Method for producing core / shell type semiconductor nanoparticles, and semiconductor nanoparticle composites

Abstract

To provide a manufacturing method for semiconductor nano-particles capable of manufacturing core / shell type structured semiconductor nanoparticles convenient and excellent in optical characteristics, when core / shell type structured semiconductor nanoparticles are manufactured with two or more kinds of shell precursors.SOLUTION: A manufacturing method for core / shell type semiconductor nanoparticles characterized by comprising adding a raw material zinc carboxylate and a group VI element precursor to a dispersion of core particles to react the raw material zinc carboxylate and the group VI element precursor in the presence of the core particles to form a shell containing zinc and group VI element on a surface of the core particles, wherein a ratio of carboxylic acid having 8 to 10 carbon atoms among all the carboxylic acids forming the raw material zinc carboxylate is 80.0 mass% or more, and an average branching degree of the entire carboxylic acid forming the raw material zinc carboxylate is 1.1 to 2.9.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing core / shell type semiconductor nanoparticles and a semiconductor nanoparticle composite.

Background Art

[0002] As a wavelength conversion material for displays, semiconductor nanoparticles (quantum dots: QD) with a small particle size are used. Such semiconductor nanoparticles are minute particles that can exhibit the quantum confinement effect, and the width of the band gap varies depending on the size of the nanoparticles. Then, excitons formed in the semiconductor particles by means such as photoexcitation and charge injection emit photons of energy corresponding to the band gap by recombination, so by adjusting the crystal size of the semiconductor nanoparticles, it becomes possible to control the emission wavelength and obtain light emission of a desired wavelength.

[0003] Currently, as semiconductor nanoparticles, semiconductor nanoparticles having a core / shell type structure are often used. This is because by adopting a core / shell structure, the effect of filling the dangling bonds on the core surface and reducing surface defects can be obtained.

[0004] As such core / shell type semiconductor nanoparticles, semiconductor nanoparticles composed of a group III-V core and a group II-VI shell are used. However, in the case of a group III-V core and a group II-VI shell, due to the difference in lattice constants, defect levels are likely to be formed, and in semiconductor nanoparticles in which defect levels are formed, non-radiative recombination of excitons via the defect levels occurs, so the optical properties are likely to deteriorate. Therefore, it is important to form a group II-VI shell that suppresses the generation of defect levels on the surface of the group III-V core.

[0005] One known method for forming a shell on the surface of core particles is the SILAR method. The SILAR method involves alternately adding shell precursors to core particles and reacting the added shell precursors on the particle surface to form a shell. For example, by first adding a Zn precursor to the core particle, then adding a S precursor, then adding another Zn precursor, then adding another S precursor, and so on, two types of shell precursors, which are the raw materials for the shell, are alternately brought into contact with the core particle, forming alternating layers of the two types of shell precursors on the particle surface, and then reacting these two types of shell precursors to form a shell. Furthermore, Patent Document 1 describes the use of zinc oleate, zinc hexanoate, zinc octanoate, zinc laurate, zinc palmitate, zinc stearate, and zinc dithiocarbamate as Zn precursors for shell formation. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Special Publication No. 2019-515338 [Non-patent literature]

[0007] [Non-Patent Document 1] Renguo Xie et al., J.AM.CHEM.SOC., 127, 7480-7488 (2005) [Non-Patent Document 2] Ken-Tye Yong et al., ACS Nano, 3, 502-510 (2009) [Disclosure of the Invention] [Problems that the invention aims to solve]

[0008] However, in the SILAR method, strict control of the amount of precursor added is required during the formation of each precursor layer. If too little precursor is added, a sufficient shell will not be formed, resulting in a decrease in optical properties. On the other hand, if too much precursor is added, the excess precursor can cause particle alteration and the generation of by-products.

[0009] Furthermore, because the two types of shell precursors are brought into contact with the particles separately and alternately multiple times, there is a problem in that the manufacturing method for semiconductor nanoparticles becomes complicated.

[0010] Therefore, the object of the present invention is to provide a method for producing semiconductor nanoparticles that is simple and can produce semiconductor nanoparticles with a core / shell structure that have excellent optical properties when using two or more types of shell precursors. [Means for solving the problem]

[0011] As a result of diligent research to solve the above problems, the present inventors have discovered that by using a zinc salt of a carboxylic acid with a specific number of carbon atoms and degree of branching as a group II element precursor to be added to a dispersion of core particles and reacted with a group VI element precursor on the surface of the core particles, it is possible to obtain core / shell type semiconductor nanoparticles with excellent optical properties even without separately and repeatedly alternating contact between the group II element precursor and the group IV element precursor. In other words, even when the entire amount of the group II element precursor and the group VI element precursor are contacted with the core particles at once and reacted, the present inventors have completed the present invention.

[0012] In other words, the present invention (1) includes a shell forming step of adding a raw material zinc carboxylate and a group VI element precursor to a dispersion of core particles and reacting the raw material zinc carboxylate and the group VI element precursor in the presence of the core particles to form a shell containing zinc and a group VI element on the surface of the core particles. Of the total carboxylic acids forming the zinc carboxylate raw material, the proportion of carboxylic acids having 8 to 10 carbon atoms is 80.0% by mass or more. The average degree of branching of the entire carboxylic acid forming the zinc carboxylate raw material is 1.1 to 2.9, and provides a method for producing core / shell type semiconductor nanoparticles characterized by the above.

[0013] Further, the present invention (2) provides a method for producing the core / shell type semiconductor nanoparticles of (1), characterized in that the core particles contain In and P.

[0014] Further, the present invention (3) provides a method for producing the core / shell type semiconductor nanoparticles of (1) or (2), characterized in that the addition amount of the zinc carboxylate raw material is such that the molar ratio of Zn to In in the zinc carboxylate raw material with respect to In in the core particles (Zn / In) is 5 to 50.

[0015] Further, the present invention (4) provides a method for producing the core / shell type semiconductor nanoparticles of any one of (1) to (3), characterized in that the reaction of the zinc carboxylate raw material and the group VI element precursor is carried out in the presence of a halogen element.

[0016] Further, the present invention (5) is a core / shell type semiconductor nanoparticle composite having core / shell type semiconductor nanoparticles and a ligand coordinated on the surface of the core / shell type semiconductor nanoparticles, where the shell contains at least Zn, the ligand contains a carboxylic acid, among all the carboxylic acids contained as the ligand, the proportion of the carboxylic acid having 8 to 10 carbon atoms is 80% by mass or more, the average degree of branching of all the carboxylic acids contained as the ligand is 1.1 to 2.9, and provides a core / shell type semiconductor nanoparticle composite characterized by the above.

[0017] Further, the present invention (6) provides the core / shell type semiconductor nanoparticle composite of (5), characterized in that the core contains In and P.

[0021] Furthermore, the present invention (7) provides the core / shell type semiconductor nanoparticle composite according to (5) or (6), characterized in that the emission peak wavelength of the core / shell type semiconductor nanoparticle composite is 590 to 650 nm.

[0019] Furthermore, the present invention (8) provides the core / shell type semiconductor nanoparticle composite according to any one of (5) to (7), characterized in that the full width at half maximum (FWHM) of the emission spectrum of the core / shell type semiconductor nanoparticle composite is 37.0 nm or less.

[0020] Furthermore, the present invention (9) provides the core / shell type semiconductor nanoparticle composite according to any one of (5) to (8), characterized in that the shell further contains at least one of Se and S.

[0021] Furthermore, the present invention (10) provides the core / shell type semiconductor nanoparticle composite according to any one of (5) to (9), characterized in that the quantum efficiency (QY) of the core / shell type semiconductor nanoparticle composite is 90.0% or more.

[0022] Furthermore, the present invention (11) provides the core / shell type semiconductor nanoparticle composite according to any one of (5) to (10), characterized in that the proportion of the carboxylic acid among all the ligands coordinated to the core / shell type semiconductor nanoparticle composite is 1.0 to 15.0% by mass.

Advantages of the Invention

[0023] According to the present invention, when manufacturing semiconductor nanoparticles having a core / shell structure using two or more types of shell precursors, it is possible to provide a method for manufacturing semiconductor nanoparticles that is simple and can produce semiconductor nanoparticles having a core / shell structure with excellent optical properties.

Embodiments for Carrying Out the Invention

[0024] The present invention provides a method for producing core / shell type semiconductor nanoparticles, comprising a shell formation step (hereinafter also referred to as shell formation step (1)) in which a raw material zinc carboxylate and a group VI element precursor are added to a dispersion of core particles, and the raw material zinc carboxylate and the group VI element precursor are reacted in the presence of the core particles to form a shell containing zinc and a group VI element on the surface of the core particles. Of the total carboxylic acids forming the zinc carboxylate raw material, the proportion of carboxylic acids having 8 to 10 carbon atoms is 80% by mass or more. The average degree of branching of the entire carboxylic acid forming the zinc carboxylic acid salt is 1.1 to 2.9. This is a method for manufacturing core / shell type semiconductor nanoparticles characterized by the following.

[0025] In the following, the symbol "~" indicating a numerical range includes the numbers written before and after the symbol "~" unless otherwise specified. In other words, ○~△ means greater than or equal to ○ and less than or equal to △.

[0026] The present invention relates to a method for producing core / shell type semiconductor nanoparticles, which includes a shell formation step (1). The shell formation step (1) involves adding at least a raw material zinc carboxylate and a group VI element precursor to a dispersion of core particles, and reacting the raw material zinc carboxylate and the group VI element precursor in the presence of the core particles to form a shell containing zinc and a group VI element on the surface of the core particles.

[0027] In the shell formation step (1), the core particles from which the shell layer is formed are not particularly limited as long as they are used as core particles in core / shell type semiconductor nanoparticles, and are preferably core particles containing In and P, and particularly preferably core particles containing In, P and halogens. The inclusion of In and P in the core particles is preferable because it yields semiconductor nanoparticles with low environmental impact and high optical properties. The inclusion of halogens in the core particles is preferable because it can enhance the optical properties of the core particles and semiconductor nanoparticles. Examples of halogens to be included in the core particles include F, Cl, Br, and I. Of these, Cl and Br are preferred halogens because they result in a narrower full width at half maximum. The core particles may also contain other elements such as Ga, Al, Zn, N, S, Si, and Ge.

[0028] The Cd content of the core particles is 100 ppm by mass or less, preferably 80 ppm by mass or less, and particularly preferably 50 ppm by mass or less.

[0029] The average particle size of the core particles is not particularly limited, but is preferably 1.0 nm to 5.0 nm. Having an average particle size within this range allows the excitation light at 450 nm to be converted into green to red emission. In this invention, the average particle size of the core particles is determined by calculating the area circle equivalent diameter (Heywood diameter) of 10 or more particles from a particle image observed using a transmission electron microscope (TEM).

[0030] The method for synthesizing the core particles is not particularly limited and can be selected as appropriate. In the present invention, the In precursor, P precursor, and halogen precursor are as follows.

[0031] The In precursor is not particularly limited and includes, for example, indium carboxylates such as indium acetate, indium propionate, indium myristate, and indium oleate, indium halides such as indium fluoride, indium bromide, and indium iodide, indium thiolate, and trialkylindium.

[0032] The P precursor is not particularly limited and examples include tris(trimethylsilyl)phosphine, tris(trimethylgermyl)phosphine, tris(dimethylamino)phosphine, tris(diethylamino)phosphine, tris(dioctylamino)phosphine, trialkylphosphine, and pH3 gas. When tris(trimethylsilyl)phosphine is used as the P precursor, Si may be incorporated into the semiconductor nanoparticles, but this does not impair the function of the present invention.

[0033] The halogen precursor is not particularly limited and examples include carboxylic acid halides such as HF, HCl, HBr, HI, oleyl chloride, oleyl bromide, octanoyl chloride, octinoyl bromide, and oleoyl chloride, and metal halides such as zinc chloride, indium chloride, and gallium chloride.

[0034] The following methods are examples of methods for synthesizing core particles containing In and P. Note that the following methods for synthesizing core particles are illustrative and not limited to those synthesized by these methods. Core particles can be synthesized, for example, by reacting an In precursor with a P precursor. First, the In precursor solution is mixed with a solvent, and if necessary, a dispersant and / or additives are added. This mixture is then mixed under vacuum or under a nitrogen atmosphere, heated at 100-300°C for 6-24 hours, followed by the addition of the P precursor. After heating at 200-400°C for a few seconds (e.g., 2-3 seconds) to 60 minutes, the mixture is cooled to obtain a core particle dispersion containing dispersed core particles. Next, a halogen precursor is added to the core particle dispersion. After heating at 25-350°C for a few seconds (e.g., 2-3 seconds) to 60 minutes, the mixture is cooled to obtain a halogen-added core particle dispersion having halogens on a portion of the particle surface.

[0035] The dispersant is not particularly limited and includes, for example, carboxylic acids, amines, thiols, phosphines, phosphine oxides, phosphines, and phosphonic acids. The dispersant can also serve as a solvent. The solvent is not particularly limited and includes, for example, 1-octadecene, hexadecane, squalane, oleylamine, trioctylphosphine, and trioctylphosphine oxide. Additives include the above-mentioned S precursor, Zn precursor, and halogen precursor.

[0036] The dispersion of core particles in the shell formation step (1) is a dispersion in which core particles are dispersed in a dispersion medium. The dispersion medium in which the core particles are dispersed is not particularly limited and includes 1-octadecene, hexadecane, squalane, squalene, mineral spirits, liquid paraffin, trioctylamine, trioctylphosphine, trioctylphosphine oxide, toluene, hexane, diphenyl ether, etc. These may be used individually or in combination of two or more, and preferably at least one selected from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral spirits, and liquid paraffin.

[0037] The zinc carboxylate raw material in the shell formation step (1) is a zinc precursor added to the dispersion of core particles, and is a zinc precursor that reacts with the element VI precursor in the shell formation step (1).

[0038] Of the total carboxylic acids forming the zinc carboxylate raw material, the proportion of carboxylic acids having 8 to 10 carbon atoms is 80.0% by mass or more, preferably 85.0% by mass or more, more preferably 90.0% by mass or more, and particularly preferably 100.0% by mass. In other words, the proportion of carboxylic acids having 8 to 10 carbon atoms in the total carboxylic acids forming the zinc carboxylate raw material is 80.0% by mass or more, preferably 85.0% by mass or more, more preferably 90.0% by mass or more, and particularly preferably 100.0% by mass. By having the proportion of carboxylic acids having 8 to 10 carbon atoms within the total carboxylic acids forming the zinc carboxylate raw material within the above range, semiconductor nanoparticles with high optical properties can be obtained.

[0039] Examples of carboxylic acids having 8 to 10 carbon atoms include octanoic acid, 2-ethylhexanoic acid, isooctanoic acid, nonanoic acid, isononanoic acid, neononanoic acid, decanoic acid, isodecanoic acid, and neodecanoic acid. One or more of these carboxylic acids are selected and used in combination to achieve a predetermined average branching degree. It is desirable to use a combination of two or more carboxylic acids with 2-ethylhexanoic acid, isononanoic acid, and neodecanoic acid as the main components.

[0040] In this invention, the proportion of carboxylic acids with 8 to 10 carbon atoms among the total carboxylic acids forming the raw material zinc carboxylate is determined by identifying the types and amounts of carboxylic acids using gas chromatography, liquid chromatography-mass spectrometry, etc., and calculating the proportion based on the measurement results. For example, when analyzing the carboxylic acids used as raw materials for the production of the raw material zinc carboxylate (a mixture of carboxylic acids if the carboxylic acids forming the raw material zinc carboxylate consist of two or more carboxylic acids), that is, the carboxylic acids before being reacted with a zinc compound to produce the raw material zinc carboxylate (a mixture of carboxylic acids if the carboxylic acids forming the raw material zinc carboxylate consist of two or more carboxylic acids), using gas chromatography, a portion of the carboxylic acid is taken, subjected to methyl esterification treatment, introduced into gas chromatography, heated at 350°C or higher, passed through a column with a carrier gas, and then the types and amounts of carboxylic acids are identified from the retention time and peak area of ​​the signal obtained by the detector. From these results, the proportion of carboxylic acids with 8 to 10 carbon atoms among the total carboxylic acids forming the raw material zinc carboxylate can be calculated. Furthermore, for example, a portion of the raw material zinc carboxylate salt before being added to the core particle dispersion can be taken, a strong acid such as hydrochloric acid or nitric acid can be added to separate the carboxylic acid, followed by methyl esterification. This sample is then introduced into the sample vaporization chamber of a gas chromatography system, heated to over 350°C, and passed through a column with a carrier gas. The type and amount of carboxylic acid can then be identified from the retention time and peak area of ​​the signal obtained by the detector. From these results, the proportion of carboxylic acids with 8 to 10 carbon atoms among the total carboxylic acids forming the raw material zinc carboxylate salt can be calculated.

[0041] The average degree of branching of the entire carboxylic acid that forms the raw material zinc carboxylate is 1.1 to 2.9, preferably 1.3 to 2.7, and particularly preferably 1.5 to 2.5. In other words, the average degree of branching of the entire carboxylic acid that forms the raw material zinc carboxylate is 1.1 to 2.9, preferably 1.3 to 2.7, and particularly preferably 1.5 to 2.5. Having the above average degree of branching of the entire carboxylic acid that forms the raw material zinc carboxylate results in high solubility in organic hydrocarbon solvents and improved workability. Furthermore, when using the zinc carboxylate of the present invention as a Zn precursor in the production of semiconductor nanoparticles, semiconductor nanoparticles with high optical properties can be obtained. It is thought that the above average degree of branching allows the zinc carboxylate to have a certain bulk and react with other precursors that form shells on the surface of the core particles.

[0042] In this invention, the average degree of branching of the entire carboxylic acid forming the zinc carboxylic acid salt represents the degree of branching of the alkyl group from the main chain of the carboxylic acid. First, the sample is analyzed by gas chromatography or the like, and the average molecular weight (14n+32) of the carboxylic acid is calculated from the obtained composition ratio. 1 The carboxylic acid is analyzed by 1H-NMR, and from the resulting NMR chart, the integral value of the chemical shifts indicating hydrogen atoms in all alkyl chains of the carboxylic acid is taken as 2n-1, and the integral value of the chemical shift δ = 0.7 to 1.1 ppm indicating hydrogen atoms of primary carbons is divided by 3 to obtain the number of methyl groups in that carboxylic acid. The degree of branching is calculated by subtracting 1, the number of terminal methyl groups in the main chain structure, from the obtained number of methyl groups. For example, a portion of the carboxylic acid used as a raw material for the production of the raw material zinc carboxylate (if the carboxylic acid forming the raw material zinc carboxylate consists of two or more carboxylic acids, then a mixture of those carboxylic acids) is taken, that is, the carboxylic acid before it is reacted with a zinc compound to form the raw material zinc carboxylate (if the carboxylic acid forming the raw material zinc carboxylate consists of two or more carboxylic acids, then a mixture of those carboxylic acids) is taken, 1It is calculated by analyzing with 1H-NMR and subtracting 1, the number of terminal methyl groups in the main chain structure, from the number of methyl groups obtained from the resulting NMR chart. Alternatively, for example, after taking a portion of the raw material zinc carboxylate before adding it to the core particle dispersion and adding a strong acid such as hydrochloric acid or nitric acid to separate the carboxylic acid of the manufacturing raw material, 1 It is calculated by analyzing with 1H-NMR and subtracting 1, the number of terminal methyl groups in the main chain structure, from the number of methyl groups obtained from the resulting NMR chart.

[0043] The raw material zinc carboxylate is obtained by the reaction of a carboxylic acid with a zinc raw material. Zinc carboxylate is generally produced by two methods: the direct method and the double decomposition method. In the present invention, either method may be used. The direct method is a method of obtaining a metal carboxylate by the direct reaction of a molten carboxylic acid with a metal oxide or metal hydroxide. On the other hand, the double decomposition method is a method of obtaining a metal carboxylate by the reaction of an aqueous solution of an alkali metal carboxylate with an inorganic metal salt. The raw material zinc carboxylate can be produced by either the direct method or the double decomposition method, but the zinc carboxylate produced by the direct method is more preferable because it is less likely for water to be mixed into the zinc carboxylate.

[0044] When preparing a zinc salt composed of two or more carboxylic acids, the carboxylic acids may be mixed beforehand to adjust the degree of branching, or the carboxylic acids may be mixed after preparation to adjust the degree of branching. However, from the viewpoint of manufacturability, it is preferable to mix the carboxylic acids beforehand. Furthermore, the zinc carboxylic acid salt may be prepared in a solvent used in the production of semiconductor nanoparticles.

[0045] In the shell formation step (1), the group VI element precursor added to the core particle dispersion, in other words, the group VI element precursor reacted with the zinc precursor, can be Se precursor, S precursor, or Te precursor. The group VI element precursor may be a single element or a combination of two or more elements, and it is preferable that it contains at least a Se precursor. That is, the group VI element precursor reacted with the zinc precursor may be a precursor of any one of the VI elements, such as only a Se precursor, or it may be a combination of precursors of two or more elements from the VI elements, such as a combination of a Se precursor and an S precursor, a combination of a Se precursor and a Te precursor, or a combination of a Se precursor, an S precursor, and a Te precursor.

[0046] In the shell formation step (1), the Se precursor is not particularly limited and examples include trialkylphosphine selenide and selenol. Trialkylphosphine selenide is preferred as the Se precursor. The Se precursor may be a single type or a combination of two or more types.

[0047] In the shell formation step (1), the S precursor is not particularly limited and examples include trialkylphosphine sulfides such as trioctylphosphine sulfide and tributylphosphine sulfide, thiols, and bis(trimethylsilyl) sulfides. Trioctylphosphine sulfide is preferred as the S precursor. The S precursor may be a single type or a combination of two or more types.

[0048] In the shell formation step (1), the Te precursor is not particularly limited, and examples include tellurated trioctylphosphine. Tellurated trioctylphosphine is preferred as the Te precursor. The Te precursor may be a single type or a combination of two or more types.

[0049] In the shell formation step (1), if only the Se precursor is used as the group VI element precursor, a shell layer containing zinc and Se is formed. If the Se precursor and S precursor are used in combination, a shell layer containing zinc, Se, and S is formed. If the Se precursor and Te precursor are used in combination, a shell layer containing zinc, Se, and Te is formed. If the Se precursor, S precursor, and Te precursor are used in combination, a shell layer containing zinc, Se, S, and Te is formed.

[0050] In the shell formation step (1), the method for forming a shell containing zinc and a group VI element on the surface of the core particles by adding the raw material zinc carboxylate and the group VI element precursor to the core particle dispersion and reacting the raw material zinc carboxylate and the group VI element precursor in the presence of the core particles is not particularly limited, and any method in which both the raw material zinc carboxylate and the group VI element precursor are added to the core particle dispersion and the reaction between the raw material zinc carboxylate and the group VI element precursor takes place in the presence of the core particles is acceptable.

[0051] Then, in the shell formation step (1), a zinc carboxylate raw material and a group VI element precursor are added to a dispersion of core particles, and the zinc carboxylate raw material and the group VI element precursor are reacted in the presence of the core particles to form a shell containing zinc and a group VI element on the surface of the core particles.

[0052] In the shell formation step (1), when the raw material zinc carboxylate and the group VI element precursor are added to the core particle dispersion, the temperature of the core particle dispersion is appropriately selected within the range of 180 to 320°C. By keeping the temperature of the core particle dispersion within the above range when reacting the raw material zinc carboxylate and the group VI element precursor, the added raw material zinc carboxylate and group VI element precursor can form a shell on the core particle in which non-luminescent recombination of excitons via defect levels is less likely to occur, thereby obtaining core / shell type semiconductor nanoparticles with excellent optical properties.

[0053] In the shell formation step (1), the addition time when the raw material zinc carboxylate is added to the core particle dispersion is appropriately selected within the range of 5 to 600 minutes. By having the addition time of the raw material zinc carboxylate solution or the raw material zinc carboxylate and group VI element precursor to the core particle dispersion be within the above range, the added shell precursor can efficiently form a shell on the core particle surface.

[0054] In the shell formation step (1), the addition time for adding the group VI element precursor to the core particle dispersion is appropriately selected within the range of 5 to 600 minutes. By having the addition time of the group VI element precursor solution or the group VI element precursor solution to the core particle dispersion be within the above range, the added shell precursor can efficiently form shells on the core particle surface.

[0055] In the shell formation step (1), the reaction between the raw material zinc carboxylate and the group VI element precursor can be carried out in the presence of a dispersant. Examples of dispersants to be present in the core particle dispersion include amines such as oleylamine and trioctylamine, carboxylic acids such as oleic acid, and thiols such as dodecanethiol. The amount of dispersant used is selected as appropriate, but is preferably 5 to 200 in molar ratio to In of the core particles, and more preferably 10 to 100 in molar ratio to In of the core particles.

[0056] In the shell formation step (1), the reaction between the raw material zinc carboxylate and the group VI element precursor can be carried out in the presence of a halogen precursor. The halogen precursor is not particularly limited and examples include carboxylic acid halides such as HF, HCl, HBr, HI, oleyl chloride, oleyl bromide, octanoyl chloride, and octinoyl bromide, and metal halides such as zinc chloride, indium chloride, and gallium chloride. The amount of halogen used is selected as appropriate, but is preferably 0.3 to 100.0 in molar ratio to In of the core particles, and more preferably 0.3 to 30.0 in molar ratio to In of the core particles. In the shell formation step (1), by presenting the halogen precursor in the dispersion of core particles, core / shell type semiconductor nanoparticles are obtained in which halogen is present on the surface of the core particles or in the shell layer.

[0057] In the shell formation step (1), in addition to the above, carboxylic acids, amines, thiols, phosphines, phosphine oxides, phosphines, phosphonic acids, etc. may be present in the dispersion of core particles as needed, and the reaction between the raw material zinc carboxylate and the group VI element precursor may be carried out.

[0058] In the method for producing core / shell type semiconductor nanoparticles of the present invention, the core particles used in the shell formation step (1) can be the core particles produced after the synthesis of the core particles without purification. In other words, core particles that have not undergone the purification step can be used as the core particles used in the shell formation step (1). To put it another way, the reaction solution in which the core particles after the synthesis of the core particles are dispersed can be used as the dispersion of core particles used in the shell formation step (1). In the shell formation step (1), a zinc salt of a carboxylic acid with a specific number of carbon atoms and degree of branching is used as a zinc precursor for the formation of the shell layer. The inventors surmise that because this zinc salt of carboxylic acid and the group VI element precursor react readily on the surface of the core particles, impurities in the dispersion medium are less likely to be incorporated into the shell layer during shell formation, and a shell with suppressed defect levels on the core surface can be formed. Therefore, core particles that have not undergone the purification step can be used as the core particles used in the shell formation step (1).

[0059] In the method for producing core / shell type semiconductor nanoparticles of the present invention, the shell formation step (1) is simple because it only requires adding the entire amount of the raw material zinc carboxylate and group VI element precursor used for shell formation to the core particle dispersion at once. Furthermore, in the method for producing core / shell type semiconductor nanoparticles of the present invention, by using a raw material zinc carboxylate, which is a zinc salt of a carboxylic acid with a specific number of carbon atoms and degree of branching, as the group II element precursor added to the core particle dispersion to react with the group VI element precursor on the surface of the core particles, core / shell type semiconductor nanoparticles with excellent optical properties can be obtained even if the entire amount of the group II element precursor and group VI element precursor are brought into contact with the core particles at once and reacted, without the need to separately and alternately bring the group II element precursor and group VI element precursor into contact multiple times. In particular, the method for producing core / shell type semiconductor nanoparticles of the present invention has the advantage of obtaining core / shell type semiconductor nanoparticles with excellent optical properties even if the entire amount of the group II element precursor and group VI element precursor are brought into contact with the core particles at once and reacted in the shell formation step (1).

[0060] The present invention provides a method for producing core / shell type semiconductor nanoparticles, in which, in the shell formation step (1), a group VI element precursor and a raw material zinc carboxylate are added to a dispersion of core particles, and the raw material zinc carboxylate reacts with the group VI element precursor. The raw material zinc carboxylate is a raw material zinc carboxylate in which the proportion of carboxylic acids with 8 to 10 carbon atoms in the total carboxylic acid forming the raw material zinc carboxylate is 80.0% by mass or more, preferably 85.0% by mass or more, more preferably 90.0% by mass or more, and particularly preferably 100.0% by mass, and the average branching degree of the total carboxylic acids forming the raw material zinc carboxylate is 1.1 to 2.9, preferably 1.3 to 2.7, and particularly preferably 1.5 to 2.5. This method provides a core / shell type semiconductor nanoparticle with a small full width at half maximum (FWHM) of the emission spectrum and high quantum efficiency (QY).

[0061] Generally, in the fabrication of core / shell type semiconductor nanoparticles, the emission peak wavelength λ max However, compared to core / shell type semiconductor nanoparticles for green light emission in the 500-560nm range, the emission peak wavelength λ max However, for core / shell type semiconductor nanoparticles used for red light emission in the 590-650 nm range, it is difficult to obtain core / shell type semiconductor nanoparticles with a small full width at half maximum (FWHM) of the emission spectrum and high quantum efficiency (QY) due to their large particle size.

[0062] In the method for producing core / shell type semiconductor nanoparticles of the present invention, in the shell formation step (1), a group VI element precursor and a raw material zinc carboxylate are added to a dispersion of core particles, and the raw material zinc carboxylate reacts with the group VI element precursor. The raw material zinc carboxylate is a raw material zinc carboxylate in which the proportion of carboxylic acids with 8 to 10 carbon atoms in the total carboxylic acid forming the raw material zinc carboxylate is 80.0% by mass or more, preferably 85.0% by mass or more, more preferably 90.0% by mass or more, and particularly preferably 100.0% by mass, and the average branching degree of the total carboxylic acids forming the raw material zinc carboxylate is 1.1 to 2.9, preferably 1.3 to 2.7, and particularly preferably 1.5 to 2.5, thereby achieving an emission peak wavelength λ maxIn the production of core / shell type semiconductor nanoparticles for red emission in the 590-650 nm range, core / shell type semiconductor nanoparticles with a small full width at half maximum (FWHM) and high quantum efficiency (QY) of the emission spectrum can be obtained. Although the mechanism is not clear, it is speculated that zinc salts of carboxylic acids with a specific number of carbon atoms and branching degree are easily arranged on the surface of the core particles of semiconductor nanoparticles, and that the reaction between the zinc salts of carboxylic acids with a specific number of carbon atoms and branching degree arranged on the surface of the core particles and group VI element precursors allows for the formation of a group II-VI shell on the surface of the core particles with suppressed defect level generation.

[0063] In the method for producing core / shell type semiconductor nanoparticles of the present invention, after performing the shell formation step (1), the generated core / shell type structure particles may be obtained as core / shell type semiconductor particles as the target product. Alternatively, the generated core / shell type particles may be used to perform one or more shell formation steps to obtain core / shell type semiconductor nanoparticles having two or more shell layers. In other words, the method for producing core / shell type semiconductor nanoparticles of the present invention may include, in addition to the shell formation step (1), one or more shell formation steps in which a shell is formed on the core / shell type particles containing zinc and group VI elements obtained by the shell formation step (1). A further shell formation step of one or more times may be the same as that of the shell formation step (1). That is, the shell formation step can be performed in the same way as the shell formation step (1), except that core / shell type particles having one or more shell layers formed on the surface of the core particles are used instead of core particles. Furthermore, a further shell formation step of one or more times may be a method other than that of the shell formation step (1).

[0064] For example, a method for manufacturing core / shell type semiconductor nanoparticles in which two layers of shells are formed on the surface of core particles can be described as a method for manufacturing core / shell type semiconductor nanoparticles, characterized by comprising: a shell formation step (1); and a shell formation step (2) in which a raw material zinc carboxylate and a group VI element precursor are added to a dispersion of "particles consisting of core particles and one layer of shell formed on the surface of the core particles" obtained by the shell formation step (1), thereby forming a shell containing zinc and a group VI element on the surface of the "particles consisting of core particles and one layer of shell formed on the surface of the core particles".

[0065] In the method for producing core / shell type semiconductor nanoparticles of the present invention, if the shell formation step (1) is performed once or more times after the shell formation step (1), a branched carboxylic acid derived from the zinc carboxylate raw material used as a zinc precursor in the shell formation step (1) is coordinated to the surface of the core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention. The branched carboxylic acid coordinated to the surface of the core / shell type semiconductor nanoparticles functions as a ligand to enhance the dispersibility of the core / shell type semiconductor nanoparticles in the dispersion medium.

[0066] Furthermore, a method for manufacturing core / shell type semiconductor nanoparticles in which (n+1) layers of shells are formed on the surface of core particles is provided, characterized by comprising: a shell formation step (1); and a shell formation step (x) which is repeated n times, in which raw material zinc carboxylate and a group VI element precursor are added to a dispersion of "particles consisting of core particles and one or more layers of shells formed on the surface of the core particles" obtained by the preceding shell formation step, and a shell containing zinc and a group VI element is formed on the surface of the "particles consisting of core particles and one or more layers of shells formed on the surface of the core particles".

[0067] In the method for producing core / shell type semiconductor nanoparticles of the present invention, when the shell formation step (1) is performed and then the shell formation step (x) is repeated one or more times, the surface of the core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention has carboxylic acids derived from the raw material zinc carboxylate used as a zinc precursor in the shell formation step (1) and the shell formation step (x) coordinated thereto. The carboxylic acids coordinated to the surface of the core / shell type semiconductor nanoparticles function as ligands that enhance the dispersibility of the core / shell type semiconductor nanoparticles in the dispersion medium.

[0068] In the core / shell type semiconductor nanoparticle manufacturing method of the present invention, the core / shell type semiconductor nanoparticles generated by the shell formation step can be purified. For example, by adding a polarity-reversing solvent such as acetone, the core / shell type semiconductor nanoparticles can be precipitated from the solution. The precipitated core / shell type semiconductor nanoparticles can then be recovered by filtration or centrifugation. Furthermore, the filtrate or supernatant containing unreacted starting materials and other impurities can be reused. Next, the recovered semiconductor nanoparticles can be washed with a further solvent and dissolved again. This purification operation can be repeated, for example, 2 to 4 times, or until the desired purity is reached. Other purification methods include, for example, flocculation, liquid-liquid extraction, distillation, electrodeposition, size exclusion chromatography, and ultrafiltration. These purification methods can be performed individually or in combination.

[0069] Furthermore, the surface of the core / shell type semiconductor nanoparticles obtained as described above may be modified with a ligand. Known methods such as ligand exchange can be used for ligand modification.

[0070] The core / shell type semiconductor nanoparticles obtained by the method for manufacturing core / shell type semiconductor nanoparticles of the present invention are particles with a core / shell structure having at least one shell layer. In the core / shell type semiconductor nanoparticles obtained by the method for manufacturing core / shell type semiconductor nanoparticles of the present invention, the shell layer formed on the surface of the core particle, that is, the first shell layer as viewed from the core particle side, is a shell layer formed by the shell formation step (1). In the core / shell type semiconductor nanoparticles obtained by the method for manufacturing core / shell type semiconductor nanoparticles of the present invention, the number of formed shell layers is at least one, preferably 1 to 4. When the core / shell type semiconductor nanoparticles obtained by the method for manufacturing core / shell type semiconductor nanoparticles of the present invention have two or more shell layers, the method for forming the second and subsequent shell layers as viewed from the core particle may be any method, but it is preferable to use a shell formation method that is the same as the shell layer formation step (1), except that the target for shell layer formation is a core / shell type particle on which one or more shell layers have been formed by the aforementioned shell layer formation step, instead of a core particle.

[0071] In the core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention, the core is preferably a core containing In and P from the viewpoint of obtaining semiconductor nanoparticles that have a low environmental impact and high optical properties.

[0072] The average particle size of the core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention is not particularly limited, but is preferably 1.0 to 20.0 nm, and particularly preferably 1.0 to 10.0 nm.

[0073] The core / shell semiconductor nanoparticles obtained by the method for producing core / shell semiconductor nanoparticles of the present invention have at least the carboxylic acid that formed the raw material zinc carboxylate coordinated to the core / shell semiconductor nanoparticles as a ligand. Furthermore, if the core / shell semiconductor nanoparticles are modified with a ligand, ligands other than the carboxylic acid derived from the raw material zinc carboxylate may also coordinate to the core / shell semiconductor nanoparticles. Therefore, the core / shell semiconductor nanoparticles obtained by the method for producing core / shell semiconductor nanoparticles of the present invention are core / shell semiconductor nanoparticle composites having core / shell semiconductor nanoparticles and ligands coordinated to the surface of the core / shell semiconductor nanoparticles, and contain at least a carboxylic acid derived from the raw material zinc carboxylate as a ligand. In addition, the shell of the core / shell semiconductor nanoparticles obtained by the method for producing core / shell semiconductor nanoparticles of the present invention contains at least zinc and selenium.

[0074] In other words, the core / shell type semiconductor nanoparticle composite of the present invention is a core / shell type semiconductor nanoparticle composite having core / shell type semiconductor nanoparticles and ligands coordinated to the surface of the core / shell type semiconductor nanoparticles, The aforementioned shell contains at least Zn, The ligand includes a carboxylic acid, Of the total carboxylic acids included as ligands, the proportion of carboxylic acids with 8 to 10 carbon atoms is 80.0% by mass or more. The average degree of branching of all carboxylic acids included as ligands is 1.1 to 2.9. This is a core / shell type semiconductor nanoparticle composite characterized by the above. Furthermore, the shell of the core / shell type semiconductor nanoparticle composite of the present invention may further include at least one of Se and S.

[0075] The core / shell type semiconductor nanoparticle composite of the present invention contains at least a carboxylic acid as a ligand. In the core / shell type semiconductor nanoparticle composite of the present invention, the proportion of carboxylic acids having 8 to 10 carbon atoms among the total carboxylic acids included as ligands is 80.0% by mass or more, preferably 85.0% by mass or more, more preferably 90.0% by mass or more, and particularly preferably 100.0% by mass. In the core / shell type semiconductor nanoparticle composite of the present invention, the average degree of branching of all carboxylic acids included as ligands is 1.1 to 2.9, preferably 1.3 to 2.7, and particularly preferably 1.5 to 2.5.

[0076] In the core / shell type semiconductor nanoparticle composite of the present invention, the proportion of carboxylic acid among the total ligands coordinated to the core / shell type semiconductor nanoparticle composite is preferably 1.0 to 15.0% by mass, and particularly preferably 1.0 to 8.0% by mass.

[0077] In the core / shell type semiconductor nanoparticle composite of the present invention, the shell precursor readily reacts on the surface of the core particles during the shell formation step (1), thus forming a shell on the core surface that suppresses the generation of defect levels. Therefore, the full width at half maximum (FWHM) of the emission spectrum of the core / shell type semiconductor nanoparticle composite of the present invention is preferably 37.0 nm or less, and particularly preferably 35.0 nm or less. Furthermore, the quantum efficiency (QY) of the core / shell type semiconductor nanoparticle composite of the present invention is preferably 90.0% or more, and particularly preferably 93.0% or more.

[0078] The core / shell semiconductor nanoparticles in the core / shell semiconductor nanoparticle composite of the present invention, that is, core / shell semiconductor nanoparticles to which a ligand is coordinated, are particles with a core / shell structure having at least one shell layer. In the core / shell semiconductor nanoparticles in the core / shell semiconductor nanoparticle composite of the present invention, the shell layer formed on the surface of the core particle, that is, the first shell layer as viewed from the core particle side, contains at least Zn and a group VI element (preferably Se or S). In the core / shell semiconductor nanoparticles in the core / shell semiconductor nanoparticle composite of the present invention, the number of shell layers formed is at least one, and preferably 1 to 4. When the core / shell semiconductor nanoparticles in the core / shell semiconductor nanoparticle composite of the present invention have two or more shell layers, the second and subsequent shell layers as viewed from the core particle preferably contain Zn and a group VI element, particularly preferably Zn and Se or S.

[0079] In the core / shell type semiconductor nanoparticle composite of the present invention, the core is preferably a core containing In and P from the viewpoint of obtaining semiconductor nanoparticles that have a low environmental impact and high optical properties.

[0080] <Measurement> Elemental analysis of semiconductor nanoparticles can be performed using an inductively coupled plasma emission spectrometer (ICP) or an X-ray fluorescence spectrometer (XRF). In ICP measurements, purified semiconductor nanoparticles are dissolved in nitric acid, heated, diluted with water, and measured using a calibration curve method with an ICP emission spectrometer (Shimadzu Corporation, ICPS-8100). In XRF measurements, a dispersion is impregnated into filter paper, placed in a sampling holder, and quantitative analysis is performed using an X-ray fluorescence spectrometer (Rigaku Corporation, ZSX100e).

[0081] Furthermore, the optical identification of semiconductor nanoparticles can be performed using a fluorescence quantum efficiency measurement system (Otsuka Electronics, QE-2100) and a visible ultraviolet spectrophotometer (JASCO, V-670). An emission spectrum is obtained by irradiating a dispersion of semiconductor nanoparticles in a dispersion medium with excitation light. The peak wavelength (λ) is then determined from the re-excitation corrected emission spectrum, which excludes the re-excitation fluorescence emission spectrum of the nanoparticles that have been re-excited and emitted fluorescence. max ), the fluorescence quantum efficiency (QY) and full width at half maximum (FWHM) are calculated. Examples of dispersion media include n-hexane, octadecene, toluene, acetone, and PGMEA. The excitation light used for measurement is a single light at 450 nm, and the dispersion is prepared by adjusting the concentration of semiconductor nanoparticles so that the absorption rate is 20-30%. On the other hand, the absorption spectrum can be measured by irradiating the dispersion of semiconductor nanoparticles in the dispersion medium with ultraviolet to visible light.

[0082] Furthermore, the ligands coordinated to core / shell type semiconductor nanoparticles can be identified and their mole fractions calculated using gas chromatography. Core / shell type semiconductor nanoparticles are introduced into a sample vaporization chamber, heated to over 350°C, and passed through a column with a carrier gas. The type and amount of each ligand are then identified from the retention time and peak area of ​​the signal obtained by the detector. From the obtained types and amounts of each ligand, the types and relative abundances of ligands coordinated to the core / shell type semiconductor nanoparticles can be calculated.

[0083] Furthermore, the configurations, methods, procedures, and processes described herein are illustrative and do not limit the present invention; numerous variations are applicable within the scope of the present invention.

[0084] The zinc carboxylate used in the production of semiconductor nanoparticles of the present invention is a zinc salt of a carboxylic acid. Of the total carboxylic acids forming the zinc salt of the carboxylic acid, the proportion of carboxylic acids having 8 to 10 carbon atoms is 80.0% by mass or more. The average degree of branching of the entire carboxylic acid that forms the zinc salt of the carboxylic acid is 1.1 to 2.9. This is a zinc carboxylate salt used in the manufacture of semiconductor nanoparticles characterized by [specific features].

[0085] The zinc carboxylate used in the production of semiconductor nanoparticles of the present invention is used for shell formation in the production of core / shell type semiconductor nanoparticles. The zinc carboxylate used in the production of semiconductor nanoparticles of the present invention is a zinc salt of a carboxylic acid, wherein the proportion of carboxylic acids having 8 to 10 carbon atoms in the total carboxylic acids forming the zinc carboxylate is 80.0% by mass or more, preferably 85.0% by mass or more, more preferably 90.0% by mass or more, and particularly preferably 100.0% by mass, and the average branching degree of the total carboxylic acids forming the zinc carboxylate is 1.1 to 2.9, preferably 1.3 to 2.7, and particularly preferably 1.5 to 2.5.

[0086] The present invention will be described below based on specific experimental examples, but the present invention is not limited to these. [Examples]

[0087] <Production of zinc carboxylate> Branched zinc carboxylates were prepared according to the following method. The carboxylic acids used were 3,5,5-trimethylhexanoic acid (reagent manufactured by Tokyo Chemical Industries, Ltd.; purity >98.0%), neodecanoic acid (reagent manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), 2-ethylhexanoic acid (reagent manufactured by Tokyo Chemical Industries, Ltd.; purity >99.0%), and decanoic acid (NAA-102 manufactured by NOF Corporation). The results of the analysis of the carbon number composition of each carboxylic acid are shown in Table 1, and the carboxylic acid blending ratios are shown in Table 2.

[0088] A carboxylic acid mixture was prepared by stirring neodecanoic acid (158 g, 0.91 mol), 2-ethylhexanoic acid (91.8 g, 0.64 mol), and decanoic acid (47.1 g, 0.27 mol) while heating at 40°C. The prepared carboxylic acid mixture and zinc oxide (58.8 g, 0.90 mol) were placed in a separable flask equipped with a moisture detector and stirred, then heated to 170°C under a nitrogen atmosphere. The generated water was removed from the moisture detector, and the mixture was held at 170°C for 2 hours. After vacuuming for 1 hour, the mixture was purged with nitrogen and cooled to room temperature (25°C) to obtain zinc carboxylate salt 1.

[0089] A carboxylic acid mixture was prepared by stirring 3,5,5-trimethylhexanoic acid (144 g, 0.91 mol) and neodecanoic acid (158 g, 0.91 mol) while heating at 40°C. The prepared carboxylic acid mixture and zinc oxide (58.8 g, 0.90 mol) were placed in a separable flask equipped with a moisture detector and stirred, then heated to 170°C under a nitrogen atmosphere. The generated water was removed from the moisture detector, and the mixture was held at 170°C for 2 hours. After vacuuming for 1 hour, the mixture was purged with nitrogen and cooled to room temperature (25°C) to obtain zinc carboxylate salt 2.

[0090] A carboxylic acid mixture was prepared by stirring 3,5,5-trimethylhexanoic acid (71.9 g, 0.45 mol) and neodecanoic acid (237 g, 1.36 mol) while heating at 40°C. The prepared carboxylic acid mixture and zinc oxide (58.8 g, 0.90 mol) were placed in a separable flask equipped with a moisture detector and stirred, then heated to 170°C under a nitrogen atmosphere. The generated water was removed from the moisture detector, and the mixture was held at 170°C for 2 hours. After vacuuming for 1 hour, the mixture was purged with nitrogen and cooled to room temperature (25°C) to obtain zinc carboxylate salt 3.

[0091] Neodecanoic acid (316 g, 1.82 mol) and zinc oxide (58.8 g, 0.90 mol) were placed in a separable flask equipped with a moisture detector and stirred, then heated to 170°C under a nitrogen atmosphere. The generated water was removed from the moisture detector, and the mixture was held at 170°C for 2 hours. After vacuuming for 1 hour, the mixture was purged with nitrogen and cooled to room temperature (25°C) to obtain zinc carboxylate 4.

[0092] A carboxylic acid mixture was prepared by stirring neodecanoic acid (261 g, 1.50 mol) and decanoic acid (54.6 g, 0.32 mol) while heating at 40°C. The prepared carboxylic acid mixture and zinc oxide (58.8 g, 0.90 mol) were placed in a separable flask equipped with a moisture detector and stirred, then heated to 170°C under a nitrogen atmosphere. The generated water was removed from the moisture detector, and the mixture was held at 170°C for 2 hours. After vacuuming for 1 hour, the mixture was purged with nitrogen and cooled to room temperature (25°C) to obtain zinc carboxylate salt 5.

[0093] A carboxylic acid mixture was prepared by stirring 3,5,5-trimethylhexanoic acid (95.8 g, 0.61 mol), 2-ethylhexanoic acid (17.8 g, 0.12 mol), and decanoic acid (188 g, 1.09 mol) while heating at 40°C. The prepared carboxylic acid mixture and zinc oxide (58.8 g, 0.90 mol) were placed in a separable flask equipped with a moisture detector and stirred, then heated to 170°C under a nitrogen atmosphere. The generated water was removed from the moisture detector, and the mixture was held at 170°C for 2 hours. After vacuuming for 1 hour, the mixture was purged with nitrogen and cooled to room temperature (25°C) to obtain zinc carboxylate salt 6.

[0094] 3,5,5-trimethylhexanoic acid (288 g, 1.82 mol) and zinc oxide (58.8 g, 0.90 mol) were placed in a separable flask equipped with a moisture detector and stirred, then heated to 170°C under a nitrogen atmosphere. The generated water was removed from the moisture detector, and the mixture was held at 170°C for 2 hours. After vacuuming for 1 hour, the mixture was purged with nitrogen and cooled to room temperature (25°C) to obtain zinc carboxylate salt 7.

[0095] Decanoic acid (316 g, 1.82 mol) and water (2000 g) were placed in a separable flask and heated to 60°C. Then, 48.0 wt% sodium hydroxide aqueous solution (154 g, 1.82 mol) was added and stirred for 20 minutes, after which 25.0 wt% zinc sulfate aqueous solution (650 g, 2.00 mol) was added dropwise over 60 minutes. After the addition was complete, the resulting zinc carboxylate slurry was filtered by suction and washed three times with 1000 g of water. The resulting cake was left to stand in a shelf dryer at 60°C for 36 hours, then cooled to room temperature (25°C) to obtain zinc carboxylate salt 8.

[0096] <Measurement of zinc carboxylate salts> The physical properties of zinc carboxylate salts 1-8 obtained above were measured. The results are shown in Table 3.

[0097] (C8-10 carboxylic acid ratio) The C8-10 carboxylic acid ratio (mass%) of zinc carboxylate salts 1-8 was calculated from the carbon number composition of the carboxylic acids in Table 1 and the carboxylic acid blending ratio in Table 2.

[0098] (Average branching rate) The average branching degree of zinc carboxylate salts 1-8 was calculated from the branching degree of carboxylic acids in Table 1 and the carboxylic acid blending ratios in Table 2.

[0099] (Metal content; Zn content) 0.1 g each of zinc carboxylate salts 1-8 were accurately weighed and heated in a porcelain crucible at 650°C for 4 hours to remove organic matter. 1 ml of hydrochloric acid was added to the residue to dissolve it, and water was added to make a total volume of 100 ml. This solution was used as a sample, and the metal content (Zn content) was measured by atomic absorption spectrophotometry.

[0100] (viscosity) Dynamic viscosity was measured for zinc carboxylate salts 1-8 using a dynamic viscoelasticity analyzer (Anton Paar, Modular Concept Rheometer MCR302). Zinc carboxylate was placed on the rheometer's hot plate and heated to 130°C, then kept warm with a sample cover. Dynamic viscosity was measured when sweeping from 1.0 rpm to 1000 rpm using a cone plate (CP25-2), and the viscosity at 130°C (Pa·s) at 150 rpm was calculated. Subsequently, the temperature was lowered to 50°C, and dynamic viscosity was measured again when sweeping from 1.0 rpm to 1000 rpm, and the viscosity at 50°C (Pa·s) at 150 rpm was calculated.

[0101] (Viscosity change rate) The viscosity change rate with respect to temperature was calculated by taking the difference between the viscosity at 130°C (Pa·s) and the viscosity at 50°C (Pa·s), dividing the result by the viscosity at 50°C (Pa·s), and raising the result to 100. Viscosity change rate (%) = ((Viscosity at 130°C (Pa·s) - Viscosity at 50°C (Pa·s)) / Viscosity at 50°C (Pa·s)) × 100

[0102] Semiconductor nanoparticles and semiconductor nanoparticle composites were fabricated according to the following method, and the optical properties of the obtained semiconductor nanoparticles and semiconductor nanoparticle composites were measured.

[0103] <Synthesis of core particles> Indium acetate (0.5 mmol), myristic acid (1.5 mmol), zinc myristate (0.2 mmol), and octadecene (10 mL) were placed in a two-necked flask. The flask was then evacuated and heated to 120°C under vacuum (<10 Pa). After the vacuum level dropped below 10 Pa, it was maintained for 30 minutes. Nitrogen was then introduced into the flask, and the mixture was cooled to room temperature (25°C) to obtain the In precursor. Furthermore, tris(trimethylsilyl)phosphine was mixed with tri-n-octylphosphine in a glove box under a nitrogen atmosphere to a molar concentration of 0.2 M to obtain a P precursor. Next, 2 mL of the P precursor was injected into the In precursor at room temperature (25 °C) under a nitrogen atmosphere, and the temperature was raised to 300 °C at a rate of 30 °C / min. After holding at 300 °C for 2 minutes, the reaction solution was cooled to room temperature to obtain a dispersion of InP core particles.

[0104] <Solution of zinc precursor> The zinc carboxylate salt and octadecene described in Table 2 were mixed so that the molar concentration of zinc was 0.3 M, evacuated at 100 °C for 1 hour, then purged with nitrogen and cooled to room temperature (25 °C) to obtain a solution of each zinc precursor.

[0105] <Solution of Se precursor> 100 mmol of powdered selenium and 50 mL of tri-n-octylphosphine were mixed under a nitrogen atmosphere and stirred until the selenium powder was completely dissolved to obtain a solution of the Se precursor.

[0106] <Solution of S precursor> 100 mmol of powdered sulfur and 50 mL of tri-n-octylphosphine were mixed under a nitrogen atmosphere and stirred until the sulfur powder was completely dissolved to obtain a solution of the S precursor.

[0107] <Production of core / shell semiconductor nanoparticles> (Example 1) 5 mL of trioctylamine was added to 10 mL of a dispersion of InP core particles (In: 0.4 mmol), and the temperature of the dispersion of InP core particles was raised to 230 °C. Then, when the dispersion of InP core particles reached 230 °C, 20 mL of the solution of the zinc precursor shown in Table 4 and 2.0 mL of the solution of the Se precursor were added within 1 minute, and the temperature of the dispersion of InP core particles was raised to 300 °C at a rate of 1 °C / min. Then, 180 minutes after the dispersion of InP core particles reached 300 °C, heating was terminated and cooled to room temperature (25 °C) to obtain a dispersion of core / shell semiconductor nanoparticles (reaction solution). Next, acetone was added to the resulting dispersion of core / shell semiconductor nanoparticles to cause aggregation of the semiconductor nanoparticles. Then, after centrifugation (4000 rpm, 10 minutes), the supernatant was removed, and the core / shell semiconductor nanoparticles were redispersed in hexane. This process was repeated to obtain purified core / shell semiconductor nanoparticles. The optical properties of the obtained core / shell semiconductor nanoparticles were measured. The results are shown in Table 5. For the measurement of the optical properties of semiconductor nanoparticles, a single excitation wavelength of 450 nm was used. The same method was used for the following measurements of the optical properties of semiconductor nanoparticles.

[0108] <Manufacturing of core / shell / shell semiconductor nanoparticles> (Examples 2-7, Comparative Examples 1-2) A dispersion (reaction solution) of core / shell semiconductor nanoparticles was obtained by following the same procedure as in each of the above examples or comparative examples. Next, the obtained dispersion (reaction solution) of core / shell semiconductor nanoparticles was heated to 300°C. After reaching 300°C, the zinc precursor solution shown in Table 4 was added to the dispersion (reaction solution) at a rate of 0.2 mL / min, and the Se precursor solution and S precursor solution were added at a rate of 0.03 mL / min simultaneously. The addition of both solutions was stopped simultaneously 100 minutes after the start of the addition (addition time: 100 minutes). Next, 180 minutes after the completion of the addition, heating was stopped, and the mixture was cooled to room temperature (25°C) to obtain the core / shell / shell semiconductor nanoparticle dispersion (reaction solution). Next, acetone was added to the resulting dispersion of core / shell / shell semiconductor nanoparticles to cause aggregation of the semiconductor nanoparticles. Then, after centrifugation (4000 rpm, 10 minutes), the supernatant was removed, and the core / shell / shell semiconductor nanoparticles were redispersed in hexane. This process was repeated to obtain purified core / shell / shell semiconductor nanoparticles. The optical properties of the obtained core / shell / shell semiconductor nanoparticles were measured. The results are shown in Table 5.

[0109] [Table 1]

[0110] Table 2

[0111] Table 3

[0112] Table 4

[0113] Table 5

Claims

1. The process includes a shell-forming step in which a zinc carboxylate raw material and a group VI element precursor are added to a dispersion of core particles, and the zinc carboxylate raw material and the group VI element precursor are reacted in the presence of the core particles to form a shell containing zinc and a group VI element on the surface of the core particles. Of the total carboxylic acids forming the zinc carboxylate raw material, the proportion of carboxylic acids having 8 to 10 carbon atoms is 80.0% by mass or more. The average degree of branching of the entire carboxylic acid forming the zinc carboxylic acid salt is 1.1 to 2.

9. A method for producing core / shell type semiconductor nanoparticles characterized by the above.

2. The method for producing core / shell type semiconductor nanoparticles according to claim 1, characterized in that the core particles contain In and P.

3. The method for producing core / shell type semiconductor nanoparticles according to claim 2, characterized in that the amount of the raw material zinc carboxylate added is such that the molar ratio of Zn in the raw material zinc carboxylate to In in the core particles (Zn / In) is 5 to 50.

4. A method for producing core / shell type semiconductor nanoparticles according to any one of claims 1 to 3, characterized in that the reaction between the raw material zinc carboxylate and the group VI element precursor is carried out in the presence of a halogen element.

5. A core / shell type semiconductor nanoparticle composite comprising core / shell type semiconductor nanoparticles and ligands coordinated to the surface of the core / shell type semiconductor nanoparticles, The aforementioned shell includes at least Zn, The ligand includes a carboxylic acid, Of the total carboxylic acids included as ligands, the proportion of carboxylic acids with 8 to 10 carbon atoms is 80% by mass or more. The average degree of branching of all carboxylic acids included as ligands is 1.1 to 2.

9. A core / shell type semiconductor nanoparticle composite characterized by the following.

6. The core / shell type semiconductor nanoparticle composite according to claim 5, characterized in that the core contains In and P.

7. The core / shell type semiconductor nanoparticle composite according to claim 5 or 6, characterized in that the emission peak wavelength of the core / shell type semiconductor nanoparticle composite is 590 to 650 nm.

8. The core / shell type semiconductor nanoparticle composite according to any one of claims 5 to 7, characterized in that the full width at half maximum (FWHM) of the emission spectrum of the core / shell type semiconductor nanoparticle composite is 37.0 nm or less.

9. The core / shell type semiconductor nanoparticle composite according to any one of claims 5 to 8, characterized in that the shell further comprises at least one of Se and S.

10. The core / shell type semiconductor nanoparticle composite according to any one of claims 5 to 9, characterized in that the quantum efficiency (QY) of the core / shell type semiconductor nanoparticle composite is 90.0% or higher.

11. The core / shell type semiconductor nanoparticle composite according to any one of claims 5 to 10, characterized in that the proportion of the carboxylic acid among all ligands coordinated to the core / shell type semiconductor nanoparticle composite is 1.0 to 15.0% by mass.

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