine, and octylamine to react, mixing evenly, cooling to room temperature, washing three times under inert gas, and dispersing the washed product in n-hexane; Step 23: dissolving cuprous chloride and trioctylphosphine in oleylamine and octadecene, heating and degassing, and heating under inert gas; adding a mixed solution of the product dispersed in n-hexane in step 22, octadecene, tri(trimethylsilyl)phosphine, and octylamine to react, mixing evenly, cooling to room temperature, washing three times under inert gas, and obtaining a nanosheet template with a core-shell structure after washing.

[0079] In some embodiments, in step 21, the molar ratio of cuprous chloride to trioctylphosphine is 1:9.

[0080] In some embodiments, in step 21, the volume ratio of oleylamine to octadecene is 4:1.

[0081] In some embodiments, in step 21, after cuprous chloride and trioctylphosphine are dissolved in oleylamine and octadecene, the molar concentration of cuprous chloride is 0.3 mmol / 5 mL.

[0082] In some embodiments, in step 21, the temperature of heating degassing is 80° C. and the time is 50 min-60 min.

[0083] In some embodiments, in step 21, heating under inert gas specifically includes: heating to 180° C. under nitrogen atmosphere.

[0084] In some embodiments, in step 21, the molar concentration of the cuprous arsenide nanocrystal solution is 0.04 mmol / mL.

[0085] In some embodiments, in step 21, the method for preparing the cuprous arsenide nanocrystal solution includes dispersing the cuprous arsenide nanocrystals in n-hexane.

[0086] In some embodiments, in step 21, the volume ratio of the cuprous arsenide nanocrystal solution to octadecene is 7:5.

[0087] In some embodiments, in step 21, in the mixed solution, the molar concentration of octylamine is 0.018 mmol / 1.2 mL, and the molar concentration of tris(trimethylsilyl)phosphine is 6 μmol / 1.2 mL.

[0088] In some embodiments, the inert atmosphere is nitrogen.

[0089] In some embodiments, in step 22, the molar ratio of cuprous chloride to trioctylphosphine is 1:9.

[0090] In some embodiments, in step 22, the volume ratio of oleylamine to octadecene is 4:1.

[0091] In some embodiments, in step 22, after cuprous chloride and trioctylphosphine are dissolved in oleylamine and octadecene, the molar concentration of cuprous chloride is 0.3 mmol / 5 mL.

[0092] In some embodiments, in step 22, the temperature of heating degassing is 80° C. and the time is 50 min-60 min.

[0093] In some embodiments, in step 22, heating under inert gas specifically includes: heating to 180° C. under nitrogen atmosphere.

[0094] In some embodiments, in step 22, the molar concentration of the product dispersed in n-hexane in step 21 is 0.04 mmol / mL.

[0095] In some embodiments, in step 22, the volume ratio of the product dispersed in n-hexane to octadecene is 1:1.

[0096] In some embodiments, in step 22, in the mixed solution, the molar concentration of octylamine is 0.026 mmol / mL, and the molar concentration of tris(trimethylsilyl)phosphine is 7.2 μmol / mL.

[0097] In some embodiments, in step 23, the molar ratio of cuprous chloride to trioctylphosphine is 1:9.

[0098] In some embodiments, in step 23, the volume ratio of oleylamine to octadecene is 4:1.

[0099] In some embodiments, in step 23, after cuprous chloride and trioctylphosphine are dissolved in oleylamine and octadecene, the molar concentration of cuprous chloride is 0.3 mmol / 5 mL.

[0100] In some embodiments, in step 23, the temperature of heating degassing is 80° C. and the time is 50 min-60 min.

[0101] In some embodiments, in step 23, heating under inert gas specifically includes: heating to 180° C. under nitrogen atmosphere.

[0102] In some embodiments, in step 23, the molar concentration of the product dispersed in n-hexane in step 22 is 0.028 mmol / mL.

[0103] In some embodiments, in step 23, the volume ratio of the product dispersed in n-hexane to octadecene is 1:1.

[0104] In some embodiments, in step 23, in the mixed solution, the molar concentration of octylamine is 0.024 mmol / mL, and the molar concentration of tris(trimethylsilyl)phosphine is 8 μmol / mL.

[0105] In some embodiments, the step of obtaining the nanosheets by using an ion exchange method on the nanosheet template is as follows: The indium precursor solution is heated under a nitrogen atmosphere, octadecene dispersed with a nanosheet template is added, reacted, cooled to room temperature, and washed.

[0106] In some embodiments, the volume ratio of the indium precursor solution to octadecene dispersed with the nanosheet template is 4.75:2.

[0107] In some embodiments, the molar concentration of the nanosheet template in octadecene is 0.1 mmol / 2 mL.

[0108] In some embodiments, the indium precursor solution is heated to 180° C. in a nitrogen atmosphere.

[0109] In some embodiments, the reaction temperature is 180° C., and the reaction time is 40 min-50 min.

[0110] In some embodiments, the molar concentration of the indium precursor solution is 1.2 mmol / 4.75 mL, calculated based on the indium element in the indium precursor solution.

[0111] In some embodiments, the preparation method of the indium precursor solution includes: mixing indium chloride, trioctylphosphine and octadecene, heating and degassing, continuing to heat in a nitrogen atmosphere for reaction, and cooling to room temperature to obtain an indium precursor solution.

[0112] In some embodiments, the volume ratio of trioctylphosphine to octadecene is 11.8:13.2.

[0113] In some embodiments, the temperature of the heating degassing is 80°C.

[0114] In some embodiments, the nitrogen atmosphere is continuously heated to a temperature of 200° C. for a reaction time of 2 h.

[0115] The following is described in conjunction with some specific embodiments: Embodiment 1: Preparation of indium precursor solution: 6.28mmol (1.39g) indium chloride, 26.46mmol (11.8mL) trioctylphosphine (TOP) and 13.2mL 1-octadecene (ODE) were added to a 100mL three-necked flask and mixed and stirred evenly, heated to 80°C, and degassed for 1 hour. Under nitrogen protection, continue to heat to 200°C and stir for 2 hours. After removing the heating jacket and cooling to room temperature, store in a glove box for later use.

[0116] In the present invention, tri(trimethylsilyl)arsenic and tri(trimethylsilyl)phosphorus ((TMS)3P) can be purchased commercially or prepared according to the method of the present invention. The synthesis of tri(trimethylsilyl)arsenic ((TMS)3As) is as follows: (1) Preparation of sodium-potassium alloy: In an inert environment, 14.5 g (0.63 mol) of metallic sodium and 20.3 g (0.52 mol) of metallic potassium were weighed after washing with heptane, and the washed metallic sodium and metallic potassium were placed in the same dropping funnel, and the mixture was heated to melt the metals and form a sodium-potassium alloy; (2) Synthesis: In an inert environment, add 25g of elemental arsenic powder to 1L of ethylene glycol dimethyl ether, stir, and then drop the sodium-potassium alloy into the mixed solution. The mixed solution in the flask gradually turns black. After the addition is completed, heat the mixed solution to reflux, stir for 24 hours, and then cool to room temperature. Use a dropping funnel to add 1.34mol of trimethylsilyl chloride dropwise, heat to reflux, continue the reaction for 30 minutes, and then cool to room temperature to obtain a black mixed solution.

[0117] Purification process: Centrifuge the above black mixed solution and collect the supernatant. Distill under reduced pressure at room temperature to obtain a bright yellow oily (TMS)3As crude product. Continue heating and distill under reduced pressure to finally obtain a clear (TMS)3As product. All are completed under the protection of inert gas to avoid the reaction from contacting with air throughout the process.

[0118] Preparation of nanosheet templates: (1) 0.6mmol (0.06g) cuprous chloride, 1.5mmol (0.667g) TOP and 5mL oleylamine (OAm) were dissolved in a 50mL three-necked flask and heated to 80℃ for degassing for 1 hour. Under nitrogen protection, the solution was heated to 150℃, and 1mL of arsenic precursor solution (tri(trimethylsilyl)arsenic was added to octadecene, where the molar concentration of tri(trimethylsilyl)arsenic in octadecene was 0.1mmol / mL, and it was prepared under inert gas protection) was quickly injected), stirred rapidly for 3 minutes, and the heating jacket was removed and cooled to room temperature, and the reaction was completed. The three-necked flask was transferred to a glove box, toluene and acetonitrile were added, centrifuged and washed three times, and dispersed in 2.5mL of n-hexane to obtain a Cu3As nanocrystal solution with a molar concentration of 0.04mmol / mL; First growth of Cu3P shell: 0.3mmol (0.03g) cuprous chloride, 2.7mmol (1g) TOP, 4mL oleylamine and 1mL octadecene were mixed evenly in a three-necked flask. Heat to 80℃ for degassing for 1 hour, and heat to 180℃ under nitrogen protection. 0.7mL Cu3As nanocrystal solution, 0.5mL octadecene, 6μmol (TMS)3P and 0.018mmol octylamine were mixed evenly and then quickly injected into the heated mixed solution, stirred for 3 minutes, cooled to room temperature, washed three times under inert atmosphere, and dispersed in 1mL n-hexane to obtain Cu3As / Cu3P n-hexane dispersion with a molar concentration of 0.04mmol / mL; Second growth process: 0.3mmol (0.03g) cuprous chloride, 2.7mmol (1g) TOP, 4mL oleylamine and 1mL octadecene were mixed evenly in a three-necked flask. Heat to 80℃ for degassing for 1 hour, heat to 180℃ under nitrogen protection, inject 0.5mL Cu3As / Cu3P n-hexane dispersion, 0.5mL ODE, 7.2μmol (TMS)3P and 0.0216mmol octylamine mixture, stir for three minutes, and stop the reaction. The product was centrifuged and washed three times and then dispersed in 0.5mL n-hexane to obtain an intermediate product dispersion with a molar concentration of 0.028mmol / mL. The third growth process: 0.3mmol (0.03g) cuprous chloride, 2.7mmol (1g) TOP, 4mL oleylamine and 1mL octadecene were mixed evenly in a three-necked flask. Heated to 80℃ for degassing for 1 hour, heated to 180℃ under nitrogen protection, injected with 0.5mL intermediate product dispersion, 0.5mL ODE, 8μmol (TMS)3P and 0.024mmol octylamine mixture, stirred for three minutes, stopped the reaction, and the product was centrifuged and washed three times to obtain a nanosheet template.

[0119] (2) Using the ion exchange method to obtain nanosheets Add 4.75mL of indium precursor solution (1.2mmol indium) into a three-necked flask and heat to 180°C under nitrogen protection. Add 2mL of ODE to the synthesized nanosheet template (0.1mmol) and disperse it evenly by ultrasonication, then quickly inject it into the heated indium precursor solution. After reacting at 180°C for 45 minutes, lower the temperature to room temperature, transfer to a glove box, wash with toluene and ethanol, and centrifuge three times.

[0120] Comparative Example 1: 0.6mmol (0.06g) cuprous chloride, 1.5mmol (0.667g) TOP and 5mL oleylamine (OAm) were dissolved in a 50mL three-necked flask and heated to 80℃ for degassing for 1 hour. Under nitrogen protection, the solution was heated to 150℃, and (TMS)3As ODE solution (0.1mmol / mL, prepared immediately) was quickly injected, stirred rapidly for 3 minutes, and the heating jacket was removed and cooled to room temperature, and the reaction was completed. The three-necked flask was transferred to a glove box, toluene and acetonitrile were added, and the solution was centrifuged and washed three times to obtain Cu3As nanocrystals.

[0121] Add 4.75mL of indium precursor solution (1.2mmol indium) into a three-necked flask and heat to 180°C under nitrogen protection. Add 2mL of ODE to the synthesized Cu3As nanocrystals (0.1mmol) and disperse them uniformly by ultrasonication, then quickly inject them into the heated indium precursor solution. After reacting at 180°C for 15 minutes, lower the temperature to room temperature, transfer to a glove box, wash with toluene and ethanol, and centrifuge three times.

[0122] The embodiments of the present invention and the comparative examples were tested: Absorption Spectra is performed by UV-Vis spectrophotometer (JASCO V-770). Absorption spectrum can be used for qualitative and quantitative analysis of substances. In the present invention, the exciton absorption peak of semiconductor nanocrystals is mainly determined by absorption spectrum. When the test range is 300nm-900nm, toluene is used as solvent. When the test range is greater than 1000nm, tetrachloroethylene is used as solvent to minimize the influence of alkanes in the near-infrared region.

[0123] Photoluminescence (PL) was performed by Edinburgh Instruments FLS1000. Fluorescence spectrometers can be used to study the luminescence behavior of carriers, defect states, and electronic structures. When testing the emission spectrum, the excitation light is a 420nm xenon lamp light source. When the emission spectrum test range is greater than 1000nm, tetrachloroethylene is used as the solvent, and toluene is used as the solvent in other cases.

[0124] Results and Analysis: The method of the present invention successfully uses Cu3As / Cu3P nanocrystals as templates to synthesize a nanosheet InAs / InP with a core-shell structure and a wurtzite crystal structure by a step-by-step heating method. Figure 1 c. Figure 1 In a, the average particle size of the obtained nanosheets is 5.69nm, and the interplanar spacing of 0.36nm in the high-resolution transmission electron microscopy photograph belongs to the

[100] crystal plane of the wurtzite nanocrystal structure. The core-shell nanocrystals have high crystallinity and no obvious defects, indicating that the shell-structured InP grows on the shell-structured InAs surface. Figure 1 b is the EDX element distribution diagram of the nanosheet template of the present invention, which can also verify that the In element is evenly dispersed in the nanosheet structure, while the As element is distributed in the core structure and the P element is distributed in the shell structure. Figure 1In c, the characteristic diffraction peak of the core-shell nanosheet is shifted to a higher angle than that of pure InAs, and the peak shape remains unchanged, indicating that the nanocrystals retain the crystal structure of the wurtzite crystal form, and the wurtzite crystal form is conducive to the formation of the nanocrystal morphology structure in the present invention. Nanocrystals under this morphology have anisotropic luminescence characteristics, which can not only emit deflected light, but also achieve higher external quantum efficiency.

[0125] exist Figure 2 It can be found that the nanosheet InAs / InP obtained in Example 1 of the present invention can achieve an emission wavelength of 1050 nm, while the InAs obtained in Comparative Example 1 cannot achieve an emission wavelength. It can be seen that fluorescence emission can be achieved by forming a shell structure InP on the surface of the core structure InAs.

[0126] It should be noted that the terms used in the present invention are only for describing specific embodiments, rather than limiting the scope of the present application. As shown in the present specification, unless the context clearly indicates an exception, the words "one", "a", "a kind of" and / or "the" do not specifically refer to the singular, but may also include the plural. The terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method or device. In the absence of more restrictions, the elements defined by the sentence "include one..." do not exclude the presence of other identical elements in the process, method or device including the elements.

[0127] It should also be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", etc. should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0128] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A nanosheet, characterized in that: The nanosheet has a core-shell structure, wherein the core structure is indium arsenide and the shell structure is indium phosphide.

2. The nanosheet according to claim 1, characterized in that The nanosheet has a wurtzite crystal structure.

3. The method for preparing the nanosheet according to any one of claims 1 to 2, characterized in that: The preparation method comprises: A nanosheet template with a core-shell structure is prepared, and the nanosheet template is subjected to an ion exchange method to obtain a nanosheet.

4. The preparation method according to claim 3, characterized in that: The method for preparing the nanosheet template having a core-shell structure comprises: Step 1: dissolving cuprous chloride and trioctylphosphine in oleylamine, heating and degassing, heating and reacting under an inert gas, washing, and obtaining an intermediate product, cuprous arsenide nanocrystals; Step 2: By growing at least one layer of cuprous phosphide shell on the surface of cuprous arsenide nanocrystals, a nanosheet template with a core-shell structure is obtained.

5. The preparation method according to claim 4, characterized in that: In the step 1, the molar ratio of cuprous chloride to trioctylphosphine in cuprous chloride is 1:2-1:6, calculated as copper ions; In the step 1, the molar concentration of cuprous chloride in oleylamine is 0.6 mmol / 5 mL; In step 1, the specific process of heating degassing includes heating to 80° C. and performing vacuum degassing for 1 hour while maintaining the temperature at 80° C.; In the step 1, the specific process of the temperature-raising reaction under the inert gas includes: heating to 150° C. in a nitrogen atmosphere, adding an arsenic precursor solution, maintaining for 2 min-4 min, and cooling to room temperature; The volume ratio of the arsenic precursor solution to oleylamine is 1:5; The room temperature is 16°C-28°C.

6. The preparation method according to claim 4, characterized in that: In step 2, the specific process of growing three layers of cuprous phosphide shell on the surface of cuprous arsenide nanocrystals includes: Step 21: dissolving cuprous chloride and trioctylphosphine in oleylamine and octadecene, heating and degassing, and heating under inert gas; adding a mixed solution of cuprous arsenide nanocrystal solution, octadecene, tri(trimethylsilyl)phosphine, and octylamine to react, mixing evenly, cooling to room temperature, washing three times under inert gas, and dispersing the washed product in n-hexane; Step 22: dissolving cuprous chloride and trioctylphosphine in oleylamine and octadecene, heating and degassing, and heating under inert gas; adding a mixed solution of the product dispersed in n-hexane in step 21, octadecene, tri(trimethylsilyl)phosphine, and octylamine to react, mixing evenly, cooling to room temperature, washing three times under inert gas, and dispersing the washed product in n-hexane; Step 23: dissolving cuprous chloride and trioctylphosphine in oleylamine and octadecene, heating and degassing, and heating under inert gas; adding a mixed solution of the product dispersed in n-hexane in step 22, octadecene, tri(trimethylsilyl)phosphine, and octylamine to react, mixing evenly, cooling to room temperature, washing three times under inert gas, and obtaining a nanosheet template with a core-shell structure after washing.

7. The preparation method according to claim 6, characterized in that: In the step 21, the molar ratio of cuprous chloride to trioctylphosphine is 1:9; In the step 21, the volume ratio of oleylamine to octadecene is 4:1; In the step 21, after cuprous chloride and trioctylphosphine are dissolved in oleylamine and octadecene, the molar concentration of cuprous chloride is 0.3 mmol / 5 mL; In step 21, the temperature of heating and degassing is 80° C. and the time is 50 min-60 min; In the step 21, heating under inert gas specifically includes: heating to 180° C. under nitrogen atmosphere; In step 21, the molar concentration of the cuprous arsenide nanocrystal solution is 0.04 mmol / mL; In the step 21, the volume ratio of the cuprous arsenide nanocrystal solution to octadecene is 7:5; In step 21, in the mixed solution, the molar concentration of octylamine is 0.018 mmol / 1.2 mL, and the molar concentration of tris(trimethylsilyl)phosphine is 6 μmol / 1.2 mL; The inert atmosphere is nitrogen.

8. The preparation method according to claim 6, characterized in that: In the step 22, the molar ratio of cuprous chloride to trioctylphosphine is 1:9; In the step 22, the volume ratio of oleylamine to octadecene is 4:1; In the step 22, after cuprous chloride and trioctylphosphine are dissolved in oleylamine and octadecene, the molar concentration of cuprous chloride is 0.3 mmol / 5 mL; In step 22, the temperature of heating and degassing is 80° C. and the time is 50 min-60 min; In the step 22, heating under inert gas specifically includes: heating to 180° C. under nitrogen atmosphere; In the step 22, the molar concentration of the product dispersed in n-hexane in step 21 is 0.04 mmol / mL; In the step 22, the volume ratio of the product dispersed in n-hexane to octadecene is 1:1; In step 22, in the mixed solution, the molar concentration of octylamine is 0.026 mmol / mL, and the molar concentration of tris(trimethylsilyl)phosphine is 7.2 μmol / mL; In the step 23, the molar ratio of cuprous chloride to trioctylphosphine is 1:9; In the step 23, the volume ratio of oleylamine to octadecene is 4:1; In the step 23, after cuprous chloride and trioctylphosphine are dissolved in oleylamine and octadecene, the molar concentration of cuprous chloride is 0.3 mmol / 5 mL; In step 23, the temperature of heating and degassing is 80° C. and the time is 50 min-60 min; In the step 23, heating under inert gas specifically includes: heating to 180° C. under nitrogen atmosphere; In the step 23, the molar concentration of the product dispersed in n-hexane in step 22 is 0.028 mmol / mL; In the step 23, the volume ratio of the product dispersed in n-hexane to octadecene is 1:1; In step 23, in the mixed solution, the molar concentration of octylamine is 0.024 mmol / mL, and the molar concentration of tris(trimethylsilyl)phosphine is 8 μmol / mL.

9. The preparation method according to claim 3, characterized in that: The method of obtaining the nanosheets by using the ion exchange method for the nanosheet template is specifically as follows: The indium precursor solution is heated under a nitrogen atmosphere, octadecene dispersed with a nanosheet template is added, reacted, cooled to room temperature, and washed; The volume ratio of the indium precursor solution to octadecene dispersed with the nanosheet template is 4.75:2; The molar concentration of the nanosheet template in octadecene was 0.1 mmol / 2 mL; The indium precursor solution was heated to 180° C. under a nitrogen atmosphere; The reaction temperature is 180°C and the reaction time is 40-50 minutes; Calculated based on the indium element in the indium precursor solution, the molar concentration of the indium precursor solution is 1.2 mmol / 4.75 mL; The preparation method of the indium precursor solution comprises: mixing indium chloride, trioctylphosphine and octadecene, heating and degassing, continuing to heat in a nitrogen atmosphere for reaction, and cooling to room temperature to obtain an indium precursor solution; The volume ratio of trioctylphosphine to octadecene is 11.8:13.2; The temperature of the heating degassing is 80°C; The nitrogen atmosphere was heated continuously until the reaction temperature reached 200° C. and maintained for 2 h.

10. Use of the nanosheet according to any one of claims 1 to 2 or the nanosheet prepared by the preparation method according to any one of claims 3 to 9 in semiconductor nanocrystals.

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