Zinc carboxylates used in the manufacture of semiconductor nanoparticles

Abstract

The present invention is a carboxylic acid zinc salt used in manufacturing semiconductor nanoparticles, the carboxylic acid zinc salt being characterized by: being a zinc salt of a carboxylic acid; the proportion of C8-10 carboxylic acid in the total carboxylic acid forming the zinc salt of a carboxylic acid being 80.0 wt.% or greater; and the average branching degree of the total carboxylic acid forming the zinc salt of a carboxylic acid being 1.1 to 2.9. The present invention is capable of providing a zinc salt that is used for manufacturing semiconductor nanoparticles having a core / shell structure having outstanding optical properties and is convenient when manufacturing semiconductor nanoparticles having a core / shell structure by using two or more types of shell precursors.

Description

Technical Field

[0001] The present invention relates to a zinc salt of carboxylic acid for producing semiconductor nanoparticles used for producing core / shell type semiconductor nanoparticles.

Background Art

[0002] As wavelength conversion materials for displays, semiconductor nanoparticles (quantum dots: QDs) 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. And excitons formed in 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 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 a group III-V core and a group II-VI shell, due to the difference in lattice constants, defect levels are easily 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, the linear zinc carboxylate described in Patent Document 1 does not form a sufficient shell when used as a zinc (Zn) precursor, making it insufficient for obtaining high optical properties. In addition, since the two types of shell precursors are brought into contact with the core separately and alternately multiple times, there is a problem in that the method for manufacturing semiconductor nanoparticles becomes complicated.

[0010] Therefore, the object of the present invention is to provide a zinc salt that can be used to produce core / shell semiconductor nanoparticles with excellent optical properties, which is simple to produce when using two or more 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) 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. the law of nature, The carboxylic acid is selected from at least one of 3,5,5-trimethylhexanoic acid, neodecanoic acid, 2-ethylhexanoic acid, and decanoic acid. Zinc carboxylate salt used for manufacturing semiconductor nanoparticles, characterized by composition Provided is

[0013] In addition, the present invention (2) provides a zinc carboxylate salt used for manufacturing semiconductor nanoparticles according to (1), characterized in that the average degree of branching of the whole carboxylic acid forming the zinc carboxylate salt is 1.3 to 2.7. composition Provided is

[0014] In addition, the present invention (3) provides a zinc carboxylate salt used for manufacturing semiconductor nanoparticles according to (1) or (2), characterized in that the proportion of carboxylic acids having 8 to 10 carbon atoms in the whole carboxylic acid forming the zinc carboxylate salt is 85.0% by mass or more. composition Provided is

[0015] In addition, the present invention (4) provides a zinc carboxylate salt used for manufacturing semiconductor nanoparticles according to any one of (1) to (3), characterized in that the viscosity change rate represented by the following formula (1) of the zinc carboxylate salt is 95.0 to 100.0%. composition Provided is General formula (1) Viscosity change rate (%) = ((viscosity at 130 °C (Pa·s) - viscosity at 50 °C (Pa·s)) / viscosity at 50 °C (Pa·s)) × 100 (1) (In the formula, the viscosity at 130 °C (Pa·s) is the value measured by a dynamic viscoelasticity measuring device at a temperature of 130 °C for the zinc carboxylate salt, and the viscosity at 50 °C is the value measured by a dynamic viscoelasticity measuring device at a temperature of 50 °C for the zinc carboxylate salt.)

Advantages of the Invention

[0016] According to the present invention, when manufacturing semiconductor nanoparticles with a core / shell structure using two or more types of shell precursors, it is possible to provide a zinc carboxylate salt that is simple to use and is used for manufacturing semiconductor nanoparticles with a core / shell structure having excellent optical properties.

Mode for Carrying Out the Invention

[0017] The zinc carboxylate of the present invention is such that, among the total carboxylic acids forming the zinc carboxylate, 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 total carboxylic acids forming the raw material zinc carboxylate is 1.1 to 2.9, and it is a zinc carboxylate used for the production of semiconductor nanoparticles, characterized in this way.

[0018] And the zinc carboxylate of the present invention is used for the production of semiconductor nanoparticles. That is, in a method for producing semiconductor nanoparticles having 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, it is used as the raw material zinc carboxylate.

[0019] In the following, the symbol "~" indicating a numerical range indicates a range including the numerical values described before and after the symbol "~" unless otherwise specified. That is, ○~△ represents ○ or more and △ or less.

[0020] 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.

[0021] 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.

[0022] 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).

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] The zinc carboxylate raw material for the shell formation step (1) is the zinc carboxylate salt of the present invention, a zinc precursor added to the core particle dispersion, and a zinc precursor that reacts with the element VI precursor in the shell formation step (1).

[0031] Of the total carboxylic acids forming the zinc carboxylate of the present invention, 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 of the present invention 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 of the present invention be within the above range, semiconductor nanoparticles with high optical properties can be obtained.

[0032] 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.

[0033] In the present invention, the proportion of carboxylic acids with 8 to 10 carbon atoms among the total carboxylic acids forming the zinc carboxylate of the present invention is determined by identifying the type and amount 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 acid used as a raw material for the production of the zinc carboxylate of the present invention (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 acid before reacting with a zinc compound to produce the zinc carboxylate of the present invention (a mixture of carboxylic acids if the carboxylic acids forming the zinc carboxylate of the present invention 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 type and amount of carboxylic acid are identified from the retention time and peak area of ​​the signal obtained by the detector. From the results, the proportion of carboxylic acids with 8 to 10 carbon atoms among the total carboxylic acids forming the zinc carboxylate of the present invention 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. The sample is then introduced into the sample vaporization chamber of a gas chromatography system, heated at 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 zinc carboxylate salt of the present invention can be calculated.

[0034] The average degree of branching of the entire carboxylic acid forming the zinc carboxylate of the present invention 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 forming the zinc carboxylate of the present invention when measured is 1.1 to 2.9, preferably 1.3 to 2.7, and particularly preferably 1.5 to 2.5. Having the average degree of branching of the entire carboxylic acid forming the zinc carboxylate within the above range results in high solubility in organic hydrocarbon solvents and improved workability. Furthermore, by using the zinc carboxylate of the present invention as a Zn precursor during the production of semiconductor nanoparticles, semiconductor nanoparticles with high optical properties can be obtained. It is believed that the semiconductor nanoparticles obtained have high optical properties because the average degree of branching within the above range allows the zinc carboxylate to have a certain bulk and react with precursors that form other shells on the surface of the core particles.

[0035] In this invention, the average degree of branching of the entire carboxylic acid forming the zinc carboxylate of the present invention represents the degree of branching of the alkyl group from the main chain of the carboxylic acid. First, the sample to be measured 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 zinc carboxylate of the present invention (if the carboxylic acid forming the zinc carboxylate of the present invention consists of two or more carboxylic acids, a mixture of those carboxylic acids) is taken, that is, the carboxylic acid before it is reacted with a zinc compound to produce the raw material zinc carboxylate (if the carboxylic acid forming the raw material zinc carboxylate consists of two or more carboxylic acids, 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, if a portion of the zinc carboxylate salt of the present invention is taken before being added to the core particle dispersion, and a strong acid such as hydrochloric acid or nitric acid is added 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.

[0036] The zinc carboxylate salt of the present invention is obtained by the reaction of a carboxylic acid with a zinc raw material. Zinc carboxylate salts are generally produced by two methods called the direct method and the double decomposition method, but either method may be used in the present invention. The direct method is a method of obtaining a metal carboxylate salt 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 salt by the reaction of an aqueous solution of an alkali metal carboxylate salt with an inorganic metal salt. The zinc carboxylate salt of the present invention may be produced by either the direct method or the double decomposition method, but the zinc carboxylate salt produced by the direct method is more preferable because it is less likely to be contaminated with water into the zinc carboxylate.

[0037] 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.

[0038] The zinc carboxylate salt of the present invention exhibits excellent dispersibility in solvents and solubility stability, with a viscosity change rate represented by the following formula (1) preferably being 95.0 to 100.0%, more preferably 97.0 to 100.0%, and particularly preferably 97.0% to 99.9%. General formula (1) Viscosity change rate (%) = ((Viscosity at 130°C (Pa·s) - Viscosity at 50°C (Pa·s)) / Viscosity at 50°C (Pa·s)) × 100 (1) (In the formula, the viscosity at 130°C (Pa·s) is the value measured by a dynamic viscoelasticity measuring device at a temperature of 130°C for zinc carboxylate, and the viscosity at 50°C is the value measured by a dynamic viscoelasticity measuring device at a temperature of 50°C for zinc carboxylate.)

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] In the method for producing semiconductor nanoparticles using zinc carboxylate salts 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).

[0053] In the method for producing semiconductor nanoparticles using zinc carboxylates 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 having to perform the operation of bringing the group II element precursor and group VI element precursor into contact separately and alternately 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).

[0054] The zinc carboxylate of the present invention has a proportion of carboxylic acids with 8 to 10 carbon atoms among the total carboxylic acids forming the zinc carboxylate of 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. By using this zinc carboxylate in the shell formation step (1), core / shell type semiconductor nanoparticles with a small full width at half maximum (FWHM) of emission spectrum and high quantum efficiency (QY) can be obtained.

[0055] 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.

[0056] In the method for producing semiconductor nanoparticles using the zinc carboxylate 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, i.e., the zinc carboxylate of the present invention, thereby achieving the 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.

[0057] In the method for producing semiconductor nanoparticles using zinc carboxylate salts of the present invention, after performing the shell formation step (1), the generated core / shell-type structured 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 semiconductor nanoparticles using zinc carboxylate salts 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 in the shell formation step (1). A further shell formation step of the same method as the shell formation step (1) can be performed. In other words, 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 the same method as the shell formation step (1) can be performed.

[0058] 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".

[0059] In the method for producing semiconductor nanoparticles using the zinc carboxylate 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 raw material zinc carboxylate 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 semiconductor nanoparticles using the zinc carboxylate 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.

[0060] 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".

[0061] In the method for producing semiconductor nanoparticles using the zinc carboxylate salt 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 carboxylic acid derived from the raw material zinc carboxylate salt used as a zinc precursor in the shell formation step (1) and shell formation step (x) is coordinated to the surface of the core / shell type semiconductor nanoparticles obtained by the method for producing semiconductor nanoparticles using the zinc carboxylate salt of the present invention. The 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.

[0062] <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).

[0063] 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, V670). 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.

[0064] 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.

[0065] 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.

[0066] The zinc salt 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 salt used in the manufacture of semiconductor nanoparticles characterized by [specific features].

[0067] The zinc salt 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 salt 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 salt of the carboxylic acid 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 degree of branching of the total carboxylic acids forming the zinc salt of the carboxylic acid is 1.1 to 2.9, preferably 1.3 to 2.7, and particularly preferably 1.5 to 2.5.

[0068] The present invention will be described below based on specific experimental examples, but the present invention is not limited to these. [Examples]

[0069] <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.

[0070] (Example 1) 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.

[0071] (Example 2) 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.

[0072] (Example 3) 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.

[0073] (Example 4) 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.

[0074] (Example 5) 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.

[0075] (Example 6) 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.

[0076] (Comparative Example 1) 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.

[0077] (Comparative Example 2) 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.

[0078] <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.

[0079] (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.

[0080] (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.

[0081] (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.

[0082] (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.

[0083] (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

[0084] 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.

[0085] <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 as the reaction solution.

[0086] <Solution of zinc precursor> The zinc carboxylate salt and octadecene described in Table 2 were mixed so that the molar concentration of zinc became 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.

[0087] <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.

[0088] <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.

[0089] <Production of core / shell semiconductor nanoparticles> (Example 7) 5 mL of trioctylamine was added to 10 mL of the 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 and 2.0 mL of the solution of the Se precursor shown in Table 4 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.

[0090] <Manufacturing of core / shell / shell semiconductor nanoparticles> (Examples 8-13, Comparative Examples 3-4) 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.

[0091] [Table 1]

[0092] Table 2

[0093] Table 3

[0094] Table 4

[0095] Table 5

Claims

1. It 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. The carboxylic acid is selected from at least one of 3,5,5-trimethylhexanoic acid, neodecanoic acid, 2-ethylhexanoic acid, and decanoic acid. A zinc carboxylate composition used in the manufacture of semiconductor nanoparticles characterized by the following.

2. The zinc carboxylic acid salt composition used in the production of semiconductor nanoparticles according to claim 1, characterized in that the average degree of branching of the entire carboxylic acid forming the zinc salt of the carboxylic acid is 1.3 to 2.

7.

3. The zinc carboxylate composition used for producing semiconductor nanoparticles according to claim 1 or 2, characterized in that the proportion of carboxylic acids having 8 to 10 carbon atoms among the total carboxylic acids forming the zinc salt of the carboxylic acid is 85.0% by mass or more.

4. A zinc carboxylic acid composition used in the production of semiconductor nanoparticles according to any one of claims 1 to 3, characterized in that the viscosity change rate of the zinc salt of the carboxylic acid represented by the following formula (1) is 95.0 to 100.0%. General formula (1) Viscosity change rate (%) = ((Viscosity at 130°C (Pa·s) - Viscosity at 50°C (Pa·s)) / Viscosity at 50°C (Pa·s)) × 100 (1) (In the formula, the viscosity at 130°C (Pa·s) is the value obtained by measuring the zinc carboxylate salt at a temperature of 130°C using a dynamic viscoelasticity measuring device, and the viscosity at 50°C is the value obtained by measuring the zinc carboxylate salt at a temperature of 50°C using a dynamic viscoelasticity measuring device.)

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