Method for quantum dot ligand exchange in microfluidic reactor
By accurately controlling the heating conditions in a microfluidic reactor, the problem of difficult temperature and time in quantum dot synthesis and ligand exchange is solved, and the rapid, precise ligand exchange and particle size stability of quantum dots are achieved. It is suitable for Massive production and improved fluorescence efficiency.
Patent Information
- Application Number
- CN202411542879.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-10-24
- Filing Date
- 2024-10-31
- Publication Date
- 2025-01-17
AI Technical Summary
In the existing quantum dot synthesis and ligand exchange technologies, temperature and reaction time are difficult to accurately regulate, and are not suitable for large-scale industrial production, resulting in increased particle size and decreased performance of quantum dots.
The microfluidic reactor is used to perform quantum dot synthesis and ligand exchange. By accurately controlling the heating temperature and time, the rapid and precise controllable surface ligand exchange of cadmium selenide quantum dots can be achieved, avoiding further growth of quantum dots, and is suitable for batching. Production.
It realizes fast, precise and controllable ligand exchange of quantum dots, inhibits particle size increase, improves particle size stability, reduces energy consumption, is suitable for large-scale production and improves the fluorescence efficiency of quantum dots.
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Figure CN119320633A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of nanoparticle synthesis, and in particular relates to a method for synthesizing quantum dots and exchanging ligands. Background Art
[0002] Quantum dots are a new type of semiconductor material with a particle size smaller than or close to the Bohr radius, size-dependent characteristics, high molar extinction coefficient, wide absorption range and narrow emission range. These unique properties make quantum dots widely used in many fields, such as biomedicine, display technology, lighting, solar cells, etc. In order to improve the performance of quantum dots, the surface ligands of quantum dots are usually replaced with oil-soluble organic ligands, such as oleic acid, to improve the dispersion and stability of quantum dots and enhance the fluorescence efficiency of quantum dots. Quantum dots with oleic acid as ligands are currently widely used in display and solar cells and other fields, and have broad application prospects. The continuous progress of the preparation of quantum dot materials and surface ligand modification processes has promoted the research and development of quantum dots in various fields.
[0003] At present, the synthesis of quantum dots and ligand exchange are mainly based on the hot injection method. However, the hot injection method usually has the following defects: (1) The temperature and reaction time cannot be precisely controlled. (2) Large-scale industrial production is not possible. (3) Ligand exchange usually requires high reaction temperature and long reaction time, which will cause the particle size of quantum dots to increase after the second heating. Summary of the invention
[0004] The purpose of the present invention is to provide a method for quantum dot synthesis and ligand exchange in a microfluidic reactor. By constructing a simple microfluidic reactor to accurately control relevant experimental parameters including heating time and heating temperature, cadmium selenide synthesis and surface ligand exchange are achieved, and further batch quantum dot ligand exchange is achieved.
[0005] In order to achieve the above-mentioned object of the invention, the present invention proposes the following technical solutions:
[0006] In a first aspect, the present invention provides a method for synthesizing quantum dots and exchanging ligands in a microfluidic reactor, comprising:
[0007] The cadmium precursor and the selenium precursor are uniformly mixed at room temperature to obtain a reaction solution 1, which is heated and synthesized in a microfluidic reactor, and then purified for the first time to obtain cadmium selenide quantum dots of various particle sizes whose surface ligand is octadecyl phosphate, and dissolved in 1-octadecene to obtain a cadmium selenide quantum dot solution;
[0008] The cadmium oleate precursor and the cadmium selenide quantum dot solution are mixed evenly at room temperature to obtain a second reaction solution, which is heated in a microfluidic reactor to replace the oleic acid ligand with the phosphate n-octadecyl ester ligand. After a second purification, cadmium selenide quantum dots with oleic acid as the surface ligand are obtained.
[0009] In some embodiments, the microfluidic reactor includes a quantum dot synthesis part and a ligand exchange part, both parts contain an injection unit, a microfluidic channel, a heating unit and an injection bottle, and the microfluidic channel further includes an injection port, a sample tube tray and a sample outlet.
[0010] In some embodiments, the cadmium precursor is made of cadmium oxide, n-octadecyl phosphate, and n-trioctylphosphine.
[0011] In some embodiments, the selenium precursor is made of selenium powder and n-trioctylphosphine.
[0012] In some embodiments, further, the cadmium selenide quantum dots whose surface ligand is octadecyl phosphate are purified with anhydrous ethanol, and then the solid is dissolved with toluene, and the first purification is completed through excess acetone; the cadmium selenide quantum dots whose surface ligand is oleic acid are purified twice with excess acetone, and then the solid is dissolved with toluene to complete the second purification.
[0013] In some embodiments, the cadmium oleate precursor is made from cadmium oxide, oleic acid, and 1-octadecene.
[0014] In some embodiments, the method further includes adjusting the heating time by adjusting the heating temperature of the synthesis part of the microfluidic reactor and the injection flow rate of the reaction solution to obtain cadmium selenide quantum dots with different particle sizes whose surface ligands are octadecyl phosphate.
[0015] In some embodiments, the quantum dot synthesis step further sets the heating temperature to 230-260°C, the relative molar concentration ratio of cadmium to selenium is 1:1.5, and the heating temperature in the ligand exchange is 150°C.
[0016] In some embodiments, the residence time of the reaction solution 1 in the heating unit in the quantum dot synthesis part is 0.4 to 2.0 minutes; the residence time of the reaction solution 2 in the heating unit in the ligand exchange part is 5 minutes.
[0017] In a second aspect, a method for batch quantum dot synthesis and ligand exchange in a microfluidic reactor comprises:
[0018] A cadmium precursor and a selenium precursor are mixed uniformly at room temperature to obtain a reaction solution 1 in batches, a microfluidic reactor is controlled by a host computer to perform a continuous reaction, and after batch heating synthesis in the microfluidic reactor, cadmium selenide quantum dots with surface ligands of octadecyl phosphate are obtained through a first batch purification, and the cadmium selenide quantum dots of various particle sizes are obtained, and the cadmium selenide quantum dots are dissolved in 1-octadecene to obtain a cadmium selenide quantum dot solution in batches;
[0019] The cadmium oleate precursor and the above-mentioned cadmium selenide quantum dot solution are evenly mixed at room temperature to obtain reaction solution 2 in batches, which is heated in a microfluidic reactor to replace the phosphate n-octadecyl ligand with the oleic acid ligand. After a second batch purification, cadmium selenide quantum dots with oleic acid as the surface ligand are obtained in batches.
[0020] Compared with the prior art, the beneficial technical effects and technical progress achieved by the present invention are as follows:
[0021] 1) For the first time, ligand exchange on the surface of cadmium selenide quantum dots was carried out in a microfluidic reactor, which can react continuously and realize a fast, precisely controllable surface ligand exchange process of cadmium selenide quantum dots; the microfluidic reactor has a simple structure and low cost; the inner diameter of the microtube is small and the heating volume is small, which can realize rapid and uniform heating within a unit volume, and the liquid fully absorbs the surrounding heat, so that the surface ligand exchange of cadmium selenide quantum dots can be carried out at a lower temperature and in a shorter time, inhibiting the further growth of quantum dots and precisely controlling the size of quantum dots; the microfluidic reactor can provide sufficient heat to the reaction liquid at a lower temperature in a short time, achieving low energy consumption and high efficiency;
[0022] 2) Based on the continuous reaction of the microfluidic reactor, a method for realizing ligand exchange on the surface of cadmium selenide in batches in a microfluidic reactor was proposed for the first time, which provides a path for the automated and large-scale realization of quantum dot ligand exchange;
[0023] 3) Since the microfluidic reactor can accurately control the reaction temperature and heating time, and because the volume of the reaction liquid is small, sufficient heat can be provided for ligand exchange by heating at a low temperature in a short time, thereby avoiding the increase of the quantum dot particle size due to excessive heating during the ligand exchange process, inhibiting the further growth of the quantum dots, and accurately controlling the size of the quantum dots to be consistent before and after the ligand exchange, thereby enhancing the stability of the particle diameter. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 Schematic diagram of the microfluidic reactor structure;
[0025] Figure 2 A block diagram of the method implementation for batch quantum dot synthesis and ligand exchange in a constructed microfluidic reactor;
[0026] Figure 3 This is an overall flow chart of a method for quantum dot ligand exchange in a microfluidic reactor of the present invention;
[0027] Figure 4 This is a diagram showing an example of a method for quantum dot ligand exchange in a microfluidic reactor of the present invention;
[0028] Figure 5 A flow chart of a method for batch quantum dot synthesis and ligand exchange in a microfluidic reactor of the present invention;
[0029] Figure 6 The UV-visible absorption spectra of the cadmium selenide quantum dots whose surface ligands are n-octadecyl phosphate synthesized in Examples 1 to 5;
[0030] Figure 7 The fluorescence spectra of the cadmium selenide quantum dots whose surface ligands are octadecyl phosphate synthesized in Examples 1 to 5;
[0031] Figure 8 The UV-visible absorption spectra of the cadmium selenide quantum dots whose surface ligands are octadecyl phosphate and the cadmium selenide quantum dots whose surface ligands are oleic acid synthesized in Example 1;
[0032] Fig. 9 The fluorescence spectra of the cadmium selenide quantum dots whose surface ligands are octadecyl phosphate and the cadmium selenide quantum dots whose surface ligands are oleic acid synthesized in Example 1;
[0033] Fig.10 The UV-visible absorption spectra of the cadmium selenide quantum dots whose surface ligands are octadecyl phosphate and the cadmium selenide quantum dots whose surface ligands are oleic acid synthesized in Example 5;
[0034] Fig.11 The fluorescence spectra of the cadmium selenide quantum dots whose surface ligands are octadecyl phosphate and the cadmium selenide quantum dots whose surface ligands are oleic acid synthesized in Example 5;
[0035] Reference numerals:
[0036] 1. Injection unit, 2. Heating unit, 3. Microfluidic pipeline, 31. Sample injection port, 32. Material storage unit, 33. Sample outlet, 4. Sample injection bottle, 5. Microfluidic reactor, 6. Host computer. DETAILED DESCRIPTION
[0037] The technical solutions in the embodiments of the present invention will be described clearly below in conjunction with the accompanying drawings.
[0038] like Figure 1 The microfluidic reactor is shown, and its structure consists of an injection unit 1, a heating unit 2, a microfluidic pipeline 3 and a sample injection bottle 4. The present invention utilizes this microfluidic reactor to realize quantum dot synthesis and ligand exchange respectively. Specifically, the injection unit 1 is composed of a 20ml disposable syringe and a stepping motor. The heating unit 2 adopts a magnetic stirring oil bath pot to provide a stable and uniform heating environment. The microfluidic pipeline 3 is made of a 316 stainless steel pipe with a length of 0.5m and an inner diameter of 0.75mm, and further includes an inlet 31, a sample tube tray 32 and a sample outlet 33.
[0039] i. When quantum dot synthesis is realized by using a microfluidic reactor, the injection unit controls a 20 ml disposable syringe and a stepper motor to inject the reaction liquid from the injection port of the microfluidic pipeline 3; the injected reaction liquid flows through the microfluidic pipeline 3 through the sample tube disk 32 to realize transmission; the sample tube disk 32 of the microfluidic pipeline 3 is placed in a magnetic stirring oil bath; the reaction liquid flowing through the sample tube disk 32 is heated in a magnetic stirring oil bath, and the heated reaction liquid flows into the injection bottle 4 through the sample outlet 33 of the microfluidic pipeline 3. The quantum dots synthesized in the quantum dot synthesis part of the microfluidic reactor are cadmium selenide quantum dots whose surface ligands are octadecyl phosphate (ODPA).
[0040] ii. When a microfluidic reactor is used to realize ligand exchange, similarly, the injection unit 1, the heating unit 2, the microfluidic channel 3 and the injection bottle 4 are combined and connected to form the ligand exchange part of the microfluidic reaction system. The quantum dots synthesized in this part are cadmium selenide quantum dots whose surface ligand is oleic acid (OA).
[0041] like Figure 2 As shown, the microfluidic reactor 5 is connected to a host computer 6 , and the host computer 6 controls the microfluidic reactor to achieve continuous reaction, thereby providing a path for automated and large-scale quantum dot ligand exchange.
[0042] A cadmium precursor and a selenium precursor are mixed uniformly at room temperature to obtain a reaction solution 1 in batches, a microfluidic reactor is controlled by a host computer to perform a continuous reaction, and after batch heating synthesis in the microfluidic reactor, cadmium selenide quantum dots with surface ligands of octadecyl phosphate are obtained through a first batch purification, and the cadmium selenide quantum dots of various particle sizes are obtained, and the cadmium selenide quantum dots are dissolved in 1-octadecene to obtain a cadmium selenide quantum dot solution in batches;
[0043] The cadmium oleate precursor and the above-mentioned cadmium selenide quantum dot solution are evenly mixed at room temperature to obtain a reaction solution 2 in batches, which is heated in a microfluidic reactor to replace the oleic acid ligand with the phosphate n-octadecyl ester ligand. After a second batch purification, cadmium selenide quantum dots with oleic acid as the surface ligand are obtained in batches.
[0044] For the embodiments of the present invention, the following preliminary preparations are required:
[0045] 1-1. Preparation of cadmium precursor: 300 mg of cadmium oxide (CdO), 1400 mg of octadecyl phosphate (ODPA), and 15 ml of trioctylphosphine (TOP) were placed in a 100 ml three-necked flask. When the solution was heated to 120°C, vacuum and nitrogen were alternately pumped three times to exhaust the air in the flask. The solution was heated to 300°C until the mixed solution was transparent. The solution was cooled to room temperature to obtain the cadmium precursor.
[0046] 1-2. Preparation of selenium precursor: Take 290 mg of selenium powder (Se) and 2.2 ml of trioctylphosphine (TOP), stir at 200°C until the selenium powder is completely dissolved and the solution is transparent, and cool the solution to room temperature to obtain a cadmium precursor;
[0047] 1-3. Preparation of reaction solution 1: Mix the above-mentioned cadmium precursor and selenium precursor at room temperature, stir with a magnetic stirrer to fully mix, and obtain reaction solution 1;
[0048] 1-4. Preparation of cadmium oleate precursor: 150 mg of cadmium oxide (CdO), 1.5 ml of oleic acid (OA), and 25 ml of 1-octadecene (ODE) are placed in a 100 ml three-necked flask. When the solution is heated to 120° C., vacuum and nitrogen are alternately evacuated three times to exhaust the air in the flask. The solution is heated to 250° C. until the solution becomes transparent, and the solution is cooled to room temperature to obtain a cadmium oleate precursor.
[0049] 1-5. Preparation of reaction solution 2: The cadmium selenide quantum dot solution prepared in the quantum dot synthesis part whose surface ligand is octadecyl phosphate (ODPA) is mixed with a cadmium oleate precursor at room temperature, and stirred with a magnetic stirrer to mix thoroughly and evenly to obtain reaction solution 2.
[0050] The above preliminary preparation results will be used in the following examples.
[0051] Example 1: Figure 3 and Figure 4 As shown, the overall process of a method for quantum dot ligand exchange in a microfluidic reactor of the present invention includes the following steps:
[0052] S1, quantum dot synthesis step: use a 20 ml disposable syringe to absorb the above reaction solution 1, fix it on the stepper motor, inject trioctylphosphine (TOP) into the stainless steel tube, and rinse the tube;
[0053] Set the temperature of the oil bath to 230°C. After the temperature of the oil bath stabilizes, immerse the microfluidic reaction tube with a length of 0.5 m below the oil level for 10 minutes to ensure that the stainless steel tube is fully and evenly heated to 230°C.
[0054] Turn on the stepper motor, set the flow rate to 500 μL / min, and the heating time per unit volume of the reaction solution to 0.4 minutes. Use a sample bottle to collect the synthesized cadmium selenide quantum dots;
[0055] S2, in the first purification step:
[0056] Add two volumes of ethanol to the cadmium selenide quantum dot solution whose surface ligand is octadecyl phosphate synthesized in the above step S1, shake it slightly until the liquid becomes turbid, put it in a centrifuge tube, set the centrifuge to 8000 rpm, and centrifuge the turbid liquid for 3 minutes to obtain a preliminarily purified quantum dot precipitate;
[0057] The above-preliminarily purified quantum dot precipitate was fully dissolved in 5 ml of toluene, 10 ml of acetone was added, the liquid became turbid, the centrifuge was set to 8000 rpm, the turbid liquid was centrifuged for 3 min, and the obtained precipitate was fully dissolved in 10 ml of ODE to obtain a quantum dot solution whose surface ligand was octadecyl phosphate (ODPA);
[0058] S3, ligand exchange step:
[0059] A quantum dot solution whose surface ligand is ODPA is mixed with a cadmium oleate precursor at room temperature to form a second reaction solution;
[0060] Use a 20ml disposable syringe to draw the reaction solution 2 and fix it on the stepper motor. Inject TOP into the stainless steel tube to rinse the tube;
[0061] Set the temperature of the oil bath to 150°C. After the temperature of the oil bath stabilizes, immerse a 1.5m long microfluidic reaction tube below the oil level for 10 minutes to ensure that the reaction tube is fully heated to 150°C.
[0062] Turn on the motor, set the flow rate to 120 μL / min, and the heating time per unit volume of reaction solution 2 to 5 minutes. Use a sample bottle to collect the synthesized cadmium selenide quantum dots.
[0063] S4, in the second purification step:
[0064] 10 ml of acetone was added to the cadmium selenide quantum dot solution with oleic acid as the surface ligand produced in the above step, and the liquid was placed in a centrifuge tube after it became turbid. The centrifuge was set at 8000 rpm, and the turbid liquid was centrifuged for 3 minutes. The obtained precipitate was fully dissolved in toluene to obtain quantum dots with OA as the surface ligand.
[0065] like Figure 5 As shown, a method for batch synthesis of quantum dots and ligand exchange in a microfluidic reactor of the present invention comprises the following steps:
[0066] The microfluidic reactor is controlled by a host computer to perform continuous reactions;
[0067] The cadmium precursor and the selenium precursor are mixed evenly at room temperature to obtain a reaction solution 1 in batches, which is heated and synthesized in batches in a microfluidic reactor, and then purified for the first time in batches to obtain cadmium selenide quantum dots of various particle sizes whose surface ligand is n-octadecyl phosphate, which are dissolved in 1-octadecene to obtain cadmium selenide quantum dot solutions in batches;
[0068] The cadmium oleate precursor and the above-mentioned cadmium selenide quantum dot solution are evenly mixed at room temperature to obtain reaction solution 2 in batches, which is heated in a microfluidic reactor to replace the phosphate n-octadecyl ligand with the oleic acid ligand. After a second batch purification, cadmium selenide quantum dots with oleic acid as the surface ligand are obtained in batches.
[0069] Example 2
[0070] The difference between Example 2 and Example 1 is that the flow rate is set to 300 μL / min, and the heating time per unit volume of the reaction solution 1 is 0.6 min.
[0071] Example 3
[0072] The difference between Example 3 and Example 1 is that the flow rate is set to 100 μL / min, and the heating time per unit volume of the reaction solution 1 is 2.0 min.
[0073] Example 4
[0074] The difference between Example 3 and Example 1 is that the temperature of the oil bath is set to 260° C., the flow rate is set to 500 μL / min, and the heating time per unit volume of the reaction solution 1 is 0.4 min.
[0075] Example 5
[0076] S1 in Example 1 was modified as follows: the temperature of the oil bath was set to 260° C., the flow rate was set to 100 μL / min, and the heating time per unit volume of the reaction solution 1 was 2.0 min.
[0077] As shown in Table 1, it is the comparison result before and after the ligand exchange of CdSe quantum dots.
[0078] Table 1
[0079]
[0080] Since the particle size of the cadmium selenide quantum dots is positively correlated with the absorption peak position, the quantum dot particle sizes in all embodiments 1-5 of the present invention are different, that is, by adjusting the heating temperature of the synthesis part of the microfluidic reactor and the reaction solution injection flow rate (heating time), cadmium selenide quantum dot nanoparticles with surface ligands of octadecyl phosphate of different particle sizes can be obtained. Before and after the ligand exchange, the particle size of the cadmium selenide quantum dots is almost unchanged.
[0081] In summary, the present invention can effectively add oleic acid to the surface of cadmium selenide quantum dots of any particle size, significantly improving the fluorescence quantum efficiency of cadmium selenide quantum dots. At the same time, the ligand exchange process in the microfluidic reactor only needs to heat the reaction solution for a short time at a relatively low heating temperature to complete, which not only reduces the heating temperature required in the quantum dot synthesis and ligand exchange process, reduces energy consumption, but also avoids the further growth of quantum dots caused by excessive heating in the previous ligand exchange process. The method of quantum dot synthesis and ligand exchange in a microfluidic reactor described in this application is suitable for large-scale production of quantum dots, and the quality of the produced quantum dots is uniform.
[0082] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be deemed to fall within the scope of protection of the present invention.
Claims
1. A method for quantum dot synthesis and ligand exchange in a microfluidic reactor, characterized in that: include: The cadmium precursor and the selenium precursor are uniformly mixed at room temperature to obtain a reaction solution 1, which is heated and synthesized in a microfluidic reactor, and then purified for the first time to obtain cadmium selenide quantum dots of various particle sizes whose surface ligand is octadecyl phosphate, and dissolved in 1-octadecene to obtain a cadmium selenide quantum dot solution; The cadmium oleate precursor and the cadmium selenide quantum dot solution are mixed evenly at room temperature to obtain a second reaction solution, which is heated in a microfluidic reactor to replace the oleic acid ligand with the phosphate n-octadecyl ester ligand. After a second purification, cadmium selenide quantum dots with oleic acid as the surface ligand are obtained.
2. The method for quantum dot synthesis and ligand exchange in a microfluidic reactor according to claim 1, characterized in that: The microfluidic reactor comprises a quantum dot synthesis part and a ligand exchange part, both of which contain an injection unit, a microfluidic pipeline, a heating unit and a sample injection bottle, and the microfluidic pipeline further comprises a sample injection port, a sample tube tray and a sample outlet.
3. The method for quantum dot synthesis and ligand exchange in a microfluidic reactor according to claim 1, characterized in that: The cadmium precursor is made of cadmium oxide, n-octadecyl phosphate and n-trioctylphosphine.
4. The method for quantum dot synthesis and ligand exchange in a microfluidic reactor according to claim 1, characterized in that: The selenium precursor is prepared from selenium powder and n-trioctylphosphine.
5. The method for synthesizing quantum dots according to claim 1, characterized in that: Furthermore, the cadmium selenide quantum dots whose surface ligand is octadecyl phosphate are purified with anhydrous ethanol, and then the solid is dissolved with toluene, and the first purification is completed through excess acetone; the cadmium selenide quantum dots whose surface ligand is oleic acid are purified twice with excess acetone, and then the solid is dissolved with toluene to complete the second purification.
6. The method for quantum dot synthesis and ligand exchange in a microfluidic reactor according to claim 1, characterized in that: The cadmium oleate precursor is prepared from cadmium oxide, oleic acid and 1-octadecene.
7. The method for quantum dot synthesis and ligand exchange in a microfluidic reactor according to claim 1, characterized in that: The method also includes adjusting the heating time by adjusting the heating temperature of the synthesis part of the microfluidic reactor and the injection flow rate of the reaction solution to obtain cadmium selenide quantum dots with different particle sizes whose surface ligands are octadecyl phosphate.
8. The method for quantum dot synthesis and ligand exchange in a microfluidic reactor according to claim 1, characterized in that: The quantum dot synthesis step further sets the heating temperature to 230-260° C., the relative molar concentration ratio of cadmium to selenium to 1:1.5, and the heating temperature in the ligand exchange is 150° C.
9. The method for quantum dot synthesis and ligand exchange in a microfluidic reactor according to claim 1, characterized in that: The residence time of the reaction solution 1 in the heating unit in the quantum dot synthesis part is 0.4 to 2.0 minutes; the residence time of the reaction solution 2 in the heating unit in the ligand exchange part is 5 minutes.
10. A method for batch synthesis of quantum dots and ligand exchange in a microfluidic reactor according to any one of claims 1 to 9, characterized in that: include: A cadmium precursor and a selenium precursor are mixed uniformly at room temperature to obtain a reaction solution 1 in batches, a microfluidic reactor is controlled by a host computer to perform a continuous reaction, and after batch heating synthesis in the microfluidic reactor, cadmium selenide quantum dots with surface ligands of octadecyl phosphate are obtained through a first batch purification, and the cadmium selenide quantum dots of various particle sizes are obtained, and the cadmium selenide quantum dots are dissolved in 1-octadecene to obtain a cadmium selenide quantum dot solution in batches; The cadmium oleate precursor and the above-mentioned cadmium selenide quantum dot solution are evenly mixed at room temperature to obtain reaction solution 2 in batches, which is heated in a microfluidic reactor to replace the phosphate n-octadecyl ligand with the oleic acid ligand. After a second batch purification, cadmium selenide quantum dots with oleic acid as the surface ligand are obtained in batches.