Method of producing core / shell semiconductor nanoparticles and semiconductor nanoparticle composite

Abstract

The method for manufacturing core / shell type semiconductor nanoparticles of the present invention is characterized by a shell formation step, wherein a zinc carboxylate salt and a group VI element precursor are added to a dispersion of core particles. In the presence of the core particles, the zinc carboxylate salt and the group VI element precursor react to form a shell containing zinc and a group VI element on the surface of the core particles. Furthermore, in the total carboxylic acids forming the zinc carboxylate salt, the proportion of carboxylic acids with 8 to 10 carbon atoms is 80.0% by mass or more; and the average branching degree of the total carboxylic acids forming the zinc carboxylate salt is 1.1 to 2.9. According to the present invention, a method for manufacturing core / shell type semiconductor nanoparticles that is simple and capable of producing core / shell type semiconductor nanoparticles with excellent optical properties can be provided when using two or more shell precursors to manufacture core / shell type semiconductor nanoparticles.

Description

Technical Field

[0001] This invention relates to a method for manufacturing core / shell type semiconductor nanoparticles and a semiconductor nanoparticle composite. Prior Technology

[0002] The wavelength conversion material of the display uses semiconductor nanoparticles (quantum dots: QDs) with tiny particle sizes. These semiconductor nanoparticles are tiny particles that can exhibit quantum confinement effects, and the band gap width is changed by utilizing the size of the nanoparticles. Then, excitons formed within the semiconductor particles through photoexcitation, charge injection, etc., recombine to release photons with energy matching the band gap. Therefore, by adjusting the crystal size of the semiconductor nanoparticles, the emission wavelength can be controlled, and the desired wavelength of light emission can be obtained.

[0003] Currently, most semiconductor nanoparticles use a core / shell structure. The reason for this is that by using a core / shell structure, it is possible to fill dangling bonds on the core surface and reduce surface defects.

[0004] This core / shell type semiconductor nanoparticle system uses semiconductor nanoparticles composed of a III-V group core and a II-VI group shell. However, due to the difference in lattice constants between the III-V group core and the II-VI group shell, defect levels are easily formed. Semiconductor nanoparticles with defect levels undergo non-luminescent recombination via excitons at these defect levels, thus easily resulting in degraded optical properties. Therefore, forming a II-VI group shell on the surface of the III-V group core to suppress the formation of defect levels is crucial.

[0005] The SILAR method is known as a method for forming a shell on the surface of core particles. The SILAR method involves alternately adding shell precursors to core particles, causing the added precursors to react on the particle surface, thereby forming the shell. For example, in core particles, a Zn precursor is added first, followed by a sulfur precursor, then another Zn precursor, then another sulfur precursor, and so on, so that the two shell precursors that become shell materials are alternately contacted with the core particles, forming alternating layers of the two shell precursors on the particle surface, and then allowing these two shell precursors to react, thereby forming the shell. Furthermore, Patent Document 1 describes that the Zn precursor system for shell formation uses zinc oleate, zinc hexanoate, zinc octanoate, zinc laurate, zinc palmitate, zinc stearate, zinc dithiocarbamate, etc. [Previous Technical Documents] [Patent Literature]

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

[0007] [Non-Patent Literature 1] Renguo Xie et al., J.AM.CHEM.SOC., 127, 7480-7488 (2005) [Non-Patent Literature 2] Ken-Tye Yong et al., ACS Nano, 3, 502-510 (2009) Summary of the Invention

[0008] (The problem the invention aims to solve)

[0009] However, in the SILAR method, the amount of precursor added must be strictly controlled when forming each precursor layer. If the amount of precursor added is too small, a sufficient shell cannot be formed, resulting in a decrease in optical properties. On the other hand, if the amount of precursor added is too large, problems such as particle deterioration or the generation of by-products may occur due to the excess amount of precursor.

[0010] Furthermore, since the two types of shell precursors are contacted with the particles separately and repeatedly, the manufacturing method of semiconductor nanoparticles tends to become more complicated.

[0011] Therefore, the purpose of this invention is to provide a method for manufacturing semiconductor nanoparticles that is simple and capable of producing semiconductor nanoparticles with excellent optical properties when using two or more shell precursors to manufacture core / shell type semiconductor nanoparticles. (Technical means to solve the problem)

[0012] Through in-depth research, the inventors discovered that, by using a zinc salt of a carboxylic acid with a specific number of carbon atoms and a high degree of branching, a group II element precursor added to a dispersion of core particles and reacting with a group VI element precursor on the surface of the core particles can still produce core / shell type semiconductor nanoparticles with excellent optical properties, even without performing the operation of separately and repeatedly alternating contact between the group II element precursor and the group IV element precursor, that is, by contacting the core particles and reacting with the total amount of the group II element precursor and the group VI element precursor at once. Thus, the present invention was completed.

[0013] That is, the present invention (1) provides a method for manufacturing core / shell type semiconductor nanoparticles, characterized by a shell forming step, wherein a zinc carboxylate salt and a group VI element precursor are added to a dispersion of core particles, and in the presence of the core particles, the zinc carboxylate salt and the group VI element precursor react to form a shell containing zinc and a group VI element on the surface of the core particles; and, Of all the carboxylic acids that form the zinc carboxylate salt of this raw material, the proportion of carboxylic acids with 8 to 10 carbon atoms is 80.0% by mass or more. The average branching degree of all carboxylic acids that form the zinc carboxylate salt of this raw material is 1.1 to 2.9.

[0014] Furthermore, the present invention (2) provides a method for manufacturing core / shell type semiconductor nanoparticles as in (1), wherein the core particles contain In and P.

[0015] Furthermore, the present invention (3) provides a method for manufacturing core / shell type semiconductor nanoparticles as in (1) or (2), wherein the amount of the above-mentioned raw material zinc carboxylate salt added is calculated as the molar ratio (Zn / In) of Zn in the above-mentioned raw material zinc carboxylate salt to In in the above-mentioned core particles, which is 5 to 50.

[0016] Furthermore, the present invention (4) provides a method for manufacturing core / shell type semiconductor nanoparticles as described in any of (1) to (3), wherein the reaction of the above-mentioned raw material zinc carboxylate salt with the above-mentioned group VI element precursor is carried out in the presence of halogen elements.

[0017] Furthermore, the present invention (5) provides a core / shell type semiconductor nanoparticle composite, comprising: core / shell type semiconductor nanoparticles and ligands disposed on the surface of the core / shell type semiconductor nanoparticles; characterized in that, The aforementioned outer shell contains at least Zn; Carboxylic acids are present as the ligands mentioned above; Of the total carboxylic acids contained as ligands, the proportion of carboxylic acids with 8 to 10 carbon atoms is 80% or more by mass; The average branching degree of the total carboxylic acids contained in the ligands is 1.1 to 2.9.

[0018] Furthermore, the present invention (6) provides a core / shell type semiconductor nanoparticle composite as in (5), wherein the core contains In and P.

[0019] Furthermore, the present invention (7) provides a core / shell type semiconductor nanoparticle composite as in (5) or (6), wherein the emission peak wavelength of the core / shell type semiconductor nanoparticle composite is 590~650nm.

[0020] Furthermore, the present invention (8) provides a core / shell type semiconductor nanoparticle composite as described in any one of (5) to (7), wherein the half width at half maximum (FWHM) of the emission spectrum of the core / shell type semiconductor nanoparticle composite is less than 37.0 nm.

[0021] Furthermore, the present invention (9) provides a core / shell type semiconductor nanoparticle composite as described in any one of (5) to (8), wherein the shell further contains at least one of Se and S.

[0022] Furthermore, the present invention (10) provides a core / shell type semiconductor nanoparticle composite as described in any one of (5) to (9), wherein the quantum efficiency (QY) of the core / shell type semiconductor nanoparticle composite is 90.0% or higher.

[0023] Furthermore, the present invention (11) provides a core / shell type semiconductor nanoparticle composite as described in any one of (5) to (10), wherein the proportion of the carboxylic acid in the total ligand of the core / shell type semiconductor nanoparticle composite is 1.0 to 15.0 by mass. (Compared to the effectiveness of previous technologies)

[0024] According to the present invention, a method for manufacturing semiconductor nanoparticles with excellent optical properties is provided, which is simple to manufacture core / shell type semiconductor nanoparticles when using two or more shell precursors to manufacture core / shell type semiconductor nanoparticles. Implementation

[0025] The method for manufacturing core / shell type semiconductor nanoparticles of the present invention includes a shell formation step (hereinafter also referred to as "shell formation step (1)"). This shell formation step involves adding zinc carboxylate and a group VI element precursor to a dispersion of the core particles. In the presence of the core particles, the zinc carboxylate and the group VI element precursor react to form a shell containing zinc and a group VI element on the surface of the core particles. Of all the carboxylic acids that form the zinc carboxylate salt of this raw material, the proportion of carboxylic acids with 8 to 10 carbon atoms is 80% or more by mass; The average branching degree of all carboxylic acids that form the zinc carboxylate salt of this raw material is 1.1 to 2.9.

[0026] Additionally, the symbol "~" used to indicate a range of values, unless otherwise specified, refers to the range including the values ​​recorded before and after the symbol "~". That is, "〇~△" means above 0 and below △.

[0027] The method for manufacturing core / shell type semiconductor nanoparticles of the present invention includes a shell forming step (1). Moreover, the shell forming step (1) involves adding at least a zinc carboxylate salt and a group VI element precursor to a dispersion of core particles, and reacting the zinc carboxylate salt and the group VI element precursor in the presence of core particles, thereby forming a shell containing zinc and a group VI element on the surface of the core particles.

[0028] In the shell formation step (1), the core particles used to form the shell layer are not particularly limited as long as they are core particles used as core / shell type semiconductor nanoparticles. Preferably, they are core particles containing In and P, and even more preferably, they are core particles containing In, P, and halogens. From the viewpoint of low environmental impact and obtaining semiconductor nanoparticles with high optical properties, core particles containing In and P are preferred. Furthermore, from the viewpoint of improving the optical properties of both the core particles and the semiconductor nanoparticles, core particles containing halogens are preferred. Examples of halogens contained in the core particles include F, Cl, Br, and I. Among these, from the viewpoint of narrowing the half-width, halogens Cl and Br are preferred. In addition, the core particles may also contain other elements such as Ga, Al, Zn, N, S, Si, and Ge.

[0029] The Cd content of the core particles is below 100 ppm by mass, below 80 ppm by mass for better quality, and below 50 ppm by mass for exceptional quality.

[0030] There is no particular limitation on the average particle size of the core particles, but it is preferably 1.0 nm to 5.0 nm. By ensuring that the average particle size of the core particles is within the above range, the 450 nm excitation light can be converted into green to red light emission. In addition, in this invention, the "average particle size of the core particles" is calculated based on the particle image observed using a transmission electron microscope (TEM), by calculating the particle size of 10 or more particles according to the equivalent area circle diameter (Heywood diameter).

[0031] There are no particular limitations on the method for synthesizing core particles; any appropriate method can be selected. In this invention, the In precursor, P precursor, and halogen precursor are as follows.

[0032] There are no particular limitations on the precursors of indium, and examples include: indium acetate, indium propionate, indium myristate, indium oleate and other indium carboxylate; indium fluoride, indium bromide and indium iodide and other indium halides; indium thiolate, trialkyl indium, etc.

[0033] There are no particular limitations on the phosphorus precursor, and examples include: trimethylsilylphosphine, trimethylgermanylphosphine, dimethylaminophosphine, diethylaminophosphine, dioctylaminophosphine, trialkylphosphine, and pH 3 gas. Furthermore, when using trimethylsilylphosphine as the phosphorus precursor, Si may be embedded within the semiconductor nanoparticles, but this does not hinder the function of the present invention.

[0034] There are no particular limitations on halogen precursors; examples include carboxylic acid halides such as HF, HCl, HBr, HI, oleyl chloride, oleyl bromide, octyl chloride, octyl bromide, and oleyl chloride; and metal halides such as zinc chloride, indium chloride, and gallium chloride.

[0035] The following are examples of methods for synthesizing core particles containing In and P. However, the methods described below are illustrative, and the synthesis of core particles is not limited to those described. Core particles are synthesized, for example, by reacting an In precursor with a P precursor. First, the In precursor is mixed with a solvent. If necessary, the In precursor solution with added dispersant and / or additives is mixed under vacuum or nitrogen. After temporarily heating at 100–300°C for 6–24 hours, the P precursor is added, and the mixture is heated at 200–400°C for a few seconds (e.g., 2 or 3 seconds) to 60 minutes, followed by cooling, thereby obtaining a core particle dispersion containing the core particles. Next, a halogen precursor is added to the core particle dispersion, and the mixture is heated at 25–350°C for a few seconds (e.g., 2 or 3 seconds) to 60 minutes, followed by cooling, thereby obtaining a halogen-added core particle dispersion in which a portion of the particle surface has halogen.

[0036] There are no particular limitations on dispersants; examples include carboxylic acids, amines, thiols, phosphine derivatives, phosphine oxides, phosphine, and phosphonic acids. Dispersants can also function as solvents. There are no particular limitations on solvents; examples include 1-octadecene, hexadecane, squalane, oleylamine, trioctylphosphine, and trioctylphosphine oxide. Additives can include, for example, the aforementioned sulfur precursors, zinc precursors, and halogen precursors.

[0037] The core particle dispersion in the shell forming step (1) is a dispersion in which the core particles are dispersed in a dispersion medium. There are no particular limitations on the dispersion medium in which the core particles are dispersed, and examples include: 1-octadecene, hexadecane, squalane, squalene, mineral oil, liquid paraffin, trioctylamine, trioctylphosphine, trioctylphosphine oxide, toluene, hexane, diphenyl ether, etc. One of these can be used alone or two or more can be used in combination. It is preferred to select at least one from the group consisting of 1-octadecene, hexadecane, squalane, squalene, mineral oil and liquid paraffin.

[0038] The zinc carboxylate raw material in the shell forming step (1) is a zinc precursor added to the core particle dispersion, and is a zinc precursor that reacts with the VI element precursor in the shell forming step (1).

[0039] In the total carboxylic acids forming the zinc carboxylate raw material, the proportion of carboxylic acids with 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 especially preferably 100.0% by mass. That is, the proportion of carboxylic acids with 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 especially preferably 100.0% by mass. By ensuring that the proportion of carboxylic acids with 8 to 10 carbon atoms in the total carboxylic acids forming the zinc carboxylate raw material is within the above-mentioned range, semiconductor nanoparticles with high optical properties can be obtained.

[0040] Examples of carboxylic acids with 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 degree of branching. Ideally, 2-ethylhexanoic acid, isononanoic acid, and neodecanoic acid are used as the main components, and two or more carboxylic acids are used in combination.

[0041] In this invention, the proportion of carboxylic acids with 8 to 10 carbon atoms in the total carboxylic acids forming the zinc carboxylate raw material is determined by using a gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-mass spectrometry (LC-MS) to identify the types and amounts of carboxylic acids, and then calculating the proportion based on the measurement results. For example, when analyzing the carboxylic acids used in the production of the zinc carboxylate raw material (in the case where the carboxylic acids forming the zinc carboxylate raw material are composed of two or more carboxylic acids, it is a mixture of such carboxylic acids), i.e., the carboxylic acids before reacting with zinc compounds to form the zinc carboxylate raw material (in the case where the carboxylic acids forming the zinc carboxylate raw material are composed of two or more carboxylic acids, it is a mixture of such carboxylic acids), a portion of the carboxylic acid is subjected to methyl esterification, introduced into the GC-MS, heated to above 350°C, and passed through a column along with a carrier gas. The type and amount of carboxylic acids are identified by the residence time and peak area of ​​the signal obtained by the detector. Based on the results, the proportion of carboxylic acids with 8 to 10 carbon atoms in the total carboxylic acids forming the zinc carboxylate raw material can be calculated. For example, a portion of the zinc carboxylate salt used as raw material before being added to the core particle dispersion is treated with strong acids such as hydrochloric acid and nitric acid. After separating the carboxylic acid, it undergoes methylation treatment and is introduced into the sample vaporization chamber of a gas chromatograph. It is heated to above 350°C and passes through the column with the carrier gas. The type and amount of carboxylic acid are identified based on the residence time and peak area of ​​the signal obtained by the detector. Based on the results, the proportion of carboxylic acids with 8 to 10 carbon atoms in the total carboxylic acids that form the zinc carboxylate salt can be calculated.

[0042] The average branching degree of all carboxylic acids forming the zinc carboxylate raw material is 1.1~2.9, preferably 1.3~2.7, and particularly preferably 1.5~2.5. That is, the average branching degree of the total carboxylic acids in the zinc carboxylate raw material is 1.1~2.9, preferably 1.3~2.7, and particularly preferably 1.5~2.5. By ensuring that the average branching degree of all carboxylic acids forming the zinc carboxylate raw material is within the above range, the solubility in organic hydrocarbon solvents is high, workability is improved, and in the manufacture of semiconductor nanoparticles, by using the zinc carboxylate of this invention as a Zn precursor, semiconductor nanoparticles with high optical properties can be obtained. The reason for this is that with an average branching degree within the above range, the zinc carboxylate has a certain volume, allowing it to react with other shell-forming precursors on the surface of the core particles.

[0043] In this invention, the average branching degree of all carboxylic acids forming the zinc carboxylic acid salt is defined as the branching degree of the alkyl group from the main chain of the carboxylic acid. First, the sample is analyzed using a gas chromatograph or similar instrument, and the average molecular weight (14n+32) of the carboxylic acid is calculated from the obtained composition ratio. The sample is then analyzed using 1H-NMR. From the obtained NMR chromatogram, the integral value of the chemical shifts of the hydrogen atoms representing all alkyl chains of the carboxylic acid is set as 2n-1, and the integral value of the chemical shifts of the hydrogen atoms representing the primary carbons (δ = 0.7~1.1 ppm) divided by 3 is defined as the number of methyl groups in the carboxylic acid. The branching degree is calculated by subtracting 1 from the number of terminal methyl groups belonging to the main chain structure from the obtained number of methyl groups. For example, a portion of the carboxylic acid used in the production of zinc carboxylate (in the case where the carboxylic acid forming the zinc carboxylate is composed of two or more carboxylic acids, it is a mixture of such carboxylic acids), specifically the carboxylic acid before it reacts with a zinc compound to form the zinc carboxylate (in the case where the carboxylic acid forming the zinc carboxylate is composed of two or more carboxylic acids, it is a mixture of such carboxylic acids), is analyzed using 1H-NMR. The result is calculated by subtracting 1 from the number of terminal methyl groups belonging to the main chain structure from the number of methyl groups obtained. Alternatively, for example, a portion of the zinc carboxylate used in the production of zinc carboxylate is taken before it is added to the core particle dispersion. After separating the carboxylic acid used in the production process by adding strong acids such as hydrochloric acid or nitric acid, the result is analyzed using 1H-NMR. The result is calculated by subtracting 1 from the number of terminal methyl groups belonging to the main chain structure from the number of methyl groups obtained.

[0044] The zinc carboxylate salt is obtained by reacting carboxylic acid with zinc. Zinc carboxylate salts are generally manufactured using either the direct method or the metathesis method; either method can be used in this invention. The direct method involves the direct reaction of molten carboxylic acid with a metal oxide or metal hydroxide to obtain the metal carboxylate salt. Conversely, the metathesis method involves the reaction of an aqueous solution of an alkali metal carboxylate salt with an inorganic metal salt to obtain the metal carboxylate salt. The zinc carboxylate salt can be prepared using either the direct method or the metathesis method; however, from the viewpoint that moisture is less likely to contaminate the zinc carboxylate, the direct method is preferred.

[0045] When preparing zinc salts composed of two or more carboxylic acids, carboxylic acids with known branching degrees can be pre-mixed and the branching degree adjusted before preparation. Alternatively, the branching degree can be adjusted after the zinc carboxylic acid is prepared. From a manufacturing point of view, pre-mixing the carboxylic acids is preferable. Furthermore, zinc carboxylic acid salts can also be prepared using the solvents used in the fabrication of semiconductor nanoparticles.

[0046] 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 that reacts with the zinc precursor, can be, for example, a Se precursor, a S precursor, or a Te precursor. The group VI element precursor can be used alone or in combination with two or more, preferably containing at least a Se precursor. That is, the group VI element precursor that reacts with the zinc precursor is, for example, a precursor of any one of the VI elements such as the Se precursor, or a combination of precursors of two or more of the VI elements, such as in combination with the Se precursor and the S precursor, in combination with the Se precursor and the Te precursor, or in combination with the Se precursor, the S precursor, and the Te precursor.

[0047] In the shell formation step (1), there are no particular restrictions on the Se precursor, and examples include: trialkylphosphine selenide, selenool, etc. Trialkylphosphine selenide is preferred as the Se precursor. One Se precursor can be used alone, or two or more can be used in combination.

[0048] In the shell formation step (1), there are no particular restrictions on the S precursor, and examples include: trioctylphosphine sulfide, tributylphosphine sulfide, and other trialkylphosphine sulfides; thiols, bis(trimethylsilyl) sulfides, etc. The S precursor is preferably trioctylphosphine sulfide. One type of S precursor can be used alone, or two or more types can be used in combination.

[0049] In the shell formation step (1), there are no particular restrictions on the Te precursor, such as trioctylphosphine telluride. Trioctylphosphine telluride is preferred as the Te precursor. One Te precursor can be used alone, or two or more can be used in combination.

[0050] In the shell formation step (1), as a Group VI element precursor, when only the Se precursor is used, a shell layer containing zinc and Se is formed. Furthermore, when both the Se and S precursors are used, a shell layer containing zinc, Se, and S is formed. Also, when both the Se and Te precursors are used, a shell layer containing zinc, Se, and Te is formed. Finally, when the Se, S, and Te precursors are used, a shell layer containing zinc, Se, S, and Te is formed.

[0051] In the shell formation step (1), zinc carboxylate and group VI element precursors are added to the dispersion of core particles. In the presence of core particles, the zinc carboxylate and group VI element precursors react to form a shell containing zinc and group VI elements on the surface of the core particles. There are no particular restrictions on the method, as long as the zinc carboxylate and group VI element precursors are added to the dispersion of core particles and the reaction between the zinc carboxylate and group VI element precursors is carried out in the presence of core particles.

[0052] Moreover, in the shell formation step (1), zinc carboxylate and group VI element precursors are added to the dispersion of the core particles. In the presence of the core particles, the zinc carboxylate and group VI element precursors react to form a shell containing zinc and group VI elements on the surface of the core particles.

[0053] In the shell formation step (1), when adding zinc carboxylate and group VI element precursors to the dispersion of core particles, the temperature of the dispersion of core particles is appropriately selected within the range of 180~320°C. By keeping the temperature of the core particle dispersion within the above range when the zinc carboxylate and group VI element precursors react, the added zinc carboxylate and group VI element precursors can form a shell on the core particles that is not prone to non-luminescent recombination via excitons at defect sites, thus obtaining core / shell type semiconductor nanoparticles with excellent optical properties.

[0054] In the shell formation step (1), the addition time of the zinc carboxylate raw material to the dispersion of the core particles is appropriately selected within the range of 5 to 600 minutes. By using a solution of the zinc carboxylate raw material, or a solution of the zinc carboxylate raw material and a Group VI element precursor, and adding it to the dispersion of the core particles within the above range, the added shell precursor can efficiently form a shell on the surface of the core particles.

[0055] In the shell formation step (1), the addition time of the group VI element precursor in the dispersion of the core particles is appropriately selected within the range of 5 to 600 minutes. By using a solution of group VI element precursor or a solution of group VI element precursor in the dispersion of core particles within the above range, the added shell precursor can efficiently form a shell on the surface of the core particles.

[0056] In the shell formation step (1), the reaction between the zinc carboxylate salt and the Group VI element precursor can be carried out in the presence of a dispersant. Examples of dispersants present in the core particle dispersion include amines such as oleylamine and trioctylamine; carboxylic acids such as oleic acid; and thiols such as dodecyl mercaptan. The amount of dispersant used can be appropriately selected; preferably, the molar ratio of the dispersant to In relative to the core particles is 5-200, and more preferably, it is 10-100.

[0057] In the shell formation step (1), the reaction between the zinc carboxylate salt and the Group VI element precursor can be carried out in the presence of a halogen precursor. There are no particular limitations on the halogen precursor; examples include carboxylic acid halides such as HF, HCl, HBr, HI, oleyl chloride, oleyl bromide, octyl chloride, and octyl bromide; and metal halides such as zinc chloride, indium chloride, and gallium chloride. The amount of halogen used is appropriately selected; preferably, the molar ratio of halogen to In relative to the core particles is 0.3 to 100.0, and more preferably, the molar ratio is 0.3 to 30.0. In the shell formation step (1), by presenting the halogen precursor in the dispersion of the core particles, core / shell type semiconductor nanoparticles containing halogen on the surface of the core particles or in the shell layer can be obtained.

[0058] In the shell formation step (1), in addition to the above, carboxylic acids, amines, thiols, phosphines, phosphine oxides, phosphine, phosphonic acids, etc., may also be present in the dispersion of the core particles as needed, and then the reaction of the raw material zinc carboxylic acid salt with the group VI element precursor is carried out.

[0059] In the method for manufacturing core / shell type semiconductor nanoparticles of the present invention, the core particles used in the shell forming step (1) can be used without refining the generated core particles after the core particles are synthesized. That is, the core particles used in the shell forming step (1) can be core particles that have not undergone a refining step. In other words, the reaction solution containing the core particles after the core particles have been synthesized can be used as the core particle dispersion solution used in the shell forming step (1). In the shell forming step (1), when the shell layer is formed, a zinc salt of carboxylic acid with a specific number of carbon atoms and a branching degree is used as a zinc precursor. The inventors of this invention speculate that since the zinc salt of carboxylic acid and the group VI element precursor react easily on the surface of the core particles, impurities in the dispersion medium are not easily taken into the shell layer during shell formation, and a shell that suppresses the occurrence of defect levels can be formed on the core surface. Therefore, the core particles used in the shell forming step (1) can be core particles that have not undergone a refining step.

[0060] In the method for manufacturing core / shell type semiconductor nanoparticles of the present invention, since the shell layer is formed in the shell formation step (1), only the total amount of zinc carboxylate salt and group VI element precursor used for shell formation is added to the dispersion of core particles at one time, it is simple. Moreover, in the method for manufacturing core / shell type semiconductor nanoparticles of the present invention, as the group II element precursor added to the dispersion of core particles and reacting with the group VI element precursor on the surface of core particles, the zinc carboxylate salt is used as the raw material zinc carboxylate salt with a specific number of carbon atoms and branching degree. Therefore, even if the operation of contacting the group II element precursor and the group VI element precursor separately and repeatedly is not performed, that is, even if the total amount of group II element precursor and group VI element precursor is contacted with the core particles at one time and reacted, core / shell type semiconductor nanoparticles with excellent optical properties can still be obtained. In particular, the method for manufacturing core / shell type semiconductor nanoparticles of the present invention can improve the effect of obtaining core / shell type semiconductor nanoparticles with excellent optical properties even if the total amount of group II element precursor and group VI element precursor is brought into contact with the core particle and reacted at once in the shell formation step (1).

[0061] The method for manufacturing core / shell type semiconductor nanoparticles of the present invention involves adding a group VI element precursor and a raw material zinc carboxylate to a dispersion of core particles in the shell formation step (1). The raw material zinc carboxylate reacts with the group VI element precursor. The raw material zinc carboxylate is configured such that the proportion of carboxylic acids with 8 to 10 carbons in all carboxylic acids 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. Furthermore, the average branching degree of all 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 yields core / shell type semiconductor nanoparticles with a small half-width (FWHM) and high quantum efficiency (QY) in the emission spectrum.

[0062] Generally speaking, in the manufacture of core / shell semiconductor nanoparticles, compared with green luminescent core / shell semiconductor nanoparticles with a emission peak wavelength λmax of 500~560nm, red luminescent core / shell semiconductor nanoparticles with an emission peak wavelength λmax of 590~650nm have a larger particle size, making it difficult to obtain core / shell semiconductor nanoparticles with a small half-width (FWHM) and high quantum efficiency (QY) in the emission spectrum.

[0063] In the method for manufacturing 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 the dispersion of core particles, and the raw material zinc carboxylate reacts with the group VI element precursor. The raw material zinc carboxylate is set such that the proportion of carboxylic acids with 8 to 10 carbons in all carboxylic acids 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 especially preferably 100.0% by mass, and the average branching degree of all carboxylic acids forming the raw material zinc carboxylate is 1.1 to 2.9, preferably 1.3 to 2.7, and especially preferably 1.5 to 2.5. In this way, even in the manufacturing of red luminescent core / shell type semiconductor nanoparticles with a emission peak wavelength λmax of 590 to 650 nm, core / shell type semiconductor nanoparticles with a small half-width (FWHM) of emission spectrum and high quantum efficiency (QY) can still be obtained. Although the mechanism is not yet clear, it can be inferred that zinc salts of carboxylic acids with specific carbon numbers and branching degrees are easily configured on the surface of the core particles of semiconductor nanoparticles. The zinc salts of carboxylic acids with specific carbon numbers and branching degrees configured on the surface of the core particles react with group VI element precursors, thereby forming a II-VI system shell on the surface of the core particles that suppresses the occurrence of defect levels.

[0064] In the method for manufacturing core / shell type semiconductor nanoparticles of the present invention, core / shell type semiconductor particles can be obtained as the target product after performing the shell formation step (1), or the generated core / shell type structure particles can be further used to perform one or more shell formation steps to obtain core / shell type semiconductor nanoparticles with two or more shells. That is, in addition to the shell formation step (1), the method for manufacturing core / shell type semiconductor nanoparticles of the present invention can also have one or more shell formation steps to form a shell on the core / shell type particles containing zinc and group VI elements obtained by performing the shell formation step (1). Furthermore, performing one or more shell formation steps can be, for example, the same method as the shell formation step (1) described above. That is, except for using core / shell type particles with one or more shells already formed on the surface of the core particles to replace the core particles, the shell formation steps can be performed in the same way as the shell formation step (1). Furthermore, as a further step of performing one or two or more shell forming steps, it may be a method other than the same as the shell forming step (1) described above.

[0065] For example, a method for manufacturing core / shell type semiconductor nanoparticles with two shells formed on the surface of core particles can be exemplified by a method for manufacturing core / shell type semiconductor nanoparticles characterized by the following steps: a shell forming step (1) and a shell forming step (2), wherein the shell forming step (2) involves adding zinc carboxylate and a group VI element precursor to a dispersion of "particles consisting of core particles and a shell formed on the surface of the core particles" obtained by performing the shell forming step (1), thereby forming a shell containing zinc and a group VI element on the surface of the "particles consisting of core particles and a shell formed on the surface of the core particles".

[0066] In the method for manufacturing core / shell type semiconductor nanoparticles of the present invention, when the shell forming step (1) is performed once or twice or more, a branched carboxylic acid derived from zinc carboxylic acid salt used as a zinc precursor is coordinated on the surface of the core / shell type semiconductor nanoparticles obtained by the method of manufacturing core / shell type semiconductor nanoparticles of the present invention. The branched carboxylic acid coordinated on the surface of the core / shell type semiconductor nanoparticles functions as a ligand to improve the dispersibility of the core / shell type semiconductor nanoparticles in a dispersion medium.

[0067] Furthermore, a method for manufacturing core / shell type semiconductor nanoparticles with (n+1) layers of shell on the surface of core particles can be exemplified by a method for manufacturing core / shell type semiconductor nanoparticles characterized by the following steps: a shell forming step (1) and a step of repeating the shell forming step (x) n times. The shell forming step (x) involves adding zinc carboxylate and a group VI element precursor to a dispersion of "particles consisting of core particles and one or more layers of shell formed on the surface of the core particles" obtained by performing the previous shell forming step, thereby forming a shell containing zinc and group VI elements on the surface of the "particles consisting of core particles and one or more layers of shell formed on the surface of the core particles".

[0068] In the method for manufacturing core / shell type semiconductor nanoparticles of the present invention, when the shell formation step (1) is performed once or twice or more, a carboxylic acid derived from zinc carboxylate salt, a raw material used as a zinc precursor, is coordinated on the surface of the core / shell type semiconductor nanoparticles obtained by the method of manufacturing core / shell type semiconductor nanoparticles of the present invention.

[0069] The core / shell semiconductor nanoparticle manufacturing method of the present invention can purify the core / shell semiconductor nanoparticles generated by performing a shell formation step. For example, by adding a polarity-reversing solvent such as acetone, the core / shell semiconductor nanoparticles can be precipitated from the solution. Then, the precipitated core / shell semiconductor nanoparticles can 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 are further washed with a solvent to dissolve them again. This purification operation can be repeated, for example, 2 to 4 times, or repeated until the desired purity is achieved. Other purification methods include, for example, coagulation, liquid-liquid extraction, distillation, electrodeposition, particle size chromatography, ultrafiltration, etc. During purification, these purification methods can be performed individually or in combination.

[0070] Furthermore, the surface of the core / shell type semiconductor nanoparticles obtained in the manner described above can also be modified using ligands. Known methods such as ligand exchange can be used for ligand modification.

[0071] The core / shell type semiconductor nanoparticles obtained by the manufacturing method of the core / shell type semiconductor nanoparticles of the present invention are core / shell type structured particles having at least one shell layer. In the core / shell type semiconductor nanoparticles obtained by the manufacturing method of the core / shell type semiconductor nanoparticles of the present invention, the shell layer formed on the surface of the core particle, i.e., the first shell layer seen from the core particle side, is the shell layer formed in the shell formation step (1). In the core / shell type semiconductor nanoparticles obtained by the manufacturing method of the core / shell type semiconductor nanoparticles of the present invention, the number of shell layers formed is at least one, preferably one to four. When the core / shell type semiconductor nanoparticles obtained by the manufacturing method of the core / shell type semiconductor nanoparticles of the present invention have two or more shell layers, the method for forming the shell layers beyond the second layer seen from the core particle can be any method. However, except for replacing the core particle and using the core / shell type particle that has formed one or more shell layers by the previous shell layer forming step as the shell layer forming object, it is preferable to use the shell forming method that is performed in the same way as the shell layer forming step (1).

[0072] In the core / shell type semiconductor nanoparticles obtained by the manufacturing method of the core / shell type semiconductor nanoparticles of the present invention, from the viewpoint of having a low environmental impact and being able to obtain semiconductor nanoparticles with high optical properties, the core is preferably a core containing In and P.

[0073] The average particle size of the core / shell type semiconductor nanoparticles obtained by the manufacturing method of the core / shell type semiconductor nanoparticles of the present invention is not particularly limited, but is preferably 1.0~20.0 nm and particularly preferably 1.0~10.0 nm.

[0074] The core / shell semiconductor nanoparticles obtained by the manufacturing method of the present invention have a coordination system in which at least the carboxylic acid of the zinc carboxylate salt is coordinated on the core / shell semiconductor nanoparticles. Furthermore, when the core / shell semiconductor nanoparticles are modified with ligands, ligands other than the carboxylic acid derived from the zinc carboxylate salt can also be coordinated on the core / shell semiconductor nanoparticles. Therefore, the core / shell semiconductor nanoparticles obtained by the manufacturing method of the present invention are a core / shell semiconductor nanoparticle complex comprising: core / shell semiconductor nanoparticles and ligands coordinated on the surface of the core / shell semiconductor nanoparticles, wherein the coordination system contains at least the carboxylic acid derived from the zinc carboxylate salt. Additionally, the shell of the core / shell semiconductor nanoparticles obtained by the manufacturing method of the present invention contains at least zinc and selenium.

[0075] That is, the core / shell type semiconductor nanoparticle composite of the present invention comprises: core / shell type semiconductor nanoparticles and ligands disposed on the surface of the core / shell type semiconductor nanoparticles, characterized in that, The aforementioned outer shell contains at least Zn; Carboxylic acids are present as the ligands mentioned above; Of the total carboxylic acids contained as ligands, the proportion of carboxylic acids with 8 to 10 carbon atoms is 80.0% by mass or more; The average branching degree of the total carboxylic acids contained in the ligands is 1.1 to 2.9. Furthermore, the shell of the core / shell type semiconductor nanoparticle composite of the present invention may further contain at least one of Se and S.

[0076] The core / shell type semiconductor nanoparticle composite of the present invention contains at least carboxylic acids in its coordination system. In the core / shell type semiconductor nanoparticle composite of the present invention, the proportion of carboxylic acids with 8 to 10 carbon atoms in the total carboxylic acids contained 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 branching degree of the total carboxylic acids contained as ligands is 1.1 to 2.9, preferably 1.3 to 2.7, and more preferably 1.5 to 2.5.

[0077] In the core / shell type semiconductor nanoparticle composite of the present invention, the proportion of carboxylic acid in the total ligands of 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.

[0078] In the core / shell type semiconductor nanoparticle composite of the present invention, during the shell formation step (1), the shell precursor readily reacts on the surface of the core particles, thus forming a shell on the core surface that suppresses the occurrence of defect levels. Therefore, the half-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 more 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 more preferably 93.0% or more.

[0079] The core / shell type semiconductor nanoparticles of the core / shell type semiconductor nanoparticle composite of the present invention, i.e., core / shell type semiconductor nanoparticles with ligands, are core / shell type structured particles having at least one shell layer. In the core / shell type semiconductor nanoparticles of the core / shell type semiconductor nanoparticle composite of the present invention, the shell layer formed on the surface of the core particle, i.e., the first shell layer seen from the core particle side, contains at least Zn and a group VI element (preferably Se or S). In the core / shell type semiconductor nanoparticles of the core / shell type semiconductor nanoparticle composite of the present invention, the number of shell layers formed is at least one, preferably one to four. When the core / shell type semiconductor nanoparticles of the core / shell type semiconductor nanoparticle composite of the present invention have two or more shell layers, the shell layers after the second layer seen from the core particle preferably contain Zn and a group VI element, and more preferably contain Zn and Se or S.

[0080] In the core / shell type semiconductor nanoparticle composite of the present invention, from the viewpoint of having a low environmental impact and being able to obtain semiconductor nanoparticles with high optical properties, the core is preferably a core containing In and P.

[0081] <Measurement> Elemental analysis of semiconductor nanoparticles can be performed using either inductively coupled plasma emission spectrometry (ICP) or X-ray fluorescence spectrometry (XRF). For ICP analysis, purified semiconductor nanoparticles are dissolved in nitric acid and heated, then diluted with water. The analysis is then performed using an ICP emission spectrometer (Shimadzu ICPS-8100) following the calibration curve method. For XRF analysis, filter paper impregnated with the dispersion is placed in a sample holder, and quantitative analysis is performed using an X-ray fluorescence spectrometer (Rigaku ZSX100e).

[0082] Furthermore, the optical properties of semiconductor nanoparticles can be measured using a fluorescence quantum efficiency measurement system (Otsuka Electronics, QE-2100) and a visible-ultraviolet spectrophotometer (Nippon Spectrophotometer, V-670). The emission spectrum is obtained by irradiating the dispersion in which the semiconductor nanoparticles are dispersed in a dispersion medium with excitation light. The re-excitation fluorescence spectrum, obtained by subtracting the portion of the emission spectrum from the obtained emission spectrum after re-excitation, is the re-excitation corrected emission spectrum. The peak wavelength (λmax), fluorescence quantum efficiency (QY), and half-width at half-maximum (FWHM) are then calculated from this. Examples of dispersion media include: n-hexane, octadecene, toluene, acetone, and PGMEA. The excitation light used in the measurement is a single 450 nm light, and the dispersion system uses semiconductor nanoparticles with an absorptivity adjusted to 20-30%. On the other hand, the absorption spectrum can be measured by irradiating the dispersion in which the semiconductor nanoparticles are dispersed in a dispersion medium with ultraviolet-visible light.

[0083] Furthermore, regarding ligands located on core / shell semiconductor nanoparticles, gas chromatography can be used for species identification and molar fraction calculation. Core / shell semiconductor nanoparticles are introduced into a sample vaporization chamber and heated to above 350°C. After passing through a column along with a carrier gas, the type and quantity of each ligand are identified using the residence time and peak area of ​​the signal obtained by the detector. From the obtained types and quantities of each ligand, the types and proportions of ligands located on the core / shell semiconductor nanoparticles can be calculated.

[0084] Furthermore, the structures, methods, procedures, and processes described in this specification are illustrative and are not intended to limit the invention. Various variations may be applied within the scope of this invention.

[0085] The zinc carboxylate salt used in the manufacture of the semiconductor nanoparticles of this invention is a zinc salt of carboxylate; Of all the carboxylic acids that form this zinc carboxylate salt, the proportion of carboxylic acids with 8 to 10 carbon atoms is 80.0% by mass or more. The average branching degree of all carboxylic acids that form this zinc carboxylate is 1.1 to 2.9.

[0086] The zinc carboxylate salt used in the manufacture of semiconductor nanoparticles of the present invention is used for shell formation in the manufacture of core / shell type semiconductor nanoparticles. The zinc carboxylate salt used in the manufacture of semiconductor nanoparticles of the present invention is a zinc salt of carboxylic acids. In the total carboxylic acids forming the zinc carboxylate salt, the proportion of carboxylic acids with 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. Furthermore, the average branching degree of the total carboxylic acids forming the zinc carboxylate salt is 1.1 to 2.9, preferably 1.3 to 2.7, and more preferably 1.5 to 2.5.

[0087] The present invention will now be described with reference to specific experimental examples; however, the present invention is not limited thereto. [Example]

[0088] <Manufacturing of Zinc Carboxylate> The zinc salts of branched carboxylic acids were prepared according to the following method. The carboxylic acids used were 3,5,5-trimethylhexanoic acid (reagent manufactured by Tokyo Chemical Industry Co., Ltd.; purity >98.0%), neodecanoic acid (reagent manufactured by Fujifilm and Kako Pure Chemical Industries Co., Ltd.), 2-ethylhexanoic acid (reagent manufactured by Tokyo Chemical Industry Co., Ltd.; purity >99.0%), and decanoic acid (NAA-102 manufactured by Nippon Oil Co., Ltd.). The analytical results 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.

[0089] A carboxylic acid mixture was prepared by heating and 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) at 40 °C to obtain a carboxylic acid mixture. The prepared carboxylic acid mixture was then added to a separable flask equipped with a moisture metering container and stirred. The mixture was heated to 170 °C under nitrogen. The generated water was removed from the moisture metering container, and the mixture was maintained at 170 °C for 2 hours. After evacuation for 1 hour, nitrogen replacement was performed, and the mixture was cooled to room temperature (25 °C) to obtain zinc carboxylate salt 1.

[0090] A carboxylic acid mixture was prepared by heating 144 g (0.91 mol) of 3,5,5-trimethylhexanoic acid and 158 g (0.91 mol) of neodecanoic acid at 40 °C with stirring. The prepared carboxylic acid mixture was then added to a separable flask equipped with a moisture metering container and stirred. The mixture was heated to 170 °C under nitrogen. The generated water was removed from the moisture metering container, and the mixture was kept at 170 °C for 2 hours. After evacuation for 1 hour, nitrogen replacement was performed, and the mixture was cooled to room temperature (25 °C) to obtain zinc carboxylate 2.

[0091] A carboxylic acid mixture was prepared by heating 3,5,5-trimethylhexanoic acid (71.9 g, 0.45 mol) and neodecanoic acid (237 g, 1.36 mol) at 40 °C with stirring. The prepared carboxylic acid mixture was then added to a separable flask equipped with a moisture metering container and stirred. The mixture was heated to 170 °C under nitrogen. The generated water was removed from the moisture metering container, and the mixture was maintained at 170 °C for 2 hours. After evacuation for 1 hour, nitrogen replacement was performed, and the mixture was cooled to room temperature (25 °C) to obtain zinc carboxylate 3.

[0092] Neodecanoic acid (316 g, 1.82 mol) and zinc oxide (58.8 g, 0.90 mol) were added to a separable flask equipped with a moisture metering container and stirred. The mixture was heated to 170 °C under nitrogen. The generated water was removed from the moisture metering container, and the mixture was kept at 170 °C for 2 hours. After evacuating to vacuum for 1 hour, nitrogen replacement was performed, and the mixture was cooled to room temperature (25 °C) to obtain zinc carboxylate 4.

[0093] A carboxylic acid mixture was prepared by heating neodecanoic acid (261 g, 1.50 mol) and decanoic acid (54.6 g, 0.32 mol) at 40 °C with stirring. The prepared carboxylic acid mixture was then added to a separable flask equipped with a moisture metering container and stirred. The mixture was heated to 170 °C under nitrogen. The generated water was removed from the moisture metering container, and the mixture was maintained at 170 °C for 2 hours. After evacuation for 1 hour, nitrogen replacement was performed, and the mixture was cooled to room temperature (25 °C) to obtain zinc carboxylate 5.

[0094] A carboxylic acid mixture was prepared by heating and 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) at 40 °C to obtain a mixture of carboxylic acids. The prepared carboxylic acid mixture was then added to a separable flask equipped with a moisture metering container and stirred. The mixture was heated to 170 °C under nitrogen. The generated water was removed from the moisture metering container, and the mixture was maintained at 170 °C for 2 hours. After evacuation for 1 hour, nitrogen replacement was performed, and the mixture was cooled to room temperature (25 °C) to obtain zinc carboxylate 6.

[0095] 3,5,5-Trimethylhexanoic acid (288 g, 1.82 mol) and zinc oxide (58.8 g, 0.90 mol) were added to a separable flask equipped with a moisture metering container and stirred. The mixture was heated to 170 °C under nitrogen. The generated water was removed from the moisture metering container, and the mixture was kept at 170 °C for 2 hours. After evacuation for 1 hour, nitrogen replacement was performed, and the mixture was cooled to room temperature (25 °C) to obtain zinc carboxylate 7.

[0096] 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. Following this, 25.0 wt% zinc sulfate aqueous solution (650 g, 2.00 mol) was added dropwise over 60 minutes. After the dropwise addition was complete, the resulting zinc carboxylate slurry was filtered by suction and then washed three times with 1000 g of water. The resulting filter cake was then dried in a rack dryer at 60°C for 36 hours, and then cooled to room temperature (25°C) to obtain zinc carboxylate salt 8.

[0097] <Determination of Zinc Carboxylate> The physical properties of the zinc carboxylate salts 1-8 obtained above were determined. The results are shown in Table 3.

[0098] (C8~10 carboxylic acid ratio) Based on the carbon number composition of carboxylic acids in Table 1 and the carboxylic acid blending ratio in Table 2, the C8-10 carboxylic acid ratio (mass %) of zinc carboxylic acid salts 1-8 can be calculated.

[0099] (Average branching degree) The average branching degree of zinc carboxylate salts 1 to 8 was calculated from the branching degree of carboxylic acids shown in Table 1 and the blending ratio of carboxylic acids shown in Table 2.

[0100] (Metal content; Zn content) Weigh 0.1g of zinc carboxylate salts 1-8 and heat in a magnetic crucible at 650℃ for 4 hours to remove organic matter. Dissolve the residue in 1ml of hydrochloric acid, and then add water to make 100ml. Use this solution as a sample to determine the metal content (Zn content) using atomic absorption spectrophotometry.

[0101] (Viscosity) For zinc carboxylate salts 1–8, dynamic viscosity was determined using a dynamic viscoelasticity assay apparatus (Anton Paar MCR302 modular rheometer). The zinc carboxylate was placed on the heating plate of the rheometer and heated to 130°C, then kept warm using a sample cover. Using a cone plate (CP25-2), the dynamic viscosity was measured from 1.0 rpm to 1000 rpm, and the viscosity at 130°C (150 rpm) was calculated. Then, the temperature was lowered to 50°C, and the dynamic viscosity was similarly measured from 1.0 rpm to 1000 rpm, and the viscosity at 50°C (150 rpm) was calculated.

[0102] (Vitality change rate) The difference between the viscosity at 130℃ (Pa·s) and the viscosity at 50℃ (Pa·s) is divided by the value of the viscosity at 50℃ (Pa·s) multiplied by 100, thereby calculating the rate of change of viscosity relative to temperature change. Viscosity change rate (%) = ((viscosity at 130℃ (Pa·s) - viscosity at 50℃ (Pa·s)) / viscosity at 50℃ (Pa·s)) × 100

[0103] The 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.

[0104] 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 double-necked flask to create a vacuum. The flask was heated to 120 °C under vacuum (<10 Pa) and maintained for 30 minutes from the point when the vacuum level was below 10 Pa. Nitrogen was then introduced into the flask, and the mixture was cooled to room temperature (25 °C) to obtain the In precursor. Furthermore, in a nitrogen-environmental glove-operated chamber, trimethylsilylphosphine (TMS) phosphine was mixed with tri-n-octylphosphine at a concentration of 0.2 M to obtain the P precursor. Next, at room temperature (25 °C) under a nitrogen atmosphere, 2 mL of the P precursor was injected into the In precursor, and the temperature was raised to 300 °C at a rate of 30 °C per minute. After maintaining at 300 °C for 2 minutes, the reaction solution was cooled to room temperature to obtain a reaction solution as a dispersion of InP core particles.

[0105] <Solution of zinc precursor> The zinc carboxylate salt described in Table 2 and octadecene were mixed in such a way that the molar concentration of zinc became 0.3 M. After evacuating at 100 °C for 1 hour, nitrogen replacement was carried out and cooled to room temperature (25 °C) to obtain a solution of each zinc precursor.

[0106] <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.

[0107] <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.

[0108] <Manufacture of core / shell semiconductor nanoparticles> (Example 1) 5 mL of trioctylamine was added to 10 mL of the dispersion of InP core particles (In: 0.4 mmol), and the dispersion of InP core particles was heated 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 dispersion of InP core particles was further heated to 300 °C at a rate of 1 °C per minute. Then, 180 minutes after the dispersion of InP core particles reached 300 °C, the 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 obtained dispersion of core / shell semiconductor nanoparticles to cause the semiconductor nanoparticles to aggregate. Then, after centrifugation (4000 rpm, 10 minutes), the supernatant was removed, and the core / shell semiconductor nanoparticles were redispersed in hexane. This step 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. Furthermore, when measuring the optical properties of semiconductor nanoparticles, the excitation wavelength is set to a single wavelength of 450 nm. The same applies to the following measurements of the optical properties of semiconductor nanoparticles.

[0109] <Manufacturing of Core / Shell / Shell Semiconductor Nanoparticles> (Examples 2-7, Comparative Examples 1-2) The process was carried out in the same manner as in the above embodiments or comparative examples to obtain a dispersion (reaction solution) of core / shell semiconductor nanoparticles. Next, the obtained dispersion (reaction solution) of core / shell semiconductor nanoparticles was heated to 300°C. After reaching 300°C, solutions of zinc precursor (as shown in Table 4) and solutions of Se precursor and S precursor (as shown in Table 4) were simultaneously added to the dispersion (reaction solution) at a rate of 0.2 mL / min. The addition of the zinc and S precursor solutions was stopped simultaneously 100 minutes after the start of addition (addition time: 100 minutes). Then, heating was stopped 180 minutes after the end of addition, and the mixture was cooled to room temperature (25°C) to obtain core / shell / shell semiconductor nanoparticles. A dispersion (reaction solution) was obtained. Next, acetone was added to the obtained dispersion of core / shell / shell semiconductor nanoparticles to cause the semiconductor nanoparticles to aggregate. Then, after centrifugation (4000 rpm, 10 minutes), the supernatant was removed, and the core / shell / shell semiconductor nanoparticles were redispersed in hexane. This step 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.

[0110] [Table 1] Carboxylic acid reagent name · product name mark C8 (quality%) C9 (quality%) C10 (quality%) C7 or below or C11 (quality%) Average branching degree 3,5,5-Trimethylhexanoic acid A 0.6 98.5 0.5 0.4 3.1 Neodecanoic acid B 0.0 0.6 90.9 8.5 2.3 2-Ethylhexanoic acid C 99.5 0.0 0.3 0.2 1.0 Decanoic acid (NAA-102) D 0.2 0.0 99.5 0.3 0.0

[0111] [Table 2] Carboxylic acid blending ratio (mass%) Blending carboxylic acids A B C D Zinc carboxylate 1 0.0 50.0 35.0 15.0 Zinc carboxylate 2 50.0 50.0 0.0 0.0 Zinc carboxylate 3 25.0 75.0 0.0 0.0 Zinc carboxylate 4 0.0 100.0 0.0 0.0 Zinc carboxylate 5 0.0 82.6 0.0 17.4 Zinc carboxylate 6 33.3 0.0 6.8 59.9 Zinc carboxylate 7 100.0 0.0 0.0 0.0 Zinc carboxylate salt 8 0.0 0.0 0.0 100.0

[0112] [Table 3] C8-10 carboxylic acid ratio (quality%) Average branching degree Metal content (quality%) Viscosity at 130°C (Pa·s) Viscosity at 50°C (Pa·s) viscosity change rate (%) Zinc carboxylate 1 95.6 1.5 16.8 2.0 1730.0 99.8 Zinc carboxylate 2 95.6 2.7 16.5 30.3 2120.0 98.6 Zinc carboxylate 3 93.5 2.5 16.2 11.2 1270.0 99.1 Zinc carboxylate 4 91.5 2.3 15.9 0.1 22.0 99.4 Zinc carboxylate 5 92.9 1.9 15.9 1.5 402.0 99.6 Zinc carboxylate 6 99.7 1.1 16.5 2.7 9080.0 100.0 Zinc carboxylate 7 99.6 3.1 17.2 11.6 120.0 90.3 Zinc carboxylate salt 8 99.7 0.0 16.0 14400.0 10400.0 11.1

[0113] [Table 4] Zinc precursors solvent VI family Other additions Additives Add to Zn / In Mörby Add time (point) Temperature before addition (°C) reaction temperature (°C) reaction time (point) Zinc carboxylate salt Average branching degree Example 1 Zinc carboxylate 1 1.5 Octadene Se Oil chlorine 15 50 230 300 180 Example 2 Zinc carboxylate 2 2.7 Octadene Se、S Oil chlorine 15 50 230 300 180 Example 3 Zinc carboxylate 3 2.5 Octadene Se、S Oil chlorine 15 50 230 300 180 Example 4 Zinc carboxylate 4 2.3 Octadene Se、S Oil chlorine 15 50 230 300 180 Example 5 Zinc carboxylate 5 1.9 Octadene Se、S Oil chlorine 15 50 230 300 180 Example 6 Zinc carboxylate 1 1.5 Octadene Se、S Oil chlorine 15 50 230 300 180 Example 7 Zinc carboxylate 6 1.1 Octadene Se、S Oil chlorine 15 50 230 300 180 Comparative Example 1 Zinc carboxylate 7 3.1 Octadene Se、S Oil chlorine 15 50 230 300 180 Comparative Example 2 Zinc carboxylate salt 8 0.0 Octadene Se、S Oil chlorine 15 50 230 300 180

[0114] [Table 5] shell λmax (nm) FWHM (nm) QY(%) Example 1 ZnSe 630.5 36.6 91.3 Example 2 ZnSe / ZnS 630.3 36.4 92.2 Example 3 ZnSe / ZnS 629.2 36.4 91.2 Example 4 ZnSe / ZnS 626.7 35.3 91.0 Example 5 ZnSe / ZnS 628.8 36.5 90.3 Example 6 ZnSe / ZnS 632.5 37.0 90.2 Example 7 ZnSe / ZnS 629.3 36.8 90.0 Comparative Example 1 ZnSe / ZnS 628.8 37.7 87.3 Comparative Example 2 ZnSe / ZnS 631.7 36.7 85.0

Claims

1. A method for manufacturing core / shell type semiconductor nanoparticles, characterized in that it includes a shell formation step, wherein a zinc carboxylate salt and a group VI element precursor are added to a dispersion of core particles, and the zinc carboxylate salt and the group VI element precursor react 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; and wherein, in all carboxylic acids forming the zinc carboxylate salt, the proportion of carboxylic acids with 8 to 10 carbon atoms is 80.0% by mass or more; and the average branching degree of all carboxylic acids forming the zinc carboxylate salt is 1.1 to 2.

9.

2. The method for manufacturing core / shell type semiconductor nanoparticles as described in claim 1, wherein, The aforementioned core particle system contains In and P.

3. The method for manufacturing core / shell type semiconductor nanoparticles as described in claim 2, wherein, The amount of zinc carboxylate added is calculated as 5 to 50 based on the molar ratio (Zn / In) of Zn in the zinc carboxylate to In in the core particles.

4. A method for manufacturing core / shell type semiconductor nanoparticles as described in claim 1 or 2, wherein, The reaction between the above-mentioned zinc carboxylate salt and the above-mentioned Group VI element precursor is carried out in the presence of halogen elements.

5. A core / shell type semiconductor nanoparticle composite comprising: core / shell type semiconductor nanoparticles and ligands disposed on the surface of the core / shell type semiconductor nanoparticles; characterized in that: the core contains In and P; the shell contains at least Zn and a Group VI element; a carboxylic acid is contained as the ligand; of the total carboxylic acid contained as the ligand, the proportion of carboxylic acids with 8 to 10 carbon atoms is 80% by mass or more; and the average branching degree of the total carboxylic acid contained as the ligand is 1.1 to 2.

9.

6. As in claim 5, a core / shell type semiconductor nanoparticle composite, wherein, The emission peak wavelength of the aforementioned core / shell type semiconductor nanoparticle composite is 590~650nm.

7. The core / shell type semiconductor nanoparticle composite as described in claim 5 or 6, wherein, The half-width at half maximum (FWHM) of the emission spectrum of the aforementioned core / shell type semiconductor nanoparticle composite is below 37.0 nm.

8. The core / shell type semiconductor nanoparticle composite as described in claim 5 or 6, wherein, The aforementioned shell further contains at least one of Se and S.

9. The core / shell type semiconductor nanoparticle composite as described in claim 5 or 6, wherein, The quantum efficiency (QY) of the aforementioned core / shell type semiconductor nanoparticle composite is above 90.0%.

10. The core / shell type semiconductor nanoparticle composite as described in claim 5 or 6, wherein, The proportion of the carboxylic acid in the total ligand of the above core / shell type semiconductor nanoparticle complex is 1.0 to 15.0 by mass.