WO2018056114A1

WO2018056114A1 - Method for producing semiconductor quantum dots

Info

Publication number: WO2018056114A1
Application number: PCT/JP2017/032833
Authority: WO
Inventors: 有次吉田; 和田　健二
Original assignee: 富士フイルム株式会社
Priority date: 2016-09-23
Filing date: 2017-09-12
Publication date: 2018-03-29
Also published as: JP6651024B2; JPWO2018056114A1

Abstract

[Problem] To provide a method for producing group III-V semiconductor quantum dots, said method making it possible to obtain group III-V semiconductor quantum dots exhibiting sharp light emitting properties and a narrow emission peak half width, and achieving high luminance as a result of excellent quantum yield. [Solution] This method for producing group III-V semiconductor quantum dots includes the following steps (a) and (b): (a) a step wherein a solution, which contains a solvent, a compound a1 including a group III element, and a compound a2 including a group V element, is maintained between 270 to 400°C, and the compound a1 and the compound a2 are reacted to form group III-V semiconductor nanoparticles in said solution; and (b) a step wherein the solution having said nanoparticles formed therein is cooled to 250°C at a cooling speed of 0.3 to 3°C/min.

Description

Manufacturing method of semiconductor quantum dots

The present invention relates to a method for producing semiconductor quantum dots.

Semiconductor quantum dots are nanoscale (several nanometers to several tens of nanometers) semiconductor crystals that exhibit characteristic light absorption and emission characteristics based on the quantum size effect. The application range expected for semiconductor quantum dots is wide. For example, application research to displays, illumination, biological imaging, solar cells, and the like is underway based on strong light emission characteristics corresponding to the particle size. In addition, applied research as a quantum dot laser, a single electron transistor, and the like that realize high brightness and low power consumption by utilizing the unique electronic characteristics of semiconductor quantum dots is also underway.

Currently, the mainstream of semiconductor quantum dots is cadmium-based quantum dots using nanocrystals (nanocrystals such as CdSe and CdS) having cadmium as a cation. However, cadmium is concerned about its toxicity, and the need for non-cadmium quantum dots is increasing. As such non-cadmium quantum dots, quantum dots using III-V semiconductor nanocrystals having indium or the like as a cation (hereinafter referred to as “III-V semiconductor quantum dots”) are known. However, III-V semiconductor quantum dots still have many problems in terms of performance.

Under such circumstances, technological development is underway to improve the performance of III-V semiconductor quantum dots. For example, Patent Document 1 prepares an InP core as a nanostructure, and then reacts with indium laurate in the presence of a C5-C8 carboxylic acid ligand to reinforce the InP core, and then ZnSeS shell and ZnS shell Are sequentially formed to obtain InP / ZnSeS / ZnS dots, and that this InP / ZnSeS / ZnS dot exhibits a high quantum yield (high luminance). Patent Document 2 discloses that an in-ligand complex is formed by reacting indium acetate with a ligand such as a fatty acid and octadecene, which is a non-coordinating solvent, and then reacting with tris (trimethylsilyl) phosphine. To obtain InP nanocrystals.

JP2015-529698A Japanese Patent No. 4344613

However, the conventional III-V group semiconductor quantum dots including the techniques described in Patent Documents 1 and 2 have improved the light emission characteristics (quantum yield and half-value width of the light emission peak) to some extent. It has not yet achieved sufficient characteristics.
The present invention realizes a high luminance due to an excellent quantum yield and also provides a group III-V semiconductor quantum dot capable of obtaining a group III-V semiconductor quantum dot having a narrow half-value width of the emission peak and exhibiting sharp emission characteristics. It is an object to provide a method for manufacturing dots.

As a result of intensive studies in view of the above problems, the present inventors have made a reaction between a compound containing a Group III element and a compound containing a Group V element at a high temperature in the production of III-V semiconductor quantum dots. When the III-V semiconductor nanoparticles are formed and then the high temperature reaction liquid is cooled to stop the growth of the nanoparticles, rapid cooling (cooling) is performed until the high temperature reaction liquid is cooled to a specific temperature. ) Without controlling the cooling rate, the quantum yield of the obtained group III-V semiconductor quantum dots can be effectively increased, and higher brightness can be realized. It was found that quantum dots have a narrow emission peak half-value width and show sharp emission characteristics.
The present invention has been completed through further studies based on these findings.

That is, the subject of this invention was solved by the following means.
[1]
A method for producing a group III-V semiconductor quantum dot, comprising the following steps (a) and (b):
(A) A liquid containing a compound a1 containing a Group III element, a compound a2 containing a Group V element, and a solvent is maintained at 270 to 400 ° C. to react the compound a1 with the compound a2, and react Forming III-V semiconductor nanoparticles in the liquid;
(B) A step of cooling the reaction liquid in which the nanoparticles are formed to 250 ° C. at a cooling rate of 0.3 to 3 ° C./min.
[2]
The method for producing a group III-V semiconductor quantum dot according to [1], wherein the reaction time at 270 to 400 ° C. in the step (a) is 10 seconds to 120 minutes.
[3]
The method for producing a group III-V semiconductor quantum dot according to [1] or [2], wherein the group III element contained in the compound a1 is In.
[4]
The method for producing a III-V semiconductor quantum dot according to any one of [1] to [3], wherein the group V element contained in the compound a2 is P or As.
[5]
The method for producing a group III-V semiconductor quantum dot according to any one of [1] to [4], wherein the group III-V semiconductor quantum dot is an InP quantum dot.
[6]
The method for producing a group III-V semiconductor quantum dot according to any one of [1] to [5], wherein the solvent is a non-coordinating solvent.
[7]
The method for producing a group III-V semiconductor quantum dot according to any one of [1] to [6], wherein the water content of the solvent is 10 ppm or less.
[8]
The method for producing a group III-V semiconductor quantum dot according to any one of [1] to [7], wherein the reaction temperature in the step (a) is 280 to 350 ° C.
[9]
The step (b) includes holding the reaction liquid cooled to 250 ° C. at a temperature of 150 to 250 ° C. for 0.5 to 4 hours, III according to any one of [1] to [8] A method for producing a group V semiconductor quantum dot.
[10]
The method for producing a group III-V semiconductor quantum dot according to any one of [1] to [9], further comprising a step (c) of introducing Ga into the surface layer of the nanoparticles after the step (b).
[11]
[10] The method for producing a group III-V semiconductor quantum dot according to [10], comprising a step (d) of forming a shell layer on the surface of the nanoparticles having Ga introduced into the surface layer obtained in the step (c).
[12]
The method for producing a group III-V semiconductor quantum dot according to [11], wherein the shell layer is ZnS, ZnO, ZnSe, ZnSe _X S _1-X , ZnTe, or CuO. However, 0 <X <1.

In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
In the present invention, the “III-V semiconductor quantum dot” means a nanoparticle (nanocrystal) composed of a compound semiconductor composed of a group III element and a group V element, and in the crystal structure of the nanoparticle. It is also used to mean that the surface layer is doped or introduced with an element other than a crystal component (for example, Zn, Ga, etc.), and that a shell layer (for example, ZnS shell layer) is formed on the surface of these nanoparticles. . In other words, in the present invention, the “III-V group semiconductor quantum dot” has a III-V group semiconductor nanoparticle in its structure, and can exhibit the functions or characteristics of the group III-V semiconductor nanoparticle. It is used to include all nanoparticles in the state. For example, in the case of “InP quantum dots”, in addition to nanoparticles of InP, for example, nanoparticles of In (Zn) P alloy doped with Zn, atoms other than In on the surface of these nanoparticles It is meant to include all of the forms in which (Zn, Ga, etc.) are introduced and the shell layer (ZnS, etc.) formed on the surface of these nanoparticles.
In the present specification, the “nanoparticle” means a particle having an average particle diameter of less than 20 nm, preferably 15 nm or less, more preferably 10 nm or less. The average particle size of the “nanoparticles” is usually 1 nm or more, preferably 2 nm or more.

According to the method for producing a group III-V semiconductor quantum dot of the present invention, a group III-V semiconductor quantum dot that achieves high luminance with an excellent quantum yield and has a narrow emission peak half-value width and sharp emission characteristics. Dots can be obtained.
The above and other features and advantages of the present invention will become more apparent from the following description.

Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

[Method for Producing III-V Semiconductor Quantum Dots]
The method for producing a group III-V semiconductor quantum dot of the present invention (hereinafter simply referred to as “the production method of the present invention”) includes the following steps (a) and (b).
(A) A liquid containing a compound a1 containing a Group III element, a compound a2 containing a Group V element, and a solvent is maintained at 270 to 400 ° C. to react the compound a1 with the compound a2, A step of forming III-V group semiconductor nanoparticles in the reaction solution (hereinafter, the reaction between compound a1 and compound a2 at 270 to 400 ° C. is also referred to as “nanoparticle formation reaction”);
(B) A step of cooling the reaction liquid in which the nanoparticles are formed to 250 ° C. at a cooling rate of 0.3 to 3 ° C./min.
Each step in the production method of the present invention will be described in order.

<Process (a)>
In the step (a), a liquid containing a compound a1 containing a Group III element, a compound a2 containing a Group V element, and a solvent is subjected to a high temperature reaction at 270 to 400 ° C. This is a step of forming III-V semiconductor nanoparticles. The formed nanoparticles are usually in a state of being dispersed in the liquid by the selection of the solvent species and the action of a dispersant or the like.
As the compound a1, one type of compound is usually used, but two or more types of compounds may be used. When using 2 or more types of compounds as compound a1, it is preferable that the group III element which each of these 2 or more types compound has is the same. Similarly, one compound is usually used as the compound a2, but two or more compounds may be used. When using 2 or more types of compounds as compound a2, it is preferable that the group V element which each of these 2 or more types compound has is the same. That is, in the production method of the present invention, it is preferable that all the III-V group semiconductor quantum dots obtained have the same chemical structure.
The compound a1 serves as a supply source of the cation component constituting the nanocrystal of the III-V semiconductor quantum dot. The group III element contained in the compound a1 is preferably aluminum (Al), gallium (Ga) or indium (In), more preferably In. The compound a1 is usually a metal salt containing Al, Ga or In.
As a form of the metal salt containing Al, Ga or In, an organic acid salt of Al, Ga or In (for example, a monocarboxylate such as acetate or propionic acid, a hydroxycarboxylate such as glycolate or lactate, etc. , Dicarboxylates such as succinate and oxalate, polycarboxylates such as citric acid, aliphatic or aromatic sulfonates such as methanesulfonate and toluenesulfonate, carbonates, bicarbonates, Sulfamate, metal alkoxide, metal acetylacetonate, etc.) and inorganic acid salts of Al, Ga or In (eg nitrate, sulfate, hydroiodide, hydrochloride, hydrobromide, fluoride) Hydrogenates, perchlorates, phosphates, hydrocyanates, etc.). In consideration of solubility in an organic solvent, the metal salt containing Al, Ga or In is preferably an organic acid salt.

Among the above metal salts, preferred specific examples of the Al salt include aluminum nitrate, aluminum sulfate, aluminum carbonate, aluminum phosphate, aluminum perchlorate, aluminum cyanide, aluminum fluoride, aluminum chloride, aluminum bromide, and iodide. Inorganic acid salts of Al such as aluminum; and aluminum acetate, aluminum oxalate, aluminum tartrate, aluminum alkoxide (eg, aluminum isopropoxide, aluminum butoxide, aluminum ethoxide, aluminum methoxyethoxide), aluminum sulfamate, acetylacetone aluminum, etc. The organic acid salt of Al can be mentioned. These Al salts may be used alone or in combination.

Among the above metal salts, preferable specific examples of the Ga salt include gallium nitrate, gallium sulfate, gallium carbonate, gallium phosphate, gallium perchlorate, gallium cyanide, gallium fluoride, gallium chloride, gallium bromide, and iodide. Inorganic acid salts of Ga such as gallium; and gallium acetate, gallium oxalate, gallium tartrate, gallium alkoxide (eg, gallium isopropoxide, gallium butoxide, gallium ethoxide, gallium methoxyethoxide), gallium sulfamate, acetylacetone gallium, etc. An organic acid salt of Ga. These Ga salts may be used alone or in combination.

Among the above metal salts, preferred specific examples of the In salt include indium nitrate, indium sulfate, indium carbonate, indium phosphate, indium perchlorate, indium cyanide, indium fluoride, indium chloride, indium bromide, and iodide. Inorganic acid salts of In such as indium; and indium acetate, indium oxalate, indium tartrate, indium alkoxide (for example, indium isopropoxide, indium butoxide, indium ethoxide, indium methoxyethoxide), indium sulfamate, indium acetylacetone, etc. In organic acid salts of In. These metal salts may be used alone or in combination.

The compound a2 serves as a supply source of the anion component constituting the nanocrystal of the III-V semiconductor quantum dot. The group V element contained in the compound a2 is preferably nitrogen (N), phosphorus (P), arsenic (As) or antimony (Sb), more preferably P or As, and still more preferably P.
When the compound a2 is a nitrogen-containing compound containing N, examples of the nitrogen-containing compound include ammonia, ammonium nitrosophenylhydroxylamine, ammonium fluoride, ammonium chloride, ammonium bromide, ammonium iodide, and the like.
When the compound a2 is a phosphorus-containing compound containing P, examples of the phosphorus-containing compound include tris (trimethylsilyl) phosphine, tris (triethylsilyl) phosphine, tris (tri-n-propylsilyl) phosphine, and tris (triisopropylsilyl). ) Phosphine, tris (dimethylphenylsilyl) phosphine, tris (dimethylbenzylsilyl) phosphine, bis (trimethylsilyl) phosphine, tris (diethylamino) phosphine and tris (dimethylamino) phosphine.
When the compound a2 is an arsenic compound containing As, examples of the arsenic compound include trimethylarsine, triphenylarsine, triphenoxyarsine, tris (trimethylsilyl) arsine, dimethylarsine chloride, dimethylarsine and the like.
When the compound a2 is an antimony-containing compound containing Sb, examples of the antimony-containing compound include tris (trimethylsilyl) antimony and triphenylantimony.

There is no restriction | limiting in particular in the said solvent used for nanoparticle formation reaction, Usually, it is an organic solvent. From the viewpoint of the dispersibility of the formed particles, it is preferable to contain a nonpolar solvent. The nonpolar solvent that may be contained in the dispersion may be only one type or two or more types. It is preferable to use a solvent selected from alkane, alkene, benzene and toluene as the nonpolar solvent.
The nonpolar solvent preferably has a boiling point of 170 ° C. or higher. Preferred specific examples of such nonpolar solvents include aliphatic saturated hydrocarbons such as n-decane, n-dodecane, n-hexadecane, and n-octadecane, 1-undecene, 1-dodecene, 1-hexadecene, and 1-octadecene. Aliphatic unsaturated hydrocarbons and trioctylphosphine are exemplified. Among these, the nonpolar solvent is preferably an aliphatic unsaturated hydrocarbon having 12 or more carbon atoms, and more preferably 1-octadecene. By using an organic solvent having a boiling point of 170 ° C. or higher, the particles are less likely to aggregate during particle formation, and the solution dispersibility of the nanoparticles becomes better.
The proportion of the nonpolar solvent in the solvent is preferably 80% by volume or more, more preferably 90% by volume or more, more preferably 95% by volume or more, further preferably 99% by volume or more, and all of the solvents are nonpolar solvents. It is particularly preferred.

In the nanoparticle formation reaction, one or more of the following solvents may be used in addition to or in place of the above solvent.
Amide compounds such as N-methyl-2-pyrrolidone (NMP), N, N-dimethylacetamide (DMAC), N, N-dimethylformamide, N, N-dimethylethyleneurea, N, N-dimethylpropyleneurea, tetramethyl Urea compounds such as urea, lactone compounds such as γ-butyrolactone and γ-caprolactone, carbonate compounds such as propylene carbonate, ketone compounds such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ethyl acetate, n-butyl acetate, butyl cellosolve acetate, butyl carb Ester compounds such as tall acetate, ethyl cellosolve acetate, ethyl carbitol acetate, diglyme, triglyme, tetraglyme, diethylene glycol, diethylene glycol ethyl methyl acetate And ether compounds such as tellurium, diethylene glycol diethyl ether, diethylene glycol monomethyl ether, triethylene glycol butyl methyl ether, triethylene glycol monoethyl ether, triethylene glycol monomethyl ether and diphenyl ether, and sulfone compounds such as sulfolane.
The solvent used for the nanoparticle formation reaction is preferably a non-coordinating solvent. In this specification, the “non-coordinating solvent” is a solvent that does not have a structure capable of coordinating to a metal atom. More specifically, it means a solvent that does not have a hetero atom selected from an oxygen atom, a sulfur atom, a nitrogen atom, and a phosphorus atom in the molecule. By using a non-coordinating solvent, the particle formation reaction can be further accelerated, and nanoparticles having a more uniform composition and size distribution can be synthesized.
In addition, the water content of the solvent used for the nanoparticle formation reaction is preferably 10 ppm or less on a mass basis from the viewpoint of preventing hydrolysis of the compound a2, and is usually 0 to 8 ppm. In particular, when a compound having an alkylsilyl group is used as the compound a2, the water content is preferably as low as possible.

In the nanoparticle formation reaction, the content of the solvent in the reaction solution is preferably 90 to 99.8% by mass, and more preferably 95 to 99.5% by mass.

In the nanoparticle formation reaction, it is also preferable to add a compound capable of coordinating to the nanoparticles (hereinafter referred to as “coordinating compound”) in the reaction solution. By carrying out the particle formation reaction in the presence of the coordinating compound, the coordinating compound coordinates to the formed particle surface layer, effectively suppressing particle aggregation and stabilizing the dispersion state of the nanoparticles. Can be produced.
The coordination compound preferably has a hydrocarbon chain having 6 or more carbon atoms and more preferably has a hydrocarbon chain having 10 or more carbon atoms from the viewpoint of improving the dispersibility of the particles. Specific examples of such coordination compounds include, for example, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, oleic acid, erucic acid, oleylamine, dodecylamine, dodecanethiol, 1,2-hexadecanethiol. , Trioctylphosphine oxide, and cetrimonium bromide.
When the nanoparticle forming reaction is performed in the presence of the coordinating compound, the content of the coordinating compound in the reaction solution is preferably 0.1 to 5% by mass at the start of the reaction. It is more preferably 3 to 5% by mass, further preferably 0.5 to 5% by mass, and particularly preferably 1 to 3% by mass.

In the above nanoparticle formation reaction, a liquid containing a reaction component may contain a compound containing a metal atom other than the Group III element. For example, in the synthesis of InP nanoparticles, it is known that optical properties are improved by doping In into an InP crystal lattice to form an In (Zn) P alloy. The group III-V semiconductor quantum dots in the present invention also include an alloy form doped with metal atoms other than group III elements.

In the above nanoparticle formation reaction, the reaction temperature is 270 to 400 ° C. When compound a1 and compound a2 are mixed, a reaction occurs instantaneously and a III-V semiconductor cluster nucleus is generated. In order to grow the cluster nuclei into III-V semiconductor nanoparticles having a desired particle size, a high temperature reaction at 270 to 400 ° C. is required. The reason why such a high temperature reaction is required is not clear, but it is presumed that there is a thermal equilibrium accompanied by size convergence between the cluster nucleus and the nanoparticle. The reaction temperature of this nanoparticle formation reaction is preferably 280 to 350 ° C., more preferably 290 to 320 ° C., from the viewpoint of particle size uniformity.

In the above nanoparticle formation reaction, known reaction conditions can be modified as needed according to the purpose, except that the reaction temperature is 270 to 400 ° C. For example, in an inert atmosphere, raw materials, a solvent, and if necessary, a coordinating compound (dispersing agent) are placed in a reaction vessel, sealed, heated using a heater or the like, and reacted at high temperature and high pressure. A method (solvothermal method) can be employed. In addition, a method of heating a reaction vessel containing a solvent and a coordinating compound as necessary using an oil bath or the like while passing an inert gas, and injecting a raw material using a syringe to cause a reaction ( Hot soap method) is known. These methods are disclosed in, for example, JP-A-2006-265022, JP-A-2008-44827, WO2007 / 138851, JP-A-2009-19067, JP-A-2009-40633, JP-A-2008. -2799591, JP-A 2010-106119, and JP-A 2010-138367, which can be referred to in the nanoparticle formation reaction in the present invention.
In the nanoparticle formation reaction, the content of the compound a1 in the reaction solution is preferably 0.05 to 5% by mass, more preferably 0.1 to 2% by mass at the start of the reaction. Further, at the start of the reaction of the nanoparticle formation reaction, the content of the compound a2 in the reaction solution is preferably 0.05 to 5% by mass, and more preferably 0.1 to 2% by mass. .

The reaction time of the above nanoparticle formation reaction is not particularly limited as long as desired nanoparticles can be formed. From the viewpoint of making the size of the obtained nanoparticles more uniform, the reaction time of the nanoparticle formation reaction is preferably 10 seconds or more, more preferably 5 minutes or more, and more preferably 10 minutes or more. Is more preferable, and it is particularly preferable that the time be 20 minutes or longer. Further, from the viewpoint of preventing aggregation of the formed nanoparticles and increasing the uniformity of the nanoparticle size, the reaction time of the nanoparticle formation reaction is preferably 120 minutes or less, more preferably 90 minutes or less. 60 minutes or less is more preferable, 50 minutes or less is further preferable, and 40 minutes or less is particularly preferable. By making the nanoparticle size uniform, the half-value width of the emission peak can be further narrowed, and a semiconductor quantum dot exhibiting sharper emission characteristics can be obtained.

Examples of the III-V group semiconductor nanoparticles formed in the nanoparticle formation reaction include AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaN, GaP, GaAs, and GaSb. Among them, a group III-V semiconductor selected from InN, InP, InAs, InSb, GaN, GaP, GaAs and GaSb is preferable, a group III-V semiconductor selected from InN, InP, InAs and InSb is more preferable, and InP or InAs is used. Further, InP is particularly preferable. Each of the nanoparticles mentioned here is meant to include the above-described alloy form (a form having doped atoms).

<Step (b)>
In step (b), the liquid (reaction solution) subjected to the nanoparticle formation reaction in step (a) at a temperature state of 270 to 400 ° C. is reduced to 250 ° C. at a cooling rate of 0.3 to 3 ° C./min. This is a cooling step (hereinafter also referred to as “slow cooling step”). “Cooling to 250 ° C.” means cooling a high temperature reaction solution of 270 to 400 ° C. to a temperature of 250 ° C.
In the formation of group III-V semiconductor nanoparticles, the reaction solution subjected to a high temperature reaction for particle growth is subsequently cooled to stop the particle growth. In the prior art, the reaction solution is usually cooled by simply releasing the reaction solution from the heat source and allowing it to cool, so that the reaction solution is in a virtually quenched state. In contrast, in the present invention, the reaction liquid in which nanoparticles are formed by the reaction at 270 to 400 ° C. is gradually cooled from this reaction temperature to 250 ° C. at a slow rate of 0.3 to 3 ° C./min. It is characterized by. This slow cooling can effectively increase the quantum yield of the obtained group III-V semiconductor quantum dots. The reason for this is not clear yet, but is estimated as follows.
Nanoparticles formed by a high temperature reaction at 270 to 400 ° C. are considered to be in an amorphous state having structural defects inside the particles, and when the amorphous nanoparticles are rapidly cooled, the internal defects remain as they are. It is thought that it remains. On the other hand, when the nanoparticles formed by the high temperature reaction are cooled to 250 ° C. over time at a predetermined cooling rate, the amorphous state inside the particles is changed during the slow cooling process at a slightly high temperature. A certain structure can be changed into a crystalline state. As a result, the obtained group III-V semiconductor quantum dots can be in a state where the crystal structure is formed in a wider range, and the quantum yield is increased. Conceivable.

There is no restriction | limiting in particular in the slow cooling means in a process (b). For example, it can be gradually cooled at a desired cooling rate by manually operating the external temperature of the oil bath or appropriately setting the temperature program of the heating device. There are no particular restrictions on the oil bath and heating device. For example, a thermostatic oil tank T-300 (manufactured by Thomas Scientific Instruments) or the like is used as the “oil bath”, and a synthesis / reaction apparatus Chemist Plaza CP-300 (manufactured by Shibata Kagaku) or the like is used as the “heating device”. be able to.
In the step (b), the cooling rate of the reaction solution is preferably 0.5 to 2 ° C./min, more preferably 1 to 1.5 ° C./min. If the cooling rate is too slow, the time until the temperature reaches 250 ° C. is too long, and the nanoparticles tend to aggregate. On the other hand, if the cooling rate is too high, it becomes difficult to sufficiently change the amorphous phase to the crystalline phase. The cooling rate does not have to be constant as long as it is within the range defined by the present invention.
The length of the slow cooling step in step (b) (the time required for slow cooling the reaction solution to 250 ° C. in step (b)) is preferably 10 to 180 minutes, and preferably 20 to 120 minutes. More preferably, it is more preferably 20 to 90 minutes, and particularly preferably 30 to 60 minutes.

The step (b) preferably includes a step of holding the reaction liquid cooled to 250 ° C. at a temperature of 150 to 250 ° C. for 0.5 to 4 hours (hereinafter also referred to as “ripening step”). By this step, the amorphous structure present in the nanoparticles can be changed more reliably into a crystalline state, and the quantum yield of the resulting III-V semiconductor quantum dots can be increased more effectively. it can.
In addition, it is preferable that there is no process which raises the temperature of a reaction liquid between this aging process. That is, it is preferable that the temperature in the aging step is constant or lowered to 150 ° C. (That is, it is preferable not to raise the temperature of the reaction solution in the whole process of step (b).) More preferably, the aging step is set to a constant temperature. The temperature of the aging step is preferably 200 to 250 ° C, more preferably 220 to 240 ° C. The length of the ripening step is preferably 1 to 3 hours, more preferably 1.5 to 2.5 hours.

At the end of the step (b), the group III-V semiconductor nanoparticles have an average particle size of preferably 1 to 10 nm, and more preferably 2 to 10 nm. The group III-V semiconductor nanoparticles obtained through the step (b) are usually obtained in the form of a dispersion, and the content of group III-V semiconductor nanoparticles in the dispersion is 0.05 to 3 mass. % Is preferred. The nanoparticles in the dispersion are usually used for the intended reaction or application in the state of the dispersion without being separated and recovered.
In the present invention, the average particle diameter of the nanoparticles is a value measured by a transmission electron microscope. More specifically, for 100 particles randomly selected with a transmission electron microscope, the occupied area of the particles is obtained from the projected area by an image processing apparatus, and the total occupied area of 100 particles is determined by the number of selected particles. Dividing by (100), it can be calculated as the average value of the diameter of the circle corresponding to the obtained value (average circle equivalent diameter). The average particle size does not include the particle size of secondary particles formed by aggregation of primary particles.

The production method of the present invention may include a step of introducing gallium (Ga) into the surface of the III-V semiconductor nanoparticles obtained in the above step (b) (hereinafter referred to as “step (c)”). preferable.
In the step (c), first, the group III-V semiconductor nanoparticles obtained in the step (b) are reacted with at least one metal c1 salt selected from the following metal group [c] (this reaction is performed). Then, the obtained particles are reacted with a Ga salt (this reaction is also referred to as “Ga introduction reaction”). Note that the step (c) can also be performed when the group III-V semiconductor nanoparticles obtained in the step (b) are in a form containing Ga as a group III element.

Metal group [c]:
Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn

The metal c1 is one or more metals selected from the above metal group [c], and is preferably one metal. Metal c1 can be introduced into the nanoparticle surface layer by a metal c1 introduction reaction. The metal c1 introduction reaction may be performed in the presence of the compound a2 described above as an anion supply source, or may be performed in the absence of the compound a2. Moreover, the compound a1 used in the nanoparticle formation reaction may coexist. Although it is not sufficiently clear how the metal c1 is introduced by the metal c1 introduction reaction, it is presumed that at least one of the following reactions proceeds.
That is, when the metal c1 introduction reaction is performed in the presence of the compound a2, a crystal structure composed of a cation and an anion of the metal c1 grows on the surface of the nanoparticle and the metal c1 is introduced into the surface of the nanoparticle, or the surface of the nanoparticle It is considered that the metal c1 is introduced into the nanoparticle surface layer by cation exchange between the group III element present in the metal and the metal c1 or by doping the metal c1 into the crystal lattice of the nanoparticle surface layer. .
In addition, when the metal c1 introduction reaction is performed in the absence of the compound a2, cation exchange occurs between the group III element present in the nanoparticle surface layer and the metal c1, or a metal is present in the crystal lattice of the nanoparticle surface layer. It is considered that the metal c1 is introduced into the surface of the nanoparticle by being doped with c1.

The metal c1 introduction reaction may be carried out by mixing the reaction solution after completion of the step (b) and the salt of metal c1. Further, after the completion of the step (b), the obtained nanoparticles may be redispersed in another solvent, the redispersed liquid and the metal c1 salt may be mixed, and the metal c1 introduction reaction may be performed.

In the metal c1 introduction reaction, the solvent species that can be used in the reaction and the solvent content in the reaction solution are respectively the solvent species that can be used in the nanoparticle formation reaction in the step (a) and the solvent content in the reaction solution. The same and preferred forms are also the same.
Moreover, when performing metal c1 introduction | transduction reaction, you may contain the coordinating compound (dispersant) mentioned above in the reaction liquid. In this case, the content of the coordinating compound in the reaction solution in the metal c1 introduction reaction is preferably 0.1 to 5% by mass, more preferably 0.3 to 5% by mass, More preferably, it is set to ˜5% by mass, and particularly preferably 1 to 3% by mass.
For the metal c1, a salt of the metal c1 and a coordination compound are mixed and heated in advance, the coordination compound is coordinated with the metal c1, and this is added to the reaction liquid of the metal c1 introduction reaction. It is also preferable to react with the group III-V semiconductor nanoparticles obtained in b).

In the metal c1 introduction reaction, a salt of the metal c1 is an organic acid salt of the metal c1 (for example, a monocarboxylate such as acetate or propionic acid, a hydroxycarboxylate such as glycolate or lactate, a succinate, Dicarboxylates such as oxalate, polycarboxylates such as citric acid, aliphatic or aromatic sulfonates such as methanesulfonate, toluenesulfonate, carbonate, bicarbonate, sulfamate, metal Alkoxides, metal acetylacetonates, etc.) and inorganic acid salts of metal c1 (eg nitrates, sulfates, hydroiodides, hydrochlorides, hydrobromides, hydrofluorates, perchlorates) , Phosphates, hydrocyanates, etc.).

In the case where the metal c1 is Ca, the organic acid salt of Ca is, for example, aliphatic such as calcium acetate, calcium propionate, calcium stearate, calcium glycolate, calcium oxalate, calcium methanesulfonate, calcium toluenesulfonate, or the like. Aromatic sulfonates, calcium carbonate, calcium hydrogen carbonate, calcium sulfamate, calcium ethoxide, and calcium acetylacetone. Examples of Ca inorganic acid salts include calcium sulfate, calcium chloride, calcium bromide, and calcium phosphate.

When the metal c1 is Sc, examples of the Sc organic acid salt include scandium acetate, scandium stearate, scandium methanesulfonate, scandium carbonate, scandium sulfamate, scandium ethoxide, and acetylacetone scandium. Examples of the inorganic acid salt of Sc include scandium nitrate, scandium chloride, scandium bromide, and scandium phosphate.

When the metal c1 is Ti, examples of the organic acid salt of Ti include aliphatic or aromatic sulfones such as titanium acetate, titanium stearate, titanium glycolate, titanium oxalate, titanium methanesulfonate, titanium toluenesulfonate, and the like. Acid salts, titanium carbonate, titanium isopropoxide, titanium t-butoxide, and titanium acetylacetone. An example of the Ti inorganic acid salt is titanium chloride.

When the metal c1 is V, examples of the organic acid salt of V include vanadium acetate, vanadium stearate, vanadium carbonate, triisopropoxy vanadium oxide, and acetylacetonato vanadium. Examples of the inorganic acid salt of V include vanadium oxide sulfate, vanadium chloride, vanadium bromide, and vanadium fluoride.

When the metal c1 is Cr, examples of the organic acid salt of Cr include chromium acetate, chromium pstearate, and acetylacetone chromium. Examples of the inorganic acid salt of Cr include chromium nitrate, chromium chloride, and chromium phosphate.

When the metal c1 is Mn, examples of the organic acid salt of Mn include manganese acetate, manganese stearate, manganese 2-ethylhexanoate, manganese oxalate, manganese carbonate, manganese formate, acetylacetone manganese, tris (2, 2,6,6-tetramethyl-3,5-heptanedionato) manganese, bis (trifluoromethanesulfonyl) imidomanganese, N, N′-ethylenebis (salicylideneiminato) manganese. Examples of the inorganic acid salt of Mn include manganese nitrate, manganese sulfate, manganese chloride, and manganese phosphate.

In the case where the metal c1 is Fe, examples of the organic acid salt of Fe include iron acetate, iron stearate, iron 2-ethylhexanoate, iron oxalate, iron citrate, iron methanesulfonate, iron diethyldithiocarbamate, Examples thereof include iron methoxide, acetylacetone iron, ferrocene, N, N′-ethylenebis (salicylideneiminato) iron and the like. Examples of the inorganic acid salt of Fe include iron nitrate, iron sulfate, iron chloride, iron bromide, iron iodide, and iron phosphate.

In the case where the metal c1 is Co, examples of the organic acid salt of Co include cobalt acetate, cobalt stearate, cobalt oxalate, cobalt citrate, cobalt carbonate, cobalt sulfamate, tris (2,2,6,6- Tetramethyl-3,5-heptanedionato) cobalt, acetylacetonecobalt, N, N′-ethylenebis (salicylideneiminato) cobalt and the like. Examples of the inorganic acid salt of Co include cobalt nitrate, cobalt sulfate, cobalt chloride, cobalt bromide, cobalt iodide, and cobalt phosphate.

When the metal c1 is Ni, examples of the organic acid salt of Ni include aliphatic groups such as nickel acetate, nickel stearate, nickel 2-ethylhexanoate, nickel lactate, nickel trifluoromethanesulfonate, nickel toluenesulfonate, and the like. Aromatic sulfonate, nickel carbonate, nickel 2-methoxyethoxide, nickel diethyldithiocarbamate, acetylacetone nickel, trifluoroacetylacetonatonickel, [1,2-bis (diphenylphosphino) ethane] nickel dichloride, N, N Examples include '-ethylenebis (salicylideneiminato) nickel. Examples of the inorganic acid salt of Ni include nickel nitrate, nickel sulfate, nickel chloride, nickel bromide, nickel iodide and the like.

In the case where the metal c1 is Cu, examples of the organic acid salt of Cu include copper acetate, copper stearate, copper 2-ethylhexanoate, copper citrate, copper oxalate, copper trifluoromethanesulfonate, copper toluenesulfonate Aliphatic or aromatic sulfonates such as copper carbonate, copper formate, copper ethoxide, copper diethyldithiocarbamate, acetylacetone copper, trifluoroacetylacetonatocopper, bis (1,3-propanediamine) copper dichloride, bis ( (Trifluoromethanesulfonyl) imide copper, N, N′-ethylenebis (salicylideneiminato) copper and the like. Examples of Cu inorganic acid salts include copper nitrate, copper sulfate, copper chloride, copper bromide, and copper iodide.

When the metal c1 is Zn, examples of the organic acid salt of Zn include zinc acetate, zinc propionate, zinc stearate, zinc laurate, zinc 2-ethylhexanoate, copper citrate, copper oxalate, and trifluoro Aliphatic or aromatic sulfonates such as zinc acetate, zinc pt-butylbenzoate, zinc trifluoromethanesulfonate, zinc toluenesulfonate, zinc carbonate, zinc formate, zinc tert-butoxide, zinc diethyldithiocarbamate, Zinc acetylacetone, bis (2,2,6,6-tetramethyl-3,5-heptanedionato) zinc, trifluoroacetylacetonatozinc, dichloro (N, N, N ′, N′-tetramethylethane-1,2) -Diamine) zinc, bis (trifluoromethanesulfonyl) imidozinc, N, N'-ethylenebis ( Li Chile potential Minato) zinc, and the like. Examples of the inorganic acid salt of Zn include zinc nitrate, zinc sulfate, zinc chloride, zinc bromide, zinc iodide, and zinc phosphate.

At the start of the metal c1 introduction reaction, the content of the metal c1 salt in the reaction solution is preferably 0.1 to 5% by mass, more preferably 0.2 to 4% by mass, and 0.5 to 2% by mass. Is more preferable.
Further, at the start of the metal c1 introduction reaction, the content of III-V group semiconductor nanoparticles in the reaction solution is preferably 0.05 to 5% by mass, more preferably 0.05 to 2% by mass, More preferably, the content is 0.1 to 2% by mass. In addition, the content of the salt of the metal c1 in the reaction solution is such that when the metal c1 is added to the reaction solution with the coordination compound coordinated as described above, the metal c1 is added to the coordination compound. It is set as the value converted into the salt state before coordinating.

The reaction temperature of the metal c1 introduction reaction is usually 100 ° C. or higher, preferably 150 ° C. or higher, more preferably 180 ° C. or higher from the viewpoint of the reaction rate. Further, from the viewpoint of solvent boiling point and operational safety, the reaction temperature of the metal c1 introduction reaction is usually 400 ° C or lower, preferably 350 ° C or lower, more preferably 300 ° C or lower, further preferably 250 ° C or lower, 220 More preferably, it is not higher than ° C.

The reaction time of the metal c1 introduction reaction is appropriately adjusted according to the purpose, and is usually 1 to 240 minutes, preferably 5 to 180 minutes, more preferably 8 to 120 minutes, and particularly preferably 10 to 60 minutes.

The group III-V semiconductor nanoparticles obtained through the metal c1 introduction reaction are usually obtained in the form of a dispersion, and the content of group III-V semiconductor nanoparticles in the dispersion is 0.05-3 mass%. % Is preferred. The nanoparticles in the dispersion are usually used for the next Ga introduction reaction in the state of dispersion without being separated and recovered.

In the Ga introduction reaction, nanoparticles obtained by the metal c1 introduction reaction and having the metal c1 introduced into the surface layer are reacted with a Ga salt. By this reaction, Ga can be introduced into the surface of the nanoparticle obtained by the metal c1 introduction reaction, in which the metal c1 is introduced into the surface layer. The Ga introduction reaction may be performed in the presence of the compound a2 described above as an anion supply source, or may be performed in the absence of the compound a2. Although it is not sufficiently clear how Ga is introduced by the Ga introduction reaction, it is presumed that at least one of the following reactions proceeds.
That is, when the Ga introduction reaction is performed in the presence of the compound a2, a crystal layer or an amorphous layer made of Ga ions and anions grows on the nanoparticle surface layer in which the metal c1 is introduced into the surface layer, and Ga is present on the nanoparticle surface layer. Introduced or separated from this reaction, it is considered that Ga is also introduced into the nanoparticle surface layer by cation exchange between Ga and metal c1 existing on the nanoparticle surface layer.
In addition, when the Ga introduction reaction is performed in the absence of the compound a2, it is considered that Ga is introduced into the nanoparticle surface layer by cation exchange between the metal c1 and Ga existing in the nanoparticle surface layer.

The Ga introduction reaction may be performed by mixing a Ga salt into the reaction solution of the metal c1 introduction reaction after the metal c1 introduction reaction. Further, after the completion of the metal c1 introduction reaction, the obtained nanoparticles in which the metal c1 is introduced into the surface layer are redispersed in another solvent, and the redispersed liquid and a Ga salt are mixed to obtain a Ga introduction reaction. May be performed.

In the Ga introduction reaction, the solvent species that can be used in the reaction and the content of the solvent in the reaction solution are the same as the solvent species that can be used in the nanoparticle formation reaction and the content of the solvent in the reaction solution, respectively. Is the same.
Moreover, when performing Ga introduction | transduction reaction, you may contain the coordinating compound mentioned above in the reaction liquid. In this case, the content of the coordinating compound in the reaction solution in the Ga introduction reaction is preferably 0.1 to 5% by mass, more preferably 0.3 to 5% by mass, The content is more preferably 5% by mass, and particularly preferably 1 to 3% by mass.
Ga is obtained by the metal c1 introduction reaction by mixing and heating a Ga salt and a coordination compound in advance, and coordinating the coordination compound to Ga, and adding this to the reaction solution for Ga introduction reaction. It is also preferable to react with the nanoparticles having the metal c1 introduced into the surface layer.

In the Ga introduction reaction, the Ga salt used is an organic acid salt of Ga (for example, monocarboxylate such as acetate or propionic acid, hydroxycarboxylate such as glycolate or lactate, succinate or oxalic acid. Dicarboxylates such as salts, polycarboxylates such as citric acid, aliphatic or aromatic sulfonates such as methanesulfonate and toluenesulfonate, carbonates, bicarbonates, sulfamates, metal alkoxides, Metal acetylacetonate etc.), and inorganic salts of Ga (eg nitrate, sulfate, hydroiodide, hydrochloride, hydrobromide, hydrofluoride, perchlorate, phosphoric acid) Salt, hydrocyanate, etc.).
Examples of the organic acid salt of Ga include aliphatic or aromatic sulfonates such as gallium acetate, gallium stearate, gallium 2-ethylhexanoate, gallium trifluoromethanesulfonate, gallium toluenesulfonate, gallium ethoxide, and gallium. Examples include isopropoxide, acetylacetone gallium, and trifluoroacetylacetonatogallium. Examples of Ga inorganic acid salts include gallium nitrate, gallium sulfate, gallium chloride, gallium bromide, gallium iodide, and gallium phosphate.

At the start of the Ga introduction reaction, the Ga salt content in the reaction solution is preferably 0.1 to 5% by mass, more preferably 0.2 to 4% by mass, and further 0.5 to 2% by mass. preferable.
Further, at the start of the Ga introduction reaction, the content of the nanoparticles in which the metal c1 is introduced into the surface layer in the reaction solution is preferably 0.05 to 5% by mass, more preferably 0.05 to 2% by mass. Preferably, 0.1 to 2% by mass is more preferable. Note that the Ga salt content in the reaction solution is such that when Ga is added to the reaction solution with the coordination compound coordinated as described above, Ga is coordinated with the coordination compound. The value converted to the previous salt state.

The reaction temperature of the Ga introduction reaction is usually 100 ° C. or higher, preferably 150 ° C. or higher, and more preferably 180 ° C. or higher. The reaction temperature of the Ga introduction reaction is usually 400 ° C. or lower, preferably 350 ° C. or lower, more preferably 300 ° C. or lower, further preferably 250 ° C. or lower, and further preferably 220 ° C. or lower.

The reaction time of the Ga introduction reaction is appropriately adjusted according to the purpose, and is usually 1 to 240 minutes, preferably 10 to 180 minutes, more preferably 15 to 120 minutes, and particularly preferably 30 to 90 minutes. For minutes.

The group III-V semiconductor nanoparticles obtained through the Ga introduction reaction are usually obtained in the form of a dispersion, and the content of group III-V semiconductor nanoparticles in the dispersion is 0.05 to 3% by mass. It is preferable that The nanoparticles in the dispersion are usually used for the intended reaction or application in the state of the dispersion without being separated and recovered.

The production method of the present invention preferably includes a step of forming a shell layer on the surface of the nanoparticles into which Ga has been introduced (hereinafter referred to as “step (d)”) after the step (c) is completed. This shell layer can adopt a form that can be usually adopted as a shell layer of quantum dots. Preferred examples include ZnS, ZnO, ZnSe, ZnSe _X S _1-X (0 <X <1), Examples thereof include a shell layer formed of ZnTe, In ₂ O ₃ or CuO.
The shell layer can be formed by a conventional method. For example, JP-A-2012-525467, JP-A-2015-529698, JP-A-2014-523634, JP-A-2015-127362, JP-A-4565152. Publication, Japanese Patent No. 4344613, US Pat. No. 7,1050,051, US Pat. No. 8,848,111, APPLIED PHYSICS LETTERS 97, 193104, 2010, ACS Appl. Mater. Interfaces 2014, 6, p. Reference can be made to the description of 18233-18242.

For example, in the case of a shell layer made of ZnS, after completion of the reaction in step (c), Zn acetate, 1-dodecanethiol, and a coordinating compound are added to the reaction solution as necessary, and the reaction is performed at a temperature of, for example, 200 ° C. Can be formed. Other shell layers can also be formed in accordance with this method by changing the raw materials used according to the purpose. It can also be formed by a reaction under a high temperature condition using an organic metal such as dimethylzinc or diethylzinc as a Zn supply source, or a thermal decomposition reaction of zinc dialkyldithiocarbamate.
The shell layer is preferably ZnS, ZnO, ZnSe or ZnSe _X S _1-X , more preferably ZnS.

The group III-V semiconductor quantum dots obtained by the production method of the present invention preferably have an average particle diameter of 1 to 10 nm, more preferably 1 to 6 nm, in a form in which no shell layer is provided. When the group III-V semiconductor quantum dots obtained by the production method of the present invention have a shell layer, the average particle diameter of the quantum dots including the shell layer is preferably 2 to 10 nm. It is more preferable that

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[Example 1]
According to the following reaction scheme, InP quantum dots formed by introducing Ga into the surface layer of InP nanoparticles were prepared.

In a glove box filled with dry nitrogen, octadecene (22 mL), indium acetate (140 mg) and palmitic acid (369 mg) were added to a 200 ml three-necked flask, and vacuum deaeration was performed at 130 ° C. for 30 minutes. The 1-octadecene used in this experiment was distilled from calcium hydride under reduced pressure and the water content calculated by Karl Fischer method was 6 ppm. The reaction vessel was heated to 300 ° C., and 4 ml of a solution (P (TMS) ₃ concentration: 45 mM) in which tris (trimethylsilyl) phosphine [P (TMS) ₃ ] was dissolved in octadecene [ODE] was quickly added. InP nanoparticles were formed in the reaction solution by holding for a minute (InP nanoparticle formation reaction). Next, the reaction solution was cooled from 300 ° C. to 250 ° C. at a cooling rate of 1.4 ° C./min (slow cooling step). Subsequently, the reaction solution was kept at 230 ° C. and aged for 2 hours to obtain a dispersion of InP nanoparticles. In this dispersion, the content of InP nanoparticles was 0.3% by mass.
This dispersion was sampled and the particle size was measured using HR-TEM (high resolution transmission electron microscope). As a result, the average particle size of InP particles was 3 nm. Subsequently, after cooling to 200 ° C., a solution obtained by vacuum degassing a mixture of zinc solution (zinc acetate (66 mg), palmitic acid (185 mg), octadecene (15 ml) at 130 ° C. for 30 minutes [in the scheme, Zn (C ₁₅ H ₃₁ CO ₂ ) ₂ ]) 10 mL was added and reacted at 200 ° C. for 15 minutes to introduce Zn into the surface layer of the InP particles. Subsequently, a solution in which a mixture of gallium solution (gallium chloride (19 mg), oleic acid (119 μl), and octadecene (5 ml) was heated at 90 ° C. for 1 hour [shown as Ga (C ₁₇ H ₃₃ CO ₂ ) ₃ in the scheme] 8 mL was added, reacted at 200 ° C. for 1 hour, Ga was introduced into the surface layer of the InP particles, and allowed to cool to room temperature to obtain an InP quantum dot dispersion. The average particle diameter of InP quantum dots in the obtained dispersion was 4 nm. Moreover, in this InP quantum dot dispersion, the content of InP quantum dots (Ga introduced) was 0.3% by mass. This InP quantum dot dispersion is diluted 5-fold with toluene, and a fluorescence spectrum (F-7000, manufactured by Hitachi High-Tech Science Co., Ltd., excitation wavelength: 450 nm) is measured to measure the maximum emission, the half width of the emission peak, and the quantum yield. did. The results are shown in Table 1 below.

[Example 2]
In Example 1, the slow cooling process “cooling from 300 ° C. to 250 ° C. at a cooling rate of 1.4 ° C./min” was changed to “cooling from 300 ° C. to 250 ° C. at a cooling rate of 1.0 ° C./min”. Except for this, an InP quantum dot having an average particle diameter of 4 nm was obtained in the same manner as in Example 1, and the fluorescence spectrum, emission maximum, half width of emission peak, and quantum yield were measured. The results are shown in Table 1 below.

[Example 3]
InP quantum dots having an average particle diameter of 4 nm were obtained in the same manner as in Example 1 except that the conditions of InP nanoparticle formation reaction “300 ° C. for 30 minutes” were changed to “300 ° C. for 10 seconds” in Example 1. The fluorescence spectrum, the emission maximum, the half-value width of the emission peak, and the quantum yield were measured. The results are shown in Table 1 below.

[Example 4]
In Example 1, the slow cooling process “cooling from 300 ° C. to 250 ° C. at a cooling rate of 1.4 ° C./min” was changed to “cooling from 300 ° C. to 250 ° C. at a cooling rate of 2.8 ° C./min”. Except for this, an InP quantum dot having an average particle diameter of 4 nm was obtained in the same manner as in Example 1, and the fluorescence spectrum, emission maximum, half width of emission peak, and quantum yield were measured. The results are shown in Table 1 below.

[Example 5]
InP quantum dots having an average particle diameter of 4 nm were obtained in the same manner as in Example 4 except that the conditions of InP nanoparticle formation reaction “300 ° C. for 30 minutes” were changed to “300 ° C. for 3 seconds” in Example 4. The fluorescence spectrum, the emission maximum, the half-value width of the emission peak, and the quantum yield were measured. The results are shown in Table 1 below.

[Example 6]
InP quantum dots having an average particle diameter of 4 nm were obtained in the same manner as in Example 1 except that the conditions of InP nanoparticle formation reaction “300 ° C. for 30 minutes” were changed to “300 ° C. for 180 minutes” in Example 1. The fluorescence spectrum, the emission maximum, the half-value width of the emission peak, and the quantum yield were measured. The results are shown in Table 1 below.

[Example 7]
In Example 1, the InP nanoparticle formation reaction condition “300 ° C. for 30 minutes” was changed to “270 ° C. for 30 minutes”, and the cooling step “cooling rate of 1.4 ° C./min from 300 ° C. to 250 ° C.” InP quantum dots having an average particle diameter of 4 nm were obtained in the same manner as in Example 1 except that “cooling at 270 ° C. was changed from 270 ° C. to 250 ° C. at a cooling rate of 0.8 ° C./min”. The spectrum, emission maximum, half width of emission peak, and quantum yield were measured. The results are shown in Table 1 below.

[Example 8]
In Example 7, the slow cooling process “cooling from 270 ° C. to 250 ° C. at a cooling rate of 0.8 ° C./min” was changed to “cooling from 270 ° C. to 250 ° C. at a cooling rate of 1.4 ° C./min”. Except for this, an InP quantum dot having an average particle diameter of 4 nm was obtained in the same manner as in Example 7, and the fluorescence spectrum, emission maximum, half width of emission peak, and quantum yield were measured. The results are shown in Table 1 below.

[Example 9]
In Example 1, in place of 1-octadecene having a water content of 14 ppm instead of 1-octadecene having a water content of 6 ppm used in the InP nanoparticle formation reaction, an average particle diameter of 4 nm was obtained in the same manner as in Example 1. InP quantum dots were obtained, and the fluorescence spectrum, emission maximum, half width of emission peak, and quantum yield were measured. The results are shown in Table 1 below.

[Example 10]
A ZnS layer was further formed on the InP quantum dots obtained in Example 1. More specifically, after adding a gallium solution and reacting at 200 ° C. for 1 hour in Example 1, the reaction solution was heated to 240 ° C., and a zinc solution (zinc acetate (66 mg), palmitic acid (185 mg), 1- 10 ml of a mixture of octadecene (15 ml) obtained by vacuum degassing at 130 ° C. for 30 minutes and 182 mg of 1-dodecanethiol was added, reacted at 240 ° C. for 6 hours, and allowed to cool to room temperature. Thus, a dispersion liquid of InP quantum dots having an average particle diameter of 5 nm in which Ga was introduced into the surface layer of InP nanoparticles and a ZnS shell layer was formed was obtained. In this InP quantum dot dispersion, the content of InP quantum dots (with a shell layer) was 0.3% by mass. This InP quantum dot dispersion was diluted 5-fold with toluene, and the emission maximum, the half width of the emission peak, and the quantum yield were measured in the same manner as in Example 1. The results are shown in Table 1 below.

[Comparative Example 1]
In Example 1, except that the slow cooling process “cooling from 300 ° C. to 250 ° C. at a cooling rate of 1.4 ° C./min” was changed to “cooling from 300 ° C. to 250 ° C. at a cooling rate of 7 ° C./min”. Obtained InP quantum dots having an average particle diameter of 4 nm in the same manner as in Example 1, and the fluorescence spectrum, emission maximum, half width of emission peak, and quantum yield were measured. The results are shown in Table 1 below.

[Comparative Example 2]
In Comparative Example 1, InP quantum dots having an average particle diameter of 4 nm were formed in the same manner as in Comparative Example 1, except that the conditions of InP nanoparticle formation reaction “300 ° C. for 30 minutes” were changed to “300 ° C. for 10 seconds”. The fluorescence spectrum, the emission maximum, the half-value width of the emission peak, and the quantum yield were measured. The results are shown in Table 1 below.

[Comparative Example 3]
In Example 1, the slow cooling process “cooling from 300 ° C. to 250 ° C. at a cooling rate of 1.4 ° C./min” was changed to “cooling from 300 ° C. to 250 ° C. at a cooling rate of 0.1 ° C./min”. Except for this, an InP quantum dot having an average particle diameter of 4 nm was obtained in the same manner as in Example 1, and the fluorescence spectrum, emission maximum, half width of emission peak, and quantum yield were measured. The results are shown in Table 1 below.

As shown in Table 1, in the cooling step up to 250 ° C. after the nanoparticle formation reaction, Comparative Examples 1 and 2 in which the cooling rate was faster than that defined in the present invention and Comparative Example 3 in which the cooling rate was slow were obtained. The quantum yield of quantum dots was low.
In contrast, in Examples 1 to 10 in which the cooling rate was within the range specified in the present invention in the cooling step up to 250 ° C. after the nanoparticle formation reaction, the obtained quantum dots had excellent quantum yields, It was also found that the half-value width was narrow and sharp emission characteristics were exhibited.
In addition, when compared between Examples 1 to 10 above, Examples 7 and 8 in which the reaction temperature in the nanoparticle formation reaction was set to be as low as 270 ° C., the quantum yield of the obtained quantum dots was slightly reduced, Compared with the comparative example, the quantum yield is much higher. In addition, it has been shown that the reaction time in the nanoparticle formation reaction and the water content in the solvent can also affect the half-value width or quantum yield, but its performance is greatly improved compared to the comparative example. .

While this invention has been described in conjunction with its embodiments, we do not intend to limit our invention in any detail of the description unless otherwise specified and are contrary to the spirit and scope of the invention as set forth in the appended claims. I think it should be interpreted widely.

This application claims priority based on Japanese Patent Application No. 2016-185860 filed in Japan on September 23, 2016, which is hereby incorporated herein by reference. Capture as part.

Claims

A method for producing a group III-V semiconductor quantum dot, comprising the following steps (a) and (b):
(A) A liquid containing a compound a1 containing a Group III element, a compound a2 containing a Group V element, and a solvent is maintained at 270 to 400 ° C. to react the compound a1 with the compound a2, and react Forming III-V semiconductor nanoparticles in the liquid;
(B) A step of cooling the reaction liquid in which the nanoparticles are formed to 250 ° C. at a cooling rate of 0.3 to 3 ° C./min.
The method for producing a group III-V semiconductor quantum dot according to claim 1, wherein a reaction time of 270 to 400 ° C in the step (a) is 10 seconds to 120 minutes.
The method for producing a group III-V semiconductor quantum dot according to claim 1 or 2, wherein the group III element contained in the compound a1 is In.
The method for producing a group III-V semiconductor quantum dot according to any one of claims 1 to 3, wherein the group V element contained in the compound a2 is P or As.
The method for producing a group III-V semiconductor quantum dot according to any one of claims 1 to 4, wherein the group III-V semiconductor quantum dot is an InP quantum dot.
The method for producing a group III-V semiconductor quantum dot according to any one of claims 1 to 5, wherein the solvent is a non-coordinating solvent.
The method for producing a group III-V semiconductor quantum dot according to any one of claims 1 to 6, wherein the water content of the solvent is 10 ppm or less.
The method for producing a group III-V semiconductor quantum dot according to any one of claims 1 to 7, wherein a reaction temperature in the step (a) is 280 to 350 ° C.
The III of any one of claims 1 to 8, wherein the step (b) comprises maintaining the reaction liquid cooled to 250 ° C at a temperature of 150 to 250 ° C for 0.5 to 4 hours. A method for producing a group V semiconductor quantum dot.
The method for producing a group III-V semiconductor quantum dot according to any one of claims 1 to 9, further comprising a step (c) of introducing Ga into a surface layer of the nanoparticles after the step (b).
The method for producing a group III-V semiconductor quantum dot according to claim 10, comprising a step (d) of forming a shell layer on the surface of the nanoparticles having Ga introduced into the surface layer obtained in the step (c).
The method for producing a group III-V semiconductor quantum dot according to claim 11, wherein the shell layer is ZnS, ZnO, ZnSe, ZnSe X S 1-X , ZnTe, or CuO. However, 0 <X <1.