Preparation method of quantum dot and quantum dot

Abstract

The invention relates to a preparation method of a quantum dot and the quantum dot. According to the preparation method provided by the invention, a quantum dot core is firstly formed by adopting a positive ion-rich precursor formula, and then the quantum dots with expected large particle sizes can be controllably obtained through multiple times of cyclic growth. The preparation method disclosed by the invention has the advantages of multiple adjustable parameters in the technological process, strong controllability, high consistency of the obtained product, simplicity in operation, lower cost and easiness in practical application.

Description

Technical Field

[0001] The invention belongs to the field of materials, and in particular relates to a quantum dot preparation method and quantum dots. Background Art

[0002] Quantum dots (QDs) are nano-sized semiconductor crystals with unique optical and electronic properties. Due to their small size and significant quantum confinement effect, quantum dots have excellent luminescence properties such as color, brightness and stability. Quantum dots have a wide range of applications, including bioimaging, medical diagnosis, photodetection, light-emitting diodes (LEDs) and solar cells.

[0003] At present, quantum dots are usually prepared from II-VI, IV-VI or III-V semiconductor materials. Common quantum dots include II-VI semiconductor quantum dots such as cadmium sulfide (CdS), cadmium selenide (CdSe), cadmium telluride (CdTe) and zinc sulfide (ZnS); IV-VI semiconductor quantum dots such as lead sulfide (PbS) and lead selenide (PbSe); III-V semiconductor quantum dots such as indium phosphide (InP) and indium arsenide (InAs). In addition, quantum dot materials based on perovskite structure and carbon quantum dot materials have also been developed.

[0004] The performance of quantum dots is closely related to their size, especially their radius. The radius of a quantum dot determines its band structure and emission wavelength. Generally, the smaller the radius, the shorter the emission wavelength. Currently, there is an increasing demand for quantum dots with long emission wavelengths, but there are still challenges in the controllable synthesis of quantum dots and the synthesis of large-size quantum dots.

[0005] At present, conventional synthesis methods of quantum dots include hot injection method, one-pot method, and the microreactor method that has emerged in recent years. The radius of quantum dots obtained by these synthesis methods is generally 2 to 4.5 nm, and the absorption peak range is 500 to 600 nm. For example, Patent Document 1 discloses an oil-soluble zinc sulfide quantum dot and a preparation method thereof, and the oil-soluble zinc sulfide quantum dots provided therein have a particle size of less than 2 nm and an absorption peak range of 250 to 280 nm. Patent Document 2 discloses a dual-particle size quantum dot-sensitized solar cell, in which the quantum dot sensitizer includes quantum dots of the same chemical composition with two different particle sizes. For example, in Example 1, two particle sizes of cadmium sulfide quantum dots with co-sensitized solar cells with particle sizes of 5.2 nm and 6.8 nm were obtained. However, the method disclosed in Patent Document 2 is limited to porous membranes, which has great restrictions on its use and cannot be widely used.

[0006] References:

[0007] Patent document 1: CN108485648A

[0008] Patent document 2: CN102629520A Summary of the invention

[0009] Problem that the invention aims to solve

[0010] In view of the above situation, in order to broaden the absorption range of quantum dots, it is necessary to provide a preparation method for quantum dots with controllable particle size, narrow particle size distribution and large particle size.

[0011] Solutions for solving problems

[0012] To solve the above problems, the present invention adopts a cation-rich precursor formula to form quantum dot cores under appropriate reaction conditions, and then grows through multiple cycles, so that quantum dots with a desired large particle size can be obtained in a controllable manner. Moreover, in the present invention, the particle size and absorption peak of the quantum dots can be adjusted by adding different reactants at different reaction stages. Therefore, the particle size of the quantum dots obtained by the preparation method of the present invention is controllable, large-particle quantum dots can be obtained, the product consistency is high, and there are many adjustable parameters and strong controllability during the process.

[0013] [1] The present invention provides a method for preparing quantum dots, characterized in that the preparation method comprises the following steps:

[0014] The step of preparing a cationic precursor solution and an anionic precursor solution;

[0015] Quantum dot core synthesis step: heating a mixed precursor solution containing a cationic precursor solution and an anionic precursor solution to obtain a quantum dot core solution;

[0016] The first growth step: adding an anion precursor solution to the quantum dot core solution and heating to react; repeating the first growth step until the growth rate of the quantum dot particle size reaches a plateau to obtain a first product solution;

[0017] The second growth step: adding a cationic precursor solution and an anionic precursor solution to the first product solution and heating to react, wherein the ratio of the added cationic precursor solution to the anionic precursor solution is a preset first ratio; repeating the second growth step until a second product solution is obtained, and the second product solution is a quantum dot solution that can obtain a set particle size.

[0018] [2] The preparation method according to [1] above, wherein, in the quantum dot nucleus synthesis step, the ratio X0 of cations and anions in the mixed precursor solution is 70:1 to 3:1 in terms of molar ratio.

[0019] [3] The preparation method according to [1] or [2] above, wherein the first ratio is 10:5 to 10:7 in terms of molar ratio; and / or, when the growth rate of the quantum dot particle size reaches a plateau, the ratio of cations to anions in the first product solution is 10:5 to 10:7 in terms of molar ratio.

[0020] [4]. The preparation method according to any one of items [1] to [3] above, wherein the first ratio is the ratio of cations to anions in the first product solution when the growth rate of the quantum dot particle size reaches a plateau; and / or, repeating the first growth step until the growth rate of the quantum dot particle size reaches a plateau to obtain the first product solution, comprises: repeating the first growth step until the growth rate of the quantum dot particle size reaches a plateau, and purifying the solution that reaches the plateau to obtain the first product solution.

[0021] [5]. The preparation method according to any one of [1] to [4] above, wherein the first growth step is repeated 2 to 6 times; and / or the total amount of the anion precursor added in the first growth step is 0.05 to 0.2 times the amount of the cationic precursor; and / or, in the first growth step, the reaction temperature is 200 to 290°C and the reaction time is 10 seconds to 60 seconds.

[0022] [6] The preparation method according to any one of [1] to [5] above, wherein the second growth step is repeated 2 to 8 times to controllably obtain quantum dots with different particle sizes; and / or, in the second growth step, the reaction temperature is 200 to 290°C and the reaction time is 10 seconds to 60 seconds.

[0023] [7]. The preparation method according to any one of [1] to [6] above, wherein the particle size of the quantum dots is 2 nm to 9 nm, preferably 2.2 nm to 8.6 nm.

[0024] [8]. A preparation method according to any one of [1] to [7] above, wherein the quantum dots are single-core quantum dots, and the quantum dots are quantum dots of Group II-VI compounds selected from CdS, CdSe, CdTe, ZnS, ZnSe, PbS, and PbSe, and quantum dots of Group III-V compounds selected from InP, GaP, GaN, and AlN.

[0025] [9]. The preparation method according to any one of items [1] to [8] above, wherein the preparation method further comprises a quantum dot purification step: mixing and separating the second product solution obtained in the second growth step with an alcohol solvent, and redissolving the solid precipitate with a good solvent for quantum dots, thereby obtaining purified quantum dots.

[0026]

[10] . The present invention also provides a quantum dot, wherein the quantum dot is obtained according to the preparation method described in any one of [1] to [9] above, the quantum dot is a single-core quantum dot, and the particle size of the quantum dot is 2nm to 9nm.

[0027] Effects of the Invention

[0028] The method for preparing quantum dots of the present invention has the following beneficial effects:

[0029] The preparation method of the present invention can controllably obtain large-size quantum dots with narrow particle size distribution, thereby increasing the absorption peak range of the quantum dots;

[0030] The preparation method of the present invention has many adjustable parameters and strong controllability during the process, and the obtained product has high consistency;

[0031] The preparation method of the invention is simple to operate, low in cost and easy to apply in practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The flowchart of the method for preparing quantum dots of the present invention is schematically shown.

[0033] Figure 2 The figure schematically shows the microfluidic synthesis device used for preparing quantum dots in the present invention. DETAILED DESCRIPTION

[0034] The following is a detailed description of the present invention. The following description of the technical features is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

[0035] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0036] In the present specification, the use of “substantially” or “essentially” means that the standard deviation from a theoretical model or theoretical data is within a range of 5%, preferably 3%, and more preferably 1%.

[0037] In this specification, unless otherwise specified, "%" means mass percentage.

[0038] In this specification, "room temperature" is used to refer to a temperature range of 25°C±5°C.

[0039] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0040] In this specification, the "boiling point" refers to the boiling point under normal pressure.

[0041] In this specification, "quantum dot", "quantum dot" and "quantum dot crystal" have equivalent physical and chemical meanings.

[0042] In the present specification, "optional" or "optionally" means that the event or situation described below may or may not occur, and the description includes cases where the event occurs and cases where it does not occur.

[0043] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0044] like Figure 1 As shown, the quantum dot synthesis method of the present invention includes the following steps: a step of preparing a precursor solution (i.e., a step of preparing a cationic precursor solution and an anionic precursor solution); a quantum dot nucleus synthesis step; a first growth step; a second growth step; and an optional purification step.

[0045] The preparation method of the present invention can be used to synthesize quantum dots of substantially all II-VI group compounds and III-V group compounds.

[0046] The quantum dots in the present invention are single-core quantum dots, which are core-structured quantum dots without shells.

[0047] In some specific embodiments of the present invention, examples of quantum dots may include: quantum dots of II-VI group compounds, such as quantum dots of CdS, CdSe, CdTe, ZnS, ZnSe, PbS, and PbSe; quantum dots of III-V group compounds, such as quantum dots of InP, GaP, GaN, and AlN; and the like.

[0048] Preparation steps of quantum dot precursor solution

[0049] The preparation method of the quantum dot precursor solution is not particularly limited, and can be prepared by methods known in the art. The following is an example of synthesizing quantum dots of II-VI group compounds.

[0050] (1) Preparation of cationic precursor solution

[0051] In some specific embodiments of the present invention, oxides, inorganic salts or organic acid salts of Group II metals are mixed with solvents and ligands, dissolved under heating and oxygen-free atmosphere, and sealed and stored in oxygen-free atmosphere for later use after cooling.

[0052] The inorganic salt may be, for example, nitrates and chlorides of Group II metals, and the organic acid salt may be, for example, oleates of Group II metals.

[0053] The solvent here can be a commonly used solvent in the art, and examples can include octadecene, trioctylamine, etc. Examples of ligands can include one or more of oleic acid, palmitic acid, stearic acid, and adipic acid. The heating temperature can be 200 to 350° C. The above-mentioned oxygen-free atmosphere can be a nitrogen atmosphere or an argon atmosphere, etc.

[0054] The ratio of Group II metal to ligand may be a ratio commonly used in the art, and the ligand is usually required to be in excess. For example, the molar ratio of Group II metal to ligand may be 1:5 to 1:15, preferably 1:8 to 1:12.

[0055] (2) Preparation of anion precursor solution

[0056] In some specific embodiments of the present invention, powder of the Group VI element is mixed with a solvent and a ligand, dissolved under heating or ultrasound in an oxygen-free atmosphere, and then sealed and stored in an oxygen-free atmosphere for later use.

[0057] The solvent here can be a commonly used solvent in the art, preferably the same solvent as in the "preparation of a cationic precursor solution". Examples of ligands can include one or more of tri-n-octylphosphine, tri-n-octylphosphine oxide, tributylphosphine, etc. The heating temperature can be 100 to 150° C., preferably 120 to 150° C. The above-mentioned oxygen-free atmosphere can be a nitrogen atmosphere or an argon atmosphere, etc.

[0058] The ratio of the Group VI element to the ligand may be a ratio commonly used in the art, for example, a molar ratio of 1:2 to 1:5, preferably 1:2 to 1:4.

[0059] Quantum dot nucleosynthesis steps

[0060] The quantum dot nucleus synthesis step of the present invention and the subsequent first growth step and second growth step can be carried out in a microfluidic synthesis device. Figure 2 As shown, the microfluidic synthesis device used in the present invention includes: a microchannel or microfluidic reactor pipeline for performing reactions; an injection port connected to one end of the pipeline; and a cooler connected to the other end of the pipeline.

[0061] Regarding the material of the microfluidic reactor pipeline, considering the affinity to the inner wall of the pipeline, the pipeline can be made of polytetrafluoroethylene (PTFE), glass or ceramic.

[0062] In the present invention, there is no particular limitation on the length, outer diameter and inner diameter of the microfluidic reactor pipeline, and they can be adjusted as needed. For example, the length of the pipeline can be 1m to 10m, preferably 3m to 8m, the outer diameter can be 1 / 4 inch to 1 / 32 inch, preferably 1 / 8 inch to 1 / 16 inch, and the inner diameter can be 0.2mm to 3mm, preferably 0.5mm to 1mm.

[0063] In the microfluidic reactor pipeline, a heating device is provided ( Figure 2 In some specific embodiments of the present invention, for example, the microfluidic reactor pipeline portion can be placed in an oil bath.

[0064] like Figure 2 As shown, a cooler is connected to the other end of the microfluidic reactor pipeline to cool the reaction product and then collect it in Figure 2 in the container shown on the right.

[0065] In addition, in the preparation method of the present invention, ultraviolet-visible absorption spectroscopy is used for monitoring in the quantum dot nucleus synthesis step and the subsequent first growth step and second growth step to confirm whether the target product is obtained.

[0066] In the quantum dot core synthesis step, a cation-rich precursor formula is used to synthesize quantum dot cores under appropriate reaction conditions. Specifically, a cationic precursor solution is mixed with an anionic precursor solution to obtain a mixed precursor solution, and the mixed precursor solution is injected into a microfluidic synthesis device and heated to perform a nuclear reaction. The reaction is monitored using ultraviolet-visible spectroscopy, and after the spectral peak position is stabilized, the reaction product is collected to obtain a quantum dot core solution.

[0067] In some specific embodiments, the molar ratio of cations to anions in the mixed precursor solution is greater than 1. Optionally, the molar ratio X0 of cations to anions in the mixed precursor solution is 70:1 to 3:1, for example, 60:1, 50:1, 40:1, 30:1, 20:1, 15:1, 10:1, 8:1, 5:1, 4:1, etc.

[0068] In the quantum dot synthesis step, the heating temperature may be 200-290° C., for example, 210° C., 220° C., 230° C., 240° C., 250° C., 260° C., 270° C., 280° C., etc. The holding time may be 10-60 s, for example, 15 s, 20 s, 30 s, 40 s, 50 s, etc.

[0069] The flow rate of injecting the cationic precursor solution and the anionic precursor solution into the microfluidic synthesis device can be 2000μL / min to 6000μL / min, for example, 2500μL / min, 3000μL / min, 3500μL / min, 4000μL / min, 4500μL / min, 5000μL / min, 5500μL / min, etc.

[0070] First growth step

[0071] In the first growth step, an anion precursor solution is added to the synthesized quantum dot core solution, and then the mixed solution is injected into a microfluidic synthesis device and heated to react. The first growth step is repeated until the growth rate of the quantum dot particle size reaches a plateau, and a first product solution is obtained. The reaction is monitored using ultraviolet-visible spectroscopy, and the reaction product is collected after the spectral peak position stabilizes.

[0072] The "plateau phase" mentioned in this specification means that even if the anion precursor solution is repeatedly added, the particle size of the quantum dots no longer increases further as the reaction proceeds.

[0073] In some specific embodiments, in the first growth step, when the growth rate of the quantum dot particle size reaches a plateau, the ratio X1 of cations to anions in the first product solution is 10:5 to 10:7 in terms of molar ratio.

[0074] The addition of the anion precursor solution can be repeated multiple times until the desired ratio of cations to anions X1 is reached. The number of repetitions can be 2 to 6 times. After each addition of the anion precursor solution and the reaction, the reaction product can be collected, so that the desired product can be obtained in a controllable manner. The total amount of the anion precursor added can be 0.05 to 0.2 times the cationic precursor added in the quantum dot core synthesis step.

[0075] The heating temperature in the first growth step is 200-290° C., for example, 210° C., 220° C., 230° C., 240° C., 250° C., 260° C., 270° C., 280° C., etc. The holding time can be 10-60 s, for example, 15 s, 20 s, 30 s, 40 s, 50 s, etc.

[0076] The flow rate of injecting the mixed solution after adding the anion precursor solution into the microfluidic synthesis device can be 6000μL / min to 9000μL / min, for example, it can be 6000μL / min, 6500μL / min, 7000μL / min, 7500μL / min, 8000μL / min, 8500μL / min, etc.

[0077] Optionally, repeating the first growth step until the growth rate of the quantum dot particle size reaches a plateau to obtain a first product solution includes: repeating the first growth step until the growth rate of the quantum dot particle size reaches a plateau, and purifying the solution that reaches the plateau to obtain the first product solution. That is, the second growth step is performed after purifying the quantum dot solution that reaches the plateau in the first growth. This can make the particle size grow more uniformly.

[0078] Second growth step

[0079] In the second growth step, a cationic precursor solution and an anionic precursor solution are added to the first product solution, and the mixed solution is injected into a microfluidic synthesis device for heating to react, wherein the ratio of the added cationic precursor solution to the anionic precursor solution is a preset first ratio. The second growth step is repeated until a second product solution is obtained. The second product solution is a quantum dot solution that can obtain a set particle size. The reaction is monitored using ultraviolet-visible spectroscopy, and the reaction product is collected after the spectral peak position is stabilized.

[0080] The first ratio is 10:5 to 10:7 in terms of molar ratio. Preferably, the first ratio is the ratio of cations to anions in the first product solution when the growth rate of the quantum dot particle size reaches a plateau.

[0081] In the second growth step, the cationic precursor solution and the anionic precursor solution are repeatedly added, so that quantum dots with different particle sizes can be obtained in a controllable manner. The number of repetitions is 2 to 8 times. After each addition of the cationic precursor solution and the anionic precursor solution and the reaction, the product can be collected, so that the product with the desired particle size can be obtained in a controllable manner.

[0082] The heating temperature in the second growth step may be 200-290° C., for example, 210° C., 220° C., 230° C., 240° C., 250° C., 260° C., 270° C., 280° C., etc. The holding time may be 10-60 s, for example, 15 s, 20 s, 30 s, 40 s, 50 s, etc.

[0083] The heating temperatures in the quantum dot nucleosynthesis step, the first step, and the second step can be the same or different. In addition, in each of the above steps, the particle size and absorption wavelength of the quantum dots can be adjusted by adjusting the reaction temperature and the insulation time. Generally, the higher the temperature, the larger the particle size, and the longer the insulation time, the larger the particle size.

[0084] The flow rate of injecting the mixed solution after adding the anion precursor solution and the anion precursor solution into the microfluidic synthesis device can be 6000μL / min~9000μL / min, for example, it can be 6000μL / min, 6500μL / min, 7000μL / min, 7500μL / min, 8000μL / min, 8500μL / min, etc.

[0085] Purification steps

[0086] The quantum dot preparation method of the present invention may optionally include a quantum dot purification step.

[0087] If necessary, the quantum dot solution obtained in the second growth step can be mixed with an alcohol solvent and separated, and the solid precipitate can be redissolved using a good solvent for quantum dots to obtain purified quantum dots.

[0088] The alcohol solvent may be, for example, methanol, ethanol, propanol, etc. The good solvent for quantum dots may be, for example, a hydrocarbon solvent, for example, carbon tetrachloride, chloroform, n-hexane, cyclohexane, toluene, etc.

[0089] The separation can be performed by centrifugation, adsorption or filtration.

[0090] The above method of the present invention can controllably obtain quantum dots of different particle sizes and large particle sizes, thereby expanding the absorption peak range of the quantum dots. Specifically, the particle size of the quantum dots of the present invention can be 2nm to 9nm, preferably 2.2nm to 8.6nm, for example, 2.5nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, etc.

[0091] The present invention further provides a quantum dot, which is obtained by the above-mentioned preparation method, is a single-core quantum dot, and has a particle size of 2nm to 9nm.

[0092] Example

[0093] The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, 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 obtained commercially.

[0094] Example 1 (Synthesis of Ultra-Large Particle Size CdSe Material)

[0095] (1) Preparation of Cd precursor

[0096] Weigh 6 g of cadmium oxide powder and add it to the reactor, and measure 120 mL of octadecene and 120 mL of oleic acid and add them to the reactor in sequence; build a reaction device on the heating jacket with the reactor loaded with drugs, condenser and adapter in order from bottom to top; adjust the stirring speed of the agitator to 200 rpm; use nitrogen to ventilate at room temperature; set the target temperature to 200 °C and start heating; after the temperature rises to 200 °C, keep warm for 10 minutes; remove the heating jacket and cool it down naturally; when the temperature drops to 50 °C, transfer the liquid in the reactor to a clean and dry sample bottle, fill it with nitrogen and seal it, label it as Cd_pre, and set it aside.

[0097] (2) Se precursor preparation

[0098] Weigh 5 g of Se powder and add it to a sample bottle, measure 120 mL of octadecene and add it to the sample bottle, measure 120 mL of tri-n-octylphosphine in a glove box and add it to the sample bottle, and seal it; put the above sample bottle into an ultrasonic machine for ultrasonication; when the solid in the sample bottle is completely dissolved and a colorless and transparent liquid appears, stop ultrasonication, label it as Se_pre, and set it aside.

[0099] (3) Quantum dot nucleosynthesis

[0100] Take 30mL Cd_pre and 3mL Se_pre and add them into the sample bottle and record them as pre_N0; use Figure 2 The temperature of the microfluidic synthesis device shown is set to 230°C; pre_N0 is pumped into the heater at a flow rate of 4000 μL / min; after the spectral peak position is stabilized, the reaction product is collected and recorded as N0.

[0101] (4) First growth stage

[0102] Add 1.9mL Se_pre to N0, recorded as pre_N1; pump pre_N1 into the microfluidic synthesis device at a flow rate of 8000μL / min; after the spectral peak is stable, collect the reaction product, recorded as N1. Repeat the above steps 5 times, and the reaction products are recorded as N2, N3, N4, N5, and N6 in sequence. Until the ratio of anions to cations is 6:3. The temperature of the first growth stage is 250℃ and the time is 45s.

[0103] (5) Second growth stage

[0104] Add 6mL Cd_pre and 3mL Se_pre to N6, recorded as pre_N7; pump pre_N1 into the microfluidic synthesis device at a flow rate of 8000μL / min; collect the reaction product after the spectral peak is stable, recorded as N7; repeat the above steps 5 times, and the obtained reaction products are recorded as N8, N9, N10, N11, and N12 in sequence, among which the N12 product is the CdSe quantum dots with an absorption peak at 655nm. The particle size is 8.21nm. The temperature of the second growth stage is 250℃ and the time is 45s.

[0105] (5) Purification

[0106] About 3 times the volume of ethanol was added to the quantum dot solution obtained above, and after being mixed evenly, the solution was placed in a centrifuge and centrifuged at 5000 rpm for 3 min. The supernatant was discarded, and the solid precipitate was redissolved with carbon tetrachloride to obtain purified quantum dots.

[0107] Comparative Example 1

[0108] (1) Preparation of Cd precursor

[0109] Weigh 6g of cadmium oxide (cadmium oleate, cadmium chloride, etc.) powder and add it to the reaction bottle, measure 120mL of octadecene and 120mL of oleic acid (octadecanoic acid, oleylamine, etc.) and add them to the reactor in sequence; build a reaction device on the heating jacket with the reactor, condenser and adapter loaded with drugs in order from bottom to top; adjust the stirring speed of the agitator to 200rpm; ventilate with nitrogen at room temperature; set the temperature to 200℃ and start heating; after the temperature rises to 200℃, keep warm for 10min; remove the heating jacket and cool it down naturally; when the temperature drops to 50℃, transfer the liquid in the reactor to a clean and dry sample bottle, fill it with nitrogen and seal it, label it as Cd_pre, and set it aside.

[0110] (2) Se precursor preparation

[0111] Weigh 5 g of Se powder and add it to a sample bottle, measure 120 mL of octadecene and add it to the sample bottle, measure 120 mL of tri-n-octylphosphine and add it to the sample bottle, and seal it; put the above sample bottle into an ultrasonic machine for ultrasonication; when the solid in the sample bottle is completely dissolved and a colorless and transparent liquid appears, stop ultrasonication, label it as Se_pre, and set it aside.

[0112] (3) Quantum dot nucleosynthesis

[0113] Take 30mL Cd_pre and 15mL Se_pre and add them into a sample bottle, record it as pre_N0; use a microfluidic synthesis device and set the temperature to 230℃; pump pre_N0 into the heater at a flow rate of 4000μL / min; after the spectral peak position is stable, collect the reaction product, record it as N0.

[0114] (4) Quantum dot regrowth stage

[0115] Take 30mL Cd_pre and 15mL Se_pre and add them to the sample bottle as pre_R0; use a microfluidic synthesis device (including two liquid inlets, responsible for the liquid inlet of N0 and pre_R0 respectively), set the temperature to 230℃; adjust the liquid inlet speed of N0 and pre_R0 to 2000μL / min and 2000μL / min respectively; after the spectral peak position is stable, collect the reaction product, and obtain CdSe material with a particle size of 5.3nm. The absorption peak position is at 615nm.

[0116] Example 2 (Synthesis of ZnS material with extremely large particle size)

[0117] Except that cadmium oxide was replaced by zinc oxide and selenium powder was replaced by sulfur powder, a ZnS material with a very large particle size was prepared in the same manner as in Example 1. The particle size of the obtained ZnS material was 2.2 nm.

[0118] Comparative Example 2

[0119] Except that cadmium oxide was replaced by zinc oxide and selenium powder was replaced by sulfur powder, a ZnS material was prepared in the same manner as in Comparative Example 1. The particle size of the obtained ZnS material was 1.5 nm.

[0120] By comparing Example 1 with Comparative Example 1 and Example 2 with Comparative Example 2, it can be seen that quantum dots with large particle sizes can be obtained by the method of the present invention, and the size of the quantum dots can be adjusted according to actual needs.

[0121] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing quantum dots, characterized in that: The preparation method comprises the following steps: The step of preparing a cationic precursor solution and an anionic precursor solution; Quantum dot core synthesis step: heating a mixed precursor solution containing a cationic precursor solution and an anionic precursor solution to obtain a quantum dot core solution; The first growth step: adding an anion precursor solution to the quantum dot core solution and heating to react; repeating the first growth step until the growth rate of the quantum dot particle size reaches a plateau to obtain a first product solution; The second growth step: adding a cationic precursor solution and an anionic precursor solution to the first product solution and heating to react, wherein the ratio of the added cationic precursor solution to the anionic precursor solution is a preset first ratio; repeating the second growth step until a second product solution is obtained, and the second product solution is a quantum dot solution that can obtain a set particle size.

2. The preparation method according to claim 1, characterized in that: In the quantum dot core synthesis step, the ratio X0 of cations to anions in the mixed precursor solution is 70:1 to 3:1 in terms of molar ratio.

3. The preparation method according to claim 1 or 2, characterized in that: The first ratio is 10:5 to 10:7 in terms of molar ratio; and / or, when the growth rate of the quantum dot particle size reaches a plateau, the ratio of cations to anions in the first product solution is 10:5 to 10:7 in terms of molar ratio.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The first ratio is the ratio of cations to anions in the first product solution when the growth rate of the quantum dot particle size reaches a plateau; and / or, repeating the first growth step until the growth rate of the quantum dot particle size reaches a plateau to obtain the first product solution, comprising: repeating the first growth step until the growth rate of the quantum dot particle size reaches a plateau, and purifying the solution that reaches the plateau to obtain the first product solution.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The first growth step is repeated 2 to 6 times; and / or, the total amount of the anion precursor added in the first growth step is 0.05 to 0.2 times that of the cationic precursor; and / or, in the first growth step, the reaction temperature is 200 to 290° C. and the reaction time is 10 seconds to 60 seconds.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The second growth step is repeated 2 to 8 times, so as to controllably obtain quantum dots with different particle sizes; and / or, in the second growth step, the reaction temperature is 200 to 290° C., and the reaction time is 10 seconds to 60 seconds.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The particle size of the quantum dots is 2 nm to 9 nm, preferably 2.2 nm to 8.6 nm.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The quantum dots are single-core quantum dots, which are quantum dots of II-VI group compounds selected from CdS, CdSe, CdTe, ZnS, ZnSe, PbS, and PbSe, and quantum dots of III-V group compounds selected from InP, GaP, GaN, and AlN.

9. The preparation method according to any one of claims 1 to 8, wherein the preparation method further comprises a quantum dot purification step: mixing and separating the second product solution obtained in the second growth step with an alcohol solvent, and redissolving the solid precipitate using a good solvent for quantum dots, thereby obtaining purified quantum dots.

10. A quantum dot, characterized in that: The quantum dots are obtained according to the preparation method according to any one of claims 1 to 9, the quantum dots are single-core quantum dots, and the particle size of the quantum dots is 2 nm to 9 nm.

Images