Purification method and device and preparation method of quantum dot material

Abstract

The present invention relates to a purification method and apparatus, and a method for preparing a quantum dot material, the purification method comprising: a contact step in which a quantum dot system to be purified is in contact with a stationary phase; in the first elution step, an extraction agent is used for eluting non-target components in the quantum dot system to be purified, the non-target components comprise one or more of unreacted components, impurity components and free ligand components, and in the first elution step, the target components are substantially reserved in a stationary phase; a second elution step of eluting the target component from the stationary phase using an eluent; and a regeneration step, the regeneration step comprising cleaning the stationary phase with a cleaning agent, and performing one or more times of the above-mentioned steps, or performing one or more times of a cycle formed by the above-mentioned steps, and after the start of the cycle, performing the regeneration while the regeneration step is performed. At least one of the contacting step, the first elution step, and the second elution step is being performed.

Description

Technical Field

[0001] The invention belongs to the field of materials and relates to a purification method, in particular to a purification method, a device and a preparation method of quantum dot materials. Background Art

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

[0003] At present, quantum dot materials are usually prepared from II-VI, IV-VI or III-V semiconductor materials. Common quantum dot materials include II-VI semiconductor quantum dots such as cadmium sulfide (CdS), cadmium tin (CdSe), cadmium telluride (CdTe) and zinc sulfide (Zns); IV-VI semiconductor quantum dots such as lead sulfide (PbS) and lead selenide (PbSe); III-V semiconductor quantum dots such as indium phosphide (InP) and indium arsenide (InAs). In addition, in recent years, quantum dot materials based on perovskite structure have also been developed.

[0004] In addition, quantum dots can be aggregates of atoms or molecules at the nanometer dimension, and their composition can be a single semiconductor material or a core-shell structure formed by multiple semiconductor materials.

[0005] The synthesis of quantum dot materials can be completed in organic media and aqueous media. Among them, the organic phase synthesis can obtain quantum dot materials with high crystal quality by screening high boiling point organic solvents, precursors and ligands and / or surfactants. In addition, the organic solvent can also be combined with the precursor material as a ligand to prevent the agglomeration of nanomaterials. During the aqueous phase synthesis, the precursor is combined into a nano quantum dot material in the presence of a surfactant (such as mercaptopropionic acid, etc.).

[0006] Furthermore, by synthesizing quantum dot materials in an organic medium or an aqueous medium, a purification step is usually required to obtain the final product. During the purification process, impurities, solvents, unreacted precursors or excess ligands can be removed by purification. On the one hand, the composition of the purified system is relatively complex, and on the other hand, the result of purification will have a significant impact on the quality of the quantum dot product. Therefore, the purification step is also very important for quantum dot materials, especially for colloidal quantum dot materials.

[0007] Quantum dot purification technology is a method of purifying quantum dot stock solution after synthesis to remove impurities and excess ligands, thereby improving the purity and optical properties of quantum dots. Traditional purification methods, including precipitant precipitation filtration, solvent extraction, membrane filtration, electrophoretic separation, and chromatographic separation, usually need to be combined according to actual needs to achieve the best purification effect.

[0008] Reference 1 discloses a method for preparing a rare earth colloidal quantum dot material, wherein after heating a quantum dot precursor mixture to grow crystals, the quantum dots are precipitated by adding ethanol or acetone solution, and then the final purified quantum dots are obtained by centrifugal separation. Reference 2 discloses a method for preparing lead sulfide colloidal quantum dots, wherein after obtaining a lead sulfide colloidal quantum dot stock solution, impurities are removed by centrifugal treatment. Reference 3 adds a certain amount of precipitant to a system to be purified containing quantum dots, mixes, precipitates the quantum dots, separates the quantum dots from the system to be purified, and obtains powdered quantum dots. Reference 4 discloses a method for purifying quantum dots and a device for purifying quantum dots, which removes impurities such as oil-soluble ligands in the quantum dot stock solution through an ultrafiltration membrane. Similar to Reference 4, Reference 5 removes long-chain ligand substances on quantum dots by designing an ultrafiltration membrane. Reference 6 discloses a method for purifying quantum dots, wherein the quantum dot solution is adjusted to be alkaline, DNA is added to the alkaline quantum dot solution and mixed, and further a gel electrophoresis method is used to obtain quantum dots coated with DNA on the surface. Reference 7 uses molecular sieves to separate the required graphene quantum dot materials through adsorption and desorption.

[0009] In addition, it is known that solid phase extraction (SPE) is a sample pretreatment technology that has been developed since the mid-1980s. It is developed by combining liquid-solid extraction and liquid chromatography technology. It is mainly used for the pretreatment of liquid chromatography samples to separate, purify and enrich target detection objects. SPE technology is based on the theory of liquid-solid chromatography and uses selective adsorption and selective elution to enrich, separate and purify samples. It is a physical extraction process that includes liquid and solid phases; it can also be roughly regarded as a simple chromatographic process.

[0010] There are not many reports on the direct treatment of quantum dot reaction systems using solid phase extraction technology. Reference 8 describes a simple and universal carbon dot purification procedure. After the hydrothermal heating process, the reaction mixture usually contains unreacted starting materials and by-products as well as carbon dots, and the purification method is based on solid phase extraction technology, in which the reaction mixture is adsorbed on porous alumina, and the carbon dots are separated from the by-products and unreacted organic matter using an appropriate solvent, and finally the carbon dots are recovered from the alumina using a simple method.

[0011] Although the above-mentioned prior art has conducted research on the purification of quantum dot materials to a certain extent, it is still not sufficient to provide a continuous and efficient treatment method for quantum dot stock solution (reaction product system).

[0012] References:

[0013] Reference 1: CN106340592A

[0014] Reference 2: CN 111635759A

[0015] Reference 3: CN 108219792A

[0016] Reference 4: CN106474932A

[0017] Reference 5: CN 111375312A

[0018] Reference 6: CN 110938422A

[0019] Reference 7: CN104777081A Summary of the invention

[0020] Problem that the invention aims to solve

[0021] As mentioned above, on the one hand, the solid phase extraction technology in the prior art is usually used for the pre-treatment of liquid chromatography, but not directly used for the direct purification of quantum dot reaction stock solution.

[0022] In addition, there are no reports on the existing technology for solid phase extraction stationary phase regeneration and online continuous purification. In contrast, when the current purification technology is scaled up, batch purification requires more manual operations, and the cost of semi-automatic or fully automatic purification is quite high. In addition, these conventional technical methods have great limitations in continuous repeated production and are difficult to couple to the downstream of quantum dot automated synthesis. In particular, considering that the regeneration of the stationary phase / extraction column and the purification efficiency are mutually restricted, online continuous purification has not been widely used.

[0023] Therefore, based on the above-mentioned problems existing in the prior art, the present invention primarily provides a purification method that can be directly used to treat a quantum dot synthesis reaction product system. This method is a continuous and efficient treatment method, and through the adjustment of different elution steps, the final quantum dot material obtained by the method of the present invention can have good purity even without further cooperation with other purification methods.

[0024] In addition, another object of the present invention is to provide a device or system for online continuous processing of quantum dot materials, which can directly process the quantum dot synthesis reaction product system in an efficient and high-purity manner by executing the above-mentioned method, and obtain well-purified quantum dot materials.

[0025] In addition, another object of the present invention is to provide a method for preparing a quantum dot material. The purification method in the preparation method adopts the above method, so that the quantum dot material can be prepared continuously and efficiently.

[0026] Solutions for solving problems

[0027] [1] The present invention primarily provides a method for continuous purification of quantum dot materials, wherein the purification method comprises the following steps:

[0028] A contacting step, so that the quantum dot system to be purified is in contact with the stationary phase;

[0029] A first elution step, using an extractant to elute non-target components in the quantum dot system to be purified, wherein the non-target components include one or more of unreacted components, impurity components, and free ligand components, and in the first elution step, the target component is substantially retained in the stationary phase;

[0030] A second elution step, using an eluent to elute the target component from the stationary phase;

[0031] a regeneration step, wherein the regeneration step comprises using a cleaning agent to clean the stationary phase,

[0032] Furthermore, each of the above steps is performed once or multiple times, or a cycle formed by each of the steps is performed once or multiple times, and after the cycle starts, while the regeneration step is being performed, at least one of the contacting step, the first elution step, and the second elution step is being performed.

[0033] [2] The purification method according to [1], wherein the quantum dot system to be purified is an untreated reaction product system directly obtained from a quantum dot material synthesis reaction; and the regeneration step also includes a step of drying the cleaned stationary phase.

[0034] [3]. The purification method according to [1] or [2], wherein the quantum dot system to be purified is an oily quantum dot system or an aqueous quantum dot system.

[0035] [4] The purification method according to any one of [1] to [3], wherein the stationary phase is composed of particles, the surface of the particles is modified by silane having a long-chain alkyl group, and the long-chain alkyl group is selected from one or more alkyl groups having 12 to 32 carbon atoms;

[0036] [5] The purification method according to any one of [1] to [4], wherein one or more extractants are used in the first elution step; and / or

[0037] In the first elution step, the non-target components are eluted by the solvation effect of the extractant.

[0038] [6] The purification method according to any one of [1] to [5], wherein in the first elution step, one or more of the following conditions are adjusted to elute the non-target components:

[0039] i. Polarity of the extractant

[0040] ii. Solubility of the extractant

[0041] iii. Flow rate of the extractant

[0042] iv. Working time of the extractant

[0043] v. Extraction temperature.

[0044] [7] The purification method according to any one of [1] to [6], wherein one or more eluents are used in the second elution step, and / or the target component is eluted by the solvation effect of the eluent in the second elution step.

[0045] [8] The purification method according to any one of [1] to [7], wherein in the second elution step, one or more of the following conditions are adjusted to elute the target component:

[0046] i. Polarity of the eluent

[0047] ii. Solubility of the eluent

[0048] iii. Eluent flow rate

[0049] iv. Working time of the eluent

[0050] v. Elution temperature.

[0051] [9]. Furthermore, the present invention also provides a method for preparing a quantum dot material, wherein the method comprises:

[0052] Steps for the synthesis of quantum dot materials;

[0053] Purification steps of quantum dot materials,

[0054] The step of purifying the quantum dot material comprises purifying the reaction product system obtained in the step of synthesizing the quantum dot material according to the purification method described in any one of [1] to [8] above.

[0055]

[10] . In addition, the present invention also provides a device for use in the purification method described in any one of [1] to [8] above, wherein the device comprises:

[0056] Injection unit, solid phase extraction unit and sample recovery unit,

[0057] Wherein, the injection unit is used to place the quantum dot system to be purified.

[0058] The solid phase extraction unit comprises a mobile phase providing unit, a stationary phase unit and optionally a solvent / waste liquid collecting unit.

[0059] Furthermore, the solid phase extraction unit comprises more than two independent solid phase extraction columns, and the solid phase extraction unit is configured such that when one or more solid phase extraction columns perform solid phase extraction operations, at least one of the other solid phase extraction columns is in a regenerating or regenerated state.

[0060] Effects of the Invention

[0061] By implementing the above technical solution, the present invention can achieve the following technical effects:

[0062] 1) The method of the present invention is a purification method, which can directly purify the reaction product system obtained from the quantum dot synthesis step and not processed by other steps, and obtain a high-purity quantum dot material.

[0063] 2) The method and device of the present invention can provide a continuous, online and efficient treatment method through multiple purification cycles, thereby increasing the scale of purification treatment.

[0064] 3) The method and device of the present invention have good scalability and compatibility, and can be coupled with subsequent processing methods and devices for quantum dots, providing more flexibility in the processing of quantum dot materials.

[0065] 4) In some preferred embodiments, the retention characteristics and regeneration capacity are balanced by adjusting the stationary phase characteristics, thereby improving the efficiency of continuous purification. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 A schematic diagram of the online solid phase extraction purification system of the present invention;

[0067] Figure 2 The figure and schematic diagram of the solid phase extraction column;

[0068] Figure 3 Schematic diagram of the quantum dot adsorption-extraction-redissolution process;

[0069] Figure 4 Schematic diagram of the movement of quantum dots and impurities during the purification process;

[0070] Figure 5 Microscope morphology of the quantum dot film before and after purification. DETAILED DESCRIPTION

[0071] The following is a detailed description of the present invention. The following description of the technical features is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

[0072] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0073] In the present specification, the use of “substantially” or “essentially” means that the standard deviation from a theoretical model or theoretical data is within a range of 1%, preferably 0.9%, and more preferably 0.8%.

[0074] In this specification, unless otherwise specified, "%" means mass percentage.

[0075] In this specification, "room temperature" is used to refer to a temperature range of 23±2°C.

[0076] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0077] In this specification, the term "plurality" or "multiple" refers to a number greater than 2.

[0078] In this specification, the "boiling point" refers to the boiling point under normal pressure.

[0079] In this specification, unless otherwise specified, "quantum dot" and "quantum dot material" have equivalent physical and chemical meanings.

[0080] In the present specification, "optional" or "optionally" means that the event or situation described below may or may not occur, and the description includes cases where the event occurs and cases where it does not occur.

[0081] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0082] The present invention primarily provides a new strategy for purifying quantum dot materials based on solid phase extraction, and more specifically, relates to a method and apparatus for continuous and efficient purification based on solid phase extraction technology. The purification method and apparatus of the present invention are particularly suitable for directly purifying the reaction product system obtained by synthesizing quantum dot materials. Furthermore, by performing multiple purification cycles, online, large-scale and continuous purification of quantum dot materials can be achieved.

[0083] <First aspect>

[0084] like Figure 1 to Figure 3 As shown, in the first aspect of the present invention, a purification method is provided, and the method of the present invention mainly comprises the following steps:

[0085] A contacting step, so that the quantum dot system to be purified is in contact with the stationary phase;

[0086] A first elution step, using an extractant to elute non-target components in the quantum dot system to be purified, wherein the non-target components include one or more of unreacted components, impurity components, and free ligand components, and in the first elution step, the target component is substantially retained in the stationary phase;

[0087] In the second elution step, an eluent is used to elute the target components from the stationary phase; the target components include purified quantum dots.

[0088] A regeneration step, wherein the regeneration step comprises using a cleaning agent to clean the stationary phase.

[0089] Furthermore, the above steps or the cycles formed by the steps are performed once or multiple times, and after the cycle starts (i.e., after the second elution step is completed for the first time), at least one of the contacting step, the first elution step, and the second elution step is being performed while the regeneration step is being performed. This allows the reaction to continue, and the chemical products to continue to flow out continuously, which can be adapted to the production capacity of quantum dots in the previous synthesis process, so that the entire process can continue.

[0090] Furthermore, in principle, there is no particular limitation on the temperature at which the above steps are performed. The steps may be performed at room temperature, or the relevant elements or devices may be heated whenever necessary.

[0091] (Quantum dot system to be purified)

[0092] In principle, there is no particular limitation on the quantum dot system to be purified in the present invention, and the system may include any non-target components in addition to the target quantum dot material. These non-target components may include one or more of: unreacted raw material components, solvents, excess or free ligand components, and other impurity components (e.g., byproducts during quantum dot synthesis).

[0093] Further, in some specific embodiments, the quantum dot system to be purified according to the present invention can be a reaction product system directly obtained by the synthesis reaction of the synthetic quantum dot material, and the "directly" here means that after the reaction, no other steps that may cause changes in the system composition are performed. Such a reaction product system may also be referred to as a "quantum dot stock solution" in some occasions.

[0094] The reaction product system of the present invention can usually be prepared by cooling the reaction mixture to room temperature or other treatment temperatures after the quantum dot synthesis reaction is completed for subsequent purification treatment.

[0095] In principle, the present invention has no particular limitation on the synthesis method of quantum dots, for example, methods for preparing quantum dot materials from II-VI, IV-VI or III-V semiconductor elements may be used.

[0096] In some specific embodiments of the present invention, the synthesis method of the quantum dot material includes a method for synthesizing II-VI semiconductor quantum dot materials such as cadmium sulfide (CdS), cadmium tin (CdSe), cadmium telluride (CdTe) and zinc sulfide (Zns); a method for synthesizing IV-VI semiconductor quantum dot materials such as lead sulfide (PbS) and lead selenide (PbSe); a method for synthesizing III-V semiconductor quantum dot materials such as indium phosphide (InP) and indium arsenide (InAs); a method for synthesizing a core-shell structure Quantum dot materials such as CdS / ZnS, CdSe / CdS, CdSe / ZnS, CdSe / CdS / ZnS, CdTe / CdS, CdTe / CdS / ZnS, ZnSe / ZnS, InP / ZnSe, InP / ZnS, InP / ZnSe / ZnS, InP / GaP / ZnS; methods for synthesizing carbon quantum dot materials, noble metal single substances such as Au, Ag and other quantum dot materials, and methods for synthesizing quantum dot materials based on perovskite structure. These methods can be methods based on organic media (oily quantum dot materials) or methods based on aqueous media (aqueous quantum dot materials). For such methods, more specifically, hot injection methods or microfluidic methods can be included.

[0097] In some preferred embodiments of the present invention, the synthesis method applicable to the present invention can be selected from those synthesis methods for forming (semiconductor) colloidal quantum dot materials; in some other preferred embodiments, the synthesis method applicable to the present invention can be selected from those quantum dot synthesis methods based on hot injection or microfluidic synthesis.

[0098] Furthermore, in the synthesis method of quantum dot materials based on organic media, the following can be cited: first, the raw materials are dissolved in an organic solvent or a ligand to form a precursor, and then they are mixed under heating conditions to form the quantum dot material through a chemical reaction.

[0099] Regarding the above-mentioned organic solvents or ligands, it should be noted that, when preparing the precursor, the organic solvent itself can also be a ligand. Therefore, in some specific embodiments, the organic solvent can generally be divided into a ligand organic solvent and a non-ligand organic solvent.

[0100] In some specific embodiments of the present invention, the ligand or ligand-containing organic solvent usually has a relatively high boiling point (preferably, for example, a boiling point above 300° C.), dissolving the raw materials to form a quantum dot precursor. For the ligand or ligand-containing organic solvent, common ones include some polar organic solvents with long-chain (10-30 carbon atoms) alkyl groups, including acid compounds, amine compounds, thiol compounds, and phosphorus-containing compounds with long-chain alkyl groups. Specifically, oleylamine, dodecyl mercaptan, oleic acid, dioctyl ether, trioctyl phosphine oxide (TOPO), trioctyl phosphine (TOP), hexylphosphonic acid (HPA), tetradecylphosphonic acid (TDPA), etc. and mixtures thereof can be cited.

[0101] For non-ligand organic solvents, they can generally be octadecene, diphenyl ether, paraffin oil, methyl pyrrolidone, etc. In addition, it is related to the required reaction temperature. When the reaction temperature allows, the non-ligand organic solvent can also be a low boiling point solvent such as ethanol and toluene. For the use of non-ligand organic solvents, after using ligands or ligand organic solvents to dissolve raw materials to obtain quantum dot precursors, the precursors can be dissolved or dispersed in these solvents.

[0102] There is no particular limitation on the reaction method. After preparing precursors with the aid of ligands or ligand-containing organic solvents, two or more precursors may be simultaneously injected into another organic solvent to carry out the growth reaction of quantum crystals under heating conditions. Alternatively, one ligand may be injected into another ligand solution to carry out the growth reaction of quantum crystals under heating conditions.

[0103] The above raw materials are mainly the sources of various elements in quantum dots. These raw materials can be one or more of their simple substances, oxides, salt compounds, organic compounds, etc. For example, in some specific embodiments, when synthesizing AxBy type quantum dots (wherein A can be Cd, Hg, Pb, Zn, Ag, Cu, Mn, Sn, Ni, Bi or Eu, etc.; B can be S, Se or Te), the oxide, salt compound or organic compound of A can be dissolved in a ligand or a ligand organic solvent to obtain a precursor, and in addition, the simple substance of B is dissolved in an organic solvent to form another precursor, and then the two precursors are mixed in a heated state to prepare quantum dots.

[0104] In addition, the present invention has no particular limitation on the temperature conditions for preparing quantum dots. For example, in the hot injection method, the reaction temperature can usually be controlled within the range of 180 to 380° C. as required.

[0105] The present invention is not particularly limited to the above-mentioned synthesis method based on aqueous media, and the raw materials can be dissolved in water and hydrothermally synthesized in the presence of a surfactant. Such a surfactant can be a compound having a bipolar head, typically an alkyl acid compound having a thiol group, etc.

[0106] The quantum dot stock solution obtained by the above-mentioned synthesis reaction usually contains organic solvents, unreacted raw materials (precursors), excess free ligands and other impurities (such as by-products, etc.) in addition to the target quantum dot crystals. Substances other than quantum dots need to be removed through subsequent purification treatment.

[0107] There is no particular limitation on the morphology of the quantum dot crystals in the above stock solution, for example, they may have a spherical or substantially spherical structure, a rod-like structure, a sheet-like structure, a cone-like structure, a tower-like structure, a polygonal structure, a cubic structure, etc. In some preferred embodiments of the present invention, the obtained quantum dot crystals have a spherical or substantially spherical morphology; in other preferred embodiments, the obtained quantum dot crystals have a (spherical or substantially spherical) core-shell structure.

[0108] There is no particular restriction on the particle size of the target quantum dot crystal material. In some specific embodiments of the present invention, the quantum dot stock solution may include quantum dot crystal material with a particle size of 1 to 70 nm. Preferably, the particle size range may be 2 to 60 nm, more preferably 3 to 50 nm, and further preferably 4 to 40 nm.

[0109] In addition, there is no particular limitation on the apparatus used for synthesizing quantum dot materials, and in some preferred embodiments, such an apparatus has stirring and / or inert gas supply components.

[0110] In some preferred embodiments of the present invention, the quantum dot system to be purified in the present invention may be an oily quantum dot system containing colloidal quantum dots, especially semiconductor colloidal quantum dots, etc. The ligands of these quantum dots usually have double-end different polarity characteristics, and compared with quantum dots (carbon quantum dots, etc.) that are stabilized only by functional groups, purification and separation are somewhat difficult.

[0111] (Contact steps)

[0112] In the contacting step of the present invention, the quantum dot system to be purified is mainly contacted with the stationary phase so that the stationary phase adsorbs, especially completely adsorbs the quantum dot system. In some specific embodiments, the additional solvent provided in the mobile phase providing unit described below can be used as a carrier to transport the quantum dot system to be purified to the stationary phase.

[0113] For the stationary phase in the present invention, it can be an organic or inorganic substance with a porous surface structure. In some preferred embodiments, from the perspective of convenient stationary phase regeneration, preferably, a porous inorganic substance is used as the stationary phase. For such a stationary phase, in some specific embodiments of the present invention, it can be a metal or semi-metal oxygen-containing system. Preferably, it can be a silicon oxygen-containing system. For such a stationary phase, various forms of silicon dioxide can be listed, such as silica gel, glass (fused silica), etc.

[0114] The stationary phase of the present invention can be used in a granular form, that is, the stationary phase can be composed of particles, and such particles can be substantially spherical particles. From the perspective of solid phase extraction effect, the particle size of such particles can be less than 1000 μm, preferably less than 800 μm, more preferably less than 600 μm, and more preferably less than 400 μm. If the particle size is too high, the pores between the filled particles will be too large. In addition, from the perspective of smooth flow of the mobile phase and prevention of leakage, the particle size of the particles can be greater than 100 μm.

[0115] Furthermore, from the perspective of effective retention of the quantum dot material, the pore size of the surface openings of the above-mentioned stationary phase is less than 700 angstroms, preferably less than 500 angstroms, and more preferably less than 400 angstroms. In principle, there is no particular restriction on the lower limit of the pore size, and for example, it can be greater than 10 angstroms, preferably greater than 20 angstroms, and more preferably greater than 30 angstroms.

[0116] In addition, from the perspective of adsorption, preferably, the surface of the above-mentioned stationary phase can be further modified. The method of modification can be adjusted according to the different objects to be treated. For example, in some specific embodiments, when a reversed-phase stationary phase is required, a non-polar, hydrophobic stationary phase can be obtained by modifying the surface of the stationary phase with an alkyl group or the like. For such silanes, long-chain alkyl groups are preferably used, such as one or more alkyl groups with 12 to 32 carbon atoms. Specific examples include octadecyltrimethoxysilane and the like.

[0117] The above-mentioned stationary phase of the present invention is mainly set to take into account the realization of the following performances:

[0118] For the stationary phase, its adsorption selectivity and the difficulty of desorption usually show opposite trends, that is, in the solid phase extraction process, the better the selective retention effect of the stationary phase on the target component, the more difficult it is to desorb the target component during desorption. Of course, this does not always cause great trouble for discontinuous operation, because for such discontinuous operation, there is a higher degree of freedom in the control time, but this still affects the operating efficiency. For continuous operation, for example, after the operation cycle described in the present invention is started, before the next contact step begins, at least one regenerated stationary phase must be prepared. Therefore, this requires that the balance between the selective retention and desorption of the stationary phase should be regulated. It has been found that in the present invention, when the particle size of the stationary phase particles is preferably controlled at 105 μm to 250 μm (for example, 105 μm, 110 μm, 130 μm, 150 μm, 170 μm, 190 μm, 200 μm, 210 μm, 230 μm, 250 μm, etc.) (especially when the pore size of the openings on the surface of the particles is 10 to 700 angstroms), the above-mentioned balance can be better achieved. Through this particle characteristic, not only can a suitable specific surface area be retained, but also a suitable spacing / gap between particles can be provided, so that good retention selectivity is achieved, and better efficiency is also achieved during desorption. This allows the stationary phase to immediately enter the contact step of the next cycle after regeneration. This greatly improves the efficiency for large-scale continuous online purification of quantum dots.

[0119] Through experiments, it was found that the number of quantum dots adsorbed by the stationary phase with a particle size of 200 μm was 166, the number of quantum dots adsorbed by the stationary phase with a particle size of 750 μm was 55, and the number of quantum dots adsorbed by the stationary phase with a particle size of 350 μm was about 70. The particle size of the stationary phase provided in the present application is smaller, and it has been surface-etched, so its specific surface area is greatly increased, and the final adsorption amount is also greatly increased. For the use of the stationary phase of the present invention, typically, the stationary phase can be filled into a tube to form a columnar stationary phase. For such a tube, from the perspective of ease of operation, it is preferred that the inner diameter is less than 8 cm, for example, 1 to 6 cm, 2 to 5 cm. In addition, there is no particular limitation on the tube length in principle, which can usually be 10 to 80 cm, and preferably 20 to 50 cm.

[0120] Furthermore, the filling rate (filling volume rate) of the stationary phase in the tube can generally be 50 V% or more and 95 V% or less from the perspective of solid phase extraction efficiency.

[0121] The contacting step of the present invention mainly uses the above-mentioned stationary phase to completely adsorb the quantum dot system to be purified. For such an operation, the quantum dot system to be purified can be injected into a tube containing the stationary phase with the aid of an injection device.

[0122] (First elution step)

[0123] After the contacting step, the first elution step of the present invention may be performed.

[0124] The first elution step of the present invention is mainly to elute non-target components other than the target quantum dot material. As mentioned above, the non-target components mainly include one or more of unreacted raw material components, solvents, excess or free ligand components and other impurity components (such as by-products during quantum dot synthesis).

[0125] In the present invention, the above elution is mainly performed by the difference in solvation (affinity) of the mobile phase. In the present invention, the mobile phase used in this step is also referred to as "extractant" for the convenience of distinguishing it from the mobile phase of the subsequent second elution step.

[0126] The extractant used in the first elution step of the present invention can be selected from one or more solvents, and these solvents can be single-component solvents or multi-component mixed solvents.

[0127] When these solvents are used as extractants, in some specific embodiments, the extractant has a lower solvation effect on the target quantum dots than on the non-target components. In other specific embodiments, multiple solvents can be used continuously to elute the non-target components. Among them, when each solvent is used as an extractant, the solvation effect on the target quantum dots is lower than the solvation effect on any one of the non-target components, and the extractant provides sufficient solvation for at least one of the non-target components to elute it from the stationary phase.

[0128] In some other specific embodiments, in the step of performing the first elution, the target quantum dots are precipitated on the surface of the stationary phase due to the use of an extractant.

[0129] In addition, due to the porous structure of the stationary phase surface, for example, it can accommodate target quantum dots with a wide particle size range, thereby ensuring that the recovery rate of the quantum dots is sufficient.

[0130] Furthermore, the strength of the difference in the solvation effect of the extractant or the degree of elution can be adjusted by one or more of the following methods:

[0131] i. Polarity of the extractant

[0132] ii. Solubility of the extractant

[0133] iii. Flow rate of the extractant

[0134] iv. Working time of the extractant

[0135] v. Extraction temperature.

[0136] Furthermore, the completion of the step of determining the first elution may be performed by conventional detection or monitoring methods in the art, which may include optical detection methods and the like.

[0137] In addition, the eluate in the first elution step can be collected by a solvent recovery or waste liquid collection device.

[0138] (Second elution step)

[0139] In the present invention, by performing the first elution step, all non-target components in the quantum dot system to be purified can be eluted. Furthermore, in the second elution step, the mobile phase is adjusted to elute and collect the target quantum dots from the stationary phase.

[0140] The mobile phase that can be used in the second elution step can generally be selected according to the properties of the target quantum dots. The properties of the quantum dots here mainly include the properties of the functional groups on the surface of the quantum dots, the properties of the surface ligands, and the like.

[0141] For such a mobile phase, it is mainly to provide sufficient solvation (affinity) for the target quantum dots to elute the quantum dots adsorbed on the surface of the stationary phase. In the present invention, the mobile phase used in this step is also referred to as "eluent" for the convenience of distinguishing it from the mobile phase of the first elution step.

[0142] The eluent used in the second elution step of the present invention can be selected from one or more solvents, and these solvents can be single-component solvents or multi-component mixed solvents.

[0143] When these solvents are used as eluents, in some specific embodiments, the eluent can provide sufficient solvation for all target quantum dots so that all target quantum dots can be eluted from the surface of the stationary phase under the action of the eluent. In other specific embodiments, multiple solvents can be used continuously to elute the above-mentioned target quantum dot components. Among them, when each solvent is used as an eluent, the solvation effect on the target quantum dots in some particle size ranges is greater than that on the target quantum dots in other particle size ranges so that the former can be preferentially eluted from the stationary phase relative to the latter.

[0144] Furthermore, the strength of the difference in solvation of the eluent or the degree of elution can be adjusted by one or more of the following methods:

[0145] i. Polarity of the eluent

[0146] ii. Solubility of the eluent

[0147] iii. Eluent flow rate

[0148] iv. Working time of the eluent

[0149] v. Elution temperature.

[0150] Furthermore, the completion of the step of determining the second elution may be performed by conventional detection or monitoring methods in the art, which may include optical detection methods and the like.

[0151] In addition, the components obtained in the second elution step (the purified product system) can be subjected to any other treatments as needed after collection, and these treatments may include one or more of solid-liquid separation, further particle size classification, drying, redispersion, etc.

[0152] (Steps of regeneration)

[0153] The regeneration step of the present invention is mainly used to regenerate the stationary phase so that the stationary phase can be reused.

[0154] The regeneration step of the present invention includes using a cleaning agent to clean the stationary phase.

[0155] In principle, there is no particular limitation on the cleaning agent, as long as it can substantially completely desorb the components adsorbed on the stationary phase.

[0156] In some specific embodiments, the cleaning agent may be a fluid having a strong solvation effect on the quantum dot material, and examples of the fluid include organic solvents of a single type or a mixture of multiple substances, supercritical fluids, and the like.

[0157] In some other specific embodiments, the cleaning agent may be the same as or different from the mobile phase used in the second elution step.

[0158] Furthermore, the cleaning effect can be adjusted by adjusting the flow rate of the cleaning agent, the working time, the cleaning temperature and other conditions (if necessary).

[0159] Cleaning agents can also be recovered through solvent recovery devices.

[0160] In addition, in the regeneration step, the stationary phase after being cleaned with the cleaning agent may be further treated by heating, drying, etc. without limitation.

[0161] (Continuous cycle processing)

[0162] The purification method of the present invention may be performed once or multiple times in each of the above steps, or may be a continuous treatment method in which multiple cycles of the above steps are sequentially performed.

[0163] In particular, when the cycle starts, while the regeneration step is being performed, at least one of the contacting step, the first elution step, and the second elution step is being performed.

[0164] In some preferred embodiments of the present invention, after the regeneration step of the current cycle is completed, the contacting step of the next cycle can be immediately entered.

[0165] In some other preferred embodiments of the present invention, after the contacting step is completed, the next contacting step is immediately performed using a purified stationary phase / solid phase extraction column.

[0166] Such a continuous processing method provides the possibility for large-scale, online purification of quantum dot materials.

[0167] <Second Aspect>

[0168] In a second aspect of the present invention, a system or device for continuous, online purification of quantum dot materials is provided, which is used to perform the purification method described in the first aspect above.

[0169] Furthermore, the system or device mainly includes: a sample injection unit, a solid phase extraction unit and a sample recovery unit, and optionally includes a detection unit, a temperature control unit, a valve, a diversion unit, etc.

[0170] Wherein, the sampling unit is used to place the quantum dot system to be purified. In some preferred embodiments, the sampling unit can be an automatic sampling unit, and preferably, can be connected to the quantum dot synthesis unit.

[0171] The solid phase extraction unit may include a mobile phase providing unit, a stationary phase unit and optionally a solvent / waste liquid recovery or collection unit, and the solid phase extraction unit includes two or more independent solid phase extraction columns. The solid phase extraction unit is configured so that when one or more solid phase extraction columns perform a solid phase extraction operation, at least one of the other solid phase extraction columns is in a regenerated or regenerated state.

[0172] The mobile phase supply unit may supply one or more solvents through a mobile phase pump.

[0173] For the stationary phase unit, it is preferred that it can be a cylindrical particle-filled column. In addition, in some other specific embodiments, the stationary phase unit has a plurality of substantially identical filling columns connected in parallel, such as 2 to 4, etc. Thus, when a filling column is regenerated, a new filling column can be directly used to perform the method in the first aspect, thereby improving the purification efficiency.

[0174] In addition, for the solvent collection unit, in some preferred embodiments, it can be allowed to be connected to the mobile phase providing unit to directly return the collected solvent to the mobile phase providing unit. For the waste liquid recovery unit, in some specific embodiments, it can also be allowed to be connected to the quantum dot synthesis unit to directly return the waste liquid to the quantum dot synthesis unit for new quantum dot synthesis.

[0175] Through the above-mentioned system or device for purifying quantum dot materials of the present invention, the purification cycle of the present invention can be performed once or multiple times, and online and continuous purification can be achieved. Therefore, the continuous treatment of the present invention includes two meanings. On the one hand, it is the continuous purification of the directly obtained quantum dot reactants, and on the other hand, the purified system can also be further purified continuously.

[0176] Regarding the liquid inlet and outlet mode of the stationary phase, in order to improve the consistency of the liquid flow path and improve the purification efficiency, the present invention preferably enters from the lower end of the stationary phase unit and flows out from the upper end.

[0177] <Third Aspect>

[0178] The present invention also provides a method for preparing a quantum dot material, wherein the method comprises:

[0179] Steps for synthesizing quantum dot materials;

[0180] Purification steps of quantum dot materials,

[0181] The step of purifying the quantum dot material includes purifying the reaction product system obtained by the step of synthesizing the quantum dot material according to any of the purification methods described above, and the quantum dots can be purified continuously and efficiently, so that the preparation process of the quantum dot material is continuous.

[0182] Example

[0183] The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0184] The CdSe quantum dot solution was synthesized by hot injection or microfluidics, and its absorption peak position, concentration and half-peak width were detected by Agilent Cary8454 UV-visible spectrophotometer.

[0185] Solid phase extraction column packing (two, of which Figure 1The solid phase extraction column represents two parallel columns): fill the modified glass microspheres into the solid phase extraction column (the addition range is between 50% and 100%), tighten the lid, and set aside. The diameter of the glass microspheres is 200μm; column specifications: inner diameter 3cm, length 40cm.

[0186] Solid phase extraction online purification:

[0187] The quantum dots to be purified were divided into two groups and subjected to the following treatments:

[0188] Quantum dot adsorption process (contact step) :

[0189] Open valve 4, open valve 1, draw 5 mL of quantum dots (the first group of quantum dots to be purified) into syringe No. 1, and adjust the injection speed to 5 mL min -1 ; Open valve 2, draw 60mL of extractant into syringe No. 2, and adjust the injection speed to 50mL·min -1 ; Two phases are injected simultaneously, and the injection speed ratio of pump 1 and pump 2 is controlled at 5 (the ratio of quantum dots and extractant is regulated by controlling the injection speed ratio). After the quantum dot solution is injected (injected from the lower end to the higher end of the column), pump 1, valve 1, pump 2, and valve 2 are closed; after the contact step is completed, the next identical solid phase extraction column is used to continue the contact step of the second group of quantum dots to be purified.

[0190] Cleaning process (first elution step) :

[0191] Open valve 2, draw 50 mL of extractant into syringe No. 2, and adjust the injection speed to 50 mL min -1 ; Inject 60mLA, after injection, close pump 2 and valve 2; repeat the above steps 8 times (the number of repetitions affects the degree of cleaning). After the first elution step, continue the first elution step for the next solid phase extraction column that has completed the contact step.

[0192] Reconstitution process (second elution step) :

[0193] Close valve 4 and open valve 5. Open valve 3 and draw 60 mL of resolvent (cleaning agent) into syringe No. 3. Adjust the injection speed to 60 mL min. -1 After the sample collection is completed, close pump 1, valve 1, and valve 5. After the second elution step, the next First elution step The solid phase extraction column is continued to the second elution step.

[0194] Regeneration (steps of regeneration) :

[0195] Open valve 4, open valve 1, draw 60 mL of resolvent into syringe No. 1, and adjust the injection speed to 60 mL min -1After the residual quantum dots in the pipeline are rinsed clean, close pump 1 and valve 1. Open valve 2, draw 60 mL of resolvent into syringe No. 2, and adjust the injection speed to 60 mL min -1 , inject 60mL of resolvent, and after the injection, close pump 2 and valve 2. After the regeneration step, continue the regeneration step for the next solid phase extraction column that has completed the second elution step.

[0196] After the regeneration of one solid phase extraction column is completed, the other solid phase extraction column is in the second elution step. The extraction column obtained after the regeneration step continues to purify the first group of quantum dots, and the second group of quantum dots is processed in the same way.

[0197] The above steps were repeated three times for each group of quantum dots, and then mixed to obtain the total purified product.

[0198] Evaluation of purification results:

[0199] After diluting the solution before and after purification to a certain concentration, use a pipette to draw 10-15 μL of it and apply it on a glass slide. After drying, observe the morphology under a microscope (such as Figure 4 ). The results showed that there were a lot of impurities in the membrane before purification, but no impurities in the membrane after purification, indicating that the purification was effective.

[0200] It should be noted that, although the technical solution of the present invention is introduced with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto.

[0201] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A purification method for continuous purification of quantum dots, characterized in that: The purification method comprises the following steps: A contacting step, so that the quantum dot system to be purified is in contact with the stationary phase; A first elution step, using an extractant to elute non-target components in the quantum dot system to be purified, wherein the non-target components include one or more of unreacted components, impurity components, and free ligand components, and in the first elution step, the target component is substantially retained in the stationary phase; A second elution step, using an eluent to elute the target component from the stationary phase; a regeneration step, wherein the regeneration step comprises using a cleaning agent to clean the stationary phase, and, The above steps are performed one or more times, or a cycle formed by performing the steps one or more times is performed, and after the cycle starts, while the regeneration step is being performed, at least one of the contacting step, the first elution step, and the second elution step is being performed.

2. The purification method according to claim 1, characterized in that The quantum dot system to be purified is an untreated reaction product system directly obtained from the synthesis reaction of the quantum dot material; the regeneration step also includes a step of drying the stationary phase after cleaning.

3. The purification method according to claim 1 or 2, characterized in that The quantum dot system to be purified is one of an oily quantum dot system and an aqueous quantum dot system.

4. The purification method according to any one of claims 1 to 3, characterized in that The stationary phase consists of particles whose surfaces are modified by silanes having long-chain alkyl groups.

5. The purification method according to any one of claims 1 to 4, characterized in that: One or more extractants are used in the first elution step; and / or, in the first elution step, the non-target components are eluted by the solvation effect of the extractant.

6. The purification method according to any one of claims 1 to 5, characterized in that: In the first elution step, one or more of the following conditions are adjusted to elute the non-target components: i. Polarity of the extractant ii. Solubility of the extractant iii. Flow rate of the extractant iv. Working time of the extractant v. Extraction temperature.

7. The purification method according to any one of claims 1 to 6, characterized in that: In the second elution step, one or more eluents are used; and / or, in the second elution step, the target component is eluted by the solvation effect of the eluent.

8. The purification method according to any one of claims 1 to 7, characterized in that In the second elution step, one or more of the following conditions are adjusted to elute the target component: i. Polarity of the eluent ii. Solubility of the eluent iii. Eluent flow rate iv. Working time of the eluent v. Elution temperature.

9. A method for preparing a quantum dot material, characterized in that: The method comprises: Steps for synthesizing quantum dot materials; Purification steps of quantum dot materials, The step of purifying the quantum dot material comprises purifying the reaction product system obtained by the step of synthesizing the quantum dot material according to the purification method according to any one of claims 1 to 8.

10. A device for the purification method according to any one of claims 1 to 8, characterized in that: The device comprises: Injection unit, solid phase extraction unit and sample recovery unit, Wherein, the injection unit is used to place the quantum dot system to be purified. The solid phase extraction unit comprises a mobile phase providing unit, a stationary phase unit and optionally a solvent / waste liquid collecting unit. Furthermore, the solid phase extraction unit comprises more than two independent solid phase extraction columns, and the solid phase extraction unit is configured such that when one or more solid phase extraction columns perform solid phase extraction operations, at least one of the other solid phase extraction columns is in a regenerating or regenerated state.

Images