ZnCdSe quantum dots and a preparation method thereof

Abstract

This invention provides a ZnCdSe quantum dot and its preparation method, relating to the field of nanomaterial preparation technology. The method involves mixing a zinc precursor solution and a selenium precursor solution to obtain ZnSe clusters; then adding a cadmium precursor solution to the ZnSe clusters and heating the reaction to obtain ZnCdSe quantum dots. This invention forms ZnCdSe quantum dots through a non-injection synthesis method. First, ZnSe clusters are synthesized, then a cadmium precursor solution is added, and the temperature is increased to decompose the ZnSe clusters, forming ZnSe monomers that combine with the Cd precursor to prepare ZnCdSe quantum dots. The obtained ZnCdSe quantum dots exhibit good size uniformity and high alloying degree, facilitating industrial production.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, and in particular to a ZnCdSe quantum dot and its preparation method. Background Technology

[0002] Since Bawendi et al. first synthesized high-quality quantum dots via high-temperature injection in 1993, laboratory-synthesized quantum dots have primarily relied on this method. This method involves rapidly injecting another precursor solution into a high-temperature, high-boiling-point precursor solution, causing a rapid increase in monomer supersaturation and triggering "explosive nucleation." Subsequently, the rapid consumption of monomers and a rapid decrease in temperature separate the nucleation and growth processes, resulting in well-dispersed quantum dot materials. However, with the increasing maturity of applications in optoelectronic displays, the demand for quantum dot materials is growing exponentially. Laboratory-scale gram (g) synthesis systems are insufficient to meet industrial needs. Furthermore, the high-temperature injection process is difficult to control precisely, and the uniformity of the synthesized system during "explosive nucleation" is poor, hindering industrial scale-up.

[0003] Besides the high-temperature injection method, existing preparation methods include non-injection / direct heating methods. These methods produce homogeneous synthesized systems, have simple reaction operations, and are easier to industrialize. However, due to issues such as continuous nucleation, size uniformity is poor, leading to a broad full width at half maximum (FWHM) in the fluorescence emission spectrum. This is particularly true for the widely used ZnCdSe alloy quantum dots, where the FWHM depends not only on the size but also on the degree of alloying. In the non-injection method, due to the significant difference in reactivity between Cd and Zn precursors, CdSe is preferentially formed during heating, making it difficult to improve the alloying degree of non-ZnCdSe quantum dot materials. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention provides a ZnCdSe quantum dot and its preparation method, which results in a ZnCdSe quantum dot with a narrow half-maximum width, high alloying degree, simple reaction operation, and good system uniformity, making it suitable for industrial production.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing ZnCdSe quantum dots, comprising the following steps: ZnSe clusters were prepared by mixing zinc precursor solution and selenium precursor solution; A cadmium precursor solution was added to ZnSe clusters, and the reaction was carried out by heating to obtain ZnCdSe quantum dots. The average particle size of the ZnSe clusters was 0.2-1.5 nm.

[0006] Preferably, the molar ratio of Zn, Cd, and Se is 1:x:(1+x); where the value of x is 0.1-10.

[0007] Preferably, mixing the zinc precursor solution and the selenium precursor solution includes: Mix the zinc precursor solution and the selenium precursor solution and heat to 120~210℃.

[0008] Preferably, the method for preparing the zinc precursor solution includes: Zinc source, ligand A, and solvent A are mixed, an inert gas is introduced, and the mixture is heated until the zinc source is completely dissolved. After evacuation, the mixture is cooled. The zinc source includes one or more of the following: zinc powder, zinc chloride, zinc carbonate, zinc oxide, zinc oxalate, zinc acetate, zinc stearate, zinc undecenoate, and zinc diethyldithiocarbamate. The ligand A includes one or more of saturated fatty acids or unsaturated fatty acids with 8 or more carbon atoms. Solvent A includes one or more of tetradecane, hexadecane, octadecane, eicosane, 1-octadecene, phenyl ether, benzyl ether, and liquid paraffin.

[0009] Preferably, the preparation steps of the selenium precursor solution include: Mix the selenium source and solvent B, introduce an inert gas, heat until the selenium source is completely dissolved, and then cool to room temperature; The selenium source includes one or more of inorganic selenium, organic selenium, and organophosphorus complexes of selenium; Solvent B includes one or more of tri-n-octylphosphine and tri-n-butylphosphine.

[0010] Preferably, the inorganic selenium includes one or both of selenium powder and selenium dioxide.

[0011] Preferably, the organic selenium includes one or more of selenool, selenium ether, selenazole, selenophene, selenoester, selenoprotein, diseleno compounds, and selenoamide.

[0012] Preferably, the organophosphorus complex of selenium includes one or more of tri-n-butylphosphine selenium, tri-n-octylphosphine selenium, and diphenylphosphine selenium; Preferably, the heating reaction to obtain ZnCdSe quantum dots is carried out at a temperature of 200-300℃.

[0013] Preferably, the preparation steps of the cadmium precursor solution include: The cadmium source, ligand A, and solvent A are mixed, and an inert gas is introduced. After the cadmium source is completely dissolved, the mixture is evacuated and cooled to room temperature. The cadmium source includes one or more of cadmium powder, cadmium chloride, cadmium carbonate, cadmium oxide, cadmium oxalate, cadmium acetate, cadmium stearate, cadmium undecenoate, and cadmium diethyldithiocarbamate.

[0014] Preferably, the step of adding the cadmium precursor solution to the ZnSe cluster further includes adding an organic amine ligand.

[0015] Preferably, the organic amine ligand includes oleylamine.

[0016] Secondly, the present invention provides a ZnCdSe quantum dot, which is prepared by the ZnCdSe quantum dot preparation method described above.

[0017] Compared with the prior art, the advantages of the present invention are as follows: 1. This invention forms ZnCdSe quantum dots through a non-injection synthesis method. First, ZnSe clusters are synthesized, then a cadmium precursor solution is added, and the mixture is heated to decompose the ZnSe clusters, forming ZnSe monomers that bind to the Cd precursor, thus preparing ZnCdSe quantum dots. Controlling the size of the ZnSe clusters to 0.2-1.5 nm allows for adjustment of their reactivity as a precursor with the Cd precursor, improving the size uniformity of the obtained ZnCdSe quantum dots and facilitating industrial production.

[0018] 2. In this invention, the reaction process between ZnSe clusters and cadmium precursor solution has two reaction pathways: Pathway 1, Cd is coated on the surface of ZnSe clusters, and then ZnCdSe quantum dots are formed through cation exchange; Pathway 2, ZnSe clusters decompose to form ZnSe monomers, which combine with Cd precursors in solution to form ZnCdSe quantum dots.

[0019] 3. This invention forms ZnCdSe quantum dots through a two-step, non-injection synthesis method. The first step controls the holding temperature during ZnSe cluster preparation to ensure the required size of the ZnSe clusters. The second step controls the temperature to regulate the decomposition rate of the ZnSe clusters and adds organic amine ligands to comprehensively regulate the reaction ratios of pathway one and pathway two (organic amine ligands accelerate ZnSe cluster decomposition, increasing the proportion of pathway two). This results in ZnCdSe quantum dots with higher alloying degree and narrower half-width. In existing technologies, direct heating methods are generally used (such as the direct mixing and heating of multiple precursor solutions in Comparative Example 1). Since Cd has a much higher reactivity than Zn, direct heating preferentially generates CdSe quantum dots. As the temperature rises, a CdSe@ZnSe core-shell structure gradually forms, followed by cation exchange during high-temperature holding, forming a gradient alloy structure at the core-shell interface. Therefore, existing technologies struggle to form highly alloyed ZnCdSe quantum dots and to prepare quantum dot materials with shorter wavelengths.

[0020] 4. The synthesis scheme of the present invention can be stably reacted in a system of more than 3000 mL, and the obtained ZnCdSe quantum dots have good size uniformity and high degree of alloying, which can be industrialized. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram illustrating the mechanism of synthesizing ZnCdSe quantum dots according to the present invention.

[0023] Figure 2 This diagram illustrates two reaction pathways for the reaction between ZnSe clusters and cadmium precursor solution according to the present invention.

[0024] Figure 3 This is a low-magnification electron microscope image of the ZnCdSe quantum dots synthesized in Example 1.

[0025] Figure 4 for Figure 3 Enlarged image.

[0026] Figure 5 The image shows the XRD pattern of the ZnCdSe quantum dots synthesized in Example 1.

[0027] Figure 6 This is a high-magnification electron microscope image of the ZnCdSe quantum dots synthesized in Example 1.

[0028] Figure 7 The image shows the Cd element mapping of the ZnCdSe quantum dots synthesized in Example 1.

[0029] Figure 8 The image shows the Se element mapping diagram of the ZnCdSe quantum dots synthesized in Example 1.

[0030] Figure 9 The image shows the Zn element mapping diagram of the ZnCdSe quantum dots synthesized in Example 1.

[0031] Figure 10 The elemental distribution diagram is shown for the ZnCdSe quantum dots synthesized in Example 1.

[0032] Figure 11 The fluorescence spectrum of the ZnCdSe quantum dots synthesized in Example 1 is shown. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] This invention provides a ZnCdSe quantum dot and its preparation method. The method involves forming ZnCdSe quantum dots via a non-injection synthesis approach. First, ZnSe clusters are synthesized. Then, a cadmium precursor solution is added, and the mixture is heated to decompose the ZnSe clusters, forming ZnSe monomers that combine with the Cd precursor to obtain ZnCdSe quantum dots. The ZnCdSe quantum dots prepared by this invention have a narrow half-maximum width (HWHM) and a high degree of alloying. Furthermore, the preparation process is simple, and the system exhibits good homogeneity, making it suitable for industrial production. This invention solves the technical problems of poor uniformity in the synthesis system, difficulty in achieving industrial scale-up, poor size uniformity of ZnCdSe quantum dots, wide HWHM, and low degree of alloying in existing technologies.

[0035] To achieve the above-mentioned technical effects, the overall concept of this invention is as follows: In a first aspect, the present invention provides a method for preparing ZnCdSe quantum dots, the method comprising: ZnSe clusters were prepared by mixing zinc precursor solution and selenium precursor solution; A cadmium precursor solution was added to the ZnSe clusters, and the reaction was heated to obtain ZnCdSe quantum dots.

[0036] This invention first prepares ZnSe clusters as precursors, then controls the decomposition process of the ZnSe clusters by heating to form ZnSe monomers, which combine with Cd precursors in solution to obtain ZnCdSe quantum dot materials with different fluorescence emission wavelengths. Compared with existing technologies, the ZnCdSe quantum dots obtained by this invention have a high degree of alloying, a simple synthesis process, better uniformity of the synthesis system, and are easier to industrialize.

[0037] Preferably, the molar ratio of Zn, Cd, and Se during the preparation process is 1:x:(1+x); where x is 0.1-10. This ratio ensures that the total amount of Se is sufficient to completely combine with Zn and Cd, preventing metal residues or crystal defects due to insufficient Se source, thereby improving the crystallization quality and yield of quantum dots.

[0038] Preferably, the mixing of the zinc precursor solution and the selenium precursor solution comprises: mixing the zinc precursor solution and the selenium precursor solution and heating to 120~210℃. Extensive experimental research has shown that excessively low temperatures make it difficult to form stable ZnSe clusters; while excessively high temperatures lead to the synthesis of stable ZnSe quantum dots, which are difficult to decompose as precursors in subsequent reactions. This invention controls the temperature for preparing ZnSe clusters to 120~210℃, resulting in an average particle size of 0.2-1.5 nm for the ZnSe clusters. This allows for adjustment of their reactivity as precursors with Cd precursors, improving the size uniformity of the obtained ZnCdSe quantum dots and facilitating industrial production.

[0039] Preferably, the method for preparing the zinc precursor solution includes: mixing a zinc source, ligand A, and solvent A, introducing an inert gas, heating until the zinc source is completely dissolved, and then cooling after evacuation; The zinc source includes one or more of zinc powder, zinc chloride, zinc carbonate, zinc oxide, zinc oxalate, zinc acetate, zinc stearate, zinc undecenoate, and zinc diethyldithiocarbamate. The ligand A includes one or more of saturated or unsaturated fatty acids with 8 or more carbon atoms.

[0040] Preferably, the ligand A includes one or more of oleic acid and stearic acid.

[0041] Preferably, solvent A includes one or more of tetradecane, hexadecane, octadecane, eicosane, 1-octadecene, phenyl ether, benzyl ether, and liquid paraffin.

[0042] The temperature of the heating reaction is 200-300℃.

[0043] Liquid paraffin or octadecene, as high-boiling-point solvents, can withstand subsequent reaction temperatures of 200-300℃ without volatilizing or decomposing, ensuring the stability of the reaction system.

[0044] Preferably, the preparation steps of the selenium precursor solution include: Mix the selenium source and solvent B, introduce an inert gas, heat until the selenium source is completely dissolved, and then cool to room temperature; The selenium source includes one or more of inorganic selenium, organic selenium, and organophosphorus complexes of selenium; Preferably, the preparation steps of the selenium precursor solution include: Se powder and solvent B are mixed, an inert gas is introduced, and the mixture is heated until the Se powder is completely dissolved, and then cooled to room temperature; the solvent B includes one or more of tri-n-octylphosphine and tri-n-butylphosphine.

[0045] Se powder is poorly soluble in common organic solvents. However, using tri-n-octylphosphine (TOP) or tri-n-butylphosphine (TBP) as solvents can form stable TOP-Se or TBP-Se complexes. This not only improves the solubility of Se but also makes the release of the Se source in the reaction system more uniform, which helps to form well-dispersed nanoclusters.

[0046] Preferably, the heating reaction to obtain ZnCdSe quantum dots is carried out at a temperature of 200-300℃. Too low a temperature results in insufficient reactivity, while too high a temperature will exceed the boiling point of the solution.

[0047] Preferably, the preparation steps of the cadmium precursor solution include: The cadmium source, ligand A, and solvent A are mixed, and an inert gas is introduced. After the cadmium source is completely dissolved, the mixture is evacuated and cooled to room temperature. The cadmium source includes one or more of cadmium powder, cadmium chloride, cadmium carbonate, cadmium oxide, cadmium oxalate, cadmium acetate, cadmium stearate, cadmium undecenoate, and cadmium diethyldithiocarbamate.

[0048] Preferably, the step of adding the cadmium precursor solution to the ZnSe cluster further includes adding an organic amine ligand.

[0049] The addition of organic amine ligands promotes the decomposition of ZnSe clusters to form ZnSe monomers, enhances the reactivity of ZnSe clusters as precursors, improves the uniformity of the distribution of Zn, Cd and Se in the formed ZnCdSe quantum dots, and results in a higher degree of alloying.

[0050] Preferably, the organic amine is one or more of a saturated fatty amine or an unsaturated fatty amine with 8 or more carbon atoms.

[0051] Preferably, the organic amine ligand includes oleylamine.

[0052] Oleylamine exhibits excellent steric stabilization properties, preventing component aggregation. Furthermore, the synergistic effect of oleylamine with carboxylic acid ligands such as oleic acid better balances reaction rate and crystal growth, resulting in ZnCdSe quantum dots with uniform size and high luminescence efficiency.

[0053] Preferably, the method for preparing the zinc precursor solution includes: Mix ZnO, oleic acid, and liquid paraffin, introduce an inert gas, heat to 150℃-180℃, wait for ZnO to completely dissolve, evacuate under vacuum for 0.5~1.5 hours, and then cool to room temperature.

[0054] Excessive vacuuming time wastes energy, while insufficient vacuuming time results in incomplete removal of water and oxygen.

[0055] Preferably, the preparation steps of the selenium precursor solution include: Mix Se powder and TOP, introduce inert gas, heat to 25-180℃, and after the Se powder is completely dissolved, maintain the temperature for at least 24 hours. Then, cool to room temperature under nitrogen purging for later use. If the holding time is too short, the Se powder will not dissolve completely.

[0056] Preferably, the preparation steps of the cadmium precursor solution include: CdO, oleic acid, and liquid paraffin are mixed, an inert gas is introduced, and the mixture is heated to 150℃-180℃ until the CdO is completely dissolved. The mixture is then evacuated under vacuum for 0.5~1.5 hours and then cooled to room temperature.

[0057] Secondly, the present invention also provides ZnCdSe quantum dots prepared using the above-described method for preparing ZnCdSe quantum dots.

[0058] The ZnCdSe quantum dots have a narrow half-peak width, a high degree of alloying, and the preparation process is simple, with good system uniformity, making them suitable for industrial production.

[0059] The fluorescence emission wavelength of the ZnCdSe quantum dots obtained was 450-700 nm.

[0060] The following specific embodiments illustrate a ZnCdSe quantum dot and its preparation method according to the present invention.

[0061] Example 1: Mix 50 mmol ZnO, 50 mL oleic acid, and 50 mL liquid paraffin, introduce Ar gas under stirring, heat to 180 °C, wait for ZnO to completely dissolve, vacuum pump for 1 h, and then cool to room temperature to obtain zinc precursor solution. Mix 50 mmol CdO, 50 mL oleic acid, and 50 mL liquid paraffin, introduce Ar gas under stirring, heat to 180 °C, wait for CdO to completely dissolve, vacuum pump for 1 h, and then cool to room temperature to obtain cadmium precursor solution. Mix 100 mmol Se powder and 100 mL TOP, introduce Ar gas under stirring, heat to 80 °C, keep warm for 24 h after the Se powder is completely dissolved, and cool to room temperature under nitrogen gas to obtain a selenium precursor solution. 20 mL of zinc precursor solution, 80 mL of liquid paraffin and 5 mL of selenium precursor solution were mixed and heated to 180 °C for 4 h under stirring and Ar atmosphere, and then cooled to room temperature to obtain ZnSe cluster solution. Add 2 mL of cadmium precursor solution and 10 mL of oleylamine to a ZnSe cluster solution, introduce Ar gas under stirring, heat to 220 °C, hold for 30 min, and then cool to room temperature to obtain ZnCdSe quantum dots.

[0062] The ZnCdSe quantum dots prepared in Example 1 were tested, and the test results are shown in [reference needed]. Figure 3-11 : based on Figure 3 , Figure 4 It can be seen that ZnCdSe quantum dots have good size uniformity.

[0063] based on Figure 6 , Figure 7 , Figure 8 , Figure 9 , Figure 10 It can be seen that the Zn, Cd and Se elements are evenly distributed in the ZnCdSe quantum dots, and the degree of alloying is high.

[0064] Figure 11 The fluorescence spectrum shows that the peak width is relatively narrow. The measured full width at half maximum (FWHM) of the ZnCdSe quantum dots is 23.5 nm, and the fluorescence emission wavelength is 522.3 nm.

[0065] Example 2: Based on the preparation method of Example 1, only the heating temperature for preparing the ZnSe cluster solution was adjusted to 120°C, while all other conditions remained the same.

[0066] Experiments showed that ZnCdSe quantum dots exhibited good size uniformity; the Zn, Cd, and Se elements were evenly distributed within the ZnCdSe quantum dots, indicating a high degree of alloying. The full width at half maximum (FWHM) of the ZnCdSe quantum dots was 29.7 nm, and the fluorescence emission wavelength was 580 nm.

[0067] Example 3: Based on the preparation method of Example 1, only the heating temperature for preparing the ZnSe cluster solution was adjusted to 150°C, while all other conditions remained the same.

[0068] Experiments showed that ZnCdSe quantum dots exhibited good size uniformity; the Zn, Cd, and Se elements were evenly distributed within the ZnCdSe quantum dots, indicating a high degree of alloying. The full width at half maximum (FWHM) of the ZnCdSe quantum dots was 25.2 nm, and the fluorescence emission wavelength was 552.5 nm.

[0069] Example 4: Based on the preparation method of Example 1, only the heating temperature for preparing the ZnSe cluster solution was adjusted to 210°C, while all other conditions remained the same.

[0070] Experiments showed that ZnCdSe quantum dots exhibited good size uniformity; the Zn, Cd, and Se elements were evenly distributed within the ZnCdSe quantum dots, indicating a high degree of alloying. The full width at half maximum (FWHM) of the ZnCdSe quantum dots was 23.7 nm, and the fluorescence emission wavelength was 501.2 nm.

[0071] Example 5: Based on the preparation method of Example 1, only the amount of oleylamine was adjusted to 20 mL, and all other conditions were exactly the same.

[0072] Experiments showed that ZnCdSe quantum dots exhibited good size uniformity; the Zn, Cd, and Se elements were evenly distributed within the ZnCdSe quantum dots, indicating a high degree of alloying. The full width at half maximum (FWHM) of the ZnCdSe quantum dots was 25.9 nm, and the fluorescence emission wavelength was 550.4 nm.

[0073] Example 6: Based on the preparation method of Example 1, only the amount of each raw material was increased by 5 times proportionally, while the other conditions were exactly the same.

[0074] Experiments showed that the full width at half maximum (FWHM) of the ZnCdSe quantum dots was 24.3 nm, and the fluorescence emission wavelength was 521.9 nm. The ZnCdSe quantum dots exhibited good size uniformity; the Zn, Cd, and Se elements were evenly distributed within the quantum dots, indicating a high degree of alloying.

[0075] Example 7: Based on the preparation method of Example 1, only the amount of each raw material was increased by 20 times proportionally, while all other conditions remained the same.

[0076] Experiments showed that the full width at half maximum (FWHM) of the ZnCdSe quantum dots was 23.7 nm, and the fluorescence emission wavelength was 521.6 nm. The ZnCdSe quantum dots exhibited good size uniformity; the Zn, Cd, and Se elements were evenly distributed within the quantum dots, indicating a high degree of alloying.

[0077] Example 8: Based on the preparation method of Example 1, only the amount of each raw material was increased by 60 times proportionally, while all other conditions remained the same.

[0078] The experimentally measured full width at half maximum (FWHM) of the ZnCdSe quantum dots was 24.1 nm, and the fluorescence emission wavelength was 522.5 nm. The ZnCdSe quantum dots exhibited good size uniformity; the Zn, Cd, and Se elements were evenly distributed within the ZnCdSe quantum dots, indicating a high degree of alloying.

[0079] Example 9: Mix 50 mmol ZnO, 50 mL oleic acid, and 50 mL liquid paraffin, introduce Ar gas under stirring, heat to 180 °C, wait for ZnO to completely dissolve, vacuum pump for 1 h, and then cool to room temperature to obtain zinc precursor solution. Mix 50 mmol cadmium acetate, 50 mL oleic acid, and 50 mL octadecene, introduce Ar gas under stirring, heat to 180 °C, wait for cadmium acetate to completely dissolve, vacuum pump for 1.5 h, and then cool to room temperature to obtain cadmium precursor solution. 100 mmol Se powder and 100 mL TBP were mixed, Ar gas was introduced under stirring, the temperature was raised to 80 °C, and after the Se powder was completely dissolved, the temperature was maintained for 24 h. The mixture was then cooled to room temperature under nitrogen gas to obtain the selenium precursor solution. 20 mL of zinc precursor solution, 80 mL of octadecene and 5 mL of selenium precursor solution were mixed and heated to 150 °C for 4 h under stirring and Ar atmosphere, and then cooled to room temperature to obtain ZnSe cluster solution. Add 2 mL of cadmium precursor solution and 10 mL of oleylamine to a ZnSe cluster solution, introduce Ar gas under stirring, heat to 220 °C, hold for 30 min, and then cool to room temperature to obtain ZnCdSe quantum dots.

[0080] Experiments showed that the full width at half maximum (FWHM) of the ZnCdSe quantum dots was 24.1 nm, and the fluorescence emission wavelength was 530 nm. The ZnCdSe quantum dots exhibited good size uniformity; the Zn, Cd, and Se elements were evenly distributed within the ZnCdSe quantum dots, indicating a high degree of alloying.

[0081] Comparative Example 1: Mix 50 mmol ZnO, 50 mL oleic acid, and 50 mL liquid paraffin, introduce Ar gas under stirring, heat to 180 °C, wait for ZnO to completely dissolve, vacuum pump for 1 h, and then cool to room temperature to obtain zinc precursor solution. Mix 50 mmol CdO, 50 mL oleic acid, and 50 mL liquid paraffin, introduce Ar gas under stirring, heat to 180 °C, wait for CdO to completely dissolve, vacuum pump for 1 h, and then cool to room temperature to obtain cadmium precursor solution. Mix 100 mmol Se powder and 100 mL TOP, introduce Ar gas under stirring, heat to 80 °C, keep warm for 24 h after the Se powder is completely dissolved, and cool to room temperature under nitrogen gas to obtain a selenium precursor solution. 20 mL of zinc precursor solution, 80 mL of liquid paraffin, 5 mL of selenium precursor solution, 2 mL of cadmium precursor solution, and 10 mL of oleylamine were mixed, Ar gas was introduced under stirring, the temperature was raised to 220 °C, held for 30 min, and then cooled to room temperature to obtain ZnCdSe quantum dots.

[0082] Experiments showed that the full width at half maximum (FWHM) of the ZnCdSe quantum dots was 44.7 nm, and the fluorescence emission wavelength was 605.4 nm. The quantum dots exhibited poor size uniformity; the distribution of Zn, Cd, and Se elements in the ZnCdSe quantum dots was uneven, and the degree of alloying was low.

[0083] Comparative Example 2: The preparation method is based on Example 1, with the only difference being that oleylamine is not added, while all other conditions are exactly the same.

[0084] Experiments showed that the full width at half maximum (FWHM) of the ZnCdSe quantum dots was 36.1 nm, and the fluorescence emission wavelength was 505.2 nm. The ZnCdSe quantum dots exhibited poor size uniformity; the distribution of Zn, Cd, and Se elements within them was uneven, and the degree of alloying was low.

[0085] Comparative Example 3: Based on the preparation method of Example 1, only the heating temperature for preparing the ZnSe cluster solution was adjusted to 100°C, while all other conditions remained the same.

[0086] Experiments showed that the full width at half maximum (FWHM) of ZnCdSe quantum dots was 32.5 nm, and the fluorescence emission wavelength was 600 nm. The size uniformity of ZnCdSe quantum dots was poor; the distribution of Zn, Cd, and Se elements within the quantum dots was uneven, and the degree of alloying was low.

[0087] Comparative Example 4: Based on the preparation method of Example 1, only the heating temperature for preparing the ZnSe cluster solution was adjusted to 240°C, while all other conditions remained the same.

[0088] Experiments showed that the full width at half maximum (FWHM) of ZnCdSe quantum dots was 40.5 nm, and the fluorescence emission wavelength was 605.7 nm. ZnCdSe quantum dots exhibited poor size uniformity; the distribution of Zn, Cd, and Se elements within them was uneven, and the degree of alloying was low.

[0089] Based on the experimental results of Examples 1-9 and Comparative Examples 1-4 above, it can be seen that the present invention forms ZnCdSe quantum dots through a two-step heating non-injection synthesis method. First, ZnSe clusters are synthesized, then a cadmium precursor solution is added, and the temperature is increased to decompose the ZnSe clusters, forming ZnSe monomers that combine with the Cd precursor to prepare ZnCdSe quantum dots. The obtained ZnCdSe quantum dots have good size uniformity and high alloying degree, which is convenient for industrial production.

[0090] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0091] It should be noted that in this invention, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified.

[0092] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing ZnCdSe quantum dots, characterized in that, ZnSe clusters were prepared by mixing zinc precursor solution and selenium precursor solution; A cadmium precursor solution was added to the ZnSe clusters, and the reaction was heated to obtain ZnCdSe quantum dots.

2. The method for preparing ZnCdSe quantum dots as described in claim 1, characterized in that, The molar ratio of Zn, Cd, and Se is 1:x:(1+x); The value of x ranges from 0.1 to 10.

3. The method for preparing ZnCdSe quantum dots as described in claim 1, characterized in that, The mixing of the zinc precursor solution and the selenium precursor solution includes: Mix the zinc precursor solution and the selenium precursor solution and heat to 120-210℃.

4. The method for preparing ZnCdSe quantum dots as described in claim 1, characterized in that, The method for preparing the zinc precursor solution includes: Zinc source, ligand A, and solvent A are mixed, an inert gas is introduced, and the mixture is heated until the zinc source is completely dissolved. After evacuation, the mixture is cooled. The zinc source includes one or more of zinc powder, zinc chloride, zinc carbonate, zinc oxide, zinc oxalate, zinc acetate, zinc stearate, zinc undecenoate, and zinc diethyldithiocarbamate. The ligand A includes one or more of saturated fatty acids or unsaturated fatty acids with 8 or more carbon atoms. Solvent A includes one or more of tetradecane, hexadecane, octadecane, eicosane, 1-octadecene, phenyl ether, benzyl ether, and liquid paraffin.

5. The method for preparing ZnCdSe quantum dots as described in claim 1, characterized in that, The preparation steps of the selenium precursor solution include: Mix the selenium source and solvent B, introduce an inert gas, heat until the selenium source is completely dissolved, and then cool to room temperature; The selenium source includes one or more of inorganic selenium, organic selenium, and organophosphorus complexes of selenium; Solvent B includes one or more of tri-n-octylphosphine and tri-n-butylphosphine.

6. The method for preparing ZnCdSe quantum dots as described in claim 1, characterized in that, The heating reaction yields ZnCdSe quantum dots at a temperature of 200-300℃.

7. The method for preparing ZnCdSe quantum dots as described in claim 1, characterized in that, The preparation steps of the cadmium precursor solution include: The cadmium source, ligand A, and solvent A are mixed, and an inert gas is introduced. After the cadmium source is completely dissolved, the mixture is evacuated and cooled to room temperature. The cadmium source includes one or more of cadmium powder, cadmium chloride, cadmium carbonate, cadmium oxide, cadmium oxalate, cadmium acetate, cadmium stearate, cadmium undecenoate, and cadmium diethyldithiocarbamate.

8. The method for preparing ZnCdSe quantum dots as described in claim 1, characterized in that, The step of adding a cadmium precursor solution to the ZnSe cluster also includes adding an organic amine ligand.

9. The method for preparing ZnCdSe quantum dots as described in claim 1, characterized in that, The organic amine is one or more of a saturated fatty amine or an unsaturated fatty amine with 8 or more carbon atoms.

10. A ZnCdSe quantum dot, characterized in that, The ZnCdSe quantum dots were prepared using the preparation method described in any one of claims 1-9.

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