Preparation method of CdZnSe quantum dots
By controlling the precursor reactivity in stages, CdZnSe quantum dots were prepared by in-situ epitaxial growth, solving the problem of low quantum yield of large-size quantum dots and realizing the efficient preparation of large-size, high-quality quantum dots suitable for quantum dot light-emitting diodes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-01
- Publication Date
- 2026-03-10
AI Technical Summary
Existing technologies suffer from low quantum yield when preparing large-size quantum dots, especially due to the obvious core-shell interface, high lattice stress, and increased defect states, which leads to a decline in the performance of quantum dot light-emitting diodes.
CdZnSe quantum dots were prepared by in-situ epitaxial growth using a staged regulation of precursor reactivity. This included the preparation of CdZnSe crystal nuclei, early, middle, and late epitaxial growth, with different active cadmium, zinc, and selenium precursors added to control the growth process of the quantum dots.
Controllable growth of CdZnSe quantum dots larger than 30 nm was achieved with a quantum yield of over 80% and uniform particle size distribution, making it suitable for optoelectronic devices such as quantum dot light-emitting diodes.
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Figure CN121628636A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for preparing CdZnSe quantum dots, belonging to the field of semiconductor nanomaterials technology. Background Technology
[0002] Quantum dots have shown broad application prospects in display, lighting, and bioimaging due to their advantages such as narrow emission spectrum, high color purity, and good stability. In particular, in quantum dot light-emitting diodes (QLEDs), large-size (>15 nm) quantum dots can effectively enhance carrier recombination efficiency and improve device performance.
[0003] Currently, large-size quantum dots can increase the carrier recombination probability, thereby improving the brightness and efficiency of quantum dot light-emitting diodes. However, although traditional layer-by-layer growth methods can prepare quantum dots larger than 30 nm, they suffer from problems such as obvious core-shell interface, high lattice stress, and increased defect states, leading to a decrease in quantum yield. Therefore, it is of great significance to develop a simple and efficient method for preparing large-size, high-quality quantum dots. Summary of the Invention
[0004] This invention proposes a method for preparing CdZnSe quantum dots, which aims to solve the problem of low quantum yield of quantum dots when preparing large-size quantum dots in existing technologies.
[0005] The technical solution of this invention: a method for preparing CdZnSe quantum dots, the method comprising: Step 1) Prepare a CdZnSe nucleus reaction solution containing CdZnSe nuclei; Step 2) Based on the CdZnSe nucleation reaction solution, perform preliminary in-situ epitaxial growth to form the first-stage CdZnSe quantum dot reaction system; Step 3) Based on the first-stage CdZnSe quantum dot reaction system, perform mid-term in-situ epitaxial growth to form the second-stage CdZnSe quantum dot reaction system; Step 4) Based on the second-stage CdZnSe quantum dot reaction system, perform in-situ epitaxial growth to form the third-stage CdZnSe quantum dot reaction system.
[0006] Furthermore, the process of preparing the CdZnSe nucleus reaction solution containing CdZnSe nuclei includes: under nitrogen protection, mixing a mixed precursor of low-reactivity cadmium precursor and low-reactivity zinc precursor with octadecene, heating and evacuating for a certain time, gradually increasing the temperature to the nucleation temperature, injecting a medium-reactivity selenium precursor at the nucleation temperature to form a nucleation reaction solution, and after a nucleation reaction time, obtaining the CdZnSe nucleus reaction solution containing CdZnSe nuclei.
[0007] Further, the volume ratio of the low-reactivity cadmium precursor, the low-reactivity zinc precursor, and the medium-reactivity selenium precursor is (1-10):(1-10):(1-10); the volume ratio of the octadecene to the mixed precursor of the low-reactivity cadmium precursor and the low-reactivity zinc precursor is (1-10):(1-10); the heating, evacuation, and heat preservation for a certain period of time involves heating to 120 ℃-180 ℃, evacuating to 1 Pa-0.1 Pa, and holding for 30-60 min; the gradient heating to the nucleation temperature is achieved at a heating rate of 10 ℃ / min, the nucleation temperature is 280 ℃-350 ℃, and the nucleation reaction time is 60 min-120 min; The low-reactivity cadmium precursor is a mixed solution formed by a cadmium source, a solvent, and a dispersant; wherein the volume ratio of the solvent to the dispersant is (1-10):(1-10); the solvent in the low-reactivity cadmium precursor is a long-chain carboxylic acid, and the long-chain carboxylic acid is any one of pentadecanoic acid, hexadecanoic acid, oleic acid, and stearic acid; the dispersant is octadecene.
[0008] Furthermore, the process of forming the first-stage CdZnSe quantum dot reaction system by performing early-stage in-situ epitaxial growth on the basis of the CdZnSe nucleation reaction solution includes: Step 2-1) Maintain the temperature of the CdZnSe nucleation reaction solution at the reaction temperature and continuously purge with nitrogen for protection; then add a low-reactivity zinc precursor to the CdZnSe nucleation reaction solution; Step 2-2) After adding the low-reactivity zinc precursor, continue annealing at the reaction temperature for a certain period of time; Steps 2-3) Then add a mixed solution of medium-reactive cadmium precursor and medium-reactive selenium precursor; continue annealing the reaction at the reaction temperature for a certain time, and then naturally cool to room temperature to obtain the first-stage CdZnSe quantum dot reaction system.
[0009] Further, the reaction temperature is 280℃~320℃; the volume ratio of the low-reactivity zinc precursor to the CdZnSe nucleation reaction solution is (1~10):(1~10); the annealing time while maintaining the reaction temperature is 10min~30min; the volume ratio of the mixed solution of the medium-reactivity cadmium precursor and the medium-reactivity selenium precursor to the CdZnSe nucleation reaction solution is (1~10):(1~10); the volume ratio of the medium-reactivity cadmium precursor to the medium-reactivity selenium precursor in the mixed solution of the medium-reactivity cadmium precursor and the medium-reactivity selenium precursor is (1~10):(1~10). The low-reactivity zinc precursor is preferably a mixed solution formed by a zinc source, octadecene, and a long-chain carboxylic acid; wherein the volume ratio of octadecene to the long-chain carboxylic acid is (1-10):(1-10); the long-chain carboxylic acid is one or a combination of several of pentadecanoic acid, hexadecanoic acid, oleic acid, stearic acid, eicosanoic acid, and icosanoic acid. The reactive cadmium precursor is a mixed solution of cadmium source, octadecene, and intermediate-chain carboxylic acid; wherein the volume ratio of octadecene to intermediate-chain carboxylic acid is (1-10):(1-10); the intermediate-chain carboxylic acid is any one or a combination of several of tetradecanoic acid, undecanoic acid, decanoic acid, and heptanoic acid.
[0010] Furthermore, the process of forming the second-stage CdZnSe quantum dot reaction system through intermediate in-situ epitaxial growth based on the first-stage CdZnSe quantum dot reaction system includes: Step 3-1) Maintain the temperature of the first-stage CdZnSe quantum dot reaction system at the reaction temperature, and add a moderately reactive zinc precursor to the first-stage CdZnSe quantum dot reaction system; Step 3-2) After adding the medium-reactivity zinc precursor, anneal at the reaction temperature; then add a mixed solution of the highly reactive cadmium precursor and the medium-reactivity selenium precursor; continue annealing at the reaction temperature to form the second-stage CdZnSe quantum dot reaction system.
[0011] Further, the reaction temperature is 280℃~320℃, more preferably 310℃; the volume ratio of the medium-reactivity zinc precursor to the first-stage CdZnSe quantum dot reaction system is (1~10):(1~10); the volume ratio of the mixed solution of the highly reactive cadmium precursor and the medium-reactivity selenium precursor to the first-stage CdZnSe quantum dot reaction system is (1~10):(1~10); the volume ratio of the highly reactive cadmium precursor to the medium-reactivity selenium precursor in the mixed solution of the highly reactive cadmium precursor and the medium-reactivity selenium precursor is (1~10):(1~10). The highly reactive cadmium precursor is a mixed solution of cadmium source, oleylamine, and octadecene; wherein the volume ratio of oleylamine to octadecene is (1-10):(1-10).
[0012] Furthermore, the process of forming the third-stage CdZnSe quantum dot reaction system through intermediate in-situ epitaxial growth based on the second-stage CdZnSe quantum dot reaction system includes: Step 4-1) Maintain the temperature of the second-stage CdZnSe quantum dot reaction system at the reaction temperature and add a highly reactive zinc precursor; Step 4-2) After the highly reactive zinc precursor is added, maintain the reaction temperature and anneal; then add the highly reactive cadmium precursor, and anneal again after the addition is complete. Step 4-3) Then add the highly reactive selenium precursor and react for a certain period of time, then stop heating and let it cool naturally.
[0013] Further, the reaction temperature is 280℃~320℃; the volume ratio of the highly reactive zinc precursor to the second-stage CdZnSe quantum dot reaction system is (1~10):(1~10); the volume ratio of the highly reactive cadmium precursor to the second-stage CdZnSe quantum dot reaction system is (1~10):(1~10); the volume ratio of the highly reactive selenium precursor to the second-stage CdZnSe quantum dot reaction system is (1~10):(1~10). The highly reactive zinc precursor is a mixed solution of zinc source, oleylamine, and octadecene; wherein the volume ratio of oleylamine to octadecene is (1-10):(1-10). The highly reactive selenium precursor is a mixed solution formed by a selenium source, a solvent, and a dispersant, with a volume ratio of solvent to dispersant of (1-10):(1-10). The solvent in the highly reactive selenium precursor is any one or a combination of several of diphenylphosphine, tri-n-butylphosphine, and triphenylphosphine.
[0014] Further, the intermediate reactive selenium precursor is a mixed solution formed by a selenium source, a solvent, and a dispersant; wherein the volume ratio of the solvent to the dispersant is (1-10):(1-10); the solvent is any one of tri-n-octylphosphine, tri-n-octylphosphine oxide, octylamine, octadecylamine, and oleylamine; the dispersant is octadecene; the intermediate reactive zinc precursor is a mixed solution formed by a zinc source, a medium-chain carboxylic acid, and octadecene; wherein the volume ratio of octadecene to the medium-chain carboxylic acid is (1-10):(1-10); the medium-chain carboxylic acid is any one or a combination of several of tetradecanoic acid, undecanoic acid, decanoic acid, and heptanoic acid.
[0015] The beneficial effects of this invention are: 1) This invention is a synthesis method for ultra-large CdZnSe quantum dots based on precursor activity regulation and epitaxial growth; the method for preparing ultra-large CdZnSe quantum dots based on precursor activity regulation achieves controllable epitaxial growth of quantum dots by controlling the precursor reactivity in stages, and can obtain quantum dots with a size greater than 30 nm and a quantum yield of more than 80%. 2) The method of the present invention controls the reactivity of zinc precursor, cadmium precursor and selenium precursor, and adds precursors with different activities in stages to achieve isotropic and uniform epitaxial growth on quantum dot nuclei, and finally obtains CdZnSe quantum dots with a size greater than 30nm and a quantum yield of more than 80%. 3) The present invention is simple to operate, and the prepared quantum dots have uniform particle size distribution and excellent fluorescence performance, which can be applied to optoelectronic devices such as quantum dot light-emitting diodes. Attached Figure Description
[0016] Appendix Figure 1 The image shows a transmission electron microscope (TEM) image of the CdZnSe quantum dot crystal nuclei prepared in step 1 of Example 1.
[0017] Appendix Figure 2 The image shows the histogram of the size distribution of CdZnSe quantum dot nuclei prepared in step 1 of Example 1.
[0018] Appendix Figure 3 TEM image of CdZnSe quantum dots prepared in step 2 of Example 1.
[0019] Appendix Figure 4 The image shows the CdZnSe quantum dots and size distribution histogram prepared in step 2 of Example 1.
[0020] Appendix Figure 5 TEM image of the CdZnSe quantum dots prepared in step 3 of Example 1, in the second stage.
[0021] Appendix Figure 6 The histogram of the size distribution of CdZnSe quantum dots prepared in step 3 of Example 1 is shown.
[0022] Appendix Figure 7 The image shows a TEM image of the CdZnSe quantum dots prepared in step 4 of Example 1, representing the third stage.
[0023] Appendix Figure 8 TEM image and size distribution histogram of the CdZnSe quantum dots prepared in step 4 of Example 1.
[0024] Appendix Figure 9 The image shows a high-resolution transmission electron microscope (HRTEM) image and a top-left Fourier transform of the CdZnSe quantum dots prepared in step 2 of Example 1.
[0025] Appendix Figure 10 The image shows a high-resolution transmission electron microscope (HRTEM) image and a top-left Fourier transform of the CdZnSe quantum dots prepared in step 3 of Example 1.
[0026] Appendix Figure 11The image shows a high-resolution transmission electron microscope (HRTEM) image and a top-left Fourier transform of the CdZnSe quantum dots prepared in step 4 of Example 1.
[0027] Appendix Figure 12 The graph shows the quantum yield data of quantum dots prepared in different steps and stages in Example 1.
[0028] Appendix Figure 13 TEM image of CdZnSe quantum dots prepared in step 2 of Example 2.
[0029] Appendix Figure 14 The image shows the CdZnSe quantum dots and size distribution histogram prepared in step 2 of Example 2.
[0030] Appendix Figure 15 TEM image of the CdZnSe quantum dots prepared in step 3 of Example 2.
[0031] Appendix Figure 16 The histogram of the size distribution of CdZnSe quantum dots prepared in step 3 of Example 2 is shown.
[0032] Appendix Figure 17 The image shows a TEM image of the CdZnSe quantum dots prepared in step 4 of Example 2, representing the third stage.
[0033] Appendix Figure 18 TEM image and size distribution histogram of the CdZnSe quantum dots prepared in step 4 of Example 2.
[0034] Appendix Figure 19 TEM image of CdZnSe quantum dots prepared in step 2 of Example 3.
[0035] Appendix Figure 20 The image shows the CdZnSe quantum dots and size distribution histogram prepared in step 2 of Example 3.
[0036] Appendix Figure 21 TEM image of the CdZnSe quantum dots prepared in step 3 of Example 3.
[0037] Appendix Figure 22 The histogram of the size distribution of CdZnSe quantum dots prepared in step 3 of Example 3 is shown.
[0038] Appendix Figure 23 The image shows a TEM image of the CdZnSe quantum dots prepared in step 4 of Example 3, representing the third stage.
[0039] Appendix Figure 24 TEM image and size distribution histogram of the CdZnSe quantum dots prepared in step 4 of Example 3. Detailed Implementation
[0040] A method for preparing CdZnSe quantum dots, the method comprising: Step 1) Prepare a CdZnSe nucleus reaction solution containing CdZnSe nuclei; Step 2) Based on the CdZnSe nucleation reaction solution, perform preliminary in-situ epitaxial growth to form the first-stage CdZnSe quantum dot reaction system; Step 3) Based on the first-stage CdZnSe quantum dot reaction system, perform mid-term in-situ epitaxial growth to form the second-stage CdZnSe quantum dot reaction system; Step 4) Based on the second-stage CdZnSe quantum dot reaction system, perform in-situ epitaxial growth to form the third-stage CdZnSe quantum dot reaction system.
[0041] A method for preparing CdZnSe quantum dots, the method further comprising: Step 6) After the in-situ epitaxial growth of the third-stage CdZnSe quantum dot reaction system is formed, it is naturally cooled and then separated by sedimentation and centrifugation to obtain the final CdZnSe quantum dots.
[0042] The process for preparing the CdZnSe nucleus reaction solution containing CdZnSe nuclei includes: under nitrogen protection, mixing a mixed precursor of low-reactivity cadmium precursor and low-reactivity zinc precursor with octadecene, heating and holding at a certain temperature under vacuum for a certain period of time, gradually increasing the temperature to the nucleation temperature, injecting a medium-reactivity selenium precursor at the nucleation temperature to form a nucleation reaction solution, and after a nucleation reaction time, obtaining the CdZnSe nucleus reaction solution containing CdZnSe nuclei; the size of the formed CdZnSe nuclei is 13. nm~16nm; the volume ratio of the low-reactivity cadmium precursor, the low-reactivity zinc precursor, and the medium-reactivity selenium precursor is preferably (1~10):(1~10):(1~10), more preferably 1:2:1; the volume ratio of the octadecene (ODE) to the mixed precursor of the low-reactivity cadmium precursor and the low-reactivity zinc precursor is (1~10):(1~10), more preferably 2:3; the heating, evacuation, and heat preservation for a certain period of time is preferably heating to 120 ℃~180 ℃, evacuating to 1 Pa~0.1 Pa, and holding for 30~60 min; the evacuation is to remove the by-products generated after mixing the low-reactivity cadmium precursor and the low-reactivity zinc precursor, the by-products being water vapor, acetic acid, etc.; the gradient heating to the nucleation temperature is preferably heated at a heating rate of 10℃ / min to the nucleation temperature, the nucleation temperature is preferably 280℃~350℃, and the nucleation reaction time is preferably 60 min~120 min.
[0043] During the preparation of the CdZnSe crystal nuclei, the low-reactivity cadmium precursor and the medium-reactivity zinc precursor form intermediate monomers during the heating process. From a thermodynamic perspective, the solubility product (Ksp) of CdSe is much lower than that of ZnSe, indicating that CdSe crystals are more thermodynamically stable, leading to preferential binding of Se with Cd. However, the proportion of low-reactivity zinc precursor added to the reaction system is higher than that of low-reactivity cadmium precursor, resulting in a consistently higher concentration of zinc monomers than cadmium monomers. This high concentration of zinc creates a significant concentration gradient, driving zinc atoms to compete with cadmium atoms for bonding with selenium. Under the dominance of this kinetic factor, some zinc is embedded in the crystal lattice, thus forming a structure with a gradient distribution of elemental content from the inside to the outside. Ultimately, a quantum nucleus with a gradient distribution of elemental content is obtained. This structure can effectively alleviate lattice mismatch stress and reduce interface defects, which is key to obtaining high-performance quantum dots. As the reaction proceeds, CdZnSe quantum dot crystal nuclei with a size of 13nm to 16nm are finally formed.
[0044] The process of forming the first-stage CdZnSe quantum dot reaction system by performing early-stage in-situ epitaxial growth based on the CdZnSe nucleation reaction solution includes: Step 2-1) Maintain the temperature of the CdZnSe nucleation reaction solution at the reaction temperature and continuously purge with nitrogen for protection; then add a low-reactivity zinc precursor to the CdZnSe nucleation reaction solution; the reaction temperature is preferably 280℃~320℃, more preferably 310℃; the volume ratio of the low-reactivity zinc precursor to the CdZnSe nucleation reaction solution is preferably (1~10):(1~10), more preferably 2:3; Step 2-2) After adding the low-reactivity zinc precursor, continue annealing at the reaction temperature for a certain period of time; preferably, annealing for 10 min to 30 min, and more preferably annealing for 15 min; this step ensures the presence of reactive monomers in the reaction system; Steps 2-3) Then, add a mixed solution of moderately reactive cadmium precursor and moderately reactive selenium precursor; after adding the mixed solution of moderately reactive cadmium precursor and moderately reactive selenium precursor, continue annealing at the reaction temperature for a certain time, preferably 5 min to 30 min, more preferably 10 min, and then naturally cool to room temperature to obtain a sample containing a size of 16 nm to 25 nm. The first-stage CdZnSe quantum dot reaction system for nm CdZnSe quantum dots; the volume ratio of the mixed solution of the moderately reactive cadmium precursor and the moderately reactive selenium precursor to the CdZnSe crystal nucleation reaction solution is preferably (1-10):(1-10), more preferably 1:3; the volume ratio of the moderately reactive cadmium precursor to the moderately reactive selenium precursor in the mixed solution is preferably (1-10):(1-10), more preferably 1:1; the mixed solution is added uniformly within 90-120 minutes; the quantum dot size is sampled and tested; the sampling volume and the volume ratio of the dispersant to the precipitant are (1-10):(1-10):(1-10); more preferably 1:1:1; the dispersant is preferably n-hexane, and the precipitant is preferably ethanol.
[0045] In the preparation process of this invention, during the initial 13nm-16nm CdZnSe quantum dot nucleus growth step, there are unreacted monomers in the CdZnSe nucleus solution reaction system. In step 2-1), a low-reactivity zinc precursor is first added to form zinc monomers. As the reaction proceeds, the low-reactivity zinc precursor forms zinc monomers that participate in the reaction at a lower rate. This lower zinc monomer formation rate is conducive to the growth of low-defect CdZnSe quantum dots. Since the concentration of Zn monomers in the system is higher than the concentration of CdSe intermediates, the concentration barrier promotes the increase of CdZnSe quantum dot size.
[0046] The process of forming the second-stage CdZnSe quantum dot reaction system by intermediate in-situ epitaxial growth based on the first-stage CdZnSe quantum dot reaction system includes: Step 3-1) Maintain the temperature of the first-stage CdZnSe quantum dot reaction system at the reaction temperature, and add a medium-reactivity zinc precursor to the first-stage CdZnSe quantum dot reaction system; the reaction temperature is preferably 280℃~320℃, more preferably 310℃; the volume ratio of the medium-reactivity zinc precursor to the first-stage CdZnSe quantum dot reaction system is preferably (1~10):(1~10), more preferably 1:3; Step 3-2) After adding the intermediate reactive zinc precursor, anneal at the reaction temperature; the preferred annealing time is 10 min to 30 min, and more preferably 15 min. min; then add a mixed solution of highly reactive cadmium precursor and moderately reactive selenium precursor, adding the mixed solution at a uniform rate, preferably adding the mixed solution uniformly for 90 min to 240 min; continue annealing at the reaction temperature for 10 min to 30 min to form the second-stage CdZnSe quantum dot reaction system; the volume ratio of the mixed solution of highly reactive cadmium precursor and moderately reactive selenium precursor to the first-stage CdZnSe quantum dot reaction system is preferably (1-10):(1-10), more preferably 1:4; the volume ratio of highly reactive cadmium precursor to moderately reactive selenium precursor in the mixed solution of highly reactive cadmium precursor and moderately reactive selenium precursor is preferably (1-10):(1-10), more preferably 1:2; sample and test the quantum dot size, TEM shows that the quantum dot size in the second-stage CdZnSe quantum dot reaction system formed in this step has increased to 25 nm to 30 nm, and the fluorescence quantum yield has increased to over 82%.
[0047] The process of forming the third-stage CdZnSe quantum dot reaction system by intermediate-term in-situ epitaxial growth based on the second-stage CdZnSe quantum dot reaction system includes: Step 4-1) Maintain the temperature of the second-stage CdZnSe quantum dot reaction system at the reaction temperature and add a highly reactive zinc precursor; the reaction temperature is preferably 280℃~320℃, more preferably 310℃; the volume ratio of the highly reactive zinc precursor to the second-stage CdZnSe quantum dot reaction system is preferably (1~10):(1~10), more preferably 1:4; Step 4-2) After the highly reactive zinc precursor is added, maintain the reaction temperature and anneal, preferably for 5 min to 10 min, more preferably for 5 min, to ensure sufficient zinc monomer formation; then add the highly reactive cadmium precursor, and anneal again for 5 min after addition; the highly reactive cadmium precursor is preferably added at a uniform rate within 60 min to 240 min; the volume ratio of the highly reactive cadmium precursor to the second-stage CdZnSe quantum dot reaction system is preferably (1 to 10):(1 to 10), more preferably 1:5; Step 4-3) Subsequently, a highly reactive selenium precursor is added and reacted for a certain period of time, preferably 10 min to 20 min, then heating is stopped and the mixture is allowed to cool naturally; the highly reactive selenium precursor is preferably added uniformly within 60 min to 360 min; the volume ratio of the highly reactive selenium precursor to the second-stage CdZnSe quantum dot reaction system is preferably (1 to 10):(1 to 10), and more preferably 1:6; the size of the quantum dots is sampled and tested. In the third-stage CdZnSe quantum dot reaction system formed in this step, the quantum dot size increases to more than 30 nm (about 32 nm to 35 nm), and the fluorescence quantum yield is as high as 85%.
[0048] The sampling and testing of quantum dot size refers to the following: the original solution of CdZnSe quantum dot solution at different stages is taken, purified, and then the size is tested; the volume of the original solution is preferably 2mL to 3mL; the purification process refers to the purification of the original solution, dispersant: precipitant by dispersing, precipitating, and centrifuging at a volume ratio of 1:1:1; the dispersant is preferably n-hexane; the precipitant is preferably ethanol; the volume ratio of original solution, dispersant: precipitant is preferably (1~10):(1~10):(1~10); preferably 1:1:1; the centrifugation method is preferably a centrifuge; the rotation speed is sufficient to precipitate all the quantum dots, preferably 6000rpm.
[0049] The low-reactivity zinc precursor described in this invention is preferably a mixed solution formed by a zinc source, octadecene, and a long-chain carboxylic acid; wherein, the volume ratio of octadecene to the long-chain carboxylic acid (with more than 12 carbon atoms in the carbon chain) is preferably (1-10):(1-10); more preferably 1:1; the zinc source is preferably zinc oxide and / or zinc acetate; the zinc source is preferably zinc acetate; the long-chain carboxylic acid is preferably one or a combination of pentadecanoic acid, hexadecanoic acid, oleic acid, stearic acid, eicosanoic acid, and icosanoic acid; the Zn concentration in the low-reactivity zinc precursor is preferably 0.1 mmol / mL to 1 mmol / mL, more preferably 0.5 mmol / mL, and the amount of zinc source is determined according to the required Zn concentration in the system during actual operation.
[0050] The intermediate-reactive zinc precursor of this invention is preferably a mixed solution formed by a zinc source, a medium-chain carboxylic acid, and octadecene; wherein, the volume ratio of octadecene to medium-chain carboxylic acid (with less than 12 and more than 9 carbon atoms in the carbon chain) is preferably (1-10):(1-10), and the volume ratio of octadecene to medium-chain carboxylic acid is further preferably 1:1; the zinc source in the intermediate-reactive zinc precursor is preferably zinc acetate and / or zinc oxide; more preferably zinc acetate; the medium-chain carboxylic acid is preferably any one or a combination of several of tetradecanoic acid, undecanoic acid, decanoic acid, and heptanoic acid; the Zn concentration in the intermediate-reactive zinc precursor is preferably 0.1 mmol / mL to 1 mmol / mL, more preferably 0.5 mmol / mL, and the amount of zinc source is determined according to the required Zn concentration in the system during actual operation; the intermediate-reactive zinc precursor undergoes a displacement reaction with the ligands in the reaction system, and the release rate of monomers is moderate, which is conducive to controllable growth.
[0051] The highly reactive zinc precursor described in this invention is preferably a mixed solution formed by a zinc source, oleylamine (OAm), and octadecene (ODE); wherein, the volume ratio of oleylamine (OAm) to ODE is preferably (1-10) ml:(1-10) ml, and the volume ratio of oleylamine (OAm) to octadecene (ODE) is further preferably 1:1; the zinc source in the highly reactive zinc precursor is preferably any one or a combination of zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, and zinc nitrate; the Zn concentration in the highly reactive zinc precursor is preferably 0.1 mmol / mL to 1 mmol / mL, and further preferably 0.5 mmol / mL, and the amount of zinc source is determined according to the required Zn concentration in the system during actual operation; the highly reactive zinc precursor is further preferably a mixed solution formed by pre-coordinated zinc chloride and oleylamine in ODE.
[0052] The low-reactivity cadmium precursor described in this invention is preferably a mixed solution formed by a cadmium source, a solvent, and a dispersant; wherein, the volume ratio of the solvent to the dispersant is preferably (1-10):(1-10), and the volume ratio of the solvent to the dispersant is further preferably 1:1; the cadmium concentration in the low-reactivity cadmium precursor is preferably 0.1 mmol / mL to 1 mmol / mL, and further preferably 0.5 mmol / mL. In actual operation, the amount of cadmium source is determined according to the required cadmium concentration in the system; the cadmium source in the low-reactivity cadmium precursor is preferably cadmium oxide; the solvent in the low-reactivity cadmium precursor is preferably a long-chain carboxylic acid, and the long-chain carboxylic acid is preferably any one of pentadecanoic acid, hexadecanoic acid, oleic acid, and stearic acid; the dispersant is preferably octadecene; the strongly coordinated long-chain carboxylic acid group is very stable at high temperature and requires high energy to break the bond and release cadmium monomer, thereby achieving slow and controllable growth.
[0053] The moderately reactive cadmium precursor described in this invention is preferably a mixed solution formed by a cadmium source, octadecene, and a medium-chain carboxylic acid; wherein the volume ratio of octadecene to the medium-chain carboxylic acid is preferably (1-10):(1-10), and the volume ratio of octadecene to the medium-chain carboxylic acid is further preferably 1:1; the amount of cadmium source is determined according to the desired cadmium concentration in the system; the cadmium concentration in the moderately reactive cadmium precursor is preferably 0.1 mmol / mL to 1 mmol / mL, and further preferably 0.5 mmol / mL; the cadmium source is preferably cadmium oxide; the medium-chain carboxylic acid is preferably any one or a combination of several of tetradecanoic acid, undecanoic acid, decanoic acid, and heptanoic acid.
[0054] The highly reactive cadmium precursor of this invention is preferably a mixed solution formed by a cadmium source, oleylamine (OAm), and octadecene; wherein, the volume ratio of oleylamine (OAm) to octadecene is preferably (1-10):(1-10), and the volume ratio of oleylamine (OAm) to octadecene is further preferably 1:1; the cadmium concentration in the highly reactive cadmium precursor is preferably 0.1 mmol / mL to 1 mmol / mL, and further preferably 0.5 mmol / mL, and the amount of cadmium source is determined according to the required cadmium concentration in the system during actual operation; the cadmium source in the highly reactive cadmium precursor is preferably one or more of cadmium acetylacetonate, cadmium iodide, cadmium bromide, cadmium chloride, cadmium nitrate, and cadmium perchlorate; the highly reactive cadmium precursor is further preferably a mixed solution formed by pre-coordinated cadmium chloride (CdCl2) and oleylamine (OAm) in octadecene.
[0055] The reactive selenium precursor described in this invention is preferably a mixed solution formed by a selenium source, a solvent, and a dispersant; wherein, the volume ratio of the solvent to the dispersant is preferably 1:(1-10), and the volume ratio of the solvent to the dispersant is further preferably 1:1; the selenium concentration in the reactive selenium precursor is preferably 0.1 mmol / mL to 1 mmol / mL, and further preferably 0.5 mmol / mL. In actual operation, the amount of selenium source is determined according to the required selenium concentration in the system; the selenium source is preferably selenium powder; the solvent is preferably any one of tri-n-octylphosphine, tri-n-octylphosphine oxide, octylamine, octadecylamine, and oleylamine; and the dispersant is preferably octadecene.
[0056] The highly reactive selenium precursor described in this invention is preferably a mixed solution formed by a selenium source, a solvent, and a dispersant. The volume ratio of the solvent to the dispersant is preferably (1-10):(1-10), and the volume ratio of the solvent to the dispersant is further preferably 1:1. The selenium concentration in the highly reactive selenium precursor is preferably 0.1 mmol / mL to 1 mmol / mL, and further preferably 0.5 mmol / mL. In actual operation, the amount of selenium source is determined according to the required selenium concentration in the system. The selenium source and dispersant in the highly reactive selenium precursor of this invention are the same as those in the moderately reactive selenium precursor. The solvent is preferably any one or a combination of several of diphenylphosphine, tri-n-butylphosphine, and triphenylphosphine.
[0057] The reactivity of different cadmium / zinc precursors used in this invention refers to their anion leaving ability, solubility / dispersibility in organic solvents, and thermal stability. Different reactivity cadmium / zinc precursors decompose or react at different rates to generate active monomers, thus determining their reactivity. The reactivity of different selenium precursors is determined by the bonding strength between their ligands and selenium atoms, the steric hindrance of the ligands, and the stability of the ligands at the reaction temperature. Highly reactive selenium precursors readily dissociate or react with metal cations, while less reactive selenium precursors provide a slow release of selenium monomers. Highly reactive selenium precursors typically use ligands with strong electron donation, low steric hindrance, or low bond energy, which can rapidly release active selenium monomers at high temperatures, facilitating rapid nucleation.
[0058] This invention, based on CdZnSe crystal nuclei, involves the sequential addition of cadmium, zinc, and selenium precursors with varying activities in three stages: early, middle, and late. By controlling the concentration and annealing time, a gradient growth of quantum dots from 16 nm to over 30 nm is achieved. A CdZnSe layer is then epitaxially grown on the CdZnSe crystal nuclei in stages, corresponding to the quantum dot size growth processes from 16 nm to 25 nm, 25 nm to 30 nm, and over 30 nm, respectively. Controllable growth of quantum dots is achieved by regulating the reactivity, concentration, and addition order of the cadmium, zinc, and selenium precursors.
[0059] In the preparation process of this invention, during the intermediate and late stages, as the quantum dot size increases, under the same ligand modification conditions, the decrease in its specific surface area reduces the surface ligand coverage per unit area, leading to a relative increase in the density of unpassivated dangling bonds. This increase in surface states introduces defects, forming additional nonradiative recombination channels. Simultaneously, the weakening of the ligand protective layer promotes quantum dot aggregation in solution or thin films, thereby triggering exciton energy transfer and fluorescence quenching. These factors collectively lead to a sharp decline in quantum yield. During the intermediate 25nm–30nm quantum dot growth process, a mixed solution of moderately reactive zinc precursor, highly reactive cadmium precursor, and moderately reactive selenium precursor (Se) is required for coordination dangling bonds. While bonding, it is necessary to avoid the formation of small-sized quantum dot materials from highly reactive precursors. In the later growth process of quantum dots larger than 30 nm, further coordination of surface defects is required. Highly reactive precursors are used. Since there is a certain amount of unreacted precursor in the reaction system, when adding highly reactive precursors, highly reactive cadmium precursors and highly reactive selenium precursors need to be added separately to avoid the formation of CdSe monomers after mixing. The order of precursor addition is as follows: annealing of highly reactive Zn precursor, then uniformly drop-adding of highly reactive Cd precursor, and finally uniformly adding of highly reactive Se precursor, ultimately forming CdZnSe quantum dots with a size greater than 30 nm and a quantum yield greater than 80%.
[0060] The present invention will be further described below with reference to specific embodiments. Example 1
[0061] A method for preparing CdZnSe quantum dots, the method comprising: Step 1) Under nitrogen protection, add 10 mL of octadecene, then add 5 mL of low-reactivity cadmium precursor and 10 mL of low-reactivity zinc precursor, mix, and heat to 120 °C at a heating rate of 10 °C / min, maintaining a vacuum of 0.2 Pa. Evacuate for 40 min, and continue heating at a rate of 10 °C / min until the nucleation temperature reaches 310 °C. At 310 °C, inject 5 mL of medium-reactivity selenium precursor to form a nucleation reaction solution. After 90 min of nucleation reaction, naturally cool to room temperature (25 °C) to obtain a CdZnSe nucleus reaction solution containing CdZnSe nuclei. Take 3 mL of the CdZnSe nucleus reaction solution and purify it 2-3 times using a CdZnSe nucleus reaction solution: hexane: ethanol volume ratio of 1:1:1. Finally, disperse it in a hexane solution. The size can be determined by transmission electron microscopy, as shown in the attached figure. Figure 1 The obtained CdZnSe crystal nuclei have a size of approximately 15 nm, and the size distribution of the CdZnSe crystal nuclei is concentrated. Statistical distribution of their size is shown in the attached figure. Figure 2Analysis of the figure shows that the proposed method can produce quantum dots with a size distribution of 13-16 nm and uniform particle size distribution. Step 2) Maintain the temperature of the CdZnSe nucleation reaction system at 310℃ and continuously purge with nitrogen for protection; then add 20 mL of low-reactivity zinc precursor to the CdZnSe nucleation reaction system; after adding the low-reactivity zinc precursor, continue annealing at 310℃ for 15 min; then add dropwise a mixed solution of 5 mL of medium-reactivity cadmium precursor and 5 mL of medium-reactivity selenium precursor; the mixed solution is added at a uniform rate over a period of 90 min to 120 min; after the mixed solution of medium-reactivity cadmium precursor and medium-reactivity selenium precursor is added, continue annealing at 310℃ for 10 min, and then allow to cool naturally to room temperature to obtain a first-stage CdZnSe quantum dot reaction system containing CdZnSe quantum dots with a size of 16 nm to 25 nm; characterize the CdZnSe quantum dots obtained in the first-stage CdZnSe quantum dot reaction system, as shown in the attached figure. Figure 3 As shown, the statistical distribution of its dimensions is illustrated in the attached figure. Figure 4 The CdZnSe quantum dots obtained here have a size of approximately 23 nm. Figure 9 The CdZnSe quantum dots obtained at this stage show clear lattice fringes, indicating that these CdZnSe quantum dots have no lattice defects and no obvious lattice interfaces; (See attached image) Figure 12 The fluorescence quantum yield (PL QY) of the CdZnSe quantum dots obtained here reached 78%; Step 3) Maintain the temperature of the first-stage CdZnSe quantum dot reaction system at 310℃. Add 20 mL of moderately reactive zinc precursor to the first-stage CdZnSe quantum dot reaction system; anneal at 310℃ for 15 min; then add 5 mL of a mixed solution of highly reactive cadmium precursor and 10 mL of moderately reactive selenium precursor. The mixed solution is added uniformly over a period of 90 min to 240 min. Continue annealing at 310℃ for 15 min to form the second-stage CdZnSe quantum dot reaction system; characterize the CdZnSe quantum dots in the second-stage CdZnSe quantum dot reaction system, as shown in the attached figure. Figure 5 As shown, the statistical distribution of its dimensions is illustrated in the attached figure. Figure 6 The CdZnSe quantum dots obtained here have a size of approximately 27 nm. Figure 10 The CdZnSe quantum dots obtained here show clear lattice fringes, indicating that the quantum dots have no lattice defects and no obvious lattice interfaces; (See attached image) Figure 12 The fluorescence quantum yield of the CdZnSe quantum dots obtained in this stage reached over 82%; Step 4) Maintain the temperature of the second-stage CdZnSe quantum dot reaction system at 310℃, add 25 mL of highly reactive zinc precursor; anneal at 310℃ for 5 min; then add 19 mL of highly reactive cadmium precursor, and after the addition is complete, anneal at 310℃ again for 5 min; the highly reactive cadmium precursor is preferably added uniformly within 60 min to 90 min; subsequently, add 16 mL of highly reactive selenium precursor, maintaining 310℃, and add uniformly within 60 min to 240 min, react for 10 min, then stop heating and allow to cool naturally to room temperature to form the third-stage CdZnSe quantum dot reaction system; characterize the CdZnSe quantum dots in the third-stage CdZnSe quantum dot reaction system formed in this step, as shown in the attached figure. Figure 7 As shown, the statistical distribution of its dimensions is illustrated in the attached figure. Figure 8 The CdZnSe quantum dots obtained here have a size of approximately 31 nm. Figure 11 The CdZnSe quantum dots obtained here show clear lattice fringes and no obvious lattice interfaces; the CdZnSe quantum dots obtained here have no lattice defects. Figure 12 The fluorescence quantum yield of the CdZnSe quantum dots obtained in this stage reached over 85%.
[0062] The low-reactivity zinc precursor described in Example 1 is a mixed solution of zinc acetate, oleic acid, and octadecene (ODE). 20 mmol of zinc acetate, 20 mL of oleic acid, and 20 mL of octadecene are mixed, heated to 150°C, and the vacuum is maintained at 0.2 Pa for 20 min. The mixture is then heated to 300°C and held for 30 min, before being cooled to room temperature to obtain a 0.5 mmol / mL low-reactivity zinc precursor solution. This solution can be heated to melt before use.
[0063] In Example 1, the reactive zinc precursor was a mixed solution of zinc acetate, decanoic acid, and octadecene (ODE). The preparation method for the moderately reactive precursor was as follows: 20 mmol of zinc acetate, 20 mL of decanoic acid, and 20 mL of octadecene were mixed, heated to 150°C, and the vacuum was maintained at 0.2 Pa for 20 min. The temperature was then raised to 300°C and held for 30 min, followed by cooling to room temperature to obtain a 0.5 mmol / mL moderately reactive precursor solution. The solution can be heated until melted before use.
[0064] In Example 1, the highly reactive zinc precursor is a mixed solution of zinc chloride, oleylamine, and octadecene (ODE). The preparation method of the highly reactive zinc precursor is as follows: 20 mmol of zinc chloride, 20 mL of oleylamine, and 20 mL of octadecene are mixed and heated to 60 °C under nitrogen protection for 20 min to obtain a 0.5 mmol / mL ZnCl2-OAm solution.
[0065] The low-reactivity cadmium precursor described in Example 1 is a mixed solution of cadmium oxide, oleic acid, and octadecene (ODE). The preparation method of the low-reactivity cadmium precursor is as follows: 20 mmol of cadmium oxide, 20 ml of oleic acid, and 20 mL of octadecene are mixed, heated to 150°C, and the vacuum degree is maintained at 0.2 Pa. The gas is pumped for 20 min, then heated to 300°C and held for 30 min. Finally, the temperature is lowered to room temperature to obtain a low-reactivity precursor solution of 0.5 mmol / mL. The solution can be heated to melt before use.
[0066] The moderately reactive cadmium precursor described in Example 1 is a mixed solution of cadmium oxide, decanoic acid, and octadecene (ODE). The preparation method of the moderately reactive precursor is as follows: 20 mmol of cadmium oxide, 20 mL of decanoic acid, and 20 mL of octadecene are mixed, heated to 150°C, and the vacuum degree is maintained at 0.2 Pa. The gas is pumped for 20 min, then heated to 300°C and held for 30 min. Finally, the temperature is lowered to room temperature to obtain a 0.5 mmol / mL moderately reactive precursor solution. The solution can be heated until melted before use.
[0067] The highly reactive cadmium precursor described in Example 1 is a mixed solution of cadmium chloride (CdCl2) and oleylamine (OAm) pre-coordinated in octadecene. The preparation method of the highly reactive precursor is as follows: 4.3868 g of CdCl2·2H2O, 20 mL of oleylamine, and 20 mL of octadecene are mixed and heated to 60 °C under nitrogen protection for 20 min to obtain a highly reactive precursor solution with a concentration of 0.5 mmol / mL.
[0068] The reactive selenium precursor described in Example 1 is further preferably a tri-n-octylphosphine selenium solution formed by dissolving selenium powder in tri-n-octylphosphine; the preparation method of tri-n-octylphosphine selenium solution is as follows: take 10 mmol of Se powder, add 10 mL of tri-n-octylphosphine solution and 10 mL of octadecene, and sonicate until the solution is clarified to obtain a 0.5 mmol / mL reactive selenium precursor solution.
[0069] The highly reactive selenium precursor described in Example 1 is further preferably a diphenylphosphine selenium solution formed by dissolving selenium powder in diphenylphosphine. The diphenylphosphine selenium solution is prepared as follows: 10 mmol of Se powder is added to 10 mL of diphenylphosphine solution and 10 mL of octadecene. The solution is sonicated until it is clear, resulting in a 0.5 mmol / mL highly reactive selenium precursor solution. Example 2
[0070] A method for preparing CdZnSe quantum dots, the method comprising: Step 1) is the same as step 1 in Example 1. Step 2) Maintain the temperature of the CdZnSe nucleation reaction solution at 310℃ and continuously purge with nitrogen for protection; then add 15 mL of low-reactivity zinc precursor to the CdZnSe nucleation reaction solution; after adding the low-reactivity zinc precursor, continue annealing at 310℃ for 15 min; then add dropwise a mixed solution of 4 mL of medium-reactivity cadmium precursor and 4 mL of medium-reactivity selenium precursor; the mixed solution is added at a uniform rate over a period of 90 min to 120 min; after the mixed solution of medium-reactivity cadmium precursor and medium-reactivity selenium precursor is added, continue annealing at 310℃ for 10 min, then allow to cool naturally to room temperature, as shown in the attached figure. Figure 14 A first-stage CdZnSe quantum dot reaction system with CdZnSe quantum dots of size 23.2 nm was obtained. Figure 15 Its size distribution ratio; Step 3) Maintain the temperature of the first-stage CdZnSe quantum dot reaction system at 310℃. Add 15 mL of moderately reactive zinc precursor to the first-stage CdZnSe quantum dot reaction system; anneal at 310℃ for 15 min; then add a mixed solution of 5 mL of highly reactive cadmium precursor and 10 mL of moderately reactive selenium precursor, adding the mixed solution at a uniform rate over 90-240 min; continue annealing at 310℃ for 15 min to form the second-stage CdZnSe quantum dot reaction system; as shown... Figure 15 CdZnSe quantum dots with a size of 27.2 nm were obtained. Figure 16 Its size distribution ratio; Step 4) Maintain the temperature of the second-stage CdZnSe quantum dot reaction system at 310℃, add 20 mL of highly reactive zinc precursor; anneal at 310℃ for 5 min; then add 10 mL of highly reactive cadmium precursor, and after the addition is complete, anneal at 310℃ again for 5 min; the highly reactive cadmium precursor is preferably added at a uniform rate within 60 min to 120 min; then add 10 mL of highly reactive selenium precursor; the highly reactive selenium precursor is preferably added at a uniform rate within 60 min to 120 min; maintain the reaction at 310℃ for 10 min, then stop heating and allow to cool naturally to room temperature to form the third-stage CdZnSe quantum dot reaction system; as... Figure 17 CdZnSe quantum dots with a size of 32.7 nm were obtained. Figure 18 The proportion of its size distribution.
[0071] In Example 2, the preparation methods for various precursors were the same as in Example 1, and the concentration of each precursor was 0.7 mmol / mL. Example 3
[0072] A method for preparing CdZnSe quantum dots, the method comprising: Step 1) is the same as step 1 in Example 1. Step 2) Maintain the temperature of the CdZnSe nucleation reaction solution at 310℃ and continuously purge with nitrogen for protection; then add 25 mL of low-reactivity zinc precursor to the CdZnSe nucleation reaction solution; after adding the low-reactivity zinc precursor, continue annealing at 310℃ for 15 min; then add 6 mL of a mixed solution of medium-reactivity cadmium precursor and 6 mL of medium-reactivity selenium precursor dropwise at a uniform rate; the mixed solution is added uniformly over a period of 90 min to 120 min; after the mixed solution of medium-reactivity cadmium precursor and medium-reactivity selenium precursor is added, continue annealing at 310℃ for 10 min; Figure 19 CdZnSe quantum dots with a size of 24.2 nm were obtained. Figure 20 Its size distribution ratio; Step 3) Maintain the temperature of the first-stage CdZnSe quantum dot reaction system at 310℃. Add 30 mL of moderately reactive zinc precursor to the first-stage CdZnSe quantum dot reaction system and anneal at 310℃ for 15 min. Then add 8 mL of a mixed solution of highly reactive cadmium precursor and 16 mL of moderately reactive selenium precursor. Add the mixed solution at a uniform rate over 90-360 min. Continue annealing at 310℃ for 15 min to form the second-stage CdZnSe quantum dot reaction system. Figure 21 CdZnSe quantum dots with a size of 27 nm were obtained. Figure 22Its size distribution ratio; Step 4) Maintain the temperature of the second-stage CdZnSe quantum dot reaction system at 310℃, add 35ml of highly reactive zinc precursor; anneal at 310℃ for 5 min; then add 15ml of highly reactive cadmium precursor, and after the addition is complete, anneal at 310℃ again for 5 min; the highly reactive cadmium precursor is preferably added uniformly within 60 min to 240 min; subsequently, add 20ml of highly reactive selenium precursor, maintaining 310℃, and add uniformly within 60 min to 360 min, react for 10 min, then stop heating and allow to cool naturally to room temperature to form the third-stage CdZnSe quantum dot reaction system; Figure 23 CdZnSe quantum dots with a size of 27 nm were obtained. Figure 24 The proportion of its size distribution.
[0073] The preparation methods for various precursors in Example 3 are the same as in Example 1, and the concentration of each precursor is 0.4 mmol / mL.
Claims
1. A method for preparing CdZnSe quantum dots, characterized in that The application relates to a preparation method of a CdZnSe quantum dot reaction system. The preparation method comprises the following steps: step 1, preparing a CdZnSe crystal nucleus reaction solution containing CdZnSe crystal nuclei; step 2, performing in-situ epitaxial growth in an early stage on the basis of the CdZnSe crystal nucleus reaction solution to form a first-stage CdZnSe quantum dot reaction system; step 3, performing in-situ epitaxial growth in a middle stage on the basis of the first-stage CdZnSe quantum dot reaction system to form a second-stage CdZnSe quantum dot reaction system; and step 4, performing in-situ epitaxial growth in a late stage on the basis of the second-stage CdZnSe quantum dot reaction system to form a third-stage CdZnSe quantum dot reaction system. The process of preparing the CdZnSe crystal nucleus reaction solution containing CdZnSe crystal nuclei comprises the following steps: under the condition of nitrogen protection, mixing a mixed precursor of a low-reactivity cadmium precursor and a low-reactivity zinc precursor with octadecene, heating, vacuumizing, maintaining for a certain time, gradient heating to a nucleation temperature, injecting a medium-reactivity selenium precursor into the nucleation reaction solution at the nucleation temperature to form a nucleation reaction solution, and maintaining for a nucleation reaction time to obtain the CdZnSe crystal nucleus reaction solution containing CdZnSe crystal nuclei. The volume ratio of the low-reactivity cadmium precursor, the low-reactivity zinc precursor and the medium-reactivity selenium precursor is (1-10):(1-10):(1-10); the volume ratio of the octadecene to the mixed precursor of the low-reactivity cadmium precursor and the low-reactivity zinc precursor is (1-10):(1-10); the heating, vacuumizing and maintaining for a certain time are as follows: heating to 120-180 DEG C, vacuumizing to 1-0.1 Pa and maintaining for 30-60 min; the gradient heating to the nucleation temperature is heating to the nucleation temperature at a heating speed of 10 DEG C / min; the nucleation temperature is 280-350 DEG C; and the nucleation reaction time is 60-120 min. The low-reactivity cadmium precursor is a mixed solution formed by a cadmium source, a solvent and a dispersing agent; the volume ratio of the solvent to the dispersing agent is (1-10):(1-10); the solvent in the low-reactivity cadmium precursor is a long-chain carboxylic acid, and the long-chain carboxylic acid is any one of pentadecanoic acid, hexadecanoic acid, oleic acid and stearic acid; and the dispersing agent is octadecene.
2. The method for preparing CdZnSe quantum dots according to claim 1, characterized in that The process of performing in-situ epitaxial growth in an early stage on the basis of the CdZnSe crystal nucleus reaction solution to form a first-stage CdZnSe quantum dot reaction system comprises the following steps: step 2-1, maintaining the temperature of the CdZnSe crystal nucleus reaction solution at a reaction temperature and continuously supplying nitrogen protection; then adding a low-reactivity zinc precursor into the CdZnSe crystal nucleus reaction solution; step 2-2, after adding the low-reactivity zinc precursor, continuously maintaining the reaction temperature and annealing for a certain time; step 2-3, then adding a mixed solution of a medium-reactivity cadmium precursor and a medium-reactivity selenium precursor; continuously annealing at the reaction temperature for a certain time, and then naturally cooling to room temperature to obtain the first-stage CdZnSe quantum dot reaction system.
3. The method for preparing CdZnSe quantum dots according to claim 2, characterized in that: 4. The method for preparing CdZnSe quantum dots according to claim 1, characterized in that: 5. The method for preparing CdZnSe quantum dots according to claim 4, characterized in that: The reaction temperature is 280-320 DEG C; the volume ratio of the low reactivity zinc precursor to the CdZnSe crystal nucleus reaction liquid is (1-10):(1-10); the annealing time for continuously maintaining the reaction temperature is 10-30 minutes; the volume ratio of the mixed solution of the medium reactivity cadmium precursor and the medium reactivity selenium precursor to the CdZnSe crystal nucleus reaction liquid is (1-10):(1-10); the volume ratio of the medium reactivity cadmium precursor to the medium reactivity selenium precursor in the mixed solution of the medium reactivity cadmium precursor and the medium reactivity selenium precursor is (1-10):(1-10); The low reactivity zinc precursor is a mixed solution of a zinc source, octadecene and a long-chain carboxylic acid; the volume ratio of the octadecene to the long-chain carboxylic acid is (1-10):(1-10); the long-chain carboxylic acid is one or a combination of several of pentadecanoic acid, hexadecanoic acid, oleic acid, stearic acid, eicosanoic acid and tetracosanoic acid; The medium reactivity cadmium precursor is a mixed solution of a cadmium source, octadecene and a medium-chain carboxylic acid; the volume ratio of the octadecene to the medium-chain carboxylic acid is (1-10):(1-10); the medium-chain carboxylic acid is one or a combination of several of n-tetradecanoic acid, n-undecanoic acid, decanoic acid and heptanoic acid.
6. The method for preparing CdZnSe quantum dots according to claim 1, characterized in that: The process for forming a third-stage CdZnSe quantum dot reaction system by in-situ epitaxial growth in the middle stage on the basis of the second-stage CdZnSe quantum dot reaction system comprises: Step 3-1) maintaining the temperature of the first-stage CdZnSe quantum dot reaction system at the reaction temperature and adding a medium reactivity zinc precursor into the first-stage CdZnSe quantum dot reaction system; Step 3-2) after adding the medium reactivity zinc precursor, annealing is performed by maintaining the reaction temperature, then a mixed solution of a high reactivity cadmium precursor and a medium reactivity selenium precursor is added, and the second-stage CdZnSe quantum dot reaction system is formed by continuously annealing at the reaction temperature.
7. The method for preparing CdZnSe quantum dots according to claim 6, characterized in that: The reaction temperature is 280-320 DEG C, and is further preferably 310 DEG C; the volume ratio of the medium reactivity zinc precursor to the first-stage CdZnSe quantum dot reaction system is (1-10):(1-10); the volume ratio of the mixed solution of the high reactivity cadmium precursor and the medium reactivity selenium precursor to the first-stage CdZnSe quantum dot reaction system is (1-10):(1-10); the volume ratio of the high reactivity cadmium precursor to the medium reactivity selenium precursor in the mixed solution of the high reactivity cadmium precursor and the medium reactivity selenium precursor is (1-10):(1-10). The high reactivity cadmium precursor is a mixed solution of a cadmium source, oleylamine and octadecene; the volume ratio of the oleylamine to the octadecene is (1-10):(1-10).
8. The method for preparing CdZnSe quantum dots according to claim 1, characterized in that... The process for forming a third-stage CdZnSe quantum dot reaction system by in-situ epitaxial growth in the middle stage on the basis of the second-stage CdZnSe quantum dot reaction system comprises: Step 4-1) maintaining the temperature of the second-stage CdZnSe quantum dot reaction system at the reaction temperature and adding a high reactivity zinc precursor; Step 4-2) After the high-reactivity zinc precursor is added completely, anneal the reaction temperature; then add the high-reactivity cadmium precursor, and after the addition is completed, anneal again; Step 4-3) Then add the high-reactivity selenium precursor and react for a certain time, then stop heating and cool naturally.
9. The method for preparing CdZnSe quantum dots according to claim 8, characterized in that: The reaction temperature is 280-320°C; the volume ratio of the high-reactivity zinc precursor to the second-stage CdZnSe quantum dot reaction system is (1-10):(1-10); the volume ratio of the high-reactivity cadmium precursor to the second-stage CdZnSe quantum dot reaction system is (1-10):(1-10); and the volume ratio of the high-reactivity selenium precursor to the second-stage CdZnSe quantum dot reaction system is (1-10):(1-10). The high-reactivity zinc precursor is a mixed solution of a zinc source, oleylamine and octadecene; the volume ratio of oleylamine to octadecene is (1-10)ml:(1-10)ml. The high-reactivity selenium precursor is a mixed solution of a selenium source, a solvent and a dispersing agent; the volume ratio of the solvent to the dispersing agent is (1-10):(1-10); and the solvent in the high-reactivity selenium precursor is any one or a combination of several of diphenylphosphine, tri-n-butylphosphine and triphenylphosphine.
10. The method of claim 6, wherein the reactive selenium precursor is a mixed solution of a selenium source, a solvent, and a dispersing agent. The volume ratio of the solvent to the dispersing agent is (1-10):(1-10); the solvent is any one of tri-n-octylphosphine, tri-n-octylphosphine oxide, octylamine, octadecylamine and oleylamine; the dispersing agent is octadecene; the medium-reactivity zinc precursor is a mixed solution of a zinc source, a medium carbon chain carboxylic acid and octadecene; the volume ratio of octadecene to the medium carbon chain carboxylic acid is (1-10):(1-10); and the medium carbon chain carboxylic acid is any one or a combination of several of n-tetradecanoic acid, n-undecanoic acid, decanoic acid and heptanoic acid.