Quantum dot synthesis method and quantum dot

Abstract

The invention relates to a quantum dot synthesis method and a quantum dot. The method comprises the following steps: (1) mixing a solution A containing a cationic precursor and a solution B containing an anionic precursor, and carrying out a nucleation reaction to obtain a solution C; (2) supplementing the solution B into the solution C, mixing, and reacting to obtain a solution D1, in which the amount of the supplemented anion precursor converted by the ion mole number is smaller than the amount of the cation precursor converted by the ion mole number; (3) supplementing the solution B into the solution Dn-1 in the manner of the step (2), mixing, and reacting to obtain a solution Dn, n being an integer greater than 2 and being the number of supplementing times; (4) supplementing the solution A and the solution B into the solution Dn, mixing, and reacting to obtain a solution E1; and (4) is an optional step, and is executed until the molar ratio of anions to cations in the system reaches a set threshold value, and then the step (4) is executed.

Description

Technical Field

[0001] The present invention relates to the technical field of quantum dots, and in particular to a synthesis method of quantum dots and quantum dots. Background Art

[0002] Quantum dots (QDs) usually refer to nanocrystals with a radius less than or close to the Bohr radius of the exciton, especially semiconductor nanocrystals. The particle size of quantum dots is generally 1 nanometer to tens of nanometers, usually spherical or quasi-spherical. Since electrons and holes are quantum confined, the continuous energy band structure becomes a discrete energy level structure with molecular characteristics, and the band gap increases as the size decreases. Therefore, fluorescence can occur after being stimulated, and it has a variety of special physical effects (for example, quantum size effect, surface effect, dielectric confinement effect, quantum tunneling effect and Coulomb blockade effect, etc.). Generally, quantum dot materials can be widely used in energy conversion, light-emitting display devices, photoelectric detection molecular probes, spectral equipment, biological markers and development.

[0003] Particle size distribution is an important indicator of quantum dot performance. For absorption quantum dots, the narrower the particle size distribution, the narrower the half-peak width of its absorption spectrum; while for fluorescent quantum dots, narrow particle size distribution helps to improve the monochromaticity of quantum dots.

[0004] Taking absorption quantum dots CdSe as an example, conventional synthesis methods include hot injection method, one-pot method, and the microreactor method that has emerged in recent years. However, the half-peak width of the absorption spectrum of quantum dots obtained by these synthesis methods is usually in the range of 40 to 60nm, and it is difficult to achieve a smaller half-peak width through process optimization.

[0005] Patent document 1 provides a method for improving the particle size dispersion of quantum dots based on a solvothermal method, which requires encapsulating part of the quantum dot precursor in an organic polymer carrier. In addition, Patent document 2 provides a method for preparing a quantum dot display material with controllable particle size, which selects aerogel with uniform pore distribution as a reaction carrier, adds the quantum dot raw material precursor to the aerogel, disperses it evenly, and reacts it. However, these methods have high production cost requirements and are complicated to operate.

[0006] Therefore, there is a need for a low-cost synthesis method that can further narrow the half-peak width of the absorption spectrum of quantum dots.

[0007] Patent document 1: CN 115433562 A

[0008] Patent document 2: CN 106905975 A Summary of the invention

[0009] Problem that the invention aims to solve

[0010] In view of the above, the object of the present invention is to provide a method for synthesizing quantum dots, which can obtain quantum dots with a further narrowed half-peak width of the absorption spectrum (hereinafter sometimes referred to as the half-peak width), and is simple to operate and low in cost. In addition, the object of the present invention is to provide a quantum dot whose half-peak width of the absorption spectrum can be further narrowed and is easy to obtain.

[0011] Solutions for solving problems

[0012] After careful research, the inventor surprisingly found that the following technical solution can achieve the purpose of the present invention.

[0013] [1]. A method for synthesizing quantum dots, comprising:

[0014] (1) mixing a solution A including a cationic precursor and a solution B including an anionic precursor and performing a nucleation reaction to obtain a solution C including quantum dot cores, wherein the amount of the cationic precursor converted in terms of the number of moles of ions is greater than the amount of the anionic precursor converted in terms of the number of moles of ions;

[0015] (2) Adding the solution B to the solution C and mixing them to react to obtain a solution D 1 , wherein the amount of the added anion precursor converted in terms of the number of moles of ions is less than the amount of the cationic precursor converted in terms of the number of moles of ions;

[0016] (3) To solution D n-1 In the same manner as in step (2), the solution B is added and mixed, and reacted to obtain a solution D n , wherein n is an integer greater than 2 and is the number of times the solution B is added and reacted;

[0017] (4) Add the solution D n Then, the solution A and the solution B are added and mixed, and reacted to obtain a solution E. 1 ,

[0018] The above step (4) is an optional step. After the above step (3) is performed until the molar ratio of anions to cations in the reaction system reaches a set threshold, the above step (4) is performed.

[0019] [2] The synthesis method according to [1], wherein in step (1), the ratio of the amount of the cationic precursor converted in terms of the number of moles of ions to the amount of the anionic precursor converted in terms of the number of moles of ions is 70:1 to 3:1; and / or

[0020] In step (1), the reaction temperature of the nucleation reaction is 200 to 290° C., and the reaction time of the nucleation reaction is 10 seconds to 60 seconds.

[0021] [3] The synthesis method according to [1] or [2], wherein in step (2), the amount of the anion precursor added in terms of ion moles is 0.05 to 0.2 times the amount of the cationic precursor in terms of ion moles; and / or

[0022] In step (2), the reaction temperature is 200 to 290° C., and the reaction time is 10 to 60 seconds.

[0023] [4] The synthesis method according to any one of [1] to [3], wherein the operation in step (3) is performed until the set threshold value in the reaction system is 10:5 to 10:7.

[0024] [5] A synthesis method according to any one of [1] to [4], wherein in step (4), the ratio of the amount of the anion precursor added in terms of the number of moles of ions to the amount of the cation precursor added in terms of the number of moles of ions is 10:5 to 10:7.

[0025] [6] The synthesis method according to any one of [1] to [5], wherein in step (4), the ratio of the amount of the anion precursor added in terms of ions to the amount of the cation precursor added in terms of ions is equal to the mole of the solution D n The molar ratio of anions to cations in the ions is basically the same.

[0026] [7] The synthesis method according to any one of [1] to [6], wherein in step (4), the reaction temperature is 200 to 290°C and the reaction time is 10 seconds to 60 seconds.

[0027] [8] The synthesis method according to any one of [1] to [7], further comprising: (5) adding solution E m-1 In the same manner as in step (4), solution A and solution B are added and mixed, and reacted to obtain solution E. m , wherein m is an integer greater than 2 and is the number of times solution A and solution B are added and reacted.

[0028] [9]. The synthesis method according to any one of [1] to [8], 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, quantum dots of Group III-V compounds selected from InP, GaP, GaN, and AlN, perovskite quantum dots, and quantum dots of precious metals selected from Au, Ag, and Pt.

[0029]

[10] . A quantum dot obtained by the synthesis method according to any one of [1] to [9].

[0030] Effects of the Invention

[0031] The method for synthesizing quantum dots of the present invention has the following beneficial effects:

[0032] The invention uses a method of first nucleating and then growing quantum dots in multiple cycles and using precursor materials of specific composition in different stages to effectively reduce the half-peak width of the absorption spectrum of the obtained quantum dots. In addition, the preparation process has many adjustable parameters, strong controllability, and high product consistency. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The absorption spectra of the quantum dot product obtained in Example 1 (present method 581-38) and the quantum dot product obtained in the comparative example (conventional method 581-58) are shown.

[0034] Figure 2 The absorption spectra of the quantum dot product obtained in Example 2 (present method 600-36) and the quantum dot product obtained in the comparative example (conventional method 600-62) are shown.

[0035] Figure 3 The absorption spectra of the quantum dot product obtained in Example 3 (present method 612-32) and the quantum dot product obtained in the comparative example (conventional method 612-50) are shown.

[0036] Figure 4 The absorption spectrum of the quantum dot product obtained in Example 4 is shown. DETAILED DESCRIPTION

[0037] Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The word "exemplary" used here means "used as an example, embodiment or illustrative". Any embodiment described here as "exemplary" is not necessarily interpreted as being superior or better than other embodiments.

[0038] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In other examples, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0039] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0040] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0041] 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.

[0042] In this specification, the numerical range expressed using "value A to value B" means a range including the endpoint values ​​A and B. The numerical range expressed using "above" and "below" means a range including the endpoint values. The numerical range expressed using "greater than" and "less than" means a range excluding the endpoint values.

[0043] 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.

[0044] <<Synthesis Method of Quantum Dots>>

[0045] The synthesis method of quantum dots of the present invention comprises:

[0046] (1) mixing a solution A including a cationic precursor and a solution B including an anionic precursor and performing a nucleation reaction to obtain a solution C including quantum dot cores, wherein the amount of the cationic precursor converted in terms of the number of moles of ions is greater than the amount of the anionic precursor converted in terms of the number of moles of ions;

[0047] (2) Adding the solution B to the solution C and mixing them to react to obtain a solution D 1, wherein the amount of the added anion precursor converted in terms of the number of moles of ions is less than the amount of the cationic precursor converted in terms of the number of moles of ions;

[0048] (3) To solution D n-1 In the same manner as in step (2), the solution B is added and mixed, and reacted to obtain a solution D n , wherein n is an integer greater than 2 and is the number of times the solution B is added and reacted;

[0049] (4) Add the solution D n Then, the solution A and the solution B are added and mixed, and reacted to obtain a solution E. 1 ,

[0050] The above step (4) is an optional step. After the above step (3) is performed until the molar ratio of anions to cations in the reaction system reaches a set threshold, the above step (4) is performed.

[0051] In the present invention, the synthesis method of quantum dots can be carried out using various reaction equipment known in the art, for example, various closed or unclosed containers and microreactors, etc. In some preferred embodiments, the reaction of synthesizing quantum dots of the present invention is carried out in a microreactor. The microreactor of the present invention can be various microreactors known in the art, usually including a microchannel (or microreactor pipeline) for carrying out the reaction. Regarding the material of the microreactor pipeline, for example, it can be polytetrafluoroethylene (PTFE), ceramic material, stainless steel, glass, etc.

[0052] In the present invention, there is no particular limitation on the length, outer diameter and inner diameter of the microreactor pipeline, and they can be adjusted as needed. For example, the length of the pipeline can be 1m to 25m, preferably 1.5m to 2.5m, 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.

[0053] Examples of tubing specifications include but are not limited to: OD (outer diameter) - 1 / 16 inch, ID (inner diameter) - 1 mm, L (length) - 5 m; or OD - 1 / 16 inch, ID - 2 mm, L - 1.3 m; or OD - 1 / 16 inch, ID - 0.5 mm, L - 20 m; etc.

[0054] In the present invention, there is no particular limitation on quantum dots. The synthesis method of the present invention can be used to synthesize substantially all possible quantum dots.

[0055] In some specific embodiments of the present invention, the quantum dots are single-core quantum dots. Examples of quantum dots may include: quantum dots of II-VI group compounds selected from CdS, CdSe, CdTe, ZnS, ZnSe, PbS, PbSe, quantum dots of III-V group compounds selected from InP, GaP, GaN, AlN, perovskite quantum dots, quantum dots of noble metals selected from Au, Ag, Pt.

[0056] The term "single-core quantum dots" mentioned above refers to quantum dots without a shell structure, without an interface between the core and the shell, and are formed of the same material.

[0057] Each step will be described in detail below. In addition, each step can be implemented independently of each other, or a part or all of each step can be implemented continuously. When multiple steps are implemented continuously, the next step can be performed after one step is completed, or two steps can be performed simultaneously or partially simultaneously.

[0058] <Step (1)>

[0059] In step (1), a solution A including a cationic precursor and a solution B including an anionic precursor are mixed and subjected to a nucleation reaction to obtain a solution C including quantum dot cores. The amount of the cationic precursor converted in terms of the mole number of ions is greater than the amount of the anionic precursor converted in terms of the mole number of ions.

[0060] In the present invention, there is no particular restriction on the specific types of cationic precursors and anionic precursors. For example, for quantum dots of II-VI compounds, the selected cationic precursors may include precursors of Cd, Zn or Pb elements, and the selected anionic precursors may include precursors of S, Se or Te elements. For quantum dots of III-V compounds, the selected cationic precursors may include precursors of Al, Ga, In, elements, and the selected anionic precursors may include precursors of N, P or As elements. For perovskite quantum dots, the selected precursors may include precursors of methylamine ions, methylammonium ions, cesium ions, or precursors of lead ions, tin ions, manganese ions, and halogen ions.

[0061] In the present invention, there is no particular limitation on the composition of solution A including a cationic precursor, as long as it includes a cationic precursor. In some specific embodiments, solution A preferably includes a cationic precursor, a solvent and a ligand. It should be noted that "solution A including a cationic precursor" means that the cationic precursor is dissolved in solution A and is not carried or encapsulated in other substances (e.g., other organic substances).

[0062] In the present invention, there is no particular limitation on the method for preparing the solution A including the cationic precursor, and methods known in the art may be selected according to the type of quantum dots to be prepared.

[0063] In some specific embodiments, oxides, halides (such as chlorides or bromides) or organic acid salts (such as oleates) of Group II metals are mixed with solvents and ligands, dissolved under heating and an oxygen-free atmosphere, and then sealed and stored in an oxygen-free atmosphere for later use after cooling.

[0064] 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 oleylamine, oleic acid, palmitic acid, stearic acid (octadecanoic acid), and adipic acid. The heating temperature can be 180 to 350° C. The above-mentioned oxygen-free atmosphere can be a nitrogen atmosphere or an argon atmosphere, etc.

[0065] 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.

[0066] In the present invention, there is no particular limitation on the composition of solution B including anionic precursors, as long as it includes anionic precursors. In some specific embodiments, solution B preferably includes anionic precursors, solvents and ligands. It should be noted that "solution B including anionic precursors" means that the anionic precursors are dissolved in solution B and are not carried or encapsulated in other substances (e.g., other organic substances, gels, etc.).

[0067] In the present invention, there is no particular limitation on the method for preparing the solution B including the anion precursor, and methods known in the art may be selected according to the type of quantum dots to be prepared.

[0068] In some specific embodiments, a powder of a simple substance of a 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.

[0069] The solvent here can be a commonly used solvent in the art, preferably the same solvent as in the preparation of solution A. Examples of the ligand can include one or more of trioctylphosphine, trioctylphosphine oxide, tributylphosphine, etc. The heating temperature can be 100-150° C., preferably 120-150° C. The above-mentioned oxygen-free atmosphere can be a nitrogen atmosphere or an argon atmosphere, etc.

[0070] 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.

[0071] In the present invention, there is no particular limitation on the method for mixing solution A and solution B, and methods known in the art may be selected according to the type of quantum dots to be prepared.

[0072] In some specific embodiments, solution A and solution B are mixed and stirred at a temperature of 0 to 80° C. (e.g., an ambient temperature of 10 to 40° C.), and then stored in an oxygen-free atmosphere for later use (the resulting mixture is sometimes referred to as a premix for later use). The oxygen-free atmosphere here can be a nitrogen atmosphere or an argon atmosphere, etc.

[0073] After solution A and solution B are mixed, there is no particular restriction on the specific ratio between the two as long as the amount of the cationic precursor in the mixed system converted by the molar number of ions is greater than the amount of the anionic precursor in the mixed system converted by the molar number of ions (sometimes referred to as a cation-rich formula in this article).

[0074] In some preferred embodiments, from the viewpoint of more easily achieving the technical effects of the present invention, the ratio of the amount of the cationic precursor converted in terms of the molar number of ions to the amount of the anionic precursor converted in terms of the molar number of ions is preferably 70:1 to 3:1, more preferably 50:1 to 5:1, and further preferably 35:1 to 15:1.

[0075] In addition, there is no particular limitation on the conditions of the nucleation reaction, as long as the reaction can be carried out, and it can be appropriately adjusted according to the specific types of raw materials, etc. In some specific embodiments, the reaction temperature of the nucleation reaction can be 200 to 290° C., for example, 210 to 280° C., or 220 to 260° C., etc. In other specific embodiments, the reaction time (i.e., the holding time) of the nucleation reaction can be 10 seconds to 60 seconds.

[0076] In some specific embodiments, when the reaction for synthesizing quantum dots is carried out in a microreactor, there is no particular limitation on the supply flow rate of the standby premix, and it is preferably 500 to 15000 μL / min, and more preferably 1000 to 8000 μL / min.

[0077] In addition, in some specific embodiments, the absorption spectrum of the reaction product during the nucleation reaction can be monitored, and after the spectral peak is stable (for example, the spectral peak of three consecutive samples is almost the same), the nucleation reaction can be considered complete.

[0078] After the nucleation reaction is completed, the solution C including the quantum dot cores can be obtained directly, or the solution C including the quantum dot cores can be obtained after the reaction product is purified, concentrated, diluted and / or other substances are added thereto.

[0079] <Step (2)>

[0080] In step (2), solution B is further added to solution C including quantum dot cores and mixed to react to obtain solution D. 1 The amount of the added anion precursor converted in terms of the number of moles of ions is less than the amount of the cationic precursor (the cationic precursor added in step (1)) converted in terms of the number of moles of ions.

[0081] In step (2), the added solution B may be the same or different in composition from the solution B in step (1), but is preferably the same.

[0082] In the present invention, there is no particular limitation on the method for mixing solution C and solution B, and methods known in the art may be selected according to the type of quantum dots to be prepared.

[0083] In some specific embodiments, solution C and solution B are mixed and stirred at a temperature of 0 to 80° C. (e.g., an ambient temperature of 10 to 40° C.), and then stored in an oxygen-free atmosphere for later use (the resulting mixture is sometimes referred to as a standby mixture (B+C) hereinafter). The oxygen-free atmosphere here can be a nitrogen atmosphere or an argon atmosphere, etc.

[0084] In some preferred embodiments, the amount of the anion precursor in the added solution B, calculated on the basis of the mole of ions, is preferably 0.05 to 0.2 times, more preferably 0.08 to 0.18 times, and further preferably 0.1 to 0.15 times, the amount of the cationic precursor in the solution A in step (1) calculated on the basis of the mole of ions.

[0085] In addition, in step (2), there is no particular limitation on the reaction conditions in which the additional solution B participates, as long as the reaction can be carried out, and the conditions can be appropriately adjusted according to the specific types of raw materials, the wavelength of the synthesized quantum dots, etc. In addition, generally, the higher the reaction temperature, the larger the particle size of the quantum dots; the longer the insulation time, the larger the particle size of the quantum dots.

[0086] In some specific embodiments, the reaction temperature may be 200-290° C., for example, 210-280° C., or 220-260° C., etc. In other specific embodiments, the reaction time (ie, the holding time) may be 10 seconds to 60 seconds.

[0087] The reaction conditions in step (2) may be the same as or different from the reaction conditions of the nucleation reaction in step (1), but are preferably the same.

[0088] In some specific embodiments, when the reaction of synthesizing quantum dots is carried out in a microreactor, there is no particular restriction on the supply flow rate of the standby mixture (B+C), and it is preferably 500-15000 μL / min, more preferably 1000-12000 μL / min, and further preferably 3000-10000 μL / min.

[0089] <Step (3)>

[0090] In step (3), solution D n-1 In the same manner as in step (2), the solution B is added and mixed, and reacted to obtain a solution D n Wherein n is an integer greater than 2 and is the number of times the solution B is added and reacted (covering all additions in step (2) and step (3)).

[0091] In the present invention, the upper limit of the number of times n is determined according to the number of times the reaction reaches the plateau phase, and can be appropriately adjusted as needed. For example, the upper limit of the number of times n can be 10, preferably, the upper limit of the number of times n is 8, and more preferably, the upper limit of the number of times n is 6.

[0092] Taking the number n as 4 as an example, step (3) is performed as follows: Add solution D 1 In the same manner as in step (2), the solution B is added and mixed, and reacted to obtain a solution D 2 ; Then, to solution D 2 In the same manner as in step (2), the solution B is added and mixed, and reacted to obtain a solution D 3 ; Then, to solution D 3 In the same manner as in step (2), the solution B is added and mixed, and reacted to obtain a solution D 4 .

[0093] In the present invention, for solution D n-1 The mixing method with solution B is not particularly limited, and methods known in the art may be selected according to the type of quantum dots to be prepared.

[0094] In some specific embodiments, the solution D n-1 After being mixed and stirred uniformly with solution B at a temperature of 0 to 80° C. (e.g., an ambient temperature of 10 to 40° C.), the mixture is stored in an oxygen-free atmosphere for later use (the resulting mixture is sometimes referred to as a standby mixture (B+D) in the following description). n-1 )). The oxygen-free atmosphere here can be a nitrogen atmosphere or an argon atmosphere, etc.

[0095] In step (3), when performing the operation in step (3), the solution B added each time may be the same or different in composition from the solution B added in step (2), but is preferably the same.

[0096] In the present invention, in step (3), the details of the amount of the anion precursor in solution B added each time in terms of the mole of ions are the same as the details of the amount of the anion precursor in solution B added in step (2) in terms of the mole of ions.

[0097] In some preferred embodiments, in step (3), the amount of the anion precursor in solution B added each time, calculated as the mole of ions, is preferably substantially the same as the amount of the anion precursor in solution B added in step (2), calculated as the mole of ions. Here, the term "substantially the same" means that the two amounts are the same, but includes the error allowed in calculation and / or actual operation.

[0098] In step (3), when performing the operation in step (3), the reaction conditions of each reaction in which the added solution B participates may be the same as or different from the reaction conditions of the reaction in step (2), but are preferably the same.

[0099] In some specific embodiments, when the reaction for synthesizing quantum dots is carried out in a microreactor, for the reserve mixture (B+D n-1 ) is not particularly limited, but is preferably 500 to 15000 μL / min, more preferably 1000 to 12000 μL / min, and further preferably 3000 to 10000 μL / min.

[0100] There is no particular restriction on the timing of stopping the execution of step (3), and the process may be stopped based on whether the half-peak width of the obtained quantum dots reaches a desired value.

[0101] In some specific embodiments, in step (3), the half-peak width of the quantum dots obtained during each reaction can be monitored, regardless of whether the molar ratio of anions to cations in the reaction system reaches a set threshold, that is, even if the set threshold is not reached, as long as the desired half-peak width of the quantum dots is reached, step (3) can be stopped. In addition, if the molar ratio of anions to cations in the reaction system reaches the set threshold, step (3) can be stopped.

[0102] In the present invention, the term "the molar ratio of anions to cations in the reaction system reaches a set threshold value" means that even if the operation of further adding solution B is repeated, it is difficult to advance the reaction.

[0103] In some preferred embodiments, the operation in step (3) is performed, preferably, until the molar number of anions in the system is greater than the molar number of cations, and more preferably, until the set threshold value in the reaction system is 10:5 to 10:7.

[0104] After stopping step (3), a solution D including quantum dots can be directly obtained. n The solution D including quantum dots can also be obtained by subjecting the reaction product to purification, concentration, dilution and / or adding other substances thereto. n .

[0105] In addition, in the present invention, step (2) and step (3) are sometimes collectively referred to as the first production stage.

[0106] <Step (4)>

[0107] In step (4), solution D n Then, solution A and solution B are added and mixed, and reacted to obtain solution E. 1 .

[0108] The above step (4) is an optional step. After the above step (3) is performed until the quantum dot particle size growth rate in the reaction reaches a plateau, the above step (4) is performed. In the present invention, whether to perform the above step (4) is usually determined based on whether the desired half-peak width of the quantum dots is achieved.

[0109] In the present invention, for solution D n The mixing method with solution A and solution B is not particularly limited, and those methods known in the art may be selected according to the type of quantum dots to be prepared.

[0110] In some specific embodiments, the solution D n After mixing with solution A and solution B at a temperature of 0 to 80° C. (e.g., an ambient temperature of 10 to 40° C.), stirring uniformly, the mixture is stored in an oxygen-free atmosphere for later use (the resulting mixture is sometimes referred to as a standby mixture (A+B+D) in the following description). n )). The oxygen-free atmosphere here can be a nitrogen atmosphere or an argon atmosphere, etc.

[0111] In step (4), the added solution A and solution B may be the same or different in composition from the solution A and solution B in step (1), but are preferably the same.

[0112] In step (4), there is no particular limitation on the ratio between the anion precursor to be added and the cation precursor to be added.

[0113] In some preferred embodiments, in step (4), the ratio of the amount of the anion precursor added back in terms of the number of moles of ions to the amount of the cation precursor added back in terms of the number of moles of ions is preferably 10:5 to 10:7.

[0114] In other preferred embodiments, in step (4), the ratio of the amount of the anion precursor added in terms of ions to the amount of the cation precursor added in terms of ions is proportional to the amount of the solution D n The molar ratio of anions to cations in the mixture is substantially the same. Here, the term "substantially the same" means that the two quantities are the same, but includes errors allowed in calculation and / or actual operation.

[0115] In addition, in step (4), there is no particular limitation on the reaction conditions, as long as the reaction can be carried out, and the reaction conditions can be appropriately adjusted according to the specific types of raw materials, the wavelength of the synthesized quantum dots, etc. In addition, generally, the higher the reaction temperature, the larger the particle size of the quantum dots; the longer the insulation time, the larger the particle size of the quantum dots.

[0116] In some specific embodiments, the reaction temperature may be 200-290° C., for example, 210-280° C., or 220-260° C., etc. In other specific embodiments, the reaction time (ie, the holding time) may be 10 seconds to 60 seconds.

[0117] In some specific embodiments, when the reaction for synthesizing quantum dots is carried out in a microreactor, for the reserve mixture (A+B+D n ) is not particularly limited, but is preferably 500 to 15000 μL / min, more preferably 1000 to 12000 μL / min, and further preferably 3000 to 10000 μL / min.

[0118] After the reaction is completed, a solution E including quantum dots can be directly obtained. 1 The solution E including quantum dots can also be obtained by subjecting the reaction product to purification, concentration, dilution and / or adding other substances thereto. 1 .

[0119] <Step (5)>

[0120] Similar to the case of adding solution B in step (3), the synthesis method of the present invention may also optionally include the step of repeating the step of adding solution A and solution B in step (4). Specifically, the synthesis method of the present invention may also optionally include the following step (5): adding solution E m-1 In the same manner as in step (4), solution A and solution B are added and mixed, and reacted to obtain solution E. m. wherein m is an integer greater than 2 and is the number of times solution A and solution B are added and reacted (covering all additions in step (4) and step (5)).

[0121] In the present invention, there is no particular limit on the upper limit of the number m, and it can be adjusted appropriately as needed. For example, the upper limit of the number m can be 10, preferably, the upper limit of the number m is 8, and more preferably, the upper limit of the number n is 6.

[0122] Taking the number m as 4 as an example, step (5) is performed as follows: Add solution E 1 In the same manner as in step (4), solution A and solution B are added and mixed, and reacted to obtain solution E. 2 ; Then, to solution E 2 In the same manner as in step (4), solution A and solution B are added and mixed, and reacted to obtain solution E. 3 ; Then, to solution E 3 In the same manner as in step (4), solution A and solution B are added and mixed, and reacted to obtain solution E. 4 .

[0123] In the present invention, for solution E m-1 The mixing method with solution A and solution B is not particularly limited, and those methods known in the art may be selected according to the type of quantum dots to be prepared.

[0124] In some specific embodiments, solution E m-1 After mixing with solution A and solution B at a temperature of 0 to 80° C. (e.g., an ambient temperature of 10 to 40° C.), stirring uniformly, the mixture is stored in an oxygen-free atmosphere for later use (the resulting mixture is sometimes referred to as a standby mixture (A+B+E) in the following description). m-1 )). The oxygen-free atmosphere here can be a nitrogen atmosphere or an argon atmosphere, etc.

[0125] In step (5), when performing the operation in step (5), the solution A and solution B added each time may be the same or different in composition from the solution A and solution B added in step (4), but are preferably the same.

[0126] In the present invention, in step (5), the details of the ratio between solution A and solution B added each time are the same as the details of the ratio between solution A and solution B added in step (4).

[0127] In some preferred embodiments, in step (5), the details of the ratio between solution A and solution B added each time are substantially the same as the ratio between solution A and solution B added in step (4). Here, the term "substantially the same" means that the two quantities are the same, but covers the errors allowed in calculation and / or actual operation.

[0128] In step (5), when performing the operation in step (5), the reaction conditions of each reaction in which the additional solution A and solution B participate may be the same as or different from the reaction conditions in step (4), but are preferably the same.

[0129] In some specific embodiments, when the reaction for synthesizing quantum dots is carried out in a microreactor, for the reserve mixture (A+B+E m-1 ) is not particularly limited, but is preferably 500 to 15000 μL / min, more preferably 1000 to 12000 μL / min, and further preferably 3000 to 10000 μL / min.

[0130] There is no particular restriction on the timing of stopping the execution of step (5), and the process may be stopped based on whether the half-peak width of the obtained quantum dots reaches a desired value.

[0131] After the reaction is completed, a solution E including quantum dots can be directly obtained. m The solution E including quantum dots can also be obtained by subjecting the reaction product to purification, concentration, dilution and / or adding other substances thereto. m .

[0132] In the present invention, step (4) and step (5) (when step (5) does not exist, only step (4)) are sometimes collectively referred to as the second production stage.

[0133] <Specific implementation plan>

[0134] In some particularly specific embodiments, the method for synthesizing quantum dots of the present invention may include the following steps:

[0135] (1) A cation-rich precursor formula is used, wherein the molar ratio of the cationic precursor to the anionic precursor in terms of ions is between 70:1 and 3:1; a nucleation reaction is carried out at a temperature between 200 and 290° C. and a holding time between 10 seconds and 60 seconds.

[0136] (2) Add an anion precursor to the obtained quantum dot core solution, and react at a temperature of 200-290° C. and a holding time of 10-60 s. The amount of the anion precursor added is between 0.05 and 0.2 times the molar number of the cationic precursor in the system in terms of ions.

[0137] (3) Repeat step (2) until the molar ratio of anions to cations in the reaction system reaches a set threshold, generally between 10:5 and 10:7, and change the reaction mode.

[0138] (4) Adding anion and cation precursors to the quantum dot solution simultaneously, the addition ratio is basically the same as the plateau ratio in step (3), about 10:5 to 10:7; reacting at a reaction temperature of 200 to 290° C. and a holding time of 10 s to 60 s.

[0139] <Other Steps>

[0140] The method for synthesizing quantum dots of the present invention may also optionally include various other steps known in the art, for example, purifying the resulting quantum dot solution (such as solution D or solution E), ligand exchange of the resulting quantum dot solution, and purifying the reaction products obtained in each step or any process in each step, extracting quantum dots, etc.

[0141] Each of these other steps can be implemented using means commonly used in the art.

[0142] <<Quantum dot>>

[0143] The quantum dots of the present invention are obtained by the above-mentioned synthesis method of the present invention. Through the technical solution of the present invention, the half-peak width of the quantum dots can be further narrowed and can be easily obtained.

[0144] Example

[0145] 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 normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0146] <Test Method>

[0147] The absorption spectra of the quantum dots obtained in the examples and comparative examples were tested, and the half-peak width was calculated based on each spectrum.

[0148] Calculation of half-width: the peak wavelength position is recorded as λ0, the absorbance corresponding to the peak position is recorded as A0, and the wavelength position corresponding to the absorbance of 0.5×A0 on the right side of λ0 is recorded as λ1, then the half-width FWHM=2×(λ1-λ0).

[0149] <Example 1 (Synthesis of CdSe Material with Absorption Peak at 581nm)>

[0150] (1) Preparation of Cd precursor (cationic precursor)

[0151] Weigh 6g of cadmium oxide powder and add it to the reactor, measure 120mL of octadecene and 120mL of ethanol 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 200rpm, and ventilate at room temperature; set the temperature to 200℃, and start heating from room temperature; 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.

[0152] (2) Preparation of Se precursor (anion precursor)

[0153] 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.

[0154] (3) Quantum dot nucleosynthesis

[0155] Take 30mL Cd_pre and 3mL 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.

[0156] (4) First growth stage

[0157] Add 1.9 mL of Se_pre to N0, recorded as pre_N1; pump pre_N1 into the microfluidic reactor at a flow rate of 8000 μL / min, set the temperature to 250°C, and set the time to 45 s; after the peak position of the spectrum stabilizes, collect the reaction product, recorded as N1. Repeat the above steps twice, and the reaction products are recorded as N2 and N3 respectively.

[0158] The N3 product is a CdSe quantum dot with an absorption peak at 581 nm and a half-peak width of 38 nm (e.g. Figure 1 ) as indicated by the solid black line on the

[0159] (5) Purification

[0160] 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 chloroform (CF) to obtain purified quantum dots.

[0161] <Example 2 (Synthesis of CdSe Quantum Dots with Absorption Peak at 600nm)>

[0162] The basic operation is the same as that of Example 1, except for the following: the steps in step (4) (first growth stage) are repeated 4 times, and the resulting products are recorded as N2, N3, N4, and N5 in sequence.

[0163] The N5 product is a CdSe quantum dot with an absorption peak at 600 nm and a half-peak width of 36 nm (e.g. Figure 2 ) as indicated by the solid black line on the

[0164] <Example 3 (Synthesis of CdSe Quantum Dots with Absorption Peak at 612nm)>

[0165] The basic operation is the same as that of Example 1, except that: the steps in step (4) (first growth stage) are repeated 5 times, and the products obtained are recorded as N2, N3, N4, N5, and N6 in sequence. After repeating 5 times, Cd:Se=6:3 (mol), reaching a plateau; further, the following step (5) (second growth stage) is added after step (4) (first growth stage).

[0166] (5) Second growth stage

[0167] Add 6mL Cd_pre and 3mL Se_pre (the ratio is the same as the ratio when the first growth stage reaches the plateau period) to N6, recorded as pre_N7; pump pre_N1 into the microfluidic reactor at a flow rate of 8000μL / min, set the temperature to 250℃, and set the time to 45s; after the spectral peak position stabilizes, collect the reaction product, recorded as N7.

[0168] The N7 product is a CdSe quantum dot with an absorption peak at 612 nm, and the half-peak width of the quantum dot is 32 nm (e.g. Figure 3 ) as indicated by the solid black line on the

[0169] <Example 4 (Synthesis of CdSe Quantum Dots with Absorption Peak at 632nm)>

[0170] The basic operation is the same as that in Example 3, wherein step (4) (second growth stage) needs to be further repeated twice, and the obtained products are respectively denoted as N8 and N9, wherein N9 is a CdSe quantum dot with an absorption peak at 632nm and a half-peak width of 28nm (such as Figure 4 ) as indicated by the solid black line on the

[0171] <Comparative Example>

[0172] (1) Quantum dot synthesis

[0173] Take 30mL Cd_pre and 30mL Se_pre and add them into the sample bottle and record it as pre_N0.

[0174] A microfluidic synthesis apparatus was used and the temperature was set to 230 °C.

[0175] Pre_N0 was pumped into the heater at a flow rate of 4000 μL / min; after the spectral peak position was stabilized, the reaction product was collected and recorded as N0.

[0176] In addition, according to the actual peak position requirements, the spectral peak position can be adjusted by adjusting the flow rate and reaction temperature; the basic principle is that the higher the flow rate, the smaller the peak position, and the lower the temperature, the smaller the peak position. Based on this, various comparative products (such as Figures 1 to 3 are shown separately in ).

[0177] Specifically, the CdSe with an absorption peak of 581 nm formed by the method listed in the comparative example has a corresponding half-peak width of 58 nm. Figure 1 As shown by the red solid line; the absorption peak of the formed CdSe quantum dots is 600nm, and the corresponding half-peak width is 62nm, as shown in Figure 2 As shown by the red solid line; the absorption peak of the formed CdSe quantum dots is 612nm, and the corresponding half-peak width is 50nm, as shown in Figure 3 Shown as solid red line.

[0178] (2) Purification

[0179] About 3 times the volume of ethanol was added to the quantum dot solution obtained above, and after mixing evenly, the mixture was placed in a centrifuge and centrifuged at 5000 rpm for 3 min. The supernatant was discarded and the solid precipitate was redissolved with CF to obtain purified quantum dots.

[0180] It should be noted that, although the technical solution of the present invention is introduced with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto.

[0181] 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 terms used herein are selected 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 synthesizing quantum dots, characterized in that: include: (1) mixing a solution A including a cationic precursor and a solution B including an anionic precursor and performing a nucleation reaction to obtain a solution C including quantum dot cores, wherein the amount of the cationic precursor converted in terms of the number of moles of ions is greater than the amount of the anionic precursor converted in terms of the number of moles of ions; (2) further adding the solution B to the solution C, mixing and reacting to obtain a solution D1, wherein the amount of the added anion precursor converted in terms of the number of moles of ions is less than the amount of the cationic precursor converted in terms of the number of moles of ions; (3) To solution D n-1 In the same manner as in step (2), the solution B is added and mixed, and reacted to obtain a solution D n , wherein n is an integer greater than 2 and is the number of times the solution B is added and reacted; (4) Add the solution D n The solution A and the solution B are added and mixed, and reacted to obtain a solution E1. The above step (4) is an optional step. After the above step (3) is performed until the molar ratio of anions to cations in the reaction system reaches a set threshold, the above step (4) is performed.

2. The synthesis method according to claim 1, characterized in that In step (1), the ratio of the amount of the cationic precursor converted in terms of the number of moles of ions to the amount of the anionic precursor converted in terms of the number of moles of ions is 70:1 to 3:1; and / or In step (1), the reaction temperature of the nucleation reaction is 200 to 290° C., and the reaction time of the nucleation reaction is 10 to 60 seconds.

3. The synthesis method according to claim 1 or 2, characterized in that In step (2), the amount of the anion precursor added in terms of ion moles is 0.05 to 0.2 times the amount of the cationic precursor in terms of ion moles; and / or In step (2), the reaction temperature is 200 to 290° C., and the reaction time is 10 to 60 seconds.

4. The synthesis method according to any one of claims 1 to 3, characterized in that The operation in step (3) is performed until the set threshold value in the reaction system is 10:5 to 10:

7.

5. The synthesis method according to any one of claims 1 to 4, characterized in that In step (4), the ratio of the amount of the anion precursor added in terms of ions to the amount of the cation precursor added in terms of ions is 10:5 to 10:

7.

6. The synthesis method according to any one of claims 1 to 5, characterized in that In step (4), the ratio of the amount of the anion precursor added in terms of ions to the amount of the cation precursor added in terms of ions is proportional to the amount of the solution D n The molar ratio of anions to cations in the ions is basically the same.

7. The synthesis method according to any one of claims 1 to 6, characterized in that In step (4), the reaction temperature is 200 to 290° C., and the reaction time is 10 to 60 seconds.

8. The synthesis method according to any one of claims 1 to 7, characterized in that Further including: (5) To solution E m-1 In the same manner as in step (4), solution A and solution B are added and mixed, and reacted to obtain solution E. m , wherein m is an integer greater than 2 and is the number of times solution A and solution B are added and reacted.

9. The synthesis method according to any one of claims 1 to 8, 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, quantum dots of III-V group compounds selected from InP, GaP, GaN, and AlN, perovskite quantum dots, and quantum dots of precious metals selected from Au, Ag, and Pt.

10. A quantum dot, characterized in that: It is obtained by the synthesis method according to any one of claims 1 to 9.

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