阅读说明：本技术 量子点的提纯方法 (Purification method of quantum dots ) 是由 陈开敏 杨一行 于 2019-11-01 设计创作，主要内容包括：本发明属于量子点工艺技术领域,具体涉及一种量子点的提纯方法。该提纯方法包括如下步骤：提供初始油溶性量子点溶液；将第一溶剂和第二溶剂加入所述初始油溶性量子点溶液中混合,进行离心处理,去上清后得到沉淀物；将所述沉淀物溶解在第三溶剂中,得到量子点溶液；其中,所述第一溶剂用于沉淀油溶性量子点,所述第三溶剂用于分散油溶性量子点,所述第一溶剂的极性＞第二溶剂的极性＞第三溶剂的极性。该提纯方法最终得到的量子点产物纯度高,对量子点表面的配体影响小,可保持甚至提升最终量子点的物化性能,而且该方法简化操作,定制程度高,适合量产。(The invention belongs to the technical field of quantum dot processes, and particularly relates to a purification method of quantum dots. The purification method comprises the following steps: providing an initial oil-soluble quantum dot solution; adding a first solvent and a second solvent into the initial oil-soluble quantum dot solution, mixing, performing centrifugal treatment, and removing a supernatant to obtain a precipitate; dissolving the precipitate in a third solvent to obtain a quantum dot solution; wherein the first solvent is used for precipitating the oil-soluble quantum dots, the third solvent is used for dispersing the oil-soluble quantum dots, and the polarity of the first solvent is more than that of the second solvent and more than that of the third solvent. The quantum dot product finally obtained by the purification method has high purity, has small influence on the ligand on the surface of the quantum dot, can maintain and even improve the physicochemical property of the final quantum dot, and the method simplifies the operation, has high customization degree and is suitable for mass production.)

1. A method for purifying quantum dots is characterized by comprising the following steps:

providing an initial oil-soluble quantum dot solution;

adding a first solvent and a second solvent into the initial oil-soluble quantum dot solution, mixing, performing centrifugal treatment, and removing a supernatant to obtain a precipitate;

dissolving the precipitate in a third solvent to obtain a quantum dot solution;

wherein the first solvent is used for precipitating the oil-soluble quantum dots, the third solvent is used for dispersing the oil-soluble quantum dots, and the polarity of the first solvent is more than that of the second solvent and more than that of the third solvent.

2. The method for purifying a quantum dot according to claim 1, wherein the second solvent is miscible with the first solvent and the third solvent; and/or the presence of a gas in the gas,

the first solvent is selected from polar solvents used to precipitate oil-soluble quantum dots; and/or the presence of a gas in the gas,

the third solvent is selected from non-polar solvents for dispersing the oil-soluble quantum dots.

3. The method for purifying a quantum dot according to claim 2, wherein the first solvent is at least one selected from acetonitrile, methanol, ethanol, acetic acid, isopropanol, acetone, and n-butanol.

4. The method for purifying a quantum dot according to claim 2, wherein the third solvent is at least one selected from chloroform, toluene, cyclohexane, hexane, heptane, and octane.

5. The method for purifying a quantum dot according to claim 1, wherein the second solvent is at least one selected from the group consisting of n-butanol, tetrahydrofuran, methyl formate, ethyl acetate, trioctylamine, diethyl ether, and n-butyl ether.

6. The method for purifying a quantum dot according to claim 1, wherein the first solvent is ethanol, the second solvent is trioctylamine, and the third solvent is chloroform; alternatively, the first and second electrodes may be,

the first solvent is methanol, the second solvent is ethyl acetate, and the third solvent is hexane.

7. The method of claim 1, wherein the polarity value of the third solvent x the molar amount of the third solvent + the polarity value of the second solvent x the molar amount of the second solvent-the polarity value of the surface of the quantum dot x the molar amount of the quantum dot < the polarity value of the first solvent x the molar amount of the first solvent-the polarity value of the surface of the quantum dot x the molar amount of the quantum dot.

8. The method for purifying a quantum dot according to claim 7, wherein a polarity value of the third solvent x a molar amount of the third solvent + a polarity value of the second solvent x a molar amount of the second solvent-a polarity value of a surface of the quantum dot x a molar amount of the quantum dot < M; the polarity value of the first solvent is multiplied by the molar quantity of the first solvent-the polarity value of the surface of the quantum dot is multiplied by the molar quantity of the quantum dot is larger than M, and M is a value corresponding to the beginning of the precipitation of the quantum dot in the solvent system in the purification method.

9. The method for purifying a quantum dot according to any one of claims 1 to 8, wherein the step of adding a first solvent and a second solvent to the initial oil-soluble quantum dot solution for mixing comprises: and adding the second solvent into the initial oil-soluble quantum dot solution, adding the first solvent into the initial oil-soluble quantum dot solution, and standing.

10. The method for purifying a quantum dot according to any one of claims 1 to 8, wherein the speed of the centrifugal treatment is 5000rpm to 6000 rpm; and/or the presence of a gas in the gas,

the time of the centrifugal treatment is 5min-10 min; and/or the presence of a gas in the gas,

the volume ratio of the initial oil-soluble quantum dot solution to the first solvent to the second solvent to the third solvent is (1-10): (1-5): (5-30): (1-10).

Technical Field

The invention belongs to the technical field of quantum dot processes, and particularly relates to a purification method of quantum dots.

Background

A quantum dot is an inorganic semiconductor luminescent nanocrystal having a particle size less than or close to its bohr radius. Due to its characteristic quantum confinement effect, quantum dots have excellent luminescent properties, such as: controllable particle size, narrow half-peak width, adjustable light-emitting peak, high light-emitting efficiency, strong light temperature property and the like, and has wide application in the fields of illumination, display, solar energy conversion and the like.

The oil-soluble quantum dots prepared by the colloid method contain a large amount of unreacted precursors and organic solvents, and the final applicable quantum dot product can be obtained by purification after the preparation is completed. In the prior art, a purification method of an oil-soluble quantum dot generally adopts a certain polar solvent and a certain nonpolar solvent to repeatedly dissolve and precipitate, and the purity of the quantum dot obtained by the purification method is not high, and the method has a large influence on a ligand on the surface of the quantum dot, and even influences on the final performance of the quantum dot. Therefore, the prior art is in need of improvement.

Disclosure of Invention

The invention aims to provide a method for purifying quantum dots, and aims to solve the technical problem that the existing method for purifying oil-soluble quantum dots is not ideal in effect.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a purification method of quantum dots, which comprises the following steps:

providing an initial oil-soluble quantum dot solution;

adding a first solvent and a second solvent into the initial oil-soluble quantum dot solution, mixing, performing centrifugal treatment, and removing a supernatant to obtain a precipitate;

dissolving the precipitate in a third solvent to obtain a quantum dot solution;

wherein the first solvent is used for precipitating the oil-soluble quantum dots, the third solvent is used for dispersing the oil-soluble quantum dots, and the polarity of the first solvent is more than that of the second solvent and more than that of the third solvent.

The method for purifying the quantum dots is a method for purifying the oil-soluble quantum dots, and the method also applies a second solvent with the polarity between the first solvent and the third solvent on the basis of using the first solvent for precipitating the oil-soluble quantum dots and the third solvent for dispersing the oil-soluble quantum dots; the purification method comprises the following process steps: the first solvent and the second solvent are added into the initial oil-soluble quantum dot solution to be mixed and centrifugally treated, the oil-soluble quantum dots are higher in dispersion degree during precipitation due to the fact that the polarity of the second solvent is smaller than that of the first solvent in the centrifugal precipitation process, and are not prone to agglomeration, the phenomenon that the oil-soluble quantum dots are wrapped with impurities during agglomeration is avoided, the oil-soluble quantum dots are not agglomerated during centrifugal precipitation, the obtained precipitate is more easily and fully dissolved and dispersed in the third solvent, the precipitate is dissolved without high-strength mechanical vibration, and therefore ligand falling is avoided. The quantum dot product finally obtained by the purification method has high purity, has small influence on the ligand on the surface of the quantum dot, can maintain and even improve the physicochemical property of the final quantum dot, and the method simplifies the operation, has high customization degree and is suitable for mass production.

Drawings

Fig. 1 is a schematic flow chart of a quantum dot purification method according to an embodiment of the present invention.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The embodiment of the invention provides a method for purifying quantum dots, which comprises the following steps as shown in figure 1:

s01: providing an initial oil-soluble quantum dot solution;

s02: adding a first solvent and a second solvent into the initial oil-soluble quantum dot solution, mixing, performing centrifugal treatment, and removing a supernatant to obtain a precipitate;

s03: dissolving the precipitate in a third solvent to obtain a quantum dot solution;

wherein the first solvent is used for precipitating the oil-soluble quantum dots, the third solvent is used for dispersing the oil-soluble quantum dots, and the polarity of the first solvent is more than that of the second solvent and more than that of the third solvent.

The method for purifying the quantum dots is a method for purifying the oil-soluble quantum dots, and the method is characterized in that a second solvent with polarity between the first solvent and the third solvent is also applied on the basis of using the first solvent for precipitating the oil-soluble quantum dots and the third solvent for dispersing the oil-soluble quantum dots; the purification method comprises the following process steps: the first solvent and the second solvent are added into the initial oil-soluble quantum dot solution to be mixed and centrifugally treated, the oil-soluble quantum dots are higher in dispersion degree during precipitation due to the fact that the polarity of the second solvent is smaller than that of the first solvent in the centrifugal precipitation process, and are not prone to agglomeration, the phenomenon that the oil-soluble quantum dots are wrapped with impurities during agglomeration is avoided, the oil-soluble quantum dots are not agglomerated during centrifugal precipitation, the obtained precipitate is more easily and fully dissolved and dispersed in the third solvent, the precipitate is dissolved without high-strength mechanical vibration, and therefore ligand falling is avoided. The quantum dot product finally obtained by the purification method has high purity, has small influence on the ligand on the surface of the quantum dot, can maintain and even improve the physicochemical property of the final quantum dot, and the method simplifies the operation, has high customization degree and is suitable for mass production.

In step S01, the initial oil-soluble quantum dot solution is the oil-soluble quantum dot solution to be purified, and may be an existing quantum dot solution, such as a quantum dot solution dispersed in a non-polar solvent after previous purification, or may be a temporarily prepared oil-soluble quantum dot prepared by a colloid method just after the reaction is completed, where the solvent in the initial quantum dot solution is one or more of a saturated fatty acid or an unsaturated fatty acid having a C greater than 14, octadecene, and TOP. In the initial oil-soluble quantum dot solution system, the quantum dots can be commonly used quantum dots, such as one or more of II-VI compounds, III-V compounds, II-V compounds, III-VI compounds, IV-VI compounds, I-III-VI compounds, II-IV-VI compounds or IV simple substances, or core-shell quantum dots, wherein the core and shell compounds of the core-shell quantum dots are CdSe, CdS, ZnSe, ZnS, CdTe, ZnTe, CdZnS, CdZnSe, CdZnTe, ZnSeS, ZnSeTe, ZnTeS, CdSeS, CdSeTe, CdZnSeSt, ZnSeStTe or CdeStTe of II-VI groups; or InP, InAs or InAsP from group III-V; or group IV-VI PbS, PbSe, PbTe, PbSeS, PbSeTe or PbSTe; or a combination of any one or more of the above.

The temperature of the initial oil-soluble quantum dot solution can be room temperature (25 ℃) when the initial oil-soluble quantum dot solution is used for purification, and the temperature can be reduced to the room temperature if the initial oil-soluble quantum dot solution is prepared temporarily, and the initial oil-soluble quantum dot solution can be used for purification at the room temperature to 100 ℃ as long as the solution is not solidified and does not damage equipment and operators.

In the above steps S02 and S03, the first solvent is selected from polar solvents for precipitating oil-soluble quantum dots; the first solvent is mainly used for precipitating the oil-soluble quantum dots, and can be understood as a precipitating agent for the oil-soluble quantum dots, so that a polar solvent with high polarity is selected for better precipitating the oil-soluble quantum dots, and specifically, the first solvent is selected from at least one of acetonitrile, methanol, ethanol, acetic acid, isopropanol, acetone and n-butanol. And the third solvent is selected from non-polar solvents for dispersing the oil-soluble quantum dots; the third solvent is mainly used for dissolving and dispersing the oil-soluble quantum dots, and is understood to be a dispersing agent for the oil-soluble quantum dots, so that a nonpolar solvent with low polarity is selected for better dispersing the oil-soluble quantum dots, and specifically, the third solvent is selected from at least one of chloroform, toluene, cyclohexane, hexane, heptane and octane. In the embodiment of the present invention, the second solvent mainly makes the oil-soluble quantum dots not easily agglomerate when being precipitated under the action of the first solvent, so long as the polarity order of the three types of solvents is: the polarity of the first solvent > the polarity of the second solvent > the polarity of the third solvent can achieve the object of the present invention. Specifically, in one embodiment, the second solvent is selected from at least one of n-butanol, tetrahydrofuran, methyl formate, ethyl acetate, trioctylamine, diethyl ether, and n-butyl ether. In the embodiment of the invention, the second solvent can be mutually soluble with the initial oil-soluble quantum dot solution, the first solvent and the third solvent.

Specifically, in a preferred embodiment of the present invention, the first solvent is ethanol, the second solvent is trioctylamine, and the third solvent is chloroform. In another preferred embodiment of the present invention, the first solvent is methanol, the second solvent is ethyl acetate, and the third solvent is hexane. The selection of the solvent not only meets the condition that the polarity of the first solvent is more than that of the second solvent is more than that of the third solvent, but also enables the purification effect of the oil-soluble quantum dots to be optimal.

Specifically, in the method for purifying quantum dots provided by the embodiment of the present invention, the polarity value of the third solvent × the molar amount of the third solvent + the polarity value of the second solvent × the molar amount of the second solvent — the polarity value of the quantum dot surface × the molar amount of the quantum dot < the polarity value of the first solvent × the molar amount of the first solvent — the polarity value of the quantum dot surface × the molar amount of the quantum dot. Specifically, the polarity value of the third solvent × the molar amount of the third solvent + the polarity value of the second solvent × the molar amount of the second solvent — the polarity value of the surface of the quantum dot × the molar amount of the quantum dot < M; meanwhile, the polarity value of the first solvent x the molar amount of the first solvent-the polarity value of the surface of the quantum dot x the molar amount of the quantum dot > M. Wherein M is an empirically determined value, and is determined according to the selected polar values and molar amounts of the first solvent, the second solvent and the quantum dots in the practical purification process, where M is a value corresponding to the beginning of the quantum dot precipitation in the solvent system used in the purification method, for example, when the molar amount of the first solvent is determined, the polarity of the surface of the quantum dot and the molar amount of the quantum dot are determined, the polar value of the first solvent x the molar amount of the first solvent-the polar value of the surface of the quantum dot x the molar amount of the quantum dot equals M, the quantum dot begins to precipitate from the solvent system, and when the formula is calculated, the molar amount unit and the solvent volume unit are different, and M has different values, and in one embodiment, the molar amount unit and the solvent volume unit can be made by international units, at this time, M can be measured out to obtain a specific value. The polarity value is a parameter value commonly used by those skilled in the chemical industry to represent the polarity of a solvent, and can be generally measured according to the magnitude of dipole moment, for example, the polarity value of methanol is 6.6, and the polarity value of water is 10.2.

In an embodiment of the present invention, the step of adding the first solvent and the second solvent into the initial oil-soluble quantum dot solution and mixing includes: and adding the second solvent into the initial oil-soluble quantum dot solution, adding the first solvent into the initial oil-soluble quantum dot solution, and standing. In one embodiment, the second solvent is added into the initial oil-soluble quantum dot solution, the mixture is shaken, the first solvent is added, the mixture is shaken, and then the mixture is kept stand for 5 to 60 seconds.

In an embodiment of the present invention, the centrifugation process may be: the turbid mixed solution is put into a centrifuge for centrifugal separation, and the rotating speed and the centrifugal time can be freely adjusted so as to achieve the full separation effect; in a preferred embodiment of the invention, the speed of the centrifugal treatment is 5000-6000 rpm, and the time of the centrifugal treatment is 5-10 min. And pouring out the supernatant after the centrifugal separation is finished, adding a third solvent into the residual precipitate, namely the solid quantum dot product, and re-dispersing, wherein the third solvent can be kept stand for a long time for natural dispersion at the moment, and can also be quickly dispersed by means of mechanical vibration.

In an embodiment of the present invention, the volume ratio of the initial oil-soluble quantum dot solution, the first solvent, the second solvent, and the third solvent is (1-10): (1-5): (5-30): (1-10). In the range of the volume ratio, the purification is carried out, and the purification effect is optimal.

In an embodiment of the present invention, after dissolving the precipitate in the third solvent to obtain the quantum dot solution, the method further includes the step of repeating the purification method for 1 to 9 times on the quantum dot solution. Namely, the whole process of the purification method is repeated again in the redispersed quantum dot solution, the steps of each time are basically the same, and the specific types of the first solvent, the second solvent and the third solvent can be the same or different. The whole purification times are generally 1-10 times according to the actual situation and the application requirements.

The invention is described in further detail with reference to a part of the test results, which are described in detail below with reference to specific examples.

Example 1

At room temperature, taking oil-soluble quantum dot Cd to be purified_xZn_1-x20ml of S/ZnS solution, wherein the main organic solvents are oleic acid and octadecene, and the main impurities are anion and cation precursor residues.

Cleaning for the 1 st time: and (3) adding 5ml of a second solvent, namely trioctylamine, into the oil-soluble quantum dot solution (the solvent in the oil-soluble quantum dot solution is selected from saturated fatty acid or unsaturated fatty acid with the C being more than 14 or octadecene and TOP), shaking uniformly, adding 10ml of a first solvent, namely polar solvent ethanol, shaking uniformly, and standing for 5 secs. Putting the mixed solution into a centrifugal device, and centrifuging at the rotating speed of 6000rpm for 5 mins. And after the separation is finished, pouring out the supernatant, adding 20ml of a third solvent, namely a nonpolar solvent chloroform, into the residual solid quantum dot product, and oscillating the mixture on an oscillator for 2mins to redisperse.

Cleaning for the 2 nd pass: and adding 5ml of second solvent trioctylamine into the quantum dot-chloroform solution, shaking uniformly, adding 10ml of first solvent polar solvent ethanol, shaking uniformly, and standing for 5 secs. Putting the mixed solution into a centrifugal device, and centrifuging at the rotating speed of 6000rpm for 5 mins. And after the separation is finished, pouring out the supernatant, adding a third solvent, namely a nonpolar solvent chloroform, into the residual solid quantum dot product, and oscillating for 1mins on an oscillator for redispersion.

Finally, purified Cd is obtained_xZn_1-xAnd (3) an S/ZnS quantum dot solution.

Example 2

Taking oil-soluble quantum dot Cd to be purified at 100 DEG C_xZn_1-xSe/ZnSe_yS_1-y20ml of solution, wherein the main organic solvent is oleic acid, octadecene and oleylamine, and the main impurities are residual anion and cation precursors.

Cleaning for the 1 st time: adding 40ml of second solvent ethyl acetate into the oil-soluble quantum dot solution, shaking uniformly, adding 5ml of first solvent namely polar solvent methanol, shaking uniformly, and standing for 60 secs. And putting the mixed solution into a centrifugal device, and centrifuging at the rotating speed of 5000rpm for 10 mins. And after the separation is finished, pouring off the supernatant, adding 20ml of a third solvent, namely a nonpolar solvent hexane, into the residual solid quantum dot product, and oscillating on an oscillator for 2mins to redisperse.

Finally, purified Cd is obtained_xZn_1-xSe/ZnSe_yS_1-yA quantum dot solution.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.