CN113801654A

CN113801654A - Cleaning method and preparation method of quantum dots

Info

Publication number: CN113801654A
Application number: CN202111246931.6A
Authority: CN
Inventors: 孙培川; 宋斌; 梁凯旋; 姚琪
Original assignee: Hefei Funa Technology Co ltd
Current assignee: Hefei Funa Technology Co ltd
Priority date: 2021-10-26
Filing date: 2021-10-26
Publication date: 2021-12-17

Abstract

The application provides a cleaning method and a preparation method of quantum dots, and belongs to the technical field of quantum dots. The cleaning method of the quantum dots comprises the following steps: dispersing the quantum dots in a first non-coordination solvent, adding the first coordination solvent, and stirring and reacting at 80-120 ℃ for 20-40 min. The ligand of the quantum dot is tri-n-octyl phosphine oxide and/or octadecyl orthophosphate. The mole number of the first coordination solvent is 2-3 times of the mole number of the cation of the quantum dot. The first coordination solvent is oleic acid and/or zinc oleate. For the quantum dots with the ligands of tri-n-octylphosphine oxide and/or octadecyl orthophosphate, the method for cleaning the quantum dots adopts oleic acid and/or zinc oleate to exchange the ligands on the surfaces of the quantum dots, so that the ligands on the surfaces of the quantum dots become oleic acid and/or zinc oleate, and the cleaning yield of the quantum dots can be improved in the subsequent cleaning process.

Description

Cleaning method and preparation method of quantum dots

Technical Field

The application relates to the technical field of quantum dots, in particular to a quantum dot cleaning method and a preparation method.

Background

Quantum Dots (QDs), also known as semiconductor nanocrystals, are nanoparticles composed of elements of group II-VI or III-V, with a diameter of about 1-100 nm. The quantum dots have small sizes, so that the quantum dots have special small-size effect, surface effect, quantum size effect and macroscopic quantum tunneling effect. The quantum dots show unique optical characteristics, such as high quantum yield, long fluorescence lifetime, large extinction coefficient, strong light tolerance, narrow emission spectrum, wide excitation spectrum range and the like. The preparation and application of the quantum dots arouse extensive research interest of people and have wide application prospects in the fields of biomedicine and photoelectron.

The reaction system of the II-VI group or III-V group quantum dots is an oily system, and a large amount of organic ligands exist around the quantum dots, so that the agglomeration of the quantum dots is prevented and the surface defects of the quantum dots are reduced. In order to obtain monodisperse and uniform CdSe quantum dots, the reactivity of the precursor is usually controlled, and the cation precursors commonly used at present usually include cation-TOPO (tri-n-octylphosphine oxide), cation-ODPA (octadecyl orthophosphate), and cation-OA (oleic acid). When cation-TOPO (tri-n-octylphosphine oxide) and cation-ODPA (octadecyl orthophosphate) are used as precursors of cations, the cleaning yield of the obtained quantum dots is low.

Disclosure of Invention

The application provides a quantum dot cleaning method and a preparation method, which can improve the cleaning yield of quantum dots.

The embodiment of the application is realized as follows:

in a first aspect, the present application provides a method for cleaning quantum dots, including: dispersing the quantum dots in a first non-coordination solvent, adding the first coordination solvent, and stirring and reacting at 80-120 ℃ for 20-40 min.

The ligand of the quantum dot is tri-n-octyl phosphine oxide and/or octadecyl orthophosphate.

The mole number of the first coordination solvent is 2-3 times of the mole number of the cation of the quantum dot.

The first coordination solvent is oleic acid and/or zinc oleate.

In the technical scheme, for the quantum dots with the ligands of tri-n-octyl phosphine oxide and/or octadecyl orthophosphate, the method for cleaning the quantum dots adopts oleic acid and/or zinc oleate to exchange the ligands on the surfaces of the quantum dots, so that the ligands on the surfaces of the quantum dots are changed into oleic acid and/or zinc oleate, and the cleaning yield of the quantum dots can be improved in the subsequent cleaning process.

In a first possible example of the first aspect of the present application in combination with the first aspect, the quantum dots are ii-vi group quantum dots and/or iii-v group quantum dots.

In the above examples, the ligand exchange methods of the present application are applicable to group II-VI quantum dots and group III-V quantum dots.

In combination with the first aspect, in a second possible example of the first aspect of the present application, after the quantum dot is dispersed in the first non-coordinating solvent, the concentration of the cation of the quantum dot in the first non-coordinating solvent is 0.25 to 0.5 mol/L.

In a third possible example of the first aspect of the present application in combination with the first aspect, the first non-coordinating solvent includes any one or more of octadecene, n-hexane, n-octane, and chloroform.

In a fourth possible example of the first aspect of the present application in combination with the first aspect, the above reaction is performed under an inert gas atmosphere.

In the above example, performing the above reaction under an inert gas atmosphere is advantageous for maintaining the stability of the quantum dots.

With reference to the first aspect, in a fifth possible example of the first aspect of the present application, after stirring and reacting at 80 to 120 ℃ for 20 to 40min, adding a nonpolar solvent and a polar solvent to the prepared first solution, performing centrifugal precipitation to obtain a first precipitate, dispersing the first precipitate in the nonpolar solvent, performing centrifugal impurity removal to obtain a supernatant, adding the polar solvent to the supernatant, performing centrifugal precipitation to obtain a second precipitate, and dispersing the second precipitate in a target solvent to obtain quantum dots dispersed in the target solvent.

In a fifth possible example of the first aspect of the present application in combination with the first aspect, optionally, the volume ratio of the non-polar solvent to the first solution is 0.8-1.2: 1.

In a fifth possible example of the first aspect of the present application in combination with the first aspect, optionally, the volume ratio of the polar solvent to the first solution is 2-2.5: 1.

In a fifth possible example of the first aspect of the present application in combination with the first aspect, optionally, the non-polar solvent comprises any one or more of n-hexane, cyclohexane and ethyl acetate.

In a fifth possible example of the first aspect of the present application in combination with the first aspect, optionally, the polar solvent comprises an alcoholic solvent.

In the above example, the quantum dot cleaning method of the present application precipitates the ligand-exchanged quantum dots by coordination of the polar solvent and the nonpolar solvent, dissolves the quantum dot precipitate in the nonpolar solvent, removes other components except the nonpolar solvent in the quantum dot solution by centrifugation, and precipitates the quantum dots by coordination of the polar solvent and the nonpolar solvent.

In a second aspect, the present application provides a method for preparing quantum dots, which comprises preparing quantum dots, and cleaning the quantum dots according to the method for cleaning quantum dots, wherein the quantum dots are prepared by the following steps:

mixing the precursor solution containing the cations and the precursor solution containing the anions, preserving the heat at 280-310 ℃ to form a reaction solution with quantum dot nanocrystal cores, detecting the wavelength of quantum dots in the reaction solution to move to a target position, stopping the reaction to prepare a solution containing the quantum dots, and carrying out centrifugal precipitation on the solution containing the quantum dots to prepare the quantum dots.

The precursor solution containing the cations comprises a second coordination solvent, and the second coordination solvent is tri-n-octyl phosphine oxide and/or octadecyl orthophosphate.

In the technical scheme, the preparation method of the quantum dots can prepare stable quantum dots, and meanwhile, the yield of the quantum dots is improved.

In combination with the second aspect, in a first possible example of the second aspect of the present application, the number of moles of cations in the cation-containing precursor solution is 1.1 to 1.5 times the number of moles of anions in the anion-containing precursor solution.

In the above examples, in preparing a solution containing quantum dots, the formation of quantum dots is generally facilitated by preparing a cation in excess of an anion.

In a second possible example of the second aspect of the present application in combination with the second aspect, the above-mentioned cation-containing precursor solution is prepared by:

mixing the precursor containing the cation, a second coordination solvent and a second non-coordination solvent, and reacting for 0.5-3 h at 100-180 ℃.

In combination with the second aspect, in a second possible example of the second aspect of the present application, optionally, the number of moles of the second non-coordinating solvent is 2 to 3 times the number of moles of the cation in the cation-containing precursor.

In combination with the second aspect, in a second possible example of the second aspect of the present application, optionally, a molar volume ratio of the cation in the cation-containing precursor and the second coordinating solvent is 0.25 to 0.5:1 mol/L.

In a third possible example of the second aspect of the present application, in combination with the second aspect, the method for performing centrifugal precipitation on the solution of the quantum dots includes: and adding a nonpolar solvent and a polar solvent into the solution of the quantum dots, and performing centrifugal precipitation to obtain the quantum dots.

In the above example, the method for preparing quantum dots of the present application precipitates quantum dots in a quantum dot solution by coordination of a polar solvent and a nonpolar solvent.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.

FIG. 1 is a quantum dot with octadecyl orthophosphate as a ligand in the embodiment of the application;

FIG. 2 is a quantum dot with tri-n-octylphosphine oxide as a ligand in an example of the present application;

FIG. 3 is a quantum dot with zinc oleate as ligand in the present application;

fig. 4 is a quantum dot with oleic acid as a ligand in the examples of the present application.

Detailed Description

Embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

The following description is made specifically for a method for cleaning and a method for preparing a quantum dot in the embodiments of the present application:

the application provides a quantum dot cleaning method, which comprises the following steps: dispersing the quantum dots in a first non-coordinating solvent, adding the first coordinating solvent, and stirring for reaction.

Wherein, the ligand of the quantum dot is tri-n-octyl phosphine oxide and/or octadecyl orthophosphate.

The first coordination solvent is oleic acid and/or zinc oleate.

The cleaning yield of the quantum dots prepared by using the cation-OA (oleic acid) as the precursor of the cation is higher than that of the quantum dots prepared by using the cation-TOPO (tri-n-octyl phosphine oxide) and/or the cation-ODPA (octadecyl orthophosphate) as the precursor of the cation. Namely, the cleaning yield of the quantum dot-OA is higher than that of the quantum dot-TOPO and/or quantum dot-ODPA.

The inventors found that this is due to the difference of the ligands on the surface of the quantum dots caused by different systems, and TOPO and ODPA are present in solid form at normal temperature. When a large amount of TOPO and ODPA ligands exist on the surface of the quantum dot, the quantum dot is easily deposited and is difficult to disperse during the cleaning process, eventually resulting in a difference between cleaning yields of the quantum dot.

When the ligand of the prepared quantum dot is TOPO or ODPA, the structures of the quantum dot and the ligand are shown in figures 1 and 2. The method for cleaning the quantum dots adopts oleic acid and/or zinc oleate to exchange ligands on the surfaces of the quantum dots, so that the ligands on the surfaces of the quantum dots are changed into oleic acid and/or zinc oleate, as shown in fig. 3 and 4. In the subsequent cleaning process, the cleaning yield of the quantum dots can be improved.

The first coordination solvent used in the method for cleaning the quantum dots may be oleic acid or zinc oleate liquid alone, or may be a mixture of oleic acid and zinc oleate mixed in any ratio.

Optionally, the first coordinating solvent is zinc oleate.

The quantum dots are II-VI group quantum dots and/or III-V group quantum dots.

For example, for ii-vi quantum dots, the quantum dots suitable for the cleaning method of quantum dots of the present application include ZnS, ZnSe, ZnTe, CdS, CdSe, or CdTe;

for III-V group quantum dots, quantum dots suitable for the quantum dot cleaning method comprise InP, AlAs, GaP, GaAs or InAs.

The first non-coordinating solvent comprises any one or more of octadecene, n-hexane, n-octane, and chloroform.

Optionally, the first non-coordinating solvent is octadecene.

In one embodiment of the present application, the first non-coordinating solvent is octadecene. In some other embodiments of the present application, the first non-coordinating solvent may also be n-hexane, n-octane, or chloroform, or a mixture of octadecene and n-hexane, or a mixture of octadecene and n-octane, or a mixture of n-hexane, n-octane, and chloroform.

The concentration of the cation of the quantum dot in the first non-coordinating solvent is 0.25-0.5 mol/L.

In one embodiment of the present application, after the quantum dot and the first non-coordinating solvent are mixed, the concentration of the cation of the quantum dot in the first non-coordinating solvent is 0.5 mol/L. In some other embodiments of the present application, the concentration of the cation of the quantum dot in the first non-coordinating solvent may also be 0.25mol/L, 0.3mol/L, 0.35mol/L, 0.4mol/L, or 0.45 mol/L.

It should be noted that the cation of the quantum dot in the present application does not refer to a free cation, but all cations present in any form in the whole system.

In one embodiment of the present application, the number of moles of the first coordinating solvent is 2.5 times the number of moles of the cation of the quantum dot. In some other embodiments of the present application, the number of moles of the first coordinating solvent is 2, 2.1, 2.2, 2.3, 2.4, 2.6, 2.7, 2.8, 2.9, or 3 times the number of moles of the cation of the quantum dot.

The temperature of the ligand exchange reaction of the quantum dots is 80-120 ℃.

In one embodiment of the present application, the temperature of the ligand exchange reaction of the quantum dots is 100 ℃. In some other embodiments of the present application, the temperature of the ligand exchange reaction of the quantum dot may be 80 ℃, 85 ℃, 90 ℃, 95 ℃, 105 ℃, 110 ℃, 115 ℃ or 120 ℃.

The time of the ligand exchange reaction of the quantum dots is 20-40 min.

In one embodiment of the present application, the time of the ligand exchange reaction of the quantum dot is 30 min. In other embodiments of the present application, the time for the ligand exchange reaction of the quantum dot may be 20min, 25min, 35min, or 40 min.

The ligand exchange reaction of the quantum dots is performed under an inert gas atmosphere.

After the ligand exchange reaction of the quantum dots is completed, adding a nonpolar solvent and a polar solvent into the prepared first solution, carrying out centrifugal precipitation to obtain a first precipitate, dispersing the first precipitate in the nonpolar solvent, carrying out centrifugal impurity removal to obtain a supernatant, adding the polar solvent into the supernatant, carrying out centrifugal precipitation to obtain a second precipitate, dispersing the second precipitate in a target solvent, and preparing the quantum dots dispersed in the target solvent.

The method for cleaning the quantum dots enables the quantum dots subjected to ligand exchange to be precipitated through the coordination of the polar solvent and the nonpolar solvent, then the quantum dot precipitates are dissolved in the nonpolar solvent to obtain the quantum dot precipitates, other components except the nonpolar solvent in a quantum dot solution are removed through a centrifugal mode, and then the quantum dots are precipitated through the coordination of the polar solvent and the nonpolar solvent.

The volume ratio of the nonpolar solvent to the first solution is 0.8-1.2: 1.

In one embodiment of the present application, the volume ratio of the non-polar solvent to the first solution is 1: 1. In other embodiments of the present application, the volume ratio of the non-polar solvent to the first solution is 0.8:1, 0.9:1, 1.1:1, or 1.2: 1.

The volume ratio of the polar solvent to the first solution is 2-2.5: 1.

In one embodiment of the present application, the volume ratio of the polar solvent to the first solution is 2: 1. In other embodiments of the present application, the volume ratio of the polar solvent to the first solution is 2.1:1, 2.2:1, 2.3:1, 2.4:1, or 2.5: 1.

The non-polar solvent includes any one or more of n-hexane, cyclohexane and ethyl acetate.

In one embodiment herein, the nonpolar solvent is n-hexane. In other embodiments of the present application, the non-polar solvent may also be cyclohexane or ethyl acetate, or a mixture of n-hexane and cyclohexane, or a mixture of n-hexane and ethyl acetate, or a mixture of cyclohexane and ethyl acetate, or a mixture of n-hexane, cyclohexane and ethyl acetate.

Polar solvents include alcoholic solvents.

In one embodiment of the present application, the polar solvent is absolute ethanol. In some other embodiments herein, the polar solvent is methanol, propylene glycol or glycerol, or a mixture of methanol and ethanol, or a mixture of methanol and propylene glycol, or a mixture of propylene glycol and glycerol, or a mixture of ethanol and glycerol.

The application also provides a preparation method of the quantum dot, which comprises the following steps: and preparing the quantum dots, and cleaning the quantum dots according to the cleaning method of the quantum dots.

The method for preparing the quantum dots comprises the following steps:

mixing a precursor solution containing cations and a precursor solution containing anions, preserving heat at 280-310 ℃ to form a reaction solution with quantum dot nanocrystal cores, detecting that the wavelength of quantum dots in the reaction solution moves to a target position, stopping the reaction to prepare a solution containing the quantum dots, adding a nonpolar solvent and a polar solvent into the solution containing the quantum dots, and performing centrifugal precipitation to obtain the quantum dots.

The mole number of the cations in the precursor solution containing the cations is 1.1 to 1.5 times of that of the anions in the precursor solution containing the anions.

In the preparation of a solution containing quantum dots, the formation of quantum dots is generally facilitated by preparing so that the cation phase is in excess compared to the anion phase.

In one embodiment of the present application, the number of moles of cations in the cation-containing precursor solution is 1.2 times the number of moles of anions in the anion-containing precursor solution. In other embodiments of the present application, the number of moles of cations in the cation-containing precursor solution may also be 1.1, 1.3, 1.4, or 1.5 times the number of moles of anions in the anion-containing precursor solution.

Both the cation-containing precursor solution and the anion-containing precursor solution can be prepared by themselves or purchased.

Wherein the precursor solution containing the cations is prepared by the following method:

The number of moles of the second non-coordinating solvent is 2 to 3 times the number of moles of the cation in the cation-containing precursor.

The molar volume ratio of the cation in the precursor containing the cation to the second coordination solvent is 0.25-0.5: 1 mol/L.

The second non-coordinating solvent comprises any one or more of octadecene, n-hexane, n-octane and chloroform.

Optionally, the second non-coordinating solvent is octadecene.

The precursor solution containing anions is prepared by the following method:

uniformly mixing the anionic solid simple substance and a coordination solvent tri-n-octylphosphorus in a molar volume ratio of 1-2: 1mol/L, stirring and heating until the solution is clear.

The preparation reaction of the quantum dots is carried out in an inert gas atmosphere.

The following describes a method for cleaning and a method for preparing a quantum dot in detail with reference to the following examples.

Example 1

The embodiment of the application provides a preparation method of quantum dots, which comprises the following steps:

1. preparation of Quantum dots

Adding 1.5mmol of cadmium oxide, 3mmol of octadecyl orthophosphate and 20mL of octadecene into a three-necked bottle, introducing argon into the three-necked bottle at room temperature for purging for 20min, heating the three-necked bottle to 110 ℃ at the heating rate of 20 ℃/min, and keeping the temperature for 30 min. And then heating to 300 ℃, quickly injecting 1.0mmol of selenium simple substance-tri-n-octylphosphonium solution below the liquid surface of the three-necked bottle to form reaction liquid with quantum dot nanocrystal cores, detecting that the wavelength of the quantum dots in the reaction liquid moves to 530nm, and stopping the reaction to prepare the solution containing the quantum dots.

And (3) when the solution containing the quantum dots is cooled to 100 ℃, mixing the solution containing the quantum dots with 50mL of absolute ethyl alcohol and 25mL of n-hexane, and carrying out centrifugal precipitation to obtain the quantum dots.

2. Ligand exchange of quantum dots

The resulting centrifugal precipitate was dispersed in 5mL of octadecene, 2mL of oleic acid was added, and the mixture was stirred at 100 ℃ for 30min to prepare a first solution.

3. Cleaning of

Adding 14mL of anhydrous ethanol and 7mL of n-hexane into the prepared first solution, carrying out centrifugal precipitation to obtain a first precipitate, dispersing the first precipitate in 5mL of n-hexane, carrying out centrifugal impurity removal to obtain a supernatant, adding 5mL of anhydrous ethanol into the supernatant, carrying out centrifugal precipitation to obtain a second precipitate, dispersing the second precipitate in 5mL of n-hexane, and preparing the CdSe quantum dots dispersed in the n-hexane.

Example 2

1. preparation of Quantum dots

Adding 1.5mmol of cadmium oxide, 3mmol of tri-n-octylphosphine oxide and 20mL of octadecene into a three-necked bottle, introducing argon into the three-necked bottle at room temperature for purging for 20min, heating the three-necked bottle to 110 ℃ at the heating rate of 20 ℃/min, and keeping the temperature for 30 min. And then heating to 300 ℃, quickly injecting 1.0mmol of selenium simple substance-tri-n-octylphosphonium solution below the liquid surface of the three-necked bottle to form reaction liquid with quantum dot nanocrystal cores, detecting that the wavelength of the quantum dots in the reaction liquid moves to 530nm, and stopping the reaction to prepare the solution containing the quantum dots.

And (3) when the solution containing the quantum dots is cooled to 100 ℃, mixing the solution containing the quantum dots with 40mL of absolute ethyl alcohol and 20mL of n-hexane, and carrying out centrifugal precipitation to obtain the quantum dots.

2. Ligand exchange of quantum dots

Adding 2mmol of zinc acetate, 2mL of oleic acid and 8mL of octadecene into a three-necked bottle, introducing argon into the three-necked bottle at room temperature for purging for 20min, heating the three-necked bottle to 180 ℃ at the heating rate of 20 ℃/min, preserving heat for 30min, and cooling to 100 ℃ to obtain a zinc oleate precursor. Dispersing the prepared centrifugal precipitate into 5mL of octadecene, injecting into a zinc oleate precursor, and stirring at 100 ℃ for 30min to prepare a first solution.

3. Cleaning of

And adding 30mL of anhydrous ethanol and 15mL of n-hexane into the prepared first solution, performing centrifugal precipitation to obtain a first precipitate, dispersing the first precipitate in 5mL of n-hexane, performing centrifugal impurity removal to obtain a supernatant, adding 5mL of anhydrous ethanol into the supernatant, performing centrifugal precipitation to obtain a second precipitate, and dispersing the second precipitate in 5mL of n-hexane to obtain the CdSe quantum dots dispersed in the n-hexane.

Example 3

1. preparation of Quantum dots

2. Ligand exchange of quantum dots

The resulting centrifugal precipitate was dispersed in 5mL of octadecene, 2mL of oleic acid was added, and the mixture was stirred at 80 ℃ for 40min to prepare a first solution.

3. Cleaning of

Example 4

1. preparation of Quantum dots

2. Ligand exchange of quantum dots

Adding 2mmol of zinc acetate, 2mL of oleic acid and 8mL of octadecene into a three-necked bottle, introducing argon into the three-necked bottle at room temperature for purging for 20min, heating the three-necked bottle to 180 ℃ at the heating rate of 20 ℃/min, preserving heat for 30min, and cooling to 100 ℃ to obtain a zinc oleate precursor. Dispersing the prepared centrifugal precipitate into 5mL of octadecene, injecting into a zinc oleate precursor, and stirring at 120 ℃ for 20min to prepare a first solution.

3. Cleaning of

Example 5

1. preparation of Quantum dots

Adding 1.5mmol of cadmium oxide, 3mmol of octadecyl orthophosphate and 20mL of octadecene into a three-necked bottle, introducing argon into the three-necked bottle at room temperature for purging for 20min, heating the three-necked bottle to 110 ℃ at the heating rate of 20 ℃/min, and keeping the temperature for 30 min. And then heating to 300 ℃, quickly injecting 1.0mmol of elemental sulfur-tri-n-octylphosphine under the liquid surface of the three-necked bottle to form a reaction solution with quantum dot nanocrystal cores, detecting that the wavelength of the quantum dots in the reaction solution moves to 530nm, and stopping the reaction to prepare the solution containing the quantum dots.

2. Ligand exchange of quantum dots

Adding 2mmol of zinc acetate, 2mL of oleic acid and 8mL of octadecene into a three-necked bottle, introducing argon into the three-necked bottle at room temperature for purging for 20min, heating the three-necked bottle to 180 ℃ at the heating rate of 20 ℃/min, preserving heat for 30min, and cooling to 100 ℃ to obtain a zinc oleate precursor. And dispersing the prepared centrifugal precipitate in 5mL of octadecene, and injecting the obtained centrifugal precipitate into a zinc oleate precursor. Stirring at 100 deg.C for 30min to obtain a first solution.

3. Cleaning of

Adding 30mL of anhydrous ethanol and 15mL of n-hexane into the prepared first solution, carrying out centrifugal precipitation to obtain a first precipitate, dispersing the first precipitate in 5mL of n-hexane, carrying out centrifugal impurity removal to obtain a supernatant, adding 5mL of anhydrous ethanol into the supernatant, carrying out centrifugal precipitation to obtain a second precipitate, dispersing the second precipitate in 5mL of n-hexane, and preparing the CdS quantum dots dispersed in the n-hexane.

Example 6

1. preparation of Quantum dots

Adding 1.5mmol of cadmium oxide, 3mmol of octadecyl orthophosphate and 20mL of octadecene into a three-necked bottle, introducing argon into the three-necked bottle at room temperature for purging for 20min, heating the three-necked bottle to 110 ℃ at the heating rate of 20 ℃/min, and keeping the temperature for 30 min. And then heating to 300 ℃, quickly injecting 1.0mmol of tellurium simple substance-tributyl phosphate under the liquid surface of the three-necked bottle to form a reaction liquid with quantum dot nanocrystal cores, detecting that the wavelength of the quantum dots in the reaction liquid moves to 530nm, and stopping the reaction to prepare a solution containing CdTe quantum dots.

2. Ligand exchange of quantum dots

3. Cleaning of

Adding 30mL of anhydrous ethanol and 15mL of n-hexane into the prepared first solution, carrying out centrifugal precipitation to obtain a first precipitate, dispersing the first precipitate in 5mL of n-hexane, carrying out centrifugal impurity removal to obtain a supernatant, adding 5mL of anhydrous ethanol into the supernatant, carrying out centrifugal precipitation to obtain a second precipitate, dispersing the second precipitate in 5mL of n-hexane, and preparing the CdTe quantum dots dispersed in the n-hexane.

Example 7

1. preparation of Quantum dots

Adding 1.5mmol of indium acetate, 3mmol of octadecyl orthophosphate and 20mL of octadecene into a three-necked bottle, introducing argon into the three-necked bottle at room temperature for purging for 20min, heating the three-necked bottle to 110 ℃ at the heating rate of 20 ℃/min, and keeping the temperature for 30 min. Then the temperature is raised to 300 ℃, 1.0mmol of tri (trimethylsilyl) phosphine tri-n-octylphosphine solution is quickly injected under the liquid surface of the three-necked bottle to form reaction liquid with quantum dot nanocrystal cores, and the reaction is stopped after the wavelength of quantum dots in the reaction liquid is detected to move to 530nm, so that the solution containing the quantum dots is prepared.

2. Ligand exchange of quantum dots

3. Cleaning of

Adding 30mL of anhydrous ethanol and 15mL of n-hexane into the prepared first solution, carrying out centrifugal precipitation to obtain a first precipitate, dispersing the first precipitate in 5mL of n-hexane, carrying out centrifugal impurity removal to obtain a supernatant, adding 5mL of anhydrous ethanol into the supernatant, carrying out centrifugal precipitation to obtain a second precipitate, dispersing the second precipitate in 5mL of n-hexane, and preparing the InP quantum dots dispersed in n-hexane.

Comparative example 1

The comparative example of the application provides a preparation method of quantum dots, which comprises the following steps:

1. preparation of Quantum dots

2. Cleaning of

Dispersing the quantum dots in 5mL of n-hexane, carrying out centrifugal impurity removal to obtain a supernatant, adding 5mL of absolute ethyl alcohol into the supernatant, carrying out centrifugal precipitation to obtain a second precipitate, and dispersing the second precipitate in 10mL of n-hexane to obtain the CdSe quantum dots dispersed in the n-hexane.

Comparative example 2

1. preparation of Quantum dots

2. Cleaning of

Dispersing the quantum dots in 5mL of n-hexane, carrying out centrifugal impurity removal to obtain a supernatant, adding 5mL of absolute ethyl alcohol into the supernatant, carrying out centrifugal precipitation to obtain a second precipitate, and dispersing the second precipitate in 5mL of n-hexane to obtain the CdS quantum dots dispersed in the n-hexane.

Comparative example 3

1. preparation of Quantum dots

Adding 1.5mmol of cadmium oxide, 3mmol of octadecyl orthophosphate and 20mL of octadecene into a three-necked bottle, introducing argon into the three-necked bottle at room temperature for purging for 20min, heating the three-necked bottle to 110 ℃ at the heating rate of 20 ℃/min, and keeping the temperature for 30 min. And then heating to 300 ℃, quickly injecting 1.0mmol of tellurium simple substance-tributyl phosphate under the liquid surface of the three-necked bottle to form a reaction liquid with quantum dot nanocrystal cores, detecting that the wavelength of the quantum dots in the reaction liquid moves to 530nm, and stopping the reaction to prepare the solution containing the quantum dots.

2. Cleaning of

Dispersing the quantum dots in 5mL of n-hexane, carrying out centrifugal impurity removal to obtain a supernatant, adding 5mL of absolute ethyl alcohol into the supernatant, carrying out centrifugal precipitation to obtain a second precipitate, and dispersing the second precipitate in 5mL of n-hexane to obtain the CdTe quantum dots dispersed in n-hexane.

Comparative example 4

1. preparation of Quantum dots

2. Cleaning of

Dispersing the quantum dots in 5mL of n-hexane, carrying out centrifugal impurity removal to obtain a supernatant, adding 5mL of absolute ethyl alcohol into the supernatant, carrying out centrifugal precipitation to obtain a second precipitate, and dispersing the second precipitate in 5mL of n-hexane to obtain the InP quantum dots dispersed in n-hexane.

Comparative example 5

1. preparation of Quantum dots

2. Ligand exchange of quantum dots

The resulting centrifugal precipitate was dispersed in 5mL of octadecene, 2mL of oleic acid was added, and the mixture was stirred at 70 ℃ for 30min to prepare a first solution.

3. Cleaning of

Comparative example 6

1. preparation of Quantum dots

2. Ligand exchange of quantum dots

The resulting centrifugal precipitate was dispersed in 5mL of octadecene, 2mL of oleic acid was added, and the mixture was stirred at 130 ℃ for 30min to prepare a first solution.

3. Cleaning of

Test example 1

The wavelength and the cleaning yield of the quantum dots cleaned in the examples 1 to 7 and the comparative examples 1 to 6 were measured, as shown in table 1:

wherein the calculation formula of the cleaning yield is as follows:

the yield of the washing is the actual mass after washing/the theoretical mass produced.

TABLE 1 wavelength and cleaning yield of quantum dots after cleaning for examples 1-7 and comparative examples 1-6

As can be seen from the comparison of examples 1, 2, 5 to 7 and comparative examples 1 to 4, the reaction stock solution of quantum dots without ligand exchange lost a large amount of quantum dots after washing. In the quantum dot using the oleic acid for ligand exchange, because the tri-n-octylphosphine oxide or octadecyl orthophosphate ligand on the surface is replaced by the oleic acid ligand, the washed quantum dot is blue-shifted to a certain extent, and the washing yield is improved to a certain extent. In the quantum dot using zinc oleate for ligand exchange, because the tri-n-octylphosphine oxide or octadecyl orthophosphate ligand on the surface is replaced by the zinc oleate ligand which is easy to clean and separate, the quantum dot generates blue shift, and the cleaning yield is greatly improved. And oleic acid can be subjected to simple ligand exchange, but the exchange efficiency is low, so that the final cleaning yield is not greatly improved, but zinc ions in the zinc oleate and Cd ions or other cations on the surfaces of the quantum dots can generate a replacement process, so that ligands in a Zn-OA form are formed on the surfaces, more blue shifts are generated, and the cleaning yield is greatly improved.

As can be seen from the comparison of example 1 with comparative examples 5 to 6, the cleaning yield slightly decreased when the temperature at which the ligand exchange was carried out was increased or decreased.

The foregoing is illustrative of the present application and is not to be construed as limiting thereof, as numerous modifications and variations will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for cleaning quantum dots is characterized by comprising the following steps: dispersing the quantum dots in a first non-coordination solvent, adding the first coordination solvent, and stirring and reacting at 80-120 ℃ for 20-40 min;

the ligand of the quantum dot is tri-n-octyl phosphine oxide and/or octadecyl orthophosphate;

the mole number of the first coordination solvent is 2-3 times of that of the cation of the quantum dot;

the first coordination solvent is oleic acid and/or zinc oleate.

2. The method for cleaning the quantum dots according to claim 1, wherein the quantum dots are II-VI quantum dots and/or III-V quantum dots.

3. The method for cleaning the quantum dots according to claim 1, wherein after the quantum dots are dispersed in the first non-coordinating solvent, the concentration of the cations of the quantum dots in the first non-coordinating solvent is 0.25-0.5 mol/L.

4. The method for cleaning the quantum dots according to claim 1, wherein the first non-coordinating solvent comprises any one or more of octadecene, n-hexane, n-octane and chloroform.

5. The method for cleaning a quantum dot according to claim 1, wherein the reaction is performed under an inert gas atmosphere.

6. The method for cleaning the quantum dots according to any one of claims 1 to 5, wherein after the stirring reaction at 80 to 120 ℃ for 20 to 40min, a nonpolar solvent and a polar solvent are added to the prepared first solution, and centrifugal precipitation is performed to obtain a first precipitate, the first precipitate is dispersed in the nonpolar solvent to perform centrifugal impurity removal to obtain a supernatant, the polar solvent is added to the supernatant to perform centrifugal precipitation to obtain a second precipitate, and the second precipitate is dispersed in a target solvent to prepare the quantum dots dispersed in the target solvent;

optionally, the volume ratio of the non-polar solvent to the first solution is 0.8-1.2: 1;

optionally, the volume ratio of the polar solvent to the first solution is 2-2.5: 1;

optionally, the non-polar solvent comprises any one or more of n-hexane, cyclohexane and ethyl acetate;

optionally, the polar solvent comprises an alcoholic solvent.

7. A preparation method of quantum dots, which is characterized in that the preparation method of the quantum dots comprises the steps of preparing the quantum dots, and cleaning the quantum dots according to the cleaning method of the quantum dots as claimed in any one of claims 1 to 6, wherein the quantum dots are prepared by the following steps:

mixing a precursor solution containing cations and a precursor solution containing anions, preserving heat at 280-310 ℃ to form a reaction solution with quantum dot nanocrystal cores, detecting that the wavelength of quantum dots in the reaction solution moves to a target position, stopping reaction to prepare a solution containing the quantum dots, and performing centrifugal precipitation on the solution containing the quantum dots to prepare the quantum dots;

8. The method according to claim 7, wherein the number of moles of cations in the cation-containing precursor solution is 1.1 to 1.5 times the number of moles of anions in the anion-containing precursor solution.

9. The method for preparing a quantum dot according to claim 7, wherein the precursor solution containing cations is prepared by:

mixing a precursor containing cations, the second coordination solvent and the second non-coordination solvent, and reacting at 100-180 ℃ for 0.5-3 h;

optionally, the number of moles of the second non-coordinating solvent is 2 to 3 times the number of moles of the cations in the cation-containing precursor;

optionally, the molar volume ratio of the cation in the cation-containing precursor to the second coordinating solvent is 0.25-0.5: 1 mol/L.

10. The method for preparing quantum dots according to claim 7, wherein the method for performing centrifugal precipitation on the solution of quantum dots comprises: and adding a nonpolar solvent and a polar solvent into the solution of the quantum dots, and performing centrifugal precipitation to obtain the quantum dots.