WO2017034228A1

WO2017034228A1 - Quantum-dot surface-processing method for imparting chemical resistance, and quantum dots produced thereby

Info

Publication number: WO2017034228A1
Application number: PCT/KR2016/009160
Authority: WO
Inventors: 김재일; 임태윤
Original assignee: 주식회사 두하누리
Priority date: 2015-08-21
Filing date: 2016-08-19
Publication date: 2017-03-02
Also published as: KR101668480B1

Abstract

The present invention relates to: a quantum-dot surface-processing method for imparting chemical resistance by subjecting metal ions present on the surface of quantum dots to a cation exchange reaction and thereby subjecting same to place exchange with metal ions of another type which were previously present on the outside of the quantum dots; and quantum dots produced by means of the method. The present invention is devised in such a way that an inorganic shell coating is constituted on the quantum dot surface in straightforward yet also stable fashion, and in such a way that external environmental effects are not experienced, and, as a result, in such a way that the invention has outstanding chemical resistance and heat resistance, and in such a way that an inorganic layer, that has the nature of a buffer formed on the outermost shell of the quantum dot, can have a thickness that does not affect the light-emitting properties.

Description

Chemical resistance surface treatment method of quantum dots and quantum dots produced by

The present invention relates to a method for imparting chemical resistance to quantum dots and a quantum dot manufactured by the method, and more particularly, to impart chemical resistance to quantum dots so as not to be affected by the external environment, thereby having excellent chemical resistance and heat resistance. A surface treatment method and a quantum dot produced thereby.

In general, when a material is reduced to nanometers in size, it has new physical properties that were not seen in bulk because the material changes as its size and shape change.

Among such nanomaterials, there is a quantum dot (QD), which is a semiconductor material corresponding to a nano size of about 2 to 10 nm in diameter, and when it is smaller than a certain size, electron motion characteristics in the bulk semiconductor material are further restricted. It is a material that gives a quantum confinement effect that the emission wavelength is different from the bulk state. When the quantum dot receives light from an excitation source and reaches an energy excited state, the quantum dot emits energy according to a corresponding energy band gap. Therefore, by adjusting the size of the quantum dot it is possible to adjust the band gap, the energy of various wavelength bands can be obtained, thereby showing optical, electrical and magnetic properties that are completely different from the original physical properties.

These quantum dots have recently been studied for use in various fields, including a wide range of applications, such as displays, solar energy conversion, molecular and cellular imaging, and the like.

As a technique related to the conventional quantum dots, there is a "quantum dot-matrix thin film" of Korea Patent Publication No. 10-2013-0067137, which includes a plurality of quantum dots; An inorganic matrix embedded with a plurality of said quantum dots; And an interface layer positioned between the quantum dots and the inorganic matrix and surrounding the surface of the quantum dots.

Conventional quantum dots as well as such conventional quantum dots are usually synthesized at a high temperature using a high temperature pyrolysis method, and the higher the crystallinity, the higher the luminescence property. The presence of an alkyl chain on the surface of the particle makes it hydrophobic, thereby dissolving only in non-polar organic solvents.

Therefore, the quantum dot is sensitive to the external chemical environment due to the nano-sized small particles and metal ions, together with the above-described characteristics, thereby causing a sudden change in luminescence and poor chemical resistance, and reaction with oxygen in the atmosphere at a high temperature of 100 ° C. or higher. As a result, the surface was damaged, resulting in a problem of poor heat resistance in which the luminescence dropped sharply. Poor chemical resistance of quantum dots is evidence that the luminescence deteriorates during the quantum dot surface ligand substitution experiment, and the quantum dots are not completely protected from the external environment except for a very thick CdS shell, and an inorganic shell coating The coating is not complete and the external environment is affected. Therefore, there was a need to improve these disadvantages.

In order to solve the problems of the prior art as described above, the present invention allows the inorganic shell coating to be simply and stably formed on the surface of the quantum dots so as not to be influenced by the external environment, thereby providing excellent resistance to It is intended to have chemical and heat resistance, and to have a thickness that does not affect the luminescence of the buffer-type inorganic layer formed on the outermost quantum dots.

Other objects of the present invention will be readily understood through the following description of the embodiments.

In order to achieve the above object, according to one aspect of the invention, the metal ions present on the surface of the quantum dots by a cation exchange reaction (cation exchange reaction), the heterogeneous metal ions existing outside the quantum dots Provided is a method for treating a chemically imparted surface of a quantum dot to allow for site exchange.

The material exchanged with the heterogeneous metal ions has a larger atom or ion than the metal ions on the surface of the quantum dot, and thus has a lower band gap when the metal ions on the surface of the quantum dot are replaced. It may be a forming material.

The material exchanged with the heterogeneous metal ions may include some of Cd, Al, Ga (Gallium), and In (Indium) when the outermost metal atom of the quantum dot is Zn.

Mixing the quantum dots with a solution containing the heterogeneous metal ions and exchanging metal ions on the surface of the quantum dots at a temperature of 100 to 300 ° C .; And cooling the quantum dot mixed solution after the exchange of the metal ions, and then purifying the quantum dots with an organic solvent.

CdO, ligand, and 1-octadecene (ODE) are added to the container, and based on 10 mmol of the CdO, the ligand is 5-100 mmol, and the 1-octadecene (ODE) is 10 Bringing to 2000 mL; Dissolving the CdO by bringing the vessel to a temperature of 100 to 300 ° C. in a vacuum state; Adding a quantum dot to the solution in which the CdO is dissolved so that the metal ion of the surface of the quantum dot is exchanged at a temperature of 100 to 300 ° C .; And cooling the solution to purify the quantum dots with an organic solvent.

The ligand may be an alkyl acid, an alkyl phosphonic acid, an alkyl phosphinic acid, an aryl acid, or an aryl phosph that may react with a metal to form a metal salt. It may include any one of arylphosphonic acid and aryl phosphinic acid.

According to another aspect of the present invention, there is provided a quantum dot produced by the method for imparting chemical resistance of the quantum dot according to one aspect of the present invention.

According to the method for treating the chemical resistance of the quantum dots according to the present invention and the quantum dots manufactured thereby, an inorganic shell coating is simply and stably performed on the surface of the quantum dots, thereby preventing them from being affected by the external environment. Therefore, it is possible to have excellent chemical resistance and heat resistance, and to have a thickness that does not affect the luminescence of a buffer-type inorganic layer formed on the outermost quantum dots.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the chemical resistance provision surface treatment method of the quantum dot which concerns on this invention.

2 is a view for explaining the reason that the change in the luminescence is small by the chemical resistance imparting surface treatment method of the quantum dots according to the present invention.

3 is a flowchart illustrating a chemical treatment-resistant surface treatment method of a quantum dot according to an embodiment of the present invention.

4 is a view comparing before and after chemical resistance imparting surface treatment according to the present invention.

As the inventive concept allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to the specific embodiments, but should be understood in a way that includes all changes, equivalents, and substitutes included in the spirit and scope of the present invention, and may be modified in various other forms. It is to be understood that the scope of the present invention is not limited to the following examples.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and like reference numerals denote the same or corresponding elements regardless of reference numerals, and redundant description thereof will be omitted.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view for explaining a chemical treatment-resistant surface treatment method of a quantum dot according to the present invention, which shows that the CdSe / ZnS quantum dots are surface-treated with Cd ions.

As shown in (a) of FIG. 1, in the method for treating chemical resistance of a quantum dot according to the present invention, metal ions existing on the surface of the quantum dot are present outside the quantum dot by a cation exchange reaction. Replace with other metal ions. Here, the temperature for causing the metal ions present on the surface of the quantum dot to be exchanged with the different metal ions is less than the temperature at which the core and the shell of the quantum dot form an alloy, and the metal ions of the surface and the hetero ions are cations as described above. It may be a temperature range to allow a cation exchange reaction.

Substances exchanged with heterogeneous metal ions have a larger atom or ion than metal ions on the surface of the quantum dots, thereby forming a layer having a lower band gap when the metal ions on the surface of the quantum dots are replaced. As shown in (b) of FIG. 1, when the outermost metal atom of the quantum dot is Zn, it may include some of Cd, Al, Ga (Gallium) and In (Indium), for example, the outermost portion of the quantum dot. When the material is ZnS, the material that is exchanged with heterogeneous metal ions may be, for example, CdS, in addition to ZnSe. In addition, within the range that satisfies these conditions, the quantum dots may be selected from any one of Si-based nanocrystals, II-VI compound semiconductor nanocrystals, III-V compound semiconductors, and IV-VI compound semiconductor nanocrystals and compounds thereof. Nanocrystals. Here, the group II-VI compound semiconductor nanocrystals are CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, PbSe, PbS, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeS, HgSeS, HgSeS Among CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HggZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgZTSe, HdHgZTT, In addition, group III-V compound semiconductor nanocrystals are GaN, GaP, GaAs, AlN, AlP, AlAs, InN, InP, InAs, GaNP, GaNAs, GaPAs, AlNP, AlNAs, AlPAs, InNP, InNAs, InPAs, GaAlNP, GaAlNAs, GaAlPAs, GaInNPs, GaInNAs, GaInPAs, InAlNPs, InAlNAs, and InAlPAs may be any one selected from. In addition, the quantum dot may be a Cd compound such as CdS, CdSe, CdTe, CdTe, or the like, or an In compound such as InP, InN, InAs, etc., and the shell surrounding the core may be a Zn compound such as a quantum dot core and a lattice parameter. May be similar ZnS or ZnSe, and thus may include nanocrystals made of CdSe / ZnS as shown in FIG. 1 or nanocrystals made of InP / ZnS as another example.

According to the method for imparting chemical resistance of the quantum dots according to the present invention as described above, it is possible to form an inorganic shell coating simply and reliably and not to affect the internal size of the particles, It has a buffer characteristic at the outermost part of the quantum dot but does not affect the luminescence by forming a very thin inorganic film due to the thickness of less than 1 monolayer.

In the present invention, for example, the change in the luminescence, when the quantum dot is CdSe / ZnS as shown in Fig. 2 (a), the ZnS crystal lattice grows on the CdSe crystal lattice, at a predetermined thickness, for example 1.7 mL or more Crack is generated, as shown in (b) of FIG. 2, in the case of the quantum dot manufactured by the chemical resistance surface treatment method of the quantum dot according to the present invention, for example, CdSe / ZnS / CdS is formed on the CdSe crystal lattice. As the ZnS crystal lattice grows and Cd larger than Zn enters the outermost quantum dot, cracks caused by the increase in ZnS thickness are prevented. It can be seen that Cd enters the position where the crack occurs, and as a result, the crack disappears on the crystal lattice, thereby suppressing lattice mismatch, minimizing energy loss and improving luminescence. In addition, the phenomenon that chemicals penetrate into the space formed when the crack is generated to reduce the luminescence is prevented by suppressing the occurrence of the crack as described above. This also improves the high temperature heat resistance in the presence of oxygen and reduces the likelihood of attacking foreign chemicals due to high density ligand binding. Since CdS is not a shell of sufficient thickness, it does not affect the quantum dot emission wavelength.

As shown in FIG. 3, in the method for treating chemical resistance of quantum dots according to an embodiment of the present invention, for example, the quantum dots are mixed with a solution containing heterogeneous metal ions, and the quantum dots are mixed at a temperature of 100 to 300 ° C. Comprising a step (S11) to exchange the metal ions on the surface, and cooling the quantum dot mixed solution after the exchange of the metal ions, and may comprise the step of purifying the quantum dots with an organic solvent (S12).

According to another embodiment of the present invention, a method for treating chemical resistance of a quantum dot is prepared by adding CdO, a ligand, and 1-octadecene (ODE) to a container, based on 10 mmol of CdO, wherein the ligand is 5 to 100 to 1 mmol of octadecene (ODE) to 10 to 2000 mL, to dissolve the CdO by bringing the vessel to a temperature of 100 to 300 ° C. in a vacuum state, and the CdO Adding a quantum dot to the dissolved solution to allow the solution to exchange metal ions on the surface of the quantum dot at a temperature of 100 to 300 ° C., and cooling the solution to purify the quantum dot with an organic solvent. have. Wherein the ligand is an alkyl acid, alkyl phosphonic acid, alkyl phosphinic acid, aryl which can react with metals such as Cd, Al, Ga, In and the like to form metal salts Acid (aryl acid), aryl phosphonic acid (aryl phosphonic acid) and aryl phosphinic acid (aryl phosphinic acid) may include any one, and the structure and molecular weight of the material is not limited.

The quantum dot according to an embodiment of the present invention is a quantum dot manufactured by the chemical resistance imparting surface treatment method of the quantum dots according to the embodiments of the present invention as described above, the chemical resistance imparting surface treatment method of the quantum dots has already been described in detail. Since the description thereof will be omitted, more specific embodiments will be described below.

Example 1 Green QD Synthesis

Selenium and sulfur were dissolved in tri-n-octylphosphine, respectively, to prepare a 1M selenium solution (TOP-Se) and 1M sulfur (TOP-S) solution, which is a chalcogenide standard solution for red quantum dot synthesis. In a 100 mL two neck round bottom flask, 0.128 g (1.0 mmol) of cadmium oxide and 0.878 g (4.0 mmol) of zinc acetate, 6.34 mL (20.0 mmol) of oleic acid, 2.7 g (10 mmol) Oleylamine) and 10 mL of octadecine were added and heated to 180 ° C. until the solution became clear to obtain metal precursors of cadmium oleate and zinc oleate. The resulting water was then removed by heating to 150 ° C. and degassing for 20 minutes. The temperature of the mixed solution was raised to 300 ° C, 0.4 mL of 1 M selenium solution (TOP-Se) and 3 mL of 1 M sulfur solution (TOP-S) were mixed at room temperature, and then injected. After the growth step to adjust the temperature to 280 ℃ 10 minutes to proceed with a reaction to obtain a quantum dot.

Example 2 Yellow QD Synthesis

Se and S were dissolved in tri-n-octylphosphine, respectively, to prepare a 1M selenium solution (TOPSe) and 1M sulfur (TOPS) solution, which is a chalcogenide standard solution for red quantum dot synthesis. In a 100 mL two neck round bottom flask, 0.128 g (1.0 mmol) of cadmium oxide, 0.634 mL (2.0 mmol) of oleic acid, and 10 mL of octadecine were added until the solution became clear. It heated to C, and obtained the cadmium oleate metal precursor. The resulting water was then removed by heating in vacuo to 150 ° C. and degassing for 20 minutes. The temperature of the mixed solution was raised to 300 ° C. and 2 mL of 1 M selenium solution (TOPSe) was injected. After the growth step to adjust the temperature to 280 ℃ and proceeded for 12 minutes to obtain a CdSe core quantum dot.

0.1 g of the CdSe Core QD obtained above is dissolved in 10 mL of ODE. After raising the temperature of the reaction vessel to 200 ° C. under vacuum, the temperature is increased to 280 ° C. after N2 purging. Mix 1 mmol of zinc stearate with 1 mL of the prepared TOP-S and dilute by adding 5 mL of TOP (referred to as Zn-S precursor solution). The Zn-S precursor solution is slowly dropped into the CdSe core QD / ODE solution using a syringe pump. After the reaction for 3 hours to lower the temperature of the reaction vessel to room temperature, EtOH is added to the container in excess, the quantum dots are precipitated, and the particles are recovered at 15,000rpm using a centrifuge.

Example 3 Red QD Synthesis

Se and S were dissolved in tri-n-octylphosphine, respectively, to prepare a 1M selenium solution (TOP-Se) and 1M sulfur (TOP-S) solution, which is a chalcogenide standard solution for red quantum dot synthesis. In a 100 mL two neck round bottom flask, 0.128 g (1.0 mmol) of cadmium oxide, 0.878 g (4.0 mmol) of zinc acetate, 5.7 g (20.0 mmol) of stearic acid, 10 ml of 2.7 g (10 mmol) oleylamine octadecine was added and heated to 180 ° C. until the solution became clear, thereby obtaining metal precursors of cadmium oleate and zinc oleate. The resulting water was then removed by heating to 150 ° C. and degassing for 20 minutes. The temperature of the mixed solution was raised to 300 ° C. and 0.4 mL of 1 M selenium solution (TOP-Se) was injected, and after 30 seconds, 1 M sulfur solution (TOP-S) was injected. In the growth stage, the temperature was adjusted to 280 ° C., and the reaction was performed for 10 minutes to obtain a quantum dot.

Example 4 InP-ZnS Synthesis

Dissolve 0.2g InCl3 and 0.12g anhydrous ZnCl2 in Oleyamine (OLA), add 100 mL 1-neck RBF and raise the temperature to 220 ℃. An intermediate medium vacuum is applied to remove the volatiles in the solution and the container is filled with nitrogen. Then dissolve 0.25 mL of Tris (dimethylamino) phosphine (P (DA) 3) in 1 mL of 1-octadecene. P (DA) 3 / ODE solution is injected into the In-Zn-OLA solution at 220 ° C. and the temperature of the vessel is maintained at 220 ° C. for 3 minutes. After 3 minutes, the vessel was removed from the heating mantle, and when the temperature of the solution reached 100 ° C. or lower, EtOH was poured to recover InP-ZnS quantum dots. The collected quantum dots emit green light.

Example 5 Fast Cation Exchange Reaction

Prepare 100 mL 2-neck RBF, add 10 mmol of CdO and 22 mmol of oleic acid (OA), and fill with 50 mL of 1-octadecene (ODE). Then, the temperature of the solution is raised to 200 ° C. under vacuum and maintained for 12 hours in that state to completely dissolve the CdO. Fill a batch of quantum dots (purified quantum dots) prepared above, raise the temperature of the entire solution to 220 ° C, and attempt to exchange metal ions on the surface for 2 hours at that temperature. Then, when the temperature of the solution is lowered to room temperature, the quantum dots are purified using excess EtOH.

Example 6 Slow Cation Exchange Reaction

Prepare 100 mL 2-neck RBF, add 10 mmol of CdO and 21 mmol of stearic acid (SA), and fill with 50 mL of 1-octadecene (ODE). Then, the temperature of the solution is raised to 200 ° C. under vacuum and maintained for 12 hours in that state to completely dissolve the CdO. Fill a batch of quantum dots (purified green quantum dots or InP-ZnS) prepared above, raise the temperature of the entire solution to 220 ° C, and attempt to exchange metal ions present on the surface for 24 hours at that temperature. Then, when the temperature of the solution is lowered to room temperature, the quantum dots are purified using excess EtOH.

The luminescence and chemical resistance of quantum dots surface-treated and quantum dots not treated by Example 3 as described above were tested.

First, mercaptoproponic acid is dropped into the CHCl3 solution in which the surface-treated quantum dots and the surface-treated quantum dots are dissolved according to the present invention. As a result, the quantum dots that were not surface treated rapidly decreased the luminescence, whereas the quantum dots that were surface treated according to the present invention did not change greatly.

In addition, in Figure 4, as shown in (a), the surface-treated quantum dots show low luminescence, but as shown in (b) it can be observed that the surface-treated quantum dots maintained a high luminescence properties. Here, before surface treatment refers to a quantum dot stock solution obtained by synthesis, and after surface treatment refers to a case of quantum dots substituted with surface metal by Cd obtained through Cd-alkyl acid. As such, it can be seen that the luminescence is increased by more than 10% after the surface treatment, while under room light means that the camera was photographed under a fluorescent lamp.

According to the chemical resistance surface treatment method of the quantum dot according to the present invention and the quantum dot manufactured thereby, the inorganic shell coating (simple and stable) to the surface of the quantum dot is made to be affected by the external environment Therefore, it is possible to have excellent chemical resistance and heat resistance, and to have a thickness that does not affect the luminescence of a buffer-type inorganic layer formed on the outermost of the quantum dots.

As described above with reference to the accompanying drawings, the present invention, of course, various modifications and variations can be made within the scope without departing from the spirit of the invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

Claims

A method for providing chemical resistance to a quantum dot, wherein the metal ion present on the surface of the quantum dot is exchanged with a heterogeneous metal ion existing outside the quantum dot by a cation exchange reaction.
The method according to claim 1,

The material which is exchanged with the heterogeneous metal ions,

Chemical resistance surface treatment of quantum dots, which is larger in size of atoms or ions than metal ions on the surface of the quantum dots, thereby forming a layer having a lower band gap when the metal ions on the surface of the quantum dots are replaced. Way.
The method according to claim 2,

The material which is exchanged with the heterogeneous metal ions,

When the outermost metal atom of the quantum dot is Zn, Cd, Al, Ga (Gallium) and In (indium) containing a part of, the chemical resistance of the quantum dot surface treatment method.
The method according to claim 1,

Mixing the quantum dots with a solution containing the heterogeneous metal ions and exchanging metal ions on the surface of the quantum dots at a temperature of 100 to 300 ° C .; And

Cooling the quantum dot mixed solution after the exchange of the metal ions, and then purifying the quantum dots with an organic solvent;

A surface treatment method for imparting chemical resistance of the quantum dots, including.
The method according to claim 1,

CdO, ligand, and 1-octadecene (ODE) are added to the container, and based on 10 mmol of the CdO, the ligand is 5-100 mmol, and the 1-octadecene (ODE) is 10 Bringing to 2000 mL;

Dissolving the CdO by bringing the vessel to a temperature of 100 to 300 ° C. in a vacuum state;

Adding a quantum dot to the solution in which the CdO is dissolved so that the metal ion of the surface of the quantum dot is exchanged at a temperature of 100 to 300 ° C .; And

Cooling the solution to purify the quantum dots with an organic solvent:

A surface treatment method for imparting chemical resistance of the quantum dots, including.
The method according to claim 5,

The ligand is,

Alkyl acid, alkyl phosphonic acid, alkyl phosphinic acid, aryl acid, aryl phosphonic acid which can react with metal to form metal salt phosphonic acid) and aryl phosphinic acid (aryl phosphinic acid), comprising a method for treating chemical resistance of the quantum dots.
The method according to claim 1,

Chemistry dot produced by chemical resistance imparting surface treatment method.