CN114763473A

CN114763473A - Quantum dot, quantum dot composition, and light-emitting device comprising same

Info

Publication number: CN114763473A
Application number: CN202110059325.7A
Authority: CN
Inventors: 余世荣; 赵飞; 康永印; 罗飞
Original assignee: Najing Technology Corp Ltd
Current assignee: Najing Technology Corp Ltd
Priority date: 2021-01-15
Filing date: 2021-01-15
Publication date: 2022-07-19
Anticipated expiration: 2041-01-15
Also published as: CN114763473B

Abstract

The invention provides a quantum dot, a quantum dot composition and a light-emitting device containing the same. The surface of the quantum dot comprises a first quantum dot ligand and a second quantum dot ligand, wherein the first quantum dot ligand and the second quantum dot ligand both comprise at least two binding groups, the first quantum dot ligand comprises a carboxyl binding groups, the second quantum dot ligand comprises b sulfydryl binding groups, a is more than or equal to 2 and less than or equal to 100, b is more than or equal to 2 and less than or equal to 100, and the binding groups are used for coordinating with the surface of the quantum dot; the binding group of the first quantum dot ligand comprises a carboxyl group and the binding group of the second quantum dot ligand comprises a thiol group. The first quantum dot ligand and the second quantum dot ligand are different and respectively have different lengths, so that the stability and designability of the quantum dots are improved, and the specific application range of the quantum dots is expanded.

Description

Quantum dot, quantum dot composition, and light-emitting device comprising same

Technical Field

The invention relates to the field of quantum dots, in particular to a quantum dot, a quantum dot composition and a light-emitting device containing the quantum dot.

Background

The particle size of the quantum dot is generally between 1-30 nm, and because electrons and holes are limited by quanta, a continuous energy band structure is changed into a discrete energy level structure with molecular characteristics, and the quantum dot can emit fluorescence after being excited. The quantum dots have excellent fluorescence characteristics of wide and continuous distribution of excitation spectrum, narrow and symmetrical emission spectrum, adjustable color, high photochemical stability, long fluorescence life and the like. By controlling the shape, structure and size of the quantum dots, the electronic states such as the energy gap width, the size of exciton binding energy, energy blue shift of excitons and the like can be conveniently adjusted. Therefore, the spectrum in the visible light region can be obtained by controlling the size of the quantum dots, the half-peak width can be controlled, pure monochromatic light can be obtained, and the color gamut and the color saturation can be greatly improved when the quantum dots are used in the display field.

However, the stability of the quantum dots still needs to be improved, thereby limiting further industrial application of the quantum dots.

Disclosure of Invention

The invention aims to provide a quantum dot, a quantum dot composition and a light-emitting device containing the quantum dot composition, and aims to solve the problem that the stability of the quantum dot in the quantum dot composition in the prior art is insufficient.

In order to solve the above technical problem, according to a first aspect of the present application, there is provided a quantum dot, a surface of the quantum dot includes a first quantum dot ligand and a second quantum dot ligand, each of the first quantum dot ligand and the second quantum dot ligand includes at least two binding groups, the first quantum dot ligand includes a carboxyl binding groups, the second quantum dot ligand includes b mercapto binding groups, a is greater than or equal to 2 and less than or equal to 100, b is greater than or equal to 2 and less than or equal to 100, and the binding groups are used for coordinating with the surface of the quantum dot; the binding group of the first quantum dot ligand comprises a carboxyl group and the binding group of the second quantum dot ligand comprises a thiol group.

Furthermore, the solvent capable of dissolving the quantum dots has a Hansen solubility parameter SP value of 8-12, wherein the polarization term δ p is more than 2.

Further, a is greater than or equal to 2 and less than or equal to 12, b is greater than or equal to 2 and less than or equal to 12; preferably, a equals b.

Further, a is 6, b is 6; preferably, the chemical structure of the first quantum dot ligand is:

the chemical structure of the second quantum dot ligand is as follows:

R1-R7 and R1 '-R7' are respectively and independently selected from one of the group consisting of alkoxy, ester group, alkyl with substituent, siloxane group, aromatic group, cycloolefine group, cycloalkane group, amido group and phosphate group.

Further, a is 2, b is 2; preferably, the chemical structure of the first quantum dot ligand is:

the chemical structure of the second quantum dot ligand is as follows:

R8-R12 and R8 '-R12' are respectively and independently selected from one of the group consisting of alkoxy, ester group, alkyl with substituent, siloxane group, aromatic group, cycloolefine group, cycloalkane group, amido group and phosphate group.

Further, the number of carbon atoms of each of R1 to R12 and R1 'to R12' is 10 or less; preferably, the number of carbon atoms in each of R1 to R12 and R1 'to R12' is 6 or less.

The alkoxy is C1-C4, the ester group is C1-C4, the alkyl is C1-C4, and the carbon main chain of the alkyl with substituent is C1-C4.

Further, R1, R2, R3, R5, R6, R7 are the same, and R1 ', R2', R3 ', R5', R6 ', R7' are the same; or R1 and R5 are identical and R2 and R6 are identical and R3 and R7 are identical and R1 'and R5' are identical and R2 'and R6' are identical and R3 'and R7' are identical.

Further, R8, R9, R11, R12 are the same, and R8 ', R9', R11 ', R12' are the same; or R8, R11 are identical and R9 and R12 are identical and R8 'and R11' are identical and R9 'and R12' are identical.

Further, the substituent is selected from one or more of alkoxy, ester group, alkyl, siloxane group, aromatic group, cyclic olefin group, naphthenic hydrocarbon group, amide group and phosphate group.

Furthermore, the molecular weight of the first quantum dot ligand is 200-2000, and the molecular weight of the second quantum dot ligand is 200-2000.

Further, the molar ratio of the first quantum dot ligand to the second quantum dot ligand is 1: 2-2: 1, preferably the molar ratio of the first quantum dot ligand to the second quantum dot ligand is 1: 1.

further, the surface of the quantum dot further comprises a third quantum dot ligand, the third quantum dot ligand comprises at least two binding groups, and the binding group of the third quantum dot ligand comprises an amino group.

Further, the third quantum dot ligand comprises c amino binding groups, wherein c is greater than or equal to 2 and less than or equal to 100; preferably, c is 2 or more and 12 or less, and more preferably, c is 6.

According to a second aspect of the present application, there is provided a quantum dot composition comprising any of the quantum dots described above.

According to a third aspect of the present application, there is provided a light emitting device comprising the quantum dot composition described above.

The first quantum dot ligand and the second quantum dot ligand both have more than two binding groups, so that the stability of the quantum dots is improved to a certain extent. Furthermore, different first quantum dot ligands and second quantum dot ligands are used together, the length of each quantum dot is obtained, the stability and designability of the quantum dots are improved, and the specific application range of the quantum dots is expanded. The mercapto group of the second quantum dot ligand has strong coordination capacity to the quantum dot, the carboxyl binding group can improve the stability of the quantum dot under the conventional condition, the binding group which does not participate in coordination in the multi-binding group can participate in other subsequent reactions, such as subsequent high-molecular polymerization reaction, and the polymer further coats the quantum dot to improve the stability. However, the sulfhydryl ligand is unstable at high temperature (such as above 65 ℃), the carboxyl ligand can overcome the defect that the sulfhydryl ligand is not resistant to high temperature and falls off, and the sulfhydryl ligand can still be stably coordinated on the surface of the quantum dot under high temperature environment, so as to play a role in protecting the quantum dot.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It should be noted that the terms "first," "second," and the like in the description and in the claims of the present application are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It should be understood that the data so used may be interchanged under appropriate circumstances in order to facilitate the description of the embodiments of the application herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

According to a first aspect of the present application, there is provided a quantum dot, the surface of which comprises a first quantum dot ligand and a second quantum dot ligand, each of the first quantum dot ligand and the second quantum dot ligand comprises at least two binding groups, the first quantum dot ligand comprises a carboxyl binding groups, the second quantum dot ligand comprises b mercapto binding groups, a is greater than or equal to 2 and less than or equal to 100, b is greater than or equal to 2 and less than or equal to 100, and the binding groups are used for coordinating with the surface of the quantum dot; the binding group of the first quantum dot ligand comprises a carboxyl group and the binding group of the second quantum dot ligand comprises a sulfhydryl group.

The first quantum dot ligand and the second quantum dot ligand both have more than two binding groups, for example, after the ligands fall off, the ligands of the multiple binding groups can be more probably coordinated and combined with the quantum dots again, and the stability of the quantum dots is improved to a certain extent. Furthermore, the first quantum dot ligand and the second quantum dot ligand are used together, the first quantum dot ligand and the second quantum dot ligand are different and have different lengths, the stability and the designability of the quantum dots are improved, and the specific application range of the quantum dots is expanded. The mercapto group of the second quantum dot ligand has strong coordination capacity to the quantum dot, the carboxyl binding group can improve the stability of the quantum dot under the conventional condition, and the binding group which does not participate in coordination in the multi-binding group can participate in other subsequent reactions, such as a high-molecular polymerization reaction, so that the quantum dot is further coated to improve the stability. However, the sulfhydryl ligand is unstable at high temperature (such as above 65 ℃), the carboxyl ligand can overcome the disadvantage that the sulfhydryl ligand is not resistant to high temperature and falls off, and the sulfhydryl ligand can still be stably coordinated on the surface of the quantum dot under high temperature environment, thereby playing the role of protecting the quantum dot.

It should be noted that "binding group" refers to a group having binding ability, and does not mean that the group is bound to the surface of the quantum dot, and not necessarily all binding groups are attached to the surface of the quantum dot due to steric hindrance and the like. The quantum dot ligands according to the present invention are not all structures in a state of being bound to a quantum dot, and for example, when the quantum dot ligands are carboxyl ligands, the bound ligands bound to the quantum dot are carboxylate metal salts (metal ions are metal ions of the quantum dot matrix), and the mercapto ligands form coordinate bonds with the metal ions of the quantum dot matrix. For convenience of description, and considering that there may be a dynamic equilibrium between the ligand on the surface of the quantum dot and the free ligand, the quantum dot ligand is not described in terms of the bound ligand, but the ligand is described in the state of the raw material, and the scope of the present application should be extended to the bound ligand, and the scope of the present application should not be limited by the above description.

In some embodiments, the binding group of the first quantum dot ligand is only a carboxyl group and the binding group of the second quantum dot ligand is only a thiol group.

The ligand of the quantum dot influences the solubility of the quantum dot, and in some embodiments, the solvent in which the quantum dot is soluble has a hansen solubility parameter having an sp (solubility parameter) value of 8 to 12, wherein the polarization term δ p is 2 or more. By controlling the ligand structure of the quantum dots, the solubility of the quantum dots is regulated and controlled, and the compatibility of the quantum dot solution and ester-based glue in the specific product processing is improved. Meanwhile, the ligand and a resin matrix (formed after glue is cured) are good in compatibility, the quantum dots can be better protected by the resin matrix, the ligand is wound with a polymer chain of the matrix resin, the quantum dots are more stable, and the quantum dots cannot migrate due to the follow-up long-term use of a quantum dot product.

In some embodiments, the solvent for the quantum dots has a Hansen solubility parameter SP value of 8 to 10, wherein the polarization term δ p is 2 to 3.

In some embodiments, the solvent for the quantum dots has a Hansen solubility parameter SP value of 8.8 to 9.4, wherein the polarization term δ p is 2.6 to 2.7.

In some embodiments, the solvent for the quantum dots is ethyl acetate or Propylene Glycol Methyl Ether Acetate (PGMEA).

In some embodiments, the quantum dots are insoluble in a solvent having a hansen solubility parameter with an SP value of 8 to 9 and a polarization term δ p of 1 or less. In some embodiments, the quantum dots are insoluble in toluene. In some embodiments, a is equal to or greater than 2 and equal to or less than 12, b is equal to or greater than 2 and equal to or less than 12, and preferably, a is equal to b. The larger the number of a and b, the more the stability of the quantum dot can be improved, and it is preferable that a and b are within the above-defined ranges in view of convenience and cost of ligand synthesis.

In some embodiments, a ═ 6 and b ═ 6, preferably, the chemical structure of the first quantum dot ligand is:

the chemical structure of the second quantum dot ligand is as follows:

R1-R7 and R1 '-R7' are respectively and independently selected from alkoxy, ester, alkyl with substituent, siloxane, aryl, cycloolefine, cycloalkane, amide or phosphate. R1-R7 and R1 '-R7' can improve the compatibility (dispersion stability) of the quantum dots and the polymer, for example, ester groups can be highly compatible with polyester, alkoxy groups can be highly compatible with epoxy resin, and alkyl groups can be highly compatible with nonpolar polymer. So that the quantum dots can be more stable in the corresponding polymer. The binding groups are arranged on the two sides of the ligand, and can participate in high-molecular polymerization reaction, so that the effect of coating the quantum dots with the polymer can be realized, and the stability of the quantum dots can be improved. In the chemical structural formula, the intersection of three lines is a C atom.

In some embodiments, a ═ 2 and b ═ 2, preferably, the chemical structure of the first quantum dot ligand is:

the chemical structure of the second quantum dot ligand is as follows:

R8-R12 and R8 '-R12' are respectively and independently selected from one of the group consisting of alkoxy, ester group, alkyl with substituent, siloxane group, aromatic group, cycloolefine group, naphthenic hydrocarbon group, amide group and phosphate group. R8-R12 and R8 '-R12' can improve the compatibility (dispersion stability) of the quantum dot and the polymer, for example, ester group can have high compatibility with polyester, alkoxy group can have high compatibility with epoxy resin, and alkyl group can have high compatibility with nonpolar polymer. So that the quantum dots are in correspondenceCan be more stable in the polymer. By arranging the binding groups on both sides of the ligand, the binding groups can participate in high-molecular polymerization reaction, the effect of coating the quantum dots with polymers can be realized, and the stability of the quantum dots can be improved. The intersection of the two lines in the chemical structural formula is CH.

In some embodiments, the number of carbon atoms in each of R1 to R12 and R1 'to R12' is 10 or less, and preferably, the number of carbon atoms in each of R1 to R12 and R1 'to R12' is 6 or less. Within this range of the number of carbon atoms, the coordination ability between the quantum dot and the ligand is better. R1 to R12 represent a single set of R1 and R2 … R12, and other similar expressions in the present application represent a single set.

In some embodiments, the alkoxy group is a C1 to C4 alkoxy group, the ester group is a C1 to C4 ester group, the alkyl group is a C1 to C4 alkyl group, and the carbon main chain of the substituted alkyl group is a C1 to C4 alkyl group. Within this range of the number of carbon atoms, the coordination ability between the quantum dot and the ligand is better.

In some embodiments, R1, R2, R3, R5, R6, R7 are the same, and R1 ', R2', R3 ', R5', R6 ', R7' are the same. In other embodiments, R8, R9, R11, R12 are the same, and R8 ', R9', R11 ', R12' are the same. Thereby the quantum dot ligand is easy to prepare and the production cost of the ligand is reduced.

In some embodiments, R1 is the same as R5, R2 is the same as R6, R3 is the same as R7, R1 'is the same as R5', R2 'is the same as R6', and R3 'is the same as R7'. In other embodiments, R8 is the same as R11, R9 is the same as R12, R8 'is the same as R11', and R9 'is the same as R12'. Thereby the quantum dot ligand is easy to prepare and the production cost of the ligand is reduced.

In some embodiments, the substituent is selected from one or more of alkoxy, ester, alkyl, siloxane, aryl, cycloalkenyl, cycloalkyl, amide, and phosphate. The substituent can improve the compatibility (dispersion stability) of the quantum dot and a polymer, for example, ester group can be high in compatibility with polyester, alkoxy can be high in compatibility with epoxy resin, and alkyl can be high in compatibility with a nonpolar polymer. So that the quantum dots can be more stable in the corresponding polymer.

In some embodiments, the molecular weight of the first quantum dot ligand is 200 to 2000, and the molecular weight of the second quantum dot ligand is 200 to 2000.

In some embodiments, the molar ratio of the first quantum dot ligand to the second quantum dot ligand is 1: 2-2: 1, preferably, the molar ratio of the first quantum dot ligand to the second quantum dot ligand is 1: 2. the mol number of the ligand is based on carboxyl and sulfhydryl. The excessive second quantum dot ligand contains sulfydryl, can participate in subsequent polymerization reaction, improves the compatibility of the quantum dot and a polymer, and the polymer can wrap the quantum dot more firmly, thereby realizing chemical bonding and improving the stability. The molar ratio of the two quantum dot ligands is determined by the initial amounts of the two quantum dot ligands, and is not the ratio determined after the two quantum dot ligands are combined with each other.

In some embodiments, the quantum dots comprise only one of the first quantum dot ligands and only one of the second quantum dot ligands.

The quantum dots can be CdSe/ZnS, CdS/ZnS, ZnSe/ZnS, CdSe/CdS, CdTe/ZnS, CdSe/CdS/ZnS, CdTe/CdSe/ZnS core-shell type nanocrystals, or doped ZnO nanocrystals and CdSN, CdSSe, CdSZnSeS alloy type nanocrystals, or other non-Cd perovskite quantum dots, carbon quantum dots, zinc oxide quantum dots, carbon quantum dots, PbSe quantum dots, PbTe quantum dots, PbS quantum dots, ZnSe quantum dots, CuInS quantum dots₂One or a combination of at least two of quantum dots, InP quantum dots, InAs quantum dots, CuZnSe quantum dots, ZnMnSe quantum dots, and the like, but is not limited thereto. The quantum dot synthesis refers to a traditional synthesis method and is not detailed here.

Preferably, the quantum dots are covalent compounds. The quantum dots may have a rod-like, sheet-like, spherical, flower-like shape, or the like.

In some embodiments, the surface of the quantum dot further comprises a third quantum dot ligand comprising at least two binding groups, the binding groups of the third quantum dot ligand comprising amino groups. The introduction of the third quantum dot ligand can improve the diversity of the polymer (and the precursor thereof) for dispersing the quantum dots, namely, the selection range of the polymer is improved, and the third quantum dot ligand has a help effect on the specific application of the quantum dots.

In some embodiments, the third quantum dot ligand comprises c amino binding groups, c being greater than or equal to 2 and less than or equal to 100; preferably, c is 2 or more and 12 or less, and more preferably, c is 6.

In some embodiments, the structure of the third quantum dot ligand and the first quantum dot ligand corresponds to formula (1) or formula (3) except that the binding group is an amino group, that is, the groups of the third quantum dot ligand and the first quantum dot ligand other than the binding group may be different or the same in specific selection, but the basic structure corresponds to formula (1) or formula (3), for example, formula (5) below, the selection range of each group of R13 to R19 corresponds to the selection range of R1 to R7 of the first quantum dot ligand, and the selection range of each group of R20 to R24 corresponds to the selection range of R8 to R12 of the first quantum dot ligand in formula (6) below.

Or

In some embodiments, the molar ratio of the first quantum dot ligand to the second quantum dot ligand to the third quantum dot ligand is 1:1:1, calculated as binding group.

In some embodiments, there may be a fifth quantum dot ligand and a sixth quantum dot ligand, the fifth quantum dot ligand may be structurally similar to the first quantum dot ligand, and the sixth quantum dot ligand may be structurally similar to the second quantum dot ligand.

According to a second aspect of the present application, there is provided a quantum dot composition comprising the quantum dots described above. The first quantum dot ligand or the second quantum dot ligand may react with other species in the composition to form a covalent bond.

In some embodiments, the preparation method of the quantum dot comprises providing an original quantum dot solution, mixing the original quantum dot solution and the two or more quantum dot ligands, and performing ligand exchange at a certain temperature to obtain the quantum dot with multiple ligands.

In some embodiments, the quantum dot composition further comprises a polymer precursor. The polymer precursor is selected from the group consisting of N, N-methylenebisacrylamide, acrylic acid, methyl acrylate, ethyl acrylate, N-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, N-octyl acrylate, decyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-ethoxyethyl acrylate, 2-cyanoethyl acrylate, cyclohexyl acrylate, isobornyl acrylate, methyl methacrylate, isobutyl methacrylate, pentaerythritol triacrylate, methylpropane trimethacrylate, ethoxylated trimethylolpropane triacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, tetrahydrofurfuryl acrylate, ethoxyethoxyethyl acrylate, 3- (2-thienyl) acrylate, di-or tri-butyl acrylate, tetra-butyl acrylate, tri-or tetra-butyl acrylate, di-or tetra-butyl acrylate, tri-butyl acrylate, di-or tetra-butyl acrylate, di-or tri-butyl acrylate, di-butyl acrylate, tri-or tri-butyl acrylate, methacrylate, di-butyl acrylate, di-or tri-butyl acrylate, tri-or tri-butyl acrylate, tri-or tetra-or tri-butyl acrylate, tri-or tetra-acrylate, tri-or tetra-or tri-or tetra-acrylate, tri-or tri-acrylate, tri-or-acrylate, tri-or tri-acrylate, di-or tri-or tetra-or-acrylate, tri-or-acrylate, or-acrylate, tri-or-acrylate, or-acrylates, or-acrylates, or-acrylates, 3- (4-pyridyl) acrylic acid, 3- (trimethylsilyl) propyl acrylate, triisopropylsilyl acrylate, 4-hydroxybutyl acrylate, hydroxyethyl methacrylate, ethylene glycol dimethacrylate, 3-benzoylethyl acrylate, benzyl methacrylate, p-phenylene diacrylate, furfuryl methacrylate, tetraethylene glycol dimethacrylate, 2-thiopheneacrylic acid, 3-methoxy methyl acrylate, dimethylaminoethyl methacrylate, acrylamide.

In some embodiments, the quantum dot composition further comprises a polymer. The polymer may be PMMA, or polystyrene, or polyacrylate. In some embodiments, the polymer is one or more polymers having a water oxygen barrier effect.

In some embodiments, the quantum dot composition further comprises a diffusion particle. In other embodiments, the quantum dot composition further comprises additives, such as a stabilizer and a dispersant.

The quantum dot composition may be solid or liquid or semisolid. In some embodiments, when solid, the quantum dot composition is in the form of a plate, or a pellet, or a sphere.

In some embodiments, the above-described quantum dot compositions are solids, wherein the quantum dots are encapsulated by a polymer.

In some embodiments, the original quantum dot solution, the two or more quantum dot ligands, and the polymer monomer are mixed uniformly, ligand exchange is completed at a certain temperature to obtain a mixture, and then an initiator is added into the mixture to be cured, so as to obtain the quantum dot composition.

In some embodiments, the quantum dots are first mixed with a polymer precursor to form a first mixture, and then a solution of the quantum dots with the original ligands is mixed with the first mixture to form a quantum dot composition through a curing reaction.

In some embodiments, the solvent in the original quantum dot solution is toluene.

According to a third aspect of the present application, there is provided a light emitting device comprising the quantum dot composition described above. The composition has improved stability, thereby improving the stability of the light emitting device.

In some embodiments, the light emitting device includes an initial light source, and the quantum dot composition receives light from the initial light source to perform light conversion.

The advantageous effects of the present application will be further described below with reference to examples and comparative examples.

Example 1

The quantum dots are self-prepared by the applicant, and the method refers to CN201910418886.4, wherein the chemical structure of the quantum dots is CdZnSeS/ZnS core-shell quantum dots, the original ligand of the quantum dots is TOP, the average size of the quantum dots is 11nm, the fluorescence emission half-peak width of the quantum dots is 28nm, the fluorescence emission wavelength of the quantum dots is 520nm, and the quantum dots are dispersed in toluene to obtain a toluene solution of the original quantum dots.

Ligand I-1 and ligand II-1 (100. mu.L undiluted ligand stock solution, the ratio of the two ligands is such that the molar ratio of carboxyl to mercapto is 1:1) are added to 2mL of methyl methacrylate monomer to form a mixed solution for later use.

The crude 200. mu.L of the toluene solution of the original quantum dots (10 wt%) was purified by precipitation with 300. mu.L of anhydrous methanol and 150. mu.L of oleylamine, and centrifugation, and the quantum dot precipitate obtained by the purification was redispersed with 100. mu.L of chloroform to obtain a chloroform solution of the quantum dots.

Subsequently, a chloroform solution of the quantum dots was injected into the prepared ligand-containing mixture to form a turbid suspension. The suspension was then stirred or sonicated at 60 ℃ for about 1 hour to give an optically clear solution indicating successful surface ligand exchange.

And finally, carrying out rotary evaporation on the transparent solution at the temperature of 65 ℃, and completely removing the chloroform solvent to obtain the quantum dot methyl methacrylate dispersion liquid containing the two ligands.

Diluting the prepared quantum dot methyl methacrylate dispersion with methyl methacrylate monomer according to a mass ratio of 1:100, adding 100mL of diluted quantum dot methyl methacrylate monomer solution into a 250mL three-necked bottle, adding 0.01g of dibenzoyl peroxide as an initiator, introducing nitrogen, bubbling, evacuating air in a reaction system, keeping a nitrogen atmosphere until the reaction is finished, stirring and dissolving the initiator, heating the oil bath to 85 ℃ for reaction for about 1hr, removing a heating device after the system is viscous, introducing a reaction product into a proper mold, placing the mold into a 65 ℃ oven for reaction for 12hr, and then heating the oven to 100 ℃ for continuous reaction for 12 hr. And taking out the die after the reaction is finished to obtain the solid quantum dot polymethyl methacrylate composition.

The quantum dot polymethyl methacrylate composition is ground into powder (10-30 micrometers) with the required particle size to obtain quantum dot powder, the quantum dot powder and silica gel are mixed according to the mass ratio of 1:20 to obtain a silica gel reactant A, the silica gel reactant A and an ultraviolet curing agent are mixed according to the mass ratio of 1:50 to obtain quantum dot packaging glue, the quantum dot packaging glue is packaged on a blue light LED chip (2835 chip) with the proper size by adopting a glue dispensing process, the quantum dot packaging glue is photocured to obtain a chip packaging body, and the chip packaging body is used for carrying out blue light illumination stability test and storage and lighting tests under different conditions of 65 ℃/95% RH, 85 ℃ and the like.

Example 2

The difference from example 1 is that ligand I-2 and ligand II-2 (100. mu.L, molar ratio of carboxyl group to mercapto group: 1) were added to 2mL of methyl methacrylate monomer.

Example 3

The difference from example 1 is that ligand I-3 and ligand II-3 (100. mu.L, molar ratio of carboxyl group to mercapto group: 1) were added to 2mL of methyl methacrylate monomer.

Example 4

The difference from example 1 is that ligand III-1 and ligand IV-1 (100. mu.L, molar ratio of carboxyl group to mercapto group: 1) were added to 2mL of methyl methacrylate monomer.

Example 5

The difference from example 1 is that ligand III-2 and ligand IV-2 (100. mu.L, molar ratio of carboxyl group to mercapto group: 1) were added to 2mL of methyl methacrylate monomer.

Example 6

The difference from example 1 is that ligand III-3 and ligand IV-3 (100. mu.L, molar ratio of carboxyl group to mercapto group: 1) were added to 2mL of methyl methacrylate monomer.

Example 7

The difference from example 1 is that ligand I-1 and ligand II-1 (100. mu.L, carboxyl group: mercapto group molar ratio 1: 2) as in example 1 were added to 2mL of methyl methacrylate monomer.

Example 8

The difference from example 1 is that ligand I-1 and ligand II-1 (100. mu.L, molar ratio of carboxyl group to mercapto group: 2: 1) were added to 2mL of methyl methacrylate monomer.

Example 9

The difference from example 1 is that ligand I-1 and ligand II-4 (100. mu.L, molar ratio of carboxyl group to mercapto group: 1) were added to 2mL of methyl methacrylate monomer.

Example 10

The difference from example 1 is that ligand I-1 and ligand II-5 (100. mu.L, molar ratio of carboxyl group to mercapto group: 1) were added to 2mL of methyl methacrylate monomer.

Example 11

The difference from example 1 is that the above ligand I-1 and ligand II-6 (100. mu.L, molar ratio of carboxyl group: mercapto group: 1) were added to 2mL of methyl methacrylate monomer.

Example 12

The difference from example 1 is that the above ligand I-1 and ligand II-7 (100. mu.L, carboxyl group: mercapto group molar ratio 1:1) were added to 2mL of methyl methacrylate monomer.

Example 13

The difference from example 1 is that the above ligand I-1, ligand II-1 and ligand VI-1 (100. mu.L, molar ratio of carboxyl group: mercapto group: amino group: 1:1) were added to 2mL of methyl methacrylate monomer.

Example 14

The difference from example 1 is that the above ligand I-1, ligand II-1 and ligand VI-2 (100. mu.L, molar ratio of carboxyl group: mercapto group: amino group: 1:1) were added to 2mL of methyl methacrylate monomer.

Example 15

The difference from example 1 is that the above ligand I-1, ligand II-1 and ligand VI-3 (100. mu.L, molar ratio of carboxyl group: mercapto group: amino group: 1:1) were added to 2mL of methyl methacrylate monomer.

Comparative example 1

The difference from example 1 is that 100. mu.L of a single monodentate quantum dot carboxyl ligand V-1 is added to 2mL of methyl methacrylate monomer. Obtaining quantum dot methyl methacrylate dispersion liquid containing single ligand.

Comparative example 2

The difference from example 1 is that 100. mu.L of a single monodentate quantum dot thiol ligand V-2 was added to 2mL of methyl methacrylate monomer. Obtaining quantum dot methyl methacrylate dispersion liquid containing single ligand.

Comparative example 3

The difference from example 1 is that 100. mu.L of a single bidentate quantum dot carboxy ligand V-3 was added to 2mL of methyl methacrylate monomer. Obtaining quantum dot methyl methacrylate dispersion liquid containing single ligand.

Comparative example 4

The difference from example 1 is that 100. mu.L of single bidentate quantum dot thiol ligand V-4 was added to 2mL of methyl methacrylate monomer. Obtaining quantum dot methyl methacrylate dispersion liquid containing single ligand.

Comparative example 5

The difference from example 1 is that 100. mu.L of a single monodentate quantum dot amino ligand VII-1 was added to 2mL of methyl methacrylate monomer. Obtaining quantum dot methyl methacrylate dispersion liquid containing single ligand.

Comparative example 6

The difference from example 1 is that 100. mu.L of a single ligand VII-2 was added to 2mL of methyl methacrylate monomer.

Obtaining quantum dot methyl methacrylate dispersion liquid containing single ligand.

Comparative example 7

The difference from example 1 is that monodentate quantum dot carboxyl ligand V-1 and monodentate quantum dot thiol ligand V-2 (100. mu.L total, carboxyl group: thiol group molar ratio 1:1) are added to 2mL of methyl methacrylate monomer. Obtaining the quantum dot methyl methacrylate dispersion liquid containing two monodentate ligands.

Comparative example 8

The difference from example 1 is that only ligand I-1 was added to 2mL of methyl methacrylate monomer. Obtaining quantum dot methyl methacrylate dispersion liquid containing single ligand.

Comparative example 9

The difference from example 1 is that only ligand II-2 was added to 2mL of methyl methacrylate monomer. Obtaining quantum dot methyl methacrylate dispersion liquid containing single ligand.

The detection method of the fluorescence efficiency of the quantum dot packaging adhesive comprises the following steps: the 450nm blue LED chip is used as a backlight source, an integrating sphere is used for respectively testing a blue backlight spectrum and a spectrum penetrating through quantum dot packaging glue, and the quantum dot light efficiency is calculated by using the integral area of a spectrogram. The fluorescence efficiency of the quantum dot packaging adhesive is (quantum dot packaging adhesive emission peak area)/(blue backlight peak area-blue peak area unabsorbed through the quantum dot packaging adhesive) 100%.

The stability of the quantum dot packaging adhesive is characterized by the percentage of the fluorescence efficiency of the chip packaging body after being stored for 1000 hours under specific conditions relative to the initial fluorescence efficiency of the quantum dot packaging adhesive (the result of immediate test immediately after preparation), and the change degree of the fluorescence efficiency can be seen. The results of the stability test of each example and comparative example are shown in table 1 below.

TABLE 1

As can be seen from table 1, the examples of quantum dots containing two kinds of quantum dot ligands, carboxyl and mercapto, are significantly higher than the comparative examples in terms of stability, and the multidentate ligand having multiple binding groups can further improve the stability of quantum dots compared to the monodentate ligand. From examples 1 to 3 and examples 4 to 6, it is seen that the quantum dots of the multi-thiol ligand have significantly improved stability to blue light and the carboxyl ligand has significantly improved stability to high temperature compared to the quantum dots of the low-thiol ligand. In examples 10 to 11, the use of the silicon-containing ligand contributes to the improvement of the high-temperature stability of the quantum dot. The quantum dot solubility test is as follows:

the toluene solution of the original quantum dots was the same as in example 1.

The same ligand composition as in each example (100. mu.L of undiluted ligand stock solution) was added to 2mL of ethyl acetate to form a mixed solution for use.

Subsequently, a chloroform solution of the quantum dots was injected into the mixed solution containing the ligand composition to form a turbid suspension. The suspension was then stirred or sonicated at 60 ℃ for about 1 hour to give an optically clear solution indicating successful surface ligand exchange.

And finally, carrying out rotary evaporation on the transparent solution at the temperature of 65 ℃, and completely removing chloroform and ethyl acetate solvents to obtain the quantum dot powder containing two ligands.

0.01g of the quantum dot powder was dispersed in 10g of ethyl acetate, 10g of propylene glycol methyl ether acetate, and 10g of toluene, respectively, and the solubility of the quantum dot was visually observed. See table 2 for specific results.

TABLE 2

Note: "+" indicates a heavy level and "-" indicates a light level.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A quantum dot, wherein the surface of the quantum dot comprises a first quantum dot ligand and a second quantum dot ligand, wherein the first quantum dot ligand and the second quantum dot ligand each comprise at least two binding groups, wherein the first quantum dot ligand comprises a carboxyl binding groups, wherein the second quantum dot ligand comprises b mercapto binding groups, wherein a is greater than or equal to 2 and less than or equal to 100, wherein b is greater than or equal to 2 and less than or equal to 100, and wherein the binding groups are configured to coordinate to the surface of the quantum dot; the binding group of the first quantum dot ligand comprises a carboxyl group, and the binding group of the second quantum dot ligand comprises a sulfhydryl group.

2. The quantum dot according to claim 1, wherein the solvent in which the quantum dot is soluble has a hansen solubility parameter SP value of 8 to 12, and wherein the polarization term δ p is 2 or more.

3. The quantum dot according to claim 1, wherein a is 2 or more and 12 or less, and b is 2 or more and 12 or less; preferably, said a is equal to said b.

4. The quantum dot of claim 3, wherein a is 6, and b is 6; preferably, the chemical structure of the first quantum dot ligand is:

the chemical structure of the second quantum dot ligand is as follows:

the R1-R7 and the R1 'to R7' are respectively and independently selected from one of the group consisting of alkoxy, ester group, alkyl with substituent, siloxane group, aromatic group, cyclic olefin group, naphthenic hydrocarbon group, amide group and phosphate group.

5. The quantum dot of claim 3, wherein a is 2, and b is 2; preferably, the chemical structure of the first quantum dot ligand is:

the chemical structure of the second quantum dot ligand is as follows:

R8-R12 and R8 '-R12' are respectively and independently selected from one of the group consisting of alkoxy, ester group, alkyl with substituent, siloxane group, aromatic group, cyclic olefin group, naphthenic hydrocarbon group, amido and phosphate group.

6. The quantum dot according to claim 4 or 5, wherein the number of carbon atoms in each of R1 to R12 and R1 'to R12' is 10 or less; preferably, the number of carbon atoms in each of R1 to R12 and R1 'to R12' is 6 or less.

7. The quantum dot according to claim 4 or 5, wherein the alkoxy is C1-C4, the ester is C1-C4, the alkyl is C1-C4, and the carbon main chain of the alkyl with substituent is C1-C4.

8. The quantum dot of claim 4, wherein the R1, R2, R3, R5, R6, R7 are the same, and the R1 ', R2', R3 ', R5', R6 ', R7' are the same; or the R1 and the R5 are the same, the R2 and the R6 are the same, the R3 and the R7 are the same, the R1 'and the R5' are the same, the R2 'and the R6' are the same, and the R3 'and the R7' are the same.

9. The quantum dot of claim 5, wherein the R8, R9, R11, R12 are the same, and the R8 ', R9', R11 ', R12' are the same; or the R8 and the R11 are the same, the R9 is the same as the R12, the R8 'is the same as the R11', and the R9 'is the same as the R12'.

10. A quantum dot according to claim 4 or 5, wherein the substituent is selected from one or more of alkoxy, ester, alkyl, siloxane, aryl, cyclic olefin, cycloalkane, amide, and phosphate.

11. The quantum dot according to claims 1 to 5, wherein the molecular weight of the first quantum dot ligand is 200 to 2000, and the molecular weight of the second quantum dot ligand is 200 to 2000.

12. The quantum dot of claims 1-5, wherein the molar ratio of the first quantum dot ligand to the second quantum dot ligand is 1: 2-2: 1, preferably the molar ratio of the first quantum dot ligand to the second quantum dot ligand is 1: 1.

13. the quantum dot of claims 1-5, wherein the surface of the quantum dot further comprises a third quantum dot ligand, wherein the third quantum dot ligand comprises at least two binding groups, and wherein the binding group of the third quantum dot ligand comprises an amino group.

14. The quantum dot of claim 13, wherein the third quantum dot ligand comprises c amino binding groups, wherein c is 2 or more and 100 or less; preferably, c is 2 or more and 12 or less, and more preferably, c is 6.

15. A quantum dot composition comprising the quantum dot according to any one of claims 1 to 14.

16. A light emitting device comprising the quantum dot composition of claim 15.