A kind of alloy quantum dot core and its synthesis method

Abstract

The present invention discloses an alloy quantum dot core and a synthesis method thereof, and relates to the technical field of quantum dot materials. The synthesis method of the alloy quantum dot core comprises reacting a mixed solution containing two cationic precursors with an anionic precursor at a crystal cluster generation temperature to obtain a first mixture; mixing the first mixture and a non-eutectic solvent and heating the mixture to a quantum dot generation temperature for reaction. The inventor creatively forms a crystal cluster first and then reacts to form quantum dots, so that the reaction rate can be better controlled, and the size of the quantum dots obtained is relatively uniform. The color purity, fluorescence quantum rate and stability of the quantum dots prepared by the synthesis method provided in the embodiment of the present invention are relatively ideal.

Description

Technical Field

[0001] The present invention relates to the technical field of quantum dot materials, and in particular to an alloy quantum dot core and a synthesis method thereof. Background Art

[0002] At present, the methods for synthesizing quantum dot materials are mainly divided into water phase and oil phase. The oil phase method for synthesizing quantum dots mainly uses two main steps: hot injection nucleation and continuous ion layer method to grow the shell. For different reaction systems, the oil phase synthesis path is different. For example, the conventional hot injection nucleation and continuous ion layer method can be used to grow the shell of group 2-6 quantum dots to obtain quantum dots with better quality.

[0003] However, the quantum dots obtained by conventional synthesis routes for group 3-5 quantum dots have poor color purity, low fluorescence quantum yield, and less than ideal stability, especially when other metal elements are doped based on group 3-5 quantum dots. Summary of the invention

[0004] The object of the present invention is to provide a method for synthesizing alloy quantum dot cores, wherein the quantum dots prepared by the method have good color purity, high fluorescence quantum rate and ideal stability.

[0005] Another object of the present invention is to provide an alloy quantum dot core having high size uniformity, and relatively ideal color purity, fluorescence quantum rate and stability.

[0006] The present invention solves the technical problem by adopting the following technical solutions.

[0007] The present invention provides a method for synthesizing an alloy quantum dot core, comprising reacting a mixed solution containing two cationic precursors with an anionic precursor at a crystal cluster formation temperature to obtain a first mixture; mixing the first mixture with a non-eutectic solvent and heating the mixture to a quantum dot formation temperature for reaction.

[0008] The present invention also provides an alloy quantum dot core, which is prepared by the above-mentioned synthesis method of the alloy quantum dot core.

[0009] The beneficial effect of the synthesis method of alloy quantum dot core provided by the embodiment of the present invention is that: the method first uses a mixed solution containing two cationic precursors to react with an anionic precursor to form a crystal cluster, and then mixes with a non-eutectic solvent and heats to the quantum dot generation temperature for reaction. The inventor creatively forms a crystal cluster first and then reacts to form quantum dots, so that the reaction rate can be better controlled, and the size of the obtained quantum dots is relatively uniform. The color purity, fluorescence quantum rate and stability of the quantum dots prepared by the synthesis method provided in the embodiment of the present invention are relatively ideal.

[0010] It should be added that the inventors found that the reason why the quality of quantum dots prepared by doping other metal elements in group 3-5 quantum dots is poor is mainly because the particularity of the P source and As source of group 3-5 quantum dots makes the reaction activity of anion and cation precursors in the process of preparing quantum dot cores vary greatly, resulting in poor size uniformity, many surface defects, and difficulty in control. The improved reaction route by the inventors can well avoid the occurrence of the above problems, mainly by reducing the reaction rate to effectively control the particle size. DETAILED DESCRIPTION

[0011] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0012] An alloy quantum dot core and a synthesis method thereof provided in an embodiment of the present invention are described in detail below.

[0013] The embodiment of the present invention provides a method for synthesizing alloy quantum dot cores, which forms alloy crystal clusters first and then reacts to generate quantum dots, so that the rate of quantum dot generation is significantly reduced and the controllability of the reaction is increased. Specifically, the method includes the following steps:

[0014] S1. Preparation of crystal clusters

[0015] A mixed solution containing two cationic precursors reacts with an anionic precursor at a cluster formation temperature to obtain a first mixture, the cluster formation temperature is 90-350°C, and the reaction time is 10-600s. The cluster formation temperature is selected according to different anionic and cationic precursors, and the selection of temperature for different reaction systems is quite different.

[0016] Specifically, according to different reaction systems, the cluster formation temperature can be divided into 90℃-110℃, 110℃-150℃, 150℃-200℃, 200℃-250℃, 250℃-300℃, 300℃-350℃; the reaction time can be divided into 10-60s, 60-120s, 120s-300s, 300s-600s. The cluster formation temperature of different reaction systems can refer to the prior art, and no further details are given here. Specifically, in the InZnP quantum dot system, the cluster formation temperature is 110℃-150℃, and the reaction time is 60-120s; in the CdZnSe quantum dot system, the cluster formation temperature is: 150℃-200℃, and the reaction time is 120-300s.

[0017] Furthermore, the preparation of the first mixture includes: after heating the mixed solution containing two cationic precursors to the crystal cluster formation temperature, the anion precursor is quickly injected into the mixed solution to react and form a crystal cluster, and then maintained at this temperature. Preferably, the mixed solution is first vacuumed, then heated to an intermediate temperature and vacuumed again, then an inert gas is introduced and heated to the crystal cluster formation temperature for exhaust, and the anion precursor is dissolved and then injected into the mixed solution for reaction. Through two vacuum treatments, an oxygen-free and water-free solution can be formed to prevent the occurrence of side reactions.

[0018] Specifically, the intermediate temperature may be 25°C-180°C, and may be divided into 25°C-80°C, 25°C-110°C, 25°C-150°C, and 25°C-180°C according to different reaction systems.

[0019] Further, the two cationic precursors are independently selected from any one of Zn(OA)2, Cd(OA)2, Pb(OA)2, In2(OA)3, Cu(OA)2, Ag2(OA)2, Hg(OA)2, Zn(MA)2, Cd(MA)2, Pb(MA)2, In2(MA)3, Cu(MA)2, Ag2(MA)2, Hg(MA)2, Zn(PA)2, Cd(PA)2, Pb(PA)2, In2(PA)3, Cu(PA)2, Ag2(PA)2, Hg(PA)2, Zn(LA)2, Cd(LA)2, Pb(LA)2, In2(LA)3, Cu(LA)2, Ag2(LA)2 and Hg(LA)2; preferably, the molar ratio of the two cationic precursors is 1:0.05-20. The anion precursor is selected from any one of S-ODE, S-TOP, S-OA, Se-TOP, S-OLA, S-TBP, Se-TBP, Te-ODE, Te-OA, Te-TOP, Te-TBP, (TMS)3S, (TMS)3P and (TMS)3As; preferably, the molar ratio of the total molar amount of the two cationic precursors to the anionic precursor is 1-10:1. The above cationic precursors and anionic precursors are all suitable for the reaction system in the embodiment of the present invention, and are all suitable for first preparing to form crystal clusters and then generating quantum dots. According to different reaction systems, the molar ratio of the total molar amount of the two cationic precursors to the anionic precursor is 1-2:1, 1-4:1, 1-6:1, 1-10:1.

[0020] It should be noted that the inventors have improved the quality of the prepared quantum dots by further controlling the selection and dosage of the two cationic precursors and the anionic precursors, thereby further improving the color purity, stability and other properties of the quantum dots.

[0021] Specifically, the first mixture contains ternary phase clusters and the above-mentioned anion and cation precursors, wherein the composition of the ternary phase clusters is the same as that of the ternary phase quantum dots. The ternary phase clusters are CdZnS, CdZnSe, CdZnTe, InZnP, AgZnS, PbZnS, PbZnSe, HgAgS, CuInS, etc., but not limited to one of them. The ternary phase cluster is an atomic aggregate between a single atom and a solid state formed by anion and cation precursors within a certain temperature range, and the atomic aggregate will participate in the epitaxial growth of quantum dot nanocrystals; the rate at which the atomic aggregate participates in epitaxial crystallization will be slower than the rate of separately utilizing anion and cation precursors (anion and cation precursors are separated as epitaxial raw materials).

[0022] S2. Preparation of quantum dots

[0023] The first mixture and the non-eutectic solvent are mixed and heated to the quantum dot generation temperature for reaction. The quantum dot generation temperature of different anion and cation precursors is different. Generally speaking, the quantum dot generation temperature is 110-350° C. and the reaction time is 3-10 minutes.

[0024] Specifically, according to different reaction systems, the quantum dot generation temperature can be divided into 110°C-150°C, 150°C-180°C, 180°C-210°C, 210°C-250°C, 250°C-300°C, 300°C-350°C. After the reaction is completed, the number of residual crystal clusters accounts for 0-5% of the number of quantum dots. According to different reaction systems, the ratio of the number of residual crystal clusters to the number of quantum dots can be divided into 0-1%, 1-3%, and 3-5%.

[0025] In a preferred embodiment, after the non-eutectic solvent is evacuated, the non-eutectic solvent is injected into the first mixture and the temperature is raised to the quantum dot generation temperature to obtain a second mixture, and then the second mixture is cooled to a suitable temperature. By evacuating to form an oxygen-free and water-free raw material, side reactions are avoided. The temperature of the second mixture after cooling is 80-180°C so that the reaction is no longer in progress. The temperature of the non-eutectic solvent is 25-180°C, which varies according to different reaction systems. According to different reaction systems, it can be divided into 25°C-80°C, 25°C-110°C, 25°C-150°C, and 25°C-180°C.

[0026] Furthermore, the non-eutectic solvent is selected from at least one of octadecene, paraffin oil and paraffin oil; preferably, the volume ratio of the non-eutectic solvent to the first mixture is 5-30: 1. The non-eutectic solvent refers to a conventional solvent for preparing quantum dots that does not dissolve the anion precursor and the cationic precursor at the same time.

[0027] S3. Separation of quantum dots

[0028] In some embodiments, the process further includes separating the quantum dots in the second mixture. The specific steps of separating the quantum dots can refer to the prior art.

[0029] In a preferred embodiment, the process of separating quantum dots includes: mixing the second mixture with an organic solvent, and then centrifuging with a non-polar solvent and a polar solvent, wherein the organic solvent is selected from at least one of trioctylphosphine, tributylphosphine, trioctylamine, oleylamine and oleic acid; the volume ratio of the second mixture to the organic solvent is 4-20:1, and the mixing time is 5-60 minutes. The use of an organic solvent can reduce the freezing point of the second mixture, and the use of an organic reagent to chemically coordinate with unreacted cationic precursors and incompletely reacted crystal clusters in the second mixture increases the solubility of the unreacted cationic precursors and incompletely reacted crystal clusters, thereby improving the yield and purity of quantum dots.

[0030] Furthermore, the non-polar solvent is selected from at least one of toluene, chloroform, n-hexane and n-heptane; the polar solvent is selected from at least one of ethanol, methanol, butanol and isopropanol; the volume ratio of the non-polar solvent to the second mixture is 1-5:10; the volume ratio of the polar solvent to the second mixture is 5-15:10. By further controlling the selection and dosage of the non-polar solvent and the polar solvent, the separation efficiency is significantly improved, and the yield of quantum dots is increased.

[0031] The embodiment of the present invention further provides an alloy quantum dot core, which is prepared by the above-mentioned synthesis method of the alloy quantum dot core, and can also form a quantum dot with a core layer and a shell layer structure by further growing a shell layer.

[0032] It should be noted that the core size of the alloy quantum dots prepared in the embodiments of the present invention is relatively uniform, and the color purity, fluorescence quantum rate and stability of the quantum dots prepared by the synthesis method provided in the embodiments of the present invention are relatively ideal.

[0033] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0034] Example 1

[0035] This embodiment provides a method for synthesizing alloy quantum dot cores, comprising the following steps:

[0036] (1) Indium oleate / In2(OA )3 Preparation of zinc oleate / Zn(OA)2: Take 1mmol InCl3, 0.3mmol Zn(Ac)2 and 3.6mmol oleic acid (OA) and add them to a 50mL three-necked flask. First, vacuum it at low temperature for 10min, then heat the mixed solution to 110℃ and vacuum it for 2h. After the vacuuming is completed, switch to normal pressure and pass nitrogen for protection. Heat the solution to 120℃ and exhaust it for 30min to keep it warm for use.

[0037] (2) Preparation of InZnP-containing crystal clusters: 0.3 mmol of (TMS)3P was uniformly dispersed in 1 mL of octadecene, and the p source was rapidly injected into the above (1) using a syringe and reacted for 2 minutes while maintaining the temperature.

[0038] (3) Preparation of alloy InZnP quantum dots: Take 10 mL of octadecene and add it to another 50 mL three-necked flask for low-temperature vacuum treatment. Then quickly inject all of the 10 mL of octadecene into the mixed solution containing InZnP clusters and short-wave InZnP quantum dots and quickly heat it to 280 °C for 5 min to obtain long-wave InZnP quantum dots. Then cool the temperature to 160 °C, add 2 mL of trioctylphosphine reagent, stir for 20 min, and stop heating to allow the solution to cool to room temperature.

[0039] (4) Cleaning of InZnP quantum dots: Add 3 mL of toluene reagent and 15 mL of ethanol reagent to the above (3) to make the solution into a turbid liquid, and then centrifuge the mixed solution to obtain the desired InZnP quantum dots.

[0040] Example 2

[0041] This embodiment provides a method for synthesizing alloy quantum dot cores, comprising the following steps:

[0042] (1) Preparation of Cadmium Oleate / Cd(OA)2 and Zinc Oleate / Zn(OA)2: 1 mmol of CdO, 3 mmol of Zn(OA)2 and 8 mmol of oleic acid (OA) were added to a 50 mL three-necked flask. The mixture was first vacuumed at low temperature for 10 min. The mixture was then heated to 110°C and vacuumed for 2 h. After the vacuuming was completed, the mixture was switched to normal pressure and nitrogen was passed through for protection. The solution was heated to 180°C and vented for 30 min to keep warm for later use.

[0043] (2) Preparation of CdZnSe clusters: 0.3 mmol of Se-TOP was uniformly dispersed in 1 mL of octadecene, and the selenium source was rapidly injected into the above (1) using a syringe and reacted for 5 minutes while maintaining the temperature.

[0044] (3) Preparation of alloy CdZnSe quantum dots: Take 10 mL of octadecene and add it to another 50 mL three-necked flask for low-temperature vacuum treatment. Then, all of the 10 mL of octadecene is quickly injected into the mixed solution containing CdZnSe clusters and short-wave CdZnSe quantum dots and the temperature is quickly raised to 300°C for reaction for 5 min to obtain long-wave CdZnSe quantum dots. Then, the temperature is cooled to 160°C, 2 mL of trioctylphosphine reagent is added, and stirring is carried out for 20 min. After that, heating is stopped and the solution is cooled to room temperature.

[0045] (4) Cleaning of CdZnSe quantum dots: 3 mL of toluene reagent and 15 mL of ethanol reagent were added to the above (3) to make the solution into a turbid liquid, and then the mixed solution was centrifuged to obtain the desired CdZnSe quantum dots.

[0046] Comparative Example 1

[0047] This comparative example provides a method for synthesizing alloy quantum dot cores, using the same anion and cation precursor raw materials as in Example 1, but using traditional steps to directly form quantum dots, the specific steps are as follows:

[0048] CdZnSe quantum dots were synthesized by high-temperature hot injection method; CdO and ZnO were used as raw materials, wherein ZnO was in excess; 0.5mmolCdO and 5mmolZnO were added into a three-necked flask, and then 4mloleic acid and 6mloctadecene were added, and the temperature was raised to 130°C within 20min, and the system was vacuumed during the heating process, and then the vacuum was continued at 130°C for 30min, and then heated to 300°C in an inert gas environment, 1mmolSe-ODE dispersion was injected, and the reaction was terminated after keeping the temperature for 10min to obtain CdZnSe quantum dots.

[0049] Comparative Example 2

[0050] This comparative example provides a method for synthesizing alloy quantum dot cores, which is different from Example 1 only in that in step (1), the mixed solution is heated to 200° C. and evacuated for 2 h.

[0051] Comparative Example 3

[0052] This comparative example provides a method for synthesizing alloy quantum dot cores, which is different from Example 1 only in that in step (1), the mixed solution is heated to 90° C. and evacuated for 2 h.

[0053] The synthesis method in Example 1 was tested, and the fluorescence wavelength, half-peak width and quantum dot yield of the alloy quantum dots were obtained by testing the above experimental examples and comparative examples. The results are shown in Table 1.

[0054] Table 1 Crystal cluster and quantum dot test results

[0055]

[0056]

[0057] It can be seen from Table 1: As can be seen from the above table, the present invention provides a method for preparing alloy quantum dots. Compared with the traditional preparation method, the half-peak width and quantum dot yield are improved. In addition, the change in reaction temperature in step 1 has a greater impact on the size of crystal clusters and alloy quantum dots. A higher reaction temperature will lead to over-reaction and the proportion of crystal clusters in the crystal cluster-quantum dot system is too low, while a lower reaction temperature will lead to incomplete reaction and the proportion of crystal clusters in the crystal cluster-quantum dot system is too high. Too high or too low a proportion of crystal clusters will destroy the uniformity of the quantum dot size and the quantum dot yield will also be reduced.

[0058] In summary, the method for synthesizing alloy quantum dot cores provided by the present invention is to first use a mixed solution containing two cationic precursors to react with an anionic precursor to form a crystal cluster, and then mix it with a non-eutectic solvent and heat it to the quantum dot generation temperature for reaction. The inventor creatively forms a crystal cluster first and then reacts to form quantum dots, so that the reaction rate can be better controlled, and the size of the quantum dots obtained is relatively uniform. The color purity, fluorescence quantum rate and stability of the quantum dots prepared by the synthesis method provided in the embodiment of the present invention are relatively ideal.

[0059] The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for synthesizing alloy quantum dot cores, characterized in that: The method comprises reacting a mixed solution containing two cationic precursors with an anionic precursor at a crystal cluster formation temperature to obtain a first mixture; Mixing the first mixture and the non-eutectic solvent and heating them to a quantum dot generation temperature for reaction; The preparation of the first mixture includes: firstly subjecting a mixed solution containing two cationic precursors to a vacuum treatment, then heating it to an intermediate temperature and subjecting it to a vacuum treatment again, then introducing an inert gas and heating it to the crystal cluster formation temperature for exhaust, dissolving the anionic precursor and then injecting it into the mixed solution for reaction for 10-600 seconds; After the non-eutectic solvent is evacuated, the non-eutectic solvent is injected into the first mixture and the temperature is raised to the quantum dot generation temperature to obtain a second mixture, and then the second mixture is cooled; The crystal cluster formation temperature is 90-350°C and the reaction time is 10-600s; The two cationic precursors are independently selected from any one of Zn(OA)2, Cd(OA)2, Pb(OA)2, In2(OA)3, Cu(OA)2, Ag2(OA)2, Hg(OA)2, Zn(MA)2, Cd(MA)2, Pb(MA)2, In2(MA)3, Cu(MA)2, Ag2(MA)2, Hg(MA)2, Zn(PA)2, Cd(PA)2, Pb(PA)2, In2(PA)3, Cu(PA)2, Ag2(PA)2, Hg(PA)2, Zn(LA)2, Cd(LA)2, Pb(LA)2, In2(LA)3, Cu(LA)2, Ag2(LA)2 and Hg(LA)2; The anion precursor is selected from any one of S-ODE, S-TOP, S-OA, Se-TOP, S-OLA, S-TBP, Se-TBP, Te-ODE, Te-OA, Te-TOP, Te-TBP, (TMS)3S, (TMS)3P and (TMS)3As; The quantum dot generation temperature is 110-350° C., and the reaction time is 3-10 minutes; the temperature of the second mixture after cooling is 80-180° C.

2. The method for synthesizing alloy quantum dot cores according to claim 1, characterized in that: The molar ratio of the two cationic precursors is 1:0.05-20.

3. The method for synthesizing alloy quantum dot cores according to claim 1, characterized in that: The molar ratio of the total molar amount of the two cationic precursors to the anionic precursor is 1-10:

1.

4. The method for synthesizing alloy quantum dot cores according to claim 1, characterized in that: After the reaction is completed, the number of residual clusters accounts for 0-5% of the number of quantum dots.

5. The method for synthesizing alloy quantum dot cores according to claim 1, characterized in that: The temperature of the non-eutectic solvent during vacuum evacuation is 25-180°C.

6. The method for synthesizing alloy quantum dot cores according to claim 1, characterized in that: The non-eutectic solvent is selected from at least one of octadecene, paraffin oil and paraffin oil.

7. The method for synthesizing alloy quantum dot cores according to claim 6, characterized in that: The volume ratio of the non-eutectic solvent to the first mixture is 5-30:

1.

8. The method for synthesizing alloy quantum dot cores according to claim 4, characterized in that: Also included is separating the quantum dots in the second mixture.

9. The method for synthesizing alloy quantum dot cores according to claim 8, characterized in that: The process of separating quantum dots includes: mixing the second mixture with an organic solvent, and then centrifuging and separating the mixture using a non-polar solvent and a polar solvent, wherein the organic solvent is selected from at least one of trioctylphosphine, tributylphosphine, trioctylamine, oleylamine and oleic acid.

10. The method for synthesizing alloy quantum dot cores according to claim 9, characterized in that: The volume ratio of the second mixture to the organic solvent is 4-20:1, and the mixing time is 5-60 minutes.

11. The method for synthesizing alloy quantum dot cores according to claim 9, characterized in that: The non-polar solvent is selected from at least one of toluene, chloroform, n-hexane and n-heptane.

12. The method for synthesizing alloy quantum dot cores according to claim 11, characterized in that: The polar solvent is selected from at least one of ethanol, methanol, butanol and isopropanol.

13. The method for synthesizing alloy quantum dot cores according to claim 12, characterized in that: The volume ratio of the non-polar solvent to the second mixture is 1-5:

10.

14. The method for synthesizing alloy quantum dot cores according to claim 12, characterized in that: The volume ratio of the polar solvent to the second mixture is 5-15:

10.

15. An alloy quantum dot core, characterized in that: The alloy quantum dot core is prepared by the synthesis method of the alloy quantum dot core described in any one of claims 1 to 14.

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