KR102832094B1 - Hydrophilic quantum dots, synthetic method thereof, and devices using the same - Google Patents

Abstract

The present invention relates to a method for producing a hydrophilic quantum dot, comprising the steps of: (S1) preparing a quantum dot capped with a ligand having a single-digit coordination number; and (S2) treating the capped quantum dot with polyethyleneimine.

Description

Hydrophilic quantum dots, synthetic method thereof, and devices using the same

The present invention relates to hydrophilic quantum dots, a method for producing the same, and a device using the same.

Organic and inorganic fluorescent emitters are of great interest in biomedical applications, and can be used to detect or label changes in complex biological environments (cells, organisms) through appropriate functionalization. Quantum dots are one type of organic and inorganic fluorescent emitters, and are semiconductor crystals that are nanometer-sized and emit light by themselves due to the quantum effect.

Quantum dots consist of a core, a shell, and a ligand (Fig. 1). The emission wavelength is determined by the size of the quantum dot core, and in order to obtain an effective quantum confinement effect, the quantum dot core must be smaller than the exciton Bohr radius. The shell promotes the quantum confinement effect of the core and controls the oxidation reaction and traps on the surface of the core quantum dot, thereby improving the stability and quantum efficiency of the quantum dot. The ligand increases the dispersibility of the quantum dot and prevents the aggregation of the quantum dot.

Quantum dots synthesized with these cores and shells have attracted much attention in the fields of quantum dot light-emitting diodes (QD-LEDs), solar cells, chemical analysis, biomedical imaging, and biomedical diagnosis because of their high photoluminescence quantum yield, thermal stability, high color purity, and ability to emit light in a wide visible range. However, most successful studies in biology and medicine have been conducted using quantum dots based on heavy metals such as cadmium (Cd) and lead (Pb), which are highly biotoxic.

Recently reported indium phosphide (InP)-based quantum dots are environmentally friendly quantum dots that, like cadmium-based quantum dots, exhibit high luminescence efficiency of over 80% and long life of over 10,000 hours, and are attracting attention as quantum dots for biomedical imaging and biomedical diagnosis, as well as as quantum dot ink materials for color conversion layers in display devices. However, since the quantum dot surface uses a ligand capped with a long alkyl chain that has hydrophobicity, it exhibits low solubility and low dispersibility in hydrophilic solvents, making these quantum dots unsuitable for biomedical use.

Accordingly, there is a need to develop quantum dots with low biotoxicity, hydrophilicity, and excellent coordination ability.

In order to solve the above problems, the present invention provides a method for manufacturing indium phosphide (InP)-based hydrophilic quantum dots by treating a multi-dentate coordination number ligand having hydrophilic properties using a quantum dot itself capped with a single-dentate coordination number ligand having polymer properties.

However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

According to one embodiment of the present invention, there is provided a step (S1) of preparing a quantum dot capped with a ligand having a single-digit coordination number; and

A method for manufacturing a hydrophilic quantum dot is provided, comprising: a step (S2) of treating the capped quantum dot with polyethyleneimine.

According to one side, as an indium phosphide quantum dot capped with a single-digit coordination number ligand,

A hydrophilic quantum dot is provided, which is hydrophilically treated by substituting the ligand of the above single-digit coordination number with polyethyleneimine.

According to another aspect, a composition for in vivo diagnostics comprising the quantum dots is provided.

According to another aspect, an optical device comprising the composition is provided.

Through the manufacturing method of the present invention, hydrophilic quantum dots that have low biotoxicity and can easily dissolve in water and alcohol can be synthesized. It is expected that the quantum dots synthesized in this way will receive great attention as biomedical imaging and biomedical diagnostic devices in the future. In addition, if red and green quantum dots are encapsulated using the technology of the present invention and used together with a blue LED, it will be possible to implement a high-purity white LED based on the RGB primary colors, and it can also be used as a core material for the color filter of a QD-OLED display that uses a blue light-emitting substance and red and green quantum dot color filters, and it can also be used as a material for an electroluminescent QD-LED display device.

It should be understood that the effects of the present invention are not limited to the effects described above, but include all effects that can be inferred from the composition of the invention described in the detailed description or claims of the present invention.

Figure 1 is a diagram showing the structure of a luminescent quantum dot and the energy levels of the quantum dot.
Figure 2 is a drawing showing a method for synthesizing OLA InP quantum dots.
Figure 3 is a drawing showing that the monodentate OLA ligand located on the surface of the OLA InP quantum dot is replaced with PEI.
Figure 4 is a drawing showing the molecular structure of various polyalkylamines.
Figure 5 illustrates an example of the structure of a QD-LED utilizing the quantum dots of the present invention.
Figure 6 shows a comparison of the photoluminescence (PL) results of PEI InP quantum dots and OLA InP quantum dots.
Figure 7 shows a comparison of thermogravimetric analysis (TGA) results of PEI InP quantum dots and OLA InP quantum dots.
Figure 8 shows the results of hydrogen nuclear magnetic resonance spectroscopy ( ^1H NMR) of OLA InP quantum dots, PEI InP quantum dots, and polyethyleneimine.

Hereinafter, embodiments will be described in detail with reference to the attached drawings. However, since various modifications may be made to the embodiments, the scope of rights of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, or substitutes to the embodiments are included in the scope of rights.

The terms used in the examples are used for the purpose of description only and should not be construed as limiting. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, the terms "comprises" or "has" and the like are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but should be understood to not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the embodiment belongs. Terms defined in commonly used dictionaries, such as those defined in common usage dictionaries, should be interpreted as having a meaning consistent with the meaning they have in the context of the relevant art, and will not be interpreted in an idealized or overly formal sense unless expressly defined in this application.

In addition, when describing with reference to the attached drawings, the same components will be given the same reference numerals regardless of the drawing numbers, and redundant descriptions thereof will be omitted. When describing an embodiment, if it is determined that a detailed description of a related known technology may unnecessarily obscure the gist of the embodiment, the detailed description thereof will be omitted.

Additionally, in describing components of an embodiment, terms such as first, second, A, B, (a), (b), etc. may be used. These terms are only intended to distinguish the components from other components, and the nature, order, or sequence of the components are not limited by these terms.

Components included in one embodiment and components including common functions will be described using the same names in other embodiments. Unless otherwise stated, descriptions given in one embodiment can be applied to other embodiments, and specific descriptions will be omitted to the extent of overlap.

Throughout the specification, when it is said that a part "includes" a component, this does not mean that it excludes other components, but rather that it may include other components.

Throughout the specification, 'hydrophilic quantum dot' means a quantum dot capped with a hydrophilic ligand. 'PEI InP quantum dot' means a hydrophilic quantum dot capped with a PEI ligand and having a core layer comprising indium phosphide (InP). Here, 'PEI' means polyethyleneimine.

Throughout the specification, 'hydrophobic quantum dots' means quantum dots capped with hydrophobic ligands. 'OLA InP quantum dots' means hydrophobic quantum dots capped with OLA ligands and having a core layer comprising indium phosphide (InP). Here, 'OLA' means oleylamine.

According to one embodiment of the present invention, a method for producing a hydrophilic quantum dot is provided. This may include a step (S1) of preparing a quantum dot capped with a monodentate ligand; and a step (S2) of treating the capped quantum dot with a multi-dentate ligand. As an example of the multi-dentate ligand, polyethyleneimine can be used.

The S1 step may include a step (a1) of forming a core layer, a step (a2) of forming an inner shell layer, and a step (a3) of forming an outer shell layer (FIG. 2). Specifically, the a1 step may include a step of reacting an In precursor and a ligand having a single-dentate coordination number by mixing them under an inert gas. Then, the a2 step may include a step of increasing the temperature of the mixture and repeatedly adding a precursor stock solution dropwise to react. At this time, the inner shell layer may be formed outside the core layer. For successful formation of the outer shell layer, the a3 step may include a step of lowering the temperature of the mixture and adding a precursor dropwise to react. The outer shell layer may be formed outside the inner shell layer. The quantum dots capped with the ligand having a single-dentate coordination number may be obtained by lowering the temperature of the reaction mixture to room temperature and performing purification and centrifugation.

The S2 step can utilize quantum dots capped with ligands having a single-dentate coordination number and can cause a ligand substitution reaction (Fig. 3). That is, a ligand having a single-dentate coordination number with a relatively weak coordination ability on the surface of the quantum dot can be replaced with a ligand having a multi-dentate coordination number with a strong coordination ability. Specifically, a ligand having a multi-dentate coordination number can be slowly added dropwise to the capped quantum dot and stirred to cause a reaction. Thereafter, the solution is centrifuged to remove unreacted quantum dots and polyethyleneimine. The finally obtained precipitate is dried in a vacuum to obtain hydrophilic quantum dots substituted with multi-dentate ligands.

In one embodiment of the present invention, the ligand having a single digit coordination number may be any one of trioctylphosphine, trioctylphosphine oxide, an alkyl amine (including a monomer and a polymer), and a conjugate base of a carboxylic acid (including a monomer and a polymer). In this case, the conjugate base of the alkyl amine or the carboxylic acid may be oleylamine. However, the present invention is not limited thereto.

In one embodiment of the present invention, the core layer of the quantum dot may include at least one selected from the group consisting of compounds of Group IB, Group IIB, Group IIIB, Group IVB, Group VB and Group VIB, preferably any one of compounds of Group IVB, Group IIB-Group VIB, Group IVB-Group VIB, Group IIIB-Group VB and Group IB-Group IIIB-Group VIB, and most preferably a Group IIIB-Group VB compound.

For example, the Group IVB compounds can include Si, Ge, SiC, etc. The Group IIB-VIB compounds can include CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnSeTe, etc. The Group IVB-VIB compounds can include PbS, PbSe, PbTe, etc. The Group IIIB-VB compounds can include AlP, AlAs, AlSb, InN, InP, InAs, GaN, GaP, GaAs, GaSb, InGaP, etc. The Group IB-IIIB-VIB compounds can include AgGaS ₂ , AgGaSe ₂ , AgGaTe ₂ , AgInS ₂ , AgInSe ₂ , AgInTe ₂ , CuInS ₂ , CuInSe ₂ , CuInTe ₂ , CuGaS ₂ , CuGaSe ₂ , CuGaTe ₂ . Preferably, the group IIIB-VB compound may be InP, but is not limited thereto.

The inner and outer shell layers of the quantum dots to which the technology of the present invention is applicable can be formed from a semiconductor compound precursor composed of a metal and a non-metal.

For example, for InP/ZnSeS/ZnS quantum dots, the core can be formed from a group IIIB-VB compound, the inner shell layer can be formed from a Zn precursor compound and a Se-S precursor compound, and the outer shell layer can be formed from a Zn precursor compound and a S precursor compound.

In one embodiment of the present invention, the ligand of the OLA InP quantum dot can be substituted using a polyalkylamine among the ligands having multiple coordination numbers (FIG. 4). At this time, the polyalkylamine can be polyethyleneimine. Since polyethyleneimine has a secondary amine functional group, it can induce a quantum dot substitution reaction as a multidentate amine ligand.

Polyethyleneimine can be classified as linear, branched, or dendritic. Generally, the nitrogen atoms within the above molecular structure can be connected by 1 to 10 carbon atoms, but is not limited thereto.

Polyethyleneimine can contain alkyl groups or aryl groups. For example, electron donating groups such as -NR ₃ , -NHR ₃ , NH ₃ H, -OR or electron withdrawing groups such as -CF ₃ , -CCl ₃ , -CN, -NO ₂ , -COR, -CONH ₂ can be bonded as substituents in place of hydrogen, thereby enabling precise control of the coordination properties of multidentate amine ligands.

According to another embodiment of the present invention, a quantum dot is provided which is a phosphorous indium quantum dot capped with a ligand having a single-digit coordination number, wherein the ligand having the single-digit coordination number is substituted with polyethyleneimine to render it hydrophilic.

The above quantum dots may be hydrophilic. Specifically, polyethyleneimine is hydrophilic and dissolves well in water, alcohol, and chloroform solvents, and the PEI InP quantum dots formed by the substitution reaction also exhibit hydrophilic quantum dot characteristics by dissolving well in one or more solvents selected from the group consisting of water, alcohol, and chloroform.

In addition, since quantum dots contain ligands with excellent coordination capabilities, they can have high dispersibility. In this specification, 'high dispersibility' means a property of excellent dispersibility in the solvent.

Therefore, according to the present invention, biocompatible quantum dots can be synthesized.

According to one embodiment of the present invention, an in vivo diagnostic composition including the quantum dot can be provided. This is because the quantum dot is not only hydrophilic but also has a highly dispersible characteristic by using a ligand with excellent coordination ability, and the surface properties of the quantum dot are modified to have biocompatibility.

According to another embodiment of the present invention, an optical device including the quantum dots can be provided. For example, a display device including quantum dots can be provided. If red and green quantum dots are encapsulated using the technology of the present invention and used together with a blue LED, a white LED can be implemented based on RGB primary colors. In addition, as shown in FIG. 5, it can also be used as a core material of a color filter of a QD-OLED display using a blue light-emitting material and red and green quantum dot color filters.

Hereinafter, embodiments will be described in detail with reference to the attached drawings. However, since various modifications may be made to the embodiments, the scope of rights of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, or substitutes to the embodiments are included in the scope of rights.

Example

PEI InP/ZnSeS/ZnS was manufactured. The manufacturing method is described in detail below.

Comparative Example 1

OLA InP/ZnSeS/ZnS was manufactured. The manufacturing method was referred to the following prior literature and is described in detail below.

(1) Electrical resonant effects of ligands on the luminescent properties of InP/ZnSeS/ZnS quantum dots and devices configured therefrom, Organic Electronics, 2020.

Comparative Example 2

Polyethyleneimine was prepared for comparison with the present invention without manufacturing quantum dots.

1. Experimental Example 1: Synthesis of PEI InP/ZnSeS/ZnS quantum dots

(1) Comparative Example 1 Synthesis (S1 stage)

Referring to Fig. 2, first, to form a core layer (a1), an In precursor, a Zn precursor, and oleylamine were mixed under an inert gas, and then tris(dimethylamino)phosphine was added dropwise and reacted at 180°C.

For the composition of the inner shell layer (a2), Se-S stock solution was added dropwise to the above solution at 195°C and reacted for 30 minutes (b1). Then, Zn stock solution was added dropwise at 210°C and reacted for 30 minutes (b2). The above b1 and b2 steps were repeated by increasing the temperature by 15°C each time until the temperature reached 300°C.

For successful formation of the outer shell layer (a3), 1-dodecanethiol was added to the growth solution at 220 °C for 1 hour. Then, Zn precursor dissolved in oleylamine and octadecene was added dropwise at 190 °C and reacted for 2 hours.

Ethanol was added to the above reaction mixture, and the mixture was purified and centrifuged to obtain Comparative Example 1.

(2) Example synthesis (Step S2)

The above Comparative Example 1 was dissolved in chloroform. Polyethyleneimine was slowly added dropwise to the solution and stirred for 24 hours.

To remove unreacted quantum dots, the solution mixed with cyclohexane was centrifuged. To remove unreacted polyethyleneimine, the obtained precipitate was dissolved in chloroform, mixed with methanol, and the solution was centrifuged.

The finally obtained orange precipitate was dried in vacuum for 24 h to obtain PEI InP/ZnSeS/ZnS quantum dots.

2. Experimental Example 2: Confirmation of Synthesis of Example

Fluorescence analysis was performed on Examples and Comparative Example 1, and is shown in Fig. 6. When oleylamine was substituted with polyethyleneimine, a 9.9 nm bathochromic shift was observed. When a new strong organic-inorganic hybrid orbital was formed at the quantum dot-ligand interface, an optical red shift of the quantum dot compound appeared. This confirmed that it was substituted with a stronger polyethyleneimine ligand.

Thermogravimetric analysis was performed on Examples and Comparative Example 1, and the results are shown in Fig. 7. At the final temperature (800°C), the weight change of the OLA InP quantum dots was confirmed to be 36%, and the weight change of the PEI InP quantum dots was confirmed to be 77%. This is because the successfully substituted polyethyleneimine ligand has a relatively larger molecular weight than oleylamine (polyethyleneimine: ~10,000 g/mol, oleylamine: 267.49 g/mol).

In addition, hydrogen nuclear magnetic resonance spectroscopy analysis was performed on the examples and comparative examples, and the results are shown in Fig. 8. In the hydrogen nuclear magnetic resonance spectroscopy spectra of Comparative Examples 1 and 2, a multiplet spectrum peak of the methyl functional group (CH ₃ group) of oleylamine appeared at 0.9 ppm. In the spectra of the examples, the above peak did not appear, whereas only a broad peak of the methylene functional group (CH ₂ group) of polyethyleneimine was confirmed at 2.4 to 3.0 ppm. That is, in the examples, it can be confirmed that oleylamine capping the quantum dots was substituted with polyethyleneimine, since the peak for the methyl functional group of Comparative Examples 1 and 2 disappeared and the peak for the methylene functional group was generated.

From the results of the above Figures 6 to 8, it was confirmed that the ligand oleylamine of Comparative Example 1 was replaced with polyethyleneimine to form an example.

3. Use as a composition for in-vivo diagnostics, etc.

From the PEI InP quantum dots manufactured from Example 1, an in vivo diagnostic composition, an optical element, etc. can be manufactured. Using the in vivo diagnostic composition, optical imaging, bio-imaging such as magnetic resonance imaging (MRI) and computed tomography (CT), cancer detection probe quantum dots, drug delivery vehicles, etc. can be manufactured. The optical element includes a display element and a solar cell. However, the present invention is not limited thereto.

Although the embodiments have been described with limited drawings as described above, those skilled in the art can apply various technical modifications and variations based on the above. For example, even if the described techniques are performed in a different order than the described method, and/or the components of the described system, structure, device, circuit, etc. are combined or combined in a different form than the described method, or are replaced or substituted by other components or equivalents, appropriate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents to the claims are also included in the scope of the claims described below.

Claims (14)

Step (S1) of preparing a quantum dot capped with a ligand having a single-digit coordination number; and
A step (S2) of treating a ligand having multiple coordination numbers on the capped quantum dot; including;
The above step (S1) is a step of forming a core layer;
A step of forming an inner shell layer outside the core layer; and
A step of forming an outer shell layer outside the inner shell layer; including;
The above multi-coordinate ligand is a polyalkylamine.
Method for producing hydrophilic quantum dots.
delete In the first paragraph,
A method for producing a hydrophilic quantum dot, wherein the ligand having the above single-digit coordination number is any one of trioctylphosphine, trioctylphosphine oxide, an alkyl amine, and a conjugate base of a carboxylic acid.
In the third paragraph,
A method for producing a hydrophilic quantum dot, wherein the conjugate base of the above alkylamine or the above carboxylic acid is oleylamine.
In the first paragraph,
A method for producing a hydrophilic quantum dot, wherein the core layer of the quantum dot comprises at least one compound selected from the group consisting of compounds of group IB, group IIB, group IIIB, group IVB, group VB, and group VIB.
In paragraph 5,
A method for producing a hydrophilic quantum dot, wherein the core layer of the quantum dot comprises any one of compounds of group IVB, group IIB-group VIB, group IVB-group VIB, group IIIB-group VB, and group IB-group IIIB-group VIB.
In Article 6,
A method for producing a hydrophilic quantum dot, wherein the group IIIB-VB compound is any one of AlP, AlAs, AlSb, InN, InP, InAs, GaN, GaP, GaAs, GaSb, and InGaP.
In the first paragraph,
A method for producing a hydrophilic quantum dot, wherein the inner and outer shell layers of the quantum dot are formed from a semiconductor compound precursor composed of a metal and a non-metal.
delete In the first paragraph,
A method for producing hydrophilic quantum dots, wherein the above polyalkylamine is polyethyleneimine.
A hydrophilic quantum dot is a quantum dot capped with a single-digit coordination number ligand, wherein the single-digit coordination number ligand is replaced with polyethyleneimine, a multi-digit coordination number ligand, thereby making it hydrophilic.
The above indium quantum dot comprises a core layer, an inner shell layer on the core layer, and an outer shell layer surrounding the inner shell layer.
A hydrophilic quantum dot characterized in that the hydrophilic quantum dot has biocompatibility.
delete An in vivo diagnostic composition comprising the hydrophilic quantum dot of claim 11.
An optical device comprising the in vivo diagnostic composition of claim 13.