Quantum dot complex and preparation method thereof, quantum dot composition and application thereof

Abstract

The present disclosure provides a quantum dot complex, a preparation method thereof, a quantum dot composition, and its application. The quantum dot complex comprises quantum dots and surface ligands of the quantum dots, wherein the number of the surface ligands is greater than or equal to one, and the surface ligands are magnetic. The magnetic quantum dots can be better separated or distributed at different densities.

Description

Technical Field

[0001] The present disclosure relates to the field of quantum dot luminescence technology, and in particular to a quantum dot complex and a preparation method thereof, a quantum dot composition and applications thereof. Background Art

[0002] Currently, most photoluminescent devices developed and produced using quantum dot materials achieve a white field display effect by using a blue backlight combined with a mixture of red and green quantum dots. With the increasing diversity and richness of quantum dot display applications and increasingly stringent market requirements, the separation of red and green quantum dots and the control of their distribution density (concentration) to achieve optimal performance have become increasingly important. Summary of the Invention

[0003] The purpose of the present disclosure is to provide a quantum dot complex and a preparation method thereof, a composition containing the same, a quantum dot photoluminescent device and a preparation method thereof, so as to solve the problems of the prior art in that it is difficult to separate different quantum dots and that the luminescence efficiency is reduced due to self-absorption between quantum dots in actual applications.

[0004] To achieve the above objectives, according to the first and second aspects of the present invention, a quantum dot complex and a method for preparing the same are provided, wherein the quantum dot complex has a special magnetic ligand. When placed in an external magnetic field, the magnetic quantum dot complex will orient itself in an orderly manner and generate a magnetic moment; interaction forces will be generated between magnetic fields. Compared with traditional ferroferric oxide quantum dot magnetic complexes, the magnetic ligands of the present application have more selectivity, and the strength of the magnetism can be adjusted according to structural control, making them better suited for practical applications. The preparation of magnetic quantum dot complexes can be achieved through ligand exchange.

[0005] According to a third aspect of the present invention, a quantum dot composition is provided. The quantum dot composition has good separability of different quantum dots and reduces self-absorption.

[0006] According to the fourth and fifth aspects of the present invention, a quantum dot photoluminescent device and its preparation method are provided. Under the influence of an external magnetic field, different quantum dot complexes have different interactions with the magnetic field. As a result, quantum dot complexes with strong mass magnetic susceptibility tend to concentrate on one side, thereby achieving stratification of different quantum dots or a density distribution of quantum dots, reducing self-absorption between quantum dots. During the preparation of the quantum dot photoluminescent device, separation can be achieved using a magnetic field. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are intended to explain the present disclosure and do not constitute an improper limitation of the present disclosure. In the accompanying drawings:

[0008] Figure 1Schematic diagram of the structure of a quantum dot complex disclosed in the present invention.

[0009] Figure 2 This is a schematic diagram of an initial state in which a quantum dot complex of a quantum dot photoluminescent device disclosed herein is not separated.

[0010] Figure 3 This is a schematic diagram of the separation state of a quantum dot complex in a quantum dot photoluminescent device disclosed herein under a magnetic field.

[0011] Figure 4 This is a graph showing the change in the mass magnetic susceptibility ratio of green and red quantum dots under different magnetic field intensities according to an example of the present disclosure.

[0012] Figure 5 This is a fluorescence microscope photograph of the delamination of the red and green quantum dot composite glue layer (under excited state) of a quantum dot photoluminescent device obtained in one embodiment of the present disclosure.

[0013] 1. First quantum dot complex; 2. Second quantum dot complex; 3. Substrate; 4. Magnet; 5. Green quantum dot light-emitting layer; 6. Red quantum dot light-emitting layer.

[0014] Note that in the embodiments described below, the same reference numerals are sometimes used in common across different drawings to denote the same parts or parts having the same functions, and their repeated descriptions are omitted. In some cases, similar reference numerals and letters are used to denote similar items, so once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0015] For ease of understanding, the positions, sizes, and ranges of various structures shown in the drawings and the like may not represent actual positions, sizes, and ranges, etc. Therefore, the present disclosure is not limited to the positions, sizes, and ranges disclosed in the drawings and the like. DETAILED DESCRIPTION

[0016] Various exemplary embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure.

[0017] The following description of at least one exemplary embodiment is merely illustrative and is not intended to limit the present disclosure, its application, or use. In other words, the structures and methods herein are presented in an exemplary manner to illustrate various embodiments of the structures and methods of the present disclosure. However, those skilled in the art will appreciate that these are merely exemplary of the disclosure that may be implemented, and are not exhaustive. Furthermore, the drawings are not necessarily drawn to scale, and some features may be exaggerated to illustrate details of specific components.

[0018] In addition, technologies, methods and devices known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, such technologies, methods and devices should be considered part of the authorization specification.

[0019] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0020] The words "left," "right," "front," "back," "top," "bottom," "up," "down," "high," "low," and the like, if any, in the specification and claims, are used for descriptive purposes and are not necessarily intended to describe invariant relative positions. It should be understood that the words so used are interchangeable under appropriate circumstances so that the embodiments of the present disclosure described herein, for example, can operate in other orientations than those shown or otherwise described herein. For example, when the device in the figures is turned over, features previously described as "above" other features could now be described as "below" the other features. The device can also be otherwise oriented (rotated 90 degrees or in other orientations) and relative spatial relationships will be interpreted accordingly.

[0021] In the specification and claims, when an element is referred to as being "on," "attached," "connected," "coupled," or "coupled" to another element, the element may be directly on, directly attached, directly connected, directly coupled, or directly coupled to another element, or one or more intervening elements may be present. In contrast, when an element is referred to as being "directly" on, "directly attached," "directly connected," "directly coupled," or "directly coupled" to another element, there may be no intervening elements. In the specification and claims, when a feature is arranged "adjacent" to another feature, it may mean that the feature has a portion that overlaps with the adjacent feature or a portion that is located above or below the adjacent feature.

[0022] As used herein, the word "exemplary" means "serving as an example, instance, or illustration," rather than as a "model" to be precisely copied. Any implementation described as exemplary is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, this disclosure is not to be bound by any expressed or implied theory presented in the technical field, background, summary, or detailed description.

[0023] As used herein, the term "substantially" is intended to encompass any minor variations due to design or manufacturing imperfections, device or component tolerances, environmental influences, and / or other factors. The term "substantially" also allows for deviations from a perfect or ideal condition due to parasitic effects, noise, and other practical considerations that may be present in actual implementations.

[0024] Additionally, terms such as "first," "second," and the like may also be used herein for reference purposes only and are not intended to be limiting. For example, the terms "first," "second," and other numerical terms referring to structures or elements do not imply a sequence or order unless the context clearly indicates otherwise.

[0025] It should also be understood that when the term “include / comprises” is used in this document, it indicates the presence of the specified features, integers, steps, operations, units and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, units and / or components and / or their combinations.

[0026] In this disclosure, the term "providing" is used in a broad sense to encompass all ways of obtaining an object, so "providing an object" includes, but is not limited to, "purchasing," "preparing / manufacturing," "arranging / setting," "installing / assembling," and / or "ordering" an object, etc. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit this disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0027] According to a first aspect of the present application, a quantum dot complex is provided, comprising a quantum dot and a surface ligand of the quantum dot, wherein the number of the surface ligand is greater than or equal to 1, and the surface ligand is magnetic; and a connection structure between the surface ligand and the quantum dot is selected from one of Formulas 1 to 10:

[0028]

[0029]

[0030]

[0031]

[0032] Wherein, Q is a quantum dot, A is a functional group, atom or anion covalently connected to the quantum dot, B is a functional group, atom or anion covalently connected to the metal element M, L is a ligand coordinated to the metal element M, and the metal element M in Formula 1 to Formula 4 is Ni2+ , Mn 2+ , Cu 2+ or Mn 4+ , the metal element M in formula 5 to formula 10 is Fe 3+ ,Co 2+ or Cr 3+ ; n is an integer greater than or equal to 0.

[0033] Quantum dots are semiconductor nanocrystal structures with a specific group of elements at the center, and the outer layer of the quantum dot structure usually has an organic ligand. The ligands of quantum dots can achieve ligand exchange through the strength of the ligand coordination ability to obtain the ligands that people expect to perform specific functions. The ligands of Formulas 1 to 10 are magnetic organic ligands, and the magnetization of quantum dot materials can be achieved by using the ligand exchange principle. When the magnetic quantum dot complex is placed in an external magnetic field environment, it will be oriented in an orderly manner to generate a magnetic moment; an interaction force will be generated between the magnetic fields. Compared with traditional ferroferric oxide quantum dot magnetic complexes, the magnetic ligands of this application are more selective, and the strength of the magnetism can be adjusted according to structural control, which is better adapted to practical applications. Moreover, only the surface of the quantum dots is modified, which will not affect the internal structure of the quantum dots themselves.

[0034] These quantum dot complexes can be applied in a variety of fields, including display, catalytic chemical reactions, biomedicine, and heavy metal detection. For example, the fluorescence effect of quantum dots can be fully utilized for calibration, further enriching the practical applications of quantum dot complexes.

[0035] In the structures of formulas 1 to 10, the mass magnetic susceptibility of the metal element M is similar, and the mass magnetic susceptibility of the structures of formulas 1 to 4 is greater than that of the structures of formulas 5 to 10. The structure of formula 1 is preferred.

[0036] In some embodiments, n ranges from 0-18.

[0037] In some embodiments, A is selected from one of the following groups, atoms, or anions: -SH, -OH, -COO - ,-NH2.

[0038] In some embodiments, B is selected from one of the following groups, atoms, or anions: N, O, -O-, -COO - , -N3, -CN, carbon-carbon double bond, carbon-carbon triple bond.

[0039] In some embodiments, L is a molecule or ion having at least one atom containing a lone pair of electrons or a delocalized electron. Preferably, L is one of F-, Cl-, Br-, OH-, SCN-, CN-, H2O, NH3, ethylenediamine, olefins, alkynes, and aromatic hydrocarbons.

[0040] In some embodiments, multiple surface ligands surround a quantum dot, and the quantum dot complex is a triangular, tetrahedral, or spherical structure. The spatial structure is mainly affected by steric hindrance. Figure 1 Schematic diagrams of three structures are shown. The aforementioned structure is formed by the metal element M and the quantum dot connected by L coordination. The triangular structure has three surface ligands connected to one quantum dot, the tetrahedron has four surface ligands connected to one quantum dot, and the sphere has multiple surface ligands connected to one quantum dot. The structure in which the metal element M and L are coordinated is referred to as a magnetic group in some places below.

[0041] The material of the quantum dots is not limited and can be a core-shell structure, or a cadmium-containing or cadmium-free material.

[0042] According to the second aspect of the present application, a method for preparing any of the above-mentioned quantum dot complexes is provided, preparing quantum dots with a first ligand, and performing ligand exchange on the quantum dots with the first ligand and a second ligand to obtain the quantum dot complex; or preparing quantum dots with a first ligand, performing ligand exchange on the quantum dots with the first ligand and a third ligand to obtain quantum dots with a third ligand, and performing ligand exchange on the quantum dots with the third ligand and a fourth ligand to obtain the quantum dot complex; wherein the first ligand and the third ligand are non-magnetic ligands, and the second ligand and the fourth ligand are magnetic ligands.

[0043] The first ligand can be selected from trialkylphosphines, oleic acid, oleylamine, and the like, so that the quantum dots are oil-soluble. The third ligand can be L. Those skilled in the art will appreciate the appropriate ligand structure to obtain the magnetic surface ligand shown in the above structural formula. Ligand exchange can be performed based on the coordination strength of the ligand and the quantum dot.

[0044] In some embodiments, a metal organic compound having a structural formula such as Formula 13 to Formula 15 is prepared.

[0045]

[0046] The metal organic compound and the fifth ligand are mixed and reacted to obtain the second ligand. The structural formula of the fifth ligand is Formula 16.

[0047] A' and B' are precursors of the aforementioned A and B, respectively. The quantum dots having the first ligand are subjected to ligand exchange with the second ligand to obtain the aforementioned quantum dot complex.

[0048] The above method can be used to connect a compound containing a metal element M with quantum dots to obtain a magnetic quantum dot complex. It should be noted that the exchange rate of the above ligand exchange is not necessarily 100%, but is preferably above 50%.

[0049] In some embodiments, the exchange rate of a single ligand exchange between quantum dots and magnetic ligands during the coordination process may be very low, so multiple ligand exchanges are performed to increase the magnetic properties of the quantum dot complex. After the completion of each of the above reactions, separation and purification operations, such as centrifugation, may be performed.

[0050] In some embodiments, before the quantum dots (whether quantum dots with the first ligand or quantum dots with the third ligand) undergo ligand exchange, the surface of the quantum dots is pretreated to enhance the coordination effect between the quantum dots and the magnetic ligands.

[0051] In some embodiments, the specific structures of A' and B' refer to the specific selections of A and B mentioned above. Those skilled in the art know which A' and B' should be selected to obtain A and B. In some selections, A and A' are the same, and B and B' are the same.

[0052] In the process of preparing metal organic compounds, the type of metal organic compound formed mainly depends on the structure of the ligand L (the number of chelating teeth of L) and the ratio of the raw materials input into the reaction of the metal element M and L. In one reaction, generally one structure is formed.

[0053] For quantum dot complexes with the same central metal element M, generally, the mass magnetic susceptibility of the multi-nuclear central metal element M quantum dot complex is greater than the mass magnetic susceptibility of the binuclear central metal element M quantum dot complex and is greater than the mass magnetic susceptibility of the mononuclear central metal element M quantum dot. Therefore, when selecting ligands and preparing quantum dot complexes, binuclear or multi-nuclear magnetic metal organic compound groups are preferred.

[0054] In some embodiments, the ratio of the number of quantum dots to the number of metal elements in the second ligand or the fourth ligand is 1:3 to 6:1. Different number ratios can achieve different mass magnetic susceptibilities.

[0055] The number of molecules in the magnetic structure connected to a single quantum dot is determined by factors such as the steric hindrance of the magnetic group and the coordination ability between the quantum dot and the magnetic group. A magnetic group, through the coordination of the primary ligand, is surrounded by many quantum dots, forming a large aggregate or cluster. This results in a small volume or mass magnetic susceptibility of the individual quantum dot, and its interaction with the external magnetic field is weak. The more magnetic groups connected to a single quantum dot, the stronger the interaction of the resulting quantum dot complex with the external magnetic field.

[0056] By selecting different magnetic group precursors, controlling the ratio of quantum dots and magnetic group reaction raw materials, controlling the number of ligand exchanges between quantum dots and magnetic groups, and controlling the ligand exchange reaction conditions between quantum dots and magnetic groups, different numbers of magnetic groups can be coordinated on the surface of quantum dots to obtain quantum dot complexes with different magnetic susceptibilities.

[0057] According to a third aspect of the present application, a quantum dot composition is provided, comprising a first quantum dot complex and a second quantum dot complex, wherein the first quantum dot complex and the second quantum dot complex are each any one or both of the aforementioned quantum dot complexes, and the first quantum dot complex and the second quantum dot complex have different peak emission wavelengths. The quantum dot composition exhibits good separability of different quantum dots and reduces self-absorption.

[0058] In some embodiments, the peak emission wavelengths of the first quantum dot complex and the second quantum dot complex are 615-635 nm and 525-545 nm, respectively.

[0059] In some embodiments, the mass magnetic susceptibility of the first quantum dot complex and the second quantum dot complex are different. Preferably, the metal elements M in the complexes are different. The mass magnetic susceptibility (magnetic intensity control) of the magnetic quantum dot complex depends on two aspects: one is the metal elements / ion types with different spin quantum numbers, for example, Fe 3+ ,Co 2+ , Ni 2+ , Mn 2+ , Cu 2+ The second factor is the difference in the number of magnetic metal elements connected to a single molecule quantum dot. Therefore, by adjusting these two factors, the magnetic strength of the magnetic quantum dot complex can be controlled.

[0060] In some embodiments, quantum dot complexes with the same peak emission wavelength (band) can be modified and controlled to produce quantum dot complexes with different mass magnetic susceptibilities by adjusting and controlling the magnetic groups. This allows for a gradient variation in the concentration or distribution density of quantum dot complexes with the same peak emission wavelength (band) along a specific direction within a single color light-emitting layer.

[0061] In some embodiments, the surface ligand of the first quantum dot complex binds to the quantum dot in a structural formula of Formula 11:

[0062]

[0063] The structural formula of the surface ligand of the second quantum dot complex combined with the quantum dot is formula 12:

[0064]

[0065] In some embodiments, the composition further comprises a polymerizable polymer precursor or scattering particles or an initiator or other functional components.

[0066] In some embodiments, the ratio of the mass magnetic susceptibility of the second quantum dot complex to the mass magnetic susceptibility of the first quantum dot complex is greater than 1, preferably greater than 2. The greater the difference between the two, the more conducive the separation is.

[0067] According to the third aspect of the present application, a method for preparing a quantum dot photoluminescent device is provided, wherein the above-mentioned composition containing quantum dot complexes with different mass magnetic susceptibilities is arranged on a substrate to form a quantum dot composition layer, a magnetic field is applied to the quantum dot composition layer, the first quantum dot complex and the second quantum dot complex have different movement speeds in the quantum dot composition layer, the quantum dot composition layer is cured to obtain a quantum dot layer, and the first quantum dot complex and the second quantum dot complex have different distribution densities in the direction of the magnetic field in the quantum dot layer. Under the action of an external magnetic field, different quantum dot complexes have different interaction forces with the magnetic field, so that quantum dot complexes with strong mass magnetic susceptibility will be concentrated on one side, thereby achieving stratification of different quantum dots or density distribution of quantum dots. When preparing a quantum dot photoluminescent device, separation can be achieved using a magnetic field. The working principle is as follows: Figure 2 and 3 shown.

[0068] The curing process is light curing, heat curing or drying. In some embodiments, the applied magnetic field is perpendicular to the quantum dot composition layer.

[0069] In some embodiments, when a magnetic field is applied, the quantum dot composition layer is exposed to an ambient temperature of 50-300 K. Preferably, the ambient temperature is 180-300 K. The magnetic susceptibility decreases with increasing temperature, while the viscosity of polymer precursors, such as monomers, in the composition increases with decreasing temperature. Curves showing changes in magnetic susceptibility and monomer viscosity as a function of temperature indicate that the magnetic susceptibility curve does not change significantly within the range of 180-300 K.

[0070] In another aspect of the present application, a quantum dot photoluminescent device is provided, comprising a first quantum dot complex and a second quantum dot complex, wherein at least one of the first quantum dot complex and the second quantum dot complex is any of the aforementioned quantum dot complexes.

[0071] In some embodiments, the quantum dot photoluminescent device further includes a polymer matrix, and the first quantum dot complex and the second quantum dot complex have different distribution densities in the polymer matrix.

[0072] In some embodiments, the ligand L and the polymer matrix are selected to be well matched and compatible, forming a monodisperse system. The resulting magnetic quantum dot complex exhibits low resistance to movement in a magnetic field. Preferably, the ligand L is pentaerythritol triacrylate or di-trimethylolpropane tetraacrylate.

[0073] In some embodiments, the first quantum dot complex and the second quantum dot complex have different distribution densities in the vertical direction in the polymer matrix. Preferably, the first quantum dot complex and the second quantum dot complex are arranged in layers.

[0074] In some embodiments, the first quantum dot complex and the second quantum dot complex have different distribution densities in the vertical direction in the polymer matrix. In the same spatial reference system, the distribution density of the first quantum dot complex gradually decreases, while the distribution density of the second quantum dot complex gradually increases.

[0075] In some embodiments, the first quantum dot complex and the second quantum dot complex have different distribution densities in the vertical direction in the polymer matrix. The above-mentioned quantum dot photoluminescent device also includes an LED. The distribution density of the first quantum dot complex gradually decreases in the direction away from the LED, and the distribution density of the second quantum dot complex gradually increases in the direction away from the LED.

[0076] In some embodiments, the first quantum dot complex and the second quantum dot complex are respectively a red quantum dot complex and a green quantum dot complex, so that the luminous efficiency of the quantum dot photoluminescent device is improved.

[0077] In some embodiments, the quantum dot photoluminescent device is a quantum dot film, a quantum dot diffusion plate, or a quantum dot LED (the size of the LED is not limited).

[0078] Hereinafter, the embodiments are described in more detail with reference to specific examples. However, they are illustrative examples of the present disclosure, and the present disclosure is not limited thereto.

[0079] Example 1: Synthesis of magnetic green quantum dot complex:

[0080] An analytical balance was used to accurately weigh 4.76 g of nickel chloride hexahydrate, 20.00 g of ethanol, 8.50 g of 3-mercaptopropionic acid, and 8.10 g of triethylamine. These four compounds were placed in a clean round-bottom flask and stirred at room temperature for 24 hours. The mixture was then extracted with ethyl acetate and centrifuged at 6000 RPM for 5 minutes. The precipitate at the bottom of the test tube, representing the nickel metal organic compound, was dried in a vacuum oven. An analytical balance was used to weigh 5.00 g of a toluene solution of green quantum dots (PL = 538 nm, green quantum dot mass concentration of 38.33% wt, original ligand: trioctylphosphine), 10.00 g of toluene solvent, and 5.00 g of the nickel metal organic compound. The mixture was stirred at room temperature in the dark for 24 hours. After the reaction is complete, methanol solvent is used for extraction, followed by high-speed centrifugation at a speed of 6000 RPM for 5 minutes. The precipitate at the bottom of the test tube is dried to obtain a magnetic green quantum dot complex. The structure of the complex combined with the quantum dots is shown in Formula 11.

[0081] Example 2: Synthesis of magnetic red quantum dot complex:

[0082] An analytical balance was used to accurately weigh 2.37 g of ferric chloride, 20.00 g of ethanol, 9.29 g of 3-mercaptopropionic acid, and 8.85 g of triethylamine. These four compounds were placed in a clean round-bottom flask and stirred at room temperature for 24 hours. The mixture was then extracted with ethyl acetate and centrifuged at 6000 RPM for 5 minutes. The iron metal organic compound was located at the bottom of the test tube and dried in a vacuum oven. An analytical balance was used to weigh 10.00 g of a red quantum dot solution (PL = 617 nm, red quantum dot mass concentration of 31.78% wt, original ligand: tributylphosphine), 10.00 g of toluene solvent, and 2.00 g of the iron metal organic compound. The mixture was stirred at room temperature in the dark for 24 hours. After the reaction is complete, methanol solvent is used for extraction, followed by high-speed centrifugation at a speed of 6000 RPM for 5 minutes. The precipitate at the bottom of the test tube is dried to obtain a magnetic red quantum dot complex. The structure of the complex combined with the quantum dots is shown in Formula 12.

[0083] The obtained red and green magnetic quantum dot composites (powder state) were subjected to mass magnetic susceptibility testing using a vibrating sample magnetometer. Figure 4 is the ratio of the mass magnetic susceptibility of the magnetic green quantum dot composite of Example 1 to the magnetic red quantum dot composite of Example 2 under different magnetic field environments.

[0084] Example 3

[0085] The magnetic green quantum dot complex and the magnetic red quantum dot complex synthesized in Examples 1 and 2 were dispersed in isobornyl acrylate, and then a photoinitiator (2,4,6-trimethylbenzoyl) diphenylphosphine oxide was added, and the mixture was subjected to ultrasonic treatment to obtain a red and green dual-color quantum dot ink. The red and green dual-color quantum dot ink was then coated on a glass substrate in an environment with a magnetic field strength of 1 T and an ambient temperature of about 300K. After standing for a period of time (such as 20 minutes), it was cured using a UV-LED lamp and magnified 120 times using an optical microscope (blue light source), to obtain the following: Figure 5 A photo of the layers of a quantum dot composite structure shows a green magnetic quantum dot composite layer (5), a red magnetic quantum dot composite layer (6), and a mixed red and green magnetic quantum dot composite layer (the middle layer between 5 and 6). This allows for separation and controlled distribution density of the magnetic quantum dot composites.

[0086] Although some specific embodiments of the present disclosure have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present disclosure. The various embodiments disclosed herein may be combined in any manner without departing from the spirit and scope of the present disclosure. It should also be understood by those skilled in the art that various modifications may be made to the embodiments without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A quantum dot composite, characterized in that The quantum dot complex includes quantum dots and surface ligands of the quantum dots, the number of the surface ligands is greater than or equal to 1, and the surface ligands are magnetic; a connection structure between the surface ligand and the quantum dot is selected from one of Formulas 1 to 10: Wherein, Q is a quantum dot, A is -SH, and B is -COO - , L is a ligand coordinated with the metal element M, L is F - 、Cl - Br - One of the following; the metal element M in formula 1 to formula 4 is Ni 2+ , Mn 2+ , Cu 2+ or Mn 4+ , the metal element M in formula 5 to formula 10 is Fe 3+ ,Co 2+ or Cr 3+ ; n is an integer greater than or equal to 0 and less than or equal to 18.

2. A method for preparing a quantum dot composite according to claim 1, characterized in that: Prepare quantum dots with a first ligand, perform ligand exchange on the quantum dots with the first ligand and a second ligand to obtain the quantum dot complex; or prepare quantum dots with a first ligand, perform ligand exchange on the quantum dots with the first ligand and a third ligand to obtain quantum dots with a third ligand, perform ligand exchange on the quantum dots with the third ligand and a fourth ligand to obtain the quantum dot complex; wherein the first ligand and the third ligand are non-magnetic ligands, and the second ligand and the fourth ligand are magnetic ligands.

3. The method for preparing the quantum dot complex according to claim 2, wherein: The ratio of the number of the quantum dots to the number of the metal elements in the second ligand or the fourth ligand is 1:3 to 6:

1.

4. A quantum dot composition, characterized in that The invention comprises a first quantum dot complex and a second quantum dot complex, wherein the first quantum dot complex and the second quantum dot complex are both the quantum dot complexes according to claim 1, and the first quantum dot complex and the second quantum dot complex have different peak emission wavelengths.

5. The quantum dot composition according to claim 4, characterized in that The peak emission wavelengths of the first quantum dot complex and the second quantum dot complex are 615-635 nm and 525-545 nm, respectively.

6. The quantum dot composition according to claim 4, characterized in that The M metal elements in the first quantum dot complex and the second quantum dot complex are different.

7. The quantum dot composition according to claim 4, characterized in that The structural formula of the surface ligand of the first quantum dot complex binding to the quantum dot is Formula 11: The structural formula of the surface ligand of the second quantum dot complex combined with the quantum dot is Formula 12:

8. The quantum dot composition according to claim 4, characterized in that The composition also includes a polymerizable polymer precursor or scattering particles or an initiator.

9. The quantum dot composition according to claim 4, characterized in that The ratio of the mass magnetic susceptibility of the second quantum dot complex to the mass magnetic susceptibility of the first quantum dot complex is greater than 2.

10. A method for preparing a quantum dot photoluminescent device, characterized in that: The quantum dot composition as described in claim 9 is arranged on a substrate to form a quantum dot composition layer, a magnetic field is applied to the quantum dot composition layer, the first quantum dot complex and the second quantum dot complex have different movement speeds in the quantum dot composition layer, the quantum dot composition layer is cured to obtain a quantum dot layer, and the first quantum dot complex and the second quantum dot complex have different distribution densities in the direction of the magnetic field in the quantum dot layer.

11. The method for preparing a quantum dot photoluminescent device according to claim 10, wherein: When the magnetic field is applied, the temperature of the environment in which the quantum dot composition layer is located is 50-300K.

12. A quantum dot photoluminescent device, characterized in that: The invention comprises a first quantum dot complex and a second quantum dot complex, wherein at least one of the first quantum dot complex and the second quantum dot complex is the quantum dot complex according to claim 1.

13. The quantum dot photoluminescent device according to claim 12, characterized in that: A polymer matrix is ​​also included, and the first quantum dot complex and the second quantum dot complex have different distribution densities in the polymer matrix.

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