Method for producing core / shell semiconductor nanoparticles

Abstract

Provided is a method for producing core / shell semiconductor nanoparticles, the method being characterized by comprising a shell formation step in which intermediate particles of the core / shell semiconductor nanoparticles having a core particle and one or more shells, a dispersion medium, and a shell precursor are mixed and reacted, thereby forming a shell on at least part of the surface of the intermediate particles of core / shell semiconductor nanoparticles having a core particle and one or more shells, to obtain core / shell semiconductor nanoparticles, the method furthermore being characterized in that the dispersion medium contains benzyl alcohol and / or a substituted compound thereof. The present invention makes it possible to provide a method for producing core / shell semiconductor nanoparticles which is capable of increasing the quantum efficiency of the core / shell semiconductor nanoparticles.

Description

Method for producing core / shell type semiconductor nanoparticles

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

[0002] Semiconductor nanoparticles that are so small that the quantum confinement effect appears have a bandgap that depends on the particle size. Excitons formed in semiconductor nanoparticles by means such as photoexcitation and charge injection emit photons of energy corresponding to the bandgap by recombination. Therefore, by appropriately selecting the composition and particle size of the semiconductor nanoparticles, light emission at a desired wavelength can be obtained.

[0003] Semiconductor nanoparticles have been tried for various applications such as display applications, biological labeling applications, and solar cell applications. In particular, as a display application, the use of semiconductor nanoparticles formed into a film as a wavelength conversion layer has started.

[0004] As semiconductor nanoparticles, Cd chalcogenide semiconductor nanoparticles and semiconductor nanoparticles based on InP are known (for example, Patent Documents 1 to 3). In particular, research on Cd-based semiconductor nanoparticles represented by Cd chalcogenide has been actively conducted in this field relatively early.

[0005] U.S. Patent Application Publication No. 2015 / 083969, U.S. Patent No. 9169435, U.S. Patent No. 9884993

[0006] Cd chalcogenide semiconductor nanoparticles have an advantage that the change in the emission wavelength due to the change in the particle size is relatively gentle compared to InP-based semiconductor nanoparticles, so that it is easy to adjust the emission wavelength.

[0007] However, as Cd chalcogenide semiconductor nanoparticles, those with relatively high quantum efficiency have been obtained. However, when used in applications that emphasize the light conversion efficiency such as display applications, further improvement in the quantum efficiency is required.

[0008] Also, for InP-based semiconductor nanoparticles, further improvement in the quantum efficiency is required.

[0009] Therefore, an object of the present invention is to provide a method for producing core / shell semiconductor nanoparticles that can increase the quantum efficiency of the core / shell semiconductor nanoparticles.

[0010] As a result of diligent research to solve the above problems, the present inventors have found that core / shell type semiconductor nanoparticles with high quantum efficiency can be obtained by a method for producing core / shell type semiconductor nanoparticles, comprising a shell formation step of mixing and reacting core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells, a dispersion medium, and a shell precursor to form a shell on at least a part of the surface of the core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells, and wherein the dispersion medium contains benzyl alcohol and / or a substituted compound thereof. In other words, the present invention (1) provides a method for producing core / shell type semiconductor nanoparticles, comprising a shell formation step of mixing and reacting core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells, a dispersion medium, and a shell precursor to form a shell on at least a part of the surface of the core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells, thereby obtaining core / shell type semiconductor nanoparticles, wherein the dispersion medium contains benzyl alcohol and / or a substituted compound thereof.

[0011] Furthermore, the present invention (2) provides a method for producing core / shell type semiconductor nanoparticles according to (1), characterized in that the ester compound is benzyl alcohol.

[0012] Furthermore, the present invention (3) provides a method for producing core / shell type semiconductor nanoparticles according to (1) or (2), characterized in that the core particles mixed in the shell formation step are a dispersion of core particles.

[0013] Furthermore, the present invention (4) provides a method for producing core / shell type semiconductor nanoparticles according to (3), characterized in that the temperature of the dispersion of the core particles is 200°C to 380°C.

[0014] Furthermore, the present invention (5) provides a method for producing core / shell type semiconductor nanoparticles according to any of (1) to (4), characterized in that the core particles of the core / shell type semiconductor nanoparticles contain Cd and Se.

[0015] Furthermore, the present invention (6) provides a method for producing core / shell type semiconductor nanoparticles according to any of (1) to (5), characterized in that the shell of the core / shell type semiconductor nanoparticle contains Cd and S.

[0016] Furthermore, the present invention (7) provides a method for producing the core / shell type semiconductor nanoparticles of (6), characterized in that the shell of the core / shell type semiconductor nanoparticles further contains Zn and S.

[0017] Furthermore, the present invention (8) provides a method for producing core / shell type semiconductor nanoparticles according to any of (1) to (7), characterized in that the reaction temperature in the shell formation step is 200°C to 380°C.

[0018] According to the present invention, it is possible to provide a method for producing core / shell type semiconductor nanoparticles that can increase the quantum efficiency of the core / shell type semiconductor nanoparticles.

[0019] The core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention are semiconductor nanoparticles having a core particle and one or more layers of shell formed on at least a part of the surface of the core particle. In the core / shell type semiconductor nanoparticles, the shell only needs to be at least one layer, and examples include core / shell type semiconductor nanoparticles consisting of a core particle and one layer of shell, core / shell type semiconductor nanoparticles consisting of a core particle and two layers of shell, and core / shell type semiconductor nanoparticles consisting of a core particle and three or more layers of shell.

[0020] Core particles related to core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention include core particles containing Cd and a chalcogen element. Because the core particles related to the core / shell type semiconductor nanoparticles contain Cd and a chalcogen element, the change in emission wavelength due to the change in particle size is relatively gradual, making it easier to adjust the emission wavelength. Examples of chalcogen elements include Se, S, and Te. In particular, when the core particles contain Cd and Se, it is preferable in that monodisperse particles with high color purity are easily obtained. When the core particles are core particles containing Cd and a chalcogen element, the core particles may inevitably or intentionally contain elements such as P, N, Si, Al, and Zn, as long as it does not impair the scope of the present invention.

[0021] When the core particles of the core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention contain Cd and a chalcogen element, the shell of the core / shell type semiconductor nanoparticle mainly contains S, Cd and / or Zn. When the shell mainly contains S, Cd and / or Zn, the shell may, in addition to S, Cd and / or Zn, inevitably or intentionally contain elements such as P, N, Si, F, Cl, and Br, to the extent that it does not impair the scope of the present invention.

[0022] In the case where the core particles of the core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention contain Cd and a chalcogen element, the shell form of the core / shell type semiconductor nanoparticles may include, for example, a shell containing CdS. Another example of a shell form is a shell containing ZnS. These shells do not need to have a stoichiometric composition and may have an elemental concentration gradient within the shell.

[0023] Core particles related to core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention include core particles containing In and P. By using core particles related to core / shell type semiconductor nanoparticles that contain In and P, it is possible to obtain light-emitting particles while reducing environmental impact. When the core particles are core particles containing In and P, the core particles may inevitably or intentionally contain elements such as P, N, Zn, S, Si, F, Cl, and Br, as long as it does not impair the scope of the present invention.

[0024] When the core particles of the core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention are core particles containing In and P, the shell of the core / shell type semiconductor nanoparticles mainly contains Zn and S and / or Se. When the shell mainly contains Zn and S and / or Se, the shell may, inevitably or intentionally, contain elements other than Zn and S and / or Se, as long as it does not impair the scope of the present invention.

[0025] In the case where the core particles of the core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention are core particles containing In and P, the shell form of the core / shell type semiconductor nanoparticles can be, for example, a shell containing ZnSe. Another shell form can be a shell containing ZnS. Yet another shell form can be a shell containing ZnSeS. These shell forms do not need to have a stoichiometric composition and may have an elemental concentration gradient within the shell.

[0026] The average particle size of the core particles in the core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention is preferably 1 to 20 nm. When the average particle size of the core particles is 1 to 20 nm, excitation light of 450 nm can be converted into light with a wavelength of 500 to 680 nm. 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 by a transmission electron microscope (TEM).

[0027] Examples of shell configurations include a shell consisting of two or more layers, where the innermost core shell is made of CdS. Another example of a shell configuration is one in which the innermost first shell is made of CdS, and the second shell covering the outer surface of the first shell is made of ZnS.

[0028] The average particle size of the core / shell semiconductor nanoparticles obtained by the method for producing core / shell semiconductor nanoparticles of the present invention is not particularly limited, but is preferably 2 to 30 nm, and particularly preferably 2 to 25 nm. When the average particle size of the core / shell semiconductor nanoparticles is 2 to 30 nm, excitation light of 450 nm can be converted into light with a wavelength of 500 to 680 nm. In this invention, the average particle size of the core / shell semiconductor nanoparticles is determined by calculating the area circle equivalent diameter (Heywood diameter) of 10 or more particles from a particle image observed by a transmission electron microscope (TEM).

[0029] The quantum efficiency (QY) of the core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention is 90% or higher, preferably 92% or higher, and more preferably 94% or higher. Although the mechanism is not clear, the inventors believe that uniform shell formation is promoted by using an ester compound having an aromatic ring as the dispersion medium in the shell formation process.

[0030] The emission spectrum of the core / shell semiconductor nanoparticles obtained by the method for producing core / shell semiconductor nanoparticles of the present invention has a half-width (FWHM) of preferably 30 nm or less, and particularly preferably 29 nm or less. This high FWHM of the core / shell semiconductor nanoparticles of the present invention results in high color purity, making them suitable for display applications.

[0031] The core / shell semiconductor nanoparticles obtained by the method for producing core / shell semiconductor nanoparticles of the present invention may have their shell surfaces modified with ligands to stabilize dispersion in the matrix and / or impart weather resistance. Furthermore, if necessary, the ligand modifying the core / shell semiconductor nanoparticles may be replaced with another ligand to enhance dispersibility in dispersion media of different polarities. Additionally, the ligand-modified core / shell semiconductor nanoparticles of the present invention can bind to other structures through the ligand.

[0032] In the method for producing core / shell type semiconductor nanoparticles of the present invention, when benzyl alcohol and / or its substituted compounds are used as the dispersion medium when carrying out the shell formation reaction, a substance having an aromatic ring derived from the dispersion medium may coordinate as a ligand to the surface of the core / shell type semiconductor nanoparticles. Examples of substances having an aromatic ring derived from the dispersion medium include benzyl alcohol and / or its substituted compounds, and benzaldehyde and / or its substituted compounds.

[0033] The core / shell type semiconductor nanoparticles obtained by the method for producing core / shell type semiconductor nanoparticles of the present invention may have an oxide layer on their surface. The oxide that forms the oxide layer is not particularly limited as long as it is within the range that the effects of the present invention are achieved, and examples include oxides of Si, Ti, and Al.

[0034] The present invention relates to a method for producing core / shell type semiconductor nanoparticles, comprising a shell formation step of mixing and reacting core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells with a dispersion medium and a shell precursor to form a shell on at least a portion of the surface of the core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells, thereby obtaining core / shell type semiconductor nanoparticles, wherein the dispersion medium contains benzyl alcohol and / or a substituted compound thereof.

[0035] The present invention provides a method for producing core / shell type semiconductor nanoparticles, which includes a shell formation step.

[0036] The shell formation step in the method for producing core / shell type semiconductor nanoparticles of the present invention is a step of mixing core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells with a dispersion medium and a shell precursor and reacting them to form a shell on at least a part of the surface of core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells, thereby obtaining core / shell type semiconductor nanoparticles.

[0037] Core particles used in the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention include core particles containing Cd and a chalcogen element. Because the core particles contain Cd and a chalcogen element, the change in emission wavelength due to the change in particle size is relatively gradual, making it easier to adjust the emission wavelength. Examples of chalcogen elements include Se, S, and Te. In particular, when the core particles contain Cd and Se, it is preferable in that monodisperse particles with high color purity are easily obtained. When the core particles contain Cd and a chalcogen element, the core particles may inevitably or intentionally contain elements such as P, N, Si, Al, and Zn, as long as it does not impair the scope of the present invention.

[0038] Core particles used in the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention include core particles containing In and P. By using core particles containing In and P, it is possible to obtain light-emitting particles while reducing the environmental burden. When the core particles are core particles containing In and P, the core particles may inevitably or intentionally contain elements such as P, N, Zn, S, Si, F, Cl, and Br, as long as it does not impair the scope of the present invention.

[0039] The average particle size of the core particles is preferably 1 to 20 nm. When the average particle size of the core particles is 1 to 20 nm, excitation light at 450 nm can be converted into light with a wavelength of 500 to 680 nm. 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 by a transmission electron microscope (TEM).

[0040] The core particles can be obtained by any method. For example, known methods include the hot injection method and the flow reactor method.

[0041] The intermediate particles of a core / shell type semiconductor nanoparticle having one or more shells used in the shell formation step of the method for manufacturing core / shell type semiconductor nanoparticles of the present invention are intermediate particles used in the manufacture of core / shell type semiconductor nanoparticles having two or more shells formed on the core. For example, when a first layer of shell is formed on a core particle to obtain intermediate particles of a core / first layer shell type semiconductor nanoparticle, and then a second layer of shell is formed on the obtained intermediate particles of the core / first layer shell type semiconductor nanoparticle to manufacture a core / first layer shell / second layer shell type semiconductor nanoparticle having two shells, the intermediate particles of the core / first layer shell type semiconductor nanoparticle correspond to the intermediate particles of a core / shell type semiconductor nanoparticle having one or more shells used in the shell formation step of the method for manufacturing core / shell type semiconductor nanoparticles of the present invention. Furthermore, for example, when manufacturing a core / first-layer shell / second-layer shell type semiconductor nanoparticle having three shells, the intermediate particles of the core / first-layer shell type semiconductor nanoparticle and the intermediate particles of the core / first-layer shell type semiconductor nanoparticle obtained in the manufacturing process correspond to the intermediate particles of the core / shell type semiconductor nanoparticle having one or more shells used in the shell formation step of the method for manufacturing core / shell type semiconductor nanoparticles of the present invention.

[0042] In the intermediate particles of core / shell type semiconductor nanoparticles having one or more shells used in the shell formation step according to the method for producing core / shell type semiconductor nanoparticles of the present invention, the compositions of the core and the shell are adjusted so as to be the composition of the core / shell type semiconductor nanoparticles to be produced.

[0043] The shell precursor used in the shell formation step according to the method for producing core / shell type semiconductor nanoparticles of the present invention is appropriately selected according to the composition of the shell to be formed. Examples of the precursor of Cd include cadmium carboxylates such as cadmium oxide, cadmium chloride, cadmium acetate or cadmium oleate. Examples of the precursor of Se include trialkylphosphine selenide, selenol, a Se-TBP solution in which selenium powder is dispersed in tributylphosphine (TBP) or trioctylphosphine (TOP), a Se-TOP solution, and the like. The precursor of S is not particularly limited, and examples thereof include trioctylphosphine sulfide, tributylphosphine sulfide, thiols, bis(trimethylsilyl) sulfide, and the like. The Zn precursor is not particularly limited, and examples thereof include zinc carboxylates such as zinc acetate, zinc propionate, zinc myristate, zinc oleate, and the like.

[0044] For example, when the core particles are core particles containing Cd and a chalcogen element, and a shell mainly containing S and Cd and / or Zn is formed, the shell precursor contains, for example, mainly an S precursor and a Cd precursor and / or a Zn precursor. Further, for example, when the core particles are core particles containing In and P, and a shell mainly containing Zn and S and / or Se is formed, the shell precursor contains, for example, mainly a Zn precursor and an S precursor and / or a Se precursor.

[0045] In the shell formation step according to the method for producing core / shell type semiconductor nanoparticles of the present invention, the amount of the shell precursor used is appropriately selected according to the thickness of the shell to be formed.

[0046] In the shell formation step in the method for producing core / shell type semiconductor nanoparticles of the present invention, the dispersion medium used is a dispersion medium for dispersing core particles before mixing the shell precursor or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells, and is the dispersion medium when performing the shell formation reaction.

[0047] The dispersion medium used in the shell formation step in the method for producing core / shell type semiconductor nanoparticles of the present invention contains benzyl alcohol and / or a substituted compound thereof. By the dispersion medium used in the shell formation step containing benzyl alcohol and / or a substituted compound thereof, core / shell type semiconductor nanoparticles with high quantum efficiency can be obtained. Although the mechanism is not clear, the inventor believes that in the shell formation step, the inclusion of benzyl alcohol and / or a substituted compound thereof may promote uniform shell formation.

[0048] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, the benzyl alcohol substitution compounds used as the dispersion medium include compounds in which a substituent is bonded to an aromatic ring, compounds in which a substituent is bonded to a carbon atom to which a hydroxyl group is bonded, and compounds in which substituents are bonded to both an aromatic ring and a carbon atom to which a hydroxyl group is bonded. Examples of substituents bonded to the aromatic ring include nitrogen-containing functional groups such as alkyl groups, alkoxy groups, and amino groups having 1 to 5 carbon atoms. Examples of substituents bonded to a carbon atom to which a hydroxyl group is bonded include alkyl groups having 1 to 5 carbon atoms. Examples of compounds in which a substituent is bonded to an aromatic ring include o-methylbenzyl alcohol, p-methylbenzyl alcohol, m-methylbenzyl alcohol, o-methylbenzyl alcohol, p-methylbenzyl alcohol, m-methylbenzyl alcohol, and p-methoxybenzyl alcohol. Examples of compounds in which a substituent is bonded to a carbon atom to which a hydroxyl group is bonded include α-methylbenzyl alcohol, α-ethylbenzyl alcohol, and α,α-dimethylbenzyl alcohol. As for benzyl alcohol and / or its substituted compounds, it is preferable that they do not have substituents on the aromatic ring, and benzyl alcohol is more preferable, in that the quantum efficiency of the core / shell type semiconductor nanoparticles is higher. As for the substituted compounds of benzyl alcohol, it is preferable that the substituent is a hydrocarbon group, in that the quantum efficiency of the core / shell type semiconductor nanoparticles is higher.

[0049] The benzyl alcohol and / or its substituted compound used as a dispersion medium in the shell formation process may be one type or a combination of two or more types.

[0050] Benzyl alcohol and / or its substituted compounds are preferably those with a boiling point of 200°C or higher at 1 atm, and more preferably those with a boiling point of 205°C or higher, in that they are less likely to volatilize during the shell formation process.

[0051] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, the dispersion medium used may contain compounds other than benzyl alcohol and its substituted compounds, such as carboxylic acids, amines, and phosphines.

[0052] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, the content of benzyl alcohol and / or its substituted compound in the dispersion medium is preferably 1.0% by mass or more, more preferably 2.0% by mass or more, and more preferably 5.0% by mass or more. By having the content of benzyl alcohol and / or its substituted compound in the dispersion medium within the above range, the quantum efficiency of the core / shell type semiconductor nanoparticles can be increased.

[0053] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, the amount of dispersion medium used is preferably 5 to 2000, more preferably 5 to 1500, in terms of the molar ratio to Cd in the core particles when the core particles contain Cd and a chalcogen element, and in terms of the molar ratio to In in the core particles when the core particles contain In and P. By using an amount of dispersion medium within the above range, the quantum efficiency of the core / shell type semiconductor nanoparticles can be increased.

[0054] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, the amount of benzyl alcohol and / or its substituted compound used is preferably 5 to 500, more preferably 5 to 300, in terms of the molar ratio to Cd in the core particles when the core particles contain Cd and a chalcogen element, and in terms of the molar ratio to In in the core particles when the core particles contain In and P. By using benzyl alcohol and / or its substituted compound within the above range, the quantum efficiency of the core / shell type semiconductor nanoparticles can be increased. When two or more types of benzyl alcohol and / or its substituted compounds are used as a dispersion medium, the above amount refers to the total amount of benzyl alcohol and / or its substituted compounds used.

[0055] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, a substance having an aromatic ring derived from the dispersion medium may coordinate as a ligand to the surface of the core / shell type semiconductor nanoparticles. Examples of substances having an aromatic ring derived from the dispersion medium include decomposition products of benzyl alcohol and / or its substituted compounds, or by-products of precursors or additives in the manufacturing process of core / shell type semiconductor nanoparticles. There are no particular limitations, but examples include benzyl alcohol and / or its substituted compounds, benzaldehyde and / or its substituted compounds, carboxylic acids, etc.

[0056] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, it is preferable that the dispersion medium further contains a carboxylic acid in addition to benzyl alcohol and / or its substituted compound. By including a carboxylic acid in addition to benzyl alcohol and / or its substituted compound in the dispersion medium, the quantum efficiency of the core / shell type semiconductor nanoparticles is increased.

[0057] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, when a carboxylic acid is used as a dispersion medium together with benzyl alcohol and / or its substituted compound, the carboxylic acid used may be either a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. The quantum efficiency of the core / shell type semiconductor nanoparticles is increased by including benzyl alcohol and / or its substituted compound and an aliphatic carboxylic acid in the dispersion medium. Examples of saturated aliphatic carboxylic acids that can be used as a dispersion medium include pelargonic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid, stearic acid, nonadecylic acid, arachidic acid, henicosyl acid, and nonadecylic acid. Examples of unsaturated aliphatic carboxylic acids that can be used as a dispersion medium include myristoleic acid, sapienic acid, palmitoleic acid, oleic acid, elaidic acid, erucic acid, linoleic acid, and linolenic acid.

[0058] The carboxylic acid used as the dispersion medium is preferably one with a boiling point of 200°C or higher at 1 atm, and more preferably one with a boiling point of 220°C or higher, in order to prevent volatilization during the shell formation process.

[0059] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, it is more preferable that the carboxylic acid used together with benzyl alcohol as the dispersion medium is an aromatic carboxylic acid, as this enhances the effect of increasing the quantum efficiency of the core / shell type semiconductor nanoparticles. Examples of aromatic carboxylic acids include benzoic acid and phenylacetic acid.

[0060] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, when the dispersion medium contains a carboxylic acid, the amount of carboxylic acid used is preferably 5 to 500, more preferably 5 to 300, in terms of the molar ratio to Cd in the core particles when the core particles contain Cd and a chalcogen element, and in terms of the molar ratio to In in the core particles when the core particles contain In and P. By having the amount of carboxylic acid used within the above range, the effect of increasing the quantum efficiency of the core / shell type semiconductor nanoparticles is enhanced.

[0061] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, when the dispersion medium contains a carboxylic acid, the amount of carboxylic acid used relative to benzyl alcohol and / or its substituted compound is preferably 5 to 1000, more preferably 5 to 500, in molar ratio. Having the amount of carboxylic acid used relative to benzyl alcohol and / or its substituted compound within this range enhances the effect of increasing the quantum efficiency of the core / shell type semiconductor nanoparticles.

[0062] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, the core particles may be in the form of a dispersion of core particles. That is, a dispersion of core particles may be used as the core particles in the shell formation step. Preferably, the dispersion of core particles is one in which the core particles are dispersed in an organic dispersion medium such as octadecene. In this case, the shell formation step may be carried out not only by simply replacing the core particles with a dispersion of core particles as described above, but also by adding a dispersion medium and a shell precursor to the dispersion of core particles. When adding a dispersion medium and a shell precursor to a dispersion of core particles, there are no particular limitations on the order, but it is preferable that the shell precursor be added in the presence of the dispersion of core particles and the dispersion medium.

[0063] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, when mixing a dispersion of core particles as core particles, it is preferable that the dispersion of core particles is heated. The temperature of the dispersion of core particles is preferably 200°C to 380°C, more preferably 220°C to 350°C, and even more preferably 250°C to 350°C. It is believed that by having the temperature of the dispersion of core particles within the above range, the reaction activity with the dispersion medium and the shell precursor is increased, and a uniform shell can be formed.

[0064] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, the reaction temperature of the shell formation reaction is preferably 200°C to 380°C, more preferably 220°C to 350°C, and even more preferably 250°C to 350°C. It is believed that by having the reaction temperature of the shell formation reaction within the above range, the reaction activity with the dispersion medium and the shell precursor is increased, and a uniform shell can be formed.

[0065] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells, a dispersion medium, and a shell precursor are mixed and a shell formation reaction is carried out. In the shell formation process, a method for mixing core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells, a dispersion medium, and a shell precursor to carry out a shell formation reaction includes, for example, (i) first mixing core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells, a dispersion medium, and a shell precursor, and then heating to cause a reaction; (ii) heating a mixture of core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells and a dispersion medium, and reacting while adding a shell precursor; (iii) heating a mixture of a dispersion medium and a shell precursor, and reacting while adding core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells; and (iv) heating the dispersion medium while reacting while adding core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells and a shell precursor, respectively.

[0066] In the shell formation step of the method for producing core / shell type semiconductor nanoparticles of the present invention, a mixed precursor, which is a pre-mixed mixture of precursors of each element that forms the shell, may be mixed as the shell precursor, or the precursors of each element that forms the shell may be mixed separately as shell precursors. When a mixed precursor, which is a pre-mixed mixture of precursors of each element that forms the shell, is mixed, the shell precursors can react uniformly with the core particles, enabling uniform shell formation. When the precursors of each element that forms the shell are mixed separately, it is possible to prevent the precursors of each element from reacting before the shell formation step, thereby suppressing the generation of by-products.

[0067] In this way, core / shell type semiconductor nanoparticles are obtained by performing the shell formation step according to the method for producing core / shell type semiconductor nanoparticles of the present invention.

[0068] In the method for producing core / shell type semiconductor nanoparticles of the present invention, in order to form two or more shells of different compositions on a core particle, the shell formation step according to the method for producing core / shell type semiconductor nanoparticles of the present invention can be performed using a shell precursor to obtain the composition of each shell in the formation of each shell. For example, in order to form a first layer shell on a core particle, the shell formation step according to the method for producing core / shell type semiconductor nanoparticles of the present invention is performed to obtain an intermediate particle of core / first layer shell type semiconductor nanoparticles. Then, in order to form a second layer shell on the obtained intermediate particle of core / first layer shell type semiconductor nanoparticles, the shell formation step according to the method for producing core / shell type semiconductor nanoparticles of the present invention is performed to obtain a core / first layer shell / second layer shell type semiconductor nanoparticle having two shells. Furthermore, for example, in order to form a first layer shell on a core particle, a shell formation step according to the method for manufacturing core / shell type semiconductor nanoparticles of the present invention is performed to obtain an intermediate particle of core / first layer shell type semiconductor nanoparticles. Then, in order to form a second layer shell on the obtained intermediate particle of core / first layer shell type semiconductor nanoparticles, a shell formation step according to the method for manufacturing core / shell type semiconductor nanoparticles of the present invention is performed. ... Then, in order to form an nth layer shell on the obtained intermediate particle of core / first layer shell / second layer shell / ... / (n-1)th layer shell type semiconductor nanoparticles, a shell formation step according to the method for manufacturing core / shell type semiconductor nanoparticles of the present invention is performed to obtain a core / first layer shell / second layer shell / ... / nth layer shell type semiconductor nanoparticle having n layers of shells.

[0069] Furthermore, in the method for producing core / shell type semiconductor nanoparticles of the present invention, by applying the method for producing core / shell type semiconductor nanoparticles of the present invention when forming a shell that is directly formed on the surface of the core particle, core / shell type semiconductor nanoparticles with high quantum efficiency can be obtained.

[0070] In the method for producing core / shell type semiconductor nanoparticles of the present invention, in order to form two or more shells on a core particle, the shell formation step according to the method for producing core / shell type semiconductor nanoparticles of the present invention can be performed in at least one of the shell formations. For example, in a method for producing core / shell type semiconductor nanoparticles in which a first layer shell is formed on a core particle to obtain an intermediate particle of the core / first layer shell type semiconductor nanoparticle, then a second layer shell is formed on the obtained intermediate particle of the core / first layer shell type semiconductor nanoparticle, ... and then an nth layer shell is formed on the obtained intermediate particle of the core / first layer shell / second layer shell / ... / (n-1)th layer shell type semiconductor nanoparticle to obtain a core / first layer shell / second layer shell / ... / nth layer shell type semiconductor nanoparticle having n layers of shells, the shell formation step according to the method for producing core / shell type semiconductor nanoparticles of the present invention can be performed in at least one of the shell formations.

[0071] After obtaining core / shell semiconductor nanoparticles using the method for producing core / shell semiconductor nanoparticles of the present invention, the surface of the shell can be modified with a ligand to stabilize the dispersion of the obtained core / shell semiconductor nanoparticles in a matrix and / or to impart weather resistance. Furthermore, if necessary, after obtaining core / shell semiconductor nanoparticles using the method for producing core / shell semiconductor nanoparticles of the present invention and then surface-modifying them with a ligand, the ligand modifying the core / shell semiconductor nanoparticles can be replaced with another ligand to improve dispersibility in dispersion media of different polarities. Additionally, after obtaining core / shell semiconductor nanoparticles using the method for producing core / shell semiconductor nanoparticles of the present invention and then surface-modifying them with a ligand, the ligand-modified core / shell semiconductor nanoparticles can be bound to other structures via the ligand.

[0072] The method for producing core / shell type semiconductor nanoparticles of the present invention allows for the formation of an oxide layer on the surface of core / shell type semiconductor nanoparticles after obtaining them. The oxide used to form the oxide layer is not particularly limited as long as it is within the range that achieves the effects of the present invention, and examples include oxides of Si, Ti, and Al.

[0073] The present invention will be described below based on specific experimental examples, but the present invention is not limited to these.

[0074] Semiconductor nanoparticles were fabricated according to the following method, and the composition and optical properties of the obtained semiconductor nanoparticles were measured.

[0075] (Example 1) <Cadmium oleate (Cd(Ol) ２ Synthesis of ) > First, 20 mmol of tetramethylammonium hydroxide pentahydrate and 6.4 mL of oleic acid (OAc) were added to 50 mL of methanol, and the mixture was stirred to form a homogeneous solution A. Next, 10 mmol of cadmium acetate hydrate was added to 50 mL of methanol, and the mixture was stirred to form a homogeneous solution B. Then, solution B was slowly added to solution A with stirring, and a milky white cadmium oleate precipitate was formed. After adding all the mixture, the solution was stirred for 20 minutes. Finally, the precipitate was centrifuged about three times with methanol and dried in a vacuum oven at 40°C. The dried cadmium oleate was stored in a vial.

[0076] <Preparation of Selenium Precursor> 10 mmol of Se powder was dissolved in 2.4 g of tributylphosphine (TBP) to prepare a 0.1 mol / L TBP-Se solution, which was then diluted with 6.9 g of octadecene (ODE) to obtain the selenium precursor.

[0077] <Preparation of mixed precursor> First, 0.3 mmol of cadmium oleate and 0.6 mmol of S powder were added to a vial (5 mL). Subsequently, 1.5 mmol of oleylamine, 1.5 mmol of octanoic acid, and 2.26 mL of ODEN were added to the vial to prepare a total of 3 mL of mixed precursor solution. The mixed solution was ultrasonically dispersed at 50°C and stored after complete dissolution.

[0078] <Synthesis of CdSe core particles> 0.2 mmol of cadmium oxide (CdO) and 0.8 mmol of stearic acid were added to a three-necked flask containing 10 mL of ODEN, and the flask was then mounted on a heating magnetic stirrer. The three-necked flask was degassed at room temperature for 30 minutes, and then heated at 270°C for 1 hour under a nitrogen atmosphere until the liquid turned pale yellow. It was cooled to room temperature, and 0.5 g of trioctylphosphine oxide (TOPO) and 1.5 g of amine stearate were added to the above solution. Then, it was heated to 60°C and stirred to completely dissolve the solid, and then degassed again until there were no more bubbles in the solution. Next, N ２ The mixture was transferred to a three-necked flask, stirred for 10 minutes, and then heated to 290°C. At this temperature, 1 mL of TBP-Se solution was rapidly injected, and after injection, the temperature was lowered to 250°C over 5 minutes, and then cooled to room temperature. The precipitate was centrifuged 1-2 times with 5 mL of hexane and 15 mL of ethanol.

[0079] <Synthesis of CdSe / CdS Core / Shell Type Semiconductor Nanoparticles> 7.5 mL of ODE and 40 mg of CdSe core particles were placed in a three-necked flask, and the flask was mounted on a heated magnetic stirrer. The mixture was degassed at 150°C for 30 minutes until no more bubbles remained in the solution. Then, under a nitrogen atmosphere, the temperature was increased to 300°C at a rate of 10°C / min, and when the temperature of the mixture reached 280°C, 0.5 g of benzyl alcohol was added while simultaneously injecting 3 mL of mixed precursor at a rate of 1.5 mL / h. At the same rate, the temperature was increased to 310°C, held for 15 minutes, and then cooled to room temperature. The obtained CdSe / CdS core / shell type semiconductor nanoparticles were centrifuged 1-2 times with 5 mL of hexane and 15 mL of ethanol to obtain CdSe / CdS core / shell type semiconductor nanoparticles.

[0080] (Example 2) <Synthesis of CdSe / CdS / ZnS core / shell type semiconductor nanoparticles> 0.6 mmol of sulfur powder and 2 mL of trioctylphosphine (TOP) were placed in a 5 mL test flask and dispersed and dissolved before sonication to obtain a sulfur precursor. Next, 0.7 mmol of zinc acetate dihydrate was added to a three-necked flask along with 2 mL of oleic acid (OAc) and 6 mL of ODÉ, and the flask was mounted on a heating magnetic stirrer. The mixture was degassed at 120°C for 30 minutes, and then heated at 250°C for 1 hour under a nitrogen atmosphere to completely dissolve the solid. The solution was then cooled to 70°C, and a hexane solution of CdSe / CdS dispersed in 1 mL of hexane from Example 1 was quickly poured into the flask. After degassing for 30 minutes, the mixture was heated to 250°C under a nitrogen atmosphere. Next, the precursor was slowly injected into the solution at a rate of 0.1 mL / min and reacted for a further 40 minutes after the injection process. The solution was cooled to room temperature and centrifuged once or twice using 5 mL of hexane and 15 mL of ethanol to obtain CdSe / CdS / ZnS core / shell semiconductor nanoparticles. The obtained CdSe / CdS / ZnS core / shell semiconductor nanoparticles were dispersed in 4 mL of hexane.

[0081] (Example 3) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were synthesized in the same manner as in Example 2, except that 0.25 g of benzyl alcohol was used instead of 0.5 g of benzyl alcohol added in Example 2.

[0082] (Example 4) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were synthesized in the same manner as in Example 2, except that 0.25 g of benzyl alcohol was used instead of 0.75 g of benzyl alcohol added in Example 2.

[0083] (Comparative Example 1) CdSe / CdS core / shell type semiconductor nanoparticles were synthesized in the same manner as in Example 1, but without adding 0.5 g of benzyl alcohol, which was added in Example 1.

[0084] (Comparative Example 2) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were synthesized in the same manner as in Example 1, but without adding 0.5 g of benzyl alcohol, which was added in Example 2, and with the other steps being the same.

[0085] (Example 5) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were synthesized in the same manner as in Example 2, except that 0.5 g of p-methylbenzyl alcohol was used instead of 0.5 g of benzyl alcohol added in the synthesis of CdSe / CdS / ZnS core / shell type semiconductor nanoparticles in Example 2.

[0086] (Example 6) CdSe / CdS core / shell type semiconductor nanoparticles were synthesized in the same manner as in Example 1, except that 0.5 g of benzyl alcohol and 0.9 g of octanoic acid were used instead of 0.5 g of benzyl alcohol added in Example 1.

[0087] (Example 7) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 2, except that 0.5 g of benzyl alcohol and 0.9 g of octanoic acid were used instead of 0.5 g of benzyl alcohol added in the synthesis of the CdSe / CdS / ZnS core / shell type semiconductor nanoparticles in Example 2.

[0088] (Example 8) CdSe / CdS core / shell type semiconductor nanoparticles were synthesized in the same manner as in Example 1, except that 0.5 g of benzyl alcohol and 1.7 g of oleic acid were used instead of 0.5 g of benzyl alcohol added in Example 1.

[0089] (Example 9) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 2, except that 0.5 g of benzyl alcohol and 1.7 g of oleic acid were used instead of 0.5 g of benzyl alcohol added in the synthesis of the CdSe / CdS / ZnS core / shell type semiconductor nanoparticles in Example 2.

[0090] (Example 10) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 2, except that 0.125 g of benzyl alcohol and 1.7 g of oleic acid were used instead of 0.5 g of benzyl alcohol added in the synthesis of the CdSe / CdS / ZnS core / shell type semiconductor nanoparticles in Example 2.

[0091] (Example 11) After obtaining CdSe core particles in the same manner as in Example 1, 7.5 mL of ODE and 40 mg of CdSe core particles were placed in a three-necked flask, and the flask was mounted on a heated magnetic stirrer. The mixture was degassed at 150°C for 30 minutes until no more bubbles remained in the solution. Then, the temperature was raised to 300°C at a rate of 10°C / min under a nitrogen atmosphere, and when the temperature of the mixture reached 280°C, a mixture of 0.5 g of benzyl alcohol and 1.7 g of oleic acid was added, while simultaneously injecting 3 mL of mixed precursor at a rate of 1.5 mL / h. At the same time, the temperature was raised to 310°C, held for 15 minutes, and then cooled to room temperature. The obtained CdSe / CdS core / shell type semiconductor nanoparticles were centrifuged 1 to 2 times with 5 mL of hexane and 15 mL of ethanol to obtain CdSe / CdS core / shell type semiconductor nanoparticles. Subsequently, CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 2.

[0092] (Example 12) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 2, except that 0.5 g of benzyl alcohol and 2.0 g of erucic acid were used instead of 0.5 g of benzyl alcohol added in the synthesis of the CdSe / CdS / ZnS core / shell type semiconductor nanoparticles in Example 2.

[0093] (Example 13) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 2, except that 0.7 g of p-methylbenzyl alcohol and 1.7 g of oleic acid were used instead of 0.5 g of benzyl alcohol added in the synthesis of the CdSe / CdS / ZnS core / shell type semiconductor nanoparticles in Example 2.

[0094] (Example 14) CdSe / CdS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 1, except that 0.5 g of benzyl alcohol and 0.7 g of benzoic acid were used instead of 0.5 g of benzyl alcohol added in the synthesis of the CdSe / CdS core / shell type semiconductor nanoparticles in Example 1.

[0095] (Example 15) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 1, except that 0.5 g of benzyl alcohol and 0.7 g of benzoic acid were used instead of 0.5 g of benzyl alcohol added in the synthesis of the CdSe / CdS / ZnS core / shell type semiconductor nanoparticles in Example 2.

[0096] (Example 16) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 2, except that 0.5 g of benzyl alcohol and 2.1 g of benzoic acid were added instead of 0.5 g of benzyl alcohol added in the synthesis of the CdSe / CdS / ZnS core / shell type semiconductor nanoparticles in Example 2.

[0097] (Example 17) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 2, except that 0.5 g of benzyl alcohol and 3.5 g of benzoic acid were added instead of 0.5 g of benzyl alcohol added in the synthesis of the CdSe / CdS / ZnS core / shell type semiconductor nanoparticles in Example 2.

[0098] (Comparative Example 3) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 1, except that 1.1 g of oleyl alcohol was used instead of 0.5 g of benzyl alcohol added in Example 2.

[0099] (Comparative Example 4) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 1, except that 12.5 g of oleyl alcohol was used instead of 0.5 g of benzyl alcohol added in the synthesis of the CdSe / CdS / ZnS core / shell type semiconductor nanoparticles in Example 2.

[0100] (Comparative Example 5) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 1, except that 1.7 g of oleic acid was used instead of 0.5 g of benzyl alcohol added in Example 2 to the synthesis of CdSe / CdS / ZnS core / shell type semiconductor nanoparticles.

[0101] (Comparative Example 6) After obtaining CdSe core particles in the same manner as in Example 1, 7.5 mL of ODE and 40 mg of CdSe core particles were placed in a three-necked flask, and the flask was mounted on a heated magnetic stirrer. The mixture was degassed at 150°C for 30 minutes until no more bubbles remained in the solution. Then, the temperature was raised to 310°C at a rate of 10°C / min under a nitrogen atmosphere, 8.5 g of oleic acid was added, and then 3 mL of mixed precursor was injected at a rate of 1.5 mL / h. After that, the temperature was raised again to 310°C, held for 15 minutes, and then cooled to room temperature. The obtained CdSe / CdS core / shell type semiconductor nanoparticles were centrifuged once or twice with 5 mL of hexane and 15 mL of ethanol to obtain CdSe / CdS core / shell type semiconductor nanoparticles. Then, CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 2.

[0102] (Comparative Example 7) CdSe / CdS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 1, except that 0.7 g of benzoic acid was used instead of 0.5 g of benzyl alcohol added to the synthesis of the CdSe / CdS core / shell type semiconductor nanoparticles in Example 1.

[0103] The CdSe / CdS core / shell type semiconductor nanoparticles obtained in Comparative Example 7 showed significantly reduced luminescence, and their optical properties could not be adequately measured. Although the synthesis of CdSe / CdS / ZnS core / shell type semiconductor nanoparticles was carried out in the same manner as in Example 2, no nanoparticles with adequately measurable optical properties were ultimately obtained.

[0104] (Comparative Example 8) CdSe / CdS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 1, except that 1.0 g of decanol and 1.7 g of oleic acid were used instead of 0.5 g of benzyl alcohol added in Example 1.

[0105] (Comparative Example 9) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 2, except that 1.0 g of decanol and 1.7 g of oleic acid were used instead of 0.5 g of benzyl alcohol added in Example 2.

[0106] (Comparative Example 10) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 2, except that 1.3 g of decanol and 1.7 g of oleic acid were used instead of 0.5 g of benzyl alcohol added in Example 2.

[0107] (Comparative Example 11) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 2, except that a mixture of 1.3 g of decanol and 1.7 g of oleic acid was added instead of 8.5 g of oleic acid added in the synthesis of the CdSe / CdS / ZnS core / shell type semiconductor nanoparticles in Comparative Example 6.

[0108] (Comparative Example 12) CdSe / CdS / ZnS core / shell type semiconductor nanoparticles were obtained in the same manner as in Example 2, except that 1.6 g of triphenylmethanol and 1.7 g of oleic acid were used instead of 0.5 g of benzyl alcohol added in Example 2.

[0109] (Comparative Example 13) After obtaining CdSe core particles in the same manner as in Example 1, 7.5 mL of ODE and 40 mg of CdSe core particles were placed in a three-necked flask, and the flask was mounted on a heated magnetic stirrer. The mixture was degassed at 150°C for 30 minutes until no more bubbles remained in the solution. Then, under a nitrogen atmosphere, the temperature was raised to 300°C at a rate of 10°C / min, and when the temperature of the mixture reached 250°C, 0.5 g of benzyl alcohol was added while simultaneously injecting 3 mL of mixed precursor at a rate of 1.5 mL / h. At the same rate, the temperature was raised to 310°C, held for 15 minutes, and then cooled to room temperature. The obtained CdSe / CdS core / shell type semiconductor nanoparticles were centrifuged 1 to 2 times with 5 mL of hexane and 15 mL of ethanol to obtain CdSe / CdS core / shell type semiconductor nanoparticles.

[0110] The optical identification of the obtained core / shell type semiconductor nanoparticles was measured as follows. The obtained core / shell type semiconductor nanoparticles were dispersed in octane, and the concentration of the semiconductor nanoparticles was adjusted so that the absorption rate of the dispersion was 20-30%, and this was injected into a measurement cell. For the measurement, a fluorescence quantum efficiency measurement system (Otsuka Electronics: QE-2100) was used, and a single 450 nm light was used as the excitation light, and the emission spectrum was obtained by irradiating the sample with the excitation light. From the emission spectrum obtained here, the fluorescence quantum efficiency (QY), full width at half maximum (FWHM), and emission peak wavelength (PWL) were calculated from the re-excitation corrected emission spectrum, which excludes the re-excitation fluorescence emission spectrum of the portion that was re-excited and emitted fluorescence. The results of fluorescence quantum efficiency (QY), full width at half maximum (FWHM), and emission peak wavelength (PWL) for each sample are shown in Tables 1 to 3.

[0111]

[0112]

[0113]

[0114] In the table, the boiling point is the boiling point at 1 atm. For substances whose boiling point is shown in parentheses in the table, the boiling point is listed in parentheses as a reference value only, because the substance may decompose before reaching its boiling point when heated at 1 atm. "Alcohol to core Cd (mol ratio)" is the molar ratio of the alcohol used as the dispersion medium to the Cd in the core particles. "Carboxylic acid to core Cd (mol ratio)" is the molar ratio of the carboxylic acid used as the dispersion medium to the Cd in the core particles. The composition shows the composition of the core particles and the shell, and indicates the composition of "core particle / first layer shell" or "core particle / first layer shell / second layer shell".

[0115] In the shell formation process, Examples 1 and 2, which used benzyl alcohol as the dispersion medium, yielded CdSe / CdS core / shell type semiconductor nanoparticles or CdSe / CdS / ZnS core / shell type semiconductor nanoparticles with high QY compared to Comparative Examples 1 and 2, which did not use benzyl alcohol as the dispersion medium, and Comparative Example 4, which used oleyl alcohol as the dispersion medium. Furthermore, it was found that Examples 6 to 17, which used benzyl alcohol and carboxylic acid as the dispersion medium, yielded CdSe / CdS core / shell type semiconductor nanoparticles or CdSe / CdS / ZnS core / shell type semiconductor nanoparticles with high QY. Comparative Examples 3 to 4 and 8 to 12 are examples where alcohols other than carboxylic acid and benzyl alcohol were used as the dispersion medium, but even compared to these, Examples 6 to 17 yielded CdSe / CdS / ZnS core / shell type semiconductor nanoparticles with high QY.

Claims

1. A method for producing core / shell type semiconductor nanoparticles, comprising a shell formation step of mixing and reacting core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells, a dispersion medium, and a shell precursor to form a shell on at least a portion of the surface of the core particles or intermediate particles of core / shell type semiconductor nanoparticles having one or more shells, thereby obtaining core / shell type semiconductor nanoparticles, wherein the dispersion medium contains benzyl alcohol and / or a substituted compound thereof.

2. The method for producing core / shell type semiconductor nanoparticles according to claim 1, characterized in that the benzyl alcohol and / or its substituted compound is benzyl alcohol.

3. The method for producing core / shell type semiconductor nanoparticles according to claim 1, characterized in that the core particles mixed in the shell formation step are a dispersion of core particles.

4. The method for producing core / shell type semiconductor nanoparticles according to claim 5, characterized in that the temperature of the dispersion of the core particles is 200°C to 380°C.

5. The method for producing core / shell type semiconductor nanoparticles according to claim 1, characterized in that the core particles of the core / shell type semiconductor nanoparticles contain Cd and Se.

6. The method for producing core / shell type semiconductor nanoparticles according to claim 1, characterized in that the shell of the core / shell type semiconductor nanoparticle contains Cd and S.

7. The method for producing core / shell type semiconductor nanoparticles according to claim 6, characterized in that the shell of the core / shell type semiconductor nanoparticle further comprises Zn and S.

8. The method for producing core / shell type semiconductor nanoparticles according to claim 1, characterized in that the reaction temperature in the shell formation step is 200°C to 380°C.

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