KR102618858B1 - Preparing method for nanocrystals, composition for preparing nanocrystals, and nanocrystals prepared by the same - Google Patents

Abstract

The present invention is intended to provide a method for manufacturing nanocrystals that can finely control the light emission wavelength.
In the present invention, when manufacturing nanocrystals, the light emission wavelength can be finely controlled by attaching a crystal growth inhibitor, which is a chain-shaped organic compound containing electron donor atoms, to the surface of the nanocrystals to control the growth rate of the nanocrystals.

Description

Method for producing nanocrystals, composition for producing nanocrystals, and nanocrystals produced thereby

The present invention relates to a method for producing nanocrystals, a composition for producing nanocrystals, and nanocrystals produced thereby.

Nanocrystals are semiconductor crystals of several nanometers in size made of inorganic semiconductor materials as shown in Figure 1, and are composed of a core part, a shell part, and an organic layer bonded to the surface of the shell part of the nanocrystal to increase solubility in organic solvents. It is made up of a substance called a ligand.

Nanocrystalline materials generally have the characteristic that the energy band gap (Eg) between the valence band and conduction band changes depending on the size. In addition, nanocrystalline materials have several material advantages, such as excellent absorption coefficient, high electron mobility, and the ability to control the emission wavelength by controlling the particle size. In particular, nanocrystalline materials are attracting attention as next-generation display device materials due to their excellent photostability because the core light emitting agent is an inorganic material rather than an organic material.

Nanocrystals composed of semiconductor elements can be synthesized through various methods. Nanocrystals consisting of a core/shell/ligand structure with excellent optical properties are generally synthesized through a wet chemical solution process. In particular, nanocrystals applied to the inkjet printing method are synthesized through hot-injection batch synthesis because the nanocrystals must have excellent dispersion characteristics in organic solvents due to the nature of the process. According to this method, various precursors as reactants are injected into a high-temperature metal compound solution to form the core and shell of nanocrystals. At this time, agglomeration between crystals due to rapid growth of the core and shell is prevented and the resulting nanocrystals are formed. For the purpose of increasing solubility, a capping ligand with a high boiling point is used as a reaction solvent. Representative capping ligands used in high-temperature solution synthesis methods include oleylamine and trioctylphosphine oxide (TOPO), and these ligands are bound to the surface of the shell of the finally synthesized nanocrystals to protect the nanocrystals. and increases solubility in organic solvents. Therefore, by selecting appropriate metal compounds and precursors and controlling reaction conditions (concentration, temperature, time), nanocrystals with various elements and structures can be manufactured.

In the method of producing CdSe, a representative nanocrystal material, by high-temperature solution synthesis, the nanocrystal crystal growth process is shown in Figure 2. In a high-temperature solution, the metal compound and precursor decompose to create very small nanocrystal nuclei, and the small nuclei created at this time attach to the surface of a larger nanocrystal and grow into a large nanocrystal. When grown into a large crystal, the volume-to-surface area ratio of the crystal is lowered compared to a small nanocrystal, making it more energetically stable. On the other hand, because small crystals have a high surface area to volume ratio, they decompose into each element and reattach to the larger crystal, becoming more energetically stable. Therefore, the size of nanocrystals can be considered to be determined by the reaction conditions under which crystals are formed, in addition to the characteristics of the metal compounds and precursors participating in the reaction.

As an example, when InCl, ZnCl ₂ , and P4 (white phosphorus) compounds are reacted at a reaction temperature of 150°C and high-temperature solution processing conditions for 30 minutes, InP/ZnS nanocrystals that emit green light are produced. However, under the reaction temperature of 210°C and high-temperature solution processing conditions for 1 hour, InP/ZnS nanocrystals that emit red light are produced. The sizes of the green and red InP/ZnS nanocrystals produced at this time are 3.31 ± 0.22 nm and 3.83 ± 0.22 nm, respectively, with an average size difference of only 0.5 nm. Because the wavelength of light emitted varies greatly and sensitively depending on the size of the nanocrystals, reaction conditions must be accurately controlled during high-temperature solution synthesis of nanocrystals. In addition, in order to use nanocrystals as a display device material, the emission wavelength must be finely controlled from a few nanometers to tens of nanometers, which poses many difficulties using existing synthesis methods.

Korean Patent No. 10-1468985

The purpose of the present invention is to provide a method for manufacturing nanocrystals that can finely control the light emission wavelength.

Additionally, an object of the present invention is to provide a composition capable of producing nanocrystals capable of finely controlling the light emission wavelength.

Additionally, an object of the present invention is to provide nanocrystals prepared according to the above nanocrystal production method.

According to the first aspect of the present invention, it includes forming nanocrystals from a core precursor compound and a shell precursor compound and combining the nanocrystals with a crystal growth inhibitor, wherein the crystal growth inhibitor is a compound of formula 1 and formula A method for producing a nanocrystal, which is at least one compound among the compounds of 2, is provided.

[Formula 1]

[Formula 2]

(In Formulas 1 and 2, X ₁ and X ₂ are each independently one or more atoms selected from the group consisting of O, S, Se, and Te,

R _1, R ₂ , R ₃ and R ₄ are each independently hydrogen, a straight-chain or branched alkyl group having 1 to 10 carbon atoms, a straight-chain or branched alkenyl group having 2 to 12 carbon atoms, a straight-chain or branched group having 2 to 20 carbon atoms. It is a branched alkynyl group, or an aryl group having 6 to 15 carbon atoms, and R _1, R ₂ , R ₃ and R ₄ are each independently -NR ₅ R ₆ , -OR ₅ , -CF ₃ , -CCl ₃ , -CN , -NO ₂ , -COR ₅ or -CONH ₂ , where R ₅ and R ₆ are each independently hydrogen, an alkyl group with 1 to 10 carbon atoms, an alkenyl group with 2 to 12 carbon atoms, or a carbon number of 2 to 20. It is an alkynyl group or an aryl group having 6 to 15 carbon atoms, and R ₁ and R ₂ may not form a bond, or may form a bond and be connected in the form of a chain or ring,

n is an integer from 2 to 18.)

According to a second aspect of the present invention, a composition for producing nanocrystals comprising a core precursor compound, a shell precursor compound, and a crystal growth inhibitor, wherein the crystal growth inhibitor is at least one compound of the compound of Formula 1 and the compound of Formula 2. This is provided.

According to a third aspect of the present invention, nanocrystals prepared according to the above method are provided.

According to the present invention, the growth rate of nanocrystals can be controlled by adding a cyclic compound containing an electron donor atom in the solution process for producing nanocrystals. By controlling the growth rate of nanocrystals in this way, the light emission wavelength of nanocrystals can be finely controlled.

Figure 1 shows the nanocrystal structure, nanocrystal energy level, and energy band gap according to nanocrystal particle size.
Figure 2 schematically shows the crystal growth process of nanocrystals in a method of manufacturing CdSe, a nanocrystal material, by high-temperature solution synthesis.
Figure 3 shows exciton transition energy according to nanocrystal particle size.
Figure 4 is a schematic diagram showing that tetraethylene glycol dimethyl ether (tetraglyme) coordinates with the surface of a nanocrystal to form a coordination compound.
Figures 5 to 8 are graphs comparing the light emission wavelengths of nanocrystals prepared in Examples 1 to 4 and Comparative Examples.
Figure 9 shows the CIE color coordinate system.

Hereinafter, preferred embodiments of the present invention will be described. However, the embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention relates to a method for producing nanocrystals. Referring to Figure 1, a nanocrystal is a semiconductor crystal of several nanometers in size made of an inorganic semiconductor material, and is bonded to the core part, the shell part, and the surface of the shell part of the nanocrystal to increase solubility in organic solvents. It is made up of ligands, which are organic substances.

Unlike bulk materials, nanocrystals have a property in which the energy band gap changes depending on size and shape, showing unique electrical and optical properties. As shown in Figure 3, since the exciton transition energy changes depending on the size of the nanocrystal, the energy band gap can be broadly adjusted to the ultraviolet, infrared, and visible light regions only by controlling the nanocrystal size. In general, the visible light emission wavelength of a nanocrystal material is determined depending on the size of the core and shell. Therefore, in order to use nanocrystalline materials as display device materials that emit visible light spectrum with high quantum efficiency and excellent color purity, it is necessary to be able to finely control the size of the core and shell of the nanocrystalline material.

The present invention provides a new high-temperature solution synthesis system capable of controlling the size of nanocrystals. Hereinafter, the present invention will be described in detail.

The method for producing nanocrystals according to the present invention may include forming nanocrystals from a core precursor and a shell precursor and combining the nanocrystals with a crystal growth inhibitor. Crystal growth inhibitors contain electron donor atoms such as O, S, Se, and Te, which have relatively strong coordination abilities, and are bonded to the surface of the nanocrystal during the nanocrystal formation process to form a host guest compound with the nanocrystal metal ion or provide stable coordination. forms a compound.

The crystal growth inhibitor may be at least one of the compounds of Formula 1 and the compounds of Formula 2.

[Formula 1]

[Formula 2]

In Formulas 1 and 2, X ₁ and X ₂ may each independently be one or more atoms selected from the group consisting of O, S, Se, and Te.

In addition, R _{1 ,} R ₂ , R ₃ and R ₄ are each independently hydrogen, a straight-chain or branched alkyl group having 1 to 10 carbon atoms, a straight-chain or branched alkenyl group having 2 to 12 carbon atoms, or a straight-chain or branched alkenyl group having 2 to 20 carbon atoms. It is a straight-chain or branched alkynyl group, or an aryl group having 6 to 15 carbon atoms, and R _1, R ₂ , R ₃ and R ₄ are each independently -NR ₅ R ₆ , -OR ₅ , -CF ₃ , -CCl ₃ , -CN, -NO ₂ , -COR ₅ or -CONH ₂ , where R ₅ and R ₆ are each independently hydrogen, an alkyl group with 1 to 10 carbon atoms, an alkenyl group with 2 to 12 carbon atoms, and 2 carbon atoms. It is an alkynyl group of 20 to 20 carbon atoms, or an aryl group of 6 to 15 carbon atoms, R ₁ and R ₂ may not form a bond or may form a bond and be connected in the form of a chain or ring, and n may be an integer of 2 to 18. .

In the present invention, an alkyl group refers to a monovalent hydrocarbon, such as methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, t-butyl, n-pentyl, n-hexyl, n- Octyl, n-decyl, etc. may be mentioned, but are not limited thereto.

alkenyl group It refers to an unsaturated hydrocarbon having one or more carbon-carbon double bonds, and examples include, but are not limited to, ethylenyl, propenyl, butenyl, and pentenyl.

An alkynyl group refers to an unsaturated hydrocarbon having one or more carbon-carbon triple bonds, and examples include, but are not limited to, acetylenyl, propynyl, and butynyl.

Aryl groups include both aromatic groups, heteroaromatic groups, and partially reduced derivatives thereof. An aromatic group has a simple ring form or a fused ring form, and a heteroaromatic group refers to an aromatic group containing one or more oxygen, sulfur, or nitrogen. Aryl groups are, for example, phenyl, naphthyl, pyridinyl, furanyl, thiophenyl, indolyl, quinolinyl, imidazoly. Examples include, but are not limited to, imidazolinyl, oxazolyl, thiazolyl, and tetrahydronaphthyl.

During the growth process of nanocrystals, the crystal growth inhibitor represented by Formula 1 or Formula 2 forms a host-guest compound with the nanocrystals or forms a coordination compound to surround the surface of the nanocrystals. This can slow down the growth rate of nanocrystals.

In the present invention, the crystal growth inhibitor may be, for example, glycol ether (glyme). Glyme is a compound in which the oxyethylene group is in the form of -(OCH ₂ CH ₂ ) _n - and has a chain-like skeleton with alternating oxygen atoms and ethylene substituents. Figure 4 is a schematic diagram showing that tetraethylene glycol dimethyl ether (tetraglyme), an example of a glycol ether, combines with a metal ion to form a stable coordination compound. Referring to Figure 4, since there is an oxygen atom capable of coordination bonding and intermolecular dipole-dipole interaction inside the tetraethylene glycol dimethyl ether molecule, a stable coordination compound is formed by donating electrons to the metal ion, which increases the nanocrystal growth rate. It is delayed.

When a crystal growth inhibitor and a nanocrystal form a host-guest compound, the energy state of the host-guest compound is determined depending on the number of electron donor atoms such as O, S, Se, or Te present in the crystal growth inhibitor. If the chain length of the crystal growth inhibitor is too long or short compared to the nanocrystal size, the host-guest compound may not be properly formed, so it is desirable to select the crystal growth inhibitor considering the nanocrystal size.

In the present invention, the size of nanocrystals may vary depending on the amount of crystal growth inhibitor added compared to the core precursor compound and the shell precursor compound.

Specifically, the molar equivalent ratio of the core precursor compound and the crystal growth inhibitor added when manufacturing nanocrystals may be 1:0.1 to 1:4, preferably 1:1 to 1:4. If the molar equivalent ratio of the core precursor compound and the crystal growth inhibitor is less than 1:0.1, the amount of the crystal growth inhibitor compared to the core precursor compound may be too small, reducing the effect of delaying the growth of nanocrystals. On the other hand, if the molar equivalent ratio of the core precursor compound and the crystal growth inhibitor exceeds 1:4, there is a risk that the nanocrystals will not grow properly due to excessive addition of the crystal growth inhibitor.

Additionally, the molar equivalent ratio of the shell precursor compound and the crystal growth inhibitor added when producing nanocrystals may be 1:0.1 to 1:4, and preferably 1:0.1 to 1:1. If the molar equivalent ratio of the shell precursor compound and the crystal growth inhibitor is less than 1:0.1, the amount of the crystal growth inhibitor compared to the shell precursor compound may be too small, thereby reducing the effect of delaying the growth of nanocrystals. On the other hand, if the molar equivalent ratio of the shell precursor compound and the crystal growth inhibitor exceeds 1:4, there is a risk that the nanocrystals will not grow properly due to excessive addition of the crystal growth inhibitor.

According to the present invention, the core precursor and the shell precursor may be semiconductor compound precursors made of metal and/or non-metal, for example, InCl ₃ , InBr ₃ , InI ₃ , ZnCl ₂ , ZnBr ₂ , ZnI ₂ , etc. It is not limited.

In the present invention, the core portion and the shell portion of the nanocrystal may be one or more selected from the group consisting of group IB, group IIB, group IIIB, group IVB, group VB, and group VIB of the periodic table of elements, preferably group IVB, group IIB- It may be a compound of group VIB, group IVB-group VIB, group IIIB-VB, or group IB-IIIB-VIB.

Examples of group IVB precursors include Si, Ge, and SiC. Examples of group IIB-VIB precursors include CdS, CdSe, CdTe, ZnS, ZnSe, and ZnTe. Examples of group IVB-VIB precursors include PbS. , PbSe, PbTe, etc. Also examples of group IIIB-VB precursors are AlP, AlAs, AlSb, and InN. InP, InAs, GaN, GaP, GaAs, GaSb, InGaP, etc. are included, and examples of group IB-IIIB-VIB precursors 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 , etc.

On the other hand, pure nanocrystals without ligands in the shell exhibit strong polar characteristics due to dangling bond atoms present on the crystal surface, and intermolecular dipole-dipole interaction occurs between these nanocrystals and the ligands. and coordination bonding exists. Therefore, if an electron donor atom with high electronegativity (N-atom electronegativity = 3.0, O-atom electronegativity = 3.5), such as a nitrogen atom or oxygen atom, exists inside the ligand, the nanocrystal-ligand A strong intermolecular dipole-dipole interaction is formed between them. And if there is an atom inside the ligand with lone pair electrons of sp ³ hybrid orbital function with excellent coordination ability, the ligand forms a relatively strong coordination bond with the metal surface of the nanocrystal surface.

In the present invention, a capping ligand may be used as a reaction solvent. The capping ligand is bound to the surface of the shell of the final nanocrystal and serves to protect the nanocrystal and increase its solubility in organic solvents. Examples of such capping ligands include, but are not limited to, oleylamine, trioctylphosphine oxide, and oleic acid.

According to the present invention, the crystal growth inhibitor can be finally removed after nanocrystal growth is completed. The crystal growth inhibitor removal process may be performed by centrifuging the nanocrystals in a solution state and then vacuum drying them, but is not limited to this and may be removed by a known method.

The present invention provides a composition for producing nanocrystals that includes a core precursor compound, a shell precursor compound, and a crystal growth inhibitor, wherein the crystal growth inhibitor is at least one compound of the compound of Formula 1 and the compound of Formula 2. The composition may further include a capping ligand, and the metal compound, semiconductor compound precursor, crystal growth inhibitor, and capping ligand have the technical characteristics described above.

Example

Hereinafter, embodiments of the present invention will be described in detail. The following examples are only for understanding of the present invention and do not limit the present invention.

1. Preparation of InP/ZnS nanocrystals

(1) Example 1

In a 50 mL Schrank flask, 100 mg (0.45 mmol) of tetraglyme (tetraethylene glycol dimethyl ether) as a crystal growth inhibitor, 160 mg (0.45 mmol) of indium (III) bromide (InBr ₃ ) as a metal compound, and shell. As a secondary metal precursor, 300 mg (2.2 mmol) of zinc chloride (ZnCl ₂ ) and 5 mL of oleylamine were added, and then the reaction mixture was stirred at 120°C for 1 hour under an argon gas atmosphere and degassed. After heating the reaction mixture to 180°C, 0.45 mL (1.6 mmol) of tris(diethylamine)phosphine was quickly added. The obtained solution was further stirred for 30 minutes, heated to 210°C, and 2.282 g (11.27 mmol) of 1-dodecanethiol was slowly injected into the solution. The reaction solution was maintained at 210°C for 90 minutes and then naturally cooled to room temperature to obtain a light green-orange solid. Chloroform solvent was slowly added to the reaction flask until the light green-orange solid was completely dissolved. Ethanol was added to this solution to precipitate the nanocrystals, and the solid was separated using a centrifuge. The obtained InP/ZnS nanocrystals were purified several times using a solvent combination of chloroform/ethanol and dried under vacuum.

(2) Example 2

InP/ZnS nanocrystals were prepared in the same manner as in Example 1, except that 400 mg (1.80 mmol) of tetraglyme was used as a crystal growth inhibitor.

(3) Example 3

InP/ZnS nanocrystals were prepared in the same manner as in Example 1, except that 80 mg (0.45 mmol) of triglyme (triethylene glycol dimethyl ether) was used as a crystal growth inhibitor.

(4) Example 4

InP/ZnS nanocrystals were prepared in the same manner as in Example 1, except that 320 mg (1.80 mmol) of triglyme was used as a crystal growth inhibitor.

(5) Comparative example

InP/ZnS nanocrystals were prepared in the same manner as Example 1, except that a crystal growth inhibitor was not used.

2. Measurement of photoluminescence wavelength of InP/ZnS nanocrystals

A solution was prepared by dissolving the InP/ZnS nanocrystals prepared in Examples 1 to 4 and Comparative Examples in a small amount of chloroform. The solution was placed in a quartz cell for measurement, and the photoluminescence spectrum was measured using a spectrophotometer (JASCO, FP-6500).

Table 1 below and Figures 5 to 8 show the results of comparing the photoluminescence spectra of InP/ZnS nanocrystals obtained when a crystal growth inhibitor was not used (Comparative Example) and when a crystal growth inhibitor was used (Examples 1 to 4).

compound InBr ₃ with
crystal growth
inhibitor's
molar equivalence ratio ZnCl ₂ and
crystal growth
inhibitor's
molar equivalence ratio photoluminescence
peak
wavelength
(nm) wavelength
change ^*
(nm) InBr ₃
input
(mmol) ZnCl ₂
input
(mmol) crystal growth
inhibitor type input
(mmol) Example 1 0.45 2.2 tetra
Glim 0.45 1:1 1:0.20 548 20 Example 2 0.45 2.2 1.8 1:4 1:0.82 550 18 Example 3 0.45 2.2 triglim 0.45 1:1 1:0.20 537 31 Example 4 0.45 2.2 1.8 1:4 1:0.82 543 25 Comparative example 0.45 2.2 - - - - 568 -

* The wavelength change indicates the degree to which the photoluminescence peak wavelength of the nanocrystals prepared in Examples 1 to 5 is reduced compared to the photoluminescence peak wavelength of the nanocrystals prepared in Comparative Examples.

Referring to Table 1, it can be seen that when a crystal growth inhibitor was added during the production of nanocrystals as in Examples 1 to 4, the photoluminescence peak wavelength was decreased compared to the comparative example in which the crystal growth inhibitor was not added. This is the result of the crystal growth inhibitor suppressing nanocrystal growth by covering the surface of the nanocrystal.

Comparing Examples 1 and 2 and Examples 3 and 4, respectively, under the same conditions, as the amount of crystal growth inhibitor added, the growth of nanocrystals was relatively more inhibited, resulting in a low photoluminescence peak wavelength and a large wavelength change.

The potential application of nanocrystalline materials that can finely control wavelength can be found in the electronics field, and in particular, they can be actively applied to the display industry in the future as display device materials. As can be seen in the CIE color coordinate system of FIG. 8, it is essential for display devices to adjust red, green, and blue color coordinates (green coordinate change A→B in FIG. 8) and fine control of white balance depending on the product. In other words, display element materials used in displays must basically have color control functions, so nanocrystalline materials that facilitate fine color control can show excellent competitiveness as display element materials in the future.

Claims (8)

forming nanocrystals from the core precursor compound and the shell precursor compound, and
Comprising a step of combining nanocrystals and a crystal growth inhibitor,
The crystal growth inhibitor is at least one compound of Formula 1 and Formula 2,
The molar equivalent ratio of the core precursor compound and the crystal growth inhibitor is 1:1 to 1:4,
The molar equivalent ratio of the shell precursor compound and the crystal growth inhibitor is 1:0.1 to 1:1.
[Formula 1]

[Formula 2]

(In Formulas 1 and 2, X ₁ and X ₂ are each independently one or more atoms selected from the group consisting of O, S, Se, and Te,
R _1, R ₂ , R ₃ and R ₄ are each independently hydrogen, a straight-chain or branched alkyl group having 1 to 10 carbon atoms, a straight-chain or branched alkenyl group having 2 to 12 carbon atoms, a straight-chain or branched group having 2 to 20 carbon atoms. It is a branched alkynyl group, or an aryl group having 6 to 15 carbon atoms, and R _1, R ₂ , R ₃ and R ₄ are each independently -NR ₅ R ₆ , -OR ₅ , -CF ₃ , -CCl ₃ , -CN , -NO ₂ , -COR ₅ or -CONH ₂ , where R ₅ and R ₆ are each independently hydrogen, an alkyl group with 1 to 10 carbon atoms, an alkenyl group with 2 to 12 carbon atoms, or a carbon number of 2 to 20. It is an alkynyl group or an aryl group having 6 to 15 carbon atoms, and R ₁ and R ₂ may not form a bond, or may form a bond and be connected in the form of a chain or ring,
n is an integer from 2 to 18.)
According to paragraph 1,
A method of producing nanocrystals, wherein the nanocrystals form a host-guest compound or a coordination compound with a crystal growth inhibitor.
According to paragraph 1,
Method for producing nanocrystals where the crystal growth inhibitor is glycol ether.
Contains a core precursor compound, a shell precursor compound and a crystal growth inhibitor,
The crystal growth inhibitor is at least one compound of Formula 1 and Formula 2,
The molar equivalent ratio of the core precursor compound and the crystal growth inhibitor is 1:1 to 1:4,
A composition for producing nanocrystals, wherein the molar equivalent ratio of the shell precursor compound and the crystal growth inhibitor is 1:0.1 to 1:1.
[Formula 1]

[Formula 2]

(In Formulas 1 and 2, X ₁ and X ₂ are each independently one or more atoms selected from the group consisting of O, S, Se, and Te,
R _1, R ₂ , R ₃ and R ₄ are each independently hydrogen, a straight-chain or branched alkyl group having 1 to 10 carbon atoms, a straight-chain or branched alkenyl group having 2 to 12 carbon atoms, a straight-chain or branched group having 2 to 20 carbon atoms. It is a branched alkynyl group, or an aryl group having 6 to 15 carbon atoms, and R _1, R ₂ , R ₃ and R ₄ are each independently -NR ₅ R ₆ , -OR ₅ , -CF ₃ , -CCl ₃ , -CN , -NO ₂ , -COR ₅ or -CONH ₂ , where R ₅ and R ₆ are each independently hydrogen, an alkyl group with 1 to 10 carbon atoms, an alkenyl group with 2 to 12 carbon atoms, or a carbon number of 2 to 20. It is an alkynyl group or an aryl group having 6 to 15 carbon atoms, and R ₁ and R ₂ may not form a bond, or may form a bond and be connected in the form of a chain or ring,
n is an integer from 2 to 18.)
delete delete According to paragraph 4,
A composition for producing nanocrystals, wherein the composition for producing nanocrystals further includes a capping ligand.
Nanocrystals prepared according to the method of any one of claims 1 to 3.