Quantum dot pigment particle complex as well as preparation method and application thereof

Abstract

The invention discloses a quantum dot pigment particle complex as well as a preparation method and application thereof. The preparation method of the quantum dot pigment particle complex comprises the following steps: step 1, providing a cross-linkable ligand A and a cross-linkable ligand B which comprise two different functional groups, and a polar short-chain ligand; 2, respectively replacing ligands of the quantum dots through a cross-linkable ligand B and a polar short-chain ligand, and replacing ligands of the pigment particles through a cross-linkable ligand A and a polar short-chain ligand; and step 3, carrying out a ligand cross-linking reaction on the quantum dots and the pigment particles after ligand replacement to prepare the quantum dot and pigment particle complex. High-luminous-efficiency quantum dots are connected to the surfaces of pigment particles in a ligand cross-linking mode, meanwhile, the surfaces of the quantum dots are electrified by exchanging polar ligands, the moving capacity of color particles under the action of an electric field is improved, and the synergistic moving effect of the quantum dots and the pigment particles is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and particularly relates to a quantum dot pigment particle composite, a preparation method thereof, and an application thereof. Background Art

[0002] Compared with active light-emitting technologies (OLED, micro-LED), reflective display technologies have the advantages of eye protection, high contrast under strong light, extremely low power consumption, natural lighting, lightness, thinness, portability, flexibility, and long lifespan. Electronic paper is a paper-like technology that does not emit light by itself, relies on natural light reflection to form an image, and maintains static images in a bistable state without electricity consumption, belonging to reflective display. Black-and-white electronic paper can no longer meet people's display requirements for electronic paper. Color electronic paper is an inevitable trend in the development of electronic paper. In 2019, the electrophoretic color electronic paper technology officially entered the stage of mature application. However, due to factors such as the luminous efficiency, emission spectral line width, dispersion ability, and voltage migration rate of pigment particles (the existing pigment particles have a relatively low zeta potential and move slowly under an electric field), the currently mass-produced electrophoretic color electronic paper technology has problems of low brightness, slow response speed, and narrow color gamut.

[0003] Quantum dots have the advantages of high luminous efficiency, narrow emission spectrum, and wide color gamut. Applying quantum dots to electronic paper can effectively improve the problems of low brightness and narrow color gamut. There are mainly two existing methods to enhance the brightness and color gamut of electronic paper by using quantum dots. One is to introduce an excitation light source to excite the quantum dots, and the other is to let the quantum dots alone act as colored electrophoretic particles to reflect and emit light.

[0004] However, both of the two existing methods of using quantum dots to increase brightness and broaden the color gamut have relatively large technical defects. For example, in the method of introducing an excitation light source, not only does it require continuous power consumption for backlight illumination, but there are still problems of flicker and blue light leakage. Using quantum dots alone as colored electrophoretic particles to reflect and emit light has a relatively large color display deviation. This is because quantum dots have no absorption in the long wavelength band and directly reflect all long wavelength band light, resulting in a display effect that is a mixture of all long wavelength band light. Summary of the Invention

[0005] To solve the above problems, the present invention provides a quantum dot pigment particle composite, a preparation method thereof, and an application thereof. The high luminous efficiency quantum dots are connected to the surface of the pigment particles by means of ligand crosslinking, and at the same time, the quantum dots are charged by exchanging polar ligands on the surface to improve the movement ability of the color particles under the action of an electric field, realizing the synergistic movement effect of the quantum dots and the pigment particles (after the pigment particles are combined with the quantum dots with a high zeta potential after ligand exchange, their zeta potential increases and their movement ability is enhanced).

[0006] The present invention is realized through the following technical solutions:

[0007] On the one hand, the present invention provides a method for preparing a quantum dot pigment particle complex, comprising the following steps:

[0008] Step 1: Provide a crosslinkable ligand A and a crosslinkable ligand B each including two different functional groups, and a polar short-chain ligand;

[0009] Step 2: Replace the ligands of the quantum dots through the crosslinkable ligand B and the polar short-chain ligand, and replace the ligands of the pigment particles through the crosslinkable ligand A and the polar short-chain ligand respectively;

[0010] Step 3: Prepare a quantum dot pigment particle complex by a ligand crosslinking reaction of the ligand-replaced quantum dots and pigment particles.

[0011] Further, the structural formula of the crosslinkable ligand A is HOOC-R-SH or a dimethyl ketone structure containing a methyl ketone functional group, where R is an alkane chain -(CH 2 ) n -, n is 7-15.

[0012] Further, the structural formula of the crosslinkable ligand B is:

[0013] or an oleic acid ligand;

[0014] where R 1 represents an alkane chain with a carbon chain length of 5-13.

[0015] Further, the structural formula of the dimethyl ketone structure containing a methyl ketone functional group is:

[0016]

[0017] where R 2 is -O- or -S-, R 3 is -H or -N(CH 2 ) 4 ,R 4 is -(CH 2 ) n -, R 5 is -SH, -COOH, -PO 3 H 2 any one of.

[0018] Further, the polar short-chain ligand is selected from any one of the following:

[0019]

[0020] where R’ is an alkane chain -(CH 2 ) n -, n is 2-5.

[0021] Further, the specific method for replacing ligands of quantum dots in step two is as follows: Add crosslinkable ligand B and polar short-chain ligand to the uniformly monodisperse quantum dot solution respectively. One functional group of crosslinkable ligand B is used to connect with the surface of the quantum dots, and the other functional group of crosslinkable ligand B is used to connect with crosslinkable ligand A. Finally, quantum dots with crosslinkable ligand B and polar short-chain ligand on the surface are obtained.

[0022] Further, the specific method for replacing ligands of pigment particles in step two is as follows: Add crosslinkable ligand A and polar short-chain ligand to the uniformly monodisperse pigment particle solution respectively. One functional group of crosslinkable ligand A is used to connect with the surface of the pigment particles, and the other functional group of crosslinkable ligand A is used to connect with crosslinkable ligand B. Finally, pigment particles with crosslinkable ligand A and polar short-chain ligand on the surface are obtained.

[0023] Further, the specific method for step three is as follows: Use one or more of ultraviolet light irradiation, heating, adding initiator, and catalyst to initiate the crosslinking reaction between crosslinkable ligand A and crosslinkable ligand B for the quantum dots and pigment particles after ligand replacement, so that the quantum dots are connected to the pigment particles, and a quantum dot pigment particle complex is obtained.

[0024] In the second aspect, the present invention provides a quantum dot pigment particle complex prepared by the preparation method of the quantum dot pigment particle complex.

[0025] In the third aspect, the present invention provides an application of the quantum dot pigment particle complex in color electronic paper display technology.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. The present invention utilizes the characteristics of quantum dots with narrow linewidth, high luminous efficiency, and strong mobility of high zeta potential after ligand exchange, connects the quantum dots to the surface of the pigment particles, so that the obtained quantum dot pigment particle complex can emit the fluorescence of the quantum dots, which is superimposed with the reflected light of the pigment particles themselves, improving the brightness and light extraction ability;

[0028] 2. The narrow linewidth of the quantum dot fluorescence enables the complex to have a wider color gamut than the pigment particles. To achieve color display by the three primary colors of red, green, and blue, the three primary colors of red, green, and blue need to emit light with high color purity, that is, a narrow emission linewidth. For example, for red, its emission peak position is 630 nm, and the narrower the emission linewidth, the higher the red color purity. The quantum dot fluorescence has a narrower spectral linewidth than the reflected light of the pigment particles. Therefore, the quantum dot pigment particle complex has a higher color purity than the pigment particles, and thus can achieve a wider color gamut than the pigment particles;

[0029] 3. At the same time, quantum dots have a relatively high zeta potential and electrophoretic mobility, and move faster under an electric field, enabling the pigment particle complex to have a higher movement rate under an electric field than the pigment particles, thus improving the response speed.

[0030] In summary, the quantum dot pigment particle complex prepared by the present invention has a zeta potential higher than that of the pigment particles, improving the movement ability of the pigment particles. At the same time, the quantum dot pigment particle complex has a higher luminous efficiency and a wider color gamut than the pigment particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of connecting two ligands to the surface of pigment particles in the present invention;

[0032] Figure 2 It is a schematic diagram of connecting two ligands to the surface of quantum dots in the present invention;

[0033] Figure 3 It is a schematic diagram of the crosslinking reaction between quantum dots and pigment particles in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0034] The principle of the present invention is as follows: Through ligand exchange, two ligands are attached to the surface of the quantum dots. One polar short-chain ligand enables the quantum dots to have a relatively high zeta potential, and one crosslinkable ligand. This crosslinkable ligand has specific functional groups and can undergo a crosslinking reaction (without self-crosslinking) with specific ligands in the form of light or heat.

[0035] The pigment particles used in the present invention also have two ligands attached to their surface through ligand exchange. One polar short-chain ligand enables the pigment particles to have a relatively high zeta potential, and one crosslinkable ligand A. This crosslinkable ligand A has specific functional groups and can undergo a crosslinking reaction with the crosslinkable ligand B on the quantum dots in the form of light or heat without self-crosslinking, thereby enabling the quantum dots to be connected to the pigment particles.

[0036] The preparation method of the quantum dot pigment particle complex is as follows:

[0037] Step 1: First, add the crosslinkable ligand A to the uniformly monodisperse pigment particle solution for ligand exchange to replace the original ligand on the surface of the pigment particles. The functional group of the crosslinkable ligand A used to connect the pigment particles usually has a stronger coordination ability than the original ligand, or the crosslinkable ligand A has a shorter chain length than the original ligand. Effective ligand exchange is achieved through a specific temperature and the concentration of the added crosslinkable ligand A. Then, add a small amount of polar short-chain ligand used to replace part of the crosslinkable ligand A;

[0038] The ligand exchange process is as Figure 1As shown (two ligands are connected to the surface of the pigment particles, where the crosslinkable ligand A contains two different functional groups. Usually, one of these two functional groups can connect to the pigment particles, and the other can connect to the crosslinkable ligand B on the quantum dots through a chemical reaction);

[0039] The structural formula of the crosslinkable ligand A can be:

[0040]

[0041] where R represents an alkane chain -(CH 2 ) n -, where n is between 7 and 15, that is, the carbon chain length of the ligand used is between 8 and 16. Its carboxylic acid functional group can be connected to the surface of the pigment particles through a coordination reaction, and the mercapto group at the other end can react with the crosslinkable ligand B through a thiol-ene click reaction to connect to the quantum dots. The crosslinking reaction is photo-initiated, and the light source used is ultraviolet light with a wavelength of 254 - 420 nm.

[0042] The structural formula of the crosslinkable ligand A can also be a dimethyl ketone structure containing a methyl ketone functional group, for example, the following structural formulas:

[0043]

[0044] where R 2 is -O- or -S-, R 3 is -H or -N(CH 2 ) 4 ), R 4 is -(CH 2 ) n -, R 5 is any one of -SH, -COOH, -PO 3 H 2 2 . The crosslinking reaction that occurs is a dimethyl ketone double bond addition reaction. The crosslinking reaction is photo-initiated, and the light source used is ultraviolet light with a wavelength of 254 - 420 nm.

[0045] Another polar short-chain ligand can significantly increase the zeta potential of the pigment particles. It has the following several general structural formulas:

[0046]

[0047] where R' is an alkane chain -(CH 2 ) n -, n is between 2 and 5, that is, the carbon chain length of the ligand used is between 3 and 6.

[0048] Finally, pigment particles with crosslinkable ligand A and polar short-chain ligand on the surface are obtained;

[0049] Step 2: Add crosslinkable ligand B to the uniformly monodisperse quantum dot solution for ligand exchange to replace the original ligands on the surface of the quantum dots. The crosslinkable ligand B used to connect the functional groups of the pigment particles usually has a stronger coordination ability than the original ligand, or the crosslinkable ligand B has a shorter chain length than the native ligand. Effective ligand exchange is achieved through a specific temperature and the concentration of the added crosslinkable ligand B. Then add a small amount of polar short-chain ligand to replace part of the crosslinkable ligand B;

[0050] The ligand exchange process is as Figure 2 shown (two ligands are connected to the surface of the quantum dots, where the crosslinkable ligand B contains two different functional groups. One functional group is coordinately connected to the quantum dots, and the other functional group can react with the crosslinkable ligand A on the pigment particles). For example, the structural formula of the crosslinkable ligand B contains a carbon-carbon double bond or a carbon-carbon triple bond, and it can be or or a common oleic acid ligand; its carboxylic acid functional group can be connected to the quantum dot cation, and the other end, the alkene (double bond) or alkyne (triple bond), can undergo a thiol-ene click reaction with the thiol functional group to be connected to the pigment particles.

[0051] Another polar short-chain ligand can significantly increase the zeta potential of the quantum dots, and it has the following several structural general formulas:

[0052]

[0053] where R’ is an alkane chain -(CH 2 ) n -, and n is 2 - 5, that is, the carbon chain length of the ligand used is between 3 - 6.

[0054] Finally, quantum dots with crosslinkable ligand B and polar short-chain ligands on the surface are obtained.

[0055] Step 3: Add a certain amount and concentration of the ligand-exchanged quantum dot solution to the ligand-exchanged pigment particle solution, and through ultraviolet light irradiation (the light source used is ultraviolet light with a wavelength of 254 - 420 nm), enable the crosslinkable ligand A and the crosslinkable ligand B to undergo a crosslinking reaction. It is also possible to use heating or adding initiators, catalysts, etc. according to the types of the crosslinkable ligand A and the crosslinkable ligand B, or it can be a combination of one or at least two of the above methods to connect the quantum dots to the pigment particles to obtain a quantum dot pigment particle complex.

[0056] This application can be a replacement of different types of crosslinkable ligands. In theory, any combination of crosslinkable ligand functional groups that can achieve non-self-crosslinking should fall within the scope of protection of this patent.

[0057] It can be a replacement for the ligand exchange method of quantum dots or pigment particles, including but not limited to multiple exchanges, different ligand exchange sequences, and ligand exchange methods. For example, it includes but is not limited to first exchanging short-chain polar ligands and then crosslinkable ligands, or using different solvents, ligand concentrations, temperatures, and exchange times.

[0058] The solvent, as the reaction medium for preparing the above composite material, can be selected from common organic solvents in the art, including but not limited to chloroform, toluene, chlorobenzene, alkanes, alkenes, aromatic hydrocarbons, alcohols, ethyl acetate, halogenated alkanes, halogenated alkenes, halogenated aromatic hydrocarbons, glycol derivatives, ketones, toluene, o-xylene, m-xylene, p-xylene, chlorofluorocarbons, esters, tetrahydrofuran, petroleum ether, dimethyl sulfoxide, water, and a mixture of one or more of these solvents.

[0059] It can be a replacement for the ligand exchange method of quantum dots or pigment particles, including but not limited to multiple exchanges, different ligand exchange sequences, and ligand exchange methods. For example, it includes but is not limited to first exchanging polar short-chain ligands and then crosslinkable ligands, or using different solvents, ligand concentrations, temperatures, and exchange times.

[0060] It can be a replacement of the types, morphologies, and emission wavelengths of quantum dots and pigment particles, including but not limited to the connection of one or more quantum dot luminescent materials with different morphologies having a central emission wavelength in the range of 400 nm - 700 nm to different pigment particles, or nanorod or nanosheet luminescent materials, or a mixture of several narrow-emission and high-luminescence-efficiency quantum dot nanomaterials.

[0061] It can be a replacement of the quantum dot material or the core and shell of the quantum dot. For example, it includes but is not limited to group II-VI, group III-V, and group I-III-V semiconductor compounds such as CdSe, CdS, ZnSe, ZnTe, ZnS, AgInS, AgInSeS, InP, CuZnSe, ZnMnSe, PbS, PbSe, Cd-based alloy materials, In-based alloy materials, Zn-based alloy materials, or perovskite materials, etc., which are single-core nanoparticles. It can also be that a layer or multiple layers including but not limited to any one or at least two combinations of CdSe, CdS, ZnO, ZnS, ZnSe, ZnTe, or alloy materials are further coated outside the above-mentioned materials;

[0062] It can be a replacement of the pigment particles and the oxides coated on their surfaces, such as titanium dioxide, zirconium dioxide, etc. It can also be any one or at least two combinations of the above-mentioned materials.

[0063] The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0064] Example 1

[0065] The preparation method of the quantum dot pigment particle complex is as follows:

[0066] Step 1: First, add the crosslinkable ligand A to the uniformly monodisperse pigment particle solution for ligand exchange to replace the original ligand on the surface of the pigment particles. Then, add a small amount of short-chain polar ligand to replace part of the crosslinkable ligand A. As shown in Figure 1 the ligand exchange process shown, finally obtain pigment particles with crosslinkable ligand A and polar short-chain ligand on the surface.

[0067] The structural formula of the crosslinkable ligand A can be:

[0068]

[0069] where R represents an alkane chain -(CH 2 ) n -, and n is between 7 and 15, that is, the carbon chain length of the ligand used is between 8 and 16.

[0070] Another polar short-chain ligand can greatly improve the zeta potential of the pigment particles, and its general structural formula is:

[0071] where R’ is an alkane chain -(CH 2 ) n -, and n is between 2 and 5, that is, the carbon chain length of the ligand used is between 3 and 6.

[0072] Step 2: Add the crosslinkable ligand B to the uniformly monodisperse quantum dot solution for ligand exchange to replace the original ligand on the surface of the quantum dots. Then, add a small amount of polar short-chain ligand used to replace part of the crosslinkable ligand B; the ligand exchange process is as shown in Figure 2 shown;

[0073] The structural formula of the crosslinkable ligand B is

[0074] Another polar short-chain ligand can greatly improve the zeta potential of the quantum dots, and its general structural formula is:

[0075] where R’ is an alkane chain -(CH 2 ) n -, and n is between 2 and 5, that is, the carbon chain length of the ligand used is between 3 and 6. Finally, obtain quantum dots with crosslinkable ligand B and polar short-chain ligand on the surface.

[0076] Step 3: Add a certain amount and concentration of the ligand-exchanged quantum dot solution to the ligand-exchanged pigment particle solution, and irradiate with ultraviolet light (the light source used is ultraviolet light with a wavelength of 254 - 420 nm), so that the crosslinkable ligand A and the crosslinkable ligand B undergo a crosslinking reaction to obtain a quantum dot pigment particle complex.

[0077] Example 2

[0078] The preparation method of the quantum dot pigment particle complex is as follows:

[0079] Step 1: First, add the crosslinkable ligand A to the uniformly monodisperse pigment particle solution for ligand exchange to replace the original ligand on the surface of the pigment particles. Then add a small amount of short-chain polar ligand to replace part of the crosslinkable ligand A, as Figure 1 shown in the ligand exchange process, and finally obtain pigment particles with crosslinkable ligand A and polar short-chain ligand on the surface.

[0080] The structural formula of the crosslinkable ligand A can be:

[0081]

[0082] Where R 2 is -O- or -S-, R 3 is -H or -N(CH 2 ) 4 and R 4 is -(CH 2 ) n -, R 5 is any one of -SH, -COOH, -PO 3 H 2 .

[0083] Another polar short-chain ligand can greatly increase the zeta potential of the pigment particles, and its general structural formula is:

[0084] Where R' is an alkane chain -(CH 2 ) n -, n is 2 - 5, that is, the carbon chain length of the ligand used is between 3 - 6. Finally, pigment particles with crosslinkable ligand A and polar short-chain ligand on the surface are obtained;

[0085] Step 2: Add the crosslinkable ligand B to the uniformly monodisperse quantum dot solution for ligand exchange to replace the original ligand on the surface of the quantum dots, and then add a small amount of polar short-chain ligand used to replace part of the crosslinkable ligand B; the ligand exchange process is as Figure 2 shown;

[0086] The structural formula of the crosslinkable ligand B is

[0087]

[0088] Another kind of polar short-chain ligand can greatly improve the zeta potential of quantum dots, and its general structural formula is:

[0089] wherein R' is an alkane chain -(CH 2 ) n -, n is 2 - 5, that is, the carbon chain length of the ligand used is between 3 - 6. Finally, quantum dots with crosslinkable ligand B and polar short-chain ligand on the surface are obtained.

[0090] Step 3: Add a certain amount and concentration of the ligand-exchanged quantum dot solution to the ligand-exchanged pigment particle solution, and through ultraviolet light irradiation (the light source used is ultraviolet light with a wavelength of 254 - 420 nm), make the crosslinkable ligand A and the crosslinkable ligand B undergo a crosslinking reaction to obtain a quantum dot pigment particle complex.

[0091] It should be noted that although the present invention has been described through the above embodiments, the present invention can also have many other embodiments. Without departing from the spirit and scope of the present invention, those skilled in the art can obviously make various corresponding changes and deformations to the present invention, but these changes and deformations should all fall within the scope protected by the appended claims of the present invention and their equivalents.

Claims

1. A method for preparing a quantum dot pigment particle complex, characterized in that: The following steps are involved: Step 1: providing a cross-linkable ligand A and a cross-linkable ligand B having two different functional groups, and a polar short-chain ligand; Step 2: Replacing the ligands of the quantum dots through the cross-linkable ligand B and the polar short-chain ligands and the pigment particles through the cross-linkable ligand A and the polar short-chain ligands respectively; Step 3: The quantum dots and pigment particles after the ligands are replaced are subjected to ligand cross-linking reaction to obtain a quantum dot-pigment particle complex.

2. The method for preparing a quantum dot pigment particle complex according to claim 1, characterized in that: The cross-linkable ligand A has a structural formula of HOOC-R-SH or a dimethyl ketone structure containing a methyl ketone functional group, wherein R is an alkane chain -(CH2) n -, n is 7-15.

3. The method for preparing a quantum dot pigment particle complex according to claim 1, characterized in that: The structural formula of the cross-linkable ligand B is: or oleic acid ligand; Wherein R1 represents an alkane chain with a carbon chain length of 5 to 13.

4. The method for preparing a quantum dot pigment particle complex according to claim 2, characterized in that: The structural formula of the dimethyl ketone structure containing the methyl ketone functional group is: Wherein R2 is -O- or -S-, R3 is -H or -N(CH2)4, and R4 is -(CH2) n -, R5 is any one of -SH, -COOH, and -PO3H2.

5. The method for preparing a quantum dot pigment particle complex according to claim 1, characterized in that: The polar short chain ligand is selected from any one of the following: Where R' is an alkane chain -(CH2) n -, n is 2-5.

6. The method for preparing a quantum dot pigment particle complex according to claim 1, characterized in that: The specific method for replacing the ligand of quantum dots in step 2 is: add cross-linkable ligand B and polar short-chain ligand respectively to the uniform monodisperse quantum dot solution, one functional group of cross-linkable ligand B is used to connect with the surface of quantum dots, and another functional group of cross-linkable ligand B is used to connect with cross-linkable ligand A, and finally obtain quantum dots with cross-linkable ligand B and polar short-chain ligand on the surface.

7. The method for preparing a quantum dot pigment particle complex according to claim 1, characterized in that: The specific method for replacing the ligand of the pigment particles in step 2 is: add cross-linkable ligand A and polar short-chain ligand respectively to the uniform monodisperse pigment particle solution, one functional group of the cross-linkable ligand A is used to connect with the surface of the pigment particles, and another functional group of the cross-linkable ligand A is used to connect with the cross-linkable ligand B, and finally obtain pigment particles with cross-linkable ligand A and polar short-chain ligand on the surface.

8. The method for preparing a quantum dot pigment particle complex according to claim 1, characterized in that: The specific method of step three is: the quantum dots after replacing the ligand and the pigment particles are subjected to ultraviolet light irradiation, heating, adding an initiator, or one or more of the initiation methods of a catalyst, so that the cross-linkable ligand A and the cross-linkable ligand B undergo a cross-linking reaction, so that the quantum dots are connected to the pigment particles to obtain a quantum dot-pigment particle complex. 9 . The quantum dot pigment particle complex obtained by the method for preparing a quantum dot pigment particle complex according to any one of claims 1 to 8 .

10. Application of the quantum dot pigment particle complex according to claim 9 in color electronic paper display technology.

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