Modified zinc-based nanosheets and preparation method thereof
By using high-binding-energy selenide and controlling the reaction conditions, highly symmetrical growth of zinc-based nanosheets was achieved, solving the asymmetry problem of the nanosheet shell and improving the fluorescence performance.
Patent Information
- Application Number
- CN202311801210.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-25
- Publication Date
- 2025-09-26
- Estimated Expiration
- 2043-12-25
AI Technical Summary
Existing technologies are unable to synthesize high-quality blue-light-emitting zinc-based nanosheets, and the asymmetric growth of the nanosheet shell leads to low fluorescence quantum yield and high fluorescence half-width.
High-binding-energy selenium ether is used as the selenium source. By controlling the crystal plane reaction space and binding energy gap of the nanosheet core, highly symmetric epitaxial shell growth of zinc-based nanosheet layers is achieved. The preparation method using phosphine- and nitrogen-containing ligands is used to control reaction conditions such as temperature and time.
Modified zinc-based nanosheets with high structural symmetry, high fluorescence quantum yield and low fluorescence half-width were obtained, which improved the optical properties of the nanosheets.
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Figure CN117778011B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of colloidal nanocrystal synthesis, and in particular to a modified zinc-based nanosheet and a preparation method thereof. Background Art
[0002] Colloidal semiconductor nanocrystals are an important semiconductor material with enormous application prospects in optoelectronic devices, fluorescent materials, absorbers, solar cells, and photocatalysis. The morphology and material composition of nanocrystals significantly influence their properties. Compared to the common zero-dimensional quantum dots, two-dimensional structures (hereafter referred to as nanosheets) possess unique optical, electrical, and magnetic properties, potentially significantly improving the efficiency of optoelectronic devices. Regarding material composition, compounds of zinc and chalcogenides (such as zinc sulfide, zinc selenide, and zinc telluride, collectively referred to as zinc-based) possess suitable band structures and are non-toxic and environmentally friendly, making them preferred blue-light emitting materials. They are also commonly used as shell materials in nanosheet crystals and possess high research and practical value. However, existing technologies have been unable to synthesize zinc-based nanosheets with high practical value that emit blue light, and growing the zinc selenide shell within the nanosheets also presents difficulties.
[0003] High-quality colloidal nanocrystals typically have a core / shell structure, and their synthesis is typically divided into a nucleation stage and a shell epitaxial growth stage: first, a small-sized colloidal nanocrystal is synthesized as a core, and then the shell is epitaxially grown along the surface planes of the core. To avoid the influence of surface defects on the core and at the same time improve the luminescence purity, the growth of the shell needs to have a high degree of symmetry, that is, it must be relatively uniform in all directions. Generally, because quantum dots are spherical and inherently highly symmetrical, it is easy to achieve symmetric growth of the quantum dot shell. In nanosheets, due to the strong asymmetry of the nanosheets themselves, the highly symmetric growth is non-thermodynamically stable during nanosheet growth. Specifically, the growth rate in the thickness direction of the nanosheet is about three orders of magnitude lower than the growth rate in other directions.
[0004] In order to achieve highly symmetric epitaxial growth of nanosheet shells, it is necessary to carefully control the activity of each crystal face of the nanosheet. Taking the epitaxial growth of wurtzite nanocrystals as an example, its surface is (0001), ( )and( ) three crystal faces. The number of dangling bonds of the surface cations of these three crystal faces are 3, 2, and 1 respectively. Because more dangling bonds mean that the new layer of cations has a larger space and higher binding energy, which is more conducive to its coordination with anions, thus leading to (0001), ( )and( ) The three crystal planes have completely different growth rates, which makes the final nanosheets have a strong asymmetric growth, resulting in the problems of asymmetric nanosheet structure, low fluorescence quantum yield and high fluorescence half-maximum width. Summary of the Invention
[0005] The main purpose of the present invention is to provide a modified zinc-based nanosheet and a preparation method thereof, so as to solve the problems in the prior art of strong asymmetric growth of nanosheets leading to their asymmetric structure, low fluorescence quantum yield and high fluorescence half-width.
[0006] In order to achieve the above object, according to one aspect of the present invention, a modified zinc-based nanosheet is provided, wherein the modified zinc-based nanosheet comprises a nanosheet crystal core and a zinc-based nanosheet layer coated on the surface of the nanosheet crystal core, and the modified zinc-based nanosheet comprises a (0001) crystal plane, a ( ) crystal plane and ( ) crystal plane, among which the thickness of (0001) crystal plane is 5~40 nm, ( ) crystal plane thickness is 5~40 nm, ( ) The thickness of the crystal plane is 1~10 nm.
[0007] Furthermore, the mass ratio of the nanosheet core to the zinc-based nanosheet layer is 1:2-1:20, and / or the zinc-based nanosheet layer is a single layer or multiple layers, and the thickness of the zinc-based nanosheet layer is 1-10 nm.
[0008] Furthermore, the particle size of the nanosheet core is 3-20 nm, and / or the thickness of the nanosheet core is 0.6-2 nm, and / or the particle size of the modified zinc-based nanosheet is 5-40 nm.
[0009] Furthermore, the above-mentioned nanosheet crystal core is selected from any one or more of zinc selenide nanosheet crystal core, tellurium-doped zinc selenide nanosheet crystal core, and cadmium selenide nanosheet crystal core, and / or the tellurium doping amount in the tellurium-doped zinc selenide nanosheet crystal core is 1~5%, and / or the shape of the nanosheet crystal core is nanodisc and / or nanotriangular disk.
[0010] According to another aspect of the present invention, a method for preparing the aforementioned modified zinc-based nanosheets is provided, the method comprising: sequentially mixing, reacting, and cooling raw materials comprising nanosheet cores, phosphine-containing ligands, a selenium source, a zinc carboxylate source, a nitrogen-containing ligand, and a solvent to obtain modified zinc-based nanosheets; wherein the reaction temperature is 220-340°C, and the selenium source is a selenoether compound.
[0011] Furthermore, the above preparation method includes: step S1, mixing a first raw material including a nanosheet crystal core, a phosphine-containing ligand, a first nitrogen-containing ligand and a first solvent to obtain a mixed liquid; step S2, reacting a second raw material including the mixed liquid, a selenium source, a zinc carboxylate source, a second nitrogen-containing ligand and a second solvent to obtain a product system; step S3, cooling the product system to obtain modified zinc-based nanosheets.
[0012] Furthermore, in the above step S2, the ratio between the amount of the selenium source and the mass of the nanosheet core is 0.1~1 mmol:10 mg; the molar ratio of the zinc carboxylate source, the second nitrogen-containing ligand and the selenium source is 0.5~4:5~50:1; the volume ratio of the second solvent to the second nitrogen-containing ligand is ≤10:1; and / or the second nitrogen-containing ligand is an organic amine, and the organic amine is selected from any one or more of oleylamine, behenylamine, octadecylamine, hexadecylamine, tetradecylamine, dodecylamine, decadecylamine, octylamine and butylamine; and / or the zinc carboxylate source is selected from zinc formate, zinc acetate, zinc propionate, zinc butyrate, zinc octanoate, isopropylamine, butylamine, octylamine and butylamine. Any one or more of zinc octanoate, zinc neodecanoate, zinc oleate, zinc undecylenate, zinc stearate, zinc myristate, and zinc laurate; and / or the selenium source is selected from any one or more of dimethyl diselenide, dimethyl selenoether, diethyl diselenide, dihexyl diselenide, dioctyl diselenide, diphenyl diselenide, and dibenzyl diselenide; and / or the second solvent is selected from any one or more of octadecene, octadecane, hexadecane, tetradecane, dodecane, paraffin oil, and trioctylamine.
[0013] Furthermore, in the above step S1, the mixing temperature is 20~250°C, and / or the mass concentration of the nanosheet cores in the mixed solution is 0.1~10 mg / mL; and / or the molar concentration of the phosphine-containing ligand in the mixed solution is 0.05~1 mmol / mL; and / or the molar concentration of the first nitrogen-containing ligand in the mixed solution is 0.05~1 mmol / mL; and / or the first solvent is selected from any one or more of octadecene, octadecane, hexadecane, tetradecane, dodecane, paraffin oil, and trioctylamine; and / or the phosphine-containing ligand is an alkyl phosphine, and the alkyl phosphine is selected from any one or more of triethyl phosphine, tributyl phosphine, and trioctyl phosphine; and / or the first nitrogen-containing ligand is an organic amine, and the organic amine is selected from any one or more of oleylamine, dodecylamine, octadecylamine, hexadecylamine, tetradecylamine, dodecylamine, decaamine, octylamine, and butylamine.
[0014] Furthermore, the second raw material further comprises a carboxylic acid source, the molar ratio of the carboxylic acid source to the selenium source is ≤25:1, and / or the carboxylic acid source is selected from any one or more of oleic acid, stearic acid, palmitic acid, myristic acid, lauric acid, capric acid, and nonanoic acid.
[0015] Furthermore, the preparation method further comprises: injecting the second raw material into the first raw material, the injection time being 0.5 to 24 hours.
[0016] The key point of the present invention lies in the use of high binding energy selenium ether to achieve highly symmetric zinc-based nanosheet epitaxial shell growth in nanosheets. Specifically, due to the small molecular size of selenium ether, it is easy to quickly adsorb on the crystal surface of the nanosheet core, thereby reducing the (0001), ( )and( ) The difference in the size of the reaction space of the three crystal planes has narrowed the gap between (0001), ( )and( ) The size of the gap in binding energy between the crystal planes; on the other hand, compared with the selenium source of selenium-phosphorus bond conventionally used in the prior art, the selenium-carbon bond in the selenoether of the present application is more difficult to break than the selenium-phosphorus bond, so that the growth rate is mainly controlled by the strength of the selenium-carbon bond, which can induce the uniform growth of the three crystal planes, and further, obtain nanosheets with more symmetrical structure, high fluorescence quantum yield and low fluorescence half-width. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:
[0018] Figure 1 The figure shows a transmission electron microscope (TEM) image of the modified zinc-based nanosheet obtained in Comparative Example 1 of the present invention;
[0019] Figure 2 The figure shows a transmission electron microscope (TEM) image of the modified zinc-based nanosheets obtained according to Example 1 of the present invention;
[0020] Figure 3 shows the absorption spectrum of the modified zinc-based nanosheets obtained according to Example 1 of the present invention;
[0021] Figure 4 The fluorescence spectrum of the modified zinc-based nanosheets obtained according to Example 1 of the present invention is shown. DETAILED DESCRIPTION
[0022] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.
[0023] As analyzed in the background technology, the existing technology has the problem that the nanosheets have strong asymmetric growth, resulting in their structural asymmetry, low fluorescence quantum yield and high fluorescence half-maximum width. To solve this problem, the present invention provides a modified zinc-based nanosheet and a preparation method thereof.
[0024] In a typical embodiment of the present application, a modified zinc-based nanosheet is provided, wherein the modified zinc-based nanosheet comprises a nanosheet core and a zinc-based nanosheet layer coated on the surface of the nanosheet core, and the modified zinc-based nanosheet comprises a (0001) crystal plane, a ( ) crystal plane and ( ) crystal plane, among which the thickness of (0001) crystal plane is 5~40 nm, ( ) crystal plane thickness is 5~40 nm, ( ) The thickness of the crystal plane is 1~10 nm.
[0025] The key point of the present invention is to use high binding energy selenide to achieve highly symmetric zinc-based nanosheet epitaxial shell growth in nanosheets. Specifically, on the one hand, due to the small molecular size of selenide, it is easy to quickly adsorb on the crystal surface of the nanosheet core, thereby reducing the ( 、( )、( )The difference in the size of the reaction space of the three crystal planes has narrowed the gap ( 、( )、( ) between the two crystals; on the other hand, compared with the selenium source of selenium-phosphorus bond conventionally used in the prior art, the selenium-carbon bond in the selenoether of the present application is more difficult to break than the selenium-phosphorus bond, so that the growth rate is mainly controlled by the strength of the selenium-carbon bond, which can induce the uniform growth of the three crystal planes, and further, obtain nanosheets with more symmetrical structure, high fluorescence quantum yield and low fluorescence half-width.
[0026] In some embodiments of the present application, the mass ratio of the above-mentioned nanosheet core to the zinc-based nanosheet layer is preferably 1:2~1:20, the mass ratio of the nanosheet core to the zinc-based nanosheet layer is preferably 1:8~1:15, and / or the zinc-based nanosheet layer is a single layer or a multilayer, and the thickness of the zinc-based nanosheet layer is 1~10 nm.
[0027] The preferred mass ratio of nanosheet cores to zinc-based nanosheet layers is within the above range, which further helps improve the fluorescence quantum yield of the modified zinc-based nanosheets. A zinc-based nanosheet layer that is too thick is not conducive to improving its dispersibility. A zinc-based nanosheet layer thickness within the above range is preferred to improve its dispersibility, thereby enhancing the processability of the modified zinc-based nanosheets. Furthermore, the zinc-based nanosheet layer structure and thickness described above facilitate the selection of modified zinc-based nanosheets with varying zinc-based nanosheet layer thicknesses based on actual needs, providing greater market choice.
[0028] The particle size of the nanosheet cores and modified zinc-based nanosheets is too large, resulting in poor dispersion of the raw materials in the reaction system, which is not conducive to the growth of the zinc-based nanosheet layer and can easily lead to uneven growth of the zinc-based nanosheet layer, thereby reducing the final fluorescence quantum yield and increasing the fluorescence half-width. Therefore, in some embodiments of the present application, the particle size of the nanosheet cores is preferably 3-20 nm, and / or the thickness of the nanosheet cores is preferably 0.6-2 nm, and / or the particle size of the modified zinc-based nanosheets is preferably 5-40 nm.
[0029] In one embodiment of the present application, the above-mentioned nanosheet core is selected from any one or more of zinc selenide nanosheet core, tellurium-doped zinc selenide nanosheet core, and cadmium selenide nanosheet core, and / or the tellurium doping amount in the tellurium-doped zinc selenide nanosheet core is 1~5%, and / or the shape of the nanosheet core is a nanodisc and / or a nanotriangular disk.
[0030] When the type of nanosheet crystal core changes, the corresponding luminescence wavelength band changes, thereby obtaining modified zinc-based nanosheets with different luminescence wavelength bands, thereby greatly enriching the selectivity of the types of modified zinc-based nanosheets.
[0031] In another typical embodiment of the present application, a method for preparing the above-mentioned modified zinc-based nanosheets is provided, which comprises: sequentially mixing, reacting and cooling raw materials including nanosheet cores, phosphine-containing ligands, selenium sources, zinc carboxylate sources, nitrogen-containing ligands and solvents to obtain modified zinc-based nanosheets; wherein the reaction temperature is 220~340°C, and the selenium source is a selenoether compound.
[0032] The key point of the present invention is to use high binding energy selenide to achieve highly symmetric zinc-based nanosheet epitaxial shell growth in nanosheets. Specifically, on the one hand, due to the small molecular size of selenide, it is easy to quickly adsorb on the crystal surface of the nanosheet core, thereby reducing the ( 、( )、( )The difference in the size of the reaction space of the three crystal planes has narrowed the gap ( 、( )、( ) between the two crystals; on the other hand, compared with the selenium source of selenium-phosphorus bond conventionally used in the prior art, the selenium-carbon bond in the selenoether of the present application is more difficult to break than the selenium-phosphorus bond, so that the growth rate is mainly controlled by the strength of the selenium-carbon bond, which can induce the uniform growth of the three crystal planes, and further, obtain nanosheets with more symmetrical structure, high fluorescence quantum yield and low fluorescence half-width.
[0033] The above preparation method of the present application utilizes high-binding-energy selenium ethers to achieve highly symmetrical epitaxial shell growth of zinc-based nanosheets. This allows for the simple and rapid preparation of nanosheets with more symmetrical structures, high fluorescence quantum yields, and low fluorescence half-widths. Furthermore, the above nitrogen-containing ligands help enhance the reaction efficiency and effectiveness of the reaction between selenium radicals and zinc carboxylate sources.
[0034] In one embodiment of the present application, the preparation method includes step S1, mixing a first raw material including a nanosheet crystal core, a phosphine-containing ligand, a first nitrogen-containing ligand and a first solvent to obtain a mixed liquid; step S2, reacting a second raw material including the mixed liquid, a selenium source, a zinc carboxylate source, a second nitrogen-containing ligand and a second solvent to obtain a product system; step S3, cooling the product system to obtain modified zinc-based nanosheets.
[0035] By mixing the nanosheet core, phosphine-containing ligand, first nitrogen-containing ligand, and first solvent to obtain a mixed solution, and then reacting it with a selenium source, zinc carboxylate source, second nitrogen-containing ligand, and second solvent, the dispersion uniformity of the components in the reaction system is improved, thereby improving the uniformity of the zinc-based nanosheet growth. This results in modified zinc-based nanosheets with better overall performance.
[0036] In one embodiment of the present application, in the above step S2, the ratio between the amount of the selenium source and the mass of the nanosheet core is 0.1~1 mmol:10 mg; the molar ratio of the zinc carboxylate source, the second nitrogen-containing ligand and the selenium source is 0.5~4:5~50:1; the volume ratio of the second solvent to the second nitrogen-containing ligand is ≤10:1; and / or the second nitrogen-containing ligand is an organic amine, and the organic amine is selected from any one or more of oleylamine, diamine, octadecylamine, hexadecylamine, tetradecylamine, dodecylamine, decadecylamine, octylamine and butylamine; and / or the zinc carboxylate source is selected from zinc formate, zinc acetate, zinc propionate, zinc butyrate, zinc octanoate, isopropylamine, butylamine, octylamine and butylamine. Any one or more of zinc octanoate, zinc neodecanoate, zinc oleate, zinc undecylenate, zinc stearate, zinc myristate, and zinc laurate; and / or the selenium source is selected from any one or more of dimethyl diselenide, dimethyl selenoether, diethyl diselenide, dihexyl diselenide, dioctyl diselenide, diphenyl diselenide, and dibenzyl diselenide; and / or the second solvent is selected from any one or more of octadecene, octadecane, hexadecane, tetradecane, dodecane, paraffin oil, and trioctylamine.
[0037] The preferred ratios of the nanosheet core, selenium source, zinc carboxylate source, and second nitrogen-containing ligand within the above ranges facilitate enhanced synergy between the components. The preferred composition of the above ingredients provides a wider range of raw material options for preparing modified zinc-based nanosheets in this application, further expanding the broad spectrum of the preparation method. The preferred reaction temperature helps improve the efficiency and effectiveness of the reaction.
[0038] In one embodiment of the present application, in step S1, the mixing temperature is 20~250°C, and / or the concentration of nanosheet nuclei in the mixed solution is 0.1~10 mg / mL and / or the molar concentration of the phosphine-containing ligand in the mixed solution is 0.05~1 mmol / mL; and / or the molar concentration of the first nitrogen-containing ligand in the mixed solution is 0.05~1 mmol / mL; and / or the first solvent is selected from any one or more of octadecene, octadecane, hexadecane, tetradecane, dodecane, paraffin oil, and trioctylamine; and / or the phosphine-containing ligand is an alkyl phosphine, and the alkyl phosphine is selected from any one or more of triethyl phosphine, tributyl phosphine, and trioctyl phosphine; and / or the first nitrogen-containing ligand is an organic amine, and the organic amine is selected from any one or more of oleylamine, dodecylamine, octadecylamine, hexadecylamine, tetradecylamine, dodecylamine, decaamine, octylamine, and butylamine.
[0039] The above preferred conditions are more conducive to improving the uniformity of dispersion of the components in the mixed solution, and the preferred types of the components provide more choices.
[0040] In one embodiment of the present application, the above-mentioned second raw material also includes a carboxylic acid source, the molar ratio of the carboxylic acid source to the selenium source is ≤25:1, and / or the carboxylic acid source is selected from any one or more of oleic acid, stearic acid, palmitic acid, myristic acid, lauric acid, capric acid, and nonanoic acid.
[0041] The preferred carboxylic acid source is beneficial in providing a complexing effect for the reaction between the selenium free radical and the zinc carboxylate source, thereby increasing the reactivity of the selenium free radical and the zinc carboxylate source.
[0042] In one embodiment of the present application, the preparation method further includes: injecting the second raw material into the first raw material, and the injection time is 0.5 to 24 hours.
[0043] The above preferred injection time helps to increase the reaction time of the mixed solution and the second raw material, and helps to reduce the problem of uneven local mixing caused by excessive mixing, which makes the resulting zinc-based nanosheet layer uneven.
[0044] The beneficial effects of the present application will be described below with reference to specific embodiments and comparative examples.
[0045] Example 1
[0046] 1) A mixture of 10 mg of 5 nm-diameter, 1.4 nm-thick zinc selenide nanosheet cores, 5 mL of octadecene, 1 mL of tributylphosphine, and 1 mL of oleylamine was heated to 250°C to obtain a mixture having a mass concentration of 1.43 mg / mL of zinc selenide nanosheet cores, a molar concentration of 0.57 mmol / mL of tributylphosphine, and a molar concentration of 0.43 mmol / mL of oleylamine.
[0047] 2) After the temperature reached the set temperature of 250°C, a mixture of 0.25 mmol of dimethyl diselenide, 0.5 mmol of zinc octoate, 0.5 ml of octanoic acid, 1 ml of oleylamine, and 1 ml of octadecene was uniformly injected over 4 hours. The molar ratio of zinc octoate, octanoic acid, oleylamine, and dimethyl diselenide was 2:13:12:1; the ratio of the amount of dimethyl diselenide to the mass of the zinc selenide nanosheets was 0.25 mmol:10 mg; 0.25 mmol of dimethyl diselenide was added for every 10 mg of nanosheet cores; and the volume ratio of octadecene to oleylamine was 1:1.
[0048] 3) After the injection, the product system is cooled and purified to obtain the final modified zinc-based nanosheets, whose particle size is 7 nm and the thickness of the zinc-based nanosheet layer is 2.5 nm. Among them, the (0001) crystal plane, ( ) crystal plane and ( The thickness of the crystal plane is 7 nm, 7 nm, and 2.5 nm respectively. The absorption spectrum and fluorescence spectrum of the modified zinc-based nanosheets are shown as follows: Figure 3 、 Figure 4 shown.
[0049] Example 2
[0050] The difference from Example 1 is that the phosphine-containing ligand is trioctylphosphine, no carboxylic acid source is added, and the reaction temperature is set to 280°C. Finally, modified zinc-based nanosheets are obtained, whose particle size is 8 nm and the thickness of the zinc-based nanosheet layer is 2.5 nm.
[0051] Example 3
[0052] The difference from Example 1 is that the selenium source is dimethyl selenide, and the ratio between the amount of dimethyl selenide and the mass of zinc selenide nanosheets is 0.5 mmol:10 mg. Finally, modified zinc-based nanosheets are obtained, whose particle size is 7 nm and the thickness of the zinc-based nanosheet layer is 2.5 nm.
[0053] Example 4
[0054] The difference from Example 1 is that the selenoether is diethyl diselenide, and the modified zinc-based nanosheets finally obtained have a particle size of 7 nm and a thickness of the zinc-based nanosheet layer of 2.5 nm.
[0055] Example 5
[0056] The difference from Example 1 is that the zinc source is zinc laurate, and the modified zinc-based nanosheets are finally obtained, the particle size of which is 7 nm and the thickness of the zinc-based nanosheet layer is 2.5 nm.
[0057] Example 6
[0058] The difference from Example 1 is that the nitrogen-containing ligand is dodecylamine, and the modified zinc-based nanosheets are finally obtained, the particle size of which is 8 nm and the thickness of the zinc-based nanosheet layer is 2.5 nm.
[0059] Example 7
[0060] The difference from Example 1 is that the carboxylic acid source is nonanoic acid, and the modified zinc-based nanosheets are finally obtained, whose particle size is 7 nm and the thickness of the zinc-based nanosheet layer is 2.5 nm.
[0061] Example 8
[0062] The difference from Example 1 is that the injection time is set to 8 hours, and the modified zinc-based nanosheets are finally obtained, whose particle size is 9 nm and the thickness of the zinc-based nanosheet layer is 2.8 nm.
[0063] Example 9
[0064] The difference from Example 1 is that the nanosheet core is a tellurium-doped zinc selenide nanosheet core, the tellurium doping amount is 2.5%, and the modified zinc-based nanosheet is finally obtained, the particle size of which is 7 nm and the thickness of the zinc-based nanosheet layer is 2.5 nm.
[0065] Example 10
[0066] The difference from Example 2 is that the carboxylic acid source is 0.1 ml of oleic acid, the molar ratio of oleic acid to dimethyl diselenide is 1.26:1, and the reaction temperature is set to 310°C. Finally, modified zinc-based nanosheets are obtained, whose particle size is 8 nm and the thickness of the zinc-based nanosheet layer is 2.5 nm.
[0067] Example 11
[0068] The difference from Example 2 is that the nanosheet core is a cadmium selenide nanosheet core with a particle size of 10 nm and a thickness of 1.2 nm, and the modified zinc-based nanosheets finally obtained have a particle size of 13 nm and a thickness of 2.2 nm.
[0069] Example 12
[0070] The difference from Example 1 is that the amount of tributylphosphine added is 0.5 ml, and its concentration in the mixed solution is 0.36 mmol / mL. Finally, modified zinc-based nanosheets are obtained, whose particle size is 6 nm and the thickness of the zinc-based nanosheet layer is 2.3 nm.
[0071] Example 13
[0072] The difference from Example 1 is that the amount of zinc selenide nanosheet core added is 15 mg, the mass concentration of zinc selenide nanosheet core is 2.5 mg / mL, and 0.17 mmol of dimethyl diselenide is added for every 10 mg of zinc selenide nanosheet core. Finally, modified zinc-based nanosheets are obtained, whose particle size is 7 nm and the thickness of the zinc-based nanosheet layer is 2.5 nm.
[0073] Comparative Example 1
[0074] The difference from Example 2 is that dimethyl diselenide is replaced by trioctylphosphine selenide, and the reaction temperature is set to 310°C. Finally, modified zinc-based nanosheets are obtained, wherein the (0001) crystal plane, ( ) crystal plane and ( ) The thicknesses of the crystal planes are 14 nm, 8 nm, and 2.5 nm, respectively.
[0075] Comparative Example 2
[0076] The difference from Example 2 is that dimethyl diselenide is replaced by bis(trimethylsilyl)selenoether, and finally modified zinc-based nanosheets are obtained.
[0077] The fluorescence properties of the modified zinc-based nanosheets obtained in the above examples and comparative examples are summarized in Table 1.
[0078] Table 1
[0079]
[0080] In Comparative Example 1, the inventors of this application used trioctylphosphine selenide as a selenium precursor to grow zinc-based nanosheets, and successfully obtained luminescent modified zinc-based nanosheets. However, the morphology of the nanosheets was poor, with a "branch" shape, and the optical properties of the nanosheets were also poor. Specifically, it was manifested in a low fluorescence quantum yield and a wide fluorescence half-peak width, as shown in Figure 1. Figure 1 and Table 1. In addition, this method needs to be carried out at a temperature of 310° C. or even higher, which is very unfavorable for improving the synthesis efficiency.
[0081] Compared with Comparative Example 1, it can be seen that the modified zinc-based nanosheets synthesized by the present invention have the advantages of high morphological uniformity, high fluorescence quantum yield, narrow luminescence half-height width, etc., and the reaction only needs to be carried out at about 250°C. Taking the epitaxial growth of zinc selenide shells grown as zinc selenide nanosheets as the core as an example, the fluorescence quantum yield of the final product of the present invention can reach up to 82%, the fluorescence peak is around 460 nm, the fluorescence half-height width is less than or equal to 30 nm, and it also has good morphological uniformity, as shown below Figure 2 shown.
[0082] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:
[0083] The key point of the present invention is to use high binding energy selenide to achieve highly symmetrical zinc-based nanosheet epitaxial shell growth. Specifically, on the one hand, due to the small molecular size of selenide, it is easy to quickly adsorb on the crystal surface of the nanosheet core, thereby reducing the (0001), ( )and( ) The difference in the size of the reaction space of the three crystal planes has narrowed the gap between (0001), ( )and( ) The size of the gap in binding energy between the crystal planes; on the other hand, compared with the selenium source of selenium-phosphorus bond conventionally used in the prior art, the selenium-carbon bond in the selenoether of the present application is more difficult to break than the selenium-phosphorus bond, so that the growth rate is mainly controlled by the strength of the selenium-carbon bond, which can induce the uniform growth of the three crystal planes, and further, obtain nanosheets with more symmetrical structure, high fluorescence quantum yield and low fluorescence half-width.
[0084] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.
Claims
1. A method for preparing modified zinc-based nanosheets, characterized in that: The preparation method comprises: The raw materials including nanosheet crystal core, phosphine-containing ligand, selenium source, zinc carboxylate source, nitrogen-containing ligand and solvent are sequentially mixed, reacted and cooled to obtain modified zinc-based nanosheets; Wherein, the reaction temperature is 220~340℃; The selenium source is selected from any one or more of dimethyl diselenide, dimethyl selenoether, diethyl diselenide, dihexyl diselenide, dioctyl diselenide, diphenyl diselenide, and dibenzyl diselenide; The ratio between the amount of the selenium source and the mass of the nanosheet core is 0.1-1 mmol:10 mg; The nitrogen-containing ligand is an organic amine, and the organic amine is selected from any one or more of oleylamine, behenylamine, octadecylamine, hexadecylamine, tetradecylamine, dodecylamine, decadecylamine, octylamine, and butylamine; The phosphine-containing ligand is an alkyl phosphine.
2. The preparation method according to claim 1, characterized in that The preparation method comprises: Step S1, mixing a first raw material including the nanosheet core, the phosphine-containing ligand, the first nitrogen-containing ligand and a first solvent to obtain a mixed solution; Step S2, reacting the second raw material including the mixed solution, the selenium source, the zinc carboxylate source, the second nitrogen-containing ligand and the second solvent to obtain a product system; Step S3, cooling the product system to obtain modified zinc-based nanosheets; The first nitrogen-containing ligand and the second nitrogen-containing ligand are independently selected from any one or more of oleylamine, behenylamine, octadecylamine, hexadecylamine, tetradecylamine, dodecylamine, decadecylamine, octylamine and butylamine.
3. The preparation method according to claim 2, characterized in that In step S2, the molar ratio of the zinc carboxylate source, the second nitrogen-containing ligand, and the selenium source is 0.5-4:5-50:1; and / or the volume ratio of the second solvent to the second nitrogen-containing ligand is ≤10:1; and / or the zinc carboxylate source is selected from any one or more of zinc formate, zinc acetate, zinc propionate, zinc butyrate, zinc octanoate, zinc isooctanoate, zinc neodecanoate, zinc oleate, zinc undecylenate, zinc stearate, zinc myristate, and zinc laurate; And / or the second solvent is selected from any one or more of octadecene, octadecane, hexadecane, tetradecane, dodecane, paraffin oil, and trioctylamine.
4. The preparation method according to claim 2, characterized in that In step S1, the mixing temperature is 20-250° C., and / or the mass concentration of the nanosheet cores in the mixed solution is 0.1-10 mg / mL. and / or the molar concentration of the phosphine-containing ligand in the mixed solution is 0.05 to 1 mmol / mL; and / or the molar concentration of the first nitrogen-containing ligand in the mixed solution is 0.05 to 1 mmol / mL; and / or the first solvent is selected from any one or more of octadecene, octadecane, hexadecane, tetradecane, dodecane, paraffin oil, and trioctylamine; And / or the alkyl phosphine is selected from any one or more of triethyl phosphine, tributyl phosphine and trioctyl phosphine.
5. The preparation method according to claim 2, characterized in that The second raw material further includes a carboxylic acid source, the molar ratio of the carboxylic acid source to the selenium source is ≤25:1, and / or the carboxylic acid source is selected from any one or more of oleic acid, stearic acid, palmitic acid, myristic acid, lauric acid, capric acid, and nonanoic acid.
6. The preparation method according to claim 2, characterized in that The preparation method further includes: injecting the second raw material into the first raw material, and the injection time is 0.5 to 24 hours.
7. A modified zinc-based nanosheet prepared by the preparation method according to any one of claims 1 to 6, characterized in that: The modified zinc-based nanosheet includes a nanosheet crystal core and a zinc-based nanosheet layer coated on the surface of the nanosheet crystal core. The modified zinc-based nanosheet includes a (0001) crystal plane, a ( ) crystal plane and ( ) crystal plane, wherein the thickness of the (0001) crystal plane is 5-40 nm, and the ( ) crystal plane thickness is 5~40 nm, the ( ) The thickness of the crystal plane is 1~10nm.
8. The modified zinc-based nanosheet according to claim 7, characterized in that The mass ratio of the nanosheet core to the zinc-based nanosheet layer is 1:2-1:20, and / or the zinc-based nanosheet layer is a single layer or multiple layers, and the thickness of the zinc-based nanosheet layer is 1-10 nm.
9. The modified zinc-based nanosheet according to claim 7, characterized in that The particle size of the nanosheet crystal core is 3-20 nm, and / or the thickness of the nanosheet crystal core is 0.6-2 nm, and / or the particle size of the modified zinc-based nanosheet is 5-40 nm.
10. The modified zinc-based nanosheet according to claim 7, characterized in that The nanosheet core is selected from any one or more of a zinc selenide nanosheet core, a tellurium-doped zinc selenide nanosheet core, and a cadmium selenide nanosheet core, and / or the tellurium doping amount in the tellurium-doped zinc selenide nanosheet core is 1-5%, and / or the shape of the nanosheet core is a nanodisc and / or a nanotriangular disk.