A method for the controllable synthesis of high-quality quantum dots based on preformed nuclei clusters that reach a potential energy minimum through chemical self-assembly.

Abstract

This invention provides a method for the controllable synthesis of high-quality quantum dots based on pre-nucleated clusters that reach a minimum potential energy surface through chemical self-assembly, belonging to the field of semiconductor nanomaterials technology. The quantum dots of this invention are prepared by reacting a pre-nucleated sample of semiconductor material with pre-prepared quantum dots to obtain high-quality quantum dots grown heterogeneously (core-shell structure) or homogeneously. This method, based on the pre-nucleated clusters, allows for the control of quantum dot size growth, narrowing the quantum dot distribution and avoiding the need to control the bonding temperature of the semiconductor material. This method improves the accuracy of quantum dot size control, and the quantum dots prepared by this method also exhibit significant luminescent properties, effectively expanding the applications of quantum dots and showing great promise.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor nanomaterials technology, specifically relating to a method for the controllable synthesis of high-quality quantum dots based on pre-nucleated clusters (PNCs) that reach a minimum potential energy surface generated by chemical self-assembly. Background Technology

[0002] Quantum dots are a class of nanocrystals, semiconductor materials with diameters ranging from 2 to 10 nanometers (100 to 10,000 atoms). Quantum dot materials possess advantages such as high fluorescence quantum yield, easily tunable emission peaks, and ease of synthesis. Since their photoelectric properties vary with size, the physicochemical properties of quantum dot materials can be tuned by controlling their size. Therefore, quantum dots show promising application potential in fields such as electronic displays, solar cells, bioimaging, and energy.

[0003] Core-shell quantum dots, due to their unique structural characteristics, integrate the properties of both the inner and outer layers of material, complementing each other's shortcomings. This has become an important research direction in recent years, demonstrating the principle that morphology determines properties, and they have broad application prospects in biomedicine, catalysis, photocatalysis, batteries, gas storage, and separation. Currently, there are two strategies for constructing core-shell structures: one is to first form a nucleus and then coat it with a shell; the other is to form the core-shell structure in a single step. In recent years, strategy one has been widely used to synthesize various bimetallic nanomaterials with core-shell structures.

[0004] Existing literature (10.1007 / s12274-024-7106-3) discloses a type II core-shell structured quantum dot ZnSe / Cd x Zn 1-x S / ZnS. Its photoluminescent quantum yield exceeds 90%; the maximum external quantum efficiency is 6.7%, and the maximum luminance is 39766 cd·m. -2 However, its brightness is limited.

[0005] There is an urgent need to find new strategies to prepare core-shell quantum dots with higher brightness.

[0006] Besides core-shell quantum dots, controllable size is also crucial for their widespread application. In traditional synthesis methods, the size of quantum dots exhibits a complex nonlinear relationship with time under isothermal conditions, making their size unpredictable. When synthesizing ZnSe quantum dots using the organometallic method, the size can be effectively controlled by adjusting the solvent ratio, reaction time, and temperature. However, the synthesis of zinc selenide (ZnSe) quantum dots in the organic phase often requires temperatures above 200°C. Higher temperatures result in faster nucleation and growth rates, and to obtain quantum dots of ideal size, quenching during the reaction is often necessary to stop growth.

[0007] The literature (Wang Xiang, Ma Xuliang, Feng Xue, et al. Controllable synthesis and characterization of ZnSe and ZnS quantum dots [J]. Journal of Luminescence, 2009, 30(06): 818-823.) discloses a method for controlling the synthesis of ZnSe and ZnS quantum dots. Nucleation at 280℃ and growth maintained at 240℃ yields quantum dots with an average diameter in the range of 4.5–8 nm. High-temperature nucleation and growth make quantum dot preparation conditions demanding and require strict control, resulting in poor reproducibility of quantum dot synthesis and difficulty in controlling size and size distribution. Furthermore, there is currently a lack of methods for precise control of quantum dot sizes in the small size range (~2-3 nm). Summary of the Invention

[0008] To address the problems of existing technologies, the present invention aims to provide a method for the controllable synthesis of high-quality quantum dots based on pre-nucleated clusters that reach a minimum potential energy level through chemical self-assembly.

[0009] This invention provides a method for the controllable synthesis of high-quality quantum dots based on pre-nucleated clusters that reach a minimum potential energy surface generated by chemical self-assembly. The method includes the following steps: reacting a pre-nucleated sample of semiconductor material with quantum dots of semiconductor material to obtain high-quality quantum dots;

[0010] The semiconductor material is a semiconductor material containing metal elements of Group II, Group III, Group IV, Group V or Group VI.

[0011] Furthermore, the semiconductor material is selected from ZnSe, ZnSeS, ZnTe, ZnS, CdSe, CdSeS, CdTe, or CdS.

[0012] Furthermore, the method for preparing the pre-nucleation sample of the semiconductor material includes the following steps: adding a precursor solution to a reaction medium and reacting to obtain a pre-nucleation sample of the semiconductor material; or, adding a precursor solution to a reaction medium, adding an activator, and reacting to obtain a pre-nucleation sample of the semiconductor material.

[0013] Furthermore, the method for preparing quantum dots of the semiconductor material includes the following steps: adding a precursor solution to a reaction medium and reacting to obtain quantum dots of the semiconductor material; or adding a precursor solution to a reaction medium, adding an activator, and reacting to obtain quantum dots of the semiconductor material.

[0014] Further, the precursor includes a metal carboxylate or a metal oleylamine salt and a trioctylphosphine precursor; preferably, the metal carboxylate is cadmium carboxylate or zinc carboxylate; the metal oleylamine salt is oleylamine; and the trioctylphosphine precursor is trioctylphosphine sulfide, trioctylphosphine selenide, or trioctylphosphine telluride.

[0015] Furthermore, the preparation of the metal carboxylate or metal oleylamine salt includes the following steps: reacting a metal oxide or metal acetate with a carboxylic acid to obtain a metal carboxylate; or reacting a metal acetate with oleylamine to obtain a metal oleylamine salt.

[0016] The molar ratio of the metal oxide or metal acetate to the carboxylic acid is 1:2-3; the molar ratio of the metal acetate to oleylamine is 1:2-3; the solvent for the reaction is an organic solvent; the reaction conditions are: first react at 60-130℃ for 0.5-3h, then react at 100-300℃ for 0.5-3h, and finally react at 110-260℃ for 10min-3h.

[0017] Further, the metal carboxylate is selected from cadmium precursors and / or zinc precursors; the metal oxide is selected from cadmium oxide and / or zinc oxide; and the metal acetate is selected from zinc acetate or cadmium acetate.

[0018] Furthermore, the preparation of the cadmium precursor includes the following steps: reacting cadmium oxide with carboxylic acid to obtain a cadmium carboxylic acid precursor; and reacting cadmium acetate with oleylamine to obtain an oleylamine cadmium precursor.

[0019] The molar ratio of cadmium oxide to carboxylic acid is 1:2-3; the solvent for the reaction is an organic solvent; the reaction conditions are as follows: under inert gas conditions, the reaction is first carried out at 60-100℃ for 0.5-3h, then at 100-140℃ for 0.5-3h, and finally at 200-260℃ for 10-50min.

[0020] Alternatively, the molar ratio of cadmium acetate to oleylamine is 1:2-3; the solvent for the reaction is an organic solvent; the reaction conditions are: under vacuum, first react at 60-100℃ for 0.5-1h, then react at 100-150℃ for 0.5-1h.

[0021] Alternatively, the molar ratio of cadmium acetate to oleylamine is 1:2.2; the solvent for the reaction is 1-octadecene; and the reaction conditions are: under vacuum, the reaction is first carried out at 80°C for 1 hour, and then under vacuum, the reaction is carried out at 120°C for 1 hour.

[0022] Furthermore, the preparation of the zinc precursor includes the following steps: reacting zinc oxide or zinc acetate with carboxylic acid to obtain the zinc precursor;

[0023] The molar ratio of zinc oxide or zinc acetate to carboxylic acid is 1:2-3; the solvent for the reaction is an organic solvent; the reaction conditions are: under vacuum, the reaction is first carried out at 110-130℃ for 1-3 hours, under nitrogen conditions at 280-300℃ for 1-3 hours, and under vacuum conditions at 110-130℃ for 1-3 hours.

[0024] Further, the molar ratio of zinc oxide or zinc acetate to carboxylic acid is 1:2.2; the solvent for the reaction is 1-octadecene; the reaction conditions are: under vacuum, the reaction is first carried out at 120°C for 2 hours, under nitrogen at 290°C for 2 hours, and under vacuum at 120°C for 2 hours.

[0025] Furthermore, the preparation of the trioctylphosphine precursor includes the following steps: reacting oxalic element powder with trioctylphosphine to obtain the trioctylphosphine precursor;

[0026] The molar ratio of the oxalic element powder to trioctylphosphine is 1:2-5; the reaction conditions are: 10-300℃ for 10-50 min.

[0027] Furthermore, the trioctylphosphine precursor is selected from selenium precursors and / or sulfur precursors; the oxalic element powder is selected from selenium powder and / or sulfur powder and / or tellurium powder.

[0028] Furthermore, the preparation of the selenium precursor includes the following steps: reacting selenium powder with trioctylphosphine to obtain the selenium precursor;

[0029] The molar ratio of selenium powder to trioctylphosphine is 1:2.2-5; the reaction conditions are: under nitrogen atmosphere, reaction at 30-50℃ for 20-40 min;

[0030] Preferably, the molar ratio of selenium powder to trioctylphosphine is 1:4; the reaction conditions are: under nitrogen atmosphere, reaction at 40°C for 30 min.

[0031] Furthermore, the preparation of the sulfur precursor includes the following steps: reacting sulfur powder with trioctylphosphine to obtain the sulfur precursor;

[0032] The molar ratio of sulfur powder to trioctylphosphine is 1:2-3; the reaction conditions are: under vacuum, at 10-40°C for 10-50 min.

[0033] Furthermore, the preparation of the tellurium precursor includes the following steps: reacting tellurium powder with trioctylphosphine to obtain the tellurium precursor;

[0034] The molar ratio of tellurium powder to trioctylphosphine is 1:2-4; the reaction conditions are: under vacuum, react at 10-40℃ for 10-50 min, react at 80-120℃ for 10-50 min, and under nitrogen, react at 280-310℃ for 30-60 min.

[0035] Further, the activator is diphenylphosphine; the solvent is an organic solvent; the reaction conditions are as follows: under vacuum conditions, the precursor solution and solvent are reacted at 100-140°C for 10-50 min, under inert gas conditions, the activator is added, and then the reaction is carried out at 160-240°C for 5-120 min.

[0036] Furthermore, the high-quality quantum dots are core-shell structured quantum dots and / or quantum dots with increased size and narrower distribution.

[0037] Furthermore, the core-shell structured quantum dots are formed by mixing quantum dots of semiconductor material with a pre-nucleated sample of semiconductor material and reacting to form core-shell structured quantum dots.

[0038] Furthermore, the method for preparing the core-shell structured quantum dots includes the following steps: mixing quantum dots of semiconductor material with a pre-nucleated sample of semiconductor material, and forming core-shell structured quantum dots after reaction.

[0039] Furthermore, the volume ratio of the quantum dots of the semiconductor material to the pre-nucleated sample of the semiconductor material is 1:1 or 1:4.

[0040] Furthermore, the reaction temperature is 60–300°C, and the time is 1 min–68 h.

[0041] Furthermore, the quantum dots with increased size and narrower distribution are formed by reacting pre-nucleated samples of the same semiconductor material with quantum dots, resulting in quantum dots with increased size and narrower distribution.

[0042] Furthermore, the method for preparing the quantum dots with increased size and narrower distribution includes the following steps:

[0043] (1) At 20-60℃, the pre-nucleated sample of semiconductor material is dispersed in a solvent and reacted for 1-166 h to obtain quantum dots with controllable size;

[0044] (2) Add the pre-nucleated sample of semiconductor material and methanol again and react for 1 to 166 hours. Repeat this process n times to obtain quantum dots with increased size and narrower distribution.

[0045] Where n is selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10;

[0046] The semiconductor material is a binary semiconductor material or a ternary semiconductor material, and the semiconductor material is preferably ZnSe, ZnSeS, ZnTe or ZnS.

[0047] Further, in step (1), the solvent is selected from one or a mixture of two of cyclohexane and methanol, preferably a mixture of cyclohexane and methanol.

[0048] Further, in step (1), the volume ratio of the pre-nucleated sample of the semiconductor material to cyclohexane and methanol is 1-5:200-800:1-10;

[0049] Preferably, the volume ratio of the pre-nucleated sample of the semiconductor material to cyclohexane and methanol is 3:600:2.

[0050] Furthermore, in the preparation of the pre-nucleation sample of the binary semiconductor material, the mass-volume ratio of selenium precursor, zinc precursor and activator is 1-3 g: 200-400 μL: 30-70 μL; the solvent for the reaction is an organic solvent; the reaction conditions are: under nitrogen atmosphere, at 80-250 °C for 20-80 min.

[0051] In the preparation of the pre-nucleation sample of the ternary semiconductor material, the mass-volume ratio of selenium precursor, zinc precursor, sulfur powder and activator is 1-3 g: 200-400 μL: 0.001-0.01 g: 30-70 μL; the solvent for the reaction is an organic solvent; the reaction conditions are: under nitrogen atmosphere, at 80-250 °C for 20-80 min.

[0052] Furthermore, in the preparation of the pre-nucleation sample of the binary semiconductor material, the mass-volume ratio of selenium precursor, zinc precursor and activator is 1.832 g: 330 μL: 52 μL; the solvent for the reaction is 1-octadecene; the reaction conditions are: under nitrogen atmosphere, reaction at 160 °C for 30 min.

[0053] In the preparation of the prenucleation sample of the ternary semiconductor material, the mass-volume ratio of selenium precursor, zinc precursor, sulfur powder and activator is 1.832 g: 300 μL: 0.0096 g: 52 μL; the solvent for the reaction is 1-octadecene; the reaction conditions are: under nitrogen atmosphere, at 170 °C for 60 min.

[0054] This invention discovers that at low temperatures (25°C and 45°C), the size of quantum dots is related to the concentration of the pre-nucleation sample, the decomposition rate, and the reaction temperature. Examples demonstrate that ZnSe and ZnSeS pre-nucleation samples can be repeatedly added to prepare ZnSe and ZnSeS quantum dots with controllable sizes. Therefore, those skilled in the art can anticipate that other quantum dots (e.g., ZnTe or ZnS) can also be prepared using the method of this invention to further improve the control and distribution of quantum dot size.

[0055] The quantum dots of this invention are prepared by reacting a pre-nucleated sample of semiconductor material with pre-prepared quantum dots to obtain high-quality quantum dots grown heterogeneously (core-shell structure) or homogeneously. This method, based on the pre-nucleated clusters that reach a minimum potential energy level through chemical self-assembly, allows for the control of quantum dot size growth, narrowing the quantum dot distribution and avoiding the need to control the bonding temperature of the semiconductor material. This method improves the accuracy of quantum dot size control, and the quantum dots prepared by this method also exhibit significant luminescent properties, effectively expanding the applications of quantum dots and showing great promise.

[0056] This invention employs a method of generating pre-nucleated clusters that reach a potential energy minimum through chemical self-assembly. Compared to separately adding shell material precursors, this method is simpler and more controllable. Furthermore, since the pre-nucleated clusters that reach a potential energy minimum through chemical self-assembly already possess covalent bonds, they can decompose into monomers, allowing shell growth to be carried out under milder conditions than conventional methods. The slow decomposition of the pre-nucleated clusters allows for precise control of the monomer release kinetics, achieving atomic-level layer-by-layer epitaxial growth on the quantum dot surface. The resulting core-shell structures exhibit significantly improved brightness and high reproducibility.

[0057] Obviously, based on the above description of the present invention, and according to the common technical knowledge and conventional methods in the field, without departing from the basic technical idea of ​​the present invention (using pre-nucleated clusters generated by chemical self-assembly to achieve a minimum value on the potential energy surface to synthesize quantum dots), other modifications, substitutions or alterations can be made (such as preparing multi-core shell structure CdSe / CdS / ZnS quantum dots, or preparing InP and InP / ZnS quantum dots).

[0058] The following detailed embodiments further illustrate the above-described content of the present invention. However, this should not be construed as limiting the scope of the present invention to the following embodiments. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Attached Figure Description

[0059] Figure 1A The absorption (a) and emission spectra (b, 520 nm) of CdSeS / CdS core-shell structured quantum dots prepared by adding CdS pre-nucleated clusters to CdSeS quantum dots in Example 1, and the absorption (a) and emission spectra (b) of CdSeS quantum dots without adding pre-nucleated clusters are shown.

[0060] Figure 1B For comparison Figure 1AAbsorption and emission spectra of CdSeS / CdS core-shell quantum dots were synthesized by adding a mixture of cadmium precursor (Cd(OAc)2 / OLA) and sulfur precursor (STOP) (a and b, PL 531 nm) and adding sulfur precursor alone (c and d, PL 523 nm).

[0061] Figure 2 For Example 2, CdS pre-nucleated clusters were added to CdSe quantum dots, and the absorption (a) and emission spectra (b, 521 nm) of CdSe / CdS core-shell quantum dots were prepared by gradient heating; CdS pre-nucleated clusters were added to CdSe quantum dots, and the absorption (c) and emission spectra (d, 535 nm) of CdSe / CdS core-shell quantum dots were prepared by isothermal heating at 260 °C; A mixture of cadmium precursor (Cd(OAc)2 / OLA) and sulfur precursor (STOP) was added to CdSe quantum dots, and the absorption (e) and emission spectra (f, 535 nm) of CdSe / CdS core-shell quantum dots were prepared by isothermal heating at 260 °C.

[0062] Figure 3 The absorption (a) and emission spectra (b, 568 nm) of CdSe / CdS core-shell structured quantum dots were prepared by adding CdS pre-nucleated clusters to CdSe quantum dots in Example 3.

[0063] Figure 4 The absorption (a) and emission spectra (b, 598 nm) of CdSe / CdS core-shell structured quantum dots prepared by adding CdS pre-nucleated clusters to CdSe quantum dots in Example 4, and the absorption (c) and emission spectra (d, 584 nm) of octadecene (ODE) as a reaction medium are shown.

[0064] Figure 5 For Example 5, CdSe pre-nucleated clusters were added to CdTe quantum dots, and CdTe / CdSe core-shell structure quantum dots were prepared by isothermal treatment at 140℃. The absorption (a) and emission spectra (b, 648 nm) of the CdTe quantum dot sample were obtained by isothermal treatment at 140℃. The absorption (c) and emission spectra (d, 602 nm) of the CdTe quantum dot sample were obtained by isothermal treatment at 140℃.

[0065] Figure 6 The absorption (a) and emission (b, 501 nm) spectra of ZnTeSe / ZnSe core-shell structured quantum dots were prepared by adding ZnSe pre-nucleation clusters to ZnTeSe quantum dots in Example 6.

[0066] Figure 7For Example 7, 100 μL of CdTe quantum dots were dispersed in 20 mL of toluene, and then 400 μL of CdSe pre-nucleated clusters were added. The absorption (a) and emission spectra (b, 592 nm) of CdTe / CdSe core-shell structured quantum dots were prepared by isothermal treatment at 60 °C. The absorption (c) and emission spectra (d, 549 nm) of the CdTe quantum dot sample were also prepared by isothermal treatment at 60 °C.

[0067] Figure 8 Example 8: Controlling the size and size distribution of ZnSe quantum dots by pre-nucleation cluster concentration: Increasing pre-nucleation cluster concentrations were obtained at (a) 120℃, (b) 160℃, and (c) 200℃. The absorption spectra of quantum dots synthesized at room temperature were fitted using the pre-nucleation clusters.

[0068] Figure 9 To regulate the ZnSe quantum dot size and size distribution by controlling the decomposition rate of pre-nucleated clusters in Example 9: (a) 15 μL PNC + 3 mL CH (cyclohexane) + 0 μL MeOH (methanol), 15 μL PNC + 3 mL CH + 2 μL MeOH; (b) 15 μL PNC + 3 mL CH + 5 μL MeOH; (c) 15 μL PNC + 3 mL CH + 10 μL MeOH; (d) 15 μL PNC + 3 mL CH + 20 μL MeOH; (e) 15 μL PNC + 3 mL CH + 40 μL MeOH; (f) 15 μL PNC + 3 mL CH + X MeOH (X is 0 μL, 2 μL, 5 μL, 10 μL, 20 μL, 40 μL) + 0.5 mL BTA (butylamine).

[0069] Figure 10 To regulate the size and size distribution of ZnSe and ZnSeS quantum dots, pre-nucleated samples were repeatedly added in Example 10: (a) ZnSe QD-325, QD-327, QD-329, and QD-330 were obtained at 9, 17, 49, and 97 h, respectively; (b) the change in the full width at half maximum (FWHM) of the UV absorption of ZnSe quantum dots after incubation for 1 h following the addition of the ZnSe pre-nucleated sample; (c) the ZnSeS quantum dot sample obtained after incubation at 45 °C for 24 h; and (d) the change in the FWHM of the UV absorption of ZnSeS quantum dots after incubation for 2 h following the addition of the ZnSeS pre-nucleated sample.

[0070] Figure 11 For (a, c) Control Example 1, the size and size distribution of ZnSe quantum dots were regulated by adding pre-nucleated samples at different temperatures (a) room temperature and (c) 45°C in a single step; for (b, d) Example 11, the size and size distribution of ZnSe quantum dots were regulated by repeatedly adding pre-nucleated samples at (b) room temperature and (d) 45°C.

[0071] Figure 12High-resolution transmission electron microscopy (TEM) image of small-sized zinc selenide quantum dots with UV absorption of ~345 nm, prepared at low temperature. The quantum dots exhibit a dot-like morphology with a diameter of approximately 2.3 nm. Detailed Implementation

[0072] The raw materials and equipment used in this invention are all known products, obtained by purchasing commercially available products.

[0073] In this invention, "room temperature" refers to 25±5℃.

[0074] Example 1: Preparation of CdSeS / CdS core-shell quantum dots

[0075] I. Experimental Methods

[0076] 1. Substrate preparation:

[0077] 1) Preparation of cadmium oleate precursor:

[0078] Cadmium oleate (Cd(OA)2 / ODE) precursor was prepared by mixing cadmium oxide (CdO), oleic acid (HOA), and octadecene (ODE):

[0079] (1) Place cadmium oxide, oleic acid, and octadecene in a three-necked flask, evacuate at room temperature for 8 minutes, then purge with nitrogen for 2 minutes. Perform three cycles of vacuum / nitrogen exchange (complete within 30 minutes), and finally maintain a nitrogen atmosphere.

[0080] (2) Under nitrogen protection, heat to 80°C, then evacuate and maintain the reaction for 1 hour. After the vacuum reaction is completed, purge with nitrogen and maintain the nitrogen atmosphere for the next temperature reaction.

[0081] (3) Under nitrogen protection, heat to 120°C, then evacuate and maintain the reaction for 1 hour. After the vacuum reaction is completed, purge with nitrogen to maintain a nitrogen atmosphere.

[0082] (4) Under nitrogen protection, the temperature is raised to 240℃ and the reaction is maintained for 30 min;

[0083] (5) Cool down to room temperature and collect the product. The product obtained is the cadmium oleate precursor (liquid).

[0084] 2) Preparation of trioctylphosphine selenium (selenium precursor, SeTOP) precursor:

[0085] SeTOP was obtained by reacting selenium powder (Se, 3.00 mmol) with trioctylphosphine (TOP, 6.60 mmol) under vacuum at room temperature for 30 min.

[0086] 3) Preparation of trioctylphosphine sulfur (sulfur precursor, STOP) precursor:

[0087] STOP was obtained by reacting sulfur powder (S, 3.00 mmol) with trioctylphosphine (TOP, 6.60 mmol) under vacuum at room temperature for 30 min.

[0088] 2. Preparation of CdSeS quantum dots

[0089] Take cadmium oleate precursor and octadecene, vacuum at room temperature for 8 min, then purge with nitrogen for 2 min, perform three cycles of vacuum / nitrogen exchange (completed within 30 min), heat to 120℃ under nitrogen protection and vacuum for 30 min, finally add SeTOP and STOP while maintaining nitrogen atmosphere, heat to 180℃ and react for 90 min to obtain CdSeS quantum dot reaction stock solution.

[0090] 3. Preparation of CdS PNC (pre-nucleation) samples

[0091] Take cadmium oleate precursor and octadecene, vacuum at room temperature for 8 min, then purge with nitrogen for 2 min, perform three cycles of vacuum / nitrogen exchange (complete within 30 min), heat to 120℃ and vacuum for 30 min under nitrogen protection, finally maintain nitrogen atmosphere and cool down to 80℃, add STOP and heat to 180℃ and react for 15 min, the obtained product is CdS PNC sample.

[0092] 4. Preparation of CdSeS / CdS quantum dots

[0093] An equal volume of CdS PNC sample was added to the CdSeS quantum dot reaction stock solution. The solution was heated from 180℃ to 260℃ in a gradient heating manner. After holding at different temperatures for 15 min, samples were taken. 30 μL of the sample was dispersed in 3 mL of cyclohexane for testing.

[0094] Add Cd precursor Cd(OA)2 or Cd(OA)2+STOP to the CdSeS quantum dot reaction stock solution, and heat the solution from 180℃ to 260℃ in a gradient manner. After holding at different temperatures for 15 min, take samples and disperse 30 μL or 10 μL of the sample in 3 mL of cyclohexane for testing.

[0095] II. Experimental Results

[0096] Comparative experimental results of samples with and without CdS prenucleation show that adding prenucleation clusters can narrow the quantum dot size distribution and enhance luminescence properties. The quantum dots obtained at 240℃ exhibited the strongest luminescence properties. Since residual Cd precursors remain in the reaction after generating CdSeS quantum dots, adding Cd precursors or Cd precursors and STOP can react with the Cd precursors to generate CdS PNCs, similarly achieving narrower quantum dot size distribution and enhanced luminescence properties.

[0097] Example 2: Preparation of CdSe / CdS core-shell quantum dots

[0098] I. Experimental Methods

[0099] 1. Substrate preparation:

[0100] 1) Preparation of cadmium oleate precursor as in Example 1

[0101] 2) Preparation of trioctylphosphine selenium (selenium precursor, SeTOP) precursor as in Example 1

[0102] 3) Preparation of trioctylphosphine sulfur (sulfur precursor, STOP) precursor as in Example 1

[0103] 2. Preparation of CdSe quantum dots

[0104] Take cadmium oleate precursor and octadecene, vacuum at room temperature for 8 min, then purge with nitrogen for 2 min, perform three cycles of vacuum / nitrogen exchange (complete within 30 min), heat to 120℃ under nitrogen protection and vacuum for 30 min, finally maintain nitrogen, add SeTOP, heat to 160℃ and react for 15 min to obtain CdSe quantum dot reaction stock solution.

[0105] 3. Preparation of CdS PNC (pre-nucleation) samples

[0106] Take octadecene, the precursor of cadmium oleate, and vacuum it at room temperature for 8 minutes. Then, purge it with nitrogen for 2 minutes. Perform three cycles of vacuum / nitrogen purging (completed within 30 minutes). Under nitrogen protection, heat it to 120°C and vacuum it for 30 minutes. Finally, maintain the nitrogen atmosphere and cool it down to 80°C. Add STOP and heat it to 160°C to react for 10 minutes. The product obtained is the CdS PNC sample.

[0107] 4. Preparation of CdSe / CdS quantum dots

[0108] An equal amount of CdS PNC sample was added to the CdSe quantum dot reaction stock solution. The solution was heated from 160℃ to 260℃ using a gradient heating method, and samples were taken after holding at each temperature for 15 min. 75 μL of the sample was dispersed in 3 mL of cyclohexane for testing. Figure 2 (a and b).

[0109] An equal amount of CdS PNC sample was added to the CdSe quantum dot reaction stock solution. The solution was rapidly heated from 160℃ to 260℃, and samples were taken within 60 min of reaction at 260℃. 30 μL of the sample was dispersed in 3 mL of cyclohexane for testing. Figure 2 c and d).

[0110] Cd precursor Cd(OA)2 and S precursor STOP were added to the CdSe quantum dot reaction stock solution. The solution was rapidly heated from 160℃ to 260℃, and samples were taken within 60 min of reaction at 260℃. 30 μL of the sample was dispersed in 3 mL of cyclohexane for testing. Figure 2 e and f).

[0111] II. Experimental Results

[0112] The luminescence properties of quantum dots are affected by surface defects, and the non-radiative release of energy leads to a decrease in photoluminescence quantum yield. Using CdS as a shell and adding CdS pre-nucleated samples to CdSe quantum dots to provide monomers for surface passivation of CdSe quantum dots significantly improves their photoluminescence quantum yield. Figure 2 (a) and (b) both methods, which involve adding CdS prenucleation samples and adding anion and cation precursors, yielded CdSe / CdS quantum dots with the same absorption and emission peak positions, but the CdSe / CdS quantum dots obtained by adding CdS prenucleation samples exhibited better fluorescence performance.

[0113] Example 3: Preparation of CdSe / CdS core-shell quantum dots

[0114] I. Experimental Methods

[0115] 1. Substrate preparation:

[0116] 1) Preparation of cadmium oleate precursor as in Example 1

[0117] 2) Preparation of trioctylphosphine selenium (selenium precursor, SeTOP) precursor as in Example 1

[0118] 3) Preparation of trioctylphosphine sulfur (sulfur precursor, STOP) precursor as in Example 1

[0119] 2. Preparation of CdSe quantum dots

[0120] Take cadmium oleate precursor and octadecene, vacuum at room temperature for 8 min, then purge with nitrogen for 2 min, perform three cycles of vacuum / nitrogen exchange (complete within 30 min), under nitrogen protection, heat to 120℃ and vacuum for 30 min, maintain nitrogen atmosphere, add diphenylphosphine oxide (DPPO) and SeTOP, heat to 200℃ and react for 30 min to obtain CdSe quantum dot reaction stock solution.

[0121] 3. Preparation of CdS PNC (pre-nucleation) samples as in Example 1

[0122] 4. Preparation of CdSe / CdS quantum dots

[0123] An equal amount of CdS PNC sample was added to the CdSe quantum dot reaction stock solution. The solution was heated from 200℃ to 260℃ in a gradient manner. After holding at each temperature for 15 min, a sample was taken. 20 μL of the sample was dispersed in 3 mL of cyclohexane for testing.

[0124] II. Experimental Results

[0125] The size of quantum dots is affected by the additive DPPO; using DPPO results in larger quantum dot sizes. The luminescence properties of quantum dots are influenced by the shell material. Using CdS pre-nucleated samples to provide monomers for surface passivation of CdSe quantum dots significantly improved their photoluminescence quantum yield. Figure 3 ).

[0126] Example 4: Preparation of CdSe / CdS core-shell quantum dots

[0127] I. Experimental Methods

[0128] 1. Substrate preparation:

[0129] 1) Preparation of cadmium oleate precursor as in Example 1

[0130] 2) Preparation of trioctylphosphine selenium (selenium precursor, SeTOP) precursor:

[0131] SeTOP was obtained by reacting selenium powder (Se, 4.00 mmol) with trioctylphosphine (TOP, 12.00 mmol) under vacuum at room temperature for 30 min.

[0132] 2. Preparation of CdSe quantum dots

[0133] Take cadmium oleate precursor and octadecene, vacuum at room temperature for 8 min, then purge with nitrogen for 2 min, perform three cycles of vacuum / nitrogen purging (completed within 30 min), heat to 120℃ under nitrogen protection and vacuum for 60 min, finally maintain nitrogen atmosphere and heat to 240℃, then add 225 μL of SeTOP mixture, maintain temperature at 220℃ and react for 15 min to obtain CdSe quantum dot reaction stock solution.

[0134] 3. Preparation of CdS PNC (pre-nucleation) samples

[0135] Take octadecene, the precursor of cadmium oleate, and vacuum it for 8 minutes at room temperature. Then, purge it with nitrogen for 2 minutes. Perform three cycles of vacuum / nitrogen exchange (completed within 30 minutes). Under nitrogen protection, heat it to 120°C and vacuum it for 60 minutes. Finally, maintain the nitrogen atmosphere and heat it to 180°C. Add sulfur powder and react for 15 minutes. The product obtained is the CdS PNC sample.

[0136] 4. Preparation of CdSe / CdS quantum dots

[0137] An equal amount of CdS PNC sample was added to the CdSe quantum dot reaction stock solution. The solution was heated from 180℃ to 260℃ in a gradient manner. After holding at each temperature for 15 min, samples were taken. The solution was then held at 260℃ for 120 min. Samples were taken at different time points. 10 μL of the sample was dispersed in 3 mL of cyclohexane for testing.

[0138] An equal mass of octadecene, the reaction medium, was added to the CdSe quantum dot reaction stock solution. The solution was heated from 180°C to 260°C in a gradient manner. After holding at each temperature for 15 min, a sample was taken. 10 μL of the sample was dispersed in 3 mL of cyclohexane for testing.

[0139] II. Experimental Results

[0140] Using CdS as a shell to encapsulate CdSe quantum dots and adding CdS pre-nucleated samples to provide monomers for surface passivation of CdSe quantum dots can significantly improve their photoluminescence quantum yield. The core-shell structured quantum dots exhibit the strongest luminescence properties at 260℃ for 120 min. Figure 4 ).

[0141] Example 5: Preparation of CdTe / CdSe core-shell quantum dots

[0142] I. Experimental Methods

[0143] 1. Substrate preparation:

[0144] 1) Preparation of trioctylphosphine selenium (selenium precursor, SeTOP) precursor as in Example 1

[0145] 2) Preparation of trioctylphosphine tellurium (tellurium precursor, TeTOP) precursor:

[0146] (1) Take tellurium powder (Te, 14.0 mmol) and trioctylphosphine (56.0 mmol), vacuum at room temperature for 8 min, then purge with nitrogen for 2 min. Perform three cycles of vacuum / nitrogen exchange (complete within 30 min), and finally maintain a nitrogen atmosphere.

[0147] (2) Under nitrogen protection, the temperature is raised to 120°C, then a vacuum is drawn and the reaction is carried out for 30 minutes. After the vacuum reaction is completed, nitrogen is introduced and the nitrogen atmosphere is maintained for the next temperature reaction.

[0148] (3) Under nitrogen protection, the temperature was raised to 300℃ and reacted for 1 hour. The product was collected after cooling to room temperature to obtain TeTOP.

[0149] 2. Preparation of CdTe quantum dots

[0150] (1) Place cadmium acetate dihydrate (0.6 mmol), oleylamine and octadecene in a three-necked flask, evacuate at room temperature for 8 min, then purge with nitrogen for 2 min, perform three cycles of vacuum / nitrogen exchange (complete within 30 min), and finally maintain a nitrogen atmosphere.

[0151] (2) Under nitrogen protection, heat to 80°C, then evacuate and maintain the reaction for 1 hour. After the vacuum reaction is completed, purge with nitrogen and maintain the nitrogen atmosphere for the next temperature reaction.

[0152] (3) Under nitrogen protection, the temperature is raised to 120°C, then a vacuum is drawn and the reaction is carried out for 1 hour. After the vacuum reaction is completed, nitrogen is introduced and diphenylphosphine oxide (DPPO) is added. The nitrogen atmosphere is maintained and the temperature is lowered to room temperature.

[0153] (4) After adding TeTOP to the above reaction solution, the temperature is raised to 140℃ under nitrogen atmosphere and reacted for 15 min to obtain CdTe quantum dot stock solution.

[0154] 3. Preparation of CdSe PNC (pre-nucleation) samples

[0155] 1) Place 0.6 mmol of cadmium acetate dihydrate and oleylamine in a three-necked flask, evacuate at room temperature for 8 min, then purge with nitrogen for 2 min. Perform three cycles of vacuum / nitrogen purging (complete within 30 min), and finally maintain a nitrogen atmosphere.

[0156] (2) Under nitrogen protection, heat to 80°C, then evacuate and maintain the reaction for 1 hour. After the vacuum reaction is completed, purge with nitrogen and maintain the nitrogen atmosphere for the next temperature reaction.

[0157] (3) Under nitrogen protection, the temperature is raised to 120°C, then vacuum is applied and the reaction is maintained for 1 hour. Then nitrogen is introduced and the nitrogen atmosphere is maintained until the temperature drops to room temperature.

[0158] (4) After adding SeTOP to the above reaction solution, the mixture is heated to 140°C under a nitrogen atmosphere and reacted for 30 min to obtain CdSe PNC stock solution.

[0159] 4. Preparation of CdTe / CdSe quantum dots

[0160] An equal volume of CdSe PNC sample was added to the CdTe quantum dot reaction stock solution, and the reaction was carried out at 140℃. Samples were taken at different time points, and 20 μL of the sample was dispersed in 3 mL of cyclohexane for testing.

[0161] II. Experimental Results

[0162] The luminescence properties of core-shell quantum dots are affected by size. The core-shell quantum dots with the strongest luminescence properties were obtained by adding CdSe PNC sample to CdTe quantum dots at 140℃ and reacting for 30 minutes. Figure 5 ).

[0163] Example 6: Preparation of ZnTeSe / ZnSe core-shell quantum dots

[0164] I. Experimental Methods

[0165] 1. Substrate preparation:

[0166] 1) Preparation of zinc oleate precursor (for ZnTeSe quantum dot synthesis):

[0167] Zinc oleate (Zn(OA)2 / ODE) precursor was prepared by mixing zinc acetate (Zn(OAc)2), oleic acid (HOA), and octadecene (ODE):

[0168] Zinc acetate, oleic acid, and octadecene were placed in a three-necked flask and evacuated at 80°C for 9 minutes. Then, nitrogen was purged for 1 minute. The vacuum / nitrogen purging operation was repeated three times (completed within 30 minutes). Under nitrogen protection, the temperature was raised to 120°C and then the reaction was carried out under vacuum for 1 hour. The product obtained was the zinc oleate precursor (liquid).

[0169] 2) Preparation of trioctylphosphine selenium (selenium precursor, SeTOP) precursor:

[0170] SeTOP was obtained by reacting 6.0 mmol of selenium powder with 12.0 mmol of trioctylphosphine under vacuum at room temperature for 30 min.

[0171] 3) Preparation of diphenylphosphine selenium (selenium precursor, SeDPP) precursor:

[0172] SeDPP was obtained by dissolving selenium powder (0.3 mmol) in diphenylphosphine (DPP) under nitrogen atmosphere.

[0173] 4) Preparation of trioctylphosphine tellurium (tellurium precursor, TeTOP) precursor:

[0174] Take tellurium powder (6.0 mmol) and trioctylphosphine (24.0 mmol) and place them in a three-necked flask. Vacuum the flask at room temperature for 9 min, then purge with nitrogen for 1 min. Perform three cycles of vacuum / nitrogen purging (completed within 30 min). Heat the flask to 80 °C under nitrogen purging and maintain this temperature while evacuating for 30 min. Further heat the flask to 300 °C under nitrogen purging and maintain this temperature for 1 h to obtain TeTOP.

[0175] 2. Preparation of ZnSe prenucleation clusters (PNCs) samples

[0176] SeTOP and DPP were added to the zinc oleate precursor at 80℃, and the mixture was heated to 160℃ and reacted for 30 min under nitrogen protection. The resulting product was the ZnSe PNCs sample.

[0177] 3. Preparation of ZnTeSe quantum dots

[0178] The zinc oleate precursor was heated to 270°C, and then SeDPP and TeTOP were added sequentially. The reaction was carried out for 1 hour to obtain ZnTeSe quantum dots.

[0179] 4. Preparation of ZnTeSe / ZnSe quantum dots

[0180] An equal mass of ZnSe PNCs sample was added to the ZnTeSe quantum dot reaction stock solution at 270℃, and the reaction was carried out at this temperature for 60 min to obtain ZnTeSe / ZnSe quantum dots.

[0181] II. Experimental Results

[0182] The luminescence properties of ZnTeSe quantum dots are affected by surface defects, and the energy is released in a non-radiative manner, resulting in a low photoluminescence quantum yield. Using ZnSe PNCs as a shell coating material, the monomers generated from their decomposition form a ZnSe shell on the surface of the ZnTeSe quantum dots, passivating the surface and thus significantly improving its photoluminescence quantum yield. Figure 6 Example 7: Preparation of CdTe / CdSe core-shell quantum dots under low-temperature conditions.

[0183] I. Experimental Methods

[0184] 1. Substrate preparation:

[0185] 1) Preparation of oleylamine cadmium precursor:

[0186] The oleylamine cadmium precursor (Cd(OAc)2 / OLA) was prepared by mixing cadmium acetate dihydrate and oleylamine:

[0187] (1) Place cadmium acetate dihydrate (6.00 mmol) and oleylamine in a three-necked flask, evacuate at room temperature for 8 min, then purge with nitrogen for 2 min, and perform three cycles of vacuum / nitrogen exchange (complete within 30 min);

[0188] (2) Under nitrogen protection, the temperature is raised to 120°C, then vacuum is applied, and the reaction is maintained for 1 hour until the solution becomes completely transparent. Then nitrogen is introduced, and the solution is cooled to room temperature under nitrogen conditions. The solution is collected and refrigerated in a refrigerator.

[0189] 2) Preparation of trioctylphosphine selenium (selenium precursor, SeTOP) precursor as in Example 1

[0190] 3) Preparation of trioctylphosphine tellurium (tellurium precursor, TeTOP) precursor:

[0191] Take tellurium powder (Te, 3.00 mmol) and trioctylphosphine (TOP, 12.0 mmol) and place them in a three-necked flask. Vacuum the solution at room temperature for 8 min, then purge with nitrogen for 2 min. Perform three cycles of vacuum / nitrogen purging (completed within 30 min). Purge with nitrogen again, and heat to 300 °C under nitrogen protection. Maintain this temperature in nitrogen for 40 min, until the solution turns orange and transparent. Cool to room temperature and vacuum for 30 min; the solution eventually turns pale green. Collect the solution and store it in a glove box.

[0192] 2. Preparation of CdTe PNC (pre-nucleation) samples

[0193] The cadmium oleylamine precursor and oleylamine were placed in a 50 mL three-necked flask at room temperature. The mixture was evacuated for 8 min at room temperature, followed by nitrogen purging for 2 min. This vacuum / nitrogen purging process was repeated three times (completed within 30 min). The solution was heated to 120 °C under a nitrogen atmosphere, then switched to a vacuum state and evacuated until no bubbles remained. Nitrogen was then introduced, TeTOP was added, and the temperature was raised to 135 °C. The reaction was maintained for 35 min to obtain the CdTe PNC stock solution.

[0194] 3. Preparation of CdTe quantum dots

[0195] 100 μL of CdTe PNC was dispersed in 20 mL of toluene to obtain a solution containing the pre-nucleated sample. The solution was placed in a water bath at 60 °C for 4 h to obtain CdTe quantum dots.

[0196] 4. Preparation of CdSe PNC (pre-nucleation) samples

[0197] The cadmium oleylamine precursor and oleylamine were placed in a 50 mL three-necked round-bottom flask. The mixture was evacuated three times at room temperature (8 min evacuation, 2 min nitrogen purging, repeated three times) until no bubbles were generated. Then, under nitrogen protection, the temperature was raised to 80 °C and evacuated for 60 min. Under nitrogen protection, the temperature was further raised to 120 °C and evacuated for 60 min. Under nitrogen protection, the temperature was lowered to 80 °C, SeTOP was added, and the temperature was raised to 140 °C. The reaction was carried out for 25 min to obtain the CdSe PNC stock solution.

[0198] 5. Preparation of CdTe / CdSe quantum dots

[0199] Add CdS pre-nucleated sample to the CdTe quantum dot stock solution prepared in step 3, and continue the reaction in a water bath at 60°C for 68 hours. Samples were taken at different time points and tested.

[0200] II. Experimental Results

[0201] Comparing experimental data from CdTe quantum dots with and without pre-nucleated CdTe clusters at 60℃ for 4 h, it is evident that the UV and PL peak positions of the type II core-shell CdTe / CdSe quantum dots formed by the former are significantly shifted towards the near-infrared region compared to CdTe quantum dots without pre-nucleated clusters. In the CdTe / CdSe structure, the effective band gap is the difference between the CdSe conduction band bottom (-0.7 eV) and the CdTe valence band top (-0.06 eV), approximately 0.64 eV, significantly smaller than the band gap of the single material. This reduction in effective band gap leads to a redshift in absorption and emission spectra, achieving a larger luminescence range than single CdTe quantum dots. This experimental method also enables the low-temperature synthesis of core-shell quantum dots. Figure 7 ).

[0202] Example 8: Controlling the size and size distribution of ZnSe quantum dots by controlling the concentration of pre-nucleation clusters that reach a minimum potential energy surface based on chemical self-assembly in the sample using cyclohexane as a solvent.

[0203] I. Experimental Methods

[0204] 1. Substrate preparation:

[0205] 1) Preparation of zinc oleate precursor stock solution:

[0206] A zinc oleate (Zn(OA)2 / ODE) precursor stock solution was prepared by mixing zinc oxide (ZnO), oleic acid (OA), and 1-octadecene (ODE);

[0207] The specific steps are as follows:

[0208] (1) Place zinc oxide (0.492 g, 6.04 mmol), oleic acid (3.729 g, 13.2 mmol), and 1-octadecene (5.000 g) in a three-necked flask;

[0209] (2) Vacuuming at room temperature, followed by three vacuum / nitrogen exchange operations (to be completed within 30 minutes);

[0210] (3) Under nitrogen protection, the temperature was raised to 120°C and the reaction was carried out under vacuum for 2 hours;

[0211] (4) Under nitrogen protection, the temperature was raised to 290℃ and the reaction was carried out for 2 hours to obtain a clear solution;

[0212] (5) Under nitrogen protection, the temperature was lowered to 120℃ and the reaction was carried out under vacuum for 2 hours;

[0213] The resulting product is the zinc oleate precursor stock solution.

[0214] 2) Preparation of trioctylphosphine selenium precursor:

[0215] Trioctylphosphine selenium (SeTOP) precursor stock solution was prepared by mixing selenium powder (Se) with trioctylphosphine (TOP);

[0216] The specific steps are as follows:

[0217] (a) Selenium powder (0.328 g, 4.15 mmol), trioctylphosphine (3.390 g, 9.15 mmol) and 1-octadecene (0.437 g) were mixed at room temperature;

[0218] (b) Evacuate at room temperature and perform vacuum / nitrogen exchange three times (complete within 30 minutes).

[0219] (c) Under nitrogen protection, the temperature is raised to 40°C and the reaction is carried out for 30 min;

[0220] The resulting product is a stock solution of trioctylphosphine selenium precursor, which is stored in a glove box.

[0221] 2. Preparation of ZnSe prenucleation samples

[0222] The specific steps are as follows:

[0223] Zinc oleate precursor stock solution (1.832 g), trioctylphosphine selenide precursor stock solution (330 μL), 1-octadecene (2.868 g), and diphenylphosphine (52 μL) were reacted under a nitrogen atmosphere with a programmed temperature increase (~10 °C / min) at 80, 120, 160, 200, and 240 °C for 30 min each; the samples reacted at 120 °C / 30 min, 160 °C / 30 min, and 200 °C / 30 min were ZnSe pre-nucleation samples.

[0224] 3. Controlling the number of prenucleation clusters in prenucleation samples to control quantum dot size and size distribution.

[0225] 15 μL of pre-nucleated samples (ZnSe) prepared at three different temperatures (120℃, 160℃, and 200℃) were dispersed in 3 mL of cyclohexane and 10 μL of methanol at room temperature, respectively. After incubation at room temperature for one hour, the samples were tested to obtain QD-322, QD-313, and QD-310, respectively. The fitted curves of their absorption spectra are shown below. Figure 8 As shown in (ac).

[0226] II. Experimental Results

[0227] Table 1. Results of ZnSe quantum dot size and size distribution regulated by pre-nucleation cluster concentration.

[0228]

[0229] Figure 8As shown in Table 1, quantum dots with sizes QD-322, QD-313, and QD-310 can be prepared using pre-nucleation samples prepared at 120℃, 160℃, and 200℃, respectively, with the absorbance of QD-322, QD-313, and QD-310 quantum dots increasing progressively. Since absorbance is proportional to the concentration of pre-nucleation clusters and the number of quantum dots, it can be seen that the concentration of pre-nucleation clusters in the pre-nucleation samples increases with increasing temperature. These results indicate that the size of quantum dots prepared from the pre-nucleation samples decreases while the number of pre-nucleation clusters increases with increasing pre-nucleation cluster concentration, and the full width at half maximum (FWHM) of the ultraviolet absorption decreases (i.e., the size distribution of the quantum dots narrows).

[0230] Example 9: Controlling the decomposition rate of prenucleation clusters generated by chemical self-assembly in prenucleated samples to reach a minimum potential energy surface, thereby controlling quantum dot size and size distribution.

[0231] I. Experimental Methods

[0232] 1. Substrate preparation:

[0233] 1) Preparation of zinc oleate precursor stock solution: The preparation process is as described in Example 8.

[0234] 2) Preparation of trioctylphosphine selenium stock solution: The preparation process is as described in Example 8.

[0235] 2. Preparation of ZnSe pre-nucleation samples:

[0236] Zinc oleate precursor stock solution (1.832 g), trioctylphosphine selenide precursor stock solution (330 μL), 1-octadecene (2.868 g), and diphenylphosphine (52 μL) were reacted at 160 °C for 30 min under a nitrogen atmosphere to obtain a ZnSe prenucleation sample.

[0237] 3. Controlling the decomposition rate of prenucleation clusters in prenucleation samples to control quantum dot size and size distribution.

[0238] Take 15 μL of pre-nucleated sample and disperse it in different types of solvents at room temperature. After incubating at room temperature for 1 hour, test each group.

[0239] Specifically, the following groups were used: 15 μL PNC + 3 mL CH + 0 μL MeOH, 15 μL PNC + 3 mL CH + 2 μL MeOH, 15 μL PNC + 3 mL CH + 5 μL MeOH, 15 μL PNC + 3 mL CH + 10 μL MeOH, 15 μL PNC + 3 mL CH + 20 μL MeOH, 15 μL PNC + 3 mL CH + 40 μL MeOH, and 15 μL PNC + 3 mL CH + XMeOH (X is 0 μL, 2 μL, 5 μL, 10 μL, 20 μL, or 40 μL) + 0.5 mL BTA (butanylamine).

[0240] Its absorption spectrum curves in different types of solvents are as follows: Figure 9 As shown.

[0241] II. Experimental Results

[0242] Table 2 Results of quantum dot size and size distribution controlled by the decomposition rate of prenuclear clusters (1 hour)

[0243]

[0244]

[0245] " / " indicates that no prenuclear clusters remain or no ZnSe quantum dots were obtained.

[0246] result( Figure 9 The results (ae) show that, while keeping the ratio of the prenucleation sample to the organic solvent cyclohexane constant (15 μL PNC: 3 mL CH4), different volumes (0 μL, 2 μL, 5 μL, 10 μL, 20 μL, 40 μL) of methanol can prepare ZnSe quantum dots of varying numbers and sizes. Therefore, the decomposition rate of the prenucleation clusters and the number and size of ZnSe quantum dots can be controlled by adjusting the volume ratio of the prenucleation sample, organic solvent, and methanol. Specifically, within the range of 0–10 μL, more methanol results in a faster decomposition rate of the prenucleation clusters and yields larger and more numerous ZnSe quantum dots. When the methanol volume exceeds 10 μL, the increase in the decomposition rate of the prenucleation clusters is not significant, and the changes in the size and number of ZnSe quantum dots are relatively small. Figure 9 f shows that when the ratio of the pre-nucleated sample to the organic solvents CH and BTA (15 μL PNC: 3 mL CH: 0.5 mL BTA) remains constant, ZnSe quantum dots cannot be obtained when the volume of methanol is 0–5 μL; ZnSe quantum dots can be prepared when the volume of methanol is 10–40 μL, but the difference in the number and size of ZnSe quantum dots is not significant.

[0247] Example 10: Controlling the size and size distribution of ZnSe and ZnSeS quantum dots by repeatedly adding pre-nucleated samples using cyclohexane as solvent.

[0248] I. Experimental Methods

[0249] 1. Substrate preparation:

[0250] 1) Preparation of zinc oleate precursor stock solution: The preparation process is as described in Example 8.

[0251] 2) Preparation of trioctylphosphine selenium stock solution: The preparation process is as described in Example 8.

[0252] 2. Preparation of ZnSe and ZnSeS prenucleation samples

[0253] The specific steps are as follows:

[0254] (1) Preparation of ZnSe prenucleation sample: Zinc oleate precursor stock solution (1.832 g), trioctylphosphine selenide precursor stock solution (330 μL), 1-octadecene (2.868 g), and diphenylphosphine (52 μL) were reacted in a nitrogen atmosphere at 160 °C for 30 min to obtain ZnSe prenucleation sample.

[0255] (2) Preparation of ZnSeS prenucleation sample: Zinc oleate stock solution (1.832 g), trioctylphosphine selenide precursor stock solution (300 μL), sulfur powder (0.0096 g), 1-octadecene (2.868 g), and diphenylphosphine (52 μL) were reacted at 170 °C for 60 min under a nitrogen atmosphere to obtain ZnSeS prenucleation sample.

[0256] 3. Preparation of ZnSe and ZnSeS quantum dot samples by adding pre-nucleated samples.

[0257] (1) Preparation of ZnSe quantum dot samples by adding ZnSe prenucleation samples:

[0258] 150 μL of pre-nucleated ZnSe sample was dispersed in 30 mL of cyclohexane and 100 μL of methanol at room temperature and incubated at room temperature. ZnSe QD-325, QD-327, QD-329, and QD-330 were obtained at 9, 17, 49, and 97 h, respectively, with UV absorption half-widths (FWHM) of 22.9, 23.3, 23.6, and 23.8 nm, respectively. Figure 10 ab).

[0259] (2) Preparation of ZnSeS quantum dot samples by adding ZnSeS pre-nucleated sample: 5 μL of ZnSeS pre-nucleated sample was dispersed in 3 mL of cyclohexane and 10 μL of methanol at room temperature and incubated at 45 °C. ZnSeS QD-307 was obtained after 24 h, with a UV absorption half-width (FWHM) of 21.7 nm. Figure 10 cd).

[0260] 4. Secondary addition of pre-nucleated samples to regulate the size and size distribution of ZnSe and ZnSeS quantum dots

[0261] (1) Adding ZnSe pre-nucleation sample to regulate the size and size distribution of ZnSe quantum dots: After adding 15 μL of ZnSe pre-nucleation sample to 3 mL of the above 4 different ZnSe quantum dots, and incubating at room temperature for 1 h, ZnSe QD-332 was obtained in all cases, and the FWHM decreased to 20.6, 20.6, 21.0, and 21.2 nm, respectively. The quantum dot size was consistent and the size distribution became narrower. Figure 10 b).

[0262] (2) Adding ZnSeS pre-nucleation sample to regulate the size and size distribution of ZnSeS quantum dots: After adding 5 μL of ZnSeS pre-nucleation sample to the above ZnSeS quantum dots (3 mL), and incubating at 45 °C for 24 h, ZnSeS QD-312 was obtained, and the UV absorption half-width was reduced to 20.6 nm. Figure 10 d).

[0263] II. Experimental Results

[0264] (1) Results of repeatedly adding pre-nucleated samples to regulate the size and size distribution of ZnSe quantum dots

[0265] Table 3. Results of repeated addition of prenucleated samples to regulate the size and size distribution of ZnSe quantum dots

[0266]

[0267] result( Figure 10 a, b, and Table 3) show that adding the ZnSe pre-nucleation stage sample to a solution containing ZnSe quantum dots, or adding the ZnSeS pre-nucleation stage sample to a solution containing ZnSeS quantum dots, results in quantum dot growth and a narrower size distribution when the number of quantum dots in the solution is small. Adding the ZnSe pre-nucleation sample to different incubation times yielded different ZnSe quantum dots (ZnSe QD-325, QD-327, QD-329, QD-330). However, by adding the ZnSe pre-nucleation sample twice, all of the above quantum dots could be obtained with a consistent size and a narrower distribution (ZnSe QD-332). This indicates that adding the pre-nucleation sample twice can achieve quantum dot size consistency and improve the accuracy of quantum dot size control.

[0268] (2) Results of repeatedly adding pre-nucleated samples to regulate the size and size distribution of ZnSeS quantum dots

[0269] Table 4. Results of controlling the size and size distribution of ZnSeS quantum dots by repeated addition of prenucleation samples

[0270]

[0271] result( Figure 10 c, d, and Table 4) show that adding the ZnSeS pre-nucleation stage sample to a solution containing ZnSeS quantum dots results in quantum dot growth and a narrower size distribution when the quantum dots in the solution are small. Adding the ZnSeS pre-nucleation sample and incubating for 24 hours yielded smaller ZnSeS quantum dots (ZnSeS QD-307). However, by adding the ZnSeS pre-nucleation sample a second time and incubating for another 24 hours, the original smaller ZnSeS quantum dots (ZnSeS QD-307) underwent quantum dot growth, resulting in larger and narrower quantum dots (ZnSeS QD-312). This indicates that adding the pre-nucleation sample a second time can achieve both size growth and a narrower distribution of ZnSeS quantum dots.

[0272] Example 11: Using cyclohexane as a solvent, pre-nucleated samples were repeatedly added at different temperatures to regulate the size and size distribution of ZnSe quantum dots.

[0273] I. Experimental Methods

[0274] 1. Substrate preparation:

[0275] 1) Preparation of zinc oleate precursor stock solution: The preparation process is as described in Example 8.

[0276] 2) Preparation of trioctylphosphine selenium stock solution: The preparation process is as described in Example 8.

[0277] 2. Preparation of ZnSe prenucleation samples

[0278] Zinc oleate stock solution (1.832 g), trioctylphosphine selenide stock solution (330 μL), 1-octadecene (2.868 g), and diphenylphosphine (52 μL) were reacted at 160 °C for 30 min under a nitrogen atmosphere to obtain a ZnSe prenucleation sample.

[0279] 3. Preparation of ZnSe quantum dot samples by adding pre-nucleated samples

[0280] 15 μL of the pre-nucleated sample was dispersed in 3 mL of cyclohexane and 10 μL of methanol at room temperature, and incubated at room temperature and 45 °C for 24 hours respectively to obtain ZnSe QD-326 (room temperature) and QD-337 (45 °C).

[0281] 4. Repeated addition of ZnSe prenucleation samples to regulate quantum dot size and size distribution

[0282] At the two different temperatures mentioned above, in ZnSe QD-326 and QD-337 (3 mL), 10 μL of methanol and 15 μL of pre-nucleated sample were added every 24 hours. After repeated additions 6 times, the quantum dot size increased without ripening, and the full width at half maximum (FWHM) gradually narrowed. After 7 days, ZnSe QD-351 was obtained. Figure 11 a), QD-358 Figure 11 b).

[0283] II. Experimental Results

[0284] Table 5. Results of controlling the size and size distribution of ZnSe quantum dots by repeatedly adding pre-nucleated samples at different temperatures.

[0285]

[0286] result( Figure 11 b, d and Table 5) show that by repeatedly adding samples in the pre-nucleation stage and adjusting the temperature, ZnSe quantum dots with increased size and narrower distribution can be obtained at room temperature or 45°C. Among them, ZnSe quantum dots obtained at 45°C with the same incubation time show greater growth and maintain a narrower size distribution compared to ZnSe quantum dots obtained at room temperature.

[0287] The following describes the preparation of control samples using control examples.

[0288] Comparative Example 1: Using cyclohexane as a solvent, a pre-nucleated sample was added at different temperatures in a single step to control the size and size distribution of ZnSe quantum dots.

[0289] I. Experimental Methods

[0290] 1. Substrate preparation:

[0291] 1) Preparation of zinc oleate precursor stock solution: The preparation process is as described in Example 8.

[0292] 2) Preparation of trioctylphosphine selenium stock solution: The preparation process is as described in Example 8.

[0293] 2. Preparation of ZnSe prenucleation samples

[0294] Zinc oleate stock solution (1.832 g), trioctylphosphine selenide stock solution (330 μL), 1-octadecene (2.868 g), and diphenylphosphine (52 μL) were reacted at 160 °C for 30 min under a nitrogen atmosphere to obtain a ZnSe prenucleation sample.

[0295] 3. Single addition of pre-nucleated sample to control quantum dot size and size distribution

[0296] 105 μL of the pre-nucleated sample was dispersed in 3 mL of cyclohexane and 70 μL of methanol at room temperature, and incubated at room temperature and 45 °C for 144 hours respectively, yielding only QD-340.

[0297] II. Experimental Results

[0298] Table 6. Results of controlling the size and size distribution of ZnSe quantum dots by adding pre-nucleated samples at different temperatures.

[0299]

[0300]

[0301] result( Figure 11 a, c, and Table 6) show that by adding the pre-nucleation stage sample in one step and controlling the temperature, ZnSe quantum dots with increased size and narrower distribution can be obtained at room temperature or 45°C. However, at room temperature, after incubation for 144 h, the growth of quantum dots stopped at ZnSe QD-340, and further incubation did not result in any further growth; at 45°C, after incubation for 72 h, the growth of quantum dots stopped at ZnSe QD-340, and further incubation did not result in any further growth.

[0302] In both Example 11 and Comparative Example 1, 105 μL of pre-nucleation sample, 3 mL of cyclohexane, and 70 μL of methanol were used in the reaction system. In Comparative Example 1, the raw materials in the reaction system were added all at once, while in Example 4, the raw materials in the reaction system were added repeatedly in six separate batches. Comparing the data from Example 11 and Comparative Example 1, it was found that after 24 h of incubation, the quantum dot size in Comparative Example 1 was larger than that in Example 11; however, after 48 h of incubation at room temperature in Example 11, the quantum dot size reached ZnSe QD-340, and the ZnSe quantum dot size increased with repeated additions of the pre-nucleation sample; after 48 h of incubation at 45 °C in Example 11, the quantum dot size reached ZnSe QD-344, and the ZnSe quantum dot size increased with repeated additions of the pre-nucleation sample over an incubation period of 144 h. In contrast, in Comparative Example 1, ZnSe quantum dots with a size of QD-340 could only be obtained after incubation at room temperature for 144 hours (72 hours at 45°C). Furthermore, as the incubation time increased, the size of the quantum dots stagnated at QD-340 and ceased to grow.

[0303] The above results demonstrate that the strategy of repeatedly adding pre-nucleation samples to regulate the size and size distribution of ZnSe quantum dots is more effective than adding pre-nucleation samples all at once, resulting in a higher quantum dot size increase.

[0304] Figure 12This is a high-resolution transmission electron microscope image of small-sized zinc selenide quantum dots with ultraviolet absorption of ~345 nm prepared at low temperature according to the present invention. The quantum dots exhibit a dot-like morphology and have a diameter of approximately 2.3 nm.

[0305] The above results demonstrate that this invention provides a method for controlling the size and size distribution of binary and / or ternary quantum dots based on pre-nucleated clusters that reach a minimum potential energy surface generated by chemical self-assembly (Examples 8-11). Figure 8-12 This invention achieves increased quantum dot size and narrowed size distribution by repeatedly adding corresponding ZnSe and ZnSeS pre-nucleation samples to ZnSe and / or ZnSeS quantum dot samples at low temperatures (25℃ and 45℃). This invention reveals that at low temperatures, the size of quantum dots is related to the concentration of the pre-nucleation sample, the decomposition rate, and the reaction temperature. The size control strategy of this invention achieves quantum dot size growth and narrowed size distribution, avoiding the problem of difficult-to-control reactions at high temperatures. Size control is superior to traditional heating methods, and multiple additions of pre-nucleation samples improve the accuracy of quantum dot size control compared to single additions, demonstrating promising application prospects.

[0306] In summary, this invention provides a method for the controllable synthesis of high-quality quantum dots based on pre-nucleated clusters that reach a minimum potential energy surface generated by chemical self-assembly. The quantum dots of this invention are prepared by reacting a pre-nucleated sample of semiconductor material with pre-prepared quantum dots to obtain high-quality quantum dots grown heterogeneously (core-shell structure) or homogeneously. This method, based on the pre-nucleated clusters, allows for the control of quantum dot size growth, narrowing the quantum dot distribution and avoiding the need to control the bonding temperature of the semiconductor material. This method improves the accuracy of quantum dot size control, and the quantum dots prepared by this method also exhibit significant luminescent properties, effectively expanding the applications of quantum dots and showing great promise.

Claims

1. A method for controllable synthesis of high-quality quantum dots based on pre-formed nucleation clusters that reach a minimum potential energy surface generated by chemical self-assembly, characterized in that, The method includes the following steps: reacting a pre-nucleated sample of semiconductor material with quantum dots of semiconductor material to obtain high-quality quantum dots; The semiconductor material is a semiconductor material containing metal elements of Group II, Group III, Group IV, Group V or Group VI.

2. The method according to claim 1, characterized in that, The semiconductor material is selected from ZnSe, ZnSeS, ZnTe, ZnS, CdSe, CdSeS, CdTe, or CdS.

3. The method according to claim 1 or 2, characterized in that, The method for preparing the pre-nucleation sample of the semiconductor material includes the following steps: adding a precursor solution to a reaction medium and reacting to obtain a pre-nucleation sample of the semiconductor material; or, adding a precursor solution to a reaction medium, adding an activator, and reacting to obtain a pre-nucleation sample of the semiconductor material. The method for preparing quantum dots of the semiconductor material includes the following steps: adding a precursor solution to a reaction medium and reacting to obtain quantum dots of the semiconductor material; or adding a precursor solution to a reaction medium, adding an activator, and reacting to obtain quantum dots of the semiconductor material.

4. The method according to claim 3, characterized in that, The precursor includes a metal carboxylate or a metal oleylamine salt and a trioctylphosphine precursor; preferably, the metal carboxylate is cadmium carboxylate or zinc carboxylate; the metal oleylamine salt is oleylamine; and the trioctylphosphine precursor is trioctylphosphine sulfide, trioctylphosphine selenide, or trioctylphosphine telluride.

5. The method according to claim 4, characterized in that, The preparation of the metal carboxylate or metal oleylamine salt includes the following steps: reacting a metal oxide or metal acetate with a carboxylic acid to obtain a metal carboxylate; or reacting a metal acetate with oleylamine to obtain a metal oleylamine salt. The molar ratio of the metal oxide or metal acetate to the carboxylic acid is 1:2-3; the molar ratio of the metal acetate to oleylamine is 1:2-3; the solvent for the reaction is an organic solvent; the reaction conditions are: first react at 60-130℃ for 0.5-3h, then react at 100-300℃ for 0.5-3h, and finally react at 110-260℃ for 10min-3h.

6. The method according to claim 5, characterized in that, The metal oxide is selected from cadmium oxide and / or zinc oxide; the acetate is selected from zinc acetate or cadmium acetate.

7. The method according to claim 4, characterized in that, The preparation of the trioctylphosphine precursor includes the following steps: reacting oxalic element powder with trioctylphosphine to obtain the trioctylphosphine precursor; The molar ratio of the oxalic element powder to trioctylphosphine is 1:2-5; the solvent for the reaction is an organic solvent; the reaction conditions are: 10-300℃ for 10-50 min.

8. The method according to claim 1 or 2, characterized in that, The high-quality quantum dots are core-shell structured quantum dots and / or quantum dots with increased size and narrower distribution.

9. The method according to claim 8, characterized in that, The core-shell structured quantum dots are formed by mixing quantum dots of semiconductor material with a pre-nucleated sample of semiconductor material and reacting to form core-shell structured quantum dots.

10. The method according to claim 9, characterized in that, The method for preparing the core-shell structured quantum dots includes the following steps: mixing quantum dots of semiconductor material with a pre-nucleated sample of semiconductor material, and forming core-shell structured quantum dots after reaction.

11. The method according to claim 8, characterized in that, The quantum dots with increased size and narrower distribution are formed by reacting pre-nucleated samples of the same semiconductor material with quantum dots, resulting in quantum dots with increased size and narrower distribution.

12. The method according to claim 11, characterized in that, The method for preparing the quantum dots with increased size and narrower distribution includes the following steps: (1) At 20-60℃, the pre-nucleated sample of semiconductor material is dispersed in a solvent and reacted for 1-166 h to obtain quantum dots with controllable size; (2) Add the pre-nucleated sample of semiconductor material and methanol again and react for 1 to 166 hours. Repeat this process n times to obtain quantum dots with increased size and narrower distribution. Where n is selected from 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10; The semiconductor material is a binary semiconductor material or a ternary semiconductor material, and the semiconductor material is preferably ZnSe, ZnSeS, ZnTe or ZnS.

13. The method according to claim 12, characterized in that, In step (1), the solvent is selected from one or a mixture of two of cyclohexane and methanol, preferably a mixture of cyclohexane and methanol; The volume ratio of the pre-nucleated sample of the semiconductor material to cyclohexane and methanol is 1-5:200-800:1-10; Preferably, the volume ratio of the pre-nucleated sample of the semiconductor material to cyclohexane and methanol is 3:600:

2.

14. The method according to claim 12, characterized in that, In the preparation of pre-nucleated samples of binary semiconductor materials, the mass-volume ratio of selenium precursor, zinc precursor and activator is 1-3 g: 200-400 μL: 30-70 μL; the solvent for the reaction is an organic solvent; the reaction conditions are: under nitrogen atmosphere, at 80-250 °C for 20-80 min. In the preparation of the pre-nucleation sample of the ternary semiconductor material, the mass-volume ratio of selenium precursor, zinc precursor, sulfur powder and activator is 1-3 g: 200-400 μL: 0.001-0.01 g: 30-70 μL; the solvent for the reaction is an organic solvent; the reaction conditions are: under nitrogen atmosphere, at 80-250 °C for 20-80 min.

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