Method for preparing quantum dots, quantum dots, and display device

Abstract

Provided are a method for preparing quantum dots, quantum dots, and a display device. The method comprises the following steps: providing a first precursor solution, a second precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity lower than that of the first selenium precursor solution; adding the first selenium precursor solution to the second precursor solution to form an intermediate of the quantum dots; and performing the following steps at least once to form the quantum dots: without washing the intermediate of the quantum dots, adding the first precursor solution and the second selenium precursor solution to the intermediate of the quantum dots and reacting.

Description

Technical Field

[0001] The present disclosure relates to the technical field of nanomaterials, and in particular to a method for preparing quantum dots, quantum dots, and a display device including the quantum dots. Background Art

[0002] Semiconductor quantum dots, also known as semiconductor nanocrystals, have attracted widespread attention due to their adjustable fluorescence emission peak position, narrow half-width, and high fluorescence quantum yield. Quantum dots have a specific band gap depending on their composition and size, and can therefore absorb light and emit light with a specific wavelength. Currently, the most studied blue light-emitting quantum dots for display applications are mainly II-VI semiconductor quantum dots. ZnSe quantum dots have advantages such as no heavy metal ions, good biocompatibility, and excellent fluorescence emission peak adjustability, and are attracting more and more attention. Summary of the invention

[0003] According to one aspect of the present disclosure, a method for preparing quantum dots is provided, the method comprising the following steps: providing a first precursor solution, a second precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity lower than that of the first selenium precursor solution; adding the first selenium precursor solution to the second precursor solution to form an intermediate of the quantum dots; and performing the following steps at least once to form quantum dots: without washing the intermediate of the quantum dots, adding the first precursor solution and the second selenium precursor solution to the intermediate of the quantum dots and reacting.

[0004] In some embodiments, the first precursor solution is a first zinc precursor solution, the second precursor solution is a second zinc precursor solution, and the quantum dots are first ZnSe quantum dots.

[0005] In some embodiments, after the step of performing the following steps at least once to form quantum dots, it also includes: coating a shell layer on the surface of the first ZnSe quantum dot to form a second ZnSe quantum dot with a core-shell structure, wherein the first ZnSe quantum dot is the core of the second ZnSe quantum dot.

[0006] In some embodiments, the band gap of the shell of the second ZnSe quantum dot is larger than the band gap of the core of the second ZnSe quantum dot.

[0007] In some embodiments, one or more of ZnS, ZnSeS, MnS, and MnO are used to form the shell of the second ZnSe quantum dot.

[0008] In some embodiments, the step of coating the surface of the first ZnSe quantum dot with a shell layer to form a second ZnSe quantum dot with a core-shell structure includes: adding a sulfur precursor solution to the first ZnSe quantum dot solution to coat the surface of the first ZnSe quantum dot with a first ZnS shell to form the second ZnSe quantum dot.

[0009] In some embodiments, the step of adding a sulfur precursor solution to the first ZnSe quantum dot solution to coat the surface of the first ZnSe quantum dot with a first ZnS shell includes: adding the sulfur precursor solution to the first ZnSe quantum dot solution at 300°C to form a first ZnS shell having a thickness of two atomic layers on the surface of the first ZnSe quantum dot.

[0010] In some embodiments, the sulfur precursor solution includes sulfur and n-trioctylphosphine.

[0011] In some embodiments, the average particle size of the second ZnSe quantum dots having the first ZnS shell is about 10.2 nm.

[0012] In some embodiments, the step of coating the surface of the first ZnSe quantum dot with a shell layer to form a second ZnSe quantum dot with a core-shell structure includes: adding a zinc sulfide precursor solution to a second ZnSe quantum dot solution having the first ZnS shell to allow the first ZnS shell to continue to grow to form a second ZnS shell.

[0013] In some embodiments, the thickness of the second ZnS shell is four atomic layers thick.

[0014] In some embodiments, the step of coating the surface of the first ZnSe quantum dot with a shell layer to form a second ZnSe quantum dot having a core-shell structure includes: adding the zinc sulfide precursor solution to the second ZnSe quantum dot solution having the first ZnS shell at a rate of 4-8 mL / h at 280°C to allow the first ZnS shell to continue to grow, thereby forming the second ZnS shell on the surface of the first ZnSe quantum dot.

[0015] In some embodiments, the zinc sulfide precursor solution includes octanethiol, zinc acetate, oleylamine, and octadecene.

[0016] In some embodiments, the molar ratio of octanethiol, zinc acetate, and oleylamine in the zinc sulfide precursor solution is 1:1-1.5:1-1.5.

[0017] In some embodiments, the average particle size of the second ZnSe quantum dots having the second ZnS shell is about 11.8 nm.

[0018] In some embodiments, the fluorescence quantum yield of the second ZnSe quantum dots having the second ZnS shell is about 60%.

[0019] In some embodiments, the material of the solute in the first zinc precursor solution is the same as the material of the solute in the second zinc precursor solution, the material of the solvent in the first zinc precursor solution is the same as the material of the solvent in the second zinc precursor solution, and the ratio of the solute to the solvent in the first zinc precursor solution is different from the ratio of the solute to the solvent in the second zinc precursor solution.

[0020] In some embodiments, the step of providing a first precursor solution, a second precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity lower than that of the first selenium precursor solution comprises: mixing a zinc inorganic salt, an organic acid, an organic amine, and an inert solvent in a ratio of 1-10 mmol: 1-10 mmol: 1-10 mL: 10-50 mL, stirring the mixture under the protection of an inert gas and heating the mixture until clarified to form the first zinc precursor solution.

[0021] In some embodiments, the step of providing a first precursor solution, a second precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity less than that of the first selenium precursor solution comprises: mixing a zinc inorganic salt, an organic acid, an organic amine, and an inert solvent in a ratio of 0.1~10 mmol: 1~10 mL: 1~10 mL: 1~20 mL, stirring the mixture under the protection of an inert gas and heating the mixture to 250°C~350°C to form the second zinc precursor solution.

[0022] In some embodiments, the step of adding the first selenium precursor solution to the second precursor solution to form the intermediate of the quantum dots includes: dissolving selenium powder in diphenylphosphine to form the first selenium precursor solution; using oleic acid as the organic acid in the second zinc precursor solution, using oleylamine as the organic amine in the second zinc precursor solution, and the molar ratio of oleic acid to oleylamine is 0.2:1; and adding the first selenium precursor solution to the second zinc precursor solution to form the intermediate of the first ZnSe quantum dots with a particle size of about 4.7 nm.

[0023] In some embodiments, the first precursor solution is a first cadmium precursor solution, the second precursor solution is a second cadmium precursor solution, and the quantum dots are CdSe quantum dots.

[0024] In some embodiments, the first precursor solution is a first lead precursor solution, the second precursor solution is a second lead precursor solution, and the quantum dots are PbSe quantum dots.

[0025] In some embodiments, the step of providing a first precursor solution, a second precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity less than that of the first selenium precursor solution includes: mixing a selenium precursor and a first selenium precursor solvent in a ratio of 0.1~10 mmol:1~20 mL to form the first selenium precursor solution.

[0026] In some embodiments, the step of providing a first precursor solution, a second precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity less than that of the first selenium precursor solution includes: mixing the selenium precursor and the second selenium precursor solvent in a ratio of 0.1~10 mmol:1~20 mL to form the second selenium precursor solution.

[0027] In some embodiments, the selenium precursor is selected from one of selenium dioxide, selenium trioxide, selenium powder, sodium selenate, and selenourea.

[0028] In some embodiments, the first selenium precursor solvent includes a phosphine solvent having active electrons.

[0029] In some embodiments, the phosphine solvent is selected from one of trioctylphosphine, trioctylphosphine oxide, tributylphosphine, tri(trimethylsilyl)phosphine, tri(dimethylamino)phosphine, diphenylphosphine, diethylphosphine, bis(2-methoxyphenyl)phosphine, and tri(diethylamino)phosphine.

[0030] In some embodiments, the second selenium precursor solvent includes an inert solvent.

[0031] In some embodiments, the inert solvent is selected from one of tetradecane, hexadecane, octadecane, eicosane, tetracosane, octadecene, phenyl ether, benzyl ether, liquid paraffin, mineral oil, dodecylamine, hexadecane, and octadecane.

[0032] According to another aspect of the present disclosure, a quantum dot is provided, which is prepared by the method described in any one of the above embodiments.

[0033] In some embodiments, the quantum dots include one of ZnSe quantum dots, CdSe quantum dots, and PbSe quantum dots.

[0034] In some embodiments, the quantum dots are ZnSe quantum dots having a core-shell structure, and the band gap of the shell of the ZnSe quantum dots is greater than the band gap of the core of the ZnSe quantum dots.

[0035] In some embodiments, the material of the shell of the ZnSe quantum dots is selected from one or more of ZnS, ZnSeS, MnS, and MnO.

[0036] In some embodiments, the material of the shell of the ZnSe quantum dot is ZnS, and the thickness of the ZnS shell is two atomic layers thick or four atomic layers thick.

[0037] In some embodiments, the thickness of the ZnS shell of the ZnSe quantum dots is four atomic layers thick, and the fluorescence quantum yield of the ZnSe quantum dots is about 60%.

[0038] In some embodiments, the quantum dots are ZnSe quantum dots, and the particle size range of the ZnSe quantum dots includes 2.0-35.2 nm.

[0039] In some embodiments, the quantum dots are ZnSe quantum dots, and the wavelength of the fluorescence emission peak of the ZnSe quantum dots is greater than 455 nm and less than or equal to 470 nm.

[0040] According to yet another aspect of the present disclosure, a display device is provided, comprising the quantum dots described in any one of the foregoing embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly describe the technical solutions in the embodiments of the present disclosure, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0042] Figure 1A A flow chart of a method for preparing quantum dots according to an embodiment of the present disclosure is shown;

[0043] Figure 1B A schematic diagram showing a process of forming a quantum dot according to an embodiment of the present disclosure;

[0044] Figure 2 Shown according to Figure 1A The fluorescence spectra of the intermediate of the first ZnSe quantum dot and the first ZnSe quantum dot emitted at different stages formed by the method;

[0045] Figure 3 A transmission electron microscope image of an intermediate of a first ZnSe quantum dot prepared according to an embodiment of the present disclosure is shown;

[0046] Figure 4 A transmission electron microscope image of a first ZnSe quantum dot prepared according to an embodiment of the present disclosure is shown;

[0047] Figure 5 shows a size distribution diagram of a first ZnSe quantum dot prepared according to an embodiment of the present disclosure;

[0048] Figure 6 A comparison diagram of the first ZnSe quantum dot prepared according to an embodiment of the present disclosure under sunlight and ultraviolet light is shown;

[0049] Figure 7 The following are the absorption spectra and fluorescence spectra of the intermediate of the first ZnSe quantum dots prepared according to the embodiments of the present disclosure under different reaction conditions and reaction times (ad); (e) the emission spectrum peak wavelength and half-peak width of the intermediate of the first ZnSe quantum dots as a function of the ratio of oleic acid to oleylamine; (f) the fitting curve of the emission spectrum peak wavelength of the first ZnSe quantum dots with different particle sizes; (g) the particle size of the intermediate of the first ZnSe quantum dots as a function of reaction time under different reaction conditions;

[0050] Figure 8 The following are (a) a schematic diagram of the preparation process of the first ZnSe quantum dots prepared according to the embodiment of the present disclosure; (b) an absorption spectrum of the first ZnSe quantum dots with different particle sizes; (c) an emission spectrum of the first ZnSe quantum dots with different particle sizes; (di) a transmission electron microscope image of the first ZnSe quantum dots with different particle sizes;

[0051] Fig. 9 The following are the absorption and emission spectra of (a) the first ZnSe quantum dots, ZnSe / ZnS1 quantum dots, and ZnSe / ZnS2 quantum dots prepared according to the embodiments of the present disclosure; (b) the variation trend of the fluorescence quantum efficiency, emission peak wavelength, and half-peak width of the ZnSe / ZnS2 quantum dots with the injection amount of the Zn-S precursor; (c) the X-ray diffraction patterns of the first ZnSe quantum dots, ZnSe / ZnS1 quantum dots, and ZnSe / ZnS2 quantum dots; (d) the transmission electron microscope image and fast Fourier transform image of the first ZnSe quantum dots; (e) the transmission electron microscope image and fast Fourier transform image of the ZnSe / ZnS1 quantum dots; (f) the transmission electron microscope image and fast Fourier transform image of the ZnSe / ZnS2 quantum dots;

[0052] Fig.10 (ac) Transmission electron microscope images of CdSe quantum dots of different particle sizes prepared according to the embodiments of the present disclosure; (df) Transmission electron microscope images of PbSe quantum dots of different particle sizes; and

[0053] Fig.11 A schematic structural diagram of a display device including quantum dots according to an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present disclosure will be described clearly and completely below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0055] Figure 1A A flow chart of a method for preparing quantum dots according to an embodiment of the present disclosure is shown. Figure 1A As shown, the method 100 includes the following steps: step S101, providing a first precursor solution, a second precursor solution, a first selenium precursor solution and a second selenium precursor solution having a reaction activity lower than that of the first selenium precursor solution; step S102, adding the first selenium precursor solution to the second precursor solution to form a quantum dot intermediate; step S103, performing the following steps at least once to form quantum dots: without washing the quantum dot intermediate obtained in step S102, adding the first precursor solution and the second selenium precursor solution to the above quantum dot intermediate and reacting.

[0056] In order to enable readers to more clearly understand the growth process of the quantum dot intermediate in step S102, Figure 1B Schematic diagram showing the preparation process and formation mechanism of quantum dot intermediates. Figure 1B (a), first in stage I, the first selenium precursor and the second precursor react at high temperature (reaching the nucleation temperature) to generate monomers. Then in stage II, the monomers collide with each other in the reaction medium and aggregate, which is the nucleation process. In the nucleation process, embryos of different sizes are generated, among which the embryos exceeding the critical nucleation size are called nuclei. Only nuclei can exist stably, while embryos smaller than the critical nucleation size are unstable and will dissolve or be merged by large nuclei. Finally, in stage III, the stable nuclei further grow to form quantum dot intermediates. The process of nuclei growth is controlled by the diffusion of monomers in the reaction solution, so it is also called diffusion-controlled growth process. Figure 1B (b) is the classic Lamer nucleation model, where stages I, II, and III correspond to Figure 1B (a) Stages I, II, and III. Figure 1B (b) In stage I, the first selenium precursor and the second precursor react to generate monomers, and the monomer concentration increases continuously. When the monomer concentration exceeds the critical nucleation concentration (C min), the nucleation process of stage II is entered. Since the nucleation process consumes a large amount of monomers, when the monomer generation rate is greater than the consumption rate, the monomer concentration continues to rise, and when the monomer generation rate is less than the consumption rate, the monomer concentration begins to decrease. As the nucleation process proceeds, when the monomer concentration drops below the critical nucleation concentration, the nucleation process ends and the growth process of stage III is entered. No new crystal nuclei will be generated during the growth process, that is, the number of crystal nuclei remains unchanged during the entire growth process. Figure 1B (c) shows the size distribution of the embryos produced during the nucleation process in stage II. From a thermodynamic point of view, the size of the embryos obeys the Maxwell-Boltzmann distribution. Figure 1B (d) is the curve of the change of diffusion radius with the radius of quantum dots during the diffusion growth process in stage III. It can be seen from the figure that when the diffusion radius reaches the critical diffusion radius of the reaction system, the diffusion radius begins to increase sharply and the diffusion spheres overlap, which indicates that there is a competitive relationship in the further growth of quantum dots, making the growth of quantum dots more difficult.

[0057] It should be noted that, in the embodiments of the present disclosure, terms such as "reactivity" and "activity" refer to the activity of chemical reagents or precursor solutions in chemical reactions. The higher the reactivity or the higher the activity, the easier it is to participate in the reaction. For example, a reactant with high reactivity refers to a reactant with a high degree of reactivity, and a reactant with low reactivity refers to a reactant with a low degree of reactivity. Therefore, in step S101, the phrase "a second selenium precursor solution having a reactivity less than that of the first selenium precursor solution" means that the reactivity of the second selenium precursor solution is less than that of the first selenium precursor solution, that is, the reactivity of the second selenium precursor solution is lower than that of the first selenium precursor solution. The terms "reactivity" and "activity" can be used interchangeably in this article.

[0058] It should be noted that in the embodiments of the present disclosure, the term "intermediate" refers to (one or more) intermediate products of a certain product obtained in the chemical synthesis process. Therefore, in step S102, the phrase "intermediate of quantum dots" refers to (one or more) intermediate products of the final quantum dots obtained in the chemical synthesis process.

[0059] It should also be pointed out that in the above step S101, "providing a first precursor solution, a second precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity less than that of the first selenium precursor solution", the word "providing" includes but is not limited to preparation and purchase. For example, the applicant can prepare the first precursor solution, the second precursor solution, the first selenium precursor solution, and the second selenium precursor solution by themselves, or can prepare the first precursor solution, the second precursor solution, the first selenium precursor solution, and the second selenium precursor solution by cooperating with other companies or enterprises, or can purchase the required first precursor solution, the second precursor solution, the first selenium precursor solution, and the second selenium precursor solution from other companies or enterprises, or can adopt any other appropriate means to obtain the required first precursor solution, the second precursor solution, the first selenium precursor solution, and the second selenium precursor solution.

[0060] It should be noted that in step S103, "adding the first precursor solution and the second selenium precursor solution to the intermediate of the above-mentioned quantum dots and reacting" may refer to adding the first precursor solution and the second selenium precursor solution to the intermediate of the above-mentioned quantum dots in sequence and reacting, that is, first adding the first precursor solution to the intermediate of the above-mentioned quantum dots, and then adding the second selenium precursor solution to the intermediate of the above-mentioned quantum dots, and allowing them to react; it may also refer to adding the first precursor solution and the second selenium precursor solution to the intermediate of the above-mentioned quantum dots at the same time and allowing them to react.

[0061] It should be noted that, in the embodiments of the present disclosure, the first precursor solution and the second precursor solution can be precursor solutions of various suitable materials. For example, in some embodiments, the first precursor solution can be a first zinc precursor solution, and the second precursor solution can be a second zinc precursor solution. In this case, the quantum dots formed by method 100 are ZnSe quantum dots. In other alternative embodiments, the first precursor solution can be a first cadmium precursor solution, and the second precursor solution can be a second cadmium precursor solution. In this case, the quantum dots formed by method 100 are CdSe quantum dots. In some other alternative embodiments, the first precursor solution can be a first lead precursor solution, and the second precursor solution can be a second lead precursor solution. In this case, the quantum dots formed by method 100 are PbSe quantum dots. Therefore, the method 100 provided in the embodiment of the present disclosure has certain universality and can be used to prepare quantum dots of various suitable materials, rather than being limited to preparing quantum dots of a certain specific material.

[0062] In the method 100, a first selenium precursor solution with high reactivity is first added to the system solution to form an intermediate of quantum dots, and then a second selenium precursor solution with a lower reactivity than the first selenium precursor solution is added to form quantum dots. Through such a sequence of steps, quantum dots with a desired particle size range and a fluorescence emission peak range can be formed. In addition, since the method 100 does not need to clean the quantum dot intermediate, the waste of the quantum dot intermediate caused by the cleaning operation can be avoided, and the preparation process can be greatly simplified, reducing the process difficulty.

[0063] The following describes the steps of method 100 in detail by taking the case where the first precursor solution is a first zinc precursor solution and the second precursor solution is a second zinc precursor solution (ie, the quantum dots formed are ZnSe quantum dots, hereinafter referred to as first ZnSe quantum dots) as an example.

[0064] In some embodiments, the material of the solute in the first zinc precursor solution is the same as the material of the solute in the second zinc precursor solution, the material of the solvent in the first zinc precursor solution is the same as the material of the solvent in the second zinc precursor solution, but the ratio of the solute to the solvent in the first zinc precursor solution is different from the ratio of the solute to the solvent in the second zinc precursor solution. As used herein, the term "solute" refers to a substance dissolved by a solvent in a solution, and the term "solvent" refers to a reagent in which the solute is dispersed. The solute may contain one or more different substances, and the solvent may also contain one or more different reagents. “The ratio of solute to solvent in the first zinc precursor solution is different from the ratio of solute to solvent in the second zinc precursor solution” may include the following situations: the solute in the first zinc precursor solution and the solute in the second zinc precursor solution have the same material and the same concentration; the solvent in the first zinc precursor solution and the solvent in the second zinc precursor solution have the same material but different concentrations, in which case the ratio of solute to solvent in the first zinc precursor solution is different from the ratio of solute to solvent in the second zinc precursor solution; the solute in the first zinc precursor solution and the solute in the second zinc precursor solution have the same material but different concentrations , the solvent in the first zinc precursor solution has the same material and the same concentration as the solvent in the second zinc precursor solution, in which case the ratio of solute to solvent in the first zinc precursor solution is different from the ratio of solute to solvent in the second zinc precursor solution; and the solute in the first zinc precursor solution has the same material but different concentration as the solute in the second zinc precursor solution, and the solvent in the first zinc precursor solution has the same material but different concentration as the solvent in the second zinc precursor solution, in which case the ratio of solute to solvent in the first zinc precursor solution is different from the ratio of solute to solvent in the second zinc precursor solution.

[0065] In some embodiments, providing a first precursor solution in step S101 may include the following sub-steps: mixing a zinc inorganic salt, an organic acid, an organic amine, and an inert solvent in a ratio of 1-10 mmol: 1-10 mmol: 1-10 mL: 10-50 mL, stirring the mixture under inert gas protection and heating it until it becomes clear to form a first zinc precursor solution. It should be noted that the short sentence “mixing the zinc inorganic salt, the organic acid, the organic amine and the inert solvent in a ratio of 1~10 mmol: 1~10 mmol: 1~10 mL: 10~50 mL” means that in the synthesis process, the actual amount of the zinc inorganic salt is 1~10 mmol, the actual amount of the organic acid is 1~10 mmol, the actual amount of the organic amine is 1~10 mL and the actual amount of the inert solvent is 10~50 mL, or, it means that in the synthesis process, the actual amount of the zinc inorganic salt is x*(1~10 mmol), the actual amount of the organic acid is x*(1~10 mmol), the actual amount of the organic amine is x*(1~10 mL) and the actual amount of the inert solvent is x*(10~50 mL), where x>0. That is, 1~10 mmol: 1~10 mmol: 1~10 mL: 10~50 mL is not necessarily the actual usage ratio of zinc inorganic salt: organic acid: organic amine: inert solvent, but may be the usage ratio after taking the common divisor or common multiple of their actual usage. For example, when x is 2, the actual usage of zinc inorganic salt can be 2~20 mmol, the actual usage of organic acid can be 2~20 mmol, the actual usage of organic amine can be 2~20 mL, and the actual usage of inert solvent can be 20~100 mL. Whether it is laboratory synthesis or actual large-scale process production, the method and raw materials provided in this step can meet the requirements.

[0066] In this step, the zinc inorganic salt is called the solute in the first zinc precursor solution, and the organic acid, organic amine and inert solvent are called the solvent in the first zinc precursor solution. The zinc inorganic salt can be selected from one of the inorganic salts such as zinc chloride, zinc bromide, zinc iodide, zinc oxide, zinc nitrate, zinc acetate, zinc laurate, zinc myristate, zinc stearate, etc. The organic acid can be selected from one of the organic acids such as valeric acid, stearic acid, oleic acid, palmitic acid, levulinic acid, lactic acid, 3-hydroxypropionic acid, etc. The organic amine can be selected from one of the reagents such as oleylamine, octadecane, dodecylamine, octylamine, etc. The inert solvent can select an inert organic solvent with a boiling point higher than 200°C, including but not limited to tetradecane, hexadecane, octadecane, eicosane, tetracosane, octadecene, phenyl ether, benzyl ether, liquid paraffin, mineral oil, dodecylamine, hexadecane, octadecylamine.

[0067] In some embodiments, providing a second precursor solution in step S101 may include the following sub-steps: mixing a zinc inorganic salt, an organic acid, an organic amine, and an inert solvent in a ratio of 0.1-10 mmol: 1-10 mL: 1-10 mL: 1-20 mL, stirring the mixture under inert gas protection and heating it to 250° C.-350° C. to form a second zinc precursor solution. Similar to the above regarding the first zinc precursor solution, the short sentence "mixing the zinc inorganic salt, the organic acid, the organic amine and the inert solvent in a ratio of 0.1~10mmol:1~10mL:1~10mL:1~20mL" means that during the synthesis process, the actual amount of the zinc inorganic salt is 0.1~10mmol, the actual amount of the organic acid is 1~10mL, the actual amount of the organic amine is 1~10mL and the actual amount of the inert solvent is 1~20mL, or, it means that during the synthesis process, the actual amount of the zinc inorganic salt is x*(0.1~10mmol), the actual amount of the organic acid is x*(1~10mL), the actual amount of the organic amine is x*(1~10mL) and the actual amount of the inert solvent is x*(1~20mL), where x>0. That is, 0.1~10 mmol: 1~10 mL: 1~10 mL: 1~20 mL is not necessarily the actual usage ratio of zinc inorganic salt: organic acid: organic amine: inert solvent, but may be the usage ratio after taking the common divisor or common multiple of their actual usage. For example, when x is 2, the actual usage of zinc inorganic salt can be 0.2~20 mmol, the actual usage of organic acid can be 2~20 mL, the actual usage of organic amine can be 2~20 mL, and the actual usage of inert solvent can be 2~40 mL. Whether it is laboratory synthesis or actual large-scale process production, the method and raw materials provided in this step can meet the requirements.

[0068] In this step, the zinc inorganic salt is called the solute in the second zinc precursor solution, and the organic acid, organic amine and inert solvent are called the solvent in the second zinc precursor solution. The zinc inorganic salt can be selected from one of the inorganic salts such as zinc chloride, zinc bromide, zinc iodide, zinc oxide, zinc nitrate, zinc acetate, zinc laurate, zinc myristate, zinc stearate, etc. The organic acid can be selected from one of the organic acids such as valeric acid, stearic acid, oleic acid, palmitic acid, levulinic acid, lactic acid, 3-hydroxypropionic acid, etc. The organic amine can be selected from one of the reagents such as oleylamine, octadecane, dodecylamine, octylamine, etc. The inert solvent can select an inert organic solvent with a boiling point higher than 200°C, including but not limited to tetradecane, hexadecane, octadecane, eicosane, tetracosane, octadecene, phenyl ether, benzyl ether, liquid paraffin, mineral oil, dodecylamine, hexadecane, octadecylamine. It should be noted that the ratio of the zinc inorganic salt, organic acid, organic amine and inert solvent in the second zinc precursor solution is different from that in the first zinc precursor solution. By controlling the ratio, it is beneficial to make the particle size of the formed ZnSe quantum dots cover all particle sizes within the desired range, and it is beneficial to make the fluorescence emission peak of the formed ZnSe quantum dots cover all fluorescence emission peaks within the desired range.

[0069] In some embodiments, providing the first selenium precursor solution in step S101 may include the following sub-steps: mixing the selenium precursor and the first selenium precursor solvent in a ratio of 0.1-10 mmol:1-20 mL to form the first selenium precursor solution. The phrase "mixing the selenium precursor and the first selenium precursor solvent in a ratio of 0.1-10 mmol:1-20 mL" means that during the synthesis process, the actual amount of the selenium precursor is 0.1-10 mmol, and the actual amount of the first selenium precursor solvent is 1-20 mL, or, means that during the synthesis process, the actual amount of the selenium precursor is x*(0.1-10 mmol), and the actual amount of the first selenium precursor solvent is x*(1-20 mL), where x>0. That is, 0.1-10 mmol:1-20 mL is not necessarily the actual amount ratio of the selenium precursor: the first selenium precursor solvent, but may be the amount ratio of their actual amounts after taking a common divisor or a common multiple. For example, when x is 2, the actual amount of the selenium precursor can be 0.2-20 mmol, and the actual amount of the first selenium precursor solvent can be 2-40 mL. The method and raw materials provided in this step can meet both laboratory synthesis and actual large-scale process production.

[0070] In the first selenium precursor solution, the selenium precursor is referred to as the solute in the first selenium precursor solution, and the first selenium precursor solvent is referred to as the solvent in the first selenium precursor solution. The selenium precursor can be selected from one of selenium dioxide, selenium trioxide, selenium powder, sodium selenate, selenourea, etc. In this step, the selection and dosage of the selenium precursor play a very critical role in growing large-sized ZnSe quantum dots that emit blue light. The first selenium precursor solvent can include a phosphine solvent with active electrons. Due to the presence of active electrons, the electron pairs on the phosphorus atoms in the phosphine solvent can be combined with the selenium in the selenium precursor to form a strong coordination bond, thereby forming a phosphine selenium compound anion precursor with high reaction activity, which is very easy to react with metal cations (such as zinc cations). The phosphine solvent can be selected from, for example, trioctylphosphine, trioctylphosphine oxide, tributylphosphine, tri(trimethylsilyl)phosphine, tri(dimethylamino)phosphine, diphenylphosphine, diethylphosphine, bis(2-methoxyphenyl)phosphine, tri(diethylamino)phosphine, and the like.

[0071] In some embodiments, providing the second selenium precursor solution in step S101 may include the following sub-steps: mixing the selenium precursor and the second selenium precursor solvent in a ratio of 0.1 to 10 mmol: 1 to 20 mL to form a second selenium precursor solution. Here, the explanation of "mixing the selenium precursor and the second selenium precursor solvent in a ratio of 0.1 to 10 mmol: 1 to 20 mL" is the same as the explanation of the first selenium precursor solution above, so for the purpose of brevity, it is not repeated. Whether it is laboratory synthesis or actual large-scale process production, the method and raw materials provided in this step can be satisfied. In the second selenium precursor solution, the selenium precursor is referred to as the solute in the second selenium precursor solution, and the second selenium precursor solvent is referred to as the solvent in the second selenium precursor solution. The selenium precursor can be selected from one of selenium dioxide, selenium trioxide, selenium powder, sodium selenate, selenourea, etc. In this step, the selection and dosage of the selenium precursor play a very critical role in growing large-sized blue-light-emitting ZnSe quantum dots. The second selenium precursor solvent can include an inert solvent with inactive electrons. The inert solvent can reduce the activity of selenium after combining with the selenium in the selenium precursor. The inert solvent can be selected from inert organic solvents with a boiling point higher than 200°C, including but not limited to tetradecane, hexadecane, octadecane, eicosane, tetracosane, octadecene, phenyl ether, benzyl ether, liquid paraffin, mineral oil, dodecylamine, hexadecylamine, and octadecylamine.

[0072] It should be noted that, although the above embodiments describe their respective preparation methods in the order of the first zinc precursor solution, the second zinc precursor solution, the first selenium precursor solution, and the second selenium precursor solution, the description order is only for the convenience of readers to understand the present disclosure, and does not represent their actual preparation order. The actual preparation order of the first zinc precursor solution, the second zinc precursor solution, the first selenium precursor solution, and the second selenium precursor solution can be flexibly selected according to actual process requirements.

[0073] In some embodiments, step S102 "adding the first selenium precursor solution to the second precursor solution to form an intermediate of quantum dots" may include the following sub-steps: rapidly injecting the first selenium precursor solution prepared in the above embodiment into the second zinc precursor solution prepared in the above embodiment, reacting for 1 minute to 3 hours, and forming an intermediate of the first ZnSe quantum dot emitting blue light. The particle size of the intermediate of the first ZnSe quantum dot formed is in the range of 3 to 10 nm, and the fluorescence emission peak is in the range of 400 to 455 nm. Here, "rapidly injecting the first selenium precursor solution prepared in the above embodiment into the second zinc precursor solution prepared in the above embodiment" means injecting (e.g., dripping, pouring) the first selenium precursor solution into the second zinc precursor solution at a certain flow rate and flow rate, and it cannot be adding the second zinc precursor solution to the first selenium precursor solution. Because the second zinc precursor solution usually needs to be kept in a solution state and have reaction activity under high temperature conditions (e.g., 250°C to 350°C), while the selenium precursor can be prepared at room temperature, if the second zinc precursor solution is added to the first selenium precursor solution, the expected results of the disclosed embodiment cannot be obtained. "Rapid injection" can be understood as adding the prepared first selenium precursor solution very quickly and timely after the second zinc precursor solution is prepared, that is, the two operations of preparing the second zinc precursor solution and adding the first selenium precursor solution are as consistent as possible, and try not to leave blank time between the two operations.

[0074] It should be noted that, as described above, in the first selenium precursor solution, the selenium precursor and the first selenium precursor solvent are mixed in a ratio of x*(0.1~10 mmol:1~20 mL); in the second zinc precursor solution, the zinc inorganic salt, the organic acid, the organic amine and the inert solvent are mixed in a ratio of x*(0.1~10 mmol:1~10 mL:1~10 mL:1~20 mL), x>0. In the actual synthesis process, the volume ratio of the first selenium precursor solution and the second zinc precursor solution can be roughly in the range of 0.1~20:0.3~40. In one example, the volume of the first selenium precursor solution can be roughly in the range of 0.1~20 mL, and the volume of the second zinc precursor solution can be roughly in the range of 0.3~40 mL. In another example, the volume of the first selenium precursor solution can be roughly in the range of 0.1~20 L, and the volume of the second zinc precursor solution can be roughly in the range of 0.3~40 L. This step provides methods that can meet both laboratory synthesis and actual large-scale process production.

[0075] In some embodiments, step S103 "perform the following steps at least once to form quantum dots: without washing the intermediate of the quantum dots, add the first precursor solution and the second selenium precursor solution to the intermediate of the quantum dots and react" may include the following sub-steps: at 250°C to 350°C, add the first zinc precursor solution at room temperature and the second selenium precursor solution at room temperature prepared in the above embodiment to the intermediate of the first ZnSe quantum dots prepared in step S102 at a temperature in the range of 250°C to 350°C, react for 1 minute to 2 hours, and continue to grow a coating layer outside the intermediate of the first ZnSe quantum dots. Perform this sub-step at least once until the first ZnSe quantum dots of the desired size are grown. Then, add excess n-hexane to the above solution to stop the reaction, and transfer the above solution to a centrifuge tube. After centrifugation at 7000 rpm for about 3 minutes, pour out the supernatant in the centrifuge tube to finally obtain the first ZnSe quantum dots of the desired size that emit blue light.

[0076] The number of times the above operation is performed can be determined according to factors such as the size of the first ZnSe quantum dot, reaction time, reaction temperature, the amount and ratio of each reactant, etc., and this embodiment does not specifically limit the number of times. For example, it can be performed once, twice, three times, four times or more times.

[0077] It should be noted that if the first ZnSe quantum dot of the final desired size can be obtained by performing the operation of step S103 once, the product prepared in step S102 is an intermediate of the first ZnSe quantum dot, and the product prepared in step S103 is the final product, i.e., the first ZnSe quantum dot of the final desired size. If the operation of step S103 needs to be performed N times to obtain the first ZnSe quantum dot of the final desired size, the intermediate product prepared in step S102 and the products obtained by all N-1 operations before the N times are all intermediates of the first ZnSe quantum dot, and the product prepared by the Nth operation is the final product, i.e., the first ZnSe quantum dot of the final desired size. For example, the intermediate product obtained by performing the sub-step "at 250° C. to 350° C., successively adding the first zinc precursor solution at room temperature and the second selenium precursor solution at room temperature to the intermediate of the first ZnSe quantum dot at a temperature in the range of 250° C. to 350° C. prepared in step S102, and reacting for 1 minute to 2 hours" for the first time can be called the first intermediate of the first ZnSe quantum dot; the intermediate product obtained by performing the sub-step "at 250° C. to 350° C., successively adding the first zinc precursor solution at room temperature and the second selenium precursor solution at room temperature to the first intermediate of the first ZnSe quantum dot, and reacting for 1 minute to 2 hours" for the second time can be called the first ZnS The second intermediate of the e quantum dot; the intermediate product obtained by performing the sub-step "at 250°C~350°C, successively adding the first zinc precursor solution at room temperature and the second selenium precursor solution at room temperature to the N-2 intermediate of the first ZnSe quantum dot, and reacting for 1 minute to 2 hours" for the N-1th time can be called the N-1th intermediate of the first ZnSe quantum dot; and the final product obtained by performing the sub-step "at 250°C~350°C, successively adding the first zinc precursor solution at room temperature and the second selenium precursor solution at room temperature to the N-1th intermediate of the first ZnSe quantum dot, and reacting for 1 minute to 2 hours" for the Nth time is the first ZnSe quantum dot finally obtained. Here, N can be a positive integer greater than or equal to 3. It should be pointed out that in the execution of step S103, the respective concentrations of the first zinc precursor solution and the second selenium precursor solution added each time can be the same or different from the previous time. For example, the respective concentrations of the first zinc precursor solution and the second selenium precursor solution added when the sub-step is performed for the Nth time and the respective concentrations of the first zinc precursor solution and the second selenium precursor solution added when the sub-step is performed for the N-1th time may be the same or different. In different cases, the respective concentrations of the first zinc precursor solution and the second selenium precursor solution added when the sub-step is performed for the Nth time may be higher or lower than the respective concentrations of the first zinc precursor solution and the second selenium precursor solution added when the sub-step is performed for the N-1th time, and the embodiments of the present disclosure do not specifically limit this.

[0078] It should be noted that step S103 can be performed directly following step S102 without cleaning the intermediate of the first ZnSe quantum dot prepared in step S102. This can avoid the waste of the ZnSe quantum dot intermediate due to the cleaning operation, and can greatly simplify the preparation process and reduce the process difficulty. Therefore, if necessary, step S102 and step S103 can be combined into one step. In this step, the first zinc precursor solution is first added to the intermediate of the first ZnSe quantum dot prepared in step S102, and then the second selenium precursor solution is added. This operation sequence is conducive to the large-size growth of the first ZnSe quantum dot.

[0079] The particle size of the first ZnSe quantum dots formed in step S103 ranges from 10 to 15 nm, the fluorescence emission peak is approximately in the range of 455 to 470 nm, the fluorescence half-width is less than 30 nm, and the fluorescence quantum yield is approximately 21%. The inventors of the present application note that the particle sizes of the ZnSe quantum dots reported in the related art are relatively small (for example, less than 10 nm) and the fluorescence emission peaks are all lower than 455 nm. The blue light in this wavelength range is harmful blue light and is relatively harmful to the human eye. The first ZnSe quantum dots prepared by the method of the embodiment of the present disclosure can have a particle size of 10 to 15 nm, and the fluorescence emission peak can reach 455 to 470 nm, which is less harmful to the human eye. The first ZnSe quantum dots prepared by the method of the embodiment of the present disclosure have a larger particle size and can emit blue light that is less harmful to the human eye, so they can be widely used in the display field.

[0080] It should be noted that, although it is described here as "the particle size range of the first ZnSe quantum dot includes 10~15 nm", as the open semantics conveyed by the word "include", the particle size range of the first ZnSe quantum dot is not limited to the range of 10~15 nm. For example, in the actual preparation process, the first ZnSe quantum dot with a particle size slightly smaller than 10 nm (for example, 9.9 nm) and a particle size slightly larger than 15 nm (for example, 15.1 nm) can also be prepared. Similarly, the "fluorescence emission peak is approximately in the range of 455~470 nm" described here does not exclude that the first ZnSe quantum dot can also have a fluorescence emission peak in other wavelength ranges. For example, in the actual preparation process, the fluorescence emission peak of the first ZnSe quantum dot can also be slightly smaller than 455 nm (for example, 454 nm) and slightly larger than 470 nm (for example, 471 nm).

[0081] The first ZnSe quantum dots are environmentally friendly and pollution-free because there are no heavy metal ions with strong toxicity and serious environmental pollution. Moreover, the reaction system of this method is simple, the raw materials are easily available, the operation is easy, and the conditions are mild. It has great application value both in laboratory synthesis and actual large-scale process manufacturing. In addition, in the method provided in the embodiment of the present disclosure, the first ZnSe quantum dots required are formed by first adding a first selenium precursor solution with high reactivity and then adding a second selenium precursor solution with low reactivity, and combining the method of multi-step precursor hot injection. The first ZnSe quantum dots with a particle size in the range of 3 to 15 nm can be formed by this method, which solves the technical problem that the particle size of ZnSe quantum dots in the related art cannot exceed 10 nm. Since the emission wavelength of ZnSe quantum dots can be controlled by changing the particle size of ZnSe quantum dots, the fluorescence emission peak of the first ZnSe quantum dots prepared by this method can be realized in the range of 400~470 nm, especially in the range of 455~470 nm, thereby solving the technical problem that the fluorescence emission peak of ZnSe quantum dots in the related art cannot exceed 455 nm, which is conducive to reducing or even avoiding the damage of harmful blue light (wavelength of 400~450 nm) to the human eye. In addition, the fluorescence half-peak width of the first ZnSe quantum dot prepared by this method is less than 30 nm, so the fluorescence emission spectrum emitted by it has good color purity and color saturation. The first ZnSe quantum dot prepared by this method has good stability to water, oxygen, etc., and can be widely used in the display field. Furthermore, continuing to coat the first ZnSe quantum dot emitting blue light is expected to prepare ZnSe system quantum dots with higher fluorescence quantum yield, which will greatly promote the application process of ZnSe system materials in the display field.

[0082] The following describes the method for preparing the first ZnSe quantum dot by taking a specific example.

[0083] Step S101 , preparing a first zinc precursor solution, a second zinc precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity lower than that of the first selenium precursor solution.

[0084] Preparation of the first zinc precursor solution: 4 mmol zinc acetate, 2 mmol oleic acid, 4 mL oleylamine and 20 mL octadecene were weighed and mixed, and the mixture was stirred and heated under the protection of an inert gas to obtain a first zinc precursor solution.

[0085] Preparation of the second zinc precursor solution: 1 mmol of zinc acetate, 2 mL of oleic acid, 2 mL of oleylamine, and 10 mL of octadecene were weighed and mixed. Under the protection of an inert gas, the mixture was stirred and heated to 280° C. to obtain a second zinc precursor solution.

[0086] Preparation of the first selenium precursor solution: 1 mmol of selenium powder and 2 mL of diphenylphosphine were weighed and mixed to obtain a first selenium precursor solution.

[0087] Preparation of the second selenium precursor solution: 4 mmol of selenium powder and 20 mL of octadecene were weighed and mixed to obtain a second selenium precursor solution.

[0088] It should be noted that, although the above examples describe their respective preparation methods in the order of the first zinc precursor solution, the second zinc precursor solution, the first selenium precursor solution, and the second selenium precursor solution, the description order is only for the convenience of readers to understand the present disclosure, and does not represent their actual preparation order. The actual preparation order of the first zinc precursor solution, the second zinc precursor solution, the first selenium precursor solution, and the second selenium precursor solution can be flexibly selected according to actual process requirements.

[0089] Step S102, adding the first selenium precursor solution into the second zinc precursor solution to form a first ZnSe quantum dot intermediate.

[0090] The first selenium precursor solution prepared above was quickly injected into the second zinc precursor solution and reacted for 30 minutes to obtain an intermediate of the first ZnSe quantum dot emitting blue light with high quantum yield. Figure 2 The fluorescence spectra of the intermediate of the first ZnSe quantum dots at different reaction times are shown. Figure 2 Seven fluorescence emission spectra are shown, wherein the three fluorescence emission spectra on the far left correspond to the fluorescence emission spectra of the intermediate of the first ZnSe quantum dot when the reaction time is 1 minute, 5 minutes, and 10 minutes, respectively, in the direction from short wavelength to long wavelength along the horizontal axis, that is, from left to right. Figure 2 It can be seen that as the reaction time gradually increases, the peak wavelength of the fluorescence emission spectrum of the intermediate of the first ZnSe quantum dot also gradually increases (ie gradually shifts to the right). Figure 3 Figure 2 shows a transmission electron microscope (TEM) image of the reaction system after 20 minutes of reaction. Figure 3 As shown, after 20 minutes of reaction, the average diameter of the intermediate of the first ZnSe quantum dots was 4 nm.

[0091] Step S103, performing the following steps at least once to form a first ZnSe quantum dot: adding a first zinc precursor solution and a second selenium precursor solution to an intermediate of the first ZnSe quantum dot and reacting them.

[0092] There is no need to clean the intermediate of the first ZnSe quantum dot prepared in step S102, and ZnSe regrowth is directly performed on the basis of the intermediate of the first ZnSe quantum dot. At 300°C, first add the first zinc precursor solution at room temperature and then add the second selenium precursor solution at room temperature to the intermediate of the first ZnSe quantum dot prepared in step S102, mix them and react for 15 minutes, and continue to grow on the basis of the intermediate of the first ZnSe quantum dot. Perform the above operation four times, then add excess n-hexane to the above solution to stop the reaction, and transfer the above solution to a centrifuge tube. After centrifugation at a speed of 7000 rpm for about 3 minutes, pour out the supernatant in the centrifuge tube, and finally obtain the first ZnSe quantum dot emitting blue light of the desired size. The fluorescence quantum yield of the first ZnSe quantum dot prepared by the above method is about 21%.

[0093] It should be noted that the phrase "perform the above operation four times" specifically refers to adding the first zinc precursor solution and then the second selenium precursor solution to the intermediate of the first ZnSe quantum dots prepared in step S102 at 300°C for the first time, and reacting for 15 minutes, so that the outside of the intermediate of the first ZnSe quantum dots continues to grow, and the particle size of the obtained first ZnSe quantum dots is increased compared with the particle size of the first ZnSe quantum dots in step S102. Then, at 300°C, first add the first zinc precursor solution at room temperature and then add the second selenium precursor solution at room temperature to the first ZnSe quantum dots obtained above for the second time, and react for 15 minutes, so that the first ZnSe quantum dots continue to grow, and the particle size of the obtained first ZnSe quantum dots is increased compared with the particle size of the first ZnSe quantum dots when the first zinc precursor solution and the second selenium precursor solution are added for the first time. Then, at 300°C, the first zinc precursor solution at room temperature is first added to the first ZnSe quantum dots for the third time, and then the second selenium precursor solution at room temperature is added, and the reaction is carried out for 15 minutes, so that the first ZnSe quantum dots continue to grow, and the particle size of the first ZnSe quantum dots obtained is increased compared to the particle size of the first ZnSe quantum dots when the first zinc precursor solution and the second selenium precursor solution are added for the second time. Finally, at 300°C, the first zinc precursor solution at room temperature is first added to the first ZnSe quantum dots for the fourth time, and then the second selenium precursor solution at room temperature is added, and the reaction is carried out for 15 minutes, so that the first ZnSe quantum dots continue to grow, and the particle size of the first ZnSe quantum dots obtained is increased compared to the particle size of the first ZnSe quantum dots when the first zinc precursor solution and the second selenium precursor solution are added for the third time, thereby obtaining the first ZnSe quantum dots with the desired particle size and peak emission wavelength.

[0094] In this step, the first zinc precursor solution is added first, and then the second selenium precursor solution is added. This operation sequence is conducive to the large-size growth of the first ZnSe quantum dots.

[0095] Continue to refer Figure 2 , Figure 2 The four rightmost fluorescence emission spectra in the figure, along the direction from short wavelength to long wavelength of the horizontal axis, that is, from left to right, respectively correspond to the fluorescence emission spectrum of performing one operation (i.e., first adding the first zinc precursor solution and then adding the second selenium precursor solution, reacting for 15 minutes) (corresponding to the curve ZnSe-1ZnSe in the figure), performing two operations (i.e., first adding the first zinc precursor solution and then adding the second selenium precursor solution, reacting for 15 minutes; and then adding the first zinc precursor solution and then adding the second selenium precursor solution again, reacting for 15 minutes) (corresponding to the curve ZnSe-2ZnSe in the figure), performing three operations (i.e., first adding the first zinc precursor solution and then adding the second selenium precursor solution, reacting for 15 minutes; and then adding the first zinc precursor solution and then adding the second selenium precursor solution again, and reacting for 15 minutes). The fluorescence emission spectrum of the process of performing four operations (i.e., first adding the first zinc precursor solution and then adding the second selenium precursor solution, reacting for 15 minutes; then, once again, adding the first zinc precursor solution first and then adding the second selenium precursor solution, reacting for 15 minutes) (corresponding to the curve ZnSe-3ZnSe in the figure), and the fluorescence emission spectrum of the process of performing four operations (i.e., first adding the first zinc precursor solution and then adding the second selenium precursor solution, reacting for 15 minutes; then, once again, adding the first zinc precursor solution first and then adding the second selenium precursor solution, reacting for 15 minutes; then, once again, adding the first zinc precursor solution first and then adding the second selenium precursor solution, reacting for 15 minutes) (corresponding to the curve ZnSe-4ZnSe in the figure). Figure 2 As shown, the fluorescence emission peak of the fluorescence emission spectrum of ZnSe-1ZnSe is about 455 nm, the fluorescence emission peak of the fluorescence emission spectrum of ZnSe-4ZnSe is about 465.7 nm, and the fluorescence half-peak width is 23.98 nm.

[0096] Figure 4 FIG. 4 shows a transmission electron microscope image of the first ZnSe quantum dots formed in step S103. Figure 4 As shown, the average diameter of the first ZnSe quantum dots formed is about 13 nm.

[0097] Figure 5 The size distribution diagram of the first ZnSe quantum dots formed in step S103 is shown. Figure 5The size distribution diagram shown counts 193 first ZnSe quantum dots in total, and the average diameter of the 193 first ZnSe quantum dots is 12.95 nm, the standard deviation is 1.80 nm, the minimum diameter is 8.1 nm, and the maximum diameter is 16.7 nm.

[0098] Figure 6 A comparison diagram of the first ZnSe quantum dots formed in step S103 under sunlight (left) and ultraviolet light (right) is shown. Although the grayscale processing of the image makes it impossible to intuitively see the specific color of the first ZnSe quantum dots under sunlight and the specific color of the first ZnSe quantum dots under ultraviolet light, the difference in color between the two can be intuitively seen through the figure. In the actual experimental measurement results, the first ZnSe quantum dots under sunlight appear light green, while the first ZnSe quantum dots under ultraviolet light appear blue. That is, under ultraviolet light, the first ZnSe quantum dots can achieve blue light emission, with an emission band between 455 and 470 nm, and have a high luminous intensity.

[0099] The preparation method provided in this example has substantially the same technical effect as the preparation method described in the previous embodiment, and therefore, for the sake of brevity, it will not be described again here.

[0100] Figure 7 The characteristic curve diagram of the first ZnSe quantum dot intermediate or the first ZnSe quantum dot prepared under different reaction conditions and different reaction times is shown.

[0101] Figure 7 a shows the absorption spectrum and fluorescence emission spectrum of the first ZnSe quantum dot intermediate obtained in step S102 at different reaction times. Figure 7 The specific conditions of step S102 corresponding to step a are: the second zinc precursor solution (0.4 mmol zinc acetate, 0.2 mL oleic acid (OA), 1 mL oleylamine (OLA), 10 mL octadecene (ODE)) is heated to 280°C, and the first selenium precursor solution Se-TOP (0.2 mmol selenium powder dissolved in 0.5 mL tri-n-octylphosphine (TOP)) is quickly injected into the second zinc precursor solution to form the first ZnSe quantum dot intermediate. That is, Figure 7 In a, the volume ratio (or molar ratio) of OA to OLA is 0.2, and the first selenium precursor solution is Se-TOP. Figure 7 a shows 6 groups of absorption spectra (shown by dotted lines) and fluorescence emission spectra (shown by solid lines). The reaction times corresponding to these 6 groups of absorption spectra and fluorescence emission spectra are 1 minute, 3 minutes, 10 minutes, 30 minutes, 50 minutes, and 70 minutes, respectively. Figure 7 It can be seen from a that when the reaction time is within 30 minutes, as the reaction time gradually increases, the peak wavelengths of the absorption spectrum and fluorescence emission spectrum of the first ZnSe quantum dot intermediate also gradually increase (i.e. gradually shift to the right). When the reaction time exceeds 30 minutes, the peak wavelengths of the absorption spectrum and fluorescence emission spectrum of the first ZnSe quantum dot intermediate almost no longer move, which indicates that the precursor is basically consumed and the reaction is close to the end point.

[0102] Figure 7 b shows the absorption spectrum and fluorescence emission spectrum of the first ZnSe quantum dot intermediate obtained in step S102 at different reaction times. Figure 7 b The specific conditions of step S102 corresponding to step b are: the second zinc precursor solution (0.4 mmol zinc acetate, 0.2 mL oleic acid, 1 mL oleylamine, 10 mL octadecene) is heated to 280°C, and the first selenium precursor solution Se-DPP (0.2 mmol selenium powder dissolved in 0.5 mL diphenylphosphine (DPP)) is quickly injected into the second zinc precursor solution to form the first ZnSe quantum dot intermediate. That is, Figure 7 In b, the volume ratio of OA to OLA is 0.2, and the first selenium precursor solution is Se-DPP. Figure 7 b shows 7 groups of absorption spectra (shown by dotted lines) and fluorescence emission spectra (shown by solid lines). The reaction times corresponding to these 7 groups of absorption spectra and fluorescence emission spectra are 1 minute, 3 minutes, 5 minutes, 10 minutes, 30 minutes, 50 minutes, and 70 minutes, respectively. Figure 7 b It can be seen that when the reaction time is within 30 minutes, as the reaction time gradually increases, the peak wavelength of the absorption spectrum and fluorescence emission spectrum of the first ZnSe quantum dot intermediate also gradually increases (i.e. gradually shifts to the right). When the reaction time exceeds 30 minutes, the peak wavelength of the absorption spectrum and fluorescence emission spectrum of the first ZnSe quantum dot intermediate almost no longer moves, which indicates that the precursor is basically consumed and the reaction is close to the end point.

[0103] Figure 7 c shows the absorption spectrum and fluorescence emission spectrum of the first ZnSe quantum dot intermediate obtained in step S102 at different reaction times. Figure 7 The specific conditions of step S102 corresponding to step c are: the second zinc precursor solution (0.4 mmol zinc acetate, 0.6 mL oleic acid, 1 mL oleylamine, 10 mL octadecene) is heated to 280°C, and the first selenium precursor solution Se-DPP (0.2 mmol selenium powder dissolved in 0.5 mL diphenylphosphine) is quickly injected into the second zinc precursor solution to form the first ZnSe quantum dot intermediate. Figure 7In c, the volume ratio of OA to OLA is 0.6, and the first selenium precursor solution is Se-DPP. Figure 7 c shows 6 groups of absorption spectra (shown by dotted lines) and fluorescence emission spectra (shown by solid lines). The reaction times corresponding to these 6 groups of absorption spectra and fluorescence emission spectra are 1 minute, 3 minutes, 5 minutes, 10 minutes, 30 minutes, and 60 minutes, respectively. Figure 7 c It can be seen that when the reaction time is within 30 minutes, as the reaction time gradually increases, the peak wavelengths of the absorption spectrum and fluorescence emission spectrum of the first ZnSe quantum dot intermediate also gradually increase (i.e. gradually shift to the right). When the reaction time exceeds 30 minutes, the peak wavelengths of the absorption spectrum and fluorescence emission spectrum of the first ZnSe quantum dot intermediate almost no longer move, which indicates that the precursor is basically consumed and the reaction is close to the end point.

[0104] Figure 7 d shows the absorption spectrum and fluorescence emission spectrum of the first ZnSe quantum dot intermediate obtained in step S102 at different reaction times. Figure 7 The specific conditions of step S102 corresponding to d are: the second zinc precursor solution (0.4 mmol zinc acetate, 1 mL oleic acid, 1 mL oleylamine, 10 mL octadecene) is heated to 280°C, and the first selenium precursor solution Se-DPP (0.2 mmol selenium powder dissolved in 0.5 mL diphenylphosphine) is quickly injected into the second zinc precursor solution to form the first ZnSe quantum dot intermediate. Figure 7 In d, the volume ratio of OA to OLA is 1, and the first selenium precursor solution is Se-DPP. Figure 7 d shows 5 groups of absorption spectra (shown by dotted lines) and fluorescence emission spectra (shown by solid lines). The reaction times corresponding to these 5 groups of absorption spectra and fluorescence emission spectra are 1 minute, 3 minutes, 10 minutes, 30 minutes, and 60 minutes, respectively. Figure 7 d It can be seen that when the reaction time is within 30 minutes, as the reaction time gradually increases, the peak wavelength of the absorption spectrum and fluorescence emission spectrum of the first ZnSe quantum dot intermediate also gradually increases (that is, gradually shifts to the right). When the reaction time exceeds 30 minutes, the peak wavelength of the absorption spectrum and fluorescence emission spectrum of the first ZnSe quantum dot intermediate almost no longer moves, which indicates that the precursor is basically consumed and the reaction is close to the end point.

[0105] Figure 7 e shows the variation trend of the peak wavelength (dashed line marked with black square) and half-peak width (dashed line marked with black circle) of the fluorescence emission spectrum of the first ZnSe quantum dot intermediate with the volume ratio of oleic acid to oleylamine. Figure 7e The conditions of step S102 corresponding to step e are: the volume ratio of oleic acid to oleylamine in the second zinc precursor solution is between 0.2 and 1.0, and the first selenium precursor solution Se-DPP (0.2 mmol selenium powder dissolved in 0.5 mL diphenylphosphine) is quickly injected into the second zinc precursor solution, and the two are mixed and reacted at 280°C for 60 minutes (the precursor is consumed) to form the first ZnSe quantum dot intermediate. Figure 7 In Figure e, we can see the peak values ​​and half-peak width values ​​of the fluorescence emission spectrum of the ZnSe quantum dot intermediate when the volume ratio of oleic acid to oleylamine is 0.2, 0.4, 0.6, 0.8, and 1.0, respectively. It can be seen that when the volume ratio of oleic acid to oleylamine is between 0.2 and 1.0, the higher the oleic acid ratio, the lower the reaction activity of the second zinc precursor solution, and the smaller the peak value of the fluorescence emission wavelength of the first ZnSe quantum dot intermediate obtained at the end of the reaction. When the volume ratio of oleic acid to oleylamine is 0.2, the reaction activity of the second zinc precursor solution is the highest; when the volume ratio of oleic acid to oleylamine is 1.0, the reaction activity of the second zinc precursor solution is the lowest.

[0106] Figure 7 f shows the fitting curve of the peak wavelength of the fluorescence emission spectrum corresponding to the first ZnSe quantum dots (including the first ZnSe quantum dot intermediate obtained by step S102 and the first ZnSe quantum dot obtained by step S103) of different particle sizes obtained according to the experimental results. Figure 7 f It can be seen that as the particle size increases, the peak wavelength of the fluorescence emission spectrum of the first ZnSe quantum dot gradually increases (i.e. gradually shifts to the right). When the particle size exceeds 9 nm, the amplitude of the change in the peak wavelength of the fluorescence emission spectrum of the first ZnSe quantum dot continues to decrease.

[0107] Figure 7 g shows the Figure 7 f is a graph showing the variation trend of the particle size of the first ZnSe quantum dot intermediate with reaction time under different reaction conditions obtained by the fitting relationship. Figure 7 g shows 5 curves, and the reaction conditions of step S102 corresponding to these 5 curves are: the volume ratio of oleic acid to oleylamine in the second zinc precursor solution OA / OLA=0.2, and the first selenium precursor solution is Se-DPP; the volume ratio of oleic acid to oleylamine in the second zinc precursor solution OA / OLA=0.4, and the first selenium precursor solution is Se-DPP; the volume ratio of oleic acid to oleylamine in the second zinc precursor solution OA / OLA=0.2, and the first selenium precursor solution is Se-TOP; the volume ratio of oleic acid to oleylamine in the second zinc precursor solution OA / OLA=0.6, and the first selenium precursor solution is Se-DPP; the volume ratio of oleic acid to oleylamine in the second zinc precursor solution OA / OLA=1, and the first selenium precursor solution is Se-DPP. From Figure 7g It can be seen that when the volume ratio of oleic acid to oleylamine in the second zinc precursor solution is 0.2 (at this time, the reactivity of the second zinc precursor solution is the highest), the particle size of the first ZnSe quantum dot intermediate obtained by the reaction of the first selenium precursor solution Se-DPP with the second zinc precursor solution is the largest, about 4.7 nm. When the volume ratio of oleic acid to oleylamine in the second zinc precursor solution is 1.0 (at this time, the reactivity of the second zinc precursor solution is the lowest), the particle size of the first ZnSe quantum dot intermediate obtained by the reaction of the first selenium precursor solution Se-DPP with the second zinc precursor solution is the smallest, about 3.3 nm. In one example, the volume ratio of oleic acid to oleylamine in the first zinc precursor solution can be 0.5~2.0. Within this range, the smaller the value, the higher the reactivity of the first zinc precursor solution. That is, the reactivity of the first zinc precursor solution when the volume ratio of oleic acid to oleylamine is 0.5 is higher than the reactivity of the first zinc precursor solution when the volume ratio of oleic acid to oleylamine is 2.0.

[0108] Figure 8 a shows the preparation process of the first ZnSe quantum dot intermediate and the first ZnSe quantum dot in a more vivid way. First, the first selenium precursor solution Se-DPP with high reactivity is added to the second zinc precursor solution with high reactivity, undergoing nucleation and growth processes to form the intermediate of the first ZnSe quantum dot; then, without washing the intermediate of the first ZnSe quantum dot, the first zinc precursor solution with low reactivity and the second selenium precursor solution Se-ODE with low reactivity are directly added (can be added in sequence or simultaneously) to the intermediate of the first ZnSe quantum dot, undergoing epitaxial growth to form the first ZnSe quantum dot with a larger particle size. Optionally, the outer surface of the first ZnSe quantum dot can also be coated with a Zn-S shell layer to further increase the particle size of the first ZnSe quantum dot and improve the fluorescence quantum yield of the first ZnSe quantum dot. The shell coating of the first ZnSe quantum dot will be described in detail later.

[0109] Figure 8 b shows the absorption spectra corresponding to the first ZnSe quantum dots (including the first ZnSe quantum dot intermediate obtained in step S102 and the first ZnSe quantum dot obtained in step S103) with different particle sizes, Figure 8 c shows the fluorescence emission spectra of the first ZnSe quantum dots (including the first ZnSe quantum dot intermediate obtained by step S102 and the first ZnSe quantum dot obtained by step S103) with different particle sizes. It can be seen that Figure 8 b and Figure 8 c shows 13 curves, and each curve is labeled with numbers 1 to 13. Figure 8 b and Figure 8In c, the curves with the same number represent the absorption spectrum and fluorescence emission spectrum of the same first ZnSe quantum dot intermediate (or the same first ZnSe quantum dot). Figure 8 The curve numbered 1 in b represents the absorption spectrum of the first ZnSe quantum dot intermediate. Figure 8 The curve numbered 1 in c represents the fluorescence emission spectrum of the first ZnSe quantum dot intermediate.

[0110] exist Figure 8 b and Figure 8 In c, the curves numbered 1 to 4 correspond to the first ZnSe quantum dot intermediates prepared in step S102 after different reaction times (i.e., the first ZnSe quantum dot intermediates prepared by steps S101 and S102); the curves numbered 5 to 13 correspond to the first ZnSe quantum dots prepared by performing different repetition times in step S103 (i.e., the first ZnSe quantum dots prepared by steps S101 to S103). Below, the preparation conditions corresponding to each of the 13 curves are briefly described.

[0111] Curve 1: Step S101, preparing 0.4 mmol of a first zinc precursor solution, 0.4 mmol of a second zinc precursor solution, 0.2 mmol of a first selenium precursor solution and 0.2 mmol of a second selenium precursor solution; Step S102, adding the first selenium precursor solution to the second zinc precursor solution, reacting for 1 minute, to form an intermediate of a first ZnSe quantum dot.

[0112] Curve 2: Step S101, preparing 0.4 mmol of a first zinc precursor solution, 0.4 mmol of a second zinc precursor solution, 0.2 mmol of a first selenium precursor solution and 0.2 mmol of a second selenium precursor solution; Step S102, adding the first selenium precursor solution to the second zinc precursor solution, reacting for 3 minutes, to form an intermediate of a first ZnSe quantum dot.

[0113] Curve 3: Step S101, preparing 0.4 mmol of a first zinc precursor solution, 0.4 mmol of a second zinc precursor solution, 0.2 mmol of a first selenium precursor solution and 0.2 mmol of a second selenium precursor solution; Step S102, adding the first selenium precursor solution to the second zinc precursor solution, reacting for 10 minutes, to form an intermediate of a first ZnSe quantum dot.

[0114] Curve 4: Step S101, preparing 0.4 mmol of a first zinc precursor solution, 0.4 mmol of a second zinc precursor solution, 0.2 mmol of a first selenium precursor solution and 0.2 mmol of a second selenium precursor solution; Step S102, adding the first selenium precursor solution to the second zinc precursor solution, reacting for 30 minutes, to form an intermediate of a first ZnSe quantum dot.

[0115] Curve 5: Step S101, preparing 0.4 mmol of a first zinc precursor solution, 0.4 mmol of a second zinc precursor solution, 0.2 mmol of a first selenium precursor solution and 0.2 mmol of a second selenium precursor solution; Step S102, adding the first selenium precursor solution to the second zinc precursor solution, reacting for 30 minutes, to form an intermediate of a first ZnSe quantum dot; Step S103, without washing the intermediate of the first ZnSe quantum dot, adding the first zinc precursor solution and the second selenium precursor solution to the intermediate of the first ZnSe quantum dot and reacting to form a first ZnSe quantum dot with a fluorescence emission peak of 429 nm.

[0116] Curve 6: Step S101, preparing 0.4 mmol of a first zinc precursor solution, 0.4 mmol of a second zinc precursor solution, 0.2 mmol of a first selenium precursor solution and 0.2 mmol of a second selenium precursor solution; Step S102, adding the first selenium precursor solution to the second zinc precursor solution, reacting for 30 minutes, to form an intermediate of a first ZnSe quantum dot; Step S103, without washing the intermediate of the first ZnSe quantum dot, adding the first zinc precursor solution and the second selenium precursor solution to the intermediate of the first ZnSe quantum dot and reacting, repeating step S103 once, to form a first ZnSe quantum dot with a fluorescence emission peak of 438 nm.

[0117] Curve 7: Step S101, preparing 0.4 mmol of a first zinc precursor solution, 0.4 mmol of a second zinc precursor solution, 0.2 mmol of a first selenium precursor solution and 0.2 mmol of a second selenium precursor solution; Step S102, adding the first selenium precursor solution to the second zinc precursor solution, reacting for 30 minutes, to form an intermediate of a first ZnSe quantum dot; Step S103, without washing the intermediate of the first ZnSe quantum dot, adding the first zinc precursor solution and the second selenium precursor solution to the intermediate of the first ZnSe quantum dot and reacting, repeating step S103 four times, to form a first ZnSe quantum dot with a fluorescence emission peak of 445 nm.

[0118] Curve 8: Step S101, preparing 0.4 mmol of a first zinc precursor solution, 0.4 mmol of a second zinc precursor solution, 0.2 mmol of a first selenium precursor solution and 0.2 mmol of a second selenium precursor solution; Step S102, adding the first selenium precursor solution to the second zinc precursor solution, reacting for 30 minutes, to form an intermediate of a first ZnSe quantum dot; Step S103, without washing the intermediate of the first ZnSe quantum dot, adding the first zinc precursor solution and the second selenium precursor solution to the intermediate of the first ZnSe quantum dot and reacting, repeating step S103 six times, to form a first ZnSe quantum dot with a fluorescence emission peak of 449 nm.

[0119] Curve 9: Step S101, preparing 0.4 mmol of a first zinc precursor solution, 0.4 mmol of a second zinc precursor solution, 0.2 mmol of a first selenium precursor solution and 0.2 mmol of a second selenium precursor solution; Step S102, adding the first selenium precursor solution to the second zinc precursor solution, reacting for 30 minutes, to form an intermediate of a first ZnSe quantum dot; Step S103, without washing the intermediate of the first ZnSe quantum dot, adding the first zinc precursor solution and the second selenium precursor solution to the intermediate of the first ZnSe quantum dot and reacting, repeating step S103 eight times, to form a first ZnSe quantum dot with a fluorescence emission peak of 453 nm.

[0120] Curve 10: Step S101, preparing 0.4 mmol of a first zinc precursor solution, 0.4 mmol of a second zinc precursor solution, 0.2 mmol of a first selenium precursor solution and 0.2 mmol of a second selenium precursor solution; Step S102, adding the first selenium precursor solution to the second zinc precursor solution, reacting for 30 minutes, to form an intermediate of a first ZnSe quantum dot; Step S103, without washing the intermediate of the first ZnSe quantum dot, adding the first zinc precursor solution and the second selenium precursor solution to the intermediate of the first ZnSe quantum dot and reacting, repeating step S103 ten times, to form a first ZnSe quantum dot with a fluorescence emission peak of 458 nm.

[0121] Curve 11: Step S101, preparing 0.4 mmol of a first zinc precursor solution, 0.4 mmol of a second zinc precursor solution, 0.2 mmol of a first selenium precursor solution and 0.2 mmol of a second selenium precursor solution; Step S102, adding the first selenium precursor solution to the second zinc precursor solution, reacting for 30 minutes, to form an intermediate of a first ZnSe quantum dot; Step S103, without washing the intermediate of the first ZnSe quantum dot, adding the first zinc precursor solution and the second selenium precursor solution to the intermediate of the first ZnSe quantum dot and reacting, repeating step S103 twelve times, to form a first ZnSe quantum dot with a fluorescence emission peak of 462 nm.

[0122] Curve 12: Step S101, preparing 0.4 mmol of a first zinc precursor solution, 0.4 mmol of a second zinc precursor solution, 0.2 mmol of a first selenium precursor solution and 0.2 mmol of a second selenium precursor solution; Step S102, adding the first selenium precursor solution to the second zinc precursor solution, reacting for 30 minutes, to form an intermediate of a first ZnSe quantum dot; Step S103, without washing the intermediate of the first ZnSe quantum dot, adding the first zinc precursor solution and the second selenium precursor solution to the intermediate of the first ZnSe quantum dot and reacting, repeating step S103 fourteen times, to form a first ZnSe quantum dot with a fluorescence emission peak of 465 nm.

[0123] Curve 13: Step S101, preparing 0.4 mmol of a first zinc precursor solution, 0.4 mmol of a second zinc precursor solution, 0.2 mmol of a first selenium precursor solution and 0.2 mmol of a second selenium precursor solution; Step S102, adding the first selenium precursor solution to the second zinc precursor solution, reacting for 30 minutes, to form an intermediate of a first ZnSe quantum dot; Step S103, without washing the intermediate of the first ZnSe quantum dot, adding the first zinc precursor solution and the second selenium precursor solution to the intermediate of the first ZnSe quantum dot and reacting, repeating step S103 seventeen times, to form a first ZnSe quantum dot with a fluorescence emission peak of 470 nm.

[0124] Figure 8 d is a transmission electron microscope image of the first ZnSe quantum dots obtained by executing step S103 six times. The average particle size of the first ZnSe quantum dots is 8.3 nm and the standard deviation is 0.7 nm. Figure 8 e is a transmission electron microscope image of the first ZnSe quantum dots obtained by executing step S103 eight times. The average particle size of the first ZnSe quantum dots is 10.3 nm, and the standard deviation is 0.9 nm. Figure 8f is a transmission electron microscope image of the first ZnSe quantum dots obtained by executing step S103 thirteen times. The average particle size of the first ZnSe quantum dots is 13.4 nm, and the standard deviation is 1.3 nm. Figure 8 g is a transmission electron microscope image of the first ZnSe quantum dots obtained by executing step S103 twenty times. The average particle size of the first ZnSe quantum dots is 17.6 nm, and the standard deviation is 1.4 nm. Figure 8 h shows that the average particle size of the first ZnSe quantum dots is 27.1 nm and the standard deviation is 1.9 nm. Figure 8 The first ZnSe quantum dot of h can be obtained by the following method: Figure 8 g, and then continue to repeat step S103 five times, then add excess n-hexane to the solution to stop the reaction, and transfer the above solution to a centrifuge tube to obtain a first ZnSe quantum dot with an average particle size of 27.1 nm and a standard deviation of 1.9 nm. The reason for this operation is that if the first ZnSe quantum dots with an average particle size of 27.1 nm are obtained by directly executing step S103 several times, a large amount of precursor raw materials are required, and the reaction time is very long. By taking a certain amount of the first ZnSe quantum dot solution with an average particle size of 17.6 nm, and repeating step S103 on the basis thereof, the first ZnSe quantum dots with an average particle size of 27.1 nm are obtained, which can greatly reduce the amount of precursor raw materials used and significantly shorten the reaction time. Figure 8 The average particle size of the first ZnSe quantum dots shown in FIG. 1 is 35.2 nm, and the standard deviation is 2.4 nm. Figure 8 The first ZnSe quantum dot i can be obtained by the following method: Figure 8 h, and then continue to repeat step S103 four times on this basis, then add excess n-hexane to the solution to stop the reaction, and transfer the above solution to a centrifuge tube to obtain the first ZnSe quantum dots with an average particle size of 35.2 nm and a standard deviation of 2.4 nm.

[0125] The first ZnSe quantum dots prepared by the method 100 can be used without coating the surface with a shell layer, for example, can be applied to display products to provide blue light emission. Of course, in an alternative embodiment, the surface of the first ZnSe quantum dots can also be further coated with a shell layer to form a second ZnSe quantum dot with a core-shell structure, so that the particle size of the second ZnSe quantum dot can be further increased, thereby helping to further improve the fluorescence quantum yield of the second ZnSe quantum dot.

[0126] A second ZnSe quantum dot with a core-shell structure is prepared by coating the surface of the first ZnSe quantum dot with a shell layer. Therefore, in the second ZnSe quantum dot, the first ZnSe quantum dot prepared by the aforementioned steps S101 to S103 can be referred to as the core structure of the second ZnSe quantum dot, and the shell layer coated on the surface of the first ZnSe quantum dot can be referred to as the shell structure of the second ZnSe quantum dot.

[0127] In some embodiments, after step S103, method 100 may further include step S104: coating a shell layer on the surface of the first ZnSe quantum dot to form a second ZnSe quantum dot having a core-shell structure. Here, the first ZnSe quantum dot obtained by step S103 can be referred to as the core of the second ZnSe quantum dot having a core-shell structure, and the shell layer coated by step S104 can be referred to as the shell of the second ZnSe quantum dot having a core-shell structure. The band gap of the shell of the second ZnSe quantum dot needs to be larger than the band gap of the core of the second ZnSe quantum dot, thereby forming a "type I core-shell structure", so that the electrons and holes in the second ZnSe quantum dot can be confined in the core, thereby helping to further improve the chemical stability and fluorescence quantum yield of the second ZnSe quantum dot. In some embodiments, one or more of ZnS, ZnSeS, MnS, and MnO can be used to form the shell of the second ZnSe quantum dot.

[0128] In some embodiments, step S104 may include the following sub-step S105: adding a sulfur precursor solution to the first ZnSe quantum dot solution obtained by step S103 to form a first ZnS shell on the surface of the first ZnSe quantum dot to form a second ZnSe quantum dot, and the obtained second ZnSe quantum dot may be referred to as a ZnSe / ZnS1 quantum dot. In one example, sub-step S105 may include: adding a sulfur precursor solution to the first ZnSe quantum dot solution having an average particle size of 8.8 nm obtained by step S103 at 300°C, so that the sulfur in the sulfur precursor solution reacts with the excess zinc in the first ZnSe quantum dot solution, thereby forming a first ZnS shell having a thickness of two atomic layers on the surface of the first ZnSe quantum dot to form a ZnSe / ZnS1 quantum dot having a core-shell structure. The sulfur precursor solution may include sulfur and trioctylphosphine. The average particle size of the formed ZnSe / ZnS1 quantum dots is about 10.2 nm.

[0129] In some embodiments, step S104 may further include the following sub-step S106: adding a zinc sulfide precursor solution to the ZnSe / ZnS1 quantum dot solution obtained by step S105, so that the first ZnS shell continues to grow to form a second ZnS shell, thereby obtaining a second ZnSe quantum dot with a second ZnS shell coated on the surface of the first ZnSe quantum dot, and the second ZnSe quantum dot may be referred to as a ZnSe / ZnS2 quantum dot. In one example, sub-step S106 may include: adding a zinc sulfide precursor solution to the ZnSe / ZnS1 quantum dot solution at a rate of 4 to 8 mL / h at 280°C, so that the first ZnS shell continues to grow epitaxially to form a second ZnS shell, and finally forming a second ZnS shell with a thickness of four atomic layers on the surface of the first ZnSe quantum dot to form a ZnSe / ZnS2 quantum dot with a core-shell structure. The zinc sulfide precursor solution may include octanethiol, zinc acetate, oleylamine, and octadecene. In one example, at 280°C, a zinc sulfide precursor solution is added to a ZnSe / ZnS1 quantum dot solution at a rate of 5 mL / h, wherein the molar ratio of octanethiol, zinc acetate, and oleylamine in the zinc sulfide precursor solution is 1:1~1.5:1~1.5, thereby forming a second ZnS shell having a thickness of four atomic layers on the surface of the first ZnSe quantum dot to form a ZnSe / ZnS2 quantum dot having a core-shell structure. The average particle size of the formed ZnSe / ZnS2 quantum dots is about 11.8 nm, and the fluorescence quantum yield is about 60%. It can be seen that the ZnSe / ZnS2 quantum dots coated with the Zn-S shell layer have been significantly improved in fluorescence quantum yield compared to those without the shell layer. As known to those skilled in the art, the larger the particle size of the quantum dot, the more difficult it is to achieve a high fluorescence quantum yield. The inventors of the present application have found that the particle size of the ZnSe quantum dots prepared in the related art cannot exceed 10 nm, and it is even more impossible to provide ZnSe quantum dots with both large particle size (for example, greater than 10 nm) and high fluorescence quantum yield. In contrast, the second ZnSe quantum dots with a core-shell structure provided in the embodiment of the present disclosure can have a large particle size of 11.8 nm and a high fluorescence quantum yield of 60%, which greatly promotes the application of ZnSe quantum dots in the display field.

[0130] It should be noted that in sub-step S105, a first ZnS shell is formed on the surface of the first ZnSe quantum dot by adding a sulfur precursor solution. In sub-step S106, a second ZnS shell is formed on the surface of the first ZnSe quantum dot by adding a zinc sulfide precursor solution. That is, the precursors added in sub-step S105 and sub-step S106 are different. The inventors found that if the same precursor as that in sub-step S106, i.e., a zinc sulfide precursor, is used in sub-step S105, the morphology of the ZnSe / ZnS2 quantum dots finally obtained is relatively poor, which is not conducive to improving the chemical stability of the ZnSe / ZnS2 quantum dots and increasing the fluorescence quantum yield. By using a sulfur precursor different from the zinc sulfide precursor in sub-step S105, sulfur can act as a barrier layer, so that the ZnSe / ZnS2 quantum dots finally formed have a better morphology, thereby improving the chemical stability and fluorescence quantum yield of the ZnSe / ZnS2 quantum dots.

[0131] Fig. 9 a shows the absorption spectra (three curves on the left in the figure) and fluorescence emission spectra (three curves on the right in the figure) of the first ZnSe quantum dot emitting light at a wavelength of 455 nm, the ZnSe / ZnS1 quantum dot after coating the first ZnS shell, and the ZnSe / ZnS2 quantum dot after coating the second ZnS shell. The test conditions corresponding to the three groups of absorption spectra are that the absorbance at 365 nm is 0.1, and the test conditions corresponding to the three groups of emission spectra are that the absorbance is 0.1 and excited with 365 nm.

[0132] Fig. 9 b is the change trend of fluorescence quantum efficiency (curve marked with black squares), emission peak wavelength (curve marked with black circles), and half-peak width (curve marked with black stars) with the injection amount of Zn-S precursor during the coating process of the second ZnS shell layer of ZnSe / ZnS2 quantum dots. Fig. 9 b It can be seen that during the second ZnS shell coating process, the fluorescence quantum efficiency of ZnSe / ZnS2 quantum dots shows a trend of first increasing and then decreasing, and the emission peak wavelength and half-peak width have almost no change.

[0133] Fig. 9 c is the X-ray diffraction pattern (XRD) of the first ZnSe quantum dot, ZnSe / ZnS1 quantum dot, and ZnSe / ZnS2 quantum dot. Fig. 9 c It can be seen that with the increase of ZnS shell thickness, the diffraction peak of the sample shifts to a larger angle.

[0134] Fig. 9d corresponds to an image of the first ZnSe quantum dot without a ZnS shell, which is obtained by executing step S103 seven times, and has an average particle size of 8.8 nm and a standard deviation of 0.9 nm. Fig. 9 The lower left of d shows a high-resolution transmission electron microscopy (HRTEM) image of a first ZnSe quantum dot. Fig. 9 The lower right side of d shows a high-resolution fast Fourier transform (FFT) image of the entire first ZnSe quantum dot.

[0135] Fig. 9 e corresponds to the image of ZnSe / ZnS1 quantum dots. The conditions for forming the ZnSe / ZnS1 quantum dots are: at 300°C, 1 mmol of sulfur precursor (1 mmol of sulfur powder dissolved in 1 mL of trioctylphosphine) is injected into the first ZnSe quantum dot solution with an average particle size of 8.8 nm and reacted for one hour to obtain ZnSe / ZnS1 quantum dots with an average particle size of 10.2 nm and a standard deviation of 0.8 nm. Fig. 9 The lower left of e shows a high-resolution transmission electron microscope image of a ZnSe / ZnS1 quantum dot. Fig. 9 The lower right corner of e shows the fast Fourier transform image of the entire ZnSe / ZnS1 quantum dot in high resolution.

[0136] Fig. 9 f corresponds to the image of ZnSe / ZnS2 quantum dots, which are formed under the following conditions: at 280°C, 5 mL of 0.2 mol / L Zn-S precursor solution (1 mmol octanethiol, 1 mmol zinc acetate, 1.5 mL oleylamine, 3.5 mL octadecene, mixed and dissolved at 120°C) is slowly injected (5 mL / h) into a ZnSe / ZnS1 quantum dot solution with an average particle size of 10.2 nm, forming ZnSe / ZnS2 quantum dots with an average particle size of 11.8 nm and a standard deviation of 0.9 nm. The fluorescence quantum dot yield of the ZnSe / ZnS2 quantum dots can reach 60%. Fig. 9 The lower left of f shows a high-resolution transmission electron microscope image of a ZnSe / ZnS2 quantum dot. Fig. 9 The lower right corner of f shows the fast Fourier transform image of the entire ZnSe / ZnS2 quantum dot in high resolution.

[0137] The above description uses ZnSe quantum dots as an example to introduce the method 100 for preparing quantum dots according to the embodiment of the present disclosure. However, as mentioned above, the method 100 is not only applicable to preparing ZnSe quantum dots, but also applicable to preparing quantum dots of any other appropriate materials.

[0138] Below, taking CdSe quantum dots as an example, how to prepare CdSe quantum dots by method 100 is described.

[0139] Step S101: providing a first precursor solution, a second precursor solution, a first selenium precursor solution and a second selenium precursor solution with a reaction activity lower than that of the first selenium precursor solution. Here, the first precursor solution is a first cadmium precursor solution, and the second precursor solution is a second cadmium precursor solution.

[0140] Preparation of the first cadmium precursor solution: 8 mmol of cadmium oxide, 6 mL of oleic acid, 4 mL of oleylamine and 30 mL of octadecene were weighed and mixed, and the mixture was stirred and heated under the protection of an inert gas to obtain a first cadmium precursor solution.

[0141] Preparation of the second cadmium precursor solution: 0.4 mmol of cadmium oxide, 0.5 mL of oleic acid, 0.5 mL of oleylamine, and 10 mL of octadecene were weighed and mixed. Under the protection of an inert gas, the mixture was stirred and heated to 280° C. to obtain a second cadmium precursor solution.

[0142] Preparation of the first selenium precursor solution: 1 mmol of selenium powder and 2 mL of n-trioctylphosphine were weighed and mixed to obtain a first selenium precursor solution.

[0143] Preparation of the second selenium precursor solution: 4 mmol of selenium powder and 20 mL of octadecene were weighed and mixed to obtain a second selenium precursor solution.

[0144] The following describes several CdSe quantum dots with different particle sizes and their preparation methods.

[0145] Fig.10 a shows CdSe quantum dots with an average particle size of 12.6 nm and a standard deviation of 1.3 nm. The method for preparing the CdSe quantum dots is: prepare the required precursor solution according to the method of step S101 above. Then, step S102, quickly inject the first selenium precursor solution prepared in step S101 above into the second cadmium precursor solution, react for 30 minutes, and obtain an intermediate of CdSe quantum dots with an average particle size of 4 nm. Step S103, without washing the intermediate of the CdSe quantum dots, first add the first cadmium precursor solution at room temperature prepared in step S101 to the intermediate of the CdSe quantum dots at 280°C, and then add the second selenium precursor solution at room temperature prepared in step S101, react for 15 minutes, and continue to grow on the basis of the intermediate of the CdSe quantum dots. Repeat step S103 five times, then add excess n-hexane to the solution to stop the reaction, transfer the solution to a centrifuge tube, centrifuge at 7000 rpm for about 3 minutes, and then pour out the supernatant in the centrifuge tube to obtain Fig.10 CdSe quantum dots shown in a.

[0146] Fig.10 b shows CdSe quantum dots with an average particle size of 31.1 nm and a standard deviation of 3.1 nm. The method for preparing the CdSe quantum dots is as follows: Step S103, take one-tenth of the CdSe quantum dot solution with an average particle size of 12.6 nm prepared above (to be used as an intermediate of CdSe quantum dots), without washing it, at 280°C, first add the first cadmium precursor solution at room temperature prepared in step S101 and then add the second selenium precursor solution at room temperature prepared in step S101, react for 15 minutes, and continue to grow on the basis of the CdSe quantum dot intermediate. Repeat step S103 four times, then add excess n-hexane to the above solution to stop the reaction, and transfer the above solution to a centrifuge tube. After centrifugation at 7000 rpm for about 3 minutes, pour out the supernatant in the centrifuge tube to finally obtain Fig.10 CdSe quantum dots shown in b.

[0147] Fig.10 c shows CdSe quantum dots with an average particle size of 76.3 nm and a standard deviation of 8.3 nm. The method for preparing the CdSe quantum dots is as follows: Step S103, take one-tenth of the CdSe quantum dot solution with an average particle size of 31.1 nm prepared above (to be used as an intermediate of CdSe quantum dots), without washing it, at 280°C, first add the first cadmium precursor solution at room temperature prepared in step S101 and then add the second selenium precursor solution at room temperature prepared in step S101, react for 15 minutes, and continue to grow on the basis of the CdSe quantum dot intermediate. Repeat step S103 five times, then add excess n-hexane to the above solution to stop the reaction, and transfer the above solution to a centrifuge tube. After centrifugation at 7000 rpm for about 3 minutes, pour out the supernatant in the centrifuge tube to finally obtain Fig.10 CdSe quantum dots shown in c.

[0148] The particle size of the CdSe quantum dots prepared by method 100 can be adjusted within the range of 4 nm to 76.3 nm.

[0149] Next, PbSe quantum dots are taken as an example to describe how to prepare PbSe quantum dots by method 100 .

[0150] Step S101: providing a first precursor solution, a second precursor solution, a first selenium precursor solution, and a second selenium precursor solution with a reaction activity lower than that of the first selenium precursor solution. Here, the first precursor solution is a first lead precursor solution, and the second precursor solution is a second lead precursor solution.

[0151] Preparation of the first lead precursor solution: 8 mmol lead oxide, 6 mL oleic acid, 4 mL oleylamine and 30 mL octadecene were weighed and mixed, and the mixture was stirred and heated under the protection of an inert gas to obtain a first lead precursor solution.

[0152] Preparation of the second lead precursor solution: 0.4 mmol of cadmium oxide, 0.5 mL of oleic acid, 0.5 mL of oleylamine, and 10 mL of octadecene were weighed and mixed. Under the protection of an inert gas, the mixture was stirred and heated to 220° C. to obtain a second lead precursor solution.

[0153] Preparation of the first selenium precursor solution: 1 mmol of selenium powder and 2 mL of n-trioctylphosphine were weighed and mixed to obtain a first selenium precursor solution.

[0154] Preparation of the second selenium precursor solution: 4 mmol of selenium powder and 20 mL of octadecene were weighed and mixed to obtain a second selenium precursor solution.

[0155] The following describes several PbSe quantum dots with different particle sizes and their preparation methods.

[0156] Fig.10 d shows PbSe quantum dots with an average particle size of 15.5 nm and a standard deviation of 0.9 nm. The preparation method of the PbSe quantum dots is: prepare the required precursor solution according to the method of step S101 above. Then, step S102, quickly inject the first selenium precursor solution prepared in step S101 above into the second lead precursor solution, react for 10 minutes, and obtain an intermediate of PbSe quantum dots with an average particle size of 4.7 nm. Step S103, without washing the intermediate of the PbSe quantum dots, first add the first lead precursor solution at room temperature prepared in step S101 and then add the second selenium precursor solution at room temperature prepared in step S101 at 200°C to the intermediate of the PbSe quantum dots, react for 5 minutes, and continue to grow on the basis of the intermediate of the PbSe quantum dots. Repeat step S103 four times, then add excess n-hexane to the solution to stop the reaction, transfer the solution to a centrifuge tube, centrifuge at 7000 rpm for about 3 minutes, and then pour out the supernatant in the centrifuge tube to obtain Fig.10 PbSe quantum dots shown in d.

[0157] Fig.10e shows PbSe quantum dots with an average particle size of 24.6 nm and a standard deviation of 2.2 nm. The preparation method of the PbSe quantum dots is as follows: Step S103, take one tenth of the PbSe quantum dot solution with an average particle size of 15.5 nm prepared above (to be used as an intermediate of PbSe quantum dots), without washing it, at 200°C, first add the first lead precursor solution at room temperature prepared in step S101 and then add the second selenium precursor solution at room temperature prepared in step S101, react for 5 minutes, and continue to grow on the basis of the PbSe quantum dot intermediate. Repeat step S103 four times, then add excess n-hexane to the above solution to stop the reaction, and transfer the above solution to a centrifuge tube. After centrifugation at 7000 rpm for about 3 minutes, pour out the supernatant in the centrifuge tube to finally obtain Fig.10 PbSe quantum dots shown in e.

[0158] Fig.10 f shows PbSe quantum dots with an average particle size of 86.6 nm and a standard deviation of 10.4 nm. The preparation method of the PbSe quantum dots is as follows: Step S103, take one tenth of the PbSe quantum dot solution with an average particle size of 24.6 nm prepared above (to be used as an intermediate of PbSe quantum dots), without washing it, at 200°C, first add the first lead precursor solution at room temperature prepared in step S101 and then add the second selenium precursor solution at room temperature prepared in step S101, react for 5 minutes, and continue to grow on the basis of the PbSe quantum dot intermediate. Repeat step S103 ten times, then add excess n-hexane to the above solution to stop the reaction, and transfer the above solution to a centrifuge tube. After centrifugation at 7000 rpm for about 3 minutes, pour out the supernatant in the centrifuge tube to finally obtain Fig.10 f PbSe quantum dots shown.

[0159] The particle size of the PbSe quantum dots prepared by method 100 can be adjusted within the range of 4 nm to 86.6 nm.

[0160] According to another aspect of the present disclosure, a quantum dot is provided, which can be prepared by the method described in any of the previous embodiments. The quantum dot includes but is not limited to ZnSe quantum dots, CdSe quantum dots, and PbSe quantum dots. In the embodiment where the quantum dot is a ZnSe quantum dot, the wavelength of the fluorescence emission peak of the ZnSe quantum dot can be greater than or equal to 455 nm and less than or equal to 470 nm, such as 455nm, 458nm, 465nm, 470nm. The fluorescence half-peak width of the ZnSe quantum dot is less than 30 nm. The particle size of the ZnSe quantum dot is in the range of 2.0 to 35.2 nm, such as 8.3 nm, 10.3 nm, 13.4 nm, 17.6 nm, 27.1 nm, 35.2 nm.

[0161] The particle size of the ZnSe quantum dots provided in the embodiments of the present disclosure is in the range of 2.0 to 35.2 nm, the fluorescence half-width is less than 30 nm, and the fluorescence emission peak is in the range of 455 to 470 nm, thereby solving the technical problem that the fluorescence emission peak of the ZnSe quantum dots in the related art cannot exceed 455 nm and the particle size cannot exceed 10 nm, which is conducive to reducing or even avoiding the damage of harmful blue light (wavelength of 400 to 450 nm) to the human eye. The ZnSe quantum dots are environmentally friendly and pollution-free, and have good stability to water, oxygen, etc., and can be widely used in the display field. The above-mentioned ZnSe quantum dots can be used alone in products to provide blue light emission, or they can be applied to products after being coated with a shell layer on the outside.

[0162] In some embodiments, a ZnSe quantum dot having a core-shell structure can be formed by coating the surface of the above-mentioned ZnSe quantum dot with a shell layer. The band gap of the shell of the ZnSe quantum dot is greater than the band gap of the ZnSe quantum dot core, thereby forming a "type I core-shell structure", so that the electrons and holes in the ZnSe quantum dot can be confined in the core, thereby helping to further improve the chemical stability and fluorescence quantum yield of the ZnSe quantum dot. The material of the shell of the ZnSe quantum dot can be any appropriate material, and the embodiments of the present disclosure are not specifically limited to this. For example, the material of the shell can be selected from one or more of ZnS, ZnSeS, MnS, and MnO. In some examples, the material of the shell of the ZnSe quantum dot is ZnS, and the thickness of the ZnS shell is two atomic layers thick. In some alternative examples, the material of the shell of the ZnSe quantum dot is ZnS, the thickness of the ZnS shell is four atomic layers thick, and the fluorescence quantum yield of the ZnSe quantum dot can reach 60%. As known to those skilled in the art, the larger the particle size of the quantum dot, the more difficult it is to achieve a high fluorescence quantum yield. The inventors of the present application have found that the particle size of the ZnSe quantum dots prepared in the related art cannot exceed 10 nm, and it is even more impossible to provide ZnSe quantum dots with both large particle size (for example, greater than 10 nm) and high fluorescence quantum yield. In contrast, the ZnSe quantum dots with a core-shell structure provided in the embodiments of the present disclosure can have both a large particle size (for example, 11.8 nm) and a high fluorescence quantum yield of 60%, which greatly promotes the application of ZnSe quantum dots in the display field.

[0163] In the embodiment where the quantum dots are CdSe quantum dots, the particle size of the CdSe quantum dots can be adjusted within a range of 4.0 nm to 76.3 nm. In the embodiment where the quantum dots are PbSe quantum dots, the particle size of the PbSe quantum dots can be adjusted within a range of 4.0 nm to 86.6 nm.

[0164] According to yet another aspect of the present disclosure, a display device is provided. The display device may include the quantum dots described in any of the foregoing embodiments, such as ZnSe quantum dots, CdSe quantum dots, or CdSe quantum dots.

[0165] Fig.11 2 shows a schematic structural diagram of a display device 200. Fig.11As shown, the display device 200 includes a first substrate 201 and a second substrate 202 arranged opposite to each other and other necessary elements arranged therebetween. The display device 200 includes but is not limited to a liquid crystal display device (LCD), an organic light emitting diode (OLED), a micro light emitting diode (Micro LED), and the like.

[0166] The display device 200 includes an optoelectronic element, which may be, for example, a color film, a backlight source, a light-emitting device, or the like including the above-mentioned ZnSe quantum dots. In one example, the ZnSe quantum dots can be used as a blue light source of a blue color film and / or a backlight source in a liquid crystal display device by utilizing the photoluminescent properties of the ZnSe quantum dots. In another example, the ZnSe quantum dots can be used to make a light-emitting device, such as a quantum dot light emitting diode (QLED), by utilizing the electroluminescent properties of the ZnSe quantum dots. The QLED includes a cathode, an electron transport layer, a ZnSe quantum dot layer, a hole transport layer, a hole injection layer, an anode, and other structures. When a voltage is applied between the anode and the cathode, under the action of the electric field, the cathode and the anode generate electrons and holes, respectively, and the electrons and holes are transmitted to the ZnSe quantum dot layer via the corresponding film layer and are compounded into excitons in the ZnSe quantum dot layer, generating energy level transitions, thereby emitting light. According to specific design requirements, the QLED may be a positive structure or an inverted structure, and may be a top emission type or a bottom emission type. Compared with traditional organic light-emitting diodes, QLED has better color purity, better contrast and stronger stability.

[0167] The display device provided by the embodiment of the present disclosure can have substantially the same technical effect as the quantum dots described in the previous embodiment. Therefore, for the sake of brevity, a repeated description will not be given here.

[0168] As will be appreciated by those skilled in the art, although the various steps of the method in the disclosed embodiment are described in a particular order in the accompanying drawings, this does not require or imply that the steps must be performed in this particular order, unless the context clearly states otherwise. Additionally or alternatively, multiple steps may be combined into one step for execution, and / or one step may be decomposed into multiple steps for execution. In addition, other method steps may be inserted between steps. The inserted steps may represent improvements to the method described herein, or may be unrelated to the method. In addition, a given step may not be fully completed before the next step begins.

[0169] In the description of the embodiments of the present disclosure, the directions or positional relationships indicated by the terms "up", "down", "left", "right", etc. are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the embodiments of the present disclosure rather than requiring that the embodiments of the present disclosure must be constructed and operated in a specific direction. Therefore, they should not be understood as limitations on the present disclosure.

[0170] In the description of this specification, the description with reference to the terms "one embodiment", "another embodiment", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art may combine the different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory. In addition, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0171] The above is only a specific implementation of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A method for preparing quantum dots, comprising the following steps: Providing a first zinc precursor solution, a second zinc precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity lower than that of the first selenium precursor solution; adding the first selenium precursor solution to the second zinc precursor solution to form an intermediate of a first ZnSe quantum dot; Perform the following steps at least once to form a first ZnSe quantum dot: without washing the first ZnSe quantum dot intermediate, adding the first zinc precursor solution and the second selenium precursor solution to the first ZnSe quantum dot intermediate and reacting; as well as A shell layer is coated on the surface of the first ZnSe quantum dot to form a second ZnSe quantum dot with a core-shell structure, wherein the first ZnSe quantum dot is the core of the second ZnSe quantum dot, wherein the band gap of the shell of the second ZnSe quantum dot is greater than the band gap of the core of the second ZnSe quantum dot, Wherein, the step of coating the surface of the first ZnSe quantum dot with a shell layer to form a second ZnSe quantum dot with a core-shell structure comprises: A sulfur precursor solution is added to the first ZnSe quantum dot solution to coat the surface of the first ZnSe quantum dot with a first ZnS shell to form the second ZnSe quantum dot.

2. The method according to claim 1, wherein: The step of adding a sulfur precursor solution to the first ZnSe quantum dot solution to coat the surface of the first ZnSe quantum dot with a first ZnS shell comprises: At 300° C., the sulfur precursor solution is added to the first ZnSe quantum dot solution to form a first ZnS shell having a thickness of two atomic layers on the surface of the first ZnSe quantum dot.

3. The method according to claim 1 or 2, wherein: The sulfur precursor solution includes sulfur and n-trioctylphosphine.

4. The method according to claim 1 or 2, wherein: The average particle size of the second ZnSe quantum dots having the first ZnS shell is 10.2 nm.

5. The method according to claim 1 or 2, wherein: The step of coating the surface of the first ZnSe quantum dot with a shell layer to form a second ZnSe quantum dot with a core-shell structure comprises: A zinc sulfide precursor solution is added to the second ZnSe quantum dot solution having the first ZnS shell, so that the first ZnS shell continues to grow to form a second ZnS shell.

6. The method according to claim 5, wherein: The thickness of the second ZnS shell is four atomic layers.

7. The method according to claim 6, wherein: The step of adding a zinc sulfide precursor solution to the second ZnSe quantum dot solution having the first ZnS shell so that the first ZnS shell continues to grow to form a second ZnS shell: At 280° C., the zinc sulfide precursor solution is added to the second ZnSe quantum dot solution having the first ZnS shell at a rate of 4 to 8 mL / h to allow the first ZnS shell to continue to grow, thereby forming the second ZnS shell on the surface of the first ZnSe quantum dot.

8. The method according to claim 6 or 7, wherein: The zinc sulfide precursor solution comprises octanol, zinc acetate, oleylamine and octadecene.

9. The method according to claim 8, wherein: The molar ratio of octanethiol, zinc acetate and oleylamine in the zinc sulfide precursor solution is 1:1-1.5:1-1.

5.

10. The method according to claim 9, wherein: The average particle size of the second ZnSe quantum dots having the second ZnS shell is 11.8 nm.

11. The method according to claim 10, wherein: The fluorescence quantum yield of the second ZnSe quantum dots having the second ZnS shell is 60%.

12. The method according to claim 1, wherein: The material of the solute in the first zinc precursor solution is the same as the material of the solute in the second zinc precursor solution, the material of the solvent in the first zinc precursor solution is the same as the material of the solvent in the second zinc precursor solution, and the ratio of the solute to the solvent in the first zinc precursor solution is different from the ratio of the solute to the solvent in the second zinc precursor solution.

13. The method according to claim 12, wherein: The step of providing a first zinc precursor solution, a second zinc precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity lower than that of the first selenium precursor solution comprises: The zinc inorganic salt, organic acid, organic amine and inert solvent are mixed in a ratio of 1-10 mmol: 1-10 mmol: 1-10 mL: 10-50 mL, the mixture is stirred under the protection of inert gas and the mixture is heated until it is clear to form the first zinc precursor solution.

14. The method according to claim 12, wherein: The step of providing a first zinc precursor solution, a second zinc precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity lower than that of the first selenium precursor solution comprises: The zinc inorganic salt, organic acid, organic amine and inert solvent are mixed in a ratio of 0.1-10 mmol: 1-10 mL: 1-10 mL: 1-20 mL, the mixture is stirred under the protection of inert gas and the mixture is heated to 250° C. to 350° C. to form the second zinc precursor solution.

15. The method according to claim 14, wherein: The step of adding the first selenium precursor solution to the second zinc precursor solution to form the quantum dot intermediate comprises: dissolving selenium powder in diphenylphosphine to form the first selenium precursor solution; Using oleic acid as the organic acid in the second zinc precursor solution, using oleylamine as the organic amine in the second zinc precursor solution, and the molar ratio of oleic acid to oleylamine is 0.2:1; and The first selenium precursor solution is added to the second zinc precursor solution to form a first ZnSe quantum dot intermediate with a particle size of 4.7 nm.

16. The method according to claim 1, wherein: The step of providing a first zinc precursor solution, a second zinc precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity lower than that of the first selenium precursor solution comprises: The selenium precursor and the first selenium precursor solvent are mixed in a ratio of 0.1-10 mmol:1-20 mL to form the first selenium precursor solution.

17. The method according to claim 1, wherein: The step of providing a first zinc precursor solution, a second zinc precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity lower than that of the first selenium precursor solution comprises: The selenium precursor and the second selenium precursor solvent are mixed in a ratio of 0.1-10 mmol:1-20 mL to form the second selenium precursor solution.

18. The method according to claim 16 or 17, wherein: The selenium precursor is selected from one of selenium dioxide, selenium trioxide, selenium powder, sodium selenate and selenourea.

19. The method according to claim 16, wherein: The first selenium precursor solvent includes a phosphine solvent having active electrons.

20. The method according to claim 19, wherein: The phosphine solvent is selected from one of trioctylphosphine, trioctylphosphine oxide, tributylphosphine, tri(trimethylsilyl)phosphine, tri(dimethylamino)phosphine, diphenylphosphine, diethylphosphine, bis(2-methoxyphenyl)phosphine and tri(diethylamino)phosphine.

21. The method according to claim 17, wherein: The second selenium precursor solvent includes an inert solvent.

22. The method according to claim 21, wherein: The inert solvent is selected from one of tetradecane, hexadecane, octadecane, eicosane, tetracosane, octadecene, phenyl ether, benzyl ether, liquid paraffin, mineral oil, dodecylamine, hexadecane and octadecane.

23. A method for preparing quantum dots, comprising the following steps: Providing a first cadmium precursor solution, a second cadmium precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity lower than that of the first selenium precursor solution; adding the first selenium precursor solution to the second cadmium precursor solution to form an intermediate of a first CdSe quantum dot; as well as The following steps are performed at least once to form a first CdSe quantum dot: without washing the first CdSe quantum dot intermediate, the first cadmium precursor solution and the second selenium precursor solution are added to the first CdSe quantum dot intermediate and reacted.

24. A method for preparing quantum dots, comprising the following steps: Providing a first lead precursor solution, a second lead precursor solution, a first selenium precursor solution, and a second selenium precursor solution having a reaction activity lower than that of the first selenium precursor solution; adding the first selenium precursor solution to the second lead precursor solution to form an intermediate of a first PbSe quantum dot; as well as The following steps are performed at least once to form a first PbSe quantum dot: without washing the first PbSe quantum dot intermediate, the first lead precursor solution and the second selenium precursor solution are added to the first PbSe quantum dot intermediate and reacted.

25. A quantum dot prepared by the method according to any one of claims 1 to 24.

26. The quantum dot according to claim 25, wherein The quantum dots include one of ZnSe quantum dots, CdSe quantum dots and PbSe quantum dots.

27. The quantum dot according to claim 26, wherein The quantum dots are ZnSe quantum dots having a core-shell structure, and a band gap of a shell of the ZnSe quantum dots is larger than a band gap of a core of the ZnSe quantum dots.

28. The quantum dot according to claim 27, wherein The material of the shell of the ZnSe quantum dot is ZnS, and the thickness of the ZnS shell is two atomic layers thick or four atomic layers thick.

29. The quantum dot according to claim 28, wherein The thickness of the ZnS shell of the ZnSe quantum dot is four atomic layers thick, and the fluorescence quantum yield of the ZnSe quantum dot is 60%.

30. The quantum dot according to any one of claims 25 to 29, wherein The quantum dots are ZnSe quantum dots, and the particle size range of the ZnSe quantum dots includes 2.0 to 35.2 nm.

31. The quantum dot according to any one of claims 25 to 29, wherein The quantum dots are ZnSe quantum dots, and the wavelength of the fluorescence emission peak of the ZnSe quantum dots is greater than 455 nm and less than or equal to 470 nm.

32. A display device comprising the quantum dots according to any one of claims 25-31.

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