Quantum dot purification method suitable for quantum dot fluorescent microsphere application

Abstract

The invention provides a quantum dot purification method suitable for quantum dot fluorescent microsphere application, which comprises the following steps: (1) mixing a polar solvent and a quantum dot reaction stock solution to obtain a quantum dot precipitate; (2) mixing a non-polar solvent with the quantum dot precipitate to obtain a first quantum dot solution; (3) mixing a surface ligand with the first quantum dot solution obtained in the step (2); (4) mixing a polar solvent with the quantum dot mixed solution obtained in the step (3), centrifuging, and carrying out solid-liquid separation to obtain quantum dot precipitates; (5) repeating the steps (2)-(4) for a plurality of times; and (6) mixing a non-polar solvent with the quantum dot precipitate obtained in the step (5) to obtain a second quantum dot solution. Quantum dot purification and quantum dot surface ligand exchange can be achieved at the same time.

Description

Technical Field

[0001] The invention relates to a quantum dot purification method suitable for application of quantum dot fluorescent microspheres. Background Art

[0002] Quantum dot nanocrystals are an important type of nanomaterial, and their applications are quite broad, such as light-emitting diodes, batteries, biology, display, lighting and many other fields. Quantum dot fluorescent coded microspheres used for in vitro diagnosis are generally encoded using the emission wavelength and intensity of fluorescence. The coding elements of quantum dot fluorescent coded microspheres include semiconductor quantum dots, organic fluorescent dyes, and upconversion nanoparticles as the main coding elements. Compared with fluorescent dyes, quantum dots have high fluorescence intensity, long fluorescence lifetime, narrow emission band, continuous and adjustable spectrum, can be excited by a single wavelength laser, are highly stable to photobleaching, are spatially separated from each other and do not transfer fluorescence energy, and have narrow emission peaks. The theoretical coding capacity of the 6-color 10-intensity scheme is 1 million. Therefore, quantum dot fluorescent coded microspheres have great application potential.

[0003] Fluorescent microspheres have certain requirements for the purity and surface ligands of quantum dot nanocrystals. Quantum dot nanocrystals with low purity or incompatible surface ligands will affect the performance of related applications. In different applications, the types of ligands required on the surface of quantum dots are also different. In the preparation process of quantum dots, there are residual anion and cation precursors and a large amount of organic solvents in the quantum dot solution. For the residual anion and cation precursors and organic solvents, there are corresponding technologies in the existing technology that can remove them; and some precursors can be coordinated on the surface of quantum dots, affecting the solubility, optical properties and application performance of quantum dots. When the residual anion and cation precursors and organic solvents are washed away, the ligands on the surface of quantum dots will also be washed away at the same time. In order to re-coordinate the washed ligands back to the quantum dots, or to coordinate other ligands, a long period of ligand exchange is required. The number and type of ligands on the surface of quantum dots will significantly affect their application effects. When preparing quantum dot fluorescent microspheres, it will significantly affect the amount of quantum dots deposited on the microspheres, thereby affecting the fluorescence intensity and service life of the microspheres. Therefore, it is very necessary to effectively remove residual anion and cation precursors and organic solvents in the quantum dot solution while ensuring that there are sufficient and suitable ligands on the surface of the quantum dots.

[0004] At present, the commonly used purification method for these residual anion and cation precursors and organic solvents is to extract the quantum dot stock solution or perform multiple precipitation-centrifugation processes to achieve the separation purpose. Multiple washing can clean the residual solvents and precursors, but at the same time, it will cause the ligands on the surface of the quantum dots to be cleaned. Although the purity of the quantum dots is improved, the lack of ligands on the surface greatly affects the effect of quantum dots on the surface of microspheres, which in turn affects the application performance of quantum dot fluorescent microspheres. In order to re-coordinate the washed ligands back to the quantum dots, use the original ligands of the quantum dots or coordinate other ligands, it is necessary to carry out long-term ligand exchange and re-purification, which requires a lot of time, energy and manpower. Therefore, it is of great application value to improve or develop a purification method that can simply and effectively separate quantum dot products and remove residual precursor impurities, but at the same time can retain ligands suitable for microsphere application on the surface of the quantum dots. Summary of the invention

[0005] The purpose of the present invention is to provide a simple quantum dot purification method, which can simultaneously achieve the purpose of quantum dot purification and quantum dot surface ligand exchange, aiming to solve the problem that the existing purification technology cannot quickly obtain relatively pure quantum dots containing specified ligands.

[0006] The quantum dots in the initial quantum dot solution are selected from at least one of single structure quantum dots and core-shell structure quantum dots, the single structure quantum dots are selected from at least one of II-VI group compounds, III-V group compounds and I-III-VI group compounds, the II-VI group compounds are selected from at least one of CdSe, CdS, CdTe, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdTeS, CdZnSeS, CdZnSeTe and CdZnSTe, the I The II-V group compounds are selected from at least one of InP, InAs, GaP, GaAs, GaSb, AlN, AlP, InAsP, InNP, InNSb, GaAlNP and InAlNP, and the I-III-VI group compounds are selected from at least one of CuInS2, CuInSe2 and AgInS2; the core of the core-shell structured quantum dots is selected from any one of the above-mentioned single structure quantum dots, and the shell material of the core-shell structured quantum dots is selected from at least one of CdS, CdTe, CdSeTe, CdZnSe, CdZnS, CdSeS, ZnSe, ZnSeS and ZnS.

[0007] The solvent in the synthesis system is 1-octadecene, and the residual reaction precursor is an alkyl carboxylic acid (at least one of acetic acid, propionic acid, butyric acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid); the sulfide element precursor in the system is selected from (tributylphosphine sulfide (S-Tributylphosphine), trioctylphosphine sulfide (S-Trioctylphosphine), 1-octadecene sulfide (S-1-Octadecene), tributylphosphine selenide (Se-Tributylphosphine), trioctylphosphine selenide (Se-TOP), 1-octadecene selenide (Se-1-Octadecene)); the metal cation salt in the system is selected from at least one of Zn2+, Cd2+, In3+, Ga2+, Al2+, Cu2+, Sb2+, Ag+, and Pb2+.

[0008] The quantum dot surface ligand is a long-chain organic carboxylic acid selected from at least one of acetic acid, propionic acid, butyric acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and oleic acid; the alkyl phosphine ligand is selected from at least one of tri-n-butylphosphine, tri-n-butylphosphine oxide, tri-n-octylphosphine, and tri-n-octylphosphine oxide; the metal cation salt is selected from Zn 2+ 、Cd 2+ 、In 3+ , Ga 2+ 、Al 2+ , Cu 2+ , Sb 2+ 、Ag + , Pb 2+ At least one of .

[0009] To achieve the purpose of the present invention, the present invention adopts the following technical solutions:

[0010] A quantum dot purification method suitable for quantum dot fluorescent microspheres, characterized in that the quantum dot purification method comprises the following steps:

[0011] (1) mixing a polar solvent and a quantum dot reaction stock solution, wherein the quantum dots are precipitated in the mixed solution due to the difference in polarity, and the quantum dot precipitate is obtained after solid-liquid separation by centrifugation;

[0012] (2) mixing a non-polar solvent and the quantum dot precipitate to obtain a first quantum dot solution;

[0013] (3) mixing the surface ligands with the first quantum dot solution obtained in step (2), wherein the volume ratio of the first quantum dot solution to the surface ligands is (1-4):1, and the mixing method is: heating the surface ligands to a predetermined temperature in a water bath and performing ultrasound to obtain a ligand-modified quantum dot mixed solution; the predetermined temperature may be 50° C.-80° C.;

[0014] (4) mixing a polar solvent with the quantum dot mixed solution obtained in step (3), centrifuging, and obtaining a quantum dot precipitate after solid-liquid separation;

[0015] (5) Repeat steps (2) to (4) several times;

[0016] (6) Mixing a non-polar solvent with the quantum dot precipitate obtained in step (5) to obtain a second quantum dot solution.

[0017] The surface ligands may be alkylamines with an alkyl length of 8-20, alkylthiols with an alkyl length of 2-16, alkylphosphines with an alkyl length of 4-10, etc.;

[0018] The polar solvent may be one or more of methanol, ethanol, isopropanol, methyl formate, propanol, butanol, acetonitrile, propylene glycol, glycerol, and acetone.

[0019] The non-polar solvent may be one of a straight-chain alkane with an alkyl length of 6-20, toluene, chloroform, benzene, carbon tetrachloride, cyclohexane, carbon disulfide, and dichloromethane.

[0020] Preferably, steps (2) to (4) are repeated 1 to 5 times.

[0021] Preferably, the ultrasonic power may be 100W.

[0022] Compared with the existing technology, the present invention adds ligands in the form of common solvents during the quantum dot purification process and cooperates with ultrasound of a certain power. At the same time, the ligands can further help clean out some precursor impurities, making the quantum dots more cleanly purified and allowing the quantum dots to have arbitrarily adjustable ligands on their surfaces.

[0023] In summary, the present invention proposes a method for purifying a quantum dot solution. By adding an excess of the required ligand during the purification, the required ligand can be coordinated on the surface of the quantum dots while purifying the quantum dots. The quantum dots obtained after multiple purifications not only have no weakening of fluorescence intensity but also have high purity and good solubility, which can avoid unpredictable effects on the application of quantum dot fluorescent microspheres, and also improve the repeatability of quantum dot fluorescent microspheres, effectively solving the problem of time-consuming and costly whole process of traditional quantum dot purification followed by ligand exchange. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0025] Comparative Example 1

[0026] (1) Existing conventional purification methods for quantum dots

[0027] 1. The system reacts in a 100ml three-necked flask. After the quantum dots are synthesized, the main components of the system are quantum dots, 1-octadecene, long-chain organic carboxylic acid, sulfide element precursor, and organic metal precursor. The temperature of the quantum dot reaction system solution (total volume of about 50 ml) after the reaction is completed is reduced from 310 degrees Celsius to 100 degrees Celsius, and poured into 4 50ml centrifuge tubes on average, with about 12.5ml in each centrifuge tube;

[0028] 2. Methanol, ethyl acetate and quantum dot stock solution were mixed in a volume ratio of 1:2:1, and the quantum dots were precipitated from the solution. The quantum dot precipitate was obtained after centrifugation;

[0029] 3. Use an appropriate amount of toluene to preserve the solution of the quantum dots precipitated in step 2.

[0030] (2) Purification effect and application performance testing

[0031] 1. Take 3 small glass bottles and weigh them respectively. Add 100 μL of purified quantum dot solution to each glass bottle and dry them in a vacuum drying oven. After cooling, weigh them again. The difference is W.

[0032] 2. The quantum dot solution is configured to the concentration and solvent conditions required for assembling fluorescent microspheres, quantum dot fluorescent microspheres are prepared, and the analysis and detection are performed by flow cytometry to obtain intensity data.

[0033] Comparative Example 2

[0034] (1) Existing conventional multiple purification methods for quantum dots

[0035] 1. The system reacts in a 100ml three-necked flask. After the quantum dots are synthesized, the main components of the system are quantum dots, 1-octadecene, long-chain organic carboxylic acid, sulfide element precursor, and organic metal precursor. The temperature of the quantum dot reaction system solution (total volume of about 50 ml) after the reaction is completed is reduced from 310 degrees Celsius to 100 degrees Celsius, and poured into 4 50ml centrifuge tubes on average, with about 12.5ml in each centrifuge tube;

[0036] 2. Methanol, ethyl acetate and quantum dot stock solution were mixed in a volume ratio of 1:2:1, and the quantum dots were precipitated from the solution. The quantum dot precipitate was obtained after centrifugation;

[0037] 3. The quantum dot precipitate obtained in step 2 was dissolved in 5 ml of non-polar solvent n-hexane, and methanol, ethyl acetate, and quantum dot n-hexane solution were mixed in a volume ratio of 1:2:1. The quantum dots precipitated from the solution and the quantum dot precipitate was obtained after centrifugation.

[0038] 4. Use an appropriate amount of toluene to preserve the solution of the quantum dots precipitated in step 3.

[0039] (2) Purification effect and application performance testing

[0040] 1. Take 3 small glass bottles and weigh them respectively. Add 100 μL of purified quantum dot solution to each glass bottle and dry them in a vacuum drying oven. After cooling, weigh them again. The difference is W.

[0041] 2. The quantum dot solution is configured to the concentration and solvent conditions required for assembling fluorescent microspheres, quantum dot fluorescent microspheres are prepared, and the analysis and detection are performed by flow cytometry to obtain intensity data.

[0042] Comparative Example 3

[0043] (1) Existing conventional purification methods and ligand exchange methods for quantum dots

[0044] 1. The system reacts in a 100ml three-necked flask. After the quantum dots are synthesized, the main components of the system are quantum dots, 1-octadecene, long-chain organic carboxylic acid, sulfide element precursor, and organic metal precursor. The temperature of the quantum dot reaction system solution (total volume of about 50 ml) after the reaction is completed is reduced from 310 degrees Celsius to 100 degrees Celsius, and poured into 4 50ml centrifuge tubes on average, with about 12.5ml in each centrifuge tube;

[0045] 2. Methanol, ethyl acetate and quantum dot stock solution were mixed in a volume ratio of 1:2:1, and the quantum dots were precipitated from the solution. The quantum dot precipitate was obtained after centrifugation;

[0046] 3. The quantum dot precipitate obtained in step 2 was dissolved in 5 ml of non-polar solvent n-hexane, and methanol, ethyl acetate, and quantum dot n-hexane solution were mixed in a volume ratio of 1:2:1. The quantum dots precipitated from the solution and the quantum dot precipitate was obtained after centrifugation.

[0047] 4. The separated quantum dots are dispersed and preserved again and the ligand is added: the purified quantum dots are added to 10 ml of 1-octadecene for dispersion, and 2 ml of oleic acid is added, a magnetic bar is put in, nitrogen is introduced to exhaust, the temperature is raised to 100 degrees, and after keeping warm for 3 hours, it is poured into a centrifuge tube, and methanol, ethyl acetate, and quantum dot oleic acid-octadecene solution are mixed in a volume ratio of 1:2:1. The quantum dots are precipitated from the solution and the quantum dot precipitate is obtained after centrifugation.

[0048] 5. Use an appropriate amount of toluene to preserve the solution of the quantum dots precipitated in step 3.

[0049] (2) Purification effect and application performance testing

[0050] 1. Take 3 small glass bottles and weigh them respectively. Add 100 μL of purified quantum dot solution to each glass bottle and dry them in a vacuum drying oven. After cooling, weigh them again. The difference is W.

[0051] 2. The quantum dot solution is configured to the concentration and solvent conditions required for assembling fluorescent microspheres, quantum dot fluorescent microspheres are prepared, and the analysis and detection are performed by flow cytometry to obtain intensity data.

[0052] Example 1

[0053] (1) Quantum dot purification and ligand exchange methods optimized by the present invention

[0054] 1. The system reacts in a 100ml three-necked flask. After the quantum dots are synthesized, the main components of the system are quantum dots, 1-octadecene, long-chain organic carboxylic acid, sulfide element precursor, and organic metal precursor. The temperature of the quantum dot reaction system solution (total volume of about 50 ml) after the reaction is completed is reduced from 310 degrees Celsius to 100 degrees Celsius, and poured into 4 50ml centrifuge tubes on average, with about 12.5ml in each centrifuge tube;

[0055] 2. Methanol, ethyl acetate and quantum dot stock solution were mixed in a volume ratio of 1:2:1, and the quantum dots were precipitated from the solution. The quantum dot precipitate was obtained after centrifugation;

[0056] 3. The obtained quantum dot precipitate was dissolved in 8 ml of n-hexane, and 1 ml of oleylamine and 1 ml of 1-dodecyl mercaptan were added to the quantum dot n-hexane solution to obtain a quantum dot solution. After ultrasonic treatment for 15 minutes using an ultrasonic cleaning machine (water temperature 50 degrees Celsius, power 100w), acetone and the quantum dot solution were mixed in a volume ratio of 1:2, and the quantum dot precipitate was obtained after centrifugation;

[0057] 4. Repeat step 3 once

[0058] 5. Use an appropriate amount of toluene to preserve the solution of the quantum dots precipitated in step 4.

[0059] (2) Purification effect and application performance testing

[0060] 1. Take 3 small glass bottles and weigh them respectively. Add 100 μL of purified quantum dot solution to each glass bottle and dry them in a vacuum drying oven. After cooling, weigh them again. The difference is W.

[0061] 2. The quantum dot solution is configured to the concentration and solvent conditions required for assembling fluorescent microspheres, quantum dot fluorescent microspheres are prepared, and the analysis and detection are performed by flow cytometry to obtain intensity data.

[0062] Example 2

[0063] (1) The invention optimizes the quantum dot purification and ligand exchange method to adjust the ratio of ligands

[0064] 1. The system reacts in a 100ml three-necked flask. After the quantum dots are synthesized, the main components of the system are quantum dots, 1-octadecene, long-chain organic carboxylic acid, sulfide element precursor, and organic metal precursor. The temperature of the quantum dot reaction system solution (total volume of about 50 ml) after the reaction is completed is reduced from 310 degrees Celsius to 100 degrees Celsius, and poured into 4 50ml centrifuge tubes on average, with about 12.5ml in each centrifuge tube;

[0065] 2. Methanol, ethyl acetate and quantum dot stock solution were mixed in a volume ratio of 1:2:1, and the quantum dots were precipitated from the solution. The quantum dot precipitate was obtained after centrifugation;

[0066] 3. The obtained quantum dot precipitate was dissolved in 8 ml of n-hexane, and 2 ml of oleylamine and 2 ml of 1-dodecyl mercaptan were added to the quantum dot n-hexane solution to obtain a quantum dot solution. After ultrasonic treatment for 15 minutes using an ultrasonic cleaning machine (water temperature 50 degrees Celsius, power 100w), acetone and the quantum dot solution were mixed in a volume ratio of 1:2, and the quantum dot precipitate was obtained after centrifugation;

[0067] 4. Repeat step 3 once

[0068] 5. Use an appropriate amount of toluene to preserve the solution of the quantum dots precipitated in step 4.

[0069] (2) Purification effect and application performance testing

[0070] 1. Take 3 small glass bottles and weigh them respectively. Add 100 μL of purified quantum dot solution to each glass bottle and dry them in a vacuum drying oven. After cooling, weigh them again. The difference is W.

[0071] 2. The quantum dot solution is configured to the concentration and solvent conditions required for assembling fluorescent microspheres, quantum dot fluorescent microspheres are prepared, and the analysis and detection are performed by flow cytometry to obtain intensity data.

[0072] Example 3

[0073] (1) The invention optimizes the quantum dot purification and ligand exchange method to adjust the ratio of ligands

[0074] 1. The system reacts in a 100ml three-necked flask. After the quantum dots are synthesized, the main components of the system are quantum dots, 1-octadecene, long-chain organic carboxylic acid, sulfide element precursor, and organic metal precursor. The temperature of the quantum dot reaction system solution (total volume of about 50 ml) after the reaction is completed is reduced from 310 degrees Celsius to 100 degrees Celsius, and poured into 4 50ml centrifuge tubes on average, with about 12.5ml in each centrifuge tube;

[0075] 2. Methanol, ethyl acetate and quantum dot stock solution were mixed in a volume ratio of 1:2:1, and the quantum dots were precipitated from the solution. The quantum dot precipitate was obtained after centrifugation;

[0076] 3. The obtained quantum dot precipitate was dissolved in 8 ml of n-hexane, and 4 ml of oleylamine and 4 ml of 1-dodecyl mercaptan were added to the quantum dot n-hexane solution to obtain a quantum dot solution. After ultrasonic treatment for 15 minutes using an ultrasonic cleaning machine (water temperature 50 degrees Celsius, power 100w), acetone and the quantum dot solution were mixed in a volume ratio of 1:2, and the quantum dot precipitate was obtained after centrifugation;

[0077] 4. Repeat step 3 once

[0078] 5. Use an appropriate amount of toluene to preserve the solution of the quantum dots precipitated in step 4.

[0079] (2) Purification effect and application performance testing

[0080] 1. Take 3 small glass bottles and weigh them respectively. Add 100 μL of purified quantum dot solution to each glass bottle and dry them in a vacuum drying oven. After cooling, weigh them again. The difference is W.

[0081] 2. The quantum dot solution is configured to the concentration and solvent conditions required for assembling fluorescent microspheres, quantum dot fluorescent microspheres are prepared, and the analysis and detection are performed by flow cytometry to obtain intensity data.

[0082] Example 4

[0083] (1) The invention optimizes the quantum dot purification and ligand exchange method and adjusts the exchange temperature

[0084] 1. The system reacts in a 100ml three-necked flask. After the quantum dots are synthesized, the main components of the system are quantum dots, 1-octadecene, long-chain organic carboxylic acid, sulfide element precursor, and organic metal precursor. The temperature of the quantum dot reaction system solution (total volume of about 50 ml) after the reaction is completed is reduced from 310 degrees Celsius to 100 degrees Celsius, and poured into 4 50ml centrifuge tubes on average, with about 12.5ml in each centrifuge tube;

[0085] 2. Methanol, ethyl acetate and quantum dot stock solution were mixed in a volume ratio of 1:2:1, and the quantum dots were precipitated from the solution. The quantum dot precipitate was obtained after centrifugation;

[0086] 3. The obtained quantum dot precipitate was dissolved in 8 ml of n-hexane, and 2 ml of oleylamine and 2 ml of 1-dodecyl mercaptan were added to the quantum dot n-hexane solution to obtain a quantum dot solution. After ultrasonic treatment for 15 minutes using an ultrasonic cleaning machine (water temperature 60 degrees Celsius, power 100w), acetone and the quantum dot solution were mixed in a volume ratio of 1:2, and the quantum dot precipitate was obtained after centrifugation;

[0087] 4. Repeat step 3 once

[0088] 5. Use an appropriate amount of toluene to preserve the solution of the quantum dots precipitated in step 4.

[0089] (2) Purification effect and application performance testing

[0090] 1. Take 3 small glass bottles and weigh them respectively. Add 100 μL of purified quantum dot solution to each glass bottle and dry them in a vacuum drying oven. After cooling, weigh them again. The difference is W.

[0091] 2. The quantum dot solution is configured to the concentration and solvent conditions required for assembling fluorescent microspheres, quantum dot fluorescent microspheres are prepared, and the analysis and detection are performed by flow cytometry to obtain intensity data.

[0092] Example 5

[0093] (1) The invention optimizes the quantum dot purification and ligand exchange method and adjusts the exchange temperature

[0094] 1. The system reacts in a 100ml three-necked flask. After the quantum dots are synthesized, the main components of the system are quantum dots, 1-octadecene, long-chain organic carboxylic acid, sulfide element precursor, and organic metal precursor. The temperature of the quantum dot reaction system solution (total volume of about 50 ml) after the reaction is completed is reduced from 310 degrees Celsius to 100 degrees Celsius, and poured into 4 50ml centrifuge tubes on average, with about 12.5ml in each centrifuge tube;

[0095] 2. Methanol, ethyl acetate and quantum dot stock solution were mixed in a volume ratio of 1:2:1, and the quantum dots were precipitated from the solution. The quantum dot precipitate was obtained after centrifugation;

[0096] 3. The obtained quantum dot precipitate was dissolved in 8 ml of n-hexane, and 2 ml of oleylamine and 2 ml of 1-dodecyl mercaptan were added to the quantum dot n-hexane solution to obtain a quantum dot solution. After ultrasonic treatment for 15 minutes using an ultrasonic cleaning machine (water temperature 70 degrees Celsius, power 100w), acetone and the quantum dot solution were mixed in a volume ratio of 1:2, and the quantum dot precipitate was obtained after centrifugation;

[0097] 4. Repeat step 3 once

[0098] 5. Use an appropriate amount of toluene to preserve the solution of the quantum dots precipitated in step 4.

[0099] (2) Purification effect and application performance testing

[0100] 1. Take 3 small glass bottles and weigh them respectively. Add 100 μL of purified quantum dot solution to each glass bottle and dry them in a vacuum drying oven. After cooling, weigh them again. The difference is W.

[0101] 2. The quantum dot solution is configured to the concentration and solvent conditions required for assembling fluorescent microspheres, quantum dot fluorescent microspheres are prepared, and the analysis and detection are performed by flow cytometry to obtain intensity data.

[0102] Example 6

[0103] (1) The invention optimizes the quantum dot purification and ligand exchange method and adjusts the exchange temperature

[0104] 1. The system reacts in a 100ml three-necked flask. After the quantum dots are synthesized, the main components of the system are quantum dots, 1-octadecene, long-chain organic carboxylic acid, sulfide element precursor, and organic metal precursor. The temperature of the quantum dot reaction system solution (total volume of about 50 ml) after the reaction is completed is reduced from 310 degrees Celsius to 100 degrees Celsius, and poured into 4 50ml centrifuge tubes on average, with about 12.5ml in each centrifuge tube;

[0105] 2. Methanol, ethyl acetate and quantum dot stock solution were mixed in a volume ratio of 1:2:1, and the quantum dots were precipitated from the solution. The quantum dot precipitate was obtained after centrifugation;

[0106] 3. The obtained quantum dot precipitate was dissolved in 8 ml of n-hexane, and 2 ml of oleylamine and 2 ml of 1-dodecyl mercaptan were added to the quantum dot n-hexane solution to obtain a quantum dot solution. After ultrasonic treatment for 15 minutes using an ultrasonic cleaning machine (water temperature 80 degrees Celsius, power 100w), acetone and the quantum dot solution were mixed in a volume ratio of 1:2, and the quantum dot precipitate was obtained after centrifugation;

[0107] 4. Repeat step 3 once

[0108] 5. Use an appropriate amount of toluene to preserve the solution of the quantum dots precipitated in step 4.

[0109] (2) Purification effect and application performance testing

[0110] 1. Take 3 small glass bottles and weigh them respectively. Add 100 μL of purified quantum dot solution to each glass bottle and dry them in a vacuum drying oven. After cooling, weigh them again. The difference is W.

[0111] 2. The quantum dot solution is configured to the concentration and solvent conditions required for assembling fluorescent microspheres, quantum dot fluorescent microspheres are prepared, and the analysis and detection are performed by flow cytometry to obtain intensity data.

[0112] The solids after drying the quantum dot solutions of Comparative Examples 1-3 and Examples 1-6 were weighed to obtain their dry weights, and the ligand content on the surface of the quantum dots can be qualitatively determined. The results are as follows:

[0113] Example Before drying avg. After drying avg. Dry weight Comparative Example 1 2536.7mg 2405.5mg 131.2mg Comparative Example 2 2514.4mg 2384.3mg 130.1mg Comparative Example 3 2543.6mg 2413.1mg 130.5mg Example 1 2522.6mg 2392.1mg 130.5mg Example 2 2563.3mg 2432.7mg 130.6mg Example 3 2501.3mg 2370.6mg 130.7mg Example 4 2517.5mg 2386.9mg 130.6mg Example 5 2596.2mg 2435.6mg 130.6mg Example 6 2578.6mg 2448.0mg 130.6mg

[0114] The quantum dot solutions of Comparative Examples 1-3 and Examples 1-6 were configured to the concentration and solvent conditions required for assembling fluorescent microspheres, quantum dot fluorescent microspheres were prepared, and analyzed and detected by flow cytometry. The results are as follows:

[0115] Example Microsphere CV Microsphere luminescence intensity Fluorescence noise interference Comparative Example 1 11.21％ 1,182,854 187 Comparative Example 2 6.18％ 781,617 205 Comparative Example 3 5.41％ 1,030,106 180 Example 1 5.85％ 1,754,039 161 Example 2 6.13％ 2,398,633 156 Example 3 14.80％ 3,708,837 503 Example 4 6.45％ 2,657,409 175 Example 5 7.46％ 2,475,953 166 Example 6 9.23％ 2,218,656 155

[0116] Quantum dots are evaluated by three indicators: quantum dot dry weight, quantum dot microsphere luminescence intensity, and microsphere CV. Fluorescence noise interference is mainly determined by the wavelength of quantum dots. The assembly capacity of quantum dots is mainly judged by CV and microsphere luminescence intensity. Under the same test conditions, the smaller the CV, the higher the fluorescence intensity, which proves that the quantum dot loading is better.

[0117] According to the experimental results measured in the above embodiments, the best results were obtained when the ultrasonic temperature was 60° C. and the ratio of quantum dot solution to ligand during the purification process was 2:1.

[0118] In summary, the present invention provides a method for purifying quantum dots. The method is simple to operate, uses alkylamines and alkylthiols to replace the ligands of the quantum dots themselves by ultrasound, and can adjust the type and quantity of ligands on the surface of the quantum dots as needed to obtain pure quantum dots with the ligands required for the application.

Claims

1. A method for purifying quantum dots suitable for use in quantum dot fluorescent microspheres, characterized in that: The quantum dot purification method comprises the following steps: (1) mixing a polar solvent and a quantum dot reaction stock solution, wherein the quantum dots are precipitated in the mixed solution due to the difference in polarity, and the quantum dot precipitate is obtained after solid-liquid separation by centrifugation; (2) mixing a non-polar solvent and the quantum dot precipitate to obtain a first quantum dot solution; (3) mixing the surface ligands with the first quantum dot solution obtained in step (2), wherein the volume ratio of the first quantum dot solution to the surface ligands is (1-4):1, and the mixing method is: heating the surface ligands to a predetermined temperature in a water bath and performing ultrasound to obtain a ligand-modified quantum dot mixed solution; the predetermined temperature may be 50° C.-80° C.; (4) mixing a polar solvent with the quantum dot mixed solution obtained in step (3), centrifuging, and obtaining a quantum dot precipitate after solid-liquid separation; (5) Repeat steps (2) to (4) several times; (6) Mixing a non-polar solvent with the quantum dot precipitate obtained in step (5) to obtain a second quantum dot solution.

2. A method for purifying quantum dots suitable for use in quantum dot fluorescent microspheres according to claim 1, characterized in that: The polar solvent may be one or more of methanol, ethanol, isopropanol, methyl formate, propanol, butanol, acetonitrile, propylene glycol, glycerol, and acetone.

3. A quantum dot purification method suitable for quantum dot fluorescent microspheres according to claim 1, characterized in that: The non-polar solvent may be one of a straight-chain alkane with an alkyl length of 6-20, toluene, chloroform, benzene, carbon tetrachloride, cyclohexane, carbon disulfide, and dichloromethane.

4. A method for purifying quantum dots suitable for use in quantum dot fluorescent microspheres according to claim 1, characterized in that: Repeat steps (2)-(4) 1-5 times.

5. The method for purifying quantum dots suitable for use in quantum dot fluorescent microspheres according to claim 1, characterized in that: The ultrasonic power was 100W.

6. A method for purifying quantum dots suitable for use in quantum dot fluorescent microspheres according to claim 1, characterized in that: The surface ligands include alkylamines with an alkyl length of 8-20, alkylthiols with an alkyl length of 2-16, and alkylphosphines with an alkyl length of 4-10.